The high-speed rail network exerts a multifaceted influence on the spatial structure of urban agglomerations. While the reduced cost of regional factor flows has the potential to enhance overall economic efficiency, it also reinforces the advantages of central towns, leading to a “siphon effect” on surrounding small and medium-sized cities, exacerbating imbalances in urban development. The conventional “Land-use Transportation Interaction” theory, centered on location accessibility, falls short in explaining the intricate network effects of high-speed rail on urban agglomeration spatial structures. This article adopts an approach grounded in the “Space of Flows” paradigm, considering both “transfer” (exclusive of time and space, e.g., capital and labor) and “sharing” (non-exclusive of time and space, e.g., information and technology) effects of factor flows. It analyzes the cascading effects of the “high-speed rail network-factor transfer and sharing-urban agglomeration spatial structure”. Using Wuhan Urban Agglomeration as a case study, the research employs big spatial data (i.e., population migration) extracted from network location-based services to identify and measure factor transfer and sharing among cities and towns. Then, a set of spatial models and “What-if” analyses were applied to demonstrate the impact of the high-speed rail network on factor transfer, sharing, and the overall spatial structure of the urban agglomeration. The findings reveal a heterogeneous impact of high-speed rail development on the spatial structure of Wuhan Urban Agglomeration. The high-speed rail development propels labor transfer from surrounding small and medium-sized towns to central cities, creating a discernible polarizing effect on Wuhan’s economy, and presenting challenges to its neighboring cities’ economic development. Simultaneously, high-speed rail facilitates the dissemination of information and technology from central cities to peripheral areas, offering opportunities for regional economic transformation. This study overcomes the shortcomings of previous research, which have often oversimplified the interactions between cities. It established a unified analytical framework to explain the impact of the high-speed rail networks on the spatial structure of urban agglomerations.The research results aim to serve as a policy reference for optimizing the spatial structure of urban agglomerations.

During the process of regionalization in the last 20 years, inter-city co-construction zones have been undergone rapid expansion as well as vital and thorough reorganization, which profoundly reflects the cutting-edge orientation of the widespread economic and social restructuring and current regional process. Located in the developed eastern coastline areas in China, the Yangtze River Delta Region (YRDR) consists of a glocal city: Shanghai (municipality) and 3 rapidly developing provinces (Jiangsu, Zhejiang and Anhui). Driven by the global metropolis of Shanghai, the YRDR has developed into one of the world-famous city-regions, with the fastest economic and social development in China over the past forty years since the opening-up policy. In particular, establishing co-construction Zones, as one of the most important approaches to promote local economic competitiveness in the YRDR, has had a huge impact on the economic and social growth of the area. Since then, the YRDR has, in part, taken the approach that has been the most encouraging in establishing the co-construction zones. As a result, the YRDR’s inter-city co-construction zones have been dispersed across the province/municipality and even outside of it, with some of them turning into growth poles in the city-regions. Co-construction zones appear to have had a significant influence on the YRDR’s and the nation’s overall economic and social growth. The purpose of this paper is to explain how the multi-dimensional characteristics of scale, network, and territory shape the dynamics of restructuring and influence the formation, dilemma, and breakthrough of co-construction zones in the YRDR under the fluctuating external policy environment by referencing Jessop’s theoretical framework of “TPSN” and proposing a conceptual framework for changing regional city cooperation. The study finds that: 1) The co-construction zones’ complex features have been continually deconstructed and rearranged by the growing regional development shift, with capital orientation and crisis orientation acting as the main driving forces behind the evolution. Hence, the co-construction zones in the Yangtze River Delta Region have undergone three stages: An initial stage aimed at enterprise transfer, a transitional period of emerging dilemmas, and a new stage of new partnership agenda after 2016, displaying changing sociospatial relations under different capital demands and space fixs in response to institutional crises. 2) The scale, network, and territorial features of the zone were significantly influenced by the organization of shifting transitions from inter-governmental partnership to socionetwork action, as well as the more varied partner agenda. 3) Finally, the evolving course of sociospatial connections moves from a specialization advantage in a specific job to a comprehensive deployment system, indicating the significant trend of regional governance change under the increasing complex regional economic and social activities. The process of restructuring a co-construction zone involves changing sociospatial linkages, and its multidimensional features are continuously enhanced and updated in accordance with guidelines for social and economic growth.

Taking the “Carbon Peak” in 2030 as the research time point, the IPCC “bottom to up” method and social network analysis method are used to explore the network pattern of carbon emission and emission reduction potential of interregional urban agglomerations road logistics under different channel scenarios, and to analyze the influence of the Bohai Channel on it. The research shows that: 1) Differences in the carbon emission network of interregional urban agglomerations road logistics of different channel scenarios in 2030: Under the Land Channel scenario, the carbon exchange of interregional urban agglomerations is concentrated in the economic and traffic developed axes and the endpoint cities of the Bohai Strait; under the Land-Sea Channel scenario, the interregional carbon exchange is concentrated in cities adjacent to the Land Channel; The Bohai Channel improves the high energy consumption situation pointed by the “Bohai Strait endpoint cities” of the interregional urban agglomerations. 2) The network pattern of road logistics emission reduction potential in interregional urban agglomerations in 2030: with Dalian as the emission reduction pivot and the Bohai Strait as the center, strong emission reduction city pairs are more in the south than in the north, and there are zero emission reduction city pairs; The Bohai Channel mainly exerts carbon emission reduction influence on other cities through endpoint cities. However, its influence on the carbon emission reduction of some cities of far away from it and on the edge of road logistics is relatively limited.

As a special cross-regional major infrastructure, the operation of high-speed rail (HSR) reduces factor constraints faced by firms along the route, information asymmetry and agency costs among enterprises, promotes capital flows in the regions along the route, and influences inter-city investment. Several studies have explored the impacts on enterprises investment decisions of the introduction of HSR evaluated by a dummy variable reflecting whether a city is passed by HSR, however, little attention has been paid to the impacts of the improvement in accessibility and connectivity caused by HSR. To this end, this paper analyzes and evaluates the impact of the enhanced accessibility and connectivity caused by HSR on enterprises inter-city investment and its spatial heterogeneity, relying on data about the new investment decisions of Chinese listed companies from 2008―2017. It is found that: 1) Connectivity is improved higher in the cities in eastern region and accessibility is improved more significantly in the western region; the disparities of the accessibility and connectivity between mega-cities and small/medium-sized cities keeps widening. 2) The inter-city investment is mainly concentrated between cities in the eastern region and mega-cities, but the regional differences are narrowing. 3) The enhanced accessibility and connectivity caused by HSR have a significant positive impact on inter-city investment, and the impact of accessibility is greater than that of connectivity. 4) The impact of HSR accessibiity and connectivity on inter-city investment varies across different regions and cities with different population scales. Amongst, the improvement in connectivity has generated larger influence on the inter-city investment flowing to the cities in eastern region and mega-cities, while the enhanced accessibility significantly enhances the attraction of inter-city investment in cities of western region and small cities.

Submarine optical cables play a vital role in social economy development, and national defense and security. Submarine optical cables are always facing the risk of natural or man-made damage. However, the current researches of the vulnerability of submarine optical cable network are still limited to local network and national scale. In this article, we construct the global submarine optical cable network with information ports as nodes, and design a set of evaluation method combining complex network theory and simulation tools to analyze network vulnerability, classify hub information ports, and measure regional survivability in turn. The research results are as follows: 1) The submarine optical cable network has typical scale-free and small-world characteristics, and its vulnerability structure, which is not significant under random attacks but significant under deliberate attacks, is confirmed by simulation. In the deliberate attack mode, the submarine optical cable network is more sensitive to intermediary centrality attacks than point-degree centrality attacks, and it can be assumed that the transit and bridging functions of the information port are more critical to the vulnerability structure of the network. 2) The submarine optical cable network shows three states of “connectivity damage” “partial collapse”, and “complete collapse” in order with the increase of attack level. Accordingly, 66 hub information ports are identified and classified into 3 levels. The hub information ports appear the characteristic of polar core structure in the submarine optical cable network, and echo the main sea lanes, which are the main reasons for the vulnerability structure of the submarine optical cable network. Singapore, Cape Town, England’s west coast area, Florida and other information ports and their surrounding waters need to be focused on security. 3) The redundant connections of hub information ports make the submarine optical cable network have a certain self-regulation mechanism. However, the regional survivability levels vary greatly in space, specifically showing that Europe and North America have higher survivability levels, while East Asia, South Asia and South-Central Asia have midstream destructivity levels, Central America and North Asia have the lowest destructivity levels, and there is still much room for optimization. Overall, the research results can provide reference and decision support for the optimization of submarine optical cable network structure.

Optimizing population density has been recognized as an important way to improve urban livability, which is also the ultimate goal that human society has been pursuing. Although many disciplines, such as geography, urban planning, psychology, economics, and ecology, have made some explorations on the relationship between population density and urban livability, none of the existing theories among these disciplines have directly and systematically introduced the relationship between population density and urban livability. Moreover, the existing theories are mainly based on low-density contexts, ignoring high-density contexts in East Asia, especially in China, leading to relatively limited applications of these theories. This paper takes Chinese and American cities as examples, which are proxies of high- and low-density contexts, respectively. By comparing the research findings in these contexts, we aim to seek a generalized relationship between population density and urban livability. After reviewing the current empirical evidence, we found that population density has an important impact on urban livability but its impacts differ between Chinese and American cities. First, in American cities, population density has positive associations with commuting durations. A possible reason is that a higher population density reduces distances to destinations and improves accessibility to facilities. However, Chinese cities provide opposite evidence, which shows that population density has a negative relationship with commuting durations. This may be because a higher population density in China often induces traffic congestion. Second, population density is mainly negatively related to air pollution in American cities, whereas it is mainly positively associated with air pollution in Chinese cities. Third, many American studies suggest that population density has a positive relationship with physical health, because a higher population density promotes active travel, leading to higher levels of physical activity. However, studies from Chinese cities show that population density has negative or inverted U-shaped associations with physical health due to limited space for physical activity. Fourthly, population density has positive associations with subjective well-being by enhancing social capital in American cities, whereas it is negatively associated with subjective well-being by reducing social capital in Chinese cities. An important explanation for the above differences is that the basis of population is different between the U.S. and China. That is, population density may have different effects on urban livability in low density contexts (i.e., American cities) and high density contexts (i.e., Chinese cities). Combining both contexts, we conclude that there is an inverted U-shaped law between population density and urban livability. In particular, in the low-density contexts, a higher population density promotes urban livability, because it is conducive to reducing travel duration, improving air quality, and enhancing citizens' physical health and subjective well-being. However, in high-density contexts, a higher population density tends to reduce urban livability, as it may prolong travel duration, worsen air quality, and decrease citizens' physical health and subjective well-being. This inverted U-shaped relationship between population density and urban livability reminds geographers and urban planners to reconsider the local contexts of population density when designing and building livable and sustainable cities in China and other countries all over the world.

China's high-quality and inclusive growth of regional economy need to cooperatively attract skilled and less-skilled labors. Based on microdata of China's 2015 one-thousandth population sample survey, this paper analyzes the spatial pattern of interprovincial skilled and less-skilled migration from 2010 to 2015, and uses zero inflation negative binomial regression models to reveal the driving forces of interprovincial skilled and less-skilled migration. The main findings are as follows: 1) The interprovincial mobility of less-skilled labors is stronger than that of skilled labors, and the spatial distribution of the interprovincial skilled migration is more dispersed than that of interprovincial less-skilled migration. 2) The eastern developed provinces and municipalities have high net inflow intensity of skilled and less-skilled labors, and the central regions have high net outflow intensity of skilled and less-skilled labors. The net migration intensity of less-skilled labors is higher than that of skilled labors, and there is high intensity of net out-migration of skilled labors in northeastern region and Gansu province. 3) Skilled labors mainly move from the central, southwestern and northeastern regions to Guangdong, Beijing and Shanghai, while the less-skilled labors mainly migrate from the central and southwestern regions to Guangdong, Zhejiang, Shanghai and Jiangsu. 4) China's interprovincial skilled and less-skilled migration are mainly driven by economic factors, and the employment complementarity between knowledge- and technology-intensive industries and consumer services leads to similar choices of destination for skilled and less-skilled labor. However, the impact of economic factors such as income, and housing price on the scale of interprovincial less-skilled migration is stronger than that of interprovincial skilled migration. The quality of children's primary education is the most important amenities that both highly skilled and less-skilled labor value, while the amenities of educational and cultural services facilities, and the climatic amenities play bigger positive roles in the interprovincial skilled migration than that of interprovincial less-skilled migration.

High-quality urbanization is key to China's modernization and low-carbon and green development transition. Based on the panel data of 195 countries (regions) from 1990 to 2020, this paper measures the comprehensive urbanization level of each country (region) from four dimensions of population, space, economy and society, and analyzes the impact mechanism of urbanization on carbon emissions in China and different groups of countries based on STIRPAT and EKC theory. The results show that: 1) The comprehensive urbanization level of all countries (regions) around the world shows an increasing trend, with the most obvious improvement in Asia and Europe. There is a large gap in the comprehensive urbanization level between countries (regions) with different income levels. China's comprehensive urbanization level shows a trend of low start and fast development. 2) The proportion of population, space and economic urbanization in countries (regions) around the world is decreasing year by year, while the proportion of social urbanization is steadily rising. And the development quality of comprehensive urbanization is steadily improving. The comprehensive urbanization development of high-income countries (regions) is mainly dominated by economic urbanization and social urbanization, while the dominant types of comprehensive urbanization in low-income countries (regions) are population urbanization and space urbanization. China's urbanization process has gradually changed from “quantity” driven by urban population to “quality” of coordinated development, but there is still a big gap in the quality of urbanization compared with developed countries. 3) There is an “inverted U-shaped” curve relationship between comprehensive urbanization and per capita carbon emissions in high-income, high-urbanization, and low-income countries (regions), and there is an “U-shaped” relationship in low-income, medium-high urbanization, and low-urbanization countries (regions). China's urbanization and per capita carbon emissions have an “inverted U-shaped” curve relationship, and the inflection point has not yet appeared. Promoting the level of economic urbanization and social urbanization is the key to achieving carbon peaking. Therefore, in the future, China needs to coordinate the relationship between urbanization development, residents' living standards improvement, energy conservation and emission reduction, so as to improve the quality of urbanization and reduce the contribution of urbanization to carbon emissions.

Over the last three decades, a growing number of studies have examined the impact of the urban environment on active travel, aiming to identify effective environmental interventions to promote active transportation. However, given the disparity in the levels of urbanization and motorization between China and the western countries, empirical evidence from the western countries may not be generalizable to China. Through analyzing and comparing relevant research from China and the western countries, this study aims to provide new insights into future research on active travel in China. First, we found that the development of active transportation in most countries has generally followed a “boom-decline-revival” pattern, which is closely correlated with the levels of urbanization and motorization in the corresponding countries. Second, we reviewed the literature on the relationship between the urban environment and active travel, and identified several general patterns linking the urban environment and active travel. We found that a high-density built environment, mixed land use patterns, good street connectivity, supportive facilities for walking and cycling, a safe travel environment, and a supportive social culture promote active travel. Moreover, environmental perceptions play a mediating and moderating role in the process of the urban environment influencing active transport travel. Third, we summarized key differences in research findings between studies from China and the western countries. Our analysis revealed that some urban environmental elements, including built environment density, land use diversity, walkability/bikeability, road design, distance to city centers or commercial centers, and environmental safety, have different effects on active travel of urban residents in China and the western countries. Furthermore, studies in the western countries have focused on the moderating effect of individual characteristics in the process of urban environment influencing active travel, empirical but evidence is lacking in China. Finally, we made recommendations for future research. We suggested that future research should explore more the causal and non-linear relationships between the built environment and active transport travel, as well as precise modeling and measurement of active transport travel behavior. More importantly, future research should focus on unique issues related to urbanization and motorization in China, and propose unique and innovative theories and practical guidelines.