A Continuous Review Model for an Inventory System with Two Supply Modes
针对两种补货模式（一种提前期更短）的库存系统，提出一个近似模型，扩展标准(Q,R)策略为双批量双再订货点，给出参数求解方法，并通过仿真验证成本优势。
In this paper we develop an approximate model of an inventory control system in which there exist two options for resupply, with one having a shorter lead time. Because the optimal policy appears to be extremely complex, we consider a reasonable extension of the standard (Q, R) policy to allow for two different lot sizes Q 1 and Q 2 , and two different reorder levels, R 1 and R 2 . Expressions for the expected on hand inventory and the expected backorders are developed and a procedure for determining the policy parameters is given. The model is validated by simulation, and calculations are included which compare the average annual cost with and without emergency ordering.