| With the acceleration of urbanization,the population is gathering to the central city,the per capita green space area is decreasing,and the green space supply services can not meet the needs of the population in the central city.As an important part of urban green space,urban parks play an important role in improving the quality of urban life by providing natural environment and recreational places.Whether the layout of urban parks is reasonable and fair directly affects the health and happiness of urban residents.The inequity of green space supply in urban parks is becoming more and more serious.Therefore,it is of great significance to accelerate the construction of research methods and models of urban park layout,expand research scales and research areas,and improve the theoretical research of urban park green space equality from a multi-dimensional perspective,so as to improve the quality of urban ecological environment,the healthy life of urban residents and the construction of urban green space in China.Taking urban park green space as the research object,this paper comprehensively evaluates the spatial eauality under the multi-dimensional supply and demand characteristics,the dynamic evaluation and the optimization of spatial layout under the objective of maximizing equality as the main thread combining spatial analysis,dynamic analysis,model construction and empirical research to study the accessibility measurement model and particle swarm optimization.The comprehensive application of fruit in the evaluation and layout optimization of urban park green space equality provides scientific decision-making and thinking for urban green space planning.The main contents and conclusions of this paper include the following three parts:Firstly,this paper comprehensively evaluates the spatial equality of urban parks from the perspective of multi-dimensional supply and demand characteristics for four aspects: the supply characteristics of different functions of park green space,the demand characteristics of different residents,the travel characteristics of different modes of transportation and the spatial and temporal behavior characteristics of residents.Different functional characteristics perspective mainly selected two important functions of leisure and emergency shelter provided by park green space,and constructed different functional evaluation models to quantify the multi-scale and multi-scenario evaluation;different needs characteristics perspective of residents considered the different needs and use purposes of different groups of residents(such as adolescents,the elderly and the disabled)for park green space services.As well as the attractiveness of different types of parks to a certain group,the traditional two-step mobile search model is improved to evaluate the equality of a group of resident accessibility to park green space services according to the characteristics of a certain group.Considering the complexity of residents' choice of traffic modes from the perspective of residents' multi-mode travel characteristics,a multi-mode traffic improvement model is proposed and compared with empirical analysis.The accessibility of the traditional model under single mode of transportation and multitraffic improvement model is discussed.The spatial behavior characteristics of residents visiting park green space in different specific periods are considered from the perspective of spatial behavior characteristics of residents,and the spatial and temporal rules of service efficiency and equality of urban park green space are revealed.This part is guided by law discovery and takes model construction as the main research means to comprehensively evaluate the urban park green space equality under the multi-dimensional supply and demand characteristics,and to provide support for the construction of the optimization model of urban park green space layout equality maximization from different perspectives.The results show that:(1)Quantitative evaluation is made from two aspects: recreational function of urban park green space and emergency disaster prevention and refuge function.The results of spatial Equality Evaluation of park green space under Leisure and recreation function based on improved 2SFCA model with different functional coefficients show that: 1)The spatial distribution analysis of accessibility shows that there are obvious spatial polarization characteristics under three traffic modes,namely,relatively high accessibility index distributes in the center of the main urban area along the Yangtze River and the East Lake area,while inadequate accessibility area distributes in the main urban area.Peripheral areas,especially the eastern and northeastern and southwestern regions;2)Multi-scale analysis of accessibility equality shows that the smaller the scale,the more accurate the unreachable areas can be identified,and the closer the difference of accessibility revealed,the more conducive to urban green space planning.The results show that the streets with different accessibility are mainly located in the areas along the East Lake and the Yangtze River,and the communities in these areas need to be paid more attention to in the green space planning of urban parks.The results of spatial equity evaluation of green space of refuge parks based on minimum cost distance model under emergency refuge function show that: 1)The spatial distribution characteristics show that the minimum time cost spatial distribution characteristics of different traffic modes of community and grid scale are basically the same whether the park has actual walls or assumes no walls: the central residents of the main urban area along the Yangtze River reach the nearest park to take refuge.The time cost of difficulty is smaller than that of other places,which can be reached within 30 minutes;the time cost of arriving at the nearest park for refuge in the eastern,southwestern and western parts of the urban area is more than one hour;2)The statistical characteristics show that the smaller the scale of residents,the more obvious the wall effect is;at the same time,the intensity of the wall effect varies under different traffic modes,walking mode.The lower wall effect is the most obvious,followed by the bicycle mode,and the fence effect is relatively weak under the driving mode.3)The analysis of the influence of fence effect on supply and demand shows that the fence effect at 600 m and 3000 m buffer zone will affect the refuge capacity of the park,and it is more evident near the park with better refuge capacity,which mainly distributes near the East Lake Park,Botanical Garden and Zoo;4)The minimum time cost of residential areas near regional parks(such as Baodao Park,Wangjiadun Park,etc.)increases under the influence of fencing effect,and the increase of walking mode is larger than that of bicycle and bicycle modes.(2)Introduce Huff model to quantify the attraction of parks,and improve the 2SFCA model from two aspects of supply and demand.After comparing and verifying the results of traditional model and improved model with the young people as an example,this paper makes a thorough analysis on the equality and influencing factors of young people's access to park green space services at different ages in the main urban area of Wuhan.The results show that: 1)the improved model can identify more areas with insufficient services than the traditional model,which is consistent with the conclusion that the traditional model may overestimate the accessibility;2)the spatial and statistical comparative analysis results show that the high-value areas of adolescent accessibility index in three scenarios are clustered in the central area of the main urban area along the Yangtze River,and the low-accessibility areas.At the same time,the average of accessibility index under three scenarios is smaller,but the standard deviation is larger,which indicates that the difference between high and low accessibility index is larger,and there is a greater degree of inequality in accessibility index.3)The results of equality analysis in different age groups show that the 0-6 yearold youth groups are scattered,so apart from the central area of urban areas and the vicinity of large parks,most people(e.g.the east,north and south)have less access to parks,so the equality is relatively low;the 7-18 year-old youth groups are scattered in the central area of urban areas.Most of the people in these two groups have relatively good accessibility.4)The results of invisible factor analysis show that single factor has a weak impact on accessibility distribution,road density and house price factors have a strong positive impact on accessibility distribution,building density and population density have a weak negative impact;commercial land has a weak positive impact on the proportion of surrounding land use types,while residential land and public facilities land have a weak positive impact on accessibility distribution.Negative impact,indicating that the current park space allocation is not very good to meet the needs of most people.(3)Based on different modes of transportation,the traditional 2SFCA model is improved by weighting the supply coefficient and multi-mode of transportation.Combining the spatial and statistical comparison between the traditional model and the improved model,the accessibility index of different time thresholds is used to analyze the sensitivity of the improved model.On this basis,the community residents in the main urban area of Wuhan are analyzed.The equality of urban park green space services.The results show that: 1)Compared with multi-traffic model,the spatial characteristics of accessibility index of single traffic model are different,that is,the high-value areas of accessibility are concentrated in the center of the main urban area of Wuhan along the Yangtze River,and the low-value areas of accessibility are distributed in the central periphery of the main urban area,especially in the Eastern and southeastern parts;statistical analysis shows that the average and standard deviation of single traffic model are slightly different.The average and standard deviation of single traffic mode are slightly higher than those of multi-traffic improvement model.2)The reachability sensitivity analysis of multi-traffic improvement models with different time thresholds showed that the high-value reachability communities with 15-minute and 20-minute thresholds were significantly less than 25,30 and 35 minutes;with the increase of time thresholds,the average and standard deviation of reachability index increased slightly,and the number,area and number of underserved communities were becoming smaller and smaller.3)Under the 25-minute threshold multi-traffic improvement model,the community accessibility of urban residents in Wuhan to park green space services shows obvious spatial polarization characteristics: the high-value accessibility index area mainly distributes in the center of the city along the Yangtze River,i.e.within the 1st and 2nd Ring Rings and the East Lake area,and the communities with less access to park green space services mainly distribute outside the 3rd Ring of the city,especially in the 3rd Ring of the Yangtze River.It is in the East and south of the main urban area.According to the statistics of community accessibility index,at least 60% of the community accessibility index is below the average level,only a few communities have high accessibility.(4)The efficiency and equality of park green space under different residents' spacetime behavior were evaluated.The POE evaluation method based on mobile signaling data was adopted.Working days,rest days and holidays were selected as characteristic periods respectively.Through the analysis of the use efficiency and carrying capacity of park green space in different periods,the comparative analysis of the use efficiency of different park green space types and the residents with different attributes(including different years).Age and gender)Use Park efficiency and preference analysis to evaluate the actual use efficiency and equality of urban park green space.The results show that: 1)from the six-time monthly average park green space visiting capacity characteristics;from different periods of six-time park green space visiting capacity continues to rise;2)from the three specific periods and the monthly average resident visiting capacity characteristics,the number of visitors began to increase at 6 a.m.,and the number of visitors maintained a relative balance between 10 and 16 a.m.,that is,visitors during this period.The number of visitors has always maintained a large number,reaching a peak at 14 o'clock and gradually decreasing after 16 o'clock.3)The analysis of monthly average park green space visits by residents with different attributes shows that all residents prefer comprehensive and regional parks,and the average number of visitors at 13-16 hours is the largest,and the park activity is relatively high in different attributes;4)From different attributes,the average number of visitors at 13-16 hours is the highest.In terms of the park visiting density of residents in different periods,the residents tend to visit community parks close to their homes or work places,and then choose comprehensive parks and regional parks with large-scale recreational facilities and other facilities.Theme parks have relatively low visiting density due to their long distance and the need for fees.Secondly,considering the changes of supply and demand factors,a framework for dynamic equity measurement and driving factors analysis of urban park green space is constructed.Based on the analysis of supply of urban park green space,changes in demand of urban residents and changes in travel time cost in different periods,the dynamic equity measurement method composed of two-step mobile search and variation coefficient is synthetically applied.At present,the changing characteristics of urban park green space accessibility equality are analyzed,and the driving factors of the change are analyzed in depth by combining various spatial correlation analysis and statistical analysis methods.The main content of this part is "dynamic measurement--Analysis of driving factors".It mainly includes the following contents: first,analysis of changes in supply of urban park green space and demand of urban residents;second,analysis of changes in equality of urban resident accessibility to park green space services on grid scale;third,in-depth analysis of the influencing factors driving these changes,and the main selection of these driving factors.Policy and planning factors,land use change factors and socio-economic factors should be included.This part aims to reveal the evolution characteristics and influencing factors of urban park green space equality under supply and demand factors,and provide scientific guidance for scientific and rational realization of urban park green space layout optimization.The results show that:(1)According to the characteristics of supply and demand of park green space services,the urban population density and per capita park green space area increased rapidly during the study period,while the travel cost of residents decreased;(2)According to the change of accessibility of park green space services for grid-scale residents,the spatial distribution of accessibility of park green space services for residents using two modes of travel is divided.With the rapid expansion of cloth scale,accessibility index first decreases and then increases;(3)According to the variation coefficient of accessibility equality of park green space service space for residents at regional and street scales,the average accessibility index of green space service shows a trend of first decreasing and then rising under the walking scenario of residents in the main urban area of Wuhan during the study period,and the variation coefficient also shows a trend of first decreasing and then rising.High phenomena;(4)From the point of view of the factors affecting the changes of accessibility equity,the main factors affecting the accessibility of green space services in pedestrian and bicycle parks are policy and planning changes and the service capacity of parks themselves(mainly reflected in the quality and scale);the surrounding land use factors and some economic and social factors also have a slight impact.According to the summary of evolution law and influence mechanism,it is found that it is of great significance for the improvement of spatial equality of urban parks in the main urban area of Wuhan to formulate pertinent strategies to enhance the spatial equality of parks at regional and street scales,to pay attention to the preparation and adjustment of park planning in the period of urban expansion,and to the quality of life and health needs of urban parks of residents.Finally,based on the fact that the unfair distribution of urban park green space services is becoming more and more evident in different cities,and with the help of related optimization research theory and empirical analysis of public facilities optimization,this study tries to design the objective of multiple schemes by constructing the objective optimization model of equity maximization,and helps urban planners to determine the location and area of park green space with more optimized planning,so as to verify it.Based on the spatial network analysis and genetic algorithm,the validity of the model of rural residential spatial reconstruction and expansion was studied in the study area.Through the application of the model,the main conclusions are as follows:(1)Improving the quality of the park itself(e.g.increasing the types of relevant infrastructure and recreational facilities)and maximizing the size of the park as much as possible can reduce the invisible inequity to a lesser extent;(2)building new park green space in candidate sites during planning,even community parks can greatly improve the access of urban residents to park green space services.Achievable equality.(3)From the optimization results of different modes of transportation,residents can choose more convenient modes of transportation to improve equality to a certain extent,which shows that the accessibility of urban traffic network and the completeness of transportation system can also help to alleviate the accessibility inequity brought by the layout of park green space.Finally,according to the analysis of comprehensive fair evaluation,dynamic evaluation,analysis of influencing factors and optimization results under the multi-dimensional supply and demand characteristics,the Optimization Countermeasures of urban park green space layout are put forward. |
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