差分方程

Basing on the nonatationary linear mild-slope equation developed by Hong Guangwen in 1995, a complete wave model is built considering the bottom friction, nonlinear dispersion relation, and allied reflection and diffraction of several islands. Integrating with corresponding physical and imaginary boundaries, it is solved through Alternating Direction Implicit difference method.

本文以洪广文(1995)推导的非定常线性波缓坡方程为基础，建立考虑底摩阻项，非线性弥散关系，及多岛屿绕射反射作用的缓坡方程求解模式，采用经典的ADI法差分格式，结合物理和虚拟边界条件进行求解。

Starting with the basic concept about particle transport and the universal form of transport equation, the discuss is concentrated upon the transport equation and the implicit difference scheme under 3-D Cartesian coordinate, as well as the transport equation and the discontinuous finite element scheme under 2-D cylindrical geometry.

从粒子输运的基本概念和输运方程的一般形式入手，重点讨论了三维直角坐标中子输运方程和隐式差分格式，以及二维柱坐标中子输运方程和间断有限元格式。

Because of spiral oil wedge, a oblique coordinate system was used to formulate the finite differential formulas of Reynolds equation, film thickness equation and velocity equation for accurate compute.

由于圆弧形油腔斜置，为计算准确在斜坐标系下推导出了雷诺方程、油膜厚度方程和速度方程的有限差分公式。

Therefore,it is necessary to research diffusion equation for suspended sediment because it describes the sediment move process in the water body.The equation is a various coefficients second-order linear partial differential equa-tion,such equation under complex boundary condition is very difficult to get its analytical solution,while its numerical solution relative analytical solution is more easier and has the obvious superiority:simple,the computation convenience.but to get a kind of difference format which is good accuracy and stability is not easy.

泥沙扩散方程实际上是一个变系数的二阶线性偏微分方程，这样的方程在各种复杂边界条件下求解是十分困难的，求它的解析解在数学上存在着难以克服的障碍，无法求出其精确解，因此常用数值方法求它的近似解，相比较而言，数值方法有着明显的优势：即简单灵活、计算方便快捷，但要寻找一种精度高、稳定性好、计算方便的差分格式也并非易事。

This section further presents three kinds of computation schemes, which are discretization schemes based on linear interpolation, locally quadratic interpolation and mixed quadratic and cubic interpolation.

吴微在[21]中使用三角剖分及外心对偶剖分给出了解双调和方程的基于Ciarlet-Raviart变分原理的混合广义差分法，理论分析部分采用了[26]中的有关思想。

Based on the wave equations of electromagnetic field, a new time-domain numerical method-direct difference solution of vector wave equation is researched. Calculating formulas of electric field and magnetic field are also given.

对电磁场波动方程进行了分析，研究了一种基于电场波动方程的时域数值方法―矢量波动方程的直接差分解法，给出了电场和磁场的计算公式。

In this paper, based on summarizing previous numerical studies on wave transformations, deriving an extended form of mild slope equation, which is taken as the governing equation. The equation simulates wave transformation in offshore area with finite difference.

本文在总结概述前人关于缓坡方程波浪数学模型的基础上，推导出一改进型缓坡方程，并以此为控制方程，采用有限差分方法，模拟近海海域的波浪变形。

Through the analysis of the flowing character of metal injection molding, a set ofessential equations describing the flowing process of metal ring injection molding areestablished on the bases of the general principles of hydrodynamics and calorifics.

通过对金属粉末注射成形流动过程规律的分析，从流体力学和传热学的基本原理出发，建立了一组描述圆筒形金属粉末注射成形流动过程的基本微分方程，经过假设与简化，得到一组简化的控制方程，采用有限差分法求解了这组微分方程，得到温度场。

Our approach to energy subbands in the active region of QCL is k · p method. Electron eigenvalues and eigenstates are calculated by solving Schrodinger and Poisson equations self-consistently.

k·p微扰方法下，利用有限差分法求解了化合物半导体的有效质量方程，在计算中考虑了超晶格界面处电子有效质量不连续性，自洽求解了掺杂有源区在不同外加电场下的薛定谔方程和泊松方程。

During the calculation of the early age temperature field, the early age physical and mechanical performance of concrete varies with its age, therefore in the second chapter we discuss the early age physical and mechanical performance of concrete and its development regulation with time, we emphasize elastic module and the development about the early age strength of concrete varying with time, at the same time consider the effect of shrink and creep upon the early age of concrete, in succession discuss how to confirm the physical parameter of thermodynamics of concrete.

之后讨论了混凝土的热物理参数的确定。为了能够正确合理的应用有限元方法求解早期混凝土温度场问题，第三章论述了求解温度场的有限元方法。第三章首先对热传导的微分方程作了阐述。之后确定温度场的边界条件。本章采用变分原理推导有限单元法计算温度场的公式。因此在第二小节叙述了变分原理，然后阐明了不稳定温度场的计算的三种方法，确定第四章分析中将采用向后差分法求解0#箱梁早期的温度场。

It has been put forward that there exists single Ball point and double Ball points on the symmetrical connecting-rod curves of equilateral mechanisms.

从鲍尔点的形成原理出发，分析对称连杆曲线上鲍尔点的产生条件，提出等边机构的对称连杆曲线上有单鲍尔点和双鲍尔点。

The factory affiliated to the Group primarily manufactures multiple-purpose pincers, baking kits, knives, scissors, kitchenware, gardening tools and beauty care kits as well as other hardware tools, the annual production value of which reaches US$ 30 million dollars.

集团所属工厂主要生产多用钳、烤具、刀具、剪刀、厨具、花园工具、美容套等五金产品，年生产总值3000万美元，产品价廉物美、选料上乘、质量保证，深受国内外客户的青睐