Department of Industrial Engineering2024-11-0920150269-964810.1017/S02699648140002292-s2.0-84920698825http://dx.doi.org/10.1017/S0269964814000229https://hdl.handle.net/20.500.14288/11469We analyze optimal replacement and repair problems of semi-Markov missions that are composed of phases with random sequence and durations. The mission process is the minimal semi-Markov process associated with a Markov renewal process. The system is a complex one consisting of non-identical components whose failure properties depend on the mission process. We prove some monotonicity properties for the optimal replacement policy and analyze the optimal repair problem under different cost structures.EngineeringIndustrial engineeringOperations ResearchManagement ScienceJournal Article1469-8951351999000004Q36274