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排序方式: 共有169条查询结果,搜索用时 15 毫秒
31.
Historic masonry buildings under earthquakes – Load‐bearing behaviour in contradiction to the currently applied methods of analysis The stability of historic masonry buildings must be guaranteed not only under normal conditions, but also during natural disasters. The seismic assessment of the masonry buildings of the Gründerzeit (1840–1918) in Vienna is a central topic in the qualitative and constructive assessment. Although masonry construction has been used for many centuries, the realistic evaluation of the load‐bearing behaviour is still a complex challenge. The methods of analysis according to current regulations are only insufficiently able to reflect the real load‐bearing behaviour and the possible activation of global failure mechanisms. As a result, the simplified verification is often difficult to calculate for many historic buildings, and questionable reinforcement measures are taken to compensate, even though the buildings have already experienced several earthquakes and survived most of them without damage. The present work deals with the approaches of current methods of analysis and aims to identify problem points and to compare them with time history analysis, which is supported by a powerful material model based on test series. It is shown that the conventional analysis for the historic masonry buildings without consideration of the interaction and load transfer effects as well as the characteristic construction methods only partially reflect the real load‐bearing behaviour. The work is intended to be a contribution to the technical expert discussions on the seismic safety of historic buildings and to stimulate the discussion on the formulation of realistic methods of analysis. 相似文献
32.
Amel A. Alaidrous 《计算机、材料和连续体(英文)》2021,67(3):2971-2988
In this paper, we study the water-wave flow under a floating body of an incident wave in a fluid. This model simulates the phenomenon of waves abording a floating ship in a vast ocean. The same model, also simulates the phenomenon of fluid-structure interaction of a large ice sheet in waves. According to this method. We divide the region of the problem into three subregions. Solutions, satisfying the equation in the fluid mass and a part of the boundary conditions in each subregion, are given. We obtain such solutions as infinite series including unknown coefficients. We consider a limited number only of the coefficients by truncating the infinite series and satisfy the remaining boundary conditions approximately. Numerical experiments show that the results are acceptable. Tables are given along with the graph of the system of the resulting streamlines and the dynamical pressure acting on the obstacle. The drawn system of streamlines shows the correctness of the solution and the pressure is maximum on the side facing the upstream extremity of the channel. The same procedure can be adequately applied for problems with more complicated geometry and other phenomenon can thus be simulated. 相似文献
33.
Perla Relkin Amel Ait-Taleb Stéphanie Sourdet Pierre-Yves Fosseux 《Journal of the American Oil Chemists' Society》2003,80(8):741-746
The thermal behavior of hydrogenated palm kernel oil-in-water emulsions, which differed in their milk-protein composition,
was studied in parallel with other characteristic parameters such as the aggregation/coalescence of fat droplets, and the
proportion of adsorbed proteins at the oil/water interface. DSC was applied to monitor the crystallization and melting behavior
of nonemulsified and emulsified fat samples. Comparison between nonemulsified and emulsified fat samples showed that in emulsified
samples the initial temperature of fat crystallization and the temperature of the completion of melting were invariably lower
and slightly higher, respectively. Furthermore, in complex food emulsions the supercooling temperature needed to initiate
fat crystallization and the variation in its growth rate in the cooling experiment were dependent on the amount and nature
of the adsorbed proteins. Our results indicate that the total replacement of milk proteins by whey proteins affected the fat
crystallization behavior of emulsified fat droplets, in parallel with changes in their protein surface coverage and in their
physical stability against fat droplet agglomeration. 相似文献
34.
Amel Boufrioua 《Journal of Computational Electronics》2018,17(3):1029-1036
An improved model is presented to study the effect of a superstrate on a resistive rectangular microstrip antenna fed by a microstrip line and printed on anisotropic substrate. A new accurate computation with different unknown currents of the electric field on overlap, feed line and resistive patch is studied by the Fourier transform, considering the Galerkin’s method and entire domain basis functions. Additionally, the scattering radar cross section (RCS) was studied for this novel resistive patch taking into account the effect of the nonzero surface resistance, the superstrate and the anisotropic substrate. To determine the unknown current modes on the patch, the electric field integral equation can be discretized into a matrix form that incorporates the effect of the superstrate, the anisotropic substrate and the currents on the feed line which are efficiently developed. Moreover, the necessary terms to represent the resistive patch are derived and are included in the equation in the form of a resistance matrix. RCS reduction is obtained for high superstrate thicknesses and low superstrate permittivities. Also, the addition of a resistance on the surface of the patch antenna provides a scattered energy diminution. Moreover, the RCS of this novel structure is affected by both \(\varepsilon _z \) and \(\varepsilon _x \) permittivities change, however, has drastically changed due to the \(\varepsilon _x \) permittivity change. In order to validate the theoretical results, a study has been achieved for a perfectly conducting patch on isotropic substrate, without superstrate and excitation, and the results were compared well with other papers. This subject has not been treated or reported previously in the literature, and there has been very little work on the scattering RCS of only simple perfectly conducting patch antennas. 相似文献
35.
36.
Sbartai A Namour P Errachid A Krejči J Šejnohová R Renaud L Larbi Hamlaoui M Loir AS Garrelie F Donnet C Soder H Audouard E Granier J Jaffrezic-Renault N 《Analytical chemistry》2012,84(11):4805-4811
Planar electrochemical microcells were micromachined in a microcrystalline boron-doped diamond (BDD) thin layer using a femtosecond laser. The electrochemical performances of the new laser-machined BDD microcell were assessed by differential pulse anodic stripping voltammetry (DPASV) determinations, at the nanomolar level, of the four heavy metal ions of the European Water Framework Directive (WFD): Cd(II), Ni(II), Pb(II), Hg(II). The results are compared with those of previously published BDD electrodes. The calculated detection limits are 0.4, 6.8, 5.5, and 2.3 nM, and the linearities go up to 35, 97, 48, and 5 nM for, respectively, Cd(II), Ni(II) Pb(II), and Hg(II). The detection limits meet with the environmental quality standard of the WFD for three of the four metals. It was shown that the four heavy metals could be detected simultaneously in the concentration ratio usually measured in sewage or runoff waters. 相似文献
37.
The Use of a Eutectic Mixture of Olive Pomace Oil Fatty Amides to Easily Prepare Sulfated Amides Applied as Lime Soap Dispersants 总被引:1,自引:0,他引:1
Faicel Rais Rochdi Baati Nesrin Damak Amel Kamoun Moncef Chaabouni 《Journal of the American Oil Chemists' Society》2008,85(9):869-877
Sulfated diethanolamides of fatty acids are known to be effective lime soap dispersing agents. However, their preparation
from fatty acids via fatty amides requires the use of organic solvents due to the high viscosity of both fatty amides and
sulfated fatty amides. This study shows that the preparation of sulfated fatty amides is relatively easy when using olive
pomace oil as the raw material. The latter, is converted into sulfated fatty amides by performing the following steps: saponification,
hydrolysis, esterification, amidation, and sulfation. In the final step, the mixture obtained has sufficient fluidity, due
to its high linoleic acid amide content, to obviate the use of organic solvents, as usually suggested in the literature. Characterization
of the product was carried out by chemical analyses, FTIR, 13C NMR, GC, and HPLC. It was shown that the yield of the amidation reaction is about 80%, and that of the sulfation reaction
can exceed 100% against the pure amide (more than one sulfate group could be linked to one amide molecule). On the other hand,
the Borghetty test showed that the product is an effective dispersant with a lime soap dispersing power equal to five. 相似文献
38.
Amel Rehaiem Beatriz Martínez Mohamed Manai Ana Rodríguez 《Food and Bioprocess Technology》2012,5(6):2140-2150
Enterococcus faecium MMRA is an enterocin A producer isolated from ‘Rayeb’, a Tunisian fermented milk drink. In this work, safety aspects and its behaviour in raw milk were investigated to assess its suitability as a protective adjunct culture. E. faecium MMRA showed interesting features such as the absence of several virulence traits, susceptibility to vancomycin and other clinically relevant antibiotics, and lack of haemolytic activity. To evaluate its performance as an adjunct culture for Rayeb, changes in the overall composition of control (non-inoculated) and experimental Rayeb (inoculated with 1%, v/v, E. faecium MMRA) were determined throughout duplicate fermentations of raw milk using microbiological, chemical, HPLC and headspace GC-MS analyses. E. faecium MMRA could multiply in raw milk and produced enterocin A. Interestingly, a higher content of volatile compounds including ethanol, diacetyl and 2-propanol was observed in the presence of this bacteriocin producer. Furthermore, this strain was capable of inhibiting the growth of Listeria monocytogenes CECT 4032 in pasteurised milk, although total killing was not achieved. Further experiments confirmed the development of resistant variants to enterocin A. On similar challenge assays, L. monocytogenes CECT 5672 growth was halted by the presence of the enterocin producer, but viability was only slightly reduced during cold storage. According to our results, E. faecium MMRA meets the criteria for an autochthonous protective adjunct culture to enhance both the hygienic and the sensory attributes of Rayeb. 相似文献
39.
This work aims to study the effects of date stone flour (DSF) on morphology, thermal, and mechanical properties of polypropylene (PP) composites in the absence and presence of ethylene‐butyl acrylate‐glycidyl methacrylate (EBAGMA) used as the compatibilizer. DSF was added to the PP matrix at loading rates of 10, 20, 30, and 40 wt %, while the amount of compatibilizer was fixed to the half of the filler content. The study showed through scanning electron microscopy analysis that EBAGMA compatibilizer improved the dispersion and the wettability of DSF in the PP matrix. Thermogravimetric analysis (TGA) indicated a slight decrease in the decomposition temperature at onset (Tonset) for all composite materials compared to PP matrix, whereas the thermal degradation rate was slower. Differential scanning calorimetry (DSC) data revealed that the melting temperature of PP in the composite materials remained almost unchanged. The nucleating effect of DSF was however reduced by the compatibilizer. Furthermore, the incorporation of DSF resulted in the increase of stiffness of the PP composites accompanied by a significant decrease in both the stress and strain at break. The addition of EBAGMA to PP/DSF composites improved significantly the ductility due to the elastomeric effect of EBAGMA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
40.