Morphological and functional polycentric structure assessment of megacity: An integrated approach with spatial distribution and interaction

Polycentric urban structures are important spatial development strategies in megacities; however, they have decentralized morphologies and functional characteristics that profoundly impact urban space development. Therefore, when promoting sustainable development in urban areas in Shenyang, the only megacity in northeast China, it is important to explore the polycentric spatial development of megacities based on multi-source data, geographic information system spatial analysis, and network model methods. This study was conducted to examine the polycentric structures of the morphological and functional dimensions. The results showed that morphological polycentric space can be defined as "centralized dispersion," with the functional polycentric only comprised "decentralized concentration." Additionally, agglomeration sub-centers of the morphological dimension were all on the periphery of the city, although the three sub-centers within the city (M6, M7, and M8) were diffusion types. In the functional dimension, sub-centers F7 and F6 exhibited high centrality and power for both agglomeration and diffusion. Finally, four-node motifs were more important than three-node motifs in the morphological polycentric micro-networks, but their frequency was low, whereas that of three-node motifs were more important than four-node motifs in functional polycentric micro-networks, and their occurrence frequency was high.