部分浸润三维振荡物体的辐射短表面波

本文讨论了水面上三维物体的任意振荡运动所产生的短表面波。在离开物体的远场区,用射线法确定了辐射波的位相与振幅函数,在振幅函数中包含了一个未定常数因子。由文献[1]的结果,求得了接近物体水线处的近场边界层解,其振幅依赖于物体的整体壁面形状与在水线的垂直横截面上物体壁面在水线的斜度。由远场解与近场边界层解的匹配确定了远场辐射波的振幅函数中的未定常数。对于半浸润球体作垂直振荡运动的特殊情形,本文的结果与文献[2]的结果完全一致。     

在集中力和集中力偶作用下不同弹性材料圆形界面的裂纹问题

运用推广的Schwarz延拓原理结合对复应力函数的奇性主部分析,求解一类有集中荷载的平面弹性问题,十分有效。文[1]用此方法研究了同种材料的弹性问题。本文把它推广于在集中力和集中力偶作用下不同弹性材料的圆形界面上有多条裂纹的情形,求出了几种典型情况复应力函数的封闭解,算出了应力强度因子,并由此导出一系列特殊解答,其中两个在文[1]、[6]中找到一致结果。     

方程λ＋a＋be^τλ=0全部根的精确分布

考虑方程其中a，b为任意实常数,τ为正常数．本文在复数域上求得了方程（*）全部根的精确分布．在文[1]和[2]中应用Laplace变换法，得到了滞后型方程初值问题的形式解公式下：其中x（t）为初值问题的解，这里H（θ）为Heaviside函数．方程（*）为初值问题（E）中方程的特征方程．应用本文结果于形式解公式（1．1），可求得初值问题（E）的精确解．篇幅所限，此问题另文讨论．     

两互相垂直的平面间的层流边界层

本文得到了两互相垂直的平面间的层流边界层的三级近似解.在边界层中,边界层方程中的粘性项和惯性项具有相同的数量级[3].本文则首先假定惯性项大于粘性项去求解边界层方程;然后,令粘性项大于贯性项.最后,取二者的平均值作为边界层方程的真实解.本文所得一级及二级近似解和文献[1]的结果相同.本文的三级近似解则较[1]的结果更精确.     

无限相似单元法的收敛性

[1]与[2、3]相互独立地提出了无限相似单元法。[2、3]讨论了拉普拉斯方程在有角点区域上的奇性解。[1]讨论了平面弹性力学方程组的奇性解及其对应的应力强度因子,但[1]中的方法对于包括拉普拉斯方程在内的一类椭圆型方程都是适用的。这一方法还可以推广到无界区域上去,这部分内容将在另文中讨论。     

钢筋混凝土板的弯曲问题解法

本以含高阶项的试函数，用Galerkin法求得了周边固支的钢筋混凝土板在均布荷载作用下的挠度表达式，所得结果在特殊情况下与[1]的各向同性均质板在均布荷载下的结果相符合．     

推广的人口理论扩散模型的初边值问题

其中 a_1>0,a_2(?)0和 a 均是常数,m 为正整数,l、h 为某个正常数.u_0(x)是[0,l]上给定的五次连续可微函数。方程(1)是人口增长和迁移问题中一类数学模型的推广形式。     

非均匀双周期裂纹场的反平面问题

本文从虎克定律与平衡方程出发,利用复变函数映象的理论.将裂纹发生的矩形区域保角变换到ζ平面的上半平面去.再根据H.И.穆斯黑里什维利[1]的理论,对非均匀双周期裂纹场的反平面问题,我们求得闭合解,并推出了应力强度因子.     

含多个非线性项的时滞积分不等式及其应用

本文在文献[Agarwal et al.,J.Inequ.Appl,2008,Art.ID 908784,15 pages]和文献[Chen et al.,J.Inequ.Appl.,2009,Art.ID 258569,15 pages]的基础上,建立了一类新的非线性时滞积分不等式。第一个参考文献中不等式的未知函数u是一元函数,右端第一项是正常数c;第二个参考文献中不等式右端第一项也是正常数c,第二项的被积函数中只含未知函数线性因子;本文研究的不等式中未知函数是二元函数,右端第一项是不减的正函数,第二项被积函数中含有未知函数的非线性因子,积分号外还有一个非常数因子.最后,本文用研究不等式得到的结果讨论了时滞偏微分方程初边值问题的有界性.     

粘弹性流体流经竖直表面时的瞬时自然对流

静止流体中,在一个竖直的、不可渗透的等温表面附近,研究粘弹性边界层的流动及其热传导.得到其控制方程,并利用MackCormak技术对其进行数值求解.与先前发表的关于该问题特例的结果相比较,有着很好的一致性.对于不同的粘弹性参数值,图示了速度和温度分布、边界层厚度、Nusselt数、局部摩擦因数等典型结果.一般而言,粘弹性流体与Newton流体相比较,由于拉应力的促进作用,流体动力边界层里的速度是增加的,热边界层里的温度是下降的.粘弹性参数值越高,摩擦因数和传热系数越高.     

几类特定边界值条件下的常微分方程特征值问题

在文献[1]的基础上,借助于图形分析方法,讨论了几类特定边界值条件下的特征值问题.同时,本文对文献[1]中的错误结论作出了更正.本文给出的方法对讨论非线性边值问题的可解性提供了一种新的途径.     

A note on the use of modified Adomian decomposition method for solving singular boundary value problems of higher-order ordinary differential equations

This paper extend the work [Yahya Qaid Hasan, Liu Ming Zhu. Solving singular boundary value problems of higher-order ordinary differential equations by modified Adomian decomposition method. Commun Nonlinear Sci Numer Simul. doi :10.1016/j.cnsns.2008.09.027] to high order of singular boundary value problems. Solution of these problems is considered by proposed modification of Adomian decomposition method. The proposed method can be applied to linear and nonlinear problems. Some examples are presented to show the ability of the method for linear and non-linear ordinary differential equation.     

A note on exact travelling wave solutions for the modified Camassa-Holm and Degasperis-Procesi equations

Exact solutions for the modified Camassa-Holm and Degasperis-Procesi equations by Liu et al. (2010) [Y.F. Liu, X.Y. Zhu, J.X. He, Factorization technique and new exact solutions for the modified Camassa-Holm and Degasperis-Procesi equations, Appl. Math. Comput. 217 (2010) 1658-1665] are investigated. Liu et al. has used the factorization technique to reduce the modified Camassa-Holm and Degasperis-Procesi equations to first-order ordinary differential equations, and then derived some exact travelling wave solutions by direct integral method. In this note, we will explain that the implementation of the so-called factorization technique is completely unnecessary. Moreover, based on the method of complete discrimination system for polynomial, we shall demonstrate that the general explicit exact solution and its classification for the above two types of equations can be obtained directly and many exact solutions by Liu et al. are our special cases. Besides, some known results in previously relevant literatures are extended and some simple remarks are also made.     

An approximate solution of the MHD Falkner–Skan flow by Hermite functions pseudospectral method

Based on a new approximation method, namely pseudospectral method, a solution for the three order nonlinear ordinary differential laminar boundary layer Falkner–Skan equation has been obtained on the semi-infinite domain. The proposed approach is equipped by the orthogonal Hermite functions that have perfect properties to achieve this goal. This method solves the problem on the semi-infinite domain without truncating it to a finite domain and transforming domain of the problem to a finite domain. In addition, this method reduces solution of the problem to solution of a system of algebraic equations. We also present the comparison of this work with numerical results and show that the present method is applicable.     

The Boltzmann equation with frictional force

The Euler equations with frictional force have been extensively studied. Since the Boltzmann equation is closely related to the equations of gas dynamics, we study, in this paper, the Boltzmann equation with frictional force when the external force is proportional to the macroscopic velocity. It is shown that smooth initial perturbation of a given global Maxwellian leads to a unique global-in-time classical solution which approaches to the global Maxwellian time asymptotically. The analysis is based on the macro-micro decomposition for the Boltzmann equation introduced in Liu et al. [Energy method for the Boltzmann equation, Physica D 188 (3-4) (2004) 178-192] and Liu and Yu [Boltzmann equation: micro-macro-decompositions and positivity of shock profiles, Comm. Math. Phys. 246(1) (2004) 133-179] through energy estimates.     

Multiple positive solutions of Dirichlet boundary value problems for second order impulsive differential equations

This paper is devoted to study the existence of multiple positive solutions for the second order Dirichlet boundary value problem with impulse effects. The main results here is the generalization of Liu and Li [L. Liu, F.Y. Li, Multiple positive solution of nonlinear two-point boundary value problems, J. Math. Anal. Appl. 203 (1996) 610-625] for ordinary differential equations. Existence is established via the theory of fixed point index in cones.     

Analysis of the stress singularity for a bi-material V-notch by the boundary element method

A new algorithm coupling the boundary element technique with the characteristic expansion method is proposed for the computation of the singular stress field in the V-notched bi-material structure. After the stress asymptotic expansions are introduced into the linear elasticity equilibrium equations, the governing equations at the small sector dug out from the bi-material V-notch tip region are transformed into the ordinary differential eigen-equations. All the parameters in the asymptotic expansions except the combination coefficients can be achieved by solving the established eigen-equations with the interpolating matrix method. Furthermore, the conventional boundary element method is applied to modeling the remaining structure without the notch tip region. The combination coefficients in the asymptotic expansion forms can be computed by the discretized boundary integral equations. Thus, the singular stress field at the V-notch tip and the generalized stress intensity factors of the bi-material notch are successfully calculated. The accurate singular stress field obtained here is very useful in the evaluation of the fracture property and the fatigue life of the V-notched bi-material structure.     

Similarity solutions for magneto-forced-unsteady free convective laminar boundary-layer flow

The group theoretic method is applied for solving problem of a unsteady free-convective laminar boundary-layer flow on a non-isothermal vertical plate under the effect of an external velocity and a magnetic field normal to the plate. The application of two-parameter transformation group reduces the number of independent variables, by two, and consequently the system of governing partial differential equations with the boundary and initial conditions reduces to a system of ordinary differential equations with appropriate corresponding conditions. The Runge–Kutta shooting method used to find the numerical solution of the velocity field, shear stress, heat transfer and heat flux has been obtained. The effect of the magnetic field on the velocity field and the Prandtl number on the heat transfer and heat flux has been discussed.     

Nonsimilarity solutions of a class of free convection problems

The nonsimilarity solutions of laminar boundary layer free convection flows along a rotating isothermal plate under nonuniform gravity and along a non isothermal vertical plate have been obtained. The governing nonlinear partial differential equations are reduced to a set of ordinary differential equations and then solved numerically using the method of ‘shooting’ with least square convergence criterion. The results for large values of axial distance are found to be more accurate than those obtained by series and integral methods, but for small values of axial distance they are in good agreement.     

Effects of thermal radiation and magnetic field on unsteady mixed convection flow and heat transfer over an exponentially stretching surface with suction in the presence of internal heat generation/absorption

In this paper, the problem of unsteady laminar two-dimensional boundary layer flow and heat transfer of an incompressible viscous fluid in the presence of thermal radiation, internal heat generation or absorption, and magnetic field over an exponentially stretching surface subjected to suction with an exponential temperature distribution is discussed numerically. The governing boundary layer equations are reduced to a system of ordinary differential equations. New numerical method using Mathematica has been used to solve such system after obtaining the missed initial conditions. Comparison of obtained numerical results is made with previously published results in some special cases, and found to be in a good agreement.