EPQ Model with Different Lost Sale Factor Relative to Inventory Level

It is important for enterprises' inventory management to find out the optimal production cycle and the length of shortage time,so that the total cost of inventory system can be reduced and the service level can be raised.Based on the classical EPQ model,this paper develops an EPQ model for deterioration items with different lost sale factor relative to the inventory level during shortage period.The existence of unique optimal solution is discussed by mathematic analysis and a numeric example.The sensitivity analysis shows that the parameter of losing sale has different impact on the costs of inventory system.The factors must be considered for the production inventory system to make management decision.     

EPQ Model with Exponential Time-varying Demand and Different Productivities

Based on the former EPQ models with partial backlogging, this paper develops an EPQ model with exponential time-varying demand and different productivities. The existence of unique optimal solution is discussed by Mathematica 5.0. A numerical example and sensitivity analysis show that the impact of backlogging parameter on all the costs is greater than that of demand increasing factor and productivity during shortage period, and the impact of backlogging parameter on holding cost, shortage cost and opportunity cost due to lost sale is greater than that on setup cost and total cost.