On a Representative Volume in the Micromechanics of Particulate Composites

A rectangle filled with closely packed spheres of random size and properties is considered as a micromechanical model of a two-phase particulate composite. A numerical simulation is used to determine the effective mechanical properties of the assembly and their scatter as a function of the number of spheres. It is shown that, in a system with relatively small number of particles (up to 300), the scatter of Young's modulus decreases with the system size. However, the rate of the scatter decrease becomes smaller with growing size of the system, so that the convergence to zero most likely takes place at infinity.     

Bergman空间B_q~p(p>0,q>1)中的Bernstein型不等式

本文在Bergman空间Bqp(p>0,q>1)中得到了关于用多项式本身的模控制其导函数的模的Bernstein型不等式．     

Testing methods for nanoindentation property of the cuticle of bovine hoof wall and dung beetle’s foreleg femur

Natural biomaterials have extensively been researched since their distinguished properties adapting to their living surroundings. The cuticle surfaces of bovine hoof and dung beetle directly contact soil when they move on soft ground or in soil. Their surface materials and structures can provide some information for designing soil-engaging components of soft terrain-machines. While, it is difficult to measure their mechanical properties since the cuticle of the bovine hoof wall and dung beetle are very thin. Nanoindenter provides a powerful tool for examining the mechanical properties such as reduced modulus and hardness in nano-scale. The testing methods for nanoindentation properties of the cuticle of the bovine hoof wall and dung beetle (Copris ochus Motschulsky) were discussed in this work.     

Deformability of expanded polystyrene under short-term compression

The results obtained in an experimental investigation of deformability of expanded polystyrene (EPS) under short-term compression are presented. The density of EPS varied from 13 to 28 kg/m³. The method of design of experiments was used to determine the elastic modulus and the ultimate strain (corresponding to the end of quasi-linear deformability) under compression stresses operating perpendicularly and parallel to the faces of EPS products. A graphical interpretation of the models is also presented. Based on the experimental data obtained, it was concluded that the expanded polystyrene was homogeneous in mutually perpendicular planes with respect to its deformability in compression. __________ Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 5, pp. 639–656, September–October, 2007.     

Pressure dependence of thermodynamic properties of NaBr,NaI and AgCl

Various state-equations, derived by expanding energy as a function of volume in Taylor series and using different order Pade’s approximants, have been combined with quasi-harmonic approximation for free energy to reproduce the pressure dependence of thermodynamic properties of NaBr, NaI and AgCl crystals. We have used these state-equations to compute the reduced volume, the isothermal bulk modulus and the pressure derivative of isothermal bulk modulus for the three crystals at various pressures (up to 80 kbar) and at room temperature (T=298 K). The results obtained are reasonably good lending support to the state-equations and the technique used to extend their applicability. The significant results obtained in the present study include the unified reduced equation of state for the three crystals which generates almost a single curve for theP – V behaviour at room temperature.     

高密度聚乙烯（HDPE）在静高压下的强度研究

 高密度聚乙烯（HDPE）在1~2 GPa的静高压下发生熔体结晶。用压缩的方法对经过高压处理后的样品进行了杨氏模量的测量。测量结果表明：样品的杨氏模量随压力和结晶度的增加而增大，最大值达到1.46 GPa。伸直链晶体的形成是杨氏模量增加的重要因素。     

A UNIFIED ENERGY APPROACH TO A CLASS OF MICROMECHANICS MODELS FOR MICROCRACKED SOLIDS

Micromechanics models have been developed for the determination ofthe elastic moduli of microcracked solids based on different approaches andinterpretations,including the dilute or non-interacting solution,the Mori-Tanakamethod,the self-consistent method,and the generalized self-consistent method.It isshown in the present study that all these micromechanics models can be unified withinan energy-equivalence framework,and that they differ only in the way in which themicrocrack opening and sliding displacements are evaluated.Relevance to thedifferential methods and the verification of these models are discussed.     

Transport properties of organic vapors in nanocomposites of isotactic polypropylene

Isotactic polypropylene nanocomposites were obtained by the melt blending of polypropylene‐graft‐maleic anhydride and organophilic layered silicate (OLS) consisting of synthetic fluorohectorite modified by cation exchange with protonated octadecylamine. The composition of the inorganic clay was varied between 2.5 and 10 wt %, and films of the composites were obtained via hot‐press molding. X‐ray analysis showed that nanocomposites in which silicate layers were either delaminated or ordered as in an intercalated structure were obtained. The elastic modulus of the samples was higher than that of the pure polymer over a wide temperature range and increased with increasing inorganic content. The transport properties, sorption and diffusion, were measured for two organic vapors, dichloromethane and n‐pentane. For both vapors, the sorption was not very different from that of the pure polymer, whereas the zero‐concentration diffusion parameter strongly decreased with increasing OLS content. Therefore, the permeability, that is, the product of sorption and diffusion, decreased for both vapors as a result of the decreased value of the diffusion parameter. The decrease was higher for the less interacting n‐pentane. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1798–1805, 2003     

关于Fejer算子的逼近度

用Ｋｎ记Ｆｅｊｅｒ算子的逼近度．本文证明是单调增加的，而且     

Construction of inversive congruential pseudorandom number generators with maximal period length

The inversive congruential method for generating uniform pseudorandom numbers is a particularly attractive alternative to linear congruential generators with their well-known inherent deficiencies like the unfavourable coarse lattice structure in higher dimensions. In the present paper the modulus in the inversive congruential method is chosen as a power of an arbitrary odd prime. The existence of inversive congruential generators with maximal period length is proved by a new constructive characterization of these generators.