A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations...A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations with working face advanc- ing was simulated by a new model.The results show that the maximum value of bed separations moved forward gradually along with the working face advancing;the maxi- mum value of bed separations is 0.31～0.50 times of mining thickness.The key strata have a great influence upon surface subsidence during the overburden movement process.The mechanics parameters of new experiment are fitted with results in fields perfectly.展开更多
In China's Mainland, the summer monsoon rainy band is referred to as the mei-yu precipitation front, which extends northward from South China to the Yangtze River, Huaihe River, and Yellow River, depending on the ...In China's Mainland, the summer monsoon rainy band is referred to as the mei-yu precipitation front, which extends northward from South China to the Yangtze River, Huaihe River, and Yellow River, depending on the season. This paper describes the structure of the mei-yu front associated with a persistent heavy rainfall event that occurred in the summer of 2007. The mei-yu front occurs when the subtropical oceanic warm, moist air mass and the extra tropical continental dry, cold air mass converge on the lee side of the Tibetan Plateau. The authors defined the equivalent temperature using two terms of dry-air temperature and the specific humidity and calculated its horizontal gradient to indicate the mei-yu front. The vertical structure of the mei-yu front and the moist thermal winds surrounding it were examined based on the equivalent temperature.展开更多
We present a scheme for estimating the noise-equivalent temperature difference(NETD)of frequency upconversion detectors(UCDs)that detect mid-infrared(MIR)light.In particular,we investigate the frequency upconversion o...We present a scheme for estimating the noise-equivalent temperature difference(NETD)of frequency upconversion detectors(UCDs)that detect mid-infrared(MIR)light.In particular,we investigate the frequency upconversion of a periodically poled crystal based on lithium niobate,where an MIR conversion bandwidth of 220 nm can be achieved in a single-poled period by a special design.Experimentally,for an MIR radiating target at a temperature of 95℃,the NETD of the device was estimated to be 56 mK with an exposure time of 1 s.Meanwhile,a direct measurement of the NETD was performed utilizing conventional methods,which resulted in 48 mK.We also compared the NETD of our UCD with commercially available direct MIR detectors.We show that the limiting factor for further NETD reduction of our device is not primarily from the upconversion process and camera noise but from the limitations of the heat source and laser performance.Our detectors have good temperature measurement performance and can be used for a variety of applications involving temperature object identification and material structure detection.展开更多
At low SNR cases, the distinction between spatial point-target and interferences as decoys is still a very difficult problem. Based on the characteristics that target and interferences as decoys and noise had differen...At low SNR cases, the distinction between spatial point-target and interferences as decoys is still a very difficult problem. Based on the characteristics that target and interferences as decoys and noise had different radiation intensity and radiation changing frequency, the concept of the equivalent blackbody temperature （EBT） was built and the calculation model of EBT was designed. The model could effectively reduce the interference of the space environment and fully show the radiation differences between point-target and interferences as decoys. It would be very effective in the detection of the target. In order to detect the target, the effective estimator of EBT was designed according to the observed data, and the system error and the variation range of the estimator of EBT were estimated. Finally the multi-frame estimator was designed to improve the estimation stability of EBT, and the use of this estimator would identify the point-target more effectively.展开更多
In this study,the characteristics of azimuthally asymmetric equivalent potential temperature(θ_(e))distributions in the outer core of tropical cyclones(TCs)encountering weak and strong vertical wind shear are examine...In this study,the characteristics of azimuthally asymmetric equivalent potential temperature(θ_(e))distributions in the outer core of tropical cyclones(TCs)encountering weak and strong vertical wind shear are examined using a Lagrangian trajectory method.Evaporatively forced downdrafts in the outer rainbands can transport low-entropy air downward,resulting in the lowestθ_(e)in the downshear-left boundary layer.Quantitative estimations ofθ_(e)recovery indicate that air parcels,especially those originating from the downshear-left outer core,can gradually revive from a low entropy state through surface enthalpy fluxes as the parcels move cyclonically.As a result,the maximumθ_(e)is observed in the downshear-right quadrant of a highly sheared TC.The trajectory analyses also indicate that parcels that move upward in the outer rainbands and those that travel through the inner core due to shear make a dominant contribution to the midlevel enhancement ofθ_(e)in the downshear-left outer core.In particular,the former plays a leading role in suchθ_(e)enhancements,while the latter plays a secondary role.As a result,moist potential stability occurs in the middle-to-lower troposphere in the downshear-left outer core.展开更多
The bituminous pavements of the city of Ouagadougou(Burkina Faso)are made using old design methods which take into account the climate from the notion of equivalent temperature.Thus an equivalent temperature of 30...The bituminous pavements of the city of Ouagadougou(Burkina Faso)are made using old design methods which take into account the climate from the notion of equivalent temperature.Thus an equivalent temperature of 30°C is often used for the design of bituminous pavements.The observation that has been made is that this temperature does not currently make it possible to reduce the problems of early degradation of the pavements linked to meteorological fluctuations.The objective of this article is to propose a numerical approach for determining the equivalent temperature from temperature measurements taken at the surface of the pavement.This approach consists in jointly using the Alizé-Lcpc sizing software and the Comsol Multiphysics software using the finite element method.For a four-layer bituminous pavement,located at 12.38°North and 1.48°West,in Ouagadougou,consisting of a surface course of bituminous concrete of 8 cm and a base course of gravel bitumen of 16 cm,an equivalent temperature of 35°C was obtained.展开更多
Breaking down the entire structure of a material implies severing all the bonds between its atoms either by applying work or by heat transfer. Because bond-breaking is indifferent to either means, there is a kind of e...Breaking down the entire structure of a material implies severing all the bonds between its atoms either by applying work or by heat transfer. Because bond-breaking is indifferent to either means, there is a kind of equivalence between heat energy and strain energy. Based on this equivalence, we assume the existence of a constant maximum storage of energy that includes both the strain energy and the corresponding equivalent heat energy. A temperaturedependent fracture strength model is then developed for ultrahigh temperature ceramics （UHTCs）. Model predictions for UHTCs, HfB2, TiC and ZrB2, are presented and compared with the experimental results. These predictions are found to be largely consistent with experimental results.展开更多
In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using...In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.展开更多
The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The uneve...The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade with a tenon into consideration, a 3D mechanical model in precision forging is built up. The distribution laws of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.展开更多
The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO i...The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH： warmer SST in the TIO changes the equivalent potential temperature （EPT） in the atmospheric boundary layer （ABL）, alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.展开更多
In designing the human comfort index (CI) used in Guangzhou, a Gaussian curve was adopted as the fundamental profile to develop a traw hat?model of comfort index. The model projects low or high temperatures into low i...In designing the human comfort index (CI) used in Guangzhou, a Gaussian curve was adopted as the fundamental profile to develop a traw hat?model of comfort index. The model projects low or high temperatures into low index values and the moderate temperatures into high index values. Air temperature was chosen as a basic factor in the model. Other factors such as humidity, sunshine and wind speed were introduced by considering them as temperature departures to an equivalent apparent temperature (EAT). Since the index is a relative index, 25C was chosen as an ideal apparent temperature (the most comfortable state) and a maximum CI value of 100 was assigned at this temperature. While in other circumstances, the index would be lower than 100. By utilizing this model, the daily comfort index values had been calculated for Guangzhou city for 1998-1999, using mean temperature, mean humidity, mean wind speed and total hours of sunshine. Results show that the new model was reasonable and practicable. Not only could it reflect the monthly variation of human comfort in Guangzhou, but also was sensitive to short-term changes of weather conditions.展开更多
One of the factors for the evaluation of the space environment is the comfort of outdoor activities spaces in urban parks. The space composed of different landscape elements has different microclimate environment. In ...One of the factors for the evaluation of the space environment is the comfort of outdoor activities spaces in urban parks. The space composed of different landscape elements has different microclimate environment. In this paper, in order to evaluate the role of thermal comfort in influencing resident’s assessment of the outdoor space and activities of the park, a thermal comfort survey was conducted on the outdoor open space of Mianyang Urban Park in summer. In this article, meteorological surveys, questionnaire surveys and observation of park attendance are selected to collect data. The physiological equivalent temperature (PET) assessment was selected as the index to evaluate resident’s thermal comfort level, and the comprehensive evaluation and analysis of the spatial thermal environment of different outdoor landscape elements in the park. The overall comfort of current visitors is mainly influenced by their subjective heat perception voting (TSV). In this article, we focus on providing microclimate adjustment considerations for urban park landscape design, and may help people understand the outdoor thermal comfort of Mianyang in summer, increase the using time of outdoor activities, and promote the use of outdoor space.展开更多
An attempt has been made to investigate the role of vertical wind shear, convective instability and the thermodynamic parameter ( θ es -θ e ) below the first lifting condensation level (FLCL) in the occurrenc...An attempt has been made to investigate the role of vertical wind shear, convective instability and the thermodynamic parameter ( θ es -θ e ) below the first lifting condensation level (FLCL) in the occurrence of instantaneous premonsoon thunderstorm over Agartala (AGT) and Ranchi (RNC) at 12 GMT. Radiosonde data of 1988 have been utilized here. The study has however been confined to 1000 hPa-500 hPa range at most. Here the convectively unstable layers with positive vertical wind shear upto 500 hPa have been termed as ‘Favourable Layers’ (FL) and the level at which an initially stable layer turns out to be convectively unstable for the first time has been termed as ‘Transition Level’ (TL). It is observed that the changes in vertical wind shear are positive at TL at the time of occurrence of thunderstorm (TS) and the corresponding change is negative on fair-weather situation. Moreover, the 90% confidence interval for ( θ es -θ e ) reveals that for AGT the upper layer thermodynamic characteristic is important at the time of occurrence of TS whereas for RNC, the value of ( θ es -θ e ) at the surface is much more effective.展开更多
Together,the heat island eff ect and air pollution pose a threat to human health and well-being in urban settings.Nature-based solutions such as planting trees are a mitigation strategy to improve outdoor temperatures...Together,the heat island eff ect and air pollution pose a threat to human health and well-being in urban settings.Nature-based solutions such as planting trees are a mitigation strategy to improve outdoor temperatures(thermal comfort)and enhance air quality in urban areas.In this study,outdoor thermal comfort,and particulate matter levels were compared between treeless and treed areas to provide a better understanding of how street trees improve thermal comfort and air quality.Street trees decreased the physiological equivalent temperature from 46.3 to 44.2℃in summer but increased it from 36.4 to 37.5℃in autumn.Air temperature and relative humidity contributed more in summer while wind speed contributed more in autumn.Particulate matter concentrations were negatively correlated with physiological equivalent temperature in summer but not in autumn.The presence of trees decreased concentrations of fi ne particulate matter in hot summer conditions but increased in hot autumn conditions.The presence of trees increased coarse particulate matter in very hot summer conditions in summer and in hot autumn conditions.Overall,the layout of trees in urban street canyons should consider the trade-off between outdoor thermal comfort and air quality improvement.展开更多
Cairo is characterized by high temperature compared to its surrounding areas,especially during the summer time.This effect is strengthened by the widespread use of sealed surfaces and the lack of vegetation.Therefore,...Cairo is characterized by high temperature compared to its surrounding areas,especially during the summer time.This effect is strengthened by the widespread use of sealed surfaces and the lack of vegetation.Therefore,the consumption of electricity in indoor spaces for cooling purposes is a critical problem especially in the summer time.The use of air conditioners has increased during the last 10 years enormously.Because of this,electricity bills increased in a huge way,which represents a burden on the citizens.Therefore,this study aims to find unconventional solutions for the reduction of energy through mitigating urban heat island(UHI)and enhancing thermal performance in Cairo.This paper studies various area cover factions of trees in an urban environment,which can be used to mitigate UHI,improve thermal performance in outdoor spaces and reduce energy consumption in high dense built up areas in Cairo.A small area of 250 m×250 m from downtown Cairo was simulated as a case study using ENVImet V.4.3.2.The comparison between reference scenario and suggested scenarios,which are 30%trees,50%trees and 30%trees+70%grass,were conducted on a summer day in Cairo.The outputs were used to estimate the amount of energy in every scenario using DesignBuilder model.The results show that the scenario with 50%trees led to the best human thermal comfort(3 K cooler).Although for the demand of energy in the buildings,the street orientation as well as the aspect ratio(H/W)play an important role and should be considered.展开更多
The urban microclimate has direct implications with regards to thermal comfort indoors as well as outdoors. In the tropics, the outdoor thermal comfort conditions during daytime are often far above acceptable comfort ...The urban microclimate has direct implications with regards to thermal comfort indoors as well as outdoors. In the tropics, the outdoor thermal comfort conditions during daytime are often far above acceptable comfort standards due to intense solar radiation and high solar elevations. This study aims to know effects of simple and fundamental building forms on microclimate and outdoor thermal comfort in a high dense tropical city, focusing on Dhaka, Bangladesh as a study city. Investigations are carried out on existing area and model areas with modified building forms （in respect of height and shape） on the microclimate as well as on outdoor thermal comfort during daytime in summer. This study has demonstrated that the model using less ground coverage and higher buildings can offer a better thermal climate than the models using maximum ground coverage in a high-density tropical city.展开更多
The recent development in Lucknow shows that the amount of built mass may increase significantly soon,which may affect outdoor thermal comfort.This study aims to achieve a better alternative to the geometrical configu...The recent development in Lucknow shows that the amount of built mass may increase significantly soon,which may affect outdoor thermal comfort.This study aims to achieve a better alternative to the geometrical configuration of vertical surfaces that helps improve the outdoor thermal comfort level.The study primarily deals with the exploration of built forms by altering the planar forms,heights,and orientations to arrive at a better composition of vertical surfaces.144 typologies were finally generated,which were then simulated in ENVI-met.The results show that,with the I-shaped typology it is difficult to reduce solar access,whereas in terms of ventilation,the typology performed better than L-shaped and C-shaped typologies.For this reason,the hours of solar access,as well as wind speed,should be seen together while developing the built-form typology.Urban neighborhoods can be designed with streets and open spaces oriented primarily to northeast-southwest and northwest-southeast directions which allow the open spaces to be thermally more comfortable than the rest of the orientation.This research highlights the importance of varying building heights to enhance thermal comfort.The findings provide valuable insights for composite climate cities like lucknow and can serve as a framework for future design strategies aimed at mitigating outdoor thermal discomfort.It is therefore important for planners,urban designers,and architects to design considering the minimal impact of the upcoming development on the thermal comfort level.展开更多
During the pandemic,face masks are one of the most significant self-protection necessities,but they also cause heat stress.By using the ERA5(ECMWF Reanalysis 5th Generation)database and the local weather bureau data,t...During the pandemic,face masks are one of the most significant self-protection necessities,but they also cause heat stress.By using the ERA5(ECMWF Reanalysis 5th Generation)database and the local weather bureau data,the effect of mask wearing on outdoor thermal sensation has been investigated by a survey conducted in the hot summer and cold winter region of eastern China in the summer of 2020.Results show that wearing a face mask for a longer period result in a higher level of discomfort,and the primary source of discomfort is hot and stuffy feelings.The effect of relative humidity is crucial for mask wearers in warm-biased thermal environments,as mean thermal sensation vote(TSV)peaks when environmental relative humidity reaches the range of 70%to 80%and decreases after this range due to the evaporation within the microclimate created by a face mask.Meanwhile,prolonged mask wearing increases participants’hot feelings,especially in warm environments.Specifically,participants wearing face masks for less than 30 min feel hot at a physiological equivalent temperature(PET)value of 34.4℃,but those who wear them for over 60 min express hot feelings even at a PET value of 24.7℃.The participants who wear a face mask while walking slowly outdoors have similar thermal sensations to those who do not wear a mask,but are in a higher activity level.The findings demonstrate that mask wearing has a crucial impact on outdoor thermal comfort assessment in a warm-biased outdoor thermal environment.展开更多
基金The National Natural Science Funds Committee(50174035)
文摘A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations with working face advanc- ing was simulated by a new model.The results show that the maximum value of bed separations moved forward gradually along with the working face advancing;the maxi- mum value of bed separations is 0.31～0.50 times of mining thickness.The key strata have a great influence upon surface subsidence during the overburden movement process.The mechanics parameters of new experiment are fitted with results in fields perfectly.
基金supported by the National Natural Science Foundation of China(Grant No.40975039)
文摘In China's Mainland, the summer monsoon rainy band is referred to as the mei-yu precipitation front, which extends northward from South China to the Yangtze River, Huaihe River, and Yellow River, depending on the season. This paper describes the structure of the mei-yu front associated with a persistent heavy rainfall event that occurred in the summer of 2007. The mei-yu front occurs when the subtropical oceanic warm, moist air mass and the extra tropical continental dry, cold air mass converge on the lee side of the Tibetan Plateau. The authors defined the equivalent temperature using two terms of dry-air temperature and the specific humidity and calculated its horizontal gradient to indicate the mei-yu front. The vertical structure of the mei-yu front and the moist thermal winds surrounding it were examined based on the equivalent temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.11934013 and 92065101)the Anhui Initiative In Quantum Information Technologies(Grant No.AHY020200)+1 种基金the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0301100)the National Key Research and Development Program of China(Grant No.2022YFB3607700).
文摘We present a scheme for estimating the noise-equivalent temperature difference(NETD)of frequency upconversion detectors(UCDs)that detect mid-infrared(MIR)light.In particular,we investigate the frequency upconversion of a periodically poled crystal based on lithium niobate,where an MIR conversion bandwidth of 220 nm can be achieved in a single-poled period by a special design.Experimentally,for an MIR radiating target at a temperature of 95℃,the NETD of the device was estimated to be 56 mK with an exposure time of 1 s.Meanwhile,a direct measurement of the NETD was performed utilizing conventional methods,which resulted in 48 mK.We also compared the NETD of our UCD with commercially available direct MIR detectors.We show that the limiting factor for further NETD reduction of our device is not primarily from the upconversion process and camera noise but from the limitations of the heat source and laser performance.Our detectors have good temperature measurement performance and can be used for a variety of applications involving temperature object identification and material structure detection.
文摘At low SNR cases, the distinction between spatial point-target and interferences as decoys is still a very difficult problem. Based on the characteristics that target and interferences as decoys and noise had different radiation intensity and radiation changing frequency, the concept of the equivalent blackbody temperature （EBT） was built and the calculation model of EBT was designed. The model could effectively reduce the interference of the space environment and fully show the radiation differences between point-target and interferences as decoys. It would be very effective in the detection of the target. In order to detect the target, the effective estimator of EBT was designed according to the observed data, and the system error and the variation range of the estimator of EBT were estimated. Finally the multi-frame estimator was designed to improve the estimation stability of EBT, and the use of this estimator would identify the point-target more effectively.
基金jointly supported by the National Key Research and Development Program of China under Grant No. 2017YFC1501601the National Natural Science Foundation of China under Grant Nos. 42175005 and 41875054
文摘In this study,the characteristics of azimuthally asymmetric equivalent potential temperature(θ_(e))distributions in the outer core of tropical cyclones(TCs)encountering weak and strong vertical wind shear are examined using a Lagrangian trajectory method.Evaporatively forced downdrafts in the outer rainbands can transport low-entropy air downward,resulting in the lowestθ_(e)in the downshear-left boundary layer.Quantitative estimations ofθ_(e)recovery indicate that air parcels,especially those originating from the downshear-left outer core,can gradually revive from a low entropy state through surface enthalpy fluxes as the parcels move cyclonically.As a result,the maximumθ_(e)is observed in the downshear-right quadrant of a highly sheared TC.The trajectory analyses also indicate that parcels that move upward in the outer rainbands and those that travel through the inner core due to shear make a dominant contribution to the midlevel enhancement ofθ_(e)in the downshear-left outer core.In particular,the former plays a leading role in suchθ_(e)enhancements,while the latter plays a secondary role.As a result,moist potential stability occurs in the middle-to-lower troposphere in the downshear-left outer core.
文摘The bituminous pavements of the city of Ouagadougou(Burkina Faso)are made using old design methods which take into account the climate from the notion of equivalent temperature.Thus an equivalent temperature of 30°C is often used for the design of bituminous pavements.The observation that has been made is that this temperature does not currently make it possible to reduce the problems of early degradation of the pavements linked to meteorological fluctuations.The objective of this article is to propose a numerical approach for determining the equivalent temperature from temperature measurements taken at the surface of the pavement.This approach consists in jointly using the Alizé-Lcpc sizing software and the Comsol Multiphysics software using the finite element method.For a four-layer bituminous pavement,located at 12.38°North and 1.48°West,in Ouagadougou,consisting of a surface course of bituminous concrete of 8 cm and a base course of gravel bitumen of 16 cm,an equivalent temperature of 35°C was obtained.
基金The project was supported by the National Natural Science Foundation of China （90505015 and 10702035）.
文摘Breaking down the entire structure of a material implies severing all the bonds between its atoms either by applying work or by heat transfer. Because bond-breaking is indifferent to either means, there is a kind of equivalence between heat energy and strain energy. Based on this equivalence, we assume the existence of a constant maximum storage of energy that includes both the strain energy and the corresponding equivalent heat energy. A temperaturedependent fracture strength model is then developed for ultrahigh temperature ceramics （UHTCs）. Model predictions for UHTCs, HfB2, TiC and ZrB2, are presented and compared with the experimental results. These predictions are found to be largely consistent with experimental results.
基金financially supported by the Shandong Natural Science Foundation (ZR2009FL020)the Shandong Transportation Innovation Foundation (2010Y20)
文摘In this paper, in order to investigate the viscoelasticity of asphalt binder at the softening point temperature, more than 30 different asphalt binders were selected and tested by dynamic rheological scan method using a dynamic shear rheometer(DSR). The softening points and the rheological parameters of the asphalt samples were measured and analyzed. The results indicated that at the softening point temperature the neat asphalt and the SBS modified asphalt showed two different rheological states. The neat asphalt binders had a majority of viscous components in viscoelastic composition, with the phase angles being mostly higher than 80 o. The SBS modified binders had lower phase angles, with their elasticity still retained. Meanwhile, the Shapiro-Wilk normality test showed that at a confidence level of 0.05, at whatever aging state, the neat asphalt had a stable complex modulus corresponding to the softening point, which was 13.034 kPa at a standard deviation of 2.105 kPa under the same test condition. The softening point of neat asphalt binder can be calculated via the equivalent modulus rule. It is found out that there is a good relationship between the calculated and the measured softening points. And it is suggested that more data are needed to validate this finding.
基金supported by the Aeronautical Science Foundation of China(No.02H53061)the National Science Found of China for Distinguished Young Scholar(No.50225518)the Shaan'xi Provincial Natural Science Foundation of China(No.2001CS0401)
文摘The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade with a tenon into consideration, a 3D mechanical model in precision forging is built up. The distribution laws of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.
基金supported by the National Key Technology R&D Program 2008BAK50B02CAS Innovation Key Program (Grant No. KZCX2-YW-BR-14)+2 种基金National Basic Research Program of China(2011CB309704)Special Scientific Research Project for Public Interest (Grant No. GYHY201006021)the National Natural Science Foundation of China (Grant Nos.40890155, 40775051, U0733002)
文摘The tropical Indian Ocean （TIO） is warmer than normal during the summer when or after the El Nio decays. The present study investigates the impact of TIO SST on the South Asian High （SAH） in summer. When the TIO is warmer, the SAH strengthens and its center shifts southward. It is found that the variations in the SAH cannot be accounted for by the precipitation anomaly. A possible mechanism is proposed to explain the connection between the TIO and SAH： warmer SST in the TIO changes the equivalent potential temperature （EPT） in the atmospheric boundary layer （ABL）, alters the temperature profile of the moist atmosphere, warms the troposphere, which produces significant positive height anomaly over South Asia and modifies the SAH. An atmospheric general circulation model, ECHAM5, which has a reasonable prediction skill in the TIO and South Asia, was selected to test the effects of TIO SST on the SAH. The experiment with idealized heating over the TIO reproduced the response of the SAH to TIO warming. The results suggest that the TIO-induced EPT change in the ABL can account for the variations in the SAH.
文摘In designing the human comfort index (CI) used in Guangzhou, a Gaussian curve was adopted as the fundamental profile to develop a traw hat?model of comfort index. The model projects low or high temperatures into low index values and the moderate temperatures into high index values. Air temperature was chosen as a basic factor in the model. Other factors such as humidity, sunshine and wind speed were introduced by considering them as temperature departures to an equivalent apparent temperature (EAT). Since the index is a relative index, 25C was chosen as an ideal apparent temperature (the most comfortable state) and a maximum CI value of 100 was assigned at this temperature. While in other circumstances, the index would be lower than 100. By utilizing this model, the daily comfort index values had been calculated for Guangzhou city for 1998-1999, using mean temperature, mean humidity, mean wind speed and total hours of sunshine. Results show that the new model was reasonable and practicable. Not only could it reflect the monthly variation of human comfort in Guangzhou, but also was sensitive to short-term changes of weather conditions.
文摘One of the factors for the evaluation of the space environment is the comfort of outdoor activities spaces in urban parks. The space composed of different landscape elements has different microclimate environment. In this paper, in order to evaluate the role of thermal comfort in influencing resident’s assessment of the outdoor space and activities of the park, a thermal comfort survey was conducted on the outdoor open space of Mianyang Urban Park in summer. In this article, meteorological surveys, questionnaire surveys and observation of park attendance are selected to collect data. The physiological equivalent temperature (PET) assessment was selected as the index to evaluate resident’s thermal comfort level, and the comprehensive evaluation and analysis of the spatial thermal environment of different outdoor landscape elements in the park. The overall comfort of current visitors is mainly influenced by their subjective heat perception voting (TSV). In this article, we focus on providing microclimate adjustment considerations for urban park landscape design, and may help people understand the outdoor thermal comfort of Mianyang in summer, increase the using time of outdoor activities, and promote the use of outdoor space.
文摘An attempt has been made to investigate the role of vertical wind shear, convective instability and the thermodynamic parameter ( θ es -θ e ) below the first lifting condensation level (FLCL) in the occurrence of instantaneous premonsoon thunderstorm over Agartala (AGT) and Ranchi (RNC) at 12 GMT. Radiosonde data of 1988 have been utilized here. The study has however been confined to 1000 hPa-500 hPa range at most. Here the convectively unstable layers with positive vertical wind shear upto 500 hPa have been termed as ‘Favourable Layers’ (FL) and the level at which an initially stable layer turns out to be convectively unstable for the first time has been termed as ‘Transition Level’ (TL). It is observed that the changes in vertical wind shear are positive at TL at the time of occurrence of thunderstorm (TS) and the corresponding change is negative on fair-weather situation. Moreover, the 90% confidence interval for ( θ es -θ e ) reveals that for AGT the upper layer thermodynamic characteristic is important at the time of occurrence of TS whereas for RNC, the value of ( θ es -θ e ) at the surface is much more effective.
基金funded by the National Natural Science Foundation of China(31901153,32130068,41801187)Natural Science Foundation of Liaoning Province of China(2020-MS-026)the Youth Innovation Promotion Association CAS(2022195).
文摘Together,the heat island eff ect and air pollution pose a threat to human health and well-being in urban settings.Nature-based solutions such as planting trees are a mitigation strategy to improve outdoor temperatures(thermal comfort)and enhance air quality in urban areas.In this study,outdoor thermal comfort,and particulate matter levels were compared between treeless and treed areas to provide a better understanding of how street trees improve thermal comfort and air quality.Street trees decreased the physiological equivalent temperature from 46.3 to 44.2℃in summer but increased it from 36.4 to 37.5℃in autumn.Air temperature and relative humidity contributed more in summer while wind speed contributed more in autumn.Particulate matter concentrations were negatively correlated with physiological equivalent temperature in summer but not in autumn.The presence of trees decreased concentrations of fi ne particulate matter in hot summer conditions but increased in hot autumn conditions.The presence of trees increased coarse particulate matter in very hot summer conditions in summer and in hot autumn conditions.Overall,the layout of trees in urban street canyons should consider the trade-off between outdoor thermal comfort and air quality improvement.
文摘Cairo is characterized by high temperature compared to its surrounding areas,especially during the summer time.This effect is strengthened by the widespread use of sealed surfaces and the lack of vegetation.Therefore,the consumption of electricity in indoor spaces for cooling purposes is a critical problem especially in the summer time.The use of air conditioners has increased during the last 10 years enormously.Because of this,electricity bills increased in a huge way,which represents a burden on the citizens.Therefore,this study aims to find unconventional solutions for the reduction of energy through mitigating urban heat island(UHI)and enhancing thermal performance in Cairo.This paper studies various area cover factions of trees in an urban environment,which can be used to mitigate UHI,improve thermal performance in outdoor spaces and reduce energy consumption in high dense built up areas in Cairo.A small area of 250 m×250 m from downtown Cairo was simulated as a case study using ENVImet V.4.3.2.The comparison between reference scenario and suggested scenarios,which are 30%trees,50%trees and 30%trees+70%grass,were conducted on a summer day in Cairo.The outputs were used to estimate the amount of energy in every scenario using DesignBuilder model.The results show that the scenario with 50%trees led to the best human thermal comfort(3 K cooler).Although for the demand of energy in the buildings,the street orientation as well as the aspect ratio(H/W)play an important role and should be considered.
文摘The urban microclimate has direct implications with regards to thermal comfort indoors as well as outdoors. In the tropics, the outdoor thermal comfort conditions during daytime are often far above acceptable comfort standards due to intense solar radiation and high solar elevations. This study aims to know effects of simple and fundamental building forms on microclimate and outdoor thermal comfort in a high dense tropical city, focusing on Dhaka, Bangladesh as a study city. Investigations are carried out on existing area and model areas with modified building forms （in respect of height and shape） on the microclimate as well as on outdoor thermal comfort during daytime in summer. This study has demonstrated that the model using less ground coverage and higher buildings can offer a better thermal climate than the models using maximum ground coverage in a high-density tropical city.
文摘The recent development in Lucknow shows that the amount of built mass may increase significantly soon,which may affect outdoor thermal comfort.This study aims to achieve a better alternative to the geometrical configuration of vertical surfaces that helps improve the outdoor thermal comfort level.The study primarily deals with the exploration of built forms by altering the planar forms,heights,and orientations to arrive at a better composition of vertical surfaces.144 typologies were finally generated,which were then simulated in ENVI-met.The results show that,with the I-shaped typology it is difficult to reduce solar access,whereas in terms of ventilation,the typology performed better than L-shaped and C-shaped typologies.For this reason,the hours of solar access,as well as wind speed,should be seen together while developing the built-form typology.Urban neighborhoods can be designed with streets and open spaces oriented primarily to northeast-southwest and northwest-southeast directions which allow the open spaces to be thermally more comfortable than the rest of the orientation.This research highlights the importance of varying building heights to enhance thermal comfort.The findings provide valuable insights for composite climate cities like lucknow and can serve as a framework for future design strategies aimed at mitigating outdoor thermal discomfort.It is therefore important for planners,urban designers,and architects to design considering the minimal impact of the upcoming development on the thermal comfort level.
基金The work described in this paper was supported by the National Natural Science Foundation of China(No.52008079,No.52278094)the China Postdoctoral Science Foundation(No.2021M691790).
文摘During the pandemic,face masks are one of the most significant self-protection necessities,but they also cause heat stress.By using the ERA5(ECMWF Reanalysis 5th Generation)database and the local weather bureau data,the effect of mask wearing on outdoor thermal sensation has been investigated by a survey conducted in the hot summer and cold winter region of eastern China in the summer of 2020.Results show that wearing a face mask for a longer period result in a higher level of discomfort,and the primary source of discomfort is hot and stuffy feelings.The effect of relative humidity is crucial for mask wearers in warm-biased thermal environments,as mean thermal sensation vote(TSV)peaks when environmental relative humidity reaches the range of 70%to 80%and decreases after this range due to the evaporation within the microclimate created by a face mask.Meanwhile,prolonged mask wearing increases participants’hot feelings,especially in warm environments.Specifically,participants wearing face masks for less than 30 min feel hot at a physiological equivalent temperature(PET)value of 34.4℃,but those who wear them for over 60 min express hot feelings even at a PET value of 24.7℃.The participants who wear a face mask while walking slowly outdoors have similar thermal sensations to those who do not wear a mask,but are in a higher activity level.The findings demonstrate that mask wearing has a crucial impact on outdoor thermal comfort assessment in a warm-biased outdoor thermal environment.
