改进的前向信息修补算法及其应用

前向信息修补算法可以对离散动态贝叶斯网络的缺失数据进行预测,该算法只适用于所有观测节点是相互独立的网络,却不能处理观测节点有依赖关系网络的缺失数据。针对该算法的这一缺陷,提出了改进的前向信息修补算法,在分析离散动态贝叶斯网络的缺失数据具有二种基本形式的基础上,推导出了每种形式的相应预测公式。继而构建了用于识别威胁源离散动态贝叶斯网络的模型。仿真实验验证了改进的前向信息修补算法的有效性。     

Study on energy release characteristics of reactive material casings under explosive loading

Reactive Materials (RMs), a new material with structural and energy release characteristics under shock-induced chemical reactions, are promising in extensive applications in national defense and military fields. They can increase the lethality of warheads due to their dual functionality. This paper focuses on the energy release characteristics of RM casings prepared by alloy melting and casting process under explosive loading. Explosion experiments of RM and conventional 2A12 aluminum alloy casings were conducted in free field to capture the explosive fireballs, temperature distribution, peak overpressure of the air shock wave and the fracture morphology of fragments of reactive material (RM) warhead casings by using high-speed camera, infrared thermal imager temperature and peak overpressure testing and scanning electron microscope. Results showed that an increase of both the fireball temperature and air shock wave were observed in all RM casings compared to conventional 2A12 aluminum ally casings. The RM casings can improve the peak overpressure of the air shock wave under explosion loading, though the results are different with different charge ratios. According to the energy release characteristics of the RM, increasing the thickness of RM casings will increase the peak overpressure of the near-field air shock wave, while reducing the thickness will increase the peak overpressure of the far-field air shock wave.     

基于ADAMS和Matlab的大口径舰炮发射系统动力学仿真

利用ADAMS和Matlab/Simulink两大软件的信息交互功能,将ADAMS中的全炮动力学仿真模型生成ADAMS_SUB模块,并将其嵌入联合后坐系统仿真模型中;通过ADAMS和 Matlab/Simulink同步运行对全炮进行发射动力学联合仿真,模拟大口径舰炮发射的全过程,分析全炮的动态响应.对全炮发射动力学联合仿真结果进行后处理分析,观察炮口扰动曲线,进行稳定性分析和炮口扰动分析.根据分析结果,对所建模型及仿真模块进行评价,结果表明,仿真结果与靶场试验数据基本吻合,为物理样机的研制提供了重要的理论参考依据.     

大气层内复合控制拦截弹切换时间的探讨

大气层内拦截弹采用空气动力与燃气动力的复合控制方式是当今世界防空导弹的发展方向之一。复合控制技术的分析研究是当前急需解决的重要问题。在考虑目标机动加速度大小、目标机动时刻以及目标角闪烁的条件下 ,确定了拦截弹的控制方式由空气动力切换到复合控制时的切换时间。     

舰艇编队协同防空武器组织的研究现状与展望

针对舰艇编队防空作战中武器的敏捷协同与优化组织问题,分析了舰艇编队防空武器运用的历史衍变,综述了国内外关于武器组织的概念认知,引入双边匹配决策理论,剖析了舰艇编队协同防空武器组织问题的本质,凝练出1个科学问题、定位了4个关键技术,提出了基于动态双边匹配的舰艇编队协同防空武器组织技术框架,可为网络中心战条件下舰艇编队协同防空武器组织方法研究提供支持。     

潜艇内部平台对舱壁支持作用的对比试验

为了研究平台对舱壁的支撑作用,针对以内部平台取代水平桁作为一级支持构件的潜艇平面舱壁结构形式,设计制作了两个平台强度不一样的舱段模型.然后,分别对两个模型进行静水压力试验,测量了其应力和承载能力.模型试验结果表明,平台的使用使舱壁的承载能力明显提高,且平台越强对舱壁的支持作用越大.平台结构的改变主要影响舱壁上垂向加强材上的应力水平,舱壁的破坏是由于平台受压失稳后失去对舱壁的支持引起的.     

A partial characterization of the optimal ordering/rationing policy for a periodic review system with two demand classes and backordering

We consider a finite horizon periodic review, single product inventory system with a fixed setup cost and two stochastic demand classes that differ in their backordering costs. In each period, one must decide whether and how much to order, and how much demand of the lower class should be satisfied. We show that the optimal ordering policy can be characterized as a state dependent (s,S) policy, and the rationing structure is partially obtained based on the subconvexity of the cost function. We then propose a simple heuristic rationing policy, which is easy to implement and close to optimal for intensive numerical examples. We further study the case when the first demand class is deterministic and must be satisfied immediately. We show the optimality of the state dependent (s,S) ordering policy, and obtain additional rationing structural properties. Based on these properties, the optimal ordering and rationing policy for any state can be generated by finding the optimal policy of only a finite set of states, and for each state in this set, the optimal policy is obtained simply by choosing a policy from at most two alternatives. An efficient algorithm is then proposed. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

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     

Military Spending,Conflict and External Debt in Sub-Saharan Africa

The damaging economic effects of the debt crises on Africa in the late 1980s encouraged considerable research on the determinants of external debt in developing economies. Although sub-Saharan Africa's (SSA) debt was cut by two-thirds by 2008, through two debt relief programmes, debt in the region has since been rising at an increasingly rapid pace. This study provides an empirical analysis of the determinants of external debt in SSA over the period 1960–2016, using dynamic panel methods. It also considers two potentially important factors that have received relatively little attention. One is military spending, rarely considered, despite a number of well-publicised scandals over the procurement of unnecessary and expensive high-tech weapons systems. A second, is the possibility that the countries studied have been involved in conflict. The empirical results point to a positive impact of military spending on external debt, but with some evidence of heterogeneity across the countries. Furthermore, findings indicate that the positive effect of military expenditure on debt becomes more marked in countries that have been affected by conflict. These results imply that policies to improve security and reduce military spending could be beneficial in reducing external debt and, potentially, improving economic performance in the region.     

弹性压应力波作用下直杆动力失稳的差分解

以受载端简支、远端固支弹性直杆为例,通过对直杆微元的动力平衡分析导出了直杆动力失稳的控制方程,这与用哈密顿原理得出的方程完全一致。利用差分方法求解了动力屈曲方程,解出了动力失稳模态以及临界力参数和动力特征参数的值。特别分析了随着动力特征参数由零增加到一定值后,由静力失稳模态过渡到动力失稳模态的过程。结果表明,对于等效长度直杆,动力失稳临界压力要远大于静力失稳的临界压力。