拟线性对称双曲组的初边值问题及其应用

本文讨论拟线性对称双曲组的初边值问题及其在空气动力学方程组中的应用。关于多个自变数拟线性对称双曲组的柯西问题,在[1,2]中有讨论,但对于边值问题的研究至今仍不多见。谷超豪教授把线性正对称型方程组的理论推广到拟线性的情形,为讨论拟线性方程组的边值问题提供了新的方法,他在文[3,4]中都指出了拟线性对称双曲组解的存在性,但必须要求该方程组为充分正的。本文所讨论的对称双曲组不要求附加充分正的     

拟线性正对称组具特征的边值问题

<正> 谷超豪在[1],[2],[3]中得到了拟线性正对称组边值问题的 C~ρ解的存在和唯一性定理.陈恕行在[4],[5]中讨论了拟线性对称双曲组的初边值问题.本文继[1]—[5],讨论拟线性正对称组的特征边值问题.     

拟线性对称双曲组具有特征边界的初边值问题

拟线性对称双曲组在数学物理中有广泛的应用.例如,流体力学方程组就可化为拟线性对称双曲组进行讨论.在文[1,2]中,对于拟线性对称双曲组具非特征边界的初边值问题已作了完整的讨论,但对于边界为特征的情形,附加了方程组中未知函数导数项的系数不依赖于u的要求.在等熵、初速为亚音速,初始密度接近于常数的固壁边界问题,     

拟线性正对称组具非线性特征的边值问题

谷超豪在[1]中就报告了拟线性正对称方程组边值问题解的存在和唯一性定理,详细的证明发表于[2],在[7]中对此有所改进,所建立的理论适用于非特征的齐次边值的情况。[3]参考了[2],[4]的做法,把[2]的结果推广到拟线性正对称组具某类特征的边值问题中去,但要求边界条件仍是齐次的。本文讨论边界条件是非齐次的,且是非线性的特征边值问题,在这种情况下建立了可微解的存在和唯一性定理。     

非线性可动边界问题的差分方法的收敛性

本文讨论了逼近两个自变量的拟线性双曲方程组具可动边界。且边界条件为非线性的初边值问题的非穿行差分方法的收敛性。这类问题来源于求解拟线性双曲方程组的初边值问题的分离奇性法。     

一阶拟线性可对称化偏微分方程组解的存在性

Hahn-Goldberg讨论了一阶拟线性正对称组解的存在性。谷超豪老师在文[4]中研究了情况更为复杂的一阶拟线性正对称组的边值问题。 本文的目的是利用类似的考虑,将Friedrichs和Lax关于一阶线性可对称化组的     

一阶拟线性双曲型方程组的解的正规性

本文考虑一阶拟线性双曲型方程组的柯西问题、角状区域上的典型边值问题以及混合初边值问题,得到了这些问题解的正规性定理,即若这些问题已经有了一个C~1解,且方程组的系数和初值或边值属于C~N(N>1),则这些问题的解也是C~N解,对线性双曲型方程组在角状区域上的线性边值问题,在||?_1}}_(mtn)<1条件下,证明了它的整体光滑解的存在和唯一性。     

非线性椭圆型方程组边值问题的可解性

研究椭圆型方程组Dirichlet边值问题的可解性,利用不动点定理证明了上述问题存在上、下解情形,存在有界非负解,并利用该结论讨论了带参数的椭圆型方程组Dirichlet边值问题通过寻找该问题的上、下解,证明了正参数充分小时,这个问题存在有界正解.这里非线性函数在+∞处可以是超线性的,从而证明了部分椭圆型方程组边值问题中非线性项为超线性时,有界正解的存在性.同时,作为定理的应用,给出了实例.     

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．     

拟线性拋物型方程

<正> 本文所研究的课题是拟线性抛物型方程的第一边值问题.一般二阶拟线性方程可以写成下列形式     

拟线性对称双曲型方程组的某些整体解及其渐近性质

<正> 1.引言 近年来,人们采用了不定常气流方程来计算定常的跨音速气流,取得了一定的成效.在这种计算中,混合型方程组的解被看成为多一个自变量的双曲型方程组解的极限.这启发我们去研究系数和t无关的双曲型方程组的解当t趋向无限时的渐近行为.在本文中,我们利用[2]中的结果,先考虑拟线性对称双曲型方程组,以方程组的充分正为代价,对初始条件作了某些限制以后,证明了这种方程组的混合问题的整体解的存在性.然     

Initial boundary value problems for quasilinear symmetric hyperbolic systems with characteristic boundary

This paper is devoted to initial boundary value problems for quasi-linear symmetric hyperbolic systems in a domain with characteristic boundary. It extends the theory on linear symmetric hyperbolic systems established by Friedrichs to the nonlinear case. The concept on regular characteristics and dissipative boundary conditions are given for quasilinear hyperbolic systems. Under some assumptions, an existence theorem for such initial boundary value problems is obtained. The theorem can also be applied to the Euler system of compressible flow. __________ Translated from Chinese Annals of Mathematics, Ser. A, 1982, 3(2): 223–232     

一类拟线性奇摄动方程的边值问题

In this paper, the Nagumo theorem and the fixed-point theorem are used to prove the existence and the uniqueness and to estimate the asymptotic expansion of the shock solutions of the boundary value problems for a class of quasilinear differential equations, the asymptotic expansion of solution of any orders including boundary is obtained.     

Infinitely Many Solutions for Second-Order Quasilinear Periodic Boundary Value Problems with Impulsive Effects

The purpose of this paper is to investigate the multiplicity of solutions for second-order quasilinear periodic boundary value problems with impulsive effects. By using symmetric mountain pass theorem and the genus properties in critical point theory, the existence results of infinitely many solutions are obtained.     

拟线性系统周期边值问题

The existence and uniqueness results about quasilinear periodic boundary value problems are established by using the global inverse function theorem and the result about the existence and uniquencess of periodic solutions for the periodic boundary value problem of nonhomogeneous linear periodic system.     

Numerical implementation of iteration processes applied in the study of nonlinear boundary value problems of the theory of elasticity and filtration

Nonlinear elastic problems for hardening media are solved by applying the universal iteration process proposed by A.I. Koshelev in his works on the regularity of solutions to quasilinear elliptic and parabolic systems. This requires numerically solving a linear elliptic system at each step of the iteration procedure. The method is numerically implemented in the MATLAB environment by using its PDE Toolbox. A modification of the finite-element procedure is suggested in order to solve a linear algebraic system at each iteration step. The computer model is tested on simple examples. The same nonlinear problems are also solved by the method of elastic solutions, which consists in replacing the Laplace operator in the universal iteration process by the Lamé operator of linear elasticity. As is known, this iteration process converges to a weak solution of the nonlinear problem, provided that the displacements are fixed on the boundary. The method is tested on examples with stresses on the boundary. The third part of the paper is devoted to the nonlinear filtration problem. General properties of the iteration process for nonlinear parabolic systems have been studied by A.I. Koshelev and V.M. Chistyakov. The numerical implementation is based on slightly modified PDE Toolbox procedures. The program is tested on simple examples.     

Boundary value problems for first-order mixed complex equations with degenerate curve

This article deals with some boundary value problems for quasilinear mixed (elliptic-hyperbolic) complex equations of first order with degenerate hyperbolic curve in a simply connected domain. First, we give the representation theorem and prove the uniqueness of solutions for the above boundary value problems. Then using the method of successive iteration, the existence of solutions for the above problems is proved.     

EXISTENCE OF POSITIVE ENTIRE SOLUTIONS FOR QUASILINEAR ELLIPTIC SYSTEMS

In this paper, the existence of positive solutions for a class of quasilinear elliptic differential equation systems are established by Schauder-TychonofF fixed point theorem.     

On global bifurcation for quasilinear elliptic systems on bounded domains

General second order quasilinear elliptic systems with nonlinear boundary conditions on bounded domains are formulated into nonlinear mappings between Sobolev spaces. It is shown that the linearized mapping is a Fredholm operator of index zero. This and the abstract global bifurcation theorem of [Jacobo Pejsachowicz, Patrick J. Rabier, Degree theory for C¹ Fredholm mappings of index 0, J. Anal. Math. 76 (1998) 289-319] allow us to carry out bifurcation analysis directly on these elliptic systems. At the abstract level, we establish a unilateral global bifurcation result that is needed when studying positive solutions. Finally, we supply two examples of cross-diffusion population model and chemotaxis model to demonstrate how the theory can be applied.     

Fixed point theorems for multivalued operators and application to discontinuous quasilinear BVP's

In this article, we prove an abstract fixed point theorem for increasing multivalued operators in ordered topological spaces, which provides an efficient tool to obtain qualitative results on the solution set of discontinuous quasilinear elliptic boundary value problems. In particular, we are able to show the existence of extremal solutions of such problems.