关于六角系统的极值问题

本文讨论六角系统中将宽度与直径结合起来的几个极值问题，并给出相应的极图构造，最后，指出并补正［４］中一个计数结果的不足。     

求总极值问题的最优性条件

郑权提出了求总极值问题的积分－水平集的概念性算法,同时给出了最优性条件。本文提出了修正的积分－水平集算法,并且给出了类似的总极值存在的最优性条件。     

非光滑向量极值问题的真有效解与最优性条件

讨论了赋范线性空间中非光滑向量极值问题的Hatley,Borwein,Benson真有效解之间的关系,指出了它们共同的标量极值问题的等价刻画,建立了问题（VMP）的广义KT-真有效解的充分条件,并给出了向量极小值问题在锥局部凸、拟凸、伪凸等条件下的最优性条件。     

关于一类向量极值问题弱有效解的充分必要条件

本文研究带集合约束的向量极值问题。运用局部凸Hausdorff拓扑向量空间中广义次似凸映射的择一定理和其他一些结论，得到了关于集合约束向量极值问题弱有效解的几个充分必要条件．     

关于Pareto极值问题

[1]中研究了Pareto极值问题.[3]中部分地改进了[2]中的结果.本文给出Pareto极值存在的一个一般结论,这一结论包含了[2][3]中的有关结论作为特殊情况.利用弱拓扑还讨论了强-Pareto极值的存在性,从而在比[2][3]有关定理更弱的条件下,获得了更强的结论.     

积分型总极值方法的最优性条件

郑权提出了求总极值问题的积分—水平集的概念性算法,同时给出了最优性条件.本文构造函数F(x),讨论了该函数的性质,证明求解原问题等价于求解方程F(c)=0的根.在文中给出了相应的总极值存在的最优性条件.     

Robertson函数族的极值问题

本文定义了α级 Robertson 函数族,确定它的闭凸包,闭凸包的极值点和它的支撑点,利用变分法讨论某些极值问题.我们还得到实系数子族有关线性极值问题的若干结果。     

非光滑非凸向量极值问题的真有效解

本文考虑非光滑非凸向量极值问题的真有效解,其主要结果如下:(1)Borwein真有效解与Benson真有效解的等价性;(2)向量极值问题的真有效解与标量极值问题的最优解的等价性;(3)广义鞍点定理;(4)真有效解的必要和充分条件。     

广义B—D逆及其应用

本文首先给出了著名的Bott-Duffrin逆(简称B-D逆)A_(L)~((-1))的许多进一步的性质与新的应用,指出了A_(L)~((-1))的存在性与方程组的解的两种唯一性之间的紧密联系;然后定义了广义B-D逆A_(L)~(+)=P_L(AP_L+P_L~⊥)~+,讨论了A_(L)~(+)的一些性质,给出了当A为一般方阵与当A为L=N(B)—非负定阵时关于方程组(1)的可解性的方便的判别条件以及有解时其解的显式,统一处理了在最优化、线性统计推断、二维插值中出现的方程组(1)与约束二次极值问题的求解问题。     

一类极值问题

本文讨论了一类极值并刻划了它的解的特征.该极值问题为:给定d_i(x₀,…,x_n),i = 0,…,n,要确定y₀<…y_n 使得     

A Survey of Algebraic Multilevel Iteration (AMLI) Methods

For the solution by preconditioned conjugate gradient methods of symmetric positive definite equations as arising in boundary value problems we consider preconditioning methods of AMLI type. Particular attention is devoted to providing methods of optimal order of computational complexity which in addition promise to be robust, i.e. with a convergence rate which is bounded above independently of size of discretization parameter h, jumps in problem coefficients, and shape of finite elements or, equivalently, anisotropy of problem coefficients. In addition, the computational cost per iteration step must have optimal order.New results on upper bounds of one of the important parameters in the methods, the Cauchy—Bunyakowski—Schwarz constant are given and an algebraic method how to improve its value is presented.This revised version was published online in October 2005 with corrections to the Cover Date.     

On boundary value problems in three-ion electrodiffusion

The existence of solutions to a class of two-point boundary value problems in three-ion electrodiffusion is investigated via an integro-differential formulation. Boundedness by upper and lower solutions corresponding to associated boundary value problems is considered and illustrated by Painlevé II solutions of a constrained version of the original boundary value problems.     

Implicit runge-kutta methods for differential inclusions

This paper is concerned with the application of implicit Runge-Kutta methods suitable for stiff initial value problems to initial value problems for differential inclusions with upper semicontinuous right-hand sides satisfying a uniform one-sided Lipschitz condition and a growth condition. The problems could stem from differential equations with state discontinuous right-hand sides. It is shown that there exist methods with higher order of convergence on intervals where the solution is smooth enough. Globally we get at least the order one.     

A practicable way for computing the directional derivative of the optimal value function in convex programming

Formulas for computing the directional derivative of the optimal value function or of lower or upper bounds of it are well-known from literature. Because they have as a rule a minmax structure, methods from nondifferentiable optimization are required.

Considering a fully parametrized convex problem, in the paper the mentioned minmax formulas are transformed into usual programming problems. Although they are nonconvex in general, the computational effort is much lower than that for minmax problems. In several special cases, for instance, for linear least squares problems, linear programming problems arise.     

一类四阶边值问题的分析

该文考虑的四阶边值问题，可用于描述飞机、轮船及建筑物的结构模型。由经典的分析方法，如辅助的截断函数，Schauder不动点定理，作者首先提出一种改进的上、下解方法；然后，利用二阶齐次边值问题的第一特征函数，构造出具体的上解，同时取0为相应下解，在更一般的假设下得到正解的存在性； 最后探讨了右端项f(x,y,z)在y=0奇异的情形。     

Spectral Bounds for Tricomi Problems and Application to Semilinear Existence and Existence with Uniqueness Results

For the linear Tricomi problem, it is shown that real eigenvalues corresponding to generalized eigenfunctions must be positive and that the energy integral methods used to prove solvability results can give lower bounds on the spectrum. Exploiting the linear solvability theory and spectral information, standard nonlinear analysis tools are employed to yield results on existence and uniqueness for semilinear problems. In particular, using the Leray-Schauder principle, existence of generalized solutions with sublinear nonlinearities is established. For sublinear or asymptotically linear nonlinearities that satisfy a Lipschitz condition, the contraction mapping principle is employed to give results on existence with uniqueness. The Lipschitz constant depends on lower bounds for the spectrum of the linear problem. For certain superlinear problems, maximum principles for the linear problem are used via the method of upper and lower solutions to give results on existence.     

An economical method of calculating Lagrange multiplier estimates for nonlinear programming problems when many of the constraints are bounds on the variables

Some recent methods for solving nonlinear programming problems make use of estimates of the Lagrange multipliers. These estimates are usually calculated by solving a system oft linear equations, wheret is the number of active constraints. It is shown that, when a large proportion of the active constraints consists of simple upper or lower bounds on the variables, then computational effort can be saved by means of a reorganization of this linear system.     

On fourth-order elliptic boundary value problems

This paper is concerned with the existence and uniqueness of a solution for a class of fourth-order elliptic boundary value problems. The existence of a solution is proven by the method of upper and lower solutions without any monotone nondecreasing or nonincreasing property of the nonlinear function. Sufficient conditions for the uniqueness of a solution and some techniques for the construction of upper and lower solutions are given. All the existence and uniqueness results are directly applicable to fourth-order two-point boundary value problems.

     

Singular second order boundary value problems on purely discrete time scales

We study singular discrete second order boundary value problems with mixed boundary conditions over a finite interval. We prove the existence of a positive solution by means of the lower and upper solutions method and the Brouwer fixed point theorem in conjunction with perturbation methods to approximate regular problems.