Pohozaev恒等式及其在非线性椭圆型方程中的应用

在非线性椭圆型偏微分方程的研究中,Pohozaev恒等式在研究非平凡解的存在性和非存在性时起着十分重要的作用.本文旨在介绍Pohozaev恒等式及其在非线性椭圆型问题研究中的应用.首先介绍有界区域和无界区域上几种典型的Pohozaev恒等式,并得到几类非线性椭圆型方程存在解的必要条件,进而得到对应的方程非平凡解的非存在性和存在性结果.其次将介绍非线性椭圆型方程的局部Pohozaev恒等式,由此证明非线性椭圆型微分方程近似解序列的紧性,并得到几类典型非线性椭圆型方程的无穷多解存在性.最后利用非线性椭圆型方程的局部Pohozaev恒等式来研究其波峰解,得到波峰解的局部唯一性,并由此判断波峰解的对称性等特征.     

具有非线性梯度项的半线性椭圆型方程的爆炸解

本文在经典摄动方法与椭圆型偏微分方程的估计理论的基础上引入了一种新的方法,对带一般非线性项的二阶椭圆型方程爆炸解的存在性进行了研究,得到了RN(N≥3)上具有C2有界区域Ω上爆炸解的存在性,进而得到全空间RN(N≥3)上爆炸解的存在性.     

一致椭圆型算子边值问题变号解的存在性

利用Banach空间锥理论、算子的指数理论、上下解理论研究了含有一致椭圆型算子的椭圆边值问题变号解的存在性,同时分别得到了一个正解和一个负解.特别当非线性项是奇函数时,该边值问题至少存在一个正解,一个负解和两个变号解.     

具有非线性梯度项的半线性椭圆型方程的爆炸解

本文在经典摄动方法与椭圆型偏微分方程的估计理论的基础上引入了一种新的方法,对带一般非线性项的二阶椭圆型方程爆炸解的存在性进行了研究,得到了RN(N≥3)上具有C2有界区域Ω上爆炸解的存在性,进而得到全空间RN(N≥3)上爆炸解的存在性.     

双参数半线性高阶椭圆型方程的奇摄动解

讨论了一类具有双参数的半线性高阶椭圆型方程边值问题.利用微分不等式理论,研究了边值问题解的存在性和渐近性态.     

椭圆型方程的内层和边界层渐近解

本文讨论了一类半线性椭圆型方程边值问题.利用微分不等式理论,研究了边值问题内层和边界层解的存在性和渐近性态.     

一类半线性椭圆方程解的存在性

本文研究了一类具有临界增长的半线性椭圆型方程.采用最近A.Ambrosetti所提出的扰动方法研究这类问题,得到这类问题的解的存在性.与通常所用的临界点理论方法相比较,本文解的存在性在较弱条件下可得.     

两参数非线性高阶椭圆型偏微分方程奇摄动边值问题的解（英文）

讨论了一类具有两参数的非线性高阶椭圆型方程边值问题.在适当的条件下,利用摄动理论和伸长变量构造了原问题解的形式渐近展开式.再利用微分不等式理论,研究了边值问题解的存在性和渐近性态.     

环域上—类拟线性椭圆型方程组的正对称解的存在性

本文运用blowup方法和拓扑度理论研究了一类拟线性椭圆型方程组在环域上的正对称解的存在性．其主要结果隐含C1ement，Manasevich和Mitidieri的文章中的一个关于一类拟线性椭圆型方程组的正解的存在性的猜测对环域上的正对称解是成立的．     

拟线性椭圆型H-半变分不等式

本文研究一类拟线性椭圆型Ｈ＿半变分不等式,即研究具有非凸、非光滑泛函的椭圆型不等式·这类问题的研究来自力学·利用Ｃｌａｒｋｅ广义梯度和伪单调算子理论,我们证明了拟线性椭圆型Ｈ＿半变分不等式解的存在性·     

Boundary point lemmas and overdetermined problems

Two elliptic boundary value problems are considered: a problem of mixed type in a cylindrical domain, and a Dirichlet problem in an annular domain. Under some overdetermined conditions on the boundary gradient, symmetry results for domain and solution are proved. The method of proof involves the classical boundary point lemma by Hopf, as well as a suitable adaptation of it that works well at certain corners.     

椭圆外区域上的自然边界元法

１．引言 二十年来,自然边界元法已在椭圆问题求解方面取得了许多研究成果。它可以直接用来解决圆内（外）区域、扇形区域、球内（外）区域及半平面区域等特殊区域上的椭圆边值问题［１,２,５］,也可以结合有限元法求解一般区域上的椭圆边值问题,例如基于自然边界归化的耦合算法及区域分解算法就是处理断裂区域问题及外问题的一种有效手段［２－４,６］。 人们在设计求解外问题的耦合算法或者区域分解算法时,通常选取圆周或球面作人工边界。但对具有长条型内边界的外问题,以圆周或球面作人工边界显然并非最佳选择,它将会导致大量的…     

SUPERCONVERGENCE OF GENERALIZED DIFFERENCE METHOD FOR ELLIPTIC BOUNDARY VALUE PROBLEM

Some superconvergence results of generalized difference solution for elliptic boundary value problem are given. It is shown that optimal points of the stresses for generalized difference method are the same as that for finite element method.     

On fourth-order elliptic boundary value problems

This paper is concerned with the existence and uniqueness of a solution for a class of fourth-order elliptic boundary value problems. The existence of a solution is proven by the method of upper and lower solutions without any monotone nondecreasing or nonincreasing property of the nonlinear function. Sufficient conditions for the uniqueness of a solution and some techniques for the construction of upper and lower solutions are given. All the existence and uniqueness results are directly applicable to fourth-order two-point boundary value problems.

     

一类各向异性外问题的重叠型区域分解算法

本文以椭圆外调和问题的自然边界归化为基础，提出了求解各向异性常系数椭圆方程的一种重叠型区域分解算法，并分析了算法的收敛性及收敛速度．理论分析及数值实验表明，该方法对于求解各向异性外问题非常有效．     

AN EMBEDDED BOUNDARY METHOD FOR ELLIPTIC AND PARABOLIC PROBLEMS WITH INTERFACES AND APPLICATION TO MULTI-MATERIAL SYSTEMS WITH PHASE TRANSITIONS

The embedded boundary method for solving elliptic and parabolic problems in geometrically complex domains using Cartesian meshes by Johansen and Colella （1998, J. Comput. Phys. 147, 60） has been extended for elliptic and parabolic problems with interior boundaries or interfaces of discontinuities of material properties or solutions. Second order accuracy is achieved in space and time for both stationary and moving interface problems. The method is conservative for elliptic and parabolic problems with fixed interfaces. Based on this method, a front tracking algorithm for the Stefan problem has been developed. The accuracy of the method is measured through comparison with exact solution to a two-dimensional Stefan problem. The algorithm has been used for the study of melting and solidification problems.     

Regularized solution for nonlinear elliptic equations with random discrete data

The aim of this paper is to study the Cauchy problem of determining a solution of nonlinear elliptic equations with random discrete data. A study showing that this problem is severely ill posed in the sense of Hadamard, ie, the solution does not depend continuously on the initial data. It is therefore necessary to regularize the in‐stable solution of the problem. First, we use the trigonometric of nonparametric regression associated with the truncation method in order to offer the regularized solution. Then, under some presumption on the true solution, we give errors estimates and convergence rate in L²‐norm. A numerical example is also constructed to illustrate the main results.     

A note on a Cauchy problem for the Laplace equation: Regularization and error estimates

In this paper, a Cauchy problem for the Laplace equation is investigated. Based on the fundamental solution to the elliptic equation, we propose to solve this problem by the truncation method, which generates well-posed problem. Then the well posedness of the proposed regularizing problem and convergence property of the regularizing solution to the exact one are proved. Error estimates for this method are provided together with a selection rule for the regularization parameter. The numerical results show that our proposed numerical methods work effectively. This work extends to earlier results in Qian et al. (2008) [14] and Hao et al. (2009) [5].     

TWO PROBLEMS OF HERMITE ELLIPTIC EQUATIONS

In this article, the author investigates some Hermite elliptic equations in a modified Sobolev space introduced by X. Ding [2]. First, the author shows the existence of a ground state solution of semilinear Hermite elliptic equation. Second, the author studies the eigenvalue problem of linear Hermite elliptic equation in a bounded or unbounded domain.     

On linear monotone iteration and Schwarz methods for nonlinear elliptic PDEs

Summary The Schwarz Alternating Method can be used to solve elliptic boundary value problems on domains which consist of two or more overlapping subdomains. The solution is approximated by an infinite sequence of functions which results from solving a sequence of elliptic boundary value problems in each subdomain. In this paper, proofs of convergence of some Schwarz Alternating Methods for nonlinear elliptic problems which are known to have solutions by the monotone method (also known as the method of subsolutions and supersolutions) are given. In particular, an additive Schwarz method for scalar as well some coupled nonlinear PDEs are shown to converge to some solution on finitely many subdomains, even when multiple solutions are possible. In the coupled system case, each subdomain PDE is linear, decoupled and can be solved concurrently with other subdomain PDEs. These results are applicable to several models in population biology. This work was in part supported by a grant from the RGC of HKSAR, China (HKUST6171/99P)