Abstract
This paper examines a functioning policy of a parallel system. We assume availability of n non-identical, non-repairable units for replacement or support. Two units start their operation simultaneously at times , and any one of them is replaced instantaneously upon its failure by one of the ( n − 2) standby units at random starting times Si ( ). Thus, with probability one, the system is functioning with two units up till the failure of the ( n − 1)th unit. Unit lifetimes Ti have a general joint distribution function F( t ). The system has to operate for a fixed period of time, c, and it stops functioning when all available units fail before c. The probability that the system is functioning for the required period of time c depends on the distribution of the unit lifetimes. The reliability of the system is evaluated by recursive relations. Independent unit lifetimes are considered as special cases.
Acknowledgements
The authors are pleased to thank the referees and the Editor for their valuable comments and suggestions.