Full-length grouted bolts play a crucial role in geotechnical engineering thanks to their excellent stability.However,few studies have been concerned with the degrading performance of grouted rock bolts caused by exte...Full-length grouted bolts play a crucial role in geotechnical engineering thanks to their excellent stability.However,few studies have been concerned with the degrading performance of grouted rock bolts caused by extensive and continuous heat conduction from surrounding rocks in high-geothermal tunnels buried more than 100 m(temperature from 28C to 100C).To investigate the damage mechanism,we examined the time-varying behaviors of grouted rock bolts in both constant and variable temperature curing environments and their damage due to the coupling effects of high temperature and humidity through mechanical and micro-feature tests,including uniaxial compression test,pull-out test,computed tomography(CT)scans,X-ray diffraction(XRD)test,thermogravimetric analysis(TGA),etc.,and further analyzed the relationship between grout properties and anchorage capability.In order to facilitate a rapid assessment and control of the anchorage performance of anchors in different conditions,results of the interface bond degradation tests were correlated to environment parameters based on the damage model of interfacial bond stress proposed.Accordingly,a thermal hazard classification criterion for anchorage design in high-geothermal tunnels was suggested.Based on the reported results,although high temperature accelerated the early-stage hydration reaction of grouting materials,it affected the distribution and quantity of hydration products by inhibiting hydration degree,thus causing mechanical damage to the anchorage system.There was a significant positive correlation between the strength of the grouting material and the anchoring force.Influenced by the changes in grout properties,three failure patterns of rock bolts typically existed.Applying a hot-wet curing regime results in less reduction in anchorage force compared to the hot-dry curing conditions.The findings of this study would contribute to the design and investigations of grouted rock bolts in high-geothermal tunnels.展开更多
Wetlands play a key role in regulating local climate as well as reducing impacts caused by climate change. Rapid observations of the land surface temperature(LST) are, therefore, valuable for studying the dynamics of ...Wetlands play a key role in regulating local climate as well as reducing impacts caused by climate change. Rapid observations of the land surface temperature(LST) are, therefore, valuable for studying the dynamics of wetland systems. With the development of thermal remote sensing technology, LST retrieval with satellite images is a practicable way to detect a wetland and its neighboring area’s thermal environment from a non-point visual angle rather than the traditional detection from a point visual angle. The mono-windows(MW) method of retrieving LST was validated. On the basis of estimated LST, we used Geographical Information System(GIS) technology to study the impact of wetland reclamation on local temperatures at a regional scale. Following that, correlations between LST and the wetland were analyzed. The results show that: 1) It is feasible to retrieve the LST from Landsat 8 OLI satellite images with MW model. The model was validated with the land surface temperature observed in four meteorological stations when the satellite scanned the study region. The satellite retrieval error was approximately 1.01°C. 2) The relationship between the spatial distribution of land surface temperatures and the Zhalong wetland was analyzed based on GIS technology. The results show that wetland has an obvious influence on LST, and that this influence decreases with increasing distance from the wetland. When the distance from the wetland was less than 500 m, its influence on LST was significant. Results also illustrated that the effect of the wetland’s different land use/land cover’s LST distribution varied with different seasons.展开更多
Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurate...Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurately evaluate the reliability of WPC,which is crucial for the design and maintenance of wind turbines.Firstly,the index of effective temperature(ET)is presented to quantify the effects of temperature and humidity on the semiconductor operation.A novel method is proposed to evaluate the lifetime and calculate the aging failure rates of the semiconductors considering the fluctuations of ET.Secondly,the failure mode and effect analysis(FMEA)of WPC is investigated based on the topology and control scheme.The conventional two-state reliability model of the WPC is extended to the multi-state reliability model where the partial working state under the fault-tolerant control scheme is allowed.Finally,a reliability evaluation framework is established to calculate the parameters of the WPC reliability model considering the variable failure rates and repair activities of semiconductors.Case studies are designed to verfify the proposed method using a practical wind turbine.展开更多
Data support for wetland protection function evaluation can be provided by quantitatively analyzing the ability of regulating the regional climate of the wetland ecosystem. In this study, the cold-humid effect of the ...Data support for wetland protection function evaluation can be provided by quantitatively analyzing the ability of regulating the regional climate of the wetland ecosystem. In this study, the cold-humid effect of the Baiyangdian wetland was analyzed by comparing the meteorological conditions of the Baiyangdian wetland and its surrounding areas. Meanwhile, the regulatory functions of the Baiyangdian wetland for the processes and magnitudes of temperature and relative humidity from August to October 2008 were evaluated. The results show that daily mean temperatures in the Baiyangdian wetland were lower than in the surrounding areas, and that temperature differences mainly occurred in the daytime but were not obvious at night. Diurnal temperature ranges in the Baiyangdian wetland were lower than in the surrounding areas, and the higher the diurnal temperature range in the surrounding areas was, the stronger the regulation ability of the Baiyangdian wetland. Compared with the surrounding areas, the decline of the daily minimum temperature in the Baiyangdian wetland was gentler, and the mean relative humidity there was higher. The present findings indicate that effects of the Baiyangdian wetland on climate and humidity regulation are significant.展开更多
Caragana microphylla is one of the key species for vegetation restoration in Horqin Sandy Land. Adopting field investigation and outdoor experiments,the microclimate effect of artificial C. microphylla communities wit...Caragana microphylla is one of the key species for vegetation restoration in Horqin Sandy Land. Adopting field investigation and outdoor experiments,the microclimate effect of artificial C. microphylla communities with different restoration years were studied by observing wind velocity,air temperature,relative humidity and soil temperature. The results show that:( 1) Caragana microphylla community has an obvious wind-breaking effect near ground surface. Compared with shifting dunes,the wind velocity in the 6-year-old and 11-year-old C. microphylla shrubs at the height of 30 cm separately decreases by 71. 9% and 76. 0%.( 2) Mean daily temperature in the 6-year-old and 11-yearold C. microphylla communities is 3. 7 ℃ and 4. 9 ℃ lower than in shifting dunes,respectively.( 3) The relative humidity of air in the Caragana microphylla shrubs is higher than in shifting dunes.( 4) Soil temperature in C. microphylla plantation is lower than in shifting dunes. These results are significant in further exploring material and energy exchange near surface layer of artificial vegetation in the extremely arid condition.展开更多
The optical fiber relative humidity sensor based on Nafion-crystal violet film was developed. The effect of samples temperature in the range from 299.15 K to 324.15 K on the sensing performance of the sensor was inv...The optical fiber relative humidity sensor based on Nafion-crystal violet film was developed. The effect of samples temperature in the range from 299.15 K to 324.15 K on the sensing performance of the sensor was investigated. The mathematical function between temperature and the sensitivity of the sensor was established according to the reactive theory of sensor to the relative humidity, which was validated with the experiment. With the research, the application range of the sensor was extended, which made the sensor keep a good veracity when it was used in situ.展开更多
Heterogeneous reactions of nitrogen dioxide （NO2） on soils collected from Dalian （S 1） and Changsha （S2） were investigated over the relative humidity （RH） range of 5%-80% and temperature range of 278-328 K usi...Heterogeneous reactions of nitrogen dioxide （NO2） on soils collected from Dalian （S 1） and Changsha （S2） were investigated over the relative humidity （RH） range of 5%-80% and temperature range of 278-328 K using a horizontal coated-wall flow tube. The initial uptake coefficients of NO2 on S2 exhibited a decreasing trend from （10 ± 1.3） × 10-8 to （3.1 ± 0.5） x 10-8 with the relative humidity increasing from 5% to 80%. In the temperature effect studies, the initial uptake coefficients of S1 and S2 decreased from （10± 1.2） × 10-8 to （3.8 ± 0.5） × 10-8 and from （16± 2.2） × 10-8 to （3.8 ±0.4） × 10-8 when temperature increased from 278 to 288 K for S1 and from 278 to 308 K for S2, respectively. As the temperature continued to increase, the initial uptake coefficients of S1 and S2 returned to （7.9 ± 1.1）× 10-8 and （20 ± 3.1） × 10-8 at 313 and 328 K, respectively. This study shows that relative humidity could influence the uptake kinetics of NO2 on soil and temperature would impact the heterogeneous chemistry of NO2.展开更多
One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for stru...One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.展开更多
The thermal environment and thermal comfort of a building are greatly affected by the desig n of the build ing interface form. Most con temporary architectural designs con sider only the relations between architectura...The thermal environment and thermal comfort of a building are greatly affected by the desig n of the build ing interface form. Most con temporary architectural designs con sider only the relations between architectural form and architectural beauty. Few studies on the correlati on of architectural form and thermal comfort address the in flue nee of architectural form on thermal comfort and thermal environment. These studies are particularly important for gymnasium architectures located in hot and humid areas, which have high requirements for thermal comfort. This paper presents an experimental investigati on and an an alysis of the effect of the building in terface form of gymnasiums on thermal comfort in hot and humid subtropical regions during summer. Results showed that the influence of the top interface forms on thermal comfort is mainly dominated by the mea n radiant temperature, which could be con trolled to improve thermal comfort. The in fluence of side interface forms on thermal comfort is mainly domi nated by air velocity, and thermal comfort could be improved by promoting natural ventilation on the side interface form design to reduce indoor heat. This research enhanced our understanding of the relation between the in terface form and the thermal comfort of gymnasiums. In addition, this paper provides a theoretical reference for the sustainable design of gymnasiums in hot and humid climates.展开更多
基金support from the National Natural Science Foundation of China(Grant No.52208387)Open Fund of Key Laboratory of Geohazard Prevention of Hilly Mountains,Ministry of Land and Resources,China(Fujian Key Laboratory of Geohazard Prevention)(Grant No.FJKLGH2022K001).
文摘Full-length grouted bolts play a crucial role in geotechnical engineering thanks to their excellent stability.However,few studies have been concerned with the degrading performance of grouted rock bolts caused by extensive and continuous heat conduction from surrounding rocks in high-geothermal tunnels buried more than 100 m(temperature from 28C to 100C).To investigate the damage mechanism,we examined the time-varying behaviors of grouted rock bolts in both constant and variable temperature curing environments and their damage due to the coupling effects of high temperature and humidity through mechanical and micro-feature tests,including uniaxial compression test,pull-out test,computed tomography(CT)scans,X-ray diffraction(XRD)test,thermogravimetric analysis(TGA),etc.,and further analyzed the relationship between grout properties and anchorage capability.In order to facilitate a rapid assessment and control of the anchorage performance of anchors in different conditions,results of the interface bond degradation tests were correlated to environment parameters based on the damage model of interfacial bond stress proposed.Accordingly,a thermal hazard classification criterion for anchorage design in high-geothermal tunnels was suggested.Based on the reported results,although high temperature accelerated the early-stage hydration reaction of grouting materials,it affected the distribution and quantity of hydration products by inhibiting hydration degree,thus causing mechanical damage to the anchorage system.There was a significant positive correlation between the strength of the grouting material and the anchoring force.Influenced by the changes in grout properties,three failure patterns of rock bolts typically existed.Applying a hot-wet curing regime results in less reduction in anchorage force compared to the hot-dry curing conditions.The findings of this study would contribute to the design and investigations of grouted rock bolts in high-geothermal tunnels.
基金Under the auspices of National Key Research and Development Program of China(No.2016YFA0602301-1)Strategic Planning Project of Northeast Institute of Geography and Agroecology(IGA)Chinese Academy of Sciences(No.Y6H2091001)
文摘Wetlands play a key role in regulating local climate as well as reducing impacts caused by climate change. Rapid observations of the land surface temperature(LST) are, therefore, valuable for studying the dynamics of wetland systems. With the development of thermal remote sensing technology, LST retrieval with satellite images is a practicable way to detect a wetland and its neighboring area’s thermal environment from a non-point visual angle rather than the traditional detection from a point visual angle. The mono-windows(MW) method of retrieving LST was validated. On the basis of estimated LST, we used Geographical Information System(GIS) technology to study the impact of wetland reclamation on local temperatures at a regional scale. Following that, correlations between LST and the wetland were analyzed. The results show that: 1) It is feasible to retrieve the LST from Landsat 8 OLI satellite images with MW model. The model was validated with the land surface temperature observed in four meteorological stations when the satellite scanned the study region. The satellite retrieval error was approximately 1.01°C. 2) The relationship between the spatial distribution of land surface temperatures and the Zhalong wetland was analyzed based on GIS technology. The results show that wetland has an obvious influence on LST, and that this influence decreases with increasing distance from the wetland. When the distance from the wetland was less than 500 m, its influence on LST was significant. Results also illustrated that the effect of the wetland’s different land use/land cover’s LST distribution varied with different seasons.
基金supported by the National Natural Science Foundation of China(No.52022016)China Postdoctoral Science Foundation(No.2021M693711)Fundamental Research Funds for the Central Universities(No.2021CDJQY-037)。
文摘Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurately evaluate the reliability of WPC,which is crucial for the design and maintenance of wind turbines.Firstly,the index of effective temperature(ET)is presented to quantify the effects of temperature and humidity on the semiconductor operation.A novel method is proposed to evaluate the lifetime and calculate the aging failure rates of the semiconductors considering the fluctuations of ET.Secondly,the failure mode and effect analysis(FMEA)of WPC is investigated based on the topology and control scheme.The conventional two-state reliability model of the WPC is extended to the multi-state reliability model where the partial working state under the fault-tolerant control scheme is allowed.Finally,a reliability evaluation framework is established to calculate the parameters of the WPC reliability model considering the variable failure rates and repair activities of semiconductors.Case studies are designed to verfify the proposed method using a practical wind turbine.
基金supported by the National Natural Science Foundation of China (Grant No. 50139020)the National Basic Research Program of China (973 Program, Grant No. 2006CB403405)
文摘Data support for wetland protection function evaluation can be provided by quantitatively analyzing the ability of regulating the regional climate of the wetland ecosystem. In this study, the cold-humid effect of the Baiyangdian wetland was analyzed by comparing the meteorological conditions of the Baiyangdian wetland and its surrounding areas. Meanwhile, the regulatory functions of the Baiyangdian wetland for the processes and magnitudes of temperature and relative humidity from August to October 2008 were evaluated. The results show that daily mean temperatures in the Baiyangdian wetland were lower than in the surrounding areas, and that temperature differences mainly occurred in the daytime but were not obvious at night. Diurnal temperature ranges in the Baiyangdian wetland were lower than in the surrounding areas, and the higher the diurnal temperature range in the surrounding areas was, the stronger the regulation ability of the Baiyangdian wetland. Compared with the surrounding areas, the decline of the daily minimum temperature in the Baiyangdian wetland was gentler, and the mean relative humidity there was higher. The present findings indicate that effects of the Baiyangdian wetland on climate and humidity regulation are significant.
基金Supported by Project of National Natural Science Foundation(71203057,41271115,41071187)Young Scholar Project of Humanities and Social Science Foundation of Ministry of Education(11YJCZH056)Ph.D Foundation Project of Henan Polytechnic University(B2011-017)
文摘Caragana microphylla is one of the key species for vegetation restoration in Horqin Sandy Land. Adopting field investigation and outdoor experiments,the microclimate effect of artificial C. microphylla communities with different restoration years were studied by observing wind velocity,air temperature,relative humidity and soil temperature. The results show that:( 1) Caragana microphylla community has an obvious wind-breaking effect near ground surface. Compared with shifting dunes,the wind velocity in the 6-year-old and 11-year-old C. microphylla shrubs at the height of 30 cm separately decreases by 71. 9% and 76. 0%.( 2) Mean daily temperature in the 6-year-old and 11-yearold C. microphylla communities is 3. 7 ℃ and 4. 9 ℃ lower than in shifting dunes,respectively.( 3) The relative humidity of air in the Caragana microphylla shrubs is higher than in shifting dunes.( 4) Soil temperature in C. microphylla plantation is lower than in shifting dunes. These results are significant in further exploring material and energy exchange near surface layer of artificial vegetation in the extremely arid condition.
文摘The optical fiber relative humidity sensor based on Nafion-crystal violet film was developed. The effect of samples temperature in the range from 299.15 K to 324.15 K on the sensing performance of the sensor was investigated. The mathematical function between temperature and the sensitivity of the sensor was established according to the reactive theory of sensor to the relative humidity, which was validated with the experiment. With the research, the application range of the sensor was extended, which made the sensor keep a good veracity when it was used in situ.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KJCX2-EW-H01)the National Basic Research Program(973) of China (No. 2011CB403401)the National Natural Science Foundation of China (No. 21077109,41005070)
文摘Heterogeneous reactions of nitrogen dioxide （NO2） on soils collected from Dalian （S 1） and Changsha （S2） were investigated over the relative humidity （RH） range of 5%-80% and temperature range of 278-328 K using a horizontal coated-wall flow tube. The initial uptake coefficients of NO2 on S2 exhibited a decreasing trend from （10 ± 1.3） × 10-8 to （3.1 ± 0.5） x 10-8 with the relative humidity increasing from 5% to 80%. In the temperature effect studies, the initial uptake coefficients of S1 and S2 decreased from （10± 1.2） × 10-8 to （3.8 ± 0.5） × 10-8 and from （16± 2.2） × 10-8 to （3.8 ±0.4） × 10-8 when temperature increased from 278 to 288 K for S1 and from 278 to 308 K for S2, respectively. As the temperature continued to increase, the initial uptake coefficients of S1 and S2 returned to （7.9 ± 1.1）× 10-8 and （20 ± 3.1） × 10-8 at 313 and 328 K, respectively. This study shows that relative humidity could influence the uptake kinetics of NO2 on soil and temperature would impact the heterogeneous chemistry of NO2.
基金Research Committee,University of Macao,China Under Grant No.RG077/07-08S/09R/YKV/FST
文摘One branch of structural health monitoring (SHM) utilizes dynamic response measurements to assess the structural integrity of civil infrastructures. In particular,modal frequency is a widely adopted indicator for structural damage since its square is proportional to structural stiffness. However,it has been demonstrated in various SHM projects that this indicator is substantially affected by fluctuating environmental conditions. In order to provide reliable and consistent information on the health status of the monitored structures,it is necessary to develop a method to filter this interference. This study attempts to model and quantify the environmental influence on the modal frequencies of reinforced concrete buildings. Daily structural response measurements of a twenty-two story reinforced concrete building were collected and analyzed over a one-year period. The Bayesian spectral density approach was utilized to identify the modal frequencies of this building and it was clearly seen that the temperature and humidity fluctuation induced notable variations. A mathematical model was developed to quantify the environmental effects and model complexity was taken into consideration. Based on a Timoshenko beam model,the full model class was constructed and other reduced-order model class candidates were obtained. Then,the Bayesian modal class selection approach was employed to select the one with the most suitable complexity. The proposed model successfully characterizes the environmental influence on the modal frequencies. Furthermore,the estimated uncertainty of the model parameters allows for assessment of the reliability of the prediction. This study not only improves the understanding about the monitored structure,but also establishes a systematic approach for reliable health assessment of reinforced concrete buildings.
文摘The thermal environment and thermal comfort of a building are greatly affected by the desig n of the build ing interface form. Most con temporary architectural designs con sider only the relations between architectural form and architectural beauty. Few studies on the correlati on of architectural form and thermal comfort address the in flue nee of architectural form on thermal comfort and thermal environment. These studies are particularly important for gymnasium architectures located in hot and humid areas, which have high requirements for thermal comfort. This paper presents an experimental investigati on and an an alysis of the effect of the building in terface form of gymnasiums on thermal comfort in hot and humid subtropical regions during summer. Results showed that the influence of the top interface forms on thermal comfort is mainly dominated by the mea n radiant temperature, which could be con trolled to improve thermal comfort. The in fluence of side interface forms on thermal comfort is mainly domi nated by air velocity, and thermal comfort could be improved by promoting natural ventilation on the side interface form design to reduce indoor heat. This research enhanced our understanding of the relation between the in terface form and the thermal comfort of gymnasiums. In addition, this paper provides a theoretical reference for the sustainable design of gymnasiums in hot and humid climates.
