Aircraft routing under the risk of detection

The deterministic problem for finding an aircraft's optimal risk trajectory in a threat environment has been formulated. The threat is associated with the risk of aircraft detection by radars or similar sensors. The model considers an aircraft's trajectory in three‐dimensional (3‐D) space and represents the aircraft by a symmetrical ellipsoid with the axis of symmetry directing the trajectory. Analytical and discrete optimization approaches for routing an aircraft with variable radar cross‐section (RCS) subject to a constraint on the trajectory length have been developed. Through techniques of Calculus of Variations, the analytical approach reduces the original risk optimization problem to a vectorial nonlinear differential equation. In the case of a single detecting installation, a solution to this equation is expressed by a quadrature. A network optimization approach reduces the original problem to the Constrained Shortest Path Problem (CSPP) for a 3‐D network. The CSPP has been solved for various ellipsoid shapes and different length constraints in cases with several radars. The impact of ellipsoid shape on the geometry of an optimal trajectory as well as the impact of variable RCS on the performance of a network optimization algorithm have been analyzed and illustrated by several numerical examples. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

考虑入口和出口容积效应的涡轮动力学模型

建立了考虑涡轮入口和出口容积效应的涡轮动力学模型 ,利用该模型计算了燃气涡轮气瓶启动的动态响应过程 ,分析了影响涡轮动态特性的主要因素。计算结果表明 :涡轮前容积对涡轮入口压力和出口背压的过渡过程均有显著的影响 ,涡轮后容积对涡轮入口压力的过渡过程影响不大 ,对涡轮出口背压的影响显著。     

应力-强度模型的Bayes可靠性分析

当应力、强度分别服从于正态分布、指数分布和Weibull分布时 ,分析了应力 -强度模型的可靠性评估 ,着重讨论了无信息验前下的Bayes可靠性评估。仿真结果表明 ,无信息验前下的评估结论可以很好地用频率学派的观点来解释。     

Military expenditure and economic growth in Middle Eastern countries and Turkey: a non-linear panel data approach

The economic growth effects of military expenditure have been the subject of a large literature in defence economics. Theories on the economic impacts of military expenditure greatly differ and include arguments that they either enhance economic growth or crowd out productive investments. Empirical literature on defence expenditure and economic growth nexus generally employs linear specifications to investigate the impact of defence expenditures on economic growth. Although it is now well established that many economic variables may have a non-linear data-generating mechanism, it seems that this reality has long been neglected in empirical work on defence–growth nexus. This paper attempts to fill this gap by employing non-linear panel data models to examine the effects of military expenditures on economic growth for Middle Eastern countries and Turkey, for the time period 1988–2012. Results show that the effect of military expenditure on economic growth is nonlinear such that the state of the economy actually determines the effect of the former on the latter. This is important not only in showing asymmetric relationship between these variables but also in revealing the reasons of mixed results of earlier literature.     

Applying Lanchester's linear law to model the Ardennes campaign

In modern warfare, many believe the decisive factor in winning a battle is seizing the right moment to shift from defense to attack, or vice versa. This paper attempts to bring that perspective to Lanchester's differential equations of warfare, and continues the application of Lanchester's linear law to the analysis of the World War II battle of Ardennes, as reported in earlier issues of Naval Research Logistics by Bracken and by Fricker. A new variable, shift time, accounting for the timing of the shift between defense and attack is explicitly included in our version of the model, and it helps obtain improved goodness of fit to historical data. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48:653–661, 2001     

Operating Costs of Aging Air Force Aircraft: Adjusting for Aggregate Budget Effects

The rate at which operating costs grow as aircraft age is important for setting operating budgets and for deciding when to replace aging systems. While studies using data from the 1990's typically found 1–3 percent real rates of growth in operating costs as aircraft age, studies using data from the 2000's found greater rates, for example in the 4–6 percent range. Growth in the total U.S. Air Force budget during the 2000s appears to explain much of the higher estimated annual growth rates in operating costs per flying hour beyond the growth rate intrinsic to the aging of the fleet.     

SpaceWire网络热点通信模式的缓存资源分配算法

基于SpaceWire网络在热点通信模式下的工作特点,研究缓存资源的分配算法。给出均匀通信模式和热点通信模式的释义;推导网络路由节点的满负荷概率和平均延时的解析方法,计算网络中的关键通信节点;再给出SpaceWire网络缓存资源分配算法。利用Opnet网络仿真平台建立SpaceWire通信模型,仿真了不同通信模式中采用缓存优化策略前后的关键性能指标。研究结果表明:在热点通信模式状态下,该缓存资源分配算法在保证总资源一定的前提下,网络系统的平均延时降低,优化了SpaceWire网络性能。     

考虑地球非球形引力摄动影响的自由段弹道解析解

针对地球非球形引力摄动影响下的自由段弹道快速计算问题,在非正交坐标系内建立考虑J2项摄动的地球引力作用下的运动微分方程,在轨道坐标系内建立扰动引力作用下的运动微分方程,并计算天向扰动引力加速度对应的质量偏差,进而通过椭圆轨道以修正J2项摄动运动微分方程;在建立上述运动微分方程解析解的基础上,给出了地心坐标系内弹道飞行器位置和绝对速度的表达式,从而提出了J2项摄动引力和扰动引力作用下的自由段弹道解析计算方法。仿真分析表明:该方法具有较高的计算效率,落点位置偏差小于20 m,满足弹道飞行器高精度实时制导、轨迹预测等应用需求。     

基于概率分析法的无人攻击机作战效能分析模型研究

未来防空战场上无人攻击机已成为一种重要的空中威胁。无人攻击机作战过程可分为飞行、突防、攻击三个阶段,运用概率分析方法分别建立了各阶段的数学模型,给出了其作战效能表达式,为进一步进行无人攻击机作战效能分析提供了模型基础。     

When is model complexity too much? Illustrating the benefits of simple models with Hughes' salvo equations

The simulations that many defense analysts rely upon in their studies continue to grow in size and complexity. This paper contrasts the guidance that the authors have received—from some of the giants of military operations research—with the current practice. In particular, the analytic utility of Hughes' simple salvo equations is compared with that of the complex Joint Warfighting System (JWARS), with respect to JWARS' key performance parameters. The comparison suggests that a family of analytic tools supports the best analyses. It follows that smaller, more agile, and transparent models, such as Hughes' salvo equations, are underutilized in defense analyses. We believe that these models should receive more attention, use, and funding. To illustrate this point, this paper uses two very simple models (by modern standards) to rapidly generate insights on the value of information relative to force strength. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003