Scheduling jobs with piecewise linear decreasing processing times

We study the problems of scheduling a set of nonpreemptive jobs on a single or multiple machines without idle times where the processing time of a job is a piecewise linear nonincreasing function of its start time. The objectives are the minimization of makespan and minimization of total job completion time. The single machine problems are proved to be NP‐hard, and some properties of their optimal solutions are established. A pseudopolynomial time algorithm is constructed for makespan minimization. Several heuristics are derived for both total completion time and makespan minimization. Computational experiments are conducted to evaluate their efficiency. NP‐hardness proofs and polynomial time algorithms are presented for some special cases of the parallel machine problems. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 531–554, 2003     

空间预警视线系统误差对弹道导弹预警精度估计分析与研究

在空间预警系统中,为了降低系统预警精度受视线测量系统误差的影响,必须对仪器进行定标,因此需要深入对视线误差进行讨论。本文在对视线误差深入研究的基础上,从理论上讨论了视线误差对发射点、射向、落点估计结果的影响,得出系统误差变化率是影响预警结果的重要因素之一,并针对常值系统误差、线性系统误差以及周期系统误差进行了相应的预警仿真计算,从而为几何定标方案的确定提供支持。     

论国防动员中军事征用制度的立法完善

新颁布的《国防动员法》为我国今后军事征用活动的开展提供了重要的法律依据,是军事征用法制发展的里程碑。文章提出,与现行军事征用的立法价值实现及实践要求相比,我国军事征用法律制度仍存在需要完善之处。应科学设立军事征用主体、不断完善军事征用程序和军事征用补偿机制。     

FQPSK和SOQPSK信号的通用准最优解调设计

FQPSK-JR和SOQPSK-TG是IRIG-106遥测标准中可以互换的两种信号体制,两种信号有着近乎相同的功率效率和带宽效率。尽管两种信号都可以采用常规的OQPSK接收机进行解调,但是基于OQPSK结构的接收机忽略了两种信号固有的记忆特性,其解调性能损失相比最优解调达2dB之多。在遥测链路中,受设备体积及电源限制,2dB的功率损失是至关重要的。虽然基于其调制体制相对应的最优接收机都能提高功率效率,但信号产生体制的不同导致了其对应的最优接收机结构不同。将IRIG-106标准中的FQPSK-JR信号用CPM调制来近似表示,将SOQPSK-TG信号的频率成型脉冲进行了截短近似,设计了基于CPM的通用准最优解调器。基于CPM近似设计出的解调器与OQPSK解调器一样无须对两种信号进行识别,仿真表明基于CPM设计的通用解调器对两种信号进行解调的渐进损失都很小,对复杂度也进行了分析对比。     

Nuclear‐ and missile‐related trade and developments for selected countries,July‐October 1997

The material in this overview is drawn from selected abstracts that appear in the Center for Nonproliferation Studies’ nuclear and missile databases. Transactions of nuclear and missile technologies, parts, and materials are listed according o the recipient country. Other developments are listed according to the country where the event or development took place.     

基于体积偏差的焊接熔敷成形分层方向的优化

定义焊接熔敷成形体积偏差的概念为:焊接熔敷成形层与CAD模型切片层之间的体积差的总和.以某一分层方向下的体积偏差来表征此分层方向下的成形精度,某一分层方向下求得的体积偏差越小,则说明沿此方向分层时得到的成形精度越高,反之,则成形精度越低.从提高成形精度方面来考虑,最佳分层方向应当使体积偏差最小.在UG的OPEN GRIP环境下实现了体积偏差的求解.     

The German Invasion of Norway, 1940: The Operational Intelligence Dimension

While many analyses of the 9 April 1940 invasion of Norway have looked at the successful interplay of German air, sea and land components, the part performed by intelligence has largely received only cursory attention. This article seeks to redress this, and investigates the pivotal role intelligence played in the planning, preparation, and carrying out of Weserübung. The study examines the dearth of relevant information in the early planning stage; the subsequent accumulation of military assessments of Norway's defensive capabilities; the process of denying London and Oslo intelligence regarding Berlin's intentions; the significance of Danish and Norwegian airfields to the operation; and the importance of maritime reconnaissance and wireless intercepts in monitoring the disposition of the Royal Navy. Although primarily concerned with German intelligence gathering and utilisation, British efforts, including the potential impact of Ultra, are also considered.     

An FPTAS for scheduling a two‐machine flowshop with one unavailability interval

We study a deterministic two‐machine flowshop scheduling problem with an assumption that one of the two machines is not available in a specified time period. This period can be due to a breakdown, preventive maintenance, or processing unfinished jobs from a previous planning horizon. The problem is known to be NP‐hard. Pseudopolynomial dynamic programming algorithms and heuristics with worst case error bounds are given in the literature to solve the problem. They are different for the cases when the unavailability interval is for the first or second machine. The existence of a fully polynomial time approximation scheme (FPTAS) was formulated as an open conjecture in the literature. In this paper, we show that the two cases of the problem under study are equivalent to similar partition type problems. Then we derive a generic FPTAS for the latter problems with O(n⁵/ε⁴) time complexity. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004.