الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Presented is a methodology to be used for the optimum selection, on a life cycle basis, of several vendors’ equipment by estimation of the failure cost of these systems. Consequently, certain characteristics are evaluated, all of which are important and are required for failure cost calculation.
These characteristics are mainly related either to reliability and maintenance engineering or to the sparing policy of the system and accordingly the life cycle analysis will be achieved. In other words, system availability, system failure times and system sparing policy are evaluated, and the system reliability characteristics are studied as wello Therefore, various techniques for the estimation andl or evaluation of each of these statoistical parameters are shownu Also, the methodology considers a Markov model which is used using a computer system purchasing process for the evaluation of various moments of times: mean time between failure, mean time to repair~ mean time to first failure and mean cycle time.
In additionf it analyzes the effect of sparing policy on system availability, and its important parameters: the probability density function of systemis availability; the time between restocking the spare supply; number of spares for a probability level that a spare will be available; the expected system down time due to lack of a spare; the number of spares for the lowest cost and the average system availability.
consequently, by using these failure statistical parameters the life cycle cost of the given system is calculated in terms of its failure cost, its operating cost and its initial cost.
Generally, the model takes an engineering point of view for cost evaluation of systems during its purchasing period, and thus affording managers a high leverage for making a quick decision during the negotiation process with vendors and consequently an opportunity ,to have an adequate contract. In addition, the cost model has wide range of applicability; for example, it could be applied to inte¬grated systems such as communication and transportation systems, aircraft, computer complex, and many kinds of electrical and mechanical systems.