Elahe Zohoorian-Azad

Background and aims: Power plants are the most important infrastructure for economic development with technological advances and sophisticated technology, are subject to risks and accidents. Despite of uncertainty and ambiguity, offering the solution that can combine the information to identify hazards, assess and rank risks can potentially be effective to control and reduce occupational accidents. This survey targeted to identify and assess hazards, determine and rank the effective safety risks in a combined cycle power plant. Methods: To identify hazard following the documentation review, interviews with experts, brainstorming sessions, knowledge and experience group of experts in occupational health and safety engineering were used. Risk analysis was performed using fuzzy classification for severity and frequency by previous studies and expert opinion. Finally the risks were ranked based on degree of Belief approach in fuzzy logic. Results: In the present study, among the 11 cases of identified hazards, explosion and fire gas turbines and bust steam pipes under pressure, with the degree of belief 0.56, ranked in the first placeand fell in tanks reservoirs and canals with degree of belief 0.21 had the second place. Conclusion: So far, few risk assessment tools and techniques have been proposed in power plants. In this study, despite of using subjective and qualitative variables, for measuring these variables the absolute numbers and mathematical methods were used. Therefore, this study is important and can be suitable and accurate approach to address the technical deficiencies in this section.

We consider the set of finite random words A*, with independent letters drawn from a finite or infinite totally ordered alphabet according to a general probability distribution. On a specific subset of A*, we consider certain factorization of the words. The factors of a word are labelled with ranks, based on the lexicographical order. In this paper we prove that the normalized position of the ranks is uniform, when the length of the word goes to infinity. © 2012 Elsevier B.V.