Research On Spatial Connection Pattern And Network Structure Of Three Major Urban Agglomerations In The Yangtze River Economic Belt

With the advancement of urbanization and informatization in our country,the economic ties between cities are getting closer and closer.Urban agglomerations have become the new subject of regional development.The integration of urban agglomerations has become the key to regional integration in China.The Yangtze River Economic Belt is a major national development strategy in China.The Yangtze River Delta urban agglomeration,the middle reaches of the Yangtze River,and the Chengdu-Chongqing urban agglomeration are three growth poles that support the coordinated development of the Yangtze River Economic Belt.This paper supplements the current gap in the comparative study of the spatial connection networks of the three major urban agglomerations in the Yangtze River Economic Belt,and is of great significance for optimizing the division of labor and cooperation of the three major agglomerations and supporting the coordinated development of the Yangtze River Economic Belt.First,based on the theory of the central place,the author analyzes the characteristics of the scale structure of the three major urban agglomerations in 2011,2014,and 2017 from the perspectives of population,urban comprehensive quality,and outward service capabilities.The Yangtze River Delta’s distribution is uniform,the city’s first degree is close to the ideal value,the middle reaches of the Yangtze River are less than ideal,the central city is not attractive,the Chengdu-Chongqing city group is too high,the scale structure appears faults,and the polarization effects of Chengdu-Chongqing appears Significantly.Secondly,based on the theory of spatial interaction,this paper improves the gravitational model from three perspectives: the comprehensive quality of the city,the amount of outward service functions,and the shortest inter-city time.The results show that the total amount of spatial connections of the three major urban agglomerations has increased year by year,the internal gap has increased year by year,and the node level has not changed much.The Yangtze River Delta urban agglomeration has the strongest spatial connection,presenting a "one core and multiple poles" spatial structure.The spatial connection pattern presents a triangular pattern of Wuhan-Changsha-Nanchang;the Chengdu-Chongqing urban agglomeration was significantly affected by the high-speed rail construction during 2014-2017,and its spatial connection pattern was based on Chengdu-Chongqing as the axis.Then,use social network analysis to study the network structure characteristics of the three major urban agglomerations in 2011,2014,and 2017.The research shows that the density of the spatial connection network of the three major urban agglomerations has an increasing trend.The density of the Yangtze River Delta urban agglomerations is much higher than that of the other two urban agglomerations.The analysis results of the agglomeration subgroups of the three major urban agglomerations all show the characteristics based on administrative divisions.The Yangtze River Delta urban agglomeration and the middle reaches of the Yangtze River have formed a stable four agglomerate subgroups,however the structure of the cohesive subgroups of the Chengdu-Chongqing urban agglomeration is still unstable.Finally,the study takes ten central cities of the three major urban agglomerations as examples,and analyzes the gravitational links and high-speed rail connection networks between the urban agglomerations.The research results indicate that the Chengdu-Chongqing urban agglomeration is clearly separated from the other two urban agglomerations.Wuhan has an important pivotal role in the interaction of the three major urban agglomerations.Chongqing is an important portal city for the Chengdu-Chongqing urban agglomeration to connect with cities in the middle and lower reaches of the Yangtze River.