Euler-Bernoulli梁的高阶二次摄动解及收敛性讨论

首次用解析的方式给出了Euler-Bernoulli梁后屈曲与非线性弯曲问题的高阶二次摄动解答.假定梁的中线不可伸长，用精确曲率公式与能量变分原理导出了非线性Euler-Bernoulli梁的模型.通过与精确解或高阶摄动解的比较，讨论了二次摄动解答的收敛性及适用域.得到主要结论如下:低阶摄动解适用于描述梁的初始后屈曲阶段及初始非线性弯曲阶段；更高阶次的摄动解适用于描述梁的深度后屈曲以及深度非线性弯曲.从这个意义上去说，该文不仅仅指出某些文献上的部分结果不精确是由于摄动解答超出了其特定的适用域，并且还进一步发展与完善了二次摄动法.     

指数型二分性与拟自治奇异摄动系统

通过对Ｋ．Ｊ．Ｐａｌｍｅｒ￣［４］中方法的改进，本文讨论了摄动系统有界解的存在性，得到了不同于［４］中的结果，并把改进了的方法运用到拟自治奇异摄动系统，得到了拟自治奇异摄动系统存在有界解的一个简洁的充分条件。本文的方法还提供了一个处理摄动项含小参数的方法。     

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.     

一类非线性奇摄动方程的激波问题

利用奇摄动理论和匹配原理，讨论了一类非线性奇摄动方程的激波问题．首先，构造了原问题的外部解和内层解．其次，研究了当激波在区间的边界附近和内部的激波解．最后，得出了与边界条件相对应的激波位置及解的表达式．     

一类非线性快慢系统非局部问题的摄动解

主要讨论了一类非线性快慢系统非局部问题的摄动解,在适当的条件下,根据不同边界层利用伸长变量和幂级数展开理论,构造了问题的形式渐近解,并利用微分不等式理论在整个区间上证明了形式渐近解的一致有效性,把奇摄动问题的摄动解推广到快慢系统非局部问题的摄动解.     

Volteera型积分微分方程组边值问题的奇摄动

该文研究二阶积分微分方程组边值问题奇摄动，在适当的条件下，利用渐近分析方法和对角化技巧，还得解的存在性和给出解的渐近展开式与相应的余项估计．然后，应用这些结果到三阶常微分方程组边值问题的奇摄动，最后也得到解的一致有效的渐近展开式．     

一个非线性波动方程的计算机代数－摄动解

本文采用计算机代数－摄动法讨论一个非线性波动方程的Ｃａｙｃｈｙ问题高阶渐近解，将特征坐标变形与重整化方法相结合，消除直接展开解的长期项，并利用计算机代数软件进行符号运算，得到该问题的四项摄动解，所得的渐近解与数值解的比较表明：对较小的ε，两者相吻合；对较大的ε（如ε＝０．２５），两者也相当符合。     

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。     

板和扁壳大挠度问题摄动参数的最小二乘法选择

本文提出了在用摄动法求解板和扁壳轴对称大挠度问题时,确定摄动参数的最小二乘方法.计算了圆板情形的算例,与准确解和其它摄动解做了比较.结果表明,本文解答较其它摄动解有更高的精确度.     

一类具有边界摄动的非线性泛函椭圆型方程奇摄动问题

研究了具有边界摄动的非线性泛函椭圆型方程奇摄动边值问题．在适当的条件下．利用伸长变量、微分不等式理论，讨论了问题解的渐近性态和原问题解的存在唯一性。     

Higher type categories

Higher types can readily be added to set theory, Bernays-Morse set theory being an example. A type for each ordinal is added in [2]. Adding higher types to set theory provides a neat solution to the problem of how to handle higher type categories. We give the basic definitions, and prove cocompleteness of some higher type categories. MSC: 14A15.     

Cluster tilting for higher Auslander algebras

The concept of cluster tilting gives a higher analogue of classical Auslander correspondence between representation-finite algebras and Auslander algebras. The n-Auslander–Reiten translation functor τn plays an important role in the study of n-cluster tilting subcategories. We study the category Mn of preinjective-like modules obtained by applying τn to injective modules repeatedly. We call a finite-dimensional algebra Λ n-complete if for an n-cluster tilting object M. Our main result asserts that the endomorphism algebra EndΛ(M) is (n+1)-complete. This gives an inductive construction of n-complete algebras. For example, any representation-finite hereditary algebra Λ(1) is 1-complete. Hence the Auslander algebra Λ(2) of Λ(1) is 2-complete. Moreover, for any n?1, we have an n-complete algebra Λ(n) which has an n-cluster tilting object M(n) such that Λ(n+1)=EndΛ(n)(M(n)). We give the presentation of Λ(n) by a quiver with relations. We apply our results to construct n-cluster tilting subcategories of derived categories of n-complete algebras.     

On higher indicators of regular association schemes

In the present paper, we will define the higher Frobenius–Schur indicators and the higher indicators of association schemes as a generalization of those of finite groups. The higher indicators of any association scheme are always positive rational numbers. Especially, for any positive integer $n$, the $n$th indicator of any regular association scheme is the number of relations such that its strong girth divides $n$. Thus, all higher indicators of any regular association scheme are natural numbers, and the sequence of the indicators is periodic. We will show that the converses of these facts are also true for finite exponent association schemes. Finally, we introduce a family of infinite exponent association schemes all higher indicators of which are natural numbers and the sequence of the indicators of which is periodic.     

High Spin Particles with Spin-Mass Coupling

The classical and quantum model of high spin particles is analyzed within the manifestly covariant framework. The model is obtained by supplementing the standard Lagrange function for relativistic point particle by additional terms governing the dynamics of internal degrees of freedom. They are described by (3, 1) Clifford algebra (Majorana) spinors. The covariant quantization leads to the spectrum of the particles with the masses depending on their spins. The particles (and anti-particles) appear to be orphaned as their potential anti-particle partners are of different mass.     

Evaluating higher derivative tensors by forward propagation of univariate Taylor series

This article considers the problem of evaluating all pure and mixed partial derivatives of some vector function defined by an evaluation procedure. The natural approach to evaluating derivative tensors might appear to be their recursive calculation in the usual forward mode of computational differentiation. However, with the approach presented in this article, much simpler data access patterns and similar or lower computational counts can be achieved through propagating a family of univariate Taylor series of a suitable degree. It is applicable for arbitrary orders of derivatives. Also it is possible to calculate derivatives only in some directions instead of the full derivative tensor. Explicit formulas for all tensor entries as well as estimates for the corresponding computational complexities are given.

     

On eigenvalue problems of real symmetric tensors

We use variational methods to give a positive answer to a conjecture posed by Liqun Qi [L. Qi, Eigenvalues of a real supersymmetric tensor, J. Symbolic Comput. 40 (2005) 1302-1324] regarding the real eigenvalues of certain higher order tensors.     

Uniqueness properties of higher order dispersive equations

In this paper we study unique continuation properties of solutions to higher (fifth) order nonlinear dispersive models. The aim is to show that if the difference of two solutions of the equations, u₁−u₂, decays sufficiently fast at infinity at two different times, then u₁≡u₂.     

做好高等数学的入门教学不让学生输在起跑线上

分析了在入门阶段影响大学生学好高等数学的诸多因素,提出了如何让学生顺利过渡到大学,早日适应高等数学学习。