This paper considers the comparison of two ðs; SÞ production inventory systems with retrials of unsatisfied customers. The time for producing and adding each item to the inventory is exponentially distributed with rate b. However, a production rate ab higher than b is used at the beginning of the production. The higher production rate will reduce customers’ loss when inventory level appro...

We analyze and compare three (s,S) inventory systems with positive service time and retrial of customers. In all of these systems, arrivals of customers form a Poisson process and service times are exponentially distributed. When the inventory level depletes to s due to services, an order of replenishment is placed. The lead-time follows an exponential distribution. In model I, an arriving cust...

This paper studies a Markov model of queuing-inventory system with primary, retrial, and feedback customers. Primary customers form Poisson flow, if an inventory level is positive upon their arrival, they instantly receive the items. If equal to zero arrival primary customer, then this according Bernoulli scheme, either leaves or goes into infinite buffer repeat request in future. The rate retr...

This article studies a perishable inventory system with production unit. The process is governed by (s, S) policy and it exponentially distributed. primary arrival follows Markovian process(MAP) the service time phase-type distributed random variable. inventoried items are subject to decay linear rate. A newly arriving customer realizes that running out of stock or server busy either moves infi...

We examine an M/M/1 retrial queue with an unreliable server whose arrival, service, failure, repair, and retrial rates are all modulated by an exogenous random environment. Provided are conditions for stability, the (approximate) orbit size distribution, and mean queueing performance measures which are obtained via matrix-analytic methods. Additionally, we consider the problem of choosing arriv...

In the previous chapter we assumed that replenishment is instantaneous and no shortage is permitted (shortage cost infinity).In this chapter we assume that replenishment of inventory does not materialize immediately as placement of order ,rather takes a random amount of time for order materialization .Thus we have now a finite shortage cost situation. Another salient feature of this chapter is ...

This paper presents the analysis of a continuous review perishable inventory system wherein the life time of each item follows an exponential distribution. The operating policy is (s,S) policy where the ordered items are received after a random time which follows exponential distribution. Primary arrival follows Poisson distribution and they may turnout to be posit...

We consider a carrier sense multiple access(CSMA) in an unslotted cognitive radio network under a mixed spectrum environment of licensed channels and unlicensed channels. In this system, primary users use only licensed channels, while secondary users use unlicensed channels and opportunistically can use licensed channels unused by primary users temporally. If an arriving secondary user(SU) does...