Stochastic framework for partially degradation systems with continuous component degradation‐rate‐interactions

Many conventional models that characterize the reliability of multicomponent systems are developed on the premise that for a given system, the failures of its components are independent. Although this facilitates mathematical tractability, it may constitute a significant departure from what really takes place. In many real‐world applications, system components exhibit various degrees of interdependencies, which present significant challenges in predicting degradation performance and the remaining lifetimes of the individual components as well as the system at large. We focus on modeling the performance of interdependent components of networked systems that exhibit interactive degradation processes. Specifically, we focus on how the performance level of one component affects the degradation rates of other dependent components. This is achieved by using stochastic models to characterize how degradation‐based sensor signals associated with the components evolve over time. We consider “Continuous‐Type” component interactions that occur continuously over time. This type of degradation interaction exists in many applications, in which interdependencies occur on a continuum. We use a system of stochastic differential equations to capture such “Continuous‐Type” interaction. In addition, we utilize a Bayesian approach to update the proposed model using real‐time sensor signals observed in the field and provide more accurate estimation of component residual lifetimes. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 286–303, 2014     

威布尔分布的战术导弹可靠性试验信息融合方法

针对战术导弹可靠性试验小子样问题,提出了基于威布尔分布,利用小概率原理,针对不同试验环境下试验数据的融合方法。该方法扩大了战术导弹可靠性试验的统计子样,提高了可靠性评定的可信度。     

放大转发双向中继网络的移动级联信道统计特征分析

针对放大转发协议下双向中继网络移动级联信道,为了分析其统计特征,结合用户完成信息交互的过程,将移动级联信道分解为传输部分和干扰部分两个时间过程。依据它们的双高斯乘积特点,分别给出了对应的一阶概率密度分布、二阶自相关函数和多普勒功率谱的表达式。与此同时,通过采用Gamma分布对级联信道进行了概率近似,得到了描述移动级联信道时变特性的电平通过率和平均衰落时间等指标的近似计算式。借助数值仿真验证了上述表达式的正确性。     

Neglected but affected: voices from the oil-producing regions of Ghana and Uganda

The ‘resource curse’ is the paradoxical theory frequently used to explain how a seemingly desirable asset, such as oil, can actually pervert an economy, erode governance, perpetuate conflict, and ruin local communities to the extent that it becomes a curse. New oil discoveries in western Ghana and western Uganda have raised concerns for the democratic prospects and future stability of these countries and their surrounding regions. Based on field interviews in these oil-producing regions, this report summarises how local communities have been affected thus far and their concerns for the future. The authors assess the extent to which each country is vulnerable to oil-induced instability, and identify groups or communities that would be most likely to perpetuate it. Lastly, it provides some assessment of the future trajectory of each country.     

基于优化蚁群算法的装备调拨决策系统研究与设计

将蚁群算法和遗传算法应用于装备调拨决策系统,实现了装备调拨决策信息的生成.同时利用遗传算法对蚁群算法的参数进行了优化,实验证明优化后的蚁群算法在平均路径长度、算法平均执行时间和总执行时间上较传统蚁群算法都有一定程度的改进.     

THE SUPPLY PRICE OF COMMITMENT: EVIDENCE FROM THE AIR FORCE ENLISTMENT BONUS PROGRAM

In fiscal year 1999, the US Air Force introduced a bonus program designed to encourage longer enlistment terms. This regime shift provides a unique opportunity to estimate the elasticity of labor supply at a new margin: the length of the employment contract. A $5000 bonus differential is estimated to increase the probability that a recruit will choose a 6‐year enlistment over a 4‐year enlistment by 30 percentage points. The program is found to be cost‐effective relative to other policies to increase man‐years.     

弹药洞库有害气体分布规律研究

以计算流体力学（CFD）为理论基础,应用GAMBIT软件对洞库内的有害气体进行几何模型构建和网络划分,用FLUENT软件对所建模型中有害气体的扩散和分布规律进行模拟分析,并对单一释放源条件下扩散规律进行比较,分析弹药堆垛对气体扩散的影响．通过对洞库内有害气体的整体分布规律的研究,找到了库房内有害气体浓度最高的位置．最后,通过实验对仿真结果进行验证．     

装备保障资源确定技术研究与需求分析系统开发

维修资源是实施装备维修工作的物质基础和重要保证,无论是平时训练还是战时抢修,维修资源都占据着十分重要的地位,不仅影响着装备的寿命周期费用(Life Cycle Costs,LCC),还直接影响着装备的战备完好率以及部队战斗力的保持和恢复.应用更加科学高效的方法确定保障资源,是维修决策面临的重要问题之一.据此,着眼于部队装备维修保障现状需求,将维修任务分配与保障资源需求紧密结合,提出了保障资源确定分析流程,并对分析过程中的关键技术进行了相应的研究,建立了典型的维修决策模型,优化了保障资源配置.最后开发了计算机辅助决策分析系统,为维修资源的优化配置起到了很好的辅助决策作用.     

应急辅助定位及精度评估方法研究

在可视导航卫星数少于四颗、无法进行传统导航解算的恶劣环境下,导航接收机可利用外部高程气压计提供的高程或者内部守时模块的钟差等信息进行应急辅助定位。在该应急辅助定位工作模式的误差分析中,传统导航定位误差传递模型无法适用。针对此问题,本文在研究三星结合高程、三星结合钟差、双星结合高程钟差等几种应急辅助定位原理的基础上,给出了新的应急辅助定位误差传递的分析模型,利用仿真算例验证了该模型的正确性。通过对定位精度的分析,说明根据卫星分布特点可以按照本文方法量化得到伪距测量与辅助信息的精度的最优数量级关系,可以用最小代价实现定位精度的提升。该结论可指导接收机外部辅助器件的选择。     

资源不确定军事任务计划预测调度模型与算法

针对军事任务计划执行环境中普遍存在的资源不确定性,提出了基于资源缓冲区的军事任务计划预测调度算法。算法首先基于平台有效资源功能向量进行任务—平台分配,分配过程中通过调节平台有效资源功能向量,获得不同的平台资源缓冲区分配方案;然后基于NSGA-Ⅱ算法框架对军事任务计划进行多目标求解,进而获得问题的Pareto最优解集。文章通过仿真算例对算法的可行性和有效性进行验证,实验结果表明,该算法能够有效求解资源不确定军事任务计划问题。