源结构无关的远程备份数据共享存储方法

针对远程容灾系统中备份数据的存储依赖数据源的结构特征和备份中心资源浪费严重的现状,提出一种远程备份数据存储方法。通过数据封装、存储空间动态分配等技术实现多备份任务的备份数据在共享的存储空间内存储,备份中心与备份数据源的存储结构无关。实验证明,该方法不仅提高系统资源的使用效率,而且能提供较好的存储性能。     

移动计算环境中的自适应混合广播

提出一种自适应混合广播算法。在周期广播数据分配时采用多信道非均匀分配,使高访问率的数据获得高广播频率。在确定周期广播数据和联机请求数据个数时考虑联机请求信道响应时间和访问率之间的关系,从而在少量比较次数后获得数据最佳分割点。实验结果表明,该算法可以根据系统负载和用户访问模式的变化动态调节信道和数据的分配,性能优于纯广播和纯基于请求的广播,访问时间少于现有的混合数据广播方式。     

基于动态默认转移的深度包检测算法

由于基于确定性有限自动机（DFA）的多模式匹配算法对内存的需求比较大,因此需要对DFA进行优化,以减少其对内存的需求量。算法通过用动态默认转移来替代DFA的failto转移,将DFA中大量的failto转移删掉,从而达到优化DFA的目的。实验结果证明,该算法能有效地优化DFA对内存的需求。     

VxWorks远程在线软件升级技术

针对单一的软件升级方式难以满足不同VxWorks软件升级需求的问题,分析各种VxWorks软件升级方式的优缺点和适用场合,设计VxWorks远程在线软件升级系统,讨论动态软件升级的原理和实现方法。介绍提高升级可靠性的设计,描述系统的具体实现。该系统组合使用3种软件升级方式,可基本满足各种不同软件的升级需求。     

一种脆弱的图像自适应置乱算法

证明在离散余弦变换和小波变换中,图像经空域置乱前后在频域内不变的系数规律,根据构造的复合混沌迭代动力系统,提出2个利用不变频域变换系数规律的构造函数,生成复合混沌迭代动力系统需要的初始值,给出脆弱的图像自适应置乱算法以及相似度和抗攻击半径的置乱算法评价概念。实验表明,算法无需任何附加信息即可提取出原始图像,对各种攻击十分敏感,平均抗攻击半径高于一般算法,适用于法庭、医学等要求极其严格的场合。     

基于动态逻辑许可证的PDF版权管理系统

电子文档版权管理是数字版权管理的重要研究领域,提出一种PDF电子文档版权保护方案,该方案的权限管理基于一种具有强大表达力、灵活性和开放权限管理能力的动态逻辑许可证,具有详细的文档权限控制方法,并通过内容级的PDF文档加密方法增强文档的安全性。对系统模型、实现结构和方法进行说明,并与相关方法进行对比和应用示例。     

Stability radius of implicit dynamic equations with constant coefficients on time scales

This paper deals with the stability radii of implicit dynamic equations on time scales when the structured perturbations act on both the coefficient of derivative and the right-hand side. Formulas of the stability radii are derived as a unification and generalization of some previous results. A special case where the real stability radius and the complex stability radius are equal is studied. Examples are derived to illustrate results.     

On the use of energy minimization for CA based analysis in elasticity

There has been recent interest in exploring alternative computational models for structural analysis that are better suited for a design environment requiring repetitive analysis. The need for such models is brought about by significant increases in computer processing speeds, realized primarily through parallel processing. To take full advantage of such parallel machines, however, the computational approach itself must be revisited from a totally different perspective; parallelization of inherently serial paradigms is subject to limitations introduced by a requirement of information coordination. The cellular automata (CA) model of decentralized computations provides one such approach which is ideally tailored for parallel computers. The proposed paper examines the applicability of the cellular automata model in problems of 2-D elasticity. The focus of the paper is in the use of a genetic algorithm based optimization process to derive the rules for local interaction required in evolving the cellular automata. Received August 28, 2000     

Guaranteed Dynamic-System State Estimation by the Method of Bidirectional Dynamic Programming

The problem of guaranteed estimation (smoothing, filtration, prediction) of a dynamic process observed on a finite discrete time interval is solved, based on generalization of the dynamic programming procedure for the case with sequential optmization in direct and inverse time.     

Design and experimental evaluation of a robust force controller for an electro-hydraulic actuator via quantitative feedback theory

This paper presents the design and experimental evaluation of an explicit force controller for a hydraulic actuator in the presence of significant system uncertainties and nonlinearities. The nonlinear version of quantitative feedback theory (QFT) is employed to design a robust time-invariant controller. Two approaches are developed to identify linear time-invariant equivalent model that can precisely represent the nonlinear plant, operating over a wide range. The first approach is based on experimental input–output measurements, obtained directly from the actual system. The second approach is model-based, and utilizes the general nonlinear mathematical model of a hydraulic actuator interacting with an uncertain environment. Given the equivalent models, a controller is then designed to satisfy a priori specified tracking and stability specifications. The controller enjoys the simplicity of fixed-gain controllers while exhibiting robustness. Experimental tests are performed on a hydraulic actuator equipped with a low-cost proportional valve. The results show that the compensated system is not sensitive to the variation of parameters such as environmental stiffness or supply pressure and can equally work well for various set-point forces.