Research On Location-Routing Problem For Three-echelon Logistics Network Of Urban-Rural With Simultaneous Pickup And Delivery

In 2019,the Ministry of Transportation proposed to speed up the construction of three-echelon logistics network outlets including the county,township,and village levels.In February 2021,the Ministry of Commerce proposed to achieve the goal of express delivery from village to village by 2025.Many government policies show that the state attaches great importance to the construction of rural circulation and logistics systems.However,the current rural-level logistics network node coverage in China is low.At the same time,due to the lack of overall planning,Rural nodes in the logistics network are not smoothly connected to the city,county,and town levels.The nodes were constructed slowly and repeated,which caused the waste of resources.Therefore,it is of great significance to conduct urban and rural logistics network research at this time.This paper summarizes the characteristics of urban and rural logistics development in China,and the information shows that the urban and rural logistics are in a stage of rapid growth in demand.However,due to rural industries and backward economic development,urban and rural logistics have many problems,including low density,high costs,low profit margins,and low speed network construction.Based on the above issues,this article summarizes the six organizational models of urban and rural logistics,the network elements and composition.According to the urban and rural logistics business process,the article considers the practical application scenarios of simultaneous pickup and delivery,and proposes to establish a two-way urban and rural three-echelon logistics network to meet the logistics needs of the rural market.The urban and rural logistics network proposed in this paper includes a three-level network and a four-level node.A two-tier planning model is established for the network to plan the logistics network.The model is divided into two layers.The upper-level decision-making model conducts a combined optimization study on the location-path arrangement of the logistics network between the first layer(regional nodes),the second layer(county-level nodes),and the third layer(township-level nodes).The author establishes a mixed-integer nonlinear programming model for the upper-level decisionmaking,designs the algorithm,and uses software to simulate and solve it.The lower-level model considers simultaneous delivery and soft time window constraints for the threetier(township)and fourth-tier(rural nodes)to conduct distribution route optimization research,and designs an adaptive genetic algorithm to solve it.Finally,the paper takes Luqu County in Gansu Province as an example to study the express logistics of Luqu County.The calculation example considers the collection demand of taking delivery at the same time,and solves the two-level programming model through MATLAB and Lingo.Finally,the county’s urban and rural three-tier logistics network layout and vehicle distribution route plan are obtained.All the data and charts in the case solution result show that the model and algorithm are reliable.NO.of pictures : 26,NO.of forms : 16,NO.of references : 75.