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Application of Acoustical Method to Characterize Nonwoven Material
Tao Yang,Xiaoman Xiong,Yuanfeng Wang,Rajesh Mishra,Michal Petrů,Jiří Militký 한국섬유공학회 2021 Fibers and polymers Vol.22 No.3
Some structural parameters, such as tortuosity, viscous and thermal characteristic lengths, are difficult to obtainthrough direct measurements. Existing indirect methods, i.e. acoustical method, make it possible to estimate theseparameters. This paper presents an application of acoustical inversion methods for estimating structural parameters ofpolyester nonwoven materials. A four-microphone impedance tube was used to measure sound reflection and transmissioncoefficients. The inversion methods used in this research are least square and Bayesian approaches. The least square methodwas achieved via Nelder-Mead algorithm. The Bayesian inversion process was conducted with Metropolis-Hastingsalgorithm and maximum a posteriori. Inversed parameters from two methods as well as front and back sides of nonwovenfabric were compared. Moreover, inversed porosity and airflow resistivity were compared with measured values. The resultsshow that the least square and Bayesian methods has a good agreement. Estimated parameters from Bayesian method wereselected for further analysis. A sizable differences on thermal characteristic length were found by comparing the values fromtwo sides, while the differences are relatively small for other parameters. It is also found that the inversed porosity, tortuosityare reasonable. The results suggest that the acoustical inversion methods can be used to accurately characterize polyesterfibrous materials.
Michal Kyllar,Petr Čížek 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.5
Cranial cruciate ligament (CCL) rupture is one of the most common orthopedic conditions in dogs. The pathogenesis of CCL rupture is not fully described and remains to be elucidated fully. Several hypotheses have been proposed to explain the etiology of these changes. The objective of this study was to investigate structural changes in the CCL in relation to the tibial plateau angle (TPA) and the intercondylar notch (ICN) width in dogs. Fifty-five skeletally mature dogs were included in this study. ICN width and TPA measurements were obtained from intact CCL stifles. Samples of the CCL, caudal cruciate ligament (CaCL), and femoral head ligament (FHL) were harvested and stained for routine histological and immunohistochemical analysis. Microscopic changes in the ligaments were observed and were found to correlate with the TPA and ICN width values. The degree of structural changes within the CCL was observed to correlate with an increasing TPA and a narrowing ICN width. Changes in the CCL are likely to be caused by excessive forces acting through the ligament in stifles with a high TPA. Chondroid metaplasia of the CCL is an adaptation to abnormal mechanics within the stifle joint caused by altered bone morphology.
Kolá,ř,, Michal,Berka, Karel,Jureč,ka, Petr,Hobza, Pavel WILEY-VCH Verlag 2010 CHEMPHYSCHEM -WEINHEIM- Vol.11 No.11
<P>The reliability of the AMBER force field is tested by comparing the total interaction energy and dispersion energy with the reference data obtained at the density functional theory–symmetry-adapted perturbation treatment (DFT–SAPT)/aug-cc-pVDZ level. The comparison is made for 194 different geometries of noncovalent complexes (H-bonded, stacked, mixed, and dispersion-bound), at the equilibrium distances as well as at longer distances (up to a relative distance of two). The total interaction energies agree very well with the reference data and only the strength of H-bonded complexes is slightly underestimated. In the case of dispersion energy, the overall agreement is even better, with the exception of the stacked aromatic systems, where the empirical dispersion energy is overestimated. The use of AMBER interaction energy and AMBER dispersion energy for different types of noncovalent complexes at equilibrium as well as at longer distances is thus justified, except for a few cases, such as the water molecule, where the dispersion energy is highly inaccurate.</P> <B>Graphic Abstract</B> <P>The reliability of the AMBER force field is tested by comparing the total interaction energy and dispersion energy with the ab initio reference data. The comparison is made for 194 different geometries of noncovalent complexes with various binding motifs (see picture), at the equilibrium distances as well as at longer distances. Despite the oversimplified form of the empirical force field a surprisingly good agreement is observed, with some exceptions. <img src='wiley_img_2010/14394235-2010-11-11-CPHC201000109-content.gif' alt='wiley_img_2010/14394235-2010-11-11-CPHC201000109-content'> </P>
Kocman, Mikulá,š,Jureč,ka, Petr,Dubecký,, Matú,š,Otyepka, Michal,Cho, Yeonchoo,Kim, Kwang S. The Royal Society of Chemistry 2015 Physical chemistry chemical physics Vol.17 No.9
<P>Hydrogen storage in carbonaceous materials and their derivatives is currently a widely investigated topic. The rational design of novel adsorptive materials is often attempted with the help of computational chemistry tools, in particular density functional theory (DFT). However, different exchange–correlation functionals provide a very wide range of hydrogen binding energies. The aim of this article is to offer high level QM reference data based on coupled-cluster singles and doubles calculations with perturbative triple excitations, CCSD(T), and a complete basis set limit estimate that can be used to assess the accuracy of various DFT-based predictions. For one complex, the CCSD(T) result is verified against diffusion quantum Monte Carlo calculations. Reference binding curves are calculated for two model compounds representing weak and strong hydrogen adsorption: coronene (−4.7 kJ mol<SUP>−1</SUP> per H<SUB>2</SUB>), and coronene modified with boron and lithium (−14.3 kJ mol<SUP>−1</SUP>). The reference data are compared to results obtained with widely used density functionals including pure DFT, M06, DFT-D3, PBE-TS, PBE + MBD, optB88-vdW, vdW-DF, vdW-DF2 and VV10. We find that whereas DFT-D3 shows excellent results for weak hydrogen adsorption on coronene, most of the less empirical density based dispersion functionals except VV10 overestimate this interaction. On the other hand, some of the less empirical density based dispersion functionals better describe stronger binding in the more polar coroB<SUB>2</SUB>Li<SUB>2</SUB>⋯2H<SUB>2</SUB> complex which is one of realistic models for high-capacity hydrogen storage materials. Our results may serve as a guide for choosing suitable DFT methods for quickly evaluating hydrogen binding potential and as a reference for assessing the accuracy of the previously published DFT results.</P> <P>Graphic Abstract</P><P>Various dispersion-corrected density functionals are compared with high level QM data for several model complexes for adsorptive hydrogen storage. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4cp04354e'> </P>
Annealing Effects in Cast Commercial Aluminium Al–Mg–Zn–Cu(–Sc–Zr) Alloys
Martin Vlach,Jakub Čížek,Veronika Kodetová,Tomáš Kekule,František Lukáč,Miroslav Cieslar,Hana Kudrnová,Lucia Bajtošová,Michal Leibner,Petr Harcuba,Jaroslav Málek,Volkmar Neubert 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
Precipitation reactions of the cast Al–3.4 at%Mg–2.7 at%Zn–0.80 at%Cu–0.10 at%Fe–0.05 at%Si alloy with and withoutaddition of 0.14 at%Sc and 0.06 at%Zr were characterized by electrical resistometry, electron microscopy, X-ray diffraction,thermal analysis, microhardness testing, and positron annihilation. The AlMgZnCuScZr alloy contains a grain boundaryT-phase (Mg32(Al,Cu,Zn)49) with a cubic and/or quasicrystalline structure. The AlMgZnCu alloy contains a mixture ofMgZn2-and the T-phase. Primary multilayer Al3(Sc,Zr) particles precipitated during casting and subsequent cooling. Theparticles have a layered Al3(Sc,Zr) + α-Al + Al3(Sc,Zr) structure, i.e. consist of regions enriched with both Sc and Zr. Smallatomic Mg,Zn(,Cu)-rich clusters coherent with the matrix were formed during the cooling of both alloys and/or in the courseof their storage at ambient temperature. Their dissolution enables precipitation of the transient η′- and/or stable η-phasesof the AlZnMgCu system in both investigated alloys. The effective activation energy for the dissolution of the clusters wascalculated as ~ 103 kJ/mol. Annealing of the AlMgZnCuScZr alloy above 300 °C leads to a formation of the secondaryAl3(Sc,Zr) particles which cause precipitation hardening and guarantee thermal stability of mechanical properties. Additionof Sc and Zr micro alloying elements resulted in a substantial grain refinement. The grain size remains unchanged upto isochronal annealing at 390 °C.