变系数Sine-Gordon方程的Bcklund变换和新的精确解

利用推广后的反演散射法获得变系数Sine-Gordon方程新的B(a|¨)cklund变换.同时,结合齐次平衡法原理并利用G'/G方法,讨论了变系数Sine-Gordon方程的精确解,从而得到了变系数Sine-Gordon方程的用双曲函数和三角函数表示的精确解.     

(2+1)-维变系数CDGKS方程的Bcklund变换及Gramm-type Pfaffian解

孤立子在非线性的流体力学、等离子物理学、光学、生物学等领域有广泛的应用.将(2+1)维常系数CDGKS方程扩展为(2+1)维变系数CDGKS方程,利用双线性方法求出了该方程的Bcklund变换,进一步求出变系数CDGKS方程及其修正变系数CDGKS方程的Gramm-type Pfaffian解,从而解决了变系数孤立子方程的精确解.     

一变系数非线性发展方程组的自-BT及其精确解

利用齐次平衡原则,导出了一变系数非线性发展方程组的自-Baecklund变换(自-BT);借助此自-BT和变系数热传导方程的各种精确解用代数的方法获得了方程组的各种精确解。     

一类广义变系数mKdV方程的Bcklund变换,Painlev检验及精确解（英文）

本文研究一类广义变系数mKdV方程,基于齐次平衡法,对方程进行Bcklund变换,进而得到方程的精确解;对方程进行Painlev检验,证明方程的可积性.利用推广的CK方法,将广义变系数mKdV方程化为常系数方程,结合幂级数法得到方程的幂级数解.     

一类变系数Boussinesq型方程的精确解

一类变系数Boussinesq型方程与变系数Broer-Kaup-Kupershmidt方程之间在某种约束下的关系.通过构造变系数Broer-Kaup-Kupershmidt方程的达布变换并应用达布变换得到这类变系数Boussinesq型方程的精确解.     

变耗散系数的柱Burgers方程和球Burgers方程的精确解

根据简化齐次平衡原则,导出一个由线性方程的解到一个具变耗散系数的柱Burgers方程解的非线性变换.该线性方程容许有指数函数形式的解,因而借助所导出的非线性变换,获得一个具变耗散系数的柱Burgers方程的精确解.完全类似地,也获得一个具变耗散系数的球Burgers方程的精确解.     

一类广义变系数mKdV方程的B\"{a}cklund变换, Painlev\'{e}检验及精确解[英文]

本文研究一类广义变系数mKdV方程, 基于齐次平衡法, 对方程进行B\"{a}cklund变换, 进而得到方程的精确解; 对方程进行Painlev\''{e}检验, 证明方程的可积性. 利用推广的CK方法, 将广义变系数mKdV方程化为常系数方程, 结合幂级数法得到方程的幂级数解.     

Wick类型的随机广义KdV的精确解

利用埃尔米特变换求出了W ick-类型的随机广义K dV方程的精确解.这种方法的基本思想是通过埃尔米特变换把W ick类型的随机广义K dV方程变成广义变系数K dV方程,利用齐次平衡法求出方程的精确解,然后通过埃尔米特的逆变换求出方程的随机解.     

带强迫项变系数组合KdV方程的有理展开式精确解

利用符号计算软件Maple,在一个新的广义的Riccati方程有理展开法的帮助下,求出了带强迫项变系数组合KdV方程的有理展开式的精确解,该方法还可被应用到其他变系数非线性发展方程中去.     

Sharma-Tasso-Olver方程的新显式行波解

借鉴(G’/G)展开法的基本思路,构造了一类变系数G展开法,并借助Mathematica计算软件,对Sharma-Tasso-Olver方程进行了求解,获得了该方程新的显式行波解.事实证明,此类变系数G展开法对于求解非线性微分方程的精确解是行之有效的.     

Comparison of approximate symmetry and approximate homotopy symmetry to the Cahn–Hilliard equation

Complete infinite order approximate symmetry and approximate homotopy symmetry classifications of the Cahn–Hilliard equation are performed and the reductions are constructed by an optimal system of one-dimensional subalgebras. Zero order similarity reduced equations are nonlinear ordinary differential equations while higher order similarity solutions can be obtained by solving linear variable coefficient ordinary differential equations. The relationship between two methods for different order are studied and the results show that the approximate homotopy symmetry method is more effective to control the convergence of series solutions than the approximate symmetry one.     

Numerical solutions of boundary value problems for variable coefficient generalized KdV equations using Lie symmetries

The exhaustive group classification of a class of variable coefficient generalized KdV equations is presented, which completes and enhances results existing in the literature. Lie symmetries are used for solving an initial and boundary value problem for certain subclasses of the above class. Namely, the found Lie symmetries are applied in order to reduce the initial and boundary value problem for the generalized KdV equations (which are PDEs) to an initial value problem for nonlinear third-order ODEs. The latter problem is solved numerically using the finite difference method. Numerical solutions are computed and the vast parameter space is studied.     

具任意次非线性项的Camassa-Holm方程的双孤子新解

给出辅助方程、函数变换与变量分离解相结合的方法,构造了具任意次非线性项的Camassa-Holm方程的双孤子和双周期新解.首先,通过两个辅助方程、函数变换与变量分离解,将具任意次非线性项的Camassa-Holm方程的求解问题转化为非线性代数方程的求解问题.然后,借助符号计算系统Mathematica求出该方程组的解,并用辅助方程的相关结论,构造了双周期解和双孤子新解.     

Exact solutions of the combined KdV-Burgers equation with variable coefficients

In this Letter, the exp-function method is used to obtain generalized solitary solutions and periodic solutions of the general types of combined KdV-Burgers equation with variable coefficients. It is shown that the exp-function method via symbolic computation provides a straightforward and powerful mathematical tool for solving nonlinear evolution equations with variable coefficients in mathematical physics.     

解非线性方程的自动调节阻尼法

解非线性方程组的一般方法是将其线性化,形成各种形式的迭代程序进行数值近似计算.对于复杂强非线性问题,在迭代过程中往往不易收敛,甚至数值失稳而发散.不能满足工程要求.常规的牛顿法及改进的牛顿法均未彻底解决这一问题,因而使得复杂强非线性问题的数值模拟计算受到了限制.本文提出一种新的方法---自动调节阻尼法,是对带阻尼因子的牛顿法的进一步改进.引进阻尼因子向量,在迭代过程中,通过判断与调整,不断地自动调节阻尼因子向量,引用有效收敛系数与加速系数,改善对赋初值的要求,加速求解的迭代过程,保证了复杂强非线性方程求解的稳定性.采用这一新的方法,已成功地数值模拟了飞机中的一些复杂的传热问题,可进一步推广用于非线性流动、传热、结构动力响应等各种复杂强非线性的工程问题的数值模拟计算.     

An Iterative Algorithm for the Coefficient Inverse Problem of Differential Equations

In this paper, an iterative algorithm for solving a coefficient inverse problem is submitted. The key of the method is to project an unknown coefficient function on a finite dimensional function space. Thus, the inverse problem can be changed into a nonlinear algebraic system of equations.     

Auxiliary equation method for solving nonlinear Wick-type partial differential equations

Using the solutions of an auxiliary differential equation, a direct algebraic method is described to construct several kinds of exact travelling wave solutions for some Wick-type nonlinear partial differential equations. By this method some physically important nonlinear equations are investigated and new exact travelling wave solutions are explicitly obtained. In addition, the links between Wick-type partial differential equations and variable coefficient partial differential equations are also clarified generally.     

Variational iteration method for solving three‐dimensional Navier–Stokes equations of flow between two stretchable disks

The similarity transform for the steady three‐dimensional Navier–Stokes equations of flow between two stretchable disks gives a system of nonlinear ordinary differential equations. In this article, the variational iteration method was used for solving these equations. The results have been compared with the numerical results. This article depicts that the VIM is an efficient and powerful method for solving nonlinear differential equations. This method is applicable to strongly and weakly nonlinear problems. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011     

MN-DPMHSS iteration method for systems of nonlinear equations with block two-by-two complex Jacobian matrices

Preconditioned modified Hermitian and skew-Hermitian splitting (PMHSS) method is an unconditionally convergent iteration method for solving large sparse complex symmetric systems of linear equation. Motivated by the PMHSS method, we develop a new method of solving a class of linear equations with block two-by-two complex coefficient matrix by introducing two coefficients, noted as DPMHSS. By making use of the DPMHH iteration as the inner solver to approximately solve the Newton equations, we establish modified Newton-DPMHSS (MN-DPMHSS) method for solving large systems of nonlinear equations. We analyze the local convergence properties under the Hölder continuous conditions, which is weaker than Lipschitz assumptions. Numerical results are given to confirm the effectiveness of our method.     

Exact Traveling Wave Solutions for Higher Order Nonlinear Schrödinger Equations in Optics by Using the (G'/G, 1/G)-expansion Method

The propagation of the optical solitons is usually governed by the nonlinear Schrödinger equations. In this article, the two variable (G'/G, 1/G)-expansion method is employed to construct exact traveling wave solutions with parameters of two higher order nonlinear Schrödinger equations describing the propagation of femtosecond pulses in nonlinear optical fibers. When the parameters are replaced by special values, the well-known solitary wave solutions of these equations rediscovered from the traveling waves. Thismethod can be thought of as the generalization of well-known original (G'/G)-expansion method proposed by M. Wang et al. It is shown that the two variable (G'/G, 1/G)-expansion method provides a more powerful mathematical tool for solving many other nonlinear PDEs in mathematical physics.