| In the post-epidemic era,the study of urban complex functions is crucial to enhancing vitality and an important way to achieve sustainable urban development.The diversification and compostion of neighborhood functions can effectively improve the efficiency of land resource utilization,which is the main theme of urban governance in the era of stock planning.The social perception data represented by POI provides a new idea for the study of urban spatial structure at a fine scale.Therefore,how to use big data to dynamically and accurately identify urban composite functions and their heterogeneous effects has become a key problem to be solved urgently.However,the spatial expansion and evolution characteristics of urban composite functions represented by long-time series POI data need to be further explored.Therefore,taking 640 blocks in Kaifeng’s main urban area as the basic research unit,this paper constructs a functional agglomeration-diffusion analysis framework at the scale of urban blocks,uses POI data,remote sensing data,population density data,bus stop data and housing price data from 2005 to 2020,uses spatial statistical indicators and location entropy index to analyze the evolution characteristics and composite function changes of urban functions,and uses geographic detector method to explore the influencing factors of the number of functional elements and built environment on the spatial differentiation of composite functions.On this basis,targeted optimization suggestions are put forward.The main conclusions are as follows:(1)The difference in the distribution process of urban activities leads to the evolution of different functions of cities.Both commercial and public service functions have a central perimeter structure,which has a high degree of agglomeration in the old city.The pattern of residential functions gradually changed from relative equilibrium to agglomeration distribution,and the separation of employment and housing became more apparent.Industrial function as a whole spreads from the center of the city to the periphery,and finally forms an agglomeration center on the periphery of the city.(2)The overall composite level of urban functions is low,but there are differences in the degree of functional compounding of different types,and the composite function types mainly include comprehensive,hybrid and dual-function complex.From 2005 to 2020,the functional composite level of the main urban area of Kaifeng City decreased,and the number of high-composite blocks gradually decreased,and continued to shift to the periphery of the city.From the perspective of the degree of composite of various types of functions,the composite level between the three types of non-central functions of public service,residential and industrial is relatively good,especially the composite of public service and residential function is the most obvious,while the composite degree of commercial function and other types of functions is weak.Among the classified composite function types,most of the commercial function-led comprehensive and multi-function compatible hybrid types,dual-function composite types accounted for only 1%.It can be seen that the compatibility of commercial functions is strong,and the composite functional area gradually expands to the western new area and the northern area,scattered in the main urban area of the city,and there is no obvious agglomeration characteristics.(3)All kinds of urban composite functions are significantly affected by road design,and other factors have different influences on different types of composite functions,and the interaction can have different degrees of enhancement factors on urban composite functions,and the manifestation is mainly nonlinear enhancement.In terms of urban complexion,commercial development foundation,road design,population density and public transport accessibility have a significant impact on it.In the sub-type composite function,all factors significantly affect the degree of composite between non-central functions,while the urban function of commercial composite is only affected by other functional bases,population density and transportation accessibility of the compound.The interaction shows that the number of commercial functional elements and the number of public management functional elements have the strongest interaction,which can explain the spatial differentiation of 15.1% of the comprehensive composite degree of urban functions.For the composite of commercial center functions and other functions,the interaction is mainly manifested as nonlinear enhancement,and there are fewer two-factor enhancement types,while the interaction between non-central functions is increased.(4)The optimization of urban complex functions should start from two aspects: introducing commercial functional elements and strengthening the construction of transport systems,and at the same time use government macro-policy regulation and control to integrate big data into the whole process of urban planning and governance.It is necessary to actively introduce commercial functional elements,improve the auxiliary service functions around urban scenic spots,and promote the enhancement of regional vitality with the intrinsic connection of functions.It is necessary to properly carry out the construction of multiple functions in the old city,strengthen the connection between the new and old cities by strengthening the construction of the transportation system,and improve the accessibility of the city to promote the composite of urban functions.For different types of composite functions,optimization measures should focus on their characteristics.For urban functional types with industrial complexes,more industrial functional elements should be actively introduced,and urban functional types compounded with residential areas should pay attention to the distribution of residential functional elements.Based on POI data,this study constructs a functional agglomeration-diffusion analysis framework at the urban block scale,which can explore the agglomeration and diffusion process of multiple functions in the city.Quantitative measurement and optimization of urban composite functions provides a new method for dynamic monitoring of urban functions at fine scales.The study of the pattern evolution of urban complex functions and its influencing factors is conducive to the coordinated layout of urban functions,comprehensive and profound understanding of urban complex functions,and provides suggestions for improving the vitality of urban blocks and urban renewal.From the perspective of urban diversity,how to make full use of urban functional space is explored,so as to provide a basis for urban land space planning. |
