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1
Liu, Chang, et Kun Xu. « A Unified Gas Kinetic Scheme for Continuum and Rarefied Flows V : Multiscale and Multi-Component Plasma Transport ». Communications in Computational Physics 22, no 5 (31 octobre 2017) : 1175–223. http://dx.doi.org/10.4208/cicp.oa-2017-0102.
Texte intégralRésumé :
AbstractAs a continuation of developing multiscale method for the transport phenomena, a unified gas kinetic scheme (UGKS) for multi-scale and multi-component plasma simulation is constructed. The current scheme is a direct modeling method, where the time evolution solutions from the Vlasov-BGK equations of electron and ion and the Maxwell equations are used to construct a scale-dependent plasma simulation model. The modeling scale used in the UGKS is the mesh size scale, which can be comparable to or much larger than the local mean free path. As a result, with the variation of modeling scales in space and time through the so-called cell's Knudsen number and normalized Larmor radius, the discretized governing equations can recover a wide range of plasma evolution from the Vlasov equation in the kinetic scale to different-type of magnetohydrodynamic (MHD) equations in the hydrodynamic scale. The UGKS provides a general evolution model, which goes to the Vlasov equation in the kinetic scale and many types of MHD equations in the hydrodynamic scale, such as the two fluids model, the Hall, the resistive, and the ideal MHD equations. All current existing governing equations become the subsets of the UGKS, and the UGKS bridges these distinguishable governing equations seamlessly. The construction of UGKS is based on the implementation of physical conservation laws and the un-splitting treatment of particle collision, acceleration, and transport in the construction of a scale-dependent numerical flux across a cell interface. At the same time, the discretized plasma evolution equations are coupled with the Maxwell equations for electro-magnetic fields, which also cover a scale-dependent transition between the Ampére's law and the Ohm's law for the calculation of electric field. The time step of UGKS is not limited by the relaxation time, the cyclotron period, and the speed of light in the ideal-MHD regime. Our scheme is able to give a physically accurate solution for plasma simulation with a wide range of Knudsen number and normalized Larmor radius. It can be used to study the phenomena from the Vlasov limit to the scale of plasma skin depth for the capturing of two-fluid effect, and the phenomena in the plasma transition regime with a modest Knudsen number and Larmor radius. The UGKS is validated by numerical test cases, such as the Landau damping and two stream instability in the kinetic regime, and the Brio-Wu shock tube problem, and the Orszag-Tang MHD turbulence problem in the hydrodynamic regime. The scheme is also used to study the geospace environment modeling (GEM), such as the challenging magnetic reconnection problem in the transition regime. At the same time, the magnetic reconnection mechanism of the Sweet-Parker model and the Hall effect model can be connected smoothly through the variation of Larmor radius in the UGKS simulations. Overall, the UGKS is a physically reliable multi-scale plasma simulation method, and it provides a powerful and unified approach for the study of plasma physics.
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Zhu, Yajun, Chengwen Zhong et Kun Xu. « GKS and UGKS for High-Speed Flows ». Aerospace 8, no 5 (19 mai 2021) : 141. http://dx.doi.org/10.3390/aerospace8050141.
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The gas-kinetic scheme (GKS) and the unified gas-kinetic scheme (UGKS) are numerical methods based on the gas-kinetic theory, which have been widely used in the numerical simulations of high-speed and non-equilibrium flows. Both methods employ a multiscale flux function constructed from the integral solutions of kinetic equations to describe the local evolution process of particles’ free transport and collision. The accumulating effect of particles’ collision during transport process within a time step is used in the construction of the schemes, and the intrinsic simulating flow physics in the schemes depends on the ratio of the particle collision time and the time step, i.e., the so-called cell’s Knudsen number. With the initial distribution function reconstructed from the Chapman–Enskog expansion, the GKS can recover the Navier–Stokes solutions in the continuum regime at a small Knudsen number, and gain multi-dimensional properties by taking into account both normal and tangential flow variations in the flux function. By employing a discrete velocity distribution function, the UGKS can capture highly non-equilibrium physics, and is capable of simulating continuum and rarefied flow in all Knudsen number regimes. For high-speed non-equilibrium flow simulation, the real gas effects should be considered, and the computational efficiency and robustness of the schemes are the great challenges. Therefore, many efforts have been made to improve the validity and reliability of the GKS and UGKS in both the physical modeling and numerical techniques. In this paper, we give a review of the development of the GKS and UGKS in the past decades, such as physical modeling of a diatomic gas with molecular rotation and vibration at high temperature, plasma physics, computational techniques including implicit and multigrid acceleration, memory reduction methods, and wave–particle adaptation.
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Venugopal, Vishnu, et Sharath S. Girimaji. « Unified Gas Kinetic Scheme and Direct Simulation Monte Carlo Computations of High-Speed Lid-Driven Microcavity Flows ». Communications in Computational Physics 17, no 5 (mai 2015) : 1127–50. http://dx.doi.org/10.4208/cicp.2014.m391.
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AbstractAccurate simulations of high-speed rarefied flows present many physical and computational challenges. Toward this end, the present work extends the Unified Gas Kinetic Scheme (UGKS) to a wider range of Mach and Knudsen numbers by implementing WENO (Weighted Essentially Non-Oscillatory) interpolation. Then the UGKS is employed to simulate the canonical problem of lid-driven cavity flow at high speeds. Direct Simulation Monte Carlo (DSMC) computations are also performed when appropriate for comparison. The effect of aspect ratio, Knudsen number and Mach number on cavity flow physics is examined leading to important insight.
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Xu, Xiaocong, Yajun Zhu, Chang Liu et Kun Xu. « UGKS-Based Implicit Iterative Method for Multiscale Nonequilibrium Flow Simulations ». SIAM Journal on Scientific Computing 44, no 4 (août 2022) : B996—B1017. http://dx.doi.org/10.1137/21m1421398.
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Wang, Yi, Guoxi Ni et Xiao Xu. « A relativistic UGKS for stimulated Raman scattering in two dimension ». Computers & ; Fluids 235 (mars 2022) : 105261. http://dx.doi.org/10.1016/j.compfluid.2021.105261.
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Huang, Juan-Chen, Kun Xu et Pubing Yu. « A Unified Gas-Kinetic Scheme for Continuum and Rarefied Flows III : Microflow Simulations ». Communications in Computational Physics 14, no 5 (novembre 2013) : 1147–73. http://dx.doi.org/10.4208/cicp.190912.080213a.
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AbstractDue to the rapid advances in micro-electro-mechanical systems (MEMS), the study of microflows becomes increasingly important. Currently, the molecular-based simulation techniques are the most reliable methods for rarefied flow computation, even though these methods face statistical scattering problem in the low speed limit. With discretized particle velocity space, a unified gas-kinetic scheme (UGKS) for entire Knudsen number flow has been constructed recently for flow computation. Contrary to the particle-based direct simulation Monte Carlo (DSMC) method, the unified scheme is a partial differential equation-based modeling method, where the statistical noise is totally removed. But, the common point between the DSMC and UGKS is that both methods are constructed through direct modeling in the discretized space. Due to the multiscale modeling in the unified method, i.e., the update of both macroscopic flow variables and microscopic gas distribution function, the conventional constraint of time step being less than the particle collision time in many direct Boltzmann solvers is released here. The numerical tests show that the unified scheme is more efficient than the particle-based methods in the low speed rarefied flow computation. The main purpose of the current study is to validate the accuracy of the unified scheme in the capturing of non-equilibrium flow phenomena. In the continuum and free molecular limits, the gas distribution function used in the unified scheme for the flux evaluation at a cell interface goes to the corresponding Navier-Stokes and free molecular solutions. In the transition regime, the DSMC solution will be used for the validation of UGKS results. This study shows that the unified scheme is indeed a reliable and accurate flow solver for low speed non-equilibrium flows. It not only recovers the DSMC results whenever available, but also provides high resolution results in cases where the DSMC can hardly afford the computational cost. In thermal creep flow simulation, surprising solution, such as the gas flowing from hot to cold regions along the wall surface, is observed for the first time by the unified scheme, which is confirmed later through intensive DSMC computation.
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Sun, Wenjun, Song Jiang et Kun Xu. « An Implicit Unified Gas Kinetic Scheme for Radiative Transfer with Equilibrium and Non-Equilibrium Diffusive Limits ». Communications in Computational Physics 22, no 4 (28 juillet 2017) : 889–912. http://dx.doi.org/10.4208/cicp.oa-2016-0261.
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AbstractThis paper is about the construction of a unified gas-kinetic scheme (UGKS) for a coupled system of radiative transport and material heat conduction with different diffusive limits. Different from the previous approach, instead of including absorption/emission only, the current method takes both scattering and absorption/emission mechanism into account in the radiative transport process. As a result, two asymptotic limiting solutions will appear in the diffusive regime. In the strong absorption/emission case, an equilibrium diffusion limit is obtained, where the system is mainly driven by a nonlinear diffusion equation for the equilibrium radiation and material temperature. However, in the strong scattering case, a non-equilibrium limit can be obtained, where coupled nonlinear diffusion system with different radiation and material temperature is obtained. In addition to including the scattering term in the transport equation, an implicit UGKS (IUGKS) will be developed in this paper as well. In the IUGKS, the numerical flux for the radiation intensity is constructed implicitly. Therefore, the conventional CFL constraint for the time step is released. With the use of a large time step for the radiative transport, it becomes possible to couple the IUGKS with the gas dynamic equations to develop an efficient numerical method for radiative hydrodynamics. The IUGKS is a valid method for all radiative transfer regimes. A few numerical examples will be presented to validate the current implicit method for both optical thin to optical thick cases.
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Xiao, Tianbai. « A Well-Balanced Unified Gas-Kinetic Scheme for Multicomponent Flows under External Force Field ». Entropy 24, no 8 (12 août 2022) : 1110. http://dx.doi.org/10.3390/e24081110.
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The study of the evolution of the atmosphere requires careful consideration of multicomponent gaseous flows under gravity. The gas dynamics under an external force field is usually associated with an intrinsic multiscale nature due to large particle density variation along the direction of force. A wonderfully diverse set of behaviors of fluids can be observed in different flow regimes. This poses a great challenge for numerical algorithms to accurately and efficiently capture the scale-dependent flow physics. In this paper, a well-balanced unified gas-kinetic scheme (UGKS) for a gas mixture is developed, which can be used for the study of cross-scale multicomponent flows under an external force field. The well-balanced scheme here indicates the capability of a numerical method to evolve a gravitational system under any initial condition to the hydrostatic equilibrium and to keep such a solution. Such a property is crucial for an accurate description of multicomponent gas evolution under an external force field, especially for long-term evolving systems such as galaxy formation. Based on the Boltzmann model equation for gas mixtures, the UGKS leverages the space–time integral solution to construct numerical flux functions and, thus, provides a self-conditioned mechanism to recover typical flow dynamics in various flow regimes. We prove the well-balanced property of the current scheme formally through theoretical analysis and numerical validations. New physical phenomena, including the decoupled transport of different gas components in the transition regime, are presented and studied.
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Jiang, Dingwu, Pei Wang, Jin Li et Meiliang Mao. « Nonlinear Modeling Study of Aerodynamic Characteristics of an X38-like Vehicle at Strong Viscous Interaction Regions ». Entropy 24, no 6 (17 juin 2022) : 836. http://dx.doi.org/10.3390/e24060836.
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Strong viscous interaction and multiple flow regimes exist when vehicles fly at high altitude and high Mach number conditions. The Navier–Stokes(NS) solver is no longer applicable in the above situation. Instead, the direct simulation Monte Carlo (DSMC) method or Boltzmann model equation solvers are usually needed. However, they are computationally more expensive than the NS solver. Therefore, it is of great engineering value to establish the aerodynamic prediction model of vehicles at high altitude and high Mach number conditions. In this paper, the hypersonic aerodynamic characteristics of an X38-like vehicle in typical conditions from 70 km to 110 km are simulated using the unified gas kinetic scheme (UGKS), which is applicable for all flow regimes. The contributions of pressure and viscous stress on the force coefficients are analyzed. The viscous interaction parameters, Mach number, and angle of attack are used as independent variables, and the difference between the force coefficients calculated by UGKS and the Euler solver is used as a dependent variable to establish a nonlinear viscous interaction model between them in the range of 70–110 km. The evaluation of the model is completed using the correlation coefficient and the relative orthogonal distance. The conventional viscous interaction effect and rarefied effect are both taken into account in the model. The model can be used to quickly obtain the hypersonic aerodynamic characteristics of X38-like vehicle in a wide range, which is meaningful for engineering design.
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Li, Shi-Yi, et Qi-Bing Li. « Thermal non-equilibrium effect of small-scale structures in compressible turbulence ». Modern Physics Letters B 32, no 12n13 (10 mai 2018) : 1840013. http://dx.doi.org/10.1142/s0217984918400134.
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The thermal non-equilibrium effect of the small-scale structures in the canonical two-dimensional turbulence is studied. Comparative studies of Unified Gas Kinetic Scheme (UGKS) and GKS-Navier–Stokes (NS) for Taylor–Green flow with initial Ma = 1, Kn = 0.01 and decaying isotropic turbulence with initial [Formula: see text], [Formula: see text] show that the discrepancy exists both in small and large scales, even beyond the dissipation range to 10[Formula: see text] with accuracy to 8% in the SGS energy transfer of the decaying isotropic turbulence, illustrating the necessity for resolving the kinetic scales even at moderated [Formula: see text].
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Dai, Lianfu, et Huiying Wu. « Conserved method for specified heat flux boundary in UGKS simulation of microscale gas flow ». Computers & ; Fluids 237 (avril 2022) : 105363. http://dx.doi.org/10.1016/j.compfluid.2022.105363.
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Dong, Qidi, Heng Lu, Xiaohong Luo, Pengman He, Di Li, Linjia Wu, Yundi Wei et Xuli Chen. « Evaluation and Optimization of Green Space Fairness in Urban Built-Up Areas Based on an Improved Supply and Demand Model : A Case Study of Chengdu, China ». Sustainability 15, no 20 (18 octobre 2023) : 15014. http://dx.doi.org/10.3390/su152015014.
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Urban green space (UGS) is an important public infrastructure. However, the rapid development of cities and the insufficient supply and uneven distribution of UGSs have led to a mismatch between them and various needs, which has seriously affected environmental justice and social equity. This study discusses the fairness of UGS from the perspective of supply and demand and improves the theoretical framework of supply and demand combination evaluation. First, this study analyzes the supply of UGSs through accessibility analysis and evaluates their demand from both subjective and objective dimensions. Second, the fairness of UGS is analyzed from a Gini coefficient and spatial evaluation perspective. Finally, the location optimization of UGSs is performed, which provides strategic guidance for the improvement of UGSs in Chengdu. The research results based on Chengdu City show that the travel mode directly affects the supply range of UGSs and is reflected in their fairness. At the same time, in the case of a highly dense population, UGSs in the city are in short supply; that is, the equity is negatively correlated with the population. This study provides a new perspective to evaluate UGS fairness and can be a reference for UGS optimization decisions.
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Du, Hongyu, Fengqi Zhou, Wenbo Cai, Yongli Cai et Yanqing Xu. « Thermal and Humidity Effect of Urban Green Spaces with Different Shapes : A Case Study of Shanghai, China ». International Journal of Environmental Research and Public Health 18, no 11 (1 juin 2021) : 5941. http://dx.doi.org/10.3390/ijerph18115941.
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Research shows that urban green spaces (UGSs) provide a number of positive effects, including enhancing human thermal comfort levels by decreasing air temperature (AT) and increasing relative humidity (RH). However, research on how the shape of an UGS influences these effects is yet to be explored. This paper explores the principles and features behind this. The AT and RH surrounding an UGS within a horizontal scale of 20 m was explored. Microclimate field measurements around 35 UGSs in Shanghai, China were carried out. The samples covered the most applied types of UGSs—punctiform, linear, and planar. Comparison spots were selected away from the sampled UGSs. The effects were studied by data collection and statistical analysis. The results indicate that the shape of the UGS had significant impact on the Temperature Humidity Index (THI). In the summer, the amplitude of THI variation decreases with the distance to UGS. For punctiform UGS, a larger total area and existence of water body results in a lower THI. A wider, linear UGS with the same orientation as the direction of the prevailing wind contributes more to decrease the surrounding THI. The total area of planar UGS is not critical. A higher landscape shape index of a planar UGS is the critical point to achieve a lower THI. The results can serve as a reference when planning and designing future UGSs.
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Hou, Yunjing, Yiming Liu, Yuxin Wu et Lei Wang. « Assessing Inequality in Urban Green Spaces with Consideration for Physical Activity Promotion : Utilizing Spatial Analysis Techniques Supported by Multisource Data ». Land 13, no 5 (7 mai 2024) : 626. http://dx.doi.org/10.3390/land13050626.
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Urban green spaces (UGSs) play a significant role in promoting public health by facilitating outdoor activities, but issues of spatial and socioeconomic inequality within UGSs have drawn increasing attention. However, current methods for assessing UGS inequality still face challenges such as data acquisition difficulties and low identification accuracy. Taking Harbin as a case study, this research employs various advanced technologies, including Python data scraping, drone imagery collection, and Amap API, to gather a diverse range of data on UGSs, including photos, high-resolution images, and AOI boundaries. Firstly, elements related to physical activity within UGSs are integrated into a supply adjustment index (SAI), based on which UGSs are classified into three categories. Then, a supply–demand improved two-step floating catchment area (SD2SFCA) method is employed to more accurately measure the accessibility of these three types of UGSs. Finally, using multiple linear regression analysis and Mann–Whitney U tests, socioeconomic inequalities in UGS accessibility are explored. The results indicate that (1) significant differentiation exists in the types of UGS services available in various urban areas, with a severe lack of small-scale, low-supply UGSs; (2) accessibility of all types of UGSs is significantly positively associated with housing prices, with higher-priced areas demonstrating notably higher accessibility compared to lower-priced ones; (3) children may be at a disadvantage in accessing UGSs with medium-supply levels. Future planning efforts need to enhance attention to vulnerable groups. This study underscores the importance of considering different types of UGSs in inequality assessments and proposes a method that could serve as a valuable tool for accurately assessing UGS inequality.
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Venugopal, Vishnu, Divya Sri Praturi et Sharath S. Girimaji. « Non-equilibrium thermal transport and entropy analyses in rarefied cavity flows ». Journal of Fluid Mechanics 864 (14 février 2019) : 995–1025. http://dx.doi.org/10.1017/jfm.2018.1028.
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Thermal transport in rarefied flows far removed from thermodynamic equilibrium is investigated using kinetic-theory-based numerical simulations. Two numerical schemes – unified gas kinetic scheme (UGKS) and direct simulation Monte Carlo (DSMC) – are employed to simulate transport at different degrees of rarefaction. Lid-driven cavity flow simulations of argon gas are performed over a range of Knudsen numbers, Mach numbers and cavity shapes. Thermal transport is then characterized as a function of lid Mach number and Knudsen number for different cavity shapes. Vast deviations from the Fourier law – including thermal transport aligned along the direction of temperature gradient – are observed. Entropy implications are examined using Sackur–Tetrode and Boltzmann $H$-theorem formulations. At low Knudsen and Mach numbers, thermal transport is shown to be amenable to both entropy formulations. However, beyond moderate Knudsen and Mach numbers, thermal transport complies only with the Boltzmann $H$-theorem entropy statement. Two extended thermodynamic models are compared against simulation data and found to account for some of the observed non-equilibrium behaviour.
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Liu, Shuhao, Chang Su, Junhua Zhang, Shiro Takeda, Jiarui Liu et Ruochen Yang. « Cross-Cultural Comparison of Urban Green Space through Crowdsourced Big Data : A Natural Language Processing and Image Recognition Approach ». Land 12, no 4 (28 mars 2023) : 767. http://dx.doi.org/10.3390/land12040767.
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Understanding the relationship between environmental features and perceptions of urban green spaces (UGS) is crucial for UGS design and management. However, quantifying park perceptions on a large spatial and temporal scale is challenging, and it remains unclear which environmental features lead to different perceptions in cross-cultural comparisons. This study addressed this issue by collecting 11,782 valid social media comments and photos covering 36 UGSs from 2020 to 2022 using a Python 3.6-based crawler. Natural language processing and image recognition methods from Google were then utilized to quantify UGS perceptions. This study obtained 32 high-frequency feature words through sentiment analysis and quantified 17 environmental feature factors that emerged using object and scene recognition techniques for photos. The results show that users generally perceive Japanese UGSs as more positive than Chinese UGSs. Chinese UGS users prioritize plant green design and UGS user density, whereas Japanese UGS focuses on integrating specific cultural elements. Therefore, when designing and managing urban greenspace systems, local environmental and cultural characteristics must be considered to meet the needs of residents and visitors. This study offers a replicable and systematic approach for researchers investigating the utilization of UGS on a global scale.
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Lahoti, Shruti Ashish, Shalini Dhyani et Osamu Saito. « Exploring the Factors Shaping Urban Greenspace Interactions : A Case Study of Nagpur, India ». Land 13, no 10 (27 septembre 2024) : 1576. http://dx.doi.org/10.3390/land13101576.
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This study aims to investigate how urban residents interact with Urban Green Spaces (UGSs) in Nagpur, India, specifically focusing on the patterns of visitation and engagement. Data were collected via a face-to-face questionnaire survey using the Survey 123 app. The analysis included interaction (types of UGSs, visitation frequency, and UGS availability); engagement (activities); demographics (age, gender, and work status); and nature connection (self-reported) aspects. Using data from 2002 participants, the study employs statistical analyses using R software (4.3.2) to explore the correlations between these variables. The results revealed key factors influencing UGS usage, highlighting the interplay between environmental and social aspects. Neighborhood UGSs, proximity, and accessibility were found to be pivotal in promoting frequent visitation, while physical activity emerged as the most common activity among daily visitors. Older adults visited UGSs less frequently, suggesting potential barriers, while employed individuals visited more often. A strong association between nature connection and UGS interaction was highlighted, emphasizing the psychological and emotional aspects of UGS usage. For example, individuals who felt more connected to nature reported using UGSs for physical activities, mental relaxation, and socializing. These findings underscore the need for integrating UGSs within broader urban social-ecological systems, which means recognizing these spaces as vital components contributing to overall health and resilience and catering to the population’s diverse needs, ensuring that these spaces are accessible and enjoyable for all community members, including those from different cultural, age, and socioeconomic backgrounds. Additionally, fostering nature connectedness through education and exposure to natural environments is recommended to enhance UGS usage, supporting broader urban planning strategies to create sustainable and healthy urban environments.
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Ji, Yaou, Qianqian Sheng et Zunling Zhu. « Assessment of Ecological Benefits of Urban Green Spaces in Nanjing City, China, Based on the Entropy Method and the Coupling Harmonious Degree Model ». Sustainability 15, no 13 (4 juillet 2023) : 10516. http://dx.doi.org/10.3390/su151310516.
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Urban green spaces (UGSs) are an important spatial carrier for carbon sequestration in the national land space. The urban ecosystem is a highly harmonious composite ecosystem of nature, society, and the economy. Therefore, this study constructed an evaluation system of the UGS ecological benefit based on two subsystems–the natural environment and the social economy–in order to quantitatively evaluate the construction level of the UGS ecological benefit in Nanjing City and to reveal its temporal evolution characteristics. The entropy method was applied to assess the ecological benefits of UGSs in Nanjing City, China, from 2011 to 2020. The coupling harmonious degree model was utilized to analyze the dynamic coordination relations among subsystems. The Robust regression analysis was used to verify the evaluation results. The results showed that: (i) Between 2011 and 2020, UGS ecological benefits in Nanjing City exhibited a substantial and consistent upward trend. (ii) Between 2011 and 2020, the coupling harmonious degree among the subsystems of UGS ecological benefits in Nanjing City showed an overall rising trend of fluctuation. With the enhancing of the coupling harmonious degree among the subsystems of UGSs, the ecological benefit of UGSs will be significantly improved. (iii) The comprehensive evaluation score of the social and economic subsystem of UGS in Nanjing City was higher than that of the natural environment subsystem; this highlights the significant constraints posed by the natural environment on the construction of UGSs in Nanjing City. The research conclusion provides a decision basis for realizing the collaborative optimization of the natural environment and the social economy in Nanjing City and further promotes the sustainable development of the UGS ecological environment.
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Xue, Chenlu, Cheng Jin et Jing Xu. « Inequality in urban green space benefits : Combining street greenery and park greenery ». PLOS ONE 17, no 9 (19 septembre 2022) : e0273191. http://dx.doi.org/10.1371/journal.pone.0273191.
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In this paper, we measured the amount of urban green space (UGS), defined here as park greenery and street greenery, in the Guangzhou Beltway region using remote sensing image data and the green view index (GVI) based on human visual images. We also evaluated the benefits of UGS comprehensively considering park greenery and street greenery within the Guangzhou Beltway region. We then calculated the urban green space score (UGSS) by assessing the amount of street greenery and park greenery and then juxtaposing the score with the population distribution of the region. The results show inequities in the spatial distribution of UGSS values within the Guangzhou Beltway region. The benefit score of street greenery is low. The service area of parks can’t cover the whole study area. The comprehensive benefit score of UGS is composed of two parts, the park greenery score and the street greenery score, but the spatial distribution of UGSS values remains uneven. The UGS benefits enjoyed by one-half of the population of the study area are low, and the UGSS values of the more densely populated areas are not high.
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Li, Qing, Kaili Peng et Peng Cheng. « Community-Level Urban Green Space Equity Evaluation Based on Spatial Design Network Analysis (sDNA) : A Case Study of Central Wuhan, China ». International Journal of Environmental Research and Public Health 18, no 19 (28 septembre 2021) : 10174. http://dx.doi.org/10.3390/ijerph181910174.
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Urban green spaces (UGSs) provide numerous irreplaceable environmental and social benefits to humankind, but the lack of baseline information makes it difficult to propose a reasonable greening strategy so as to achieve an equitable allocation of community green spaces. This paper divides UGSs into three classes using the spatial design network analysis (sDNA) and quantifies the UGS accessibility of communities in central Wuhan. Based on these results and the Gini coefficient, we analyze the UGS equity of the spatial distribution at the community level, then propose future greening strategies both at the city and community levels. The results show that the railway station and old Wuhan city are the core areas of traffic network strength (TNS). UGSs are evenly distributed in the core areas of TNS, but the number of UGSs in non-core areas is small, and their distribution is relatively uneven, and the number of communities with medium UGS accessibility is the largest, carrying the densest residential population. Most communities perform well in terms of UGS equity, but the UGS equity of 163 communities, covering a population of more than one million, remains to be improved. The method and conclusions of this study will contribute to the future greening policy making of 965 communities in central Wuhan, thus promoting the orderly planning and high-quality construction of community living circles.
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Zhao, Jiacheng, Xiang Zhao, Shunlin Liang, Haoyu Wang, Naijing Liu, Ping Liu et Donghai Wu. « Dynamic Cooling Effects of Permanent Urban Green Spaces in Beijing, China ». Remote Sensing 13, no 16 (19 août 2021) : 3282. http://dx.doi.org/10.3390/rs13163282.
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Urban green spaces (UGSs) play a critical role in human thermal comfort, energy consumption and urban ecology. Although the heat mitigation capability of UGSs has been frequently reported, many of the current understandings are based on short-term observations, and the long-term temporal dynamics of UGS cooling effects are still lacking. This gap may cause over- or underestimation and largely ignores how the cooling effects change with climate change and urban growth. Accordingly, we used Landsat-based time series data to analyze the changes in permanent UGS greenness, surface-cooling effects and their biophysical responses in Beijing in the past 40 years (1984–2020). The results demonstrate segmented changes in UGS surface cooling that were mainly linked to the responses of canopy transpiration and albedo to vegetation conditions. During a rapid greening of UGSs in the recent two decades, transpiration cooling dominated albedo-induced warming to provide a discernable cooling enhancement. In addition, such enhancement showed seasonal differences ranging from less than 1 °C to more than 2 °C, and the most evident enhancement occurred on summer days (~2.4 °C) when vegetation is most needed to provide cooling. The highlighted dynamics of UGSs help urban planners better balance the maintenance costs and the environmental gains for UGS management.
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Linh, Nguyen Hoang Khanh, Pham Gia Tung, Huynh Van Chuong, Nguyen Bich Ngoc et Tran Thi Phuong. « The Application of Geographical Information Systems and the Analytic Hierarchy Process in Selecting Sustainable Areas for Urban Green Spaces : A Case Study in Hue City, Vietnam ». Climate 10, no 6 (12 juin 2022) : 82. http://dx.doi.org/10.3390/cli10060082.
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In recent years, there has been growing awareness about the roles and benefits of urban green spaces (UGSs), particularly in the context of mitigating the negative effects of climate change, which have become increasingly serious. In Vietnam, the government has allocated considerable resources to the development of UGSs in many cities. However, regarding implementation, UGS development in Vietnam faces many challenges; many cities find it difficult to meet the set criterion regarding the number of green spaces per capita. This research was conducted in Hue City, which is known as one of the greenest cities in Vietnam. The results show that there are twenty-one UGSs in Hue City (with a total area of 88.67 ha). These are located primarily along the Huong River and around the Hue Imperial Citadel. However, under government stipulations, the current number of UGSs is not considered sufficient in proportion to the local population, and will not accommodate the future growth of the population. We applied the analytic hierarchy process (AHP) along with the participation of local residents, using six criteria to map potential areas for future UGS planning. In this, the distance from existing residential areas to potential UGS locations is the most important criterion. The suitability map identified 684 hectares of Hue City as highly suitable for UGSs. This research also proposes a scenario for UGS planning in Hue based on retaining the existing green spaces combined with creating another 35 green spaces, comprising a total area of 167 hectares. This is to meet the needs of local residents by 2030.
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Huerta, Roberto E., Fabiola D. Yépez, Diego F. Lozano-García, Víctor H. Guerra Cobián, Adrián L. Ferriño Fierro, Héctor de León Gómez, Ricardo A. Cavazos González et Adriana Vargas-Martínez. « Mapping Urban Green Spaces at the Metropolitan Level Using Very High Resolution Satellite Imagery and Deep Learning Techniques for Semantic Segmentation ». Remote Sensing 13, no 11 (21 mai 2021) : 2031. http://dx.doi.org/10.3390/rs13112031.
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Urban green spaces (UGSs) provide essential environmental services for the well-being of ecosystems and society. Due to the constant environmental, social, and economic transformations of cities, UGSs pose new challenges for management, particularly in fast-growing metropolitan areas. With technological advancement and the evolution of deep learning, it is possible to optimize the acquisition of UGS inventories through the detection of geometric patterns present in satellite imagery. This research evaluates two deep learning model techniques for semantic segmentation of UGS polygons with the use of different convolutional neural network encoders on the U-Net architecture and very high resolution (VHR) imagery to obtain updated information on UGS polygons at the metropolitan area level. The best model yielded a Dice coefficient of 0.57, IoU of 0.75, recall of 0.80, and kappa coefficient of 0.94 with an overall accuracy of 0.97, which reflects a reliable performance of the network in detecting patterns that make up the varied geometry of UGSs. A complete database of UGS polygons was quantified and categorized by types with location and delimited by municipality, allowing for the standardization of the information at the metropolitan level, which will be useful for comparative analysis with a homogenized and updated database. This is of particular interest to urban planners and UGS decision-makers.
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Lian, Zixuan, et Xianhui Feng. « Urban Green Space Pattern in Core Cities of the Greater Bay Area Based on Morphological Spatial Pattern Analysis ». Sustainability 14, no 19 (28 septembre 2022) : 12365. http://dx.doi.org/10.3390/su141912365.
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Urban green spaces (UGSs) play a crucial role in supporting urban ecological systems and improving human well-being in cities. The spatial patterns of UGS are vital bases for analyzing various ecological processes. However, few studies have investigated morphological UGS patterns, especially in high-density cities. The Guangdong–Hong Kong–Macao Greater Bay Area (GBA) in China is one of the four major bay areas in the world. The aim of this study was to investigate the patterns and distributions of UGS in the core GBA cities (Guangzhou, Shenzhen, Zhuhai, Hong Kong, and Macao), and discuss the shortcomings and potential environmental impacts of the contemporary patterns of UGS. Morphological spatial pattern analysis (MSPA) was used to analyze the spatial UGS pattern. Seven MSPA metrics (core, islet, perforation, edge, loop, bridge, and branch) were assessed to measure morphological UGS patterns. The results showed that: (1) Hong Kong has the highest quality habitat, with a large and continuous distribution of UGSs, and a few smaller green spaces scattered in built-up areas; (2) Guangzhou’s UGSs are unevenly distributed, with large green spaces concentrated in the northern part of the city and many small, scattered green spaces distributed in built-up areas, demonstrating the most prominent pattern of green space fragmentation; (3) green space patches in the Shenzhen–Hong Kong region exhibit a relatively complex form; and (4) the UGS in Zhuhai–Macao is relatively discrete, and its connectivity is relatively low. These findings not only improve the depth of understanding of the spatial pattern of UGS in the GBA, but also confirm the applicability of MSPA in the analysis of spatial patterns of UGS.
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Nikolaishvili, D., N. Kharebava et M. Tsitsagi. « Urban green space availability and change patterns (a case study of Tbilisi, Georgia) ». Journal of Environmental Biology 45, no 4 (29 juin 2024) : 408–17. http://dx.doi.org/10.22438/jeb/45/4/mrn-5261.
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Aim: This research aimed to determine the distribution of different types of Urban green spaces (UGS) in Tbilisi districts, the distribution of access zones, the number of people who have access to UGSs, how current active housing construction affects UGSs and where reduction hotspots are located. Methodology: A 500-m buffer was set around UGSs. UGS changes were detected based on the NDVI from the 2017 and 2023 (June-August) PlanetScope imagery. The NDVI classification thresholds were -1 to 0.19 (nonvegetation), 0.19 to 0.5 (shrubs), and 0.5 or greater (trees). Thereafter, UGS patterns and reduction hotspots were determined in the district. Results: The percentage of access zones was lowest for Didube (5.4%) and highest for Nadzaladevi (14.7%). Chughureti (8.3%), Mtatsminda (8.8%), Isani (9.3%), and Gldani (9.9%) had similar numbers. The worst situation was observed in Samgori (8.9%) whereas the best situation was in Didube (69.8%). UGS degradation was high in Saburtalo (35.3%), and only a 0.6% decrease was found in Chughureti. Interpretation: UGSs are better distributed spatially and available to more people in "old" districts (Mtatsminda, Chughureti) and territories that were developed in the 1970s. The urban green spaces were neglected by contemporary urban sprawl. Though legislation has helped to preserve urban green spaces with status, but locations without status are victims of active development. Key words: Hotspots, Image analysis, Land use and land cover, Normalized difference vegetation index, Tbilisi, Urban green spaces
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Lategan, Louis Gerhardus, Zene Steynberg, Elizelle Juanee Cilliers et Sarel Stephanus Cilliers. « Economic Valuation of Urban Green Spaces across a Socioeconomic Gradient : A South African Case Study ». Land 11, no 3 (11 mars 2022) : 413. http://dx.doi.org/10.3390/land11030413.
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Urban green spaces (UGSs) may present economic contributions through increases in proximate property values, encapsulated in the proximity principle (PP). More data on the PP is required from the Global South, where the quality and equitable distribution of UGSs are important considerations. This paper investigates the PP in Potchefstroom, South Africa following a quantitative approach, by statistically analyzing municipal property valuations in three districts differentiated according to their socioeconomic status (SES). Districts are divided into sample areas where three zones are demarcated according to their proximity to a UGS. The results show that property valuations are generally higher for properties in closer proximity to UGSs in lower- and higher-income samples, but are lower in middle-income areas. Neighborhood characteristics and SES, UGS amenity and maintenance, ecosystem services and disservices, domestic garden area and residential property size may be connected to the confirmation or rejection of the PP. The rejection of the PP in middle-income areas indicates a need to improve public UGSs as amenity destinations. The results confirming the PP in low-income areas could incentivize expenditures to improve UGS area and quality to increase the willingness to pay for proximity to such spaces and, reciprocally, increase revenue from municipal property taxes.
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Peng, Lixian, Liwei Zhang, Xupu Li, Pengtao Wang, Wudong Zhao, Zhuangzhuang Wang, Lei Jiao et Hao Wang. « Spatio-Temporal Patterns of Ecosystem Services Provided by Urban Green Spaces and Their Equity along Urban–Rural Gradients in the Xi’an Metropolitan Area, China ». Remote Sensing 14, no 17 (31 août 2022) : 4299. http://dx.doi.org/10.3390/rs14174299.
Texte intégralRésumé :
Urban green spaces (UGSs) are indispensable for providing various ecosystem services (ESs) to society and city-dwellers. The equitable allocation of ESs provided by UGSs is a prerequisite for maintaining urban sustainability and human well-being. However, empirical studies have assessed the dynamics of UGS equity from ES facets, while neglecting to strengthen integrated evaluation indicators and coupled spatially explicit models. A framework was developed in this study to assess the spatio-temporal patterns of ESs provided by UGSs and their equity based on models of the Intelligent Urban Ecosystem Management System, location entropy, and the Gini coefficient. The results indicated that with urban spatial expansion, in each concentric circle, the values of three ES averages were generally the lowest in the megacity (Xi’an), and the values of carbon sequestration and the recreation averages in the medium-sized cities (Baoji and Xianyang) were also lower than in the small-sized city (Tongchuan). The inequity of ESs provided by UGSs was exacerbated from 2000 to 2020 in the Xi’an Metropolitan Area. The ES equity was the worst in Xi’an and the best in Tongchuan. Areas with extremely low CR location entropy occupied 67.01% in 2020. As cities spatially expanded, areas with extremely low ES location entropy generally increased in 2020. Additionally, the zero-value area of the ES Gini coefficient in Xi’an was the largest from 2000 to 2020. The ES Gini values mostly increased in the same concentric circle of each city in 2020, which demonstrates that equity declined. Spatial equity could be improved by diversifying UGS structures, promoting spatial matching between the ES supply and beneficiaries’ demands, and integrating UGSs into any available space in future UGS planning. The findings of the study could offer insights for optimizing the equitable provision of UGS resources and the targeted planning of urban greening.
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Ajmi, Rania, Faiza Khebour Allouche, Aude Nuscia Taîbi et Safa Bel Fekih Boussema. « Developing a Qualitative Urban Green Spaces Index Applied to a Mediterranean City ». Urban Science 7, no 4 (31 octobre 2023) : 115. http://dx.doi.org/10.3390/urbansci7040115.
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As a primary goal, urban green spaces (UGSs) have been linked to several aspects of inhabitants’ wellbeing. Quality could be a way to intervene in the UGS–human health interaction. For that purpose, we developed an urban green space quality index (UGS QIndex) applied to a Mediterranean region, Sousse City. This index was based on a set of criteria, indicators, and elements chosen after bibliographical research related to UGS quality assessment tools and their contribution to the Sustainable Development Goals. Then, we evaluated the quality of the Sousse Ramparts Gardens using the UGS QIndex. In fact, this index includes 41 elements grouped into 23 indicators covering seven thematic criteria: environmental regulating capacity, functional amenities, aesthetic amenities, landscape features, integration in its surroundings, development policy objectives, and space issues. According to the UGS QIndex, Bab El Gharbi garden exceeds Bab El Finga garden in terms of its scenery, aesthetics, and functionality. This index could be used by city planners to improve their UGS’s capacity to satisfy the inhabitants’ requirements. Otherwise, it needs to be enhanced and tailored to various types of UGSs and then applied to other Mediterranean cities, as well as cities suffering from UGS degradation.
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Korohoda, N. P. « Assessment of the effectiveness of ecosystem traffic noise reduce services in urban green spaces (on the example of Kyiv) ». Constructive geography and rational use of natural resources, no 4 (2024) : 69–74. http://dx.doi.org/10.17721/2786-4561.2024.4.special-10/19.
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Noise pollution is one of the most important factors in the deterioration of the quality of life in cities. Natural vegetation in urban green spaces (UGS) is an effective instrument for reducing road noise. The primary pollution field and the parameters of the UGS determine their different ability to reduce noise levels to comfortable or at least safe levels. One of the directions in the field of recreational research is to assess the effectiveness with which UGS provide noise reduction. Accordingly, the purpose of this paper is to provide such an assessment on the example of the UGS of Kyiv. In the study, the primary field of noise pollution from roads with different traffic intensities was determined. Modelling has shown that at the border of green spaces, noise values of up to 73 dB are observed in more than half of the city's UGSs. When determining the effectiveness of the noise reduction function, it was found that the majority of UGSs (75%) have a strong potential to reduce noise levels (from 0.7 to 0.8). The modelling results showed the high efficiency of green spaces in Kyiv in performing this function - 90% of the UGSs provide safe conditions for staying. Converting the efficiency values into volumes of ecosystem services (ES) based on the Harrington's desirability function allows us to understand that, given the current levels of traffic load and the parameters of UGS, the maximum volumes of noise reduction ecosystem services provided by vast majority green spaces in Kyiv (2982 objects).
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Zhai, Chang, Ruoxuan Geng, Zhibin Ren, Chengcong Wang, Peng Zhang, Yujie Guo, Shengyang Hong, Wenhai Hong, Fanyue Meng et Ning Fang. « Spatiotemporal Dynamics of Urban Green Space Coverage and Its Exposed Population under Rapid Urbanization in China ». Remote Sensing 16, no 15 (2 août 2024) : 2836. http://dx.doi.org/10.3390/rs16152836.
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Urban green spaces (UGSs) provide important support for the health of urban residents and the realization of sustainable urban development. However, the spatiotemporal pattern of urban resident exposure to UGSs in cities is unclear, especially at the national scale in China. Based on the annual 30 m resolution Normalized Difference Vegetation Index (NDVI) data of the Landsat satellite, we quantitatively analyzed the change in UGS coverage from 2000 to 2020 for 320 cities in China and combined it with population data to understand the changing patterns of urban population exposure to different UGS coverage. The results indicated that the average UGS coverage decreased from 63% to 44% from 2000 to 2020 in China, which could be divided into two stages: a rapid decline phase (2000–2014) and a progressive decline phase (2015–2020). Geographically, UGS coverage declined faster in southwestern and eastern cities than in other regions, particularly in medium-sized cities. We also found that urban pixel-based areas in cities with the highest UGS coverage (80–100%) decreased rapidly, and the proportion of the urban population exposed to the highest UGS coverage also declined significantly from 2000 to 2020. Urban pixel-based areas with low UGS coverage (20–40%) continued to expand, and there was a rapid increase in the proportion of the urban population exposed to low UGS coverage, with an increase of 146 million people from 2000 to 2020. The expansion of impervious surfaces had the most significant effect on the change in UGS coverage during different periods (2000–2020, 2000–2014, and 2015–2020). Natural factors such as precipitation, surface maximum temperature, and soil moisture also affected UGS coverage change. These findings provide insights into the impact of urbanization on the natural environment of cities, availability of UGS for residents, and sustainable urban development under rapid urbanization.
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Hecht, R., M. Artmann, P. Brzoska, D. Burghardt, S. Cakir, A. Dunkel, M. Gröbe et al. « A WEB APP TO GENERATE AND DISSEMINATE NEW KNOWLEDGE ON URBAN GREEN SPACE QUALITIES AND THEIR ACCESSIBILITY ». ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences VIII-4/W1-2021 (3 septembre 2021) : 65–72. http://dx.doi.org/10.5194/isprs-annals-viii-4-w1-2021-65-2021.
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Abstract. Urban green spaces (UGSs) can provide important ecosystem services for citizens and their well-being. To make use of these services according to UGS user demands, urban residents, tourists, and city administrations should know where UGSs are located, what qualities they have and how to reach them on convenient routes. This paper presents a novel digital infrastructure which combines and fuses different data to map UGSs and their qualities, and makes this information available in a web app. The interactive information service of the app aims to support citizens to explore and search for suitable UGSs and to provide routing options to reach them based on their preferences. Via implicit and explicit feedback functions included in the app, further information on UGS users' preferences can be collected to enhance the overall knowledge basis, while respecting data privacy issues. The underlying data base consists primarily of open and volunteered geographic data, which allows for transferability to other cities. This paper describes the system design, its back-end and front-end components, as well as the process of development and deployment of the system in two pilot cities. Preliminary results of the piloting in the two cities are presented, focusing on user preferences for UGSs searches. The added value of the web app for city residents and the role of the newly gained knowledge for urban planning is discussed and reflected upon.
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Kolcsár, Ronald András, Ákos K. Csete, Anna Kovács-Győri et Péter Szilassi. « Age-group-based evaluation of residents’ urban green space provision : Szeged, Hungary. A case study ». Hungarian Geographical Bulletin 71, no 3 (29 septembre 2022) : 249–69. http://dx.doi.org/10.15201/hungeobull.71.3.3.
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Analysis of urban green space (UGS) provision is becoming increasingly important from an urban-planning perspective, as processes related to climate change tend to worsen the urban heat-island effect. In the present study, we aimed to map the UGS provision of Szeged, Hungary, using a GIS-based complex approach. Different age groups, especially the elderly, have different demands on the ecosystem services and infrastructure of UGSs. To provide an in-depth assessment of UGS provision for planners, we analysed the UGS availability and accessibility, using subblock-level population data, which includes not only the total number of residents but also provides information about the age-group distribution for each building of the city. We delineated areas having different UGS provision levels (called provision zones) and assessed the age distribution of the residents living in each zone. We found that the residents within 2-min walking distance to public green spaces are older than expected by comparison to the age distribution of Szeged. In provision zones with abundant locally available UGSs (measured as UGS per capita within 50-m buffers), we found that the youngest (0–18 years) and oldest (≥ 61 years) inhabitants are overrepresented age groups, while the age group 19–40 has the lowest overall UGS provision within the city of Szeged. Our research, which has the potential to be adapted to other settlements, contributes to the identification of UGS-deficit areas in a city, thereby providing essential information for urban planners about where increases in UGS are most needed and helping to assess infrastructural enhancements that would be adequate for the locally most-dominant age groups.
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Chen, Songze, Kun Xu et Qingdong Cai. « A Comparison and Unification of Ellipsoidal Statistical and Shakhov BGK Models ». Advances in Applied Mathematics and Mechanics 7, no 2 (10 mars 2015) : 245–66. http://dx.doi.org/10.4208/aamm.2014.m559.
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AbstractThe Ellipsoidal Statistical model (ES-model) and the Shakhov model (Smodel) were constructed to correct the Prandtl number of the original BGK model through the modification of stress and heat flux. With the introduction of a new parameter to combine the ES-model and S-model, a generalized kinetic model can be developed. This new model can give the correct Navier-Stokes equations in the continuum flow regime. Through the adjustment of the new parameter, it provides abundant dynamic effect beyond the ES-model and S-model. Changing the free parameter, the physical performance of the new model has been tested numerically. The unified gas kinetic scheme (UGKS) is employed for the study of the new model. In transition flow regime, many physical problems, i.e., the shock structure and micro-flows, have been studied using the generalized model. With a careful choice of the free parameter, good results can be achieved for most test cases. Due to the property of the Boltzmann collision integral, the new parameter in the generalized kinetic model cannot be fully determined. It depends on the specific problem. Generally speaking, the Smodel predicts more accurate numerical solutions in most test cases presented in this paper than the ES-model, while ES-model performs better in the cases where the flow is mostly driven by temperature gradient, such as a channel flow with large boundary temperature variation at high Knudsen number.
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Liu, Wenrui, Baoquan Jia, Tong Li, Qiumeng Zhang et Jie Ma. « Correlation Analysis between Urban Green Space and Land Surface Temperature from the Perspective of Spatial Heterogeneity : A Case Study within the Sixth Ring Road of Beijing ». Sustainability 14, no 20 (19 octobre 2022) : 13492. http://dx.doi.org/10.3390/su142013492.
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Urban greening has been widely regarded as the most effective, lasting, and economical strategy for alleviating the effects of urban heat islands (UHIs). Previous studies on the cooling effect of urban green spaces (UGSs) tend to analyze the correlation between landscape metrics and land-surface temperature (LST) based on a global parameter estimation, while ignoring urban heterogeneity and autocorrelation. This study focuses on the sixth ring road of Beijing and uses Landsat 8 imagery to retrieve the LST and extract the position of UGSs. We propose a new approach to optimize the selection of landscape metrics, to identify the least and most effective metrics to establish a geographically weighted regression (GWR) model, and to plot the distribution of local regression coefficients to investigate the spatially heterogeneous cooling effects of greenspaces. The effect of UGS landscape metrics on the LST differs according to spatial location; the method enhances our understanding of the effects of UGS spatial configuration on UHIs and better guides the planning and construction of future UGSs.
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Chen, Qiang, Cuiping Zhong, Changfeng Jing, Yuanyuan Li, Beilei Cao et Qianhao Cheng. « Rapid Mapping and Annual Dynamic Evaluation of Quality of Urban Green Spaces on Google Earth Engine ». ISPRS International Journal of Geo-Information 10, no 10 (2 octobre 2021) : 670. http://dx.doi.org/10.3390/ijgi10100670.
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In order to achieve the United Nations 2030 Sustainable Development Goals (SDGs) related to green spaces, monitoring dynamic urban green spaces (UGSs) in cities around the world is crucial. Continuous dynamic UGS mapping is challenged by large computation, time consumption, and energy consumption requirements. Therefore, a fast and automated workflow is needed to produce a high-precision UGS map. In this study, we proposed an automatic workflow to produce up-to-date UGS maps using Otsu’s algorithm, a Random Forest (RF) classifier, and the migrating training samples method in the Google Earth Engine (GEE) platform. We took the central urban area of Beijing, China, as the study area to validate this method, and we rapidly obtained an annual UGS map of the central urban area of Beijing from 2016 to 2020. The accuracy assessment results showed that the average overall accuracy (OA) and kappa coefficient (KC) were 96.47% and 94.25%, respectively. Additionally, we used six indicators to measure quality and temporal changes in the UGS spatial distribution between 2016 and 2020. In particular, we evaluated the quality of UGS using the urban greenness index (UGI) and Shannon’s diversity index (SHDI) at the pixel level. The experimental results indicate the following: (1) The UGSs in the center of Beijing increased by 48.62 km2 from 2016 to 2020, and the increase was mainly focused in Chaoyang, Fengtai, and Shijingshan Districts. (2) The average proportion of relatively high and above levels (UGI > 0.5) in six districts increased by 2.71% in the study area from 2016 to 2020, and this proportion peaked at 36.04% in 2018. However, our result revealed that the increase was non-linear during this assessment period. (3) Although there was no significant increase or decrease in SHDI values in the study area, the distribution of the SHDI displayed a noticeable fluctuation in the northwest, southwest, and northeast regions of the study area between 2016 and 2020. Furthermore, we discussed and analyzed the influence of population on the spatial distribution of UGSs. We found that three of the five cold spots were located in the east and southeast of Haidian District. Therefore, the proposed workflow could provide rapid mapping and dynamic evaluation of the quality of UGS.
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Chen, Luyang, Lingbo Liu, Hao Wu, Zhenghong Peng et Zhihao Sun. « Change of Residents’ Attitudes and Behaviors toward Urban Green Space Pre- and Post- COVID-19 Pandemic ». Land 11, no 7 (11 juillet 2022) : 1051. http://dx.doi.org/10.3390/land11071051.
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The COVID-19 pandemic has changed and influenced people’s attitudes and behaviors toward visiting green spaces. This paper aims to explore the association between residents’ health and urban green spaces (UGS) through an in-depth study of changes in residents’ use of UGS under the influence of the COVID-19 pandemic. The Wuhan East Lake Greenway Park was selected as the location for the field survey and in-depth interviews. At the same time, an online survey was also conducted (total number = 302) regarding participants’ physical and mental health and their attitude and behavior toward the UGS. A paired sample t-test and binary logistic regression were performed to investigate the association between participants’ health and UGS during COVID-19. The results show that: (1) the COVID-19 pandemic has primarily changed the leisure patterns of parks, with potential impacts on the physical and mental health of participants; (2) the purpose, frequency, timing, and preferred areas of participants’ park visits have changed to varying degrees after the pandemic, highlighting the important role and benefits of UGSs; (3) the physical and mental health of participants and urban development issues reflected by UGS use are prominent. This study reveals that awareness of the construction and protection of UGSs is an important prerequisite for ensuring the health of urban residents.
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Liu, Shuhao, Chang Su, Ruochen Yang, Jianye Zhao, Kun Liu, Kwangmin Ham, Shiro Takeda et Junhua Zhang. « Using Crowdsourced Big Data to Unravel Urban Green Space Utilization during COVID-19 in Guangzhou, China ». Land 11, no 7 (29 juin 2022) : 990. http://dx.doi.org/10.3390/land11070990.
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Urban green spaces (UGSs) can meet the spiritual and cultural needs of citizens and provide various ecosystem services. In the context of the COVID-19 pandemic, the utilization of UGSs has been affected in various countries worldwide. This study considered 13 UGSs in Guangzhou, China, as examples. It obtained user check-in data by sampling the check-in pages of Sina Weibo locations using a Python-based web crawler program. The study was conducted for 731 days from 1 October 2019 to 30 September 2021, during different phases of the pandemic. Based on automated Chinese corpus recognition technology, statistical results were obtained after periodization and sentiment calculation. The study assessed the pandemic’s impact on the use of UGSs by analyzing the time, frequency, and emotions of residents visiting UGSs. The study concluded that the emotions of UGS users during COVID-19 tended to be positive. They tended to choose UGSs with low expected population density and visited UGSs on weekdays. Additionally, the religious attributes of UGSs also influenced their utilization.
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Yao, Tianci, Shengfa Li, Lixin Su et Hongou Zhang. « Changes in Urban Green Spaces in the Pearl River Delta Urban Agglomeration : From the Perspectives of the Area, Spatial Configuration, and Quality ». Remote Sensing 16, no 23 (22 novembre 2024) : 4369. http://dx.doi.org/10.3390/rs16234369.
Texte intégralRésumé :
Urban green spaces (UGSs) are integral to urban ecosystems, providing multiple benefits to human well-being. However, previous studies mainly focus on the quantity or quality of UGSs, with less emphasis on a comprehensive analysis. This study systematically examined the spatiotemporal UGS dynamics in the Pearl River Delta urban agglomeration (PRDUA) in China from the perspectives of the area, spatial configuration, and quality, using the high spatial resolution (30 m) Landsat-derived land-cover data and Normalized Difference Vegetation Index (NDVI) data during 1985–2021. Results showed the UGS area in both the old urban districts and expanded urban areas across all nine cities in the PRDUA has experienced a dramatic reduction from 1985 to 2021, primarily due to the conversion of cropland and forest into impervious surfaces. Spatially, the fragmentation trend of UGSs initially increased and then weakened around 2010 in nine cities, but with an inconsistent fragmentation process across different urban areas. In the old urban districts, the fragmentation was mainly due to the loss of large patches; in contrast, it was caused by the division of large patches in the expanded urban areas of most cities. The area-averaged NDVI showed a general upward trend in urban areas in nearly all cities, and the greening trend in the old urban districts was more prevalent than that in the expanded urban areas, suggesting the negative impacts of urbanization on NDVI have been balanced by the positive effects of climate change, urbanization, and greening initiatives in the PRDUA. These findings indicate that urban greening does not necessarily correspond to the improvement in UGS states. We therefore recommend incorporating the three-dimensional analytical framework into urban ecological monitoring and construction efforts to obtain a more comprehensive understanding of UGS states and support effective urban green infrastructure stewardship.
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Bressane, Adriano, Anna Isabel Silva Loureiro et Ricardo Almendra. « Community Engagement in the Management of Urban Green Spaces : Prospects from a Case Study in an Emerging Economy ». Urban Science 8, no 4 (26 octobre 2024) : 188. http://dx.doi.org/10.3390/urbansci8040188.
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Urban green spaces (UGSs) play a vital role in enhancing the quality of life in cities, particularly in rapidly urbanizing regions such as the Metropolitan Region of São Paulo (MRSP). However, significant challenges related to equitable management and access persist, often exacerbated by socio-environmental inequalities. While much of the existing literature on UGS management focuses on developed economies, there is a gap in our understanding of how community engagement influences UGS outcomes in emerging economies, which face unique socio-economic and infrastructural constraints. This study addresses this gap by investigating the impact of community engagement on UGS management in the MRSP, specifically examining how increased participation correlates with improved UGS access and reduced socio-environmental inequality. Utilizing survey data from 33 municipal environmental departments across the MRSP, this research applied correlation tests, generalized linear models, and a non-parametric analysis of variance to evaluate the relationships between community engagement, UGS coverage, and inequality. The findings reveal a moderate positive correlation between community engagement and UGS coverage, alongside a negative correlation with socio-environmental inequality. Increased levels of community participation were associated with greater access to UGSs and a reduction in disparities across socio-economic groups. These results underscore the potential of fostering community involvement in UGS management to promote urban equity and environmental sustainability in emerging economies, particularly through institutional support and transparent information sharing. Future research should focus on longitudinal studies to better understand the long-term effects of sustained community engagement and incorporate qualitative data from community members to provide a more comprehensive analysis of participatory processes. Additionally, expanding the scope of analysis to include informal and private green spaces will offer a more holistic understanding of urban greening dynamics.
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Gu, Kang, Jiamei Liu, Di Wang, Yue Dai et Xueyan Li. « Analyzing the Supply and Demand Dynamics of Urban Green Spaces Across Diverse Transportation Modes : A Case Study of Hefei City’s Built-Up Area ». Land 13, no 11 (17 novembre 2024) : 1937. http://dx.doi.org/10.3390/land13111937.
Texte intégralRésumé :
With the increasing demands of urban populations, achieving a balance between the supply and demand in the spatial allocation of urban green park spaces (UGSs) is essential for effective urban planning and improving residents’ quality of life. The study of UGS supply and demand balance has become a research hotspot. However, existing studies of UGS supply and demand balance rarely simultaneously improve the supply side, demand side, and transportation methods that connect the two, nor do they conduct a comprehensive, multi-dimensional supply and demand evaluation. Therefore, this study evaluates the accessibility of UGS within Hefei’s built-up areas, focusing on age-specific demands for UGS and incorporating various travel modes, including walking, cycling, driving, and public transportation. An improved two-step floating-catchment area (2SFCA) method is applied to evaluate the accessibility of UGS in Hefei’s built-up areas. This evaluation combines assessments using the Gini coefficient, Lorenz curve, location entropy, and local spatial autocorrelation analysis, utilizing the ArcGIS 10.8 and GeoDa 2.1 platforms. Together, these methods enable a supply–demand balance analysis of UGSs to identify areas needing improvement and propose corresponding strategies. The research results indicate the following: (1) from a regional perspective, there are significant disparities in the accessibility of UGS within Hefei’s urban center, with the old city showing more imbalance than the new city. Areas with high demand and low supply are primarily concentrated in the old city, which require future improvement; (2) in terms of travel modes, higher-speed travel (such as driving) offers better and more equitable accessibility compared to slower modes (such as walking), highlighting transportation as a critical factor influencing accessibility; (3) regarding population demand, there is an overall balance in the supply of UGS, with local imbalances observed in the needs of residents across different age groups. Due to the high specific demand for UGS among older people and children, the supply and demand levels in these two age groups are more consistent. This study offers valuable insights for achieving the balanced, efficient, and sustainable development of the social benefits of UGS.
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Chowdhury, Shaswati, Jaan-Henrik Kain, Marco Adelfio, Yevheniya Volchko et Jenny Norrman. « Greening the Browns : A Bio-Based Land Use Framework for Analysing the Potential of Urban Brownfields in an Urban Circular Economy ». Sustainability 12, no 15 (4 août 2020) : 6278. http://dx.doi.org/10.3390/su12156278.
Texte intégralRésumé :
The Circular Economy (CE) is expected to accelerate the use of resources with bio-based origin. Cities have an important role in such an economy, not only as main consumers but also because vegetation provides numerous ecosystem services essential for the well-being of urban dwellers. Urban lands are, however, heavily burdened with both past and present activities and ongoing urbanization. Retrofitting obsolete and potentially contaminated brownfields provides an opportunity to engage with bio-based land uses within the city. At the same time, plants are an important part of Gentle Remediation Options (GROs), a more sustainable alternative for managing contamination risks and restoring soil health. This paper (1) provides a tentative selection of Urban Greenspaces (UGSs) relevant for brownfields, and a compilation of ecosystem services provided by the selected UGSs, and (2) presents a framework covering the 14 selected bio-based land uses on brownfields, including GRO interventions over time. This framework provides three practical tools: the conceptualization of linkages between GROs and prospective UGS uses, a scatter diagram for the realization of 14 UGS opportunities on brownfields, and a decision matrix to analyze the requirements for UGS realization on brownfields.
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Pastore, Maria Chiara, Claudia Ida Maria Parenti et Corinna Patetta. « Measuring Accessibility of Green Spaces for the Health and Wellbeing of Inhabitants of the Milan Metropolitan Area ». Land 14, no 1 (6 janvier 2025) : 97. https://doi.org/10.3390/land14010097.
Texte intégralRésumé :
Several studies have recognised the importance of urban green spaces (UGSs) in modern cities. However, the distribution and accessibility of green spaces represent a challenge for the sustainable development of territories in terms of fair distribution, reducing inequalities, and mitigating the effects of climate change, such as urban heat islands and runoff. This research identifies every UGS capable of contributing to people’s physical and mental wellbeing in the Milan metropolitan area (MMA), one of the most densely populated areas in Europe. The method allows for the various UGSs to be identified and classified using a comparative approach that considers both formal and informal green spaces through a qualitative territorial analysis and the support of open access databases (satellite and thematic maps). Based on this classification, this contribution establishes an ‘accessibility map’ of the metropolitan area that determines the actual pedestrian accessibility of a UGS within 300 m. The results show that only 37% of the residential surface of the metropolitan area offers access to a UGS within a five-minute walk. This research aims to identify the most fragile segment of the MMA, which is pivotal for the tree-planting activities sponsored by the Forestami project.
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Shan, Juan, Zhuo Huang, Sibo Chen, Yue Li et Wenli Ji. « Green Space Planning and Landscape Sustainable Design in Smart Cities considering Public Green Space Demands of Different Formats ». Complexity 2021 (24 juin 2021) : 1–10. http://dx.doi.org/10.1155/2021/5086636.
Texte intégralRésumé :
The fast urban development leads to many complex problems. A smart city aims to solve these problems using scientific approaches. Urban Green Space (UGS) is a fundamental component of urban infrastructure. It needs to be upgraded simultaneously with the concept of the smart city. Methods of smart UGS planning and sustainable landscape design help integrate ecological performance and other functions of UGS. Smart UGS planning is a technical management tool and a human-centered smart application. A novel UGS classification method based on function combinations is proposed in the present work. Five types of UGS (Scenic UGS, Residential UGS, Commercial UGS, Office UGS, and Road UGS) in Baqiao District of Xi’an, Shaanxi Province, are selected as sample sites. Interviewees’ socio-economic attributes, visiting frequencies, and differences in demands are investigated. Eventually, the UGSs researched in this work are optimized based on public preferences and the current conditions of the sites. Results demonstrate the following. (1) The public’s preference for different types of UGS is different considerably. (2) Based on the public’s preference, Scenic UGS is improved in terms of quantity, function, and management; Residential UGS is upgraded regarding quantity and accessibility; and Commercial UGS, Office UGS, and Road UGS are improved in terms of quality. The results could provide methodological references for planning different types of UGS and innovative insights for smart UGS planning and sustainable landscape design.
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KOROHODA, Nataliia, Tetiana KUPACH et Olga KOVTONIUK. « TYPIFICATION OF URBAN GREEN SPACES IN THE ASSESSMENT OF CULTURAL ECOSYSTEM SERVICES (ON THE EXAMPLE OF KYIV) ». Ekonomichna ta Sotsialna Geografiya, no 91 (2024) : 30–40. http://dx.doi.org/10.17721/2413-7154/2024.91.30-40.
Texte intégralRésumé :
Cultural ecosystem services (CES) are the benefits that urban populations receive from urban green spaces (UGS), supporting their health through interaction with the environment. Due to the dissimilarity of conditions in different UGSs, which can only be determined during a direct survey, the assessment of CES is quite complex. Analysis of the factors affecting the volume of CES allows for the typing and grouping of UGSs with similar characteristics. This makes it possible to extrapolate the survey data from key areas to all green spaces of a particular kind. The purpose of the study is to develop a typification of urban green spaces for the assessment of CES. The assessment should be based not only on perception indicators, but also take into account the current state of green spaces. The objectives of the study are as follows: to take into account the natural and anthropogenic characteristics that determine the potential of green spaces to provide CES; to typify green spaces based on these characteristics; to substantiate a set of key areas whose research data would objectively reflect the potential of UGS to provide CES on the example of Kyiv. The basis for the allocation of three classes of UGS was the general classification of green spaces by functional feature. Such a division was used because it takes into account, on the one hand, the accessibility of the green space, and, on the other hand, the presence of characteristics that are used as calculation parameters in the CES assessment. Ecological zoning of territory became the basis for the allocation of 8 types of UGS in the CES assessment. After all, green areas of the same class can provide different amounts of CES, given the different perception of their natural features. The perception of different types of forests necessitated the division of such a type as "forest and forest park areas" into kinds. This, as well as the need to take into account the "age" of the green space and/or the building area in which it is located, led to the identification of 13 kinds of UGS. Based on this typification, a set of 63 key areas was identified, the data of which objectively reflect the potential of different kinds of UGS to provide CES. The data obtained within these sites are representative of other UGSs within the same kind.
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Rigolon, Alessandro, Matthew Browning, Kangjae Lee et Seunguk Shin. « Access to Urban Green Space in Cities of the Global South : A Systematic Literature Review ». Urban Science 2, no 3 (8 août 2018) : 67. http://dx.doi.org/10.3390/urbansci2030067.
Texte intégralRésumé :
This review examines disparities in access to urban green space (UGS) based on socioeconomic status (SES) and race-ethnicity in Global South cities. It was motivated by documented human health and ecosystem services benefits of UGS in Global South countries and UGS planning barriers in rapidly urbanizing cities. Additionally, another review of Global North UGS studies uncovered that high-SES and White people have access to a higher quantity of higher quality UGSs than low-SES and racial-ethnic minority people but that no clear differences exist regarding who lives closer to UGS. Thus, we conducted a systematic review to uncover (1) whether UGS inequities in Global North cities are evident in Global South cities and (2) whether inequities in the Global South vary between continents. Through the PRISMA approach and five inclusion criteria, we identified 46 peer-reviewed articles that measured SES or racial-ethnic disparities in access to UGS in Global South cities. We found inequities for UGS quantity (high-SES people are advantaged in 85% of cases) and UGS proximity (74% of cases). Inequities were less consistent for UGS quality (65% of cases). We also found that UGS inequities were consistent across African, Asian, and Latin American cities. These findings suggest that Global South cities experience similar inequities in UGS quantity and quality as Global North cities, but that the former also face inequities in UGS proximity.
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Huang, Junda, Xinghao Lu et Yuncai Wang. « Spatio−Temporal Changes and Key Driving Factors of Urban Green Space Configuration on Land Surface Temperature ». Forests 15, no 5 (4 mai 2024) : 812. http://dx.doi.org/10.3390/f15050812.
Texte intégralRésumé :
Changes in land cover by rapid urbanization have diminished the cooling effect of urban green spaces (UGS), exacerbating the upward trend of land surface temperature (LST). A thorough and precise understanding of the spatio-temporal characteristics of UGS and LST is essential for mitigating localized high temperatures in cities. This study identified the spatio-temporal changes in UGS configuration and LST in Shanghai from 2003 to 2022. The correlation between UGS configuration and LST was explored using spatial autocorrelation analysis and causal inference. The results show that (1) the high-temperature space had grown from 721 km2 in 2003 to 3059 km2 in 2022; (2) in suburbs, the largest area of UGS tended to decrease, while the number of patches tended to increase, indicating a distinct feature of suburbanization; (3) changes in the largest area of UGS had more significant spatial correlation, indicating that urban sprawl primarily impacts large UGSs; and (4) compared to the number and shape of UGS, changes in the largest area are the key factor influencing regional LST. These findings enrich the knowledge of the spatio−temporal relationship between the UGS configuration and its cooling effect in urbanization, offering valuable insights for building cooler cities.
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Misiune, Ieva. « Do We Need Different Urban Green Spaces Now ? A Case Study of Preferences during Pandemics ». Land 12, no 12 (26 novembre 2023) : 2106. http://dx.doi.org/10.3390/land12122106.
Texte intégralRésumé :
The role of public urban green spaces (UGSs) in providing various ecosystem services, especially those related to the physical and mental health of city dwellers, has increased during the COVID-19 pandemic. While research has analyzed shifts in UGS visitation and changes in people’s attitudes, there remains a noticeable gap in our understanding of the necessary adaptations required within UGS environments. This paper presents the survey results of Vilnius city residents (Lithuania) conducted in the final days of the quarantine in 2021 and discusses the findings in the broader context of other studies. The survey is centered on preferences for UGS qualities clustered into four groups. The results provide empirical evidence that UGS users highly prioritize ergonomic and ecological characteristics related to comfort and naturalness. However, the preferences differ between those who live close to UGS and those who live further away. In contrast, aesthetic and social qualities are of relatively lesser significance for all. Similar preferences have been identified in international studies, underscoring the global nature of this phenomenon that urban planners must consider when designing or enhancing local UGS.
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Bi, Shibo, Ming Chen, Zheng Tian, Peiyi Jiang, Fei Dai et Guowei Wang. « Optimizing Urban Green Spaces for Air Quality Improvement : A Multiscale Land Use/Land Cover Synergy Practical Framework in Wuhan, China ». Land 13, no 7 (8 juillet 2024) : 1020. http://dx.doi.org/10.3390/land13071020.
Texte intégralRésumé :
Air pollution, particularly fine particulate matter (PM2.5), poses a significant health risk, especially in high-density urban areas. Urban green space (UGS) can effectively mitigate this pollution. Despite their potential, strategies for effectively leveraging Land Use/Land Cover (LULC) optimization to combat PM2.5 remain largely unexplored. Ordinary least squares (OLS), geographically weighted regression (GWR) and multiscale geographically weighted regression (MGWR) were employed to investigate the spatial heterogeneity relationship between UGS conversion and PM2.5 fluctuations across various scales and evolutionary stages, developing a multiscale practical framework for LULC synergy in combating air pollution. The areas of UGSs to/from other LULCs, PM2.5 concentrations and corresponding variation zones exhibited significant spatial clustering. These UGS conversions explained more than 65% of the PM2.5 changes in the study area, peaking at 76.4% explanatory power in the fourth stage. Compared to global spatial analysis (OLS: 0–0.48), local spatial regression analysis significantly improved the R2 value (GWR: 0.32–0.75, MGWR: 0.48–0.90), but the fitting quality of local spatial regression analysis decreased with increasing scale, highlighting the importance of scale diagnosis. A 2 km scale was identified as optimal for assessing the spatial heterogeneity impact of UGS and other LULC conversions on PM2.5 changes. Conversion areas from water bodies and bare land to UGSs maintain stable local spatial properties at this scale (bandwidths: 44–99). Our research provides new insights into LULC management and planning, offering a coordinated approach to mitigating urban air pollution. Additionally, a practical framework was established for addressing spatially continuous variables such as PM2.5, revealing effective approaches for addressing urban environmental issues.
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Dong, Tian, Churan Feng, Bangguo Yue et Zhengdong Zhang. « An Evaluation Model of Urban Green Space Based on Residents’ Physical Activity ». Sustainability 16, no 10 (17 mai 2024) : 4220. http://dx.doi.org/10.3390/su16104220.
Texte intégralRésumé :
Urban green spaces (UGSs) possess a status in improving public health; thus, it is crucial to emphasize the evaluation of UGSs in terms of residents’ physical activity (PA). This study utilizes the semantic segmentation method and Geographic Information System tools to quantify the key values of UGSs, including aesthetic and attractions, natural world experience, nature conservation, encouraging physical activity, cultural value, and social value, which are set as the evaluation indexes to investigate their impacts on residents’ PA based on the six UGSs in Changsha city, Hunan Province, China. The PA-oriented UGS evaluation model is realized through the index optimal combination weights obtained by the Improved Combination Weighting Method of Game Theory, combining the subjective and objective weights from the Uncertainty Analytic Hierarchy Process method and Entropy Weight Method, respectively. By collecting and analyzing the exercise data of residents, we can accurately assess the level of residents’ PA and frequency within various UGSs. The proposed model herein has a positive significance for evaluating the value of public green space in residents’ PA in Changsha city and provides a reference for the construction of an urban green space evaluation model from multiple perspectives in the future.
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Garcia, Cecília Souza Gontijo, Patrícia Duarte de Oliveira Paiva, Jules Bruck et Rafael de Brito Sousa. « Distribution of urban green spaces : Comparative analysis between cities in different countries ». Ornamental Horticulture 27, no 1 (mars 2021) : 8–19. http://dx.doi.org/10.1590/2447-536x.v27i1.2151.
Texte intégralRésumé :
Abstract The presence of urban green spaces (UGS) increases the human’s contact with nature and provides numerous benefits to the society and the local environment. In this way, analyzing, planning and stimulating the implementation of UGS in cities is a fundamental action to improve the life quality of urban society. In this context, the aim was to analyze the situation and distribution of the green spaces of the universities cities of Lavras, Minas Gerais State (Brazil) and Newark, Delaware (USA). For data collection, researches performed field visits and used aerial photography to survey and analysis before calculating indicators including green area index (GAI) and green space ratio (GSR). The city of Lavras has a GAI of 0.54 m2 inh-1. The GSR value was 0.29%, not meeting the minimum of 5% required by local municipal law. Furthermore, there is a bad distribution of UGSs in the urban framework. However, in Newark, the distribution of UGSs is homogeneous and covers all regions of the city. The calculated GAI was 50.2 m² inh-1 and the GSR has met the 7% minimum required by its Newark Municipal Law. When comparing the two cities, in different countries and conditions it is concluded that Newark (DE) presents UGS indicators, GAI (m² inh-1) and GSR (%), higher than the values obtained in Lavras (MG), indicating the need for Government actions to increase these values.