弹丸初速对磁阻型线圈发射器发射性能的影响分析

通过设置弹丸初速并研究其对单级磁阻型线圈发射器发射性能的影响,模拟分析前一级线圈弹丸出口速度对后一级线圈发射性能影响的规律;利用Ansoft有限元仿真软件进行了动态仿真,得到弹丸初速对单级磁阻型线圈发射器驱动电流、驱动线圈感应电压、电磁力、弹丸出VI速度、弹丸位移及能量转换效率等影响的规律．研究表明：弹丸初速越大,经过单级线圈加速后弹丸出口速度也越大,但弹丸出口速度增量减小;随着弹丸初速增大,能量转换效率呈现先增大后减小的趋势．     

基于ANSYS的舰船武器装备基准变化分析方法

舰船武器装备基准在外界环境作用下产生变化,从而影响武器系统的打击精度。应用ANSYS平台建立舰船有限元模型,利用三维波浪载荷的计算方法模拟航行条件下的波浪力,研究了舰船甲板面武器装备基准在两种极限海况下的变化情况,发现针对此类舰船横摇使武器装备基准产生较大的变化,并且靠近尾部和两舷位置处装备的基准变化较为显著。仿真结果表明：当舰船在风浪中航行使用武器系统时,应尽量采取顶浪航行,减少舰船横摇对武器系统基准的影响。     

Home-Grown Fighting: A Response to the Argument for a Byzantine Influence on MS I.33

Abstract

In an earlier issue, Dr. Timothy Dawson suggested that the fighting techniques found in Royal Armouries MS I.33 may have been influenced by earlier Byzantine sword and shield combat. For evidence, he cites a series of 9th-century ivory carvings depicting similar positions found in I.33. This article is a response to Dr. Dawson’s, in which it is argued that there is ample evidence for similar combat positions being found in Western Europe that both pre-date and are contemporary with I.33.     

基于北斗、短波的高精度时钟系统研究与设计

介绍了北斗、短波授时技术;对高稳恒温晶振及其频率特性进行分析的基础上,设计了一种基于北斗卫星、短波无线电授时的高精度时钟系统;该系统通过利用北斗接收处理模块、短波授时接收模块得到的秒脉冲信号、时间信息,经过延迟修正处理、脉冲滤波、脉冲补偿、脉冲统计得到标准的秒脉冲信号,实现对恒温晶振频率的校准,获得一个短期及长期频率稳定度都比较优良的时间频率标准,同时利用校频后恒温晶振分频出的1pps信号对时间芯片进行校准,对外输出高精度时间信息;对恒温晶振校频系统的基本工作原理及部分模块电路图进行了说明,试验结果表明,在时间不长于1h内,频率准确度优于1×10-10;该系统实用方便的方法达到了将晶体振荡器校准到较高指标的目的。     

Book Reviews

Patrick Finney (ed.), The Origins of the Second World War. London: Arnold, 1997. Pp.xvi + 461, index. £15.99. ISBN 0–340–67640‐X.

Maria Emilia Paz, Strategy, Security, and Spies: Mexico and the US as Allies in World War II. University Park, PA: The Pennsylvania State University Press, 1997. Pp.xii + 264, 10 illus., biblio., index. $55 (cloth); $19.95 (paper). ISBN 0–271–01665–5 and 01666–3.

Norman J.W. Goda, Tomorrow the World: Hitler, Northwest Africa and the Path toward America. College Station, Texas A&;M University Press, 1998. Pp.xxvi + 307, 2 maps, biblio., index. $39.95. ISBN 0–89096–807–1.

Michael J. Hogan, A Cross of Iron: Harry S. Truman and the Origins of the National Security State, 1945–1954. Cambridge; New York: Cambridge University Press, 1998. Pp.xii + 525, biblio., index. £25; $34.95. ISBN 0–521–64044‐X.

Stephen Van Evera, Causes of War: Power and the Roots of Conflict. Ithaca, NY: Cornell University Press, 1999. Pp.viii + 270, index. $35. ISBN 0–801403201–4.

Eric Arnett (ed.), Nuclear Weapons and Arms Control in South Asia after the Test Ban, SIPRI Research Report No.14. Oxford: Oxford University Press/Stockholm Int Peace Research Institute, 1998. Pp.viii + 98, index. £12.99. ISBN 0–19–8294115.

T.V. Paul, Richard J. Harknett and James J. Wirtz (eds.), The Absolute Weapon Revisited: Nuclear Arms and Emerging International Order. Ann Arbor, Michigan: The University of Michigan Press, 1998. Pp.vi + 312, index. $47.50/£36. ISBN 0–472–10863–8.     

India's Aspirations and Strategy for the Indian Ocean – Securing the Waves?

India has increasingly high aspirations in the Indian Ocean, as enunciated by politicians, naval figures and the wider elite. These aspirations, its strategic discourse, are of pre-eminence and leadership. India's maritime strategy for such a self-confessed diplomatic, constabulary and benign role is primarily naval-focused; a sixfold strategy of increasing its naval spending, strengthening its infrastructure, increasing its naval capabilities, active maritime diplomacy, exercising in the Indian Ocean and keeping open the choke points. Through such strategy, and soft balancing with the United States, India hopes to secure its own position against a perceived growing Chinese challenge in the Indian Ocean.     

NATO and the broader Middle East, 1949–2007: The history and lessons of controversial encounters

The engagement of the Atlantic Alliance in the Middle East dates back to the founding of the Alliance. With one eye on this history and one eye on current controversies, this article investigates the preconditions for and nature of the allies' engagement in the region in order to assess whether the Middle East today is causing a rupture within the Alliance. The article finds that the Alliance was never likely to engage as one in the region. The Alliance instead guarded its cohesion by either letting the Alliance leader, the United States, take a lead role or by acting as a coalition enabling framework. This latter option has prevailed since the early 1980s. Today, NATO can preserve its cohesion and simultaneously engage in the region if it continues this legacy of coalition-making from within the allied framework. Conversely, an effort to engage collectively in the region will likely set of internal tensions to the extent that the Alliance itself will be at risk.     

The effect of catastrophes on the strategic customer behavior in queueing systems

We consider the single server Markovian queue subject to Poisson generated catastrophes. Whenever a catastrophe occurs, all customers are forced to abandon the system, the server is rendered inoperative and an exponential repair time is set on. During the repair time new arrivals are allowed to join the system. We assume that the arriving customers decide whether to join the system or balk, based on a natural linear reward‐cost structure with two types of rewards: A (usual) service reward for those customers that receive service and a (compensation) failure reward for those customers that are forced to abandon the system due to a catastrophe. We study the strategic behavior of the customers regarding balking and derive the corresponding (Nash) equilibrium strategies for the observable and unobservable cases. We show that both types of strategic behavior may be optimal: to avoid the crowd or to follow it. The crucial factor that determines the type of customer behavior is the relative value of the service reward to the failure compensation. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

基于微分几何与李群的无人机编队会合方法

在领航-跟随编队模式下,设计了一种基于追缉策略的无人机编队会合方法。首先,基于微分几何曲线论和弗雷涅-塞雷标架建立了无人机非解耦三维运动模型,其中将曲率和挠率作为控制量;结合该模型给出了无人机三维编队会合问题的数学描述,它将导弹制导问题中的终端落角约束映射为编队会合问题中僚机的航迹倾角约束,同时引入额外的航迹方位角约束;然后使用特殊正交群的元素来度量长僚机方向偏差,并通过局部坐标映射将其映射为对应李代数空间中的旋量;接着,基于该旋量设计了编队会合几何导引律,并给出相应的曲率和挠率控制指令;最后,分别在长机稳定平飞和转弯机动条件下进行了多机编队会合数字仿真实验,仿真结果显示僚机能够有效地跟踪长机航向并收敛至指定位形,说明了方法的有效性。     

临近空间拦截弹非线性控制系统性能研究

针对临近空间高超声速拦截弹执行机构非线性特性影响控制系统响应,提出基于次优控制理论及bang-bang控制理论对该问题进行研究.针对舵偏角速率饱和影响控制系统响应,通过改进正定阵P,Q来确保系统响应特性;针对舵偏角饱和影响控制系统响应,通过建立bang-bang开关曲线,分析推导出开关切换次数及最优时间表达式;最后仿真结果表明临近空间拦截弹的舵偏角饱和严重影响飞行控制系统的快速性.