•Surface temperature characteristics are affected by many factors, such as building form and land use.•The spatial regression model can effectively explain the relationship between LST and each ...impact factor.•Rational planning of community land resources and landscape features can effectively mitigate urban heat islands.
Owing to increasing population densities and impervious surface areas, heat island effects increasingly dominate urban environments and hinder sustainable development. The urban spatial form plays an important role in mitigating urban heat islands. Taking Ganjingzi District, Dalian, as an example, this study considered urban spatial form at the community scale using spatial autocorrelation and spatial regression methods to explore 2003–2018 spatial and temporal differentiation characteristics and driving factors of Land Surface Temperature (LST). The LST of each community showed a gradually increasing trend; high values (>30°C) were concentrated in central and eastern areas; low values were (<25°C) was concentrated in the south and west. LSTs were influenced by spatial variables (e.g., land use); however, building form was only weakly related to LST. The global autocorrelation Moran’s I value for LST exceeded 0.7, indicating strong positive correlation in terms of spatial distribution. H-H and L-L LISA values were distributed in central and southern areas, respectively. The spatial error model (SEM) was a better fit than the spatial lag (SLM) or ordinary least squares models (OLS) and was used to explore these relationships. This study focuses on community surface temperature and hopes to provide a valuable reference for community planning, resource allocation and sustainable development.
The codend is the end and an essential part of the trawl, which plays a vital role in the selectivity and the storage of fish catches. Thus, to improve the trawl selectivity and control the ...probability of the fish escaping, it is essential to understand its hydrodynamic performance, fluttering motions, and spatial form of the codend structure. This study investigates the effects of the mesh size and simulated catch on hydrodynamic characteristics, net cross-section, and fluttering motions of the codend in the flume tank. Thus, three codends models were designed using polyethylene material with three different mesh sizes (60 mm, 80 mm, and 100 mm). Fourier analysis was performed via the Morlet wavelet analysis and the fast Fourier transform (FFT) method to observe the content of the wavelet coefficient variance and amplitude of the codend fluttering motions and time evolution of the drag forces. The results showed that at the empty stage, the decrease in mesh size led to an increase in drag force by 6.6%− 25.1%, an increase of the codend length by 2.6%− 4.3%, and a decrease in cross-sectional area by 14.9%− 51.7% of the codend. In addition, the time evolution was oscillatory quasi-periodic and related to the low-frequency activity. The codend drag oscillation frequency was mainly 0.30–0.45 Hz and decreased with the mesh size, and the amplitude and wavelet coefficient of the drag force increased with decreasing mesh size. For the codend with simulated catch, the shape of each codend was closed at the front of the mesh and bulging atthe rear contour, with the middle part of each codend being the most closed, and the cross-sectional area was about 15.1% of the empty codend (X = 104 cm). The codend position oscillates frequency was 0.30–0.45 Hz in X and Z directions. The drag oscillation frequency was mainly 0.30–0.45 Hz and synchronized with the position motion. The dominant frequencies of these codend motions and the associated drag showed low-frequency activities, with a small wavelet spectrum shifting from small-scale to large-scale motions. In addition, the codend with a greater mesh size showed a more stable behavior with a lower frequency and oscillatory motions than the codend with a small mesh size led to a decrease in drag on this codend. In addition, we recommend that the FFT can be used to obtain the amplitude and frequency directly for codend steady oscillation.
·Land surface temperature (LST) was similar in spring and autumn and was significantly lower in winter.·Urban spatial form (USF) indicators influence seasonal LST, and their correlation is ...significantly lower in autumn.·The three most important USF indicators for LST in spring and winter were SHDI, NL, and BMH, and their importance changed according to different scales.·By controlling urban building morphology of USF could effectively improve the urban thermal environment.
The urban heat island (UHI) effect is intensifying with increasing urbanization. As an important representation of the UHI effect and the urban thermal environment, it is critical to investigate the importance of evaluating urban spatial form (USF) indicators on land surface temperature (LST) to alleviate urban thermal environment problems. Therefore, in this study, we evaluated the importance of USF indicators from three perspectives: landscape pattern, building morphology, and social development, on LST at 10 grid scales in the main area of Xi'an City, using the XGBoost model. The results showed that: (1) LST was similar in spring and autumn, but significantly lower in winter. The distribution of high-temperature areas in the four seasons has its own characteristics, but the low-temperature areas are mainly distributed in the water bodies and parks in the north and south of the middle of the study area, which are less affected by the seasons. (2) Mean architecture height (MAH) is a seasonal stable factor with a cooling effect. The relationship between patch density (PD), landscape shape index (LSI), Shannon's diversity index (SHDI), contagion index (CONTAG), people density (POD), floor area ratio (FAR) and LST varies with seasons. The correlation between building density (BD) and LST is complex. (3) The degree of influence of the USF indicators on seasonal LST could be ranked in the following order: building morphology > landscape pattern > social development. (4) The appropriate size to study the relationship between USF and seasonal LST is 60 m. The highest contribution of USF to LST is building morphology, three indicators affect 43%–55% of LST. The findings of this study provide useful information for urban land-use planning and building layout, to mitigate the UHI effect.
Although considered an effective means to alleviate the urban heat island effect, the cold island effect of urban wetlands and its influencing factors remain unclear, especially in inland basin ...areas. Chengdu, a typical inland metropolis in Southwest China, was chosen as the case study area to study the cooling effect of wetlands and the impact of the spatial form of wetlands (e.g., size, shape, hydrological connectivity) on the cooling effect, and optimized strategies for the cooling efficiency of urban wetlands were proposed. The results showed that (1) the cooling intensity logarithmically increased with the wetland size and that the threshold value of efficiency (TVoE) was 1.47 ± 0.34 ha. (2) The hydrological connectivity significantly influenced the cooling effect, accounting for 28.2% of the total. (3) The wetlands within the high-density building areas had a relatively high cooling efficiency, while the green space could expand the cooling extent. We propose building a number of small and connected wetlands in densely built-up areas instead of building large and isolated wetlands to improve the cooling efficiency of urban wetlands.
•The threshold value of efficiency (TVoE) is 1.47 ± 0.34 ha in the inland megacity.•Building small wetlands is the important and cost-effective way to alleviate UHIs.•Hydrological connected wetlands exert higher cooling intensity than isolated ones.•The cooling efficiency in urban built-up areas is higher than nonurban areas.
In the context of global climate change, the increasing urban heat island (UHI) effect is a serious challenge to sustainable urban development. The construction of green roofs is an important means ...to optimize the urban thermal environment, especially in high-density urban areas. However, the cooling effect of green roofs in different urban spatial forms varies. Thus, the quantitative evaluation of the cooling effect of green roofs is significant for the scientific and effective mitigation of the UHI effect. This study took the central district of Chengdu City as a typical area, clearly classified urban spatial form types based on the LCZ theory, and quantified the relative land surface temperature (RLST) difference between before (2014) and after (2018) the implementation of green roofs based on Landsat 8 remote sensing image retrieval. Numerical analysis methods were used to statistically evaluate the cooling effect of green roofs under different urban spatial form types by GIS. The results showed that (1) the cooling effect of green roofs varied significantly among different urban spatial form types; (2) the best performance of the cooling effect of green roofs was in Compact Highrise (LCZ1), which could reduce RLST by 0.94 °C, while the worst was in Lightweight Lowrise (LCZ7). Based on the above performance of the cooling effect of green roofs, the construction of green roofs can be prioritized and zoned, and the design strategies of green roofs under different urban spatial form types can be proposed. Our study will provide a basis for developing design guidance for green roofs and scientific support for mitigating the urban thermal environment.
•Evaluation of the cooling effect of urban-scale green roofs based on actual construction results.•The cooling effect of green roofs differed significantly between different urban spatial form types.•The cooling effect of green roofs performed best in LCZ1-Compact Highrise (0.94 °C) and LCZ2-Compact Midrise (0.79 °C).•The cooling effect of green roofs performed worst in LCZ7- Lightweight Lowrise.
With urbanization, air quality problems attributed to traffic pollutants have increasingly attracted attention. Residential blocks are the basic spatial units directly related to the quality of the ...human living environment. Block spatial configuration optimization could effectively reduce the impact of pollutants on humans. The main objective of this study consists of investigating the impact of the different residential block typologies on traffic pollutant diffusion. This paper statistically analyzed various spatial morphological parameters of 236 real residential blocks in Wuhan and divided them into five block types via the k-means clustering method. Then, typical representative blocks of each type were identified. The wind environment and traffic pollutant concentration distribution in five typical representative blocks were simulated via the computational fluid dynamics (CFD) technique, and the influence of the different block types on pollutant diffusion was analyzed. This study found that residential blocks in Wuhan could be better classified according to four types of morphological parameters. The traffic pollutant diffusion routes and distribution in the different type blocks varied. Most pollutants entered the block podium through roof openings. The lateral sides of the adjacent external spaces of street canyons comprised the main channels through which traffic pollutants entered blocks. According to data analysis, the morphological indicators of the block clustering have a certain correlation with the dispersion of traffic pollutants. This paper introduced a novel workflow for traffic pollution studies in actual blocks that can be used as a reference for urban design practitioners.
•The distribution of traffic pollutants depends on the residential block typology.•Five typical representative residential blocks in Wuhan were extracted.•The adjacent external space of the street canyon is the main channel of traffic pollutant entry blocks.•The standard deviation of building height and footprint size were correlated with the pollutant concentration.
Introduction Considering that the population growth rate of the surrounding cities of Tabriz metropolis in 2006-2010 Sardroud, Ilkhichi, Osku, and Basmanj cities is 2, 1.8, 0.87 and 0.83, ...respectively, that the growth rate of Sardroud city is more than other all surrounding cities of the metropolis of Tabriz. The study of statistics related to Sardroud city shows the changes in population growth and stages of growth and development of the city so that the population has increased 2.6 times and the area of the city has increased 2.7 times during the 35 years (1976-2011). The increase of industries of Sardroud has played a significant role in the spatial-physical changes of Sardroud. By comparing the position of different economic sectors in Sardroud with East Azerbaijan province, the total growth rate of the reference economy in 1996-2006 has been equal to 1.6. Also, the province's economic structure during the mentioned period has always been negative and has had a downward trend. The variation rate of the economic structure in the province has been 3.126% in 1996-2006, in comparison with Sardroud city with a high variation coefficient of 7.164%. Population growth and increase in industries in Sardroud city have led to the unplanned constructions and many changes in the spatial-physical structure of the city, the destruction of agricultural lands (so that the area of agricultural lands and gardens in 1999 has been 6382180 square meters (65.2%) and, 3252635 square meters (26.35%) in 2011), and the emergence of various spatial-physical, environmental, social and economic problems, including land-use change, air pollution, water, soil, negative effects on green space, etc. Therefore, the current study can contribute to the logical understanding of these factors and recognizing the urban issues and problems, proper and rational dealing with these issues, and the thoughtful and tactical design for the future development of the city by recognizing and assessing the physical-spatial growth of the city in two periods of 1998 and 2012 and its changes over time. Data and Methods The research method is adjusted based on the nature, subject, and objectives of each research. Therefore, the current study is comparative-analytical research and is applied- developmental in terms of nature. The information related to the area, etc. were collected from the master plan (provided by the Rajan Ab Zagros consultant engineers) and other researchers and is classified based on the research requirements. Relative quantitative entropy model, Gini coefficient. Moran, Gary, and adjusted Gary coefficients were used to analyze the data. Results and Discussion Based on investigating the density ratio of Sardroud neighborhoods in 2011, the entropy value of Sardroud was 0.91 in 2011. The entropy value in 1999 has been 0.85 for Sardroud neighborhoods. Although it has had more concentration compared with 2011, the entropy value has been towards zero. However, its value is high and indicates the sprawl in the neighborhoods of Sardroud city. The obtained Gini coefficient for 1999 and 2011 is 0.35 and 0.36, respectively, indicating the unequal distribution in two decades. However, the Gini coefficient value for 2011 shows the unequal dispersion of the population comparing to 1999. Moran coefficient was calculated for 1999 and 2011. The obtained value for 1999 is 0.03, indicating the unipolar random accumulation pattern of Sardroud similar to most of the cities in Iran. Also, the obtained value for 2011 was 0.01, indicating the movement of Sardroud towards being multipolar in the future. Gary coefficient was also calculated for 1999 and 2011. The obtained values for 1999 and 2011 are 0.05 and 1.99, respectively. It indicates that in 2011, the city was closer to the sprawl dispersion pattern and shows that accumulation and density in Sardroud were more in 1999, comparing to 2011, and the urban sprawl increases in 2011. The calculations show that Sardroud city has been towards sprawl development, and this dispersion leads to the destruction of the agricultural lands and gardens. Conclusion According to the research findings, this type of urban structure has had many negative consequences in different environmental, social, and economic sectors, including destruction of the agricultural lands around the city and so on. - Taking efficient urban management policies to consider density, public transportation and land use that affect the urban form of Sardroud city. - Since the city is inevitable to grow and expand and population growth is always present in cities, it is necessary to use specific strategies and tools to manage the growth of cities and effectively control the sprawl expansion of cities, to avoid further waste and destruction of suitable suburban agricultural land around the cities and reduce the negative consequences of this type of urban development.
A quantitative study of urban vitality brings new insights for evaluating the external construction environment and internal development power of cities. However, it still has limited knowledge of ...the relations between people’s diverse urban life and urban vitality, although urban activities are often used as the proxy for urban vitality. This paper aims to deeply mine the content of urban social life and reveal the driving mechanism of urban vitality after inspecting human activities. We propose a general framework for exploring the spatial pattern and driving mechanism of urban vitality using multi-source big data. It builds a mapping relationship between various urban activities and urban vitality aspects, including economic and social. In addition, the physical environment (static) and human–land interaction (dynamic) indicators are designed to analyze the driving mechanism of urban vitality using the Geographically Weighted Regression model. The results show that the spatial pattern and driving factors of urban vitality are heterogeneous over space regarding both the economic and social aspects of our experimental study. This work provides us with multiple perspectives to understand the connotation of urban vitality and urges us to develop rational strategies to make the city more vital, coordinated, and sustainable.
PDF
