Solution algorithms for the parallel replacement problem under economy of scale

We consider the parallel replacement problem in which machine investment costs exhibit economy of scale which is modeled through associating both fixed and variable costs with machine investment costs. Both finite- and infinite-horizon cases are investigated. Under the three assumptions made in the literature on the problem parameters, we show that the finite-horizon problem with time-varying parameters is equivalent to a shortest path problem and hence can be solved very efficiently, and give a very simple and fast algorithm for the infinite-horizon problem with time-invariant parameters. For the general finite-horizon problem without any assumption on the problem parameters, we formulate it as a zero-one integer program and propose an algorithm for solving it exactly based on Benders' decomposition. Computational results show that this solution algorithm is efficient, i.e., it is capable of solving large scale problems within a reasonable cpu time, and robust, i.e., the number of iterations needed to solve a problem does not increase quickly with the problem size. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 279–295, 1998     

Locating a target from directional data

Statistical estimation plays an important role in locating a target in space, a task that has important applications in many areas. However, theoretical measures on the quality of various estimators reported in the literature have been difficult to obtain because of mathematical complications. As a result, choice of estimator in practice has been largely arbitrary. In this paper, we present a systematic study on major target estimators reported in the literature. Focus is on comparisons between the traditional angle method, the line method, and a recently developed line-to-point transformation method. Insights gained from the study directly lead to the development of a novel two-stage angle method that not only produces highly accurate target estimation among all known estimators but is also computationally efficient. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 353–364, 1998     

Scheduling deteriorating jobs to minimize makespan

We consider a single-machine problem of scheduling n independent jobs to minimize makespan, in which the processing time of job J_j grows by w_j with each time unit its start is delayed beyond a given common critical date d. This processing time is p_j if J_j starts by d. We show that this problem is NP-hard, give a pseudopolynomial algorithm that runs in time and O(nd) space, and develop a branch-and-bound algorithm that solves instances with up to 100 jobs in a reasonable amount of time. We also introduce the case of bounded deterioration, where the processing time of a job grows no further if the job starts after a common maximum deterioration date D > d. For this case, we give two pseudopolynomial time algorithms: one runs in O(n²d(D − d) time and O(nd(D − d)) space, the other runs in p_j)²) time and p_j) space. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 511–523, 1998     

面向多星观测调度的分层迭代算法

提出一种基于分治策略的多星观测分层调度框架,在该框架下,用蚁群优化算法把任务分配至各轨道圈次上,并利用自适应模拟退火算法求解各轨道圈次的调度问题。根据各轨道圈次调度结果的反馈情况,再调整任务分配方案,重复上述过程直到达到算法终止条件。为了提高算法的性能,在设计蚁群算法的启发式信息模型时,应充分考虑卫星调度问题的领域知识;在模拟退火算法中设计两个邻域结构,采用动态选择策略在优化过程中确定最佳邻域搜索结构。仿真实验表明,该方法有效地降低了问题求解的复杂度,尤其在求解大规模多星观测调度问题时表现出优异的性能。     

SpaceWire网络混合路由机制设计

针对星上系统总线多元性导致的星载网络接口和协议不能标准化的发展瓶颈,基于SpaceWire总线协议,通过将静态路由(时间触发)与动态路由(事件触发)机制结合,实现了控制数据和载荷数据共用网络。静态路由完全遵循SpaceWire-D协议,在保证确定性传输的同时,通过启发式调度算法首次实现了多时间窗并行调度,并提出利用最大公约数法设计时间窗,以提高网络吞吐量;动态路由通过对随机事件和载荷数据分配优先级,实现传输路径冲突时对紧急任务的优先处理。在OPENT中搭建网络系统仿真模型,对所提出的路由机制进行了仿真。实验结果表明,静态路由时段网络吞吐量较现有调度算法有明显提高,动态路由实现了紧急事件优先传输。     

低地球轨道卫星网络节能方法

通常卫星的唯一能源来源是太阳能,因此星上网络设备的能源供应问题比地面网络的更加严峻。通过修改和扩展链路容量受限的最小代价多商品流模型来适应卫星网络这一特殊的体系结构,并基于低轨道卫星网络的多重覆盖机制和流量分布模型,改进现有的启发式算法来关闭冗余的卫星节点、星地链路和星间链路。在满足链路利用率和路由跳数增加比例约束的条件下,仿真实验中关闭上述三种参数的比例分别可达59%、61%和72%,卫星网络的总体节能比例可达65%。     

采用遗传算法的弹托迎风窝结构设计

针对一体化弹丸弹托易分离性和轻质化的设计要求,构建弹托迎风窝参数化外形模型,基于激波和膨胀波理论建立弹托气动力计算模型;以弹托分离加速度和弹托质量综合最优为目标函数,采用遗传算法对弹托迎风窝的外形参数进行优化设计,从而得到弹托迎风窝的优化外形。以中口径尾翼稳定脱壳穿甲弹的弹托设计为例,采用提出的优化设计模型对其迎风窝结构进行优化设计,并采用基于动网格技术的弹托分离仿真模型验证其最优性。仿真结果表明：所提优化模型能够得到最优的弹托迎风窝结构;针对现有的中口径尾翼稳定脱壳穿甲弹,可进一步对其弹托结构进行优化,以提高其分离快速性。     

逐步Ⅰ型混合截尾试验下Burr部件的可靠性分析

在逐步Ⅰ型混合截尾试验下,研究了Burr部件寿命参数及可靠性指标的极大似然估计和Bayes估计.利用简单迭代方法,给出了寿命参数和可靠性指标的极大似然估计的数值解.然后利用Lindely Bayes近似算法得到了平方损失下寿命参数以及可靠性指标的Bayes估计.最后,运用Monte-Carlo方法对各估计结果作了模拟比较,结果表明Bayes估计较极大似然估计的误差小.     

系统仿真技术初探

为了对系统仿真技术有一个总体认识,采用归纳和分析的方法,对系统仿真技术的体系进行了初步探讨.     

基于改进遗传算法的舰载机保障调度方法

舰载机保障作业过程受到多资源约束,同时可能存在着突发事件的干扰;针对此特点,分析并制定干扰情况下的模型修正策略。在遗传算法中引入禁忌搜索算子改进传统遗传算法的变异操作,并通过具体实例进行仿真验证,其结果证明改进后的遗传算法在优化含干扰事件的多机保障问题时效率更高,并通过甘特图直观地反映重调度方案。为真实情况下有效处理舰载机保障过程中的干扰事件奠定理论基础。