迭代法

MGM is introduced to solve field distributions in 3-D electron optical systems. The difference equation, the discrete form of Laplace's equation, is deduced in 3-D Cartesian coordinates. In view of the smooth effect, MGM combines Gauss-Seidel iteration with a technique known as coarse grid correction. Formulae for restriction and prolongation are deduced and expressed in terms of tensors.

将多重网格法引入电子光学系统中三维静电场的计算，对三维笛卡尔坐标系中的差分方程，采用高斯-赛德尔迭代法求解差分方程组，并结合迭代过程讨论了粗网格的误差校正技术；在不同网格层之间进行场值的限制和延拓，推导了三维静电场中的限制、延拓公式并以张量的形式表示。

This thesis consists of two parts. The first one was that boundary value problem was discrete with five point difference method. Three kinds of memory formats were studied, which were full matrix, half band width and row compress sparse. Full matrix memory format and half band width memory format first was contrasted. The results show that half band width has efficiency in space. Then the algebraic system of finite element method was solved by Gauss-Seidel iteration method to popular row compress sparse memory format.

本论文由两部分组成，第1部分针对边值问题，用5点差分格式进行离散，并对离散矩阵这类大型稀疏矩阵，研究了系数矩阵的3种存储格式的优劣，即：满矩阵存储格式、半带宽存储格式和按行压缩稀疏存储格式，首先我们将满矩阵存储方式和半带宽存储格式进行了对比，迭代法的数值实验表明：利用半带宽存储的矩阵在空间运算方面具有高效性；然后针对目前数值实验中流行的按行压缩稀疏存储格式，实现了有限元离散代数系统的迭代法的求解。

In chapter 1, we discuss several iterative methods and their convergence conditions. While, we also present the techniques in proving the convergence theorem.

第一章，主要对几种迭代法的收敛性进行了讨论，总结了它们的收敛条件及证明各种迭代法收敛性的技巧。

In this Chapter, we establish convergence theorem by using the majorizing method.

第二章，提出了一族具有三阶收敛迭代法，这族迭代法避免了求F的二阶导数。

If the Landweber method and pre-iteration method were convergent, the residue sequence would be monotone decreasing. By analyzing the convergence, the fact is demonstrated that for the severe ill-conditioned matrix of sensitivity coefficient, because of the limitation of the precision of the computer, the residue sequence is not monotone decreasing; thereby the reconstruction images diverge from the true distribution of the conductivity. So the generalized inverse method with threshold is established and the selection way of the regularization parameter is presented, by which the better images are reconstructed.

Landweber法和预迭代法收敛，则其残差序列单调递减，通过对它们的收敛性进行分析，证实对于病态性严重的灵敏度系数矩阵，由于受计算精度的限制，迭代过程中的残差序列不再单调递减，从而导致重建图象偏离实际电导率分布，因此作者建立了带阈值的广义逆算法，提出了规则化参数选择方法，获得了较好的图象重建质量。

Including the main-element elimination method, the direct LU decomposition, Jacobi iteration, high Sisaideer iteration.

包括了列主元消元法、直接LU分解法、雅克比迭代、高斯赛德尔迭代法。

This article introduced Newton iteration method's related concept, Newton iteration method's correlation theorem, as well as when solves the misalignment equation root the theory basis, the astringent analysis, the starting value selection rule and so on.

本文介绍了牛顿迭代法的相关概念，牛顿迭代法的相关定理，以及在求解非线性方程根时的理论依据，收敛性分析，初始值的选取规则等。

The family of iterative methods avoid evaluating the second Frechet derivative.

在第一章中，我们总结了各种迭代法和它们的收敛条件及证明各种迭代法收敛性的技巧。

However,the results of a nonlinear problem will be directly affected by the choice of the iterative method.

求解这类问题的常用方法是迭代法，而迭代法的选择直接影响到各种非线性问题结果的好坏。

To study numerical solution of the linear equations,the article presents direct method ,Jacobi iterate method and Gauss-seidel iterate method to approximately calculate,and has given its process in MATLAB.

为研究线性方程组的数值解，文章用直接解法、雅可比迭代法、高斯-赛德尔迭代法进行了近似计算，并给出在MATLAB中计算的程序。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。