Optimal replacement of improving and deteriorating repairable systems

System improvement and deterioration are defined in terms of partial orderings between life distributions. The effects of ageing of 'the distribution of time to first failure' on improvement and deterioration of a repairable system subject to minimal repairs, are investigated. Under various types of life distributions we derive explicitly the times at which the system should be condemned (replaced by a new one) to minimize the total cost of maintenance and replacement in terms of parameters of the distribution and of the cost function.<
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