Research On Inventory Control And Supply Chain Coordination Models With Inventory-Level-Dependent Demand

With the globalization of the market economy, the competition is not only among enterprises, but among supply chains more and more. To achieve a global performance optimization and serve the market better, various entities and functional units in a supply chain should be coordinated in a tight activity pattern. Inventory control is an important tache in the supply chain management, since the inventory cost of items is of much more proportion in the total cost of supply chain, as a result the whole operational efficiency and the competitive edge of a supply chain are affected by the inventory control to a great extent. Therefore, studying the theory and methods of inventory control and supply chain coordination has important practical value and theory meaning for reducing the total cost of chain.In this paper, inventory control and supply chain coordination are proposed as the research objects, and the related research achievements are summarized and extended. This paper focus on stock-dependent demand and trade credit, and study the problems of inventory control and supply chain coordination from different aspects, such as different demand functions(linear and power), different items(normal items, instantaneous deteriorating items and non-instantaneous deteriorating items), different shortage forms(shortage is not permitted, shortage is fully backlogged and shortage is partially backlogged), different payment ways(traditional trade credit policy and two levels of trade credit policy), different information conditions(symmetric information and private information), different supply chain structure(single manufacturer and single retailer, two different manufacturers and a retailer). The details are given as follows.1. The extensive research for inventory control models with stock-dependent demand. Based on the EOQ model for deteriorating items under linear stock-dependent selling rate, this paper develops a more general inventory model with partial backlogging, where the backlogged demand rate is time dependent, and the necessary condition for the existence of optimal solution to the general model is derived. This paper also develops a deterministic inventory model for perishable items with stock-dependent selling rate and capacity constraint, where the unsatisfied demand is partial backlogged and the backlogged demand rate is dependent on the negative inventory level during the stock out period, and the existence and uniqueness of the solution to the problem under two cases are examined, respectively. By considering two possibilities of holding cost variation: (a) a non-linear function of the length of time the item and (b) a non-linear function of the amount of on-hand inventory, two economic lot-size models for deteriorating items with stock-dependent demand have been developed in which shortages are allowed to occur and backlogged completely. In this paper, we further develop a more general inventory model for non-instantaneous deteriorating items with stock-dependent selling rate. Unlike the related models for the inventory system, the present model assumes that the shortage is permitted and the unsatisfied demand is partially backlogged at a negative exponential rate with the waiting time and solution procedures are shown to find the optimal replenishment policy of the considered problem. This paper also studies an inventory model where the demand is a power function of current stock level, more importantly the existence and uniqueness of the solution to the problem are provided.2. This paper analyzes the impact of time value of money and trade credit policy on optimal order or production policy. Firstly, some lot-sizing problems with stock-dependent demand and shortage under the condition of inflation have been discussed, and four simulation models with various inventory replenishment policies have been compared. This makes the traditional inventory model be able to used under the economic environment of inflation. Secondly, a new two-warehouse inventory model for deteriorating items with permissible delay in payments is developed, and we provided theoretical analysis of the optimal solutions to the considered problem and a simple method is given for finding the optimal order policy. This dissertation firstly develops an EOQ model for deteriorating items under permissible delay in payments, where the demand rate of the items is dependent on the current stock level, and the inventory system with inventory-level-dependent demand rate is further extended. This paper also develops a lot-sizing model for deteriorating items with a current-stock-dependent demand and two-level trade credit policy, and some theorems are shown to find the optimal ordering policies of the considered problem. An inventory model for exponentially deteriorating items under conditions of permissible delay in payments has been built in this dissertation. Unlike the existing related models, we assume that the units are replenished at a finite rate and the demand rate of the items is dependent on the current inventory level and a simple theorem is shown for finding the optimal solution of the model based on the derived properties of the objective function. In addition, we deduce some previously published results as the special cases of the model.3. In this dissertation, the coordination issues of supply chain with stock-dependent demand have been discussed. Firstly, under common information, this paper studies a supply chain model with a manufacturer and a retailer, where the demand is a linear function of retailer's current stock level and permissible delay in payments is adopted as the coordination method. Secondly, the dissertation further discuss the case of coordination issue in which the demand is a power function of stock level and present two coordination scenarios-quantity discount and profit sharing. Thirdly, this paper contributes by analyzing how two parties behave under three scenarios if they individually have private cost information. Lastly, the dissertation studies the coordinated problem of the two-echelon supply chain that consist of a dominating retailer and two different manufacturers, where the demands rate of items are supposed as shelf-space dependent. The extensive research results presented above not only enrich the content of inventory control and supply chain coordination theory but also further accelerate the applied areas of these inventory control and supply chain coordination models, and provide more sufficient scientific evidence for decision makers making decision.