Order Exponential Evaluation Model for Road Traffic Safety in City Clusters

This study presents an order exponential model for estimating road traffic safety in city clusters.The proposed model introduces the traffic flow intrinsic properties and uses the characteristics and regular patterns of traffic development to identify road traffic safety levels in city clusters.Additionally,an evaluation index system of city cluster road traffic safety was constructed based on the spatial and temporal distribution.Then Order Exponential Evaluation Model(OEEM),a comprehensive model using order exponent function for road traffic safety evaluation,was put forward,which considers the main characteristics and the generation process of traffic accidents.The model effectively controlled the unsafe behavior of the traffic system.It could define the levels of city cluster road traffic safety and dynamically detect road safety risk.The proposed model was verified with statistical data from three Chinese city clusters by comparing the common model for road traffic safety with an ideal model.The results indicate that the order exponent approach undertaken in this study can be extended and applied to other research topics and fields.

Structural Characteristics and Influencing Factors of Carbon Emission Spatial Association Network:A Case Study of Yangtze River Delta City Cluster,China

City cluster is an effective platform for encouraging regionally coordinated development.Coordinated reduction of carbon emissions within city cluster via the spatial association network between cities can help coordinate the regional carbon emission management,realize sustainable development,and assist China in achieving the carbon peaking and carbon neutrality goals.This paper applies the improved gravity model and social network analysis(SNA)to the study of spatial correlation of carbon emissions in city clusters and analyzes the structural characteristics of the spatial correlation network of carbon emissions in the Yangtze River Delta(YRD)city cluster in China and its influencing factors.The results demonstrate that:1)the spatial association of carbon emissions in the YRD city cluster exhibits a typical and complex multi-threaded network structure.The network association number and density show an upward trend,indicating closer spatial association between cities,but their values remain generally low.Meanwhile,the network hierarchy and network efficiency show a downward trend but remain high.2)The spatial association network of carbon emissions in the YRD city cluster shows an obvious‘core-edge’distribution pattern.The network is centered around Shanghai,Suzhou and Wuxi,all of which play the role of‘bridges’,while cities such as Zhoushan,Ma'anshan,Tongling and other cities characterized by the remote location,single transportation mode or lower economic level are positioned at the edge of the network.3)Geographic proximity,varying levels of economic development,different industrial structures,degrees of urbanization,levels of technological innovation,energy intensities and environmental regulation are important influencing factors on the spatial association of within the YRD city cluster.Finally,policy implications are provided from four aspects:government macro-control and market mechanism guidance,structural characteristics of the‘core-edge’network,reconfiguration and optimization of the spatial layout of the YRD city cluster,and the application of advanced technologies.

Unprecedented Hot Extremes Observed in City Clusters in China during Summer 2022

We report here extreme daytime and nighttime temperatures,severe heatwaves,and compound hot events recorded in China's five most densely populated city clusters in summer 2022.New records were set,with daytime maximum temperatures>42℃in cities along the Yangtze River valley and extreme nighttime temperatures>30℃.Widespread prolonged heatwaves lasting for>40 days and compound hot days occurring for>32 consecutive days were experienced in these city clusters.To explore the possible causes of these extreme events,we analyzed the linkages between the changes in the mean temperatures and hot extremes for different-sized cities in the city clusters.We found that megacities(e.g.,Beijing,Shanghai,Guangzhou,etc.)and large cities(e.g.,Baoding,Wuxi,Foshan,etc.),especially those located in central and eastern China,experienced unprecedented extreme high temperatures,not only in the daytime but also at night.We observed large increases in the mean temperatures and more frequent and more intense hot extremes in cities affected by both the background global warming and intensified urbanization.Megacities and large cities experienced higher and more frequent extreme temperatures and greater warming trends than medium-and small-sized cities(e.g.,Zhangjiakou,Zhenjiang,Yaan,etc.).The evidence of the dependence of temperature trends on a city's size shows that intensified heat island effects may increase the threat of hot extremes in cities undergoing rapid urbanization.

Characteristics of atmospheric particles and heavy metals in winter in Chang-Zhu-Tan city clusters, China

To understand the pollution characteristics of atmospheric particles and heavy metals in winter in Chang-Zhu-Tan city clusters, China, total suspended particulate （TSP） and PMI0 samples were collected in cities of Changsha, Zhuzhou and Xiangtan from December 2011 to January 2012, and heavy metals of Cd, Pb, Cr, and As were analyzed. It shows that the average TSP concentration in Changsha, Zhuzhou and Xiangtan were （183 ± 73）, （201± 84） and （190 ±66） μg/m3 respectively, and the average PM10 were （171 ± 82）, （178 ± 65） and （179 ± 55） μg/m3 respectively. The lowest TSP and PM10 concentrations occurred at the background Shaping site of Changsha. The average ratio of p（PM10）/p（TSP） was 91.9%, ranging from 81.3% to 98.9%. Concerning heavy metals, in TSP samples, the concentration of Cr, As, Cd and Pb were 28.8-56.5, 18.1-76.3, 3.9-26.1 and 148.0-460.9 ng/m3, respectively, while in PMI0 samples, were 16.4--42.1, 15.5-67.9, 3.3-22.2 and 127.9-389.3 ng/m3, respectively. The enrichment factor of Cd was the highest, followed by Pb and As, while that of Cr was the lowest.

Spatial and Temporal Distribution of PM_(2.5) Pollution and Control Strategy in the Chang-Zhu-Tan City Cluster

Utilizing the initial hourly monitoring data of PM_(2.5) concentrations at 23 monitoring sites across the Chang-Zhu-Tan city cluster between January 2013 and February 2014 that released in Real-time Air Quality Reporting System in Hunan Province, this paper draws diagrams and analyzes the change rule of the pollutants concentration over time. In addition, this paper studies the regional distribution of PM_(2.5) seasonal pollution in the vicinity of the monitoring sites using Arc GIS geographic information system with the Kriging interpolation method.On this basis, this paper puts forward some effective control strategies to cope with regional PM_(2.5) pollution combined with the information of industry distribution and development status in the Chang-Zhu-Tan city cluster.

Preface to Special Topic on Atmospheric Greenhouse Gas Measurement and Application in China

China initiated a national carbon trading market in December 2017.Commitments and actions to reduce greenhouse gas(GHG)emissions require consistent,reliable and timely information on GHG emissions.GHG monitoring and modeling studies provide GHG emission estimates to evaluate and guide progress towards emission reductions.GHG monitoring has mainly focused on global-scale background networks over the last few decades,while recent efforts have been made on regional and urban scales,such as projects in the Beijing-Tianjin-Hebei city cluster,in Paris,Washington-Baltimore.

Ten Characteristics of Ba-Shu Culture in the Global Context

First of all, the article identifies the highlights of the documentary The Romantic Shudao.It adopts a panoramic view of the broad Chinese cultural community and depicts the tangible Shudao(road to the Shu area) and the intangible "Romance" associated with it by combining the oral history and collective memory as perceived by common people.The vivid stories can easily reach a wide audience and can thus help to enhance people's confidence in the ever-prospering local Ba-Shu culture.Secondly, the article explains the ten major characteristics of the Ba-Shu culture by looking at the wonderful ecological landscape, the mystical culture and literature, and the magic spiritual aesthetics of the area in an international and modern context.It also studies the Ba-Shu cultural community and the origins, historical development, and main features of the city clusters within the Chengdu-Chongqing economic circle and analyzes the historical and practical values of building a cultural corridor connecting Chengdu and Chongqing.

System and prospects of China＇s intercity rail transit technology

City clusters and metropolitan areas in China are flourishing in the midst of the deepening urbanization in the country, thereby resulting in the emergence of intercity rail transit. Intereity railways connect mainline and urban railways for an integrated regional transportation system that underpins and leads the development of city clusters and metropolitan areas. This study explores the development mode and service characteristics of intercity rail transit, as well as proposes overviews on this system and prospects of its future technology in China.

中国城市间科学合作网络空间的层级性、集聚性与差异性分析（英文）

The Chinese urban system is currently experiencing a fundamental shift, as it moves from a size-based hierarchy to a network-based system. Contemporary studies of city networks have tended to focus on economic interactions without paying sufficient attention to the issue of knowledge flow. Using data on co-authored papers obtained from China Academic Journal Network Publishing Database （CAJNPD） during 2014-2016, this study explores several features of the scientific collaboration network between Chinese mainland cities. The study concludes that： （1） the spatial organization of scientific cooperation amongst Chinese cities is shifting from a jurisdiction-based hierarchical system to a networked system; and （2） several highly intra-connected city regions were found to exist in the network of knowledge, and such regions had more average internal linkages （14.21） than external linkages （8.69）, and higher average internal linkage degrees （14.43） than external linkage degrees （10.43）; and （3） differences existed in terms of inter-region connectivity between the Western, Eastern, and Central China regional networks （the average INCD of the three regional networks were 109.65, 95.81, and 71.88）. We suggest that China should engage in the development of regional and subregional scientific centers to achieve the goal of building an innovative country. Whilst findings reveal a high degree of concentration in those networks - a characteristic which reflects the hierarchical nature of China＇s urban economic structure - the actual spatial distribution of city networks of knowledge flow was found to be different from that of city networks based on economic outputs or population.

Spatio-Temporal Changes of Population Density and Urbanization Pattern in China(2000–2010)

Population distribution and their temporal variation are a direct proxy of urbanization. This study evaluates the population density variation of China between 2000 and 2010 at the township level by using the data of the fi fth and sixth national population censuses. The urbanization patterns of China in 2000 and 2010 are depicted based on the population densities at various levels and the urbanization process of China between 2000 and 2010 is then analyzed through a comparative approach. It also tries to visualize the population density dynamics and urbanization pattern variations of China at the township level.