| The novel coronavirus first broke out in Wuhan,Hubei province,at the end of 2019 and has since spread to other parts of China.It has now become a major global epidemic.Unlike other single disasters,infectious diseases are characterized by multiple points,frequent occurrence and extensive coverage.The quantity of emergency relief supplies is no longer a problem at present.However,after the outbreak of a large number of severe epidemics,there are problems in the delivery and distribution of emergency supplies in some areas,which is largely related to the obstruction caused by road traffic control.This paper takes 41 cities in the Yangtze River Delta as the research object.Considering the impact of road traffic control on logistics activities after the outbreak of a large area of severe epidemics,this paper will build a whole-area emergency logistics network based on the hub-and-spoke theory.For the Yangtze River Delta,an area with a large population,under the guidance of the integrated development policy,administrative barriers should be broken to minimize traffic obstacles and maximize the efficiency of emergency supplies transportation for the pre-disaster whole-area emergency logistics system construction.Therefore,based on the transport network under specific conditions,this paper first uses the complex network module degree optimization algorithm to divide the logistics circle closely connected with the road network as a whole.Then,by constructing the evaluation index system of comprehensive emergency logistics capability under the epidemic situation,the improved TOPSIS method based on weighted generalized Mahalanobis distance was used to evaluate the comprehensive emergency logistics capability of each node city.Secondly,the modified gravity model and social network analysis are used to analyze the internal structure of each logistics circle network.Finally,based on the internal and external index data such as the structural characteristics of each node city in the network,the comprehensive capacity of emergency logistics,the shortest transportation distance,and the results of cluster analysis,the first and second tier axis cities are selected.The radiation range of axis cities is divided based on the logistics membership model,so as to build the hub-and-spoke emergency logistics network.Finally,based on the research results and the current situation of emergency logistics in the post-epidemic period,countermeasures and suggestions were put forward for the improvement of the capacity of trunk lines,branch lines and the overall emergency logistics in the Yangtze River Delta region.The research results obtained in this paper are as follows: First,fully considering the impact of road control on logistics activities under the epidemic situation,the complex network community discovery algorithm is used to divide four logistics circles with high accessibility by establishing a transport network under specific conditions,and each logistics circle contains7-12 cities,as a whole.Secondly,the improved TOPSIS method based on weighted generalized Mahalanobis distance is used to more accurately obtain the comprehensive emergency logistics capacity of each node city,which provides data support for the following emergency logistics network construction.Thirdly,based on the modified gravity model,the strength of logistics gravity between node cities is calculated,and the network centrality,core-edge structure,condensation subgroup and core-edge structure of each logistics circle are analyzed with the help of social network analysis method,which provides data support for the selection of axis and axis point cities below.Fourthly,based on the structural characteristics of each node city in the network,the comprehensive capacity of emergency logistics,the shortest transportation distance and other index data obtained from the above research,the hub and spoke emergency logistics network in the Yangtze River Delta is constructed by combining the cluster analysis and logistics membership model.Among them,Hangzhou,Wuxi,Wuhu and Xuzhou are the first-level axis cities,Shanghai,Jinhua,Ningbo,Suzhou,Changzhou,Hefei,Nanjing,Tongling,Suzhou,Bengbu and Huaibei are the second-level axis cities,and other cities are the axis cities.Finally,based on the constructed hub-and-spoke emergency logistics network and combined with the current situation of China’s emergency logistics during the epidemic period,the countermeasures to improve the emergency logistics capability of the trunk channel and branch channel for epidemic prevention in the Yangtze River Delta region and the suggestions to improve the overall emergency logistics capability for epidemic prevention were put forward. |
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