The Urban Heat Island (UHI) results in significant and sometimes dramatic increases in air temperature differences between the urban environment and its surrounding areas. The heat island structure may extend from the...The Urban Heat Island (UHI) results in significant and sometimes dramatic increases in air temperature differences between the urban environment and its surrounding areas. The heat island structure may extend from the ground to the top of roofs and canopy levels above ground. The Urban Heat Island effect is a leading factor in a long list of human health problems which are expected to increase with the rapid growth of urban populations and projected future climate change. Urban heat island studies can be conducted through either direct measurements of air temperature using automobile transects and weather station networks or through measuring surface temperature using airborne or satellite remote sensing. In this study, UHI was investigated over the Greater Cairo during both summer and winter seasons over two different dates. Landsat 7 ETM+ data were used and the mono-window algorithm was applied in the study. Results emphasis that both types of heat islands exist in the study area i.e. the surface and the atmospheric heat islands. Temperature differences ranged between 0.5°C to 3.5°C and these are much related to the existing land use/covers. It could be concluded that expansion of urban areas in Greater Cairo has led to increased thermal radiation of land surface on the highly populated areas.展开更多
The machining of hard-to-cut materials with a high degree of precision and high surface quality is one of the most critical considerations when fabricating various state-of-the-art engineered components.In this invest...The machining of hard-to-cut materials with a high degree of precision and high surface quality is one of the most critical considerations when fabricating various state-of-the-art engineered components.In this investigation,a comprehensive three-dimensional model was developed and numerically simulated to predict kerf profiles and material removal rates while drilling the aluminum-7075-T6 aerospace alloy.Kerf profile and material removal prediction involved three stages:jet dynamic flow modeling,abrasive particle tracking,and erosion rate pre-diction.Experimental investigations were conducted to validate the developed model.The results indicate that the jet dynamic characteristics and flow of abrasive particles alter the kerf profiles,where the top kerf diameter increases with increasing jet pressure and standoff distance.The kerf depth and hole aspect ratio increase with jet pressure,but decrease with standoff distance and machining time.Crosssectional profiles were characterized by progressive edge rounding and parabolic shapes.Defects can be minimized by utilizing high jet pressure and small standoff distance.The material removal rate increases with increasing jet pressure,abrasive particle size,and exposure time,but decreases with increasing standoff distance.展开更多
文摘The Urban Heat Island (UHI) results in significant and sometimes dramatic increases in air temperature differences between the urban environment and its surrounding areas. The heat island structure may extend from the ground to the top of roofs and canopy levels above ground. The Urban Heat Island effect is a leading factor in a long list of human health problems which are expected to increase with the rapid growth of urban populations and projected future climate change. Urban heat island studies can be conducted through either direct measurements of air temperature using automobile transects and weather station networks or through measuring surface temperature using airborne or satellite remote sensing. In this study, UHI was investigated over the Greater Cairo during both summer and winter seasons over two different dates. Landsat 7 ETM+ data were used and the mono-window algorithm was applied in the study. Results emphasis that both types of heat islands exist in the study area i.e. the surface and the atmospheric heat islands. Temperature differences ranged between 0.5°C to 3.5°C and these are much related to the existing land use/covers. It could be concluded that expansion of urban areas in Greater Cairo has led to increased thermal radiation of land surface on the highly populated areas.
基金supported by the Japan International Cooperation Agency(JICA)in the scope of the Egypt-Japan University of Science and Technology(E-JUST)and special thanks to Alexstone Co.,Ltd.for allowing us to use their machining center for experiments.
文摘The machining of hard-to-cut materials with a high degree of precision and high surface quality is one of the most critical considerations when fabricating various state-of-the-art engineered components.In this investigation,a comprehensive three-dimensional model was developed and numerically simulated to predict kerf profiles and material removal rates while drilling the aluminum-7075-T6 aerospace alloy.Kerf profile and material removal prediction involved three stages:jet dynamic flow modeling,abrasive particle tracking,and erosion rate pre-diction.Experimental investigations were conducted to validate the developed model.The results indicate that the jet dynamic characteristics and flow of abrasive particles alter the kerf profiles,where the top kerf diameter increases with increasing jet pressure and standoff distance.The kerf depth and hole aspect ratio increase with jet pressure,but decrease with standoff distance and machining time.Crosssectional profiles were characterized by progressive edge rounding and parabolic shapes.Defects can be minimized by utilizing high jet pressure and small standoff distance.The material removal rate increases with increasing jet pressure,abrasive particle size,and exposure time,but decreases with increasing standoff distance.
