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51.
针对传统故障模式与影响分析(FMEA)方法在实际应用中的不足,提出一种基于有序加权平均(OWA)算子和决策试行与评价实验法(DEMATEL)的风险排序方法。FMEA专家对故障模式的3个风险因子给出模糊评价信息,应用OWA算子对评估信息进行集结,得到各故障原因对故障模式的影响强度。采用模糊DEMATEL法构建FMEA系统要素间的初始直接影响矩阵,经过运算可得综合影响矩阵,并计算各故障原因的原因度,据此进行产品或系统的失效风险评估。运用该方法对地铁车门系统的基础部件进行安全性分析,并将所得结果与传统RPN方法的结果做对比,验证了该方法的可行性和有效性。 相似文献
52.
Risk management is becoming increasingly important for railway companies in order to safeguard their passengers and employees while improving safety and reducing maintenance costs. However, in many circumstances, the application of probabilistic risk analysis tools may not give satisfactory results because the risk data are incomplete or there is a high level of uncertainty involved in the risk data. This article presents the development of a risk management system for railway risk analysis using fuzzy reasoning approach and fuzzy analytical hierarchy decision making process. In the system, fuzzy reasoning approach (FRA) is employed to estimate the risk level of each hazardous event in terms of failure frequency, consequence severity and consequence probability. This allows imprecision or approximate information in the risk analysis process. Fuzzy analytical hierarchy process (fuzzy-AHP) technique is then incorporated into the risk model to use its advantage in determining the relative importance of the risk contributions so that the risk assessment can be progressed from hazardous event level to hazard group level and finally to railway system level. This risk assessment system can evaluate both qualitative and quantitative risk data and information associated with a railway system effectively and efficiently, which will provide railway risk analysts, managers and engineers with a method and tool to improve their safety management of railway systems and set safety standards. A case study on risk assessment of shunting at Hammersmith depot is used to illustrate the application of the proposed risk assessment system. 相似文献
53.
彭文 《自动化与仪器仪表》2011,(5)
川化股份有限公司化肥厂二化尿素装置为日产2460T尿素的大型化肥装置,其CO2压缩机采用日本三菱3V-7B型两缸四段压缩机,由抽汽注汽冷凝式透平驱动.该透平的转速控制由505E控制器实现,并与ProTech 203相结合实现压缩机的两级超速保护.Woodward 505E数字控制器适用于具有一次可调整的纯抽汽、抽补结合或纯补汽型式透平的控制,可现场编程组态,使标准的设计能适用于各种不同的控制场合.文中介绍了505E控制器在UGB151 CO2压缩机上的调速应用,并例举调速系统出现的故障,进行分析排除. 相似文献
54.
Failure detection and consensus in the crash-recovery model 总被引:2,自引:0,他引:2
Summary. We study the problems of failure detection and consensus in asynchronous systems in which processes may crash and recover,
and links may lose messages. We first propose new failure detectors that are particularly suitable to the crash-recovery model.
We next determine under what conditions stable storage is necessary to solve consensus in this model. Using the new failure
detectors, we give two consensus algorithms that match these conditions: one requires stable storage and the other does not.
Both algorithms tolerate link failures and are particularly efficient in the runs that are most likely in practice – those
with no failures or failure detector mistakes. In such runs, consensus is achieved within time and with 4 n messages, where is the maximum message delay and n is the number of processes in the system.
Received: May 1998 / Accepted: November 1999 相似文献
55.
56.
The election problem in asynchronous distributed systems with bounded faulty processes 总被引:1,自引:1,他引:0
Sung Hoon Park 《The Journal of supercomputing》2007,41(1):89-104
Determining the “weakest” failure detectors is a central topic in solving many agreement problems such as Consensus, Non-Blocking
Atomic Commit and Election in asynchronous distributed systems. So far, this has been studied extensively for several such
fundamental problems. It is stated that Perfect Failure Detector P is the weakest failure detector to solve the Election problem with any number of faulty processes. In this paper, we introduce
Modal failure detector M and show that to solve Election, M is the weakest failure detector to solve election when the number of faulty processes is less than ⌈n/2⌉. We also show that it is strictly weaker than P.
相似文献
Sung Hoon ParkEmail: |
57.
58.
Arturo J. Fernández Carlos J. Pérez-González 《Computational statistics & data analysis》2012,56(3):719-731
Assuming that the probability of obtaining a defective unit in a production process, p, is not constant, a versatile methodology is presented for determining optimal failure-censored reliability sampling plans for log-location-scale lifetime models. The optimization procedure to decide the acceptability of a product is usually sufficiently accurate for the most widely used parametric lifetime models, such as the Weibull and lognormal distributions, and fairly robust to small deviations in the prior knowledge. Moreover, lower and upper bounds on the optimal sample size, and the corresponding acceptance constants, are derived in closed-forms. The proposed approach extends the traditional sampling plans to those cases in which appreciable prior information on p exists, and also allows the analyst the flexibility to delimitate the range of p and to incorporate into the reliability analysis prior impartiality between the producer and the consumer. In addition, the practitioners may achieve substantial savings in sample size, better information on the production process and better assessment of the true producer and consumer risks. An example related to the acceptability of a certain kind of gyroscope is included for illustrative purposes. Various practical prior distributions are considered to describe the random fluctuations in the proportion defective. 相似文献
59.
吴琦 《安徽水利水电职业技术学院学报》2013,13(4):49-51
将气象灾报系统作为电网GIS系统的嵌入式子系统,与电网在GIS中的模型和拓扑结构、SCADA系统实时数据相切合,做好灾害发生前的预判和灾后故障查找,最大限度降低灾害带来的大面积停电及设备损毁的损失. 相似文献
60.
《Ergonomics》2012,55(5):891-897
Abstract To study the usefulness of a screening questionnaire for neck/upper extremity complaints, 165 women in either repetitive industrial, or mobile and varied work, were studied by the questionnaire and by a detailed clinical physical examination. A total of 94 subjects recorded complaintsin the questionnaire. In 140 subjects findingswere recorded at the examination. Most subjects with findings at the clinical examination of shoulders reported complaints in the questionnaire (sensitivity 80%). For the other anatomical regions, the sensitivity was rather low (42– 65%). For all regions, most subjects without findings reported no complaints (specificity 77–97%). A total of 75 subjects were given clinical diagnoses according to a set of predetermined diagnostic criteria. The capacity of the questionnaire to identify diagnoses of shoulders was higher (sensitivity 92%) than for the other regions (66–79%). Of subjects who did not qualify for diagnosis, a majority (specificity 71–81%) did not report complaints in the questionnaire. We conclude that the questionnaire approach gives a fairly good picture of the neck/upper extremity status of a working female population. However, a clear view of the size of a problem is obtained only by a detailed clinical examination, particularly as regards the neck, elbows and hands, for which the questionnaire gave an underestimate. 相似文献