带有非局部扩散的反应流动扩散方程的行波解

本文主要考虑带有非局部扩散项的反应流动扩散方程行波解的存在性问题.首先,利用Schauder不动点定理和上下解原理得到带有非局部扩散项的反应流动扩散方程行波解的存在性,再将所得的结论应用到带有流动项的Lotka-Volterra竞争模型上,最后,考虑了流动项对繁殖速度的影响.同时,本文得到的存在性结论可以应用到一般的反应流动扩散方程中.     

混合微通道中不稳定的广义Couette流

在一个平行板通道中,部分充满了均匀的多孔介质,部分为纯流体的流动区,对其微通道中完全发展的不稳定层流进行了数值分析,流动由其中一块板的运动和压力梯度所引起.多孔介质区域的流动,采用扩展的Brinkman模型,即Darcy模型,纯净流动区域的流动,采用Stokes方程.还对稳定的完全发展流进行了理论分析,给出了分界面速度、边界板处的速度和表面摩擦的闭式解.通过数值计算发现,稳定完全发展流的闭式解,和不稳定流动的数值解,在所有时间点上得到很好地吻合.     

Maxwell流体在震荡的矩形输送管道中的流动

分析了不可压缩Maxwell流体在震荡矩形截面管道中的非稳定流动问题.利用Fourier变换和Laplace变换作为数学工具,提出了问题的解,该解可以看成稳态解和暂态解之和.大倍数时,暂态消失,解可以表示为稳态解.在极限情况的案例中给出了Newton流体的解.当震荡频率不存在时,得到了Maxwell流体在震荡矩形截面管道中流动问题的解.最后,以图形形式给出不同参数时,矩形管道正弦震荡达到稳态所需要的时间.同时,分别描绘了x和y变化时的速度曲线.     

精确的磁流体动力学汇流解析解

就一个特殊的磁流体动力学(MHD)流动,即速度幂指数为-1时的汇流,得到著名的Falkner-Skan方程精确的解析解.解析解是封闭的,并有多重解分支.分析了磁场参数和壁面伸长参数的影响.发现了有趣的速度分布现象:即使壁面固定,回流区域依然出现.在一个罕见的FalknerSkan MHD流动中,得到了一组解,以精确封闭的解析公式表示,极大地丰富了著名的Falkner-Skan方程的解析解,也加深了对这重要又有趣方程的理解.     

Lin- Reissner-Tsien方程的自相似解

Lin-Reissner-Tsien方程描述了在跨音速近似下的不稳定跨音速流动.通过相似变换,将Lin-Reissner-Tsien方程简化为一个常微分方程.然后解析求解所得到的方程,并在某些情况下得到的正好是精确解.上述情况下无法得到精确解时,给出了数值模拟.还得到了行波解.     

宾汉流体沿斜面流动的稳定性分析*

本文讨论了在二维扰动情况下,宾汉流体沿外面流动的稳定性问题。在长波解情况下,得到了临界雷诺数的近似表示,并分析了屈服应力对流动稳定性的影响。     

低速非达西层状油藏DST段塞流试井模型研究

在分析了实际低速非达西层状油藏DST测试非自喷井渗流规律的基础上,导出了其有效井径数学模型．利用Laplace变换及特殊物理方程理论,导出了该模型的拉氏空间解析解,并利用简便的Stehfest数值算法进行数值反演,得出了实空间解,并绘制了无因次样板曲线．可有效的运用于现场DST段塞流试井分析．     

可渗透壁面上Falkner-Skan磁流体动力学流动的近似解

研究了可渗透壁面上Falkner-Skan磁流体动力学（MHD）边界层流动问题．利用结合了微分变换法（DTM）和Padé近似的DTM-Padé方法,得到了边界层问题的近似解和壁摩擦因数值．通过建立一个迭代程序,边界层问题的近似解被表示为幂级数的形式,而且以图和表形式对不同参数下的近似解结果与打靶法得到的数值结果进行了对比,近似解和数值解结果高度吻合,从而验证了所得问题近似解和结论的可靠性和有效性．并且,对求得的边界层问题近似解结果进行了讨论,分析了不同物理参数对边界层流动的影响．     

两种互不相溶流体在竖直的波状壁面和平行的平面壁面间作不稳定的混合对流传热

分析粘性、不可压缩、互不相溶流体,在竖直的波状壁面和光滑的平面壁间,传热传质混合对流的组合效应.得到无量纲控制方程的摄动解:0阶的均值部分和1阶的摄动部分.将所得到的1阶量,用小波长摄动级数展开,出现按指数阶分类的方程组.得到了0阶和1阶的解析表达式及其整体解,通过数值计算,用图形表明流体流动的显著特征以及传热特性.界面上应用适当的匹配条件,使分离的解相匹配.还针对控制参数的不同变化,分析了剪应力和Nusselt数的变化.发现Grashof数、粘性比、宽度比和导电率,对平行于流动方向的速度是有利的,对垂直于流动方向速度的影响正相反.     

悬浮固粒对二维混合层流动失稳特性的影响*

本文在不可压缩二维混合层流动方程的基础之上,通过添加固粒的作用项,推导得到了修正的瑞利方程;然后用数值计算方法解其特征方程,得到了悬浮固粒的质量密度、固粒和气流的速度比值以及Stokes数不同时二维混合层流动中扰动频率与空间增长率的关系曲线,给出了关于悬浮固粒对流场失稳特性影响的几个重要结论。     

Laminar boundary layers along an infinite porous plate in the presence of a transverse magnetic field

Exact solutions of the Navier-Stokes equations are derived by a Laplace-transform technique for two-dimensional, incompressible flow of an electrically conducting fluid past on infinite porous plate. It is assumed that the flow is independent of the distance parallel to the plate and that the velocity component normal to the plate is constant. A general formula is derived for the velocity distribution in terms of the given external velocity. The skin friction is obtained and some special cases are considered.     

边部注水时裂缝性油藏中水平井两相渗流

本文在流线不变的假定下研究边部注水时裂缝性油藏中水平井两相渗流问题,建立了双重孔隙介质中水平井两相流体垂直二维渗流的数学模型,并用特征线方法进行了精确求解,给出了裂缝系统和岩块系统中的饱和度分布以及水平井见水时间公式,从而为边部注水开发裂缝性油藏提供了必要的理论基础和工程计算方法。     

Existence and estimate of positive solutions to a nonlinear singular boundary value problem in the theory of dilatant non-Newtonian fluids

This paper presents a rigorous proof of existence and uniqueness of solutions to laminar boundary layer flow in power law non-Newtonian fluid. A theoretical estimate for skin friction coefficient is given, which is characterized by a power law exponent. The reliability and efficiency of the proposed estimate formula are verified by numerical results with a good agreement. The estimate formula can be successfully applied to give the value of the skin friction coefficient.     

关于薛定谔方程的一个注记

使用振幅-频率公式和残量可求解线性和非线性薛定谔方程,该方法在得到精确解的同时,求解过程相对其它方法比较简洁,但需对所得解进行检验,以避出现增解.     

一类交替型脉冲微分系统的解

主要讨论一类超前型与滞后型交替的脉冲微分系统.首先给出具常系数的脉冲微分系统解存在的充分条件以及解唯一的表达形式;对于变系数的微分系统也作了相应的讨论.     

Behavior near hyperbolic stationary solutions for partial functional differential equations with infinite delay

The aim of this work is to investigate the asymptotic behavior of solutions near hyperbolic stationary solutions for partial functional differential equations with infinite delay. We suppose that the linear part satisfies the Hille–Yosida condition on a Banach space and it is not necessarily densely defined. Firstly, we establish a new variation of constants formula for the nonhomogeneous linear equations. Secondly, we use this formula and the spectral decomposition of the phase space to show the existence of stable and unstable manifolds. The estimations of solutions on these manifolds are obtained. For illustration, we propose to study the stability of stationary solutions for the Lotka–Volterra model with diffusion.     

Potential flow of fluid from an elevated,two-dimensional source

When fluid is pumped from an elevated source it flows downward and then outward once it hits the base. In this paper we consider a simple two dimensional model of flow from a single line source elevated above a horizontal base and consider its downward flow into a spreading layer on the bottom. A hodograph solution and linear solutions are obtained for high flow rates and full nonlinear solutions are obtained over a range of parameter space. It is found that there is a minimum flow rate beneath which no steady solutions exist. Overhanging surfaces are found for a range of parameter values. This flow serves as a model for a two-dimensional water fountain, or approximates a similar flow in a density stratified environment.     

Optimal regularity for [`(?)] b\bar \partial _b on CR manifoldson CR manifolds

In this paper a new explicit integral formula is derived for solutions of the tangential Cauchy-Riemann equations on CR q-concave manifolds and optimal estimates in the Lipschitz norms are obtained.     

复双球垒域上一些奇异积分方程的直接求解（英文）

By means of the method of solid angle coefficients and the permutation formula on the building domain of complex biballs,direct solutions of some singular integral equations with variable coefficients are discussed and the explicit formulas for these solutions are obtained.     

Algebraic geometry and soliton dynamics

Algebro-geometric sectors of solutions of the KP hierarchy are described in terms of τ-functions and vertex operators. Some useful identities involving theta functions and prime forms on Riemann surfaces are provided which are applied to obtain explicit solutions in the bilinear formalism. By using a dressing method for τ-functions the soliton dynamics against the background of quasiperiodic solutions is characterized. Furthermore, a formula for the soliton shifts in terms of prime forms on Riemann surfaces is obtained.