Understanding the population loss and economic decline in the three provinces of Northeast China from a perspective of urban shrinkage is of great significance to deepening the transformation theory of China's old industrial bases. The main results can be summarized as follows. Since 2000, obvious differences in urban growth and shrinkage have occurred in Northeast China. Some 42.85% of cities showed an urban shrinkage. The manufacturing and service industries in cities of urban growth (growing cities) are increasingly advanced, while the development of new pattern industries and industrial structure upgrading are slow in cities of urban shrinkage (shrinking cities) and the economic competitiveness of these shrinking cities is weakening. There is a close spatial correlation between growing and shrinking cities. On the one hand, growing cities continuously absorb the production factors such as population and capital of shrinking cities through the agglomeration effect, and on the other hand, they increase the pressure of economic transformation of shrinking cities through the spatial transfer of traditional industries. The shrinkage degree varies from high to low from north to south, and shows a trend of 'first strengthening, then weakening' from east to west. The processing cities have the highest shrinkage degree, followed by industrial and mining cities, and the tourism and port cities have a relatively low shrinkage degree. The factors influencing urban shrinkage include the development lag of public service facilities, the misalignment of industrial development and market demand, the low correlation degree of industrial structure, the aging of population structure, and the agglomeration effect of regional central places, their intensity of action enhancing in turn. According to the economic long wave theory and local circumstances, Northeast China will experience a long-term urban shrinkage in the future. It should be a strategic choice to develop this region to actively adapt to the shrinkage, and optimize and reorganize population and economic factors through smart urban shrinkage.

The study of a single form of the reality human settlements cannot reasonably explain the ever-changing human settlements phenomenon under the human-land relationship regional system. At present, the theoretical basis, practical exploration, and scientific decision-making of the interaction between different forms (reality, pseudo, and imagery) of human settlements are not clear. To construct the theoretical framework of the coupling coordination of urban pseudo and reality human settlements, this paper uses the coupling coordination model, spatial trend analysis, geographical detector and other empirical analysis methods to analyze the space-time law of coupling coordination in the three provinces of Northeast China from 2011 to 2017, and discusses its influencing factors and driving mechanism. The results show that: (1) the coupling shows a rising trend, with relatively obvious stage characteristics; a dual-core and single-center coexistence pattern is formed in space, and the spatial pattern evolves from scattered clusters to "T"-shaped clusters and bands; (2) Overall coordination is on the verge of imbalance, coordination and interaction have steadily evolved to a high level, intermediate coordination has occupied a certain position, and high-level coordination has begun to emerge; The core polarization spatial pattern of the degree of coordination is obvious, the four major cities dominate the overall level of coordination and interaction in the three provinces; At the same time, the spatial pattern of regional differences, nemely, "coexistence of polarization and balance" within the province, "lower in the north and higher in the south" across the study area, and "center-periphery-low lands" for the whole region, will be formed; The overall coordination shows the spatial trend characteristics of "high in the middle and low at both ends" in the east-west direction and "higher in the south and lower in the north" in the north-south direction; (3) the coupling and coordinated development of pseudo and reality human settlements is the result of comprehensive factors, among which social and economic development is the dominant driver, "human" is the background driver, entertainment system is the emerging driver, and social system is the important media driver.

The spatial structure reflects the hierarchical structure, functional structure, and community form between cities in the urban agglomeration, representing the expansion model and development characteristics of the urban agglomeration within a certain time range. In this study, the urban agglomeration in the middle reaches of the Yangtze River (UAMRYR), which is the first approved national urban agglomeration in China, is selected as the research object. The land use / land cover datasets, Landsat images, and urban population data were used in this study to analyze the evolution process and characteristics of the UAMRYR during 1990-2019 at the macro and micro levels. The research methodology includes the development of the spatial database, construction of the grid system, calculation of the urban expansion degree, and building of the expansion rose map. Based on the characteristics and the rules of historical development, a scenario analysis is processed on the development situation for 2020 and 2030. The main conclusions are as follows: (1) From 1990 to 2019, the spatial structure of the UAMRYR has transitioned from "three centers" into "single core, double centers, and multi- clusters", and then into "double cores, multi-centers, and multi-clusters". The "double cores" of the Wuhan metropolitan area and the Changsha-Zhuzhou-Xiangtan urban agglomeration has developed into giant cores and will continue to expand during 2020-2030, becoming superlarge cores with built-up areas of about 2000 km² and 1500 km², respectively. Nanchang is relatively small and would remain as the regional development center radiating the Jiangxi Province. Seven development sub-centers have been formed, namely Xiangyang, Yichang, Jingzhou, Changde, Hengyang, Jiujiang, and Shangrao, and are expected to increase further in the future. (2) In the development process, four main axes of the Yangtze River, Wuhan to Changsha, Wuhan to Nanchang, Nanchang to Changsha, and several secondary axes have been formed. However, due to the lack of strong border hub and bridgehead city, the driving force of the axes on the urban agglomeration needs to be further improved. (3) There are several development problems in the area. The polarization effects of cores in the Wuhan metropolitan area and the Changsha-Zhuzhou-Xiangtan urban agglomeration are extremely strong and continue to present a development trend. Jiangxi Province lacks a strong core, thus various environmental problems emerged due to the over-concentration of urban built-up areas. These places are urgently adjusted in order to control the speed of expansion, cultivate new regional centers, and strengthen the axis function.

In recent years, increased attention has been given to the role of city networks in promoting economic performance. Nevertheless, the empirical evidence concerning urban network externalities and its transmission mechanisms is at best patchy. This study sets out to gain a better understanding of network externalities through the lens of corporate networks in China. Information on the headquarter and branch locations of China's top 500 public companies in 2017 are subjected to ownership linkage model to construct the urban network, resulting in a panel data with 265 cities in 2006 and 2016. Then the impacts of network linking strength and economic performance of partners on urban economic growth are quantitatively measured, and the dynamic mechanisms of network links that affect urban economic growth under the production fragmentation environment are discussed. Two conclusions are drawn. First, the transmission mechanisms of network embeddedness influencing urban economic growth in China have different effects. The analysis results of all samples show that the strength of network links has a profound impact on the quality of urban economic growth, but the impact of economic performance of partners is not obvious. This means that, in general, the transmission mechanisms of network embeddedness are to highlight the comparative advantages and economies of scale of cities, rather than to promote knowledge spillovers and technical progress. Second, the impact of network embeddedness on urban economic growth is heterogeneous in many dimensions. Cities in the eastern region, core position or with a large population size benefit more from the network competitive advantage and the knowledge flow system of "local buzz and global pipelines", while cities in the central and western regions, peripheral position or with a small population, bounded by lack of network competitiveness and "knowledge gatekeeper", increase the risks of low-end lock of industrial economy. In the future, the policy and governance of urbanization in China need to be adjusted accordingly. The Chinese government should promote network cooperation among cities on a larger spatial scale, and attach great importance to the multi-dimensional development gap between cities under the network environment.

Improving the connectivity of multi-sector enterprises at a cross-regional level can enhance knowledge and technology transfer and stimulate innovation and synergies among cities. Therefore, the study of city networks, which comprise a large number of multi-sector enterprises, can provide an important knowledge base for innovation and development at the regional and national levels. Based on an evaluation of innovative enterprises in China by authoritative institutions, data were collected on 1778 multi-sector enterprises, which included details on the headquarters, the branches (a total of 30,625) and the locations. A city-based network for the country was established, using the data for the multi-sector linkages and a model for the headquarters-branches, to explore the network connectivity characteristics via social network analysis, the GIS method and the spatial interactive model. The results showed that (1) although the network covered 353 cities across China, the spatial distribution of the network was extremely uneven. For instance, a diamond-shaped connectivity pattern emerged gradually as the network hierarchy decreased. The Beijing-Tianjin-Hebei region, the Yangtze River Delta and the Pearl River Delta were found to be the three key hubs of the network. (2) The intercity linkages between innovative enterprise sectors (innovative enterprise flows), had a clear administrative center and a provincial boundary effect. Moreover, the innovative enterprises were strongly attracted to the municipalities and provincial capitals. Beijing was at the heart of the network, followed by Shanghai and Shenzhen. (3) Differences existed in regional connectivity. There was a striking difference between the eastern region and the central-western region. The former had a high connectivity with respect to both the internal and the external networks, while the latter had lower connectivity for the internal network but a higher connectivity at the external level. At the same time, although the network structures for all the three eastern megalopolises showed strong cohesion, their connectivity characteristics were quite different. (4) The input and output of innovative enterprise flows were to varying degrees influenced by the indicator attributes for each city, and these in turn were related to the administrative hierarchy, the economic strength and the innovative environment of the region, as well as proximity indicators, which were related to geographical, technological and institutional factors. Foreign capital was not conducive to innovative enterprise flows and to the formation of innovative intercity company-based networks in China.

With the rapid development of economic globalization and regional integration, the connection between cities is increasingly close. The mobility and interdependence of elements have promoted the formation of city network and become a new regional organization model and spatial structure. Based on Tencent's migration data, this paper constructs a 372×372 relational data matrix, and systematically depicts the city network pattern in China from different modes of transportation. The results show that cities with high network correlation degree are mainly concentrated in the area east of the Hu Huanyong Line, especially in the Yangtze River Delta, Pearl River Delta, Beijing-Tianjin-Hebei region, Chengdu-Chongqing region and other urban agglomeration areas, which have the highest concentration and become the main control power of China's city network pattern; and the cities in the northwest half are at a disadvantage status. According to the amount of migration, the Chinese city network is divided into national, large regional, regional, local and pedestal networks. The city network structure changes with the mode of transportation. When the network level moves down, the number of node cities tends to increase and the network density increases, but the network range tends to shrink. There is a close correlation between the network level and the migration path. National-level network related to air transportation, regional network related to railway transportation, and local network are relevant to automobile transportation. The economic space-time distance of different transportation modes determines the network structure, which is the basic factor that causes the network to differentiate with different paths.

Based on the data of 197 suppliers of iPhone components and parts in 2019, this paper builds multidimensional world city networks from the perspective of global value chains, integrating specialized cities with global functions and the high-class world cities into the same analytical framework, which enriches the research perspective of world city networks in the era of globalization to a certain extent. The purpose of this paper is to expand the research and investigation scope of the existing field of world city networks. By means of social network analysis (i.e. the analysis of centrality, connectedness and network cohesion), rank-size rule and community detection, we study the power and prestige, the overall topological structure, the community structure and influence mechanism of the city networks of R&D-oriented, production-oriented and OEM service-oriented types. The results show that: (1) All the world city networks are characterized by polycentricity and diversification, differentiation of nodes' status and dependence on external connections. The "star" nodes in the network coexist with high power and high prestige, and the power is generally higher than the prestige. (2) The network cohesion and rank of R&D-oriented cities are the highest, and the network tends to show a primate city distribution, and the growth of small group structure and the phenomenon of R&D clusters are obvious. The production-oriented network has the highest connectedness, and it tends to present a rank-size distribution and an equilibrium structure. Its network scale is large, but the ties of many nodes are sparse and decentralized; OEM service-oriented network has the highest relative centrality, and power and information are concentrated in a few city nodes. (3) The cluster characteristics of R&D-oriented city communities are most noticeable. Moreover, the network has significant long-distance knowledge spillover and cooperation behavior. Enterprises form specialized clusters in R&D-type cities through non-tradable interdependence, and obtain the benefits of localization economies and spatial integrated effects. The cluster tendency of production-oriented city communities are relatively obvious. Geographical proximity and spatial dependence are the main factors incubating community structure. Enterprises form generalized clusters through tradable interdependence to obtain the benefits of urbanization economies and distance attenuation effect. No obvious cluster network has been incubated in OEM serviced-oriented city communities. Polarization phenomenon of the inter-community is extremely significant, that is to say, the core city community in Taiwan, China, radiates to other low-level equilibrium communities, forming a radial community structure. Contract manufacturers seek the cities with low labor costs around the world to carry out standardized production, and realize full competition through scale economies, therefore, a scatter-type city network layout structure is formed.