激波诱导异质气体界面失稳的数值模拟

基于二维N-S方程,利用有限差分数值离散方法,对激波诱导异质气体界面失稳的现象进行了数值模拟,与文献中实验结果和计算结果进行了定性比较,并进一步分析了整个流动的非定常动态变化特性和非线性特征.研究表明,本文数值模拟的非定常流场图谱与文献中的实验结果和数值结果吻合较好;数值结果捕捉到了六氟化硫界面的演变过程及流场中复杂的波系结构.     

高超声速圆球绕流流场及其近尾尾迹流场电磁散射特性分析

采用分段线性电流密度递归卷积时域有限差分(PLJERC FDTD)方法计算高超声速导电金属球绕流流场及其近尾尾迹流场电磁散射特性,分析等离子体绕流流场RCS的频率特性、双站散射特性、极化特性及随飞行高度、飞行马赫数、入射角的变化关系.计算表明,前向散射方向是全方位散射中RCS取得最大值的方向;马赫数较大(本文Ma≥14)时,入射波频率增大、马赫数增大及飞行高度降低,绕流流场前向RCS增大.马赫数较小(本文Ma≤10)时,飞行马赫数、高度及入射角变化对绕流流场UHF、L、S波段后向RCS和双站RCS影响很小;在UHF、L波段,绕流流场及本体的后向RCS差距较小.马赫数较大时,大范围过密等离子体尾迹的形成使得电磁波垂直轴线入射时绕流流场增大了目标本体的后向RCS;在L、S波段,绕流流场后向RCS曲线可用一条直线逼近.     

Strategic dynamic sourcing from competing suppliers with transferable capacity investment

We study the supplier relationship choice for a buyer that invests in transferable capacity operated by a supplier. With a long‐term relationship, the buyer commits to source from a supplier over a long period of time. With a short‐term relationship, the buyer leaves open the option of switching to a new supplier in the future. The buyer has incomplete information about a supplies efficiency, and thus uses auctions to select suppliers and determine the contracts. In addition, the buyer faces uncertain demand for the product. A long‐term relationship may be beneficial for the buyer because it motivates more aggressive bidding at the beginning, resulting a lower initial price. A short‐term relationship may be advantageous because it allows switching, with capacity transfer at some cost, to a more efficient supplier in the future. We find that there exists a critical level of the switching cost above which a long‐term relationship is better for the buyer than a short‐term relationship. In addition, this critical switching cost decreases with demand uncertainty, implying a long‐term relationship is more favorable for a buyer facing volatile demand. Finally, we find that in a long‐term relationship, capacity can be either higher or lower than in a short‐term relationship. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009     

Information security: Designing a stochastic‐network for throughput and reliability

Todas information and communication network requires a design that is secure to tampering. Traditional performance measures of reliability and throughput must be supplemented with measures of security. Recognition of an adversary who can inflict damage leads toward a game‐theoretic model. Through such a formulation, guidelines for network designs and improvements are derived. We opt for a design that is most robust to withstand both natural degradation and adversarial attacks. Extensive computational experience with such a model suggests that a Nash‐equilibrium design exists that can withstand the worst possible damage. Most important, the equilibrium is value‐free in that it is stable irrespective of the unit costs associated with reliability vs. capacity improvement and how one wishes to trade between throughput and reliability. This finding helps to pinpoint the most critical components in network design. From a policy standpoint, the model also allows the monetary value of information‐security to be imputed. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

Designing and pricing menus of extended warranty contracts

Extended warranties provide “piece of mind” to a consumer in that product failures which occur after the base warranty expires are rectified at little or no cost. They also provide an additional source of revenue for manufacturers or third‐party providers, such as retailers or insurance providers, and help cultivate consumer loyalty. In this article, we analyze a number of extended warranty contracts which differ in design, including restrictions on deferrals and renewals. With the use of dynamic programming, we compute the optimal strategy for a consumer with perfect information and determine the optimal pricing policy for the provider given the consumer's risk characterization. We also provide insight into when different contracts should be issued. Finally, we illustrate how profits can be dramatically increased by offering menus of warranty contracts, as opposed to stand alone contracts, with the use of integer programming. Surprisingly, risk‐taking consumers provide the greatest benefit to offering menus. These insights can help a company develop a comprehensive warranty planning strategy for given products or product lines. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009     

两次世界大战之间英法德三国装甲部队建设思想与实践之比较(二)

装甲部队的创建是军队建设史上的重大军事创新成果,它引发了第二次世界大战中的陆战变革,并成为机械化军事革命的重要组成部分.由于建军指导思想的巨大差异,两次世界大战之问英法德三国装甲部队的建设走过了不同的道路,表现出不同的特点,产生了不同的经验和教训,对第二次世界大战的初期战局产生了重大影响,给后人以重要启示:军事改革与创新的先决条件之一,是建立一种适合于改革与创新的组织环境与军事文化氛围.     

层次分析法在选择导弹发射阵地中的应用

探讨了最优发射阵地的选择问题 ,运用层次分析法建立了评估指标的计算模型。实例计算结果表明 ,层次分析方法能够较好地解决发射阵地选择问题。     

To Protect and Serve: Civilian Policing and the United Nations Mission in Kosovo

Since the end of the Cold War the process of nation building has become a priority in the attempt to maintain world order and security in the wake of the instability and devastation wrought by failed and war-torn states. The proliferation of nation-building missions has led to their diversification and the need to marshal a vast array of resources in order to attain substantial levels of success. This article deals with a new and important component of peacekeeping and nation-building missions, that of civilian policing. The article outlines the goals of using civilian police officers in nation-building missions and discusses a variety of problems (pragmatic, legal, and cultural) that policing may introduce to such missions. This discussion is focused around the civilian policing component of the United Nations Mission in Kosovo. It delineates the successes and hardships so far experienced during the mission in Kosovo and explores the insights that the mission may provide for similar projects in the future.     

Homeland Security and Intelligence: Can Oil Mix with Water in an Open Society?

The newest US Cabinet department is Homeland Security (DHS). One of the most controversial aspects in the process of developing this entity is the role of intelligence in providing information on the increasing terrorist threat. This article examines the intelligence challenges for homeland security. In doing so, it explores the problems of merging disparate cultures - law enforcement vs intelligence, civil entities vs military, federal vs state and local jurisdictions, and domestic focus vs international perspective. Given the nature of the globalized, asymmetric threat, the need for more and better intelligence sharing is obvious. Terrorists and other criminals do not respect international boundaries; in fact, they exploit them in an effort to prevent effective and timely countermeasures. This demands that robust multinational collaboration and interagency coordination be practiced.