应用Lagrange乘子法推导一般力学中的广义变分原理 *

应用对合变换建立了两类变量的经典变分原理———Hamilton原理 .灵活应用Lagrange乘子法 ,建立了完整系统和非完整系统的两类变量的广义变分原理和带有附加条件的广义变分原理 .推导了各类变分原理的驻值条件.     

具非线性控制变量的非自治松驰系统时间最优追踪控制问题中的若干结果

本文讨论了一类广义非自治离散松驰系统的时间最优控制问题，将R^n中点曲线的目标约束推广为凸集值函数的超曲线约束．在证明了松驰系统与原系统可达集相等的基础上，得到了最优控制的存在性．由凸集分离定理及终端时间闺值函数方程，我们获得了最大值原理及最优控制时间的确定方法．较之Hamilton方法，本文的条件更一般．离散松驰系统的相关结论可以用于分散控制．     

论非完整系统的Hamilton原理与完整系统的Hamilton原理的统一性

本文通过典型实例和理论分析证明了:在有势力作用下,对于非完整系统Hamilton原理同样有像完整系统那样使Lagrange函数取驻值的形式;使Lagrange函数变分对时间积分为零的形式是前者的演变形式;因此,两种形式是统一的。     

Hamilton体系辛半解析法及在非均匀电磁波导中的应用

力学中的Hamilton体系需用对偶变量来描述,而电磁场正好有电场和磁场这一对对偶变量．尝试将力学中的Hamilton体系理论应用于电磁波导的分析,以横向电场和磁场作为对偶变量,将电磁波导的基本方程导向辛几何的形式．基于Hamilton变分原理, 导出横向离散的半解析系统方程, 保持体系的辛结构．以非均匀波导为例, 求解了方程的辛本征值问题, 计算结果与解析解相当吻合．     

有限位移理论线弹性动力学二类和三类混合变量的最小势作用量原理和驻值余作用量原理及其应用

两个新的概念,即势作用量的概念和余作用量的概念被引入弹性动力学变分原理中.根据势作用量的概念,最小作用量原理（即Hamilton原理）被改称为最小势作用量原理.根据余作用量的概念,首次提出了驻值余作用量原理.考虑边界条件的变化并应用有限位移理论的功的互等定理,导出了以位移和应力为变分变量的二类混合变量的最小势作用量原理及驻值余作用量原理.应用应变势能密度与应力余能密度的关系式于上述二类混合变量作用量原理,导出了以位移、应力和应变为变分变量的三类混合变量的相关作用量原理.最后,应用拉氏乘子法给出了广义势作用量原理及广义余作用量原理,并且应用大挠度梁二类混合变量最小势作用量原理计算了一悬臂梁的受迫振动.     

Kaehler流形上的Lagrange力学

讨论了Kaehler流形上的Lagrange力学，并给出Lagrange算子、Lagrange方程、作用泛函、Hamilton原理和Hamilton方程等复的数学形式．     

一类二阶非自治Hamilton系统的周期解

在线性增长和次线性增长条件下,利用临界点理论中的极小作用原理和鞍点定理,研究了二阶非自治Hamilton系统周期解的存在性问题,获得了一些新的可解性条件．     

轴向变速运动弦线的非线性振动的稳态响应及其稳定性

研究具有几何非线性的轴向运动弦线的稳态横向振动及其稳定性．轴向运动速度为常平均速度与小简谐涨落的叠加．应用Hamilton原理导出了描述弦线横向振动的非线性偏微分方程．直接应用于多尺度方法求解该方程．建立了避免出现长期项的可解性条件．得到了近倍频共振时非平凡稳态响应及其存在条件．给出数值例子说明了平均轴向速度、轴向速度涨落的幅值和频率的影响．应用Liapunov线性化稳定性理论,导出倍频参数共振时平凡解和非平凡解的不稳定条件．给出数值算例说明相关参数对不稳定条件的影响．     

传递辛矩阵群收敛于辛Lie群

通过作用量变分原理,给出了Hamilton正则方程离散积分的传递辛矩阵表示,利用Hamilton正则方程给出了其对应的Lie代数．说明了当时间区段长度趋近于0时,离散系统积分的传递辛矩阵群收敛于连续时间Hamilton系统微分方程分析积分得到的辛Lie群．     

弹性正交索网结构动力学的各类非传统Hamilton型变分原理

根据古典阴阳互补和现代对偶互补的基本思想,通过罗恩早已提出的一条简单而统一的新途径,系统地建立了正交索网结构几何非线性弹性动力学的各类非传统Hamilton型变分原理．这种新的非传统Hamilton型变分原理能反映这种动力学初值-边值问题的全部特征．文中首先给出正交索网结构几何非线性动力学的广义虚功原理的表式,然后从该式出发,不仅能得到正交索网结构几何非线性动力学的虚功原理,而且通过所给出的一系列广义Legendre变换,还能系统地成对导出正交索网结构几何非线性弹性动力学的5类变量、4类变量、3类变量和2类变量非传统Hamilton型变分原理的互补泛函、以及相空间非传统Hamilton型变分原理的泛函与1类变量非传统Hamilton型变分原理势能形式的泛函．同时,通过这条新途径还能清楚地阐明这些原理的内在联系．     

AHP中增加一组元素的严格保序性条件

给出了左主特征向量法（LEM）下增加一组元素严格保序的充要条件,通过研究在右主特征向量法（REM）,左主特征向量法（LEM）,几何平均特征向量法（GMEM）下增加一组元素严格保序的条件之间的关系,从而给出GMEM下增加一组元素严格保序的充分条件。     

Pricing without no-arbitrage condition in discrete time

In a discrete time setting, we study the central problem of giving a fair price to some financial product. This problem has been mostly treated using martingale measures and no-arbitrage conditions. We propose a different approach based on convex duality instead of martingale measures duality: The prices are expressed using Fenchel conjugate and bi-conjugate without using any no-arbitrage condition. The super-hedging problem resolution leads endogenously to a weak no-arbitrage condition called Absence of Instantaneous Profit (AIP) under which prices are finite. We study this condition in detail, propose several characterizations and compare it to the usual no-arbitrage condition NA.     

Asymptotic analysis of the differences between the Stokes-Darcy system with different interface conditions and the Stokes-Brinkman system

We consider the coupling of the Stokes and Darcy systems with different choices for the interface conditions. We show that, comparing results with those for the Stokes-Brinkman equations, the solutions of Stokes-Darcy equations with the Beavers-Joseph interface condition in the one-dimensional and quasi-two-dimensional (periodic) cases are more accurate than are those obtained using the Beavers-Joseph-Saffman-Jones interface condition and that both of these are more accurate than solutions obtained using a zero tangential velocity interface condition. The zero tangential velocity interface condition is in turn more accurate than the free-slip interface boundary condition. We also prove that the summation of the quasi-two-dimensional solutions converge so that the conclusions are also valid for the two-dimensional case.     

Structured condition numbers and statistical condition estimation for the LDU factorization

In this article, we consider the structured condition numbers for LDU, factorization by using the modified matrix-vector approach and the differential calculus, which can be represented by sets of parameters. By setting the specific norms and weight parameters, we present the expressions of the structured normwise, mixed, componentwise condition numbers and the corresponding results for unstructured ones. In addition, we investigate the statistical estimation of condition numbers of LDU factorization using the probabilistic spectral norm estimator and the small-sample statistical condition estimation method, and devise three algorithms. Finally, we compare the structured condition numbers with the corresponding unstructured ones in numerical experiments.     

Topological and metrical conditions for Collet-Eckmann unimodal maps

1. IntroductionColletEchazann maps (i.e. every ColletEckmann maP has positive lower LyaPunovexponent at the critical value) play a very important role in the study of one dimensionaldynamical systems. They have very good metricaI and ergodic properties[ll2], for example,every COllet-Eckmann map admits an absolutely cootinuous invariani m.asur.[1].In I3,4] Benedicks and Carleson proved that Collet-Eckmann maps are abundant in theso-caJled quadratic family which is a typical family of one …     

关于条件极值充分条件的重新推导和证明

李文学用拉格朗日函数提出求条件极值的充分条件,但他的证明却是错误的.本文不用拉格朗日函数,而是直接通过消去一个变量将条件极值转化成无条件极值,重新推导出充分性条件.推导的过程也是条件极值充分条件的证明过程.     

A criterion for checking if a convex set belongs to the union of a finite number of convex sets

A necessary and sufficient condition for the inclusion of a convex compact set in the union of a finite number of convex sets is proved. This condition obtained using the convex analysis techniques is a condition on the maximin of a given function. Using the dynamic programming, checking this condition is reduced to evaluating a set of functions and checking a condition for their values. The reduced form of the criterion is more convenient from the computational point of view.     

An approximate algorithm for prognostic modelling using condition monitoring information

Established condition based maintenance modelling techniques can be computationally expensive. In this paper we propose an approximate methodology using extended Kalman-filtering and condition monitoring information to recursively establish a conditional probability density function for the residual life of a component. The conditional density is then used in the construction of a maintenance/replacement decision model. The advantages of the methodology, when compared with alternative approaches, are the direct use of the often multi-dimensional condition monitoring data and the on-line automation opportunity provided by the computational efficiency of the model that potentially enables the simultaneous condition monitoring and associated inference for a large number of components and monitored variables. The methodology is applied to a vibration monitoring scenario and compared with alternative models using the case data.     

一类半线性抛物型方程组解的爆破速率估计

考虑一类带有齐次Dirichlet边界条件且反应项分别为指数形式和幂函数形式的半线性抛物型方程组,利用比较原理得到了方程解爆破的充分条件,由数学分析原理和最大值原理得到了爆破解的爆破速率估计.     

非可加测度理论中的伪形式的Egoroff定理

引入一个新概念——集函数的条件(PE),并给出非可加测度理论中一种伪形式的Egoroff定理。证明这个条件对于单调测度空间上伪形式的Egoroff定理不仅是充分的而且也是必要的。