On the optimal detection of an underwater intruder in a channel using unmanned underwater vehicles

Given a number of patrollers that are required to detect an intruder in a channel, the channel patrol problem consists of determining the periodic trajectories that the patrollers must trace out so as to maximized the probability of detection of the intruder. We formulate this problem as an optimal control problem. We assume that the patrollers' sensors are imperfect and that their motions are subject to turn‐rate constraints, and that the intruder travels straight down a channel with constant speed. Using discretization of time and space, we approximate the optimal control problem with a large‐scale nonlinear programming problem which we solve to obtain an approximately stationary solution and a corresponding optimized trajectory for each patroller. In numerical tests for one, two, and three underwater patrollers, an underwater intruder, different trajectory constraints, several intruder speeds and other specific parameter choices, we obtain new insight—not easily obtained using simply geometric calculations—into efficient patrol trajectory design under certain conditions for multiple patrollers in a narrow channel where interaction between the patrollers is unavoidable due to their limited turn rate.© 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

Inventory management with advance capacity information

An important aspect of supply chain management is dealing with demand and supply uncertainty. The uncertainty of future supply can be reduced if a company is able to obtain advance capacity information (ACI) about future supply/production capacity availability from its supplier. We address a periodic‐review inventory system under stochastic demand and stochastic limited supply, for which ACI is available. We show that the optimal ordering policy is a state‐dependent base‐stock policy characterized by a base‐stock level that is a function of ACI. We establish a link with inventory models that use advance demand information (ADI) by developing a capacitated inventory system with ADI, and we show that equivalence can only be set under a very specific and restrictive assumption, implying that ADI insights will not necessarily hold in the ACI environment. Our numerical results reveal several managerial insights. In particular, we show that ACI is most beneficial when there is sufficient flexibility to react to anticipated demand and supply capacity mismatches. Further, most of the benefits can be achieved with only limited future visibility. We also show that the system parameters affecting the value of ACI interact in a complex way and therefore need to be considered in an integrated manner. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

直驱型电动舵机中永磁容错电机设计

为了提高直驱型电动舵机的可靠性和容错性、减小直驱型电动舵机的体积和重量,设计具有容错能力的电机.分析直驱型电动舵机中电机的容错性,设计了满足容错需求的三相24槽20极表面式永磁同步电机,对电机尺寸参数进行优化,建立该电机的有限元仿真模型,并对其开路和短路故障进行有限元仿真分析.有限元仿真结果表明,所设计的电机具有很强的...     

应变率和绝热软化对空腔膨胀影响的数值模拟

采用数值模拟的方法研究金属材料球形空腔膨胀的空腔面径向应力与膨胀速度关系.理想弹塑性模型和幂次硬化模型的模拟结果与理论解吻合得非常好,验证了该方法的有效性.在此基础上研究了应变率和绝热软化效应对空腔面径向力和膨胀速度的影响.结果表明,综合考虑应变率和热效应的侵深预测结果与试验值吻合得很好,只考虑应变率而不计热效应会高估...     

流化H.264编码的数据并行方法

流模型是一种源于媒体处理的新型并行计算模型.然而H.264编码作为媒体处理领域中的重要应用,在与流模型适配时,却出现重要障碍,主要是由于相关性问题极大地限制了流化过程中数据级并行的开发.针对这个问题,首先根据编码算法分析了编码过程中遇到的相关性问题,然后为各主要编码模块分别提出解除相关性限制的数据并行编码方法.采用这些...     

基于随机时间影响网络的联合火力打击方案评估

联合火力打击方案评估是作战筹划和指挥决策的核心问题之一,对于打击手段的选择、战法的运用等具有重要的影响,其难点是在不确定条件下有效地建立作战方案到使命目标达成效果之间的映射关系.作战仿真方法往往存在突出的低效率问题,而解析模型的方法难以充分反映目标体系的内部联系和整体效果.目前概率推理模型广泛应用于军事领域的作战方案评...     

面向重用的BOM概念模型相似度评估研究

针对BOM概念模型重用的问题,提出了概念模型相似度用于描述两个概念模型之间的相似程度.并提出相似度评估算法用于计算概念模型之间的相似度.根据概念模型的定义,将相似度的计算归结为名字相似度计算和最优匹配计算两个基本过程.研究了算法中接口权重参数和行为权重参数的不同组合对算法查准率和查全率的影响.通过对JC3IEDM数据模...     

基于心理调查和空间干预的人群心理仿真

突发危机事件中人群心理评估是当前危机管理急需解决的难点问题.由于突发危机事件群体心理数据采集的困难性和人群心理变化的复杂性等原因,传统方法很难准确评估群体心理效果.随着计算机科学的发展,建模仿真成为解决这类问题的有效手段.以复杂适应系统理论为指导,采用基于Agent的建模与仿真方法,研究外部事件刺激下群体的心理行为,构...     

无刷双馈电机原理及控制策略

详细分析了无刷双馈发电机的基本原理,基于不同的参考坐标系(转子轴dq0坐标系和同步坐标系),建立了无刷双馈发电机不同的数学模型.依据建立的数学模型,介绍了无刷双馈发电机的几种控制策略(标量控制、磁场定向控制、直接转矩控制、智能控制方法),并指出其优缺点.最后,指出了无刷双馈发电机运行控制中存在的难点和进一步研究的方向.     

双变因子LMS自适应滤波算法

为提高最小均方(LMS)自适应滤波算法的性能,在步长因子与误差信号满足一种改进的Sigmoid函数关系式的基础上,提出了一种双变因子控制下的变步长LMS自适应滤波算法。该算法具有初始状态收敛速度快、稳定状态均方误差小、抗噪声性能好、适应系统跃变能力强的优点。计算机仿真结果验证了该算法的优越性。