Lienard方程周期解、概周期解的存在性

本文考虑Ｌｉｅｎａｒｄ方程ｘ”十ｆ（ｘ）ｘ’＋ｇ（ｘ）＝ｅ（ｔ），我们得到：当且时，对于任意周期或概周期。数ｅ（ｔ），它有周期或概周期解．而对于Ｌｉｅｎａｒｄ方程ｘ”＋ｆ（ｘ）ｘ’＋ｃｘ＝ｅ（ｔ），我们得到：当ｃ＞０且时，对于任意周期、或概周期函数ｅ（ｔ），它有周期或概周期解．     

一类二阶非线性微分方程解的全局渐近稳定性

给出了Ｌｉｅｎａｒｄ方程零解全局渐近稳定的一个充分必要条件,并进一步研究了方程ｘ＋ｆ（ｘ）ｘ＋ｇ（ｘ）＝ｅ（ｔ）解的渐近性态与方程ｘ＋ｆ（ｘ）＋ｇ（ｘ）＝ｅ（ｔ;ｘ,ｘ）零解的全局渐近稳定性。     

具有弱阻尼项的Liénard方程周期解的存在性

本文研究具有弱阻尼项的Ｌｉéｎａｒｄ方程ｘ” ＋ ｆ（ｘ）ｘ’＋ｇ（ｘ）＝ ｅ（ｔ）周期解的存在性．在两种不同的条件下证明了Ｌｉéｎａｒｄ方程至少存在一个周期解．     

具有弱阻尼项的Liénard方程周期解的存在性

本文研究具有弱阻尼项的Ｌｉéｎａｒｄ方程ｘ” ＋ ｆ（ｘ）ｘ’＋ｇ（ｘ）＝ ｅ（ｔ）周期解的存在性．在两种不同的条件下证明了Ｌｉéｎａｒｄ方程至少存在一个周期解．     

Lienard方程的比较原理

本文证明了一个比较原理，使方程ｘ″＋ｆ（ｘ）ｘ′＋ｇ（ｘ）＝０周期解存在性定理可以用判断方程ｘ″＋ｈ（ｘ，ｘ′）ｘ′＋ｇ（ｘ）＝０的周期解存在性。     

一类二阶中立型方程的周期解

利用Ｆｏｕｒｉｅｒ级数理论，研究了一类二阶中立型方程ｘ（ｔ）＋ａ１ｘ（ｔ）＋ａ２ｘ（ｔ）＋ｍ／∑ｉ＝１《ｕｉｘ（ｔ－ｈｉ）＋ｕｉｘ（ｔ－ｈｉ）＋ｗｉｘ（ｔ－ｈ）ｉ］＝ｆ（ｔ）的周期解问题，获得了保证其具有连续二阶导数的周期解存在唯一的些简便的充分条件。     

高维非自治系统的周期解

本文利用指数型二分性理论和不动点方法考虑系统Ｘ＝ｆ（ｔ,ｘ）,Ｘ＝Ａ（ｔ,ｘ）ｘ＋ｂ（ｔ,ｘ）的周期解的存在性问题,其中Ａ（ｔ,ｘ）是ｎ×ｎ连续矩阵函数,ｆ（ｔ,ｘ）,ｂ（ｔ,ｘ）是ｎ维连续向量函数,且关于ｔ以ｗ＞０为周期,所得结果推广了王联和曾唯尧的结果．     

高阶中立型非线性泛函微分方程解的渐近性

本文在∫＾∞ｔ０ｄｔｒ（ｔ）＝∞与∫＾∞ｔ０ｄｔｒ（ｔ）〈∞这两种情况下讨论了下面高阶中立型非线性方程「ｒ（ｔ）（ｘ（ｔ）－ｃｘ（ｔ－τ））′」＾（ｎ－１）＋ｆ（ｔ，ｘ（ｇ１（ｔ）），…，ｘ（ｇｍ（ｔ）））＝０（ｔ≥ｔ０）非振动解的分类，并且给出了各类非振动解存在的条件。     

一类高维时滞微分方程的周期解

本文考虑高维时滞微分方程ｘ′（ｔ）＝Ａ（ｔ,ｘ（ｔ））ｘ（ｔ）＋ｆ（ｔ,ｘ（ｔ－ｒ（ｔ）））其中（ｔ,ｘ）∈Ｒ^ｎ,Ａ（ｔ,ｘ）是ｎ×ｎ连续矩阵,ｆ（ｔ,ｘ）是ｎ维连续向量,ｒ（ｔ）是时间依赖的滞量,应用不动点定理,在确定的条件下,证明了该系统的周期解的存在性与唯一性     

广型Lienard方程概周期解的存在性

广型Ｌｉｅｎａｒｄ方程概周期解的存在性冯春华（广西师大数学系桂林５４１００４）关键词：Ｌｅｒａｙ－Ｓｃｈａｕｄｅｒ不动点定理；Ｌｉ　ｎａｒｄ方程；概周期解ＡＭＳ（１９９１）主题分类：３４Ｃ２７本文研究微分方程ｘ＋ｆ（ｘ）ｋ（ｘ）ｘ十ｇ（ｘ）ｈ（ｘ）一...     

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.     

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     

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.     

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.     

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.