差分法

We introduce the principle and arithmetic of Finite Difference Time Domain method particularly, and primarily discuss on several essential questions including excitation sources, the conditions of stability of calculation, and Perfectly Matched Layer boundary conditions. All of these factors have effect on the results of the numerical simulation.

2详细介绍了有限时域差分法(Finite Difference Time Domain， FDTD)的原理和算法，着重讨论和分析了激励源设置、FDTD法的稳定条件、PML吸收边界条件等几个关键问题，这些因素会直接影响模拟结果。

Furthermore, The frequency-domain relationship between the electric flux density and the electric field is managed with the Z transform, which is of frequent use for digital filtering and signal processing. The optical pulse propagating in nonlinear and dispersive media is analyzed with Z transform, which is simpler than with auxiliary differential equation method.

同时利用数字滤波和信号处理中经常使用的Z变换来处理D和E间的频域关系，并具体分析了如何用Z变换法来处理非线性色散问题，此方法与辅助差分法相比要较为简单明了。

To give the definition of the mass concrete and to concrete\'s cracks together with practical meanings of control ,and give a brief review on the research in the field at home and abroad, at last, methods to control temperature crack of the mass concrete from several aspects such as design measures,concrets material, construction schedules.etc are summed up; To explain the physical mechanics of the concrete and computing methods-Difference Method and Finite Element Method, and illustrate the application of their specific methods repectively;Several temperature factors that can influence the temperature stress of mass concrete baseplate are analyzed. The influence degree of temperature factor can be got through the ANSYS simulation computation the control of temperature can control the temperature stress, consequently control the temperature crack of mass concert baseplate; through the influence of the crack resistance ability of mass concrete baseplate which takes the reinforcement as a part is analyzed. By ANSYS simulation, the best suited volume ratio of reinforcement is found out, at same time the layout of reinforcement with the same volume ratio can also affect the resistance ability of mass concrete baseplate. Sum up of above analysis, anti-crack function of steel bar in early mass concrete baseplate is obvious, so it\'s necessary to consider beneficial effect of construction steel bar in research of temperature control on mass concrete baseplate.

本文先容了大体积混凝土及混凝土裂缝的基本概念，对国内外在这个领域里的研究现状作了扼要叙述，并从结构设计、混凝土材质、施工措施等方面总结了大体积混凝土温度裂缝控制的方法及防止措施；阐述了混凝土的基本物理力学性能，总结了大体积混凝土温度计算的方法——差分法和有限元法，并分别举例说明其具体应用的方法；分析了影响大体积混凝土底板温度应力的几种温度因素，利用ANSYS模拟计算，得出了每种因素的影响程度，通过分析提出了在这几种温度影响因素下如何通过控制温度以达到控制温度应力从而来控制裂缝的具体建议；针对大体积混凝土基础底板中配筋的不同对混凝土底板抗裂能力的影响不同，利用ANSYS进行模拟分析，得出底板中最合适的体积配筋率，同时分析了在相同体积配筋率下钢筋的具体布置对大体积混凝土基础底板抗裂能力的影响，分析表明，配置钢筋对混凝土结构的开裂阻止作用明显，在研究大体积混凝土温度裂缝题目时，要考虑钢筋在其中的有利作用。

Compared with Finite Element Method and Finite Difference Method, Boundary Integral Equation Method is computationally more efficient.

与有限元法和有限差分法相比，该方法具有更高的计算效率。

The good agreement of experimental results with the simulated values shows that D'Alembert's method coupled with the finite-difference time-domain method could be used to study and accurately analyze the pulse circuit from the electromagnetic viewpoint.

仿真和实验结果良好的一致性证明了达朗伯公式行波法结合时域有限差分法可以从电磁场角度研究并精确分析脉冲产生电路。

It combines the merit of the finite element method with that of the finite difference method.

它可以吸收有限元法和有限差分法的一些重要思想与技巧。

Both finite element method and discrete operator difference method can be pushed forward from which.

由该方程不仅可以得到有限元法，还可得到离散算子差分法。

Based on finite difference method and stereolithography file schema, the key techniques of mesh generation in foundry computer aided engineering system have been studied, including the technique for fast generating outlines of cross-section, the technique for handling error tolerance and the technique for rapidly generating mesh from cross-section.

基于有限差分法和标准模板库，研究铸造计算机辅助工程系统中的网格剖分关键技术，具体包括STL实体截面轮廓快速生成、容错处理，以及截面网格信息的快速提取等技术。

The advantage of the single-ended method is that it requires only half as many switches as the differential method.

单端法的优点是所需的开关数量仅为差分法的一半。

The authors studied carefully two numerical differential methods, finite difference method and rational polynomial technique, and pointed that FDM is the special ease of RPT when the limit state function is linear. Accordingly, FDM3 can be used for the continuous linear limit state function and RPT5 for the continuous nonlinear limit state function. For the discontinuous limit state function, RPT should be used because of the large error of FDM.

对于可靠度分析中常用的有限差分法及有理多项式法这两种数值微分方法，本文详细研究了二者间的异同及其求导结果与步长的关系，指出了对于相同的步长控制系数及取样方式，FDM是RPT在线性情况下的特例；对于连续的线性功能函数，可直接用3点FDM求导；对于连续的非线性功能函数，可用5点RPT求导；对于非连续的功能函数，应采用RPT求导。

Cynanchum Lingtai apricot production in the average weight 65 grams, the brightly-colored fruit, juicy rich, sweet-sour taste, sweet from the nucleolus, when the late Qing Dynasty famous Shaanxi, Gansu provinces, the Qing imperial court Tongzhi tribute for years.

灵台生产的牛心杏平均单果重65克，果实色泽鲜艳，汁多味浓，甜酸适口，离核仁甜，清末时就驰名陕、甘两省，清同治年间曾为朝廷贡品。

Chenopodium album,Solanum nigrum, and Amaranthus retroflexus were very susceptible to the herbicides. Polygonum persicaria and Abutilon theophrasti were relatively less susceptible to the herbicides, and Lycopersicon esculentum was not susceptible to it. The relationship between reduction rates of weed biomass and PPM values of weed leaves 2,4, and 6 days after treatment was established.

供试的6种杂草对该混剂的敏感性存在显著差异：红心藜Chenopodium album、龙葵Solanum nigrum和反枝苋Amaranthus retroflexus对该混剂最敏感，ED90值分别为47.65、71.67和29.17g/hm2；春蓼Polygonum persicaria和苘麻Abutilon theophrasti敏感，ED90值分别为96.91、114.20g/hm2；而番茄不敏感。