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291.
This article considers the problem of monitoring Poisson count data when sample sizes are time varying without assuming a priori knowledge of sample sizes. Traditional control charts, whose control limits are often determined before the control charts are activated, are constructed based on perfect knowledge of sample sizes. In practice, however, future sample sizes are often unknown. Making an inappropriate assumption of the distribution function could lead to unexpected performance of the control charts, for example, excessive false alarms in the early runs of the control charts, which would in turn hurt an operator's confidence in valid alarms. To overcome this problem, we propose the use of probability control limits, which are determined based on the realization of sample sizes online. The conditional probability that the charting statistic exceeds the control limit at present given that there has not been a single alarm before can be guaranteed to meet a specified false alarm rate. Simulation studies show that our proposed control chart is able to deliver satisfactory run length performance for any time‐varying sample sizes. The idea presented in this article can be applied to any effective control charts such as the exponentially weighted moving average or cumulative sum chart. © 2013 Wiley Periodicals, Inc. Naval Research Logistics 60: 625–636, 2013 相似文献
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Kelemework Tafere Reda 《African Security Review》2013,22(3):270-278
Based on a literature review, this article examines the dynamics in pastoral systems, natural resource conservation and conflict in the drylands of East Africa. It argues that, in the context of East Africa, pastoralism and biodiversity conservation in general are distinct forms of land use that are complementary rather than competitive. The present state of natural resource degradation in the drylands is explained in terms of factors related to ecological and demographic pressures, land use conflicts and inefficient land administration policies. When the customary pastoral institutions of land administration and resource management are threatened, the problem of degradation is further exacerbated and violent conflicts occur among multiple resource users, including pastoralists, farmers and the state. The article recommends the revitalisation, empowerment and recognition of pastoral institutions in a way that ensures effective synergy between the formal and customary structures of resource governance. 相似文献
295.
The 2005 Review Conference of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) failed to produce any agreed action plan for addressing nuclear disarmament or proliferation. Detailed discussions and negotiations on such a plan were much curtailed because of procedural wrangles. This article describes the evolution of the conference and argues that changes in the international political environment and problems inherent in the revised NPT review process agreed at its 1995 Extension Conference contributed to the meager outcome. The main issues raised by delegations in their plenary statements, working papers, and the limited time available for interactive discussion are summarized, and three perspectives are offered on the reasons for the lack of any substantive product. Finally, the implications of that failure for the NPT, its review process, the wider regime for international nuclear governance, and nuclear disarmament, nuclear nonproliferation, and the peaceful use of nuclear energy are examined. 相似文献
296.
船舶领域的FPGA软件测试严重滞后于应用增长的速度,部分型号甚至未将其纳入测试范畴。在研制过程中,由FPGA故障导致的修改调试已成为影响进度和增加成本的瓶颈。因此,针对FGPA软件特点及其测试的现状,对其测试过程、测试模型和过程管理进行研究,并给出完整的过程管理体系。通过采用规范化、有序化、系统化、面向工程的、面向任务的文档及配套管理手段进行正确引导、组织和实施测试活动,持续改进测试流程中各个阶段工作质量和效用,及早及时地发现和关闭开发过程中存在的缺陷,提高设计和测试的沟通效率,最终保证FPGA产品的质量,提升客户的满意度。 相似文献
297.
由于强激光装置中金属化膜脉冲电容器高可靠长寿命的特点,导致退化试验的时间长效率低,传统的退化试验统计分析方法复杂,对先验信息依赖性大,针对这些问题提出了基于Wiener过程的金属化膜脉冲电容器步降应力加速退化建模和参数估计的方法。首先,用Wiener过程刻画电容器的退化过程,然后结合随机过程的特性采用MCMC方法进行参数估计,大大简化了统计分析过程。最后通过对电容器的仿真实验,将步降应力下的评估结果与恒定应力、步进应力的情况相对比,说明了步降应力对改善退化试验的试验效率的有效性。 相似文献
298.
王莹 《中国人民武装警察部队学院学报》2014,(6):50-53
将层次分析法引入到消防部队战勤保障体系影响因素的分析中,运用灰色理论,建立消防部队战勤保障能力综合评估的指标体系,提出了一种多层次指标体系下的分级评估模型.并通过实例验证,表明该方法的结果符合实际情况,具有实用性和可操作性. 相似文献
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针对某变质量热力系统的性能可靠性受多指标综合影响的问题,使用了一种基于 Monte Carlo 仿真的系统性能可靠性分析方法对该系统进行了可靠性分析。首先,选取系统的性能失效特征量作为载荷末速度和最大加速度,并确定了其失效标准;然后,阐述了系统中部件———调节阀开度的退化规律。在此基础上,对系统的性能可靠性进行了仿真分析,得到了系统性能失效特征量的故障概率密度及性能可靠度。仿真结果表明:随着部件性能参数的退化,系统性能可靠性逐渐降低。 相似文献
300.