一类修正的Navier—Stokes方程组Neumann边值问题的弱解

讨论一类修正的Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ型方程组Ｎｅｕｍａｎｎ边值问题的可解性及解的性质。     

ASYMPTOTIC BEHAVIOR OF SOLUTIONS TO THE HEAT EQUATIONS WITH NONLINEAR BOUNDARY CONDITIONS

The purpose of this paper is to investigate the stability and asymptotic behav-ior of the time-dependent solutions to a linear parabolic equation with nonlinear boundarycondition in relation to their corresponding steady state solutions. Then, the above resultsare extended to a semilinear parabolic equation with nonlinear boundary condition by an-alyzing the corresponding eigenvalue problem and using the method of upper and lowersolutions.     

ON DISCRETE PROJECTION AND NUMERICAL BOUNDARY CONDITIONS FOR THE NUMERICAL SOLUTION OF THE UNSTEADY INCOMPRESSIBLE NAVIER-STOKES EQUATIONS

1. IntroductionLet us consider the unsteady incompressible Navier--Stokes equations (INSE)on a two--dimensional rectangular region fl with boundary 0fl. Here w = (u, v)" is tl1e velocityvector, p is the pressure, and f a known vector function of x) y, and…     

EXISTENCE AND NONEXISTENCE OF GLOBAL POSITIVE SOLUTIONS FOR DEGENERATE PARABOLIC EQUATIONS IN EXTERIOR DOMAINS

This article deals with the degenerate parabolic equations in exterior domains and with inhomogeneous Dirichlet boundary conditions. We obtain that pc = (σ+m)n/(n-σ-2) is its critical exponent provided max{-1, [(1-m)n-2]/(n+1)} σ n-2. This critical exponent is not the same as that for the corresponding equations with the boundary value 0, but is more closely tied to the critical exponent of the elliptic type degenerate equations. Furthermore, we demonstrate that if max{1, σ + m} p ≤ pc, then every positive solution of the equations blows up in finite time; whereas for ppc, the equations admit global positive solutions for some boundary values and initial data. Meantime, we also demonstrate that its positive solutions blow up in finite time provided n ≤σ+2.     

非光滑区域上非自治Navier-Stokes 方程非齐边界问题的吸引子

本文研究在2维Lipschitz区域上Navier-Stokes方程的非齐边界问题的长时间行为，在外力是时间的拟周期下，通过引入双参过程的概念，证明一致吸引子A的存在性，并给出一致吸引子A的Hausdorff维数的上界估计。     

BLOW-UP OF SOLUTIONS TO ELLIPTIC EQUATIONS WITH SEMILINEAR DYNAMICAL BOUNDARY CONDITIONS OF HYPERBOLIC TYPE

In this paper,we present some sufficient conditions for blow-up of soluti- ons to elliptic equations under semilinear dynamical boundary conditions of hyperbolic type.     

具非线性边界条件的拟线性抛物型方程解的Blow-up

本文考虑一类具非线性边界条件的拟线性抛物方程初边值问题解的整体性态 .通过构造与解有关的适当积分 ,利用“凸性方法”及非线性抛物型方程的极大值原理 ,证明了在某些条件下 ,问题的光滑解u(x ,t)只能在一个有界区间 (0 ,T0 )中存在 ,即有 :limt→T-0sup‖u(· ,t)‖ ∞ =+∞ .     

Banach空间二阶非线性混合型脉冲微分-积分方程边值问题的解

在较弱的条件下,利用MSnch不动点定理,研究了Banach空间中二阶非线性混合型脉冲微分-积分方程边值问题解的存在性,推广和改进了某些已有的结果.     

椭圆问题的非线性边界条件均匀化

在本文我们讨论了在等值面边值问题中的非线性边界条件的均匀化,推广了相应的边界条件均匀化结果,而且可应用到用于处理热敏电阻问题中的一类非线性非局部边值问题的边界条件均匀化问题。     

EXISTENCE OF POSITIVE SOLUTIONS TOA ROBIN BOUNDARY VALUE PROBLEM FORA CLASS QUASILINEAR ORDINARYDIFFERENTIAL EQUATIONS

11尬roductlonIn this paper;we study the exlstence ofnonneg时Ive solutions ofone dl－menslonal－Lapfaclan boundary value problems一(电N》’二入M;0＜x＜1,儿1)u’仰二0,*’川十口叫)二0,队2)where入＞0md a＞0 are parmetersmd f E C’[0,1],屯(。)＝I冲－‘。,p＞1二This problem ppears In the study ofnon－Newtonlan luids(see[1;2])andnon－Newtonlan iltratlon(see[3])．The quantity p Is a characteristic of*theteristicmadium．Media with p＞2 are called dllatantn"ids and those with p＜2 arecalled pseudop…     

求解带非线性边界条件的反应扩散方程数值解的组合迭代方法

1　引　　言我们首先考虑如下抛物型方程ｕｔ-ＤΔｕ =ｆ(ｘ ,ｔ ,ｕ) (ｔ∈ ( 0 ,Ｔ],ｘ∈Ω ) ｕ/ ν+ βｕ =ｇ(ｘ ,ｔ ,ｕ) (ｔ∈ ( 0 ,Ｔ],ｘ∈ Ω )ｕ(ｘ ,0 ) =ψ(ｘ) (ｘ∈Ω )( 1 .1 )其中Ｔ为正常数 ,Ω 是ＲＰ 空间的有界区域 记ＱＴ=Ω × ( 0 ,Ｔ],ＳＴ= Ω × ( 0 ,Ｔ],假设在ＱＴ上Ｄ≡ｄ(ｘ ,ｔ) >0 ,在ＳＴ 上β≡β(ｘ ,ｔ)≥ 0 又设 ｆ(ｘ ,ｔ,ｕ) ,ｇ(ｘ ,ｔ,ｕ)为关于ｕ的非线性函数 ,且对ｘ ,ｔ各参数满足Ｈ¨ｏｌｄｅｒ连续条件 将 ( 1 .1 )离散化之后我们得到相应的有限差分系统 ,当 ｇ(ｘ ,ｔ,ｕ)为ｕ的线性…     

二阶常微分方程组积分边值问题的正解

在借助于非负矩阵获得正解的先验估计的基础上,用不动点指数理论研究二阶非线性常微分方程组积分边值问题正解和多重正解的存在性.     

GLOBAL SOLUTIONS TO THE NAVIER-STOKES EQUATIONS FOR COMPRESSIBLE HEAT-CONDUCTING FLOW WITH SYMMETRY AND FREE BOUNDARY

ABSTRACT

Global solutions of the multidimensional Navier-Stokes equations for compressible heat-conducting flow are constructed, with spherically symmetric initial data of large oscillation between a static solid core and a free boundary connected to a surrounding vacuum state. The free boundary connects the compressible heat-conducting fluids to the vacuum state with free normal stress and zero normal heat flux. The fluids are initially assumed to fill with a finite volume and zero density at the free boundary, and with bounded positive density and temperature between the solid core and the initial position of the free boundary. One of the main features of this problem is the singularity of solutions near the free boundary. Our approach is to combine an effective difference scheme to construct approximate solutions with the energy methods and the pointwise estimate techniques to deal with the singularity of solutions near the free boundary and to obtain the bounded estimates of the solutions and the free boundary as time evolves. The convergence of the difference scheme is established. It is also proved that no vacuum develops between the solid core and the free boundary, and the free boundary expands with finite speed.     

MULTIPLE POSITIVE SOLUTIONS OF BOUNDARY VALUE PROBLEMS FOR QUASILINEAR DIFFERENTIAL EQUATIONS

We consider the boundary value problem for the second order quasilinear differential equationwhere f is allowed to change sign, φ(v) = \v\p-2v, p > 1. Using a new fixed point theorem in double cones, we show the existence of at least two positive solutions of the boundary value problem.     

三维Poisson方程外问题的高阶局部人工边界条件

１引言假设Ｒ３是一分片光滑的闭曲面．是以为边界的无界区域,=Ｒ3是以为边界的有界区域,并且存在球Ｂ0＝ｘｘＲ0我们考虑下面Ｐｏｉｓｓｏｎ方程的外问题：这里f(x）,ｇ（x）是,上的已知函数,f(x)的支集是紧的,即存在一个球面=x·x=R1,使得x＝xｘＲ１,有ｆx＝０．令＝,则ｆ（ｘ）的支集包含在中,令＝xx＝,表示u在上的外法向微商．用流量为零的条件代替无限远处条件（３）,则我们得到一个新的外问题：我们将分别讨论问题（１）－（３）和（４）－（７）的数值解．由于求解区域的无界性,给数值计算带来了本质性的困难．克服此…     

一类具有吸收边界条件的二阶非线性双曲方程的混合元法分析

1　引　　言关于二阶双曲型方程的有限元解的收敛性问题 ,目前已经有不少结果 .Dupont[1 ] 给出了一类线性双曲方程 Galerkin解的 L2 误差估计 ,Baker[2 ] 对此作了改进 ,用的是一种所谓“非标准的能量方法”.这一方法为 Cowsar,Dupont,Wheeler[3] 所采用 ,分析了一类具有吸收边界条件的线性双曲方程的混合元格式的 L2收敛性 .对于非线性双曲型问题 ,袁益让 ,王宏[4,5] 等给出了标准有限元方法的 H1 与 L2 误差估计 .本文试图把 [3]的工作更进一步研究 ,我们考虑如下非线性双曲问题 :φ(x) utt= mi,j=1 xi(aij(x) p(x,u) u xj) + mi=1…     

POSITIVE SOLUTIONS TO SECOND-ORDER SINGULAR NEUMANN BOUNDARY VALUE PROBLEM WITH PARAMETERS IN THE BOUNDARY CONDITIONS

In this paper, we consider a class of nonlinear second-order singular Neumann boundary value problem with parameters in the boundary conditions. By the fixed point index, spectral theory of the linear operators, and lower and upper solutions method, we prove that there exists a constant λ* > 0 such that for λ∈ (0, λ * ), NBVP has at least two positive solutions; for λ = λ* , NBVP has at least one positive solution; for λ > λ* , NBVP has no solution.     

THE ARTIFICIAL BOUNDARY CONDITIONS FOR NUMERICAL SIMULATIONS OF THE COMPLEX AMPLITUDE IN A COUPLED BAY-RIVER SYSTEM

We consider the numerical approximations of the complex amplitude in a coupled bayriver system in this work. One half-circumference is introduced as the artificial boundary in the open sea, and one segment is introduced as the artificial boundary in the river if the river is semi-infinite. On the artificial boundary a sequence of high-order artificial boundary conditions are proposed. Then the original problem is solved in a finite computational domain, which is equivalent to a variational problem. The numerical approximations for the original problem are obtained by solving the variational probiem with the finite element method. The numerical examples show that the artificial boundary conditions given in this work are very effective.