Melnikov函数和Poincaré映射

本文中我们给出了Melnikov函数和Poincaré映射的关系,从而给出了Melnikov方法的新的证明.本文的优点是给出了更明确的解,并把次谐分支的Melnikov函数与稳定流形与不稳定流形横截相交的Melnikov函数统一成为一个公式.     

Bouncing Ball模型的弱混沌性

用异于传统的方法，作出Bouncing Ball映射不变流形的对称流形，从而成功地将稳定流形与不稳定流形的位置进行比较。应用[1]关于弱横截与弱混沌的有关概念及定理，给出了Borncing Ball映射产生弱混沌的较为一般的参数区域，进一步提示了Bouncing Ball映射的动力学行为。     

一类带有慢变参数的sine-Gordon方程的单脉冲异宿轨道

基于Fenichel的几何奇异摄动理论,结合Melnikov方法,该文研究一类带慢变参数的sine-Gordon方程单脉冲波前解的存在性.首先,基于几何奇异摄动理论进行快慢分离,获得层系统和退化系统及其动力学;接着,引入Melnikov函数度量慢流形的稳定和不稳定流形的横截相交性,获得Take-off和Touch-down曲线的解析式.控制Take-off和Touch-down曲线使之分别与两个慢流形上鞍点的不稳定和稳定流形横截相交,从而得到奇异异宿轨道的存在性.经摄动,在该奇异异宿轨附近可获得异宿于系统两个不同鞍点的异宿轨道的存在性,从而上述带慢变参数的sine-Gordon方程的单脉冲波前解的存在性可得.最后,考虑了一个具体的例子,验证理论结果的正确性.     

具有暂时免疫传染病模型同宿分支

讨论了具有暂时免疫传染病模型同宿轨道分支的存在性,利用Melnikov函数确定了系统双曲不动点的稳定和不稳定流形的相对位置,从而给出存在极限环的参数范围.     

超临界情形的Melnikov函数及应用

该文具体推导了三阶Melnikov函数的积分表达，解决了电机工程中提出的一类系统（见[5]），当参数时的超临界（一阶、二阶Melnikov函数恒为零）的情形下，系统的稳定流形与不稳定流形的相对位置的确定问题．并通过环面上的VanderPol方程，对[2]与[4]所给的二阶Melnikov函数的表达式进行了比较，结果发现[2]所给的平面自治系统的二阶，n阶表达式均是错的.该文在最后作了纠正.     

同宿流形中的奇异轨道

研究较一般的高维退化系统的同宿、异宿轨道分支问题．利用推广的Melnikov函数、横截性理论及奇摄动理论，对具有鞍—中心型奇点的带有角变量的奇摄动系统，在角变量频率产生共振的情况下，讨论其同宿、异缩轨道的扰动下保存和横截的条件．推广和改进了一些文献的结果。     

1:1内共振条件下矩形薄板的全局分叉和多脉冲混沌动力学

首次利用广义Melnikov方法研究了一个四边简支矩形薄板的全局分叉和多脉冲混沌动力学.矩形薄板受面外的横向激励和面内的参数激励.利用von Krmn模型和Galerkin方法得到一个二自由度非线性非自治系统用来描述矩形薄板的横向振动.在1∶1内共振条件下,利用多尺度方法得到一个四维的平均方程.通过坐标变换把平均方程化为标准形式,利用广义Melnikov方法研究该系统的多脉冲混沌动力学,并且解释了矩形薄板模态间的相互作用机理.在不求同宿轨道解析表达式的前提下,提供了一个计算Melnikov函数的方法.进一步得到了系统的阻尼、激励幅值和调谐参数在满足一定的限制条件下,矩形薄板系统会存在多脉冲混沌运动.数值模拟验证了该矩形薄板的确存在小振幅的多脉冲混沌响应.     

托卡马克中低模态到高模态转迁模型的混沌运动

利用Melnikov方法详细研究了在托卡马克(Tokamaks)中,等离子区边缘附近低模态到高模态转迁方程的混沌动力学.该转迁方程是一个含外激励和参数激励的系统.对含周期外激励和线性参数激励、三次参数激励的系统分别绘出了用来划分混沌区和非混沌区的临界曲线.得到的结果表明,含有线性或三次参数激励的系统存在不可控区域,在该区域中异宿轨分岔总是导致混沌发生.特别地,三次参数激励系统存在一个"可控频率",施以该频率的激励,不论激励的振幅多大,同宿轨分岔总是不会导致混沌发生.得到了这类系统的一些复杂的动力学行为.     

指数二分性与奇异摄动系统的横戳异宿轨道

本文研究奇异摄动系统的横截异宿轨道的存在性,利用指数二分性理论和Liapunov－Schmidt方法,获得了判断奇异摄动系统存在横截异宿轨道的Melnikov型函数,因而推广了一些文献的结果．     

周期时间制约的非Hamliton可积Kolmogorov系统的混沌与次谐波

本文研究一类非Hamilton可积的Kolmogorov生态系统的周期激励模型，应用Melnikov方法，得到了该系统存在混沌与次谐分枝的某些充分条件。     

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.     

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     

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     

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).     

Instructions for Authors

<正>Submission Authors must use LaTeX for typewriting,and visit our website www.actamath.com to submit your paper.Our address is Editorial Office of Acta Mathematica Sinica,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100190,P.R.China.     

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

正August 10-14,2015Beijin,China The 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