广义混合非线性Schr(o)dinger方程的拟谱方法

本文讨论了广义混合非线性Schrodinger方程的周期初值问题,构造了守恒的半离散Fourier拟谱格式,对其近似解进行了先验估计,并证明了格式的收敛性.证明了该方程存在孤立子解,并给出其孤立子解的精确表达式.研究了线性化方程的稳定性问题,即在初值有扰动的情况下,该方程只有振荡解和鞍点.最后,通过数值例子验证了格式的可信性,数值计算表明,本格式时间方向可取大步长且是长时间稳定的,我们还计算了孤立子解,并绘出了在初值有扰动的情况下,相空间的轨线图.     

广义混合非线性Schrdinger方程的拟谱方法

本文讨论了广义混合非线性Schrdinger 方程的周期初值问题,构造了守恒的半离散Fourier 拟谱格式,对其近似解进行了先验估计,并证明了格式的收敛性.证明了该方程存在孤立子解,并给出其孤立子解的精确表达式.研究了线性化方程的稳定性问题,即在初值有扰动的情况下,该方程只有振荡解和鞍点.最后,通过数值例子验证了格式的可信性,数值计算表明,本格式时间方向可取大步长且是长时间稳定的,我们还计算了孤立子解,并绘出了在初值有扰动的情况下,相空间的轨线图.     

广义混合非线性Schrödinger方程的拟谱方法

本文讨论了广义混合非线性Schrodinger方程的周期初值问题,构造了守恒的半离散Fourier拟谱格式,对其近似解进行了先验估计,并证明了格式的收敛性.证明了该方程存在孤立子解,并给出其孤立子解的精确表达式.研究了线性化方程的稳定性问题,即在初值有扰动的情况下,该方程只有振荡解和鞍点.最后,通过数值例子验证了格式的可信性,数值计算表明,本格式时间方向可取大步长且是长时间稳定的,我们还计算了孤立子解,并绘出了在初值有扰动的情况下,相空间的轨线图.     

关于广义KPP方程的数值解

广义KPP(Kolmogorov-Petrovskii-Piskunov)方程是一个积分微分方程.为了要研究其数值解,我们首先将该方程转化为一个非线性双曲型方程,然后构造了一个线性化的差分格式,得到了差分格式解的存在唯一性,利用能量不等式证明了差分格式二阶收敛性和关于初值的无条件稳定性,数值结果验证了本文提出的方法.     

Kolmogorov-Spieqel-Siveshinky方程大时间问题的Fourier拟谱逼近

该文讨论了Kolmogorov-Spieqel-Siveshinky方程的周期初值问题, 研究了半离散Fourier拟谱解的长时间行为, 证明了半离散系统的收敛性和整体吸引子的存在性. 构造了全离散的三层显式Fourier拟谱格式, 并证明了该格式的收敛性, 最后通过数值计算验证了格式的可信性. 数值结果表明: 该格式是长时间稳定并可取时间大步长. 作者模拟了方程的解在相空间的轨线, 得到了一些有意义的结论.     

计算半线性椭圆问题多解的一类谱Galerkin型搜索延拓法的收敛性分析

本文提出计算半线性椭圆边值问题多解的一类高效的谱Galerkin型搜索延拓法(SGSEM).该方法基于模型方程相应线性特征值问题的若干特征函数的线性组合构造多解初值,充分利用了传统搜索延拓法构造多解初值方面的优势.同时,采用插值系数Legendre-Galerkin谱方法离散模型问题,具有计算成本低、计算精度高的优点.运用Schauder不动点定理和其他技巧,本文严格证明了对应于每个特定真解的数值解的存在性以及限制在该真解一个充分小的邻域内的数值解的唯一性,并证明了其谱收敛性.数值结果验证了算法的可行性与高效性,并展示了不同类型的多解.     

Захаров方程周期边界条件一类有限差分格式的收敛性和稳定性

§1.前言 自从[1]中提出axapoB方程后,由于它具有孤立子解,且有不同于KdV方程孤立子的一些性质,同时也可考察孤立子和其他波(例如声波)的相互作用,对激光打靶出现密度坑的物理现象提出了比较合理的解释,因而,引起了人们很大的兴趣。它的数值求解,已在[2-4]等中用有限差分法进行了数值计算,且有不少计算结果。本文主要从计算理论上证明一类和它相应的差分格式的收敛性和稳定性。     

非线性反应扩散方程的数值解

本文采用Petrov-Galerkin有限元法构造了非线性反应扩散方程的数值格式,既适用于全场性的初值,也适用于局部性的初值,利用全场性初值求得的进波数值解与精确解高度吻合,证明本方法与其它数值方法比较,有更高的精度和稳定性,利用各种局部性初值所算出的数值解表明,任何局部的扰动都会得到充分的发展,且当时间充分长后,演变为向左、右传播的行波,其波前的形状及传播速度完全由系统本身所决定,而与初值的类型无关.     

退化抛物型方程的一个初值反演问题

研究了一类重构退化抛物型方程初值的反问题.这类问题在应用科学的若干领域有着重要的应用.数值求解该问题的关键是构造相应正问题的高阶差分格式.然而,由于退化边界上的主项系数为零,目前广泛用于求解经典热传导方程的虚拟点法不能应用于该模型.该文提出了一种构造二阶精度差分格式的新方法,并证明了该方法的稳定性和收敛性.为了加快收敛速度,采用共轭梯度法求逆问题的数值解,并对算法的效率和精度进行了数值验证.     

KdV方程纯孤立子解的整体渐近性质

研究KdV方程纯孤立子解的整体渐近性质,证明了N-孤立子解一致收敛到N个单孤立子解的叠加.进而得到了N-孤立子解在L1-范数意义下的渐近结果,并借此阐述了纯孤立子解与一般速降解的差异.     

Convergence of a finite difference method for combustion model problems

We study a finite difference scheme for a combustion model problem. A projection scheme near the combustion wave, and the standard upwind finite difference scheme away from the combustion wave are applied. Convergence to weak solutions with a combustion wave is proved under the normal Courant-Friedrichs-Lewy condition. Some con-     

Convergence of a finite difference method for combustion model problems

We study a finite difference scheme for a combustion model problem. A projection scheme near the combustion wave, and the standard upwind finite difference scheme away from the combustion wave are applied. Convergence to weak solutions with a combustion wave is proved under the normal Courant-Friedrichs-Lewy condition. Some conditions on the ignition temperature are given to guarantee the solution containing a strong detonation wave or a weak detonation wave. Convergence to strong detonation wave solutions for the random projection method is also proved.     

Finite difference method for a combustion model

We study a projection and upwind finite difference scheme for a combustion model problem. Convergence to weak solutions is proved under the Courant-Friedrichs-Lewy condition. More assumptions are given on the ignition temperature; then convergence to strong detonation wave solutions or to weak detonation wave solutions is proved.

     

Global entropy solutions to a class of quasi-linear wave equations with large time-oscillating sources

This research explores the Cauchy problem for a class of quasi-linear wave equations with time dependent sources. It can be transformed into the Cauchy problem of hyperbolic integro-differential systems of nonlinear balance laws. We introduce the generalized Glimm scheme in new version and study its stability which is proved by Glimm-type interaction estimates in a dissipativity assumption. The generalized solutions to the perturbed Riemann problems, the building blocks of generalized Glimm scheme, are constructed by Riemann problem method modeled on the source free equations. The global existence for the Lipschitz continuous solutions and weak solutions to the systems is established by the consistency of scheme and the weak convergence of source. Finally, the weak solutions are also the entropy solutions which satisfy the entropy inequality.     

二维抛物型方程的一族高精度分支稳定显格式

1 引言 在渗流、扩散、热传导等领域中经常会遇到求解二维抛物型方程的初边值问题 {(6)u/(6)=a((6)2u/(6)x2+(6)2u/(6)y2), 0＜x,y＜L,t＞0,a＞0u(x, y, 0) =φ(x, y), 0 ≤ x, y ≤ L (1)u(0,y,t) =f1(y,t),u(L,y,t) =f2...     

对流占优扩散方程的一种特征差分算法

A new kind of characteristic-difference scheme for convection-diffusion equations is constructed by characteristic method and bilinear interpolation method. The convergence of the scheme is proved. The advantages of this scheme are to obtain the solutions of the convection diffusion equations with variable coefficient expediently and to reduce the numerical oscillations of the convectiondominanted diffusion equations effectively.     

Numerical approximations of the 10-moment Gaussian closure

We propose a numerical scheme to approximate the weak solutions of the 10-moment Gaussian closure. The moment Gaussian closure for gas dynamics is governed by a conservative hyperbolic system supplemented by entropy inequalities whose solutions satisfy positiveness of density and tensorial pressure. We consider a Suliciu-type relaxation numerical scheme to approximate the solutions. These methods are proved to satisfy all the expected positiveness properties and all the discrete entropy inequalities. The scheme is illustrated by several numerical experiments.

     

Analysis of new conservative difference scheme for two-dimensional Rosenau-RLW equation

In this article, numerical solution for the Rosenau-RLW equation in 2D is considered and a conservative Crank–Nicolson finite difference scheme is proposed. Existence of the numerical solutions for the difference scheme has been shown by Browder fixed point theorem. A priori bound and uniqueness as well as conservation of discrete mass and discrete energy for the finite difference solutions are discussed. Unconditional stability and a second-order accuracy on both space and time of the difference scheme are proved. Numerical experiments are given to support our theoretical results.     

Fast Solvers of Fredholm Optimal Control Problems

<正>The formulation of optimal control problems governed by Fredholm integral equations of second kind and an efficient computational framework for solving these control problems is presented.Existence and uniqueness of optimal solutions is proved. A collective Gauss-Seidel scheme and a multigrid scheme are discussed.Optimal computational performance of these iterative schemes is proved by local Fourier analysis and demonstrated by results of numerical experiments.