Unconventional Hamilton-type variational principles for nonlinear coupled thermoelastodynamics

According to the basic idea of classical yin-yang complementarity and modern dual-complementarity, in a simple and unified new way proposed by Luo, the unconventional Hamilton-type variational principles for geometrically nonlinear coupled thermoelastodynamics can be established systematically. The new unconventional Hamilton-type variational principle can fully characterize the initial-boundaty-value problem of this dynamics. In this paper, an important integral relation is given, which can be considered as the expression of the generalized principle of virtual work for geometrically nonlinear coupled thermodynamics. Based on this relation, it is possible not only to obtain the principle of virtual work in geometrically nonlinear coupled thermodynamics, but also to derive systematically the complementary functionals for eight-field, six-field, four-field and two-field unconventional Hamilton-type variational principles by the generalized Legendre transformations given in this paper. Furthermore, with this approach, the intrinsic relationship among various principles can be explained clearly.     

有限位移理论线弹性力学二类和三类混合变量的变分原理及其应用

提出了有限位移理论线弹性力学二类混合变量和三类混合变量的变分原理.考虑已知边界条件的变化并应用有限位移理论的功的互等定理,在导出上述两类变分原理的过程中起到了关键作用和桥梁作用.首先,考虑已知位移边界条件的变化和应用功的互等定理,导出了二类混合变量的最小势能原理.用类似的方法,导出了二类混合变量的驻值余能原理.应用应变能密度和应力余能密度的关系式于上述两个变分原理,得到三类混合变量的变分原理.然后,给出了二类和三类混合变量的虚功原理和虚余功原理.同时,应用拉氏乘子法导出了广义变分原理.以一个算例说明了在某些情况下拉氏乘子法会失效,介绍了构成广义变分原理泛函的半逆法.最后,应用二类混合变量最小势能原理计算了一大挠度悬臂梁的弯曲.     

线弹性动力学的某些一般定理及广义与广义分区变分原理*

从四维空间思想出发,在四种时端条件下,系统地推导得出了弹性动力学有关的一般定理,如:可能功作用量原理,虚位移原理,虚应力一动量原理,互易定理及由此导出的位移互等定理与始末时刻条件关系定理等;得出了线弹性动力学的位能作用量变分原理,余能作用量变分原理,动力问题的胡-鹫原理,H-R原理及本构关系变分原理.Hamilton原理,Toupin原理及有关文献如[5]、[17]～[24]的工作均可作为文中一般结果的特例.对应于有限元分析.在空间分区,时间分区及时空均分区情况.给出了动力学问题的分区位能作用量原理.分区余能作用量原理,分区混合能作用量原理及相应的分区广义变变分原理.导出了分区原理的一般形式.若去掉时间维及有关量,文中有关结果可转化为静力问题中有关的相应结果.     

Some fundamental issues of basic line search algorithm for linear programming problems

In this article we present the fundamental idea, concepts and theorems of a basic line search algorithm for solving linear programming problems which can be regarded as an extension of the simplex method. However, unlike the iteration of the simplex method from a basic point to an improved adjacent basic point via pivot operation, the basic line search algorithm, also by pivot operation, moves from a basic line which contains two basic feasible points to an improved basic line which also contains two basic feasible points whose objective values are no worse than that of the two basic feasible points on the previous basic line. The basic line search algorithm may skip some adjacent vertices so that it converges to an optimal solution faster than the simplex method. For example, for a 2-dimensional problem, the basic line search algorithm can find an optimal solution with only one iteration.     

Guaranteed-accuracy approximation of reachable sets for a linear dynamic system subject to impulse actions

A method is proposed for approximating the reachable set of a dynamic system with a state space dimension no higher than six-eight considered on a finite time interval. The system is governed by linear differential equations with piecewise constant coefficients and impulse actions specified at prescribed times. The method is based on guaranteed-accuracy polyhedral approximations of reachable sets at researcher-specified times. Every approximation is constructed using the preceding one. A procedure is described for choosing parameters of the method that ensure the required accuracy with close-to-minimal time costs.     

On existence of optimal control governed by a class of the first-order linear dynamic systems on time scales

In this paper, by using the approximation of classical solution, we introduce the definition of solution and prove the existence and uniqueness of solutions of the first-order linear dynamic systems on time scales. Existence of Lagrange optimal control problem governed by the first-order linear dynamic systems on time scales is also presented. For illustration, some examples of optimal control problems on time scales are also discussed.     

一般含时线性势的量子解及有关问题

对于一般形式的含时线性势, 通过假设波函数形式的方法得到了Schr?dinger方程的精确和完备解. 同时指出, 用两个波函数φ(t)〉和ψ(t)〉定义的坐标和动量的矩阵元〈φ(t)xψ(t)〉和〈φ(t)pψ(t)〉满足经典形式的运动方程. 按照量子力学的系综理论, 这样的经典形式的运动方程实际上是流体方程. 进一步研究发现, 对于任意形式的线性系统有类似的结论.     

Robust H{infty} dynamic output feedback control for 2D linear parameter-varying systems

James Lam Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong Changhong Wang Space Control and Inertial Technology Research Center, Harbin Institute of Technology, Harbin 150001, People's Republic of China Corresponding author. Email: ligangwu{at}hit.edu.cn Email: james.lam{at}hku.hk Email: cwang{at}hit.edu.cn Received on June 28, 2006; Accepted on October 1, 2007 This paper is concerned with the problem of robust dynamicoutput feedback control for 2D discrete-time linear parameter-varyingsystems. Given a Fornasini–Marchesini local state-spacesystem with linear varying parameters, our attention is focussedon the design of full-order dynamic output feedback controller,which guarantees the closed-loop system to be asymptoticallystable and has a prescribed disturbance attenuation performance.A sufficient condition for the existence of a desired robustoutput feedback controller is established in terms of parameterizedlinear matrix inequalities, and the corresponding controllersynthesis is cast into a convex optimization problem which canbe efficiently handled by using standard numerical software.A numerical example is provided to illustrate the effectivenessof the proposed design method.