Predicting risk of water quality failures in distribution networks under uncertainties using fault-tree analysis

The water quality in a distribution system is affected by many factors, including operational and environmental conditions as well as the condition in and around the distribution network. Lack of reliable data as well as knowledge gaps with respect to the impact of these factors on water quality make the quantification of water quality failure risk very challenging. Furthermore, the variability inherent in (sometimes) thousands of kilometers of distribution pipes presents added complexities. Major modes of water quality failures can be classified into intrusion of contaminants, regrowth of bacteria (biofilm), water treatment breakthrough, leaching of chemicals or corrosion products from system components, and permeation of organic compounds through plastic pipes. Deliberate contamination and negligence of operators have in recent years become an added concern. In earlier works by Sadiq et al. (2004 Sadiq, R., Kleiner, Y. and Rajani, B. 2004. Aggregative risk analysis for water quality failure in distribution networks. Journal of Water Supply Research and Technology: Aqua, 53(4): 241–261. [Web of Science ®] , [Google Scholar], 2007 Sadiq, R., Kleiner, Y. and Rajani, B. 2007. Water quality failures in distribution networks – risk analysis using fuzzy logic and evidential reasoning. Risk Analysis – An International Journal, 27(5): 1381–1394. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), an aggregative risk analysis approach using hierarchical structure was proposed to describe all possible mechanisms of contamination. In this paper a similar structure is used as a basis for a fault-tree approach. While fault-tree analysis is widely used for many engineering applications, in this paper we specifically explore how interdependencies among factors might impact analysis results. Two types of uncertainties are considered in the proposed analysis. The first is related to the likelihood of risk events, and the second is related to non-linear dependencies among risk events. Each basic risk event (input factor) is defined using a fuzzy probability (likelihood) to deal with its inherent uncertainty. The dependencies among risk events are explored using Frank copula and Frechet's limit. The proposed approach is demonstrated using two well-documented episodes of water quality failures in Canada, namely, Walkerton (ON) and North Battleford (SK).     

Reliability analysis for the design of an inflator

Product reliability is determined at its design stage and must be identified to adequately evaluate the feasibility of the current design. Reliability prediction provides the means to design verification and optimum modification. A design team must detect any potential reliability problems before the completion of the product design. This paper presents an approach to include the use of a reliability block diagram for reliability prediction, a fault tree analysis for detecting possible failures, and the axiomatic design procedure in the product design evaluation process. The discussion includes the reliability analysis of a passenger side airbag inflator design. The modification of the current inflator design is also discussed.     

基于故障树蒙特卡洛模拟法的孤岛微电网薄弱环节识别

为增强微电网风险评估工作的针对性,采用故障树蒙特卡洛模拟法对孤岛微电网的薄弱环节进行识别。以网内不同用户供电中断为顶事件建立各用户的故障树模型,通过蒙特卡洛模拟法随机抽样建立孤岛微电网的两状态模型。从元件重要度和网络风险重要度2个方面,建立微电网薄弱环节重要度指标体系。对某典型低压孤岛微电网的薄弱环节进行识别,评估孤岛微电网的可靠运行能力,算例结果验证了所提方法的合理性。结果表明,柴油机和逆变器是该算例微电网的薄弱环节,降低其故障率有利于降低微电网的风险水平。     

通信装备诊断贝叶斯网络结构构建方法研究

诊断贝叶斯网络的构建,是应用贝叶斯网络对通信装备进行故障诊断的重要环节。分析了两种典型诊断贝叶斯网络构建方法的特点及其对于构建通信装备诊断贝叶斯网络的适用性。运用故障树转化算法建立了某型通：陪装备的诊断贝叶斯网络。实验分析表明,该方法对于通信装备诊断贝叶斯网络的构建具有较强的有效性。     

汽车制动系的故障树分析

对某型客车制动系统进行故障树分析,有效地分析了系统及零部件的故障模式、故障原因及故障种类,利用早期不交化方法精确地算出了制动系的累积失效概率、事件概率重要度及关键重要度,严格地评价了系统的可靠性,为开展可靠性维修及管理奠定了基础。     

关于建立故障树的新探索

在诊断专家系统开发的基础上，讨论了故障树的建立问题，基于对系统特性的分析，提出了通过系统故障传递关系和故障传递可达关系，由计算机自动生成故障树的方法，并以大型过程系统为例，从理论上论证了该方法的可行性及其优点。     

基于Vague集与FTA方法的麻醉流程风险评估

麻醉是提高患者安全的首要环节。围手术期麻醉过程受大量随机、模糊和不确定性因素影响而呈现出多态性,传统故障树分析(FTA)在评估面向该类流程风险问题上存在明显缺陷。通过引入Vague集解决麻醉操作中失效事件多态性和失效概率不确定性,并依据有明显边界的麻醉操作阶段来构建面向流程的故障树模型,基于医院麻醉记录、医师经验、可靠性数据并结合TOPAZ模型,对围手术期麻醉流程进行了风险评估。实例验证该方法可行且有效,与现有方法比较分析发现该结果更好地刻画出失效事件随机性和不确定性。     

溴化锂吸收式制冷机制冷量衰减问题的可靠性工程分析

可靠性工程的理论和方法已经深入到科学研究以及产品、工程设计的各个专业领域。本文通过应用可靠性工程基本概念和故障树分析方法,就溴化锂吸收式制冷机的制冷量衰减问题进行分析讨论,提出了提高机组性能和可靠性的主要途径。     

运载火箭姿控发动机故障诊断方法研究

针对排除运载火箭测试发射过程中故障的特点,研究了基于故障树模型的故障诊断理论与诊断技术,建立了姿态控制发动机故障树和故障模式,利用其对某型火箭的姿态控制发动机系统出现的故障进行了模拟与诊断.诊断故障发生的趋势与火箭飞行试验故障分析结果一致.     

基于可靠性框图和故障树的矿井运煤系统分析

指出了研究矿井运煤系统可靠性的意义,确定了安全高效矿井运煤系统的设备组成和可靠性数量指标,重点分析了单工作面的刚性矿井连接运煤系统和柔性矿井连接运煤系统的可靠性和故障树模型,对有效度进行了深入的分析,验证了所建模型的合理性。