缓慢调制波在多孔海床上的演化

本文采用多重尺度法分析了具有缓慢调制的波列在多孔海床上的演化问题.海床上部波浪采用了势流理论,海床下部的渗流采用了Darcy定律.两者在海床面上进行衔接,从而导出了上部波浪的波幅一阶和二阶的调制方程,并求出了相应的解,下部渗压场的解亦同时给出.     

跨海特大型桥梁风-浪耦合作用的随机振动分析

考虑风-浪耦合场中风和波浪特征参数的相关性,建立了基于有限元法与边界元法联合分析的特大型桥梁风-浪耦合作用运动方程.其中,作用在大型深水基础上的波浪力采用势流理论和边界元法进行计算,并建立有限单元与边界元单元组的映射关系,将边界单元组上的波浪力映射到结构有限单元上;作用在桥梁上的气动力通过有限元法进行计算,包括由脉动风激发的非定常抖振力和由气弹相互作用产生的自激力.在此基础上,基于随机振动分析的高效算法——虚拟激励法,建立了计算桥梁风-浪耦合作用响应的分析方法.最后,针对某跨海超大跨桥梁方案进行研究,结果表明:与风致响应相比,风-浪耦合作用下桥梁深水基础内力显著增大,其中波浪激发的侧向剪力占主导地位,波浪激发的侧向弯矩在海床附近与风致响应基本相当,但在海床以下更大;斜风-波浪耦合作用下的主梁内力响应和深水基础内力响应比正交风-波浪耦合作用下的结果更大.因此,在跨海桥梁设计中,必须考虑风-浪耦合作用效应.     

二维波动方程吸收边界问题的精细积分解法

波动方程一般是描述各种各样的波浪(如声波、光波和水波浪)的微分方程．在科学研究中对各种波浪的研究需转化为求解波动方程定解问题,常用的求解方法有:解析法,级数法,数值方法(如有限元法、有限差分法)等．钟万勰提出了精细积分法(Precise Inte-     

弹性力学问题解唯一的边界积分方程

从积分方程式出发,应用基本解的特性分析,说明在力边值问题中,位移边界积分方程和面力边界积分方程的位移解不唯一.提出了位移解唯一的条件,建立了唯一解的位移边界积分方程和面力边界积分方程.实例计算结果表明唯一解的边界积分方程是有效的.     

基于Gauss全局径向基函数的近岸浅水变形波高数值计算新方法

应用Gauss全局径向基函数来模拟波浪浅水变形波高变化方程中的未知函数,经实例分析探讨得到了一种可用于求解该方程数值解的新方法,并将其计算结果与常用数值分析方法得到的数值解相互对比印证,证明了基于Gauss全局径向基函数法计算结果的正确性.经验证,Gauss径向基函数法的平均计算误差相比其他方法均要小,表明该方法拥有更高的计算精度.同时,根据Gauss全局径向基函数的逼近结果,得出了浅水变形波高变化微分方程数值解的拟合函数,在实际工程中,可以利用该拟合函数来代替原方程的解析解,研究成果可为求解近岸浅水区域波浪运动提供一种新思路.     

非线性边界条件下高维拋物方程解的全局存在性及爆破现象

该文研究了非线性边界条件下高维空间上更一般化的非线性抛物问题解的爆破现象以及全局解的存在性.通过构造辅助函数,并对方程中的已知数据项进行一些必要的假设,应用微分不等式技术,当爆破发生时推导了爆破时间的下界.也推到了方程的解一定发生的条件并得到了爆破时间的上界.同时,不管方程对外施力还是受到外力的作用,也研究了方程的解全局存在的条件.     

立方准晶压电材料的半空间问题北大核心CSCD

考虑了立方准晶压电材料的半空间问题.给出了反平面机械载荷和面内电载荷作用下立方准晶压电材料弹性问题的控制方程,结合半无限区域表面边界条件,利用算子理论和复变函数方法获得了立方准晶压电材料半空间问题一般解的表达式.基于一般解得到了集中线力作用下,半空间问题的声子场和相位子场的位移、应力以及电位移的解析表达式.     

横观各向同性压电材料的基本解

推导得到一组在体积力作用下压电材料平衡方程的一般解,对横观各向同性压电材料,利用一般解结合体积势理论及构造一类调和函数的方法,得到了无限体在集中力和点电荷作用下的位移和电势的有限形式的表达式,从而给出了边界元法中可用的基本解.     

完整Coriolis力作用下带有外源强迫的非线性KdV方程

利用摄动方法,从描写既有Coriolis力垂直分量又含有水平分量的位涡方程出发,给出了近赤道非线性Rossby波所满足的具有外源强迫的非线性KdV方程,并利用Jacobi椭圆函数展开法,求解了改进后的非线性KdV方程的行波解及孤立波解.通过分析KdV方程的行波解,指出Coriolis力的水平分量和外源对Rossby波动的影响.     

非线性自由表面波问题的差分解法

本文提出计算二维非定常位势流动的有限差分法,流动是因自由表面任意瞬间扰动所产生的.自由表面上同时满足动力和运动的非线性条件.本方法的基本特征是利用坐标变换将时间相关的物理计算域变换为固定域;建立迭代格式解Poisson方程以求速度势;通过快速富氏变换化为三对角型代数方程组计算未知量,因而大量节省计算机时.为解非定常自由表面波浪问题提供了一个有效的方法.引用了两个例题验证方法的可行性.     

Existence and Nonexistence of Traveling Wave Solutions for a Bistable Reaction-Diffusion Equation in an Infinite Cylinder Whose Diameter is Suddenly Increased

ABSTRACT

We consider a reaction-diffusion equation of bistable type in a square cylinder whose diameter varies with Neumann boundary conditions in dimension 2 and 3. We prove the nonexistence of generalized traveling wave solution of this equation when the diameter is suddenly strongly increased. At the same time, we prove that the solution of the equation with an exponentially decreasing initial condition cannot pass over a certain threshold far enough in the direction of propagation.

The proof is divided in two steps. First, we extend the solution in the cylinder to a solution of the same equation in the half space. Then we overestimate it using Green's functions.     

A Problem Connected with the Oblique Incidence of Surface Waves on an Immersed Cylinder

If we wish to calculate the forces due to surface waves impingingon an obstacle held immersed in the fluid, the Haskind relationsshow that these forces can be expressed in terms of potentialswhich represent forced motions of the obstacle in initiallycalm water. We consider in this paper one such potential forwaves obliquely incident on an infinitely long circular cylinder,this potential being a generalization of the heaving potentialfor the circular cylinder considered by Ursell. We considerthe high frequency case when the angle of incidence is not smalland obtain an integral equation for the velocity potential onthe cylinder. An approximate solution of the integral equationis obtained and this is used to obtain asymptotic approximationsto the wave amplitude at infinity and the virtual mass coefficient.     

Diffraction of reaction-diffusion waves: the conformal-mapped eikonal equation

The interaction of reaction-diffusion (RD) waves with obstacles is considered. The conformal map transformation of the eikonal equation is used for investigating the behavior of waves in the presence of movable boundaries. It is shown that using the conformal map, the complicated boundary conditions become simple Neumann boundary conditions and can be easily dealt with numerically. The process is applied to diffraction of RD waves by two disks in two dimensions. The approach is extended to three-dimensions and the obstacles considered are 2 two-tori. A stable stationary solution, in the form of an unduloid, trapped between 2 two-tori, is obtained. It is shown that, if the obstacles are located a distance apart, the wave moves away from its stationary position giving rise to regular and irregular motions, depending on the choice of initial solutions.     

Interaction of a Solitary Wave with a Permeable Cylindrical Breakwater

In this paper the diffraction of a plane first‐order solitary wave at a vertical permeable cylindrical wall with calculation of the wave loading on the permeable rigid cylinder is investigated. The analytical solution is obtained by means of a Fourier transformation technique. The numerical results are obtained by using the software MATHEMATICA version 3.0 to alculate inverse Fourier transforms.     

Dynamic analysis of anisotropic half space containing an elliptical inclusion under SH waves

Based on the methods of complex function, conformal mapping, and multipolar coordinate system, dynamic response of an elliptical inclusion embedded in an anisotropic half space is investigated. In order to find the solution of SH waves, the governing equation is transferred into its normalized form. Then, the scattering wave induced by the inclusion and the standing wave in the inclusion is deduced. Different incident wave angles and the corresponding anisotropy of the half space are considered to obtain the reflected waves. The elliptical inclusion is transferred into a unit circle by conformal mapping method, and then the undetermined coefficients in scattering wave and standing wave are solved by using the continuous condition at the boundary of the inclusion. Subsequently, the dynamic stress concentration factor (DSCF) around the inclusion is calculated and analyzed. Numerical results demonstrate that the distribution of the DSCF is mainly influenced by the incident wave angle and the incident wave number. It is affected by anisotropic parameters as well.     

强非线性广义 Boussinesq 方程孤波解的波形分析及求解

上海理工大学理学院\quad 上海 200093该文建立了强非线性广义 Boussinesq 方程的耗散项、波速、渐进值与波形函数的导数之间的关系.利用适当变换和待定假设方法,作者求出了上述广义 Boussinesq 方程的扭状或钟状孤波解,还求出了以前文献中未曾提到过的余弦函数的周期波解.进一步给出了波速对波形影响的结论,即:``好'广义 Boussinesq 方程的行波当波速由小变大时,波形由钟状孤波变成余弦函数周期波解;``坏'广义 Boussinesq 方程的行波当波速由小变大时,波形由余弦函数周期波解变成钟状孤波.     

The Reissner-Sagoci type problem for a non-homogeneous elastic cylinder embedded in an elastic non-homogeneous half-space

The problem considered is that of the torsion of a non-homogeneouselastic cylinder, which is embedded in a non-homogeneous elastichalf-space (matrix) of different rigidity modulus. A rigid discis bonded to the flat surface of the cylinder and torque isapplied to the cylinder through a rigid disc. It is assumedthat there is perfect bonding at the common cylindrical surface.Using integral transformation techniques the solution of theproblem is reduced to dual integral equations. Later on thesolution of the dual integral equations is transformed intothe solution of a Fredholm integral equation of the second kind.Solving the Fredholm integral equation numerically the numericalresults for torque and shear stress inside the cylinder areobtained and displayed graphically to demonstrate the effectof non-homogeneity of the elastic material on the torque andshear stress.     

Bi-solitons, breather solution family and rogue waves for the (2+1)-dimensional nonlinear Schr\"{o}dinger equation

In this paper, bi-solitons, breather solution family and rogue waves for the (2+1)-Dimensional nonlinear Schr\"{o}dinger equations are obtained by using Exp-function method. These solutions derived from one unified formula which is solution of the standard (1+1) dimension nonlinear Schr\"{o}dinger equation. Further, based on the solution obtained by other authors, higher-order rational rogue wave solution are obtained by using the similarity transformation. These results greatly enriched the diversity of wave structures for the (2+1)-dimensional nonlinear Schr\"{o}dinger equations     

Backlund Transformation and Exact Solution to Kadomtsev-Petviashvili Equation with Variable Coefficients

By using the homogeneous balance principle, we derive a Backlund transformation (BT) to (3+1)-dimensionaI Kadomtsev-Petviashvili (K-P) equation with variable coefficients if the variable coefficients are linearly dependent. Based on the BT, the exact solution of the (3+1)-dimensional K-P equation is given. By the same method, we derive a BT and the solution to (2+1)-dimensional K-P equation. The variable coefficients can change the amplitude of solitary wave, but cannot change the form of solitary wave.     

Reduction of the Sharma–Tasso–Olver equation and series solutions

This paper considers series solutions of the Sharma–Tasso–Olver (STO) equation. By using the extended homogenous balance method, we reduce the STO equation to a linear PDE and obtain Bäcklund transformation of it. Furthermore, the self-transformation of solutions for the STO equation is obtained. By the Bäcklund transformation and various series solutions of the PDE, abundant exact solutions of the STO equation are obtained including the multi-solitary wave solution, trigonometric function series solution, rational series solution and solution consisting of the three types of solutions.