Optimization Methods Of Production Planning And Transportation Scheduling In Closed-loop Supply Chains

Nowadays the attention of more and more governments is switching from the speed of economic growth to the sustainability of the economy. An economic system that cannot sustain its development in the long run would gradually lose its competitiveness in the future global market. It is essential and that the government should help move its domestic economy into a more sustainable direction. Accordingly governments have been proposing all kinds of bills and laws. In the meanwhile, enterprises are feeling the pressure from local governments on one hand and realizing the potential economic gain; hence they are investing more and more capital in related labor, equipment and technology. As a response to this situation, the industry and academia proposed the concept of closed loop supply chains (CLSC). Besides the traditional functions of a supply chain CLSC also includes a network of recycling, inspect, remanufacturing or disposal, etc. CLSC reorganizes the traditional supply chain and provides a system where material can flow in a circle network. CLSC makes it possible to manage the material throughout it whole life cycle and reduce the negative effects the supply chain activities while serving the customers at a low price. Therefore, CLSC not only provide the service the traditional supply chain provide, but also plays a great role in achieving sustainability in economy. With more and more applications of CLCS concepts in practice, CLSC is becoming a new direction of supply chain management.This dissertation summarizes and analyzes the characteristics of return flows in the iron and steel industry, and investigates the actual situation of steel production process in several large iron and steel companies, and then focuses on the research on recovery strategies and optimization methods for reverse logistics system in the iron and steel industry. It is a constituent part of’985 project:Scientific and technological innovation of Integrated Automation of Process Industry platform research project’,’Liaoning provincial division of sciences and technology planning project’and’National Natural Science Funds for Distinguished Young Scholar project’It is worth pointing out that although this dissertation is motivated by iron industry, the work can apply to other CLSC in other industries with little or no changes. Hence throughout the dissertation the author does not specify the scenarios of the research paper unless it is necessary.With the methodology of system engineering, it studies the production planning, transportation scheduling and integrated production transportation management problems in a CLSC environment. The major results include:(1) This dissertation studies the capacitated dynamic lot sizing problem with remanufacturing (Chapter 3). It analyzes the methods of return processing under current technology restrains and how the choice of return processing can affect production planning. This dissertation provides a typical system as a benchmark, and formulates a general mathematical model. After a detailed analysis of the structure of the benchmark problem it proposes a dynamic programming algorithm. Then this dissertation studies several special cases of the benchmark problem, identifies some useful properties that greatly simplify the solution algorithms.(2) This dissertation studies capacitated dynamic lot sizing problem with as good as new returns (Chapter 4). Likewise the dissertation provides a benchmark model and provides pseudo-polynomial algorithms. It also shows that in some special cases, more effective algorithms are available.(3) This dissertation studies the efforts of recycling products on transportation scheduling (Chapter 5). It firstly generalizes the problem and then proposes the weighted vehicle routing problem. The weighted vehicle routing problem is formulated as mixed integer programming problem. Due to the complexity of the problem, a genetic algorithm is developed to solve the problem. Numerical experiments show the efficiency and effectiveness of the proposed genetic algorithm.(4) This dissertation studies the timing of collection of recycled products on transportation scheduling (Chapter 6). It applies the fuzzy theory to analyze the problem and brings up the idea of service level in this problem. In order to model the service level issues, the paper propose the concept of fuzzy time windows. With the concept of fuzzy time windows the dissertation proposes vehicle routing problem with fuzzy time widows. A multi-objective program is formulated to take into consideration of both cost and service. Based on the structure of the problem, a two-stage heuristic is developed to get a Pareto solution.(5) This dissertation studies the integrated production planning and transportation problem in the context of closed-loop supply chain (Chapter 7). Based on the mathematical structure and the complexity of the problem, this dissertation proposes the idea of hierarchical tree to classify and group the collection points and solve the problem using a heuristic algorithm.