一类非线性方程的Backlund变换以及紧孤立波解的线性稳定性

引进五阶线性色散项方程K(m,n,1),用逆算符方法得到了sin型多重compacton 解(紧孤立波解);利用齐次平衡法得到了K(2,2,1)方程的Backlund变换,并且得到一些新的孤立波解;最后研究了sin型多重compacton解的线性稳定性.     

具有高阶非线性项的广义KdV方程的孤立波及其分支

研究具有高阶非线性项的广义KdV方程ut+a(1+bun)unux+uxxx=0,这里n≥1,a,b是实数且a≠0.用动力系统的定性理论和分支方法,讨论了该方程的孤立波解的解析表达式和孤立波的分支,并给出了孤立波的分支图,解决了孤立波的存在性及其个数等问题.     

一类5阶KdV方程的孤立波解

近年来,关于3阶KdV方程的孤立波解得到迅速发展,而对于5阶KdV方程的孤立波解文献报道较少.本文主要采用Sine-Cosine展开法得到了一类5阶KdV方程的孤立波解;然后利用Matlab计算软件,获得了孤立波解的图形,其结果展示了孤立子与系数之间的相互关系;最后,应用所得的结果分别得到了Lax方程, SK方程, CDG方程的孤立波解.     

非传播孤立波及其相互作用的数值模拟

通过数值求解由Miles导出的目前公认的的非传播孤立波的控制方程——一个带复共轭项的非线性立方SchrLdinger方程,对非传播孤立波进行研究。讨论了Miles方程中的线性阻尼系数α的值,计算表明,线性阻尼α对形成稳定的非传播孤立波影响很大,Laedke等人关于非传播孤立波的稳定性条件只是一个必要条件,而不是充分条件。模拟了两个非传播孤立波的相互作用,数值模拟表明,两个波的作用模式依赖于系统的参数,对不同的初始扰动及其演化的计算表明,只有适当的初始扰动才能形成单个稳定的非传播孤立波,否则扰动可能消失或发展成多个孤立波。     

非线性波方程的精确孤立波解

立了一种求解非线性波方程精确孤立波解的双曲函数方法,并在计算机代数系统上加以实现,推导出了一大批非线性波方程的精确孤立波解.方法的基本原理是利用非线性波方程孤立波解的局部性特点,将方程的孤立波解表示为双曲函数的多项式,从而将非线性波方程的求解问题转化为非线性代数方程组的求解问题.利用吴消元法或Gröbner基方法在计算机代数系统上求解非线性代数方程组, 最终获得非线性波方程的精确孤立波解,其中有很多新的精确孤立波解.     

孤立Rossby波的fmKdV方程及其解析解（英文）

本文基于刻画非线性Rossby波浅水模式的准地转位涡方程,利用约化摄动法,推导了强迫的修正Korteweg-de Vries(fm Kd V)方程.通过分析fm Kd V方程,得到基本地形是Rossby孤立波形成的主要因素,缓变地形是外强迫因素.除此之外,推广beta效应和基本剪切流也是孤立波形成重要因素.最后,利用广义形变映射法获得fm Kd V方程的解析解,结果表明缓变地形影响孤立波的速度,而耗散影响孤立波的速度和振幅.     

Fokas方程的显示孤立尖波解和周期尖波解

利用一个独立变换和动力系统方法对Fokas方程:u_(tx)=(1+v(?)■_x~2)sin(u),x∈R,t0进行研究.在对该方程所对应的平面动力系统进行定性分析的基础上,得到了该方程所有可能的显式孤立尖波解和周期尖波解.     

George Green对早期孤立子数学理论的重要贡献

本文考察George Green 1839年关于孤立波的论文的产生背景、研究方法及影响.Green自身的科学素养、剑桥的氛围以及罗素的报告促成了他的孤立波研究,其基本思想和处理方法被19世纪一些重要的孤立波研究者不同程度继承借鉴,对孤立波理论研究产生了重要影响.     

旋转层结流体中垂直切变基本流、β效应、地形效应和强迫耗散共同作用下的Rossby波

本文运用摄动法和WKB方法(多尺度方法),从位涡守恒方程出发,分析旋转层结大气中基本流有垂直切变以及层结效应对β效应、地形效应和强迫耗散共同作用下的Rossby波的影响,得到一个非标准形式的非线性Schr?dinger方程,而在水平波数小于3时该方程有包络孤立波解;又进一步说明基本流的垂直切变对包络Rossby孤立波的波速的影响;强迫耗散对包络Rossby孤立波稳定度的影响.另外,本文还应用常数变异法求解了非齐次的Bessel方程,得到包络Rossby孤立波的经向结构.     

旋转层结流体中垂直切变基本流、$\beta$效应、地形效应和强迫耗散共同作用下的Rossby波

本文运用摄动法和WKB方法（多尺度方法）, 从位涡守恒方程出发, 分析旋转层结大气中基本流有垂直切变以及层结效应对$\beta$效应、地形效应和强迫耗散共同作用下的Rossby波的影响, 得到一个非标准形式的非线性Schr\"{o}dinger方程,而在水平波数小于3时该方程有包络孤立波解; 又进一步说明基本流的垂直切变对包络Rossby孤立波的波速的影响;强迫耗散对包络Rossby孤立波稳定度的影响.另外, 本 文还应用常数变异法求解了非齐次的Bessel方程, 得到包络Rossby孤立波的经向结构.     

Solitary wave solution for the generalized Kawahara equation

The travelling wave ansatz is used to find the solitary wave solution of the generalized Kawahara equation. The ansatz is obtained from the structure of the soliton solution of the Kawahara equation and the modified Kawahara equation. The first two integrals of motion of the generalized Kawahara equation are also computed in this work.     

Solitary waves for the perturbed nonlinear Klein–Gordon equation

In this work, we study the perturbed nonlinear Klein–Gordon equation. We shall use the sech-ansätze method to derive the solitary wave solutions of this equation.     

Klein-Gordon方程的定性分析及精确解

本文运用动力系统的定性理论,得到了Klein-Gordon方程的孤立波分支图,并求得了与定性分析结果一致的孤波解.     

Small amplitude limit of solitary waves for the Euler–Poisson system

The one-dimensional Euler–Poisson system arises in the study of phenomena of plasma such as plasma solitons, plasma sheaths, and double layers. When the system is rescaled by the Gardner–Morikawa transformation, the rescaled system is known to be formally approximated by the Korteweg–de Vries (KdV) equation. In light of this, we show existence of solitary wave solutions of the Euler–Poisson system in the stretched moving frame given by the transformation, and prove that they converge to the solitary wave solution of the associated KdV equation as the small amplitude parameter tends to zero. Our results assert that the formal expansion for the rescaled system is mathematically valid in the presence of solitary waves and justify Sagdeev's formal approximation for the solitary wave solutions of the pressureless Euler–Poisson system. Our work extends to the isothermal case.     

高维弱扰动破裂孤子波方程行波解

研究了一类高维弱扰动破裂孤子波方程.首先讨论了对应的典型破裂孤子波方程, 利用待定系数投射方法得到了孤子波精确解.再利用泛函分析和摄动理论得到了原弱扰动破裂孤子波方程的孤子行波渐近解.最后, 举出例子说明了用该方法得到的弱扰动破裂孤子波方程的行波渐近解具有简捷、有效和较高精度的优点.     

Evolution of solitary waves for a perturbed nonlinear Schrödinger equation

Soliton perturbation theory is used to determine the evolution of a solitary wave described by a perturbed nonlinear Schrödinger equation. Perturbation terms, which model wide classes of physically relevant perturbations, are considered. An analytical solution is found for the first-order correction of the evolving solitary wave. This solution for the solitary wave tail is in integral form and an explicit expression is found, for large time. Singularity theory, usually used for combustion problems, is applied to the large time expression for the solitary wave tail. Analytical results are obtained, such as the parameter regions in which qualitatively different types of solitary wave tails occur, the location of zeros and the location and amplitude of peaks, in the solitary wave tail. Two examples, the near-continuum limit of a discrete NLS equation and an explicit numerical scheme for the NLS equation, are considered in detail. For the discrete NLS equation it is found that three qualitatively different types of solitary wave tail can occur, while for the explicit finite-difference scheme, only one type of solitary wave tail occurs. An excellent comparison between the perturbation solution and numerical simulations, for the solitary wave tail, is found for both examples.     

New kinks and solitons solutions to the (2+1) -dimensional Konopelchenko–Dubrovsky equation

In this work, the (2+1)-dimensional Konopelchenko–Dubrovsky (KD) equation is studied. The tanh–sech method, the cosh–sinh method and exponential functions method are efficiently employed to handle this equation. By means of these methods, the solitary wave, periodic wave and kink solutions are formally obtained.     

Solitary wave and doubly periodic wave solutions for the Kersten–Krasil’shchik coupled KdV–mKdV system

In this work we devise an algebraic method to uniformly construct solitary wave solutions and doubly periodic wave solutions of physical interest for the Kersten–Krasil’shchik coupled KdV–mKdV system. This system as the classical part of one of superextension of the KdV equation was proposed very recently. The complete integrability, singular analysis and Lax pairs for this system have been found, but its exact solution are still unknown.     

Exact solitary wave solutions of nonlinear wave equations

The hyperbolic function method for nonlinear wave equations is presented. In support of a computer algebra system, many exact solitary wave solutions of a class of nonlinear wave equations are obtained via the method. The method is based on the fact that the solitary wave solutions are essentially of a localized nature. Writing the solitary wave solutions of a nonlinear wave equation as the polynomials of hyperbolic functions, the nonlinear wave equation can be changed into a nonlinear system of algebraic equations. The system can be solved via Wu Elimination or Gr?bner base method. The exact solitary wave solutions of the nonlinear wave equation are obtained including many new exact solitary wave solutions.     

The integral factor method for solving a class of generalized KdV equation

This paper deals with a class of generalized KdV equation by making use of a mathematical technique based on using integral factors for solving differential equations and give rise to the solitary wave, periodic cusp wave and periodic wave solutions. The work confirms the power of the proposed method.