Integration of fuzzy reliability analysis and consequence simulation to conduct risk assessment

Losses of containment within the natural gas network, located in most populated areas, could cause environmental damage, injuries, or even death. Accordingly, it is pivotal to adopt proper approaches to assess and mitigate the risk arising from potential losses. Within this context, it is required to exploit solid reliability and consequence analysis techniques. To this end, this paper presents a methodology established on the integration of a Fuzzy Bayesian Network and consequence simulation. The Bayesian Network is more flexible and realistic than classic approaches because it can consider conditional probabilities and prior information. Furthermore, Leaky Noisy-OR Gates are exploited to allow an easier filling of the Conditional Probability Tables. This task is performed through expert elicitation, adopting Intuitionistic Fuzzy Set Theory and Similarity Aggregation Method. Finally, the severity analysis is performed via a software, named Safeti, which provides an accurate evaluation of the consequences. To show the applicability of the framework, a pressure regulator of a Natural Gas Regulating and Metering Station is considered as case study. The proposed approach can assist asset managers in evaluating the risk arising from the operations, and, accordingly, it can guide them in making maintenance-related decisions to assure the safety of the operations.     

生物环境因子对树干呼吸时空变异的影响

树干呼吸是解释森林生态系统生产力变化的关键过程之一.测定树干呼吸速率,理解其生物环境调控机制,有助于构建森林碳循环模型,提供森林碳收支的估测精度.本文比较分析了树干呼吸3种测定方法,指出活体测定法与质量平衡方法的结合使用,可以更深入地进行树十呼吸机理研究.针对树十呼吸速率时空变异,着重探讨温度、树干液流的重要影响机制,并比较分析了不同森林生态系统的维持呼吸年通量,维持呼吸年通量与林龄、维度、年均温和降水量呈显著线性相关.表4参84     

基于SEM的维修资源管理对机务人员不安全行为的影响研究

为减少维修差错导致的不安全事件,从维修资源管理对机务人员不安全行为的影响进行探讨,以团队合作、沟通交流、工作压力、领导能力、工作环境及惯例作为维修资源管理变量,考虑不安全行为意向对不安全行为的中介作用,提出了维修资源管理各因素对机务人员不安全行为的影响假设。通过实证分析,采用结构方程模型(SEM)的方法验证了维修资源管理各因素对机务人员不安全行为的影响假设。实证结果表明:维修资源管理各因素对机务人员不安全行为及意向有不同的影响作用。为机务人员的安全行为管理提供理论支持。     

基于G1-DEMATEL法的通用航空维修安全影响因素研究

为定量分析影响通用航空维修安全的风险因素,进而有针对性地制定重点安全监管内容,根据 “人-机-环-管”模型,建立了通航维修安全风险因素指标体系。通过结合G1法和决策试验与评价实验法（DEMATEL）,构建基于G1-DEMATEL法的通航维修安全风险因素分析模型。利用G1法计算各个因素指标的权值,再以各指标权值之比建立直接影响矩阵;采用DEMATEL法从中心度和原因度两个视角对影响通用航空维修安全的各个风险因素进行分析,以确定因素指标间的影响程度及其作用关系。G1-DEMATEL法为定量分析安全风险因素,并确定关键因素提供可能性。同时,为局方和通用航空公司制定通航维修安全监管内容提供有价值的参考。     

A framework to estimate the risk-based shutdown interval for a processing plant

Petrochemical plants and refineries consist of hundreds of pieces of complex equipment and machinery that run under rigorous operating conditions and are subjected to deterioration over time due to aging, wear, corrosion, erosion, fatigue and other reasons. These devices operate under extreme operating pressures and temperatures, and any failure may result in huge financial consequences for the operating company. To minimize the risk and to maintain operational reliability and availability, companies adopt various maintenance strategies. Shutdown or turnaround maintenance is one such strategy. In general, shutdown for inspection and maintenance is based on the original equipment manufacturer's (OEM) suggested recommended periods. However, this may not be the most optimum strategy given that operating conditions may vary significantly from company to company.The framework proposed in this work estimates the risk-based shutdown interval for inspection and maintenance. It provides a tool for maintenance planning and decision making by considering the probability of the equipment or system for failure and the likely consequences that may follow. The novel risk-based approach is compared with the conventional fixed interval approach. This former approach, characterized as it is by optimized inspection, maintenance and risk management, leads to extended intervals between shutdowns. The result is the increase in production and the consequent income of millions of dollars.The proposed framework is a cost effective way to minimize the overall financial risk for asset inspection and maintenance while fulfilling safety and availability requirements.     

基于动态信息技术的设备主动维护预知平台的设计

石化企业规模大、设备种类繁多且分布广,为规范设备的管理流程、提高设备的管理水平及设备可靠性,提高企业的经济效益和安全性,建立了基于Oracle数据库与RBI和RCM技术的设备预知维护信息平台,并结合RBI及RCM技术信息输入与安全评价方法,实现设备的故障预知及维护规范。该平台与石化的生产运行管理相结合,可实现设备的信息化管理,在及时排除设备故障隐患的同时,保障设备的正常运行,为改善企业生产安全现状和提高设备管理水平,提供了新的方法。     

人失误模型在防止变电所检修事故中的应用

针对变电所检修事故的特点,认为人失误是导致该类事故发生的主要原因。运用安全人机工程学基本原理,分析了变电所检修过程中人失误产生的原因,在研究了以人失误为主因的事故模型基础上,进一步从人的特性、人机功能的分配、人机界面的设计、安全管理和环境因素五个方面人手构建了以人失误为主因的变电所检修事故模型,基于该模型提出了有效、合理的避免或减少变电所检修事故的五点对策措施。以期能为变电所检修事故的预防起到积极的指导作用。     

Significant human risk factors in aircraft maintenance technicians

We examined significant human risk factors in aircraft maintenance technicians (AMTs) in the airline industry. We conducted an empirical study of Taiwan’s airlines to determine these risk factors and to illustrate how a quantifiable evaluation approach integrates experts’ opinions about the relative importance of risk factors. We developed an expert questionnaire and modified the human factors SHELL model to categorize the risk factors that we derived from the literature and the opinions of 107 senior experts. The empirical results showed that there are nine significant risk factors out of 77 preliminary and 46 primary risk factors. The results also provided support for the approach and model presented in this work, demonstrating that they are both strategically effective and practically acceptable. Analyzing and ranking the significant risk factors for AMTs in this fashion may help airlines to better focus on their major operational and managerial weaknesses in order to improve maintenance operations under the condition of limited resources.     

Prospects for a self-sustainable sewage treatment system: a case study on full-scale UASB system in India's Yamuna River Basin

The government of India decided to launch a project to implement 16 full-scale Upflow Anaerobic Sludge Blanket (UASB) reactors (with a total capacity of 598,000 m(3)/d) in the Yamuna River basin under its Yamuna Action Plan (YAP). A polishing pond called the Final Polishing Unit (FPU) was utilized for post-treatment. This paper evaluates the sewage treatment efficiency of the combined system of full-scale UASB reactors and polishing ponds under Indian climatic conditions. Results have shown that the effluent from the sewage treatment plants (STPs) investigated failed to comply with applicable discharge standards in terms of BOD, SS, and fecal coliform removal. Therefore, it is proposed that such proper operation and maintenance as removing excess sludge and scum be conducted in order to increase treatment efficiency. Moreover, trained and experienced workers are also required to operate and maintain the systems, along with a scientific approach.     

Understanding Urban Vehicular Pollution Problem Vis-a-Vis Ambient Air Quality – Case Study of a Megacity (Delhi, India)

Air pollution has become a growing problem in megacities and large urban areas through out the globe, and transportation is recognized as the major source of air pollution in many cities, especially in developing countries. Contribution of automobiles is reported in the range of 40 to 80% of the total air pollution. The challenge facing megacities is how to reduce the adverse environmental impacts and other negative effects of transportation without giving up the benefits of mobility. The dilemma becomes most pressing under conditions of rapid urban growth, which is likely to increase travel demand significantly.The paper is aimed at understanding the problem of vehicular pollution vis-a-vis ambient air quality for a highly traffic affected megacity, Delhi, wherein, the contribution of transport sector was estimated to be as high as 72%. An effort has been made to review and evaluate the benefits (in terms of improved air quality) of the technological interventions/policies adopted for vehicular pollution control in Delhi. It also highlights the outcome of the efforts and suggests further improvements thereon. The importance of public participation and awareness are also discussed. The paper focuses on deriving the benefits of the implementation of management strategies, supported by scientific and technical data/interpretation, so that the people can realize and participate in the government's endeavor for clean city drive in a more effective manner.