Spatial And Temporal Heterogeneity Of The Impact Of Built Environment On Urban Vitality In Shenzhen

As an important foundation for economic development,cities are places where populations and large amounts of infrastructure gather.Since the reform and opening up of China,the rapid expansion of cities and towns has also led to many urban problems such as overpopulation,traffic congestion and resource depletion.Sensing urban dynamics is an effective means to understand urban development process,analyze urban development trend and optimize infrastructure configuration.With the continuous development of Internet and 3S technologies,spatio-temporal big data based on location information is widely applied to the study of urban problems.With its high coverage and high resolution,location big data provides a powerful information support for the study of urban dynamics.As the first special economic zone established since China’s reform and opening up,Shenzhen’s urbanization level is much higher than the national average and has become the youngest mega-city in China.Taking Shenzhen as an example,this study explores the spatio-temporal distribution characteristics of urban vitality from two perspectives,including the whole day on weekdays and weekends and different time periods within a day,based on multi-source spatio-temporal data such as Baidu heat data.A standard deviation model of vitality was introduced to investigate the single-day variation of urban vitality in Shenzhen,and a typological partitioning was conducted by combining vitality distribution and standard deviation distribution.Based on the "5Ds" built environment index system,the built environment factors were selected,and the mechanisms of the built environment factors on urban vitality were investigated by using the least squares regression model and the Geographically and Temporally Weighted Regression model to investigate the overall and local effects of the built environment factors on urban vitality,and the experimental results were combined to give insights into urban planning in Shenzhen.The results of the study showed that:(1)Urban vitality is characterized by high west and low east,high south and low north on both weekdays and rest days,and the high-vitality areas show aggregation and polycentricity.Secondly,urban vitality in different time periods in weekdays has obvious transformation characteristics in space,while there is no obvious time change pattern in weekends.(2)The single-day variation in urban vitality is more dramatic on weekdays than on weekends.Regions with high or higher standard deviation of vitality show high or higher vitality on both weekdays and rest days.The results of type-area division show that the characteristics of each type of partition are more similar on weekdays and rest days,among which,hotspot areas are richer in types and non-hotspot areas are more homogeneous in types.(3)In terms of the time dimension,the effects of different built environment factors on urban vitality show significant temporal differences.Population density,building density,bus station density and distance from subway station all show positive effects within one day,while distance from CBD shows negative effects within one day,and there are obvious diurnal differences.Road network density and functional mix show opposite effects at different time periods.(4)In terms of spatial dimension,the differences in the role of each built environment factor mostly depend on the differences between each traffic analysis zone.Among them,the effects of population density and building density on urban vitality are always positive,but the intensity of the effects show differences with spatial location.Road network density,functional mix,bus stop density,and distance to subway stations show positive and negative spatial differences.Distance from CBD has a negative effect overall,and a positive effect only in areas farther from CBD.(5)Suggestions for optimizing the vitality of areas with different vitality levels include:maintaining the vitality of "high vitality areas" such as Nanshan and Futian,optimizing the vitality of "general vitality areas" such as Bao’an and Longhua,and improving the vitality of "low vitality areas" such as Pingshan and Dapeng.From the perspective of influencing factors,urban planning insights such as "high density" but " not crowded",optimizing road network design,"mixed" but not "chaotic" multi-functional,improving public transportation accessibility,and building a polycentric urban structure are proposed for different areas.