某型制导炸弹实时仿真系统设计

采用训练仿真系统进行武器装备的维修和操作训练是当今装备的发展趋势。某型制导炸弹是我军即将装备部队的精确制导武器,为了提高训练质量、节约训练经费和延长装备寿命,迫切需要研制该型弹训练仿真系统。介绍了基于PC/104总线的该型制导炸弹实时仿真系统的软硬件设计与实现。该系统具有操作简单,模拟控制信号精确,检测迅速准确,可扩展性强等特点,满足了部队训练和院校实验室教学的要求。     

战车火控系统射击命中三要素函数误差分析

火控系统射击(函数)误差可分解为射弹散布函数误差和火控射击准备函数误差。而射击准备函数则是命中三要素函数即瞄准函数、解算函数和控制函数的合成函数。命中三要素的提出,为火控系统射击误差(精度)的分析提供了新的途径。它们均是命中目标的关键要素,又各具特色,为火控系统射击精度乃至系统反应速度的提高,指出了应该努力的方向。针对此进行了具体的分析。     

Analysis of the finite‐source multiclass priority queue with an unreliable server and setup time

In this article, we study a queueing system serving multiple classes of customers. Each class has a finite‐calling population. The customers are served according to the preemptive‐resume priority policy. We assume general distributions for the service times. For each priority class, we derive the steady‐state system size distributions at departure/arrival and arbitrary time epochs. We introduce the residual augmented process completion times conditioned on the number of customers in the system to obtain the system time distribution. We then extend the model by assuming that the server is subject to operation‐independent failures upon which a repair process with random duration starts immediately. We also demonstrate how setup times, which may be required before resuming interrupted service or picking up a new customer, can be incorporated in the model. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

基于星载照射源的被动SAR系统时频同步误差影响分析

时间和频率同步问题是基于星载照射源的被动SAR系统的关键技术之一。为了研究时、频同步误差对其成像的影响,针对系统工作特性,分析了时、频同步误差的产生机理,建立了时、频同步误差模型,并利用二阶距离模型和RD成像算法,建立了完整的时、频同步误差到成像结果的传递模型,仿真验证了理论分析的准确性。理论推导和仿真计算结果指出了基于星载照射源的被动SAR系统对时间同步和频率同步的精度要求。分析结论对于指导基于星载照射源的被动SAR系统设计及同步方法研究具有重要意义。     

非线性压电振动能量俘获行为建模及其不同参数影响机理研究

如何利用非线性特性来改善压电振动能量捕获性能是工程实际中需要解决的一个问题,为此建立了非线性压电振动能量捕获行为的数学模型,利用定积分法推导了该模型的数值计算方法,并针对不同参数对非线性压电振子输出电能的影响特性进行了数值仿真,结果表明:减小非线性阻尼、增大非线性压电耦合系数均有利于提高非线性压电振动能量俘获的性能;减小非线性刚度能提高低频振动能量俘获的输出,但减小了共振带宽。     

基于拉盖尔模型的超声信号渡越时间测量性能分析

传统窄带模型仅能通过数值计算统计出超声信号渡越时间的测量性能。针对这一问题,提出基于拉盖尔模型计算理论克拉下限的方法。研究了拉盖尔函数及其时间导数的性质,得到时间导数内积矩阵,并将其应用到费舍尔矩阵中,能够快速精确计算克拉下限。对混合指数模型仿真表明,在高斯白噪声背景下,渡越时间方差与理论克拉下限具有良好的一致性;受窄带噪声和反射等因素影响,实测数据的渡越时间方差与理论克拉下限存在较大偏差。     

基于参数化建模的包带式星箭连接结构优化设计

采用MSC.Patran参数化建模和遗传算法进行包带式星箭连接结构优化设计。首先给出了包带连接结构二维轴对称模型优化设计过程中涉及的V形卡块刚度等效、包带预紧力模拟和载荷施加方法,以及强度和刚度约束条件、优化目标等内容;然后以某直径为3m的包带连接结构为例进行了优化设计,并分析了对接框内延伸段长度和端头高度对应力及变形的影响;最后建立三维有限元模型进行静力分析。结果表明（1）该方法适用于包带连接结构的优化设计;（2）增加对接框内延伸段长度和端头高度能够提高整体连接刚度;（3）三维有限元模型与轴对称模型计算结果一致,验证了轴对称模型分析方法的正确性,以及V形卡块等效和预紧力模拟方法的有效性。     

基于虚拟飞行仿真的导弹控制系统设计

根据风洞虚拟飞行仿真系统的特点以及试验要求,设计了用于风洞虚拟飞行仿真的模型导弹的俯仰、偏航和滚转通道控制系统。导弹俯仰通道采用了迎角指令控制的三回路闭环控制结构,滚转通道采用了滚转姿态角指令控制的两回路闭环控制结构,而偏航通道采用液压驱动机构来开环控制侧滑角。利用极点配置法设计了俯仰和滚转通道的控制增益。最后通过数字仿真对所设计的控制系统进行了仿真验证。从数字仿真结果可以看出,无论是时域还是频域,所设计的俯仰和滚转通道闭环控制系统均能满足风洞虚拟飞行仿真的要求。     

What determines military allocations in Africa: Theoretical and empirical investigations

This paper investigates theoretically and empirically the determinants of military spending in Africa. It specifies a formal model and uses time‐series and cross‐sectional estimations to ascertain the reasons behind variations in military allocations across and within 40 African countries during 1960–1991. The differences in military expenditures appear to reflect a complex of economic, political, and strategic factors at both national and international levels. Strategic considerations are, however, found to be the most important factors in most African countries.     

The Economic Consequences of the Libyan Spring: A Synthetic Control Analysis

Abstract

In 2011 a wave of revolutionary movements, the so-called Arab Spring, spread in the Middle East and North Africa. Libya was one of the most affected countries, ending Gaddafi’s dictatorship after an international intervention and a civil war. This paper assesses the effects that this revolution had on Libyan economy. The analysis is made by means of the synthetic control method. Our estimates for the 2011–2014 period show (i) a cumulative loss in the growth rate of per capita real GDP of 64.15%; (ii) a cumulative loss in per capita real GDP of 56,548 dollars; and (iii) a cumulative loss in the aggregate real GDP of 350.5 billion dollars.