Spare parts provisioning for multiple k-out-of-n:G systems

In this paper, we consider a repair shop that fixes failed components from different k-out-of-n:G systems. We assume that each system consists of the same type of component; to increase availability, a certain number of components are stocked as spare parts. We permit a shared inventory serving all systems and/or reserved inventories for each system; we call this a hybrid model. Additionally, we consider two alternative dispatching rules for the repaired component. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our analysis gives the steady-state system size distribution of the two alternative models at the repair shop. We conduct numerical examples minimizing the spare parts held while subjecting the availability of each system to exceed a targeted value. Our findings show that unless the availabilities of systems are close, the HP policy is better than the HF policy

PROCUREMENT PROCESS IN POWER ENERGY ENTERPRISE

The supply and procurement processes are extremely important for properfunctioning of power plants, especially for continuous production process because anybreaks have negative effects on the costs linked to idle time.supply management, procurement process

Efficient optimization of the dual-index policy using Markov chains

3We consider the inventory control of a single product in one location with two supply sources facing stochastic demand. A premium is paid for each product ordered from the faster `emergency' supply source. Unsatistfied emand is backordered and ordering decisions are made periodically. The optimal control policy for this system is known to be complex. For this reason we study a type of base-stock policy known as the dual-index policy (DIP) as control mechanism for this inventory system. Under this policy ordering decisions are based on a regular and an emergency inventory position and their corresponding order-up-to-levels. Previous work on this policy assumes deterministic lead times and uses simulation to and their optimal order-up-to levels. We provide an alternate proof for the result that separates the optimization of the DIP in two one-dimensional problems. An insight from this proof allows us to generalize the model to accommodate stochastic regular lead times and provide an approximate evaluation method based on limiting results so that optimization can be done without simulation. An extensive numerical study shows that this approach yields excellent results for deterministic lead times and good results for stochastic lead times

A trade off between emergency repair and inventory investment

In this paper we investigate the effect of using emergency repair on the service performance of a repair shop. Failed parts arrive at the shop according to a Poisson process. If stock on hand of serviceable spare parts is positive, the failed part is exchanged for a spare part and sent into normal repair. If stock on hand is zero, the failed part is sent into an alternative emergency repair channel. The backorder is filled with the first part that becomes available from either one of the repair processes. Both repair processes are assumed to be exponentially distributed. This paper considers the trade off between using emergency repair and investment in spare parts, such that a predetermined service target for the repair shop is realized. Two service measures are considered, that is, the fraction of demand satisfied from stock on hand and the expected duration of a backorder