用微分不等式对二阶拟线性方程奇摄动群的估计

考虑二阶拟线性方程两点问题 εy″ f_1(x,y,ε)y′ f_2(x,y,ε)=0,0相似文献   

关于具有转点的常微分方程的边值问题

本文研究下面形式的边值问题εy″-f(x,ε)y′ g(x,ε)y=0 (-α≤x≤b,0<ε≤1)y(-α)=α,y(b)=β其中f(x,0)在区间[-a,b]上具有多个和多重零点.给出了出现边界层和内部层的条件,并在相应的条件下,构造解的渐近展开式.     

有限元求解一维奇异摄动问题

1 问题的引入 考虑边值问题 L_y≡-εy″+p(x)y′+q(x)y=f(x),x∈I≡(o,1), y(0)=y(1)=0, (1,1)其中ε是一常数,ε∈(0,1),p(x),q(x),f(x)是[0,1]上的光滑函数,且满足p(x)≥a_1>0,q(x)≥0,q(x)-(1/2)P′(x)≥a_2>0.以下用C和d表示一常数,仅依赖于p(x),q(x),f(x),与ε无关,在不同的地方它们可能代表不同的数. 引入双线性形式 B(u,v)=integral from n=0 to 1(εu′v′+pu′v +quv)dx,u,v∈H~1(I),及范数     

Neumann问题的渐近展开算法

一、问题的提出 Lions在[1]中引进的处理偏微分方程Stiff问题在变分形式中的渐近展开算法,多应用于含小参数0<ε<<1(在超导技术、低温物理和半导体技术中经常出现ε为10~(-21)量级的数.这时,ε比机器零还小,用通常的数值计算方法难以实施,只能应用渐近展开算法)的椭圆型方程齐次边值条件的Dirichlet问题.本文应用[1]的渐近展开方法和[2]中关     

极限方程为退缩椭圆型的一类三阶偏微分方程边值问题的奇摄动

本文研究极限方程在部分边界上为椭圆—抛物的一类三阶偏微分方程第一边值问题ε[(?)~3u]/[(?)y~3]-[y(?)~2u]/[(?)x~2]-[(?)~2u]/[(?)y~2]-a(x,y)[(?)u]/[(?)x]-b(x,y)[(?)u]/[(?)y]-c(x,y)u=f(x,y),u|_Γ=0,[(?)u]/[(?)y]|_(y=β)=0的奇摄动,在适当的假设下,证得解的存在并给出任意阶的一致有效的渐近展开式.     

极限方程为退缩椭圆型的一类三阶偏微分方程边值问题的奇摄动

本文研究极限方程在部分边界上为椭圆—抛物的一类三阶偏微分方程第一边值问题ε[(?)~3u]/[(?)y~3]-[y(?)~2u]/[(?)x~2]-[(?)~2u]/[(?)y~2]-a(x,y)[(?)u]/[(?)x]-b(x,y)[(?)u]/[(?)y]-c(x,y)u=f(x,y),u|_Γ=0,[(?)u]/[(?)y]|_(y=β)=0的奇摄动,在适当的假设下,证得解的存在并给出任意阶的一致有效的渐近展开式.     

奇摄动非线性边值问题

§ 1 .　Introduction　　AclassofintegraldifferentialequationsDirichletboundaryvalueproblemsforordinarydif ferentialequationandellipticequationarediscussedin [1]and [2 ]respectively .Andin [3]akindofnonlocalproblemsforsingularlyperturbedreactiondiffusionsystemsarestudied.Inthispaper,whatisworthpointingoutisaclassofnonlinearboundaryvalueproblemsdiscussed,applyingthemethodofcompositeexpandandthetheoryofdifferentialinequalities.εy″ =f(x ,y ,Tεy ,ε) y′ +g(x ,y ,Tεy,ε) ,0 相似文献   

无穷远分界线环的Melnikov判据及二次系统极限环的分布

1963年，Melnikov在[1]中考虑系统x=P_o(x,y)+εP_1(x,y,wt.ε),y=Q_o(x,y)+εQ_1(x,y,wt.ε)     

奇摄动非线性系统Robin边值问题

本文研究了非线性系统奇摄动问题：ε2y"－（x，y，y）＝0，0＜x＜1，0＜ε≤1，y（0）－py'（0）＝A，p＞0，y（1）＝B，其中y，f，A，B为n维向量．在相应的假设下，利用代数型边界层函数，证明了该问题存在一个解y（x，ε），并利用微分不等式方法得到了其解的渐近估计．     

含积分算子拟线性系统边值问题的奇摄动

研究奇摄动积分微分方程组边值问题εy"＝f(x,y,Ty,ε)y′++g(x,y,Ty,ε);y(0,ε)＝A(ε),y(1,ε)=B(ε)其中y、g、A和B均为n维向量函数,f是n×n矩阵函数,(Ty)(x)=∫xK(x,s,y(sε),ε)ds在一定假设条件下,利用对角化技巧和逐步逼近法证明解的存在,并给出解的直到0(εN+1)的渐近展开式.     

关于边界层方法

本文指出传统的边界层方法(包括匹配法和Vi?ik—Lyusternik方法)的不足:不能作出边界层项的渐近展开式.提出多重尺度构造边界层项的方法,得到符合实情的结果.又与Levinson所用的方法比较,本方法能更简单地导出后一方法给出的边界层项的渐近展开式.又应用此方法研究现有的关于奇异摄动的某些成果,指出这些成果的局限性,并在一般情况下作出解的渐近展开式.     

半线性奇摄动椭圆型方程边值问题的渐近解

本文运用了边界层函数构造了一类半线性奇摄动椭圆型方程边值问题解的渐近展开式，并证明了该展开式达到任一精度的一致有效性．     

非线性奇摄动抛物型方程初值问题的套层解

运用了初始层函数构造了一类非线性奇摄动抛物型方程初值问题解的渐近展开式,并证明了该展开式达到任意精度的一致有效性.     

An asymptotic expansion for the tail of compound sums of Burr distributed random variables

In this paper we show that it is possible to write the Laplace transform of the Burr distribution as the sum of four series. This representation is then used to provide a complete asymptotic expansion of the tail of the compound sum of Burr distributed random variables. Furthermore it is shown that if the number of summands is fixed, this asymptotic expansion is actually a series expansion if evaluated at sufficiently large arguments.     

Heat Content Asymptotics for Riemannian Manifolds with Zaremba Boundary Conditions

The existence of a full asymptotic expansion for the heat content asymptotics of an operator of Laplace type with classical Zaremba boundary conditions on a smooth manifold is established. The first three coefficients in this asymptotic expansion are determined in terms of geometric invariants; partial information is obtained about the fourth coefficient.      

Asymptotic Expansion and Estimate of the Landau Constant

Properties of Landau constant are investigated in this note. A new representation in terms of a hypergeometric function ₃F₂ is given and a property defining the family of asymptotic sequences of Landau constant is formalized. Moreover, we give an other asymptotic expansion of Landau constant by using asymptotic expansion of the ratio of gamma functions in the sense of Poincaré due to Tricomi and Erdélyi.     

Asymptotic Expansion and Estimate of the Landau Constant

Properties of Landau constant are investigated in this note. A new representation in terms of a hypergeometric function ₃F₂ is given and a property defining the family of asymptotic sequences of Landau constant is formalized. Moreover, we give an other asymptotic expansion of Landau constant by using asymptotic expansion of the ratio of gamma functions in the sense of Poincaré due to Tricomi and Erdélyi.     

Asymptotic Expansion for the Null Distribution of the <Emphasis Type="Italic">F</Emphasis>-statistic in One-way ANOVA under Non-normality

In this paper we derive the asymptotic expansion of the null distribution of the F-statistic in one-way ANOVA under non-normality. The asymptotic framework is when the number of treatments is moderate but sample size per treatment (replication size) is small. This kind of asymptotics will be relevant, for example, to agricultural screening trials where large number of cultivars are compared with few replications per cultivar. There is also a huge potential for the application of this kind of asymptotics in microarray experiments. Based on the asymptotic expansion we will devise a transformation that speeds up the convergence to the limiting distribution. The results indicate that the approximation based on limiting distribution are unsatisfactory unless number of treatments is very large. Our numerical investigations reveal that our asymptotic expansion performs better than other methods in the literature when there is skewness in the data or even when the data comes from a symmetric distribution with heavy tails.     

A systematization of the saddle point method. Application to the Airy and Hankel functions

The standard saddle point method of asymptotic expansions of integrals requires to show the existence of the steepest descent paths of the phase function and the computation of the coefficients of the expansion from a function implicitly defined by solving an inversion problem. This means that the method is not systematic because the steepest descent paths depend on the phase function on hand and there is not a general and explicit formula for the coefficients of the expansion (like in Watson's Lemma for example). We propose a more systematic variant of the method in which the computation of the steepest descent paths is trivial and almost universal: it only depends on the location and the order of the saddle points of the phase function. Moreover, this variant of the method generates an asymptotic expansion given in terms of a generalized (and universal) asymptotic sequence that avoids the computation of the standard coefficients, giving an explicit and systematic formula for the expansion that may be easily implemented on a symbolic manipulation program. As an illustrative example, the well-known asymptotic expansion of the Airy function is rederived almost trivially using this method. New asymptotic expansions of the Hankel function Hn(z) for large n and z are given as non-trivial examples.