Urbanization is an inevitable trend of modernization and the fundamental transition in socioeconomic structure, human production and life style. China is undergoing a rapid and unprecedented urbanization process, and has achieved the short-term goals that European and American countries attained in the past decades or even centuries ago. This kind of rapid expansion has inevitably led to a serious imbalance between urban land expansion and urban population growth. We used the demographic-landscape urbanization coupling relationship index (ratio of the annual average growth rate of demographic permanent population and urban development land) to explore the spatio-temporal characteristics of demographic-landscape urbanization coupling situation, and further explain its driving forces during the past decade in China. All analyses, based on the demographic statistics and landscape dataset of 636 cities in China, aimed to identify and diagnose six coupling types. Furthermore, we made the macro pattern of urbanization development level more visible with the help of Kernel Density spatial analysis tool. Results show that: (1) Over the past decade, the average annual growth rate of urban development land in China was 1.65 times that of the urban population, and demographic-landscape urbanization coupling situation was poorly coordinated. (2) We found that there is a spatial dependency between demographic urbanization and landscape urbanization. Moreover, the spatial agglomeration center of high-density urban population showed a gradual westward moving trend. Meanwhile, urbanization development mode shifted from "land lag" to "population lag". (3) Generally, the area of per capita urban development land has exceeded the standard threshold; and 41.96% of the cities currently have a development land area per capita more than five times of the ideal value. (4) The proportion of three coordination types was 73.25%, which is much higher than that of three incoordination types (26.75%). Among them, "Both Growth and Uncoordinated Type" took the largest proportion of 43.27%, which reflects the uncoordinated relationship between demographic urbanization and landscape urbanization. This situation will continue or even is intensified in the years to come. Additionally, the cities located at the edge of urban agglomeration seemed to be more uncoordinated than cities at the center. This is probably because that the cities at the edge of urban agglomeration, which had a small population and low property price, relied more on the "land finance" to earn their main source of urban economic income. (5) Economic development level, population size, governmental decision-making behaviors, geographical location and regional disparity were all driving factors of demographic-landscape urbanization. In addition, there are few obvious differences in the mechanism and effect of these factors. To sum up, urban population and land use management in the new era should get more attention according to the new trend in system diagnosis and comprehensive analysis, thus to provide a scientific basis in development decision for new urbanization and urban-rural integration strategy as well as the rural revitalization strategy.

The growth and spatial differentiation of housing price is a theoretical issue continuously discussed in the field of urban geography, and even a practical problem relating to whether urban residents could realize the goal of living a good life in their own residences. The paper chooses 3761 independent residential districts (or residential clusters) in Nanjing as research objects, and analyzes sample data of 30 quarters in 2009-2017 of each residential district; on this basis, it focuses on the spatial differentiation pattern and evolution process of residential price in Nanjing. It finds that, on the whole, the housing price in Nanjing presents the staged rule of mutually alternative of "fast growth" and "relative stability" in one and a half year; while, high-price residences are mainly in Hexi New Town and the districts of famous schools, as well as high-rise service apartments distributed in inner urban areas, gated communities with landscape at the periphery, and high-grade villas in suburbs. Based on the consideration of the price level, location characteristics and building attributes of residential districts, this paper has comprehensively divided the residences in Nanjing into nine typical types, those are in inner city: (a) the multi-story traditional residences, (b) high-rise apartment residences, and (c) residences within the districts of famous schools; in the peripheral areas: (d) the urban new center residences, (e) landscape-area residences, (f) other gated residences; in the suburbs: g) the residences in core areas of new towns, (h) high-grade villa residences, and i) residences in urban fringe area. The comparison of the price growth process of different residences shows that, a close connection exists between the spatial attribute of residences (centrality, comfort, and scarcity) and the characteristics of housing price growth (rapidity, stability, sustainability). This paper summarizes four models of housing price growth of residences in Nanjing, namely, leading pattern, following pattern, growth-chasing pattern, and independent pattern. In addition, it analyzes the main internal and external driving forces for the differentiation of housing price growth of different types of residences. On this basis, it discusses the deep effects of the rapid and differentiated growth of housing price on the urban social space reconstruction in Nanjing, including enlarging the gap between the rich and the poor, crowding out the middle- and low-income population, solidifying the residential spatial differentiation, etc. The study on the growth of residential housing price and its aftereffects with Nanjing as an example, which is a typical big city in China, would have a certain reference for relevant research on the general fast growth and spatial differentiation of housing prices in China after the global financial crisis in 2008.

A metropolitan area, which plays a dominant role in the regional economic development, is defined as a composite of a densely populated urban core and its surrounding interlocking territories. It is essentially a unified labor market that is delimited by the commute flows between a principal city and the peripheral area in most of foreign countries. However, due to the absence of commuting census data in China, it is either too difficult to conduct delimitations based on the commuting linkage or the results could be completely different from those in foreign countries. We based our delimitation on commuting flows identified from mobile phone data, which records the users' spatio-temporal information while they communicate with the network via towers. First, we inferred the user's residence and workplace using two weeks of China Mobile's 2G mobile signaling data in 2014. Then, we delimited the boundary of Shanghai metropolitan area according to the foreign standards. Additionally, we proposed to utilize the recreational activity, also inferred from the mobile phone data, as an auxiliary standard to adjust the boundary. The conclusions can be drawn as follows: (1) In terms of commuting flows, the Shanghai metropolitan area covers the surrounding area of the central city, the Songjiang new town and the large industrial zones in the urban fringe, while in terms of recreational activity, it includes the surrounding area of the central city, the new towns of Songjiang, Jiading, Qingpu, the Huinan area, and the Changxing Island. Morphologically, the Shanghai metropolitan area is slightly longer in the east-west direction and narrower in the north-south direction. (2) The commuting and recreational connections can be combined to delimit a metropolitan area in China, while the former could be the primary indicator with the latter as the auxiliary. (3) Huge difference exists between the metropolitan area of Shanghai and the foreign ones. The foreign metropolitan areas usually have more expanded ranges covering surrounding jurisdictional zones, while the Shanghai metropolitan area mainly grows within its administrative boundary and is confined to a relatively small area around the central city.

With the rapid development of knowledge economy, great changes have been taking place in urbanization pattern across the world in the current conjuncture. Considering the fact that traditional urbanization theory is hard to interpret these changes, innovation is the core concept to explain the phenomenon of the new urbanization dynamics. As one of important contents of urban geography, in the perspective of space of flows, urbanization dynamics needs to turn from research on the population flow between rural and urban research to studies on high skilled migrants flow among cities and regions. Against this background, we propose a conception of innovation-based urbanization, and use it to describe the effect of high skilled migrants and cultural diversity on urban innovation in China. Based on the sixth census data of 270 cities in China in 2010, our study calculates the index of cultural diversity of each city, and analyses the spatial structure of high skilled migrants and cultural diversity in China. Then this study measures the extent to which high skilled migrants and cultural diversity increase urban innovation, with a method of spatial regression analysis. Conceptual and empirical contributions are also compared to previous studies. The results are obtained as follows: (1) The migration of highly skilled to cities, which changes urban function and landscape and extends the knowledge activities and behaviors, is emphasized by innovation-based urbanization conception, which responds to the development of knowledge-based economy, providing a good explanation of new dynamics, new mechanism of urban development and new urban innovation landscape. (2) Innovation-based urbanization is the important driving force for Chinese urban development, especially for eastern coastal areas and provincial capital cities. (3) Highly skilled migrants and cultural diversity do have demonstrated positive effect on urban innovation output. A ten percent increase in the number of urban highly skilled migrants and the index of cultural diversity direct increase respectively urban patents by 3% and 2%. The conclusions could deepen the understanding of openness and dynamics of regional innovation system and help to improve decision-making ability on urbanization planning, promoting urban innovation and development.

As the main places for urban residents' recreation activity in the era of mass leisure, urban public recreational space (UPRS) is one of the major components of urban public spatial system. Its planning, layout, and the service are the main characters to measure the urban social civilization and the life quality of residents. Meanwhile, in order to meet the current demands for the construction of livable cities and meet the challenges of UPRS development in the process of urbanization, it is important to have a scientific and systematic review on the latest development of UPRS research for promoting the development of this subject. Based on a data from the China National Knowledge Internet during 1985 to 2017, this study examined and summarized the research development of UPRS in China. By using literature quantitative analysis, we divided the China's UPRS related research into three stages of development based on the number and growth rate of papers per year, namely starting period (1985-2000), growth period (2001-2009), and consolidation period (2010-2017). Then, this paper identified nine hot research topics in the UPRS and reviewed their progresses in research by using a knowledge network of UPRS built on the co-occurrence of keywords. These topics include the classifications of UPRS, spatial structure and layout, comprehensive assessment, planning and development strategies, impacts induced by UPRS development, evolution characteristics and their driving mechanism, space imagery features, sustainable utilization, and so on. Moreover, this paper systematically reviewed the research methods and the scale of the China's UPRS related studies. Finally, in response to problems and deficiencies of extant research, this paper put forward some suggestions regarding future research. Chinese UPRS studies should pay more attention to the basic theoretical research. We should construct a new research system with Chinese characteristics based on interdisciplinary and multi-level spatial integration research. Besides, we should develop the humanism philosophy and construct management systems for UPRS that can lead the development of world cities based on the global vision.

World city and world city network are one of the most important topics in international urban studies in the last two decades. The current research of the world city network exclusively reflects a Western corporate-dominated network, which comprises core world cities. However, the hegemony of the Western cities and top world cities is undermined by the globalizing economy of emerging economies. In this more complex nexus of world cities, the diversity and complexity of the world city network with the influence of newly emerging economies are far from revealed. In this research, we take the emerging banking sector of China, one of the biggest economies around the world, as a case study and see how Chinese commercial banks expanded globally and shaped the world city network from 1979 to 2015. A modified interlocking network model is applied as the main method of the research. It is found that the Asia-Pacific region, West Europe, and North America are the key arenas of the global operation of Chinese commercial banks. The oversea affiliations of Chinese commercial banks are highly agglomerated in global financial centers and specialized financial centers, especially those in the three regions mentioned above. Then they expand to the whole world through gateway cities of their respective regions. Based on such global expansion strategies, Chinese commercial banks influence the world city network by intensifying the global connection of Chinese cities, the connectivity of core world cities, and regional city networks of the Asia-Pacific region. China's outward economy, including its foreign direct investment and trade, along with the increasing number of emigrants, are main factors affecting the globalizing Chinese commercial banking network. The intervention of the Chinese government to regulate and facilitate the global expansion of Chinese commercial banks, also makes contribution to the results.

Social vulnerability assessment is an important approach to analyzing the elements of vulnerability, quantifying degree of social vulnerability, and identifying vulnerable spatial units or social groups. Meanwhile, related policies addressing targeted management of social vulnerability are necessary. Therefore, we analyzed the concept and connotations of social vulnerability in four aspects, i.e., disturbance, structure, dimension and scale. We established a framework for social vulnerability assessment that defines the evaluation process, objective, elements, data and method. Based on this framework, we developed a common evaluation index system of social vulnerability according to the three dimensions of exposure, sensitivity and adaptive capacity. Finally, the social vulnerability assessment framework was applied to the case of the urban fringe of Xi'an, which has undergone rapid urban expansion. Using a mix of qualitative and quantitative analyses, we combined data from a statistical yearbook, in-person interviews and household surveys and evaluated multi-scale social vulnerability. The spatial differentiation and types of social vulnerability were displayed according to three scales, i.e., Jiedao, communities and land-lost peasant households. The proportion of Jiedao with a low social vulnerability index was 48%. The social vulnerability index of communities requisitioned by housing estate was the highest, and the social vulnerability index was the lowest in the area of educational function. More than half of the land-lost households lay in the middle range of the social vulnerability index, with fewer households having a high index than those having a low index. With the decline of the scale from Jiedao to household, the low value distribution of the social vulnerability index changed from decentralization to centralization. Meanwhile, we found a significant correspondence at the level of the social vulnerability index between household and community, but not for other levels. Our research highlights the social vulnerability assessment framework involved in the evaluation process, index system, data organization, method and multi-scale assessment. These conclusions could be further explored for theoretical research and practical application of social vulnerability assessment.

Urban poverty in western China, where poverty is largely concentrated and distinctively different from eastern China, is a relatively less studied but noteworthy research field in China's urban poverty in the transition period. This paper analyzes spatial structure and mechanism of urban poverty in western China, through a case study of Xi'an city, an ancient capital and a traditional industrial base. The data comes from a survey of urban residents' income in main urban areas of Xi'an in 2015. The definition of relative poverty used by the World Bank and the method of FGT index are adopted to evaluate the attributes of urban poverty at the scale of sub-districts. The results show that the average poverty incidence in Xi'an is relatively high, but poverty depth and intensity are weak. Urban poverty presents U-shaped curves from the city center towards suburban areas, along with the variations of spatial heterogeneity and continuity. The inner differentiated fringe of rising extension zone and mature built-up zone are the weakest urban poverty areas. We can identify five types of areas with high poverty rates: declining old inner city areas, deprived development areas, declining traditional industrial areas, urban villages and areas near new growth poles, where people in poverty exhibit different demographic and housing characteristics. The spatial structure of urban poverty in Xi'an reflects the city's stage of socioeconomic development and regional characteristics, which having directly effects on the city's employment capacity and residents' income level. There are multiple forces shaping the spatial structure of urban poverty in Xi'an, ranging from public policy, industrial legacy, tourism and residential choices. During the process of economic transition, urban residents of different income groups are remaking the structure of urban social space of Xi'an through diversified paths, including replacing, filtering, spontaneous agglomeration, segregation, exclusion and reinforce. These findings help us to have a better understanding of the development mechanism underlying urban poverty in less developed inland cities in western China, and provide scientific basis to improve the accuracy and effectiveness of anti-poverty policies in China.

Urban vacant land has been concealed for a long time in the contradictory but unified processes of urban growth and shrinkage. The study on urban vacant land, however, is currently a rather rudimentary and subjective issue. This paper firstly presents the connotation of urban vacant land based on bibliometric analysis. Then, typology, proximate causes and values of urban vacant land are analyzed at parcel, transect, city and national levels. Results show that the study in China lags about half a century compared with North America and Europe. Moreover, geographers has seldom paid attention to this issue. Urban vacant land could be proximately categorized by land cover, land usage and land ownership. It is widespread with a large amount in cities. For example, the probabilities of urban vacant land in the cases of Guangzhou and New York are 8.46%-8.88% and 3.17%-5.08%, respectively. In addition, the average proportion of urban vacant housing land take up 11.48% in the 65 cities in the USA. Generally, urban vacant land shows fragmentation and odd shape. Significant spatial differences exist at parcel, transect, city and national levels. Proximate causes, such as land division, odd shape, demographic decline, de-industrialization, land speculation, disinvestment, and environment issues could result in urban vacant land, which has become the Grey Island in urban social, economic and ecological spaces. However, it could be considered as the potential resources for enhancing urban sustainability. To promote urban renewal and land supply-side structural reform, urban vacant land research framework is finally discussed. Specifically, the logical research themes on urban vacant land consist of unified typology, dynamic process and pattern, underlying driving forces, transformation mechanisms among different types, impacts and multifunction assessment, and sustainable use control. Focus should be given to research on social, institutional, economic and ecological interaction, comparative study in different urbanization processes and regions, as well as multi-scale study.

Spatial optimization is an important research area in geography. Most research on spatial optimization of education resource in this field is concerned with spatial efficiency, while the public is more concerned with spatial equity. In recent years, random allocation has been tested in some places, but the optimization models on the random allocation of schools have not been well formulated and developed. In China, to improve the spatial equity of education, a newly proposed reform tries to use lottery for school admission, namely "allocating several schools to one school district". However, there is little literature on how to implement the new school allocation, its impacts on school distance and educational equity. This paper constructs a quadratic programming model to minimize the variance of all students' expected values on educational quality under constraints of the maximum distance and schools' capacities. Then, Shijingshan District in Beijing is taken as a case area. The result indicates that the new allocation model can significantly improve the spatial equity of educational resources compared with the way of allocating students to the nearby school. The variance of the former decreases by 99%. Over 2/3 of the communities benefit from our model of maximum spatial equality, whose expected values of educational quality will increase. The ratio of benefit students is also about 2/3. On the other hand, the distance cost of school commuting is also significant. The average school distance increases by 3.99 times. However, it is still less than 5 km, which is commonly set as maximum distance to school. Moreover, it is also less than the survey school distance in the study area. When the parameter of the maximum distance in the model increases from 5 km to 8 km, the improvement of the variance of expected value of educational quality obeys the law of exponential growth, and the average distance increase obeys the law of arithmetic growth. When it is set at 7 km, the variance of expected value of educational quality approaches zero. It can be regarded as a state of absolute equal opportunity for every student which is usually thought to be hard or impossible to realize. Based on the results, the policy implication for China's school admission system is discussed.

Spatial configuration of urban emergency shelters is one of the hotspot issues in disaster prevention and urban emergency management. The purpose of this study is to conduct spatial configuration of urban shelters which can help urban residents have access to the emergency shelters as soon as possible with less congestion. The spatial configuration model is built on the basis of the agent-based model and multi-criteria decision-making method. Remote sensing image data, high-precision population data, road network data and expert knowledge are integrated in the model. Three types of agents involved in emergency evacuation are designed, which include the government agent, shelter agents and resident agents, to conduct evacuation simulation. A government agent can delimitate the service areas of shelters in accordance with the administrative boundaries and road distances between the positions of residents and the locations of the shelters. Shelter agents can select specified land uses as potentially available shelters for different disasters, generate the service areas of shelters, record the information of the residents in their service areas and do relative statistical work of evacuation processes. Resident agents have a series of attributes, such as ages, positions, and walking speeds. They also have several behaviors, such as reducing speed when walking in the crowd, and helping old people and children. Integrating these three types of agents which are correlated with each other, we can simulate evacuation procedures. The simulation results are utilized to support location-allocation and configuration of emergency shelters. The location-allocation method of this study is based on multi-criteria decision making and weight sensitivity analysis, so that the locations of new shelters can be selected in highly-suitable regions for location-allocation. When the new shelters are allocated, a new round of emergency evacuation simulation will be executed to realize loop optimization of location-allocation based on the new spatial distribution of shelters to generate the final spatial configuration plan. A case study in Jing'an District, Shanghai, China, was conducted to demonstrate the feasibility of the model. The simulation results convinced that the new model can provide detailed planning for spatial configuration of urban shelters, which can help the residents evacuate to nearby shelters as quickly as possible with less congestion risks. The model provides a new methodology to conduct high-quality location-allocation of urban emergency shelters. It can also be extended to conduct similar spatial configuration work in other urban regions for different kinds of emergency shelters.

The relationship between car travel and built environment is one of the hot issues in the urban studies. The existing researches mainly focus on the respective effects on car travel of individual demographic variables and built environment variables on car travel. Under the background of China's urban transformation and the social space differentiation, a growing number of scholars have examined the relationship between residents' demographics and their residential built environment. Quantifying the relative roles of the individual social attributes and the built environment in influencing car travel has a policy implication. This study applied a multilevel logit model which contains individual-level variables and neighbourhood-level variables to explore the impact on car use. It is concluded that urban residents' working-day car travel is influenced by multilevel variables associated to neighbourhood types. Most of the variation in the travel mode choice is caused by the difference among neighbourhoods. Travel mode choices have a strong neighbourhood contextual effect on car travel. As for the individual level, lower income and education level, collective unit profession, less minors in a family may help refrain the choice of automobile travel. As for the community level, improving bus stops density, building density, land mixing degree and commercial accessibility may help reduce car use ratio of working-day activities' travel. The mechanism of the relationship between two kinds of variables lies in the strength of market effect on urban residential space reconstruction. The residents who have similar social and economic attributes tend to choose the same type of neighbourhood, which has a similar built environment. These conclusions help us to have a better understanding of the mechanism behind the urban residents' working-day car travel and provide suggestions to alleviate the traffic problem by adjusting the multilevel variables in the similar type of community.

Different urban elements may exhibit various aggregation patterns. It is of great significance to quantitatively investigate the disparity and connection among various aggregation patterns of urban elements for understanding the mechanism of urban development and supporting urban planning. Taking Wuhan city, Central China, as a case, we collected five types of urban elements, namely, impervious surface, population density, Point of Interest (POI), plot ratio, and road network, to explore their spatial distribution and characteristics of aggregation patterns. We first used Kernel Density Estimation (KDE) method to identify city centers and we found that there is one major center and seven sub-centers in Wuhan. Then we partitioned the study area by gradient analysis, and calculated the densities of urban elements. The density of urban element decreases outward from the centers, which is fitted well using "Inverse S-shaped" function. We used Concentration Degree Index (CDI) to reflect the aggregation degree of urban elements. The results indicate that the degrees of the aggregation of urban elements are: Commercial POI > population > plot ratio > road. Commercial POI and population are highly aggregated in the urban core area, while plot ratio and road are moderately aggregated in the urban core area. The spatial patterns of highly aggregated commercial POI and population are the combination of point pattern and zonal pattern, while the spatial patterns of moderately aggregated road network and plot ratio are the combination of point pattern, ring pattern and axial pattern. As for the lowly aggregated impervious surface, it shows a ring pattern. The attraction effect of city centers and vertical development promote the center-oriented agglomeration of urban elements. At the same time, the transportation lines and corridor effects of the scarce landscape resources reshape the spatial distribution pattern of urban elements.

There is a debate on whether spatially-neutral or spatially-targeted policy is a better strategy for the future development of economic geography and the spatial pattern of urbanization at the national scale. Economists emphasize the spatially-neutral policy and advocate for the free flow of production factors to the developed regions in southeast China, while economic geographers support the latter and the development of central and western China. We argue that the radiation radius of an economic hub is not limitless because of geography, more precisely, it is distance that plays an important role in the distribution of production activities and urbanization. We also believe that not only should economic benefits be taken into account, but also other factors such as politics, ethnic minority and national security. The core point of this paper is that the scale of a nation is the key determinant of the spatial layout of economic geography and urbanization, and larger countries should follow a relatively balanced development path. Based on both cross-sectional and fixed-effect panel models, we explore the relationship between the scale of a nation and city size distribution, the proxy for the spatial pattern of national economic geography. The results show that, (1) all else being equal, the scale of a nation, represented by either population or land area, is positively associated with a balanced city size distribution. That is, the economic geography in large countries is inclined to a spatially balanced layout; (2) a nonlinear relationship is identified between the spatial pattern of national economic geography and per capita GDP. That is, national spatial pattern is unbalanced at lower levels of economic development and evens out at higher levels of development; (3) urbanization, industrialization, and a stable political environment also help balance the national economic geography layout. This study's policy implication is that large countries such as China should implement the strategy of a relatively balanced development of economic geography and urbanization. Considering the objectives of national security, social stability, and the fact that China has a large population and a vast territory, it is reasonable for China to promote the development of the central and western regions with spatially-targeted policies.

As two rising great powers, China and India have undergone similar development processes, but they also exhibit significant differences in development paths and patterns. The significant differences in political systems, economic systems, and developmental environment between the two countries have attracted great attention from scholars. This research focuses on the regional differences and spatial evolution processes in urbanization and urban systems between the two countries from a geographical perspective. Based on the demographic censuses of both countries and the urban population data from the United Nations, this paper systematically compared and analyzed the spatial characteristics of urbanization and urban systems in China and India using various methods including spatial analysis, parameter estimation, and nonparametric estimation. The results indicate that: (1) Since the 1990s, the regional differences in urbanization in China have transformed from south-north differences to coastal-inland differences, whereas the north-south differences in India have been stable. (2) In terms of the spatial scale at the province (state) level, the population densities and urbanization rates were positively correlated in both countries. The correlation is more significant when the urbanization rate is higher than 50%. However, in recent years, the correlation between population density and urbanization rate kept increasing in China, while such correlation has been decreasing in India. (3) Currently, the urban system is dominated by large and medium-sized cities in China and India, which complies with the characteristics of the rank-size distribution. But the economic reform has exerted significantly different effects on the spatial evolution of the urban systems in the two countries. The economic reform has changed the major driving force for urban development in China from geological and historical factors to the spatial structure of the economic system. However, in India, the driving forces for urban development have always been geological and historical factors, and the economic reform even decreased the effect of the spatial structure of the economic system on urban development.

Aging and urbanization are two major population issues currently facing the world. Urban agglomeration is an advanced form of urbanization that encompasses the spatial organization of cities within a specific geographical area, and in which the process of aging differs from that in other regions. Based on county-specific data from population surveys in 2000 and 2010, we determined the spatial patterns and variations of aging populations in 20 urban agglomerations in China using geographical detector-based and coefficient of variation methods. We also examined the contributing factors of population aging variability. Results demonstrated that in 2000, older people accounted for 7.32% of the urban agglomeration demographic structure, with 12 of the 20 urban agglomerations defined as adult-type populations. In 2010, however, older people accounted for 9.00% of the urban agglomeration demographic structure and, except for those in the Pearl River Delta and Ningxia areas along the Yellow River, all the urban agglomerations entered the elderly population stage. Moreover, high-age and moderately high-age regions expanded towards inland urban agglomerations, with population aging increasing obviously and population type changing from adult to aging. In addition, significant regional differences in the incremental increases in the number of older people and growth rates of the aging populations existed in the urban agglomerations. Low-age and high-age regions had smaller increments and growth rates, whereas moderately low-age, mid-age, and moderately high-age regions had greater increments and growth rates, indicating a declining aging rate in the order of regional, national, and local urban agglomerations. Within each urban agglomeration, the distribution pattern of aging showed the coexistence of uplift and collapse. The distribution pattern of aging within national urban agglomerations changed from an increasing to collapsing structure, and population aging in central China reduced. Conversely, regional urban agglomerations changed from a homogeneous to an increasing structure, and population aging in the central region increased. Population aging of urban agglomerations was the result of internal and external factors, with changes in base period aging, population age structure, and population fluidity being the predominant factors. Universal uplift of the population age structure was a key factor affecting aging and population types in urban agglomerations. Furthermore, low-age population immigration into urban agglomerations had a "diluting effect" on population aging, and aggregation and diffusion effects caused by different development stages of urban agglomeration played important roles in aging and population migration.

It is important to apply impervious surface product to the study of urban agglomeration spatial structure. Under the background of China's rapid urbanization, study on comparative analysis of urban agglomerations spatial structure between China and USA can provide policy proposals of urban agglomeration space optimization for Chinese government. Taking Beijing-Tianjin-Hebei (BTH) and Boswash as study areas, firstly, this paper maps the extent and density of impervious surface for BTH and Boswash respectively in seven periods of 1972, 1982, 1991, 1995, 2001, 2006 and 2011. Furthermore, at different scales of urban agglomeration and metropolitan region, landscape pattern index, gravitational index and spatial analysis were used to analyze differences of spatial structure between BTH and Boswash. The results showed that (1) impervious surface area increased rapidly in BTH, while it remained stable in Boswash. (2) BTH spatial structure had experienced different periods including isolated city development, dual-core city development, group city development and network-style city development, while Boswash spatial structure was more stable, and its spatial pattern had shown a "point-axis strip" feature. (3) The spatial pattern of high-high assembling region of impervious surface had showed a "standing pancake" feature in BTH, while a "multi-center gather and disperse group" in Boswash. (4) All of the percentages of impervious surface area in ecology, living, and production land in BTH were higher than those in Boswash. At last, from the perspective of urban agglomeration space optimization, the development proposals for BTH were proposed.

Application of the concepts of alter-based centrality and power has become a focus in the research on city networks in recent years. In this paper, the conditionality of recursive theory utilization to city networks is analyzed from the perspective of network topology structures. In addition, an urban network is constructed on the basis of Baidu migration data and measured using the complex network method, improved alter-based centrality, and the power method. The results show, in the first place, that the use of recursive theory for the analysis of urban networks has specific data structure requirements, suitable for tree structure, but not for the local existence of complete network structure measurements. Secondly, small world phenomena and spatial patterns of population mobility exhibit obvious core-periphery structures at national and regional scales. This means that the national urbanization development strategy and important transport facilities play key roles in enabling the population mobility network. In this context, the Harbin-Beijing-Xi'an-Chengdu-Dali line exhibits a significant network of spatial differences in terms of boundary divisions. Thirdly, the use of alter-based centrality and power reveal hierarchical characteristics, differences in the urban network, and the influence of different effects, including spatial ones, on the identification of network city resources. In this case, the network includes not just Beijing, Shanghai, Chongqing, and Guangzhou, high power quintessential cities with high centrality, but also a number of smaller lower power hub cities, including Wuhan, Taiyuan, Guiyang, and Fuzhou, as well as gateway cities that exhibit both low centrality and high power, such as Lanzhou and Yinchuan. Thus, the concepts of centrality and power are of great significance in broadening our understanding of complex urban diversification.

In this paper, we take Beijing as a case study and employ the residential leasing parcel data from 2004 to 2015 within the Sixth Ring Road of Beijing metropolitan area. Also, we use the GIS data of Beijing's public facilities, such as bus stations, railway stations, park, hospital, primary school and so on. With the help of ArcGIS, GS+, Surfer and Geoda Software, we explore the spatial pattern of residential land parcels, residential land price and determinants of residential land price in Beijing. In the first place, we use the methods of Spatial Trend Analysis, Nearest Neighbor Index (NNI), Exploratory Spatial Data Analysis (ESDA) to explore the spatial pattern of residential land parcels and their price in Beijing. In the second place, we compare the spatial econometric models (SLM and SEM) with traditional OLS model to further explore the determinants of residential land price in Beijing. Based on the analysis, the main conclusions are drawn as follows. (1) The number of residential land leasing parcels is not balanced among years and ring roads. The residential land leasing parcels in the last 20 years are mainly concentrated between the fifth and the sixth ring roads in Beijing. (2) Residential land parcels are generally distributed along the main roads (such as Beijing-Shijiazhuang Expressway, Beijing-Kaifeng Expressway, Beijing-Shanghai Expressway and Beijing-Tibet Expressway) and the subway lines (such as Line 1, Line 5, Line 6, Line 15, Fangshan Line, Daxing Line and Yizhuang Line), which is more obvious in outer suburban areas. (3) Generally, there exists an inverted U-shaped curve trend, indicating that residential land price declines gradually from the city center to the city fringes as a whole, and spatial pattern of residential land price has turned from mono-centric structure to poly-centric structure. (4) Residential land price demonstrates a spatial cluster distribution pattern. There exists obvious spatial autocorrelation in residential land price and it is easy to distinguish "cold spots" from "hot spots". (5) In the model selection, we compare the spatial econometric model (SLM and SEM) with the traditional OLS model. The result shows that SLM is the best, followed by SEM, indicating that there indeed exist spatial spillover effects and spatial dependence in residential land price rather than error dependence. The residential land price is mainly affected by the surrounding residential land price, distance to bus station, distance to subway station, distance to key primary school, area of land parcel, FAR and the type of land leasing. However, in this paper, one drawback is that we fail to take macroeconomic policy factors into consideration, which may play a key role in the formation of residential land price. Also, we have not considered the subway's impact in different periods such as planning period, construction period and operation period on residential land price, which needs to be further studied.