一类高阶椭圆型方程Dirichlet问题

本文讨论了一类奇摄动高阶椭圆型方程Dirichlet问题，利用伸长变量和变界层校正法，得到了问题解的形式渐近展开式．再用微分不等式理论，证明了解的一致有效性．     

关于一类椭圆型方程的衔接问题

设区域Ω=Ω_1∪Ω_2∪Γ_0∪R~n,其中Ω_1,Ω_2为Ω的子区域,且,对一类一致椭圆型方程(或方程组)的边值问题,本文证明了,当原边值问题为适定时,新的衔接问题(由在Γ_0上满足衔接条件代替满足微分方程)是适定的,并且这二个问题的解是完全相同的。     

一类拟线性椭圆型方程Robin问题的奇摄动

本文研究了一类奇摄动拟线性椭圆型方程Robin问题,在适当的假设下,构造了奇摄动问题的包括边界层的形式渐近解,并利用微分不等式理论证明了所述问题的解的存在性,且给出形式解的一致有效性。     

一类椭圆型变分不等式离散问题的迭代算法

根据一类椭圆型变分不等式离散问题所具有的非线性特征，提出了一种简明快速的迭代算法，该方法在解决障碍问题及流体润滑油膜破裂自然边值问题等工程应用问题时具有较高的效率。     

一类具有特殊区域的椭圆型方程奇摄动问题

本文讨论一类带有一阶偏导的椭圆型拟线性方程的奇摄动问题,其变量区域是特殊的三角形区域.由于PDE(偏微分方程)的特殊性,解很复杂.这里摒弃了传统单一的求渐近解的方法,而采用两种方法组合使用,成功求得一致有效的渐近解.首先通过边界层函数法求出边界直线段上的内部解,再将它们与外部解及顶点处的内层解相匹配,求得处处有效的渐近解,并借此解决方程含多重解的问题.     

一类非线性四阶椭圆型方程的极值原理及其特征值问题

主要应用 Hopf极值原理 ,对一类非线性四阶椭圆型方程Δ2 u +h( x,u,Δu) =0进行研究 ,得到解的泛函的极值原理 .类似的文章结果也有许多 ,其方法均为构造适当的“P-泛函”,但是以前的结果都对方程有较强的要求限制 .本文通过构造新的泛函 ,减弱了要求限制 .同时对方程Δ2 u +λh( x,u,Δu) =0的特征值给出了估计 .     

椭圆型问题一类广义差分法的L~2模误差估计

1.引 言 广义差分法作为处理偏微分方程的离散技术,能够保持质量,动量,能量等物理量的守恒.广义差分法（有些文献称为box method[3];finite volume element method[4],[5],[6]）利用在对偶剖分体积单元积分原始方程,并将近似解限制于某一有限元空间而得到离散方程.因此,它在局部区域保持了原始方程的物理守恒性和其他重要特性.从而被广泛地应用于数值求解数学物理方程,特别是计算流体力学和热传导问题[11]. 对广义差分法的研究已有许多文献,专著[10]有详细的介绍.早期的工作主要考虑标准的重心对偶剖分.近年来Cai et,al[4],[5],[6],在某些假定下对较一般的对偶剖分给出了能量模误差估计,Huang and Xi[9]去掉了文献[6]中的这些限制.Chou,Li[8]和Li,     

基于子结构法构造用非协调元解椭圆型问题的预处理器（Ⅰ）

基于子结构法构造用非协调元解椭圆型问题的预处理器（Ⅰ）顾金生，胡显承（清华大学应用数学系）ＴＨＥＣＯＮＳＴＲＵＣＴＩＯＮＯＦＰＲＥＣＯＮＤＩＴＩＯＮＥＲＳＦＯＲＥＬＬＩＰＴＩＣＰＲＯＢＬＥＭＳＤＩＳＣＲＥＴＩＺＥＤＢＹＮＯＮＣＯＮＦＯＲＭＩＮＧＦＩＮ...     

一类二阶椭圆型偏微分方程组的若干问题

本文研究一类二阶项为常系数的二阶椭圆型偏微分方程组:应用广义解析函数理论,我们证明了方程组(1)的复解u iv的某些性质与单复变量的解析函类似。应用Bojarski等人的研究成果,我们考察了下面的边界值问题:求满足方程组(1)和满足边界条件的解。我们得到了上述边界值问题可解的充分必要条件。     

椭圆边值问题的概率算法

本文重新建立了椭圆边值问题的概率模型,在Ｍｏｎｔｅ－Ｃａｒｌｏ算法的基础上,引入了一种新的高精度概率算法,取得很大进展．     

一类各向异性外问题的非重叠型区域分解算法

In this paper, based on the natural integral operator on elliptic boundary, a nonoverlapping domain decomposition method is presented for a kind of anisotropic elliptic problem with constant coefficients in an exterior domain, and the convergence of the method is analyzed. The choice of the relaxition factor is discussed.Some numerical examples are given. Theoretical analysis as well as numerical examples show that our method is performance.     

MODIFIED MORLEY ELEMENT METHOD FOR A FOURTH ORDER ELLIPTIC SINGULAR PERTURBATION PROBLEM

This paper proposes a modified Morley element method for a fourth order ellipticsingular perturbation problem. The method also uses Morley element or rectangle Morleyelement, but linear or bilinear approximation of finite element functions is used in the lowerpart of the bilinear form. It is shown that the modified method converges uniformly in theperturbation parameter.     

A ROBUST FINITE ELEMENT METHOD FOR A 3-D ELLIPTIC SINGULAR PERTURBATION PROBLEM

This paper proposes a robust finite element method for a three-dimensional fourth-order elliptic singular perturbation problem. The method uses the three-dimensional Morley element and replaces the finite element functions in the part of bilinear form corresponding to the second-order differential operator by a suitable approximation. To give such an approximation, a convergent nonconforming element for the second-order problem is constructed. It is shown that the method converges uniformly in the perturbation parameter.     

HIERARCHICAL BASIS METHOD FOR COVOLUME METHOD FOR NONSYMMETRIC AND INDEFINITE ELLIPTIC PROBLEM

In this paper, hierarchical basis method for second order nonsymmetric and indefinite elliptic problem on a polygonal domain (possibly nonconvex) discreted by a vertex-centered covolume method is constructed.     

SUPERCONVERGENCE OF LEAST-SQUARES MIXED FINITE ELEMENT FOR SECOND-ORDER ELLIPTIC PROBLEMS

In this paper the least-squares mixed finite element is considered for solving secondorder elliptic problems in two dimensional domains. The primary solution u and the flux er are approximated using finite element spaces consisting of piecewise polynomials of degree k and r respectively. Based on interpolation operators and an auxiliary projection,superconvergent H^1-error estimates of both the primary solution approximation uh and the flux approximation σh are obtained under the standard quasi-uniform assumption on finite element partition. The superconvergence indicates an accuracy of O(h^r 2) for the least-squares mixed finite element approximation if Raviart-Thomas or Brezzi-DouglasFortin-Marini elements of order r are employed with optimal error estimate of O(h^r l).     

RESTRICTED ADDITIVE SCHWARZ METHOD FOR A KIND OF NONLINEAR COMPLEMENTARITY PROBLEM

In this paper, a new Schwarz method called restricted additive Schwarz method （RAS） is presented and analyzed for a kind of nonlinear complementarity problem （NCP）. The method is proved to be convergent by using weighted maximum norm. Besides, the effect of overlap on RAS is also considered. Some preliminary numerical results are reported to compare the performance of RAS and other known methods for NCP.     

THE NONCONFORMING FINITE ELEMENT METHOD FOR SIGNORINI PROBLEM

We present the Crouzeix-Raviart linear nonconforming finite element approximation of the variational inequality resulting from Signorini problem. We show if the displacement field is of H2 regularity, then the convergence rate can be improved from O（h3/4） to quasi-optimal O（h｜log h｜1/4） with respect to the energy norm as that of the continuous linear finite element approximation. If stronger but reasonable regularity is available, the convergence rate can be improved to the optimal O（h） as expected by the linear approximation.     

A MIXED FINITE ELEMENT METHOD FOR THE CONTACT PROBLEM IN ELASTICITY

Based on the analysis of [7] and [10], we present the mixed finite element approximation of the variational inequality resulting from the contact problem in elasticity. The convergence rate of the stress and displacement field are both improved from O（h3/4） to quasi-optimal O（h│logh│^1/4）. If stronger but reasonable regularity is available, the convergence rate can be optimal O（h）.