Research On Spatial-temporal Characteristics Of Innovation Networks In Urban Agglomerations In The Middle Reaches Of The Yangtze River

With the rapid advancement of globalization and informatization,the development of urban agglomerations has gradually changed from "scale expansion" and "factor driven" to "structural upgrading" and "innovation driven".Urban agglomeration in the middle reaches of the Yangtze River is the key area to promote the new urbanization in China.How to explore the complex network characteristics and evolution trend of urban space at this stage in combination with the development background and innovation status of urban agglomeration has become an important starting point of this study.Based on the measurement of urban innovation capacity and traffic convenience,this paper constructs the inter-city correlation by improving the gravity model,measures and analyzes the innovation network structure system of urban agglomeration in the middle reaches of the Yangtze River by combined with the complex network analysis method,identifies the innovation spatial structure mode of urban agglomeration in different periods.In order to provide reference for the study of urban agglomeration structure optimization,the paper puts forward some suggestions for regional innovation and development.The results show that:(1)From 2015 to 2018,the spatial distribution pattern of urban agglomeration innovation in the middle reaches of the Yangtze River shows the trend of South by eastnorth by west,and the innovation track is in the shape of "N".The overall innovation ability of urban agglomeration is increasing year by year,showing a stable and progressive development pattern.(2)From 2015 to 2018,the spatial organization of innovation network in urban agglomerations in the middle reaches of the Yangtze River is in a transition period from the "three-pillar" structure to the multi-" triangle " complex structure.? From the overall state of innovation network,the innovation links between cities are more and more close,among which the innovation links within the urban cluster around Changsha-Zhuzhou-Xiangtan urban agglomeration is the most closely,Poyang Lake urban agglomeration is the second,and Wuhan urban agglomeration is the weakest.?From the perspective of the scale characteristics of urban nodes,the innovation gap of cities in the middle reaches of the Yangtze River is gradually decreasing,but the coreedge characteristics are obvious,and the innovation connection pattern shows the development law of "point-line-plane".? In terms of the structure of vertical,the number of urban agglomeration in the middle reach of Yangtze river in the first level,two level,three level,four level of innovation contact increases year by year,the fifth level of innovation contact decreasing year by year,the innovation network structure increasingly stable.The stable " triangle ",with Wuhan,Changsha and Nanchang as the nodes,plays an important supporting role in the innovation and development of urban agglomeration.The development of core city clusters drives the development of surrounding cities to become an important form of the innovation network structure development of urban agglomeration in the middle reaches of the Yangtze River.?From the perspective of the horizontal structure,the innovation connection network in the middle reaches of the Yangtze River can be divided into seven sub-groups at the three-level level.The sub-group pattern began to diverge in 2016 and remained unchanged from 2016 to 2018,forming the first sub-group with Changsha as the core and the second sub-group with Wuhan as the core.The pattern of innovation aggregation remained multi-core,but the pattern of innovation radiation changed from single-center to double-center.(3)From 2015 to 2016,the overall pattern of innovation and development of urban agglomerations in the middle reaches of the Yangtze River was only composed of dots and lines,and the "growth triangle" and "circle layer" integration patterns were the overall pattern in this period.In 2017,two innovation axes were formed in the north and south,and the expanding region centered in the middle of the urban agglomeration began to develop in the integration mode of "growth triangle".In 2018,Er Guang innovation and development axes were formed,and the innovation circle composed of core cities and key node cities intersected.The integration model of "growth triangle" has become an important development strategy for this region.(4)According to the problems in the process of urban agglomeration innovation and development,this paper puts forward optimization countermeasures from three aspects: point cultivation,line expansion and area integration.