一类四阶非线性奇摄动问题的匹配解法

利用匹配条件,讨论了一类四阶非线性奇摄动问题,得出了奇摄动边值问题的渐近展开式.     

非线性超抛物型方程广义渐近解的研究

讨论了一类超抛物型方程的非线性奇摄动问题.首先引入了相应问题的比较定理,然后利用奇摄动方法构造了问题的形式渐近解,最后利用比较定理,证明了问题广义解的存在性及其渐近性态.     

一类含有小迟滞的奇摄动方程组的渐近解

本文研究了一类含有小迟滞的奇摄动方程组的渐近解.利用原问题的退化形式和伸长变量,依据边界层特有的性质,获得了边界层的渐近解.推广了奇摄动方程组初值问题和小迟滞问题的研究结果.     

一类奇摄动边值问题解的套层现象

本文揭示了一类三阶半线性方程奇摄动边值问题解的“套层”现象。利用两次伸长变量的迭代，构造了解的形式渐近展开式。再用微分不等式理论，证明了该奇摄动问题渐近解的一致有效性。     

二阶非线性奇摄动微分方程的渐近解

研究了二阶非线性奇摄动微分方程的边值问题.利用匹配原则和微分不等式原理,得到一阶非线性问题的渐近解,进而得到二阶奇摄动问题的解的渐近估计.     

非Fourier温度场分布的奇摄动解

应用非Fourier热传导定律构建了单层材料中温度场模型，即一类在无界域上带小参数的奇摄动双曲方程，通过奇摄动展开方法，得到了该问题的渐近解.首先应用奇摄动方法得到了该问题的外解和边界层矫正项，通过对内解和外解的最大模估计和关于时间导数的最大模估计以及线性抛物方程理论，得到了内外解的存在唯一性，从而得到了解的形式渐近展开式.通过余项估计，给出了渐近解的L2估计，得到了渐近解的一致有效性，从而得到了无界域上温度场的分布.通过奇摄动分析，给出了非Fourier 温度场与Fourier 温度场的关系，描述了非Fourier温度场的具体形态.     

一类奇摄动半线性时滞抛物型偏微分方程的渐近解

文中讨论了一类奇摄动时滞抛物型偏微分方程的初边值问题,得到了其形式渐近展开,证明了奇摄动半线性时滞偏微分方程的极大值原理,从而得到了最大值估计及相应的Schuader估计.在此基础上,得到了柱状区域上解的存在唯一性和渐近解的一致有效性.     

一类热传导系数跳跃的非Fourier温度场分布的奇摄动双参数解

应用非Fourier热传导定律构建了温度场模型,即一类在有界域上带小参数的奇摄动双曲方程,由于温度急剧变化热传导系数出现跳跃的情况,得到了非线性的具有间断系数的奇摄动双参数双曲方程.通过奇摄动双参数展开方法,得到了该问题的渐近解;其次对热传导系数跳跃位置进行了定性分析,得到了确定热传导系数跳跃位置的计算公式,从而确定了解的形式渐近展开式;再通过余项估计,得到了渐近解的一致有效性,从而得到了完整温度场的分布.     

一类非线性微分-积分时滞反应扩散系统奇摄动问题的广义解

该文研究了一类非线性微分-积分时滞广义反应扩散系统奇摄动问题.在适当的条件下,利用奇摄动方法构造了初始-边值问题广义解的渐近展开式.建立了广义解的微分不等式理论,并证明了相应解的存在性及其解的渐近展开式的一致有效性.     

具有边界摄动的非线性奇摄动椭圆型问题(英文)

研究了一类具有边界摄动的非线性奇摄动椭圆型问题.并证明了边值问题解的渐近展开的一致有效性.     

Asymptotic stability analysis of autonomous systems by applying the method of localization of compact invariant sets

The asymptotic stability and global asymptotic stability of equilibria in autonomous systems of differential equations are analyzed. Conditions for asymptotic stability and global asymptotic stability in terms of compact invariant sets and positively invariant sets are proved. The functional method of localization of compact invariant sets is proposed for verifying the fulfillment of these conditions. Illustrative examples are given.     

On asymptotic expansions in nonlinear,singularly perturbed difference equations ∗

The present paper deals with the problem of constructing and proving asymptotic expansions for nonlinear, singularly perturbed difference equations. New methods for the construction of asymptotic expansions are presented and compared with well-known ones. For the proof of their validity, fundamental principles for the treatment of nonlinear singular perturbation problems are applied, based on the concepts of e-stability, formal asymptotic expansions, matching and asymptotic expansions. The results are derived from a general theory of asymptotic expansions of nonlinear operator equations that has been developed recently by the author.     

Asymptotic equivalence of probability distributions with applications to some problems of asymptotic independence

Summary The problem of asymptotic approximation is formulated in a generalized form, and the basic concepts of asymptotic equivalence of probability distributions, which are fundamental to the study of asymptotic approximation problems, are established precisely. For the purpose of practical applications, some useful criterions for the asymptotic equivalence are given.     

关于渐近循环马氏链泛函的强大数定律

研究了一类非齐次马氏链———渐近循环马氏链泛函的强大数定律,首先引出了渐近循环马氏链的概念,然后给出了若干引理.利用了渐近循环马氏链关于状态序偶出现频率的强大数定理给出并证明了关于渐近循环马氏链泛函的强大数定律,所得定理作为推论可得到已有的结果.     

Strong laws of large numbers for asymptotic even–odd Markov chains indexed by a homogeneous tree

In this paper, we are going to study the strong laws of large numbers for asymptotic even–odd Markov chains indexed by a homogeneous tree. First, the definition of the asymptotic even–odd Markov chain is introduced. Then the strong limit theorem for asymptotic even–odd Markov chains indexed by a homogeneous tree is established. Next, the strong laws of large numbers for the frequencies of occurrence of states and ordered couple of states for asymptotic even–odd Markov chains indexed by a homogeneous tree are obtained. Finally, we prove the asymptotic equipartition property (AEP) for these Markov chains.     

Asymptotic properties of the Bayes modal estimators of item parameters in item response theory

Asymptotic cumulants of the Bayes modal estimators of item parameters using marginal likelihood in item response theory are derived up to the fourth order with added higher-order asymptotic variances under possible model misspecification. Among them, only the first asymptotic cumulant and the higher-order asymptotic variance for an estimator are different from those by maximum likelihood. Corresponding results for studentized Bayes estimators and asymptotically bias-corrected ones are also obtained. It was found that all the asymptotic cumulants of the bias-corrected Bayes estimator up to the fourth order and the higher-order asymptotic variance are identical to those by maximum likelihood with bias correction. Numerical illustrations are given with simulations in the case when the 2-parameter logistic model holds. In the numerical illustrations, the maximum likelihood and Bayes estimators are used, where the same independent log-normal priors are employed for discriminant parameters and the hierarchical model is adopted for the prior of difficulty parameters.     

Boundary-value problems of the asymmetric theory of elasticity for thin plates

Boundary-value problems of the three-dimensional asymmetric micropolar, moment theory of elasticity with free rotation are considered for thin plates. It is assumed that the total stress-strain state is the sum of the internal stress-strain state and the boundary layers, which are determined in an approximation using asymptotic analysis. Three different asymptotic forms are constructed for the three-dimensional boundary-value problem posed, depending on the values of dimensionless physical constants of the plate material. The initial approximation for the first asymptotic form leads to a theory of micropolar plates with free rotation, the initial approximation for the second asymptotic form leads to a theory of micropolar plates with constrained rotation, and the initial approximation for the third asymptotic form leads to a theory of micropolar plates with “small shear stiffness.” The corresponding micropolar boundary layers are constructed and studied. The regions of applicability of each of the theories of micropolar plates constructed are indicated.     

渐近正态随机变量函数的极限分布

基于渐近正态随机变量,导出随机变量函数极限分布的两个一般性理论结果.作为应用,证明了渐近正态随机变量一系列具体函数的极限分布,其中包括泊松随机变量平方根的渐近正态性,以及随机变量部分和在正则化常数是随机变量情况下的渐近正态性.     

Parabolic cylinder functions of large order

The asymptotic behaviour of parabolic cylinder functions of large real order is considered. Various expansions in terms of elementary functions are derived. They hold uniformly for the variable in appropriate parts of the complex plane. Some of the expansions are doubly asymptotic with respect to the order and the complex variable which is an advantage for computational purposes. Error bounds are determined for the truncated versions of the asymptotic series.     

一类小周期椭圆方程的三重尺度渐近分析

利用三重尺度方法对一类小周期椭圆方程进行了三重尺度渐近展开分析,构造了对应的三重尺度形式渐近展开式,得到了均匀化常数和均匀化方程.在形式渐近展开的基础上,构造了对应边值问题解的三重尺度渐近近似解,并分析了对应三重尺度形式渐近误差估计.