一类加权种群系统边界控制的最优条件

文章讨论了一类与年龄相关且具有加权总规模的非线性时变种群系统边界控制为最优的必要条件,得到了由积分-偏微分方程和变分不等式组成的最优性组.     

星座卫星通信系统资源动态平衡模型的研究

资源动态平衡在星座卫星通信系统中具有重要的作用。针对目前星座卫星通信系统中影响资源平衡的因素,将宏观经济理论原理应用到资源平衡调配领域。从通信任务满足度出发,提出了基于虚拟工厂的资源动态平衡模型,详细阐述了模型中的3C评估指标体系,并以铱系统为例进行评估,验证了3C评估的可行性和有效性。通过模型的构建与求解,得出了星座卫星通信系统内、外部环境、用户需求及资源使用释放随时间推移和空间转换发生改变的关联关系,以及整个星座卫星通信系统达到帕累托最优的具体条件。资源动态平衡问题的研究,为解决星座卫星通信系统中的资源调配问题奠定了基础。     

Conformational origin of the molecular weight dependence of the characteristic ratio of the dipole moment in poly(A-B)

By poly(A-B) we denote a chain with repeating sequence -A-B-, such as polyoxymethylene. Here A and B stand for a single atom, e.g., -O-, or a group of atoms, e.g., -CH₂-. All n bond vectors are of the same length, l, as are all bond dipole moment vectors, m. The manner in which the characteristic ratio of the dipole moment, D_n≡〈μ²〉₀/nm² approaches its asymptotic limit is related quantitatively to the behavior of subchains of various sizes in poly(A-B). Illustrative numerical calculations with rotational isomeric state (RIS) models for several polymers are consistent with the predictions. The approach of D_n to its asymptotic limit is sensitive to longer subchains than is the approach of the characteristic ratio of the end-to-end distance, C_n≡〈r²〉₀/nl², to its asymptotic limit, due to the differences in the connectivity of the bond vectors (head-to-tail) and the bond dipole moment vectors (head-to-head, tail-to-tail).     

An asymptotic maximum likelihood for estimating the nominal angle of a spatially distributed source

This paper proposes a large-sample approximation of the maximum-likelihood estimator for direction finding in the presence of a spatially spread source. The key idea is to replace the parametric estimate of the four-dimensional nuisance parameter vector with the approximate one that depends on just one parameter of interest, called the nominal angle, thus permitting the use of one-dimensional optimization techniques. The proposed estimator is shown to be strongly consistent and asymptotically efficient, and the Cramér–Rao bound on its standard deviation is derived. Simulations show the estimator to outperform previously proposed estimators, such as the subspace-based estimator and others based on one-dimensional search.     

集值优化问题严有效意义下的鞍点与对偶

本文研究集值优化问题在严有效意义下的鞍点理论及对偶理论。首先,给出集值优化问题在严有效意义下鞍点的一个等价命题和鞍点定理。其次,在某种凸性假设下,研究严有效意义下鞍点最优性条件、弱对偶性、强对偶性、逆对偶性。     

永磁直线电机伺服系统非线性鲁棒控制器设计

针对永磁直线电机伺服系统数学模型非线性的特点设计L2鲁棒控制器,将跟踪和扰动抑制问题归结为L2控制问题.通过构造适当的存储函数得到描述系统L2控制器的定理;证明定理给出的控制器能满足干扰抑制和系统的渐近稳定.仿真结果表明,用该方法设计的系统能很好地抑制扰动和跟踪给定,满足对高性能永磁直线伺服系统控制的要求.     

半Markov决策过程折扣模型与平均模型之间的关系

首先分别在折扣代价与平均代价性能准则下,讨论了一类半M arkov决策问题.基于性能势方法,导出了由最优平稳策略所满足的最优性方程.然后讨论了两种模型之间的关系,表明了平均模型的有关结论,可以通过对折扣模型相应结论取折扣因子趋于零时的极限来得到.     

Relative hazard rate estimation for right censored and left truncated data

In medical research differences among treatment groups are a common focus of study. The concept of relative hazard rate is a tool for comparing two groups in terms of their difference in risk rates. A kernel estimator is proposed in the case where both samples are subject to left truncation and right censoring and an iid representation is obtained in this setup. The asymptotic distribution and the asymptotic mean squared error of the estimator are obtained. An application to the famous Channing House data set illustrates the theory. Research supported in part by MCyT Grants PB98-0182-C02-01 and BFM2002-00265 (ERDF support included) and XUGA Grant PGIDT00PX110501 PN for the first author and by the Ministry of the Flemish Community (Project BIL00/28, International Scientific and Technological Cooperation) and by the IAP research network nr P5/24 of the Belgian State (Federal Office for Scientific, Technical and Cultural Affairs) for the last two authors.     

On the convergence of stationary sequences in topology optimization

We consider structural topology optimization problems including unilateral constraints arising from non‐penetration conditions in contact mechanics. The resulting non‐convex non‐smooth problems are instances of mathematical programs with equilibrium constraints (MPEC), or bi‐level programs. Applying nested (implicit programming) algorithms to this class of problems is problematic owing to the singularity of the feasible set. We propose a perturbation strategy combining the relaxation of the equilibrium constraint with the restriction of the design domain to its regular part only. This strategy allows us to attack the problem numerically using standard non‐linear programming algorithms. We rigorously study the optimality conditions for the original singular problem as well as the convergence of stationary points and globally optimal solutions to approximating problems towards respective stationary points and globally optimal solutions to the original problem. A limited numerical benchmarking of the algorithm is performed. Copyright © 2005 John Wiley & Sons, Ltd.