近似方法

These calculation results indicate that the Second-order Born approximation is available on researching the electron-atom scattering in a laser field.

计算结果表明，由二阶玻恩近似方法得出的结果与实验符合比较好，从而说明这种计算方法在研究激光场中电子—原子散射时是准确的。

According to perturbation theory and local Born approximation method, we derived the full DSR migration approaches based on the dual-domain propagators.

在前人研究的基础上，本文首先参照摄动理论和局部Born近似方法，系统地推导了基于双域传播算子的DSR全偏移方法。

The interaction between chemisorption and multilayer surface segregation is discussed in detail.

采用格林函数方法和多重耦合自洽相干势近似方法，研究了氢在Au-Ag多层偏析无序二元合金表面的化学吸附，详细地讨论了DBA表面的多层偏析和化学吸附间的相互影响。

In this paper the stress analysis solution of parallel circular tunnels in elastic ground under any coefficient of lateral pressure is derived, and the stress field and displacement field of parallel circular opening subjected to continuous boundary stresses are first solved, and then the ground pressure and the internal force in lining are obtained, using the displacement compatibility equation between linin...

先求得连续洞周边界应力条件下双圆形洞室的应力场和位移场；再利用衬砌和围岩界面位移协调方程，获得平行圆形隧道的地层压力和衬砌内力公式，并可考虑开挖面的三维效应和洞室自由位移等因素。根据结论公式，对隧道间距、地层性质、衬砌厚度等诸因素进行了讨论，得到了单因素的一般规律，在此基础上，提出了平行圆形隧道最小间距的近似方法，并在某工程中予以应用，得到了满意的结果。本应力分析方法在平行圆形隧道的设计和施工中供作参考。

Based on the analysis of some aspects, such as the approximative algorithm of FOC, the Tustin transform theory and its generating function formula's character, the convergence guarantee of binomial power function by Maclaurin expanding, and the consideration of the limitation of conventional methods, an improved method is proposed to compute the numerical evalution of FOC using PSE and Tustin transform and is further applied to solving the linear FOS.

以分数阶算子近似方法的分析研究为基础，基于Tustin变换理论及其用于分数阶算子的离散生成函数公式特点，利用二项式幂函数的Maclaurin展开能够保证收敛的特性，考虑常用算法的局限性，提出了一种改进的基于幂级数展开和Tustin变换的分数阶运算方法，并应用于线性分数阶系统的求解，给出了递推算法的详细推导。

The main results can beexpressed as follows:(1)Based on πtheory, some affected factors about wave forces are given, and therelation between affected factors and wave forces is analysised by experimentalresults.(2) The distribution of wave press at representative time and reflection nature aregiven and their variety charactes are discussed by experimental results.(3)By comparing the wave forces of quarter-circular breakwater and semi-circularbreakwater under the same wave conditions,some approximately wave forcesexpressions of quarter-circular breakwater are given.(4)Based on VOF method to trace water free surface,solve numerical value ofRANS equation,and get the distributions of flow field and wave press ofquarter-circular breakwater at the same time during one period,the mechanism ofwave force is also discussed elementarily.(5) Based on the result that RANS equation of numerical simulation agree wellwith experimental results,a new approach to study hydraulic natures of quarter-circular breakwater is provided.

其主要结论如下：一、通过π定理，确定影响波浪力的无因次参变量，根据试验结果对其影响因素进行分析；二、基于模型试验，给出典型时刻圆弧面防波堤的同步波压分布和反射特性，讨论它们的变化特点；三、通过相同条件下圆弧面防波堤与半圆型防波堤两种堤型试验波浪力的比较，给出了圆弧面防波堤波浪力的近似方法；四、利用VOF法追踪自由水面，数值求解RANS方程，得到圆弧堤堤体周围的流场和压力场，初步分析了速度涡流与压力场的相互影响；五、对比数值分析与试验结果，探讨数值方法研究圆弧面防波堤水力特性的可行性，提供新的研究途径

All backscattering field s intensity from conducting plate can be calculated by complex ray method ,especially complex ray paraxial approximation in angle domain through modeling the conducting plate.

本文通过建立导电平板反射场分析模型，利用复射线方法特别是角域中的复射线近轴近似方法，有效地实现了导电平板在整个后向范围内散射场的计算，同时计算精度可以由复射线展开参数ξ来加以控制。

So, studies on the approximate methods of many-body problems and their applications are one of the most basic and active fields in quantum chemistry.

因此，研究多体问题的近似方法及方法的应用是量子化学最基本、也是最活跃的领域之一。

Based on generator self excitation theory and the characteristics of black-start, we choose this simple method to be the criterion of generator self excitation problem in black start. Later, simulation of hydraulic generator self-excitation study is given.

从适用於黑启动快速这一特点出发，在已有的方法中选择了一种简单的近似方法来作为黑启动研究中自励磁产生与否的判据，从自励磁现象本质出发进行了阐述，并对水轮机组自励磁产生的暂态过程进行了仿真计算。

A variational method with differential forms gives better precision for numerical solution of transport critical problem based on spherical geometry, and its computation seems simple than other approximate methods.

对于球几何问题，讨论了一种基于微分方程的变分形式求解方法，数值计算显示达到了较满意的精度，而且计算过程比起其他近似方法要简单

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。