Recent progress in study of singular perturbation problems

Some results for the singular perturbation theory, methods and applications in the new century are reviewed in this paper. It could be found that in the recent decade, many approximate methods have been developed and refined, including the method of averaging, boundary layer methods, methods of matched asymptotic expansion and methods of multiple scales. An overview is given on the new work about various problems, such as the reaction diffusion, turning points, boundary layers, shock waves, stability problem, solitons, attractors, canard solution, scattering light wave and neuron network, etc. And then, a great number of applied problems are solved in applied mathematics, computational mathematics, fluid mechanics, elastic mechanics, optics, thermophysics, quantum mechanics, plasm physics, physical chemistry, analytical chemistry, epidemiology, neurology, engineering science, environment science, bionomics, atmosphere physics, ocean climate, aeronautics and astrnatics and so on, from which only some examples are extracted and described in this review.     

Singular perturbation of a second-order three-point boundary value problem for nonlinear systems

This paper deals with the existence of solutions to a singularly perturbed second-order three-point boundary value problem for nonlinear differential systems. The authors construct an appropriate generalized lower- and upper-solution pair, a concept defined in this paper, and employ the Nagumo conditions and algebraic boundary layer functions to ensure the existence of solutions of the problem. The uniformly valid asymptotic estimate of the solutions is given as well. The differential systems have nonlinear dependence on all order derivatives of the unknown.     

一类高次非线性奇摄动问题的匹配解法

在适当的条件下,利用奇摄动理论中的收缩变换以及匹配技巧,讨论了一类高次非线性奇摄动两点边值问题.相应于边界条件.构造了原同题的外部解和内部解.按ε的增幂展开非线性项、比较同次幂的系数.再利用特异极限,由匹配原问题的内、外部解得出了相应于参数k=0、k=1、k<0、k>1和0摄动理论在研究微分方程上的一个应用.并为估计一些相关类型的非线性问题的解提供了一种简捷有效的方法.     

一类奇异摄动延迟积分微分方程的指数稳定性

奇异摄动延迟微分方程广泛出现于科学与工程应用领域。本文讨论了一类单参数奇异摄动积分微分方程的指数稳定性质,并应用Halanay不等式得到了稳定性成立的判定条件。     

Hirota方法在孤子方程中的应用

主要考虑一个重要的孤子方程:BLMP-方程.介绍了有关孤子理论和Hirota方法,通过适当的变量代换,将孤子方程化为双线性导数形式的微分方程,从方程的双线性导数形式出发,用摄动法得到孤子方程的n-孤子解,最后又求得它的另外一种形式的Wronsky-解.     

一类周期边值问题解的存在性及其奇异摄动

首先利用微分不等式研究如下类型的周期边值问题{y＇＇=f（t,y,y＇）,0〈t〈l y（0）=y（t）,y＇（0）=y＇（l）.的微分不等式与解的存在性,并在一定条件下把解延拓成为微分方程在无穷时间区N-Y-N期解,然后利用所得结果讨论奇异摄动现象．     

一类具有混合边界条件的三阶奇摄动非线性边值问题

研究了一类具有混合边界条件的奇摄动三阶非线性边值问题。在构造形式渐近解的基础上,用微分不等式理论证明了解的存在性,并得出了解的任意阶的一致有效展开式。     

广义Kato分解及单值延拓性质的摄动

利用与广义Kato分解有关的谱,研究单值延拓性质在紧摄动下的稳定性.此外,研究2x2上三角算子矩阵的单值延拓性质在紧摄动下的稳定性.     

一类高阶方程的激波解

利用匹配展开法，研究了一类四阶微分方程的奇摄动边值问题的解的边界层性态。     

非线性与立方非线性Schr(o)dinger方程的多级准确解

本文利用摄动法对非线性与立方非线性Schr(o)dinger方程作展开.应用Jacobi椭圆函数展开法求得了零级近似方程的准确解,并在Lame方程和Lame函数的基础上分别求得一级近似方程和二级近似方程的准确解.这样,就求得了非线性与立方非线性Schr(o)dinger方程的多级准确解.