| The connection and strength of urban interaction experience continuous dynamic evolution in spatio-temporal scales. Taking spatio-temporal coupling into account to analyze urban interaction characteristics and mining the structure patterns is one of the core issues in human geography research. This paper relies on the continuous observation massive traffic flow data in Jiangsu expressway, and combining with mathematical statistics, measurement modeling, spatial analysis of GIS, complex network analysis and data mining methods to research this problem. Our perspective is, in the form of data driven, analyzing the complex characteristics of nodes and traffic network topological structure, and then introducing tensor decomposition of multi-dimensional spatio-temporal analysis method to mining spatio-temporal coupling structure of urban interaction; and on the basis of flowing rhythm, analyzing spatial evolution mechanism and extracting urban organization pattern We aimed at providing new theoretical tools and feasible paths for the spatio-temporal network analysis of urban interaction.The number of Jiangsu expressway toll stations significantly increase, and the "short distance" spatial agglomeration distribution is its basic feature. The characteristics of topological structure of Jiangsu expressway network can be summarized as, the network scale has improved significantly, but its level is still low, whatever the development potential is larger. Overlaying traffic flow on Jiangsu expressway toll station, the statistical characteristics obviously perform as "most flow concentrated on few stations, minority flow dispersed on lots stations", and the spatial pattern has a typical differentiation with "south high and north low", and the spatial connection predominant direction is southeast-northwest, as time evolution, the spatio-temporal characteristics remain relatively stable. Keep toll stations as nodes and traffic flow as lines to construct the traffic flow network, and its characteristics showed as a small-world network and increasingly complex, and its top-level structure growth already, but the hierarchical structure is still in differentiation. In general, combining with the expressway infrastructure network and expressway traffic flow network, we can summarize that Jiangsu expressway network has a significant complex characteristics, and this situation become clearer as time evolution.The spatio-temporal structure of Jiangsu expressway traffic flow network, which roughly appears a reversed "不" structure, and its time-varying pattern and spatial pattern has significant coupling feature. According to the relative traffic flow value of six principal components, there are three time-varying patterns at the study period. Respectively are essentially immutable pattern, gradually rising gradual pattern and rapidly rising mutational pattern. Each time-varying pattern has their corresponding spatial pattern. The essentially immutable pattern highlights the main channel effect of Jiangyin Yangtze River Highway Bridge, which along Beijing-shanghai expressway connecting network, and act as a vertical axis of reversed "不" structure. The gradually rising gradual pattern highlights the Shanghai-nanjing expressway connecting network, which act as the horizontal axis of reversed "不" structure. The rapidly rising mutational pattern highlights the connecting network which constructed by "Changshu-Nantong" and "Yangzhou-Zhenjiang", respectively, and the former cross Sutong Yangtze River Highway Bridge along ShenHai expressway, the latter cross Runyang Yangtze River Highway Bridge along Yangli expressway. The connecting network they constructed together act as other two vertical axises of reversed "不" structure.The evolution process of Jiangsu expressway traffic flow network shows obvious several stage characteristics. The time can be divided into three stages, which corresponding spatial structure of whole network from reversed "T" structure to reversed "下" structure, to reversed "不" structure evolving. Along with the new cross-river bridges opened, the spatio-temporal structure of network show up time-varying patterns increasing and spatial structure evolving, which giving the signals that the difference location and function of cross-river bridges, are the important influence factors affecting spatio-temporal structure mould. The stage characteristics of network as one of the important part of the whole evolution process, which are the segmentation tendency in long scale and the volatility structure change in short scale. On the premise of summarizing the main driving factors of expressway traffic flow network, such as cross-river bridges building, regional development needs, regional development policy, administrative principles and investment and finance structure, based on the research of Jiangsu practices, we give an evolution process theoretical model with six stages. The theoretical model contains network scattered distribution stage, local network construction stage, regional preliminary into a net stage, network development extension stage, network promotion enrich stage and network integration stage.The pattern of urban spatial interaction is determined by the inflows, outflows and the origin-destination time-distance. Urban spatial interaction follow the Newton model represented as a power function. The damping coefficients of the whole distance are less than 1 in four time-points, and the value wave from 0.472 to 0.672, and the value are 0.645,0.672, and 0.649 in three time-points, respectively. From the above conclusion, the time-distance restraint urban interaction is limited, which assumes that the sensitivity of elements mobility inter-urban is common. Compared with the intra-city taxi traffic flows, inter-urban railway traffic flows, and inter-urban aviation traffic flows, the expressway traffic flows are less sensitive to time-distance with the first two, and close to the last one.The inter-urban interaction pattern includes three systems in Jiangsu province, which are Subei interaction system, cross-river interaction system and Sunan interaction system. Compared with urban spatial structure in "Jiangsu Urban System Planning (2001-2020)" and "Jiangsu Urban System Planning (2012-2030)", our inter-urban interaction pattern has coupling and differentiation with it Sunan system has an internal contact integration trend obviously, Suzhou, Wuxi, Changzhou and Nanjing exhibit prominent central functions. Cross-river system forms several "dual core" structures on two sides of the Yangtze River, mainly used to connect Sunan system and Subei system, which has obvious "channel effect". Subei system has a low connecting relationship inter-group and intra-group among three systems, and Huai’an as an important node to link different urban group in Subei system. Under the guidance of the refined inter-urban interaction pattern, as the "multi-plates synergetic development" thought to planning and layout regional development strategy are the priority scheme in Jiangsu. After comparing with the urban spatial structure in "Jiangsu Urban System Planning (2001-2020)" and "Jiangsu Urban System Planning (2012-2030)", we suggest that amend and add "Wuxi-Jiangyin-Huai’an-Xuzhou" as " Xuzhou-Wuxi urban development axis" on the basis of original planning, and then the new urban spatial structure would form as a "井" structure with "one economic belt, three development axises and three metropolitan areas, one growth pole". The coupling among different projects can provide some enlightenment for Jiangsu urban spatial planning with more closeness connecting on intra-region and inter-region in the future. |
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