A general model of heterogeneous system lifetimes and conditions for system burn‐in

Burn‐in is a technique to enhance reliability by eliminating weak items from a population of items having heterogeneous lifetimes. System burn‐in can improve system reliability, but the conditions for system burn‐in to be performed after component burn‐in remain a little understood mathematical challenge. To derive such conditions, we first introduce a general model of heterogeneous system lifetimes, in which the component burn‐in information and assembly problems are related to the prediction of system burn‐in. Many existing system burn‐in models become special cases and two important results are identified. First, heterogeneous system lifetimes can be understood naturally as a consequence of heterogeneous component lifetimes and heterogeneous assembly quality. Second, system burn‐in is effective if assembly quality variation in the components and connections which are arranged in series is greater than a threshold, where the threshold depends on the system structure and component failure rates. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 364–380, 2003.     

成败型产品验收试验方案研究

在可靠性定型试验的基础上,利用多层贝叶斯方法确定批产品可靠性指标的先验分布,从而制定出成败型产品可靠性验收试验的一种贝叶斯方案.给出利用定型试验信息确定产品可靠性指标先验分布的方法.这种验收方法充分利用了产品定型试验中的先验信息,在确保有较好验收效果的前提下,与传统的验收试验相比,可以大大减少试验量,从而得到可观的经济效益.     

基于改进空战威胁评估模型的权重计算方法比较

针对多无人机(UAV)任务网协同空战态势威胁评估问题,在现有基本模型基础上增加考虑气象环境对威胁评估要素的影响和无人机的自主可靠性系数两个实际因素,提出一种改进的超视距空战威胁评估模型;同时,应用串联电阻分压法、改进AHP法和熵权法分别计算融合模型中各威胁指标的权重系数;进而,在考虑己方战机对敌方战机综合威胁与优势的基础上,介绍了战机协同空战目标分配的基本方案。最后,应用上述3种权重计算方法进行空战威胁仿真计算,计算结果表明改进空战威胁评估模型可有效改善空战决策性能。     

基于参数自适应CS模型的机动目标跟踪算法

为提高对机动目标的跟踪精度,提出一种基于参数自适应当前统计(CS)模型的跟踪算法。即利用加速度增量与位移的关系,自适应调整加速度方差,根据量测残差的统计距离判别目标机动特性,并调整模型的机动频率和滤波器增益系数,提高算法模型与目标机动模式的匹配程度。仿真结果表明,基于参数自适应CS模型跟踪算法能够较好地改善对强机动目标的跟踪性能。     

考虑外场差异的步进加速寿命数据可靠性评估方法

针对寿命服从双参数Weibull分布的机电产品,进行单应力、定时转换的步进加速寿命试验,研究加速寿命试验数据下的可靠性评估问题。考虑到外场多应力环境与实验室单一应力环境之间的差异性,构建基于修正系数的分布参数计算模型;开展步进加速寿命试验过程的统计分析,建立各应力下的累计分布函数关系;构建极大似然函数,运用数值迭代法,求解未知参数估计;结合某型机电产品进行仿真方案设计,采用Monte Carlo仿真方法产生样本数据,通过对比分析说明所提出的模型评估精度更高。     

基于贝叶斯混合博弈的空袭火力资源分配决策模型

从博弈论的角度出发研究空袭火力资源的分配问题,针对空袭编队和防空火力单元攻防对抗过程中存在的不确定性、静态性以及动态性,建立基于贝叶斯混合博弈的空袭对抗火力分配模型。通过构造贝叶斯混合博弈树,采用逆向回溯法分别建立不同的博弈分析模型,利用混合粒子群算法求解那什均衡。仿真结果表明:以博弈论为背景研究空袭作战火力分配问题,符合真实的作战坏境,有效性好,有较高的理论应用价值。     

Estimating failure time distribution and its parameters based on intermediate data from a Wiener degradation model

Instead of measuring a Wiener degradation or performance process at predetermined time points to track degradation or performance of a product for estimating its lifetime, we propose to obtain the first‐passage times of the process over certain nonfailure thresholds. Based on only these intermediate data, we obtain the uniformly minimum variance unbiased estimator and uniformly most accurate confidence interval for the mean lifetime. For estimating the lifetime distribution function, we propose a modified maximum likelihood estimator and a new estimator and prove that, by increasing the sample size of the intermediate data, these estimators and the above‐mentioned estimator of the mean lifetime can achieve the same levels of accuracy as the estimators assuming one has failure times. Thus, our method of using only intermediate data is useful for highly reliable products when their failure times are difficult to obtain. Furthermore, we show that the proposed new estimator of the lifetime distribution function is more accurate than the standard and modified maximum likelihood estimators. We also obtain approximate confidence intervals for the lifetime distribution function and its percentiles. Finally, we use light‐emitting diodes as an example to illustrate our method and demonstrate how to validate the Wiener assumption during the testing. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

并行离散事件仿真中的DDM机制实现

在并行离散事件仿真系统中实现仿真模型间的互操作机制需要引入类似HLA中定义的声明管理(DM)和数据分发管理(DDM)服务.我们开发的KD-PADSE高性能并行离散事件仿真环境采用谓词断言和对象代理方法在面向对象的并行离散事件仿真系统中实现了基于平行结构和事件调度机制的声明管理(DM)和数据分发管理(DDM)服务.在以千兆以太网互联的10节点Linux集群计算机上,采用DDM机制后仿真模型每秒(物理时间)可以进行1万次属性更新,是没有采用DDM机制时的20倍,在功能性和性能上验证了该DDM机制在并行离散事件仿真系统中的适用性.     

布尔函数的Walsh谱绝对值分布及其性质研究

提出并研究了布尔函数的Walsh谱绝对值分布.指出布尔函数Walsh谱绝对值分布在仿射变换下的不变性,计算了n(n≤5)元布尔函数的Walsh谱绝对值分布,研究了Walsh谱绝对值分布与Walsh谱支撑和Walsh谱中非零取值个数以及其他一些密码学难题的联系,最后研究了布尔函数的Walsh谱绝对值分布的大小.     

雷达干扰资源一对多分配方法

在对雷达干扰资源分配的一般优化模型和求解算法进行分析的基础上,从提高资源利用效率的角度出发,提出了目标雷达分群思想,并建立了一种新的基于一对多策略的雷达干扰资源分配模型,通过对目标雷达群的一对一分配实现对单部雷达的一对多分配.最后,对该模型中一些关键性问题进行了探讨,如任务整合、新任务参数确定、任务优先级排序、干扰机位置部署以及单目标雷达群干扰效益评估等.