Urban areas usually experience higher temperatures compared with their rural surroundings; this is characterized as urban heat islands （UHIs）, which are the result of environmental overheating due to anthropic activ...Urban areas usually experience higher temperatures compared with their rural surroundings; this is characterized as urban heat islands （UHIs）, which are the result of environmental overheating due to anthropic activities. Urban areas,which are characterised by massive construction that reduce local vegetation coverage, are subject to the absorption of a large amount of solar radiation,which is only partially released into the atmosphere by radiation in the thermal infrared.展开更多
Based on the observation data of meteorological observation stations in Jining City during 1970-2024,MK mutation test and principal component analysis(PCA)were used to study the evolution characteristics of urban heat...Based on the observation data of meteorological observation stations in Jining City during 1970-2024,MK mutation test and principal component analysis(PCA)were used to study the evolution characteristics of urban heat island intensity(UHII)and the contribution rate of various influencing factors in Jining City over the past 55 years.The results show that from 1970 to 2024,the UHII in Jining City generally rose at a rate of 0.1℃/10 a.On the interannual scale,the correlation between temperature and UHII was most significantly positive.On the seasonal scale,there was a strong negative correlation between wind speed and UHII.PCA reveals that temperature had a significant positive impact on the increase of UHII in Jining City.展开更多
The magnetostrictive properties of <112> axial aligned Tb0.3Dy0.7(Fe1-xMx)1.95(M=Mn, Al, x=0～ 0.15) alloys prepared by directional solidification are reported. The influence of heat treatment on microstructure ...The magnetostrictive properties of <112> axial aligned Tb0.3Dy0.7(Fe1-xMx)1.95(M=Mn, Al, x=0～ 0.15) alloys prepared by directional solidification are reported. The influence of heat treatment on microstructure and the compressive stress effect of magnetostriction is discussed.展开更多
An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination ...An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.展开更多
[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding m...[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding meteorological stations and local automatic meteorological stations in suburbs,the annual variation of temperature and regional consistency was analysed,then the abrupt change of annual average temperature was tested by Mann-Kendall test,finally the influences of urban heat island effect on temperature variation in Anqing Station were studied.[Result] Affected by station migration and urban construction,the annual average temperature increased significantly in Anqing Station from 1977 to 2009,and the rising was more prominent after the middle of the 1990s.Mann-Kendall test showed that the change of temperature in Anqing Station was obviously abrupt around 1993;because of the development of urbanization,average temperature in Anqing Station was 0.8 ℃ higher than that in suburbs,and the minimum temperature rose more remarkably.In addition,urban heat island effect was the strongest in spring,followed by summer and autumn,while it was the weakest in winter.[Conclusion] The effects of urbanization development on the temperature in Anqing City were understood through this research.展开更多
An abnormal fluorescence intensity ratio （FIR） between two green emissions of Er3＋, at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has ...An abnormal fluorescence intensity ratio （FIR） between two green emissions of Er3＋, at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has seldom been done to clarify this abnormal phenomenon. In this paper, green upconversion luminescence of the β-NaLuF4：20%yb3＋,2%Er3＋ powder sample was investigated under 980 um excitation at different circumstances, different pump power densities and different temperatures as well as different air pressures. The corresponding local temperature calculated using FIR technique increased gradually with the enhancement of the pump power density. It was demonstrated that high pump power density of 980 nm laser led to the increase of local temperature of the luminescent material, which further gave the abnormal FIR.展开更多
Nanofluids have attracted many scientists due to their remarkable thermophysical properties.Small percentage of nanoparticles when added to conventional fluid significantly enhances the heat transfer features.Sustaina...Nanofluids have attracted many scientists due to their remarkable thermophysical properties.Small percentage of nanoparticles when added to conventional fluid significantly enhances the heat transfer features.Sustainability and efficiency of nanomaterials have key role in the advancement of nanotechnology.This article analyzes the Hall,Ohmic heating and velocity slip effects on the peristalsis of nanofluid.Convective boundary conditions and heat generation/absorption are considered to facilitate the heat transfer characteristics.Governing equations for the peristaltic flow through a curved channel are derived in curvilinear coordinates.The equations are numerically solved under the assumption of long wavelength and small Reynold number.It has been observed that nanofluid enhances the heat transfer rate and reduces the fluid temperature.Hartman number and Hall parameter show reverse behavior in fluid motion and heat transfer characteristics.In the presence of velocity slip,the pressure gradient rapidly decreases and dominant effect is seen in narrow portion of channel.展开更多
Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Ther...Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Thermal remote sensors measure the radiation emitted by ground objects,which can be used to estimate the land surface temperature and are beneficial for studying urban heat island effects.The present study investigates the spatial and temporal variations in the effects of urban heat island over Tiruchirappalli city in India during the summer and winter seasons.The study also identifies hot spots and cold spots within the study area.In this study,a significant land surface temperature difference was observed between the urban and rural areas,predominantly at night,indicating the presence of urban heat island at night.These diurnal land surface temperature fluctuations are also detected seasonally,with a relatively higher temperature intensity during the summer.The trend line analysis shows that the mean land surface temperature of the study area is increasing at a rate of 0.166 K/decade with p less than 0.01.By using the spatial autocorrelation method with the urban heat island index as the key parameter,hot spots with a 99 percent confidence level and a 95 percent confidence level were found within the urban area.A hot spot with 95 and 90 percent confidence level was identified outside the urban area.This spike in temperature for a particular region in the rural area is due to industry and the associated built-up area.The study also identified cold spots with a 90 percent confidence level within the rural area.However,cold spots with a 95 and 99 percent confidence level were not identified within the study area.展开更多
This paper analyzes the Urban Heat Island （UHI） effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index （NDVI）, Land Surface Temperature （LST） data obtained fr...This paper analyzes the Urban Heat Island （UHI） effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index （NDVI）, Land Surface Temperature （LST） data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer （EOS/MODIS） information, and correlation and composite analyses. The results show： （1） Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. （2） The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. （3） A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. （4） The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively corre- lated with winter evaporation. （5） UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere.展开更多
To cherish the memory of the late Professor Duzheng YE on what would have been his 100 th birthday, and to celebrate his great accomplishment in opening a new era of Tibetan Plateau（TP） meteorology, this review pape...To cherish the memory of the late Professor Duzheng YE on what would have been his 100 th birthday, and to celebrate his great accomplishment in opening a new era of Tibetan Plateau（TP） meteorology, this review paper provides an assessment of the atmospheric heat source（AHS） over the TP from different data resources, including observations from local meteorological stations, satellite remote sensing data, and various reanalysis datasets. The uncertainty and applicability of these heat source data are evaluated. Analysis regarding the formation of the AHS over the TP demonstrates that it is not only the cause of the atmospheric circulation, but is also a result of that circulation. Based on numerical experiments, the review further demonstrates that land–sea thermal contrast is only one part of the monsoon story. The thermal forcing of the Tibetan–Iranian Plateau plays a significant role in generating the Asian summer monsoon（ASM）, i.e., in addition to pumping water vapor from sea to land and from the lower to the upper troposphere, it also generates a subtropical monsoon–type meridional circulation subject to the angular momentum conservation, providing an ascending-air large-scale background for the development of the ASM.展开更多
Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon...Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO2 (320 W·m ? 1·K? 1 versus 1.4 W·m? 1·K? 1). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electri-cal characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the appli-cations of SOI to high temperature conditions.展开更多
With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is un...With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.展开更多
Microstructural evolution and Portevin-Le Chatelier（PLC） phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%Y alloy before and after heat treatment have been investigated.It has been demonstrated that for the as-extrude...Microstructural evolution and Portevin-Le Chatelier（PLC） phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%Y alloy before and after heat treatment have been investigated.It has been demonstrated that for the as-extruded and solid solution treated（T4） samples,the PLC phenomenon could be obviously observed on tensile stress-strain curves.Moreover,the PLC phenomenon in T4 samples was more salient than that in the as-extruded condition,suggesting that the occurrence of PLC phenomenon was closely related to the super-saturation degree of solute atoms in the matrix.Since most of solute atoms were consumed for the formation of Mg Zn precipitates（β1′ and a little of β2′） during the subsequent ageing treatment（T6）,the PLC phenomenon of T6 samples was eliminated.Meanwhile,due to the pinning effect of the formed Mg Zn precipitates on mobile dislocations,the tensile strength of T6 samples was relatively higher than those of the other two conditions.展开更多
This paper studies the effective properties of multi-phase thermoelastic composites. Based on the Helmholtz free energy and the Gibbs free energy of individual phases, the effective elastic tensor, thermal-expansion t...This paper studies the effective properties of multi-phase thermoelastic composites. Based on the Helmholtz free energy and the Gibbs free energy of individual phases, the effective elastic tensor, thermal-expansion tensor, and specific heats of the multi-phase composites are derived by means of the volume average of free-energies of these phases. Particular emphasis is placed on the derivation of new analytical expressions of effective specific heats at constant-strain and constant-stress situations, in which a modified Eshelby＇s micromechanics theory is developed and the interaction between inclusions is considered. As an illustrative example, the analytical expression of the effective specific heat for a three-phase thermoelastic composite is presented.展开更多
An inherent self-heating effect of the silicon-on-insulator (SOI) devices limits their application at high current levels. In this paper a novel solution to reduce the self-heating effect is proposed, based on N+ and ...An inherent self-heating effect of the silicon-on-insulator (SOI) devices limits their application at high current levels. In this paper a novel solution to reduce the self-heating effect is proposed, based on N+ and O+ co-implantation into silicon wafer to form a new buried layer structure. This new structure was simulated using Medici program, and the temperature distribution and output characteristics were compared with those of the conventional SOI counterparts. As expected, a reduction of self-heating effect in the novel SOI device was observed.展开更多
Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects.The expe...Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects.The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters：jet Reynolds number from 27000 to 130000,relative nozzle to surface distance from 3.3 to 30,and relative surface curvature from 0.005 to 0.030.Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics.On one hand,an increase of relative nozzle to surface distance（increasing jet diameter in fact）enhances the average heat transfer around the surface for the same curved surface.On the other hand,the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter.Finally,experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect.This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces,which is of high importance to the design of the aircraft anti-icing system.展开更多
On the basis of snow data and AWS (Automatic Weather Station) data obtained from the Tibetan Plateau in recent years (1993 to 1999), the features of sensible heat, latent heat and net long-wave radiations are estimate...On the basis of snow data and AWS (Automatic Weather Station) data obtained from the Tibetan Plateau in recent years (1993 to 1999), the features of sensible heat, latent heat and net long-wave radiations are estimated, and their variations in more-snow year (1997/ 1998) and less-snow year (1996/ 1997) are analyzed comparatively. The relationships between snow cover of the Tibetan Plateau and plateau’s surface heating to the atmospheric heating are also discussed. The difference between more-snow and less-snow year in spring is remarkably larger than that in winter. Therefore, the effect of anomalous snow cover of the Tibetan Plateau in winter on the plateau heating appears more clearly in the following spring of anomalous snow cover. Key words Tibetan Plateau - Snow cover - Effects - Surface heat fluxes This research was supported by the National Key Programme for Developing Basic Sciences G1998040900 (I), National Natural Science Foundation of China (40075018) and Sichuan Youth Science and Technology Fund.展开更多
The application of segmental semi-solid thixoforming of magnesium alloys is confined due to the dimensional distinction existing in solid particles of the alloy billet from edge to center zones. In the present study, ...The application of segmental semi-solid thixoforming of magnesium alloys is confined due to the dimensional distinction existing in solid particles of the alloy billet from edge to center zones. In the present study, the effects of Sm addition on the microstructural evolution of Mg-6Zn-0.4Zr and Mg-6Zn-4Sm-0.4Zr alloys by semi-solid isothermal heat treatment were investigated, to obtain optimum semi-solid microstructures for the subsequently thixoforming. The results indicate that the grains of the Sm-bearing alloy are evidently refined and gradually evolve from dendritic to globular and elliptic particles. In addition, the distinctly dimensional effect of the Mg-6Zn-0.4Zr alloy is eliminated with 4% Sm addition; the particle sizes in all zones from center to the edge of the billet are almost identical. With the increment of isothermal heat treatment temperature, the dendritic microstructures completely disappear, and meanwhile, the irregular and globular particles gradually form. The size, morphology and the distribution of solid particles mainly depend on the formation and permeation of the liquid phase in the process of isothermal heat treatment. As the isothermal temperature increases from 570 °C to 610 °C, the average size and shape factor of solid particles of both the alloys with and without Sm addition gradually decrease while the liquid fraction gradually increases.展开更多
The therapeutic actions of Qing Luo Yin (QLY清络饮) with heat property and Wen Luo Yin (WLY温络饮) with cold property on pain, swelling of the ankle, arthritis index and ultrastructures of synoviocytes were compared i...The therapeutic actions of Qing Luo Yin (QLY清络饮) with heat property and Wen Luo Yin (WLY温络饮) with cold property on pain, swelling of the ankle, arthritis index and ultrastructures of synoviocytes were compared in rats of type II collagen-induced arthritis (CIA), with tripterygium glycosidorum (TG) used as control. The results indicated that both QLY and WLY could reduce pain, swelling of the ankle and the arthritis index of CIA, and QLY had better effects in reducing the swelling of the ankle and controlling the secondary pathological lesions as compared with WLY. Investigation on the ultrastructures of synoviocytes indicated that both QLY and WLY could reduce the number of Golgi apparatus, rough surface endoplasmic reticulum, dense bodies, matrix filaments and vacuoles so as to suppress the excessive secretion of synoviocytes in rats of CIA.展开更多
基金funded by Grand Challenge-SUS(Sustainability Science)Grants GC002C-15SUS and GC002A-15SUS
文摘Urban areas usually experience higher temperatures compared with their rural surroundings; this is characterized as urban heat islands （UHIs）, which are the result of environmental overheating due to anthropic activities. Urban areas,which are characterised by massive construction that reduce local vegetation coverage, are subject to the absorption of a large amount of solar radiation,which is only partially released into the atmosphere by radiation in the thermal infrared.
基金Supported by the Project of Jining Meteorological Bureau(2024JNZL08).
文摘Based on the observation data of meteorological observation stations in Jining City during 1970-2024,MK mutation test and principal component analysis(PCA)were used to study the evolution characteristics of urban heat island intensity(UHII)and the contribution rate of various influencing factors in Jining City over the past 55 years.The results show that from 1970 to 2024,the UHII in Jining City generally rose at a rate of 0.1℃/10 a.On the interannual scale,the correlation between temperature and UHII was most significantly positive.On the seasonal scale,there was a strong negative correlation between wind speed and UHII.PCA reveals that temperature had a significant positive impact on the increase of UHII in Jining City.
文摘The magnetostrictive properties of <112> axial aligned Tb0.3Dy0.7(Fe1-xMx)1.95(M=Mn, Al, x=0～ 0.15) alloys prepared by directional solidification are reported. The influence of heat treatment on microstructure and the compressive stress effect of magnetostriction is discussed.
基金supported by the National Basic Research Program of China (973 Program, Grant Nos. 2013CB430105 and 2014CB441403)the National Natural Science Foundation of China (Grant No. 41205099)+1 种基金Guizhou Province Scientific Research Joint Project (Grant No. G[2013]4001)the Special Scientific Research Project of Meteorological Public Welfare Profession of China (Grant No. GYHY201006031)
文摘An extraordinary rainstorm that occurred in Beijing on 21 July 2012 was simulated using the Weather Research and Forecasting model. The results showed that:(1) The two precipitation phases were based on a combination of cold cloud processes and warm cloud processes. The accumulated conversion amount and conversion rate of microphysical processes in the warm-area phase were all much larger than those in the cold front phase.(2) 72.6% of rainwater was from the warm-area phase. Rainwater mainly came from the melting of graupel and the melting of snow, while the accretion of cloud water by rain ranked second.(3) The net heating rate with height appeared as an overall warming with two strong heating centers in the lower and middle layers of the troposphere and a minimum heating center around the melting layer. The net heating effect in the warm-area phase was stronger than that in the cold front phase.(4) Warm cloud processes contributed most to latent heat release, and the thermal effect of cold cloud processes on the storm in the cold front phase was enhanced compared to that in the warm-area phase.(5) The melting of graupel and snow contributed most to latent heat absorption, and the effect of the evaporation of rainwater was significantly reduced in the cold front phase.
文摘[Objective] The aim was to analyse the variation characteristics of temperature in Anqing City and urban heat island effect.[Method] Based on the observation data of temperature from Anqing Station,other surrounding meteorological stations and local automatic meteorological stations in suburbs,the annual variation of temperature and regional consistency was analysed,then the abrupt change of annual average temperature was tested by Mann-Kendall test,finally the influences of urban heat island effect on temperature variation in Anqing Station were studied.[Result] Affected by station migration and urban construction,the annual average temperature increased significantly in Anqing Station from 1977 to 2009,and the rising was more prominent after the middle of the 1990s.Mann-Kendall test showed that the change of temperature in Anqing Station was obviously abrupt around 1993;because of the development of urbanization,average temperature in Anqing Station was 0.8 ℃ higher than that in suburbs,and the minimum temperature rose more remarkably.In addition,urban heat island effect was the strongest in spring,followed by summer and autumn,while it was the weakest in winter.[Conclusion] The effects of urbanization development on the temperature in Anqing City were understood through this research.
基金Project supported by the National Natural Science Foundation of China(11374291,11274299 and 11204292)
文摘An abnormal fluorescence intensity ratio （FIR） between two green emissions of Er3＋, at room temperature, which is larger than a normal value, emerged in many reported articles. However, up to now detailed work has seldom been done to clarify this abnormal phenomenon. In this paper, green upconversion luminescence of the β-NaLuF4：20%yb3＋,2%Er3＋ powder sample was investigated under 980 um excitation at different circumstances, different pump power densities and different temperatures as well as different air pressures. The corresponding local temperature calculated using FIR technique increased gradually with the enhancement of the pump power density. It was demonstrated that high pump power density of 980 nm laser led to the increase of local temperature of the luminescent material, which further gave the abnormal FIR.
文摘Nanofluids have attracted many scientists due to their remarkable thermophysical properties.Small percentage of nanoparticles when added to conventional fluid significantly enhances the heat transfer features.Sustainability and efficiency of nanomaterials have key role in the advancement of nanotechnology.This article analyzes the Hall,Ohmic heating and velocity slip effects on the peristalsis of nanofluid.Convective boundary conditions and heat generation/absorption are considered to facilitate the heat transfer characteristics.Governing equations for the peristaltic flow through a curved channel are derived in curvilinear coordinates.The equations are numerically solved under the assumption of long wavelength and small Reynold number.It has been observed that nanofluid enhances the heat transfer rate and reduces the fluid temperature.Hartman number and Hall parameter show reverse behavior in fluid motion and heat transfer characteristics.In the presence of velocity slip,the pressure gradient rapidly decreases and dominant effect is seen in narrow portion of channel.
基金funded this research through grant NITT/R&C/SEED GRANT/2021e22/P.14.
文摘Alterations made to the natural ground surface and the anthropogenic activity elevate the surface and air temperature in the urban areas compared with the surrounding rural areas,known as urban heat island effect.Thermal remote sensors measure the radiation emitted by ground objects,which can be used to estimate the land surface temperature and are beneficial for studying urban heat island effects.The present study investigates the spatial and temporal variations in the effects of urban heat island over Tiruchirappalli city in India during the summer and winter seasons.The study also identifies hot spots and cold spots within the study area.In this study,a significant land surface temperature difference was observed between the urban and rural areas,predominantly at night,indicating the presence of urban heat island at night.These diurnal land surface temperature fluctuations are also detected seasonally,with a relatively higher temperature intensity during the summer.The trend line analysis shows that the mean land surface temperature of the study area is increasing at a rate of 0.166 K/decade with p less than 0.01.By using the spatial autocorrelation method with the urban heat island index as the key parameter,hot spots with a 99 percent confidence level and a 95 percent confidence level were found within the urban area.A hot spot with 95 and 90 percent confidence level was identified outside the urban area.This spike in temperature for a particular region in the rural area is due to industry and the associated built-up area.The study also identified cold spots with a 90 percent confidence level within the rural area.However,cold spots with a 95 and 99 percent confidence level were not identified within the study area.
基金supported by programs of the Institute of Urban Meteorology (No. UMRF200705)the China Meteorological Administration (No. CMATG2010M24)the Institute of Plateau Meteorology (No. BROP200705)
文摘This paper analyzes the Urban Heat Island （UHI） effect in Lhasa City of Tibet using meteorological observations, the Normalized Difference Vegetation Index （NDVI）, Land Surface Temperature （LST） data obtained from Earth Observing System/Moderate resolution Imaging Spectroradiometer （EOS/MODIS） information, and correlation and composite analyses. The results show： （1） Areas with high temperature are primarily located in the center of the city or nearby counties, while low temperature areas are in the suburbs of counties. The area with high temperature has expanded in recent years and some high-temperature centers have even migrated to certain other regions. （2） The UHI intensity tends to be stronger both in annual and seasonal variations, especially in winter. Also, LST is somewhat positively related to mean air temperature. （3） A negative correlation exists between the changes of LST and NDVI with the increase of vegetation from urban to rural areas in different seasons. （4） The UHI intensity is negatively correlated with precipitation while positively correlated with wind speed, and the relation between the UHI intensity and evaporation varies with the seasons, namely, the intensity is positively correlated with summer evaporation but negatively corre- lated with winter evaporation. （5） UHI intensity might be enhanced by intensified urbanization, wherein built-up areas expand, there is increased heat from human activity, and there is more artificial heat input to the atmosphere.
基金supported by the Key Research Program of Frontier Sciences of the Chinese Academy of Sciencesthe Major Research Plan of the National Natural Science Foundation of China(Grant Nos.91637312,91437219,91637208,and 41530426)the Special Program for Applied Research on Super Computation of the NSFC–Guangdong Joint Fund(second phase)(Grant No.U1501501)
文摘To cherish the memory of the late Professor Duzheng YE on what would have been his 100 th birthday, and to celebrate his great accomplishment in opening a new era of Tibetan Plateau（TP） meteorology, this review paper provides an assessment of the atmospheric heat source（AHS） over the TP from different data resources, including observations from local meteorological stations, satellite remote sensing data, and various reanalysis datasets. The uncertainty and applicability of these heat source data are evaluated. Analysis regarding the formation of the AHS over the TP demonstrates that it is not only the cause of the atmospheric circulation, but is also a result of that circulation. Based on numerical experiments, the review further demonstrates that land–sea thermal contrast is only one part of the monsoon story. The thermal forcing of the Tibetan–Iranian Plateau plays a significant role in generating the Asian summer monsoon（ASM）, i.e., in addition to pumping water vapor from sea to land and from the lower to the upper troposphere, it also generates a subtropical monsoon–type meridional circulation subject to the angular momentum conservation, providing an ascending-air large-scale background for the development of the ASM.
基金Supported by the Special Funds for Major State Basic Research Projects (No.G2000036506)the National Natural Science Foundation of China (No. 60476006)
文摘Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO2 (320 W·m ? 1·K? 1 versus 1.4 W·m? 1·K? 1). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electri-cal characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the appli-cations of SOI to high temperature conditions.
基金Under the auspices of the National Science Foundation of Sichuan Province(No.2022NSFSC1006)Science and Technology Innovation Capability Improvement Plan Project of Chengdu University of Information Technology in 2022(No.KYQN202215)the National Science Foundation of China(No.41505122)。
文摘With the advancement of urbanization,the urban heat island effect and ozone pollution have become hot issues in urban research.The urban heat island effect can impact ozone conversion,but its mechanism of action is unclear.In this study,the effects of the urban heat island effect on ozone concentration in Chengdu City,China,were investigated by comparing the ozone concentration under different heat island levels with ozone data from March 2020 to February 2021 and the temperature and wind field data of ERA5-Land during the same period.The results showed that:1)regarding the distribution characteristics,the ozone concentration in Chengdu presented a‘high in summer and low in winter’distribution.The ozone concentration in summer(189.54µg/m^(3))was nearly twice that in winter(91.99µg/m^(3)),and the ozone diurnal variation presented a‘single peak and single valley’distribution,with a peak at 16:00.2)For the characteristics of the heat island effect,the heat island intensity in Chengdu was obviously higher in spring than in other seasons,and the diurnal variation showed a‘single peak and single valley’distribution,with the peak and trough values appearing at 9:00 and 17:00,respectively.Spatially,the eastern part of Chengdu was a heat island,while the western and northwestern parts were mostly cold island.3)The correlation analysis between heat island intensity and ozone concentration showed a significant positive correlation but with a 7–8 h time lag.Ambient air temperature was not the main factor affecting ozone concentration.The heat island effect impacts the ozone concentration in two ways:changing the local heat budget to promote ozone generation and forming local urban wind,which promotes ozone diffusion or accumulation and forms different areas of low and high ozone values.
基金supported by the National Natural Science Foundation of China projects under Grant Nos.51271183 and 51301172the National Basic Research Program of China(973 Program)project under Grant No.2013CB632205the Innovation Fund of Institute of Metal Research(IMR),Chinese Academy of Sciences(CAS)
文摘Microstructural evolution and Portevin-Le Chatelier（PLC） phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%Y alloy before and after heat treatment have been investigated.It has been demonstrated that for the as-extruded and solid solution treated（T4） samples,the PLC phenomenon could be obviously observed on tensile stress-strain curves.Moreover,the PLC phenomenon in T4 samples was more salient than that in the as-extruded condition,suggesting that the occurrence of PLC phenomenon was closely related to the super-saturation degree of solute atoms in the matrix.Since most of solute atoms were consumed for the formation of Mg Zn precipitates（β1′ and a little of β2′） during the subsequent ageing treatment（T6）,the PLC phenomenon of T6 samples was eliminated.Meanwhile,due to the pinning effect of the formed Mg Zn precipitates on mobile dislocations,the tensile strength of T6 samples was relatively higher than those of the other two conditions.
基金Project supported by the National Natural Science Foundation of China (Nos. 10602002 and 10932001)the Major State Basic Research Development Program (No. 2010CB731503)
文摘This paper studies the effective properties of multi-phase thermoelastic composites. Based on the Helmholtz free energy and the Gibbs free energy of individual phases, the effective elastic tensor, thermal-expansion tensor, and specific heats of the multi-phase composites are derived by means of the volume average of free-energies of these phases. Particular emphasis is placed on the derivation of new analytical expressions of effective specific heats at constant-strain and constant-stress situations, in which a modified Eshelby＇s micromechanics theory is developed and the interaction between inclusions is considered. As an illustrative example, the analytical expression of the effective specific heat for a three-phase thermoelastic composite is presented.
基金Supported by the Special Funds for Major State Basic Research Projects(NO.G20000365)and the National Natural Science Foundation of China(No.90101012)
文摘An inherent self-heating effect of the silicon-on-insulator (SOI) devices limits their application at high current levels. In this paper a novel solution to reduce the self-heating effect is proposed, based on N+ and O+ co-implantation into silicon wafer to form a new buried layer structure. This new structure was simulated using Medici program, and the temperature distribution and output characteristics were compared with those of the conventional SOI counterparts. As expected, a reduction of self-heating effect in the novel SOI device was observed.
基金supported by the National Natural Science Foundation of China(No.51206008)the EU Marie Curie Actions-International Incoming Fellowships(No.FP7PEOPLE-2013-IIF-626576)
文摘Experimental study of the local and average heat transfer characteristics of a single round jet impinging on the concave surfaces was conducted in this work to gain in-depth knowledge of the curvature effects.The experiments were conducted by employing a piccolo tube with one single jet hole over a wide range of parameters：jet Reynolds number from 27000 to 130000,relative nozzle to surface distance from 3.3 to 30,and relative surface curvature from 0.005 to 0.030.Experimental results indicate that the surface curvature has opposite effects on heat transfer characteristics.On one hand,an increase of relative nozzle to surface distance（increasing jet diameter in fact）enhances the average heat transfer around the surface for the same curved surface.On the other hand,the average Nusselt number decreases as relative nozzle to surface distance increases for a fixed jet diameter.Finally,experimental data-based correlations of the average Nusselt number over the curved surface were obtained with consideration of surface curvature effect.This work contributes to a better understanding of the curvature effects on heat transfer of a round jet impingement on concave surfaces,which is of high importance to the design of the aircraft anti-icing system.
基金the National Key Programme for Developing Basic SciencesG1998040900 (I)National Natural Science Foundation of China (400750
文摘On the basis of snow data and AWS (Automatic Weather Station) data obtained from the Tibetan Plateau in recent years (1993 to 1999), the features of sensible heat, latent heat and net long-wave radiations are estimated, and their variations in more-snow year (1997/ 1998) and less-snow year (1996/ 1997) are analyzed comparatively. The relationships between snow cover of the Tibetan Plateau and plateau’s surface heating to the atmospheric heating are also discussed. The difference between more-snow and less-snow year in spring is remarkably larger than that in winter. Therefore, the effect of anomalous snow cover of the Tibetan Plateau in winter on the plateau heating appears more clearly in the following spring of anomalous snow cover. Key words Tibetan Plateau - Snow cover - Effects - Surface heat fluxes This research was supported by the National Key Programme for Developing Basic Sciences G1998040900 (I), National Natural Science Foundation of China (40075018) and Sichuan Youth Science and Technology Fund.
基金supported by the National Natural Science Foundations of China(51464032)the National Basic Research Program of China(grant No.2010CB635106)
文摘The application of segmental semi-solid thixoforming of magnesium alloys is confined due to the dimensional distinction existing in solid particles of the alloy billet from edge to center zones. In the present study, the effects of Sm addition on the microstructural evolution of Mg-6Zn-0.4Zr and Mg-6Zn-4Sm-0.4Zr alloys by semi-solid isothermal heat treatment were investigated, to obtain optimum semi-solid microstructures for the subsequently thixoforming. The results indicate that the grains of the Sm-bearing alloy are evidently refined and gradually evolve from dendritic to globular and elliptic particles. In addition, the distinctly dimensional effect of the Mg-6Zn-0.4Zr alloy is eliminated with 4% Sm addition; the particle sizes in all zones from center to the edge of the billet are almost identical. With the increment of isothermal heat treatment temperature, the dendritic microstructures completely disappear, and meanwhile, the irregular and globular particles gradually form. The size, morphology and the distribution of solid particles mainly depend on the formation and permeation of the liquid phase in the process of isothermal heat treatment. As the isothermal temperature increases from 570 °C to 610 °C, the average size and shape factor of solid particles of both the alloys with and without Sm addition gradually decrease while the liquid fraction gradually increases.
文摘The therapeutic actions of Qing Luo Yin (QLY清络饮) with heat property and Wen Luo Yin (WLY温络饮) with cold property on pain, swelling of the ankle, arthritis index and ultrastructures of synoviocytes were compared in rats of type II collagen-induced arthritis (CIA), with tripterygium glycosidorum (TG) used as control. The results indicated that both QLY and WLY could reduce pain, swelling of the ankle and the arthritis index of CIA, and QLY had better effects in reducing the swelling of the ankle and controlling the secondary pathological lesions as compared with WLY. Investigation on the ultrastructures of synoviocytes indicated that both QLY and WLY could reduce the number of Golgi apparatus, rough surface endoplasmic reticulum, dense bodies, matrix filaments and vacuoles so as to suppress the excessive secretion of synoviocytes in rats of CIA.
