| With the continuous progress of "One Belt and One Road" construction,China's economy,business and trade with Europe and countries along the routes are getting closer,which generates a large number of logistics demands and brings a rare opportunity for the development of China Railway Express.According to statistics,at present,more than 12,000 China Railway Express trains have been put into operation,and Chinese 59 cities have been operated,reaching 49 cities in 15 European countries,with a total of 920,000 tons of goods delivered.However,it should be noted that at present,China Railway Express are confronted with such problems as unreasonable location layout,long aggregation time,difficulty in organizing cargo,long-distance overlapping of railway lines,high transportation cost and serious congestion at entry-exit railway ports.China Railway Express is a transnational and trans-continental complex system engineering.The reasons for the above problems involve various factors such as policies,facilities and equipment,and transportation organization among countries along the routes.To solve these problems,multiple efforts should be made at the same time.Since 2016,China railway corporation has coordinated the operators of China Railway Express and selected Urumqi as the aggregation center of the western corridor.The "domestic trade train+China Railway Express train" aggregation operation mode has been adopted as the "point-to-point" direct complementary operation mode to try to improve the transportation organization problems of China Railway Express.However,problems such as the connection between the domestic trade train and China Railway Express train and the build-up pressure in Urumqi also followed,and there is still room for optimization in the operation plan of China Railway Express train.In view of the problems existing in the current "point-to-point" direct operation mode and the Urumqi aggregation center aggregation mode,this paper attempts to optimize China Railway Express train service network and the train operation scheme by changing the aggregation mode,so as to improve the aggregation efficiency and reduce the operation cost at the same time.Firstly,this paper expounds the current situation of China Railway Express operation,and summarizes and analyzes the problems existing in the current situation of China Railway Express operation,and puts forward the idea of overall planning and network operation of China Railway Express operation.This paper focuses on the analysis and research of the operation mode of China Railway Express.Based on the current situation and research status of the operation mode of China Railway Express,it puts forward the operation mode of China Railway Express considering hierarchical aggregation.Then,based on the hierarchical aggregation of China Railway Express trains operation mode to build the double-layer space-time network,based on the network,with goods flow balance constraints,traffic flow balance constraints,trains continuation constraints,trains service ability,station ability constraints as constraint rally,with optimal corporate profits as the goal,build up a China Railway Express trains operation scheme optimization model considering hierarchical aggregation.After that,a mixed integer programming algorithm based on Dantzig-Wofle decomposition was designed for solving the model,and the general modeling software GAMS was used to solve the model.Finally,the feasibility and effectiveness of the model and algorithm are verified by a small example,and the operation scheme of large example is given.The innovation of this paper is that the operation mode of China Railway Express based on hierarchical aggregation is put forward,On this basis,a mixed integer programming optimization model integrating cargo flow,vehicle flow and train flow is constructed,and a mixed integer programming algorithm for 0-1 variable structure based on Dantzig-Wofle decomposition principle is designed. |
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