Analysis of a sampling control scheme for a perishable inventory system

We consider an inventory system in which both the arrival of items and the demand for those items are Poisson processes. The stored items have two phases of shelf-life. If the item has not been taken by a demand during the first phase it is inspected. With probability q it is removed and with probability p = 1 – q it is transferred to the second phase. The blood bank model inspired this study. We compute ergodic limits for the number of items in the system, the lost demands, and the two types of outdating.