Two-Phase Stefan Problem as the Limit Case of Two-Phase Stefan Problem with Kinetic Condition

Both one-dimensional two-phase Stefan problem with the thermodynamic equilibrium condition u(R(t),t)=0 and with the kinetic rule u_ε(R_ε(t),t)=εR_ε′(t) at the moving boundary are considered. We prove, when ε approaches zero, R_ε(t) converges to R(t) in C^1+δ/2[0,T] for any finite T>0, 0<δ<1.     

Viscosity Solutions for the Two-Phase Stefan Problem

We introduce a notion of viscosity solutions for the two-phase Stefan problem, which incorporates possible existence of a mushy region generated by the initial data. We show that a comparison principle holds between viscosity solutions, and investigate the coincidence of the viscosity solutions and the weak solutions defined via integration by parts. In particular, in the absence of initial mushy region, viscosity solution is the unique weak solution with the same boundary data.     

两点混合边值问题的紧有限体积格式

本文针对常系数和变系数两点混合边值问题提出一种紧有限体积格式,该格式形成的线性代数方程组具有三对角性质,可以使用追赶法求解.证明格式按照H1半范数具有四阶收敛精度.利用节点计算值,给出单元中点值和一阶导数值的高精度后处理计算公式,这两个公式同样具有四阶精度.数值算例验证了理论分析的正确性,并说明了格式的有效性.     

Two Equivalent Finite Volume Schemes for Stefan Problem on Boundary-Fitted Grids: Front-Tracking and Front-Fixing Techniques

Differential Equations - We present finite-difference schemes on boundary-fitted grids for the two-dimensional Stefan problem. It is shown that the proposed numerical schemes constructed by...     

Conservative scheme for the thermodiffusion Stefan problem

We suggest further development of the principle of conservation for problems with moving boundaries. Using the problem of phase transitions in binary compounds as an example, we demonstrate a technique for constructing divergence and nondivergence finite difference schemes guaranteeing that the energy and mass conservation laws hold in the discrete model. In a class of front tracking methods, we prove the equivalence of the approach based on the use of moving grids with that based on a dynamic change of variables which permits one to solve the problem on a fixed grid.     

求解广义正则长波方程的守恒差分格式

本文对广义正则长波方程的初边值问题提出了—个隐式差分格式，该格式合理地模拟了方程本身所具有的两个守恒律．给出了差分解的先验估计，证明了差分解的唯一可解性、无条件收敛性及其稳定性．     

Error Estimate of a New Conservative Finite Difference Scheme for the Klein-Gordon-Dirac System

In this paper, we derive and analyze a conservative Crank-Nicolson-type finite difference scheme for the Klein-Gordon-Dirac (KGD) system. Differing from the derivation of the existing numerical methods given in literature where the numerical schemes are proposed by directly discretizing the KGD system, we translate the KGD equations into an equivalent system by introducing an auxiliary function, then derive a nonlinear Crank-Nicolson-type finite difference scheme for solving the equivalent system. The scheme perfectly inherits the mass and energy conservative properties possessed by the KGD, while the energy preserved by the existing conservative numerical schemes expressed by two-level's solution at each time step. By using energy method together with the 'cut-off' function technique, we establish the optimal error estimate of the numerical solution, and the convergence rate is $\mathcal{O}(τ^2 + h^2)$ in $l^∞$-norm with time step $τ$ and mesh size $h.$ Numerical experiments are carried out to support our theoretical conclusions.     

对称正则长波方程的一个守恒差分格式

本文考虑了具有齐次边界条件的对称正则长波方程的有限差分法．构造了一个两层守恒的有限差分格式,利用离散泛函分析方法分析了格式的收敛性和稳定性,从理论上得到了收敛阶为O(h~2 τ)．数值试验表明,我们的方法是可信的．     

Quasistationary Approximation for the Stefan Problem

To justify the quasistationary approximation for the Stefan problem, the difference between the solution to the Hele-Show problem and the solution to the Stefan problem with small parameter ε at the time-derivative in the equation is considered. Bibliography: 7 titles. __________ Translated from Problemy Matematicheskogo Analiza, No. 31, 2005, pp. 167–178.     

对称正则长波方程的一个新的守恒差分格式

本文考虑了具有齐次边界条件的对称正则长波方程的有限差分格式,提出了一个三层守恒的有限差分格式,证明了格式的收敛性和稳定性,从理论上得到了收敛阶为O(h2+τ2).通过数值试验表明,所提的方法是可靠有效的.     

广义对称正则长波方程的守恒差分格式

文章考虑了具有齐次边界条件的广义对称正则长波方程的有限差分格式.提出了一个守恒并且线性非耦合的三层有限差分格式,由于格式在计算中只需要解三对角线性方程组,从而避免了其中的迭代计算.文中先讨论了一个离散守恒量,然后我们利用离散泛函分析方法证明了格式的收敛性和稳定性,从理论上得到了收敛阶为O(h~2+τ~2).通过数值试验表明,所提的方法是可靠有效的.     

On the Modified Crystalline Stefan Problem with Singular Data

We study the behavior of solutions of the modified Stefan problem in the plane for polygonal interfaces. We are particularly interested in a solution near a singularity of either the loss of a facet or the breaking of a facet. We establish precise regularity results if a facet disappears. We use them to establish the existence of a weak solution with singular data, i.e., when some of the zero-crystalline-curvature facets have zero length.     

提高反应—扩散方程有限差分格式的稳定性问题

This paper deals with the special nonlinear reaction-diffusion equation.The finite difference scheme with incremental unknowns approximating to the differential equation (2.1) is set up by means of introducing incremental unknowns methods.Through the stability analyzing for the scheme,it was shown that the stability conditions of the finite difference schemes with the incremental unknowns are greatly improved when compared with the stability conditions of the corresponding classic difference scheme.     

TWO-GRID CHARACTERISTIC FINITE VOLUME METHODS FOR NONLINEAR PARABOLIC PROBLEMS＊

In this work, two-grid characteristic finite volume schemes for the nonlinear parabolic problem are considered. In our algorithms, the diffusion term is discretized by the finite volume method, while the temporal differentiation and advection terms are treated by the characteristic scheme. Under some conditions about the coefficients and exact solution, optimal error estimates for the numerical solution are obtained. Furthermore, the two- grid characteristic finite volume methods involve solving a nonlinear equation on coarse mesh with mesh size H, a large linear problem for the Oseen two-grid characteristic finite volume method on a fine mesh with mesh size h = O（H2） or a large linear problem for the Newton two-grid characteristic finite volume method on a fine mesh with mesh size h = 0（I log hll/2H3）. These methods we studied provide the same convergence rate as that of the characteristic finite volume method, which involves solving one large nonlinear problem on a fine mesh with mesh size h. Some numerical results are presented to demonstrate the efficiency of the proposed methods.     

一类Stefan问题的适定性

本文讨论在烧蚀缓慢的情况下发汗控制微分方程并证明了其解的适定性。     

Stability of Semi-implicit Finite Volume Scheme for Level Set Like Equation

We study numerical methods for level set like equations arising in image processing and curve evolution problems. Semi-implicit finite volume-element type schemes are constructed for the general level set like equation(image selective smoothing model) given by Alvarez et al.(Alvarez L, Lions P L, Morel J M. Image selective smoothing and edge detection by nonlinear diffusion II. SIAM J. Numer.Anal., 1992, 29: 845–866). Through the reasonable semi-implicit discretization in time and co-volume method for space approximation, we give finite volume schemes,unconditionally stable in L∞ and W1,2(W1,1) sense in isotropic(anisotropic) diffusion domain.     

On the Finite Element Approximation of an Elliptic Variational Inequality Arising from an Implicit Time Discretization of the Stefan Problem

A semi-discretization in time of the weak formulation of thetwo phase Stefan moving boundary problem results in an ellipticboundary value problem with a non-linear jump discontinuitywhich can be set as an elliptic variational inequality. Thepurpose of this paper is to consider a finite element approximationto the inequality. Assuming that the solution is in H² and thatthe length of the free boundary is finite an error estimateis proved. The resulting algebraic problem is one of solvinga system of nonlinear equations associated with a diagonal multivaluedmonotone mapping. An S.O.R. method is given and shown to beglobally convergent.     

A Posteriori Estimators for the Finite Volume Discretization of an Elliptic Problem

We analyze a residual error estimator for a finite volume discretization of a linear elliptic boundary value problem. The error estimator consists of the residual of the strong equation and the jumps across the inter-element boundaries of a primal triangulation. Some numerical experiments are presented.     

On the Problem of Finite Signature

We show that not each model can be replaced by a model of finite signature so that its automorphism group remains the same.