Transient analysis of Markov models of fault‐tolerant systems with deferred repair using split regenerative randomization

The (standard) randomization method is an attractive alternative for the transient analysis of continuous time Markov models. The main advantages of the method are numerical stability, well‐controlled computation error, and ability to specify the computation error in advance. However, the fact that the method can be computationally very expensive limits its applicability. In this paper, we develop a new method called split regenerative randomization, which, having the same good properties as standard randomization, can be significantly more efficient. The method covers reliability‐like models with a particular but quite general structure and requires the selection of a subset of states and a regenerative state satisfying some conditions. For a class of continuous time Markov models, model class C₂, including typical failure/repair reliability‐like models with exponential failure and repair time distributions and deferred repair, natural selections are available for both the subset of states and the regenerative state and, for those natural selections, theoretical results are available assessing the efficiency of the method in terms of “visible” model characteristics. Those results can be used to anticipate when the method can be expected to be competitive. We illustrate the application of the method using a large class C₂ model and show that for models in that class the method can indeed be significantly more efficient than previously available randomization‐based methods. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

A theory of war finance

This paper analyses the financial and war‐spending policies of a state that faces a conflict in which defeat would result in the loss of sovereign power and in which the material consequences, conditional on avoiding defeat, are stochastic. The analysis takes explicit account of the historical experiences of lenders, who face debt repudiation if the state to whom they have lent is defeated and who also face partial default if the material consequences of the war are unfavorable for the debtor state, even if it avoids defeat. In this analysis, the state uses war debt to smooth expected consumption intertemporally in response to temporary war spending, and the state also uses contingent debt servicing to insure realized consumption against the risk associated with the material consequences of the war. An important innovation in the analysis is to treat the equilibrium amount of war spending, the state's resulting probability of avoiding defeat, as well as the equilibrium amount of borrowing as a set of endogenous variables to be determined simultaneously.     

基于最短拦截时间的异面拦截机动轨道设计与优化

本文构建了单脉冲机动在燃耗约束下的最短时间拦截轨道设计模型与求解方法,将用数学泛函求边值问题转换为高次代数方程的求解计算,并用牛顿迭代法进行快速寻根,仿真结果表明模型及算法准确、有效,满足精度要求。     

Demand forecasting by temporal aggregation

Demand forecasting performance is subject to the uncertainty underlying the time series an organization is dealing with. There are many approaches that may be used to reduce uncertainty and thus to improve forecasting performance. One intuitively appealing such approach is to aggregate demand in lower‐frequency “time buckets.” The approach under concern is termed to as temporal aggregation, and in this article, we investigate its impact on forecasting performance. We assume that the nonaggregated demand follows either a moving average process of order one or a first‐order autoregressive process and a single exponential smoothing (SES) procedure is used to forecast demand. These demand processes are often encountered in practice and SES is one of the standard estimators used in industry. Theoretical mean‐squared error expressions are derived for the aggregated and nonaggregated demand to contrast the relevant forecasting performances. The theoretical analysis is supported by an extensive numerical investigation and experimentation with an empirical dataset. The results indicate that performance improvements achieved through the aggregation approach are a function of the aggregation level, the smoothing constant, and the process parameters. Valuable insights are offered to practitioners and the article closes with an agenda for further research in this area. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 60: 479–498, 2013     

基于行为建模的移动代理性能评估

针对移动代理的分布式应用性能评估需求,建立了移动代理生命周期中主要行为的网络负载模型和时间消耗模型.在3种典型分布式应用想定下,分析了基于C＼S模式和移动代理模式的应用实现基本过程,对两种模式下的网络负载和执行时间进行了仿真比较,结果证明了在访问节点数量较多,网络传输速率较低时,移动代理模式的具有更好性能.     

基于复杂排队系统的TOC服务模型与性能分析

三值光学计算机的运算请求处理过程缺乏合理、系统的性能评价标准与体系。基于M/M/1、M/M/n、MX/M/1和M/MB/1构成的复杂排队系统,构建了三值光学计算机的四阶段服务模型,同时建立了立即调度和结束时调度两种不同策略与算法。基于不同排队系统讨论了运算请求的接收时间、预处理时间、运算时间和发送时间的计算方法,进而得到最终响应时间。最后,通过仿真实验对两种策略的模型进行验证,结果表明结束时调度策略明显优于立即调度策略。     

基于CP CI总线的时统模块测量电路设计

为解决时统模块的测试问题,提出了一种基于CPCI总线的数字时统模块测量电路。重点对测量电路的组成、测量原理、CPCI总线接口设计与驱动设计等内容进行了介绍。提出的测量电路满足了4块某型时统模块的批量测试需求。该测量电路具有稳定性高、性价比高、易于实现等优点,适合于工程应用。     

基于备件需求预测的两步法理论

在对备件需求时间序列研究的基础上,结合指数平滑法和Croston法的特点,分析了指数平滑法与两步法的原理,通过对指数平滑法和两步法方差的研究,得到两步法是指数平滑法的一般形式的结论,为两步法的进一步研究提供一定的理论支撑。     

基于通信时延信息的被动定位精度分析

基于通信信号中的时延信息,构建了基本TDOA定位算法,详细推导出了其理论定位精度分布及理论上最优定位点精度,为其定位的主要误差影响因素分析,及基于时延信息的被动定位算法的设计和改进力度提供了参考依据。并结合通信信号实际环境,给出了较为全面的仿真案例验算。     

无人作战飞机通信延时仿真

通信作为无人作战飞机任务控制站与无人作战飞机之间的纽带,在无人作战飞机系统中起着至关重要的作用。简要阐述了引起无人作战飞机通信延时的具体因素,分析了无人作战飞机使用的几种通信方式,提出并运用网络仿真工具NS2(networksimulation-2)针对视线通信方式和不同中继方式下的通信延时进行了仿真,最后对仿真作了分析和解释。