A perishable inventory system at service facilities with negative customers

This article considers a continuous review (s,S) inventory system at a service facility, wherein an item demanded by a customer is issued after performing service on the item. The service facility is assumed to have an infinite waiting hall. The arrival time points of customers form a Poisson process. A customer turns out to be an ordinary customer with probability p and a negative customer with probability (1-p),(0≤p≤1). An ordinary customer, on arrival, joins the queue and the negative customer does not join the queue and takes away one waiting customer if any. The life time of each item and service time are assumed to have independent exponential distribution. The joint probability distribution of the number of customers in the system and the inventory level is obtained in both the transient and steady state cases. The measure of system performance in the steady state are derived.