This thesis considers an integrated (1:1:N) remanufacturer-warehouse-retailers inventory system under supply chain environment for a remanufacturable item following a Poisson process of returning from its usage where disposal at the remanufacturing facility is allowed, and customers demand for serviceable units arrives at the retailer level only. Demands at the retailers and returns at the remanufacturing facility arrive in independent stationary Poisson processes. It is assumed that return rate is less than demand rate so that procurement is required at certain times from outside supplier. Returned units are either remanufactured or disposed directly, which is decided based on with only the number of returned units at the remanufacturable inventory storage. For the system, continuous review inventory models are considered, including the (s, Q) ordering policy at the warehouse and the base-stock (S-1, S) policy at each retailer. Moreover, the procurement leadtime is assumed to be constant and any unsatisfied demands at the retailers are considered as backordered.
The objective of the integrated model is to find an optimal inventory policy that minimizes the total expected average cost of the whole system where the purchasing cost from the outside procurement, the inventory holding cost at the warehouse and all the retailers, the backorder cost at all the retailers, the disposal cost, and the remanufacturing cost are incorporated. This model is applied to leased/ rented product management as being often found in telephone, computer, projector and copying machine industries.
In the problem analysis, Markov Chain theory and Queueing theory are applied to derive the mathematical formulation of the associated objective for which some approximations are made to derive the probability distributions concerned with backorder (for the warehouse and retailers). This formulation is then used to determine the associated best inventory decisions, for which an iterative heuristic solution search procedure is derived. Numerical experiments are made to investigate the parameter associated sensitivities.
재사용이란 소비자의 사용을 거친 제품에 약간의 수리(재처리)를 한 후 다시 사용하는 것을 말한다. 재사용이란 개념은 예전부터 있어왔지만, 근래에는 경제적, 환경적 이유로 인해 사회적 관심과 요구가 증대되고 있다. 대부분의 경우 재사용이 경제적이긴 하지만, 소비자의 사용을 거친 모든 제품을 재사용하는 것은 경제적이지 못하다.
본 논문에서는 재처리와 폐기가 허용되는 (1:1:N) 재처리공장-도매상-소매상 모형에서 SC전체의 비용을 최소화 하는 최적 수준의 재고 정책을 결정하는 알고리즘을 제안하였다. 소매상과 폐기를 고려하지 않은 간단한 모형에서 시작하여 소매상을 고려한 전체 SC 모형 그리고 폐기까지 고려한 모형으로 점차 확장해 나가는 방식을 통해 모형을 완성하였다. 여러 시스템 변수들을 변화시키면서 관련 비용함수와 결정변수들의 경향을 분석하였다.
