一种求解跳系数椭圆标量方程的渐近展开方法的误差分析

本文研究了具有跳系数(或多尺度性质)的椭圆型PDEs问题.利用渐近展开方法,将具有多尺度性质的PDEs模型问题解耦为若干光滑系数(或单尺度性)的PDEs问题进行求解,获得了和经典线性有限元方法在.0意义下同样的误差阶,表明了该方法的有效性.     

一类摄动超越方程的渐近解

用直接展开法得到了一类摄动超越方程的渐近解。     

极限方程有奇性的一类六阶椭圆型方程混合边值问题解的渐近式

该文研究极限方程在部分边界上为退缩椭圆型(椭圆-抛物)的一类六阶椭圆型方程混合边值问题的奇摄动,在适当的假设下,应用改进了的多重尺度法,求得其解包括边界层和套层在内除了半圆域的两个角点外,在整个半圆域中有任意阶的一致有效的渐近展开式.     

极限方程有奇性的一类四阶椭圆型方程混合边值问题解的渐近式

本文研究极限方程在部分边界上为退缩椭圆方程（椭圆－抛物）的一类四阶椭圆型方程混合边值问题解的渐近式。在适当的假设下，应用改进了的多重尺度法，求得其解除了半圆域的两个角点外，在整个半圆域中有任意阶的一致有效的渐近展开式。     

一个带有小参数的二维椭圆方程的渐近性分析

通过数值方法研究在边界充分(逐段)光滑区域上的带有小参数的二维椭圆方程在部分Dirichlet边界控制下的渐近性问题.对于一维的情形求解析解的结果,对高维问题提出类似的问题.但高维问题解析求解一般不可能,因此采用数值分析的方法.数值结果表明,在所选的条件下,边界值对小常数仍然不是解析的.     

具有小周期孔洞弹性结构的双尺度渐近分析

本文对具有小周期孔洞的复合材料弹性结构进行研究,得到了位移函数一类可计算的双尺度渐近展开式,并给予严格的理论证明．     

非齐次小周期复合材料稳态热问题的多尺度渐近展开和收敛性分析

利用多尺度渐近展开和均匀化思想讨论了小周期复合材料的稳态热问题,得到了非齐次边界条件下二阶椭圆型方程的渐近解,并给出了原始解与渐近解之间的误差估计,数值结果表明了结论的正确性.     

一类延迟积分方程的渐近概周期解

积分方程解的性态是积分理论中一个重要而又基本的问题.其中关于方程的周期解、概周期型解的存在性问题更是具有重要的理论意义和应用价值.已有文献中,有的延迟是常数,而有的延迟虽为函数,但对延迟做了是概周期函数的假设.本文在某些延迟积分方程的概周期解的存在性的基础上,并利用渐近概周期函数的定义和不动点理论,讨论了一类延迟是渐近概周期函数的积分方程的渐近概周期解的存在性.     

一类摄动超越方程的渐近解(英文)

用直接展开法得到了一类摄动超越方程的渐近解     

小周期复合材料热传导问题的双尺度渐近展开及收敛性分析

利用双尺度渐近展开和均匀化思想讨论了小周期复合材料的热传导问题,得到了具有高阶震荡系数的抛物型方程的渐近展开式,并证明了当Ω为R~2中的光滑的区域时渐近展开式在空间L~2(0,T;H~1(Ω))中具有较好的收敛性.     

Multigrid method for coupled semilinear elliptic equation

This paper introduces a kind of multigrid finite element method for the coupled semilinear elliptic equations. Instead of the common way of directly solving the coupled semilinear elliptic problems on some fine spaces, the presented method transforms the solution of the coupled semilinear elliptic problem into a series of solutions of the corresponding decoupled linear boundary value problems on the sequence of multilevel finite element spaces and some coupled semilinear elliptic problems on a very low dimensional space. The decoupled linearized boundary value problems can be solved by some multigrid iterations efficiently. The optimal error estimate and optimal computational work are proved theoretically and demonstrated numerically. Moreover, the requirement of bounded second‐order derivatives of the nonlinear term in the existing multigrid method is reduced to a Lipschitz continuous condition in the proposed method.     

New Jacobi elliptic functions solutions for the variable-coefficient mKdV equation

In this work, a new generalized Jacobi elliptic functions expansion method based upon four new Jacobi elliptic functions is described and abundant new Jacobi-like elliptic functions solutions for the variable-coefficient mKdV equation are obtained by using this method, some of these solutions are degenerated to solitary-like solutions and triangular-like functions solutions in the limit cases when the modulus of the Jacobi elliptic functions m→1 or 0, which shows that the new method can be also used to solve other nonlinear partial differential equations in mathematical physics.     

Long-time asymptotic for the Hirota equation via nonlinear steepest descent method

We present the Riemann–Hilbert problem formalism for the initial value problem for the Hirota equation on the line. We show that the solution of this initial value problem can be obtained from that of associated Riemann–Hilbert problem, which allows us to use nonlinear steepest descent method/Deift–Zhou method to analyze the long-time asymptotic for the Hirota equation.     

A new approximate method for second order elliptic problems with rapidly oscillating coefficients based on the method of multiscale asymptotic expansions

In this paper, we consider second order elliptic problems with rapidly oscillating coefficients. On basis of [O.A. Oleinik, A.S. Shamaev, G.A. Yosifian, Mathematical Problems in Elasticity and Homogenization, North-Holland, Amsterdam, 1992; Wen-ming He, Jun-zhi Cui, A pointwise estimate on the 1-order approximation of , IMA J. Appl. Math. 70 (2005) 241-269] we propose a new approximate method to solve these problems. Of course, we present its error estimate.     

一类拟线性椭圆方程整体解的不存在性

这篇文章主要利用常微分技术讨论了一个二阶拟线性椭圆方程Lpu≡div（｜Du｜^p-2Du）=f（x,u）,x∈R^N的整体解的不存在性.我们只考虑2≤p〈N的情況并且在假设f（x,u）关于第二个变量u没有单调性的情况下得到整体解的不存在性结果.     

全空间上半线性椭圆方程的正解

采用域扩线技巧与广义Mountain-Pass引理相结合的方法,给出了全空间上方程－Δu mu=u^p-1u的正确的存在性和光滑性。     

一类奇摄动方程的PLK方法

通过对坐标作包含因变量的非线性泛函的变换,以首项渐近解和相应的坐标变换给出原问题的二阶的近似解,并把这种思想进一步推广到更复杂的非线性方程,用较为简洁的方法求得了一类非线性方程的二阶渐近解.     

Existence and asymptotic behavior of entire blow-up solutions for quasilinear elliptic equation

In this article, we discuss the blow-up problem of entire solutions of a class of second-order quasilinear elliptic equation Δ _p u ≡ div(|?u| ^p?2?u) = ρ(x)f(u), x ∈ R ^N . No monotonicity condition is assumed upon f(u). Our method used to get the existence of the solution is based on sub-and supersolutions techniques.     

The asymptotic behavior of solutions of the sine-gordon equation with singularities at zero

The problem of asymptotic analysis of radially symmetric solutions of the sine-Gordon equation reducible to the third Painlevé transcendent is posed. Solutions with singularities at the origin are studied. For finite values of the independent variable, an asymptotic expansion of such a solution is obtained; the leading term of this expansion is a modulated elliptic function. The corresponding modulation equation and phase shift are written out. Translated fromMatematicheskie Zametki, Vol. 67, No. 3, pp. 329–342, March, 2000.     

An asymptotic analysis method for the linearly shell theory

In this paper, we consider a linearly elastic shell, i.e. a three-dimensional linearly elastic body with a small thickness denoted by 2ε, which is clamped along its part of the lateral boundary and subjected to the regular loads. In the linear case, one can use the two-dimensional models of Ciarlet or Koiter to calculate the displacement for the shell. Some error estimates between the approximate solution of these models and the three-dimensional displacement vector field of a flexural or membrane shell have been obtained. Here we give a new model for a linear and nonlinear shell, prove that there exists a unique solution U of the two-dimensional variational problem and construct a three-dimensional approximate solutions UKT(x,ξ) in terms of U: We also provide the error estimates between our model and the three-dimensional displacement vector field :‖u-UKT‖1,Ω≤C∈r,r=3/2, an elliptic membrane, r = 1/2, a general membrane, where C is a constant dependent only upon the data‖u‖3,Ω,‖UKT‖3,Ω,θ.