SPEED BUMP ON THE ROAD TO GLOBAL ZERO

The prospect of the United States continuing to reduce the size of its nuclear arsenal to “very low numbers” has raised questions in Japan and South Korea, where US extended deterrence guarantees are premised on the “nuclear umbrella.” In both countries, however, concerns focus less on numerical arsenal size than on the sufficiency of specific nuclear and non-nuclear capabilities to meet evolving threats and on the degree of broader US commitment to these alliances. This article assesses developments in US-Japan and US-South Korea relationships in response to the Obama administration's nuclear disarmament policies, focusing on how the evolutionary course of those relationships may in turn condition prospects for sustaining this US nuclear policy direction. The analysis finds that the challenges of deterrence credibility and allied reassurance are difficult and long-term, but also that US nuclear arsenal size is secondary to broader political, strategic, and military factors in meeting these challenges. The evaluation concludes that strong alliance relationships and strategic stability in East Asia can be maintained while the size of the US nuclear arsenal continues to decline, but also that deterioration of these relationships could imperil core US nuclear policy and nonproliferation objectives.     

Formulations for dynamic lot sizing with service levels

In this article, we study deterministic dynamic lot‐sizing problems with a service‐level constraint on the total number of periods in which backlogs can occur over a finite planning horizon. We give a natural mixed integer programming formulation for the single item problem (LS‐SL‐I) and study the structure of its solution. We show that an optimal solution to this problem can be found in \begin{align*}\mathcal O(n^2\kappa)\end{align*} time, where n is the planning horizon and \begin{align*}\kappa=\mathcal O(n)\end{align*} is the maximum number of periods in which demand can be backlogged. Using the proposed shortest path algorithms, we develop alternative tight extended formulations for LS‐SL‐I and one of its relaxations, which we refer to as uncapacitated lot sizing with setups for stocks and backlogs. {We show that this relaxation also appears as a substructure in a lot‐sizing problem which limits the total amount of a period's demand met from a later period, across all periods.} We report computational results that compare the natural and extended formulations on multi‐item service‐level constrained instances. © 2013 Wiley Periodicals, Inc. Naval Research Logistics, 2013     

航天测控系统任务可靠性分析的EOOPN模型

提出了一种可用于航天测控系统任务可靠性分析的扩展面向对象Petri网（extend object-oriented Petri nets, EOOPN）模型,旨在对给定的航天测控方案进行可靠性评估分析。针对问题特点明确了OOPN扩展思路,给出了EOOPN模型的形式化定义、运行规则和建模步骤,模型通过引入公共库所、激发弧、消息变迁和消息处理函数等概念,体现了面向对象的思想,具有很好的层次性和模块性。所建立的EOOPN模型能够完整的描述航天测控系统的组成和任务特点。通过对算例模型仿真运行,表明实验结果具有良好收敛性,与Markov解析值对比误差在1%以内,从而验证了模型的有效性。     

多源验前信息下基于证据理论的ML-Ⅱ融合方法

在复杂新型产品的可靠性评估中,试验的样本量通常较小,而Bayes方法在小样本统计推断中比经典统计方法更为适用.针对可靠性工程中遇到的验前信息的多源性问题,给出了一种基于证据理论的ML-Ⅱ融合方法.在融合过程中考虑了信息源的可信性,减小了可信度低的信息源对评估结果的影响.以电子产品为例,算例实验表明了该方法在有“干扰信息源”存在的情况下的评估结果的有效性和合理性.     

某型发电机可靠性试验系统研究

为了对某型发电机进行可靠性试验,根据试验需求,设计了带能量反馈的试验系统。该系统与发电机输出带纯电阻性负载方案相比,大大节约了试验的耗电量,并利用仿真软件PSCAD/EMTDC建立了试验系统的仿真模型,对系统在不同扰动下的动态特性进行了仿真研究。仿真结果与试验结果相吻合,说明所建试验系统模型的正确性,也得出了该试验系统具有良好的运行稳定性的结论。     

可靠性试验与环境试验的关系

介绍了可靠性试验和环境试验的定义、目的、意义、分类,并对两者之间的联系与区别以及产品研制生产过程中两者的分布与作用等方面进行分析。     

On optimal system designs in reliability‐economics frameworks

Reliability Economics is a field that can be defined as the collection of all problems in which there is tension between the performance of systems of interest and their cost. Given such a problem, the aim is to resolve the tension through an optimization process that identifies the system which maximizes some appropriate criterion function (e.g. expected lifetime per unit cost). In this paper, we focus on coherent systems of n independent and identically distributed (iid) components and mixtures thereof, and characterize both a system's performance and cost as functions of the system's signature vector (Samaniego, IEEE Trans Reliabil (1985) 69–72). For a given family of criterion functions, a variety of optimality results are obtained for systems of arbitrary order n. Approximations are developed and justified when the underlying component distribution is unknown. Assuming the availability of an auxiliary sample of N component failure times, the asymptotic theory of L‐estimators is adapted for the purpose of establishing the consistency and asymptotic normality of the proposed estimators of the expected ordered failure times of the n components of the systems under study. These results lead to the identification of ε‐optimal systems relative to the chosen criterion function. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

基于重叠保留法及FFT的伪码快速捕获技术研究

PN码的快速捕获是设计直接序列扩频接收机的关键技术之一。对于无限长的输入序列,采用了基于分段相关的快速捕获算法。分段相关采用重叠保留法,用FFT实现每块的相关运算。在Matlab环境下验证了本算法可以在低信噪比及高动态环境下实现PN码的快速捕获。     

含微网的国防工程供电保障系统可靠性评估

为准确评估含分布式电源的国防工程供电保障系统的可靠性,基于中压配电网的可靠性级别树算法,分析了采用3级供电模式的典型国防工程供电保障系统,建立相应开关树和断路树模型,并考虑设备故障、备用电源切换等因素,提出统一的负荷点可靠性指标计算模型。以符合国防工程供电保障系统结构特点的改进RBTS-BUS6为算例,对重要负荷供电能力和系统可靠性进行评估和分析。结果显示,部分重要负荷点的可靠性指标会随微网接入得到较好改善。     

结合非负张量表示与扩展隐Dirichlet分配模型的图像标注

由于"语义鸿沟"的存在,自动图像标注是一项极具挑战性的工作。考虑到图像低层视觉特征与高层语义概念的差异,分别从图像表示与语义建模两个方面来实现自动图像标注。在图像表示方面,提出了一种正则化约束下的非负张量表示方法,用以提取符合人眼视觉直观理解的图像高阶结构特征。在语义建模方面,提出了一种三层贝叶斯模型——扩展隐Dirichlet分配。该模型利用隐变量来实现图像与标注词的关联,并通过一种基于变分推理的期望最大值方法来估计参数。实验结果表明,ELDA模型在大规模数据库NUS-WIDE上的标注结果相较于现有方法有了显著的提高。