| Adequate emergency supplies stored in advance are essential to cope with the emergencies which is full of uncertainty,such as earthquakes,floods,wars,terrorism,epdimic and so on.This conclusion was verified by the Public Health Emergency named COVID-19.Therefore,in China,many local reserves were and will be built by government for natural or man-made disasters.However,there also exists a serious expiration problem in emergency inventory system.Notably,many emergency inventories,such as water,food and medicine,have expiry dates,like the shelf-life of bottle water is 12-24 months.Here,we call those supplies who have expiry dates as perishable supplies.In fact,$200 million was wasted due to out-of-date in Australia reserve stock;the US Department of Security was reported more than 80%medical materials expired or expiring in its reserve stock;there also about 15 thousand tons'medical materials are expired in China every year.In addition to these substantial wastages,expired or expiring emergency items decline the quality and effectiveness of emergency rescue.Therefore,it is significant to explore mitigation strategies for serious expiration wastages existing in emergency perishable inventory system.As reported by National Public Radio on Febraury 26,2019.Federal Emergency Management Agency(FEMA)sold remaining trailers at auction after the hurricane named Harvey in August of 2017.This report caused much controversies on the sale strategy for remaining emergency supplies.Therefore,the research problems are coming,what should do to mitigate the expiration problem?How to deal with the remaining or expiring emergency supplies?Is it feasible to conduct sale strategy for remaining or expiring emergency supplies?When the sale strategy is prior to other inventory control strategies?What application boundaries are between different management strategies for emergency inventory?This paper aims at studying these research problems,systematically analyzing the theoretic and pratical references on emergency inventory control and management.There are still some challages between researchs and applications,including that it is hard to estimate distribution functions accurately due to the poor database of emergencies,and that local governments in China always have regulations on expropriation of emergency supplies.Thus,on the basis of resolving these challages,this paper designs inventory system under sale strategy,explores inventory control performance of sale strategy,and contrasts sale strategy with other common inventory control strategies,in order to provide proofs for conducting the controversial sale strategy.The major research work includes:(1)An distribution-free inventory model is constructed,to coping with the unkown distributed functions of stochastic variables.This model only requires part of the distribution information,i.e.,means of variables,low-and high-bounds of variables.For most emergency inventory optimization models,researchers always gave an assumption that the stochastic variables have known distributed functions.However,as mentioned above,it is hard to estimate distribution functions accurately,especially in the volatile emergency envvironment due to the poor database of emergencies.This paper derives the worst-case and best-case from all possible scenarios,then makes a decision under Hurwicz criterion.This distribution-free inventory model is robust and stable,providing optimization method and tool for sale strategy and other inventory control strategies.(2)Sale strategies are designed and studied to explore the controversial sale behaviors by FEMA.This paper computes the expected total costs by distribution-free method,consisting of expiration wastage and shortage penalty.Thus,the performance of sale strategy can be measured by expiration reduction and emergency supply capacity enhancement.Sale strategies can be classified into selling to consumers and to retailers,and the differences between these two sale strategies include sale price and market demand.To be specific,?On the consideration of both uncertainties in emergency demand quantity and emergency demand time,this paper introduces consumer's prosocial behavior into the sale process of an emergency inventory,and develops optimization models when sell remaining or expiring emergency supplies to consumers in market.With further steps,we build inventory models under passive acceptance strategy and humanitarian donation strategy,in order to illustrate the superiorities of sale strategy and explore the differences between different management strategies.The objective of optimization model is total economic value consisting of emergency reserve center's cost,retailer's profit,and social welfare.We can infer that the sale strategy to consumer in market is always superior to passive acceptance strategy,but not always superior to donation strategy,and the donation strategy is more beneficial in poor areas.While in wealth areas,compared to hunmanitarian donation strategy,the sale strategy is more suit to those critical materials with high market demand.?Observing the iteractive behavior between emeregency reserve center and retailers,this paper introduces sell-by date and discount price into the sale process from emergency reserve center to retailers,then develops an optimization model for selling expiring emergency supplies.Further,given the relationship of emergency reserve center and retailers,we add the emergency purchase to above sale model,and construct an optimization model for sale-emergency purchase.This kind of sale strategy can achieve both expiration wastage reduction and emergency supply capacity enhancement under cetain conditions.(3)Given the commonality and effectiveness of joint reserve system practically,this paper adopts pratical situation where the government always makes rescue regulations,that is,combining government purchase with government allowance for joint reserve mode,where a material requisition is first implemented to clear the way for rescue,then a settlement is second happened.Thus,we design a joint reserve strategy considering regulations on emergency rescue and study the performance of this management strategy.Two aspects of this part of research are done:?The paper first proposes a joint reserve model with government's allowance,under this proposed allowance cooperation strategy,government compensates retailer for extra operational cost,and the government shares overstocking risk of emergency with retailer through the cooperation relationship.This study finds that the allowance contract can coordinate the joint reserve system,and that the allowance cooperation strategy might be beneficial in increasing emergency supply capacity and decreasing expiration wastages.Therefore,in order to resolve the dispute of sale strategy completely,we compare sale strategy with cooperation strategy,and conclude that the sale strategy also might be superior or inferior to cooperation strategy,which depends on the types of emergency supplies and emergencies.? As studies in above chapter,combing sale strategy and cooperation strategy might be better and more effective than any pure mitigation strategy.Thus,this paper tries to introduce the sale strategy into the joint reserve mode with allowance contract,and develop an optimization model with this mixed mitigation strategy.Since the mixed model is complex,we design an algorithm for the two-level programming problem.Then we give superior of sale strategy under joint reserve mode.Finally,by studying the sale strategy under single and joint reserve modes,we form a logical framework for conducting sale strategies,which will be helpful to identify the motivation and interfering factors of sale strategies.The main contributions of this paper to perishable emergency inventory management can be summarized as:(1)Given much controversies on sale behaviors for remaining or expiring emergency supplies,we design two sale strategies,that is,strategy for sale to consumers and strategy for sale to retailers.By comparing sale strategies to passive acceptance strategy,donation strategy,and allowance cooperation strategy,we explore the superiorities of sale strategies,providing proofs to practical controversies.(2)Introducing the governement's regulations on emergency rescue into the joint reserve system,we propose a joint reserve strategy with allowance contract.This fills the gap between theoretical researches and practical applications of emergency inventory control under joint reserve mode.On the basis of this,we develop mixed strategies by combing sale strategy with cooperation strategy.Then we obtain the application boundaries of these serveral strategies for emergency inventory.(3)Facing to the unknown distributed functions of stochatic variables,the paper adopts distribution-free method,derives the high bound of expected losses and the low bound of expected profits,then makes conservative decisions under Hurwicz criterion.This method is robust,and also avoids "curse of dimensionality". |
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