查询词典 explicit difference scheme

This section presents two kinds of characteristic schemes, one is the natural use of the usual backward Euler characteristic difference scheme ( [60] ) onto the triangular mesh, the other replaces the backward Euler's method by modified Euler formula to approximate the characteristic differential equation, so that the discretization for characteristic curve can get up to second order accuracy.

本节给出了两种三角形网格上的特征差分格式，第一种是通常的向后Euler型特征差分格式（[60]）在三角形网格上的自然运用，第二种采用§3.3、§3.4的离散思想，使用改进的Euler公式代替向后Euler公式来近似特征微分方程，使其对特征线的离散达到了二阶精度。

Lastly, we study a model of the heat flow cryptosystem base on a linear pseudoparabolic equation. The C-N difference scheme arithmetic of the encryption and decryption problems is designed. Then the numerical simulation is done through computer programming. So by analysing the simulation data we deduce many regularly conclusions on the influence of the key functions to the encryption and decryption operations, which establish the theoretical base for the application of this cryptosystem.

最后，文章研究了一类基于线性伪抛物型方程的热流密码体制模型，设计了加、解密问题的C—N差分算法并通过计算机编程进行了数值模拟，得出了一些不同密钥函数对加、解密作业影响的规律性结论，为该密码体制的现实应用奠定了理论基础。

Improvement of MT migration tomography technology Based on the immanent relationship between tomography purpose and suitable frequency segment selection, we raise an entire frequency segment multi-parameter tomography scheme of MT finite difference migration. We establish a mathematical relationship among apparent electromagnetism reflectance, migration reflectance, background resistivity and the true resistivity distribution. After the introduction of TE/TM mode superpose rate, we carry out the associated resistivity tomography of two polarization mode to adapt the practical data interpolating situation.

大地电磁偏移成像的改进：针对频段选择和成像效果的内在关系，提出全频段、多参数有限差分偏移的解决方案；构建视反射系数、偏移反射系数、背景电阻率与实际电阻率分布的数学关系实现偏移电阻率成像；同时引入TE、TM模式加权因子以实现两个模式的联合偏移电阻率成像，更好的适应解释工作需要。

Not only is the method applied in this paper better to solve the iteration between unsteady convection and conduction and the boundary condition problem, but also is a developmental application on forward and backward difference of windward scheme under unsteady condition.

不仅较好地解决了对流换热和导热的迭代求解和边界条件的处理问题，还将迎风格式的向前和向后差分发展性地应用于非稳态求解过程。

By analyzing the reason of the numerical oscillation phenomenon and computing the temperature field in plate rolling process,it is found that numerical oscillation can be restrained effectively when the heat capacity matrix is lumped by using backward difference scheme.

近年来，许多研究人员采用有限元法分析热轧和淬火等过程中的瞬态温度场。

The thesis is organized as follows:In Chapter 1,a new partial differential equation model for Spontaneous Potential log in heterogeneous formations is introduced.At the same time,the existence and uniqueness of weak solution to the problem are proved,and the problem of resistance identification in SP log is studied.Furthermore,a jump condition capturing finite difference scheme is proposed and applied to solve such elliptic interface problems.The effects of various factors on SP response,which include objective layers resistivity,bed thickness,bore-hole diameter,invasion and water-flooded zones and so on,are investigated quantitatively by the proposed method, and satisfactory results are obtained.

具体安排如下：第一章首先建立复杂地层中自然电位测井的偏微分方程数学模型，证明了该边值问题弱解的存在唯一性，在此基础上研究了自然电位测井电阻率识别问题：然后发展了用于求解椭圆交界面问题的间断捕捉有限差分方法，利用该方法定量分析了目的层电阻率、地层厚度、井径、侵入带和水淹层等因素对自然电位测井响应的影响，取得了满意的结果。

Spectral element methods for partial differencial equation is introduced in this study from viewpoint of the collocation approximation of Chebyshev polynomial. Wave Equation and its space discretization are deduced. Two time integral methods, central difference method and implicit Newmark method, are introduced, and their stability and applicability are also discussed in some details. The significance of absorbing boundary conditions in spectral element methods for Aeroacoustics is explained, and Clayton-Engquist-Majda absorbing boundary conditions is emphasized and introduced, then the discrete scheme of this boundary conditions is deduced and applied to spectral element methods for wave equation.

本文从Chebyshev多项式逼近理论出发，详细介绍了谱元方法求解偏微分方程的过程；推导了流体中的声波动方程并在空间上对其进行了谱元离散；详细讨论了两种时间积分方法──中心差分法和Newmark方法，分析了它们的稳定性条件，并从理论上对比了两种方法的优缺点和适用范围；将吸收边界条件推广应用于谱元方法求解气动声学问题中，重点介绍了Clayton-Engquist-Majda吸收边界条件的原理和公式，推导了该吸收边界条件的变分形式，并将其引入波动方程的离散形式中。

VOF equation use Lax-Wendroffgeshi scheme with precision of two steps. Pressure of host field is turned into initial-boundary value problem of variable coefficient parabolic equation on regular border. We utilize implicit difference method to solve it.

VOF方程的离散求解使用Lax-Wendroffgeshi格式，这种格式具有二阶精度；主场压力的求解转化为固定边界上变系数抛物型方程的初边值问题，采用隐式差分格式。

In the color quantization phase, two schemes have been adopted,one is general palette quantization alogrithm,other is color difference-based quantization algorithm.Which scheme should be choosen depends on the size of image and the users' demands for time and qualities.

在颜色量化阶段，系统采用了两个方案：全局调色板量化方案和基于色差最小量化方案，用户可根据图像的大小和对速度及质量的需求进行选择。

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。

For the head-teacher of the class said that I had seriously broken the school rules,which led me to a three-day suspend class.

为什么呢？因为我的班主任说我严重的违反了校规，于是让我停课三天。

Many of them believe that the conversion of thousands of working-class folk in England spared that nation from the mass carnage and the tyranny that came with the revolution in France.

他们之中有许多人相信，在英国数以千计的劳工阶级之悔改信主使英国免於遭受如法国大革命所造成的大屠杀和专制暴政。