The City Network Centrality and Spatial Structure in the Beijing-Tianjin-Hebei Metropolitan Region
研究了高速公路、铁路、快速路和高铁四种交通模式下京津冀城市群的可达性、出度和入度，发现交通可达性改善了城市间的经济联系，但也加剧了极化效应，并促使空间结构从多中心向带状转变。
With the expressway and high-speed railway infrastructure construction,city'sTemporal Distanceis shortened,which cause city location and network relationship changing.On the basis of the study on GIS network analysis and social network analysis,and using O-D matrix and gravity field model,the paper analysis the accessibility,OutDegree and InDegree for different traffic mode of highway,railway,expressway and high-speed railway in the Beijing-Tianjin-Hebei Metropolitan Area.The results show that:①Inner polarization effect of accessibility is higher than the outer layer of metropolitan,according to the highway,railway,highway traffic,high-speed railway order,the city accessibility is improved more and more.②The traffic accessibility has two sides.On the one hand,it improves economic radiant ability and connection degree between city,on the other hand,it enhances the big different degree,besides,Beijing,Tianjin with radiant function,other city to agglomeration.③According to theTemporal distancein 1 hour,the city's external influence becomes obviously,the biggest changing is Langfang(0.25 hours).1 hour over,the economic influence becomes gradually weaker,which disappear in 2 hour over.④Tianjin traffic is advantageously more than Beijing,in the highway,railway,expressway and high-speed railway 4 traffic modes.But then,under the comprehensive effect of accessibility and economic influence,Beijing's Outdegree is higher than Tianjin,InDegree Tianjin than Beijing.⑤Accessibility enlarges the space scope of metropolitan,besides it causes the spatial structure fromPoly-centricity Spatial StructuretoZonal Spatial Structure