一个奇异抛物方程Neumann问题的可解性(英文)

The qualitative properties of solutions of a Neumann problem for the singular parabolic equation ut = （u^m-1 ux）x （-1 〈 m ≤0） is studied in this paper. It is proved that there exists a unique global smooth solution which depends on the initial value. The large time behavior of the solutions is also discussed.     

A MAGNUS EXPANSION FOR THE EQUATION Y''''= AY - YB

1. IntroductionThis paper is concerned with the solution of the linear ordinaly fferelltial syStemwhere both A and B are Lipschitz fUnctions that map [0, co) illto Ma, the set Of m x m ~rices,and YO E M.. The equation (1.1) features in numerous applications and the approalmation Ofits solution is of interest. Moreover, solutions of this equation often display ilitewting geondry.For example, B = A results in the isoSPectral flowwhose inVariats are the eigenvalues of YO and which feature…     

LOCAL STABILITY OF TRAVELLING FRONTS FOR A DAMPED WAVE EQUATION

The paper is concerned with the long-time behaviour of the travelling fronts of the damped wave equation αutt+ut=uxx V’(u) on R.The long-time asymptotics of the solutions of this equation are quite similar to those of the corresponding reaction-diffusion equation ut=uxxV’(u).Whereas a lot is known about the local stability of travelling fronts in parabolic systems,for the hyperbolic equations it is only briefly discussed when the potential V is of bistable type.However,for the combustion or monostable type of V,the problem is much more complicated.In this paper,a local stability result for travelling fronts of this equation with combustion type of nonlinearity is established.And then,the result is extended to the damped wave equation with a case of monostable pushed front.     

AN IMPROVEMENT OF A RESULT OF IVOCHKINA AND LADYZHENSKAYA ON A TYPE OF PARABOLIC MONGE-AMP\`ERE EQUATION

For the initial-hotmdary value problem about a type of parabolic Monge-Ampere equation of the form (IBVP): {-Dtu + (deD^2xu)^1/n = f(x,t), (x,t) ∈ Q = Ω×(0,T)}, u(x,t) =Ф(x,t)(x,t) ∈δpQ}, where Ω is a bounded convex domain in R^n, the result in [4] by Ivochkina and Ladyzheokaya is improved in the sense that, under assumptions that the data of the problempossess lower regularity and satisfy lower order compatibility conditions than than in [4], the existence of classical solution to (IBVP) is still established (see Theorem 1.1 below). This cannot be reallzed by only using the method in [4]. The main additional effort the authors have done is a kind of nonlinear perturbation.     

ON THE EQUATION □φ=｜↓△φ｜^2 IN FOUR SPACE DIMENSIONS

This paper considers the following Cauchy problem for semilinear wave equations in n space dimensions □φ=F(δφ),φ(0,x)=f(x),δtφ(0,x)=g(x),whte □=δt^2-△ is the wave operator,F is quadratic in δεφ with δ=(δt,δx1,…,δxn).The minimal value of s is determined such that the above Cauchy problem is locally wellposed in H^s.It turns out that for the general equation s must satisfy s>max(n/2,n+5/4).This is due to Ponce and Sideris (when n=3)and Tataru (when n≥5).The purpose of this paper is to supplement with a proof in the case n=2,4.     

A RIGOROUS DERIVATION OF THE GROSS-PITAEVSKII HIERARCHY FOR WEAKLY COUPLED TWO-DIMENSIONAL BOSONS

In this article, we consider the dynamics of N two-dimensional boson systems interacting through a pair potential N-1Va(xi-xj) where Va(x) = a-2V (x/a). It is well known that the Gross-Pitaevskii (GP) equation is a nonlinear Schrdinger equation and the GP hierarchy is an infinite BBGKY hierarchy of equations so that if ut solves the GP equation, then the family of k-particle density matrices {k ut, k ≥ 1} solves the GP hierarchy. Denote by ψN,t the solution to the N-particle Schrdinger equation. Under the assumption that a = N-ε for 0 ε 3/4, we prove that as N →∞ the limit points of the k-particle density matrices of ψN,t are solutions of the GP hierarchy with the coupling constant in the nonlinear term of the GP equation given by ∫V (x) dx.     

ON THE EQUATION □φ = |vφ|2 IN FOUR SPACE DIMENSIONS

This paper considers the following Cauchy problem for semilinear wave equations in n spacedimensions□φ = F( φ),φ(0, x) = f(x), tφ(0, x) = g(x),The minimal value of s is determined such that the above Cauchy problem is locally well-posed in Hs. It turns out that for the general equation s must satisfyThis is due to Ponce and Sideris (when n = 3) and Tataru (when n ≥ 5). The purpose of thispaper is to supplement with a proof in the case n = 2, 4.     

LOCAL CLASSICAL SOLUTION OF FREE BOUNDARY PROBLEM FOR A COUPLED SYSTEM

This paper considers a two-phase free boundary problem for coupled system including one parabolic equation and two elliptic equations. The problem comes from the discussion of a growth model of self-lnaintaining protocell in multidimensional case. The local classical solution of the problem with free boundary F : y = g(x,t) between two domains is being seeked. The local existence and uniqueness of the problem will be proved in multidimensional case.     

具加权非局部源反应扩散方程解的渐近行为（英文）

In this paper,we deal with the blow-up property of the solution to the diffusion equation u_t = △u + a(x)f(u) ∫_Ωh(u)dx,x∈Ω,t0 subject to the null Dirichlet boundary condition.We will show that under certain conditions,the solution blows up in finite time and prove that the set of all blow-up points is the whole region.Especially,in case of f(s) = s~p,h(s) = s~q,0 ≤ p≤1,p + q 1,we obtain the asymptotic behavior of the blow up solution.     

Quenching Phenomenon for a Parabolic MEMS Equation

This paper deals with the electrostatic MEMS-device parabolic equation u_t-?u =λf(x)/(1-u)~p in a bounded domain ? of R~N,with Dirichlet boundary condition,an initial condition u0(x) ∈ [0,1) and a nonnegative profile f,where λ 0,p 1.The study is motivated by a simplified micro-electromechanical system(MEMS for short) device model.In this paper,the author first gives an asymptotic behavior of the quenching time T*for the solution u to the parabolic problem with zero initial data.Secondly,the author investigates when the solution u will quench,with general λ,u0(x).Finally,a global existence in the MEMS modeling is shown.     

再生核空间中求解定态对流扩散方程*

本文在再生核空间W₂1中,给出定态对流扩散方程的一种级数形式的解析解,此解析解具有如下特点:1)解是由精确的形式给出;2)解是显式计算,不须解方程组;3)在数值求解中,每增加一个基数项,近似解的误差在空间范数意义下单调下降。最后对[2]中的算例,进行了计算,结果比[2]中给出的渐近解精度高。     

方程(dx/dt)=x~n sum from i=0 to (n-1) a_i(t)x~2的闭解的个数及存在的条件

本文给出方程n＝3时分别正好存在1个闭解，3个闭解，以及至少存在2个闭解的充分条件，并研究了这些闭解的稳定性．当n＝4且ai（t）（i＝0，1，2，3）为t的P次多项式时，文[1]曾猜想其时闭解重数的上界为max｛4，p＋3｝．本文举例指出，即使p＝3，闭解重数的上界也可以大于7．这说明该猜想不成立     

解y"=g(x,y)初值问题含参数线性多步方法的相容阶和收敛阶

1 引 言对于直接积分二阶常微分方程的初值问题 y"=g(x,y) y (x_0)=y_0,y'(x_0)=y"_0,x_0 x T,(1)     

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…     

关于圆柱壳定解方程的通解问题

本文证明了Vlasov[5]所提出的以应变一应力函数F(ξ,η)所表达的解,为圆柱壳的定解偏微分方程组的通解。     

Some typical behaviors of weak solutions of layered proous media equation

This paper is the continuation of [2]. Some typical behaviors of weak solutions of layered porous media equations with boundary conditions will be discussed in this paper. For example, asymptotically, the saturated regions can appear only either near the layered interface, or near the boundaries. The necessary and sufficient conditions for the occurrence of such phenomena will be given.     

OSCILLATION CRITERIA FOR NONLINEAR SECOND ORDER ELLIPTIC DIFFERENTIAL EQUATIONS

1.IntroductionOscillationtheoryforellipticdifferentialequationswithvariablecoefficielltshasbeenextensivelydevelopedinrecentyearsbymanyauthors(seee-g-,Allegretto[1,2l,Bugir['],Fiedler[5]'KitamuraandKusano['],Kural4]KusanoandNaitol1o]'NaitoandYoshidal12]'NoussairandSwanson[l3'14]'Swansonl15'l6]andthereferencescitedtherein).Inthispaper,weareconcernedwiththeoscillatorybehaviorofsolutionsofsecondorderellipticdifferelltialequatiollswithalternqtingcoefficients.Asusual,pointsinn-dimensionalEucli…     

Modelling of a deteriorating system with repair satisfying general distribution

In this paper, we model a deteriorating system that cannot be repaired “as good as new” after failures, the model comes from [19, Applied Mathematics and Computation, 217(2011), 4980-4989]. Suppose that the system has one repairman who can have multiple vacations, and if the system fails when the repairman is on vacation, it will wait for repair until the repairman is available. Herein the repair time is taken into account and supposes that the repair satisfies the general distribution. Under these assumptions, by means of the geometric process and the supplementary variable techniques, we derive a complete model of the partial differential equations, which will correct an error of mathematical model in [19]. Moreover, we deduce some important reliability indices of the system such as the availability of system, the probability of the repairman working and the rate of occurrence of failures. In particular, we prove that the rate of occurrence of failures m_f is not equal to zero.     

Blow Up of Solutions to One Dimensional Initial-boundary Value Problems for Semilinear Wave Equations with Variable Coefficients

This paper is devoted to studying the following initial-boundary value problemfor one-dimensional semilinearwave equationswith variable coefficients andwith subcritical exponent: $u_{tt}-∂_x(a(x)∂_xu)=|u|^p, x > 0, t > 0, n=1,$ where $u=u(x,t)$ is a real-valued scalar unknown function in $[0,+∞)×[0,+∞)$, here a(x) is a smooth real-valued function of the variable $x∈(0,+∞)$. The exponents p satisfies $1 < p < +∞$ in (0.1). It is well-known that the number $p_c(1)=+∞$ is the critical exponent of the semilinear wave equation (0.1) in one space dimension (see for e.g., [1]). We will establish a blowup result for the above initial-boundary value problem, it is proved that there can be no global solutions no matter how small the initial data are, and also we give the lifespan estimate of solutions for above problem.     

具有马尔可夫骨架的随机过程(英文)

在本文中，我们引入了具有马尔科夫骨架的随机过程的概念．具体讨论了一类重要的具有马氏骨架的随机过程─—（H，Q）─过程，得到了计算这种过程概率分布的向后和向前方程，计算了过程的一维分布以及给出了这种过程正则的充分必要条件．并且本文绘出了文献[3]中主要结果的证明．