Research On The Optimizing For The Logistics System Design And Operations

The development of current global economic integration has led to the rapid progress of the logistics industry, and the modern logistics industry has become an important support of the economic development of countries in the world. The modern logistics industry has been established as one of the mainstay industries in China, and the logistics industry adjustment and revitalization plan has been proposed. In recent years, how to introduce the concept of modern logistics so as to accelerate the modernization of China’s logistics industry has become a research focus in both academic and industry community.The elements of modern logistics can be divided into the hardware facilities related to logistics and the software platform related to management. Based on the concept of modern logistics and the systematic view, this dissertation takes the two elements as the background and studies relative problems of logistics systems in different levels from the macroscopic to the microscopic point of view. These problems include the modern logistics chain planning, the logistics park location, the container yard layout, and the logistics optimization of the whole process in iron and steel enterprises. The details of the research in this dissertation can be summarized as follows:1) For the regional logistics system, this dissertation studies the modern logistics chain planning problem. Based on the economic development status and characteristics of a typical resource-based city, the development environment, the basic conditions, the existing problems and the opportunities for the modern logistics industry in this region are firstly surveyed and analyzed. Then the development needs are classified and predicted accordingly. Based on the concept of modern logistics and the integrated optimization of regional logistics system, the development direction of modern logistics industry chain, the layout plan, and the supporting information construction scheme are proposed.2) For the hardware facilities related to regional logistics system, this dissertation takes the layout planning in the modern logistics industry chain planning as the background and investigates the modeling method for a kind of location problem of logistics parks. In this region, there are a number of candidate locations that can be used to establish logistics parks, and each candidate location consists of several plots. Since the size of each plot may be different, the acquisition costs are thus different between different plots. This problem is to determine the number, locations, and scales of logistics parks to be established, and the allocation of customers so as to minimize the total costs of setup and service. The difficulties of this problem are the selection of plots and the determination of the number of established logistics parks, as well as their capacities. Based on the characteristics of the problem, the size modes are introduced. All the available size modes of each candidate can be determined by means of analyzing the actual geographic distribution of this candidate location. Based on the concept of size modes, this problem is formulated as an integer linear programming (ILP) model.3) To efficiently solve the above ILP model, a tabu search method hybrid with filter-and-fan is developed. To evaluate the performance of the proposed hybrid algorithm, an improved column generation method with acceleration strategy is developed to provide the lower bounds. The computational results on a set of practical simulation data show that the improved column generation method can provide good quality lower bounds for the testing problems, and that the average gap of solutions obtained by the hybrid tabu search method is within5%, which illustrates that the proposed hybrid tabu search method can obtain satisfactory results for the problem.4) For the node logistics system, this dissertation studies a kind of container yard layout problem. This problem takes the logistics development plan of a well-known terminal as the back ground, and the task is to optimize the design of the stockpiling areas of the new terminal container yard. The cranes have restrictions on the width of the stockpiling area, and the length and layout of the stockpiling areas and berths also have important impact on the driving length of trucks. Making use of the bay, the length of the stockpiling area is discretized. An integer programming model is proposed for this problem, whose objective is to maximize the efficiency of trucks and the number of slots. In this model, there is also a lower bound on the minimum number of slots. Based on the characteristics of this model, a Filter-and-Fan algorithm is developed to solve this problem.5) For the enterprise logistics system, this dissertation starts from the logistics operation and investigates a kind of whole process logistics optimization problem. Taking the production process of an iron and steel enterprise as background, this dissertation firstly analyzed the characteristics of the steelmaking, the continuous casting, the hot rolling, the cold rolling, and the work-in-process inventory. And then based on the integrated optimization view, this problem is formulated as a mixed integer programming model, in which the material flow and directions between successive processes and the work-in-process inventory should be determined so as to minimize the whole logistics cost. To solve this model, a branch-and-price algorithm based on column generation is proposed.