Exponential stability and exponential stabilization of singularly perturbed stochastic systems with time‐varying delay

In this paper, the problems of exponential stability and exponential stabilization for linear singularly perturbed stochastic systems with time‐varying delay are investigated. First, an appropriate Lyapunov functional is introduced to establish an improved delay‐dependent stability criterion. By applying free‐weighting matrix technique and by equivalently eliminating time‐varying delay through the idea of convex combination, a less conservative sufficient condition for exponential stability in mean square is obtained in terms of ε‐dependent linear matrix inequalities (LMIs). It is shown that if this set of LMIs for ε=0 are feasible then the system is exponentially stable in mean square for sufficiently small ε?0. Furthermore, it is shown that if a certain matrix variable in this set of LMIs is chosen to be a special form and the resulting LMIs are feasible for ε=0, then the system is ε‐uniformly exponentially stable for all sufficiently small ε?0. Based on the stability criteria, an ε‐independent state‐feedback controller that stabilizes the system for sufficiently small ε?0 is derived. Finally, numerical examples are presented, which show our results are effective and useful. Copyright © 2010 John Wiley & Sons, Ltd.     

Improved delay‐dependent absolute stability and robust stability for a class of nonlinear systems with a time‐varying delay

This paper investigates the problem of the absolute stability of Lur'e systems with a time‐varying delay. By considering the relationships among the time‐varying delay, its upper bound, and the difference between them, less conservative delay‐dependent stability criteria are obtained and formulated in terms of linear matrix inequalities, without ignoring any useful terms in the derivative of a Lyapunov–Krasovskii functional. Numerical example shows that the results obtained in this paper are better than the previous results. Copyright © 2009 John Wiley & Sons, Ltd.     

Windows操作系统EFS加密方式应用及解析

本文介绍了Windows操作系统中EFS加密方式的优点、操作步骤、加密原理及解密方法,并详细列举了5个重点注意事项,为全面理解Windows操作系统中使用的EFS加密手段提供了帮助。     

量子密码研究与进展

量子密码解决了传统密码技术存在的问题,是近年来国际学术界的一个研究热点。本文论述了传统密码技术存在的问题,阐述了量子密码的基本原理,介绍了主要的量子密码协议：BB84协议、B92协议和E91协议等,并研究了量子密码通信的研究现状及其进展。量子密码必将会在网络安全通信中得到广泛的应用。     

A novel digital filter structure with minimum roundoff noise

In this paper, a novel structure is derived for efficient implementation of digital filters as well as minimizing the finite word length (FWL) errors. Such a structure is actually an improved version of that reported previously. The performance of this new structure and the famous normalized lattice structure are analyzed by deriving the corresponding expression for the roundoff noise gain. Design examples are presented to illustrate the behavior of the proposed structure and to compare it with some existing ones. It is shown that the proposed structure outperforms the others in terms of minimizing roundoff noise as well as implementation efficiency.     

New Results on Robust Exponential Stability of Uncertain Stochastic Neural Networks with Mixed Time-Varying Delays

This letter considers the robust exponential stability of uncertain stochastic neural networks with mixed time-varying delays. By using Lyapunov–Krasovskii functional and Itô’s differential formula, several new sufficient conditions guaranteeing the global robust exponential stability are derived in terms of linear matrix inequalities. Numerical examples are given to illustrate the effectiveness and less conservativeness of our results.     

A tree-based particle swarm optimization for multicast routing

QoS multicast routing is a non-linear combinatorial optimization problem. It tries to find a multicast routing tree with minimal cost that can satisfy constraints such as bandwidth, delay, and delay jitter. This problem is NP-complete. The solution to such problems is often to search first for paths from the source node to each destination node and then integrate these paths into a multicast tree. Such a method, however, is slow and complex. To overcome these shortcomings, we propose a new method for tree-based optimization. Our algorithm optimizes the multicast tree directly, unlike the conventional solutions to finding paths and integrating them to generate a multicast tree. Our algorithm also applies particle swarm optimization to the solution to control the optimization orientation of the tree shape. Simulation results show that our algorithm performs well in searching, converging speed and adaptability scale.     

飞行器姿态大角度机动联合控制物理仿真技术研究

针对空间飞行器姿态大角度机动控制要求较高的指向精度和姿态稳定度及快速机动等特点,对飞行器的联合姿态控制方法进行了物理仿真研究;采用了相平面法+PD的组合姿态控制算法,设计了组合姿态控制器;系统采用DSP作为星载计算机,光纤陀螺作为姿态敏感器、喷气系统和反作用飞轮作为执行机构,系统程序采用C语言编程,利用飞行器姿态控制单轴气浮实验台实现了物理仿真;实验结果与单独执行机构控制的实验结果进行了比较,联合控制具有机动控制精度高及快速机动等特点.     

基于电容电阻复合层析法测量糖膏结晶浓度

针对目前常规单测量点检测法在糖厂煮糖罐糖膏结晶浓度测量中精度低的不足,提出了基于电容电阻复合层析法对糖膏结晶浓度进行测量;首先采用主成分分析法消除传感器阵列测量数据集的冗余度,然后利用RBF神经网络法解决传感器检测场存在的非线性问题,同时预测出煮糖罐内糖膏结晶浓度,其中RBF神经网络法的参数学习采用遗传优化算法;对该过程进行理论分析和仿真测试,实验结果表明在低成本条件下,测量糖膏结晶浓度精度高,有很好的工业应用前景.