Research On The Evolution Of Urban Logistics Network Structure Based On Complex Network Theory

As the urban economy enters the stage of high-quality development,enterprises change the development mode and continuously enhance cooperation.As a basic and service industry closely related to manufacturing and other industries,urban logistics can promote the transformation of urban industrial structure and strengthen the supply side structural reform.At the same time,it can improve urban competitiveness,promote regional coordinated development and reduce the total social cost.The study of urban logistics is of great significance to promote urban economic development,and the study of urban logistics network structure is one of the most basic studies of urban logistics.By reading the relevant literature,it is found that there is still a lack of structural research on urban logistics from a meso perspective.Therefore,this paper regards the urban logistics network as a complex system,and makes a comprehensive and systematic study on the model construction,complex characteristics,evolution process,evolution law and evolution stage of the urban logistics network structure from the perspective of systematics and complex network theory.Based on the preferential attachment and connection direction of logistics nodes,this paper establishes a directedweighted network structure model of urban logistics with practical significance,analyzes the complex characteristics of Yangtze River Delta urban logistics network structure,and further studies the evolution of urban logistics network structure in time and space.The main research work and contents of this paper are as follows:(1)Construction and visualization of urban logistics directed-weighted network structure model.According to the impact of urban economy on urban logistics activities through logistics supply and logistics demand,it is considered that the logistics nodes follow the preferential attachment when selecting the nodes connected to them,give priority to the nodes with stronger logistics capacity,and the impact of logistics nodes on other nodes is different from the impact of other nodes on logistics nodes themselves,so the weight and direction of connection should be considered.Based on this assumption,the gravity model is improved,the logistics connection index between nodes is constructed,and it is introduced into the urban logistics network structure model.Taking the Yangtze River Delta as an example,27 prefecture level cities are abstracted into logistics nodes,and the directed connection between nodes is abstracted into logistics lines.Taking the logistics connection value between nodes,that is,the logistics gravity value,as the weight of the connection,the Yangtze River Delta urban logistics directed-weighted network structure model is established and visualized.(2)Analysis on the complex characteristics of urban logistics network structure.Using the complex network theory,this paper analyzes the Yangtze River Delta urban logistics network structure from three angles: node degree and degree distribution,clustering coefficient and average path length,describes the complex characteristics of the evolution of the Yangtze River Delta urban logistics network structure to the present stage.It is found that the Yangtze River Delta urban logistics network is a scale-free network,and its structure presents clustering characteristics and hierarchical characteristics;The connection between nodes in the network is relatively close.Most nodes are in a stable network structure and are not vulnerable to the impact of sudden connection interruption in the network.Few nodes are bridge nodes in the network.When they are in the case of attack or other risks,the whole network is prone to paralysis;The distance between nodes in the network is small,the network has fast logistics response ability,short logistics service time and small world characteristics.(3)Construction and law analysis of urban logistics network structure spatio-temporal evolution model.Based on regional economics and complex network theory,this paper respectively constructs the urban logistics network structure time series evolution model and the urban logistics network structure local world evolution model,and takes the Yangtze River Delta as an example for empirical analysis and numerical simulation.Through the results of the empirical research,it can be seen that the Yangtze River Delta urban logistics network structure has experienced an evolutionary process from agglomeration to dispersion and then to agglomeration from 2011 to 2020,but it shows a diffusion trend on the whole;In the numerical simulation of the evolution of the initial logistics network evolving into the final logistics topology network,different weight values of connection between the internal local world and the external local world are introduced.The results show that the model well reflects the powerlaw characteristics of the real network.The urban logistics network evolves into a scale-free network with a hierarchical structure.If the logistics nodes are selected as the connection points inside and outside the local world,they will develop into new hub nodes of the urban logistics network.(4)Identification and suggestions on the evolution stage of urban logistics network structure.Based on the evolution law of urban logistics network structure and the actual evolutionary process of the Yangtze River Delta urban logistics network structure,this paper analyzes and puts forward four stages of urban logistics network structure evolution: low-level equilibrium,polarization agglomeration development,radiation expansion development and high-level equilibrium.According to the evolution stage of urban logistics network structure and the previous research results,it is identified that the evolution of the Yangtze River Delta urban logistics network structure is in the radiation expansion development stage,In this stage,the circular process of logistics agglomeration and logistics diffusion occurs alternately.Then it puts forward the development suggestions of the Yangtze River Delta urban logistics network from three aspects: improve the connectivity of urban agglomeration,ensure the economic benefits of logistics industry and create a policy environment for urban logistics development.