Research On Several Types Of Inventory Optimization Problems With Demand And Supply Fluctuation

Inventory management is an important branch of operations research,which mainly applies optimization method to control the production and the order quantity so that inventory cost is minimized.Certainly,this is a very significant issue in production practice.In modern competitive market,the rapid development of the manufacturing,online retailing and global supply chain makes the replacement cycle of product shorter and shorter,and makes the market demand to fluctuate frequently.Facing the fluctuating market demand,on one hand,enterprises need to make a tradeoff between meeting market demand and reducing inventory cost.On the other hand,in order to increase the market share,enterprises may choose to launch new products and pre-sell them at a lower price in the pre-production stage.At the same time,the supply chain is also vulnerable to man-made or natural disasters,which forces enterprises to make an emergency order to reduce the loss caused by supply disruption.In order to provide reasonable order strategies under various complicated business environments such as market demand fluctuation and supply chain interruption,based on the classical economic order quantity model and newsvendor model,this paper considers three inventory optimization models with market demand fluctuation,pre-selling and supply chain disruption.In the thesis,we first consider the extended economic order quantity model with market step-shaped demand.In this model,the planning horizon of inventory system is infinite and consists of two stages,the market demand rate in each stage is stable but differs.To minimize inventory cost,the retailer needs to determine the order quantity and order times in the first stage.Based on this,we establish an inventory model which is a mixed integer optimization problem.Using the alternating minimization method and the classical optimization theory,we develop a closed-form solution to the optimal inventory model and provide an optimal replenishment strategy to the retailer.Second,we consider the inventory model with pre-selling mechanism.In this model,the planning horizon of concerned inventory consists two stages:preselling period and sclling period.In the pre-selling period,the manufacturer offers pre-selling product to the retailer at a lower price.Further,the wholesale price increases with the time.In order to minimize the inventory cost,the retailer needs to determine the optimal pre-ordering time and pre-ordering quantity.However,since the demand is random,there is a certain risk of loss for any pre-ordering strategy of the retailer.Obviously,the retailer’s risk preference will affect his replenishment decision.Based on this,by minimizing the legacy loss via CVaR measure in risk management,we establish a loss-averse pre-ordering decision model.By model analysis,we establish a closed form solution to the model and provide the optimal pre-ordering time and pre-ordering quantity to the retailer.Finally,we consider the emergency procurement model with supply chain disruption.In this model,we assume that the demand is stable and the happening time of the supply disruption is random and the ending time of the event is deterministic.For this inventory model,to minimize the inventory cost,the retailer needs to make an emergency procurement.However,if the emergency order is placed too early,then the retailcr should bear more inventory cost,and if it is made too late,then he may lose the chance to place an emergency order.Thus,the retailer should determine the optimal order time and order quantity of emergency procurement according to the time when supply chain disruption may occur and the market demand generated during supply chain disruption.Based on minimizing the inventory cost and under two possible procurement strategies,we establish an emergency procurement optimization model.By considering the model solution in all cases,we establish a closed-form solution to the optimization model and provide an optimal emergency procurement policy to the retailer.Some numerical experiments are made to test the validity of the model and the effect of the involved parameters on the emergency procurement strategy.The results obtained in this thesis can not only provide reasonable replenishment suggestions ro enterprises under complicated business environment,but also enrich the inventory theory.