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131.
The paper presents the results of density and viscosity measurements in liquid derivatives of benzene and pyridine, well purified, degassed or aerated, depending on temperature, in the whole liquidity range. Gaseous admixtures were found to affect the viscosity of liquids. From one to three Arrhenius regions were observed, depending on the structure and orientational freedom of the molecules. the results are discussed on the background of 1H NMR relaxation time studies with regard to the effect of dipole interactions on the structure of close packing. 相似文献
132.
《Wave Motion》2017
An analytical model is developed to investigate the sound transmission loss from orthogonally rib-stiffened double laminated composite plates structure under a plane sound wave excitation, in which first order shear deformation theory is presented for laminated composite plates. By using the space harmonic approach and virtual work principle, the sound transmission loss is described analytically. The validity and feasibility of the model are verified by comparing the present theoretical predictions with numerical results published previously. The influences of structure geometrical parameters on sound transmission loss are subsequently presented. Through numerical results, it can be concluded that the proposed analytical model is accurate and simple in solving the vibroacoustic behavior of an orthogonally rib-stiffened double laminated composite plates. 相似文献
133.
Elise Mourier René Fulchiron Françoise Méchin 《Journal of Polymer Science.Polymer Physics》2010,48(2):190-201
Thermoplastic segmented polyurethanes (TPUs) are an important class of thermoplastic elastomers with a two‐phase microstructure arising from the thermodynamic incompatibility between hard (HSs) and soft segments. This microphase separation observed on cooling from a homogeneous state is often combined with the solidification of either or both types of segments. In this study, the structuring mechanism of two TPUs with HSs based on 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was investigated from rheological measurements. Hence, in addition to the structuring temperature influence, the effect of an applied preshear flow in the melt polymer was analyzed, in particular. The results clearly show an enhancement of the solidification kinetics by the preshear. Indeed, the measured structuring time can be reduced by more than 1 decade. Rheo‐optical microscopy observations coupled with a shearing hot stage corroborated these results and showed the modification of the microstructure by the shear. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 190–201, 2010 相似文献
134.
Fluid dynamic properties of blood flow are implicated in cardiovascular diseases. The interaction between the blood flow and the wall occurs through the direct transmission of forces, and through the dominating influence of the flow on convective transport processes. Controlled, in vitro testing in simple geometric configurations has provided much data on the cellular-level responses of the vascular walls to flow, but a complete, mechanistic explanation of the pathogenic process is lacking. In the interim, mapping the association between local haemodynamics and the vascular response is important to improve understanding of the disease process and may be of use for prognosis. Moreover, establishing the haemodynamic environment in the regions of disease provides data on flow conditions to guide investigations of cellular-level responses. 相似文献
135.
Cascades with coupled map lattices in preferential attachment community networks 总被引:2,自引:0,他引:2 下载免费PDF全文
In this paper, cascading failure is studied by coupled map lattice (CML) methods in preferential attachment community networks. It is found that external perturbation R is increasing with modularity Q growing by simulation. In particular, the large modularity Q can hold off the cascading failure dynamic process in community networks. Furthermore, different attack strategies also greatly affect the cascading failure dynamic process. It is particularly significant to control cascading failure process in real community networks. 相似文献
136.
This paper reports a comparative study of shear banding in BMGs resulting from thermal softening and free volume creation.
Firstly, the effects of thermal softening and free volume creation on shear instability are discussed. It is known that thermal
softening governs thermal shear banding, hence it is essentially energy related. However, compound free volume creation is
the key factor to the other instability, though void-induced softening seems to be the counterpart of thermal softening. So,
the driving force for shear instability owing to free volume creation is very different from the thermally assisted one. In
particular, long wave perturbations are always unstable owing to compound free volume creation. Therefore, the shear instability
resulting from coupled compound free volume creation and thermal softening may start more like that due to free volume creation.
Also, the compound free volume creation implies a specific and intrinsic characteristic growth time of shear instability.
Finally, the mature shear band width is governed by the corresponding diffusions (thermal or void diffusion) within the band.
As a rough guide, the dimensionless numbers: Thermal softening related number B, Deborah number (denoting the relation of instability growth rate owing to compound free volume and loading time) and Lewis
number (denoting the competition of different diffusions) show us their relative importance of thermal softening and free
volume creation in shear banding. All these results are of particular significance in understanding the mechanism of shear
banding in bulk metallic glasses (BMGs).
Supported by the Chinese Academy of Sciences under the project “Multi-Scale Complex System” (Grant No. KJCX-SW-L08), the National
Natural Science Foundation of China (Grant Nos. 10725211 and 10721202), and the Doctorial Start-up Fund of Hunan University
of Science and Technology (Grant No. E50840) 相似文献
137.
T. V. Brantseva A. V. Antonov Yu. A. Gorbatkina M. L. Kerber T. P. Kravchenko A. A. Rybin 《Mechanics of Composite Materials》1999,35(6):453-460
A new device for studying the dynamic adhesive strength is created. A procedure for determining the dynamic adhesive strength in fiber—polymer systems under impact loading (pull-out technique) is developed. The adhesive strength of the interface of polymer—steel wire joints formed by polymers of different chemical nature (epoxy resin, polysulfone, and polypropylene) is examined. It is shown that the dynamic adhesive strength grows as the loading rate increases for all the systems under investigation and that the relationship between the adhesive strength and the loading rate,
, over a wide range of rates can be described by two straight lines corresponding to the quasi-static and impact loading, respectively. When passing from the quasi-static to dynamic loading, the character of scale relations of the adhesive strength does not change.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 689–700, November–December, 1999. 相似文献
138.
采用延迟扩散方程[7,9]描述了具有边界吸收条件下,非定常剪切流动中的剪切弥散特性.给出了记忆函数、中心位移函数的控制方程.特例分析结果表明:所采用的模型方程是合理的;边界吸收效应使得纵向浓度分布具有后倾的趋势.这主要是由于边界吸收使得低速强剪切区浓度减少,剪切弥散贡献减少,从而污染物对流速度高于断面的平均速度. 相似文献
139.
Sheldon M Ross 《Stochastic Processes and their Applications》1976,4(2):167-173
Consider an n-component reliability system having the property that at any time each of its components is either up (i.e., working) or down (i.e., being repaired). Each component acts independently and we suppose that each time the ith component goes up it remains up for an exponentially distributed time having mean μi, and each time it goes down it remains down for an exponentially distributed time having mean υi. We further suppose that whether or not the system itself is up at any time depends only on which components are up at that time. We are interested in the distribution of the time of first system failure when all components are initially up at time zero. In section 2 we show that this distribution has the NBU (i.e., new better than used) property, and in Section 3 we make use of this and other results to obtain a lower bound to the mean time until first system failure. 相似文献
140.