Parametric inference for component distributions from lifetimes of systems with dependent components

In system reliability analysis, for an n ‐component system, the estimation of the performance of the components in the system is not straightforward in practice, especially when the components are dependent. Here, by assuming the n components in the system to be identically distributed with a common distribution belonging to a scale‐family and the dependence structure between the components being known, we discuss the estimation of the lifetime distributions of the components in the system based on the lifetimes of systems with the same structure. We develop a general framework for inference on the scale parameter of the component lifetime distribution. Specifically, the method of moments estimator (MME) and the maximum likelihood estimator (MLE) are derived for the scale parameter, and the conditions for the existence of the MLE are also discussed. The asymptotic confidence intervals for the scale parameter are also developed based on the MME and the MLE. General simulation procedures for the system lifetime under this model are described. Finally, some examples of two‐ and three‐component systems are presented to illustrate all the inferential procedures developed here. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

基于蛇怪蜥蜴踩水机理的仿生推进装置数值计算方法研究

为突破传统排水型两栖车辆“阻力墙”现象,提高两栖车辆水上航速,从蛇怪蜥蜴高速踏水机理出发,设计一种新型轮一叶复合式水上仿生推进装置,采用滑移网格和动网格方法对不同转速下的推进装置三维模型的动力学特性进行数值计算,并对仿真结果进行对比和分析．结果表明：滑移网格和动网格方法在计算结果上获得比较一致的结果,动网格方法更能反映模型的真实运动情况,而滑移网格方法在计算过程中表现出较好的稳定性,同时显著减少计算时间     

Equivalent accelerated life testing plans for log‐location‐scale distributions

Accelerated life testing (ALT) is widely used to determine the failure time distribution of a product and the associated life‐stress relationship in order to predict the product's reliability under normal operating conditions. Many types of stress loadings such as constant‐stress, step‐stress and cyclic‐stress can be utilized when conducting ALT. Extensive research has been conducted on the analysis of ALT data obtained under a specified stress loading. However, the equivalency of ALT experiments involving different stress loadings has not been investigated. In this article, a log‐location‐scale distribution under Type I censoring is considered in planning ALT. An idea is provided for the equivalency of various ALT plans involving different stress loadings. Based on this idea, general equivalent ALT plans and some special types of equivalent ALT plans are explored. For demonstration, a constant‐stress ALT and a ramp‐stress ALT for miniature lamps are presented and their equivalency is investigated. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

基于单元变形的网格间流场信息传递方法

针对单元网格发生变形重构中新旧网格之间的数据插值问题,提出一种基于格点格式有限体积法的流场数据传递方法。利用非结构动网格技术,将旧网格单元移动到新网格单元,同时时间推进求解流场控制方程,获得移动后旧网格单元物理量,并将其赋给新网格单元,以此来实现两套网格间的信息传递。计算结果表明,该方法在信息传递过程中没有引入插值误差,理论上流场求解方法的精度就是信息传递精度,验证结果表明其显著优于二阶插值精度。     

A novel modeling approach for express package carrier planning

Express package carrier networks have large numbers of heavily‐interconnected and tightly‐constrained resources, making the planning process difficult. A decision made in one area of the network can impact virtually any other area as well. Mathematical programming therefore seems like a logical approach to solving such problems, taking into account all of these interactions. The tight time windows and nonlinear cost functions of these systems, however, often make traditional approaches such as multicommodity flow formulations intractable. This is due to both the large number of constraints and the weakness of the linear programming (LP) relaxations arising in these formulations. To overcome these obstacles, we propose a model in which variables represent combinations of loads and their corresponding routings, rather than assigning individual loads to individual arcs in the network. In doing so, we incorporate much of the problem complexity implicitly within the variable definition, rather than explicitly within the constraints. This approach enables us to linearize the cost structure, strengthen the LP relaxation of the formulation, and drastically reduce the number of constraints. In addition, it greatly facilitates the inclusion of other stages of the (typically decomposed) planning process. We show how the use of templates, in place of traditional delayed column generation, allows us to identify promising candidate variables, ensuring high‐quality solutions in reasonable run times while also enabling the inclusion of additional operational considerations that would be difficult if not impossible to capture in a traditional approach. Computational results are presented using data from a major international package carrier. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

载体感应磁场的改进积分方程法

针对几何结构复杂的载体感应磁场计算问题,提出采用面单元和体单元分别对铁磁物体薄壳体结构、非薄壳体结构剖分,并实现了感应磁场的积分方程法计算。球-球体模型解析算例表明,所提方法数值精度可靠,其平均相对误差不超过0.27%;船舶模型仿真算例表明,该方法在单元量规模较小时计算精度较好,体现了方法在载体感应磁场建模方面的优势。将该方法分别应用于潜艇主舱段-设备模型和潜艇主舱段模型磁场计算时,数值结果与实验结果平均相对误差均小于2%,数值和实验结果比较表明,铁磁设备对模型磁场影响显著。仿真和实验算例均表明所提方法可有效应用于载体的感应磁场计算,具有一定的工程实用价值。     

大型试件砂尘试验风洞有效吹风截面的论证

通过分析大型试件砂尘试验需求和现行军用标准,提出采用直吹式砂尘试验方式,实现整车状态的砂尘试验,并说明这种试验实施方法的科学性.依据射流理论并通过计算,得出距离吹风口不同位置处各个截面上的理论有效吹风截面,通过有效吹风截面与大型试件尺寸比较,说明这种形式的砂尘试验设备对常规武器系统具有很强的适应性.这项研究工作对砂尘试验设备的设计、调试和操作使用等具有技术指导作用.     

一种融合显著性的Adaboost电视制导图像变尺度目标快速检测方法研究

电视制导过程中随着弹目距离的减小,目标图像会呈现尺度的非线性放大,传统的目标检测方法不能满足目标尺度的精确变化,目标定位有偏差,且检测计算量大,无法达到实时性。将基于剩余谱的显著性检测方法融入Adaboost检测过程,并应用于电视制导图像的目标检测中,能够对海面或沙漠等背景较为单一的区域进行快速目标检测,且检测窗口能够准确适应目标尺度的变化。     

尺度自适应特征压缩跟踪

为在复杂环境中对目标进行长时间精确跟踪,提出一种尺度自适应特征压缩跟踪算法。通过结构约束性采样,获取不同尺度不同位置的扫描窗,离线计算不同尺度下的稀疏随机感知矩阵。在线跟踪时利用这些矩阵感知对应尺度的图像采样块,实现特征降维,提高运算速度。利用朴素贝叶斯分类器对降维特征判决,在线学习更新分类器参数,找出具有最高分类得分的采样块作为新的跟踪结果,实现跟踪位置及尺度的自适应更新。实验结果表明,该算法能适应目标的基本姿态变化及尺度缩放,不依赖于目标初始跟踪区域尺度选取,跟踪结果具有较强的鲁棒性。     

基于RBF神经网络的军事物流设施规模预测

确定合理的军事物流设施规模对于成功实施军事后勤保障十分重要。提出了基于RBF神经网络的军事物流设施规模预测模型的建模方法,该方法旨在确定军事物流设施规模与其影响因素之间的非线性关系;采用算例说明了基于RBF神经网络的军事物流设施规模预测的具体做法,对军事物流设施规模的确定具有指导意义。