关于高维非自治系统周期解的判据

本文利用拓扑度的理论，研究了ｎ阶非线性系统ｘ＝ｐ（ｔ）ｘ＋μｈ（ｔ，ｘ）得到，若系统（＊）对应的齐次方程ｘ＝ｐ（ｔ）ｘｄ无非平凡ω周期解，系统（＊）的ω周期解存在及其个数的重要判据。     

一类三阶非线性常微分方程的周期解

微分方程周期解的存在性问题,很早就受到重视。本文用拓扑度的方法研究一类三阶非线性方程周期的存在性。为方便起见,我们约定本文涉及到的函数都是连续的,对t是ω周期的;并且能保证方程     

二阶非线性常微分方程的正周期解

本文应用Ｋｒａｓｎｏｓｅｌｓｋｉｉ锥映射不动点定理，研究了二阶非线性常微分方程的ω-周期解的存在性，获得了若干正ω-周期解的存在性与多重性结果．     

Massera定理的拓广

考虑纯量周期系统x=f(t,x),其中f:R×R→R连续,f(t+ω,x)=f(t,x),ω>0.Massera曾证明,若该系统的解满足唯一性,且存在一正向有界解,则系统存在一个ω-周期解。本文证明了Massera定理中关于解的唯一性的要求可以去掉,从而改进了该定理。     

非自治时滞微分方程正周期解的存在性

应用Krasnoselskii锥映射不动点定理，研究了具一般时滞非线性非自治Logistic方程的ω-周期解的存在性，获得了存在正周期解的充分条件．     

具有限时滞的非自治三种群扩散捕食系统的周期解

主要讨论了具有限时滞的非自治三种群扩散捕食系统的周期解的存在性.方法是运用Yoshizawa型周期解定理的推广,得出该系统至少有一个ω周期解.     

一类二阶非线性非自治微分方程周期解的存在唯一性

本文证明了一类二阶非线性非自治系统x+ RF′(x) x+ 1L F (x) =e(t)在一定条件下存在唯一渐近稳定的ω周期解 ,推广了已有结果     

一类非线性非自治系统周期解的存在性

本文给出了系统ｄｘ／ｄｔ＝Ａ（ｔ）ｘ＋ｇ（ｔ，ｘ），ｇ∈Ｒ‘，ｘ∈Ｒ＾Ｎ，ω周期解存在的充分条件，推广了文「１」中的Ｋｒａｓｎｏｓｅｌｓｋｉｉ的结果。     

时滞Lotka-Volterra系统的持久性和周期解

本文研究具有时滞周期捕食系统的持久性和周期解,得到了系统永久持续生存的充要条件。在此条件下系统存在正的ω周期解,改进了一些已知结果。     

抽象半线性发展方程正周期解的存在唯一性

讨论有序Banach空间E中半线性发展方程 u′(t)+Au(t)=f(t,u(t)),t∈R, ω-周期解的存在性,其中A为E中正C0-半群的生成元,f:R×E→E连续,关于t 以ω为周期．我们对相应的线性发展方程建立了周期解的存在唯一性,并对周期解算子的谱半径作了精确估计．借助于这个估计,我们用单调迭代方法获得了半线性发展方程正ω-周期解的存在唯一性．     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

A unified approach to certain problems of best local approximation

In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms.     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Towards Excellence in Science Chinese Academy of Sciences

<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by     

Bounds for the zeros of polynomials

Let P(z)=∑↓j=0↑n ajx^j be a polynomial of degree n. In this paper we prove a more general result which interalia improves upon the bounds of a class of polynomials. We also prove a result which includes some extensions and generalizations of Enestrǒm-Kakeya theorem.     

Boundedness of commutators related to Marcinkiewicz integrals on hardy type spaces

In this paper, the authors study the boundedness of the operator [μΩ, b], the commutator generated by a function b ∈ Lipβ(Rn)(0 ＜β≤ 1) and the Marcinkiewicz integrals μΩ, on the classical Hardy spaces and the Herz-type Hardy spaces in the case Ω∈ Lipα(Sn-1)(0 ＜α≤ 1).     

Jacobi polynomials used to invert the laplace transform

Given the Laplace transform F(s) of a function f(t), we develop a new algorithm to find an approximation to f(t) by the use of the classical Jacobi polynomials. The main contribution of our work is the development of a new and very effective method to determine the coefficients in the finite series expansion that approximation f(t) in terms of Jacobi polynomials. Some numerical examples are illustrated.     

Generalization of the interaction between Haar approximation and polynomial operators to higher order methods

In applications it is useful to compute the local average empirical statistics on u. A very simple relation exists when of a function f（u） of an input u from the local averages are given by a Haar approximation. The question is to know if it holds for higher order approximation methods. To do so, it is necessary to use approximate product operators defined over linear approximation spaces. These products are characterized by a Strang and Fix like condition. An explicit construction of these product operators is exhibited for piecewise polynomial functions, using Hermite interpolation. The averaging relation which holds for the Haar approximation is then recovered when the product is defined by a two point Hermite interpolation.