Reflection of acoustic wave at the interface of a fluid-loaded dipolargradient elastic half-space

This paper is about the reflection of a plane acoustic wave incident on a material modeled as a dipolar gradient solid. The dipolar gradient model has been used in order to account for the micro-structure present in multi-scale materials (e.g. biological issues, composites, meta-materials). The influence of the internal lengths of the gradient model on the reflection coefficient is described and discussed. A dispersive behavior is observed at high frequency, when the wavelength of the disturbance approaches the characteristic size of the material. This topic is of major interest for understanding the role played by the micro-structure in the reflection phenomena occurring at fluid–solid interfaces and find its application to material properties characterization by means of ultrasound waves.     

非均匀法向荷载下半空间的二阶弹性效应问题

本文提供各向同性弹性半空间，在非均匀分布法向荷载下，二阶弹性效应的一个封闭形式解，运用积分变换方法，讨论了按Ｈｅｒｔｚ规律分布的荷载情形；导出了不可压缩各向同性弹性材料的极限解；算出了上述二阶弹性材料问题在ｚ方向的位移和法向应力数值。我们发现，与线弹性情形相比较，在二阶弹性材料中相应位移增大而法向应力减小。     

Rupture stress and modulus of elasticity for Nd:YAG crystals

A method for determining the rupture stress and modulus of elasticity of Nd:YAG crystals is described, and measurements are given for various kinds of surface finish.     

Water reservoir loading of long anisotropic valleys with irregular topographies

The nature of the stress field induced by water reservoir loading of long anisotropic valleys is considered using an analytical method proposed earlier by the authors. The rock mass is modeled as a linearly elastic, transversely isotropic or nearly isotropic and homogeneous continuum that deforms under a condition of plane strain. The method is used to determine stresses in symmetric and asymmetric valleys induced by water reservoir loading with or without gravity. Numerical examples are presented to analyze the disturbance associated with a water reservoir on the existing gravitational stress field. They show that the presence of a water reservoir does not much affect the horizontal and vertical gravity-induced normal stresses except near the valley bottom. There the effect of the water reservoir is to reduce the magnitude of the gravity-induced horizontal tensile stress and to increase the magnitude of the gravity-induced vertical compressive stress. On the other hand water reservoir loading affects the gravity-induced shear stress in a relatively large region below the valley. Finally a parametric study is presented on the effect of

1. (1) water reservoir height,

2. (2) degree of anisotropy, and

3. (3) orientation of anisotropy on the magnitude and distribution of stresses induced by water reservoir loading only.

     

十次对称准晶中直位错的弹性位移场

根据作者提出的准晶中缺陷的弹性模型,导出了三维空间的十次准晶中的直位错引起的弹性位移场的表达式。     

Drag reduction by an elastic rubber band?

The influence on the friction behaviour caused by a rubber band held fixed at one end of a circular tube containing a fully developed turbulent flow was investigated. The drag was slightly higher under these conditions with the drag approaching the Prandtl-Karman law at high Reynolds numbers. The results are in contrast to the behaviour of a polymer thread in heterogeneous drag reduction.     

非局部反应扩散方程奇摄动问题

本文研究了一类具有非局部初始条件的奇摄动反应扩散问题．在适当的条件下，利用比较定理讨论了问题解的渐近性态．     

中国“九五”期间城乡居民消费结构及变化趋势的比较分析

本文运用扩展的线性支出系统模型研究了我国“九五”期间城乡居民的消费结构状况。对城乡居民的消费结构和变化趋势进行了比较 ,同时给出了消费的合理性政策建议。     

On the solvability of noncoercive linear variational inequalities in separable Hilbert spaces

In this paper, we build an existence theory for linear variational inequalities associated with an operator which generalizes in Hilbert space the class of copositive plus matrices. We show how this theory can be used to study some important engineering problems governed by noncoercive variational inequalities.Thanks are due to Professor V. H. Nguyen for many valuable discussions. The author thanks the Associate Editor and the referees for their helpful suggestions     

On catenate network formation by end-linking reactions

Catenate network formation by end-linking reactions of linear chains with bifunctional regents is studied theoretically and by computer simulations. It is found that the reaction cannot reach its stationary limit, and catenate networks are never formed by this method. An alternative method that will lead to catenate networks nearly in the topological equilibrium state is proposed. It is pointed out that catenate networks are an ideal system for studying the role of entanglement in rubber elasticity. © 1993 John Wiley & Sons, Inc.