差分方程

Based on time domain Maxwell equations, the basic theory of Finite Difference Time Domain of the cartesian coordinates is introduced in detail.

本文由时域麦克斯韦方程出发，在直角坐标系下介绍了时域有限差分方法的基本原理，分析了电磁波在空间的传播规律及吸收边界的吸收效果。

The central difference explicit scheme based on the dynamic equation can get good results.

而采用基於动力学方程的中心差分显式积分方法可以得到良好的数值结果。

For the time term, we use central difference methods to discrete; for the space term,we use finite volume element methods to discrete.

对方程的时间项，我们采用中心差分的方法离散，对空间项采用有限体积元方法进行离散，文中对误差给收敛性和稳定性给出了分析，同时给出了一些数值结果。

Absorbing boundary condition ; wave equation ; spectral element ; central difference method

吸收边界条件；波动方程；谱元；中心差分法

This equation includes the characteristic term of nonlinear flow, it is impossible to get the accurate solution.

方程含有非线性渗流的特征项，无法求得解析解，直接采用有限差分方法处理非线性项，计算量大，对算法的精度要求也很高。

First of all,we construct a semidiscrete finite difference scheme to Burgers equation with initial condition and Dirichret boundary conditions.

首先，对Burgers方程的初边值问题建立了一个半离散的有限差分格式。

This paper studies semi-discrete finite difference methods of constant coefficient heat equations .

本文主要研究了常系数热传导方程的半离散有限差分方法。

In the thesis, the fundamental formula of FFD method derives from the square root that is approximated by a continued fraction expansion in the one-way wave equation. Optimizations of the parameters of the finite-difference operator improve the validity of the method.

本论文用连分式近似单程波波动方程中的平方根导出FFD算法的基本公式，并对FFD算法中的有限差分算子进行了系数优化，进一步提高了计算的有效性。

Cavity flows both with and without sound excitation are studied by solving the 2 D time dependent Reynolds averaged Navier Stokes equations using explicit predictor corrector difference algorithm of Mac Cormack.

采用显式MacCorma－ck二步预估校正有限差分格式，求解二维雷诺平均非定常Navier－Stokes方程；并用Cebeci－Smith代数紊流模型作适当修正来模拟紊流效应，对有、无前缘声激励两种情况的空腔流场作了数值模拟，计算的振荡频率及振荡幅值都与实验结果基本符合，并且较好地模拟出了声激励对流场的影响。

After determining the control equation and defined problems for infiltration, redistribution and evaporation, implicit finite difference method was used for ponded infiltration, semi-infinite soil redistribution and semi-infinite evaporation. The calculated results agreed well with measured data.

9在确定了入渗、再分布及蒸发的控制方程及定解问题基础上，采用隐式差分格式对垂直一维积水入渗、半无限土体再分布及半无限土体蒸发进行了数值模拟，与计算结果对比表明，计算值与实测值比较符合。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。