Impacts of Urban Form on Thermal Environment Near the Surface Region at Pedestrian Height: A Case Study Based on High-Density Built-Up Areas of Nanjing City in China

The continuous worsening of urban thermal environments poses a severe threat to human health and is among the main problems associated with urban climate change and sustainable development. This issue is particularly severe in high-density built-up areas. Existing studies on the thermal environments (temperature data extracted from satellite remote sensing images) are mainly focused on urban canopy areas (airspace below the average height of trees or buildings) rather than the near surface region (at pedestrian height). However, the main outdoor activity space of urban residents is the area near surface region. Hence, this study aims to investigate the influence of urban form (i.e., building density, height, and openness) on thermal environment near the surface region. The high-density built-up areas of a typical megacity (i.e., Nanjing) in China were selected, and the thermal environments of 26 typical blocks were simulated using ENVI-met software. Temperature field measurements were carried out for simulation validation. On this basis, a classified and comparative study was conducted by selecting the key spatial form elements that affect thermal environments. The results showed that in actual high-density built-up areas, single urban form parameter does not determine the thermal environments near the urban surface but mainly affected by the use (function) of space. For this study, the overall thermal environment of a street block is optimal when the building density is between 40% and 50% and the average building height is between 8 and 17 stories. Nonetheless, the urban form can be improved to optimize the overall effects on building functions and thermal environments. Furthermore, function-specific urban form optimization strategies were proposed to optimize thermal environments according to specific functional needs.

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Quantifying the Effects of Urban Form on Land Surface Temperature in Subtropical High-Density Urban Areas Using Machine Learning

Remote Sensing ◽

10.3390/rs11080959 ◽

2019 ◽

Vol 11 (8) ◽

pp. 959 ◽

Cited By ~ 12

Author(s):

Yanwei Sun ◽

Chao Gao ◽

Jialin Li ◽

Run Wang ◽

Jian Liu

Keyword(s):

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Urban Form ◽

Urban Areas ◽

Thermal Environment ◽

High Density ◽

Cooling Effects ◽

Urban Thermal Environment ◽

The Impact

It is widely acknowledged that urban form significantly affects urban thermal environment, which is a key element to adapt and mitigate extreme high temperature weather in high-density urban areas. However, few studies have discussed the impact of physical urban form features on the land surface temperature (LST) from a perspective of comprehensive urban spatial structures. This study used the ordinary least-squares regression (OLS) and random forest regression (RF) to distinguish the relative contributions of urban form metrics on LST at three observation scales. Results of this study indicate that more than 90% of the LST variations were explained by selected urban form metrics using RF. Effects of the magnitude and direction of urban form metrics on LST varied with the changes of seasons and observation scales. Overall, building morphology and urban ecological infrastructure had dominant effects on LST variations in high-density urban centers. Urban green space and water bodies demonstrated stronger cooling effects, especially in summer. Building density (BD) exhibited significant positive effects on LST, whereas the floor area ratio (FAR) showed a negative influence on LST. The results can be applied to investigate and implement urban thermal environment mitigation planning for city managers and planners.

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High-Resolution Simulations of the Urban Thermal Climate in Suzhou City, China

Atmosphere ◽

10.3390/atmos10030118 ◽

2019 ◽

Vol 10 (3) ◽

pp. 118

Author(s):

Yan Chen ◽

Ning Zhang ◽

Yan Zhu

Keyword(s):

High Resolution ◽

Urban Areas ◽

Urban Climate ◽

Urban Canopy ◽

High Density ◽

Urban Heat Islands ◽

Medium Density ◽

Heat Islands ◽

Thermal Climate ◽

Urban Heat

City thermal discomfort conditions have been exacerbated by the rapid urbanization processes in China. High-resolution urban thermal climate simulations can help us to understand urban climate features and produce better urban designs. In this paper, a single-layer urban canopy model (UCM) combined with Landsat satellite data and high-resolution meteorological forcing data was used to simulate very-high-resolution characteristics of temperature and humidity at the urban canopy level, and the heat index at the pedestrian level was also estimated. The research shows that the National center of environmental forecasting, Oregon state university, Air force and Hydrological research lab (NOAH)-UCM model can simulate the distribution of meteorological elements for different land uses in a fine and effective manner, making it an effective approach to obtaining the fundamental data for urban climate analysis. The spatial distribution pattern of urban heat islands in Suzhou is highly consistent with urban land cover fraction. High-density and medium-density urban areas are centers of urban heat islands, and the annual number of high-temperature days and heat indices over the high-density and medium-density urban areas are markedly higher than those in low-density cities and suburbs, indicating that urban development has a significant impact on the urban thermal environment.

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Surface Conversion Effects in Plasma-Damaged p-GaN

MRS Proceedings ◽

10.1557/proc-595-f99w10.8 ◽

1999 ◽

Vol 595 ◽

Author(s):

X.A. Cao ◽

S.J. Pearton ◽

G.T. Dang ◽

A.P. Zhang ◽

F. Ren ◽

...

Keyword(s):

Electrical Properties ◽

Thermal Annealing ◽

Surface Region ◽

High Density ◽

Wet Etching ◽

Ion Fluxes ◽

Type Conversion ◽

Near Surface ◽

Ion Energies ◽

Surface Conversion

AbstractThe near-surface (400-500Å) of p-GaN exposed to high density plasmas is found to become more compensated through the introduction of shallow donors. At high ion fluxes or ion energies there can be type-conversion of this surface region. Two different methods for removal of the damaged surface were investigated; wet etching in KOH, which produced self-limiting etch depths or thermal annealing under N2 which largely restored the initial electrical properties.

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Surface Conversion Effects in Plasma-Damaged p-GaN

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300004762 ◽

2000 ◽

Vol 5 (S1) ◽

pp. 558-569 ◽

Cited By ~ 1

Author(s):

X.A. Cao ◽

S.J. Pearton ◽

G.T. Dang ◽

A.P. Zhang ◽

F. Ren ◽

...

Keyword(s):

Electrical Properties ◽

Thermal Annealing ◽

Surface Region ◽

High Density ◽

Wet Etching ◽

Ion Fluxes ◽

Type Conversion ◽

Near Surface ◽

Ion Energies ◽

Surface Conversion

The near-surface (400-500Å) of p-GaN exposed to high density plasmas is found to become more compensated through the introduction of shallow donors. At high ion fluxes or ion energies there can be type-conversion of this surface region. Two different methods for removal of the damaged surface were investigated; wet etching in KOH, which produced self-limiting etch depths or thermal annealing under N2 which largely restored the initial electrical properties.

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Applications of Fisheye Imagery in Urban Environment: A Case Based Study in Nanjing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.4870 ◽

2013 ◽

Vol 726-731 ◽

pp. 4870-4874

Author(s):

Xiao Dong He ◽

Shuang He Shen ◽

Shi Guang Miao

Keyword(s):

Urban Environment ◽

Environmental Planning ◽

Thermal Environment ◽

Urban Climate ◽

High Density ◽

View Factor ◽

Environment Analysis ◽

Urban Structures ◽

Outdoor Spaces ◽

Outdoor Thermal Environment

Urban greening helps cooling and humidifying the air; shading provided by buildings also affects outdoor thermal environment. Therefore, they both influence the thermal perceptions of people in outdoor spaces. The sky view factor (SVF) is a commonly used parameter in the research on urban climate, indicates the relationship between the visible area of the sky and the area covered by urban structures. The current paper first gives a brief introduction of the SVF and fisheye imagery. It then describes a method conducted to estimate SVF for urban environment analysis by using fisheye lenses and applying the ENVI platform as well. Finally, micro-climate characteristics over three typical urban underlying surfaces, including sunlit asphalt roads, shaded roads by building and by chinars were analyzed based on on-site observations. For a high-density city such as Nanjing, the present study reveals that the higher building shaded, chinar canopy density, and the lower sky transmittance, humidification and cooling of the air is more significant under the same climate condition and the same road. For benefiting urban environmental planning and assessment in high-density cities, more cases simulation with different combinations of factors are needed, which can provide a set of better greening guides and the optimal shading level.

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Preparation of cross-sectional samples for near-surface TEM studies

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012669x ◽

1987 ◽

Vol 45 ◽

pp. 380-381

Author(s):

R.C. Dickenson ◽

K.R. Lawless

Keyword(s):

Standard Sample ◽

Surface Region ◽

Specimen Preparation ◽

Thick Sheet ◽

Drill Bit ◽

Sample Holder ◽

Metal Interface ◽

Cross Sectional ◽

Near Surface ◽

Cold Worked

In thermal oxidation studies, the structure of the oxide-metal interface and the near-surface region is of great importance. A technique has been developed for constructing cross-sectional samples of oxidized aluminum alloys, which reveal these regions. The specimen preparation procedure is as follows: An ultra-sonic drill is used to cut a 3mm diameter disc from a 1.0mm thick sheet of the material. The disc is mounted on a brass block with low-melting wax, and a 1.0mm hole is drilled in the disc using a #60 drill bit. The drill is positioned so that the edge of the hole is tangent to the center of the disc (Fig. 1) . The disc is removed from the mount and cleaned with acetone to remove any traces of wax. To remove the cold-worked layer from the surface of the hole, the disc is placed in a standard sample holder for a Tenupol electropolisher so that the hole is in the center of the area to be polished.

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The Effects of Ion Implantation on the Surface Features of Inconel 600

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118333 ◽

1985 ◽

Vol 43 ◽

pp. 288-289

Author(s):

John D. Rubio

Keyword(s):

Grain Boundary ◽

Ion Implantation ◽

Nuclear Power ◽

Power Plants ◽

Surface Region ◽

Selective Dissolution ◽

Boundary Region ◽

Near Surface ◽

Inconel 600 ◽

Steam Generator Tubing

The degradation of steam generator tubing at nuclear power plants has become an important problem for the electric utilities generating nuclear power. The material used for the tubing, Inconel 600, has been found to be succeptible to intergranular attack (IGA). IGA is the selective dissolution of material along its grain boundaries. The author believes that the sensitivity of Inconel 600 to IGA can be minimized by homogenizing the near-surface region using ion implantation. The collisions between the implanted ions and the atoms in the grain boundary region would displace the atoms and thus effectively smear the grain boundary.To determine the validity of this hypothesis, an Inconel 600 sample was implanted with 100kV N2+ ions to a dose of 1x1016 ions/cm2 and electrolytically etched in a 5% Nital solution at 5V for 20 seconds. The etched sample was then examined using a JEOL JSM25S scanning electron microscope.

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Microstructural changes of Aluminum Nitride after laser irradiation and electroless copper deposition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170918 ◽

1994 ◽

Vol 52 ◽

pp. 636-637

Author(s):

S. Cao ◽

A. J. Pedraza ◽

L. F. Allard

Keyword(s):

Aluminum Nitride ◽

Laser Irradiation ◽

Electroless Deposition ◽

Thermal Evaporation ◽

Surface Region ◽

Near Surface ◽

Laser Patterning ◽

Electroless Copper ◽

Excimer Laser Irradiation ◽

Laser Effect

Excimer-laser irradiation strongly modifies the near-surface region of aluminum nitride (AIN) substrates. The surface acquires a distinctive metallic appearance and the electrical resistivity of the near-surface region drastically decreases after laser irradiation. These results indicate that Al forms at the surface as a result of the decomposition of the Al (which has been confirmed by XPS). A computer model that incorporates two opposing phenomena, decomposition of the AIN that leaves a metallic Al film on the surface, and thermal evaporation of the Al, demonstrated that saturation of film thickness and, hence, of electrical resistance is reached when the rate of Al evaporation equals the rate of AIN decomposition. In an electroless copper bath, Cu is only deposited in laser-irradiated areas. This laser effect has been designated laser activation for electroless deposition. Laser activation eliminates the need of seeding for nucleating the initial layer of electroless Cu. Thus, AIN metallization can be achieved by laser patterning followed by electroless deposition.

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