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排序方式: 共有346条查询结果,搜索用时 31 毫秒
161.
Antoon W.J. Kolen Jan Karel Lenstra Christos H. Papadimitriou Frits C.R. Spieksma 《海军后勤学研究》2007,54(5):530-543
In interval scheduling, not only the processing times of the jobs but also their starting times are given. This article surveys the area of interval scheduling and presents proofs of results that have been known within the community for some time. We first review the complexity and approximability of different variants of interval scheduling problems. Next, we motivate the relevance of interval scheduling problems by providing an overview of applications that have appeared in literature. Finally, we focus on algorithmic results for two important variants of interval scheduling problems. In one variant we deal with nonidentical machines: instead of each machine being continuously available, there is a given interval for each machine in which it is available. In another variant, the machines are continuously available but they are ordered, and each job has a given “maximal” machine on which it can be processed. We investigate the complexity of these problems and describe algorithms for their solution. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007 相似文献
162.
提出了一种基于单脉冲频率及频率变化率联合估计和多脉冲联合估计脉冲重复周期变化率的调频脉冲信号辐射源目标多普勒参数提取方法。该方法解决了无源定位系统数据采样频率与辐射源脉冲重复周期不匹配造成的频率偏差问题,在脉冲到达时间的提取上避免了对脉冲边沿的判断,使得利用中频采样信号计算脉冲重复周期成为可能。介绍对了该方法所采用的频率及频率变化率联合估计关键技术,并在此基础上讨论了该方法所能达到的理论估计精度及误差分析,最后通过仿真试验验证了该方法的可行性和有效性。 相似文献
163.
利用微波脉冲注入实验平台,对硅基双极型晶体管低噪声放大器进行了损伤效应实验。在微波脉冲对硅基双极型晶体管低噪声放大器损伤的失效分析中,当低噪声放大器增益下降大于10d B时,发现硅基双极型晶体管出现了永久损伤。通过对比测量硅基双极型晶体管损伤前后的电特性以及利用扫描电子显微镜观测损伤后晶体管的微观特性发现:硅基双极型晶体管被微波脉冲损伤后,基区的硅材料烧蚀导致发射结和集电结短路,不再具有PN结特性,导致器件失效。 相似文献
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Surulola James Eke 《Defense & Security Analysis》2015,31(4):319-329
Boko Haram (BH) is an insurgent group that operates mainly in northeastern Nigeria. Its stated aim is to establish an Islamic state, and it employs terrorism as its strategy. Earlier interests of security analysts centred on the drivers of BH uprising and the possibility of its internationalisation. Today's concerns relate more to why the rebellion has lasted this long. In toeing the same line, this article demonstrates that BH is a purposive terror group against which the government has evolved no viable strategy. It examines some gains of BH over the past six years and how it benefitted from the government's underestimation of its capacity and determination. It concludes that to effectively engage BH, the Nigerian government must revaluate its threat and sincerely pursue an expanded strategy beyond the current military-centric approach. To be effective, government's response must be packaged in such a way as to enhance human security in the region. 相似文献
169.
无动力运载器在出水过程中受海浪的扰动作用,运动参数会产生一定的偏差。针对海浪随机性的特点,应用波能谱理论,在P-M谱基础上构建了随机海浪模型,并使用四元数法建立运载器水弹道数学模型,解决了运载器垂直出水姿态角存在的奇异性问题,通过采用二元切片法给出波浪力的计算公式。最终在Matlab/Simulink仿真工具箱下建立了运载器仿真模型,就不同海况与主浪向角影响下运载器出水的运动参数偏差进行了仿真计算,分析了其变化规律。仿真结果表明,运载器在4级海况以下各项运动参数都满足出水要求,对运载器的设计与使用具有一定的参考意义。 相似文献
170.
《防务技术》2014,10(3):316-320
An electromagnetic coupling mathematical model is established by finite element method and is verified by the contrastive experiments of copper matrix Ni–TiN cylindrical coating electrode, copper electrode and Cu50W electrode. The wear mechanism of Ni–TiN/Cu composite electrode in the case of high-frequency pulse current is studied, and the influence of the fluctuation frequency of discharge current on electrode wear in micro-EDM is found out. Compared with the electrode made from homogeneous material, the high frequency electromagnetic properties of Ni–TiN composite layer can be used effectively to inhibit the effect of high frequency pulse on the electrode and improve the distribution trend of current density. 相似文献