城市群生态综合交通网络组团特性分析与关键节点识别

Cluster characteristics analysis and critical node identification in ecologically integrated transport networks in urban agglomerations

为实现城市群生态综合交通发展目标,形成交通、经济、生态环境质量一体化发展格局,以关中平原城市群为研究对象,通过熵值法对节点功能吸引、功能辐射和碳排放强度进行赋权,通过修正引力模型计算其相互联系强度;将空间结构理论与复杂网络理论相结合,构建多维空间联系网络模型;采取改进INFORMAP算法,从交通、功能和碳排放3方面分别进行区域组团划分;基于组团划分结果,构建超图网络模型,引入邻域超度、邻域影响熵指标识别城市群生态综合交通网络关键节点。结果表明:关中平原城市群功能和碳排放空间联系呈现“一极多核”的空间分布格局,西安处于核心地位,宝鸡、渭南等地级市核心区也拥有较高影响力;城市群区域组团与行政区划具有差异性,部分区县如侯马、彬州、澄城等脱离上级行政区划约束,形成了独立区域组团;西安、咸阳是城市群生态综合交通网络建设的关键节点,且城市群东部节点重要度普遍大于西部节点,因而需重点提升西安—咸阳一体化水平,优化东部节点综合交通结构,完善西部节点交通网络布局。

[Objective]To achieve the integrated development of transport,economy,and ecological environment quality,it is necessary to identify the core clusters and key nodes properly in urban agglomerations.[Methods]In this paper,the Guanzhong Plain urban agglomeration is taken as the research object,and weights are assigned to the functional attractiveness of nodes,radiance,and carbon emission intensity through the entropy method.A modified gravity model based on the multidimensional characteristics of the integrated transport network nodes is constructed to calculate the strength of the spatial connections between districts and counties within the urban agglomeration.Furthermore,a model of spatially linked networks is constructed by combining the spatial structure theory with complex network theory.This model takes the skeleton of the comprehensive transportation network as the main body,the districts and counties as the nodes,and the indicators of transportation network level,functional attractiveness and radiance,and carbon emission correlation intensity as the connected edge weights having multidimensional and multilevel characteristics.Additionally,unnecessary parameter calculations are removed to improve the INFORMAP algorithm by combining the centralities of degree,betweenness,and closeness obtained from the complex network theory.This improved INFORMAP algorithm classifies regional clusters separately in terms of traffic,function,and carbon emissions.The result reflects the strength of the spatial linkages between the districts and counties of the urban agglomeration in different dimensions.Finally,based on the results of regional grouping and the hypergraph theory,we construct a hypergraph network model of ecologically integrated transport networks in urban agglomerations,and key indicators such as neighborhood hyper degree and neighborhood influence entropy are proposed to identify the key nodes of ecologically integrated transport networks in urban agglomerations.[Results]The high-speed railway,motorway,and mainline railway networks of the Guanzhong Plain urban agglomeration were divided into two clusters.The western cluster had a considerably lower frequency of intercity travel than the eastern cluster,and the Xi'an cluster had an increased transport network and frequency of intercity travel.The result of the high-level division of the transport network into clusters was mostly centered on prefecture-level cities.The spatial distribution pattern in terms of functions and carbon emission links had one pole and many cores,with Xi'an at the core.In terms of the relationship between cluster and administrative divisions,some districts and counties had broken through the constraints of higher administrative divisions to form independent groupings.Xi'an and Xianyang were key nodes in the construction of the ecologically integrated transport network of the city cluster.The importance of the nodes in the eastern cluster was found to be greater compared to the western part.[Conclusions]To achieve an integrated development pattern of transport,economy,and ecological environment quality in urban agglomerations,we optimize the layout of the existing transport network,increase the proportion of the low-grade transport network,supplement and connect the high-grade transport network through the articulation role of the low-grade transport network,and create an integrated multilevel transportation network pattern.