反应扩散方程的紧交替方向差分格式

本文研究二维常系数反应扩散方程的紧交替方向隐式差分格式．首先综合应用降阶法和降维法导出了紧差分格式,并给出了差分格式截断误差的表达式．其次引进过渡层变量,给出了紧交替方向隐式差分格式算法．接着用能量分析方法给出了紧交替方向隐式差分格式的解在离散H^1范数下的先验估计式,证明了差分格式的可解性、稳定性和收敛性,在离散H^1范数下收敛阶为O(r^2 H^4)．然后将Rechardson外推法应用于紧交替方向隐式差分格式,外推一次得到具有O(r^4 H^6)阶精度的近似解．最后给出了数值例子,数值结果和理论结果是吻合的．     

二维变系数反应扩散方程的紧交替方向差分格式

1 引言 在研究热传导过程、气体扩散现象和电磁场的传播等问题时,常常遇到抛物型偏微分方程。用有限差分方法研究这类问题的数值解法目前已经有了许多工作。对于二维、三维抛物方程的数值求解比较理想的方法是交替方向法。     

二维半线性反应扩散方程的交替方向隐格式

本文研究一类二维半线性反应扩散方程的差分方法.构造了一个二层线性化交替方向隐格式.利用离散能量估计方法证明了差分格式解的存在唯一性、差分格式在离散H~1模下的二阶收敛性和稳定性.最后给出两个数值例子验证了理论分析结果.     

带非局部边界条件的非线性抛物方程的隐式差分解法

在准静态弹性力学中常遇到求解带有非局部边界条件的抛物方程初边值问题.本文构造了一个数值求解带有非局部边界条件的非线性抛物方程的隐式差分格式,利用离散泛函分析的知识和不动点定理证明了差分解是存在的,且在离散最大模意义下关于时间步长一阶收敛,关于空间步长二阶收敛,并给出了数值算例.     

MONOTONE ITERATIVE TECHNIQUE FOR NONLINEAR NEUTRAL DELAY DIFFERENTIAL EQUATIONS

1Introductiondescently,themonotoneiteratiyetechniqueissuccessfultoprovetheexistenceofextremalsolutionsofvariousnonlinearproblemforordinarydifferentialequations,delaydifferentialequations,integro-differentialequationsetc.,see[1--101.Inthispapertweshallconsidertheexistenceofextremalsolutionsoftheinitialvalueproblem(IVPforshort)fornonlinearneutraldelaydifferentialequationswherefEC[IOxRxRxR,R],CO=C[[--a,0],R],IO=[to,to T],to20,T>0,a<0,T<0,--a=adn{a,T},I=f--a,0]andforanyteIO,u(t s)ECO,sE…     

LIMITED MEMORY BFGS METHOD FOR NONLINEAR MONOTONE EQUATIONS

In this paper, we propose an algorithm for solving nonlinear monotone equations by combining the limited memory BFGS method （L-BFGS） with a projection method. We show that the method is globally convergent if the equation involves a Lipschitz continuous monotone function. We also present some preliminary numerical results.     

一类多维非线性反应扩散方程有限差分格式的稳定性问题(英文)

本文研究了一类多维线性反应扩散方程差分格式的稳定性.利用量未知元方法,建立了具有增量未知元的有限差分格式;然后利用非线性Galerkin方法,得到该差分格式的稳定性条件.通过对该格式的稳定性分析,说明和经典的差分格式的稳定性相比较,带有增量未知元的有限差分格式的稳定性得到了提高.     

A LEAP FROG FINITE DIFFERENCE SCHEME FOR A CLASS OF NONLINEAR SCHRODINGER EQUATIONS OF HIGHORDER

1.IntroductionItiswellknowthatthenonlinearequationsofSchr6dingertypeareofgreatimportancetophysicsandcanbeusedtodescribeextensivephysicalphenomenatll.InthispapergwewillconsidertheperiodicinitialvalueproblemforthefollowingclassofnonlinearSchrodingerequationofhighorder:wherem',MandMIareallpositiveconstant.Inthepaper[2])therehavediscussedinitialValueproblemofsystemsuchas(1.1)(1.3),introducedadifferenceschemeofconservationtype,andresearcheditsstabilityandconvergence.Otherwise,itisanimplicitmetho…     

ANALYSIS ON A NUMERICAL SCHEME WITH SECOND-ORDER TIME ACCURACY FOR NONLINEAR DIFFUSION EQUATIONS

A nonlinear fully implicit finite difference scheme with second-order time evolution for nonlinear diffusion problem is studied.The scheme is constructed with two-layer coupled discretization (TLCD) at each time step.It does not stir numerical oscillation,while per-mits large time step length,and produces more accurate numerical solutions than the other two well-known second-order time evolution nonlinear schemes,the Crank-Nicolson (CN)scheme and the backward difference formula second-order (BDF2) scheme.By developing a new reasoning technique,we overcome the difficulties caused by the coupled nonlinear discrete diffusion operators at different time layers,and prove rigorously the TLCD scheme is uniquely solvable,unconditionally stable,and has second-order convergence in both s-pace and time.Numerical tests verify the theoretical results,and illustrate its superiority over the CN and BDF2 schemes.     

OPTIMAL POINT-WISE ERROR ESTIMATE OF A COMPACT FINITE DIFFERENCE SCHEME FOR THE COUPLED NONLINEAR SCHRODINGER EQUATIONS

In this paper, we analyze a compact finite difference scheme for computing a coupled nonlinear SchrSdinger equation. The proposed scheme not only conserves the totM mass and energy in the discrete level but also is decoupled and linearized in practical computa- tion. Due to the difficulty caused by compact difference on the nonlinear term, it is very hard to obtain the optimal error estimate without any restriction on the grid ratio. In order to overcome the difficulty, we transform the compact difference scheme into a special and equivalent vector form, then use the energy method and some important lemmas to obtain the optimal convergent rate, without any restriction on the grid ratio, at the order of O（h4 ＋r2） in the discrete L∞ -norm with time step - and mesh size h. Finally, numerical results are reported to test our theoretical results of the proposed scheme.     

A MONOTONE DOMAIN DECOMPOSITION ALGORITHM FOR SOLVING WEIGHTED AVERAGE APPROXIMATIONS TO NONLINEAR SINGULARLY PERTURBED PARABOLIC PROBLEMS

This paper presents and analyzes a monotone domain decomposition algorithm for solving nonlinear singularly perturbed reaction-diffusion problems of parabolic type. To solve the nonlinear weighted average finite difference scheme for the partial differential equation, we construct a monotone domain decomposition algorithm based on a Schwarz alternating method and a box-domain decomposition. This algorithm needs only to solve linear discrete systems at each iterative step and converges monotonically to the exact solution of the nonlinear discrete problem. domain decomposition algorithm is estimated The rate of convergence of the monotone Numerical experiments are presented.     

非线性分数阶反应扩散方程组的间断时空有限元方法

利用时间间断空间连续的时空有限元方法构造了空间分数阶反应扩散方程组的可以逐时间层求解的全离散格式.在时间离散区间上,采用Radau积分公式,将插值理论与有限元理论相结合,给出了全离散格式解的存在唯一性结果,并证明了所给格式是无条件稳定的,进而详细给出最优阶L~∞(L~2)模误差估计过程.最后用数值算例验证了理论分析的正确性.     

强单调对称非线性方程组的BFGS算法

提出一种求解强单调非线性方程组的BFGS算法,该算法的一个明显优点是Bκ的条件数比Li-Fukushima^[3]提出的GNBFGS中Bκ的条件数小得多。且该算法是一种无需计算导数的下降算法。在一定的条件下,证明了算法的全局收敛性和超线性收敛性。最后进行数值试验,结果表明,本文算法具有较好的数值结果。而且验证了本文所提出的算法中Bκ的条件数要比GNBFGS算法的条件数小得多。     

ON NUMEROV SCHEME FOR NONLINEAR TWO-POINTS BOUNDARY VALUE PROBLEM

1.IntroductionInstudyingsomeproblemsarisinginelectromagnetism,biology)astronomy,bound-arylayerandothertopics,weoftenmeetnonlineartwo--pointsboundaryproblem,i.e.,findingyECo[0,11nC2(0,1)suchthatwhereor,garecertainconstants,andf(x,z)EC'(0,1)xC'(--co,co).Undersomeconditionsonf(x,z),wecanusetheframeworkof[1]toinvestigatetheexistenceanduniquenessofitssolutions.Alsotherearealotofliteratureconcerningitsnumericalsolutio.s[2--'].Inparticular,N..ero.15]proposedafamousfinitedifferenceschemewiththeaccu…     

对流扩散方程的经济差分格式

１．引言 对流扩散方程是一类基本的运动方程,它可描述质量、热量的输运过程以及反应扩散过程等众多物理现象．寻找稳定、快速实用的数值方法,有着重要的理论和实际意义．标准的差分方法或有限元方法对它常常失效,根本原因在于“对流项”的存在．［１］提出了解对流扩散方程的特征线修正技术,这一方法考虑沿着特征线（流动方向）的离散,利用了对流扩散问题的物理力学性质,可以有效地克服数值振荡,保证数值解的稳定,尤其对“对流占优”的问题,这一方法有突出的优越性．这方面已有大量的理论和应用研究成果［２,３,７］．对大规模…     

GLOBAL BLOWUP AND BLOWUP RATE ESTIMATES OF SOLUTIONS FOR A CLASS OF NONLINEAR NON-LOCAL REACTION-DIFFUSION PROBLEMS

In this paper, the global blowup properties of solutions for a class of non-linear non-local reaction-diffusion problems are investigated by the methods of the priorestimates. Moreover, the blowup rate estimate of the solution is given.     

A FAST COMPACT DIFFERENCE METHOD FOR TWO-DIMENSIONAL NONLINEAR SPACE-FRACTIONAL COMPLEX GINZBURG-LANDAU EQUATIONS

This paper focuses on a fast and high-order finite difference method for two-dimensional space-fractional complex Ginzburg-Landau equations.We firstly establish a three-level finite difference scheme for the time variable followed by the linearized technique of the nonlinear term.Then the fourth-order compact finite difference method is employed to discretize the spatial variables.Hence the accuracy of the discretization is O(τ2 + h41 +h42) in L2-norm,where τ is the temporal step-size,both h1 and h2 denote spatial mesh sizes in x-and y-directions,respectively.The rigorous theoretical analysis,including the uniqueness,the almost unconditional stability,and the convergence,is studied via the energy argument.Practically,the discretized system holds the block Toeplitz structure.Therefore,the coefficient Toeplitz-like matrix only requires O(M1M2) memory storage,and the matrix-vector multiplication can be carried out in O(M1M2(logM1 + log M2))computational complexity by the fast Fourier transformation,where M1 and M2 denote the numbers of the spatial grids in two different directions.In order to solve the resulting Toeplitz-like system quickly,an efficient preconditioner with the Krylov subspace method is proposed to speed up the iteration rate.Numerical results are given to demonstrate the well performance of the proposed method.     

A FOURIER SPECTRAL SCHEME FOR SOLVING NONLINEAR KLEIN-GORDON EQUATION

A Fourier spectral scheme is proposed for solving the periodic problem of nonlinear Klein-Gordon equation. Its stability and convergence are investigated. Numerical results are also presented.     

一类非线性Schroedinger方程的高精度守恒数值格式

1引言 本文讨论下面非线性Schroedinger方程（NLS）方程的初边值问题： i（偏du）/（偏dt）＋（偏d^2u）/（偏dx^2）＋2｜u^2｜u=0,（1）[第一段]     

一类带有单调型算子紧扰动的半线性方程的可解性

本文在算子单调性和紧性假设下研究了一类半线性算子方程Ａｕ－Ｔｕ＋Ｃｕｆ的可解性,其中Ａ,Ｔ和Ｃ映实自反Ｂａｎａｃｈ空间Ｘ中的闭凸子集到它的对偶空间Ｘ＊．我们的结果扩展或改进了Ｇｕａｎ［１］最近宣布的全部结果．