This paper studies a periodic-review, serial inventory system in which echelon r nQ T policies are implemented. Under such a policy, each stage reviews its inventory in every T period and orders according to an echelon r nQ policy. Two types of fixed costs are considered: one is associated with each order batch Q, and the other is incurred for each inventory review. The objective is to find the...

In this paper, we devise a framework for obtaining the optimal ordering policy in a single location, continuous review inventory system with arbitrary inter-demand times. We show that it is optimal to order at demand arrival epochs only if the inter-demand time has constant or decreasing failure rate (CFR or DFR). When the inter-demand time has increasing failure rate (IFR), we show that the op...

We address multi-item inventory systems with random and seasonally fluctuating, and possibly correlated, demands. The items are produced in two stages, each with its own lead-time; in the first stage a common intermediate product is manufactured. The production volumes in the first stage are bounded by given capacity limits. We develop an accurate lower bound and close-to-optimal heuristic stra...

The popular models for repairable item inventory, both in the literature as well as practical applications, assume that the demands for items are independent of the number of working systems. However this assumption can introduce a serious underestimation of availability when the number of working systems is small, the failure rate is high or the repair time is long. In this paper, we study a m...

this paper deals with an i * corresponding author email address:   nventory system with one central warehouse and a number of identical retailers. we consider perishable-on-the-shelf items; that is, all items have a fixed shelf life and start to age on their arrival at the retailers. each retailer faces poisson demand and employs (1, t) inventory policy. although demand n...

This paper presents a study of a coordinated production inventory-system. In the proposed model, any echelon considers its successors as part of its inventory system and generates the replenishment order on the basis of operational information of its partners. We show that the coordinated decision making allows elimination of information distortion along the chain. Furthermore, we show how the ...

We consider multi-echelon supply chains, typically consisting of retailer, distributor, manufacturer, etc. The inventory of each actor is subject to its own delay in delivery time, and each chooses its own inventory replenishment strategy. We model this interaction with a system of linear differential delay equations. When put in matrix form the system is triangular and we derive an exact solut...

Nowadays, Companies have to deal with an uncertain demand which is more difficult to handle when it has a non-stationary pattern. Simultaneous decrease of customer service and increase of stock costs are the most significant effects of such demand uncertainty. To deal with this issue, inventory optimization models must be adapted to cover a multi-echelon network structure and to consider altern...

We consider the problem of minimizing the overall cost of a supply chain, over a possibility long horizon, under demand uncertainly which is known only crudely. Under such circumstances, the method of choice is Robust Optimization, in particular the Affinely Adjustable Robust Counterpart (AARC) method which leads to tractable deterministic optimization problems. The latter is due to a recent re...

We consider periodic review inventory control problems in directed networks, primary examples of which are distribution systems and assembly systems. External demand could occur at each node. When inventory is insufficient to meet requirements at a node, a portion of this demand is backordered and the remaining is lost. External demands, as well as lead times for inventory purchase, assembly, a...