공급사슬관리에서 생산입지선정 문제와 안전재고 최적화 문제의 통합모형 개발에 관한 연구

Given a bill of materials (BOM) tree T labeled by the breadth first search (BFS) order from node 0 to node n and a general network = (V,A) , where V = {1,2,…,m} is the set of production facilities and A is the set of arcs representing transportation links between any of two facilities, we assume that each node of T stands for not only a component, but also a production stage which is a possible stocking point and operates under a periodic review base-stock policy. We also assume that the random demand which can be achieved by a suitable service level only occurs at the root node 0 of T and has a normal distribution N(μ,σ²). Then our integrated model of facility location problems and safety stock optimization problem (FLP&SSOP) is to identify both the facility locations at which partitioned subtrees of T are produced and the optimal assignment of safety stocks so that the sum of production cost, inventory holding cost, and transportation cost is minimized while meeting the pre-specified service level for the final product. In this paper, we first formulate (FLP&SSOP) as a nonlinear integer programming model and show that it can be reformulated as a 0-1 linear integer programming model with an exponential number of decision variables. We then show that the linear programming relaxation of the reformulated model has an integrality property which guarantees that it can be optimally solved by a column generation method.