Two Variable Optimal Replacement Policy for Cold Standby Repairable System

A cold standby repairable system consisting of two-identical component and one repairman is studied. Assume that the component after repair is not "as good as new", by using the geometric process we consider the two variable optimal replacement policy (%N%, %T%),based on the failure number %N% and the working age %T% for the component 1. The problem is to determine the optimal replacement policy(%N%+*, %T%+*), such that the long-run average benefit per unit time is maximized. Meanwhile, the expression of the long-run average benefit per unit time is derived. Finally, under given conditions, we can derive that the policy(N+, T+)is better than the policy N+ and T+ in previous references.