The optimal linear combination of control variates in the presence of asymptotically negligible bias

The optimal linear combination of control variates is well known when the controls are assumed to be unbiased. We derive here the optimal linear combination of controls in the situation where asymptotically negligible bias is present. The small-sample linear control which minimizes the mean square error (MSE) is derived. When the optimal asymptotic linear control is used rather than the optimal small-sample control, the degradation in MSE is c/n³, where n is the sample size and c is a known constant. This analysis is particulary relevant to the small-sample theory for control variates as applied to the steady-state estimation problem. Results for the method of multiple estimates are also given.     

Incorporation dynamic aspects and uncertainty in 1‐median location problems

In this paper we present several 1‐median formulations on a tree network which incorporate dynamic evolution and/or uncertainty of node demands and transportation costs over a planning horizon. Dynamic evolution is modeled using linear demand functions for the nodes and linear length functions for the edges. Uncertainty is modeled with the use of multiple scenarios, where a scenario is a complete specification of the uncertain node demands and/or edge lengths. We formulate our objective using minimax regret like criteria. We use two different criteria, namely, robust deviation and relative robustness. We discuss what motivated the introduction of these objectives, as well as their relation to existing literature and decision making practices. For all of the models presented, we provide low‐order polynomial time algorithms. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 147–168, 1999     

Real-time task scheduling with overheads considered

n periodic tasks are to be processed by a single machine, where each task i has a maximum request rate or periodicity F_i, a processing time E_i, a deadline D_i, relative to each request of task i, a task-request interrupt overhead I_i, and a task-independent scheduling overhead S. Two scheduling strategies are considered for sequencing the execution of an arbitrary arrangement of task requests in time: the preemptive and the nonpreemptive earliest-deadline algorithms. Necessary and sufficient conditions are derived for establishing whether a given set of tasks can be scheduled by each scheduling strategy. The conditions are given in the form of limited simulations of a small number of well-defined task-request arrangements. If all simulations succeed, the schedule is feasible for the given set of tasks. If any simulation fails, the schedule is infeasible. While interrupt handling and scheduling overheads can be handled by such simulations, context switching overhead resulting from preemption cannot. A counterexample illustrates how the simulations fail to uncover unschedulable task sets when context switching overhead is considered.     

旋转稳定塑料弹体工程设计计算研究

本文以实验结果为依据,首先分析了塑料弹体影响弹丸膛内运动的物理性能,然后结合旋转弹丸的膛内运动特征,经过模拟试验,采用数学拟合法,初步建立旋转稳定弹塑料弹体工程设计计算的数学模型(包括结构尺寸设计计算、强度计算和内弹道计算)。     

基于时间融合的雷达辐射源自动识别方法

雷达辐射源识别是雷达对抗信号处理中关键环节,也是电子目标识别的重要前提.介绍了Dempster组合规则和加权M-距离法、灰关联分析法等时间融合的雷达辐射源自动识别方法,提出了基于证据理论的单传感器时间融合算法,研究了单传感器在不同时间测量周期的证据综合过程,并给出仿真试验结果.随着噪声的增大,传感器单次时间融合的正确识别率下降很快,而采用基于D-S证据理论的单传感器时间融合方法却有较高的正确识别率,该算法大大降低了错误识别率.因此提出的算法是可行的.     

Efficient generation of cycle time‐throughput curves through simulation and metamodeling

A cycle time‐throughput (CT‐TH) curve, which quantifies the relationship of long‐run average cycle time to throughput rate, plays an important role in strategic planning for manufacturing systems. In this paper, a nonlinear regression metamodel supported by queueing theory is developed to represent the underlying CT‐TH curve implied by a manufacturing simulation model. To estimate the model efficiently, simulation experiments are built up sequentially using a multistage procedure. Extensive numerical experiments are presented to demonstrate the effectiveness of the proposed procedure. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Machine maintenance with workload considerations

Machine maintenance is modeled in the setting of a single‐server queue. Machine deterioration corresponds to slower service rates and failure. This leads to higher congestion and an increase in customer holding costs. The decision‐maker decides when to perform maintenance, which may be done pre‐emptively; before catastrophic failures. Similar to classic maintenance control models, the information available to the decision‐maker includes the state of the server. Unlike classic models, the information also includes the number of customers in queue. Considered are both a repair model and a replacement model. In the repair model, with random replacement times, fixed costs are assumed to be constant in the server state. In the replacement model, both constant and variable fixed costs are considered. It is shown in general that the optimal maintenance policies have switching curve structure that is monotone in the server state. However, the switching curve policies for the repair model are not always monotone in the number of customers in the queue. Numerical examples and two heuristics are also presented. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

周恩来建设人民海军的理论和实践

周恩来协助毛泽东开创了中国人民海军事业。他高瞻远瞩,为人民海军的创建发展做好顶层设计;他呕心沥血,制定新中国海军建设的战略规划;他事必躬亲,操劳着海军建设方方面面的具体事项;他英明善断,指挥部署人民海军重要战役和重大行动。他对创建和发展年轻的共和国海军,作出了不可磨灭的贡献。周恩来建设人民海军的理论和实践,对今天的海军建设仍具有重要的理论价值和实践意义。     

雷达信号非均匀粒度聚类分选方法

聚类分析是数据挖掘中的重要技术.在比较分析了两种常用的聚类分析方法的基础上,将基于商空间的非均匀粒度聚类算法应用于雷达信号分选中,仿真实验的结果表明:该算法可以从不同层次观察聚类数据,更适用于复杂雷达信号聚类分选,具有良好的性能.