Optimization On Express Transportation Network And Vehicle Loading And Routing Plan

With the rapid development of economy in our country, how to optimize the express transportation system has become an important problem restricting the progress of express enterprises. The optimization mainly involves two aspects, one is the structure optimization of the express system, such as the selection optimization of distribution center location, and the structure optimization of the transportation network, etc.; the other is the management optimization of express operation, especially the typical vehicle filling problem and vehicle routing problem.The main work in this dissertation about the above problems is as follows:(1) A basic model of regional transportation network of international express is built. Then, based on the feature of the time threshold in express delivery industry and the freight transport discount factor of link and extension, a mixed integer programming model of regional express network optimization is established, an solver algorithm based on LINGO is designed. The analysis for example reveals the eternal contradiction between time and cost in express delivery industry, which could help to quantify the generalized cost of express delivery industry, and thus provide decision support for regional express network optimization.(2) A super network model for express transportation network is put forward, and two methods of optimization based on the cost and the efficiency of multiple transportation modes and the multiple objectives are proposed. A numerical experimental example shows the optimal relationship between transportation modes and express efficiency and cost in ETN.(3) By means of introducing the residual space and its correlative operations, an integrated optimized mixed integer programming model on both vehicle filling problem (VFP) and vehicle routing problem (VRP) for van truck transportation, based on residual space, is proposed. Then, a new interactive algorithm, suitable for the above model, is designed. The simulation experiments demonstrate that the total objective function of the integrated optimization increases by comparing with two kinds of separate sub-problem optimization instances, which preferentially consider VRP and VFP. (4) With the consideration of vehicle loading constraints, such as cargo destructibleness, loading stability, unwarrantable upside down, vehicle balance, and last-in-first-ou unloading rule, an integrated optimized mixed integer programming model is proposed. Then, a hybrid interactive algorithm, consisting of a series of heuristic loading rules for VFP and an ant colony optimization algorithm based on the C-W saving heuristic rule for VRP, has been developed suitable for the above model. The simulation experiments, from the benchmark problems, are conducted, and the results with comparison to those in the current literatures demonstrate the effectiveness and practicality of both the model and algorithm.