부산대학교 도서관

Summary: ``Urban systems present hierarchical structures at manydifferent scales. These are observed as administrative regionaldelimitations which are the outcome of complex geographical, politicaland historical processes which leave almost indelible footprints oninfrastructure such as the street network. In this work, we uncover aset of hierarchies in Britain at different scales using percolationtheory on the street network and on its intersections which are theprimary points of interaction and urban agglomeration. At the largerscales, the observed hierarchical structures can be interpreted asregional fractures of Britain, observed in various forms, from naturalboundaries, such as National Parks, to regional divisions based onsocial class and wealth such as the well-known North-South divide. Atsmaller scales, cities are generated through recursive percolations oneach of the emerging regional clusters. We examine the evolution of themorphology of the system as a whole, by measuring the fractal dimensionof the clusters at each distance threshold in the percolation. Weobserve that this reaches a maximum plateau at a specific distance. Theclusters defined at this distance threshold are in excellentcorrespondence with the boundaries of cities recovered from satelliteimages, and from previous methods using population density.''