SOME TYPICAL BEHAVIORS OF WEAK SOLUTIONS OF LAYERED POROUS MEDIA EQUATION

1.IntroductionThefiltrationproblemoflayeredporousmediacanbedescribedasfollows(see[21):whereHisHeavisidefunction.u(x,t)isthecapillarypiezometrichead,oi(u)(i~l,2)thevolumetricmoisturecontentandK4(u)thehydraulicconductivityinupperlayer(x6(1,21).Theassumptionsarethesameasthosein[2]:(0KI)oi(r),Ki(r)EC' '(R).(0K2)oi(r)>0,Ki(r)>0,6:(r)>0andK:(r)20forrE(--co,u'.),whereu"thesaturatedcapillarypiezometricheadoftheithlayer.Whenr2u",oi(r)=osiandKi(r)~K'i,whereof'andK8iaresaturatedvaluesofthemoisturec…     

Algorithmic Issues for Electromagnetic Scattering in Layered Media: Green's Functions, Current Basis, and Fast Solver

In this paper, we will address three computational issues for electromagnetic scattering in layered media: fast algorithm of calculating dyadic Green's functions, high order RWG current basis and fast solver for layered media. Numerical results will be included.     

ONE DIMENSIONAL FILTRATION PROBLEM IN PARTIALLY SATURATED LAYERED POROUS MEDIA

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Homogenization of the layered medium equation

A new partial differential equation to be called the layered medium equation is introduced, and it is proved that certain relevant initial or periodic boundary conditions give well-posed problems. Then, the homogenized limit of the layered medium equation is studied. It is shown to be preserved in limit in the limit in the physical problem in which the coefficients that arise from the dielectric layer are both proportional to thickness. Otherwise, a non-local problem is obtained as the limiting form     

层状横观各向同性饱和地基上圆板的非轴对称振动

研究了层状横观各向同性饱和地基上弹性圆板的非轴对称振动问题．首先,通过方位角的Fourier变换,将圆柱坐标系下横观各向同性饱和土的三维动力方程转化为一阶常微分方程组,基于径向Hankel变换,建立问题的状态方程,求解状态方程后得到传递矩阵;其次,利用传递矩阵,结合层状饱和地基的边界条件、排水条件及层间接触和连续条件,给出了任意简谐激振力作用下层状横观各向同性饱和地基动力响应的通解;然后,按混合边值问题建立层状饱和地基上弹性圆板非轴对称振动的对偶积分方程,并将对偶积分方程化为易于数值计算的第二类Fredholm积分方程,并给出了算例．     

Helmholtz方程周期Green函数及其偏导数截断误差收敛阶的分析

在应用边界元方法求解Helmholtz方程周期边值问题时,需要构造以周期Green函数或其偏导数为核函数的积分算子形式的解.由于Helmholtz方程的周期Green函数G~P是一个函数项级数,该级数的通项是Hankel函数,在数值求解中,需要对其进行截断,从而很有必要研究其截断误差.本文根据Hankel函数在变量趋于无穷大时的渐近展开式,并结合Abel不等式,证明了G~P及其一阶偏导和二阶混合偏导一致收敛,且其截断误差收敛阶均为O(1/p~(1/2)).最后,通过数值实验验证了理论证明的正确性.本文的证明方法也可被用于证明其它一些方程周期Green函数的收敛性问题.     

The Well Posedness in a Parabolic Multiple Free Boundary Problem

We consider a free boundary problem in a parabolic partial differential equation with multiple interfacial curves which is reduced to a reaction-diffusion equation. The forcing term of this problem is not continuously differentiable and thus we use Green's function to make a regular one. The existence, uniqueness and dependence. on initial conditions will be shown in this paper.     

FURTHER INVESTIGATION OF THE VOLTERRALOTKA COMPETITION MODEL WITH DIFFUSION

In this paper, tile existence of coexistence states in the Voterra-Lotka competition model under Dirichlet boundary conditions is the major concern. Attention will be focused on the logistic equation. With a comparison theorem an inequality satistisfied by the solution of logistic equation is established. Some improved sufficient conditions for the existence of coexistence states are obtained.     

On the ZK equation with a directional dissipation

This paper studies the generalized Zakharov-Kuznetsov-Burgers equation. The initial value problem associated to this equation will be investigated in the nonhomogeneous Sobolev spaces and some suitable weighted spaces, under appropriate conditions. Moreover, an ill-posedness result (in some sense) will be proved in the anisotropic Sobolev spaces. Furthermore some exact traveling wave solutions of this equation will be obtained.     

用微分不等式对二次方程奇摄动问题解的估计

利用微分不等式对二次方程奇异摄动问题的解作出了估计,得出了本问题任意阶的一致有效的渐近展开式.     

Projection method for solving degenerate first-order identification problem

In this paper we study an inverse problem for a degenerate differential equation on a Banach space. A projection method will be used to reduce the problem to a regular abstract inverse problem. To this end some conditions on the operators are assumed to avoid the calculations of some inverses of the involved operators.     

Generic oscillations of second order delay differential equations with impulses

In this paper, we will study generic oscillation and generic nonoscillation of second order impulsive delay differential equations. Some necessary and sufficient conditions and sufficient conditions are obtained for both phenomena based on the root of characteristic equation.     

Optimal regularity for Schrödinger equations

In this paper we study the regularity theory for the Schrödinger equations under proper conditions. Furthermore, it will be verified that these conditions are optimal.     

层状多孔介质中渗流湿峰的不稳定分析

在部分饱和与部分干的层状多孔介质中，建立了一维渗流问题的数学模型．在自然的条件下，证明了一类退化抛物方程弱解的存在唯一性．揭示了一个重要性质，即当下层介质的孔隙比上层更粗时，层状交界面具有隔水作用．这一作用将会在展状交界面不均匀时导致指状湿峰的出现．同时也说明，较粗孔隙的上层具有防止水分蒸发的作用．     

Mathematical simulation of deformation and wave processes in multilayered structures

The deformation and wave processes induced by collisions of an impactor with deformable layered targets of various configurations are analyzed. The numerical solution of such problems is associated with an adequate treatment of wave processes in a continuous medium, which is an especially difficult task in the case of layered targets. To deal with the former problem, it is proposed to use adaptive Lagrangian triangular meshes. Wave processes are simulated using the grid-characteristic method, which can serve as a basis for algorithms that do not fail near the boundary of the computational domain and at numerous material interfaces. Additionally, hybrid and hybridized grid-characteristic schemes are applied that substantially improve numerical solutions with steep gradients (discontinuous solutions). These methods provide an adequate treatment of wave processes in layered targets (wave reflection and refraction at contact surfaces, secondary-wave interaction, changes in the conditions on these boundaries, etc.).     

Stochastic flows of diffeomorphisms on an open set in rn

In this paper, we will give sufficient conditions for the solution to a stochastic differential equation (SDE) on an open set D in R" to define a stochastic flow of diffeomorphisms of D onto itself. Since a necessary and sufficient condition for the solution to determine a stochastic flow of diffeomorphisms is that the original SDE and its adjoint SDE are both strictly conservative, we will concentrate our attention on finding sufficient conditions for the SDE to be strictly conservative. It will be etablished that the strict conservativeness follows if the vector fields governing the SDE decay suitably near the boundary dD in the direction transversal to 3D and some additional assumptions are satisfied.     

奇异椭圆方程多重解的存在性

在这篇论文中,首先给出了奇异椭圆方程(1.1)正解在零点附近的一个精确的估计.然后,结合这个估计式,利用Ekeland变分原理和山路引理,在一定条件下得到了方程(1.1)多重正解的存在性.     

用时变雷诺方程模型模拟孤立波与半圆型防波堤的相互作用

以时变雷诺方程为控制方程,用k-ε模型封闭该方程,采用体积函数(VOF)方法来跟踪波动自由表面,建立了二维垂向波浪数学模型,并用已有的实验资料进行了验证．随后用该模型模拟了半圆型防波堤与孤立波在淹没、平顶水位、完全露顶且不越浪3种典型工况下的相互作用过程．得到了半圆堤附近的流场、压强场和波面的变形过程．结果表明,在淹没状态下,半圆堤背浪面的底部会产生涡旋;平顶水位时,由于越浪的冲击作用,在半圆堤的背浪面将逐渐形成一对较大的涡旋,而半圆堤背浪面的底部,速度始终相对较小;而在露顶不越浪时,半圆堤的迎浪面会出现波浪的二次爬升的现象．为进一步研究结构物附近的污染物的输移扩散和泥沙运动提供基础．     

Morse index of layered solutions to the heterogeneous Allen-Cahn equation

Let u? be a single layered radially symmetric unstable solution of the Allen-Cahn equation −?²Δu=u(u−a(|x|))(1−u) over the unit ball with Neumann boundary conditions. We estimate the small eigenvalues of the linearized eigenvalue problem at u? when ? is small. As a consequence, we prove that the Morse index of u? is asymptotically given by [μ^∗+o(1)]?−(N−1)/2 with μ^∗ a certain positive constant expressed in terms of parameters determined by the Allen-Cahn equation. Our estimates on the small eigenvalues have many other applications. For example, they may be used in the search of other non-radially symmetric solutions, which will be considered in forthcoming papers.     

Fixed point indices and invariant periodic sets of holomorphic systems

This note presents an intuitive method to study center families of periodic orbits of complex holomorphic differential equations near singularities, based on some iteration properties of fixed point indices. As an application of this method, we will prove Needham's theorem in a more general version.