Flow element is the leading force of regional integration development. High-speed rail flow and information flow are the main material flow pattern and virtual flow pattern of flow space, which have different effects on urban network pattern. Based on the high-speed rail passenger frequency and Baidu index data in 2010, 2015 and 2020, this paper uses the complex network model to describe the characteristics of urban cross-border network changes in the Bohai Rim region in recent years. The results show that:1) From 2010 to 2020, the intensity of urban linkages from the perspective of high-speed rail flow and information flow has increased significantly, both of them show a "convergence" evolution trend, jointly promoting the formation of five growth poles in the Bohai Rim region. 2) There are differences in the characteristics of urban cross-border connections. 3) High-speed rail and information have different regional organizational structures. 4) Under the action of flow factors, the Bohai Rim region has realized the coupling development of "point axis-group area".

Based on the panel data from 148 cities in China's aviation sector spanning the period of 2011-2020, this research explores the influence of air transportation linkage networks on tourism economic development. The research employs various methodologies, including complex network analysis, non-radial Super-SBM model, spatial Markov chain, and dynamic spatial panel Durbin model, to explore spatial evolution patterns and provide empirical evidence. The findings reveal that air transportation linkage networks exhibit a core sub-network characterized by a "diamond" or "overlapping triangle" structure, strengthening network balance, stability, and overlapping effect. The community structure demonstrates an "intertwined and overlapping" pattern in the central-eastern region, while the western region features "edge cities in close proximity". The spatial distribution of tourism economic efficiency levels follows an east > southwest > central > west pattern, the hierarchical solidification of spatial evolution is clearly characterized. Different from the empirical results obtained from previous researches, this research reveals that when a city becomes connected to aviation, it immediately benefits from positive tourism factors due to the spillover of aviation advantages from neighboring cities. Finally, to avoid the negative consequences of agglomeration under balanced competition, China should promote inter-city tourism capital flows, industry-related division of labor cooperation, and knowledge and technology spillover.

Previous studies on urban space growth mainly focused on the local driving forces. Against the background of the space of flows, it's significant to explore the impact of intercity interaction on urban space growth for promoting the sustainable development of urbanization. Using land use data and traffic big data inferred from passenger travels, this paper takes the Guanzhong Plain urban agglomeration as a case study to examine the impact of intercity interaction on urban space growth from 2010 to 2018. The potential driving factors of urban space growth has been divided into local and intercity interaction variables as previous studies. The results show that the spatial organization of intercity travel in Guanzhong urban agglomeration presents an organizational pattern with Xi'an as the core and Xianyang, Weinan, and Baoji as secondary nodes. Secondly, the Guanzhong urban agglomeration experienced a rapid and significant expansion of urban space during 2010—2018, with an increase of 1398.8 km², or an annual rate of 174.85 km², mainly concentrated in Xi'an, Xianyang and Yuncheng. Thirdly, similar to the developed coastal urban agglomerations, the intercity interaction, characterized by intercity passenger travel, has a gradually increasing positive driving effect on the urban space growth during the study period. Relative contribution rates are 5.50% and 7.54% in the period of 2010—2015 and 2015—2018, respectively. This study provides quantitative insights into the issue of sustainable urban space growth in western China.

In order to optimize the layout of urban construction and improve the efficiency of urban land use, this paper studies the relationship between traffic and urban land use. Based on the vector data and POI data of Qingdao traffic network, this paper analyzes the correlation between traffic network and land use intensity in the central urban area of Qingdao from the perspective of centrality by using kernel density estimation method, geographically weighted regression model and multi-center evaluation model. The study found that the proximity centrality structure and linear centrality structure of the traffic road network in the central urban area of Qingdao showed a "center-periphery" model, and the intermediary centrality had a significant point-axis model; the layout of commercial, public services and residential land all showed a multi-center structure; the centrality of traffic road network had a strong correlation with land use intensity; the correlation between commercial land and public service land and traffic road network centrality was higher than that of residential land. The research innovatively revealed the spatial heterogeneity between traffic network and land use intensity from the micro-scale, and discovered the difference in the impact of different regions from a local perspective.

Metropolitan area is the product of the development of big city. The National Development and Reform Commission pointed out that modern metropolitan area need to be fostered, since the metropolitan area is an important carrier of new urbanization. However, there are disputes about the definition of the spatial extent of metropolitan areas, and the criterion of metropolitan area are not clear. On the basis of combing the concept and connotation of metropolitan area, this paper uses mobile phone data to identify the distribution pattern of metropolitan areas in China from the perspective of the resident travel aspect. It is found that most metropolitan areas in China are still in the developmental stage, 27 metropolitan areas can be identified by using the 1% intercity trip rate as the threshold. The distribution pattern of metropolitan areas is closely related to the economic development, metropolitan areas are more dense in economically developed areas, such as the eastern area and the urban agglomerations, especially the Yangtze River delta and the Pearl River delta where there have formed contiguous or overlapping metropolitan areas. The spatial extent of the metropolitan areas is generally included in the urban agglomerations, but some cities of metropolitan areas in the northwest and southwest are not in the extent of the urban agglomerations, the future urban agglomerations planning may consider to include these cities. This paper also explores the developmental conditions of metropolitan areas, and found that the population size, economic primacy of central cities, and the travel distance affect the space extent and the internal connection of metropolitan areas. The travel size is positively correlated to the population size of the central cities, a central city with sufficient population size is the basis for large-scale travel size of the metropolitan area.

Convenient transportation is the base for urban agglomerations to expand area. Taking each county unit of the Yangtze River Delta Urban Agglomeration as the research object, and targeting at the prefecturelevel cities, 16 in 2005 and 26 in 2019, this study comprehensively contrasts and analyses how each object connects with central cities and prefecture-level cities by land transportation to explore how the land transportation connection evolves under the background of urban agglomeration expansion.Conclusionsare as follows: 1) Area expansion of the Yangtze River Delta Urban Agglomeration brings about longer average travel time by highway from research units to central cities and prefecture-level cities. 2) For the railway network of the Yangtze River Delta Urban Agglomeration, there is no tight correspondence between the unit connectivity and intensity. While urban units show higher intensity of connections and denser distribution than county ones, the connectivity of units in research region tends to be less obvious. 3) From the perspective of both highways and railways, in 2005, the average travel time by railway from each county to central cities or prefecture-level cities is in accordance with that by highway network. However, owing to the rapid expansion of high-speed railway network, the situation changes a lot in 2019 when the expansion decreases the average travel time of all the units and improves the balance in the research region.

Based on migration data from Baidu, the study compares the difference in population flow between 2020 and 2019 during three important Chinese festivals, i.e., Qingming Festival, Labor Day, and National Day, and explores the influence of the COVID-19 pandemic on the population travelling between cities during these festivals. The study first points out that the COVID-19 pandemic had a significant impact on such travel. On the Qingming Festival and Labor Day in 2020, the average daily population flow intensity, according to Baidu, decreased by 50.1% and 45.2%, respectively, compared with the same periods in 2019, and there were significant spatial differences in this effect. Second, this study argues that the flow intensity of the population travelling between cities showed a trend of recovery. Meanwhile, the weight and compactness of the population travel network continued to increase. Within this pattern, intercity travel on Labor Day showed recovery in average intensity, but a reduction in average distance, and an increase in network modularity index, indicating that under the influence of the COVID-19 pandemic, people tended to travel short distances, and they were more diversified in destination selection. Finally, this study proposes that the recurrence of local epidemics will have a significant impact on the travel intensity of the population during Chinese festivals in the short term.

With the rapid development of China's economy and society, air travel has become an important part of residents' travel mode, and affects the urban pattern. Based on the Tencent positioning request data of 215 domestic airports from April 28 to May 10, 2019, this paper analyzes the spatio-temporal characteristics of Chinese urban residents' air travel under the two scenarios of May Day holiday and working day, and further explores the relationship between them and urban pattern. The results show that:1) The spatial characteristics of air travel of urban residents in China are generally higher in the eastern coastal area than in the inland area, and lower in the central area; 2) The air travel choice of urban residents in China is mostly concentrated in working day, and the central cities in Beijing-Tianjin-Hebei region, Yangtze River Delta, Guangdong-Hong Kong-Macao Greater Bay Area, Chengdu-Chongqing area and other economically developed regions are more inclined to "working-day advantage type", while the non regional central cities in central and southwest regions are more inclined to "holiday advantage type", and residents' air travel shows a 24-hour cycle of decline, rise and fluctuation. Compared with working days, May Day holiday entered the fluctuation period 2 hours ahead of schedule, and residents preferred to choose the flight time around 3pm and 8pm. 3) In the two scenarios of working day and holiday, there is a strong correlation between the hierarchical differentiation of city cluster and the city scale. To some extent, the cluster distribution of cities is close to the pyramid of city scale.

Based on the transaction data of the housing rental samples within the Sixth Ring Road in Beijing, this article takes the Beijing Metro as an example, and uses a spatial regression model to empirically explore the impact of rail transit on housing rental prices in two different ways:Shared rental mode and unshared rental mode. The results show that:1) The employment accessibility based on rail transit has a significant value-added effect on rental prices, and tenants are willing to pay a premium for housing rent with better employment accessibility. 2) The density of subway stations has a positive impact on the rental price in unshared rental mode, and has no significant effect on the shared rental mode, while the subway transfer line variable has no significant impact both. 3) The effect of rail transit of different rental modes on the rental price shows a different regular pattern as the distance increases. The effect of the rental price of the shared rental mode decreases monotonically with the increase of the actual road network distance, and the largest impact is within 500m from the station; while the unshared rental mode exhibits an inverted "U" shape change, and the value-added effect is greatest within the range of 500-1500m. According to the research results, it is suggested that the government increase the supply of rental housing while fully considering the elements of rail transit, and implement precise measures to achieve the efficient allocation of space for public resources.