弹性力学问题解唯一的边界积分方程

从积分方程式出发,应用基本解的特性分析,说明在力边值问题中,位移边界积分方程和面力边界积分方程的位移解不唯一.提出了位移解唯一的条件,建立了唯一解的位移边界积分方程和面力边界积分方程.实例计算结果表明唯一解的边界积分方程是有效的.     

弹性力学平面问题的等价的边界积分方程

严格地推导出与弹性力学平面问题的微分方程边值问题等价的间接和直接未知量边界积分方程,用实例指出某些习用的边界积分方程有时不必要或不充分,并进行了数值比较.     

中国钢铁业上市公司并购中盈余管理研究—基于效率视角

本文通过改进度量盈余管理程度的Yoon-miller模型,测算2003-2009年中国钢铁业上市公司并购前后的可操纵性利润和全要素生产率,并对并购中盈余管理与效率的内在关系进行分析。结果表明:并购后一年全要素生产率有效的钢铁上市公司在并购当年存在向上的盈余管理,并购后一年及并购当年全要素生产率均有效的钢铁上市公司,在并购后一年容易进行较大幅度的向下盈余管理行为。     

风险投资联合投资对上市公司盈余管理的影响:基于我国创业板的实证研究

风险投资在中国的经济发展中处于越来越重要的位置,创业板355家上市公司中,近60%的公司有风险投资背景,近40%的公司有联合风投背景.本文首先以2009-2012年创业板355家上市公司为研究对象,实证研究了风险投资个数与盈余管理之间的关系,然后,以132家联合风投背景公司为研究对象,实证研究联合风投内部特征对IPO公司盈余管理的影响,试图探讨能够发挥最佳监督作用的联合投资方式.实证结果显示有风投背景公司的盈余管理程度高于无风投背景的公司,且联合风投个数越多,上市公司盈余管理程度越高.尽管如此,可以通过选择适当的联合投资方式降低联合投资的负面效应,比如:提高联合风投多样化程度、提高主导风投持股比例、选择高声誉主导风投等等.     

一维线性热弹性系统的边界控制与衰减指数

考虑边界反馈时,一维热弹性系统的衰减速度．证明了闭环系统的谱确定增长条件成立,且反馈增益常数可任意改变高本征频谱．最后谱方法给出了数值模拟结果．     

圆内平面弹性问题的边界积分公式

根据双解析函数可以得到单位圆内平面弹性问题应力函数的边界积分公式,但式中包含强奇异积分,不能用于直接计算．将边界上的应力函数展开为Fourier级数,再利用广义函数论中的几个公式进行卷积计算,可以得到不含强奇异积分核的边界积分公式,通过边界的应力函数值和法向导数的积分,直接得到圆内应力函数值,并给出几个算例,表明该结果用于求解单位圆内平面弹性问题十分方便．     

矩形弹性夹杂与裂纹相互干扰的边界元分析

使用边界元法研究了无限弹性体中矩形弹性夹杂对曲折裂纹的影响,导出了新的复边界积分方程．通过引入与界面位移密度和面力有关的未知复函数H(t),并使用分部积分技巧,使得夹杂和基体界面处的面力连续性条件自动满足,而边界积分方程减少为2个,且只具有1/r阶奇异性．为了检验该边界元法的正确性和有效性,对典型问题进行了数值计算．所得结果表明:裂纹的应力强度因子随着夹杂弹性模量的增大而减小,软夹杂有利于裂纹的扩展,而刚性较大的夹杂对裂纹有抑制作用．     

基于三维弹性问题的多极边界元法核函数分解

多极边界元法已经成功地应用于大规模工程计算中.得到并且证明了基于三维弹性问题的多极边界元法核函数分解的定理(定理1),完善了多击边界元法的数学理论.     

圆外平面弹性问题的边界积分公式

将边界上的应力函数及其法向导数展开为罗朗级数,与复应力函数的罗朗级数的表达式对比,可以确定罗朗级数的各系数,再利用傅利叶级数和卷积的几个公式进行计算,得到应力函数边界积分公式．通过边界的应力函数及其法向导数的积分,直接得到圆外应力函数值,并给出几个算例,表明结果用于求解单位圆外平面弹性问题十分方便．     

盈余管理计量模型效力的实证研究

本文以随机抽取的上海和深圳证券交易所的1000家被并购上市公司为样本,研究了盈余管理计量模型的检验效力问题。本文通过三种验证各模型效力的实证方法比较了6种盈余管理的计量模型。研究发现:第一类误差的方法认为Healy模型、修正的琼斯模型和前瞻性修正的琼斯模型能有效地检验出盈余管理行为:预测误差标准方法则认为前瞻性修正的琼斯模型是最优的模型:而根据对操纵性应计部分的短期效应的实证则认为Healy模型、修正的琼斯模型、KS模型和前瞻性修正的琼斯模型是较优的计量模型。在综合考虑各种实证结果和中国资本市场实际情况的基础上,认为前瞻性修正的琼斯模型在中国证券市场检验盈余管理行为的效力最强。     

Boundary Integral Equations for Isotropic Linear Elasticity

This articles first investigates boundary integral operators for the three-dimensional isotropic linear elasticity of a biphasic model with piecewise constant Lamé coefficients in the form of a bounded domain of arbitrary shape surrounded by a background material. In the simple case of a spherical inclusion, the vector spherical harmonics consist of eigenfunctions of the single and double layer boundary operators and we provide their spectra. Further, in the case of many spherical inclusions with isotropic materials, each with its own set of Lamé parameters, we propose an integral equation and a subsequent Galerkin discretization using the vector spherical harmonics and apply the discretization to several numerical test cases.     

Canonical Boundary Element Method for Plane Elasticity Problems

In this paper, we apply the canonical boundary reduction, suggested by Feng Kang, to the plane elasticity problems, find the expressions of canonical integral equations and Poisson integral formulas in some typical domains. We also give the numerical method for solving these equations together with their convergence and error estimates. Coupling with classical finite element method, this method can be applied to other domains.     

空间轴对称问题边界元法的程序处理

弹性力学的空间轴对称问题可以化为两个变量(r,z)的二维问题求解,但又比平面问题略复杂些.在轴对称问题边界元的程序处理上也会相应带来些麻烦.文章具体介绍了作者在调试轴对称问题边界元程序中遇到的一些问题及处理方法,并给出数值结果加以验证.     

Boundary Equations in Dynamic Problems of the Theory of Elasticity

We study various nonstationary boundary equations that arise when the mixed problems of the theory of elasticity and thermoelasticity are solved by means of dynamic surface potentials. In the review, the results obtained are presented on their unique solvability in the scales of function spaces of the Sobolev type.     

Inverse Boundary Value Problem of the Plane Theory of Elasticity

There is given the formulation and the solution of the inverse boundary value problem of the plane theory of elasticity in this paper. The solution is reduced to finding the Taylor coefficients for the function which maps the unit dick onto the unknown domain.     

Dissipative Boundary Conditions for Finite-Difference Problems in Elasticity Theory

Dissipative differential-difference boundary conditions for elasticity equations are derived and investigated. These conditions completely eliminate the longitudinal and transverse waves reflected from the boundary in case of normal incidence and substantially reduce the reflected waves in a wide range of other incidence angles. The dissipative boundary conditions reduce computer resource requirements for simulation of seismic wave propagation in unbounded regions. Grid analogues of the dissipative boundary conditions are constructed for a two-layer finite-difference scheme. Comparative results are reported for the solution of two-dimensional seismic problems using these boundary conditions for various incidence angles. __________ Translated from Prikladnaya Matematika i Informatika, No. 18, pp. 83–92, 2004.     

Homogenization of Elasticity Problems with Boundary Conditions of Signorini type

In a perforated domain $\Omega ^\varepsilon = \Omega \cap \varepsilon \omega $ formed of a fixed domain Ω and an ε-compression of a 1-periodic domain ω, we consider problems of elasticity for variational inequalities with boundary conditions of Signorini type on a part of the surface $S_0^\varepsilon $ of perforation. We study the asymptotic behavior of solutions as ε → 0 depending on the structure of the set $S_0^\varepsilon $ . In the general case, the limit (homogenized) problem has the two distinguishing properties: (i) the limit set of admissible displacements is determined by nonlinear restrictions almost everywhere in the domain Ω, i.e., in the limit, the Signorini conditions on the surface $S_0^\varepsilon $ can turn into conditions posed at interior points of Ω (ii) the limit problem is stated for an homogenized Lagrangian which need not coincide with the quadratic form usually determining the homogenized elasticity tensor. Theorems concerning the homogenization of such problems were obtained by the two-scale convergence method. We describe how the limit set of admissible displacements and the homogenized Lagrangian depend on the geometry of the set $S_0^\varepsilon $ on which the Signorini conditions are posed.     

直接边界元法中边界积分的解析处理

确立了平面位势和弹性力学问题的边界元直接法中边界积分的解析计算框架系统,从而避免了传统的主似求积分,数值算例表胆它具有较高的精度和效率,特别是在边界量和边界附近区域内点物理量的计算可获得较高的精度。     

三维弹性问题无网格分析的奇异杂交边界点方法

提出了一种求解三维线弹性问题的奇异杂交边界点方法．将修正变分原理与移动最小二乘法结合起来,利用了前者的降维优势和后者的无网格特性．使用刚体位移法处理方法中的强奇异积分,提出了一种自适应的积分方案,解决了原有的杂交边界点方法中存在的“边界层效应”．在该方法中,将基本解的源点直接布在边界上,避免了在正则化杂交边界点法中不确定参数的选取．三维弹性力学问题算例体现了这些特点．结果表明该方法与已知的精确解符合较好,同时研究了影响该方法精度的一些参数．