Bolstering components for maximizing system lifetime

This article considers the problem of which component should be “bolstered” or “improved” in order to stochastically maximize the lifetime of a parallel system, series system, or in general, k-out-of-n system. Various ways of bolstering including active redundance, standby redundancy, and burn-in are studied. Also the method of reducing working temperature or stress level according to Arrhenius models is investigated. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 497–509, 1998     

海军军事数据在指挥控制中的作用及层次关联分析

信息化条件下的海上作战中,数据的重要性不断凸显,数据建设已成为信息化建设的核心内容之一,加强数据研究愈发重要,因此以海军军事数据为研究对象,论述海军军事数据在指挥控制中的作用、特点,重点以海军水面舰艇作战能力数据为研究对象,对海军军事数据之间的层次关联性进行了分析研究,建立了海军水面舰艇作战能力数据的层次关系模型,为海军军事数据的进一步深入研究打下基础。     

短波通信组网研究

对于短波信道,目前基本上是用于点对点的通信媒介。采用组网通信方式可以在网内选择最佳链路,克服信道不稳定、干扰大、可靠性差等不足。首先介绍了网络的拓扑结构,然后针对短波通信的特点研究了短波星形组网、树形组网和网形组网的军事应用及拓扑设计,并给出了具体的构造方法。可为短波军事通信网络系统的规划与建设提高参考。     

Deterrence under nuclear asymmetry: THAAD and the prospects for missile defense on the Korean peninsula

The 2016 decision to deploy Terminal High Altitude Area Defense (THAAD) to South Korea has generated multitude of intensely politicized issues and has proved highly controversial. This has made it challenging to alleviate, let alone clarify, points of analytical and policy tensions. We instead disaggregate and revisit two fundamental questions. One is whether THAAD could really defend South Korea from North Korean missiles. We challenge the conventional “qualified optimism” by giving analytical primacy to three countermeasures available to defeat THAAD–use of decoys, tumbling and spiral motion, and outnumbering. These countermeasures are relatively inexpensive to create but exceedingly difficult to offset. Second, we assess the optimal way to ensure South Korean national security against North Korean missiles. By examining the balance of capability and issues of credibility/commitment, we show that the U.S. extended deterrence by punishment remains plentiful and sufficiently credible even without enhancing the current defense capability.     

Xunzi on the Role of the Military in a Well-Ordered State

Chapter 15 of the Xunzi stands as the most comprehensive account of the early Confucian analysis of warfare. Unlike a range of other early, non-Confucian discussions on warfare, particular strategies and tactics are taken to be of secondary importance. Thus, Xunzi refuses to discuss practical military strategy without framing it within a much broader ethical, social, and political context. On his account, a well-ordered, flourishing state necessarily rests upon a particular set of rituals and social norms in which people can cultivate themselves morally. Such a state has nothing to fear from any enemy, no matter how tactically sophisticated or militarily skilled. To many, such a view seems overly optimistic. However, given that Xunzi is anything but Pollyannaish in other parts of the text and is quite pessimistic about human nature in general, it behooves us to dig a bit more deeply into his ideas about military affairs and examine whether they can be understood in a more plausible light. This article provides a reading of Xunzi’s views on military affairs that is internally consistent and corresponds with Xunzi’s broader ethical and political views, while also showing why someone of Xunzi’s obvious intellectual acumen might hold such a view.     

零压式高空气球球形设计与参数敏感性分析

高空气球能够为临近空间科学实验提供可靠的平台,其形状直接关系到气球制作及飞行的全过程。提出将多段打靶法与序列二次规划法结合,对零压气球完全膨胀和部分膨胀状态下的球形进行求解,并运用有限元方法对球形进行稳定性及应力应变分析,验证了所推导球形的正确性。在此基础上,对影响气球形状的关键参数进行灵敏度分析及相关运用,从定量的角度得到气球载荷、飞行高度及昼夜温差对气球形状的影响规律。     

高精度CFD程序的内外子区域划分异构并行算法

对计算流体力学(Computational Fluid Dynamics, CFD)程序CNS提出一种Offload模式下对任务内外子区域划分的异构并行算法,结合结构化网格下有限差分计算和四阶龙格-库塔方法的特点,引入ghost网格点区域,设计了一种ghost区域收缩计算策略,显著降低了异构计算资源之间的数据传输开销,负载均衡时CPU端的计算与MPI通信完全和加速器端的计算重叠,提高了异构协同并行性。推导了保证计算正确性的ghost区域的参数,分析了负载均衡的条件。在"CPU(Intel Haswell Xeon E5-2670 12 cores×2)+加速器(Xeon Phi 7120A×2)"的服务器上测得该算法较直接将任务子块整体迁至加速器端计算的异构算法性能平均提升至5.9倍,较MPI/OpenMP两级并行算法使用24个纯CPU核的性能,该算法使用单加速器时加速至1.27倍,使用双加速器加速至1.45倍。讨论和分析了性能瓶颈与存在的问题。     

非奇异快速终端滑模及动态面控制的轨迹跟踪制导律

针对飞行器跟踪预设轨迹的问题,提出非奇异快速终端滑模和角度约束的轨迹跟踪制导律。通过引入虚拟目标点,提出参考轨迹曲率半径的期望视线角约束条件,建立带有视线角约束并考虑自动驾驶仪动态特性的轨迹跟踪数学模型。为了保证在有限时间内跟踪预设轨迹并避免出现奇异问题,采用快速非奇异终端滑模和动态面控制方法进行制导律设计。推导出视线角误差和轨迹跟踪误差之间的数学关系,并利用Lyapunov稳定性准则证明轨迹跟踪误差最终有界任意小。与弹道成型轨迹跟踪制导律进行仿真对比,仿真结果表明所提出的制导律具有良好的跟踪性能及鲁棒性。     

等离子体与高功率微波相互作用中电子分布特性

电子数密度是表征等离子体物理特性的一项重要因素,在等离子体与高功率微波的相互作用中,等离子体对入射电磁波的吸收、衰减和屏蔽等电磁特性可通过电子数密度的变化进行表征。基于等离子体流体近似研究方法,利用COMSOL软件求解等离子体中的波动方程、电子传递方程和重粒子传递方程,计算分析了等离子体与高功率微波相互作用中的电子分布特性,重点分析了相互作用中平均电子数密度和平均电子能的数值和空间分布变化过程。研究表明,在高功率微波作用下,等离子体区域电子数密度在数值上会产生剧烈的阶跃变化,形成雪崩效应,在空间分布上电子数密度峰值产生趋于入射方向移动的变化;电子能的变化与入射波激励和电子数密度相关,随入射激励增加呈增长趋势,随电子数密度的增加而减小。     

网格质量反馈的弹性体动网格改进

高鲁棒性的动网格变形方法是求解包含运动边界的非定常流场问题的关键技术。基于经典的弹性体动网格方法,引入两种设计合理、评价效果较好的网格质量参数——Patrick参数和Baker参数,提出了一种基于网格质量反馈的改进弹性体动网格方法。结合二维NACA0012翼型、三维ONERA M6机翼大角度俯仰运动,对比研究改进方法与经典方法的变形能力,改进方法能够保持较好的网格质量,尤其在最大变形时,可以有效改善较差网格单元,具有更高的鲁棒性。计算了NACA0012翼型、ONERA M6机翼的俯仰振荡绕流,并与实验结果及文献进行对比,结果表明,基于网格质量反馈的改进弹性体法能够显著提高变形网格的鲁棒性,可为非定常流场问题的求解提供有力支撑。