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Description:
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When insufficient data is available , the use of probability theory for risk assessment may be both difficult and highly inaccurate . In such cases , subjective expert experience may be a viable alternative . Experts can give their degree of belief that a parameter's value would fall within a given range . These parameters are interpreted as fuzzy variables .
Hazardous material transportation is one topic in which the constraints and consequences of possible actions /events are not known precisely , with no means to acquire enough statistical data . This motivates our investigation using fuzzy set theory .
We use a fuzzy fault tree to assess the risk of failure associated with transportation of hazardous material . The fault tree describes the sequence /combination of events that may lead to a failure . Such events may be due to human errors , severe weather conditions , intelligence leaks , etc . The top event of the tree is a catastrophic failure , such as environmental contamination or cross of material .
Each event in the fault tree has its own membership function in which the fuzzy variable is the probability that this even may occur . The membership grade is the degree of belief that this probability may take on a certain value . Our work is inspired by PHASER (Probabilistic Hybrid Analytical System Evaluation Routine ) , implemented at Sandia National Laboratories by R .J . Roginski and J .A . Cooper . PHASER calculates the top event probability of failure for a fault . |