Banach空间中二阶积-微分方程初值问题的解

利用半序方法和新的比较结果,研究了Banach空间中二阶积-微分方程初值问题的最大解、最小解、解的存在与相应解的迭代逼近.本文结果仅使用了下解或上解以及某些较弱的条件,并推广和改进了某些已知结果(见文[1-10]).     

Analyticity of classical steady needle crystals

This paper is a continuation of our previous work “Rigorous results in selection of steady needle crystals, J. Differential Equations 197 (2004) 349-426”. It concerns analyticity of a classical steadily translating needle crystal. It is proved that any classical solution to the needle crystal problem with sufficiently small but nonzero surface tension, if its slope deviation is close to some Ivantsov zero-surface-tension solution and if its curvature satisfies some algebraic decay conditions at ∞, must belong to the analytic function space A₀ defined in §1 and chosen in the previous study mentioned above. The analyticity result implies that there can be no classical steady needle crystal solution when anisotropy is zero.     

Existence and selection of steady bubbles in a Hele–Shaw cell

This paper concerns the existence of a steadily translating bubble in a Hele–Shaw cell for small but non-zero surface tension ². We rigorously conclude that for bubble velocity U relative to the fluid velocity at infinity in the interval (1,2), analytic symmetric solutions exist in the asymptotic limit of surface tension ²→0 if and only if the Stokes constant for a relatively simple nonlinear differential equation is zero. This Stokes constant S depends on the parameter α(0,1) corresponding to bubble size and . Earlier calculations have shown S to be zero for a discrete set of values of a.     

Existence and uniqueness of analytic solution for unsteady crystals with zero surface tension

We study the initial value problem for two-dimensional dendritic crystal growth with zero surface tension. If the initial data is analytic and close to Ivantsov steady solution, it is proved that unique analytic solution exists locally in time. The analysis is based on a Nirenberg Theorem on abstract Cauchy-Kovalevsky problem in properly chosen Banach spaces.     

Instability of steady states for nonlinear wave and heat equations

We consider time-independent solutions of hyperbolic equations such as _∂ttu−Δu=f(x,u) where f is convex in u. We prove that linear instability with a positive eigenfunction implies nonlinear instability. In some cases the instability occurs as a blow up in finite time. We prove the same result for parabolic equations such as t_∂u−Δu=f(x,u). Then we treat several examples under very sharp conditions, including equations with potential terms and equations with supercritical nonlinearities.     

On weak solution to the steady compressible flow of nematic liquid crystals

In this paper, we study the three‐dimensional‐simplified Ericksen‐Leslie system for the steady compressible flow of nematic liquid crystals in a bounded domain. It is proved that the existence of a weak solution for the adiabatic exponent γ > 1 provided the initial direction field in the upper hemisphere.     

一类积-微分参数方程的非负解

本文讨论了迁移理论中一类控制临界本征方程．运用Ｌ２空间上的线性算子理论，我们获得了这类方程的的控制参数在复平面的分布情况及非负解存在唯一的条件．     

A stability of the steady flow of compressible viscous fluid with respect to initial disturbance (v∞ ≠ 0)

We consider a compressible viscous fluid with the velocity at infinity equal to a strictly non‐zero constant vector in ?³. Under the assumptions on the smallness of the external force and velocity at infinity, Novotny–Padula (Math. Ann. 1997; 308 :439– 489) proved the existence and uniqueness of steady flow in the class of functions possessing some pointwise decay. In this paper, we study stability of the steady flow with respect to the initial disturbance. We proved that if H³‐norm of the initial disturbance is small enough, then the solution to the non‐stationary problem exists uniquely and globally in time, which satisfies a uniform estimate on prescribed velocity at infinity and converges to the steady flow in L_q‐norm for any number q? 2. Copyright © 2006 John Wiley & Sons, Ltd.     

一类Navier-Stokes方程组的弱解

本文讨论了一类Ｎａｖｉｅｒ Ｓｔｏｋｅｓ型方程组初边值问题的可解性及解的性质，在解的存在性，正则性，渐进性，周期性等方面得到了某些新结果，进而将这些结果作了适当的应用．     

广义Burger方程的解析解

本文讨论广义Burger方程的解析解,我们证明了:当粘性系数γ(t)=常数或对γ(t)=(3kt k_1)~(-1/3)时,方程满足“有条件的Painlev(?)可积”.并求出了相应的解析解.     

On a new class of abstract neutral differential equations

In this work we introduce a new class of abstract neutral differential equations and study the existence of mild and strict solutions. Some concrete applications involving partial neutral differential equations are considered.     

Asymptotic expansion for 1D steady nonuniform enthalpy compressible supersonic flow at high Reynolds number

The exact solution of one-dimensional (1D) steady compressible Navier–Stokes (N-S) equations at high Reynolds number has not been given yet under nonuniform total enthalpy when the Prandtl number ( $Pr$) is not equal to 0.75 since Becker's work in 1922. In this paper, we give an asymptotic expansion of the solution of the above equations at high Reynolds number by using the method of matched asymptotic expansions and prove convergence of the asymptotic solution under some assumptions. By analyzing the dimensionless form of one-dimensional steady compressible Navier–Stokes equations, we find that if there are extreme points inside the boundary layer, the number of extreme points of velocity is at most one more than that of total enthalpy and the extreme points of each flow variables are different from each other. Based on the second-order asymptotic expansion solution, we show that there are extreme points inside the thin boundary layer under some special conditions. Examples are given to verify theoretical analysis. The present asymptotic expansion solution is valuable for verifying the efficiency of high-order numerical methods in flow simulation of high Reynolds number.     

A series solution of the nonlinear Volterra and Fredholm integro-differential equations

In this paper, the HAM is applied to obtained the series solution of the high-order nonlinear Volterra and Fredholm integro-differential problems with power-law nonlinearity. Two cases are considered, in the first case the set of base functions is introduced to represent solution of given nonlinear problem and in the other case, the set of base functions is not introduced. However, in both cases, the convergence-parameter provides us with a simple way to adjust and control the convergence region of solution series.     

Analytical treatment and convergence of the Adomian decomposition method for a system of coupled damped wave equations

An abstract result is proved for the convergence of Adomian decomposition method for partial differential equations that model evolutionary systems. Moreover, we prove that this decomposition scheme applied to a system of wave equations coupled in parallel with homogeneous Dirichlet boundary conditions, is convergent in a suitable Hilbert space. Furthermore, this technique is utilized to find closed-form solutions for the problem under consideration.     

Analytic solutions of an iterative functional differential equation

This paper is concerned with a functional differential equation x^′(z)=1/x(az+bx(z)), where a, b are two complex numbers. By constructing a convergent power series solution y(z) of a auxiliary equation of the form b²y^′(z)=(y(μ²z)−ay(μz))(μy^′(μz)−ay^′(z)), analytic solutions of the form for the original differential equation are obtained.     

A remark on the definitions of viscosity solutions for the integro-differential equations with Lévy operators

We prove the equivalence of the three different definitions of the viscosity solution for the integro-differential equation with the Lévy operator. The two of the definitions are known in the preceding works of the author and the others, and the last one is new. A construction of a sequence of the approximating test functions to the subsolution (or the supersolution) is indispensable for the proof, and it is done explicitly in the paper.     

Existence of analytic solutions of an iterative functional equation

This paper is concern analytic solutions of an iterative functional equation of the form

f(p(z)+q(f(z)))=h(f(z)),z∈C.     

Analytic solutions of a second order iterative functional differential equation

This paper is concerned with an iterative functional differential equation

c₁x(z)+c₂x^′(z)+c₃x^″(z)=x(az+bx^′(z))