A stochastic model on an additional warranty service contract

In general, a newly purchased item or system is warranted for a specific period. When the system fails during the warranty period, it is repaired free of charge. Even if the system is repairable, there exist some warranty services under which the manufacturer replaces the failed system during the warranty period. This study considers a case where a manufacturer offers an additional warranty service under which the failed system is replaced by a new one for its first failure, but minimal repairs are carried out to the system for its succeeding failures before the warranty expires. In this paper, we propose a mathematical model for setting a suitable charge of such an additional warranty service. Numerical examples assuming a personal computer are also presented

Discrete Optimal Testing/Maintenance . . .

In this paper, we focus on the optimal software testing/maintenance problem considered in Rinsaka and Dohi (2004), and develop a stochastic model in discrete operation circumstance, under the difference between the software testing environment and the operational environment can be characterized by an environment parameter. More precisely, the total expected software cost is formulated via the discrete NHPP type of software reliability models. In the special case with the geometric fault-detection time distribution, we derive analytically the optimal testing period (release time) which minimizes the total expected software cost under a milder condition. We call the time length to complete the operational maintenance after the release a planned maintenance limit, and also derive the optimal planned maintenance limit which minimizes the total expected software cost. In numerical examples with real data, we calculate numerically the joint optimal testing/maintenance policy, combined by testing period and planned maintenance limit