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...

This paper analyzes a series inventory system with stationary costs and stochastic demand over an infinite horizon. A distinctive feature is that demand can be negative, representing returns from customers, as well as zero or positive. We observe that, as in a system with nonnegative demand, a stationary echelon base-stock policy is optimal here. However, the steadystate behavior of the system ...

The inventory management of multi-echelon repairable items systems is a major problem as these items are relatively expensive and slow-moving, so, inventory management can be a real problem due to mathematical complexities. In this work, a study was performed in a complex high-value products manufacturer, whose repairable items are both expensive and critical. Data of parts’ failure, storage an...

Abstract: This study relies on integrated inventory theory which merges with the supply chain concept and aims at the steel bar material of precast factory’s two-echelon supply chain system. In order to consider the variable demand rate, unfixed supply time, unfixed supply frequency and unfixed supply quantity, this study builds a strategic model that minimizes the total inventory cost of all p...

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 analyses an infinite horizon two-echelon supply chain inventory problem and shows that a sequence of the optimum ordering policies does not yield globally optimal solutions for the overall supply chain. First-order autoregressive demand pattern is assumed and each participant adopts the order-up-to (OUT) policy with a minimum mean square error forecasting scheme to generate replenish...

In the book “Optimal inventory modeling of systems: multi-echelon techniques” the author Craig Sherbrooke, who has developed several important model in this area, describes a part of the model cosidered in this manuscript as follows (in “aircraft language”): “When a malfunction is diagnosed on an aircraft, the malfuncioning item is removed from the aircraft and brought into base supply. If a sp...

Consider a continuous-review, serial inventory system with N stages. Material flows from stage N to stage N − 1, N − 1 to N − 2, etc., until stage 1, where stationary compound Poisson demand occurs. Let and denote the demand rate and the mean of demand size, and D t denote the demand over a time interval t. There is a constant lead time Lj for stage j . Define L̃i = ∑i j=1Lj . Inventory is contr...

The bullwhip effect is defined as the distortion of demand information as one moves upstream in the supply chain, causing severe inefficiencies in the whole supply chain. Although extensive research has been conducted to study the causes of the bullwhip effect and seek mitigation solutions with respect to several demand processes, less attention has been devoted to the ...