Reversed inventory models and reversed newsvendor models for collecting and dispatching

Abstract

Over the last decade, many previous researches have been conducted on inventory models and control policies. Recently, we have new types of logistics systems for collecting and dispatching materials, entities, energy, and etc. Such CD (Collecting and Dispatching) systems have been discovered in a variety of fields: carbon capture and storage, shale gas production, energy harvesting for wind and solar power, and product recycling. Collected entities arrive along time and are accumulated in storages, released or shipped out by a control policy. They are often dispatched in batch to reduce associated cost and maximize revenue. However, as soon as a dispatch request is made, it could be difficult to become a immediate dispatch by delays due to setup or vehicle travel. The storage itself may undergo overflow or underflow with some incurred costs. The stored entities also induce some holding costs in a storage and operating costs. Therefore, we need to determine when a dispatch should be requested and how much entities should be dispatched. A CD model can be viewed as a reversed model of a conventional inventory control model. In chapter 2, we define and examine the CD systems as the reversed inventory models for collecting and dispatching entities and suggest optimal control policies. We first give some examples of their operations such as the carbon capture and storage (CCS) system, the shale gas production, and recycling to explain the CD systems. Next, we classify the related works into conventional inventory models, dam/reservoir process and reverse logistics, and then reveal their similarities and differences. To compare with reversed inventory models and conventional inventory ones , we propose EDQ/ETQ deterministic reversed inventory model and identify analogies, differences, and relevance with EOQ/EPQ inventory model. We then explain operation of reversed inventory models and control policies. Finally, we extend the dispatch policies for the reversed inventory with overflow allowed. We also compare the characteristics of each reversed inventory model with those of its conventional one’s counterpart. In chapter 3 and 4, we propose stochastic reversed inventory models with (d, Q) and (d, S) policies comparing with (r, Q) and (s, S) policies of the inventory model as a new type of logistics systems for the CD systems, and subsequently determine the dispatch point and the dispatching quantities. In chapter 5, we introduce a new type of newsvendor problem regarding accumulating, dispatching or releasing and shipping out entities in storage by a control policy. We call it reversed newsvendor problem. Collected entities are dispatched by the contracted capacity and it occurs underflow and overflow in the course of dispatch. We define and examine the single period CD systems as reversed cases of the newsvendor model, and also discuss similarities and differences. Controlling issues of the excess amount of inflow happen during the overflow period. And thus, we suggest the overflow control policies

supplementary dispatch and carryover. According to the study, we find a new type of logistics systems and evaluate the similarities and differences between the reversed inventory model and conventional one.