变分方程

Secondly, we discuss the boundary value problem of two dimensional biharmonic equation in a rectangular field and its variational problem,discretize it by using dual tensor product of and the direct product and lining up of matrices, we get some special matrices which are the presupposition in exploring the fast computation, then solve the system of linear equations.

其次本文讨论了矩形域上二维双调和方程边值问题及其相应的变分问题，利用二元张量积小波分析和矩阵的直积、拉直技巧将变分问题离散化，从而使求解偏微分方程问题变为求解线性方程组的问题。一维情况两组基的张量积下得到的系数矩阵分别为块状七对角阵和稀疏矩阵。这些特殊结构为以后快速算法的研究打下一个基础。

This research method is independent of Green"s function and variational structure. So it can tackle with the BVP for non self-adjoint and self-adjoint difference equations and overcome the difficulties brought about by the establishment of Green"s function, a study of the sign and the estimate of below and above bounded for Greens function.

本章的研究方法既不依赖于Green函数又不依赖于变分结构，因而能解决非自共轭的差分方程边值问题，且克服了Green函数的建立、其符号的判断及其上下界的估计给研究带来的困难，该方法同样适用于研究自共轭的差分方程边值问题。

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。

It is known theoretically that to the variational problem with weak constraints in cost functional J, its Euler equation can be discreted into difference format, by using matrix theory and difference method of partial differential equation we know that there exists optimal selection of weight factors in the cost functional under the condition of minimal variance between analysis field and ideal field.

从理论上可知，对于目标泛函J带有约束条件的变分问题，将其Euler方程离散成差分形式，利用矩阵理论和偏微分方程的差分方法，则目标泛函的权重因子，在分析场和理想场的最小方差意义下存在最优选取。

And the conservation laws of moment and momentum are obtained by the combining the tiny element analysis method in continua mechanics with variation principle in analytical mechanics.

论文摘要：本文在建立时变边界挠性体的动力学方程时，将并入的质量对挠性体的作用当作时变边界上的表面力，并将连续介质力学中的微元分析法和分析力学中的变分原理相结合，导出了时变边界的变质量刚体的动量和动量矩矩方程。

Later, we estimate our variational functional to get a nontrivial solution of the new equation and so the second solution for is obtained.

然后我们利用函数平移将原来的非齐次边界问题转化为奇次边界问题，验证了其对应的变分泛函满足不带条件的山路引理的两个条件，并给出了泛函临界点存在的一个充分条件，最后对具体的变分泛函进行估计，得到了新方程非平凡解的存在性结果，从而得到了原方程第二个正解的存在性结果。

Based on the generalized potential energy variational principle of nonlinear elasticity theory with large deflection,the incomplete generalized potential energy functional is established on the space coupling free vibration of three-span self-anchored suspension bridge by considering the effect of coupling of flexural and axial action,and shearing strain energy of stifening girder.

摘 要：基于大位移非线性弹性理论的广义变分厚理，考虑了加劲梁的压弯耦合和剪切应变能的影响，建立了三跨自锚式悬索桥空间耦合自由振动的大位移不完全广义势能泛函，通过约束变分导出了自锚式悬索桥的竖向挠曲振动、横向挠曲振动和纵向振动的基础微分方程，忽略非线性项的影响，进而得到线性振动微分方程。

Mathematical analysis and experimental results show that this adaptive total variation denoising algorithm can solve the problem that Euler-Lagrange equation of the traditional total variation is not well posed, improve the deficiencies of the slow denosing speed, and reduce the step effect and noise leaving out resulting from using the traditional total variation.

数学分析和实验证明，论文提出的变分去噪模型克服了传统的总体变分模型的欧拉-拉格朗日方程非适定问题，改善了传统总体变分模型去噪速度慢、有阶梯效应、噪声遗漏等缺陷。

It is found thatthe fractal dimension D=1.25 corresponds to the lowest criticalcoupling constant αc=1.9,D=1.73 corresponds to the highest criticalratio of dielectric constants ηc=0.163,and when D≤1.145 bipolaronscan not exist at any rate.In chap,4,we will propose a novelapproach to the calculation of the exciton ground-state energy for thestrong-coupling case.Different from all previous methods,the wavefunction of the phonon part is assumed to take a form related to thewave function of the relative motion.We obtain the exciton energy bysolving the derived integrodifferential equation rather than select ahydrogen-like form to minimize the energy expectation.

结果发现，分数维的维数D＝1.25对应最小的临界的电-声耦合常数(αo＝1.9)，D＝1.73对应最大的临界的介电常数比(ηc＝0.163)，当分数维的维数D≤1.145时，双极化子无论如何也不可能存在，在第四章中，我们将提出一种新颖的变分方法来计算强耦合的激子-声子系统的基态能，不同于以前所有的方法，我们取声子的波函数与相对运动波函数有关的形式，而不是假定一个固定的关于相对运动坐标r的函数形式，得到相对运动波函数所满足的非线性的微分积分方程，我们数值求解这个微分积分方程得到系统基态能，而不是选择一个类氢原子的波函数变分使得能量的期待值最小。

An algorithm called initial function method for the solution of differential equation with tension is also given.

推导出了不考虑拉伸和考虑拉伸情况的弹性环形变微分方程，导出了求解不考虑拉伸情况的弹性环形变微分方程的差分方程和算法，还给出了可谓之初参数法的求解考虑拉伸情况的弹性环形变微分方程的算法。

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