The Spatial Structure Of The Yangtze River Urban Agglomeration In Syberspace

Cyberspace is a new spatial concept in the information age,providing a new field for geographical research.With the support of information technology,the connection between cities is no longer limited to specific physical space,but begins to take on the characteristics of network.The emergence and development of the Internet have challenged the traditional spatial concepts such as the law of distance decay and the theory of hierarchy in traditional geographical space,and influenced the interactions between cities.This paper create the Yangtze River Delta' network based on inter-city re-tweets in Sina Weibo,first analyzes the network structure of the network and its geographic dependence,then,uses LDA model to extract the topics of micro-blogs,analyzes the spatial structure of information flow in each topic and it relevance to social economic development level of cities,to study the spatial structure of the Yangtze River urban agglomeration in cyberspace and its similarity and difference from that in geographical space.The research results are as follows:(1)The topological structure of the Yangtze River Delta' network based on inter-city re-tweets in Sina Weibo shows the characteristics of small world,scale-free and heterogeneity.The density of the network is 0.64 which reflects that the information exchange is relatively extensive.The average path length of the network is 1.36,which reflects a high information accessibility.The average aggregation coefficient is 0.729 which reflects a strong agglomeration,the small world quotient is 1.69,showing that it is a small world network.The distribution of the node strength conforms to the power law distribution,reflecting that information is mainly concentrated in a few core city nodes;the connection matching between nodes is more manifested by the heterogeneous connection matching between high-degree,high-strength node and low-degree,low-strength node.The core cities have a good radiating effect on peripheral cities.(2)At the point level,the Yangtze River Delta' network based on inter-city re-tweets in Sina Weibo exhibits the characteristics of pyramid scale structure.Nanjing,Hangzhou and Hefei are strong core cities for information input and output;Shanghai and Nantong are strong core cities for information input;Wuxi and Shaoxing are strong core cities for information output;Suzhou and Ningbo are weak core cities for information input and information output.Maanshan is a weak core city for information input.Chizhou and Anqing are weak core cities for information output.At the line level,the core cities of information dissemination,Nantong,Nanjing,Shanghai,Hangzhou,and Ningbo,constitute the "M" core structure of the Yangtze River Delta' network.At the regional level,the Yangtze River Delta urban agglomeration has formed the Jiangsu information communication community centered on Nanjing,the Zhejiang information communication community centered on Hangzhou,and the Anhui Information communication community centered on Hefei.(3)There are regional differences in the structure of the dissemination of information in each topic.The main information input cities and main information output cities of each topic are different and few main information input cities and information output cities are overlapped.The backbone network of medical,meteorological,landscape and leisure information is concentrated in the eastern part of the Yangtze River Delta urban agglomeration.The backbone network of education and transportation information is mainly composed of information flows within the same province.The backbone network of education information is mainly formed by Shanghai,Hangzhou as core cities.(4)The spatial structure of the Yangtze River Delta urban agglomeration in cyberspace shows geographical dependence.The node strength in information dissemination network depends on city's social-economic development level in the real geographic space.The education level and the city construction level have the greatest impact on the city's node strength.The strength of the information flow between cities shows the law of distance decay under the impact of the interaction of the two cities in social-economic.Based on the social-economic development level of two cities and the shortest road distance between them,a gravitational model of the interaction between cities is built.The distance attenuation coefficient is 0.2,showing that the inter-city connection in the network information space is less affected by geographic proximity than that in actual geographic space.The structure of the information dissemination of each topic isrelated to the level of social-economic development.Cities with high social-economic centrality mainly input landscape,leisure and entertainment information,output medical information;cities with low socioeconomic centrality mainly input education and law information;cities with low economic development level input disaster and law information,output government affairs,law,and transportation information;cities with high economic development level mainly output leisure and entertainment information,and weather information.(5)The spatial structure of urban agglomerations in cyberspace and in geographic space shows commonness and difference.Both the information dissemination network in cyberspace and the urban network in the real geographic space show the characteristics of small world and scale-free.However,the urban network in the real geographic space is a homogeneous network,while the information flow in the information dissemination network mainly presents a heterogeneous match,and the core cities have a stronger role in radiating the peripheral cities.The hierarchical structure of the urban space in cyberspace and in geographic space both show the characteristics of the scale structure of the pyramid.Compared with hierarchical structure in real geographic space,in cyberspace,the status of Shanghai has declined and the status of the provincial capital city rise.Both in cyberspace and real geographic space,the Yangtze River Delta urban agglomeration has formed the development axis composed of several closely connected cities.In cyberspace,Nanjing and Nantong are more closely connected.Both in cyberspace and geographic space,there are several regional development groups.In cyberspace,the regional development groups are formed according to administrative divisions,while in real geographic space,the city group are formed mainly based on the strength and geographical proximity between cities.