一类N-双调和方程多解的存在性

研究一类N-双调和方程△_N~2u-△_Nu+V(x)|u|~(N-2)u=f(x,u),x∈R~N其中f(x,u)=λg(x)|u|~(p-2)u+h(u),1pN,λ≥0是参数,权函数V(x),g(x),h(u)满足一定的条件.运用对称山路定理和Schwarz对称化方证明了方程存在无穷多个弱解.     

带有位势的Schrdinger-Poisson系统解的存在性与多解性

该文讨论以下带有位势V的薛定谔-泊松(Schrdinger-Poisson)系统-△u+λVu+φu=f(x,u),x∈R~3,-△φ=u~2,x∈R~3,其中λ≥1是一个参数,位势函数V∈C(R~3,R+)满足比较一般的假设.当非线性项f在无穷远点是超四次的,并且空间嵌入缺乏紧性时,该文讨论了参数λ≥1充分大时问题解的存在性与多解性.也考虑了非线性性项f满足一般的次线性假设时问题无穷多个解的存在性.     

带有超线性项或次线性项的Schrdinger-Poisson系统解的存在性和多重性

该文研究如下Schrdinger-Poisson系统解的存在性和多重性-△u+V(x)u+K(x)φu=f(x,u),x∈R~3,-△φ=K(x)u~2,x∈R~3,其中V∈C(R~3,R)并且K∈L~2∪L~∞满足K0.在没有Ambrosetti-Rabinowitz型超二次条件以及映射t→(f(x,t))/t~3的单调性假设下,利用对称山路引理证明了无穷多个高能量解的存在性.此外,考虑了非线性项f次线性增长的情形并获得了解的存在性和多重性.     

奇异半线性椭圆方程的非径向正整体解

研究如下N维奇异半线性椭圆方程△u+f(x,u)=0, x∈RN(N≥3),其中函数f:RN× R+→R+连续,在u=0有奇异性;采用上-下解方法给出该方程具有满足如下性质的有界正整体解u的条件: u∈C2+θloc(RN)使得lim |x|→∞ u(x)=0且u(x)≥εmin{1,|x|2-N},其中ε＞0是常数;并证明:若条件添加"f关于u单调不增"的限制,则这种解是唯一的.     

一类退化抛物方程解的几何性质

本文讨论非线性退化抛物方程u_t=△φ(u)的Cauchy问题弱解u(x,t)的正则性与几何性质.本文证明:若正数β足够大,则曲面ψ=ψ(x,t)=[φ(u)]~β是随时间t的连续变化而漂浮于空间R~(n+1)中的n维完备黎曼流形,它与实欧氏空R~n相切于低维流形(?)H_n(t),而H_u(t)={x∈R~n:u(x,t)0);函数ψ(x,t)在经典的意义下满足另一退化抛物方程.     

一类非线性Schrdinger-Maxwell方程基态解的存在性

本文研究了如下Schrdinger-Maxwell方程基态解的存在性问题{-△u+V(x)u+K(x)φ(x)u=b(x)|u|p-1u+λg(x,u)in R~3,-△φ=K(x)u~2in R~3,其中λ0,V(x)∈C~1(R~3,R),且V(x)0.△在K,g,b满足一定的假设条件下,且0p1时,利用变分法和临界点理论,获得了基态解的存在性.该结论推广了文献[7]的结果.     

一类非线性Schrdinger-Maxwell方程组半经典解的存在性

本文将研究如下非线性Schrdinger-Maxwell方程组问题{-ε2△u+V(x)u+K(x)φu=|u|p-2u,x∈R3,-△φ=4πK(x)u2,x∈R3.当势函数V(x)和电量函数K(x)满足一定假设条件时,作者利用变分法证明了ε充分小时,该方程组半经典解的存在性.     

一类Choquard型方程解的存在性

该文研究如下形式的Choquard型方程-△_pu+V(x)|u|~(p-2)u=(|x|~(-(N-α))*F(u))f(u),其中,-△_pu=div(|▽u|~(p-2)▽u)),x=(y,z)∈R~K×R~(N-K).假定混合位势V(y,z)关于y具有周期性,关于z具有强制性,并且非线性项f满足一定的条件,利用变分理论,该文证明了上述Choquard型方程具有山路水平解.     

完全非线性扰动方程的线性化原理

本文讨论方程u_i=a(t,εu,ε▽u,ε▽u)·▽u f(t,x,u,▽u)带第一初边值条件的解的存在性,其中a(t,0,0,0)>0,当|ξ|相似文献   

非线性散射问题

三维介质中的谐波在遇到障碍物后的散射同题,数学上可表示为Helmholtz方程的边值问题,其中无穷远点满足Sommerfeid散射条件.在非线性介质中,波动方程可表示为utt-c2Au=F(x,u),当F(x,u)满足适当条件时,代入入射波的表达式U(x,t)=e-iwtu(x),即得到在有界区域内散射波满足的方程Au k21u=f(x,u).对非线性介质在小跳跃度和小扰动下散射问题的解的存在性进行讨论,同时对一类非线性函数f(x,u)在大跳跃度情况下给出散射问题解的存在性.     

MUSCL Type Schemes and Discrete Entropy Conditions

1.IntroductionConsiderthehyperbolicconservationlaws:Theresearchofnumericalmethodsforequations(1.1)hasbeendevelopedrapidlyinthisdecade.SincetheappearanceoftheconceptofTVD(totalvariationdiminishing)schemes,varioushighresolutionschemeshavebeenproposedl1,2,3l4]andsuccessfullyappliedtocomputationalfluiddynamics-ItiswellknownthattheconvergenceofthenumericalmethodsforhyperbolicconservationlawsdependsontheentroPyconditionofthenumericalsolutionsl5].Previouslytheconstructionofdifferenceschemeswasalway…     

On entropy stable schemes for degenerate parabolic multispecies kinematic flow models

Entropy stable schemes for the numerical solution of initial value problems of nonlinear, possibly strongly degenerate systems of convection–diffusion equations were recently proposed in Jerez and Parés's study. These schemes extend the theoretical framework of Tadmor's study to convection–diffusion systems. They arise from entropy conservative schemes by adding a small amount of viscosity to avoid spurious oscillations. The main condition for feasibility of entropy conservative or stable schemes for a given model is that the corresponding first‐order system of conservation laws possesses a convex entropy function and corresponding entropy flux, and that the diffusion matrix multiplied by the inverse of the Hessian of the entropy is positive semidefinite. As a new contribution, it is demonstrated in the present work, first, that these schemes can naturally be extended to initial‐boundary value problems with zero‐flux boundary conditions in one space dimension, including an explicit bound on the growth of the total entropy. Second, it is shown that these assumptions are satisfied by certain diffusively corrected multiclass kinematic flow models of arbitrary size that describe traffic flow or the settling of dispersions and emulsions, where the latter application gives rise to zero‐flux boundary conditions. Numerical examples illustrate the behavior and accuracy of entropy stable schemes for these applications.     

High Resolution Schemes and Discrete Entropy Conditions for 2-D Linear Conservation Laws

In this paper, fully discrete entropy conditions of a class of high resolution schemes with the MmB property are discussed by using the theory of proper discrete entropy flux for the linear scalar conservation laws in two dimensions. The theoretical resluts show that the high resolution schemes satisfying fully discrete entropy conditions with proper discrete entropy flux cannot preserve second order accuracy in the case of two dimensions.     

Discrete shock profiles for systems of conservation laws

The existence of discrete shock profiles for difference schemes approximating a system of conservation laws is the major topic studied in this paper. The basic theorem established here applies to first-order accurate difference schemes; for weak shocks, this theorem provides necessary and sufficient conditions involving the truncation error of the linearized scheme which guarantee entropy satisfying or entropy violating discrete shock profiles. Several explicit difference schemes are used as examples illustrating the interplay between the entropy condition, monotonicity, and linearized stability. Entropy violating stationary shocks for second-order accurate Lax-Wendroff schemes approximating systems are also constructed. The only tools used in the proofs are local analysis and the center manifold theorem.     

Explicit diffusive kinetic schemes for nonlinear degenerate parabolic systems

We design numerical schemes for nonlinear degenerate parabolic systems with possibly dominant convection. These schemes are based on discrete BGK models where both characteristic velocities and the source-term depend singularly on the relaxation parameter. General stability conditions are derived, and convergence is proved to the entropy solutions for scalar equations.

     

双曲型守恒律方程的熵稳定格式的一些讨论

本文讨论双曲型守恒律方程的熵稳定格式.对于给定的熵对,格式所满足的熵条件中的数值熵通量是不唯一的.Tadmor的充分条件可以唯一地确定标量方程的熵守恒通量,但不能唯一确定方程组的熵守恒通量,却可以给出方程组的空间一阶精度的熵守恒格式.也讨论了在熵守恒通量上添加数值粘性得到的显式熵稳定格式需要满足的条件及常见的时间离散对熵守恒和熵稳定的影响.     

Entropy flux-splittings for hyperbolic conservation laws part I: General framework

A general framework is proposed for the derivation and analysis of flux-splittings and the corresponding flux-splitting schemes for systems of conservation laws endowed with a strictly convex entropy. The approach leads to several new properties of the existing flux-splittings and to a method for the construction of entropy flux-splittings for general situations. A large family of genuine entropy flux-splittings is derived for several significant examples: the scalar conservation laws, the p-system, and the Euler system of isentropic gas dynamics. In particular, for the isentropic Euler system, we obtain a family of splittings that satisfy the entropy inequality associated with the mechanical energy. For this system, it is proved that there exists a unique genuine entropy flux-splitting that satisfies all of the entropy inequalities, which is also the unique diagonalizable splitting. This splitting can be also derived by the so-called kinetic formulation. Simple and useful difference schemes are derived from the flux-splittings for hyperbolic systems. Such entropy flux-splitting schemes are shown to satisfy a discrete cell entropy inequality. For the diagonalizable splitting schemes, an a priori L^∞ estimate is provided by applying the principle of bounded invariant regions. The convergence of entropy flux-splitting schemes is proved for the 2 × 2 systems of conservation laws and the isentropic Euler system. ©1995 John Wiley & Sons, Inc.     

一类TVD格式的熵强迫函数及熵条件

1.引言 在拟线性双曲型方程差分方法的研究中,数值解的收敛性是一个重要的问题,因为这一性质决定了数值解能否近似地反映真实的物理现象。数值解的收敛性实际上包含了三方面的内容: 1°当网格步长趋于零时,数值解序列包含一个按某种范数收敛到函数u的子序列。     

A minimum entropy principle of high order schemes for gas dynamics equations

The entropy solutions of the compressible Euler equations satisfy a minimum principle for the specific entropy (Tadmor in Appl Numer Math 2:211–219, 1986). First order schemes such as Godunov-type and Lax-Friedrichs schemes and the second order kinetic schemes (Khobalatte and Perthame in Math Comput 62:119–131, 1994) also satisfy a discrete minimum entropy principle. In this paper, we show an extension of the positivity-preserving high order schemes for the compressible Euler equations in Zhang and Shu (J Comput Phys 229:8918–8934, 2010) and Zhang et?al. (J Scientific Comput, in press), to enforce the minimum entropy principle for high order finite volume and discontinuous Galerkin (DG) schemes.     

Convergence of higher order finite volume schemes on irregular grids

We prove convergence to the entropy solution of a general class of higher order finite volume schemes on unstructured, irregular grids for multidimensional scalar conservation laws. Such grids allow for cells to become flat in the limit. We derive a new entropy inequality for higher order schemes built on Godunov’s numerical flux. Our result implies convergence of suitably modified versions of MUSCL-type finite volume schemes, ENO schemes and the discontinuous Galerkin finite element method.