Allocation policies of redundancies in two-parallel-series and two-series-parallel systems

摘要

In this paper comparisons of allocation policies of components in two-parallel-seriessystems with two types of components are provided with respect to both, the hazardrate and the reversed hazard rate orders. The main results indicate that the life ofthis kind of system is stochastically maximized by unbalancing as much as possiblethe two classes of components. We only assume that the two distributions impliedin the model have proportional hazard rates. The same type of comparisons arealso given for the dual model, the two-series-parallel systems but assuming thatthe distributions implied in the model have proportional reversed hazard rates, andtherefore the final conclusion is the opposite; that is, the reliability of the systemimproves as the similarity between the two parallel subsystems increases