The overall goal of this dissertation is to develop a better understanding of the supply chain network problems and to make contributions in improving the performance of the network. Specifically, the purpose of this dissertation is to investigate the supply chain design problems for high-tech product manufacturers, as they capture the impacts of scale economies and demand fluctuations on the network.
In view of this, a series of models are constructed in accordance with issues emphasized.
According to the issues of significance, there are five distinct parts in this dissertation, which can be addressed as: integrated plant capacity and production model with economies of scales; incorporating dispatching decisions into supply chain design with production and shipping economies; reliability evaluation and adjustment for supply chain network design with demand fluctuations; and determining optimal delivery service strategies for supply chain network and Internet shopping with time-dependent demand. These five parts can be illustrated as follows.
In the first part of this dissertation, this study aims at investigating how economies of scale, customer demand level and investment conditions in different locations
influence the supply chain network design. This study also investigates how the capacity utilization as well as production amount in a short run and the capacity of multiple plants in the long run relates and those two factors influence the total cost.
Note that the supply chain network design model developed in this part is the base of the dissertation. The models in the other parts are developed and extended from this network design model to tackle and deal with different issues in the supply chain network.
Following the results from the first part, the second part of this dissertation focuses on evaluating the reliability of the network design on the condition that abnormal demand fluctuations occur. To lessen the impacts of the abnormal demand on the manufacturer cost, this study further proposes adjustment procedures as they cope with different abnormal demand fluctuations. The decisions on performing an adjustment or do nothing are also investigated by comparing between the results if no adjustments are made and if adjustment are made during the duration of an abnormal state.
In the third part of this dissertation, this study extends the models developed in the first part to further include the inbound and outbound dispatching decisions with shipping economies in the supply chain. The impacts of different flow values, total material/product amount of flows between two locations as well as their spatial distance on the optimal shipping frequency and size are specially explored.
Then, the forth part of this dissertation turns the emphasis from the strategic level upon the static level. And the network is narrowed down to two echelons, such as manufacturing plants and customers in different locations, to focus on the logistics aspect in the supply chain network. The issue arises from time-dependent demand and wide spread between the manufacturing plants and customers in different locations.
This part of the dissertation aims at investigating the delivery service problems for the
manufacturer by considering time-dependent demand and demand-supply interactions.
In view of this, the demand-supply interaction models, which optimize a delivery service strategy for high-tech product manufacturer, are developed as they cope with time-dependent demand, demand-supply interaction and geographical spreads of plants and customers. Moreover, the impacts of demand-supply interaction on the optimal capacity and production allocation among the manufacturing plants are also investigated.
Furthermore, in the fifth part of the dissertation, this study focuses on the end consumer shopping behavior and employs Internet shopping as the study object. The impacts of consumer characteristics on the optimal delivery service problems are emphasized in this part. Specifically, in addition to the determination of the optimal number and duration of service cycles by exploring demand-supply interaction and time-dependent consumer demand, this part also investigates how variations in consumer socioeconomic, temporal and spatial distributions influence consumer demand and, thereby, profit.
Specifically, the objectives and contributions of this dissertation are addressed, respectively, as follows.
(1) This study constructs a nonlinear MIP model which attempts to minimize the average total cost per unit-product subject to constraints such as satisfying customer demand in various geographic regions, relationship between supply flows and demand flows within the physical configuration and the production limitation of different-size plants. A heuristic solution approach, based on the simulated annealing (SA), is also developed to solve the optimal problem. This study shows how economies of scale can be considered in solving the capacity and production problems. This study also shows the capacity utilization as well as production
allocation among the manufacturing plants in a short run and the size of capacity of multiple plants in a long run are related and those two factors influence the total cost.
(2) This study develops a series models to systematically investigate the supply chain design problems in response to production economies scale and demand fluctuations. A reliability evaluation method is developed in responding different demand fluctuations. The reliability in the study is defined, as the probability that initially proposed capacity of the manufacturing plant will operate effectively under demand fluctuations. This study further formulates supply chain network adjustment models with respect to demand expansion and shrinkage, as they cope with different fluctuant demands combined with various durations where the abnormal events continue. This study shows how the advantage and disadvantage brought by the adjustment can be carefully considered in advance when solving the network adjustment problems. This study also shows how the duration of an abnormal state and the related allocation costs influence the judgment on whether or not performing an adjustment.
(3) This study constructed a MIP model to incorporate the inbound and outbound dispatching decisions into a supply chain network design problem. This study also explores the impacts of different flow values, total amount of flows between two locations as well as their spatial distance on the optimal shipping frequency and size. Moreover, the impacts of the key-component price by suppliers, which are located at different distance to the plants, on the optimal supplier selection are also investigated.
(4) This study explores how to optimize not only decisions on the first part but also the delivery service strategy for the manufacturer in terms of service cycle frequency
and duration for different customers in various regions as well as their corresponding plant assignments in response to time and spatial dependent customer demand. Furthermore, the impacts of demand-supply interaction with on the optimal capacity and production of the manufacturing plants are investigated.
(5) This study develops a mathematical programming model that can determine the optimal number and duration of service cycles for Internet shopping by exploring demand-supply interaction and time-dependent consumer demand. In the demand side, this study formulates a consumer choice probability model for choosing between Internet and conventional shopping modes. Furthermore, this study investigates how consumer demand for goods from Internet stores influences logistics costs for Internet store operators by formulating average logistics cost for both uniform and discriminating service strategies. The optimal service strategy is also obtained by comparing profit between using discriminating and uniform service strategies.