Superconvergence of nonconforming finite element penalty scheme for Stokes problem using L^2 projection method

A modified penalty scheme is discussed for solving the Stokes problem with the Crouzeix-Raviart type nonconforming linear triangular finite element. By the L^2 projection method, the superconvergence results for the velocity and pressure are obtained with a penalty parameter larger than that of the classical penalty scheme. The numerical experiments are carried out to confirm the theoretical results.

MULTIPLICITY OF NORMALIZED SOLUTIONS FOR THE FRACTIONAL SCHR?DINGER-POISSON SYSTEM WITH DOUBLY CRITICAL GROWTH

In this paper,we are concerned with solutions to the fractional Schrodinger-Poisson system■ with prescribed mass ∫_(R^(3))|u|^(2)dx=a^(2),where a> 0 is a prescribed number,μ> 0 is a paremeter,s ∈(0,1),2 <q <2_(s)^(*),and 2_(s)^(*)=6/(3-2s) is the fractional critical Sobolev exponent.In the L2-subcritical case,we show the existence of multiple normalized solutions by using the genus theory and the truncation technique;in the L^(2)-supercritical case,we obtain a couple of normalized solutions by developing a fiber map.Under both cases,to recover the loss of compactness of the energy functional caused by the doubly critical growth,we need to adopt the concentration-compactness principle.Our results complement and improve upon some existing studies on the fractional Schrodinger-Poisson system with a nonlocal critical term.

关于微分算子Δ^2+a的一个注记

本文利用复分析中研究柯西黎曼方程的赫曼德尔L^2方法,研究了加权希尔伯特空间L^2(R^2,e-|x|2)上的微分算子Δ^2+a,证明了由该算子所构成的微分方程的整体弱解的存在性,并证明了该算子的右逆有界算子的存在性.

The Characteristics-mixed Finite Element Method for Enhanced Oil Recovery Simulation and Optimal Order L^2 Error Estimate

This article discusses the enhanced oil recovery numerical simulation of the chemical flooding(such as surfactants, alcohol, polymers) composed of two-dimensional multicomponent, ultiphase and incompressible mixed fluids. After the oil field is waterflooded, there is still a large amount of crude oil left in the oil deposit. By adding certain chemical substances to the fluid injected, its driving capacity can be greatly increased. The mathematical model of two-dimensional enhanced oil recovery simulation can be described

The Characteristic Finite Difference Methods for Enhanced Oil Recovery Simulation and L^2 Estimates

A 2-dimensional, multicomponent, multiphase, and incompressible compositional reservoir simulator has been developed and applied to chemical flooding (surfactants, alcohol and polymers) and convergence analysis. The characteristic finite difference methods for 2-dimensional enhanced oil recovery can be described as a coupled system of nonlinear partial differential equations. For a generic case of the cross interference and bounded region, we put forward a kind of characteristic finite difference schemes and make use of thick and thin grids to form a complete set, and of calculus of variations, the theory of prior estimates and techniques. Optimal order estimates in L^2 norm are derived for the error in the approximate solutions. Thus we have thoroughly solved the well-known theoretical problem proposed by a famous scientist, J. Douglas, Jr.

A New L^(2)Projection Method for the Oseen Equations

In this paper,a new type of stabilized finite element method is discussed for Oseen equations based on the local L^(2)projection stabilized technique for the velocity field.Velocity and pressure are approximated by two kinds of mixed finite element spaces,P^(2)_( l)-P_(1),(l=1,2).A main advantage of the proposed method lies in that,all the computations are performed at the same element level,without the need of nested meshes or the projection of the gradient of velocity onto a coarse level.Stability and convergence are proved for two kinds of stabilized schemes.Numerical experiments confirm the theoretical results.

关于Calderon-Zygmund算子核的光滑性的讨论

对于一般的非卷积型Calderon -Zygmund算子 ,核满足Hormander条件能否保证L2 有界性 ,这是尚未解决的一个问题 .我们已在条件∑k1 2 ε1 (k) <∞下 ,证明了L2 有界 .∑k1 2 ε1 (k) <∞条件与Hormander条件有何关系 。

ASYMPTOTIC STABILITY OF RAREFACTION WAVE FOR HYPERBOLIC-ELLIPTIC COUPLED SYSTEM IN RADIATING GAS

In this article, authors study the Cauch problem for a model of hyperbolic-elliptic coupled system derived from the one-dimensional system of the rudiating gas. By considering the initial data as a small disturbances of rarefaction wave of inviscid Burgers equation, the global existence of the solution to the corresponding Cauchy problem and asymptotic stability of rarefaction wave is proved. The analysis is based on a priori estimates and L^2-energy method.

L^2-Decay rate for non-ergodic Jackson network

We establish the additive theorem of L^2-decay rate for multi- dimensional Markov process with independent marginal processes. Using this and the decomposition method, we obtain explicit upper and lower bounds for decay rate of non-ergodic Jackson network. In some cases, we get the exact decay rate.

FINITE ELEMENT METHOD AND ANALYSIS FOR CHEMICAL-FLOODING SIMULATION

This article discusses the enhanced oil recovery numerical simulation of the chemical-flooding (such as surfactallts, alcohol, polymers) composed of three-dimensional multicomponent, multiphase and incompressible mixed fluids. The mathematical model can be described as a coupled system of nonlinear partial differential equations with initialboundary value problerns. viom the actual conditions such as the effect of cross interference and the three-dimensional charederistic of large-scale science-engineering computation,this article puts forward a kind of characteristic finite element fractional step schemes and obtain the optimal order error estdriates in L2 norm. Thus we have thoroughly solved the well-known theoretical problem proppsed by a famous scientist, R. E. Ewing.

A SECOND ORDER UNCONDITIONALLY CONVERGENT FINITE ELEMENT METHOD FOR THE THERMAL EQUATION WITH JOULE HEATING PROBLEM

In this paper,we study the finite element approximation for nonlinear thermal equation.Because the nonlinearity of the equation,our theoretical analysis is based on the error of temporal and spatial discretization.We consider a fully discrete second order backward difference formula based on a finite element method to approximate the temperature and electric potential,and establish optimal L^(2) error estimates for the fully discrete finite element solution without any restriction on the time-step size.The discrete solution is bounded in infinite norm.Finally,several numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method.

Error Estimates for the Iterative Discontinuous Galerkin Method to the Nonlinear Poisson-Boltzmann Equation

This paper is devoted to the error estimate for the iterative discontinuous Galerkin(IDG)method introduced in[P.Yin,Y.Huang and H.Liu.Commun.Comput.Phys.16:491-515,2014]to the nonlinear Poisson-Boltzmann equation.The total error includes both the iteration error and the discretization error of the direct DG method to linear elliptic equations.For the DDG method,the energy error is obtained by a constructive approach through an explicit global projection satisfying interface conditions dictated by the choice of numerical fluxes.The L^(2) error of order O(h^(m+1))for polynomials of degree m is further recovered.The bounding constant is also shown to be independent of the iteration times.Numerical tests are given to validate the established convergence theory.

A NEW CHARACTERISTIC EXPANDED MIXED METHOD FOR SOBOLEV EQUATION WITH CONVECTION TERM

In this paper,a new numerical method based on a new expanded mixed scheme and the characteristic method is developed and discussed for Sobolev equation with convection term.The hyperbolic part d(x)∂u/∂t+c(x,t)·∇u is handled by the characteristic method and the diffusion term∇·(a(x,t)∇u+b(x,t)∇ut)is approximated by the new expanded mixed method,whose gradient belongs to the simple square integrable(L^(2)(Ω))^(2)space instead of the classical H(div;Ω)space.For a priori error estimates,some important lemmas based on the new expanded mixed projection are introduced.An optimal priori error estimates in L^(2)-norm for the scalar unknown u and a priori error estimates in(L^(2))^(2)-norm for its gradientλ,and its fluxσ(the coefficients times the negative gradient)are derived.In particular,an optimal priori error estimate in H1-norm for the scalar unknown u is obtained.

A Geometric Flow Approach for Region-based Image Segmentation-theoretical Analysis

In this paper, we analyze the well-posedness of an image segmentation model. The main idea of that segmentation model is to minimize one energy functional by evolving a given piecewise constant image towards the image to be segmented. The evolution is controlled by a serial of mappings, which can be represented by B-spline basis functions. The evolution terminates when the energy is below a given threshold. We prove that the correspondence between two images in the segmentation model is an injective and surjective mapping under appropriate conditions. We further prove that the solution of the segmentation model exists using the direct method in the calculus of variations. These results provide the theoretical support for that segmentation model.

Stability of the Equilibrium to the Boltzmann Equation with Large Potential Force

The Boltzmann equation with external potential force exists a unique equilibrium—local Maxwellian. The author constructs the nonlinear stability of the equilibrium when the initial datum is a small perturbation of the local Maxwellian in the whole space R^3. Compared with the previous result [Ukai, S., Yang, T. and Zhao, H.-J.,Global solutions to the Boltzmann equation with external forces, Anal. Appl.(Singap.), 3,2005, 157–193], no smallness condition on the Sobolev norm H^1 of the potential is needed in our arguments. The proof is based on the entropy-energy inequality and the L^2-L~∞ estimates.

Asymptotic Behavior of Solutions to the Generalized BBM-Burgers Equation

We investigate the asymptotic behavior of solutions of the initial-boundaryvalue problem for the generalized BBM-Burgers equation u_t + f(u)_x = u_(xx) + u_(xxt) on the halfline with the conditions u(0, t) = u_–, u(∞, t) = u + and u_– 【 u_+, where the correspondingCauchy problem admits the rarefaction wave as an asymptotic states. In the present problem, becauseof the Dirichlet boundary, the asymptotic states are divided into five cases depending on the signsof the characteristic speeds f(u_±) of boundary state u_– = u(0) and the far fields states u_+ =u(∞). In all cases both global existence of the solution and asymptotic behavior are shown underthe smallness conditions.