Doubly periodic patterns of modulated hydrodynamic waves: Exact solutions of the Davey-Stewartson system

Exact doubly periodic standing wave patterns of the Davey-Stewartson (DS) equations are derived in terms of rational expressions of elliptic functions.In fluid mechanics,DS equations govern the evolution of weakly nonlinear,free surface wave packets when long wavelength modulations in two mutually perpendicular,horizontal directions are incorporated.Elliptic functions with two different moduli (periods) are necessary in the two directions.The relation between the moduli and the wave numbers constitutes the dispersion relation of such waves.In the long wave limit,localized pulses are recovered.     

数学史上一颗闪耀的流星——天才数学家阿贝尔

有这样一个人,生前饥寒交迫,逝后以其名命名的数学奖项奖金最高;生前学术著作横遭冷遇,逝后其文集被推崇备至.他就是挪威天才数学家尼尔斯.亨里克.阿贝尔(Niels Henrik Abel 1802-1829),近世代数的创始人之一.他于1802年8月5日出生于挪威的一个牧师家庭,兄弟姐妹共7人,生活十分清苦.尽管他很     

谈谈代数数论—代数数论百年历史回顾及分期初探

第一部序幕本文简单地讲讲代数数论的历史,希望简单的讲就比较容易看见全貌,这样就方便把握整个历史分期及对整个过程的分析.至于文中所讨论的是否属于"代数数论"的范围,大家都会有不同的意见.     

非线性薛定谔方程的新多级包络周期解

基于Lamé方程和新的Lamé函数,应用摄动方法和Jacobi椭圆函数展开法求解了非线性薛定谔方程,获得多种新的多级准确解。这些解对应着不同的形式的包络周期解。这些解在极限条件下可以退化为各种形式的包络孤波解。     

Lamé函数和非线性演化方程的新多级准确解

基于Lamé方程和新的Lamé函数,应用摄动方法和Jacobi椭圆函数展开法求解非线性演化方程,获得多种新的多级准确解.这些解在极限条件下可以退化为各种形武的孤波解.     

一类二阶非线性保守系统周期轨与同异宿轨的显式表示

给出了一类二阶非线性保守系统周期轨道族与同异宿轨道显式表示的初等积分方法;同时指出:根据周期轨道族外围分界线环类型的不同,周期轨道族需由不同的Jacobian椭圆函数来表示并揭示了其中的原因.利用文中方法,通过变量替换,旋转以及积分因子等手段,可推导获得某些更复杂非线性系统周期轨道族与同异宿轨道的显式式,因此所得结果对于非线性(扰动)系统分支与混沌的研究有帮助.     

周期裂纹和刚性线尖端场干涉效应研究

研究双周期裂纹和刚性线夹杂非均匀材料的反平面剪切问题。基于保角变换技术和椭圆函数理论,获得了问题应力场的全场精确解,给出了裂纹和刚性线尖端应力强度因子的封闭形式解答,讨论了裂纹和刚性线尖端场的干涉效应。数值结果表明：改变水平和垂直分布周期对裂纹和刚性线尖端场影响明显不同;裂纹长度2a逐渐增大时(0≤a/ω1≤0.5),裂纹尖端应力强度因子从1逐渐增大到无限大,而刚性线的尖端场变化不大;刚性线长度2d逐渐增大时(0≤d/ω2≤1),刚性线尖端应力强度因子逐渐减小,而裂纹的尖端场仅略微增大。     

Laser-Manipulating Macroscopic Quantum States of a Bose-Einstein Condensate Held in a Kronig-Penny Potential

We investigate the boundary vaJue problem （BVP） of a quasi-one-dimensional Gross-Pitaevskii equation with the Kronig-Penney potential （KPP） of period d, which governs a repulsive Bose-Einstein condensate. Under the zero and periodic boundary conditions, we show how to determine n exact stationary eigenstates {Rn} corresponding to different chemical potentials {μn} from the known solutions of the system. The n-th eigenstate P~ is the Jacobian elliptic function with period 2din for n = 1,2,…, and with zero points containing the potential barrier positions. So Rn is differentiable at any spatial point and R2 describes n complete wave-packets in each period of the KPP. It is revealed that one can use a laser pulse modeled by a 5 potential at site xi to manipulate the transitions from the states of {Rn} with zero Point x≠xi to the states of {Rn＇} with zero Point x= Xi. The results suggest an experimental scheme for applying BEC to test the BVP and to observe the macroscopic quantum transitions.     

New Periodic Solution to Jacobi Elliptic Functions of a （2d-1）-Dimensional BKP Equation and a Generalized Klein-Gordon Equation

With the help of the homogeneous balance method, the Jacobi elliptic expansion method and the auxiliary equation method, the first elliptic function equation is used to obtain the Jacobi doubly periodic wave solutions of the （2＋1）-dimensional B-type Kadomtsev-Petviashvili （BKP） equation and the generalized Klein-Gordon equation. The method is also valid for other （1＋1）-dimensional and higher dimensional systems.     

地球卫星轨道的椭圆函数解

分析了引力势作用下地球卫星的轨道．结果表明,在考虑地球扁平率后,地球卫星的轨道可用椭圆余弦函数表示,其平衡位置近似在一椭圆上．