Low Velocity Response Characteristics of Composite Plate with Embedded Shape Memory Alloy

I. INTRODUCTION Composite materials have been used extensively in aerospace and other industries owing to the factthat they have high speci?c modulus, high speci?c strength, and the capability to be designed andfabricated with greater ?exibility, and ha…     

打开近代科学之门的对话——————力学史杂谈之十八, 介绍伽利略的《关于两门新科学的对话》

 在简要介绍了伽利略生平后，介绍了他的《关于两门新科学的对话》. 撮要说明这本书 出版的困难，它的意义和简要内容. 并且摘取了书中关于批驳亚里士多德错误的两段精彩的 对话.     

多体系统动力学微分／代数方程组数值方法

多体系统动力学微分／代数混合方程组又称Ｅｕｌｅｒ－ｌａｇｒａｎｇｅ方程，是近十年来动力学和计算数学领域研究的热点之一．本文介绍这两个领域中引入的传统的数值积分方法与新的理论．     

热压电变分原理

热释电介的许多传感器及机敏结构或中的关键材料，本文系统地讨论了在基础理论和数值计算中极具重要地位的各类变分原理，包括准静态变分原理、动态变分原理和关于固有频率的变分原理。最后建立了关于静态压电要板的变分原理，并由此导出了各向异性压电板的控制方程及边界条件。     

两个自由度系统受迫振动实验装置

两个自由度系统受迫振动实验装置段德华，王冲，袁惠群，吴建中（沈阳黄金学院，沈阳１１００１５）１引言生产实践已向人们提出了各式各样的振动问题，故振动分析已成了各项工程技术研究与设计必不可少的环节，因此，追切需要工程技术人员具备有关振动学科方面的基础知识...     

SYMPLECTIC STRUCTURE OF POISSON SYSTEM

When the Poisson matrix of Poisson system is non-constant, classical symplectic methods, such as symplectic Runge-Kutta method, generating function method, cannot preserve the Poisson structure. The non-constant Poisson structure was transformed into the symplectic structure by the nonlinear transform.Arbitrary order symplectic method was applied to the transformed Poisson system. The Euler equation of the free rigid body problem was transformed into the symplectic structure and computed by the midpoint scheme. Numerical results show the effectiveness of the nonlinear transform.     

垂直激励圆柱形容器中的表面波特性研究

利用奇异摄动理论的两时间变量展开法，研究了垂直强迫激励圆柱形容器中的单一水表面驻波模式。假设流体是无粘、不可压且运动是无旋的，在忽略了表面张力的影响下，得到一个具有立方项以及底部驱动项影响的非线性振幅方程。对上述方程进行了数值计算，并研究了特定(3，4)模式的表面驻波结构和特性，如驻波的节点分布及随某些参数的变化规律等，从计算的等高线的图象来看，和以往的实验结果相当吻合。     

松质骨弹性模量计算的均匀化方法

对松质骨建立了六种单胞微观结构模型，采用均匀化方法和有限元方法计算松质骨的宏观等效弹性模量。给出了六种单胞模型的松质骨弹性模量与材料密度(体分比）的关系，与实验数据进行了对比，分析了不同微观结构模型在不同骨骼中的应用。结果表明，本文方法及六种单胞模型可以对松质骨微观结构和材料性能进行有效的模拟计算。同时本文又着重对松质骨的宏观等效弹性模量与体分比的指数关系进行了探讨。     

FLOW STRUCTURE FORMATION AND EVOLUTION IN CIRCULATING GAS-FLUIDIZED BEDS

The occurrence of heterogeneous flow structures in gas-particle flows seriously affects the gas-solid contacting and transport processes in high-velocity gas-fluidized beds. Particles do not disperse uniformly in the flow but pass through the bed in a swarm of clusters. The so-called “core-annulus“ structure in the radial direction and “S“ shaped axial distribution of solids concentration characterize the typical flow structure in the system. A computational study, using the discrete particle approach based on molecular dynamics techniques, has been carried out to explore the mechanisms underlying formation of the clusters and the core-annulus structure. Based on energybudget analysis including work done by the drag force, kinetic energy, rotational energy, potential energy, and energy dissipation due to particle-particle and particle-wall collisions, the role of gas-solid interaction and inelastic collisions between the particles are elucidated. It is concluded that the competition between gas-solid interaction and particle-particle interaction determines the pattern formation in high-velocity gas-solid flows: if the gas-solid interaction (under elevated pressure) dominates, most of particle energy obtained by drag from the gas phase is partitioned such that particle potential energy is raised, leading to a uniform flow structure. Otherwise, a heterogeneous pattern exists, which could be induced by both particle -particle collisions and gas-solid interaction. Although both factors could cause the flow instability, the non-linear drag force is demonstrated to be the necessary condition to trigger heterogeneous flow structure formation. As gas velocity increases and goes beyond a critical value, the fluid-particle interaction suppresses particle collisional dissipation, and as a consequence a more homogeneous flow regime is formed.     

动量矩变量描述的陀螺体永久转动的分岔特性

本文建立以动量矩分量和Ｄｅｐｒｉｔ正则变量为独立变量的陀螺体动力学方程，用以描述无力矩非对称陀螺体的姿态运动。在动量矩空间内讨论了陀螺体永久转动轴的数目和稳定性随转子转速变化的分岔特性。