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Stationary analysis of an (R, Q) inventory model with normal and emergency orders

Published online by Cambridge University Press:  04 October 2022

Onno Boxma*
Affiliation:
Eindhoven University of Technology
David Perry*
Affiliation:
Holon Institute of Technology
Wolfgang Stadje*
Affiliation:
University of Osnabrück
*
*Postal address: Department of Mathematics and Computer Science, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. Email address: o.j.boxma@tue.nl
**Postal address: Holon Institute of Technology, PO Box 305, Holon 5810201, Israel. Email address: dperry@stat.haifa.ac.il
***Postal address: Institute of Mathematics, University of Osnabrück, 49069 Osnabrück, Germany. Email address: wstadje@uos.de

Abstract

We consider an (R, Q) inventory model with two types of orders, normal orders and emergency orders, which are issued at different inventory levels. These orders are delivered after exponentially distributed lead times. In between deliveries, the inventory level decreases in a state-dependent way, according to a release rate function $\alpha({\cdot})$ . This function represents the fluid demand rate; it could be controlled by a system manager via price adaptations. We determine the mean number of downcrossings $\theta(x)$ of any level x in one regenerative cycle, and use it to obtain the steady-state density f (x) of the inventory level. We also derive the rates of occurrence of normal deliveries and of emergency deliveries, and the steady-state probability of having zero inventory.

Type
Original Article
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of Applied Probability Trust

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