差分法

This thesis contributed to the comprehensive study of the Finite-Difference Time-Domain method and its application to the numerical computation of radiated electromagnetic fields in switched mode power supplies. The work includes mainly three parts: the study on the performance of PML absorbing boundary condition applied to pseudo low frequency electromagnetic problems; the validation of the FDTD method with PML absorbing boundary conditions and the corresponding computer software based on the numerical study of the electromagnetic field of an electric dipole antenna, and its application to the numerical computation of radiated electromagnetic fields in switched mode power supplies; the development of an improved alternating direction implicit finite-difference time-domain method.

在综合前人工作基础上，本文对时域有限差分法及其在开关电源辐射电磁场数值计算中的应用进行了系统的分析和研究，其核心内容包括：伪低频电磁场数值计算中PML吸收边界条件性能的研究；基于基准问题—电偶极子天线三维辐射电磁场，验证了本文构造的基于PML吸收边界条件的三维FDTD法及其计算软件，并应用于高频开关电源辐射电磁场的数值分析；提出了一种改进的交替方向隐格式时域有限差分法。

A special investigation was made in some of the arithmetic,including image sequence difference method,backdrop method,luminous flux method,etc.

对其中一些算法作了着重的研究，其中包括图像序列差分法、背景差分法、光流法等，进一步的分析了这些算法所存在的优缺点，并对图像序列差分法做了改进。

The key point of this paper made a study of the application of FDTD method to dispersive, nonlinear materials. Two methods are introduced to deal with the relationship between the electric flux density vector and the electric field vector: auxiliary differential equation method and Z transform method.

本文的重点在于研究时域有限差分法在非线性色散媒质中的应用，主要采用了两种方法来处理电通量密度矢量D和电场强度矢量E之间的关系：辅助差分方程法和Z变换法。

Using finite difference time domain method, the electromagnetic field distribution of THz wave is simulated in a THz 2D PC splitter and by plane wave expansion method the dispersion relation and defect modes are achieved in a THz rotated PC waveguide.5. A woodpile three-dimensional (3D) PC with face-centered-tetragonal symmetry is one of the most popular 3D PCs because of its favorable band gap characteristics. Based on the woodpile fct lattice structure, we propose a novel woodpile THz lattice structure with comparatively decreased symmetry, better band gap properties and easy fabrication by varying some structure parameters.

计算结果为利用非线性光学差频方法产生THz辐射源的实验研究提供了深入和全面的理论基础；四、利用平面波展开法，通过改变二维THz光子晶体的结构参数，对二维THz光子晶体完全带隙进行了优化，分析出两种适合工作在THz波段的二维光子晶体结构；采用时域有限差分法和平面波展开法，计算出THz波在二维光子晶体"T"型分束波导，45度旋转波导中传输的电磁场分布以及缺陷模；五、Woodpile面心立方四角结构是三维光子晶体中被研究最广泛的结构之一。

Comparing these two results in view of computational efficiency and computational accuracy,it appears that MGM is superior to FDM in solving electrostatic field distribution for the electron optics problem.

通过与目前在场计算中常用的有限差分法进行比较，可以看出多重网格法的计算效率和计算精度优于有限差分法。

In this paper, based on an optimum difference operator for spatial differential given by Holberg, an optimum difference method of modeling crosswell elastic wavefield is put forward, which adopts the staggered-grid technique and calculates the wavefield at different grid points. When the half length of optimum difference operator is taken as four to six points, the required number of grid points per wavelength equals to three, crosshole elastic wavefield numerical modeling can attain satisfied accuracy.

本文以Holberg提出的一种空间微分的最佳差分算子为基础，采用交错网格技术，提出了一种模拟井间弹性波场的最佳差分法，该方法能在大空间网格点上得到精确的波场值，当最佳差分算子的半长度取4～6个点，每个波长只采3个样点时，井间弹性波场的模拟就可以得到满意的精度，其计算速度比常规有限差分法至少快一个数量级。

Based on investigating the short and intermittent structural plane, surrounding rockmass of the huge underground powerhouse in Three Gorge has been divided into five statistical similar areas according to its characteristic of rockmass structure by applying structure plane network simulation. Distributed characteristic of structural plane has been studied and based on it mechanics macrocharacteristic has been studied:(1) It is the first time that based on the result of structural plane network simulation rockmass quality of every structure area has been studied with applying blurred information optimum seeking technique and be compared with and RQD method. The result indicated that it has better effect to evaluate rock quality with blurred information optimum seeking technique.(2) It is the first time that the interrelated relationship of the result of in-suit rockmass deformation test and fractal characteristic of structure on test point has been applied to determine rockmass deformation parameter. The question of evaluating deformation parameters of engineering rockmass has been solved.(3) Anisotropy strength parameters have been determined by applying shear zones simulating method. The result indicated that there are different strength parameters in every structural area, after comparing the result of Fast Lagranian Analysis in continua number simulation method with that of method of weighted mean according to continuity. The result indicated that when a suitable reduction coefficient is been considered rockmass strength parameters can be simply and fast determined with method of weighted mean according to continuity where there is not enough test result.(4) Damage characteristic has been studied based on analysis fractal characteristic of structural plane network by applying fractal-damage coupling method. It is the first time that the concept of damage degree has been set up to evaluate rockmass quality according to the biggest principal damage.

通过对短小、断续性结构面统计特征的研究，将地下厂房区划分为五个岩体结构统计均质区，应用结构面网络模拟技术研究了各个岩体结构均质区结构面的发育分布特征，并以此为基础对岩体宏观力学特性进行了深入研究：(1)首次通过在结构面网络模拟计算结果的基础上，应用模糊信息优化技术研究了厂房区各个岩体结构分区的岩体质量并与岩体基本质量指标研究法、岩体质量指标RQD值研究法作了对比，结果表明以结构面网络模拟结果为基础，应用模糊信息优化技术进行岩体质量评价能够取得很好的效果，解决了工程岩体质量的定量评价问题；(2)首次通过对已有的现场大型岩体变形试验结果的分析及相应试验点岩体结构分形特征的研究，建立了结构面分布的分形维数和岩体变形指标间的相关关系，并首次应用这种相关关系根据结构面网络模拟及分形维数计算结果确定了缺少试验结果的地下厂房各工程部位的岩体变形指标而且应用于围岩稳定性计算，解决了工程岩体宏观变形参数的评价问题；(3)应用在结构面模拟网络图上模拟岩体剪切破坏带的方法，得出了岩体在不同方向上的强度参数，结果表明岩体的强度特性与结构面的发育方向和程度有着明显的关系，各个岩体结构均质区具有不同的强度参数；同时还通过应用拉格朗日差分法对岩体强度指标的数值分析并与按连通率加权平均计算法对比表明，按连通率加权平均计算法在考虑合理的折减系数情况下，可以简单快速地对缺少现场大型试验结果的具体工程部位实现岩体强度指标的估计，通过以上研究解决了工程岩体抗剪强度参数的评价问题；(4)通过结构面网络分形维数的研究，应用分形损伤耦合分析方法，研究了厂房区岩体的损伤特征，并首次引入"损伤度"的概念，建立了应用最大主损伤评价岩体质量的指标体系。

The plane adopts the joint method of both the finite element and the finite difference to divide plane domain by means of irregular triangular net in order to fit topography and coastal line complicated sea zone; Vertical application σcoordinate conversion and the finite difference method.

平面采用有限元法和有限差分法相结合的方法，用不规则三角形网格剖分计算域，以适应地形和岸线复杂的海区；垂向应用σ-坐标变换及有限差分法。

Rough error processing that frequently used to digital filtering was taken as the research object,on the basis of difference method commonly used in the past and profile method of fractile method,a synthesis algorithm-fractile method based on difference method was proposed.The algorithm for processing the rough error data was perfected .The method had been used in a detection system and result is satisfactory.

对数字滤波系统中经常使用的数据处理算法做了综合处理，对于数据采集过程中所得数据做粗差判断处理为主要研究对象，在过去常用的差分法和分位数分布图法的基础上提出了一种综合处理方法-基于差分法的分位数方法，对系统中的粗差数据处理算法做了更完善的探讨，该方法已在实际检测系统中应用，效果显著。

Magnetotelluric field finite difference migration tomography Found on the researches of Zhdanov etc. in MT finite difference migration tomography, we analyze and summarize both fruits and limitation of foregone peoples' achievements. So more precise finite difference extrapolation equation can be deduced, and it can be easily applied into the migration tomography. New equation reserved the derivative terms of wave number both at vertical and horizontal direction, so that more exquisite geoelectric diversification can still be accommodated, that is the very requirement of practical data interpolation.

大地电磁有限差分偏移成像技术：在Zhdanov等人建立的有限差分偏移成像研究的基础上，总结分析了前人在 MT成像技术方面的研究成果和存在问题；推导更精确的有限差分波场延拓方程，采用改进的有限差分法进行大地电磁场偏移成像，差分延拓方程保留波数对水平方向和垂直方向的一阶导数项而提高求解精度，可适应电性纵横方向变化剧烈的地电构造，使成像分辨率得到增强。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了