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UBC Theses and Dissertations

Three essays in supply chain management Sosic, Greys

Abstract

The three essays in this thesis address various problems in the general area of supply chain management. In general, supply chain management is concerned with management of the flow of goods, information, and funds among supply chain members, such as suppliers, manufacturers, distributors, retailers, and consumers. As such, its scope includes timing and quantity of material flow, logistics, improving efficiencies in problems with several decision makers, etc. The first essay in this thesis considers the problem of improving coordination in a decentralized system of retailers, while the second one addresses stability and profitability of Internet-based supply exchange alliances. The third essay analyzes a logistics problem, of finding an optimal route for a capacitated vehicle which travels on a graph and which can perform pickups and deliveries. In the first essay, we study a three-stage model of a decentralized distribution system with n retailers who each faces a stochastic demand for an identical product. In the first stage, before the demand is realized, each retailer independently orders her initial inventory. In the second stage, after the realization of the demand, each retailer decides what portion of her residual supply/demand she wants to share with the other retailers. In the third stage, residual inventories are transshipped in order to possibly meet residual demands, and an additional profit is allocated among the retailers. We study the effect of implementing various allocations rules in the third stage on the levels of the residual supply/demand the retailers are willing to share with others in the second stage, and the tradeoff involved in achieving a solution which is also optimal for the corresponding centralized system. The second essay is concerned with the formation of Internet-based supply exchange alliances among three or fewer retailers of possibly substitutable products. We provide some conditions, in terms of product substitutability and quality of suppliers, which would lead to the formation of a three member alliance, or a two member alliance, or no alliance at all. We also study the effect of alliance structure and quality of suppliers on the profit of a retailer. The third essay considers a vehicle routing problem with pickups and deliveries (VRPD problem) on some special graphs. Some vertices on the graph represent delivery customers, and other vertices represent pickup customers. The objective is to find a minimum length tour for a capacitated vehicle, which starts at a depot and travels on the graph while satisfying all the requests by the customers without violating the vehicle capacity constraint, and returns to a depot. We have developed linear time algorithms for the VRPD problem on a path and on tree graphs, linear and O (|V| log |V|) algorithm for a VRPD problem defined on a path with parametric initial capacity, and quadratic and O (|V|² log |V|) algorithms for a VRPD problem defined over a cycle graph.

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