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Andrea Louys
Address:
Institute for Building Materials (IfB), ETH Zurich
HIF E 14.1
Schafmattstrasse 6.
CH-8093 Zurich
Email: alouys@ethz.ch
Phone: +41 44 632 32 26
Fax: +41 44 633 10 87
Office Hours:
Monday, Tuesday 8.00 am -- 5.00 pm
Thursday, Friday 8.00 am -- 12.00 pm
Groups: Physical Chemistry of Building Materials
Andrea Merletti
Address: Institute for Building Materials (IfB), ETH Zurich
HIF E 14.1
Schafmattstrasse 6
CH-8093 Zurich
Email: amerletti@ethz.ch
Phone: +41 44 632 32 26
Fax: +41 44 632 11 74
Office Hours:
Monday: 8.00 am - 5.00 pm
Tuesday: 8.00 am - 12.00 pm
Wednesday 8.00 am - 12.00 am
Thursday 8.00 am - 5.00 pm
Groups: Wood Physics, Wood Material Science
Anke Weinberger
Address:
Institute for Building Materials (IfB), ETH Zurich
HIF E 14.1
Schafmattstrasse 6
CH-8093 Zurich
Email: comphysoffice@ethz.ch
Phone: +41 44 633 27 93
Fax: +41 44 633 11 47
Office Hours:
Monday 8.00 am -- 12.00 pm
Tuesday, Thursday 8.00 am -- 5.00 pm
Groups: Computational Physics for Building Materials, Microstructure and Rheology
International Workshop 2011
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2012
Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz
,
Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter,
2012
>>
| Author(s): | Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter |
| Title: | Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz |
| Abstract: | Ziel der Arbeit war es, ausgewählte Eigenschaften von modifiziertem und nativem Holz zu bestimmen. Es wurden mechanische und physikalische Kenngrößen thermisch modifizierter Buchen-, Eschen- und Pappelproben zweier unterschiedlicher Behandlungsintensitäten ermittelt. Zur Referenz wurden unmodifizierte Proben jeder Holzart getestet. Gegenüber anderen thermischen Vergütungsprozessen beeinflusst das Vakuumpress-Trocknungsverfahren die Eigenschaften des Holzes weniger stark. Es entstehen auch weniger Emissionen wie Essig- oder Ameisensäuren. Die thermische Behandlung von Buche erzielt eine Reduzierung der Dichte und Biegefestigkeit, während die thermisch vergütete Pappel einen leichten Anstieg beider Kenngrößen aufweist. Die Eigenschaften der Esche unterscheiden sich in Abhängigkeit der Behandlungsintensität. Die mit geringer Temperatur vergüteten Proben weisen dem Referenzholz gegenüber zum Teil gestiegene Festigkeiten auf, die höher temperierten Proben stets geringere. Die Dimensionsstabilität steigt infolge der verringerten Gleich -gewichtsfeuchte. Anhand der Ergebnisse ist zu erkennen, dass die Änderung der physikalischen wie auch mechanischen Eigenschaften sowohl von der Behandlungsintensität und dem angewandten Verfahren selbst als auch von der behandelten Holzart abhängt. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 1 - 10 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Biegefestigkeit, Brinellhrte, Bruchschlagarbeit, Dichte, Elastizittsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Wärmeleitfhigkeit |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Biegefestigkeit, Brinellhrte, Bruchschlagarbeit, Dichte, Elastizittsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Wärmeleitfhigkeit |
| DBID source: | FORM-1328528909 |
| DOI: | 10.1002/bapi.201200001 |
| Nebis system number: | 000006704 |
Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz
,
Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter,
2012
>>
| Author(s): | Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter |
| Title: | Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz |
| Abstract: | Ziel der Arbeit war es, ausgewählte Eigenschaften von modifiziertem und nativem Holz zu bestimmen. Es wurden mechanische und physikalische Kenngrößen thermisch modifizierter Buchen-, Eschen- und Pappelproben zweier unterschiedlicher Behandlungsintensitäten ermittelt. Zur Referenz wurden unmodifizierte Proben jeder Holzart getestet. Gegenüber anderen thermischen Vergütungsprozessen beeinflusst das Vakuumpress-Trocknungsverfahren die Eigenschaften des Holzes weniger stark. Es entstehen auch weniger Emissionen wie Essig- oder Ameisensuren. Die thermische Behandlung von Buche erzielt eine Reduzierung der Dichte und Biegefestigkeit, während die thermisch vergütete Pappel einen leichten Anstieg beider Kenngrößen aufweist. Die Eigenschaften der Esche unterscheiden sich in Abhängigkeit der Behandlungsintensität. Die mit geringer Temperatur vergüteten Proben weisen dem Referenzholz gegenüber zum Teil gestiegene Festigkeiten auf, die höher temperierten Proben stets geringere. Die Dimensionsstabilität steigt infolge der verringerten Gleichgewichtsfeuchte. Anhand der Ergebnisse ist zu erkennen, dass die Änderung der physikalischen wie auch mechanischen Eigenschaften sowohl von der Behandlungsintensität und dem angewandten Verfahren selbst als auch von der behandelten Holzart abhängt. The aim of this work was to analyse selected mechanical and physical behaviours of wood thermally treated with the vacuum press dewatering method, Vacu3. The density, bending and impact bending strength, modulus of elasticity, Brinell hardness and the withdrawal capacity of screws as well as the sorption capacity, change in colour and the thermal conductivity were measured. The investigated beech, ash and poplar samples were thermally treated with the patented vacuum press dewatering method, Vacu3. To test the influence of processing conditions, one type of sample was treated with medium temperatures and the other with high process temperatures. As a reference, the properties of unmodified specimen were determined. Thermal modification of beech affects a decrease in density and bending strength. The opposite is the case for heat-treated poplar. The properties of heat-treated ash differ depending on the degree of thermal treatment. The application of medium process temperatures on ash causes an increment in density and bending strength. In contrast, high process temperatures lead to a reduction in density and mechanical properties. As a consequence of the progressive reduction of equilibrium moisture content, the dimensional stability of heat-treated wood is improved. The test results show that changes in properties are influenced by the treatment intensity as well as by treatment technology. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 1 - 10 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Biegefestigkeit, Brinellhärte, Bruchschlagarbeit, Dichte, Elastizitatsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Warmeleitfähigkeit, Bending strength, Brinell hardness, Bonding, Colour, Density, Impact bending strength, Modulus of elasticity, Sorption capacity, Swelling behaviour, Thermal conductivity, Feuchte, Moisture |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Biegefestigkeit, Brinellhärte, Bruchschlagarbeit, Dichte, Elastizitatsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Warmeleitfähigkeit, Bending strength, Brinell hardness, Bonding, Colour, Density, Impact bending strength, Modulus of elasticity, Sorption capacity, Swelling behaviour, Thermal conductivity, Feuchte, Moisture |
| DBID source: | WOS-000299835000001 |
| DOI: | 10.1002/bapi.201200001 |
| Nebis system number: | 000006704 |
Farbänderung von Holz bei Freibewitterung
,
Wetzig, Melanie, Niemz, Peter,
2012
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| Author(s): | Wetzig, Melanie, Niemz, Peter |
| Title: | Farbänderung von Holz bei Freibewitterung |
| Published in: | Holz-Zentralblatt |
| Issue: | 4 |
| Pages: | 103 - 105 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Unknown |
| Language: | German |
| DBID source: | FORM-1328528374 |
Untersuchungen zum Einfluss ausgewählter verfahrenstechnischer Parameter auf die VOC-Emission und ausgewählte mechanische Kennwerte wärmebehandelten Holzes
,
Wetzig, Melanie, Kraft Redelf, Roffael, Edmone, Schmutz, Andreas, Huber, Christian, Niemz, Peter,
2012
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| Author(s): | Wetzig, Melanie, Kraft Redelf, Roffael, Edmone, Schmutz, Andreas, Huber, Christian, Niemz, Peter |
| Title: | Untersuchungen zum Einfluss ausgewählter verfahrenstechnischer Parameter auf die VOC-Emission und ausgewählte mechanische Kennwerte wärmebehandelten Holzes |
| Published in: | Holztechnologie |
| Volume: | 53 |
| Issue: | 2 |
| Pages: | 24 - 30 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Dresden |
| Publication status: | Published |
| Language: | English |
| DBID source: | FORM-1331898083 |
| Nebis system number: | 000026159 |
From invasion percolation to flow in rock fracture networks
,
Wettstein, Salomon J., Wittel, Falk K., Araújo, Nuno A.M., Lanyon, Bill, Herrmann, Hans Jürgen,
2012
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| Author(s): | Wettstein, Salomon J., Wittel, Falk K., Araújo, Nuno A.M., Lanyon, Bill, Herrmann, Hans Jürgen |
| Title: | From invasion percolation to flow in rock fracture networks |
| Abstract: | The main purpose of this work is to simulate two-phase flow in the form of immiscible displacement through anisotropic, three-dimensional (3D) discrete fracture networks (DFN). The considered DFNs are artificially generated, based on a general distribution function or are conditioned on measured data from deep geological investigations. We introduce several modifications to the invasion percolation (MIP) to incorporate fracture inclinations, intersection lines, as well as the hydraulic path length inside the fractures. Additionally a trapping algorithm is implemented that forbids any advance of the invading fluid into a region, where the defending fluid is completely encircled by the invader and has no escape route. We study invasion, saturation, and flow through artificial fracture networks, with varying anisotropy and size and finally compare our findings to well studied, conditioned fracture networks. |
| Published in: | Physica. A |
| Volume: | 391 |
| Issue: | 1-2 |
| Pages: | 264 - 277 |
| ISSN: | 0378-4371, 1873-2119 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Discrete fracture networks, Invasion percolation, Trapping, Two-phase flow, Permeability |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Discrete fracture networks, Invasion percolation, Trapping, Two-phase flow, Permeability |
| DBID source: | FORM-1320766191, WOS-000297230700029 |
| DOI: | 10.1016/j.physa.2011.07.029 |
| Nebis system number: | 001929798 |
Untersuchungen zum Einfluss der Klebstoffart auf den Diffusionswiderstand von Holzverklebungen
,
Volkmer, Thoms, Schmidt Jon-Anton, Kranitz, Katalin, Niemz, Peter,
2012
>>
| Author(s): | Volkmer, Thoms, Schmidt Jon-Anton, Kranitz, Katalin, Niemz, Peter |
| Title: | Untersuchungen zum Einfluss der Klebstoffart auf den Diffusionswiderstand von Holzverklebungen |
| Abstract: | An reinen Klebstofffilmen aus verschiedenen Klebstoffen (PVA, PUR, UF, MUF, EPI, Knochenleim) und an verklebten Holzlamellen mit einer mittigen Klebefuge wurde der Diffusionswiderstand im Dry- und im Wet-Cup-Verfahren nach DIN EN ISO 12572 bestimmt. Es wurden deutliche Unterschiede im Diffusionswiderstand zwischen den einzelnen Klebstoffarten gemessen. Der Diffusionswiderstand der Klebstofffilme war wesentlich höher als der der Verklebungen, was auf die entsprechenden Abbindemechanismen und die Eindringung der Klebstoffe in das Substrat zurückzuführen ist. Die Klebefugen der geprüften Systeme PVAc, EPI und 1K-PUR erwiesen sich im Vergleich als sehr diffusionsdicht, was bei einer bauphysikalischen Bewertung von verklebten Holzelementen zu berücksichtigen ist. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 2 |
| Pages: | 55 - 60 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1333365265 |
| DOI: | 10.1002/bapi.201200006 |
| Nebis system number: | 000006704 |
Comparison of bending stiffness of cross-laminated solid timber derived by modal analysis of full panels and by bending tests of strip-shaped specimens
,
Steiger, René, Gülzow, Arne, Czaderski, Christoph, Howald, Martin T., Niemz, Peter,
2012
>>
| Author(s): | Steiger, René, Gülzow, Arne, Czaderski, Christoph, Howald, Martin T., Niemz, Peter |
| Title: | Comparison of bending stiffness of cross-laminated solid timber derived by modal analysis of full panels and by bending tests of strip-shaped specimens |
| Abstract: | The design of cross-laminated solid timber (CLT) as load-bearing plates is mainly governed by serviceability criterions like maximal deflection and susceptibility to vibration. Hence, predicting the respective behavior of such plates requires accurate information about their elastic properties. According to product standards, the bending stiffness of CLT has to be assessed from 4-point bending tests of strip-shaped specimens, cut from the CLT panels. By comparing elastic properties of CLT derived by means of modal analysis of full panels with the results of bending tests on 100 mm and 300 mm wide strip-shaped specimens it is shown, that by testing single 100 mm wide strip-shaped specimens bending stiffness of full panels cannot be assessed correctly, whereas single 300 mm wide strips or averages of 5 to 6 100 mm wide strip-shaped specimens lead to acceptable results. Hence, strip-shaped specimens should only be used in the course of factory quality control or when assessing the bending stiffness of parts of CLT panels used as beam-like load-bearing elements but not to derive bending stiffness of gross CLT panels. Verification by carrying out static bending tests of gross CLT panels under different loading situations showed that alternatively to tests on strip-shaped specimens or estimations with the compound theory, the overall stiffness properties of CLT can be derived directly by a modal analysis of full-size panels. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 141 - 153 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591798, WOS-000298657600019 |
| DOI: | 10.1007/s00107-011-0521-7 |
| Nebis system number: | 000047744 |
Thermal and moisture flux in soft fibreboards
,
Sonderegger, Walter, Niemz, Peter,
2012
>>
| Author(s): | Sonderegger, Walter, Niemz, Peter |
| Title: | Thermal and moisture flux in soft fibreboards |
| Abstract: | The thermal conductivity of several wet and dry processed industrial soft fibreboards was determined at temperatures between 10°C and 30°C. Additionally, the thermal conductivity was tested relative to the moisture content ranging from an oven-dry sample to a moisture content of 85% relative humidity. Furthermore, the water vapour diffusion was investigated to determine the resistance factor and the diffusion coefficient under ‘dry cup’ and ‘wet cup’ conditions and the sorptions were tested by means of the sorption isotherms. The thermal conductivity increases with increasing temperature at about 0.45% per Kelvin and with increasing moisture at about 0.17×10−2 W/mK per percent volumetric moisture content. Furthermore, the thermal conductivity depends on the manufacture (dry or wet process) and is influenced by density. The water vapour resistance factor increases and the diffusion coefficient decreases with increasing density. Both factors decrease with increasing moisture content and they are dependant on board thickness, composition and manufacturing. The sorption isotherm is similar to solid wood below about 80% relative humidity but strongly increases for soft fibreboards with binding fibres and additives of ammonium phosphate or sodium borate and boric acid when above 80% relative humidity. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 25 - 35 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591478, WOS-000298657600004 |
| DOI: | 10.1007/s00107-010-0498-7 |
| Nebis system number: | 000047744 |
Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition
,
Schrenk, K. J., Felder, A., Deflorin, S., Araujo, N. A. M., D'Souza, R. M., Herrmann, H. J.,
2012
>>
| Author(s): | Schrenk, K. J., Felder, A., Deflorin, S., Araujo, N. A. M., D'Souza, R. M., Herrmann, H. J. |
| Title: | Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition |
| Abstract: | The BFW model introduced by Bohman, Frieze, and Wormald [Random Struct. Algorithms 25, 432 (2004)], and recently investigated in the framework of discontinuous percolation by Chen and D'Souza [Phys. Rev. Lett. 106, 115701 (2011)], is studied on the square and simple-cubic lattices. In two and three dimensions, we find numerical evidence for a strongly discontinuous transition. In two dimensions, the clusters at the threshold are compact with a fractal surface of fractal dimension d(f) = 1.49 +/- 0.02. On the simple-cubic lattice, distinct jumps in the size of the largest cluster are observed. We proceed to analyze the tree-like version of the model, where only merging bonds are sampled, for dimension two to seven. The transition is again discontinuous in any considered dimension. Finally, the dependence of the cluster-size distribution at the threshold on the spatial dimension is also investigated. |
| Published in: | Physical Review E |
| Volume: | 85 |
| Issue: | 3 |
| Pages: | 031103 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000301339900001 |
| DOI: | 10.1103/PhysRevE.85.031103 |
| Nebis system number: | 004109079 |
Fracturing ranked surfaces
,
Schrenk, K. J., Araujo, N. A. M., Andrade, J. S., Herrmann, H. J.,
2012
>>
| Author(s): | Schrenk, K. J., Araujo, N. A. M., Andrade, J. S., Herrmann, H. J. |
| Title: | Fracturing ranked surfaces |
| Abstract: | Discretized landscapes can be mapped onto ranked surfaces, where every element (site or bond) has a unique rank associated with its corresponding relative height. By sequentially allocating these elements according to their ranks and systematically preventing the occupation of bridges, namely elements that, if occupied, would provide global connectivity, we disclose that bridges hide a new tricritical point at an occupation fraction p = p(o), where p(c) is the percolation threshold of random percolation. For any value of p in the interval p(c) < p <= 1, our results show that the set of bridges has a fractal dimension d(BB) approximate to 1.22 in two dimensions. In the limit p -> 1, a self-similar fracture is revealed as a singly connected line that divides the system in two domains. We then unveil how several seemingly unrelated physical models tumble into the same universality class and also present results for higher dimensions. |
| Published in: | Scientific Reports |
| Volume: | 2 |
| Pages: | 348 |
| ISSN: | 2045-2322 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Nature Publishing Group |
| Publication status: | Published |
| Subjects: | Wissenschaft und Technik allgemein|Science and Technology, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000302458500002 |
| DOI: | 10.1038/srep00348 |
| Nebis system number: | 006751867 |
CHITINASE-LIKE1/POM-POM1 and Its Homolog CTL2 Are Glucan-Interacting Proteins Important for Cellulose Biosynthesis in Arabidopsis
,
Sanchez-Rodriguez, Clara, Bauer, Stefan, Hematy, Kian, Saxe, Friederike, Ibanez, Ana Belén, Vodermaier, Vera, Konlechner, Cornelia, Sampathkumar, Arun, Ruggeberg, Markus, Aichinger, Ernst, Neumetzler, Lutz, Burgert, Ingo, Somerville, Chris, Hauser, Marie-Theres, Persson, Staffan,
2012
>>
| Author(s): | Sanchez-Rodriguez, Clara, Bauer, Stefan, Hematy, Kian, Saxe, Friederike, Ibanez, Ana Belén, Vodermaier, Vera, Konlechner, Cornelia, Sampathkumar, Arun, Ruggeberg, Markus, Aichinger, Ernst, Neumetzler, Lutz, Burgert, Ingo, Somerville, Chris, Hauser, Marie-Theres, Persson, Staffan |
| Title: | CHITINASE-LIKE1/POM-POM1 and Its Homolog CTL2 Are Glucan-Interacting Proteins Important for Cellulose Biosynthesis in Arabidopsis |
| Abstract: | Plant cells are encased by a cellulose-containing wall that is essential for plant morphogenesis. Cellulose consists of beta-1,4-linked glucan chains assembled into paracrystalline microfibrils that are synthesized by plasma membrane-located cellulose synthase (CESA) complexes. Associations with hemicelluloses are important for microfibril spacing and for maintaining cell wall tensile strength. Several components associated with cellulose synthesis have been identified; however, the biological functions for many of them remain elusive. We show that the chitinase-like (CTL) proteins, CTL1/POM1 and CTL2, are functionally equivalent, affect cellulose biosynthesis, and are likely to play a key role in establishing interactions between cellulose microfibrils and hemicelluloses. CTL1/POM1 coincided with CESAs in the endomembrane system and was secreted to the apoplast. The movement of CESAs was compromised in ctl1/pom1 mutant seedlings, and the cellulose content and xyloglucan structures were altered. X-ray analysis revealed reduced crystalline cellulose content in ctl1 ctl2 double mutants, suggesting that the CTLs cooperatively affect assembly of the glucan chains, which may affect interactions between hemicelluloses and cellulose. Consistent with this hypothesis, both CTLs bound glucan-based polymers in vitro. We propose that the apoplastic CTLs regulate cellulose assembly and interaction with hemicelluloses via binding to emerging cellulose microfibrils. |
| Published in: | The plant cell |
| Volume: | 24 |
| Issue: | 2 |
| Pages: | 589 - 607 |
| ISSN: | 1040-4651, 1531-298X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Rockville, MD |
| Publication status: | Published |
| Subjects: | Umweltwissenschaften, Umwelterziehung|Environmental Sciences, Environmental Education, Botanik |Botany |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000302131000017 |
| DOI: | 10.1105/tpc.111.094672 |
| Nebis system number: | 000492783 |
How dense can one pack spheres of arbitrary size distribution ?
,
Reis, S.D.S., Araujo, N.A.M., Andrade Jr., J.S., Herrmann, Hans J.,
2012
>>
| Author(s): | Reis, S.D.S., Araujo, N.A.M., Andrade Jr., J.S., Herrmann, Hans J. |
| Title: | How dense can one pack spheres of arbitrary size distribution ? |
| Abstract: | We present the first systematic algorithm to estimate the maximum packing density of spheres when the grain sizes are drawn from an arbitrary size distribution. With an Apollonian filling rule, we implement our technique for disks in 2d and spheres in 3d. As expected, the densest packing is achieved with power-law size distributions. We also test the method on homogeneous and on empirical real distributions, and we propose a scheme to obtain experimentally accessible distributions of grain sizes with low porosity. Our method should be helpful in the development of ultra-strong ceramics and high-performance concrete. |
| Published in: | EPL : a letters journal exploring the frontiers of physics |
| Volume: | 97 |
| Issue: | 1 |
| Pages: | 18004 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1329818382, WOS-000300250800049 |
| DOI: | 10.1209/0295-5075/97/18004 |
| Nebis system number: | 000033031 |
The apparent roughness of a sand surface blown by wind from an analytical model of saltation
,
Pähtz, Thomas, Kok, F.J., Herrmann, Hans J.,
2012
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| Author(s): | Pähtz, Thomas, Kok, F.J., Herrmann, Hans J. |
| Title: | The apparent roughness of a sand surface blown by wind from an analytical model of saltation |
| Abstract: | We present an analytical model of aeolian sand transport. The model quantifies the momentum transfer from the wind to the transported sand by providing expressions for the thickness of the saltation layer and the apparent surface roughness. These expressions are derived from basic physical principles and a small number of assumptions. The model further predicts the sand transport rate (mass flux) and the impact threshold (the smallest value of the wind shear velocity at which saltation can be sustained). We show that, in contrast to previous studies, the present model's predictions are in very good agreement with a range of experiments, as well as with numerical simulations of aeolian saltation. Because of its physical basis, we anticipate that our model will find application in studies of aeolian sand transport on both Earth and Mars. |
| Published in: | New journal of physics |
| Volume: | 14 |
| Pages: | 043035 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bristol, UK |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1336052435 |
| DOI: | 10.1088/1367-2630/14/4/043035 |
| Nebis system number: | 001997538 |
Reorientation of Cellulose Nanowhiskers in Agarose Hydrogels under Tensile Loading
,
Osorio-Madrao, Anayancy, Eder, Michaela, Rueggeberg, Markus, Pandey, Jitendra Kumar, Harrington, Matthew James, Nishiyama, Yoshiharu, Putaux, Jean-Luc, Rochas, Cyrille, Burgert, Ingo,
2012
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| Author(s): | Osorio-Madrao, Anayancy, Eder, Michaela, Rueggeberg, Markus, Pandey, Jitendra Kumar, Harrington, Matthew James, Nishiyama, Yoshiharu, Putaux, Jean-Luc, Rochas, Cyrille, Burgert, Ingo |
| Title: | Reorientation of Cellulose Nanowhiskers in Agarose Hydrogels under Tensile Loading |
| Abstract: | Agarose hydrogels filled with cellulose nanowhiskers were strained in uniazial stretching under different humidity conditions. The orientation of the cellulose whiskers was examined before and after testing with an X-ray laboratory source and monitored in situ during loading by synchrotron Xray diffraction. The aim of this approach was to determine the process parameters for reorienting the cellulose nanowhiskers toward a preferential direction. Results show that a controlled drying of the hydrogel is essential to establish interactions between the matrix and the cellulose nanowhiskers which allow for a stress transfer during stretching and thereby promote their alignment. Rewetting of the sample after reorientation of the cellulose nanowhiskers circumvents a critical increase of stress. This improves the extensibility of the hydrogel and is accompanied by a further moderate alignment of the cellulose nanowhiskers. Following this protocol, cellulose nanowhiskers with an initial random distribution can be reoriented toward a preferential direction, creating anisotropic nanocomposites. |
| Published in: | Biomacromolecules |
| Volume: | 13 |
| Issue: | 3 |
| Pages: | 850 - 856 |
| ISSN: | 1525-7797, 1526-4602 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Washington |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000301318100033 |
| DOI: | 10.1021/bm201764y |
| Nebis system number: | 003899084 |
Holz besser verkleben
,
Niemz, Peter,
2012
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| Author(s): | Niemz, Peter |
| Title: | Holz besser verkleben |
| Abstract: | Am 1. Dezember 2011 veranstaltete die Arbeitsgruppe Holzphysik (Leitung Prof. Dr. Peter Niemz) des Instituts for Building Materials (IFB) an der ETH Zürich ein Kolloquium zur „Verklebung von Vollholz“. Das Kolloquium fand anlässlich des Abschlusses eines von 2005 bis 2011 bearbeiteten Forschungsprojektes zur Verbesserung der Temperaturbeständigkeit von 1K-PUR Klebstoffen statt. |
| Published in: | Holz-Zentralblatt |
| Issue: | 3 |
| Pages: | 78 - 78 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting), Natürliche Werkstoffe|Natural Materials |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1328528498 |
| Nebis system number: | 000047754 |
Forschung zur Verklebung von Vollholz
,
Niemz, Peter,
2012
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| Author(s): | Niemz, Peter |
| Title: | Forschung zur Verklebung von Vollholz |
| Published in: | Schweizer Holz-Zeitung |
| Volume: | 124 |
| Issue: | 1/2 |
| Pages: | 17 - 17 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Baden-Dättwil |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials |
| Language: | English |
| Review status: | Not reviewed |
| DBID source: | FORM-1326454779 |
| Nebis system number: | 001616552 |
Adhesive penetration of hardwood
,
Mendoza, Miller, Hass, Philipp, Wittel, Falk K., Niemz, Peter, Herrmann, Hans J.,
2012
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| Author(s): | Mendoza, Miller, Hass, Philipp, Wittel, Falk K., Niemz, Peter, Herrmann, Hans J. |
| Title: | Adhesive penetration of hardwood |
| Subtitle: | A generic penetration model |
| Abstract: | An analytical model to predict the penetration of adhesives into hardwood is proposed. Penetration into hardwood is dominated by the vessel network which prohibits porous medium approximations. The model considers two scales: (1) a one dimensional capillary fluid transport of a hardening adhesive through a single, straight vessel with diffusion of solvent through the walls of the vessel; and (2) a mesoscopic scale based on topological characteristics of the vessel network. Given an initial amount of adhesive and applied bonding pressure, the portion of the filled structure could be calculated. The model was applied to beech samples joined with three different types of adhesive (PUR, UF, PVAc) under various growth ring angles as described by Hass et al. (2011). The model contains one free parameter that can be adjusted in order to fit the experimental data. |
| Published in: | Wood Science and Technology |
| Volume: | 46 |
| Issue: | 1-3 |
| Pages: | 529 - 549 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General, Agrar- und Forstwissenschaften|Agriculture and Forestry, phenol-formaldehyde, surface-tension, beech wood, network |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | phenol-formaldehyde, surface-tension, beech wood, network |
| DBID source: | WOS-000298993100038 |
| DOI: | 10.1007/s00226-011-0422-2 |
| Nebis system number: | 000057691 |
Traffic gridlock on complex networks
,
Mendes, G.A., Silva, L.R. da, Herrmann, Hans Jürgen,
2012
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| Author(s): | Mendes, G.A., Silva, L.R. da, Herrmann, Hans Jürgen |
| Title: | Traffic gridlock on complex networks |
| Abstract: | Here we study how a traffic jam spreads on complex networks when driven by an increasing flux between certain initial and final points. For that purpose, we developed two new traffic models based on vehicular traffic and applied them on the Apollonian network and the Swiss road network. The first model is an electrical analog, using ohmic and non-ohmic resistors which is a classical approach in Physics while the second one which we call the herding model, is based on human driving behavior. For both models, we study the sequence of clogged roads up to the traffic gridlock and display the fragilities of the network. In the electrical model, by increasing the external potential, resistors burn out, as the voltage drop between the ends increases above a certain threshold. Analyzing both models, we observed some power-law functions that occur only near a traffic gridlock as well as the dependence on topological features of the network and influence on flux and the robustness in Apollonian networks of different generations. |
| Published in: | Physica A |
| Volume: | 391 |
| Issue: | 1-2 |
| Pages: | 362 - 370 |
| ISSN: | 0378-4371, 1873-2119 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General, Vehicular traffic, Complex networks, Apollonian network |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Vehicular traffic, Complex networks, Apollonian network |
| DBID source: | WOS-000297230700039 |
| DOI: | 10.1016/j.physa.2011.07.046 |
| Nebis system number: | 001929798 |
Overspill avalanching in a dense reservoir network
,
Mamede, George L., Araujo, Nuno A.M., Schneider, Christian M., Araujo, José C. de, Herrmann, Hans J.,
2012
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| Author(s): | Mamede, George L., Araujo, Nuno A.M., Schneider, Christian M., Araujo, José C. de, Herrmann, Hans J. |
| Title: | Overspill avalanching in a dense reservoir network |
| Abstract: | Sustainability of communities, agriculture, and industry is strongly dependent on an effective storage and supply of water resources. In some regions the economic growth has led to a level of water demand that can only be accomplished through efficient reservoir networks. Such infrastructures are not always planned at larger scale but rather made by farmers according to their local needs of irrigation during droughts. Based on extensive data from the upper Jaguaribe basin, one of the world’s largest system of reservoirs, located in the Brazilian semiarid northeast, we reveal that surprisingly it self-organizes into a scale-free network exhibiting also a power-law in the distribution of the lakes and avalanches of discharges. With a new self-organized-criticality-type model we manage to explain the novel critical exponents. Implementing a flow model we are able to reproduce the measured overspill evolution providing a tool for catastrophe mitigation and future planning. |
| Published in: | Proceedings of the National Academy of Sciences of the United States of America : PNAS |
| Volume: | 109 |
| Issue: | 19 |
| Pages: | 7191 - 7195 |
| ISSN: | 0027-8424, 1091-6490 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Washington, DC |
| Publication status: | Published |
| Subjects: | Wissenschaft und Technik allgemein|Science and Technology, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1336659091 |
| DOI: | 10.1073/pnas.1200398109 |
| Nebis system number: | 001003347 |
Untersuchungen zu Eigenschaften von Mooreiche
,
Kránitz, Katalin, Baradit, Erik, Dobrowolska, Ewa, Plötze, Michael, Niemz, Peter,
2012
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| Author(s): | Kránitz, Katalin, Baradit, Erik, Dobrowolska, Ewa, Plötze, Michael, Niemz, Peter |
| Title: | Untersuchungen zu Eigenschaften von Mooreiche |
| Abstract: | An Mooreichenproben (Quercus robur L.), präpariert aus einem im Fluss Bug (Polen) gelagertem Stamm, wurden Untersuchungen zu physikalisch-mechanischen Eigenschaften durchgeführt. Der auf ein Alter von 150 Jahren datierte Baumstamm lagerte für 7100 ± 50 Jahre im Boden unter einer 3 m dicken Schicht aus Sand und Schlick. Die äußere Zone des Holzes war sehr dunkel (tiefschwarz) gefärbt, wohingegen die Farbe zur Stammmitte heller wurde. Es konnten keine wesentlichen Veränderungen der mechanischen Eigenschaften und des Sorptionsverhaltens am geprüften Holz festgestellt werden. Die Quellung in radialer Richtung sank zur äußeren Zone des Stammes leicht ab und korreliert mit der Farbe. Je dunkler das Holz und damit intensiver die Farbänderung, umso geringer war die radiale Quellung. Tangential war der Einfluss der Position im Stamm auf die Quellung gering. Die Porosität blieb annähernd unverändert. Hinsichtlich der mechanischen Eigenschaften wurde die bekannte Differenzierung von E- und G-Modul in den Hauptachsen ermittelt. Eine leichte Reduzierung des dynamischen E-Modul wurde bei Messungen mittels Ultraschall und dem Gerät BP5 (Frequenz 50 kHz) in Faserrichtung beobachtet. Vor allem mit Zunahme der Dunkelfärbung sank der E-Modul des subfossilen Holzes. |
| Published in: | Holztechnologie |
| Volume: | 53 |
| Issue: | 1 |
| Pages: | 11 - 17 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Dresden |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1326715004 |
| Nebis system number: | 000026159 |
Einfluss verschiedener mechanischer Holzbearbeitungsverfahren auf die Verklebungsgüte von Buchenholz
,
Kläusler, Oliver, Elstermann, Falko, Rehm, Klaus, Hänsel, Andreas, Niemz, Peter,
2012
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| Author(s): | Kläusler, Oliver, Elstermann, Falko, Rehm, Klaus, Hänsel, Andreas, Niemz, Peter |
| Title: | Einfluss verschiedener mechanischer Holzbearbeitungsverfahren auf die Verklebungsgüte von Buchenholz |
| Book title: | Tagungsband des 15. Holztechnologischen Kolloquiums |
| Pages: | 146 - 158 |
| ISBN: | 978-3-86780-266-6 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Not yet published |
| Event name: | 15. Holztechnologischen Kolloquiums |
| Event date: | March 29-30, 2012 |
| Place: | Dresden, Germany |
| Language: | German |
| DBID source: | FORM-1333360355 |
Extractives in some tropical woods
,
Kilic, Ayben, Niemz, Peter,
2012
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| Author(s): | Kilic, Ayben, Niemz, Peter |
| Title: | Extractives in some tropical woods |
| Abstract: | Total amount and composition of extractives from 12 different tropical wood species were determined by sequential extraction followed by silylation and GC, GC/MS analysis. Hexane and then acetone/water (5:1) mixture was used successively for the extraction. Generally, very low amounts of lipophilics were found (0.05–0.38 mg/g) and the constituent consisted of fatty acids. Hydrophilics were composed of phenolic acids, flavonoids, sterols, stilbenes and a lignan. The highest amount of hydrophilics was found in Afzelia (36.1 mg/g), while the lowest in Wenge and Opepe (0.30 mg/g). Also, cold-hot water, 1% NaOH and some solvent (acetone, dichloromethane) solubilities were determined. The solubility values of tropical woods except for Canalete were found to increase in the order of solvent, cold water, hot water and 1% NaOH. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 79 - 83 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591302, WOS-000298657600010 |
| DOI: | 10.1007/s00107-010-0489-8 |
| Nebis system number: | 000047744 |
Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz
,
Joscak, Matus, Sonderegger, Walter, Niemz, Peter, Oppikofer, Reinhard, Lammar, Laura, Schnider, Thomas,
2012
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| Author(s): | Joscak, Matus, Sonderegger, Walter, Niemz, Peter, Oppikofer, Reinhard, Lammar, Laura, Schnider, Thomas |
| Title: | Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz |
| Abstract: | An ausgewählten Holzwerkstoffen (Buchenfurnier, MDF- und Spanplatten) wurde der Einfluss des Einbringens von Hohlräumen auf die Wärmeleitfähigkeit untersucht. Für die Versuche wurden die Platten in mehreren Lagen geschichtet (Lagendicke je nach Material 2,7 bis 5 mm) und die Aufbauten variiert, wobei Platten mit und ohne Hohlräume verwendet wurden. Um den Einfluss der Wärmestrahlung in den Hohlräumen zu untersuchen, wurden zusätzlich Aluminiumfolien (geringer Emissionsgrad) eingelegt. Es konnte festgestellt werden, dass durch das Einbringen von Hohlräumen (Volumenanteil ca. 46 %) eine Reduzierung der Wärmeleitfähigkeit um bis zu 51 % erreicht wird. Ein zusätzliches Einlegen von Aluminiumfolie quer zur Wärmestromrichtung reduziert die Wärmeleitfähigkeitswerte nochmals wesentlich (bis zu 64 %) aufgrund der stark reduzierten Wärmestrahlung in den Hohlräumen. Dies ist besonders ausgeprägt bei den Aufbauten mit größeren Hohlraumdicken. Um das Potential des Anbringens von Hohlräumen im Holzbauwesen zu nutzen, wurde ein Vorschlag für ein neues Produkt auf Holzbasis präsentiert. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 32 - 37 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Holzbau, Dämmstoffe, Wärmeleitfhigkeit, Hohlrume, Luftschichten, Neue Produkte, Reflexionsgrad, Energieeinsparung |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Holzbau, Dämmstoffe, Wärmeleitfhigkeit, Hohlrume, Luftschichten, Neue Produkte, Reflexionsgrad, Energieeinsparung |
| DBID source: | FORM-1328535998 |
| DOI: | 10.1002/bapi.201200005 |
| Nebis system number: | 000006704 |
A numerical and experimental study of aggregate induced shrinkage cracking in cementitious composites
,
Idiart, Andrés, Bisschop, Jan, Caballero, Antonio, Lura, Pietro,
2012
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| Author(s): | Idiart, Andrés, Bisschop, Jan, Caballero, Antonio, Lura, Pietro |
| Title: | A numerical and experimental study of aggregate induced shrinkage cracking in cementitious composites |
| Abstract: | Aggregates in cementitious composites subject to drying lead to mechanical restraint of the matrix shrinkage, which under certain conditions may lead to internal microcracking. In the present work this phenomenon is investigated using a two-dimensional (2D) numerical model and an approximate 2D experimental approach. Experimental and simulated samples with simplified and matching spatial aggregate distributions were produced to make a quantitative comparison between experiments and model predictions. In particular, the effects of aggregate size and volume fraction on the degree of internal microcracking are assessed. The main challenges of performing a quantitative comparison are highlighted and discussed. These are related to: (i) the difficulty of designing experiments without moisture gradient effects; (ii) the experimental crack detection limit; and (iii) the role of the creep response of the matrix phase in the model. The results suggest the existence of a critical aggregate size below which aggregate-restraint does not cause detectable microcracking. |
| Published in: | Cement and concrete research |
| Volume: | 42 |
| Issue: | 2 |
| Pages: | 272 - 281 |
| ISSN: | 0008-8846 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Drying, Shrinkage, Finite element analysis, Fracture mechanics, Crack detection |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Drying, Shrinkage, Finite element analysis, Fracture mechanics, Crack detection |
| DBID source: | WOS-000300812000005 |
| DOI: | 10.1016/j.cemconres.2011.09.013 |
| Nebis system number: | 000034576 |
Granular packings of cohesive elongated particles
,
Hidalgo, R.C., Kadau, D., Kanzaki, T., Herrmann, Hans J.,
2012
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| Author(s): | Hidalgo, R.C., Kadau, D., Kanzaki, T., Herrmann, Hans J. |
| Title: | Granular packings of cohesive elongated particles |
| Abstract: | We report numerical results of effective attractive forces on the packing properties of two-dimensional elongated grains. In deposits of non-cohesive rods in 2D, the topology of the packing is mainly dominated by the formation of ordered structures of aligned rods. Elongated particles tend to align horizontally and the stress is mainly transmitted from top to bottom, revealing an asymmetric distribution of local stress. However, for deposits of cohesive particles, the preferred horizontal orientation disappears. Very elongated particles with strong attractive forces form extremely loose structures, characterized by an orientation distribution, which tends to a uniform behavior when increasing the Bond number. As a result of these changes, the pressure distribution in the deposits changes qualitatively. The isotropic part of the local stress is notably enhanced with respect to the deviatoric part, which is related to the gravity direction. Consequently, the lateral stress transmission is dominated by the enhanced disorder and leads to a faster pressure saturation with depth. |
| Published in: | Granular matter |
| Volume: | 14 |
| Issue: | 2 |
| Pages: | 191 - 196 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Kondensierte Materie|Condensed Matter, Granular matter, Molecular dynamics, Non-spherical particles quicksand, Collapsible soil |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Granular matter, Molecular dynamics, Non-spherical particles quicksand, Collapsible soil |
| DBID source: | FORM-1336052128 |
| DOI: | 10.1007/s10035-011-0303-2 |
| Nebis system number: | 002003491 |
Characterisation of moisture-dependent plasticity of beech wood and its application to a multi-surface plasticity model
,
Hering, Stefan, Saft, Susanne, Resch, Eckart, Niemz, Peter, Kaliske, Michael,
2012
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| Author(s): | Hering, Stefan, Saft, Susanne, Resch, Eckart, Niemz, Peter, Kaliske, Michael |
| Title: | Characterisation of moisture-dependent plasticity of beech wood and its application to a multi-surface plasticity model |
| Abstract: | The moisture-dependent stress-strain behaviour of European beech wood (Fagus sylvatica L.) has been determined under compression, analytically described for the radial and tangential direction using a modified Ramberg-Osgood approach and realized numerically by a multi-surface plasticity model. The conspicuous decrease of the stress-strain characteristic perpendicular to the grain with increasing moisture content is similar to the behaviour of the presented ultimate strength values in the longitudinal direction. Based on input parameters previously quantified by means of an inverse finite element analysis, the simulation of a crosswise laminated two-layer arrangement during moistening was carried out. A distinct development of plastified regions can be observed due to the resulting swelling stresses. |
| Published in: | Holzforschung |
| Volume: | 66 |
| Issue: | 3 |
| Pages: | 373 - 380 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting), Beech, Compression test, Finite element method, Inverse analysis, Material strength, Moisture, Multi-surface plasticity (MSP) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Beech, Compression test, Finite element method, Inverse analysis, Material strength, Moisture, Multi-surface plasticity (MSP) |
| DBID source: | FORM-1331638556 |
| DOI: | 10.1515/HF.2011.162 |
| Nebis system number: | 000047746 |
Adhesive penetration in beech wood
,
Hass, Philipp, Wittel, Falk K., Mendoza, Miller, Herrmann, Hans J., Niemz, Peter,
2012
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| Author(s): | Hass, Philipp, Wittel, Falk K., Mendoza, Miller, Herrmann, Hans J., Niemz, Peter |
| Title: | Adhesive penetration in beech wood |
| Subtitle: | Experiments |
| Abstract: | A study with synchrotron radiation X-ray tomographic microscopy (SRXTM) of PUR, PVAc, and UF adhesive bond lines in beech wood, bonded under various growth ring angles, is presented. The bond line morphologies and the adhesive penetration into the wood structure were evaluated after determining the hardening characteristics of the adhesives. Distinct bond line imperfections were found for the different adhesive systems. To describe the adhesive distribution inside the bond line, the saturation of the pore space instead of the commonly used maximum penetration depth seems to be adequate. |
| Published in: | Wood science and technology |
| Volume: | 46 |
| Issue: | 1-3 |
| Pages: | 243 - 256 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General, Landwirtschaft allgemein|Agriculture, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317740361, WOS-000298993100018 |
| DOI: | 10.1007/s00226-011-0410-6 |
| Nebis system number: | 000057691 |
Aggregate morphology evolution by sintering
,
Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E.,
2012
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| Author(s): | Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E. |
| Title: | Aggregate morphology evolution by sintering |
| Subtitle: | Number and diameter of primary particles |
| Abstract: | The structure of fractal-like agglomerates (physically bonded) and aggregates (chemically or sinter-bonded) is important in aerosol synthesis of nanoparticles, and in monitoring combustion emissions and atmospheric particles. It also influences particle mobility, scattering and eventually performance of nanocomposites, suspensions and devices made with such particles. Here, aggregate sintering by viscous flow of amorphous materials (silica, polymers) and grain boundary diffusion of crystalline ceramics (titania, alumina) or metals (Ni, Fe, Ag, etc.) is investigated. A scaling law is found between average aggregate projected area and equivalent number of constituent primary particles during sintering: from fractal-like agglomerates to aggregates and eventually compact particles (e.g. spheres). This is essentially a relation independent of time, material properties and sintering mechanisms. It is used to estimate the equivalent primary particle diameter and number in aggregates. The evolution of aggregate morphology or structure is quantified by the effective fractal dimension (Df) and mass–mobility exponent (Dfm) and the corresponding prefactors. The Dfm increases monotonically during sintering converging to 3 for a compact particle. Therefore Dfm and its prefactor could be used to gage the degree or extent of sintering of agglomerates made by a known collision mechanism. This analysis is exemplified by comparison to experiments of silver nanoparticle aggregates sintered at different temperatures in an electric tube furnace. |
| Published in: | Journal of aerosol science |
| Volume: | 46 |
| Pages: | 7 - 19 |
| ISSN: | 0021-8502 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Umweltdaten, Boden, Luft, Klima, Schadstoffe|Environmental Data, Soil, Air, Climate, Pollutants, Aggregate, Fractal dimension, Grain boundary diffusion, Mass-mobility exponent, Primary particle size |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Aggregate, Fractal dimension, Grain boundary diffusion, Mass-mobility exponent, Primary particle size |
| DBID source: | FORM-1329817714, WOS-000301760900002 |
| DOI: | 10.1016/j.jaerosci.2011.11.005 |
| Nebis system number: | 000034158 |
Influence of the Filler Material on the Thermal Stability of One-Compoent Moisture-Curing Polyurethane Adhesives
,
Clauss, Sebastian, Dijkstra, Dirk J., Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Meckel, Walter, Niemz, Peter,
2012
>>
| Author(s): | Clauss, Sebastian, Dijkstra, Dirk J., Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Meckel, Walter, Niemz, Peter |
| Title: | Influence of the Filler Material on the Thermal Stability of One-Compoent Moisture-Curing Polyurethane Adhesives |
| Abstract: | Filler materials are part and parcel for the adjustment of adhesives, in particular, their rheological and mechanical properties. Furthermore, the thermal stability of adhesives can be positively influenced by the addition of an expedient filler, with inorganic types common practice in most cases. In this study, one-component moisture-curing polyurethane adhesives for engineered wood products based on isocyanate prepolymers with different polymer-filled polyether polyols were investigated with regard to the filler's potential to increase the thermal stability of bonded wood joints. The property changes due to the addition of fillers were determined by means of mechanical tests on bonded wood joints and on pure adhesive films at different temperatures up to 200°C. Additional analyses by atomic force and environmental scanning electron microscopy advanced the understanding of the effects of the filler. The tested organic fillers, styrene acrylonitrile, a polyurea dispersion, and polyamide, caused increases in the cohesive strength and stiffness over the whole temperature range. However, the selected filler type was hardly important with regard to the tensile shear strength of the bonded wood joints at high temperatures, although the tensile strength and Young's modulus of the adhesive films differed over a wide range. Prepolymers with a lower initial strength and stiffness resulted in worse cohesion, in particular, at high temperatures. This disadvantage, however, could be compensated by means of the filler material. Ultimately, the addition of filler material resulted in optimized adhesive properties only in a well-balanced combination with the prepolymer used. |
| Published in: | Journal of applied polymer science |
| Volume: | 124 |
| Issue: | 5 |
| Pages: | 3641 - 3649 |
| ISSN: | 0021-8995, 1097-4628 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Kunststoffe|Plastics, Adhesion, Adhesives, Fillers, Mechanical properties, Polyurethanes |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Adhesion, Adhesives, Fillers, Mechanical properties, Polyurethanes |
| DBID source: | FORM-1333431209, WOS-000300971400015 |
| DOI: | 10.1002/APP.35223 |
| Nebis system number: | 000031978 |
Klebstoffe auch bei tiefen Temperaturen verarbeiten
,
Brandmair, Anton, Steiner, Patrick, Niemz, Peter,
2012
>>
| Author(s): | Brandmair, Anton, Steiner, Patrick, Niemz, Peter |
| Title: | Klebstoffe auch bei tiefen Temperaturen verarbeiten |
| Abstract: | Die Firma Nolax AG hat mit "Lignofast" eine Klebstofftechnologie entwickelt, mit der sich die Produktivität in der holzverarbeitenden Industrie steigern lässt. Grund dafür ist das sekundenschnelle Abbinden des Zweikomponenten-Klebstoffs. Mit "Lignofast" lassen sich kurze Presszeiten realisieren, die je nach Einstellung des Klebstoffsystems, lediglich 15 s betragen können. Bei dem Klebstoff handelt es sich um ein Zweikomponenten-Polyurea-System. Eingesetzt werden kann "Lignofast" beispielsweise für Verklebung von Massivholzplatten oder Mehrschichtparkett. |
| Published in: | Holz-Zentralblatt |
| Volume: | 2012 |
| Issue: | 5 |
| Pages: | 152 - 152 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting) |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1333604584 |
| Nebis system number: | 000047754 |
Effect of pre-pressing of veneer on the glueability and properties of veneer-based products
,
Bekhta, Pavlo, Niemz, Peter, Sedliacik, Jan,
2012
>>
| Author(s): | Bekhta, Pavlo, Niemz, Peter, Sedliacik, Jan |
| Title: | Effect of pre-pressing of veneer on the glueability and properties of veneer-based products |
| Abstract: | The study used a physical and environmentally friendly method to enhance the properties of both veneer and plywood. The effect of pre-pressing process factors (pressure, temperature and time) on the compression ratio, surface roughness, tensile strength perpendicular-to-grain of rotary cut veneer sheets of birch (Betula pubescens), and on the shear strength of plywood made from these compressed veneer sheets were studied in laboratory tests. The effect of pressing factors (such as pressure and glue spread) on the properties of plywood made from pre-pressed veneer was also studied. Three-layer plywood panels were manufactured from pre-pressed and non-pre-pressed veneers using phenol formaldehyde glue resins. Test results revealed that the greatest influence on properties of veneer is the pre-pressing temperature followed by the pre-pressing pressure and pre-pressing time. Meanwhile, the veneer’s properties such as surface roughness can be improved, and the properties of plywood were also improved when the birch veneers were pre-pressed. Linear relationship between the compression ratio and surface roughness was found. The tensile strength of veneer was not significantly influenced by the pre-pressing factors. The pre-pressing temperature has the largest effect on shear strength of plywood. The initial veneer densification allows lowering both glue spread from 150 to 90 g/m2 (a 40% reduction) and pressing pressure from 1.8 to 1.0 MPa (a 45% reduction). The shear strength obtained for the tested plywood meets EN 314-1 requirements. It is expected that the results of this preliminary study will lead to new gluing approaches, which will result in significant performance improvements of veneer-based products. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 99 - 106 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591105, WOS-000298657600013 |
| DOI: | 10.1007/s00107-010-0486-y |
| Nebis system number: | 000047744 |
Stiffness moduli of various extraneous species determined with ultrasound
,
Baradit, Erik, Keunecke, Daniel, Schnider, Thomas, Niemz, Peter,
2012
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| Author(s): | Baradit, Erik, Keunecke, Daniel, Schnider, Thomas, Niemz, Peter |
| Title: | Stiffness moduli of various extraneous species determined with ultrasound |
| Abstract: | Comprehensive datasets of the elastic constants are available for only a few European wood Species, especially spruce. The goal of this study, therefore, was to provide Young’s and shear moduli for the principal directions and planes for further selected extraneous species to extend the currently existing datasets. For this purpose, a dynamic technique was chosen: The moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modeling approaches. |
| Published in: | Wood research |
| Volume: | 57 |
| Issue: | 1 |
| Pages: | 173 - 178 |
| ISSN: | 1336-4561, 0012-6136 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bratislava |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Elastic constants, Shear modulus, Ultrasound, Stiffness modulus |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Elastic constants, Shear modulus, Ultrasound, Stiffness modulus |
| DBID source: | FORM-1336473506 |
| Nebis system number: | 001541175 |
Activity-dependent neuronal model on complex networks
,
Arcangelis, Lucilla de, Herrmann, Hans J.,
2012
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| Author(s): | Arcangelis, Lucilla de, Herrmann, Hans J. |
| Title: | Activity-dependent neuronal model on complex networks |
| Abstract: | Neuronal avalanches are a novel mode of activity in neuronal networks, experimentally found in vitro and in vivo, and exhibit a robust critical behavior: these avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems. We present a recent model inspired in self-organized criticality, which consists of an electrical network with threshold firing, refractory period, and activity-dependent synaptic plasticity. The model reproduces the critical behavior of the distribution of avalanche sizes and durations measured experimentally. Moreover, the power spectra of the electrical signal reproduce very robustly the power law behavior found in human electroencephalogram (EEG) spectra. We implement this model on a variety of complex networks, i.e., regular, small-world, and scale-free and verify the robustness of the critical behavior. |
| Published in: | Frontiers in physiology |
| Volume: | 3 |
| Pages: | 62 |
| ISSN: | 1664-042X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Published |
| Subjects: | Neuronal model, Complex networks, Self-organized criticality |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Neuronal model, Complex networks, Self-organized criticality |
| DBID source: | FORM-1337066103 |
| DOI: | 10.3389/fphys.2012.00062 |
| Nebis system number: | 006386708 |
2011
1 to 100 (of 108 items)
Synchrotron based tomographic microscopy of wood under compression
,
Zauner, Michaela, Keunecke, Daniel, Stampanoni, Marco, Niemz, Peter,
2011
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| Author(s): | Zauner, Michaela, Keunecke, Daniel, Stampanoni, Marco, Niemz, Peter |
| Title: | Synchrotron based tomographic microscopy of wood under compression |
| Abstract: | Spatial reconstruction of the wood structure enables temporally resolved observation of the response to mechanical load |
| Published in: | International Academy of Wood Science: Bulletin |
| Volume: | 2011 |
| Issue: | 1 |
| Pages: | 25 - 27 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Hamburg |
| Publication status: | Published |
| Language: | English |
| Review status: | Internally reviewed |
| DBID source: | FORM-1311237092 |
Synchrotron based tomographic in-situ microscopy of wood under uniaxial compression in fiber direction
,
Zauner, Michaela, Keunecke, Daniel, Stampanoni, Marco, Niemz, Peter,
2011
>>
| Author(s): | Zauner, Michaela, Keunecke, Daniel, Stampanoni, Marco, Niemz, Peter |
| Title: | Synchrotron based tomographic in-situ microscopy of wood under uniaxial compression in fiber direction |
| Book title: | 17th International Nondestructive Testing and Evaluation of Wood Symposium, September 14-16, 2011 |
| Volume: | 1 |
| Pages: | 629 - 635 |
| ISBN: | 978-963-9883-81-9, 978-963-9883-82-6 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Budapest |
| Publication status: | Published |
| Event name: | 17th International Nondestructive Testing and Evaluation of Wood Symposium |
| Event date: | September 14-16, 2011 |
| Place: | Sopron, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317892950 |
Shear-Driven Solidification of Dilute Colloidal Suspensions
,
Zaccone, Alessio, Gentili, Daniele, Wu, Hua, Morbidelli, Massimo, Del Gado, Emanuela,
2011
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| Author(s): | Zaccone, Alessio, Gentili, Daniele, Wu, Hua, Morbidelli, Massimo, Del Gado, Emanuela |
| Title: | Shear-Driven Solidification of Dilute Colloidal Suspensions |
| Abstract: | We show that shear-induced solidification of dilute charge-stabilized colloids is due to the interplay between shear-induced formation and breakage of large non-Brownian clusters. While their size is limited by breakage, their number density increases with shearing time. Upon flow cessation, the dense packing of clusters interconnects into a rigid state by means of grainy bonds, each involving a large number of primary colloidal bonds. The emerging picture of shear-driven solidification in dilute colloidal suspensions combines the gelation of Brownian systems with the jamming of athermal systems. |
| Published in: | Physical review letters |
| Volume: | 106 |
| Issue: | 13 |
| Pages: | 138301 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000288901200027 |
| DOI: | 10.1103/PhysRevLett.106.138301 |
| Nebis system number: | 000003868 |
Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz
,
Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter,
2012
>>
| Author(s): | Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter |
| Title: | Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz |
| Abstract: | Ziel der Arbeit war es, ausgewählte Eigenschaften von modifiziertem und nativem Holz zu bestimmen. Es wurden mechanische und physikalische Kenngrößen thermisch modifizierter Buchen-, Eschen- und Pappelproben zweier unterschiedlicher Behandlungsintensitäten ermittelt. Zur Referenz wurden unmodifizierte Proben jeder Holzart getestet. Gegenüber anderen thermischen Vergütungsprozessen beeinflusst das Vakuumpress-Trocknungsverfahren die Eigenschaften des Holzes weniger stark. Es entstehen auch weniger Emissionen wie Essig- oder Ameisensäuren. Die thermische Behandlung von Buche erzielt eine Reduzierung der Dichte und Biegefestigkeit, während die thermisch vergütete Pappel einen leichten Anstieg beider Kenngrößen aufweist. Die Eigenschaften der Esche unterscheiden sich in Abhängigkeit der Behandlungsintensität. Die mit geringer Temperatur vergüteten Proben weisen dem Referenzholz gegenüber zum Teil gestiegene Festigkeiten auf, die höher temperierten Proben stets geringere. Die Dimensionsstabilität steigt infolge der verringerten Gleich -gewichtsfeuchte. Anhand der Ergebnisse ist zu erkennen, dass die Änderung der physikalischen wie auch mechanischen Eigenschaften sowohl von der Behandlungsintensität und dem angewandten Verfahren selbst als auch von der behandelten Holzart abhängt. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 1 - 10 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Biegefestigkeit, Brinellhrte, Bruchschlagarbeit, Dichte, Elastizittsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Wärmeleitfhigkeit |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Biegefestigkeit, Brinellhrte, Bruchschlagarbeit, Dichte, Elastizittsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Wärmeleitfhigkeit |
| DBID source: | FORM-1328528909 |
| DOI: | 10.1002/bapi.201200001 |
| Nebis system number: | 000006704 |
Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz
,
Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter,
2012
>>
| Author(s): | Wetzig, Melanie, Sieverts, Tom, Bergemann, Holger, Niemz, Peter |
| Title: | Mechanische und physikalische Eigenschaften von mit dem Vakuumpress-Trocknungsverfahren thermisch behandeltem Holz |
| Abstract: | Ziel der Arbeit war es, ausgewählte Eigenschaften von modifiziertem und nativem Holz zu bestimmen. Es wurden mechanische und physikalische Kenngrößen thermisch modifizierter Buchen-, Eschen- und Pappelproben zweier unterschiedlicher Behandlungsintensitäten ermittelt. Zur Referenz wurden unmodifizierte Proben jeder Holzart getestet. Gegenüber anderen thermischen Vergütungsprozessen beeinflusst das Vakuumpress-Trocknungsverfahren die Eigenschaften des Holzes weniger stark. Es entstehen auch weniger Emissionen wie Essig- oder Ameisensuren. Die thermische Behandlung von Buche erzielt eine Reduzierung der Dichte und Biegefestigkeit, während die thermisch vergütete Pappel einen leichten Anstieg beider Kenngrößen aufweist. Die Eigenschaften der Esche unterscheiden sich in Abhängigkeit der Behandlungsintensität. Die mit geringer Temperatur vergüteten Proben weisen dem Referenzholz gegenüber zum Teil gestiegene Festigkeiten auf, die höher temperierten Proben stets geringere. Die Dimensionsstabilität steigt infolge der verringerten Gleichgewichtsfeuchte. Anhand der Ergebnisse ist zu erkennen, dass die Änderung der physikalischen wie auch mechanischen Eigenschaften sowohl von der Behandlungsintensität und dem angewandten Verfahren selbst als auch von der behandelten Holzart abhängt. The aim of this work was to analyse selected mechanical and physical behaviours of wood thermally treated with the vacuum press dewatering method, Vacu3. The density, bending and impact bending strength, modulus of elasticity, Brinell hardness and the withdrawal capacity of screws as well as the sorption capacity, change in colour and the thermal conductivity were measured. The investigated beech, ash and poplar samples were thermally treated with the patented vacuum press dewatering method, Vacu3. To test the influence of processing conditions, one type of sample was treated with medium temperatures and the other with high process temperatures. As a reference, the properties of unmodified specimen were determined. Thermal modification of beech affects a decrease in density and bending strength. The opposite is the case for heat-treated poplar. The properties of heat-treated ash differ depending on the degree of thermal treatment. The application of medium process temperatures on ash causes an increment in density and bending strength. In contrast, high process temperatures lead to a reduction in density and mechanical properties. As a consequence of the progressive reduction of equilibrium moisture content, the dimensional stability of heat-treated wood is improved. The test results show that changes in properties are influenced by the treatment intensity as well as by treatment technology. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 1 - 10 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Biegefestigkeit, Brinellhärte, Bruchschlagarbeit, Dichte, Elastizitatsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Warmeleitfähigkeit, Bending strength, Brinell hardness, Bonding, Colour, Density, Impact bending strength, Modulus of elasticity, Sorption capacity, Swelling behaviour, Thermal conductivity, Feuchte, Moisture |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Biegefestigkeit, Brinellhärte, Bruchschlagarbeit, Dichte, Elastizitatsmodul, Farbe, Holzbau, Quellverhalten, Sorptionsvermögen, Verklebung, Warmeleitfähigkeit, Bending strength, Brinell hardness, Bonding, Colour, Density, Impact bending strength, Modulus of elasticity, Sorption capacity, Swelling behaviour, Thermal conductivity, Feuchte, Moisture |
| DBID source: | WOS-000299835000001 |
| DOI: | 10.1002/bapi.201200001 |
| Nebis system number: | 000006704 |
Farbänderung von Holz bei Freibewitterung
,
Wetzig, Melanie, Niemz, Peter,
2012
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| Author(s): | Wetzig, Melanie, Niemz, Peter |
| Title: | Farbänderung von Holz bei Freibewitterung |
| Published in: | Holz-Zentralblatt |
| Issue: | 4 |
| Pages: | 103 - 105 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Unknown |
| Language: | German |
| DBID source: | FORM-1328528374 |
Untersuchungen zum Einfluss ausgewählter verfahrenstechnischer Parameter auf die VOC-Emission und ausgewählte mechanische Kennwerte wärmebehandelten Holzes
,
Wetzig, Melanie, Kraft Redelf, Roffael, Edmone, Schmutz, Andreas, Huber, Christian, Niemz, Peter,
2012
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| Author(s): | Wetzig, Melanie, Kraft Redelf, Roffael, Edmone, Schmutz, Andreas, Huber, Christian, Niemz, Peter |
| Title: | Untersuchungen zum Einfluss ausgewählter verfahrenstechnischer Parameter auf die VOC-Emission und ausgewählte mechanische Kennwerte wärmebehandelten Holzes |
| Published in: | Holztechnologie |
| Volume: | 53 |
| Issue: | 2 |
| Pages: | 24 - 30 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Dresden |
| Publication status: | Published |
| Language: | English |
| DBID source: | FORM-1331898083 |
| Nebis system number: | 000026159 |
Physical, mechanical and chemical properties of wood, heat-treated with the vacuum-press-dewatering method
,
Wetzig, Melanie, Hofmann, Tamás, Rétfalvi, Tamás, Sieverts, Tom, Bergemann, Holger, Niemz, Peter,
2011
>>
| Author(s): | Wetzig, Melanie, Hofmann, Tamás, Rétfalvi, Tamás, Sieverts, Tom, Bergemann, Holger, Niemz, Peter |
| Title: | Physical, mechanical and chemical properties of wood, heat-treated with the vacuum-press-dewatering method |
| Book title: | Mechano-chemical transformations of wood during thermo-hydro-mechanical processing, workshop : Program & book of abstracts : COST Action FP0904 Thermo-hydro-mechanical wood behaviour and processing, February 16-18, 2011, Biel, Switzerland |
| Pages: | 35 - 36 |
| ISBN: | 978-3-9523787-0-0 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Biel |
| Publication status: | Published |
| Event name: | COST Action FP0904 Thermo-hydro-mechanical wood behaviour and processing |
| Event date: | February 16-18, 2011 |
| Place: | Biel, Switzerland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1298042364 |
| Nebis system number: | 006373698 |
Mechanical, physical and chemical properties of wood, heat-treated with the vacuum-press-dewatering method
,
Wetzig, Melanie, Hofmann, Tamás, Rétfalvi, Tamás, Niemz, Peter,
2011
>>
| Author(s): | Wetzig, Melanie, Hofmann, Tamás, Rétfalvi, Tamás, Niemz, Peter |
| Title: | Mechanical, physical and chemical properties of wood, heat-treated with the vacuum-press-dewatering method |
| Book title: | Novel materials from Wood or cellulose : Proceedings of the 2011 IAWS annual meeting on Novel materials from Wood or cellulose, August 31st to September 2nd, 2011, Stockholm, Sweden |
| Pages: | 72 - 73 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Stockholm |
| Publication status: | Published |
| Event name: | Annual meeting of IAWS 2011 |
| Event date: | August 31-September 2, 2011 |
| Place: | Stockholm, Sweden |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1316435090 |
Ermittlung ausgewählter mechanischer Kennwerte thermisch modifizierter Buche
,
Wetzig, Melanie, Heldstab, Corina, Tauscher, Tom, Niemz, Peter,
2011
>>
| Author(s): | Wetzig, Melanie, Heldstab, Corina, Tauscher, Tom, Niemz, Peter |
| Title: | Ermittlung ausgewählter mechanischer Kennwerte thermisch modifizierter Buche |
| Abstract: | Untersuchungen zu physikalisch-mechanischen und chemischen Eigenschaften thermisch modifizierten Holzes sind bereits seit den frühen 1950er Jahren durchgeführt und wieder verstärkt in den letzten zehn bis zwanzig Jahren aufgenommen worden. Generelle Zusammenhänge zwischen den Behandlungsparametern und den Eigenschaften des vergüteten Holzes sind weitgehend bekannt. Gegenstand und Ziel der vorliegenden Untersuchungen war die Ermittlung ausgewählter mechanischer Kennwerte von im Autoklaven nach zwei unterschiedlichen Verfahren thermisch behandeltem Buchenholz. Die Resultate zeigen, dass die Zug- und Druckfestigkeit sowie der Elastizitäts- und Schubmodul im Vergleich zum unbehandelten Referenzholz um bis zu 50 % sinken. Die Zugfestigkeit wurde dabei stärker beeinträchtigt als die Druckfestigkeit. Determination of select mechanical properties of heat-treated beech wood. Studies on mechanical and chemical properties of heat-treated wood have been conducted since the early 1950ies. General interrelationships between process parameters and properties of heat-treated wood are reasonably well known. The present study deals with select mechanical properties of heat-treated beech wood in the autoclave in two different treatment atmospheres. The results show, that the tensile and compression strength as well as modulus of elasticity and modulus of rigidity decrease about 50 % compared to untreated wood. The tensile strength was less affected by the treatment than the compression strength. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 6 |
| Pages: | 366 - 373 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Druckfestigkeit, Elastizittäsmodul, Poissonzahl, Schubmodul, Ultraschall, Zugfestigkeit, Compression strength, Modulus of elasticity, Modulus of rigidity, Poisson’s ratio, Tensile strength, Ultrasonic sound, Messverfahren, Measurement procedures, Wärme, Thermal insulation, Heat |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Druckfestigkeit, Elastizittäsmodul, Poissonzahl, Schubmodul, Ultraschall, Zugfestigkeit, Compression strength, Modulus of elasticity, Modulus of rigidity, Poisson’s ratio, Tensile strength, Ultrasonic sound, Messverfahren, Measurement procedures, Wärme, Thermal insulation, Heat |
| DBID source: | FORM-1322662143 |
| DOI: | 10.1002/bapi.201110794 |
| Nebis system number: | 000006704 |
Untersuchungen zur Verklebung dreischichtiger Massivholzplatten unter Verwendung von Laubholz
,
Wetzig, Melanie, Haß, Philipp, Hänsel, Andreas, Niemz, Peter,
2011
>>
| Author(s): | Wetzig, Melanie, Haß, Philipp, Hänsel, Andreas, Niemz, Peter |
| Title: | Untersuchungen zur Verklebung dreischichtiger Massivholzplatten unter Verwendung von Laubholz |
| Abstract: | Aufgrund ansteigender Nutzlaubholzbestände sind die physikalisch-mechanischen Eigenschaften sowie mögliche Verwendungsbereiche von Laubholz in den letzten Jahren wieder verstärkt Inhalt verschiedener Forschungsarbeiten. Die meisten Laubholzarten haben einen wesentlich höheren Elastizitätsmodul und deutlich höhere Quell-und Schwindmaße als Nadelhölzer, was in Klebfugen bei Feuchteänderungen zu höheren Spannungen führt. Die nachfolgenden Untersuchungen wurden an dreischichtigen Massivholzplatten durchgeführt, die völlig bzw. teilweise aus Laubholz gefertigt wurden. Die Einzellagen der Platten wurden sowohl in den Holzarten als auch in den Schichtdicken variiert. Kern der Untersuchungen war, ob und in welchem Maße durch Variation der Klebstoffart und der Fugendicke feuchteinduzierte Spannungen kompensiert werden können, die aufgrund unterschiedlicher Plattenaufbauten hervorgerufen werden. Die im Zuge erhöhter relativer Luftfeuchten auftretenden Dehnungen und Spannungen innerhalb der Massivholzplatten wurden durch drei Versuchsanordnungen geprüft. Die Ergebnisse zeigten einen deutlichen Einfluss der Verklebung auf das Quellverhalten der Platten. Because of growing hardwood quantity the physical-mechanical properties as well as possible application areas of hardwoods are increasingly topic of different research projects. The following investigations were carried out on three-layer cross laminated timber which was partially or totally made from hardwood. The respective layers were varied in wood species as well as in thickness. The main point of the work was to determine how far strains, induced by the bigger swelling of hardwood compared to softwood, can be compensated in elastic glue joint. Occurred strains into the panels were determined by three test set-ups. The results showed influences of the used glue joint on swelling behaviour of the panel configurations. |
| Published in: | Bautechnik |
| Volume: | 88 |
| Issue: | 10 |
| Pages: | 687 - 693 |
| ISSN: | 0932-8351, 1437-0999 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Eigenspannungen, Laubholz, Massivholzplatten, Verklebung dicke Klebstofffuge, Holzbau, Baustoffe, Hardwood, Residual stresses, Bonding with thick glue joint, Solid wood panels, Timber construction, Building materials |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Eigenspannungen, Laubholz, Massivholzplatten, Verklebung dicke Klebstofffuge, Holzbau, Baustoffe, Hardwood, Residual stresses, Bonding with thick glue joint, Solid wood panels, Timber construction, Building materials |
| DBID source: | FORM-1318339557, WOS-000296231900004 |
| DOI: | 10.1002/bate.201101490 |
| Nebis system number: | 000043243 |
From invasion percolation to flow in rock fracture networks
,
Wettstein, Salomon J., Wittel, Falk K., Araújo, Nuno A.M., Lanyon, Bill, Herrmann, Hans Jürgen,
2012
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| Author(s): | Wettstein, Salomon J., Wittel, Falk K., Araújo, Nuno A.M., Lanyon, Bill, Herrmann, Hans Jürgen |
| Title: | From invasion percolation to flow in rock fracture networks |
| Abstract: | The main purpose of this work is to simulate two-phase flow in the form of immiscible displacement through anisotropic, three-dimensional (3D) discrete fracture networks (DFN). The considered DFNs are artificially generated, based on a general distribution function or are conditioned on measured data from deep geological investigations. We introduce several modifications to the invasion percolation (MIP) to incorporate fracture inclinations, intersection lines, as well as the hydraulic path length inside the fractures. Additionally a trapping algorithm is implemented that forbids any advance of the invading fluid into a region, where the defending fluid is completely encircled by the invader and has no escape route. We study invasion, saturation, and flow through artificial fracture networks, with varying anisotropy and size and finally compare our findings to well studied, conditioned fracture networks. |
| Published in: | Physica. A |
| Volume: | 391 |
| Issue: | 1-2 |
| Pages: | 264 - 277 |
| ISSN: | 0378-4371, 1873-2119 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Discrete fracture networks, Invasion percolation, Trapping, Two-phase flow, Permeability |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Discrete fracture networks, Invasion percolation, Trapping, Two-phase flow, Permeability |
| DBID source: | FORM-1320766191, WOS-000297230700029 |
| DOI: | 10.1016/j.physa.2011.07.029 |
| Nebis system number: | 001929798 |
Untersuchungen zum Einfluss der Klebstoffart auf den Diffusionswiderstand von Holzverklebungen
,
Volkmer, Thoms, Schmidt Jon-Anton, Kranitz, Katalin, Niemz, Peter,
2012
>>
| Author(s): | Volkmer, Thoms, Schmidt Jon-Anton, Kranitz, Katalin, Niemz, Peter |
| Title: | Untersuchungen zum Einfluss der Klebstoffart auf den Diffusionswiderstand von Holzverklebungen |
| Abstract: | An reinen Klebstofffilmen aus verschiedenen Klebstoffen (PVA, PUR, UF, MUF, EPI, Knochenleim) und an verklebten Holzlamellen mit einer mittigen Klebefuge wurde der Diffusionswiderstand im Dry- und im Wet-Cup-Verfahren nach DIN EN ISO 12572 bestimmt. Es wurden deutliche Unterschiede im Diffusionswiderstand zwischen den einzelnen Klebstoffarten gemessen. Der Diffusionswiderstand der Klebstofffilme war wesentlich höher als der der Verklebungen, was auf die entsprechenden Abbindemechanismen und die Eindringung der Klebstoffe in das Substrat zurückzuführen ist. Die Klebefugen der geprüften Systeme PVAc, EPI und 1K-PUR erwiesen sich im Vergleich als sehr diffusionsdicht, was bei einer bauphysikalischen Bewertung von verklebten Holzelementen zu berücksichtigen ist. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 2 |
| Pages: | 55 - 60 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1333365265 |
| DOI: | 10.1002/bapi.201200006 |
| Nebis system number: | 000006704 |
Comparison of two optical methods for contactless, full field and highly sensitive in-plane deformation measurements using the example of plywood
,
Valla, Andreas, Konnerth, Johannes, Keunecke, Daniel, Niemz, Peter, Müller, Ulrich, Gindl Wolfgang,
2011
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| Author(s): | Valla, Andreas, Konnerth, Johannes, Keunecke, Daniel, Niemz, Peter, Müller, Ulrich, Gindl Wolfgang |
| Title: | Comparison of two optical methods for contactless, full field and highly sensitive in-plane deformation measurements using the example of plywood |
| Abstract: | In the present paper, the suitability of Electronic Speckle Pattern Interferometry (ESPI) and Digital Image Correlation (DIC) for the measurement of two-dimensional strain distribution on mechanically stressed wood specimens is evaluated. Particular attention is dedicated to the basics of the individual techniques in order to discuss potential advantages and disadvantages. The results of a model experiment with plywood show that the results delivered by both methods are very similar and of high quality. ESPI provides reasonably fast experimental set up and data acquisition, and fast, straightforward post-processing. Compared to ESPI, DIC is a more versatile method demanding skilled sample preparation, and postprocessing may be time consuming. |
| Published in: | Wood science and technology |
| Volume: | 45 |
| Issue: | 4 |
| Pages: | 755 - 765 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1318837957, WOS-000296006000010 |
| DOI: | 10.1007/s00226-010-0394-7 |
| Nebis system number: | 000057691 |
Focussed ion beam nanotomography reveals the 3D morphology of different solid phases in hardened cement pastes
,
Trtik, P., Muench, B., Gasser, P., Leemann, A., Loser, R., Wepf, R., Lura, P.,
2011
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| Author(s): | Trtik, P., Muench, B., Gasser, P., Leemann, A., Loser, R., Wepf, R., Lura, P. |
| Title: | Focussed ion beam nanotomography reveals the 3D morphology of different solid phases in hardened cement pastes |
| Abstract: | P>Due to the development of integrated low-keV back-scattered electron detectors, it has become possible in focussed ion beam nanotomography to segment not only solid matter and porosity of hardened cement paste, but also to distinguish different phases within the solid matter. This paper illustrates a method that combines two different approaches for improving the contrast between different phases in the solid matrix of a cement paste. The first approach is based on the application of a specially developed 3D diffusion filter. The second approach is based on a modified data-acquisition procedure during focussed ion beam nanotomography. A pair of electron images is acquired for each slice in the focussed ion beam nanotomography dataset. The first image is captured immediately after ion beam milling; the second image is taken after a prolonged exposure to electron beam scanning. The acquisition of complementary focussed ion beam nanotomography datasets and processing the images with a 3D anisotropic diffusion filter allows distinguishing different phases within the hydration products. |
| Published in: | Journal of microscopy |
| Volume: | 241 |
| Issue: | 3 |
| Pages: | 234 - 242 |
| ISSN: | 0022-2720, 1365-2818 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Oxford, UK |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General, Focussed ion beam, Cement, Nanotomography |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Focussed ion beam, Cement, Nanotomography |
| DBID source: | WOS-000287365500003 |
| DOI: | 10.1111/j.1365-2818.2010.03433.x |
| Nebis system number: | 000019891 |
Comparison of bending stiffness of cross-laminated solid timber derived by modal analysis of full panels and by bending tests of strip-shaped specimens
,
Steiger, René, Gülzow, Arne, Czaderski, Christoph, Howald, Martin T., Niemz, Peter,
2012
>>
| Author(s): | Steiger, René, Gülzow, Arne, Czaderski, Christoph, Howald, Martin T., Niemz, Peter |
| Title: | Comparison of bending stiffness of cross-laminated solid timber derived by modal analysis of full panels and by bending tests of strip-shaped specimens |
| Abstract: | The design of cross-laminated solid timber (CLT) as load-bearing plates is mainly governed by serviceability criterions like maximal deflection and susceptibility to vibration. Hence, predicting the respective behavior of such plates requires accurate information about their elastic properties. According to product standards, the bending stiffness of CLT has to be assessed from 4-point bending tests of strip-shaped specimens, cut from the CLT panels. By comparing elastic properties of CLT derived by means of modal analysis of full panels with the results of bending tests on 100 mm and 300 mm wide strip-shaped specimens it is shown, that by testing single 100 mm wide strip-shaped specimens bending stiffness of full panels cannot be assessed correctly, whereas single 300 mm wide strips or averages of 5 to 6 100 mm wide strip-shaped specimens lead to acceptable results. Hence, strip-shaped specimens should only be used in the course of factory quality control or when assessing the bending stiffness of parts of CLT panels used as beam-like load-bearing elements but not to derive bending stiffness of gross CLT panels. Verification by carrying out static bending tests of gross CLT panels under different loading situations showed that alternatively to tests on strip-shaped specimens or estimations with the compound theory, the overall stiffness properties of CLT can be derived directly by a modal analysis of full-size panels. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 141 - 153 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591798, WOS-000298657600019 |
| DOI: | 10.1007/s00107-011-0521-7 |
| Nebis system number: | 000047744 |
Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions
,
Sonderegger, Walter, Vecellio, Manuele, Zwicker, Pascal, Niemz, Peter,
2011
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| Author(s): | Sonderegger, Walter, Vecellio, Manuele, Zwicker, Pascal, Niemz, Peter |
| Title: | Combined bound water and water vapour diffusion of Norway spruce and European beech in and between the principal anatomical directions |
| Abstract: | The combined bound water and water vapour diffusion of wood is of great interest in the field of building physics. Due to swelling stresses, the steady-state-determined diffusion coefficient clearly differs from the unsteady-state-determined diffusion coefficient. In this study, both diffusion coefficients and the water vapour resistance factor of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) were investigated for the principal anatomical directions (radial, tangential and longitudinal) and in 15° steps between these directions. The values were determined with the cup method as the basic principle. The unsteady-state-determined diffusion coefficient is, independent of the direction, about half that of the steady-state-determined diffusion coefficient. Both diffusion coefficients are about two to three times higher for spruce than for beech. They are up to 12 times higher in the longitudinal direction than perpendicular to the grain for spruce, and up to 15 times higher for beech. With increasing moisture content, the diffusion coefficients exponentially increase. The water vapour resistance factor shows converse values to the diffusion coefficients. |
| Published in: | Holzforschung |
| Volume: | 65 |
| Issue: | 6 |
| Pages: | 819 - 828 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Beech, Bound water diffusion, Cup method, Sorption, Spruce, Water vapour diffusion, Water vapour resistance factor |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Beech, Bound water diffusion, Cup method, Sorption, Spruce, Water vapour diffusion, Water vapour resistance factor |
| DBID source: | FORM-1318339055, WOS-000297527600006 |
| DOI: | 10.1515/HF.2011.091 |
| Nebis system number: | 000047746 |
Thermal and moisture flux in soft fibreboards
,
Sonderegger, Walter, Niemz, Peter,
2012
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| Author(s): | Sonderegger, Walter, Niemz, Peter |
| Title: | Thermal and moisture flux in soft fibreboards |
| Abstract: | The thermal conductivity of several wet and dry processed industrial soft fibreboards was determined at temperatures between 10°C and 30°C. Additionally, the thermal conductivity was tested relative to the moisture content ranging from an oven-dry sample to a moisture content of 85% relative humidity. Furthermore, the water vapour diffusion was investigated to determine the resistance factor and the diffusion coefficient under ‘dry cup’ and ‘wet cup’ conditions and the sorptions were tested by means of the sorption isotherms. The thermal conductivity increases with increasing temperature at about 0.45% per Kelvin and with increasing moisture at about 0.17×10−2 W/mK per percent volumetric moisture content. Furthermore, the thermal conductivity depends on the manufacture (dry or wet process) and is influenced by density. The water vapour resistance factor increases and the diffusion coefficient decreases with increasing density. Both factors decrease with increasing moisture content and they are dependant on board thickness, composition and manufacturing. The sorption isotherm is similar to solid wood below about 80% relative humidity but strongly increases for soft fibreboards with binding fibres and additives of ammonium phosphate or sodium borate and boric acid when above 80% relative humidity. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 25 - 35 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591478, WOS-000298657600004 |
| DOI: | 10.1007/s00107-010-0498-7 |
| Nebis system number: | 000047744 |
Vergleichende Untersuchungen zum Feuchte- und Wärmeverhalten in unterschiedlichen Holzwandelementen
,
Sonderegger, Walter, Joscak, Matus, Niemz, Peter,
2011
>>
| Author(s): | Sonderegger, Walter, Joscak, Matus, Niemz, Peter |
| Title: | Vergleichende Untersuchungen zum Feuchte- und Wärmeverhalten in unterschiedlichen Holzwandelementen |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Published |
| Event name: | Statusseminar der Schweizerischen Arbeitsgemeinschaft für Holzforschung (SAH) |
| Event date: | April 27, 2011 |
| Place: | Bad Säckingen, Germany |
| Language: | German |
| Review status: | Unknown |
| DBID source: | FORM-1311859668 |
Holzwandelemente bei Feuchte und Wärme
,
Sonderegger, Walter, Joscak, Matus, Niemz, Peter,
2011
>>
| Author(s): | Sonderegger, Walter, Joscak, Matus, Niemz, Peter |
| Title: | Holzwandelemente bei Feuchte und Wärme |
| Abstract: | Das Projekt "Vergleichende Untersuchungen zum Feuchte- und Wärmeverhalten in unterschiedlichen Holzwandelelementen" hat eine gute Verknüpfung zwischen Praxis und Forschung ergeben. Kleinere Betriebe ohne Kapazitäten im Bereich Forschung und Entwicklung konnten sich an dem Projekt beteiligen und in Zusammenarbeit mit der ETH Zürich und dem Fraunhofer-Institut ihre Produkte testen lassen. Eine weitere Zusammenarbeit mit den beteiligten Betrieben und der ETH Zürich (Arbeitsgruppe Holzphysik), um die Kenntnisse im Holzbaubereich zu erweitern, läuft im Rahmen des Projektes "Datenbank für Kennwerte zum Feuchte- und Wärmetransport in Holz und Holzwerkstoffen", das durch den Aktionsplan Holz (BAFU) gefördert wird |
| Published in: | Holzforschung Schweiz |
| Volume: | 19 |
| Issue: | 1 |
| Pages: | 9 - 12 |
| ISSN: | 1660-6957, 1662-6168 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Zürich |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1311858462 |
| Nebis system number: | 004342733 |
Feuchte- und Wärmeverhalten verschiedener Holzaussenwände im Vergleich
,
Sonderegger, Walter, Joscak, Matus, Niemz, Peter,
2011
>>
| Author(s): | Sonderegger, Walter, Joscak, Matus, Niemz, Peter |
| Title: | Feuchte- und Wärmeverhalten verschiedener Holzaussenwände im Vergleich |
| Abstract: | Wandaufbauten aus Vollholzelementen und Holzwerkstoffen verschiedener Hersteller wurden im Rahmen eines ETH-Projekts bezüglich ihres Feuchte- und Wärmeverhaltens untersucht und miteinander verglichen. Dabei ergab sich eine gute Übereinstimmung von Messung und Simulation, sofern die an der ETH gemessenen, thermischen Kennwerte für Holz (deutlich tiefer als die Normwerte) in die Simulation eingesetzt werden. Bei vier Wandaufbauten wurde eine nicht hinterlüftete Holzfassade verwendet. Trotzdem wurden keine kritischen, relativen Luftfeuchten (hohe Luftfeuchte bei hohen Temperaturen) innerhalb dieser Wandaufbauten gemessen. Die Holzfeuchte erreichte bei keiner Wand eine kritische Grenze von 20 Prozent. |
| Published in: | Schweizer Holzbau |
| Volume: | 77 |
| Issue: | 6 |
| Pages: | 18 - 23 |
| ISSN: | 1421-7651 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Zürich |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1311858885 |
| Nebis system number: | 000014022 |
Thermal behaviour of Norway spruce and European beech in and between the principal anatomical directions
,
Sonderegger, Walter, Hering, Stefan, Niemz, Peter,
2011
>>
| Author(s): | Sonderegger, Walter, Hering, Stefan, Niemz, Peter |
| Title: | Thermal behaviour of Norway spruce and European beech in and between the principal anatomical directions |
| Abstract: | Thermal conductivity (ThCond), thermal diffusivity and heat capacity of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) have been determined for all principal directions - radial (R), tangential (T) and longitudinal (L) - depending on the moisture content (MC) and ThCond was additionally measured in 15 degrees steps between these directions. The ThCond was determined in a guarded hot plate apparatus. For determining thermal diffusivity and heat capacity, the same apparatus was supplemented with thermocouples and the temperature evolution was evaluated numerically by a partial differential equation. The results show expectedly that ThCond increases with increasing MC, whereby the highest increment was observed in T and the lowest in L direction. ThCond is higher for beech than for spruce in all anatomical directions and the conductivity for both species is more than twice as high in L direction than perpendicular to grain. The highest ThCond is found for beech at a grain angle of approximately 15 degrees. The lowest ThCond shows spruce at an angle of approximately 60 degrees between T and R direction. Thermal diffusivity is similar for both species and decreases with increasing MC. Its differences with regard to the anatomical directions correlate with those of the ThCond values. Heat capacity is lower for beech than for spruce and shows a clear increase with increasing MC. |
| Published in: | Holzforschung |
| Volume: | 65 |
| Issue: | 3 |
| Pages: | 369 - 375 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Beech, Heat capacity, Moisture content, Spruce, Thermal conductivity, Thermal diffusivity |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Beech, Heat capacity, Moisture content, Spruce, Thermal conductivity, Thermal diffusivity |
| DBID source: | WOS-000290378900012 |
| DOI: | 10.1515/HF.2011.036 |
| Nebis system number: | 000047746 |
Gaussian model of explosive percolation in three and higher dimensions
,
Schrenk, K.J., Araújo, N.A.M., Herrmann, Hans Jürgen,
2011
>>
| Author(s): | Schrenk, K.J., Araújo, N.A.M., Herrmann, Hans Jürgen |
| Title: | Gaussian model of explosive percolation in three and higher dimensions |
| Abstract: | The Gaussian model of discontinuous percolation, recently introduced by Araújo and Herrmann [ Phys. Rev. Lett. 105 035701 (2010)], is numerically investigated in three dimensions, disclosing a discontinuous transition. For the simple cubic lattice, in the thermodynamic limit we report a finite jump of the order parameter J=0.415±0.005. The largest cluster at the threshold is compact, but its external perimeter is fractal with fractal dimension dA=2.5±0.2. The study is extended to hypercubic lattices up to six dimensions and to the mean-field limit (infinite dimension). We find that, in all considered dimensions, the percolation transition is discontinuous. The value of the jump in the order parameter, the maximum of the second moment, and the percolation threshold are analyzed, revealing interesting features of the transition and corroborating its discontinuous nature in all considered dimensions. We also show that the fractal dimension of the external perimeter, for any dimension, is consistent with the one from bridge percolation and establish a lower bound for the percolation threshold of discontinuous models with a finite number of clusters at the threshold. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 84 |
| Issue: | 4 |
| Pages: | 041136 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1320766368, WOS-000296533900002 |
| DOI: | 10.1103/PhysRevE.84.041136 |
| Nebis system number: | 004109079 |
Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition
,
Schrenk, K. J., Felder, A., Deflorin, S., Araujo, N. A. M., D'Souza, R. M., Herrmann, H. J.,
2012
>>
| Author(s): | Schrenk, K. J., Felder, A., Deflorin, S., Araujo, N. A. M., D'Souza, R. M., Herrmann, H. J. |
| Title: | Bohman-Frieze-Wormald model on the lattice, yielding a discontinuous percolation transition |
| Abstract: | The BFW model introduced by Bohman, Frieze, and Wormald [Random Struct. Algorithms 25, 432 (2004)], and recently investigated in the framework of discontinuous percolation by Chen and D'Souza [Phys. Rev. Lett. 106, 115701 (2011)], is studied on the square and simple-cubic lattices. In two and three dimensions, we find numerical evidence for a strongly discontinuous transition. In two dimensions, the clusters at the threshold are compact with a fractal surface of fractal dimension d(f) = 1.49 +/- 0.02. On the simple-cubic lattice, distinct jumps in the size of the largest cluster are observed. We proceed to analyze the tree-like version of the model, where only merging bonds are sampled, for dimension two to seven. The transition is again discontinuous in any considered dimension. Finally, the dependence of the cluster-size distribution at the threshold on the spatial dimension is also investigated. |
| Published in: | Physical Review E |
| Volume: | 85 |
| Issue: | 3 |
| Pages: | 031103 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000301339900001 |
| DOI: | 10.1103/PhysRevE.85.031103 |
| Nebis system number: | 004109079 |
Fracturing ranked surfaces
,
Schrenk, K. J., Araujo, N. A. M., Andrade, J. S., Herrmann, H. J.,
2012
>>
| Author(s): | Schrenk, K. J., Araujo, N. A. M., Andrade, J. S., Herrmann, H. J. |
| Title: | Fracturing ranked surfaces |
| Abstract: | Discretized landscapes can be mapped onto ranked surfaces, where every element (site or bond) has a unique rank associated with its corresponding relative height. By sequentially allocating these elements according to their ranks and systematically preventing the occupation of bridges, namely elements that, if occupied, would provide global connectivity, we disclose that bridges hide a new tricritical point at an occupation fraction p = p(o), where p(c) is the percolation threshold of random percolation. For any value of p in the interval p(c) < p <= 1, our results show that the set of bridges has a fractal dimension d(BB) approximate to 1.22 in two dimensions. In the limit p -> 1, a self-similar fracture is revealed as a singly connected line that divides the system in two domains. We then unveil how several seemingly unrelated physical models tumble into the same universality class and also present results for higher dimensions. |
| Published in: | Scientific Reports |
| Volume: | 2 |
| Pages: | 348 |
| ISSN: | 2045-2322 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Nature Publishing Group |
| Publication status: | Published |
| Subjects: | Wissenschaft und Technik allgemein|Science and Technology, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000302458500002 |
| DOI: | 10.1038/srep00348 |
| Nebis system number: | 006751867 |
Untersuchungen zum Versagen von Klebfugen unter klimatischer Langzeitbeanspruchung
,
Schnider, Thomas, Niemz, Peter, Steiger, Benjamin, Arx, Urs von,
2011
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| Author(s): | Schnider, Thomas, Niemz, Peter, Steiger, Benjamin, Arx, Urs von |
| Title: | Untersuchungen zum Versagen von Klebfugen unter klimatischer Langzeitbeanspruchung |
| Abstract: | An Klebverbindungen werden im Konstruktiven Holzbau hohe Anforderungen hinsichtlich Güte und Dauerhaftigkeit gestellt. Mit 1-K PUR, MUF und PRF verklebte Lamellen aus Rotbuche und Fichte wurden einer Freibewitterung, einer künstlichen Bewitterung und einem feucht-trocken Wechselklima ausgesetzt. Nach einer abgestuften Behandlungsdauer wurden die Zugscherfestigkeit sowie die Schalllaufzeit senkrecht zur Klebfuge und die Eigenfrequenz bei Biegeschwingungen bestimmt. Ergnzend wurde die Delaminierungsbestndigkeit an Brettschichtholz aus Fichte nach DIN EN 302-2 durchgeführt. Im untersuchten Behandlungszeitraum wurde bei allen Proben keine erkennbare Delaminierung festgestellt. Ein Zusammenhang zwischen Behandlungsdauer und Zugscherfestigkeit konnte nicht nachgewiesen werden. Ebenso bestand keine gesicherte Korrelation zwischen der Zugscherfestigkeit und der Schalllaufzeit sowie der Eigenfrequenz. Investigations on the failure of bond lines under long-term climatic stress. With 1-K PUR, MUF and PRF parallel to the grain glued lamellas of spruce and beech were exposed to different climatic loads (natural and artificial weathering, controlled alternating moist-dry climate). All adhesives are approved for use in timber construction. After shortening the weathering duration running time of ultrasonic, vertical to the bonding layer and tensile shear strength were measured. In addition, delamination tests of glued spruce wood were carried out according to DIN EN 302-2. Investigation of the samples after the test period revealed no signs of delamination. No correlation was verified between the number of cycles and tensile shear strength and NDT methods. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 1 |
| Pages: | 27 - 32 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung |Architecture, Built Environment and Environmental Design, Klebstoffe, Buche, Fichte, Holzscherfestigkeit, Delaminierung, Wechselklima, Freibewitterung, Künstliche Bewitterung, Feuchte, Versuche |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Klebstoffe, Buche, Fichte, Holzscherfestigkeit, Delaminierung, Wechselklima, Freibewitterung, Künstliche Bewitterung, Feuchte, Versuche |
| DBID source: | WOS-000288108700004 |
| DOI: | 10.1002/bapi.201110003 |
| Nebis system number: | 000006704 |
Mitigation of malicious attacks on networks
,
Schneider, Christian M., Moreira, André A., Andrade, José S., Havlin, Shlomo, Herrmann, Hans J.,
2011
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| Author(s): | Schneider, Christian M., Moreira, André A., Andrade, José S., Havlin, Shlomo, Herrmann, Hans J. |
| Title: | Mitigation of malicious attacks on networks |
| Abstract: | Terrorist attacks on transportation networks have traumatized modern societies. With a single blast, it has become possible to paralyze airline traffic, electric power supply, ground transportation or Internet communication. How and at which cost can one restructure the network such that it will become more robust against a malicious attack? We introduce a new measure for robustness and use it to devise a method to mitigate economically and efficiently this risk. We demonstrate its efficiency on the European electricity system and on the Internet as well as on complex networks models. We show that with small changes in the network structure (low cost) the robustness of diverse networks can be improved dramatically whereas their functionality remains unchanged. Our results are useful not only for improving significantly with low cost the robustness of existing infrastructures but also for designing economically robust network systems. |
| Published in: | Proceedings of the National Academy of Sciences of the United States of America |
| Volume: | 108 |
| Issue: | 10 |
| Pages: | 3838 - 3841 |
| ISSN: | 0027-8424, 1091-6490 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Washington, D.C. |
| Publication status: | Published |
| Subjects: | percolation, power grid |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | percolation, power grid |
| DBID source: | WOS-000288120400009 |
| DOI: | 10.1073/pnas.1009440108 |
| Nebis system number: | 001003347 |
Suppressing epidemics with a limited amount of immunization units
,
Schneider, Christian M., Mihaljev, Tamara, Havlin, Shlomo, Herrmann, Hans J.,
2011
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| Author(s): | Schneider, Christian M., Mihaljev, Tamara, Havlin, Shlomo, Herrmann, Hans J. |
| Title: | Suppressing epidemics with a limited amount of immunization units |
| Abstract: | The way diseases spread through schools, epidemics through countries, and viruses through the internet is crucial in determining their risk. Although each of these threats has its own characteristics, its underlying network determines the spreading. To restrain the spreading, a widely used approach is the fragmentation of these networks through immunization, so that epidemics cannot spread. Here we develop an immunization approach based on optimizing the susceptible size, which outperforms the best known strategy based on immunizing the highest-betweenness links or nodes. We find that the network's vulnerability can be significantly reduced, demonstrating this on three different real networks: the global flight network, a school friendship network, and the internet. In all cases, we find that not only is the average infection probability significantly suppressed, but also for the most relevant case of a small and limited number of immunization units the infection probability can be reduced by up to 55%. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 84 |
| Issue: | 6 |
| Pages: | 061911 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1324395765, WOS-000298135300006 |
| DOI: | 10.1103/PhysRevE.84.061911 |
| Nebis system number: | 004109079 |
Modeling the topology of protein interaction networks
,
Schneider, Christian M., Arcangelis, Lucilla de, Herrmann, Hans J.,
2011
>>
| Author(s): | Schneider, Christian M., Arcangelis, Lucilla de, Herrmann, Hans J. |
| Title: | Modeling the topology of protein interaction networks |
| Abstract: | A major issue in biology is the understanding of the interactions between proteins. These interactions can be described by a network, where the proteins are modeled by nodes and the interactions by edges. The origin of these protein networks is not well understood yet. Here we present a two-step model, which generates clusters with the same topological properties as networks for protein-protein interactions, namely, the same degree distribution, cluster size distribution, clustering coefficient, and shortest path length. The biological and model networks are not scale-free but exhibit small-world features. The model allows the fitting of different biological systems by tuning a single parameter. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 84 |
| Issue: | 1 |
| Pages: | 016112 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1314002067 |
| DOI: | 10.1103/PhysRevE.84.016112 |
| Nebis system number: | 004109079 |
Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography
,
Sanabria, Sergio J., Wyss, Peter, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2011
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| Author(s): | Sanabria, Sergio J., Wyss, Peter, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography |
| Abstract: | Glued timber products have an extensive range of applications in construction. In this work a Microfocus X-ray Computed Tomography method was developed to inspect gluing defects in timber samples and was applied successfully on experimental data. The bonding plane was segmented into glued and non-glued regions and imaged with 5 mm resolution. Moreover, the gap topology between timber lamellas was precisely characterised. A limited-angle reconstruction with anisotropic frame binning together with a specific glue line readout method efficiently filters out undesired wood structure highlighting the information of the adhesive joint. This method imposes limitations on the size of the specimen in only one dimension. The presence and absence of glue could be detected for glue line thicknesses over 50 μm and air gaps larger than 150 μm could be characterised. Several information reduction approaches were combined in the reconstruction process to implement the assessment of a 100×100 mm2 bonding plane in less than 40 s. Holzverklebungen gewinnen zunehmend an Bedeutung. Im Rahmen dieser Arbeit wurde ein Mikrofokus Röntgen-Computertomographie Messverfahren zur Beurteilung von Fehlverklebungen in Holzbauteilen entwickelt und in experimentellen Versuchen erfolgreich überprüft. Fehlverklebungen und die Topologie der Klebfugen wurden mit einer räumlichen Auflösung von 5 mm abgebildet. Verfahrensspezifische Bildrekonstruktions- und Klebfugen-Auslesealgorithmen mit eingeschränktem Aufnahmewinkelbereich filtern unerwünschte Holzstrukturen heraus und heben die Leimschicht hervor. Die Größe der Holzbauteile ist bei diesem Messverfahren nur in einer Dimension beschränkt. Die An- und Abwesenheit von Klebstoff lässt sich für Leimfugen dicker als 50 μm nachweisen; Luftspalten größer als 150 μm sind feststellbar. Die Informations-Reduktionsverfahren ermöglichten die Beurteilung von 100×100 mm2 verleimten Holzoberflächen in einer Messzeit von weniger als 40 s. |
| Published in: | European journal of wood and wood products |
| Volume: | 69 |
| Issue: | 4 |
| Pages: | 605 - 617 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295011041, WOS-000295787600014 |
| DOI: | 10.1007/s00107-010-0509-8 |
| Nebis system number: | 000047744 |
Glue Line Nondestructive Assessment in Timber Laminates with an Air-Coupled Ultrasonic Technique
,
Sanabria, Sergio J., Müller, Christian, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2011
>>
| Author(s): | Sanabria, Sergio J., Müller, Christian, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Glue Line Nondestructive Assessment in Timber Laminates with an Air-Coupled Ultrasonic Technique |
| Abstract: | Glued solid wood products have gained much importance during the last years, as they allow an efficient and versatile use of the renewable timber material. Current standardized methods for bonding quality assessment consist of tests of small specimens cut from the structure during production or visual in-service inspection. Ultrasonic diagnostics are traditionally based on discrete point measurements using contact techniques. Transducers are generally pressed onto the timber surface with a coupling gel, liquid, or membrane couplant. Large glue line defects in glued timber constructions have been detected with this method (Dill-Langer et al. 2005). The disadvantages are a low precision in signal level measurements, which are highly dependent on the coupling pressure, and that the coupling agent may deteriorate the object. Better repeatability and one-dimensional continuous scanning is achieved with roller transducers, which have been applied to defect inspection in hardwood lumber (Kabir et al. 2002). Non-linear effects have been used to assess delaminations between veneer lamina and particle board (Solodov et al. 2004); a welding piezoelectric stack couples high power ultrasound into the sample and its surface is scanned with a laser vibrometer. |
| Book title: | Delamination in wood, wood products and wood-based composites |
| Pages: | 379 - 387 |
| ISBN: | 978-90-481-9549-7, 978-90-481-9550-3 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Dordrecht |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295013523 |
| DOI: | 10.1007/978-90-481-9550-3_19 |
| Nebis system number: | 006370067 |
Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber
,
Sanabria, Sergio J., Mueller, Christian, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2011
>>
| Author(s): | Sanabria, Sergio J., Mueller, Christian, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber |
| Abstract: | Glued timber products are widely used in construction; therefore, it is necessary to develop non-destructive bonding quality assessment methods for long-term structural health monitoring. Air-coupled ultrasound (ACU) inspection is a novel technique, with phenomenal improvements in reproducibility compared to traditional contact ultrasonics, unlimited scanning possibilities, and a high potential for delamination detection in wood products. As part of an ongoing project, glued timber samples of 10 mm thickness with artificial glue line defects were inspected. A normal through-transmission set-up with 120 kHz transducers allowed for successful and accurate imaging of the geometry of glued and non-glued areas in all inspected objects. The influence of wood heterogeneity and the reproducibility of ACU amplitude measurements were analysed in detail, identifying the main sources of variation. Future work is planned for the inspection of more complex glued timber objects. |
| Published in: | Wood science and technology |
| Volume: | 45 |
| Issue: | 4 |
| Pages: | 645 - 659 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295011225, WOS-000296006000003 |
| DOI: | 10.1007/s00226-010-0357-z |
| Nebis system number: | 000057691 |
Monitored assessment of structural integrity of multilayered glued laminated timber beams with air-coupled ultrasound and contact ultrasound imaging
,
Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs,
2011
>>
| Author(s): | Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs |
| Title: | Monitored assessment of structural integrity of multilayered glued laminated timber beams with air-coupled ultrasound and contact ultrasound imaging |
| Book title: | Proceedings / 17th International Nondestructive Testing and Evaluation of Wood Symposium |
| Volume: | 1 |
| Pages: | 359 - 366 |
| ISBN: | 978-963-9883-81-9, 978-963-9883-82-6 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Sopron |
| Publication status: | Published |
| Event name: | 17th International Nondestructive Testing and Evaluation of Wood Symposium |
| Event date: | September 14-16, 2011 |
| Place: | Sopron, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1331132260 |
Air-coupled ultrasound inspection of glued laminated timber
,
Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs,
2011
>>
| Author(s): | Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs |
| Title: | Air-coupled ultrasound inspection of glued laminated timber |
| Abstract: | A novel air-coupled ultrasound (ACU) 120 kHz normal transmission system enabled successful imaging of bonding and saw cut defects in multilayered glulam beams up to 280 mm in height with a signal-to-noise ratio (SNR) of 40 dB. The main wave propagation paths were modeled; quasi-longitudinal and quasi-transverse modes were coupled in each lamella and the sound field was found to be shifted from the insonification axis as a function of the ring angle, leading to interference of wave paths in the receiver and to 15 dB amplitude variability in defect-free glulam. The assessment was improved with spatial processing algorithms that profited from the arbitrary scanning resolution and high reproducibility of ACU. Overlapped averaging reduced in-band noise by 15 dB, amplitude tracking captured only the first incoming oscillation, thus minimizing diffraction around defect regions, and image normalization compensated 6 dB of systematic amplitude variability across the fiber direction. The application of ACU to in situ defect monitoring was demonstrated by using multiparameter difference imaging of measurements of the same sample with and without saw cut defects. The segmentation of the defect geometry was improved significantly and the amplitude variability was reduced by 10 dB. Further work is planned to model additional insonification setups and grain and density heterogeneities. |
| Published in: | Holzforschung |
| Volume: | 65 |
| Issue: | 3 |
| Pages: | 377 - 387 |
| ISSN: | 1437-434X, 0018-3830 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Werkstoffe|Materials Sciences, Air-coupled ultrasound, Amplitude tracking, Bonding quality, Delamination, Energy flux shift, Glued laminated timber, In situ flaw monitoring, Multiparameter difference imaging, Non-contact ultrasonics, Non-destructive evaluation, Saw cut defect, Spatial signal processing, Ultrasound wave propagation, Wood heterogeneity |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Air-coupled ultrasound, Amplitude tracking, Bonding quality, Delamination, Energy flux shift, Glued laminated timber, In situ flaw monitoring, Multiparameter difference imaging, Non-contact ultrasonics, Non-destructive evaluation, Saw cut defect, Spatial signal processing, Ultrasound wave propagation, Wood heterogeneity |
| DBID source: | WOS-000290378900013 |
| DOI: | 10.1515/HF.2011.050 |
| Nebis system number: | 000047746 |
Wellenformanalyse von Schallemissionssignalen ausgewählter Zugversuche an Vollholz- und Sperrholz/LVL-Prüfkörpern
,
Ritschel, Franziska, Niemz, Peter, Brunner, Andreas J.,
2011
>>
| Author(s): | Ritschel, Franziska, Niemz, Peter, Brunner, Andreas J. |
| Title: | Wellenformanalyse von Schallemissionssignalen ausgewählter Zugversuche an Vollholz- und Sperrholz/LVL-Prüfkörpern |
| Book title: | 18. Kolloquium Schallemission: Statusberichte zur Entwicklung und Anwendung der Schallemissionsanalyse, Berichtsband, BB-131-CD |
| Pages: | 04 |
| ISBN: | 978-3-940283-37-5 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Event name: | 18. Kolloquium Schallemission, Statusberichte zur Entwicklung und Anwendung der Schallemissionsanalyse |
| Event date: | October 27-28, 2011 |
| Place: | Wetzlar, Germany |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1321265464 |
Combining Image Correlation from Optical Methods and Acoustic Analysis for Investigating Damage Evolution in Plywood
,
Ritschel, Franziska, Niemz, Peter, Brunner, Andreas J.,
2011
>>
| Author(s): | Ritschel, Franziska, Niemz, Peter, Brunner, Andreas J. |
| Title: | Combining Image Correlation from Optical Methods and Acoustic Analysis for Investigating Damage Evolution in Plywood |
| Book title: | Proceedings of the 17th International Nondestructive Testing and Evaluation of Wood Symposium |
| Pages: | 343 - 350 |
| ISBN: | 978-963-9883-81-9 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Budapest |
| Publication status: | Published |
| Event name: | 17th International Nondestructive Testing and Evaluation of Wood Symposium |
| Event date: | September 14-16, 2011 |
| Place: | Budapest, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317889461 |
Damage evolution in layered wood materials monitored by acoustic emission & optical method
,
Ritschel, Franziska, Brunner, Andreas J., Niemz, Peter,
2011
>>
| Author(s): | Ritschel, Franziska, Brunner, Andreas J., Niemz, Peter |
| Title: | Damage evolution in layered wood materials monitored by acoustic emission & optical method |
| Abstract: | A methodological approach allowing insights into micromechanical phenomena during destructive testing of the macroscopic specimens is introduced for layered wood materials. Tensile tests of samples made from Laminated Veneer Lumber (LVL) and from Plywood (PW) are performed with in-situ monitoring of acoustic emission (AE) and surface displacement with the application of digital image correlation (DIC). The mechanical behavior of the specimens is correlated with information from DIC and AE analysis. Due to the influence of the varying morphological structure of the samples, especially the number of adhesive layers and the fiber orientation of the wooden layers, different mechanisms dominate the damage evolution. These differences are reflected by the results of the first AE analysis dealing with AE activity and AE intensity, as well as by the varying formation of strain field distributions. |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Published |
| Event name: | Empa PhD Students' Symposium 2011 |
| Event date: | October 18, 2011 |
| Place: | St. Gallen, Switzerland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1321605125 |
How dense can one pack spheres of arbitrary size distribution ?
,
Reis, S.D.S., Araujo, N.A.M., Andrade Jr., J.S., Herrmann, Hans J.,
2012
>>
| Author(s): | Reis, S.D.S., Araujo, N.A.M., Andrade Jr., J.S., Herrmann, Hans J. |
| Title: | How dense can one pack spheres of arbitrary size distribution ? |
| Abstract: | We present the first systematic algorithm to estimate the maximum packing density of spheres when the grain sizes are drawn from an arbitrary size distribution. With an Apollonian filling rule, we implement our technique for disks in 2d and spheres in 3d. As expected, the densest packing is achieved with power-law size distributions. We also test the method on homogeneous and on empirical real distributions, and we propose a scheme to obtain experimentally accessible distributions of grain sizes with low porosity. Our method should be helpful in the development of ultra-strong ceramics and high-performance concrete. |
| Published in: | EPL : a letters journal exploring the frontiers of physics |
| Volume: | 97 |
| Issue: | 1 |
| Pages: | 18004 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1329818382, WOS-000300250800049 |
| DOI: | 10.1209/0295-5075/97/18004 |
| Nebis system number: | 000033031 |
The apparent roughness of a sand surface blown by wind from an analytical model of saltation
,
Pähtz, Thomas, Kok, F.J., Herrmann, Hans J.,
2012
>>
| Author(s): | Pähtz, Thomas, Kok, F.J., Herrmann, Hans J. |
| Title: | The apparent roughness of a sand surface blown by wind from an analytical model of saltation |
| Abstract: | We present an analytical model of aeolian sand transport. The model quantifies the momentum transfer from the wind to the transported sand by providing expressions for the thickness of the saltation layer and the apparent surface roughness. These expressions are derived from basic physical principles and a small number of assumptions. The model further predicts the sand transport rate (mass flux) and the impact threshold (the smallest value of the wind shear velocity at which saltation can be sustained). We show that, in contrast to previous studies, the present model's predictions are in very good agreement with a range of experiments, as well as with numerical simulations of aeolian saltation. Because of its physical basis, we anticipate that our model will find application in studies of aeolian sand transport on both Earth and Mars. |
| Published in: | New journal of physics |
| Volume: | 14 |
| Pages: | 043035 |
| ISSN: | 1367-2630 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bristol, UK |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1336052435 |
| DOI: | 10.1088/1367-2630/14/4/043035 |
| Nebis system number: | 001997538 |
Porosity and pore size distribution of different wood types as determined by mercury intrusion porosimetry
,
Plötze, Michael, Niemz, Peter,
2011
>>
| Author(s): | Plötze, Michael, Niemz, Peter |
| Title: | Porosity and pore size distribution of different wood types as determined by mercury intrusion porosimetry |
| Abstract: | In this work, densities and porosity parameters are determined on domestic and overseas soft- and hardwoods by application of pycnometric methods and mercury intrusion porosimetry (MIP). Great variability was found in bulk density, porosity and in the specific surface area. According to the pore size distribution, four pore size classes could be distinguished: macropores (radius 58–2 μm and 2–0.5 μm), mesopores (500–80 nm), and micropores (80–1.8 nm). The pore size distribution can vary even in the case of comparable pore volumes. The hardwoods, particularly the European diffuse-porous ones, show a higher amount of micropores, which represent the microvoids or cell wall capillaries. A high cumulative pore volume can also be the result of a high content of micropores with poorer accessibility. The value of the total specific surface area from MIP measurements is, generally, below those values obtained by the water vapour adsorption technique. These results can provide information for further investigations on the sorption behaviour and the fluid intake as technological characteristics in industrial processes of impregnation and penetration of coating materials or adhesives. Im Rahmen der vorliegenden Arbeit wurden an ausgewählten einheimischen und überseeischen Nadel- und Laubhölzern mit pyknometrischen Methoden und der Quecksilberdruckporosimetrie verschiedene Dichte- und Porositätsparameter bestimmt. Große Unterschiede wurden in der Normal-Rohdichte, der Porosität und Porengrößenverteilung sowie in der spezifischen Oberfläche gefunden. Anhand der Porengrößenverteilungskurven können vier Porenklassen unterschieden werden: Makroporen (Radius 58–2 μm und 2–0,5 μm), Mesoporen (500–80 nm) sowie Mikroporen (80–1,8 nm). Laubhölzer, insbesondere die untersuchten europäischen Zerstreutporigen, zeigen einen höheren Anteil an Mikroporen. Auch bei vergleichbarem totalem Porenvolumen kann die Porengrößenverteilung variieren. Ein vergleichsweise hohes kumulatives Porenvolumen kann auch durch einen hohen Anteil an Mikroporen mit niedrigerer Zugänglichkeit verursacht werden. Die aus den Daten der Druckporosimetrie bestimmte spezifische Oberfläche ist im Allgemeinen kleiner als die mittels Wasserdampfadsorption gemessene. Die vorgestellten Ergebnisse liefern Informationen für weitergehende Untersuchungen zum Sorptions- und Eindringverhalten von Flüssigkeiten in industriellen Prozessen der Imprägnierung, Beschichtung und Verklebung. |
| Published in: | European journal of wood and wood products |
| Volume: | 69 |
| Issue: | 4 |
| Pages: | 649 - 657 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1318515618, WOS-000295787600018 |
| DOI: | 10.1007/s00107-010-0504-0 |
| Nebis system number: | 000047744 |
Transverse Instability of Dunes
,
Parteli, Eric J.R., Andrade, José S., Herrmann, Hans Jürgen,
2011
>>
| Author(s): | Parteli, Eric J.R., Andrade, José S., Herrmann, Hans Jürgen |
| Title: | Transverse Instability of Dunes |
| Abstract: | The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show, by means of numerical simulations, that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the dune turnover time. We estimate the distance covered by a transverse dune before fully decaying into barchans and identify the patterns produced by different types of perturbation. |
| Published in: | Physical review letters |
| Volume: | 107 |
| Issue: | 18 |
| Pages: | 188001 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1320766087, WOS-000297003500008 |
| DOI: | 10.1103/PhysRevLett.107.188001 |
| Nebis system number: | 000003868 |
Oil displacement through a porous medium with a temperature gradient
,
Oliveira, Claudio L.N., Andrade, Jose S., Jr., Herrmann, Hans J.,
2011
>>
| Author(s): | Oliveira, Claudio L.N., Andrade, Jose S., Jr., Herrmann, Hans J. |
| Title: | Oil displacement through a porous medium with a temperature gradient |
| Abstract: | We investigate the effect of a temperature gradient on oil recovery in a two-dimensional pore-network model. The oil viscosity depends on temperature as mu(o) proportional to e(B/T), where B is a physicochemical parameter, depending on the type of oil, and T is the temperature. Atemperature gradient is applied across the medium in the flowdirection. Initially, the porous medium is saturated with oil, and then another fluid is injected. We have considered two cases representing different injection strategies. In the first case, the invading fluid viscosity is constant (finite viscosity ratio), while in the second one, the invading fluid is inviscid (infinite viscosity ratio). Our results show that for the case of finite viscosity ratio, recovery increases with Delta T independent of strength or sign of the gradient. For an infinite viscosity ratio, a positive temperature gradient is necessary to enhance recovery. Moreover, we show that for Delta T > 0, the percentage of oil recovery generally decreases (increases) with B for a finite (infinite) viscosity ratio. Finally, we also extend our results for infinite viscosity ratio to a three-dimensional porous media geometry. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 83 |
| Issue: | 6 |
| Pages: | 066307 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000291702100005 |
| DOI: | 10.1103/PhysRevE.83.066307 |
| Nebis system number: | 004109079 |
Auf spezielle Einsatzbereiche konzentriert
,
Niemz, Peter, Wetzig, Melanie,
2011
>>
| Author(s): | Niemz, Peter, Wetzig, Melanie |
| Title: | Auf spezielle Einsatzbereiche konzentriert |
| Published in: | Holz-Zentralblatt |
| Volume: | 137 |
| Issue: | 1 |
| Pages: | 24 - 26 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General, Werkstoffe allgemein|Materials Sciences, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1309438105 |
| Nebis system number: | 000047754 |
Untersuchungen zur Wärmeleitung von Vollholz und Werkstoffen auf Vollholzbasis, wesentliche Einflussfaktoren
,
Niemz, Peter, Sonderegger, Walter,
2011
>>
| Author(s): | Niemz, Peter, Sonderegger, Walter |
| Title: | Untersuchungen zur Wärmeleitung von Vollholz und Werkstoffen auf Vollholzbasis, wesentliche Einflussfaktoren |
| Abstract: | An Fichtenvollholz und Massivholzplatten sowie an massiven Wandelementen aus Fichtenholz mit variablem Aufbau wurde die Wärmeleitfähigkeit gemessen. Bei Vollholz ist ein gewisser Einfluss der Jahrringlage (radial-tangential) sowie ein deutlicher des Faser-Last-Winkels (LR, LT) vorhanden. Die Wärmeleitzahl von Massivholzplatten mit statistisch regelloser Orientierung der Jahrringlage ist geringer als die von Vollholz radial oder tangential. Geringe Hohlräume in der Mittellage (z. B. Schlitze zum Spannungsabbau) bewirken eine Reduzierung der Wärmeleitzahl. Die Wärmeleitzahl steigt mit zunehmender Temperatur und Holzfeuchte an. Bei mehrschichtigen Wandelementen auf Vollholzbasis ist ein Einfluss der Schichtenanzahl, der Jahrringlage sowie der Hohlräume zwischen den Lagen zu beobachten. Ein in der Mittellage vorhandener Hohlraumanteil bewirkt eine Reduzierung der Wärmeleitzahl. Kommt es allerdings infolge der Hohlraumgestaltung zur Konvektion, steigt die Wärme leitzahl wieder an. Mechanische Verbindungs - elemente (Dübel aus Laubholz hoher Dichte) senkrecht zur Plattenebene bewirken einen geringen Anstieg der Wärmeleitzahl. Die ermittelten Kenn werte für den Einfluss von Jahrringlage, Faser-Last-Winkel, Dichte und Holzfeuchte ermöglichen eine rechnerische Vorausbestimmung der Wärmeleitzahl von Materialverbunden. The thermal conductivity was measured on spruce wood, solid wood panels, as well as massive wood walls with a variable structure. In solid wood a slight influence of the growth ring position (radial-tangential) and a considerable influence of the fibre-load-angle (LR, LT) was observed. In contrast to solid wood in radial and tangential direction solid wood panels with an irregular orientation of the growth rings have a lower thermal conductivity. Marginal holes in the middle layer (e.g. slits to reduce strains) cause a decrease of the values. With increasing temperature and moisture content the thermal conductivity has been rising. Multi-layered wood elements of solid wood show an influence of the number of layers, the growth ring position and holes between the layers. The thermal conductivity is reduced by presenting holes in the middle layer. However, this effect reverses if the holes cause convection. The values also increase a little if mechanical bond elements perpendicular to panel pane such as dowels made of hardwood with a high density are used. The determined parameters about the influence of the position of growth rings, the fibre-load-angle, density and moisture content render the possibility to calculate the thermal conductivity of material combinations by using different computer programs. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 5 |
| Pages: | 299 - 305 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Faser-Last-Winkel, Holzfeuchte, Jahrringneigung, Wandaufbau, Versuche, Wärme, Growth ring position, Fibre-load-angle, Wall composition, Wood moisture content, Experimental set-ups, Thermal insulation and heat |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Faser-Last-Winkel, Holzfeuchte, Jahrringneigung, Wandaufbau, Versuche, Wärme, Growth ring position, Fibre-load-angle, Wall composition, Wood moisture content, Experimental set-ups, Thermal insulation and heat |
| DBID source: | FORM-1318336399 |
| DOI: | 10.1002/bapi.201110793 |
| Nebis system number: | 000006704 |
Untersuchungen zur Wrmeleitung von Vollholz und Werkstoffen auf Vollholzbasis, wesentliche Einflussfaktoren
,
Niemz, Peter, Sonderegger, Walter,
2011
>>
| Author(s): | Niemz, Peter, Sonderegger, Walter |
| Title: | Untersuchungen zur Wrmeleitung von Vollholz und Werkstoffen auf Vollholzbasis, wesentliche Einflussfaktoren |
| Abstract: | Thermal conductivity from solid wood and solid wood materials, important parameters. The thermal conductivity was measured on spruce wood, solid wood panels, as well as massive wood walls with a variable structure. In solid wood a slight influence of the growth ring position (radial-tangential) and a considerable influence of the fibre-load-angle (LR, LT) was observed. In contrast to solid wood in radial and tangential direction solid wood panels with an irregular orientation of the growth rings have a lower thermal conductivity. Marginal holes in the middle layer (e. g. slits to reduce strains) cause a decrease of the values. With increasing temperature and moisture content the thermal conductivity has been rising. Multi-layered wood elements of solid wood show an influence of the number of layers, the growth ring position and holes between the layers. The thermal conductivity is reduced by presenting holes in the middle layer. However, this effect reverses if the holes cause convection. The values also increase a little if mechanical bond elements perpendicular to panel pane such as dowels made of hardwood with a high density are used. The determined para meters about the influence of the position of growth rings, the fibre-load-angle, density and moisture content render the possibility to calculate the thermal conductivity of material combinations by using different computer programs. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 5 |
| Pages: | 299 - 305 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Faser-Last-Winkel, Holzfeuchte, Jahrringneigung, WandaufbauGrowth ring position, Fibre-load-angle, Wall composition, Wood moisture contentVersuche, WärmeExperimental set-ups, Thermal insulation and heat |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Faser-Last-Winkel, Holzfeuchte, Jahrringneigung, WandaufbauGrowth ring position, Fibre-load-angle, Wall composition, Wood moisture contentVersuche, WärmeExperimental set-ups, Thermal insulation and heat |
| DBID source: | WOS-000296292400004 |
| DOI: | 10.1002/bapi.201110793 |
| Nebis system number: | 000006704 |
Holz besser verkleben
,
Niemz, Peter,
2012
>>
| Author(s): | Niemz, Peter |
| Title: | Holz besser verkleben |
| Abstract: | Am 1. Dezember 2011 veranstaltete die Arbeitsgruppe Holzphysik (Leitung Prof. Dr. Peter Niemz) des Instituts for Building Materials (IFB) an der ETH Zürich ein Kolloquium zur „Verklebung von Vollholz“. Das Kolloquium fand anlässlich des Abschlusses eines von 2005 bis 2011 bearbeiteten Forschungsprojektes zur Verbesserung der Temperaturbeständigkeit von 1K-PUR Klebstoffen statt. |
| Published in: | Holz-Zentralblatt |
| Issue: | 3 |
| Pages: | 78 - 78 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting), Natürliche Werkstoffe|Natural Materials |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1328528498 |
| Nebis system number: | 000047754 |
Forschung zur Verklebung von Vollholz
,
Niemz, Peter,
2012
>>
| Author(s): | Niemz, Peter |
| Title: | Forschung zur Verklebung von Vollholz |
| Published in: | Schweizer Holz-Zeitung |
| Volume: | 124 |
| Issue: | 1/2 |
| Pages: | 17 - 17 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Baden-Dättwil |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials |
| Language: | English |
| Review status: | Not reviewed |
| DBID source: | FORM-1326454779 |
| Nebis system number: | 001616552 |
Untersuchungen zur Erkennung von Delaminierungen in Holzverklebungen mittels Ultraschall
,
Müller, Christian, Schnider, Thomas, Niemz, Peter,
2011
>>
| Author(s): | Müller, Christian, Schnider, Thomas, Niemz, Peter |
| Title: | Untersuchungen zur Erkennung von Delaminierungen in Holzverklebungen mittels Ultraschall |
| Abstract: | Die Erkennung von delaminierten Klebfugen ist für die Qualitätskontrolle während der Herstellung und für eine spätere Inspektion im Gebrauchszustand von großer Bedeutung. Es wurden Untersuchungen an Fichtenholz mit künstlich erzeugten Fehlverklebungen durchgeführt. Zu Vergleichszwecken wurden Prüfkörper aus 10 mm Fichtenholz-Lamellen (unverklebt und verklebt) und Brettschichtholz (BSH) untersucht. Unter Einsatz verschiedener Messgeräte wurde mittels Transmissionsverfahren die Schalllaufzeit gemessen. Fehlverklebungen zeichneten sich insbesondere bei zweilagigem Material gut ab. Beim Brettschichtholz wurde eine sichere Interpretation der Messergebnisse durch die Schwankung der Laufzeiten infolge der Variation der Holzeigenschaften teilweise erschwert. |
| Published in: | Holztechnologie |
| Volume: | 52 |
| Issue: | 1 |
| Pages: | 37 - 43 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1310558706 |
| Nebis system number: | 000026159 |
Fractality of eroded coastlines of correlated landscapes
,
Morais, P.A., Oliveira, E.A., Araújo, Nuno A.M., Herrmann, Hans J., Andrade Jr., J.S.,
2011
>>
| Author(s): | Morais, P.A., Oliveira, E.A., Araújo, Nuno A.M., Herrmann, Hans J., Andrade Jr., J.S. |
| Title: | Fractality of eroded coastlines of correlated landscapes |
| Abstract: | Using numerical simulations of a simple sea-coast mechanical erosion model, we investigate the effect of spatial long-range correlations in the lithology of coastal landscapes on the fractal behavior of the corresponding coastlines. In the model, the resistance of a coast section to erosion depends on the local lithology configuration as well as on the number of neighboring sea sides. For weak sea forces, the sea is trapped by the coastline and the eroding process stops after some time. For strong sea forces erosion is perpetual. The transition between these two regimes takes place at a critical sea force, characterized by a fractal coastline front. For uncorrelated landscapes, we obtain, at the critical value, a fractal dimension D=1.33, which is consistent with the dimension of the accessible external perimeter of the spanning cluster in two-dimensional percolation. For sea forces above the critical value, our results indicate that the coastline is self-affine and belongs to the Kardar-Parisi-Zhang universality class. In the case of landscapes generated with power-law spatial long-range correlations, the coastline fractal dimension changes continuously with the Hurst exponent H, decreasing from D=1.34 to 1.04, for H=0 and 1, respectively. This nonuniversal behavior is compatible with the multitude of fractal dimensions found for real coastlines. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 84 |
| Issue: | 1 |
| Pages: | 016102 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1314001925 |
| DOI: | 10.1103/PhysRevE.84.016102 |
| Nebis system number: | 004109079 |
Interarrival times of message propagation on directed networks
,
Mihaljev, Tamara, de Arcangelis, Lucilla, Herrmann, Hans J.,
2011
>>
| Author(s): | Mihaljev, Tamara, de Arcangelis, Lucilla, Herrmann, Hans J. |
| Title: | Interarrival times of message propagation on directed networks |
| Abstract: | One of the challenges in fighting cybercrime is to understand the dynamics of message propagation on botnets, networks of infected computers used to send viruses, unsolicited commercial emails ( SPAM) or denial of service attacks. We map this problem to the propagation of multiple random walkers on directed networks and we evaluate the interarrival time distribution between successive walkers arriving at a target. We show that the temporal organization of this process, which models information propagation on unstructured peer to peer networks, has the same features as SPAM reaching a single user. We study the behavior of the message interarrival time distribution on three different network topologies using two different rules for sending messages. In all networks the propagation is not a pure Poisson process. It shows universal features on Poissonian networks and a more complex behavior on scale free networks. Results open the possibility to indirectly learn about the process of sending messages on networks with unknown topologies, by studying interarrival times at any node of the network. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 84 |
| Issue: | 2 |
| Pages: | 026112 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000294061600002 |
| DOI: | 10.1103/PhysRevE.84.026112 |
| Nebis system number: | 004109079 |
Adhesive penetration of hardwood
,
Mendoza, Miller, Hass, Philipp, Wittel, Falk K., Niemz, Peter, Herrmann, Hans J.,
2012
>>
| Author(s): | Mendoza, Miller, Hass, Philipp, Wittel, Falk K., Niemz, Peter, Herrmann, Hans J. |
| Title: | Adhesive penetration of hardwood |
| Subtitle: | A generic penetration model |
| Abstract: | An analytical model to predict the penetration of adhesives into hardwood is proposed. Penetration into hardwood is dominated by the vessel network which prohibits porous medium approximations. The model considers two scales: (1) a one dimensional capillary fluid transport of a hardening adhesive through a single, straight vessel with diffusion of solvent through the walls of the vessel; and (2) a mesoscopic scale based on topological characteristics of the vessel network. Given an initial amount of adhesive and applied bonding pressure, the portion of the filled structure could be calculated. The model was applied to beech samples joined with three different types of adhesive (PUR, UF, PVAc) under various growth ring angles as described by Hass et al. (2011). The model contains one free parameter that can be adjusted in order to fit the experimental data. |
| Published in: | Wood Science and Technology |
| Volume: | 46 |
| Issue: | 1-3 |
| Pages: | 529 - 549 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General, Agrar- und Forstwissenschaften|Agriculture and Forestry, phenol-formaldehyde, surface-tension, beech wood, network |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | phenol-formaldehyde, surface-tension, beech wood, network |
| DBID source: | WOS-000298993100038 |
| DOI: | 10.1007/s00226-011-0422-2 |
| Nebis system number: | 000057691 |
Traffic gridlock on complex networks
,
Mendes, G.A., Silva, L.R. da, Herrmann, Hans Jürgen,
2012
>>
| Author(s): | Mendes, G.A., Silva, L.R. da, Herrmann, Hans Jürgen |
| Title: | Traffic gridlock on complex networks |
| Abstract: | Here we study how a traffic jam spreads on complex networks when driven by an increasing flux between certain initial and final points. For that purpose, we developed two new traffic models based on vehicular traffic and applied them on the Apollonian network and the Swiss road network. The first model is an electrical analog, using ohmic and non-ohmic resistors which is a classical approach in Physics while the second one which we call the herding model, is based on human driving behavior. For both models, we study the sequence of clogged roads up to the traffic gridlock and display the fragilities of the network. In the electrical model, by increasing the external potential, resistors burn out, as the voltage drop between the ends increases above a certain threshold. Analyzing both models, we observed some power-law functions that occur only near a traffic gridlock as well as the dependence on topological features of the network and influence on flux and the robustness in Apollonian networks of different generations. |
| Published in: | Physica A |
| Volume: | 391 |
| Issue: | 1-2 |
| Pages: | 362 - 370 |
| ISSN: | 0378-4371, 1873-2119 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General, Vehicular traffic, Complex networks, Apollonian network |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Vehicular traffic, Complex networks, Apollonian network |
| DBID source: | WOS-000297230700039 |
| DOI: | 10.1016/j.physa.2011.07.046 |
| Nebis system number: | 001929798 |
Overspill avalanching in a dense reservoir network
,
Mamede, George L., Araujo, Nuno A.M., Schneider, Christian M., Araujo, José C. de, Herrmann, Hans J.,
2012
>>
| Author(s): | Mamede, George L., Araujo, Nuno A.M., Schneider, Christian M., Araujo, José C. de, Herrmann, Hans J. |
| Title: | Overspill avalanching in a dense reservoir network |
| Abstract: | Sustainability of communities, agriculture, and industry is strongly dependent on an effective storage and supply of water resources. In some regions the economic growth has led to a level of water demand that can only be accomplished through efficient reservoir networks. Such infrastructures are not always planned at larger scale but rather made by farmers according to their local needs of irrigation during droughts. Based on extensive data from the upper Jaguaribe basin, one of the world’s largest system of reservoirs, located in the Brazilian semiarid northeast, we reveal that surprisingly it self-organizes into a scale-free network exhibiting also a power-law in the distribution of the lakes and avalanches of discharges. With a new self-organized-criticality-type model we manage to explain the novel critical exponents. Implementing a flow model we are able to reproduce the measured overspill evolution providing a tool for catastrophe mitigation and future planning. |
| Published in: | Proceedings of the National Academy of Sciences of the United States of America : PNAS |
| Volume: | 109 |
| Issue: | 19 |
| Pages: | 7191 - 7195 |
| ISSN: | 0027-8424, 1091-6490 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Washington, DC |
| Publication status: | Published |
| Subjects: | Wissenschaft und Technik allgemein|Science and Technology, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1336659091 |
| DOI: | 10.1073/pnas.1200398109 |
| Nebis system number: | 001003347 |
Model for the genesis of coastal dune fields with vegetation
,
Luna, Marco C.M. de M., Parteli, Eric J.R., Duran, Orencio, Herrmann, Hans J.,
2011
>>
| Author(s): | Luna, Marco C.M. de M., Parteli, Eric J.R., Duran, Orencio, Herrmann, Hans J. |
| Title: | Model for the genesis of coastal dune fields with vegetation |
| Abstract: | Vegetation greatly affects the formation and dynamics of dune fields in coastal areas. In the present work, we use dune modeling in order to investigate the genesis and early development stages of coastal dune fields in the presence of vegetation. The model, which consists of a set of coupled equations for the turbulent wind field over the landscape, the saltation flux and the growth of vegetation cover on the surface, is applied to calculate the evolution of a sand patch placed upwind of a vegetated terrain and submitted to unidirectional wind and constant sand influx. Different dune morphologies are obtained, depending on the characteristic rate of vegetation growth relative to wind strength: barchans, transverse dunes with trailing ridges, parabolic dunes and vegetated, alongshore sand barriers or foredunes. The existence of a vegetation-free backshore is found to be important for the nucleation timescale of coastal dune generations. The role of the sand influx and of the maximum vegetation cover density for the dune shape is also discussed. |
| Published in: | Geomorphology |
| Volume: | 129 |
| Issue: | 3-4 |
| Pages: | 215 - 224 |
| ISSN: | 0169-555X, 1872-695X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Geowissenschaften allgemein|Geosciences, General, Coastal dunes, Parabolic dune, Wind erosion, Sand transport, Dune model |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Coastal dunes, Parabolic dune, Wind erosion, Sand transport, Dune model |
| DBID source: | WOS-000291116800005 |
| DOI: | 10.1016/j.geomorph.2011.01.024 |
| Nebis system number: | 000039875 |
Untersuchungen zu Eigenschaften von Mooreiche
,
Kránitz, Katalin, Baradit, Erik, Dobrowolska, Ewa, Plötze, Michael, Niemz, Peter,
2012
>>
| Author(s): | Kránitz, Katalin, Baradit, Erik, Dobrowolska, Ewa, Plötze, Michael, Niemz, Peter |
| Title: | Untersuchungen zu Eigenschaften von Mooreiche |
| Abstract: | An Mooreichenproben (Quercus robur L.), präpariert aus einem im Fluss Bug (Polen) gelagertem Stamm, wurden Untersuchungen zu physikalisch-mechanischen Eigenschaften durchgeführt. Der auf ein Alter von 150 Jahren datierte Baumstamm lagerte für 7100 ± 50 Jahre im Boden unter einer 3 m dicken Schicht aus Sand und Schlick. Die äußere Zone des Holzes war sehr dunkel (tiefschwarz) gefärbt, wohingegen die Farbe zur Stammmitte heller wurde. Es konnten keine wesentlichen Veränderungen der mechanischen Eigenschaften und des Sorptionsverhaltens am geprüften Holz festgestellt werden. Die Quellung in radialer Richtung sank zur äußeren Zone des Stammes leicht ab und korreliert mit der Farbe. Je dunkler das Holz und damit intensiver die Farbänderung, umso geringer war die radiale Quellung. Tangential war der Einfluss der Position im Stamm auf die Quellung gering. Die Porosität blieb annähernd unverändert. Hinsichtlich der mechanischen Eigenschaften wurde die bekannte Differenzierung von E- und G-Modul in den Hauptachsen ermittelt. Eine leichte Reduzierung des dynamischen E-Modul wurde bei Messungen mittels Ultraschall und dem Gerät BP5 (Frequenz 50 kHz) in Faserrichtung beobachtet. Vor allem mit Zunahme der Dunkelfärbung sank der E-Modul des subfossilen Holzes. |
| Published in: | Holztechnologie |
| Volume: | 53 |
| Issue: | 1 |
| Pages: | 11 - 17 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Dresden |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1326715004 |
| Nebis system number: | 000026159 |
Schwierigkeiten und Chancen in der Laubholzverarbeitung
,
Krackler, Verena, Niemz, Peter,
2011
>>
| Author(s): | Krackler, Verena, Niemz, Peter |
| Title: | Schwierigkeiten und Chancen in der Laubholzverarbeitung |
| Subtitle: | Teil 2: Verwendungsmöglichkeiten von sägefähigem Laubholz |
| Abstract: | Teil 2 der dreiteiligen Publikation beschäftigt sich mit Einsatzgebieten, die sich für Stammholz ergeben können. Im ingenieurtechnischen Vollholzbereich besitzt Laubholz mitunter eine lange Tradition (z. B. Dachstühle, Deckenbalken), dessen Einsatz jedoch mit der Entwicklung von Holzwerkstoffen abnahm. Anwendungsgebiete sind einzelne konstruktive Elemente in Massivholzbauten, Spielplätzen, Lärmschutzwänden, Fassaden oder Eisenbahnschwellen. Zweige des Innenausbaus sind Fenster, Türen oder Parkett. Der Möbelbau beinhaltet u. a. Stühle, Tische, Regale, Polstermöbelgestelle oder Einbaumöbel aller Art. Für nicht konstruktive Vollholz-und Lagenwerkstoffe (Massivholzplatten, Sperrholz) sind Laubhölzer üblich. Hauptrohstoff tragender Produkte in diesen Bereichen (u. a. BSH, Brettsperrholz, Furnierschichtholz) ist dagegen Nadelholz, resultierend aus einer einfacheren Verarbeitung, einem geringeren Preis und der aktuellen Normensituation. Geeignete Modifizierungen, wie die thermische Behandlung oder die Imprägnierung, helfen die Dimension zu stabilisieren und die Anwendungsgebiete zu erweitern. Part 2 of the three part publication deals with possible fields of application involving stem wood. In the area of timber construction hardwoods have a long tradition (e. g. roof structures, joists etc.), however their use has decreased due to the development of wood-based materials. Application fields are single structural elements, playgrounds, noise barriers, wood-facings or railway sleepers. Fields of interior work are doors, windows and parquet flooring. Furniture includes chairs, tables, shelves, upholstery frames and all kinds of built-in furniture. Hardwoods are commonly used for non-structural solid wood materials and ply materials (solid wood panels, plywood). The main raw material for structural timber (e. g. glued laminated timber, cross laminated timber, laminated veneer lumber), however, is still softwood due to the easier processing, the lower price and the currently valid standards. Suitable modifications such as heat treatment and impregnation help to stabilise dimensions and to expand application areas. |
| Published in: | Holztechnologie : Organ der DGfH |
| Volume: | 52 |
| Issue: | 3 |
| Pages: | 5 - 10 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Laubholz, Verwendungsmöglichkeiten, Vollholzprodukte, Holzwerkstoffe, Modifizierung, Hardwood, Possible fields of application, Solid wood products, Wood-based materials, Modification |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Laubholz, Verwendungsmöglichkeiten, Vollholzprodukte, Holzwerkstoffe, Modifizierung, Hardwood, Possible fields of application, Solid wood products, Wood-based materials, Modification |
| DBID source: | FORM-1314112447 |
| Nebis system number: | 000026159 |
Schwierigkeiten und Chancen in der Laubholzverarbeitung
,
Krackler, Verena, Niemz, Peter,
2011
>>
| Author(s): | Krackler, Verena, Niemz, Peter |
| Title: | Schwierigkeiten und Chancen in der Laubholzverarbeitung |
| Subtitle: | Teil 1: Bestandssituation, Eigenschaften und Verarbeitung von Laubholz am Beispiel der Schweiz |
| Abstract: | Das dritte schweizerische Landesforstinventar von 2004 bis 2006 bescheinigte für Laubholz eine Vorratssteigerung von 10,4 %, wohingegen der Nadelholzvorrat insgesamt sank. Entgegen dieser Tendenz wurde 2009 in der Schweiz der Großteil (70 %) des geernteten Laubholzes sogleich energetisch verwertet. Neben dem geringeren Stammholzanteil und der schwierigeren Verarbeitung ist in der Schweiz besonders die nicht geschlossene Wertschöpfungskette vom Rundholz zum Endprodukt ein ausschlaggebendes Problem. In erster Linie fehlt die Weiterverarbeitung des Schnittholzes zum Halb- oder Endfabrikat. Für nicht genutzte Sortimente war daher die energetische Verwertung bisher die komfortabelste und lohnendste Lösung. Die augenblicklichen Probleme sind nur durch die Initiative und Kooperation von Forstwirtschaft, Holz- und Sägeindustrie sowie Politik lösbar. In erster Linie sind Absatzmärkte zu entwickeln, eine Weiterverarbeitungsindustrie aufzubauen, weitere Forschungsprojekte zu lancieren und die Endverbraucher aufzuklären. |
| Published in: | Holztechnologie |
| Volume: | 52 |
| Issue: | 2 |
| Pages: | 5 - 11 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1300263593 |
| Nebis system number: | 000026159 |
Schwierigkeiten und Chancen der Laubholzverarbeitung
,
Krackler, Verena, Niemz, Peter,
2011
>>
| Author(s): | Krackler, Verena, Niemz, Peter |
| Title: | Schwierigkeiten und Chancen der Laubholzverarbeitung |
| Subtitle: | Teil 3: Verwendungsmöglichkeiten von Laubholzresten |
| Abstract: | Die Verarbeitung des Holzes vom Baumstamm zum Endprodukt ist stets mit der Entstehung von Restholz und Holzresten verknüpft. Im Gegensatz zum Nadelholz hat sich jedoch die kaskadische Verwertung von Laubholz noch nicht etabliert. Eindeutig überwiegt die energetische Nutzung, obwohl auch hier die Herstellung von Holzwerkstoffen sowie die stoffliche und chemische Verwertung möglich sind. In Span- und Faserwerkstoffen könnten die derzeitigen Laubholzanteile (10 % bis 40 %) auf bis zu 100 % erhöht werden. Stofflich kann Laubholz in der Lebensmittelindustrie, zur Filtrierung von Schwermetallen und Herstellung von Kunststoffen, Linoleum oder Biowerkstoffen genutzt werden. Durch die Holzchemie lässt sich aus Cellulose Zellstoff, Papier, Celluloseester, Celluloseether, Holzzucker und Regeneratcellulose gewinnen. Besonders vielfältig ist die Verwertung von Lignin als beispielsweise Rohstoff für Vanillin, Binde- und Düngemittel oder Biomaterialien. |
| Published in: | Holztechnologie : Organ der DGfH |
| Volume: | 52 |
| Issue: | 4 |
| Pages: | 5 - 10 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1314084750 |
| Nebis system number: | 000026159 |
Possible fields of hardwood application
,
Krackler, Verena, Keunecke, Daniel, Niemz, Peter, Hurst, Andreas,
2011
>>
| Author(s): | Krackler, Verena, Keunecke, Daniel, Niemz, Peter, Hurst, Andreas |
| Title: | Possible fields of hardwood application |
| Abstract: | One crucial result of the recent Swiss National Forest Inventory (NFI) from 2004-2006 is a volume increase of 10.4 % for hardwood. The softwood volume, in contrast, has decreased. Although other European countries confirm this tendency, Switzerland still uses the bulk (60 %) of the harvested hardwood directly for energetic purposes instead of adding value on it by other applications. Besides the lower percentage of stem wood and the more complicated processing, the main problem in Switzerland is that the value chain from the round timber to an end product is not complete. Therefore the energetic use was and still is the most comfortable and profitable solution for unused assortments. Hardwood use is possible as solid wood and wood composites, but it can even be used as a substance or chemical product. As a solid wood, hardwood has a long tradition (roof structures, stairs, furniture, flooring). Today, it is also employed for wood based materials (solid wood panels, plywood). Scientific analyses reveal that hardwoods nowadays even enter softwood domains such as particle boards, medium density fibreboards, oriented strand boards and structural timber (glued laminated timber, Duo/Trio beams). At the moment, manufacturers are restrained regarding the commercial production due to current standards or failing design bases. In the pulp production, domestic hardwood is more and more repressed as usage of fast-growing plantation lumber increases. To develop marketing channels away from energetic use, it is mainly necessary to build a processing industry in Switzerland. Semi-finished or finished goods should be produced on Swiss terrain and not imported from abroad. |
| Published in: | Wood research |
| Volume: | 56 |
| Issue: | 1 |
| Pages: | 125 - 136 |
| ISSN: | 1336-4561, 0012-6136 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Bratislava |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Hardwood, Processing, Swiss saw industry, Applications |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Hardwood, Processing, Swiss saw industry, Applications |
| DBID source: | FORM-1302858179, WOS-000289875600012 |
| Nebis system number: | 001541175 |
Investigation on moisture behaviour and porosity of thermally modified timber
,
Krackler, Verena, Camathias, Ueli, Ammann, Samuel, Niemz, Peter,
2011
>>
| Author(s): | Krackler, Verena, Camathias, Ueli, Ammann, Samuel, Niemz, Peter |
| Title: | Investigation on moisture behaviour and porosity of thermally modified timber |
| Abstract: | An in Normalklima (20 °C, 65 % rel. LF) konditionierten Proben aus Fichten-, Buchen- und Eschenholz wurde der Einfluss einer thermischen Behandlung (Stickstoffatmosphre, 170 bis 180 °C) auf das Verhalten gegenüber Feuchtenderungen untersucht. In Anlehnung an DIN EN ISO 15148:2003-03 bzw. DIN EN ISO 12572: 2001-09 wurden die Sorptionsgeschwindigkeit, Wasserdampfdiffusionswiderstandszahl, der Wasseraufnahmekoeffizient und ergnzend mittels Quecksilberdruckporosimetrie der Porenanteil bestimmt. Infolge der thermischen Behandlung wurden die Rohdichten von Buche und Esche reduziert (bis –20 %) und die Gesamtporenvolumen erhöht (+3,2 % bzw. +23,4 %). Die thermisch behandelte Fichte hingegen weist zum Teil höhere Rohdichtewerte (+9 %) und damit eine Reduzierung des mittleren Porenanteils (–10 %) auf. Generell bewirkt das verwendete Modifizierungsverfahren eine Abnahme der Sorptionsgeschwindigkeit (bis –62 %) und des Wasseraufnahmekoeffizienten (bis –76 %) sowie eine Anhebung der Wasserdampfdiffusionswiderstandszahl (bis +574 %). Aus den gewonnenen Ergebnissen lsst sich ableiten, dass das Diffusions- und Sorptionsverhalten von thermisch vergütetem Holz weniger von der Änderung der Dichte und des Porenvolumenanteils, sondern mehr durch die Modifizierung hervorgerufene Hydrophobierung beeinflusst wird. Investigation on moisture behaviour and porosity of thermally modified timber. The influence of thermal modification (nitrogen atmosphere, 170 to 180 degrees C) on the moisture behaviour of samples of spruce, beech and ash conditioned under standard climatic conditions (20 degrees C, 65 % relative humidity) was investigated. The sorption rate, water vapour resistance factor and water absorption coefficient were tested according to DIN EN ISO 15148: 2003-03 and DIN EN ISO 12572: 2001-09. Further, the pore volume was determined using mercury porosimetry. As a consequence of the thermal treatment, the raw density of beech and ash was reduced (up to + 20 %) and the total pore volume increased (+ 3.2 and + 23.4 % respectively). The thermally modified spruce, in contrast, partially showed increased raw density values (+ 9 %) and thus a reduction of the pore portion (-10 %). Generally, treatment results in a decrease of the sorption rate (up to -62 %) and the water absorption coefficient (up to -76 %) as well as an increase of the water vapour resistance factor (up to + 574 %). It can be derived from the determined results that the sorption and diffusion behaviour is not dependent on the increase (spruce) or the decrease (beech and ash) of the density and changes in pore volume portion involved, respectively. Primarily it is influenced by the hydrophobising of the thermal treatment. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 6 |
| Pages: | 374 - 381 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Thermisch modifiziertes Holz, Feuchteverhalten, Sorptionsrate, Wasserdampfdiffusionswiderstandszahl, Wasseraufnahmekoeffizient, Porenvolumen, Moisture behaviour, Pore volume, Sorption rate, Thermally modified wood, Water vapour resistance factor, Water absorption coefficient, Feuchte - Moisture |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Thermisch modifiziertes Holz, Feuchteverhalten, Sorptionsrate, Wasserdampfdiffusionswiderstandszahl, Wasseraufnahmekoeffizient, Porenvolumen, Moisture behaviour, Pore volume, Sorption rate, Thermally modified wood, Water vapour resistance factor, Water absorption coefficient, Feuchte - Moisture |
| DBID source: | WOS-000297459400006 |
| DOI: | 10.1002/bapi.201110799 |
| Nebis system number: | 000006704 |
Untersuchungen zum Feuchteverhalten und zur Porosität von termisch modifiziertem Holz
,
Krackler, Verena, Camathias, Ueli, Ammann , Samuel, Niemz, Peter,
2011
>>
| Author(s): | Krackler, Verena, Camathias, Ueli, Ammann , Samuel, Niemz, Peter |
| Title: | Untersuchungen zum Feuchteverhalten und zur Porosität von termisch modifiziertem Holz |
| Abstract: | An in Normalklima (20 °C, 65 % rel. LF) konditionierten Proben aus Fichten-, Buchen- und Eschenholz wurde der Einfluss einer thermischen Behandlung (Stickstoffatmosphre, 170 bis 180 °C) auf das Verhalten gegenüber Feuchtenderungen untersucht. In Anlehnung an DIN EN ISO 15148:2003-03 bzw. DIN EN ISO 12572: 2001-09 wurden die Sorptionsgeschwindigkeit, Wasserdampfdiffusionswiderstandszahl, der Wasseraufnahmekoeffizient und ergnzend mittels Quecksilberdruckporosimetrie der Porenanteil bestimmt. Infolge der thermischen Behandlung wurden die Rohdichten von Buche und Esche reduziert (bis –20 %) und die Gesamtporenvolumen erhöht (+3,2 % bzw. +23,4 %). Die thermisch behandelte Fichte hingegen weist zum Teil höhere Rohdichtewerte (+9 %) und damit eine Reduzierung des mittleren Porenanteils (–10 %) auf. Generell bewirkt das verwendete Modifizierungsverfahren eine Abnahme der Sorptionsgeschwindigkeit (bis –62 %) und des Wasseraufnahmekoeffizienten (bis –76 %) sowie eine Anhebung der Wasserdampfdiffusionswiderstandszahl (bis +574 %). Aus den gewonnenen Ergebnissen lsst sich ableiten, dass das Diffusions- und Sorptionsverhalten von thermisch vergütetem Holz weniger von der Änderung der Dichte und des Porenvolumenanteils, sondern mehr durch die Modifizierung hervorgerufene Hydrophobierung beeinflusst wird. Investigation on moisture behaviour and porosity of thermally modified timber. The influence of thermal modification (nitrogen atmosphere, 170 to 180 °C) on the moisture behaviour of samples of spruce, beech and ash conditioned under standard climatic conditions (20 °C, 65 % relative humidity) was investigated. The sorption rate, water vapour resistance factor and water absorption coefficient were tested according to DIN EN ISO 15148: 2003-03 and DIN EN ISO 12572:2001-09. Further, the pore volume was determined using mercury porosimetry. As a consequence of the thermal treatment, the raw density of beech and ash was reduced (up to +20 %) and the total pore volume increased (+3.2 and +23.4 % respectively). The thermally modified spruce, in contrast, partially showed increased raw density values (+9 %) and thus a reduction of the pore portion (–10 %). Generally, treatment results in a decrease of the sorption rate (up to –62 %) and the water absorption coefficient (up to –76 %) as well as an increase of the water vapour resistance factor (up to +574 %). It can be derived from the determined results that the sorption and diffusion behaviour is not dependent on the increase (spruce) or the decrease (beech and ash) of the density and changes in pore volume portion involved, respectively. Primarily it is influenced by the hydrophobising of the thermal treatment. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 6 |
| Pages: | 374 - 381 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Thermisch modifiziertes Holz, Feuchteverhalten, Sorptionsrate, Wasserdampfdiffusionswiderstandszahl, Wasseraufnahmekoeffizient, Porenvolumen, Moisture behaviour, Pore volume, Sorption rate, Thermally modified wood, Water vapour resistance factor, Water absorption coefficient, Feuchte, Moisture |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Thermisch modifiziertes Holz, Feuchteverhalten, Sorptionsrate, Wasserdampfdiffusionswiderstandszahl, Wasseraufnahmekoeffizient, Porenvolumen, Moisture behaviour, Pore volume, Sorption rate, Thermally modified wood, Water vapour resistance factor, Water absorption coefficient, Feuchte, Moisture |
| DBID source: | FORM-1322661256 |
| DOI: | 10.1002/bapi.201110799 |
| Nebis system number: | 000006704 |
Einflussfaktoren auf die Verklebungsgüte von Laubholz mit 1K PUR nach Nasslagerung
,
Kläusler, Oliver, Wimmer, Rupert, Clauß, Sebastian, Niemz, Peter,
2011
>>
| Author(s): | Kläusler, Oliver, Wimmer, Rupert, Clauß, Sebastian, Niemz, Peter |
| Title: | Einflussfaktoren auf die Verklebungsgüte von Laubholz mit 1K PUR nach Nasslagerung |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | ETH Zürich, IfB, Holzphysik; Boku Wien, Department of Material Sciences and Process Engineering, Wood Technology and Renewable Resources; Wood K plus; WKI Fraunhofer Institut Braunschweig |
| Publication status: | Published |
| Event name: | 5. Kolloquium "Aktuelle Fragen der Holzforschung" |
| Event date: | September 19, 2011 |
| Place: | Tulln, Austria |
| Language: | German |
| Review status: | Unknown |
| DBID source: | FORM-1316783402 |
Einfluss verschiedener mechanischer Holzbearbeitungsverfahren auf die Verklebungsgüte von Buchenholz
,
Kläusler, Oliver, Elstermann, Falko, Rehm, Klaus, Hänsel, Andreas, Niemz, Peter,
2012
>>
| Author(s): | Kläusler, Oliver, Elstermann, Falko, Rehm, Klaus, Hänsel, Andreas, Niemz, Peter |
| Title: | Einfluss verschiedener mechanischer Holzbearbeitungsverfahren auf die Verklebungsgüte von Buchenholz |
| Book title: | Tagungsband des 15. Holztechnologischen Kolloquiums |
| Pages: | 146 - 158 |
| ISBN: | 978-3-86780-266-6 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Not yet published |
| Event name: | 15. Holztechnologischen Kolloquiums |
| Event date: | March 29-30, 2012 |
| Place: | Dresden, Germany |
| Language: | German |
| DBID source: | FORM-1333360355 |
Extractives in some tropical woods
,
Kilic, Ayben, Niemz, Peter,
2012
>>
| Author(s): | Kilic, Ayben, Niemz, Peter |
| Title: | Extractives in some tropical woods |
| Abstract: | Total amount and composition of extractives from 12 different tropical wood species were determined by sequential extraction followed by silylation and GC, GC/MS analysis. Hexane and then acetone/water (5:1) mixture was used successively for the extraction. Generally, very low amounts of lipophilics were found (0.05–0.38 mg/g) and the constituent consisted of fatty acids. Hydrophilics were composed of phenolic acids, flavonoids, sterols, stilbenes and a lignan. The highest amount of hydrophilics was found in Afzelia (36.1 mg/g), while the lowest in Wenge and Opepe (0.30 mg/g). Also, cold-hot water, 1% NaOH and some solvent (acetone, dichloromethane) solubilities were determined. The solubility values of tropical woods except for Canalete were found to increase in the order of solvent, cold water, hot water and 1% NaOH. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 79 - 83 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591302, WOS-000298657600010 |
| DOI: | 10.1007/s00107-010-0489-8 |
| Nebis system number: | 000047744 |
Combination of X-ray and digital image correlation for the analysis of moisture-induced strain in wood
,
Keunecke, Daniel, Novosseletz, Katia, Lanvermann, Christian, Mannes, David, Niemz, Peter,
2011
>>
| Author(s): | Keunecke, Daniel, Novosseletz, Katia, Lanvermann, Christian, Mannes, David, Niemz, Peter |
| Title: | Combination of X-ray and digital image correlation for the analysis of moisture-induced strain in wood |
| Subtitle: | Opportunities and challenges |
| Abstract: | In this present study, the moisture-induced deformation behaviour of a spruce sample was analysed one- and two-dimensionally with high resolution on the radial-tangential surface. For this purpose, an artificial speckle pattern was applied to the surface which was then recorded by a CCD camera during the deformation. The generated TIF images were analysed with a strain mapping software (VIC 2D) that computed the two-dimensional strain field from the surface deformation. Selected options to evaluate two-dimensional data generated with X-ray imaging and digital image correlation are presented. Combining and correlating these techniques enables detailed analysis of structure-function relationships during swelling (and shrinkage) processes in wood. However, several issues still have to be solved to enhance effectiveness and user-friendliness of such investigations, as elucidated in detail in this paper. In dieser Arbeit wurde das feuchte-induzierte Deformationsverhalten einer Fichtenholzprobe ein- und zweidimensional mit hoher Auflösung auf der radial-tangentialen Probenoberfläche analysiert. Dazu wurde ein künstliches Specklemuster auf die Probenoberfläche aufgebracht, welches dann mit einer CCD-Kamera während der Deformation gefilmt wurde. Die generierten TIF-Dateien wurden mit einer Bildkorrelationssoftware (VIC 2D) ausgewertet, welche die zweidimensionalen Dehnungen auf der Probenoberfläche berechnete. Es werden ausgewählte Möglichkeiten zur Auswertung zweidimensionaler Daten vorgestellt, die durch Röntgendurchstrahlung und digitale Bildkorrelation generiert wurden. Einerseits ermöglicht die Kombination und Korrelation dieser Techniken eine detaillierte Analyse von Struktur- Eigenschafts-Beziehungen während der Quell- (und Schwind-) Prozesse in Holz. Andererseits müssen noch einige Probleme gelöst werden, um die Effektivität und die Benutzerfreundlichkeit derartiger Untersuchungsmethoden zu verbessern, was in diesem Artikel im Detail beleuchtet wird. |
| Published in: | European journal of wood and wood products |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Accepted |
| Subjects: | Landwirtschaft allgemein|Agriculture, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317733160 |
| DOI: | 10.1007/s00107-011-0573-8 |
| Nebis system number: | 000047744 |
Stiffness moduli of various softwood and hardwood species determined with ultrasound
,
Keunecke, Daniel, Merz, Tobias, Sonderegger, Walter, Schnider, Thomas, Niemz, Peter,
2011
>>
| Author(s): | Keunecke, Daniel, Merz, Tobias, Sonderegger, Walter, Schnider, Thomas, Niemz, Peter |
| Title: | Stiffness moduli of various softwood and hardwood species determined with ultrasound |
| Abstract: | Comprehensive data sets of the elastic constants are available for only a few European wood species. The goal of this study was to provide stiffnesses for the principal directions and planes for further selected European softwoods and hardwoods, to extend the currently existing data sets. For this purpose, a dynamic technique was chosen: the moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modelling approaches. |
| Published in: | Wood material science & engineering |
| Volume: | 6 |
| Issue: | 3 |
| Pages: | 91 - 94 |
| ISSN: | 1748-0272, 1748-0280 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Colchester |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Elastic constants, Shear modulus, Stiffness modulus, Ultrasound |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Elastic constants, Shear modulus, Stiffness modulus, Ultrasound |
| DBID source: | FORM-1314106466 |
| DOI: | 10.1080/17480272.2010.534555 |
| Nebis system number: | 005350928 |
Density profiles of loose and collapsed cohesive granular structures generated by ballistic deposition
,
Kadau, Dirk, Herrmann, Hans Jürgen,
2011
>>
| Author(s): | Kadau, Dirk, Herrmann, Hans Jürgen |
| Title: | Density profiles of loose and collapsed cohesive granular structures generated by ballistic deposition |
| Abstract: | Loose granular structures stabilized against gravity by an effective cohesive force are investigated on a microscopic basis using contact dynamics. We study the influence of the granular Bond number on the density profiles and the generation process of packings, generated by ballistic deposition under gravity. The internal compaction occurs discontinuously in small avalanches and we study their size distribution. We also develop a model explaining the final density profiles based on insight about the collapse of a packing under changes of the Bond number. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 83 |
| Issue: | 3 |
| Pages: | 031301-1 - 031301-13 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Physik und Astronomie|Physics and Astronomy |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000287912800002 |
| DOI: | 10.1103/PhysRevE.83.031301 |
| Nebis system number: | 004109079 |
A micromechanical model of collapsing quicksand
,
Kadau, Dirk, Andrade, Jose S., Jr., Herrmann, Hans J.,
2011
>>
| Author(s): | Kadau, Dirk, Andrade, Jose S., Jr., Herrmann, Hans J. |
| Title: | A micromechanical model of collapsing quicksand |
| Abstract: | The discrete element method constitutes a general class of modeling techniques to simulate the microscopic behavior (i.e. at the particle scale) of granular/soil materials. We present a contact dynamics method, accounting for the cohesive nature of fine powders and soils. A modification of the model adjusted to capture the essential physical processes underlying the dynamics of generation and collapse of loose systems is able to simulate "quicksand" behavior of a collapsing soil material, in particular of a specific type, which we call "living quicksand". We investigate the penetration behavior of an object for varying density of the material. We also investigate the dynamics of the penetration process, by measuring the relation between the driving force and the resulting velocity of the intruder, leading to a "power law" behavior with exponent 1/2, i.e. a quadratic velocity dependence of the drag force on the intruder. |
| Published in: | Granular matter |
| Volume: | 13 |
| Issue: | 3 |
| Pages: | 219 - 223 |
| ISSN: | 1434-5021, 1434-7636 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Granular matter, Contact dynamics simulations, Distinct element method, Quicksand, Collapsible soil, Biomaterial |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Granular matter, Contact dynamics simulations, Distinct element method, Quicksand, Collapsible soil, Biomaterial |
| DBID source: | WOS-000290676900008 |
| DOI: | 10.1007/s10035-010-0236-1 |
| Nebis system number: | 002003491 |
Vergleichende Untersuchungen zum Feuchte- und Wärmeverhalten unterschiedlicher Holzbauelemente
,
Joščák, Matúš, Sonderegger, Walter, Niemz, Peter, Holm, Andreas, Knus, Markus, Großkinsky, Theo, Lengsfeld, Kristin, Grunewald, John, Plagge, Rudolf,
2011
>>
| Author(s): | Joščák, Matúš, Sonderegger, Walter, Niemz, Peter, Holm, Andreas, Knus, Markus, Großkinsky, Theo, Lengsfeld, Kristin, Grunewald, John, Plagge, Rudolf |
| Title: | Vergleichende Untersuchungen zum Feuchte- und Wärmeverhalten unterschiedlicher Holzbauelemente |
| Abstract: | Auf dem Freilandversuchsgelände des Fraunhofer-Instituts für Bauphysik (IBP) in Holzkirchen wurde das Feuchte- und Wärmeverhalten verschiedener Wandaufbauten aus Holz (geschlitzte Holzkonstruktion, Massivholzkonstruktion, Dämmsteinkonstruktion, Holzplattenkonstruktion, Brettstapelkonstruktion) über die Dauer eines Jahres getestet. Folgende Größen wurden gemessen: Innenraumklima, Außen- und Innenoberflächentemperaturen sowie die Temperaturen an den Grenzschichten, die Wärmestromdichte auf der Innenseite der Bauteile, die relative Luftfeuchte sowie die Holzfeuchte. Das Ziel der Arbeit war einerseits, die verschiedenen Aufbauten unter realen Bedingungen zu vergleichen, andererseits wurden die ermittelten Messdaten für Validierungsberechnungen mittels der Simulationssoftware WUFI®Pro und Delphin verwendet. Die gemessenen, instationären U-Werte stimmen in den Wintermonaten mit den stationär bestimmten Werten gut überein. Bei den Simulationsberechnungen ergeben sich deutlich bessere Ergebnisse, wenn die an der ETH Zürich gemessenen deutlich tieferen Wärmeleitfähigkeiten für Holz anstelle der Normwerte in die Simulation eingesetzt werden. Obwohl bei vier Bauelementen keine Hinterlüftung der Holzfassade bestand, wurden keine kritischen Werte bezüglich der relativen Luftfeuchte innerhalb jener Wandkonstruktionen gemessen. Bei der Simulation der relativen Luftfeuchten zeigten beide Programme teilweise starke Abweichungen gegenüber den gemessenen Werten. At the campus of the Fraunhofer Institute for Building Physics (IBP) in Holzkirchen/Germany comparative measurements of heat and moisture transfer in five different wood-based building elements were carried out (wood construction with slotted wood elements, solid wood construction connected with wooden dowels, new developed soft fibreboard brick construction, solid wood panel construction, wood frame construction with stacked wood elements). The elements were installed on the west side of the test building and examined during one year. The following physical quantities were measured: indoor climate, external and internal surface temperatures, temperatures in the boundary layers, heat flux through the internal surface of the constructions, relative humidity and moisture content. Furthermore, the measured data were used for validation of the simulation softwares WUFI®Pro and Delphin. During winter, the measured U-values (from unsteady-state values) were compared with steady-state calculated U-values. Both values were well coincident. Moreover, the simulation results achieved good agreement by using the thermal conductivity values measured at ETH Zurich, which were considerably lower than the standard values. Although, the four elements had been covered with a non rear-ventilated façade, no critical values of relative humidity were measured inside the constructions. The simulation results of relative humidity have partly shown large deviations from measured data by both simulation softwares. |
| Published in: | Bauphysik |
| Volume: | 33 |
| Issue: | 5 |
| Pages: | 287 - 298 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Delphin, Feuchteschaden, Feuchtetransport, Holzbau, Massivholz, Modellierung, Ständerkonstruktion, Wärmetransport, Validierung, Wäremdämmung, Feuchte, Wärme, WUFI, Heat transfer, Modeling, Moisture damage, Moisture transfer, Solid wood, Wood construction, Wooden post-and-beam structure, Validation, Moisture, Thermal insulation and Heat |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Delphin, Feuchteschaden, Feuchtetransport, Holzbau, Massivholz, Modellierung, Ständerkonstruktion, Wärmetransport, Validierung, Wäremdämmung, Feuchte, Wärme, WUFI, Heat transfer, Modeling, Moisture damage, Moisture transfer, Solid wood, Wood construction, Wooden post-and-beam structure, Validation, Moisture, Thermal insulation and Heat |
| DBID source: | FORM-1318335948, WOS-000296292400003 |
| DOI: | 10.1002/bapi.201110796 |
| Nebis system number: | 000006704 |
Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz
,
Joscak, Matus, Sonderegger, Walter, Niemz, Peter, Oppikofer, Reinhard, Lammar, Laura, Schnider, Thomas,
2012
>>
| Author(s): | Joscak, Matus, Sonderegger, Walter, Niemz, Peter, Oppikofer, Reinhard, Lammar, Laura, Schnider, Thomas |
| Title: | Einfluss von Hohlräumen auf die Wärmeleitfähigkeit von ausgewählten Holzwerkstoffen für den Baueinsatz |
| Abstract: | An ausgewählten Holzwerkstoffen (Buchenfurnier, MDF- und Spanplatten) wurde der Einfluss des Einbringens von Hohlräumen auf die Wärmeleitfähigkeit untersucht. Für die Versuche wurden die Platten in mehreren Lagen geschichtet (Lagendicke je nach Material 2,7 bis 5 mm) und die Aufbauten variiert, wobei Platten mit und ohne Hohlräume verwendet wurden. Um den Einfluss der Wärmestrahlung in den Hohlräumen zu untersuchen, wurden zusätzlich Aluminiumfolien (geringer Emissionsgrad) eingelegt. Es konnte festgestellt werden, dass durch das Einbringen von Hohlräumen (Volumenanteil ca. 46 %) eine Reduzierung der Wärmeleitfähigkeit um bis zu 51 % erreicht wird. Ein zusätzliches Einlegen von Aluminiumfolie quer zur Wärmestromrichtung reduziert die Wärmeleitfähigkeitswerte nochmals wesentlich (bis zu 64 %) aufgrund der stark reduzierten Wärmestrahlung in den Hohlräumen. Dies ist besonders ausgeprägt bei den Aufbauten mit größeren Hohlraumdicken. Um das Potential des Anbringens von Hohlräumen im Holzbauwesen zu nutzen, wurde ein Vorschlag für ein neues Produkt auf Holzbasis präsentiert. |
| Published in: | Bauphysik |
| Volume: | 34 |
| Issue: | 1 |
| Pages: | 32 - 37 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Holzbau, Dämmstoffe, Wärmeleitfhigkeit, Hohlrume, Luftschichten, Neue Produkte, Reflexionsgrad, Energieeinsparung |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Holzbau, Dämmstoffe, Wärmeleitfhigkeit, Hohlrume, Luftschichten, Neue Produkte, Reflexionsgrad, Energieeinsparung |
| DBID source: | FORM-1328535998 |
| DOI: | 10.1002/bapi.201200005 |
| Nebis system number: | 000006704 |
Adsorption of core-shell nanoparticles at liquid–liquid interfaces
,
Isa, Lucio, Amstad, Esther, Schwenke, Konrad, Del Gado, Emanuela, Ilg, Patrick, Kröger, Martin, Reimhult, Erik,
2011
>>
| Author(s): | Isa, Lucio, Amstad, Esther, Schwenke, Konrad, Del Gado, Emanuela, Ilg, Patrick, Kröger, Martin, Reimhult, Erik |
| Title: | Adsorption of core-shell nanoparticles at liquid–liquid interfaces |
| Abstract: | The use of nanoparticles as building blocks for the self-assembly of functional materials has been rapidly increasing in recent years. In particular, two-dimensional materials can be effectively self-assembled at liquid interfaces thanks to particle localization and mobility at the interface in combination with tailoring of specific interactions. Many recent advances have been made in the understanding of the adsorption and assembly at liquid interfaces of small hydrophobic nanoparticles stabilized by short-chain rigid dispersants but the corresponding studies on core-shell nanoparticles sterically stabilized by extended hydrophilic polymer brushes are presently missing. Such particles offer significant advantages in terms of fabrication of functional, responsive and bio-compatible materials. We present here a combination of experimental and numerical data together with an intuitive and simple model aimed at elucidating the mechanisms governing the adsorption of iron oxide nanparticles (5-10 nm) stabilized by low molecular weight poly(ethylene glycol) (1.5-10 kDa). We show that the adsorption dynamics and the structure of the final assembly depend on the free energy of the particles at the interface and discuss the thermodynamics of the adsorption in terms of the polymer solubility in each phase. |
| Published in: | Soft matter |
| Volume: | 7 |
| Issue: | 17 |
| Pages: | 7663 - 7675 |
| ISSN: | 1744-683X, 1744-6848 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Cambridge |
| Publication status: | Published |
| Subjects: | Chemie allgemein|Chemistry, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000294014200010 |
| DOI: | 10.1039/c1sm05407d |
| Nebis system number: | 005061136 |
Non-linear response of dipolar colloidal gels to external fields
,
Ilg, Patrick, Del Gado, Emanuela,
2011
>>
| Author(s): | Ilg, Patrick, Del Gado, Emanuela |
| Title: | Non-linear response of dipolar colloidal gels to external fields |
| Abstract: | Dipolar colloids can be made to gel by forming a reversible but persistent network of chain-like aggregates at very low volume fractions. Using the model of charged soft dumbbells in molecular dynamics simulations, we find that, under the effect of an external electric field, this gel displays a highly non-linear dielectrical susceptibility. We show that the latter is caused by a switch from a network to a structure of bundling chains when the field is strong enough. Such dramatic structural transformation upon applying external fields could allow to control the mechanical and dielectric response of these complex fluids, pointing to new applications of dipolar colloids as smart materials. |
| Published in: | Soft matter |
| Volume: | 7 |
| Issue: | 1 |
| Pages: | 163 - 171 |
| ISSN: | 1744-683X, 1744-6848 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Cambridge, UK |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000285360200023 |
| DOI: | 10.1039/c0sm00592d |
| Nebis system number: | 005061136 |
HPTLC Assessment of Phenolic Extractives in Selected Extraneous Woods
,
Hofmann, Tamás, Niemz, Peter, Levente Albert,
2011
>>
| Author(s): | Hofmann, Tamás, Niemz, Peter, Levente Albert |
| Title: | HPTLC Assessment of Phenolic Extractives in Selected Extraneous Woods |
| Published in: | JPC |
| Volume: | 24 |
| Issue: | 6 |
| Pages: | 539 - 540 |
| ISSN: | 0933-4173, 1789-0993 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Budapest |
| Publication status: | Published |
| Subjects: | Chemie allgemein|Chemistry, General, High-performance thin-layer chromatography (HPTLC), Fingerprinting, Phenolic extractives, Wood |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | High-performance thin-layer chromatography (HPTLC), Fingerprinting, Phenolic extractives, Wood |
| DBID source: | FORM-1318340195, 10.1556/JPC.24.2011.6.16 |
| DOI: | 10.1556/JPC.24.2011.6.16 |
| Nebis system number: | 000474209 |
Granular packings of cohesive elongated particles
,
Hidalgo, R.C., Kadau, D., Kanzaki, T., Herrmann, Hans J.,
2012
>>
| Author(s): | Hidalgo, R.C., Kadau, D., Kanzaki, T., Herrmann, Hans J. |
| Title: | Granular packings of cohesive elongated particles |
| Abstract: | We report numerical results of effective attractive forces on the packing properties of two-dimensional elongated grains. In deposits of non-cohesive rods in 2D, the topology of the packing is mainly dominated by the formation of ordered structures of aligned rods. Elongated particles tend to align horizontally and the stress is mainly transmitted from top to bottom, revealing an asymmetric distribution of local stress. However, for deposits of cohesive particles, the preferred horizontal orientation disappears. Very elongated particles with strong attractive forces form extremely loose structures, characterized by an orientation distribution, which tends to a uniform behavior when increasing the Bond number. As a result of these changes, the pressure distribution in the deposits changes qualitatively. The isotropic part of the local stress is notably enhanced with respect to the deviatoric part, which is related to the gravity direction. Consequently, the lateral stress transmission is dominated by the enhanced disorder and leads to a faster pressure saturation with depth. |
| Published in: | Granular matter |
| Volume: | 14 |
| Issue: | 2 |
| Pages: | 191 - 196 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Kondensierte Materie|Condensed Matter, Granular matter, Molecular dynamics, Non-spherical particles quicksand, Collapsible soil |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Granular matter, Molecular dynamics, Non-spherical particles quicksand, Collapsible soil |
| DBID source: | FORM-1336052128 |
| DOI: | 10.1007/s10035-011-0303-2 |
| Nebis system number: | 002003491 |
Onion-like network topology enhances robustness against malicious attacks
,
Herrmann, Hans J., Schneider, Christian M., Moreira, André A., Andrade, José S., Jr., Havlin, Shlomo,
2011
>>
| Author(s): | Herrmann, Hans J., Schneider, Christian M., Moreira, André A., Andrade, José S., Jr., Havlin, Shlomo |
| Title: | Onion-like network topology enhances robustness against malicious attacks |
| Abstract: | We develop a method to generate robust networks against malicious attacks, as well as to substantially improve the robustness of a given network by swapping edges and keeping the degree distribution fixed. The method, based on persistence of the size of the largest cluster during attacks, was applied to several types of networks with broad degree distributions, including a real network-the Internet. We find that our method can improve the robustness significantly. Our results show that robust networks have a novel 'onion-like' topology consisting of a core of highly connected nodes hierarchically surrounded by rings of nodes with decreasing degree. |
| Published in: | Journal of statistical mechanics |
| Pages: | P01027 |
| ISSN: | 1742-5468 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Subjects: | Network reconstruction, Network dynamcis, Communication, supply and information networks, Robust and stochastic optimization |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Network reconstruction, Network dynamcis, Communication, supply and information networks, Robust and stochastic optimization |
| DBID source: | WOS-000286629000030 |
| DOI: | 10.1088/1742-5468/2011/01/P01027 |
| Nebis system number: | 004699119 |
Watersheds and Explosive percolation
,
Herrmann, Hans J., Araújo, Nuno A.M.,
2011
>>
| Author(s): | Herrmann, Hans J., Araújo, Nuno A.M. |
| Title: | Watersheds and Explosive percolation |
| Abstract: | The recent work by Achlioptas, D'Souza, and Spencer opened up the possibility of obtaining a discontinuous (explosive) percolation transition by changing the stochastic rule of bond occupation. Despite the active research on this subject, several questions still remain open about the leading mechanism and the properties of the system. We review the largest cluster and the Gaussian models recently introduced. We show that, to obtain a discontinuous transition it is solely necessary to control the size of the largest cluster, suppressing the growth of a cluster di_ering significantly, in size, from the average one. As expected for a discontinuous transition, a Gaussian cluster-size distribution and compact clusters are obtained. The surface of the clusters is fractal, with the same fractal dimension of the watershed line. |
| Book title: | CSP 2011 24th Annual Workshop on Recent Developments in Computer Simulation Studies in Condensed Matter Physics (2011 02 21 - 2011 02 25 Athens, GA, USA) |
| Published in: | Physics procedia |
| Volume: | 15 |
| Pages: | 37 - 43 |
| ISSN: | 1875-3892 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Explosive percolation, Discontinuous phase transitions, Percolation threshold, Watershed, Fractal interface |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Explosive percolation, Discontinuous phase transitions, Percolation threshold, Watershed, Fractal interface |
| DBID source: | FORM-1314002508, WOS-000298500600007 |
| DOI: | 10.1016/j.phpro.2011.05.057 |
| Nebis system number: | 006360145 |
Characterisation of moisture-dependent plasticity of beech wood and its application to a multi-surface plasticity model
,
Hering, Stefan, Saft, Susanne, Resch, Eckart, Niemz, Peter, Kaliske, Michael,
2012
>>
| Author(s): | Hering, Stefan, Saft, Susanne, Resch, Eckart, Niemz, Peter, Kaliske, Michael |
| Title: | Characterisation of moisture-dependent plasticity of beech wood and its application to a multi-surface plasticity model |
| Abstract: | The moisture-dependent stress-strain behaviour of European beech wood (Fagus sylvatica L.) has been determined under compression, analytically described for the radial and tangential direction using a modified Ramberg-Osgood approach and realized numerically by a multi-surface plasticity model. The conspicuous decrease of the stress-strain characteristic perpendicular to the grain with increasing moisture content is similar to the behaviour of the presented ultimate strength values in the longitudinal direction. Based on input parameters previously quantified by means of an inverse finite element analysis, the simulation of a crosswise laminated two-layer arrangement during moistening was carried out. A distinct development of plastified regions can be observed due to the resulting swelling stresses. |
| Published in: | Holzforschung |
| Volume: | 66 |
| Issue: | 3 |
| Pages: | 373 - 380 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting), Beech, Compression test, Finite element method, Inverse analysis, Material strength, Moisture, Multi-surface plasticity (MSP) |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Beech, Compression test, Finite element method, Inverse analysis, Material strength, Moisture, Multi-surface plasticity (MSP) |
| DBID source: | FORM-1331638556 |
| DOI: | 10.1515/HF.2011.162 |
| Nebis system number: | 000047746 |
Modelling the mechanical stresses in adhesive joints of wood bondings considering the mechanical and moisture behaviour of the adherend
,
Hering, Stefan, Niemz, Peter,
2011
>>
| Author(s): | Hering, Stefan, Niemz, Peter |
| Title: | Modelling the mechanical stresses in adhesive joints of wood bondings considering the mechanical and moisture behaviour of the adherend |
| Abstract: | Wood bondings have been used in timber construction and many other applications for a long time. Using layered arrangements, the homogenisation of the anisotropic physical and mechanical properties of solid wood reduce the influence of moisture and improve the mechanical behaviour of structural elements. However, new weak points can be created and effects such as debonding and delamination can occur. These failure characteristics depend on mechanical and hygroscopic loading as well as the composition of the structural components. Hence, delamination can be reduced by adjusting the properties of the appropriate adherent or by changing the structural assembly of the specific elements. Using finite element analysis, the influence of the adherent properties during the testing procedure and an example of cross-laminated wood panels on the adhesive load is investigated. The results show significant differences in the glue line stress distribution for varied growth ring angle, longitudinal Young’s modulus, diffusion as well as swelling and shrinkage properties. |
| Book title: | Proceedings of the International Conference on Structural Health Assessment of Timber Structures |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Published |
| Subjects: | Mechanical stresses, Glued wood, Modelling, Hygroscopic load |
| Event name: | International Conference on Structural Health Assessment of Timber Structures (SHATIS´11) |
| Event date: | June 16-17, 2011 |
| Place: | Lisbon, Portugal |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Mechanical stresses, Glued wood, Modelling, Hygroscopic load |
| DBID source: | FORM-1309871249 |
Adhesive penetration in beech wood
,
Hass, Philipp, Wittel, Falk K., Mendoza, Miller, Herrmann, Hans J., Niemz, Peter,
2012
>>
| Author(s): | Hass, Philipp, Wittel, Falk K., Mendoza, Miller, Herrmann, Hans J., Niemz, Peter |
| Title: | Adhesive penetration in beech wood |
| Subtitle: | Experiments |
| Abstract: | A study with synchrotron radiation X-ray tomographic microscopy (SRXTM) of PUR, PVAc, and UF adhesive bond lines in beech wood, bonded under various growth ring angles, is presented. The bond line morphologies and the adhesive penetration into the wood structure were evaluated after determining the hardening characteristics of the adhesives. Distinct bond line imperfections were found for the different adhesive systems. To describe the adhesive distribution inside the bond line, the saturation of the pore space instead of the commonly used maximum penetration depth seems to be adequate. |
| Published in: | Wood science and technology |
| Volume: | 46 |
| Issue: | 1-3 |
| Pages: | 243 - 256 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General, Landwirtschaft allgemein|Agriculture, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317740361, WOS-000298993100018 |
| DOI: | 10.1007/s00226-011-0410-6 |
| Nebis system number: | 000057691 |
Mikromechanische Untersuchungen zum Versagensverhalten von Klebfugen
,
Hass, Philipp, Wittel, Falk K., Herrmann, Hans J., Niemz, Peter,
2011
>>
| Author(s): | Hass, Philipp, Wittel, Falk K., Herrmann, Hans J., Niemz, Peter |
| Title: | Mikromechanische Untersuchungen zum Versagensverhalten von Klebfugen |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Published |
| Event name: | 5. Kolloquium : Aktuelle Fragen der Holzforschung |
| Event date: | September 19, 2011 |
| Place: | Tulln, Austria |
| Language: | German |
| Review status: | Unknown |
| DBID source: | FORM-1326902324 |
Moisture behaviour of recent and natural aged wood
,
Gereke, Thomas, Anheuser, Kilian, Lehmann, Eberhard, Kranitz, Katalin, Niemz, Peter,
2011
>>
| Author(s): | Gereke, Thomas, Anheuser, Kilian, Lehmann, Eberhard, Kranitz, Katalin, Niemz, Peter |
| Title: | Moisture behaviour of recent and natural aged wood |
| Abstract: | Furniture and other wooden objects in historic buildings are often exposed to important variations in relative humidity. Degradation effects resulting from cyclic or irreversible swelling and shrinkage of wood are well known and pose an important threat to the preservation of our cultural heritage. This paper reports differences in behaviour between recent and naturally aged wood. Sorption hysteresis measurements were carried out at room temperature. The response of wood to moisture variations, i.e. swelling and shrinkage, was tested in different steps of relative humidity simulating realistic conditions. Additionally, Young's and shear moduli were calculated from ultrasound velocity. The results demonstrate little if any difference between the two groups, indicating that conclusions drawn from the study of modern wood are also valid for historic wood in good condition. Finite element modelling of the deformation of wooden panels subjected to environmental changes demonstrates that works of art coated with a layer of reduced permeability on one side are more at risk from mechanical damage through deformation than objects without coating. |
| Published in: | Wood research |
| Volume: | 56 |
| Issue: | 1 |
| Pages: | 33 - 42 |
| ISSN: | 1336-4561, 0012-6136 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Bratislava |
| Publication status: | Published |
| Subjects: | Werkstoffe|Materials Sciences, Dimensional stability, Elastic moduli, Finite element modeling, Moisture, Relative humidity |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Dimensional stability, Elastic moduli, Finite element modeling, Moisture, Relative humidity |
| DBID source: | WOS-000289875600004 |
| Nebis system number: | 001541175 |
Modelling the hyphal growth of the wood-decay fungus Physisporinus vitreus
,
Fuhr, M. J., Schubert, M., Schwarze, F. W. M. R., Herrmann, H. J.,
2011
>>
| Author(s): | Fuhr, M. J., Schubert, M., Schwarze, F. W. M. R., Herrmann, H. J. |
| Title: | Modelling the hyphal growth of the wood-decay fungus Physisporinus vitreus |
| Abstract: | The white-rot fungus, Physisporinus vitreus, degrades the membranes of bordered pits in tracheids and consequently increases the permeability of wood, which is a process that can be used by the wood industry to improve the uptake of wood preservatives and environmentally benign wood modification substances to enhance the use and sustainability of native conifer wood species. To understand and apply this process requires an understanding of how a complex system (fungus wood) interacts under defined conditions. We present a three-dimensional fungal growth model (FGM) of the hyphal growth of P. vitreus in the heartwood of Norway spruce. The model considers hyphae and nutrients as discrete structures and links the microscopic interactions between fungus and wood (e.g. degradation rate and degree of opening of pits) with macroscopic system properties, such penetration depth of the fungus, biomass, and distribution of destroyed pits in early- and latewood. Simulations were compared with experimental data. The growth of P. vitreus is characterized by a stepwise capture of the substrate and the effect of this on wood according to different model parameters is discussed. |
| Published in: | Fungal Biology |
| Volume: | 115 |
| Issue: | 9 |
| Pages: | 919 - 932 |
| ISSN: | 1878-6146 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Oxford |
| Publication status: | Published |
| Subjects: | Mykologie|Mycology, Bordered pit, Filamentous fungus, Fungal colony, Mycelia modelling, Picea abies |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Bordered pit, Filamentous fungus, Fungal colony, Mycelia modelling, Picea abies |
| DBID source: | WOS-000295300200013 |
| DOI: | 10.1016/j.funbio.2011.06.017 |
| Nebis system number: | 005958968 |
Mechanical behaviour of finger joints at elevated temperatures
,
Frangi, Andrea, Bertocchi, Marco, Clauß, Sebastian, Niemz, Peter,
2011
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| Author(s): | Frangi, Andrea, Bertocchi, Marco, Clauß, Sebastian, Niemz, Peter |
| Title: | Mechanical behaviour of finger joints at elevated temperatures |
| Abstract: | Finger joints are commonly used to produce engineered wood products like glued laminated timber beams. Although comprehensive research has been conducted on the structural behaviour of finger joints at ambient temperature, there is very little information about the structural behaviour at elevated temperature. A comprehensive research project on the fire resistance of bonded timber elements is currently ongoing at the ETH Zurich. The aim of the research project is the development of simplified design models for the fire resistance of bonded structural timber elements taking into account the behaviour of the adhesive used at elevated temperature. The paper presents the results of a first series of tensile and bending tests on specimens with finger joints pre-heated in an oven. The tests were carried out with different adhesives that fulfil current approval criteria for the use in loadbearing timber components. The results showed substantial differences in temperature dependant strength reduction and failure between the different adhesives tested. Thus, the structural behaviour of finger joints at elevated temperature is strongly influenced by the behaviour of the adhesive used for bonding and may govern the fire design of engineered wood products like glued laminated timber beams. |
| Published in: | Wood science and technology |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | München |
| Publication status: | Accepted |
| Subjects: | Wirtschaft, Recht und Politik|Economics, Law and Politics, Agrar- und Forstwissenschaften|Agriculture and Forestry |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1324154476 |
| DOI: | 10.1007/s00226-011-0444-9 |
| Nebis system number: | 000057691 |
Impact of perturbations on watersheds
,
Fehr, Eric Marcel, Kadau, Dirk, Andrade Jr., José S., Herrmann, Hans Jürgen,
2011
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| Author(s): | Fehr, Eric Marcel, Kadau, Dirk, Andrade Jr., José S., Herrmann, Hans Jürgen |
| Title: | Impact of perturbations on watersheds |
| Abstract: | We find that watersheds in real and artificial landscapes can be strongly affected by small, local perturbations like landslides or tectonic motions. We observe power-law scaling behavior for both the distribution of areas enclosed by the original and the displaced watershed as well as the probability density to induce, after perturbation, a change at a given distance. Scaling exponents for real and artificial landscapes are determined, where in the latter case the exponents depend linearly on the Hurst exponent of the applied fractional Brownian noise. The obtained power laws are shown to be independent on the strength of perturbation. Theoretical arguments relate our scaling laws for uncorrelated landscapes to properties of invasion percolation. |
| Published in: | Physical review letters |
| Volume: | 106 |
| Issue: | 4 |
| Pages: | 048501-1 - 048501-4 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000286736000026 |
| DOI: | 10.1103/PhysRevLett.106.048501 |
| Nebis system number: | 000003868 |
Scaling relations for watersheds
,
Fehr, E., Kadau, D., Araújo, N.A.M., Andrade, J.S., Herrmann, Hans Jürgen,
2011
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| Author(s): | Fehr, E., Kadau, D., Araújo, N.A.M., Andrade, J.S., Herrmann, Hans Jürgen |
| Title: | Scaling relations for watersheds |
| Abstract: | We study the morphology of watersheds in two and three dimensional systems subjected to different degrees of spatial correlations. The response of these objects to small, local perturbations is also investigated with extensive numerical simulations. We find the fractal dimension of the watersheds to generally decrease with the Hurst exponent, which quantifies the degree of spatial correlations. Moreover, in two dimensions, our results match the range of fractal dimensions 1.10≤df≤1.15 observed for natural landscapes. We report that the watershed is strongly affected by local perturbations. For perturbed two and three dimensional systems, we observe a power-law scaling behavior for the distribution of areas (volumes) enclosed by the original and the displaced watershed and for the distribution of distances between outlets. Finite-size effects are analyzed and the resulting scaling exponents are shown to depend significantly on the Hurst exponent. The intrinsic relation between watershed and invasion percolation, as well as relations between exponents conjectured in previous studies with two dimensional systems, are now confirmed by our results in three dimensions. |
| Published in: | Physical Review E |
| Volume: | 84 |
| Issue: | 3 |
| Pages: | 036116 - 1539-3755 |
| ISSN: | 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1318863258, WOS-000296503400001 |
| DOI: | 10.1103/PhysRevE.84.036116 |
| Nebis system number: | 004109079 |
Multiparticle Sintering Dynamics
,
Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E.,
2011
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| Author(s): | Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E. |
| Title: | Multiparticle Sintering Dynamics |
| Subtitle: | From Fractal-Like Aggregates to Compact Structures |
| Abstract: | Multiparticle sintering is encountered in almost all high temperature processes for material synthesis (titania, silica, and nickel) and energy generation (e.g., fly ash formation) resulting in aggregates of primary particles (hard- or sinter-bonded agglomerates). This mechanism of particle growth is investigated quantitatively by mass and energy balances during viscous sintering of amorphous aerosol materials (e.g., SiO2 and polymers) that typically have a distribution of sizes and complex morphology. This model is validated at limited cases of sintering between two (equally or unequally sized) particles, and chains of particles. The evolution of morphology, surface area and radii of gyration of multiparticle aggregates are elucidated for various sizes and initial fractal dimension. For each of these structures that had been generated by diffusion limited (DLA), cluster-cluster (DLCA), and ballistic particle-cluster agglomeration (BPCA) the surface area evolution is monitored and found to scale differently than that of the radius of gyration (moment of inertia). Expressions are proposed for the evolution of fractal dimension and the surface area of aggregates undergoing viscous sintering. These expressions are important in design of aerosol processes with population balance equations (PBE) and/or fluid dynamic simulations for material synthesis or minimization and even suppression of particle formation. |
| Published in: | Langmuir |
| Volume: | 27 |
| Issue: | 10 |
| Pages: | 6358 - 6367 |
| ISSN: | 0743-7463, 1520-5827 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Washington, DC |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000290292900075 |
| DOI: | 10.1021/la200546g |
| Nebis system number: | 000033499 |
Aggregate morphology evolution by sintering
,
Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E.,
2012
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| Author(s): | Eggersdorfer, Max L., Kadau, Dirk, Herrmann, Hans J., Pratsinis, Sotiris E. |
| Title: | Aggregate morphology evolution by sintering |
| Subtitle: | Number and diameter of primary particles |
| Abstract: | The structure of fractal-like agglomerates (physically bonded) and aggregates (chemically or sinter-bonded) is important in aerosol synthesis of nanoparticles, and in monitoring combustion emissions and atmospheric particles. It also influences particle mobility, scattering and eventually performance of nanocomposites, suspensions and devices made with such particles. Here, aggregate sintering by viscous flow of amorphous materials (silica, polymers) and grain boundary diffusion of crystalline ceramics (titania, alumina) or metals (Ni, Fe, Ag, etc.) is investigated. A scaling law is found between average aggregate projected area and equivalent number of constituent primary particles during sintering: from fractal-like agglomerates to aggregates and eventually compact particles (e.g. spheres). This is essentially a relation independent of time, material properties and sintering mechanisms. It is used to estimate the equivalent primary particle diameter and number in aggregates. The evolution of aggregate morphology or structure is quantified by the effective fractal dimension (Df) and mass–mobility exponent (Dfm) and the corresponding prefactors. The Dfm increases monotonically during sintering converging to 3 for a compact particle. Therefore Dfm and its prefactor could be used to gage the degree or extent of sintering of agglomerates made by a known collision mechanism. This analysis is exemplified by comparison to experiments of silver nanoparticle aggregates sintered at different temperatures in an electric tube furnace. |
| Published in: | Journal of aerosol science |
| Volume: | 46 |
| Pages: | 7 - 19 |
| ISSN: | 0021-8502 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Umweltdaten, Boden, Luft, Klima, Schadstoffe|Environmental Data, Soil, Air, Climate, Pollutants, Aggregate, Fractal dimension, Grain boundary diffusion, Mass-mobility exponent, Primary particle size |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Aggregate, Fractal dimension, Grain boundary diffusion, Mass-mobility exponent, Primary particle size |
| DBID source: | FORM-1329817714, WOS-000301760900002 |
| DOI: | 10.1016/j.jaerosci.2011.11.005 |
| Nebis system number: | 000034158 |
Size distribution and structure of Barchan dune fields
,
Durán, O., Schwämmle, V., Lind, P.G., Herrmann, Hans J.,
2011
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| Author(s): | Durán, O., Schwämmle, V., Lind, P.G., Herrmann, Hans J. |
| Title: | Size distribution and structure of Barchan dune fields |
| Abstract: | Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction. |
| Published in: | Nonlinear processes in geophysics |
| Volume: | 18 |
| Issue: | 4 |
| Pages: | 455 - 467 |
| ISSN: | 1023-5809, 1607-7946 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Katlenburg-Lindau |
| Publication status: | Published |
| Subjects: | Geophysik |Geophysics |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1314002269, WOS-000294437200002 |
| DOI: | 10.5194/npg-18-455-2011 |
| Nebis system number: | 001428645 |
Scaling between structural relaxation and particle caging in a model colloidal gel
,
De Michele, C., Del Gado, E., Leporini, D.,
2011
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| Author(s): | De Michele, C., Del Gado, E., Leporini, D. |
| Title: | Scaling between structural relaxation and particle caging in a model colloidal gel |
| Abstract: | In glassy dynamics, the rattling of particles in a cage formed by their neighbors is typically limited to a length scale of the order of the particle diameter but is nevertheless strongly coupled to the overall structural arrest of the system (solidification). Furthermore, the rattling amplitude and the structural relaxation time have been recently shown to follow the same scaling form in various polymer melts and supercooled liquids. In this paper we analyze from this perspective for the first time the glassy dynamics emerging from the formation of a persistent network in a model colloidal gel at very low density. The structural relaxation time of the gel network is compared with the mean squared displacement at short times, corresponding to the localization length associated to the presence of energetic bonds. Interestingly, we find that the same type of scaling as for the dense glassy systems holds. Our findings elucidate the strong coupling between the cooperative rearrangements of the gel network and the single particle localization in the structure, and support the general nature of the scaling proposed. |
| Published in: | Soft matter |
| Volume: | 7 |
| Issue: | 8 |
| Pages: | 4025 - 4031 |
| ISSN: | 1744-683X, 1744-6848 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Cambridge |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000289173500049 |
| DOI: | 10.1039/c0sm00941e |
| Nebis system number: | 005061136 |
Influence of the adhesive formulation on the mechanical properties and bonding performance of polyurethane prepolymers
,
Clauß, Sebastian, Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Niemz, Peter,
2011
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| Author(s): | Clauß, Sebastian, Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Niemz, Peter |
| Title: | Influence of the adhesive formulation on the mechanical properties and bonding performance of polyurethane prepolymers |
| Abstract: | Only small amounts of additives are needed to formulate one-component polyurethane (1C PUR) adhesives for various applications. The current study illuminates the effects of the formulation on the mechanical properties of pure adhesives, on the one hand, and their performance in bonded wood joints on the other. Tensile shear tests on bonded wood joints, tensile tests on adhesive films, and nanoindentation measurements in the interphase region of the bond were performed. Analyses by means of infrared, atomic force, and electron microscopy provided the explanatory basis for the results obtained. Additionally to laboratory made 1C PUR, unmodified commercial 1C PUR, melamine-urea-formaldehyde (MUF), and phenol-resorcinol-formaldehyde (PRF) were tested for comparison. The results obtained confirm that the mechanical properties of 1C PUR adhesives are significantly affected by their prepolymer composition. The adhesive formulation by means of additives, on the other hand, does not affect the mechanical properties but is to a large extent responsible for the bonding performance. |
| Published in: | Holzforschung |
| Volume: | 65 |
| Issue: | 6 |
| Pages: | 835 - 844 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | 1C PUR, Adhesives for wood, AFM, ATR, ESEM, FTIR, Film, Lap-shear, Mechanical properties, Nano-indentation, Polyurethane, Prepolymer |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | 1C PUR, Adhesives for wood, AFM, ATR, ESEM, FTIR, Film, Lap-shear, Mechanical properties, Nano-indentation, Polyurethane, Prepolymer |
| DBID source: | FORM-1318338686, WOS-000297527600008 |
| DOI: | 10.1515/HF.2011.095 |
| Nebis system number: | 000047746 |
Improving the thermal stability of one-component polyurethane adhesives by adding filler material
,
Clauß, Sebastian, Allenspach, Karin, Gabriel, Joseph, Niemz, Peter,
2011
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| Author(s): | Clauß, Sebastian, Allenspach, Karin, Gabriel, Joseph, Niemz, Peter |
| Title: | Improving the thermal stability of one-component polyurethane adhesives by adding filler material |
| Abstract: | The aim of the current study is to improve the thermal stability of one-component moisture-curing polyurethane adhesives. The approach here tends to add suitable filler materials to the adhesive and to study the resulting effects. The investigation covers mechanical tests to determine the shear strength of the glued wood joints according to EN 302-1 (2004). Furthermore, the distribution of the filler material within the adhesive is shown by means of environmental scanning electron microscopy combined with energy-dispersive X-ray spectroscopy analysis. The thermal stability of the glued wood joints could be significantly improved by adding chalk with a volume fraction of 30% to the adhesive. |
| Published in: | Wood science and technology |
| Volume: | 45 |
| Issue: | 2 |
| Pages: | 383 - 388 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General, Wirtschaft, Recht und Politik allgemein|Economics, Law and Politics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV-, WOS-000289477300016 |
| DOI: | 10.1007/s00226-010-0321-y |
| Nebis system number: | 000057691 |
Improving the thermo-mechanical properties of one-component polyurethane adhesives by organic fillers
,
Clauss, Sebastian, Niemz, Peter,
2011
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| Author(s): | Clauss, Sebastian, Niemz, Peter |
| Title: | Improving the thermo-mechanical properties of one-component polyurethane adhesives by organic fillers |
| Book title: | Novel materials from Wood or cellulose : Proceedings of the 2011 IAWS annual meeting on Novel materials from Wood or cellulose |
| Pages: | 56 - 57 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Stockholm |
| Publication status: | Published |
| Event name: | Annual meeting of IAWS 2011 : Novel materials from wood or cellulose |
| Event date: | August 31 - September 2, 2011 |
| Place: | Stockholm, Sweden |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1316705538 |
Thermal stability of glued wood joints measured by shear tests
,
Clauss, Sebastian, Joscak, Matus, Niemz, Peter,
2011
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| Author(s): | Clauss, Sebastian, Joscak, Matus, Niemz, Peter |
| Title: | Thermal stability of glued wood joints measured by shear tests |
| Abstract: | The thermal stability of glued wood joints is an important criterion to determine the suitability of adhesives in the field of engineered wood. During their product life, glued wood joints can be exposed to high temperatures in various ways (direct exposure to the sun, fire, etc.). Thereby the cohesiveness of the adhesive must not degrade. This raises the question of how the strength of bonding changes under thermal load. The current investigation covers the influence of temperature (T = 20 to 220°C) on the shear strength of glued wood joints. Different adhesive systems were investigated. With increasing temperature, the shear strength of solid wood and also of glued wood joints decreased. There were big differences in thermal stability and failure behaviour between the adhesive systems as well as within the polyurethane group. The thermal stability of one-component polyurethane systems can be greatly varied by modifying their chemical structure. Well adapted onecomponent polyurethane adhesives reach a strength similar to that of phenol resorcinol resin. Die Temperaturbeständigkeit von Klebstoffverbindungen ist ein wichtiges Kriterium um die Eignung eines Klebstoffes für den Holzleimbau zu beurteilen. Klebstoffe können hohen Temperaturen in vielfältiger Weise ausgesetzt sein (direkte Sonneneinstrahlung, Feuer, etc.), jedoch sollte sich die Festigkeit der Verbindungen dabei möglichst wenig verringern. Daraus resultiert die Frage, inwiefern sich verschiedene Klebstoffsysteme unter thermischer Belastung bezüglich ihrer Festigkeit unterscheiden. In der vorliegenden Untersuchung wurden Klebstoffverbindungen im Temperaturbereich von 20 bis 220°C hinsichtlich ihrer Zugscherfestigkeit untersucht. Mit zunehmender Temperatur nahm die Festigkeit von Vollholz und auch von Holz-Klebstoffverbindungen ab. Dabei waren deutliche Unterschiede sowohl zwischen den Klebstoffsystemen als auch innerhalb der Polyurethane zu verzeichnen. Die Temperaturbeständigkeit von Polyurethanen kann durch Variation der chemischen Komponenten an den jeweiligen Temperaturbereich angepasst werden, sodass Festigkeiten wie bei Phenol-Resorcin-Formaldehyd-Klebstoff erreicht werden. |
| Published in: | European Journal of Wood and Wood Products |
| Volume: | 69 |
| Issue: | 1 |
| Pages: | 101 - 111 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV-, WOS-000286432300013 |
| DOI: | 10.1007/s00107-010-0411-4 |
| Nebis system number: | 000047744 |
Influence of the chemical structure of PUR prepolymers on thermal stability
,
Clauss, Sebastian, Dijkstra,Dirk J., Gabriel, Joseph, Kläusler, Oliver, Matner, Mathias, Meckel, Walter, Niemz, Peter,
2011
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| Author(s): | Clauss, Sebastian, Dijkstra,Dirk J., Gabriel, Joseph, Kläusler, Oliver, Matner, Mathias, Meckel, Walter, Niemz, Peter |
| Title: | Influence of the chemical structure of PUR prepolymers on thermal stability |
| Abstract: | The thermal stability of adhesives for load-bearing construction has been one of their key parameters since engineered wood products were introduced in timber construction. In the case of one-component moisture-curing polyurethane (1C PUR) adhesives, knowledge about relationships between their chemical structure and the resulting bonding properties is limited, especially under high-temperature conditions. In this study the structure–property relationships of 1C PUR prepolymers were analyzed in the temperature range from 20 to 200 °C by means of mechanical and rheological tests. NCO-terminated urethane prepolymers were prepared from systematically varied MDI and polyether mixtures. The structural parameters investigated were the urea and urethane group content, cross-link density, ethylene oxide content and the adjustment of functionality via NCO or polyether component. Bonded wood joints were tested for their tensile shear strength and polymer films were analyzed by means of DMA and DSC. The results revealed a significant influence of hard segment content and cross-link density on the thermal stability of the prepolymers. Not all parameters that affect the film properties significantly influence bonding. |
| Published in: | International journal of adhesion and adhesives |
| Volume: | 31 |
| Issue: | 6 |
| Pages: | 513 - 523 |
| ISSN: | 0143-7496, 1879-0127 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Kidlington |
| Publication status: | Published |
| Subjects: | Maschinenbau allgemein|Mechanical Engineering, General, Dynamic mechanical analysis, Lap-shear, Polyurethane, Adhesives for wood, Thermal stability |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Dynamic mechanical analysis, Lap-shear, Polyurethane, Adhesives for wood, Thermal stability |
| DBID source: | FORM-1314615550 |
| DOI: | 10.1016/j.ijadhadh.2011.05.005 |
| Nebis system number: | 000009105 |
Influence of the Filler Material on the Thermal Stability of One-Compoent Moisture-Curing Polyurethane Adhesives
,
Clauss, Sebastian, Dijkstra, Dirk J., Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Meckel, Walter, Niemz, Peter,
2012
>>
| Author(s): | Clauss, Sebastian, Dijkstra, Dirk J., Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Meckel, Walter, Niemz, Peter |
| Title: | Influence of the Filler Material on the Thermal Stability of One-Compoent Moisture-Curing Polyurethane Adhesives |
| Abstract: | Filler materials are part and parcel for the adjustment of adhesives, in particular, their rheological and mechanical properties. Furthermore, the thermal stability of adhesives can be positively influenced by the addition of an expedient filler, with inorganic types common practice in most cases. In this study, one-component moisture-curing polyurethane adhesives for engineered wood products based on isocyanate prepolymers with different polymer-filled polyether polyols were investigated with regard to the filler's potential to increase the thermal stability of bonded wood joints. The property changes due to the addition of fillers were determined by means of mechanical tests on bonded wood joints and on pure adhesive films at different temperatures up to 200°C. Additional analyses by atomic force and environmental scanning electron microscopy advanced the understanding of the effects of the filler. The tested organic fillers, styrene acrylonitrile, a polyurea dispersion, and polyamide, caused increases in the cohesive strength and stiffness over the whole temperature range. However, the selected filler type was hardly important with regard to the tensile shear strength of the bonded wood joints at high temperatures, although the tensile strength and Young's modulus of the adhesive films differed over a wide range. Prepolymers with a lower initial strength and stiffness resulted in worse cohesion, in particular, at high temperatures. This disadvantage, however, could be compensated by means of the filler material. Ultimately, the addition of filler material resulted in optimized adhesive properties only in a well-balanced combination with the prepolymer used. |
| Published in: | Journal of applied polymer science |
| Volume: | 124 |
| Issue: | 5 |
| Pages: | 3641 - 3649 |
| ISSN: | 0021-8995, 1097-4628 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Kunststoffe|Plastics, Adhesion, Adhesives, Fillers, Mechanical properties, Polyurethanes |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Adhesion, Adhesives, Fillers, Mechanical properties, Polyurethanes |
| DBID source: | FORM-1333431209, WOS-000300971400015 |
| DOI: | 10.1002/APP.35223 |
| Nebis system number: | 000031978 |
Simulation of particle mixing in turbulent channel flow due to intrinsic fluid velocity fluctuation
,
Burgener, Thomas, Kadau, Dirk, Herrmann, Hans J.,
2011
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| Author(s): | Burgener, Thomas, Kadau, Dirk, Herrmann, Hans J. |
| Title: | Simulation of particle mixing in turbulent channel flow due to intrinsic fluid velocity fluctuation |
| Abstract: | We combine a discrete-element-method simulation with a stochastic process to model the movement of spherical particles in a turbulent channel flow. With this model we investigate the mixing properties of two species of particles flowing through the channel. We find a linear increase of the mixing zone with the length of the pipe. Flows at different Reynolds number are studied. Below a critical Reynolds number at the Taylor microscale of around R-c approximate to 300 the mixing rate is strongly dependent on the Reynolds number. Above R-c the mixing rate stays nearly constant. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 83 |
| Issue: | 6 |
| Pages: | 066301 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000291447500002 |
| DOI: | 10.1103/PhysRevE.83.066301 |
| Nebis system number: | 004109079 |
Klebstoffe auch bei tiefen Temperaturen verarbeiten
,
Brandmair, Anton, Steiner, Patrick, Niemz, Peter,
2012
>>
| Author(s): | Brandmair, Anton, Steiner, Patrick, Niemz, Peter |
| Title: | Klebstoffe auch bei tiefen Temperaturen verarbeiten |
| Abstract: | Die Firma Nolax AG hat mit "Lignofast" eine Klebstofftechnologie entwickelt, mit der sich die Produktivität in der holzverarbeitenden Industrie steigern lässt. Grund dafür ist das sekundenschnelle Abbinden des Zweikomponenten-Klebstoffs. Mit "Lignofast" lassen sich kurze Presszeiten realisieren, die je nach Einstellung des Klebstoffsystems, lediglich 15 s betragen können. Bei dem Klebstoff handelt es sich um ein Zweikomponenten-Polyurea-System. Eingesetzt werden kann "Lignofast" beispielsweise für Verklebung von Massivholzplatten oder Mehrschichtparkett. |
| Published in: | Holz-Zentralblatt |
| Volume: | 2012 |
| Issue: | 5 |
| Pages: | 152 - 152 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting) |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1333604584 |
| Nebis system number: | 000047754 |
Moisture Induced Stresses and Deformations in Parquet Floors
,
Blumer, Samuel, Serrano, Erick, Gustafsson, Per Johan, Niemz, Peter,
2011
>>
| Author(s): | Blumer, Samuel, Serrano, Erick, Gustafsson, Per Johan, Niemz, Peter |
| Title: | Moisture Induced Stresses and Deformations in Parquet Floors |
| Abstract: | During the last decade the use of wood flooring systems in Europe has increased dramatically. In Sweden for example, the proportion of wood flooring systems rose steadily from 30% in the seventies to its current proportion which is 80%. This rapid growth has fostered the development of new products, enabling the industry to maintain and increase its market share. |
| Book title: | Delamination in wood, wood products and wood-based composites |
| Pages: | 365 - 378 |
| ISBN: | 978-90-481-9549-7 |
| Publication date / Date received: | 2011-01-01 |
| Publication status: | Dordrecht |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295347832 |
| DOI: | 10.1007/978-90-481-9550-3_18 |
Effect of pre-pressing of veneer on the glueability and properties of veneer-based products
,
Bekhta, Pavlo, Niemz, Peter, Sedliacik, Jan,
2012
>>
| Author(s): | Bekhta, Pavlo, Niemz, Peter, Sedliacik, Jan |
| Title: | Effect of pre-pressing of veneer on the glueability and properties of veneer-based products |
| Abstract: | The study used a physical and environmentally friendly method to enhance the properties of both veneer and plywood. The effect of pre-pressing process factors (pressure, temperature and time) on the compression ratio, surface roughness, tensile strength perpendicular-to-grain of rotary cut veneer sheets of birch (Betula pubescens), and on the shear strength of plywood made from these compressed veneer sheets were studied in laboratory tests. The effect of pressing factors (such as pressure and glue spread) on the properties of plywood made from pre-pressed veneer was also studied. Three-layer plywood panels were manufactured from pre-pressed and non-pre-pressed veneers using phenol formaldehyde glue resins. Test results revealed that the greatest influence on properties of veneer is the pre-pressing temperature followed by the pre-pressing pressure and pre-pressing time. Meanwhile, the veneer’s properties such as surface roughness can be improved, and the properties of plywood were also improved when the birch veneers were pre-pressed. Linear relationship between the compression ratio and surface roughness was found. The tensile strength of veneer was not significantly influenced by the pre-pressing factors. The pre-pressing temperature has the largest effect on shear strength of plywood. The initial veneer densification allows lowering both glue spread from 150 to 90 g/m2 (a 40% reduction) and pressing pressure from 1.8 to 1.0 MPa (a 45% reduction). The shear strength obtained for the tested plywood meets EN 314-1 requirements. It is expected that the results of this preliminary study will lead to new gluing approaches, which will result in significant performance improvements of veneer-based products. |
| Published in: | European journal of wood and wood products |
| Volume: | 70 |
| Issue: | 1-3 |
| Pages: | 99 - 106 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1325591105, WOS-000298657600013 |
| DOI: | 10.1007/s00107-010-0486-y |
| Nebis system number: | 000047744 |
Stiffness moduli of various extraneous species determined with ultrasound
,
Baradit, Erik, Keunecke, Daniel, Schnider, Thomas, Niemz, Peter,
2012
>>
| Author(s): | Baradit, Erik, Keunecke, Daniel, Schnider, Thomas, Niemz, Peter |
| Title: | Stiffness moduli of various extraneous species determined with ultrasound |
| Abstract: | Comprehensive datasets of the elastic constants are available for only a few European wood Species, especially spruce. The goal of this study, therefore, was to provide Young’s and shear moduli for the principal directions and planes for further selected extraneous species to extend the currently existing datasets. For this purpose, a dynamic technique was chosen: The moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modeling approaches. |
| Published in: | Wood research |
| Volume: | 57 |
| Issue: | 1 |
| Pages: | 173 - 178 |
| ISSN: | 1336-4561, 0012-6136 |
| Publication date / Date received: | 2012-01-01 |
| Publication status: | Bratislava |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Elastic constants, Shear modulus, Ultrasound, Stiffness modulus |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Elastic constants, Shear modulus, Ultrasound, Stiffness modulus |
| DBID source: | FORM-1336473506 |
| Nebis system number: | 001541175 |
1 to 100 (of 108 items)
2010
Synchrotron based tomographic in situ microscopy of wood under uniaxial load
,
Zauner, Michaela, Keunecke, D., Marone, F., Stampanoni, M., Niemz, Peter,
2010
>>
| Author(s): | Zauner, Michaela, Keunecke, D., Marone, F., Stampanoni, M., Niemz, Peter |
| Title: | Synchrotron based tomographic in situ microscopy of wood under uniaxial load |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Hamburg |
| Publication status: | Published |
| Event name: | COST Action FP0802 Workshop "Wood Structure/Function-Relationships" |
| Event date: | October 5-8, 2010 |
| Place: | Hamburg, Germany |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
On mean coordination and structural heterogeneity in model amorphous solids
,
Zaccone, Alessio, Del Gado, Emanuela,
2010
>>
| Author(s): | Zaccone, Alessio, Del Gado, Emanuela |
| Title: | On mean coordination and structural heterogeneity in model amorphous solids |
| Abstract: | We propose a simple route to analytically evaluate the average coordination of model disordered solids with maximally homogeneous distribution of the particles in space. The model yields the average number of contacts (z) as a function of volume fraction (phi) of a hard-sphere connected system and recovers the critical jamming point of hard spheres (z=6 at phi=0.64). Numerical simulations of Lennard-Jones glasses with a varying attraction range are used to investigate the volume fraction dependence of the average coordination in the presence of attraction. It is observed that upon decreasing phi below 0.6, structural heterogeneity is reflected in values of the coordination number which are higher than those predicted by the model for a statistically homogeneous distribution of particles in space due to the attraction-induced local aggregation. Thus the model can be usefully employed as a quantitative reference to assess the degree of structural heterogeneity in glasses in terms of a directly accessible structural parameter such as the mean number of contacts. |
| Published in: | The journal of chemical physics |
| Volume: | 132 |
| Issue: | 2 |
| Pages: | 024906 |
| ISSN: | 0021-9606, 1089-7690 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Melville, NY |
| Publication status: | Published |
| Subjects: | glass, glass structure, molecular dynamics method |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | glass, glass structure, molecular dynamics method |
| DBID source: | WOS-000273689000054 |
| DOI: | 10.1063/1.3284786 |
| Nebis system number: | 000049290 |
Verklebung von Laubhölzern
,
Wittel, Falk, Niemz, Peter, Herrmann, Hans Jürgen, Haas, Philipp, Mendoza, Miller,
2010
>>
| Author(s): | Wittel, Falk, Niemz, Peter, Herrmann, Hans Jürgen, Haas, Philipp, Mendoza, Miller |
| Title: | Verklebung von Laubhölzern |
| Published in: | Holzforschung Schweiz |
| Volume: | 2010 |
| Issue: | 2 |
| Pages: | 1 - 4 |
| ISSN: | 1660-6957, 1662-6168 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zürich |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 004342733 |
Wärmeleitfähigkeit verschiedener Holzarten
,
Wetzig, Melanie, Sonderegger, W., Niemz, Peter,
2010
>>
| Author(s): | Wetzig, Melanie, Sonderegger, W., Niemz, Peter |
| Title: | Wärmeleitfähigkeit verschiedener Holzarten |
| Published in: | Holz-Zentralblatt |
| Volume: | 136 |
| Issue: | 37 |
| Pages: | 914 - 914 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
| Nebis system number: | 000047754 |
Thermoholz aus Laubholz, neueste Arbeiten der ETH
,
Wetzig, Melanie, Niemz, Peter,
2010
>>
| Author(s): | Wetzig, Melanie, Niemz, Peter |
| Title: | Thermoholz aus Laubholz, neueste Arbeiten der ETH |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Montagskolloquien für die Praxis |
| Event date: | January 11, 2010 |
| Place: | Zürich, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Thermoholz aus Laubholz, Arbeiten an der ETH
,
Wetzig, Melanie, Niemz, Peter,
2010
>>
| Author(s): | Wetzig, Melanie, Niemz, Peter |
| Title: | Thermoholz aus Laubholz, Arbeiten an der ETH |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Böttstein |
| Publication status: | Published |
| Event name: | SAH Statusseminar : Mehr Wissen zu Holz – aktuell und aus erster Hand |
| Event date: | April 28, 2010 |
| Place: | Böttstein, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Comparison of different methods to produce heat-treated wood
,
Wetzig, M., Hofmann, T., Niemz, P.,
2010
>>
| Author(s): | Wetzig, M., Hofmann, T., Niemz, P. |
| Title: | Comparison of different methods to produce heat-treated wood |
| Book title: | The 4th Conference on Hardwood Research and Utilisation in Europe |
| Pages: | 245 - 250 |
| ISBN: | 978-963-9883-52-9 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Sopron |
| Publication status: | Published |
| Event name: | The 4th Conference on Hardwood Research and Utilisation in Europe |
| Event date: | May 17-18, 2010 |
| Place: | Sopron, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Simulating isothermal aging of snow
,
Vetter, R., Sigg, S., Singer, H. M., Kadau, Dirk, Herrmann, Hans Jürgen, Schneebeli, M.,
2010
>>
| Author(s): | Vetter, R., Sigg, S., Singer, H. M., Kadau, Dirk, Herrmann, Hans Jürgen, Schneebeli, M. |
| Title: | Simulating isothermal aging of snow |
| Abstract: | A Monte Carlo algorithm to simulate the isothermal recrystallization process of snow is presented. The snow metamorphism is approximated by two mass redistribution processes: surface diffusion and sublimation-deposition. The algorithm is justified and its parametrization is determined. The simulation results are compared to experimental data, in particular, the temporal evolution of the specific surface area and the ice thickness. We find that the two effects of surface diffusion and sublimation-deposition can accurately model many aspects of the isothermal metamorphism of snow. Furthermore, it is shown that sublimation-deposition is the dominant contribution for temperatures close to the melting point, whereas surface diffusion dominates at temperatures far below the melting point. A simple approximation of gravitational compaction is implemented to simulate density change. |
| Published in: | EPL |
| Volume: | 89 |
| Issue: | 2 |
| Pages: | 26001 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Bristol |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000274848500015 |
| DOI: | 10.1209/0295-5075/89/26001 |
| Nebis system number: | 000033031 |
New Universality Class for the Fragmentation of Plastic Materials
,
Timar, G., Bloemer, J., Kun, F., Herrmann, Hans Jürgen,
2010
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| Author(s): | Timar, G., Bloemer, J., Kun, F., Herrmann, Hans Jürgen |
| Title: | New Universality Class for the Fragmentation of Plastic Materials |
| Abstract: | We present an experimental and theoretical study of the fragmentation of polymeric materials by impacting polypropylene particles of spherical shape against a hard wall. Experiments reveal a power law mass distribution of fragments with an exponent close to 1.2, which is significantly different from the known exponents of three-dimensional bulk materials. A 3D discrete element model is introduced which reproduces both the large permanent deformation of the polymer during impact and the novel value of the mass distribution exponent. We demonstrate that the dominance of shear in the crack formation and the plastic response of the material are the key features which give rise to the emergence of the novel universality class of fragmentation phenomena. |
| Published in: | Physical review letters |
| Volume: | 104 |
| Issue: | 9 |
| Pages: | 095502 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000275252500023 |
| DOI: | 10.1103/PhysRevLett.104.095502 |
| Nebis system number: | 000003868 |
Self-Contact and Instabilities in the Anisotropic Growth of Elastic Membranes
,
Stoop, Norbert, Wittel, Falk K., Ben Amar, Martine, Müller, Martin Michael, Herrmann, Hans J.,
2010
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| Author(s): | Stoop, Norbert, Wittel, Falk K., Ben Amar, Martine, Müller, Martin Michael, Herrmann, Hans J. |
| Title: | Self-Contact and Instabilities in the Anisotropic Growth of Elastic Membranes |
| Abstract: | We investigate the morphology of thin discs and rings growing in the circumferential direction. Recent analytical results suggest that this growth produces symmetric excess cones ( e cones). We study the stability of such solutions considering self-contact and bending stress. We show that, contrary to what was assumed in previous analytical solutions, beyond a critical growth factor, no symmetric e cone solution is energetically minimal any more. Instead, we obtain skewed e cone solutions having lower energy, characterized by a skewness angle and repetitive spiral winding with increasing growth. These results are generalized to discs with varying thickness and rings with holes of different radii. |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 6 |
| Pages: | 068101 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000280555000006 |
| DOI: | 10.1103/PhysRevLett.105.068101 |
| Nebis system number: | 000003868 |
Quantitative determination of water sorption in glued multilayer boards by means of neutron imaging
,
Sonderegger, Walter, Niemz, Peter, Hering, Stefan, Mannes, David, Lehmann, Eberhard,
2010
>>
| Author(s): | Sonderegger, Walter, Niemz, Peter, Hering, Stefan, Mannes, David, Lehmann, Eberhard |
| Title: | Quantitative determination of water sorption in glued multilayer boards by means of neutron imaging |
| Book title: | Wood structure and properties '10 |
| Pages: | 101 - 106 |
| ISBN: | 9788096886852, 8096886851 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zvolen, Slovakia |
| Publication status: | Published |
| Event name: | The 6th International Symposium Wood Structure and Properties '10 |
| Event date: | September 6-9, 2010 |
| Place: | Podbanské, High Tatras, Slovakia |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Einfluss der Klebstoffart und des Materialaufbaus auf die Wasserdampfdiffusion von Holzwerkstoffen
,
Sonderegger, Walter, Niemz, Peter,
2010
>>
| Author(s): | Sonderegger, Walter, Niemz, Peter |
| Title: | Einfluss der Klebstoffart und des Materialaufbaus auf die Wasserdampfdiffusion von Holzwerkstoffen |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 4. Kolloquium: Aktuelle Fragen der Holzforschung |
| Event date: | September 20, 2010 |
| Place: | Braunschweig, Germany |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Diffusion processes at Glue Joints of Wood-Based Materials Evaluated by Neutron Imaging
,
Sonderegger, Walter, Mannes, David, Hering, Stefan, Lehmann Eberhard, Niemz, Peter,
2010
>>
| Author(s): | Sonderegger, Walter, Mannes, David, Hering, Stefan, Lehmann Eberhard, Niemz, Peter |
| Title: | Diffusion processes at Glue Joints of Wood-Based Materials Evaluated by Neutron Imaging |
| Abstract: | The influence of glue joints on the diffusion processes is scarcely known. With conventional methods, the measurement is inexact due to the fact that a differentiation between the glue part and the wood-based material is difficult or impossible. Neutron imaging is a non-destructive testing method, which allows the visualization and quantification of the distribution of the glue and the absorbed water within the wooden sample. Investigations were made on various samples composed of wood and wood-based materials bonded with different wood adhesives. The specimens (two part of wood or wood-based material with a glue joint between it) were first dried and than exposed to a differential climate. The process of water absorption into the samples was measured with neutron imaging. Thereby, the accumulation of water within the specimen in front of the adhesive joint was visualized and the total amount quantified. Furthermore, the results were used to calculate the diffusion coefficients of each part of the specimen. |
| Book title: | Wood adhesives 2009 |
| Pages: | 362 - 366 |
| ISBN: | 978-1-892529-57-2, 1892529572 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Madison, WI |
| Publication status: | Published |
| Event name: | International Conference on Wood Adhesives 2009 |
| Event date: | September 28-30, 2009 |
| Place: | Lake Tahoe, Nevada, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1314105338 |
Selected physical and mechanical properties of the Chilean wood species roble, lingue, manio and alerce
,
Sonderegger, Walter, Keunecke, Daniel, Baradit, Erik, Niemz, Peter,
2010
>>
| Author(s): | Sonderegger, Walter, Keunecke, Daniel, Baradit, Erik, Niemz, Peter |
| Title: | Selected physical and mechanical properties of the Chilean wood species roble, lingue, manio and alerce |
| Abstract: | Data sets with mechanical and physical properties of wood species can aid the recognition of biomechanical correlations, and they can also be valuable tools to assist decision making regarding the practical industrial employment of the species. However, such data sets are still lacking for many species, particularly non-European and non-North-American species. Therefore, the goal of this study was to determine the mechanical properties of four Chilean species (the softwoods alerce and manio, and the hardwoods lingue and roble), including the three Young's moduli and the three shear moduli. Dynamic methods were applied as well as static ones. The results suggest that Brinell hardness, compression strength and Young's moduli are clearly correlated with the density and can partly be related to anatomical details. Since the investigated species cover only a fraction of the Chilean species that are suitable for construction purposes, for example, further future examination of relevant species would be beneficial for basic research and industry. |
| Published in: | Wood material science & engineering |
| Volume: | 5 |
| Issue: | 1 |
| Pages: | 53 - 59 |
| ISSN: | 1748-0272, 1748-0280 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Colchester, Essex, England |
| Publication status: | Published |
| Subjects: | Alerce, Chilean wood species, Lingue, Manio, Mechanical properties, Modulus of elasticity, Roble |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Alerce, Chilean wood species, Lingue, Manio, Mechanical properties, Modulus of elasticity, Roble |
| DBID source: | CSV- |
| DOI: | 10.1080/17480271003717279 |
| Nebis system number: | 005350928 |
Quantitative determination of bound water diffusion in multilayer boards by means of neutron imaging
,
Sonderegger, Walter, Hering, Stefan, Mannes, David, Vontobel, Peter, Lehmann, Eberhard, Niemz, Peter,
2010
>>
| Author(s): | Sonderegger, Walter, Hering, Stefan, Mannes, David, Vontobel, Peter, Lehmann, Eberhard, Niemz, Peter |
| Title: | Quantitative determination of bound water diffusion in multilayer boards by means of neutron imaging |
| Abstract: | Diffusion processes into multilayered samples of Norway spruce (Picea abies [L.] Karst.) exposed to a differentiating climate (dry side/wet side) were determined and quantified by means of neutron imaging (NI). The experiments were carried out at the neutron imaging facility NEUTRA at the Paul Scherrer Institute (PSI) in Villigen (Switzerland). With NI the influence of different adhesives (polyvinyl acetate (PVAc), urea formaldehyde resin (UF), epoxy resin (EP), one-component polyurethane (1C PUR)) on the diffusion process could be determined by varying the layer number and the thickness of adhesive joints of the samples. Thereby, neutron transmission images were used to measure time dependent water profiles in the diffusion direction. Using Fick's second law, diffusion coefficients for radial and tangential water transport in spruce wood and in the adhesive joints were calculated depending on moisture content (MC). It was found that the diffusion coefficients of the adhesives (1C PUR, EP at high MC) were up to three orders of magnitude lower than those of spruce wood. PVAc and UF had a smaller barrier effect compared to wood, which in contrast to 1C PUR and EP, clearly depends on the MC. Es wurden Diffusionsprozesse an mehrlagigen Proben von Fichte (Picea abies [L.] Karst.), welche einem Differenzklima (trocken/feucht) ausgesetzt waren, mittels Neutronenradiographie untersucht und quantifiziert. Die Experimente wurden an der Radiographiestrahllinie NEUTRA am Paul Scherrer Institut (PSI) in Villigen (Schweiz) durchgeführt. Mittels Neutronenradiographie konnte der Einfluss verschiedener Klebstoffe (Polyvinylacetat (PVAc), Harnstoffharz (UF), Epoxidharz (EP) und Einkomponenten-Polyurethan (1K-PUR)) auf den Diffusionsprozess bestimmt werden, indem die Anzahl und die Dicke der Klebfugen variiert wurden. Dabei wurden Neutronen-Transmissionsbilder verwendet, womit zeitabhängige Profile in Diffusionsrichtung gemessen werden konnten. Anhand des zweiten Fick’schen Gesetzes konnten die Diffusionskoeffizienten für die Klebstoffe sowie für Fichte in radialer und tangentialer Richtung in Abhängigkeit der Feuchte berechnet werden. Dabei wiesen die Klebstoffe (1K-PUR, EP bei hohen Feuchten) bis zu drei Zehnerpotenzen niedrigere Diffusionskoeffizienten als Fichtenholz auf. Bei PVAc und UF war die Sperrwirkung gegenüber dem Holz geringer und es zeigte sich im Gegensatz zu 1K-PUR und EP eine deutliche Abhängigkeit von der Holzfeuchte. |
| Published in: | European journal of wood and wood products |
| Volume: | 68 |
| Issue: | 3 |
| Pages: | 341 - 350 |
| ISSN: | 0018-3768, 1436-736X |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000281072200011 |
| DOI: | 10.1007/s00107-010-0463-5 |
| Nebis system number: | 000047744 |
Topography of inland deltas
,
Seybold, H. J., Molnar, P., Akca, D., Doumi, M., Tavares, M. Cavalcanti, Shinbrot, T., Andrade Jr., José S., Kinzelbach, W., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Seybold, H. J., Molnar, P., Akca, D., Doumi, M., Tavares, M. Cavalcanti, Shinbrot, T., Andrade Jr., José S., Kinzelbach, W., Herrmann, Hans Jürgen |
| Title: | Topography of inland deltas |
| Subtitle: | Observations, modeling, and experiments |
| Abstract: | The topography of inland deltas is influenced by the water-sediment balance in distributary channels and local evaporation and seepage rates. In this letter a reduced complexity model is applied to simulate inland delta formation, and results are compared with the Okavango Delta, Botswana and with a laboratory experiment. We show that water loss in inland deltas produces fundamentally different dynamics of water and sediment transport than coastal deltas, especially deposition associated with expansion-contraction dynamics at the channel head. These dynamics lead to a systematic decrease in the mean topographic slope of the inland delta with distance from the apex following a power law with exponent alpha = -0.69 +/- 0.02 where the data for both simulation and experiment can be collapsed onto a single curve. In coastal deltas, on the contrary, the slope increases toward the end of the deposition zone. |
| Published in: | Geophysical research letters |
| Volume: | 37 |
| Pages: | L08402 |
| ISSN: | 0094-8276, 1944-8007 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Washington, D.C. |
| Publication status: | Published |
| Subjects: | Geophysik |Geophysics |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000277252700001, FORM-1294175379 |
| DOI: | 10.1029/2009GL041605 |
| Nebis system number: | 000047284 |
Structural Health Monitoring of Glued Laminated Timber with a Novel Air Coupled Ultrasound Method
,
Sanabria, Sergio J., Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2010
>>
| Author(s): | Sanabria, Sergio J., Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Structural Health Monitoring of Glued Laminated Timber with a Novel Air Coupled Ultrasound Method |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 11th World Conference on Timber Engineering (WCTE) |
| Event date: | June 20-24, 2010 |
| Place: | Riva del Garda, Trentino, Italy |
| Language: | English |
| Review status: | Unknown |
| DBID source: | FORM-1295010679 |
Erkennung von Fehlverklebungen mit Ultraschall
,
Sanabria, Sergio J., Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2010
>>
| Author(s): | Sanabria, Sergio J., Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Erkennung von Fehlverklebungen mit Ultraschall |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zürich, Switzerland |
| Publication status: | Published |
| Event name: | Kolloquium mit dem Schwerpunkt Verwendung von Laubholz – Stand und ausgewählte aktuelle Arbeiten im Rahmen der Reihe „Montagskolloquien für die Praxis“ |
| Event date: | January 11, 2010 |
| Place: | Zürich, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | FORM-1295012816 |
Analytical and numerical air-coupled ultasound wave propagation in glued laminated timber structures applied to bonding defect inspection
,
Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs,
2010
>>
| Author(s): | Sanabria, Sergio J., Furrer, Roman, Neuenschwander, Jürg, Niemz, Peter, Sennhauser, Urs |
| Title: | Analytical and numerical air-coupled ultasound wave propagation in glued laminated timber structures applied to bonding defect inspection |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Empa PhD Student's Symposium 2010 "Today’s Research, Tomorrow’s World" |
| Event date: | October 7, 2010 |
| Place: | Dübendorf, Switzerland |
| Language: | English |
| Review status: | Unknown |
| DBID source: | FORM-1295012611 |
Air-Coupled Ultrasound Wave Propagation in Glued Laminated Timber Structures applied to Bonding Quality Assessment
,
Sanabria, Sergio, Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs,
2010
>>
| Author(s): | Sanabria, Sergio, Furrer, Roman, Neuenschwander, Juerg, Niemz, Peter, Sennhauser, Urs |
| Title: | Air-Coupled Ultrasound Wave Propagation in Glued Laminated Timber Structures applied to Bonding Quality Assessment |
| Abstract: | Non-destructive assessment of glulam laminations is necessary in order to prevent security hazards. Air-coupled ultrasound (ACU) is sensitive to delamination, reproducible and allows for high scanning resolution. In this work we developed a novel ACU imaging system in normal transmission for inspection of up to 280 mm high glulam. The coupling and propagation of ACU waves in glulam were investigated with plane wave theory applied to an orthotropic model of wood as a function of grain and ring angles. Finite Difference Time Domain (FDTD) simulations were also carried out. The systematic amplitude heterogeneity in defect-free regions was linked to energy flux shifts and mode conversion phenomena, and compensated for in the images. Specific amplitude tracking and difference imaging algorithms allowed successful imaging of bonding and saw cut defects. |
| Book title: | 2010 IEEE Ultrasonics Symposium |
| Pages: | 1466 - 1469 |
| ISBN: | 978-1-4577-0382-9, 1457703823 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Piscataway, NJ |
| Publication status: | Published |
| Event name: | 2010 IEEE International Ultrasonics Symposium (IUS) |
| Event date: | October 11-14, 2010 |
| Place: | San Diego, California, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| DOI: | 10.1109/ULTSYM.2010.5935552 |
Why do particle clouds generate electric charges?
,
Pähtz, T., Herrmann, Hans Jürgen, Shinbrot, T.,
2010
>>
| Author(s): | Pähtz, T., Herrmann, Hans Jürgen, Shinbrot, T. |
| Title: | Why do particle clouds generate electric charges? |
| Abstract: | Grains in desert sandstorms spontaneously generate strong electrical charges; likewise volcanic dust plumes produce spectacular lightning displays. Charged particle clouds also cause devastating explosions in food, drug and coal processing industries. Despite the wide-ranging importance of granular charging in both nature and industry, even the simplest aspects of its causes remain elusive, because it is difficult to understand how inert grains in contact with little more than other inert grains can generate the large charges observed. Here, we present a simple yet predictive explanation for the charging of granular materials in collisional flows. We argue from very basic considerations that charge transfer can be expected in collisions of identical dielectric grains in the presence of an electric field, and we confirm the model's predictions using discrete-element simulations and a tabletop granular experiment. |
| Published in: | Nature physics |
| Volume: | 6 |
| Issue: | 5 |
| Pages: | 364 - 368 |
| ISSN: | 1745-2473, 1745-2481 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000278335500017, FORM-1272374499 |
| DOI: | 10.1038/NPHYS1631 |
| Nebis system number: | 005054127 |
Kinetik der freien, integralen Quellung von chemisch modifiziertem Holz entlang der Wasserdampf-Sorptionsisotherme unter luftfreien Bedingungen
,
Popper, Rudolf, Eberle, Gerhild, Niemz, Peter,
2010
>>
| Author(s): | Popper, Rudolf, Eberle, Gerhild, Niemz, Peter |
| Title: | Kinetik der freien, integralen Quellung von chemisch modifiziertem Holz entlang der Wasserdampf-Sorptionsisotherme unter luftfreien Bedingungen |
| Abstract: | Die kinetischen, dreidimensionalen Messungen der freien, integralen Quellung wurden an unbehandeltem und an acetyliertem (Acetylgehalt 8,56 %, 20,14 % und 28,63 %) Tannenholz (Abies alba Mill.) entlang der Sorptionsisotherme unter luftfreien Bedingungen durchgeführt. Der zeitliche Verlauf der Quellung in den drei anatomischen Hauptrichtungen und in der transversalen Richtung wurde für das unbehandelte und das acetylierte Holz aufgezeigt sowie der maximale Dimensionsstabilisierungseffekt (ASE) für die jeweilige Modifizierung geschätzt. Die Auswirkung des Partialdruckgradienten des Wasserdampfes auf die mittlere Quellungsgeschwindigkeit wurde behandelt. Kinetic of free integral swelling on chemically modified wood along the water vapour sorption isotherm under air-free conditions. The kinetic, three-dimensional measurements of the free integral swelling were accomplished at the untreated and at the acetylated (acetyl content 8.56 %, 20.14 % and 28.63 %) fir wood (Abies alba Mill.) along the sorption isotherm under air-free conditions. The course of the swelling in the three anatomical main directions and in the transversal direction was presented for the untreated and the acetylated wood. The anti-swelling efficiency (ASE) for the accomplished modifications was estimated. The effect of the partial pressure gradient of the water vapour on the mean swelling speed was presented. |
| Published in: | Bauphysik |
| Volume: | 32 |
| Issue: | 1 |
| Pages: | 7 - 16 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | WOS-000275349800002 |
| DOI: | 10.1002/bapi.201010002 |
| Nebis system number: | 000006704 |
Russlands Lehre und Forschung im Forst und Holz
,
Plotnikow, Sergej, Niemz, Peter,
2010
>>
| Author(s): | Plotnikow, Sergej, Niemz, Peter |
| Title: | Russlands Lehre und Forschung im Forst und Holz |
| Published in: | Holz-Zentralblatt |
| Issue: | 14 |
| Pages: | 366 - 366 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 000047754 |
Invasion Percolation with a Hardening Interface Under Gravity
,
Oliveira, C.L.N., Wittel, F.K., Andrade Jr., José S., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Oliveira, C.L.N., Wittel, F.K., Andrade Jr., José S., Herrmann, Hans Jürgen |
| Title: | Invasion Percolation with a Hardening Interface Under Gravity |
| Abstract: | We propose a modified Invasion Percolation (IP) model to simulate the infiltration of glue into a porous medium under gravity in 2D. Initially, the medium is saturated with air and then invaded by a fluid that has a hardening effect taking place from the interface towards the interior by contact with the air. To take into account that interfacial hardening, we use an IP model where capillary pressures of the growth sites are increased with time. In our model, if a site stays for a certain time at interface, it becomes a hard site and cannot be invaded anymore. That represents the glue interface becoming hard due to exposition with the air. Buoyancy forces are included in this system through the Bond number which represents the competition between the hydrostatic and capillary forces. We then compare our results with results from literature of non-hardening fluids in each regime of Bond number. We see that the invasion patterns change strongly with hardening while the non-hardening behavior remains basically not affected. |
| Published in: | International journal of modern physics. C, Computational physics, physical computation |
| Volume: | 21 |
| Issue: | 7 |
| Pages: | 903 - 914 |
| ISSN: | 0129-1831, 1793-6586 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Singapore |
| Publication status: | Published |
| Subjects: | Invasion percolation, hardening fluids, Bond number, porous media |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Invasion percolation, hardening fluids, Bond number, porous media |
| DBID source: | WOS-000281399800004 |
| DOI: | 10.1142/S0129183110015555 |
| Nebis system number: | 000552805 |
Einsatz von Thermoholz
,
Niemz, Peter, Wetzig, Melanie,
2010
>>
| Author(s): | Niemz, Peter, Wetzig, Melanie |
| Title: | Einsatz von Thermoholz |
| Subtitle: | Eigenschaften, Verarbeitung, Praxiserfahrungen |
| Book title: | Holzoberflächen in der Fassadengestaltung: 42. Fortbildungskurs, SAH Schweizerische Arbeitsgemeinschaft für Holzforschung, 26./27. Oktober 2010 in Weinfelden |
| Published in: | Fortbildungskurs / Schweizerische Arbeitsgemeinschaft für Holzforschung |
| Volume: | 42 |
| Pages: | 81 - 94 |
| ISBN: | 978-3-906703-26-8 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zürich |
| Publication status: | Published |
| Event name: | 42. Fortbildungskurs, SAH Schweizerische Arbeitsgemeinschaft für Holzforschung |
| Event date: | October 26-27, 2010 |
| Place: | Weinfelden, Switzerland |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 006199821 |
Einsatz von Thermoholz
,
Niemz, Peter, Wetzig, Melanie,
2010
>>
| Author(s): | Niemz, Peter, Wetzig, Melanie |
| Title: | Einsatz von Thermoholz |
| Subtitle: | Praxiserfahrungen |
| Published in: | Schweizer Holz-Zeitung |
| Issue: | 23 |
| Pages: | 12 - 13 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Baden-Dättwil |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 001616552 |
Thermal conductivity of Norway spruce and European beech in the anatomical directions
,
Niemz, Peter, Sonderegger, Walter, Hering, Stefan,
2010
>>
| Author(s): | Niemz, Peter, Sonderegger, Walter, Hering, Stefan |
| Title: | Thermal conductivity of Norway spruce and European beech in the anatomical directions |
| Published in: | Annals of Warsaw Agricultural University SGGW-AR |
| Volume: | 2010 |
| Issue: | 72 |
| Pages: | 66 - 72 |
| ISSN: | 0208-5704, 0208-5739 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Warsaw |
| Publication status: | Published |
| Event name: | 24th International Scientific Conference of Wood Technology Faculty |
| Event date: | November 16-17, 2010 |
| Place: | Rogow, Poland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 001547668 |
Untersuchungen zum Wasseraufnahmekoeffizienten von Holz bei Variation von Holzart und Flüssigkeit
,
Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne,
2010
>>
| Author(s): | Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne |
| Title: | Untersuchungen zum Wasseraufnahmekoeffizienten von Holz bei Variation von Holzart und Flüssigkeit |
| Abstract: | An Prüfkörpern aus Rotbuche, Robinie und Fichte wurde in den 3 Hauptschnittrichtungen längs, radial und tangential der Aufnahmekoeffizient von Flüssigkeiten (Wasser und ein hydrophobierendes wässriges Imprägniermittel mit einer Wirksubstanz aus cokondensierten nanoskaligen Silanen–Wirkstoffkonzentration 20 %) nach BS EN ISO 15148:2002 bestimmt. Es wurde eine wesentlich höhere Flüssigkeitsaufnahme in Faserrichtung als senkrecht dazu ermittelt. Rotbuche hatte die größten, Robinie die geringsten Flüssigkeitsaufnahmekoeffizienten. Die Flüssigkeitsaufnahme war bei dem hydrophobierenden Imprägniermittel geringer als bei Wasser. Dies wirkt sich auf das Imprägnierverhalten nach Druck- oder auch Streichimprägnierung aus. The absorption coefficient of liquids (water and a hydrophobic watery impregnating agent with an active agent of co-condensed nanoscale silanes; active agent concentration 20 %) by test pieces of beech, robinia and spruce was determined in the three main cutting directions: longitudinal, radial and tangential, in accordance with BS EN ISO 15148:2002. A substantially higher moisture absorption rate was found with the grain than perpendicular to it. Beech showed the highest, robinia the lowest moisture absorption coefficients. The moisture absorption was lower for the hydrophobic impregnating agent than for water. This affects the impregnation performance both with pressure impregnation and surface-applied impregnation. |
| Published in: | Bauphysik |
| Volume: | 32 |
| Issue: | 3 |
| Pages: | 149 - 153 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | WOS-000279041500004 |
| DOI: | 10.1002/bapi.201010018 |
| Nebis system number: | 000006704 |
Untersuchungen zum Verhalten von mit Nanopartikeln imprägniertem Holz bei Freibewitterung
,
Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne,
2010
>>
| Author(s): | Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne |
| Title: | Untersuchungen zum Verhalten von mit Nanopartikeln imprägniertem Holz bei Freibewitterung |
| Abstract: | Es wurde die Witterungsbeständigkeit von Fichtenholz und Buchen holz nach Beschichtung mit verschiedenen nanoskaligen Hydrophobierungsmitteln und vergleichsweise dazu mit einem üblichen Lack getestet. Die Imprägnierung des Holzes erfolgte über Streich- oder Druckimprägnierung. Erfasst wurden Änderungen der Farbkennwerte, der Benetzungswinkel, der Holzfeuchte sowie der visuelle Gesamteindruck. Bei allen Materialien und Beschichtungs arten trat bereits nach kurzer Zeit eine Vergrauung auf. Diese war beim Standardlack am geringsten. Diese Tendenz spiegeln auch die Farbmessungen wieder. Der Benetzungsrandwinkel reduzierte sich zunehmend, das zeigt, dass der Hydrophobierungseffekt nach lässt. Beim Standardlack war der Effekt deutlich geringer ausgeprägt. Insgesamt zeigt sich, dass es weder mit Streich- noch mit Druckimprägnierung gelang, das Imprägnierungsmittel ausreichend tief in das Holz einzubringen und zu fixieren. Dies deckt sich mit den Ergebnissen der Flüssigkeitsaufnahmekoeffizienten, über die in vorangegangenen Arbeiten berichtet wurde. Investigation regarding the behaviour of wood impregnated with nano-particles and exposed to the open weather. The weather resistance of Norway spruce and beech wood has been tested following coating with various nano-scale hydrophobising compounds, and has been compared with reference samples that were coated with a standard varnish. The impregnation of the timber was carried out by brush coating or a pressure process. The test results focused on changes in colorimetric values, wetting angle, timber moisture and the overall appearance. All materials and types of coating were subject to a greying of colour after a short while. The standard varnish showed the least discoloration. This tendency was also reflected in the colorimetric measurements. The wetting edge angle increasingly reduced, indicating that the hydrophobising effect was also reducing. With the standard varnish, this effect was clearly less pronounced. Overall, the tests showed that it had not been possible to inject the timber sufficiently deeply with the impregnation compound, and fix it, with either the brush or pressure impregnation method. This confirms the findings obtained in fluid retention co-efficient tests which were reported in previous articles. |
| Published in: | Bauphysik |
| Volume: | 32 |
| Issue: | 4 |
| Pages: | 226 - 232 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | WOS-000281024200003 |
| DOI: | 10.1002/bapi.201010026 |
| Nebis system number: | 000006704 |
Eindringverhalten verschiedener Flüssigkeiten in Holz
,
Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne,
2010
>>
| Author(s): | Niemz, Peter, Mannes, David, Koch, Walter, Herbers, Yvonne |
| Title: | Eindringverhalten verschiedener Flüssigkeiten in Holz |
| Subtitle: | Einfluss von Netzmitteln und Aufbringungsart |
| Abstract: | Es wurde das Eindringverhalten verschiedener Flüssigkeiten in Fichte und Buche in radialer und tangentialer Richtung sowie ergänzend in Faserrichtung für verschiedene Einbringarten (Anstrich, Tauchen, Druckimprägnierung) geprüft. Die Eindringtiefe der geprüften Systeme stieg in der Reihenfolge Anstrich, Tauchen Druckimprägnierung. Analog den Ergebnissen der Flüssigkeitsaufnahmekoeffizienten (Niemz et al., 2010) gelang es nur den oberflächennahen Bereich zu imprägnieren. Eine Tiefenimprägnierung wird nicht erreicht. Die Eindringtiefe konnte auch durch Verwendung von Netzmitteln und Lösemitteln nur geringfügig beeinflusst werden. |
| Published in: | Holztechnologie |
| Volume: | 51 |
| Issue: | 6 |
| Pages: | 5 - 11 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Flüssigkeitsaufnahme, Quellung, Nanopartikel |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Flüssigkeitsaufnahme, Quellung, Nanopartikel |
| DBID source: | CSV- |
| Nebis system number: | 000026159 |
Physical-mechanical properties of hard- and softwood industrial heat treated with different methods
,
Niemz, Peter, Hofmann, Tamàs, Wetzig, Melanie, Rétfalvi, Tamás,
2010
>>
| Author(s): | Niemz, Peter, Hofmann, Tamàs, Wetzig, Melanie, Rétfalvi, Tamás |
| Title: | Physical-mechanical properties of hard- and softwood industrial heat treated with different methods |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Array |
| Publication status: | Published |
| Event name: | 100 Jahre Forest Prod. Lab. |
| Event date: | 20. - 22.06.2010 |
| Language: | English |
| DBID source: | CSV- |
Investigation of chemical changes in the strucure of wood thermally modified
,
Niemz, Peter, Hofmann, T., Rétefalvi, T.,
2010
>>
| Author(s): | Niemz, Peter, Hofmann, T., Rétefalvi, T. |
| Title: | Investigation of chemical changes in the strucure of wood thermally modified |
| Abstract: | Thermal modification beneficially alters several technological parameters of wood. The changes in the physical parameters are due to the significant alterations of the structure and the chemical composition of wood, which take place during the modification process. These changes are complex and some aspects/processes are still far from being completely understood. What is known, is that by increasing the temperature the nature of reactions taking place changes. Still it is unknown the exact point where the individual reactions become dominant. Various industrially important hardwood and softwood have been treated in autoclave in N2 atmosphere and with Vacuum Press Drying. The physical (density, L-value, moisture content, bending strength, MOE) and chemical (pH, hemicellulose-, totalphenol-, soluble carbohydrate-, and volatile organic compound content) parameters have been measured and evaluated. Correlations between physical and chemical parameters have been established and discussed. |
| Book title: | 11th International IUFRO Wood Drying Conference Recent Advances in the Field of Wood Drying, Skellefteå, Sweden, January 18-22, 2010, Proceedings |
| Pages: | 258 - 264 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 11th International IUFRO Wood Drying Conference |
| Event date: | January 18-22, 2010 |
| Place: | Skellefteå, Sweden |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Investigation of chemical changes in the structure of the thermally modified wood
,
Niemz, Peter, Hofmann, T., Retfalvi, T.,
2010
>>
| Author(s): | Niemz, Peter, Hofmann, T., Retfalvi, T. |
| Title: | Investigation of chemical changes in the structure of the thermally modified wood |
| Abstract: | Thermal modification beneficially alters several technological parameters of wood. The changes in the physical parameters are due to the significant alterations of the structure and the chemical composition of wood, which take place during the modification process. These changes are complex and some aspects are still far from being completely understood. Various industrially important hardwoods and softwoods have been treated in an autoclave in N-2 atmosphere. The physical (density, L-value, moisture content, bending strength, MOE) and chemical (pH, hemicellulose-, total phenol- and soluble carbohydrate content) parameters have been measured and evaluated. By establishing linear correlations between physical and chemical parameters the chemical changes affecting the physical properties could be investigated and tracked. Very good correlations have been found for hardwood samples, whereas for softwoods only poor correlations have been established. Results could contribute to a better understanding of the reactions of thermal modification, and could furthermore provide a basis for wood species dependent technology optimization in the future. |
| Published in: | Maderas. Ciencia y tecnología |
| Volume: | 12 |
| Issue: | 2 |
| Pages: | 69 - 78 |
| ISSN: | 0718-221X, 0717-3644 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Concepción, Chile |
| Publication status: | Published |
| Subjects: | Thermally treated wood, Chemical properties, Mechanical properties, Linear correlations |
| Event name: | 11th IUFRO Wood Drying Conference |
| Event date: | January 2010 |
| Place: | Skelleftea, Sweden |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Thermally treated wood, Chemical properties, Mechanical properties, Linear correlations |
| DBID source: | WOS-000282903900002 |
| DOI: | 10.4067/SO718-221X2010000200002 |
Adhesive bond lines in wood
,
Niemz, Peter, Hass, Philipp, Wittel, Falk K., Stampanoni, Marco, Sonderegger, Walter,
2010
>>
| Author(s): | Niemz, Peter, Hass, Philipp, Wittel, Falk K., Stampanoni, Marco, Sonderegger, Walter |
| Title: | Adhesive bond lines in wood |
| Subtitle: | Development and influence on water diffusion by means of transmission based imaging techniques |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Joint IAWA/IAWS/IUFRO Conference and Annual IAWS Plenary Meeting 2010 |
| Event date: | June 23-26, 2010 |
| Place: | Madison, USA |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
3D Characterization of Wood Structure and Adhesive Penetration into Wood by Means of Synchrotron Radiation
,
Niemz, Peter, Hass, Philipp, Wittel, Falk K., Stampanoni, Marco,
2010
>>
| Author(s): | Niemz, Peter, Hass, Philipp, Wittel, Falk K., Stampanoni, Marco |
| Title: | 3D Characterization of Wood Structure and Adhesive Penetration into Wood by Means of Synchrotron Radiation |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Joint IAWA/IAWS/IUFRO Conference and Annual IAWS Plenary Meeting 2010 |
| Event date: | June 23-26, 2010 |
| Place: | Madison, USA |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
Verwendung von Massivholzplatten im Bauwesen
,
Niemz, Peter, Gereke, Thomas, Sonderegger, Walter,
2010
>>
| Author(s): | Niemz, Peter, Gereke, Thomas, Sonderegger, Walter |
| Title: | Verwendung von Massivholzplatten im Bauwesen |
| Subtitle: | Ausgewählte Arbeiten der ETH Zürich zur Technologie und zur Materialforschung |
| Published in: | Holz-Zentralblatt |
| Volume: | 136 |
| Issue: | 22 |
| Pages: | 544 - 545 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 000047754 |
Eigenschaften von Massivholzplatten und deren Verwendung im Bauwesen
,
Niemz, Peter, Gereke, Thomas, Sonderegger, Walter,
2010
>>
| Author(s): | Niemz, Peter, Gereke, Thomas, Sonderegger, Walter |
| Title: | Eigenschaften von Massivholzplatten und deren Verwendung im Bauwesen |
| Book title: | Tagungsband des 14. Holztechnologischen Kolloquiums : Dresden 08.-09. April 2010 |
| Published in: | Schriftenreihe Holz- und Papiertechnik |
| Volume: | 5 |
| Pages: | 64 - 79 |
| ISBN: | 978-3-86780-167-6 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Dresden |
| Publication status: | Published |
| Event name: | 14. Holztechnisches Kolloquium |
| Event date: | April 8-9, 2010 |
| Place: | Dresden, Germany |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Ausbildung auf dem Gebiet der Holztechnologie in Osteuropa
,
Niemz, Peter, Barbu, Marius, Campean, Mihaela,
2010
>>
| Author(s): | Niemz, Peter, Barbu, Marius, Campean, Mihaela |
| Title: | Ausbildung auf dem Gebiet der Holztechnologie in Osteuropa |
| Published in: | AFZ - der Wald |
| Volume: | 65 |
| Issue: | 10 |
| Pages: | 42 - 43 |
| ISSN: | 1430-2713, 0936-1294 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 001495188 |
Water Absorption of Wood and Wood-Based Panels
,
Niemz, Peter,
2010
>>
| Author(s): | Niemz, Peter |
| Title: | Water Absorption of Wood and Wood-Based Panels |
| Subtitle: | Significant Influencing Factors |
| Book title: | Wood-based panels: an introduction for specialists |
| Pages: | 95 - 122 |
| ISBN: | 978-1-902316-82-6 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | London |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 006154409 |
Uso de metodos nodestructivos en la industria madera
,
Niemz, Peter,
2010
>>
| Author(s): | Niemz, Peter |
| Title: | Uso de metodos nodestructivos en la industria madera |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Líneas de investigación en madera en el ETH y Métodos no destructivos para el control de calidad de madera |
| Event date: | May 14, 2010 |
| Place: | Madrid, Spain |
| Language: | Spanish |
| Review status: | Unknown |
| DBID source: | CSV- |
Holzindustrie Chiles
,
Niemz, Peter,
2010
>>
| Author(s): | Niemz, Peter |
| Title: | Holzindustrie Chiles |
| Published in: | Holz-Zentralblatt |
| Volume: | 2010 |
| Issue: | 14 |
| Pages: | 352 - 352 |
| ISSN: | 0018-3792 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294739134 |
| Nebis system number: | 000047754 |
Anlage zur Herstellung von Thermoholz in Betrieb genommen
,
Niemz, Peter,
2010
>>
| Author(s): | Niemz, Peter |
| Title: | Anlage zur Herstellung von Thermoholz in Betrieb genommen |
| Abstract: | In Rotleberode, Sachsen Anhalt, hat die Gemeinde ein neues Industriegebiet errichtet, in dem die Firma Timura Holzmanufaktor gerade als Ergänzung zur ansässigen Firma ante Holz (Sägewerk und Weiterverarbeitung von rund 200000 m3 Schnittholz pro Jahr) noch einen Betrieb zur Herstellung und Weiterverarbeitung von wärmebehandeltem Holz aufgenommen hat. |
| Published in: | Schweizer Holz-Zeitung |
| Volume: | 1-2 |
| Pages: | 14 - 15 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Baden-Dättwil |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 001616552 |
Hamiltonian approach for explosive percolation
,
Moreira, A.A., Oliveira, E.A., Reis, S.D.S., Herrmann, Hans Jürgen, Andrade Jr., José S.,
2010
>>
| Author(s): | Moreira, A.A., Oliveira, E.A., Reis, S.D.S., Herrmann, Hans Jürgen, Andrade Jr., José S. |
| Title: | Hamiltonian approach for explosive percolation |
| Abstract: | We present a cluster growth process that provides a clear connection between equilibrium statistical mechanics and an explosive percolation model similar to the one recently proposed by D. Achlioptas et al. [Science 323, 1453 (2009)]. We show that the following two ingredients are sufficient for obtaining an abrupt (first-order) transition in the fraction of the system occupied by the largest cluster: (i) the size of all growing clusters should be kept approximately the same, and (ii) the inclusion of merging bonds (i.e., bonds connecting vertices in different clusters) should dominate with respect to the redundant bonds (i.e., bonds connecting vertices in the same cluster). Moreover, in the extreme limit where only merging bonds are present, a complete enumeration scheme based on treelike graphs can be used to obtain an exact solution of our model that displays a first-order transition. Finally, the presented mechanism can be viewed as a generalization of standard percolation that discloses a family of models with potential application in growth and fragmentation processes of real network systems. |
| Published in: | Physical review. E, Statistical, nonlinear, and soft matter physics |
| Volume: | 81 |
| Issue: | 4 |
| Pages: | 040101 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Subjects: | Physik allgemein|Physics, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295530757 |
| DOI: | 10.1103/PhysRevE.81.040101 |
| Nebis system number: | 004109079 |
Derivation of the lattice Boltzmann model for relativistic hydrodynamics
,
Mendoza, Miller, Boghosian, B.M., Herrmann, Hans Jürgen, Succi, S.,
2010
>>
| Author(s): | Mendoza, Miller, Boghosian, B.M., Herrmann, Hans Jürgen, Succi, S. |
| Title: | Derivation of the lattice Boltzmann model for relativistic hydrodynamics |
| Abstract: | A detailed derivation of the lattice Boltzmann scheme for relativistic fluids recently proposed in M. Mendoza, B. Boghosian, H. Herrmann, and S. Succi, Phys. Rev. Lett. 105, 014502 ( 2010) is presented. The method is numerically validated and applied to the case of two quite different relativistic fluid-dynamic problems, namely, shock-wave propagation in quark-gluon plasmas and the impact of a supernova blast wave on massive interstellar clouds. Close to second-order convergence with the grid resolution, as well as linear dependence of computational time on the number of grid points and time steps, are reported. |
| Published in: | Physical review. D. Particles, fields, gravitation, and cosmology |
| Volume: | 82 |
| Issue: | 10 |
| Pages: | 105008 |
| ISSN: | 1550-7998, 0556-2821, 1550-2368 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000284049800009 |
| DOI: | 10.1103/PhysRevD.82.105008 |
| Nebis system number: | 000003717 |
Simulation of flow of mixtures through anisotropic porous media using a lattice Boltzmann model
,
Mendoza, M., Wittel, F. K., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Mendoza, M., Wittel, F. K., Herrmann, Hans Jürgen |
| Title: | Simulation of flow of mixtures through anisotropic porous media using a lattice Boltzmann model |
| Abstract: | We propose a description for transient penetration simulations of miscible and immiscible fluid mixtures into anisotropic porous media, using the lattice Boltzmann (LB) method. Our model incorporates hydrodynamic flow, advection-diffusion, surface tension, and the possibility for global and local viscosity variations to consider various types of hardening fluids. The miscible mixture consists of two fluids, one governed by the hydrodynamic equations and one by advection-diffusion equations. We validate our model on standard problems like Poiseuille flow, the collision of a drop with an impermeable, solid interface and the deformation of the fluid due to surface tension forces. To demonstrate the applicability to complex geometries, we simulate the invasion process of mixtures into wood spruce samples. |
| Published in: | The European physical journal. E, Soft matter |
| Volume: | 32 |
| Issue: | 4 |
| Pages: | 339 - 348 |
| ISSN: | 1292-8941, 1292-895X |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Heidelberg |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000283247000002 |
| DOI: | 10.1140/epje/i2010-10629-8 |
| Nebis system number: | 003870978 |
Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics
,
Mendoza, M., Boghosian, B.M., Herrmann, Hans Jürgen, Succi, S.,
2010
>>
| Author(s): | Mendoza, M., Boghosian, B.M., Herrmann, Hans Jürgen, Succi, S. |
| Title: | Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics |
| Abstract: | A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows. |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 1 |
| Pages: | 014502 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000279392400002 |
| DOI: | 10.1103/PhysRevLett.105.014502 |
| Nebis system number: | 000003868 |
Progressive Collapse Mechanisms of Brittle and Ductile Framed Structures
,
Masoero, E., Wittel, F.K., Herrmann, Hans Jürgen, Chiaia, B.M.,
2010
>>
| Author(s): | Masoero, E., Wittel, F.K., Herrmann, Hans Jürgen, Chiaia, B.M. |
| Title: | Progressive Collapse Mechanisms of Brittle and Ductile Framed Structures |
| Abstract: | In this paper, we study the progressive collapse of three-dimensional framed structures made of reinforced concrete after the sudden loss of a column. The structures are represented by elastoplastic Euler-Bernoulli beams with elongation-rotation failure threshold. We performed simulations using the discrete element method considering inelastic collisions between the structural elements. The results show what collapse initiation and impact-driven propagation mechanisms are activated in structures with different geometric and mechanical features. Namely, we investigate the influence of the cross sectional size and reinforcement alpha and of the plastic capacity beta of the structural elements. We also study the final collapse extent and the fragment size distribution and their relation to alpha, beta, and to the observed collapse mechanisms. Finally, we compare the damage response of structures with symmetric and asymmetric reinforcement in the beams. |
| Published in: | Journal of engineering mechanics |
| Volume: | 136 |
| Issue: | 8 |
| Pages: | 987 - 995 |
| ISSN: | 0733-9399, 1943-7889 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Subjects: | Framed structures |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Framed structures |
| DBID source: | WOS-000279991500006 |
| DOI: | 10.1061/(ASCE)EM.1943-7889.0000143 |
| Nebis system number: | 000018981 |
Determinitare si cuantificare nedustructiva a proceselor de difuziune in lemni cu ajutorul metodei imagistice cu neutron
,
Mannes, David, Sonderegger, Walter, Hering, Stefan, Lehmann, Eberhard, Niemz, Peter,
2010
>>
| Author(s): | Mannes, David, Sonderegger, Walter, Hering, Stefan, Lehmann, Eberhard, Niemz, Peter |
| Title: | Determinitare si cuantificare nedustructiva a proceselor de difuziune in lemni cu ajutorul metodei imagistice cu neutron |
| Abstract: | Diffusion processes in samples of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies [L.] Karst.) were determined and quantified by means of neutron imaging (NI). The experiments were carried out at the neutron imaging facility NEUTRA at the Paul Scherrer Institute (PSI) in Villigen (Switzerland) using a thermal neutron spectrum. NI is a non-destructive and non-invasive testing method with a very high sensitivity for hydrogen and thus water. Within the scope of this study, diffusion processes in the longitudinal direction were ascertained for solid wood samples exposed to a differentiating climate (dry side / wet side). With NI it was possible to determine the local distribution and consequently the total amount of water absorbed by the samples. The calculated values differ scarcely from those ascertained by weighing (= 3%). The method yields profiles of the water content over the whole sample, thus allowing the local and temporal resolution of diffusion processes within the sample in the main transport direction (longitudinal). On the basis of these profiles, it was possible to calculate the diffusion coefficients along the fibre direction according to Fick's second law. |
| Published in: | Pro ligno |
| Volume: | 6 |
| Issue: | 2 |
| Pages: | 27 - 40 |
| ISSN: | 1841-4737 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Brasov |
| Publication status: | Published |
| Subjects: | Diffusion, Diffusion coefficient, Moisture content, Neutron imaging, Non-destructive testing, Wood |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Diffusion, Diffusion coefficient, Moisture content, Neutron imaging, Non-destructive testing, Wood |
| DBID source: | CSV- |
Determination of moisture transport process by means of neutron imaging
,
Mannes, David, Sonderegger, Walter, Hering, Stefan, Lehmann, Eberhard, Niemz, Peter,
2010
>>
| Author(s): | Mannes, David, Sonderegger, Walter, Hering, Stefan, Lehmann, Eberhard, Niemz, Peter |
| Title: | Determination of moisture transport process by means of neutron imaging |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | COST Action FP0802 Workshop "Wood Structure/Function-Relationships" |
| Event date: | October 5-8, 2010 |
| Place: | Hamburg, Germany |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
Nondestructive determination of moisture transfer in wood by means of neutron imaging
,
Lehmann, E., Mannes, D., Sonderegger, W., Hering, S., Niemz, P.,
2010
>>
| Author(s): | Lehmann, E., Mannes, D., Sonderegger, W., Hering, S., Niemz, P. |
| Title: | Nondestructive determination of moisture transfer in wood by means of neutron imaging |
| Abstract: | The relationship between wood and water is of special interest within the field of wood research as all of the wood properties depend to some extent on the moisture content. With conventional methods it is practically impossible to determine moisture transport processes with high spatial and temporal resolution. Neutron imaging is a non-destructive and non-invasive testing method, which is comparable to X-ray but disposes of a considerably higher sensitivity for hydrogen and hence water. Within the scope of the presented work, diffusion processes in along the fibre (longitudinal direction) were determined for solid wood samples of European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst.). Oven-dry samples were exposed to a differential climate and the water absorption process was ascertained over several hours. With neutron imaging it was possible to determine the distribution of water contents within the wood samples for every moment during the experiment. The obtained moisture profiles were then used to calculate the diffusion coefficients in longitudinal direction for unsteady state conditions along Fick’s second law. This is particularly interesting as the only values, which can be found in literature concern the diffusion coefficient under steady state conditions. The utilisation of neutron imaging can thus be used to close gaps in the knowledge on dynamic moisture transfer processes in wood. The direction of the water transport process is for the application of the method irrelevant. With neutron imaging the absorption of water as well as desorption / drying processes in wood can be examined. The method allows to quantify and localise even very small amounts of water within wood samples and to observe moisture transfer over an arbitrary time period. |
| Book title: | 11th International IUFRO Wood Drying Conference Recent Advances in the Field of Wood Drying, Skellefteå, Sweden, January 18-22, 2010, Proceedings |
| Pages: | 63 - 69 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 11th International IUFRO Wood Drying Conference |
| Event date: | January 19-23, 2010 |
| Place: | Skellefteå, Sweden |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Multi-level analysis of lignin distribution and cell geometry in Picea abies (L. Karst.) as a basis to explain anisotropic swelling
,
Lanvermann, Christian, Schmitt, Uwe, Niemz, Peter,
2010
>>
| Author(s): | Lanvermann, Christian, Schmitt, Uwe, Niemz, Peter |
| Title: | Multi-level analysis of lignin distribution and cell geometry in Picea abies (L. Karst.) as a basis to explain anisotropic swelling |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | COST Action FP0802 Workshop "Wood Structure/Function-Relationships" |
| Event date: | October 5-8, 2010 |
| Place: | Hamburg, Germany |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
Two-dimensional swelling and shrinkage behavior of spruce wood in the LR and RT planes
,
Lanvermann, Christian, Keunecke, Daniel, Novosseletz, Katerina, Niemz, Peter,
2010
>>
| Author(s): | Lanvermann, Christian, Keunecke, Daniel, Novosseletz, Katerina, Niemz, Peter |
| Title: | Two-dimensional swelling and shrinkage behavior of spruce wood in the LR and RT planes |
| Book title: | Wood structure and properties '10 |
| Pages: | 79 - 84 |
| ISBN: | 9788096886852, 8096886851 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zvolen |
| Publication status: | Published |
| Event name: | The 6th International Symposium Wood Structure and Properties '10 |
| Event date: | September 6-9, 2010 |
| Place: | Zvolen, Slovakia |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Influence of coatings on diffusion and sorption properties of wood
,
Kránitz, Katalin, Niemz, Peter, Anheuser, Kilian,
2010
>>
| Author(s): | Kránitz, Katalin, Niemz, Peter, Anheuser, Kilian |
| Title: | Influence of coatings on diffusion and sorption properties of wood |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | International Workshop: Allowable Microclimatic Variations for Polychrome Wood - Focussed meeting of COST IE0601 |
| Event date: | February 18-19, 2010 |
| Place: | Oslo, Norway |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Untersuchungen zu Eigenschaften von gealtertem Holz
,
Kránitz, Katalin, Niemz, Peter,
2010
>>
| Author(s): | Kránitz, Katalin, Niemz, Peter |
| Title: | Untersuchungen zu Eigenschaften von gealtertem Holz |
| Abstract: | Um die Widerverwendbarkeit von natürlich gealtertem Holz beurteilen zu können, wurden Untersuchungen zu dessen Eigenschaften durchgeführt. Mit Hilfe drei verschiedener Ultraschall-Messgeräte wurden die elastischen Konstanten (E- und G-Modul) bestimmt. Die Daten zeigen im Vergleich zu frischem Holz keine signifikanten Eigenschaftsänderungen, wie es auch Literaturangaben entnommen werden kann. |
| Book title: | Holzbau Forschung + Praxis : Doktorandenkolloquium Stuttgart, 17./18. März 2010 |
| Pages: | 37 - 42 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Stuttgart |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Bauingenieurwesen allgemein, Konstruktiver Ingenieurbau|Civil Engineering (General), Structural Engineering |
| Event name: | Doktorandenkolloquium Holzbau Forschung + Praxis |
| Event date: | March 17-18, 2010 |
| Place: | Stuttgart, Germany |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 006577580 |
Strength estimation of aged wood by means of ultrasonic devices
,
Kránitz, K., Deublein, M., Niemz, Peter,
2010
>>
| Author(s): | Kránitz, K., Deublein, M., Niemz, Peter |
| Title: | Strength estimation of aged wood by means of ultrasonic devices |
| Abstract: | Because of ecological factors, recycling old (= aged) wood is getting more and more important, even in applications where mechanical strength plays a central role. The aim of this study was to examine certain mechanical parameters of old wood and to better understand the influence of aging on mechanical properties. Therefore, measurements on boards and on small, clear wood specimens were carried out. Ultrasound velocities of longitudinal and, in some cases, of transversal waves were measured. Based on the results, elastic and shear moduli were determined. The measurements were performed on specimens of aged Norway spruce, European oak and Scots pine and compared with recent wood as a reference. The measurements on boards revealed higher MOE values for old wood but the results for the small clear specimens do not confirm this observation. It is supposed that the difference is more likely a consequence of different densities and the structure of growth rings than a consequence of the wood age. |
| Book title: | The future of quality control for wood & wood products : Proceedings of the Final Conference of COST Action E53 : ‘Quality control for wood & wood products’ : 4 – 7th May 2010, Edinburgh, UK |
| Pages: | 425 - 433 |
| ISBN: | 978-0-9566187-0-2 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Edinburgh |
| Publication status: | Published |
| Event name: | Final Conference of COST Action E53: 'Quality control for wood & wood products' |
| Event date: | May 4-7, 2010 |
| Place: | Edinburgh, UK |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294665937 |
Strenght estimation of aged wood by menas of ultrasonic devices
,
Kránitz, K., Deublein, M., Niemz, P.,
2010
>>
| Author(s): | Kránitz, K., Deublein, M., Niemz, P. |
| Title: | Strenght estimation of aged wood by menas of ultrasonic devices |
| Abstract: | Because of ecological factors, recycling old (= aged) wood is getting more and more important, even in applications where mechanical strength plays a central role. The aim of this study was to examine certain mechanical parameters of old wood and to better understand the influence of aging on mecanical properties. Therefore, measurements on boards and on small, clear wood specimens were carried out. Ultrasound velocities of longitudinal and, in some cases, of transversal waves were measured. Based on the results, elastic and shear moduli were determined. The measurements were performed on specimens of aged Norway spruce, European oak and Scots pine and compared with recent wood as a reference. The measurements on boards revealed higher MOE values for old wood but the results for the small clear specimens do not confirm this observation. It is supposed that the difference is more likely a consequence of different densities and the structure of growth rings than a consequence of the wood age. |
| Book title: | The future of quality control for wood & wood products, Proceedings of the final conference of COST Action E53: Quality control for wood & wood products |
| Pages: | 425 - 433 |
| ISBN: | 978-09566187-0-2 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Edinburgh |
| Publication status: | Published |
| Event name: | The future of quality control for wood & wood products - The final conference of COST Action E53: Quality control for wood & wood products |
| Event date: | May 4-7, 2010 |
| Place: | Edinburgh, UK |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Determination of elastic parameters of aged wood by means of ultrasonic devices
,
Kránitz Katalin, Deublein, Markus, Niemz, Peter,
2010
>>
| Author(s): | Kránitz Katalin, Deublein, Markus, Niemz, Peter |
| Title: | Determination of elastic parameters of aged wood by means of ultrasonic devices |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 4th International Conference of Cost Action IE0601 |
| Event date: | October 20-22, 2010 |
| Place: | Izmir, Turkey |
| Language: | English |
| Review status: | Unknown |
| DBID source: | FORM-1294666216 |
Physical and mechanical properties of historic wood
,
Kranitz, K., Anheuser, K., Niemz, P.,
2010
>>
| Author(s): | Kranitz, K., Anheuser, K., Niemz, P. |
| Title: | Physical and mechanical properties of historic wood |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 4th International conference of Cost Action IE0601 |
| Event date: | October 20-22, 2010 |
| Place: | Izmir, Turkey |
| Language: | English |
| DBID source: | CSV- |
Verarbeitung und Verwendungsmöglichkeiten von Laubholz
,
Krackler, Verena, Niemz, Peter, Keunecke, Daniel,
2010
>>
| Author(s): | Krackler, Verena, Niemz, Peter, Keunecke, Daniel |
| Title: | Verarbeitung und Verwendungsmöglichkeiten von Laubholz |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Infoveranstaltung Laubholz |
| Event date: | September 29, 2010 |
| Place: | Olten, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Verwertung von Laubholz und Laubholzresten
,
Krackler, Verena, Niemz, Peter,
2010
>>
| Author(s): | Krackler, Verena, Niemz, Peter |
| Title: | Verwertung von Laubholz und Laubholzresten |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Montagskolloquien für die Praxis |
| Event date: | January 11, 2010 |
| Place: | Zürich, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Verarbeitung und Verwendungsmöglichkeiten von Laubholz und Laubholzresten
,
Krackler, Verena, Keunecke, Daniel, Niemz, Peter,
2010
>>
| Author(s): | Krackler, Verena, Keunecke, Daniel, Niemz, Peter |
| Title: | Verarbeitung und Verwendungsmöglichkeiten von Laubholz und Laubholzresten |
| Abstract: | Das dritte und aktuellste schweizerische Forstinventar (LFI) von 2004 bis 2006 bescheinigte für Laubholz eine Vorratssteigerung von 10,4 %. Der Nadelholzvorrat dagegen sank. Obwohl auch andere europäische Länder diese Tendenz aufweisen, wird in der Schweiz der Grossteil (ca. 60 %) des geernteten Laubholzes sogleich energetisch verwertet, ohne es einer vorherigen Nutzung zuzuführen. Neben dem geringeren Stammholzanteil und der schwierigeren Verarbeitung stellt in der Schweiz besonders die nicht geschlossene Wertschöpfungskette vom Rundholz zum Endprodukt ein ausschlaggebendes Problem dar. Für nicht genutzte Sortimente war daher die energetische Verwertung bisher die komfortabelste und lohnendste Lösung. Neben der Verarbeitung zu Vollholzprodukten und Holzwerkstoffen kann Holz auch stofflich oder chemisch genutzt werden. Im Vollholzbereich besitzt Laubholz mitunter eine lange Tradition (z.B. Dachstühle, Treppen, Möbel, Fussböden oder Innenausbauten). Für einige Holzwerkstoffe wie Massivholzplatten und Sperrholz sind Laubhölzer ebenso üblich. Zahlreiche Forschungsprojekte und –berichte bestätigen jedoch auch in Nadelholzdomänen einen Laubholzeinsatz. Dazu gehören Spanplatten, OSB, MDF sowie Holzwerkstoffe für den tragenden Bereich wie Brettschichtholz, Duo- und Triobalken. Bestehende Normen hindern Hersteller allerdings im Moment noch an einer wirtschaftlichen Umsetzung. Ein erster Schritt in die richtige Richtung fand im Oktober 2009 in Deutschland statt, als Brettschichtholz aus Buche die bauaufsichtliche Zulassung für tragende Zwecke im Innenbereich erhielt. Um neue Absatzkanäle neben der energetischen Nutzung entwickeln zu können, ist der Aufbau einer weiterverarbeitenden Industrie in der Schweiz unumgänglich. Das garantiert die inländische Produktion von Halb- und Endfabrikaten und keine Umwege über das Ausland. One crucial result of the recent Swiss National Forest Inventory (NFI) from 2004-2006 is a volume increase of 10.4 % for hardwood. The softwood volume, in contrast, has decreased. Although other European countries confirm this tendency, Switzerland still uses the bulk (ca. 60 %) of the harvested hardwood directly for energetic purposes instead of adding value on it by other applications. Besides the lower percentage of stem wood and the more complicated processing, the main problem in Switzerland is that the value chain from the round timber to an end product is not complete. Therefore the energetic use was and still is the most comfortable and profitable solution for unused assortments. Hardwood use is possible in the form of solid wood and wood composites, but it can even beused as a substance or chemical product. As a solid wood, hardwood has a long tradition (e.g.,roof structures, stairs, furniture, flooring). Today, it is also employed for wood based materials (solid wood panels, plywood). Scientific analyses reveal that hardwoods nowadays even enter softwood domains such as particle boards, medium density fibreboards, oriented strand boards and structural timber (glued laminated timber, Duo/Trio beams). At the moment, manufacturers are restrained regarding the commercial production due to current standards or failing design bases. In the pulp production, domestic hardwood is more and more repressed as usage of fast-growing plantation lumber increases. To develop marketing channels away from energetic use, it is mainly necessary to build a processing industry in Switzerland. Semi-finished or finished goods should be produced on Swiss terrain and not imported from abroad. |
| Published in: | IfB Projektstudie |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zürich |
| Publication status: | Published |
| Subjects: | Forstwissenschaften (inkl. Jagd)|Forestry (incl. Hunting) |
| Language: | German |
| Review status: | Internally reviewed |
| DBID source: | CSV- |
| DOI: | 10.3929/ethz-a-006113078 |
| Nebis system number: | 006113078 |
Possible fields of hardwood application
,
Krackler, V., Hurst, A., Keunecke, D., Niemz, P.,
2010
>>
| Author(s): | Krackler, V., Hurst, A., Keunecke, D., Niemz, P. |
| Title: | Possible fields of hardwood application |
| Book title: | The 4th Conference on Hardwood Research and Utilisation in Europe |
| Pages: | 235 - 244 |
| ISBN: | 978-963-9883-52-9 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Sopron |
| Publication status: | Published |
| Event name: | 4th Conference on Hardwood Research and Utilisation in Europe |
| Event date: | May 17-18, 2010 |
| Place: | Sopron, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
SilviScan vs. Neutron Imagin to Generate Radial Softwood Density Profiles
,
Keunecke, Daniel, Mannes, David, Niemz, Peter, Lehmann, Eberhard, Evans, Robert,
2010
>>
| Author(s): | Keunecke, Daniel, Mannes, David, Niemz, Peter, Lehmann, Eberhard, Evans, Robert |
| Title: | SilviScan vs. Neutron Imagin to Generate Radial Softwood Density Profiles |
| Abstract: | Knowing the mean and the intra-ring density of wood enables to estimate mechanical and physical wood properties, and it provides important climatological information. Many methodological approaches to determine wood density arc in use, and they undergo a permanent development and improvement. Goal of this study was to compare two up-to-date non-destructive radiographic techniques - SilviScan (based on X-rays) and Neutron Imaging - in terms of their methodology, the specimen handling, and the generated density data. At the present time, the systems clearly differ regarding their user-friendliness (and thus their suitability) especially for measurements on wooden samples. However, the measurement results of both techniques, i.e. the qualitative and quantitative characteristics of the density profiles, show good to high congruence. |
| Published in: | Wood research |
| Volume: | 55 |
| Issue: | 3 |
| Pages: | 49 - 59 |
| ISSN: | 1336-4561, 0012-6136 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Bratislava |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Wood density, Densitometry, SilviScan, Neutron imaging, Common yew, Norway spruce |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Wood density, Densitometry, SilviScan, Neutron imaging, Common yew, Norway spruce |
| DBID source: | WOS-000284027900005 |
| Nebis system number: | 001541175 |
Influence of the growth ring angle on transverse elastic properties of softwoods
,
Keunecke, Daniel, Garab, Jozsef, Hering, Stefan, Szalai, Jozsef, Niemz, Peter,
2010
>>
| Author(s): | Keunecke, Daniel, Garab, Jozsef, Hering, Stefan, Szalai, Jozsef, Niemz, Peter |
| Title: | Influence of the growth ring angle on transverse elastic properties of softwoods |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | COST Action FP0802 Workshop "Wood Structure/Function-Relationships" |
| Event date: | October 5-8, 2010 |
| Place: | Hamburg, Germany |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
2-dimensionale Dehnungsverteilung in der LR- und RT-Ebene von Fichtenholz bei Feuchteänderung
,
Keunecke, D., Niemz, Peter,
2010
>>
| Author(s): | Keunecke, D., Niemz, Peter |
| Title: | 2-dimensionale Dehnungsverteilung in der LR- und RT-Ebene von Fichtenholz bei Feuchteänderung |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Braunschweig |
| Publication status: | Published |
| Event name: | 4. Kolloquium "Aktuelle Fragen der Holzforschung" |
| Event date: | September 20, 2010 |
| Place: | Braunschweig, Germany |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Elastic parameters of softwoods loaded in transverse compression at varying growth ring angles
,
Keunecke, D., Garab, J., Hering, Stefan, Szalai, Jozsef, Niemz, Peter,
2010
>>
| Author(s): | Keunecke, D., Garab, J., Hering, Stefan, Szalai, Jozsef, Niemz, Peter |
| Title: | Elastic parameters of softwoods loaded in transverse compression at varying growth ring angles |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Podbanské, Slovakia |
| Publication status: | Published |
| Event name: | The 6th International Symposium Wood Structure and Properties '10 |
| Event date: | September 6-9, 2010 |
| Place: | Podbanské, Slovakia |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
From shear bands to rapid flow
,
Kadau, Dirk, Herrmann, Hans J., Springman, Sarah M., Puzrin, Alexander M.,
2010
>>
| Author(s): | Kadau, Dirk, Herrmann, Hans J., Springman, Sarah M., Puzrin, Alexander M. |
| Title: | From shear bands to rapid flow |
| Subtitle: | editorial |
| Published in: | Granular Matter |
| Volume: | 12 |
| Issue: | 3 |
| Pages: | 209 - 210 |
| ISSN: | 1434-7636, 1434-5021 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Event name: | Scientific Conference: From shear bands to rapid flow |
| Event date: | February 22-27, 2009 |
| Place: | Monte Verità, Switzerland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000277200800001 |
| DOI: | 10.1007/s10035-010-0183-x |
| Nebis system number: | 002003491 |
Iterative decomposition of Barabasi-Albert scale-free networks
,
Jácome, S.S.B., Silva, L.R. da, Moreira, A.A., Andrade Jr., José S., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Jácome, S.S.B., Silva, L.R. da, Moreira, A.A., Andrade Jr., José S., Herrmann, Hans Jürgen |
| Title: | Iterative decomposition of Barabasi-Albert scale-free networks |
| Abstract: | We study a decomposition process where all nodes with a targeted degree are removed from the network. Each removal step results in changes in the degrees of the remaining nodes, and other nodes may attain the targeted degree. The processes continue iteratively until no more nodes with the targeted degree are present in the decomposed network. The network model used in our study is the well known Barabasi–Albert network, that is built with an iterative growth based on preferential attachment. Our results show an exponential decay of the number of nodes removed at each step. The total number of nodes removed in the whole process depends on the targeted degree and decay with a power law controlled by the same exponent as the degree distribution of the network. |
| Published in: | Physica. A |
| Volume: | 389 |
| Pages: | 3674 - 3677 |
| ISSN: | 0378-4371, 1873-2119 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Network, Decomposition, Scaling |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Network, Decomposition, Scaling |
| DBID source: | FORM-1295530900 |
| DOI: | 10.1016/j.physa.2010.03.052 |
| Nebis system number: | 001929798 |
Wärme- und Feuchtetransport in Holzbauelementen unter freier Bewitterung = Heat and moisture transfer in wood-based constructions under natural weathering
,
Joscak, Matus, Sonderegger, Walter, Niemz, Peter,
2010
>>
| Author(s): | Joscak, Matus, Sonderegger, Walter, Niemz, Peter |
| Title: | Wärme- und Feuchtetransport in Holzbauelementen unter freier Bewitterung = Heat and moisture transfer in wood-based constructions under natural weathering |
| Abstract: | Es wurden vergleichende Untersuchungen des Wärme- und Feuchtetransportes in unterschiedlichen Holzbaukonstruktionen unter freier Bewitterung durchgeführt. Insgesamt wurden fünf Konstruktionen an Versuchsbauten auf dem Gelände der ETH Zürich getestet. Neben einer verdübelten Massivholzkonstruktion wurden zwei Ständerkonstruktionen und zwei weitere Vollholzkonstruktionen untersucht. Aus den gewonnenen Daten wurden dynamische Parameter der Gebäudehüllen ermittelt. Zusätzlich wurden Messungen an drei realen Bauten (zwei verdübelte Massivholzkonstruktionen, eine Ständerkonstruktion) durchgeführt. Die gemessenen Daten der Versuchsbauten wurden mit den Daten der Messungen an realen Bauten verglichen. Die Ergebnisse zeigen unter anderem, dass die Vollholzkonstruktionen sehr ausgewogene, hygrothermische Eigenschaften aufweisen. Heat and moisture transfer in wood-based constructions under natural weathering. In this project comparative measurements of heat and moisture transfer in wood-based constructions were carried out under natural weathering conditions at the campus of ETH Zurich. Altogether, five different constructions designed as small test buildings were investigated. In the first observation, the solid wood construction connected with wooden dowels - without any further binders is compared to two conventional wood frame constructions with one and two insulation layers. In the second observation, the mentioned solid wood construction is compared to one log construction and one solid wood construction with slotted wood elements. From the data, the dynamic parameters of the heat and moisture transfer of these building envelopes were determined. Additionally, the heat and moisture data of three real used buildings (two solid wood constructions with wooden dowels and one conventional wood frame construction) were measured. These data were compared with the data measured on the small test buildings. The results, inter alia, are showing that the solid wood constructions achieve a good balance in hygrothermal properties. |
| Published in: | Bauphysik |
| Volume: | 32 |
| Issue: | 5 |
| Pages: | 308 - 318 |
| ISSN: | 0171-5445, 1437-0980 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Behaglichkeit, Feuchtetransport, freie Bewitterung, Holzbau, Massivholz, Ständerkonstruktion, Wärmetransport, Climate comfort, Heat transfer, Moisture transfer, Solid wood, Timber structures, Wood frame construction, Feuchte, Versuche, Wärme, Experimental set-ups, Heat, Moisture |
| Language: | German |
| Review status: | Peer reviewed |
| Keyword: | Behaglichkeit, Feuchtetransport, freie Bewitterung, Holzbau, Massivholz, Ständerkonstruktion, Wärmetransport, Climate comfort, Heat transfer, Moisture transfer, Solid wood, Timber structures, Wood frame construction, Feuchte, Versuche, Wärme, Experimental set-ups, Heat, Moisture |
| DBID source: | WOS-000283888400005 |
| DOI: | 10.1002/bapi.201010035 |
| Nebis system number: | 000006704 |
Untersuchungen zum Feuchte- und Wärmetransport in unterschiedlichen Wandaufbauten aus Holz
,
Joscak, Matus, Niemz, Peter,
2010
>>
| Author(s): | Joscak, Matus, Niemz, Peter |
| Title: | Untersuchungen zum Feuchte- und Wärmetransport in unterschiedlichen Wandaufbauten aus Holz |
| Book title: | Holzbau Forschung + Praxis : Doktorandenkolloquium Stuttgart, 17./18. März 2010 |
| Pages: | 131 - 138 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Stuttgart |
| Publication status: | Published |
| Subjects: | Natürliche Werkstoffe|Natural Materials, Bauingenieurwesen allgemein, Konstruktiver Ingenieurbau|Civil Engineering (General), Structural Engineering |
| Event name: | Doktorandenkolloquium Holzbau Forschung + Praxis 2010 |
| Event date: | March 17-18, 2010 |
| Place: | Stuttgart, Germany |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 006577580 |
Comparative measurements of heat and moisture transport in wood based constructions
,
Joscak, M., Plagge, R., Niemz, Peter, Sonderegger, W.,
2010
>>
| Author(s): | Joscak, M., Plagge, R., Niemz, Peter, Sonderegger, W. |
| Title: | Comparative measurements of heat and moisture transport in wood based constructions |
| Abstract: | In this study the heat and the moisture transport parameters of three wood based constructions are compared. Two of the tested constructions are conventional wood frame constructions (with one and two insulation layers). The third construction is a solid wood construction connected with wooden dowels without any further binder. Three small test buildings without openings were constructed for this experiment the measurements were carried out under natural weather conditions at the campus of the ETH Zurich. Indoor temperature and the temperature within the walls, indoor relative humidity and the climate data of outdoor environment were measured from February 2007 for a period of one year. The results show a higher thermal protection of the indoor environment by the solid wood construction during summer. During winter, the thermal stability of the solid wood construction is advantageous compared to both conventional wood frame constructions due to a slower cooling of walls. In the conventional wood frame the relative humidity inside test buildings continuously increased during the whole experiment. In contrast, the relative humidity in the solid wood construction was constant at a level of 40 to 48 %. The measured temperatures were compared with numerical simulation results. For this purpose. The simulation software Delphin was used -. The validation shows that Delphin is useful to simulate heat transport in test buildings. Test results indicate, together with thermal parameters like phase shift of thermal oscillation and thermal damping factor, that the most comfortable indoor environment can be achieved with the solid wood construction. |
| Book title: | Research on building physics : proceedings of the 1st Central European Symposium on Building Physics 13-15 September 2010, Cracow - Lodz, Poland |
| Pages: | 201 - 207 |
| ISBN: | 978-83-7283-367-9 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Lodz |
| Publication status: | Published |
| Event name: | 1st Central European Symposium on Building Physics, CESBP 2010 |
| Event date: | September 13-15, 2010 |
| Place: | Cracow, Poland |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
| Nebis system number: | 006230170 |
Messungen zum Feuchte- und Wärmetransport an Versuchsbauten und realen Bauten mit verschiedenen Wandaufbauten
,
Joscak, M., Niemz, P.,
2010
>>
| Author(s): | Joscak, M., Niemz, P. |
| Title: | Messungen zum Feuchte- und Wärmetransport an Versuchsbauten und realen Bauten mit verschiedenen Wandaufbauten |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Montagskolloquien für die Praxis |
| Event date: | January 11, 2010 |
| Place: | Zurich, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
Biased percolation on scale-free networks
,
Hooyberghs, Hans, Schaeybroeck, Bert van, Moreira, André A., Andrade, José S., Jr., Herrmann, Hans J., Indekeu, Joseph O.,
2010
>>
| Author(s): | Hooyberghs, Hans, Schaeybroeck, Bert van, Moreira, André A., Andrade, José S., Jr., Herrmann, Hans J., Indekeu, Joseph O. |
| Title: | Biased percolation on scale-free networks |
| Abstract: | Biased degree-dependent percolation was recently shown to provide strategies for turning robust networks fragile and vice versa. Here, we present more detailed results for biased edge percolation on scale-free networks. We assume a network in which the probability for an edge between nodes i and j to be retained is proportional to kikj− with ki and kj the degrees of the nodes. We discuss two methods of network reconstruction, sequential and simultaneous, and investigate their properties by analytical and numerical means. The system is examined away from the percolation transition, where the size of the giant cluster is obtained, and close to the transition, where nonuniversal critical exponents are extracted using the generating functions method. The theory is found to agree quite well with simulations. By presenting an extension of the Fortuin- Kasteleyn construction, we find that biased percolation is well described by the q→1 limit of the q-state Potts model with inhomogeneous couplings. |
| Published in: | Physical review E, Statistical, nonlinear, and soft matter physics |
| Volume: | 81 |
| Issue: | 1 |
| Pages: | 011102-1 - 011102-16 |
| ISSN: | 1539-3755, 1063-651X |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, N.Y. |
| Publication status: | Published |
| Subjects: | Physik und Astronomie|Physics and Astronomy |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1295530650 |
| DOI: | 10.1103/PhysRevE.81.011102 |
| Nebis system number: | 004109079 |
High-Performance Thin-Layer Chromatographic Assessment of Thermally Modified Wood
,
Hofmann, Tamás, Rétfalvi, Tamás, Albert, Levente, Niemz, Peter,
2010
>>
| Author(s): | Hofmann, Tamás, Rétfalvi, Tamás, Albert, Levente, Niemz, Peter |
| Title: | High-Performance Thin-Layer Chromatographic Assessment of Thermally Modified Wood |
| Published in: | JPC |
| Volume: | 23 |
| Issue: | 3 |
| Pages: | 227 - 229 |
| ISSN: | 0933-4173, 1789-0993 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Budapest |
| Publication status: | Published |
| Subjects: | Thermal modification, Wood, OPLC, HPTLC, Extractives |
| Event name: | 8th Balaton Symposium of High-Performance Separation Methods |
| Event date: | September 2-4, 2009 |
| Place: | Siófok, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Thermal modification, Wood, OPLC, HPTLC, Extractives |
| DBID source: | WOS-000279512300013 |
| DOI: | 10.1556/JPC.23.2010.3.12 |
| Nebis system number: | 000474209 |
Modelling the mechanical stresses in adhesive joints of wood bondings considering the mechanical and moisture behaviour of the adherend
,
Hering, Stefan, Niemz, Peter,
2010
>>
| Author(s): | Hering, Stefan, Niemz, Peter |
| Title: | Modelling the mechanical stresses in adhesive joints of wood bondings considering the mechanical and moisture behaviour of the adherend |
| Abstract: | Wood bondings have been used in timber construction and many other applications for a long time. Using layered arrangements, the homogenisation of the anisotropic physical and mechanical properties of solid wood reduce the influence of moisture and improve the mechanical behaviour of structural elements. However, new weak points can be created and effects such as debonding and delamination can occur. These failure characteristics depend on mechanical and hygroscopic loading as well as the composition of the structural components. Hence, delamination can be reduced by adjusting the properties of the appropriate adherent or by changing the structural assembly of the specific elements. Using finite element analysis, the influence of the adherent properties during the testing procedure and an example of cross-laminated wood panels on the adhesive load is investigated. The results show significant differences in the glue line stress distribution for varied growth ring angle, longitudinal Young’s modulus, diffusion as well as swelling and shrinkage properties. |
| Book title: | Wood Structure and Properties '10 |
| Pages: | 227 - 227 |
| ISBN: | 8096886851, 978-80-968868-5-2 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Zvolen |
| Publication status: | Published |
| Event name: | 6th International Symposium Wood Structure and Properties'10 |
| Event date: | September 6-9, 2010 |
| Place: | Podbanské, Slovakia |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Pore space analysis of beech wood
,
Hass, Philipp, Wittel, Falk K., McDonald, Sam A., Marone, Federica, Stampanoni, Marco, Herrmann, Hans J., Niemz, Peter,
2010
>>
| Author(s): | Hass, Philipp, Wittel, Falk K., McDonald, Sam A., Marone, Federica, Stampanoni, Marco, Herrmann, Hans J., Niemz, Peter |
| Title: | Pore space analysis of beech wood |
| Subtitle: | The vessel network |
| Abstract: | Water transport in wood is vital for the survival of trees. With synchrotron radiation X-ray tomographic microscopy (SRXTM), it has become possible to characterize and quantify the three-dimensional (3D) network formed by vessels that are responsible for longitudinal transport. In the present study, the spatial size dependence of vessels and the organization inside single growth rings in terms of vessel-induced porosity was studied by SRXTM. Network characteristics, such as connectivity, were deduced by digital image analysis from the processed tomographic data and related to known complex network topologies. |
| Published in: | Holzforschung |
| Volume: | 64 |
| Issue: | 5 |
| Pages: | 639 - 644 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | Landwirtschaft allgemein|Agriculture, General, Werkstoffe allgemein|Materials Sciences, General, Beech wood, Image analysis, Synchrotron radiation X-ray tomographic microscopy (SRXTM), Vessel network |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Beech wood, Image analysis, Synchrotron radiation X-ray tomographic microscopy (SRXTM), Vessel network |
| DBID source: | FORM-1295859760, WOS-000280627400014 |
| DOI: | 10.1515/HF.2010.103 |
| Nebis system number: | 000047746 |
Adhesive penetration into the vessel network of beech wood
,
Hass, Philipp, Wittel, F.K., McDonald, S.A., Marone, F., Stampanoni, M., Herrmann, H.J., Niemz, Peter,
2010
>>
| Author(s): | Hass, Philipp, Wittel, F.K., McDonald, S.A., Marone, F., Stampanoni, M., Herrmann, H.J., Niemz, Peter |
| Title: | Adhesive penetration into the vessel network of beech wood |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | MRC Graduate Symposium |
| Event date: | May 10, 2010 |
| Place: | Zurich, Switzerland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1317740800 |
A numerical study on the influence of the bond-line diffusivity on moisture-related stresses and deformations of three-layered spruce cross-laminates
,
Gereke,Thomas, Niemz, Peter,
2010
>>
| Author(s): | Gereke,Thomas, Niemz, Peter |
| Title: | A numerical study on the influence of the bond-line diffusivity on moisture-related stresses and deformations of three-layered spruce cross-laminates |
| Abstract: | The glue lines play an important role in diffusion processes through glued wooden elements. For the numerical calculation of the moisture distribution, the diffusion coefficient of the adhesive is needed. In previous studies it was evaluated from moisture measurements and found to be significantly lower than that of wood. The aim of this article is to apply this knowledge. Numerical studies on the influence of different diffusivities on warping and stresses in three-layered spruce cross-laminates were performed. The objective was to reduce moisture-induced stresses and deformations of cross-laminates to improve their performance. The results revealed a significant influence of the bond-line diffusivity on moisture content. The influence on warping, which was induced by a moisture gradient, is also very significant. A 25% reduction of deformation was achieved by applying diffusivity identical to that of the wood. Significant differences in stresses occurring perpendicular to the grain were detected only in the middle layer. Stresses in the outer layers were not affected by changing the diffusivity of the glue. In conclusion, an adhesive with high moisture permeability should be applied to reduce the results of moisture impact on cross-laminated timber. |
| Published in: | Wood material science & engineering |
| Volume: | 5 |
| Issue: | 2 |
| Pages: | 62 - 66 |
| ISSN: | 1748-0272, 1748-0280 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Colchester, Essex, England |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General, Adhesive, Diffusion, FEM, Moisture, Stress, Wood |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Adhesive, Diffusion, FEM, Moisture, Stress, Wood |
| DBID source: | CSV- |
| DOI: | 10.1080/17480271003717261 |
| Nebis system number: | 005350928 |
Moisture-induced stresses in spruce cross-laminates
,
Gereke, Thomas, Niemz, Peter,
2010
>>
| Author(s): | Gereke, Thomas, Niemz, Peter |
| Title: | Moisture-induced stresses in spruce cross-laminates |
| Abstract: | Eigenstresses occur in cross-laminated solid wood panels exposed to changes of moisture and are caused by hygroscopicity, volume change and orthotropy of the wood. Consequently, the shape distortions that result may reduce the serviceability and drying stresses may also cause cracks on the surface. It is the objective of this present study to determine and to describe moisture-induced stresses and to determine possibilities to reduce them. In laboratory tests, the stress state was studied by exposing panels to a single moistening step. The stresses were determined by release of strain and dynamic determination of the modulus of elasticity. Numerical simulations completed these tests. A three-dimensional material model considering elastic deformation, moisture-induced swelling and mechano-sorptive deformation was applied. The results show that the annual ring angle and pre-stresses are significant influential factors. In parameter studies, the influence of the input parameters on the results of numerical simulations was studied. The mechano-sorptive effect was found to have a strong influence on the results. Furthermore, the stiffness and coefficients of hygroexpansion of the wood affect the results of the simulations. It was concluded from the findings of this study that vertical annual rings should be applied and that horizontal annual rings should be avoided in the preparation of lamellas. Compressive pre-stresses in the outer layers may be a valid method to reduce the consequences of moisture variations but production costs and relaxation of the pre-stresses are critical factors. |
| Published in: | Engineering structures |
| Volume: | 32 |
| Issue: | 2 |
| Pages: | 600 - 606 |
| ISSN: | 0141-0296 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Kidlington |
| Publication status: | Published |
| Subjects: | Architektur, Gebaute Umwelt und Umweltgestaltung allgemein|Architecture, Built Environment and Environmental Design, General, Cross-lamination, Finite element method, Eigenstress, Moisture, Wood |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Cross-lamination, Finite element method, Eigenstress, Moisture, Wood |
| DBID source: | PP-53567 |
| DOI: | 10.1016/j.engstruct.2009.11.006 |
| Nebis system number: | 000004251 |
Moisture-induced stresses and distortions in spruce cross-laminates and composite laminates
,
Gereke, Thomas, Hass, Philipp, Niemz, Peter,
2010
>>
| Author(s): | Gereke, Thomas, Hass, Philipp, Niemz, Peter |
| Title: | Moisture-induced stresses and distortions in spruce cross-laminates and composite laminates |
| Abstract: | The crosswise gluing of cross-laminated panels made of solid wood can cause problems when exposed to moisture variations. In the present study, the substitution of the spruce middle layer by a wood composite is tested for its influence on moisture-induced stresses and deformations in laboratory tests and numerical simulations. Furthermore, slits in the spruce middle layer were investigated. The hygroscopic warping due to a moisture gradient, stresses caused by moistening and cracks due to drying were studied. The results show larger warping in composite laminates compared to the spruce cross-laminate, which is governed by the modulus of elasticity of the middle layer. The in-plane swelling was found to be larger in composite laminates, while stresses were lower. The drying test discovered that cracks develop in the middle layer of spruce-medium density fiberboard laminates due to shear stresses and tensile stresses in the thickness direction. It was concluded that slits can be applied in the middle layer, as they have no significant influence on moisture-induced stresses but increase the thermal insulation. If the substitution of the spruce layer is required, the application of oriented strand board in the middle layer is recommended. |
| Published in: | Holzforschung |
| Volume: | 64 |
| Issue: | 1 |
| Pages: | 127 - 133 |
| ISSN: | 0018-3830, 1437-434X |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Berlin |
| Publication status: | Published |
| Subjects: | cross-lamination, eigenstress, FEM, medium density fiberboard (MDF), moisture, oriented strand board (OSB), particleboard, spruce (Picea abies), warping |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | cross-lamination, eigenstress, FEM, medium density fiberboard (MDF), moisture, oriented strand board (OSB), particleboard, spruce (Picea abies), warping |
| DBID source: | WOS-000273912800016 |
| DOI: | 10.1515/HF.2010.003 |
| Nebis system number: | 000047746 |
The Hygroscopic Warping of Cross-Laminated Timber
,
Gereke, Thomas, Gustafsson, Per Johan, Persson, Kent, Niemz, Peter,
2010
>>
| Author(s): | Gereke, Thomas, Gustafsson, Per Johan, Persson, Kent, Niemz, Peter |
| Title: | The Hygroscopic Warping of Cross-Laminated Timber |
| Book title: | Delamination in Wood, Wood Products and Wood-Based Composites |
| Pages: | 269 - 286 |
| ISBN: | 978-90-481-9549-7, 978-90-481-9550-3 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Dordrecht |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| DOI: | 10.1007/978-90-481-9550-3 |
Measurement of standard and off-axis elastic moduli and Poisson's ratios of spruce and yew wood in the transverse plane
,
Garab, Jozsef, Keunecke, Daniel, Hering, Stefan, Szalai, Jozsef, Niemz, Peter,
2010
>>
| Author(s): | Garab, Jozsef, Keunecke, Daniel, Hering, Stefan, Szalai, Jozsef, Niemz, Peter |
| Title: | Measurement of standard and off-axis elastic moduli and Poisson's ratios of spruce and yew wood in the transverse plane |
| Abstract: | It is well known that in the radial-tangential plane of softwoods, the elastic modulus in the principal directions is clearly higher than the off-axis elastic moduli, which decrease to a minimum at a growth ring angle alpha of about 45A degrees. However, this angular dependency was experimentally proven by only a few early publications. The aims of this study were (1) to analyze this relationship with up-to-date equipment in compression tests on miniature softwood specimens with varying growth ring angles and (2) to compare the experimental results with those calculated by a tensor transformation to assess whether it is admissible to treat the investigated wood species as orthotropic materials. Two softwoods with distinctly different anatomic structures (Norway spruce and common yew) were chosen, and further properties such as Poisson's ratios were determined. The results confirm the above-mentioned angle-dependent tendency for spruce elasticity, but also show that it is not valid for softwoods in general since the behavior of yew was completely different. The tissue textures of both species, particularly density and density distribution, were discussed as possible reason for these observed differences. The determined Poisson's ratios for principal and off-axis load directions may be useful for modeling of material behavior. |
| Published in: | Wood science and technology |
| Volume: | 44 |
| Issue: | 3 |
| Pages: | 451 - 464 |
| ISSN: | 0043-7719, 1432-5225 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | München |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000280090400009 |
| DOI: | 10.1007/s00226-010-0362-2 |
| Nebis system number: | 000057691 |
Beam theory modelling of the performance of medieval yew longbows
,
Gamstedt, Kristofer, Bjurhager, Ingela, Berglund, Lars, Keunecke, Daniel, Niemz, Peter,
2010
>>
| Author(s): | Gamstedt, Kristofer, Bjurhager, Ingela, Berglund, Lars, Keunecke, Daniel, Niemz, Peter |
| Title: | Beam theory modelling of the performance of medieval yew longbows |
| Abstract: | Yew longbows were used during the Middle Ages in Europe, and was the preferred weapon until the emergence of guns that could reach further. The structure of these longbows was improved over the centuries, presumably by trial and error rather than systematic engineering design. Recovered bows show that the inner compressive side of the bows consists of heartwood, while the outer tensile side consists of sapwood. In comparison to other candidate wood species, yew shows higher toughness and a better combination of mechanical properties. The microstructure in thick yew stems is very regular and contains fewer defects than other available species. Based on recent measurements of the tensile and compressive elastic moduli and strengths, it can be shown with a simple beam theory model, that yew, with a judicious combination of heartwood and sapwood, outperform all other species in terms of maximum stored elastic energy density in bending. This means that the maximum potential energy in yew longbows could be converted to the highest kinetic energy of the arrow, compared with bows made of other materials available at the time. |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Kraków |
| Publication status: | Published |
| Event name: | Joint Focused Meeting "Modelling Mechanical Behaviour of Wooden Cultural Objects" |
| Event date: | April 12-13, 2010 |
| Place: | Kraków, Poland |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
Multi-particle Sintering of Fractal-Like Aggregates
,
Eggersdorfer, Max, Kadau, Dirk, Herrmann, Hans Jürgen, Pratsinis, Sotiris E.,
2010
>>
| Author(s): | Eggersdorfer, Max, Kadau, Dirk, Herrmann, Hans Jürgen, Pratsinis, Sotiris E. |
| Title: | Multi-particle Sintering of Fractal-Like Aggregates |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Seminar of the Computational Physics for Engineering Materials |
| Event date: | December 8, 2010 |
| Place: | Zurich, Switzerland |
| Language: | English |
| Review status: | Unknown |
| DBID source: | FORM-1292506609 |
Fragmentation and restructuring of soft-agglomerates under shear
,
Eggersdorfer, M. L., Kadau, D., Herrmann, Hans Jürgen, Pratsinis, Sotiris E.,
2010
>>
| Author(s): | Eggersdorfer, M. L., Kadau, D., Herrmann, Hans Jürgen, Pratsinis, Sotiris E. |
| Title: | Fragmentation and restructuring of soft-agglomerates under shear |
| Abstract: | Soft-agglomerate restructuring, break-up (or fragmentation) and relaxation are studied in a simple shear flow by a discrete element method (DEM). The agglomerates, held together by van der Waals forces, rotate in the shear flow and are stretched into nearly linear structures (fractal dimension approaches unity) until they fracture at their weakest point resulting in lognormally-shaped fragment size distributions asymptotically. Individual fragments relax in the flow towards more compact agglomerates than the parent ones. The evolution of the average number of particles per fragment is described by generalized scaling laws between shear rate, onset (time-lag) of fragmentation, asymptotic fragment mass and size consistent with experimental and theoretical studies in the literature. The initial effective fractal dimension of the agglomerates influences the final one of the fragments. |
| Published in: | Journal of colloid and interface science |
| Volume: | 342 |
| Issue: | 2 |
| Pages: | 261 - 268 |
| ISSN: | 0021-9797 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Amsterdam |
| Publication status: | Published |
| Subjects: | Agglomerate, Break-up, Discrete element method, Effective fractal dimension, Restructuring, Shear flow |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Agglomerate, Break-up, Discrete element method, Effective fractal dimension, Restructuring, Shear flow |
| DBID source: | WOS-000274117400007 |
| DOI: | 10.1016/j.jcis.2009.10.062 |
| Nebis system number: | 000977842 |
A continuous model for sand dunes
,
Duran, Orencio, Parteli, Eric J.R., Herrmann, Hans J.,
2010
>>
| Author(s): | Duran, Orencio, Parteli, Eric J.R., Herrmann, Hans J. |
| Title: | A continuous model for sand dunes |
| Subtitle: | Review, new developments and application to barchan dunes and barchan dune fields |
| Abstract: | Basically, sand dunes are patterns resulting from the coupling of hydrodynamic and sediment transport. Once grains move, they modify the surface topography which in turns modifies the flow. This important feedback mechanism lies at the core of continuous dune modelling. Here we present an updated review of such a model for aeolian dunes, including important modifications to improve its predicting power. For instance, we add a more realistic wind model and provide a self-consistent set of parameters independently validated. As an example, we are able to simulate realistic barchan dunes, which are the basic solution of the model in the condition of unidirectional flow and scarce sediments. From the simulation, we extract new relations describing the morphology and dynamics of barchans that compare very well with existing field data. Next, we revisit the problem of the stability of barchan dunes and argue that they are intrinsically unstable bed-forms. Finally, we perform more complex simulations: first, a barchan dune under variable wind strength and, second, barchan dune fields under different boundary conditions. The latter has important implications for the problem of the genesis of barchan dunes. |
| Published in: | Earth surface processes and landforms |
| Volume: | 35 |
| Issue: | 13 |
| Pages: | 1591 - 1600 |
| ISSN: | 0197-9337, 1096-9837 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Chichester, UK |
| Publication status: | Published |
| Subjects: | Aeolian dunes, Hydrodynamic transport, Sediment transport |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | Aeolian dunes, Hydrodynamic transport, Sediment transport |
| DBID source: | WOS-000283570500007 |
| DOI: | 10.1002/esp.2070 |
| Nebis system number: | 000011003 |
A microscopic model for colloidal gels with directional effective interactions
,
Del Gado, Emanuela, Kob, Walter,
2010
>>
| Author(s): | Del Gado, Emanuela, Kob, Walter |
| Title: | A microscopic model for colloidal gels with directional effective interactions |
| Subtitle: | Network induced glassy dynamics |
| Abstract: | By means of molecular dynamics simulations, we study the structure and the dynamics of a microscopic model for colloidal gels at low volume fractions. The presence of directional interactions leads to the formation of a persistent interconnected network at temperatures where phase separation does not occur. We find that large scale spatial correlations strongly depend on the volume fraction and characterize the formation of the persistent network. We observe a pre-peak in the static structure factor and relate it to the network structure. The slow dynamics at gelation is characterized by the coexistence of fast collective motion of the mobile parts of the network structure (chains) with large scale rearrangements producing stretched exponential relaxations. We show that, once the network is sufficiently persistent, it induces slow, cooperative processes related to the network nodes. We suggest that this peculiar glassy dynamics is a hallmark of the physics of colloidal gels at low volume fractions. |
| Published in: | Soft matter |
| Volume: | 6 |
| Issue: | 7 |
| Pages: | 1547 - 1558 |
| ISSN: | 1744-683X, 1744-6848 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Cambridge |
| Publication status: | Published |
| Subjects: | Werkstoffe allgemein|Materials Sciences, General |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000275947800025 |
| DOI: | 10.1039/b916813c |
| Nebis system number: | 005061136 |
Struktur-Eigenschafts-Untersuchungen an 1K-PUR-Klebstoffen
,
Clauss, Sebastian, Niemz, Peter,
2010
>>
| Author(s): | Clauss, Sebastian, Niemz, Peter |
| Title: | Struktur-Eigenschafts-Untersuchungen an 1K-PUR-Klebstoffen |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 4. Kolloquium: Aktuelle Fragen der Holzforschung |
| Event date: | September 20, 2010 |
| Place: | Braunschweig, Germany |
| Language: | German |
| Review status: | Unknown |
| DBID source: | FORM-1295352200 |
Quellverhalten dreischichtiger Massivholzplatten
,
Clauss, Sebastian, Kröppelin, Ulrike, Niemz, Peter,
2010
>>
| Author(s): | Clauss, Sebastian, Kröppelin, Ulrike, Niemz, Peter |
| Title: | Quellverhalten dreischichtiger Massivholzplatten |
| Subtitle: | Teil 1: Freie Quellung |
| Abstract: | Durch die kreuzweise Verklebung der Lagen mehrschichtiger Massivholzplatten und den dadurch erzielten Absperreffekt entstehen bei Klimawechsel erhebliche Eigenspannungen, die bei der Trocknung zur Rissbildung führen können. An Einzellagen aus Fichte (Picea ab/es Karst.) und MDF sowie aus daraus gefertigten dreischichtigen Massivholzplatten wurden die freie Quellung, der bei behinderter Quellung entstehende Quelldruck sowie die in den Lagen entstehenden Eigenspannungen nach Änderung des Umgebungsklimas von 20 Grad/35 Prozent zu 20 Grad/85 Prozent rel. Luftfeuchte bestimmt. In Teil 1 der Arbeit werden der Stand des Wissens zur freien und behinderten Quellung und das verwendete Versuchsmaterial ausführlich beschrieben sowie die Resultate zum Schwerpunkt freie Quellung präsentiert. Es zeigte sich, dass Massivholzplatten ein deutlich geringeres Quellmaß gegenüber den Einzellagen aufwiesen. Die anatomisch bedingten Unterschiede im Quellmaß des Holzes führten senkrecht zur Faserrichtung der Decklage auch bei Dreischichtplatten zu einer größeren freien Quellung unter Verwendung von liegenden Jahrringen. Die Ausgleichsfeuchte der Dreischichtplatten ergab im Vergleich zu den Einzellagen um 2 Prozent geringere Werte. Die Ursache ist indem durch die Verklebung der Lagen entstehenden Absperreffekt zu suchen. Wie stark sich der Absperreffekt auf den Quelldruck und die Eigenspannungen der Platten auswirkt, wird in Teil 2 der Arbeit beschrieben. |
| Published in: | Holztechnologie |
| Volume: | 51 |
| Issue: | 1 |
| Pages: | 5 - 10 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
| Nebis system number: | 000026159 |
Quellverhalten dreischichtiger Massivholzplatten
,
Clauss, Sebastian, Kröppelin, Ulrike, Niemz, Peter,
2010
>>
| Author(s): | Clauss, Sebastian, Kröppelin, Ulrike, Niemz, Peter |
| Title: | Quellverhalten dreischichtiger Massivholzplatten |
| Subtitle: | Teil 2: Partiell behinderte Quellung |
| Published in: | Holztechnologie |
| Volume: | 51 |
| Issue: | 2 |
| Pages: | 5 - 10 |
| ISSN: | 0018-3881 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Leinfelden-Echterdingen |
| Publication status: | Published |
| Language: | German |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294760610 |
| Nebis system number: | 000026159 |
Investigation on the structure-property relationships of one-component polyurethane prepolymers and formulated adhesives
,
Clauss, Sebastian, Dijkstra, Dick, Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Niemz, Peter,
2010
>>
| Author(s): | Clauss, Sebastian, Dijkstra, Dick, Gabriel, Joseph, Karbach, Alexander, Matner, Mathias, Niemz, Peter |
| Title: | Investigation on the structure-property relationships of one-component polyurethane prepolymers and formulated adhesives |
| Book title: | 2009 International Conference on Wood Adhesives Proceedings |
| Pages: | 195 - 202 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Lake Tahoe, Nevada, USA |
| Publication status: | Published |
| Event name: | International Conference on Wood Adhesives 2009 |
| Event date: | September 28-30, 2009 |
| Place: | Lake Tahoe, Nevada, USA |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | FORM-1294744207 |
A Multi-Scale Approach for the Coupled modelling of Mechanical and Moisture Behaviour of Wood
,
Carmeliet, Jan, Derome, Dominique, Dressler, M., Gaignat, F., Herrmann, Hans Jürgen, Lanvermann, Christian, Niemz, Peter, Rahfsanjani, A., Wittel, Falk, Wu, W.,
2010
>>
| Author(s): | Carmeliet, Jan, Derome, Dominique, Dressler, M., Gaignat, F., Herrmann, Hans Jürgen, Lanvermann, Christian, Niemz, Peter, Rahfsanjani, A., Wittel, Falk, Wu, W. |
| Title: | A Multi-Scale Approach for the Coupled modelling of Mechanical and Moisture Behaviour of Wood |
| Abstract: | This presentation will focus on the general methodology and preliminary results of a research project entitled “Multiscale analysis of coupled mechanical and moisture behavior of wood”. Started last fall, this three-year project regroups five PhD students, and researchers and professors from ETHZ Institute for Building Materials and the Chair of Building Physics and EMPA Laboratories for Wood and of Building Science and Technology. Taking into account that the macroscopic mechanical and moisture properties of wood highly depend on the lower level features found at the growth ring, cellular structure, cell wall, cellulose fibril scales, a multiscale approach is used to understand the relation between macroscopic moisture and mechanical properties of softwood and its nano- and microscopic structure. The aim is to predict the coupled moisture and mechanical behavior of wood. The project is divided into three modeling projects (M1, M2, M3) and two experimental projects (E1, E2). Focusing at the microscale, the first project, M1, develops a laminate model of the cell wall, embedding sub-cell wall characteristics and implements the model into the geometry of several cells. This work will produce the cell wall constitutive relations needed for the second project M2. The aim of M2 is to bridge the gap from the cellular level to the macroscopic scale, by two upscaling steps. First, the orthotropic cell wall poromechanical model for a regular or irregular cellular structure provide, by homogenization, the continuum poromechanical parameters of earlyand latewood. Then, these parameters are used for the geometry of a few growth rings and, by a second numerical homogeneization, the continuum poromechanical parameters of wood are determined and fed to project M3. Finally, M3 will lead to the construction of an enriched constitutive model at the macroscale, embedding the micro- and mesoscale features impacts on moisture and mechanical behavior as well as mechanical and moisture hysteresis. One experimental project, E1, focuses in documenting wood behavior at the cellular level, using advanced techniques like phase-contrast synchrotron X-ray tomography (TOMCAT beamline of PSI, Villigen) under different moisture and mechanical conditions. The other experimental project, E2, will deal with the multiscale determination of the wood behavior under moisture and mechanical loading. The presentation will present the different parts of the modeling work presently undergoing, with a special attention brought to the appropriate determination of the poromechanical parameters. |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Kraków |
| Publication status: | Published |
| Event name: | Joint Focussed Meeting "Modelling mechanical behaviour of wood cultural objects"- COST Actions IE0601 |
| Event date: | April 12-13, 2010 |
| Place: | Kraków, Poland |
| Language: | English |
| Review status: | Unknown |
| DBID source: | CSV- |
Probleme bei der Flächenverklebung von Laubholz
,
Brandmair, Anton, Niemz, Peter, Clauss, Sebastian, Hass, Philipp, Wetzig, Melanie,
2010
>>
| Author(s): | Brandmair, Anton, Niemz, Peter, Clauss, Sebastian, Hass, Philipp, Wetzig, Melanie |
| Title: | Probleme bei der Flächenverklebung von Laubholz |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | Montagskolloquien für die Praxis |
| Event date: | January 11, 2010 |
| Place: | Zürich, Switzerland |
| Language: | German |
| Review status: | Unknown |
| DBID source: | CSV- |
1C PUR adhesives for hardwood in timber construction
,
Brandmair, Anton, Hass, Philipp, Clauss, Sebastian, Hering, Stefan, Niemz, Peter,
2010
>>
| Author(s): | Brandmair, Anton, Hass, Philipp, Clauss, Sebastian, Hering, Stefan, Niemz, Peter |
| Title: | 1C PUR adhesives for hardwood in timber construction |
| Abstract: | The intention of this paper is to examine the capabilities of one-component polyurethane (1C PUR) adhesives when applied to hardwoods under different moisture conditions for the purpose of glued-laminated timber. To evaluate the perofmance of bondings, tensile shear strength tests (DIN EN 302 - 1 : 2004) and compression shear strength tests (ASTM D 2559 - 04) were conducted. Before the tests, the specimens were conditioned in standard atmosphere (A1) or boling water (A4). |
| Book title: | Hardwood research and utilisation in Europe - new challenges : the fourth conference on Hardwood research and utilisation in Europe, May 17-18, 2010 University of West Hungary, Faculty of Wood Sciences, Sopron, Hungary ; proceedings |
| Pages: | 251 - 255 |
| ISBN: | 978-963-9883-52-9 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Sopron |
| Publication status: | Published |
| Event name: | The 4th Conference on Hardwood Research and Utilisation in Europe |
| Event date: | May 17-18, 2010 |
| Place: | Sopron, Hungary |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Changes in wood science education in eastern europe
,
Barbu, Marius, Niemz, Peter,
2010
>>
| Author(s): | Barbu, Marius, Niemz, Peter |
| Title: | Changes in wood science education in eastern europe |
| Abstract: | The former regions of the Austrian-Hungarian Empire hold a tradition of more than 120 years of higher education in forest science, including wood processing. After the Second World War, with the political changes and dissolutions in Central Europe, each country established a Faculty of Forestry, which included the wood processing technologies. These departments of wood science educated the first generations of wood engineers, specialists in processing technology and furniture manufacturing, all following five-year diploma programs. Some of these forestry and wood science faculties also established state research centers for forest management, harvest and transportation, primary processing of wood, and furniture manufacturing. Socialist states built a number of wood processing centers, which covered the entire processing line from logs to timber, boards and finally half-products and furniture. Between the 70s and the 90s the demand for highly qualified engineers was enormous and more than 100 students graduated each year and from each study program. Higher education in wood processing included anatomy and chemistry of wood, physics and mechanical processing of wood, chemical processing, adhesives, wood preservation, panels and half-product technologies, furniture design and manufacturing, wood finishing, and marketing. After the political reforms in 1989, the large integrated production centers were not able to survive the economic changes. Pressure from western countries was high and resulted in a decline of the paper and wood processing industries. Higher salary jobs in other sectors had a major impact on quality and number of students. The effects of these developments during the past two decades have been dramatic for wood-based industries. Imports from multinational corporations, combined with low exports of own products and furniture at low margins impacted the industry. Many of the traditional production centers had to close. The number of students and faculty reduced to half; governmental support declined. Political changes during the past decade, and the expansion of the European Community improved the situation, as foreign companies invested modern processing facilities and created new jobs. The impact of the Bologna agreement required continued reformation of the state institutions, and the quick preparation for the job market requires highly motivated students. |
| Book title: | Proceedings of the International Convention of Society of Wood Science and Technology and United Nations Economic Commission for Europe – Timber Committee |
| Pages: | ED-2 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Published |
| Event name: | 53rd International Convention |
| Event date: | October 11 - 15, 2010 |
| Place: | Geneva, Switzerland |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | CSV- |
Superdiffusion of massive particles induced by multi-scale velocity fields
,
Baram, R.M., Lind, P.G., Andrade Jr., José S., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Baram, R.M., Lind, P.G., Andrade Jr., José S., Herrmann, Hans Jürgen |
| Title: | Superdiffusion of massive particles induced by multi-scale velocity fields |
| Abstract: | We study drag-induced diffusion of massive particles in scale-free velocity fields, where superdiffusive behavior emerges due to the scale-free size distribution of the vortices of the underlying velocity field. The results show qualitative resemblance to what is observed in fluid systems, namely the diffusive exponent for the mean square separation of pairs of particles and the preferential concentration of the particles, both as a function of the response time. |
| Published in: | EPL |
| Volume: | 91 |
| Issue: | 2 |
| Pages: | 28006 |
| ISSN: | 0295-5075, 1286-4854 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Bristol, UK |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000282189500022 |
| DOI: | 10.1209/0295-5075/91/28006 |
| Nebis system number: | 000033031 |
Learning as a phenomenon occurring in a critical state
,
Arcangelis, Lucilla de, Herrmann, Hans J.,
2010
>>
| Author(s): | Arcangelis, Lucilla de, Herrmann, Hans J. |
| Title: | Learning as a phenomenon occurring in a critical state |
| Abstract: | Recent physiological measurements have provided clear evidence about scale-free avalanche brain activity and EEG spectra, feeding the classical enigma of how such a chaotic system can ever learn or respond in a controlled and reproducible way. Models for learning, like neural networks or perceptrons, have traditionally avoided strong fluctuations. Conversely, we propose that brain activity having features typical of systems at a critical point represents a crucial ingredient for learning. We present here a study that provides unique insights toward the understanding of the problem. Our model is able to reproduce quantitatively the experimentally observed critical state of the brain and, at the same time, learns and remembers logical rules including the exclusive OR, which has posed difficulties to several previous attempts. We implement the model on a network with topological properties close to the functionality network in real brains. Learning occurs via plastic adaptation of synaptic strengths and exhibits universal features. We find that the learning performance and the average time required to learn are controlled by the strength of plastic adaptation, in a way independent of the specific task assigned to the system. Even complex rules can be learned provided that the plastic adaptation is sufficiently slow. |
| Published in: | Proceedings of the National Academy of Sciences of the United States of America |
| Volume: | 107 |
| Issue: | 9 |
| Pages: | 3977 - 3981 |
| ISSN: | 0027-8424, 1091-6490 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Washington, D.C. |
| Publication status: | Published |
| Subjects: | scale-free network, scaling, self-organized criticality, synaptic plasticity |
| Language: | English |
| Review status: | Peer reviewed |
| Keyword: | scale-free network, scaling, self-organized criticality, synaptic plasticity |
| DBID source: | WOS-000275131100009 |
| DOI: | 10.1073/pnas.0912289107 |
| Nebis system number: | 001003347 |
Explosive Percolation via Control of the Largest Cluster
,
Araújo, N.A.M., Herrmann, Hans Jürgen,
2010
>>
| Author(s): | Araújo, N.A.M., Herrmann, Hans Jürgen |
| Title: | Explosive Percolation via Control of the Largest Cluster |
| Abstract: | We show that considering only the largest cluster suffices to obtain a first-order percolation transition. As opposed to previous realizations of explosive percolation, our models obtain Gaussian cluster distributions and compact clusters as one would expect at first-order transitions. We also discover that the cluster perimeters are fractal at the transition point, yielding a fractal dimension of 1.23 +/- 0.03, close to that of watersheds. |
| Published in: | Physical review letters |
| Volume: | 105 |
| Issue: | 3 |
| Pages: | 035701 |
| ISSN: | 0031-9007, 1079-7114 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | New York |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000279888400004 |
| DOI: | 10.1103/PhysRevLett.105.035701 |
| Nebis system number: | 000003868 |
Q-state Potts model on the Apollonian network
,
Araujo, Nuno A.M., Andrade, Roberto F.S., Herrmann, Hans J.,
2010
>>
| Author(s): | Araujo, Nuno A.M., Andrade, Roberto F.S., Herrmann, Hans J. |
| Title: | Q-state Potts model on the Apollonian network |
| Abstract: | The q-state Potts model is studied on the Apollonian network with Monte Carlo simulations and the transfer matrix method. The spontaneous magnetization, correlation length, entropy, and specific heat are analyzed as a function of temperature for different number of states, q. Different scaling functions in temperature and q are proposed. A quantitative agreement is found between results from both methods. No critical behavior is observed in the thermodynamic limit for any number of states. |
| Published in: | Physical review. E, Statistical, nonlinear and soft matter physics |
| Volume: | 82 |
| Issue: | 4 |
| Pages: | 046109 |
| ISSN: | 1539-3755, 1063-651X, 1550-2376, 1095-3787 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Ridge, NY |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000283053800001 |
| DOI: | 10.1103/PhysRevE.82.046109 |
| Nebis system number: | 004109079 |
Tactical Voting in Plurality Elections
,
Araujo, Nuno A.M., Andrade, José S., Herrmann, Hans J.,
2010
>>
| Author(s): | Araujo, Nuno A.M., Andrade, José S., Herrmann, Hans J. |
| Title: | Tactical Voting in Plurality Elections |
| Abstract: | How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates. |
| Published in: | PLoS ONE |
| Volume: | 5 |
| Issue: | 9 |
| Pages: | e12446 |
| ISSN: | 1932-6203 |
| Publication date / Date received: | 2010-01-01 |
| Publication status: | Lawrence, KS |
| Publication status: | Published |
| Language: | English |
| Review status: | Peer reviewed |
| DBID source: | WOS-000281815800001 |
| DOI: | 10.1371/journal.pone.0012446 |
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