Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating ag...Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the'true'ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer.展开更多
An adhesive of the SiBCN ceramic was synthesized through the polymer derived ceramics(PDC)route.Meanwhile with higher adhesion strength and simpler process condition,the polyborosilazane(PSNB)was modified by E-44 epox...An adhesive of the SiBCN ceramic was synthesized through the polymer derived ceramics(PDC)route.Meanwhile with higher adhesion strength and simpler process condition,the polyborosilazane(PSNB)was modified by E-44 epoxy resin.The E-44 epoxy resin was used to promote the oxidation process of SiBCN,in other words,to produce more amount of SiO2-B2O3 glasses.The phase composition,elemental analysis,chemical bonds and microstructure were investigated by using X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscope(SEM)measurements.The E-44 modified adhesives were cured at 120℃in air for 2 h,and were pyrolyzed at 1200,1400,and 1500℃for 2 h in air,respectively.The highest adhesion strength of the modified adhesive was up to 5.33,12.23,and 12.50 MPa after being heat treated at 1200,1400,and 1500℃,respectively.Finally,we proposed an adhesion model and revealed the adhesion mechanism of SiBCN ceramic.展开更多
This study revealed land use/cover change of Manikganj Sadar Upazila concerning with urbanization of Dhaka city. The study area also offers better residential opportunity and food support for Dhaka city. The major foc...This study revealed land use/cover change of Manikganj Sadar Upazila concerning with urbanization of Dhaka city. The study area also offers better residential opportunity and food support for Dhaka city. The major focus of this study is to find out the spatial and temporal changes of land use/cover and its effects on urbanization while Dhaka city is an independent variable. For analyzing land use/cover change GIS and remote sensing technique were used. The maps showed that, between 1989 and 2009 built-up areas increased approximately +12%, while agricultural land decreased -7%, water bodies decreased about -2% and bare land decreased about -2%. The significant change in agriculture land use is observed in the south-eastern and north eastern site of the city because of nearest distance and better transportation facilities with Dhaka city. This study will contribute to the both the development of sustainable urban land use planning decisions and also for forecasting possible future changes in growth patterns.展开更多
A field study on the estimation and analysis of iron stability in drinking water distribution system was carried out in a city of China. The stability of iron ion was estimated by pC-pH figure. It was found that iron ...A field study on the estimation and analysis of iron stability in drinking water distribution system was carried out in a city of China. The stability of iron ion was estimated by pC-pH figure. It was found that iron ion was unstable, with a high Fe （OH）3 precipitation tendency and obvious increase in turbidity. The outer layer of the corrosion scale was compact, while the inner core was porous. The main composition of the scale was iron, and the possible compound constitutes of the outer scale were α-FeOH, γ-FeOOH, α-Fe2O3, γ-F2O3, FeCl3, while the inner were Fe3O4, FeCl2, FeCO3. According to the characteristics of the corrosion scale, it was thought that the main reason for iron instability was iron release from corrosion scale. Many factors such as pipe materials, dissolved oxygen and chlorine residual affect iron release. Generally, higher iron release occurred with lower dissolved oxygen or chlorine residual concentration, while lower iron release occurred with higher dissolved oxygen or chlorine residual concentration. The reason was considered that the passivated out layer of scale of ferric oxide was broken down by reductive reaction in a condition of low oxidants concentration, which would result more rapid corrosion of the nine and red water phenomenon.展开更多
New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investiga...New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019.The proportions of the nucleation mode,Aitken mode,and accumulation mode were 24.59%,53.10%,and 22.30%,respectively,which indicates the presence of abundant ultrafine particles in Hefei.Forty-six NPF events occurred during the observation days,accounting for 41.82%of the entire observation period.Moreover,the favorable meteorological conditions,potential precursor gases,and PM_(2.5)range of the NPF events were analyzed.Compared to non-NPF days,the NPF events preferentially occurred on days with lower relative humidity,higher wind speeds,and higher temperatures.When the PM_(2.5) was 15–20,70–80,and105–115μg/m^(3),the frequency of the NPF events was higher.Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM_(2.5) ranged from 15 to 20μg/m^(3),and related to gaseous precursors like SO_(2) and NO_(2) when PM_(2.5)was located at 70-80 and 105–115μg/m^(3).On pollution days,NPF events did not directly contribute to the increase in the PM_(2.5) in the daytime,however,NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM_(2.5) contents.This could lead to pollution that lasted into the next day.These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.展开更多
The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin.There are many views on the uplift time of Helan Mountain...The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin.There are many views on the uplift time of Helan Mountain,which is Late Triassic and Late Jurassic.It is concluded by the present strata,magmatic rock and hot fluid distribution that the Helan Mountain does not uplift in Late Triassic to Middle Jurassic but after Middle Jurassic.Through the research of the sedimentary strata and deposit rate in Yinchuan Graben which is near to the Helan Mountain,it is proved that the Helan Mountain uplifts in Eocene with a huge scale and in Pliocene with a rapid speed.The fission track analysis of apatite and zircon can be used to determine the precise uplift time of Helan Mountain,which shows that four stages of uplifting or cooling:Late Jurassic to the early stage of Early Cretaceous,mid-late stage of Early Cretaceous,Late Cretaceous and since Eocene.During the later two stages the uplift is most apparent and the mid-late stage of Early Cretaceous is a regional cooling course.Together with several analysis ways,it is considered that the earliest time of Helan Mountain uplift is Late Jurassic with a limited scale and that Late Cretaceous uplift is corresponding to the whole uplift of Ordos Basin,extensive uplift happened in Eocene and rapid uplift in Pliocene.展开更多
As a consequence of recent global warming and its social impact, regional climate change is attracting an increasing amount of attention from scientists. A May-July temperature proxy extending back to 1836 was develop...As a consequence of recent global warming and its social impact, regional climate change is attracting an increasing amount of attention from scientists. A May-July temperature proxy extending back to 1836 was developed from tree-ring width of Chinese pine (Pinus tabulaeformis Carr.) found in the middle Lüliang Mountains, northern China. Correlations with climatic data from six nearby meteorological stations range from -0.58 to -0.65, indicating a strong response of tree-ring index to May-July mean temperatures, which were subsequently reconstructed. The reconstruction captures 45% (F=38.474, P<0.001) of the regional variance in the instrumental data over the calibration period 1955-2003. Reconstructed warm and cold periods were verified by additional temperature reconstructions based on tree-ring data from northern China. In addition, the reconstruction was significantly corre-lated with May-July mean temperatures from 13 other meteorological stations in northern China, suggesting that our reconstruction is also representative of north-central China. The warming trend during the second half of the 20th century is seen in the reconstruction, but only the 1994-2002 mean temperature seems unprecedented over the whole reconstructed period.展开更多
A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendroc hronological techniques. Based on the results of correlation function analysis, the total precipitati...A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendroc hronological techniques. Based on the results of correlation function analysis, the total precipitation from the previous August to current July was reconstructed for 1771-2008 AD with an explained variance of 49.3%. The reconstruction correlated well with the dryness/wetness series derived from historical documents, as well as the precipitation reconstruction of the Chifeng-Weichang region. There were eight intervals with greater precipitation than the average (associated with the strong East Asian summer monsoon) and seven intervals lower than the average (weak monsoon). A power spectrum analysis showed that there were 120 a, 80 a, 8 a and 2 a periodicities.展开更多
基金supported by the China Meteorological Administration under Grant GYHY201006024the Chinese Academy of Sciences Strategic Priority Research Program under Grant XDA05110104spon-sorship of National Science Foundation
文摘Utilizing aircraft sounding data collected from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1998) campaign, the authors evaluated commonly-used profile methods for Arctic ABL height estimation by validating against the'true'ABL height from aircraft sounding profiles, where ABL height is defined as the top of the layer with significant turbulence. Furthermore, the best performing method was used to estimate ABL height from the one-year GPS soundings obtained during SHEBA (October 1997-October 1998). It was found that the temperature gradient method produces a reliable estimate of ABL height. Additionally, the authors determined optimal threshold values of temperature gradient for stable boundary layer (SBL) and convective boundary layer (CBL) to be 6.5 K/100 m and 1.0 K/100 m, respectively. The maximum ABL height during the year was 1150 m occurred in May. Median values of Arctic ABL height in May, June, July, and August were 400 m, 430 m, 180 m, and 320 m, respectively. Arctic ABL heights are clearly higher in the spring than in the summer.
基金Funded by the Research Fund of the National Key Research and Development Program of China(No.2017YFB0703200)the State Key Laboratory of Solidification Processing(NWPU),China(No.135-QP-2015)the Fundamental Research Funds for the Central Universities(No.3102017zy058).
文摘An adhesive of the SiBCN ceramic was synthesized through the polymer derived ceramics(PDC)route.Meanwhile with higher adhesion strength and simpler process condition,the polyborosilazane(PSNB)was modified by E-44 epoxy resin.The E-44 epoxy resin was used to promote the oxidation process of SiBCN,in other words,to produce more amount of SiO2-B2O3 glasses.The phase composition,elemental analysis,chemical bonds and microstructure were investigated by using X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscope(SEM)measurements.The E-44 modified adhesives were cured at 120℃in air for 2 h,and were pyrolyzed at 1200,1400,and 1500℃for 2 h in air,respectively.The highest adhesion strength of the modified adhesive was up to 5.33,12.23,and 12.50 MPa after being heat treated at 1200,1400,and 1500℃,respectively.Finally,we proposed an adhesion model and revealed the adhesion mechanism of SiBCN ceramic.
文摘This study revealed land use/cover change of Manikganj Sadar Upazila concerning with urbanization of Dhaka city. The study area also offers better residential opportunity and food support for Dhaka city. The major focus of this study is to find out the spatial and temporal changes of land use/cover and its effects on urbanization while Dhaka city is an independent variable. For analyzing land use/cover change GIS and remote sensing technique were used. The maps showed that, between 1989 and 2009 built-up areas increased approximately +12%, while agricultural land decreased -7%, water bodies decreased about -2% and bare land decreased about -2%. The significant change in agriculture land use is observed in the south-eastern and north eastern site of the city because of nearest distance and better transportation facilities with Dhaka city. This study will contribute to the both the development of sustainable urban land use planning decisions and also for forecasting possible future changes in growth patterns.
文摘A field study on the estimation and analysis of iron stability in drinking water distribution system was carried out in a city of China. The stability of iron ion was estimated by pC-pH figure. It was found that iron ion was unstable, with a high Fe （OH）3 precipitation tendency and obvious increase in turbidity. The outer layer of the corrosion scale was compact, while the inner core was porous. The main composition of the scale was iron, and the possible compound constitutes of the outer scale were α-FeOH, γ-FeOOH, α-Fe2O3, γ-F2O3, FeCl3, while the inner were Fe3O4, FeCl2, FeCO3. According to the characteristics of the corrosion scale, it was thought that the main reason for iron instability was iron release from corrosion scale. Many factors such as pipe materials, dissolved oxygen and chlorine residual affect iron release. Generally, higher iron release occurred with lower dissolved oxygen or chlorine residual concentration, while lower iron release occurred with higher dissolved oxygen or chlorine residual concentration. The reason was considered that the passivated out layer of scale of ferric oxide was broken down by reductive reaction in a condition of low oxidants concentration, which would result more rapid corrosion of the nine and red water phenomenon.
基金supported by grants from the National Key Research and Development Program of China(Nos.2017YFC0210002,2018YFC0213104,2016YFC0203302 and 2017YFC0212800)the National Natural Science Foundation of China(Nos.41722501,51778596,and 41977184)+5 种基金the Anhui Science and Technology Major Project(No.18030801111)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102 and DQGG0205)the Natural Science Foundation of Anhui Province(No.1908085QD170)the Key Research and Development Project of Anhui Province(No.202004i07020002)the Young Talent Project of the Center for Excellence in Regional Atmospheric Environment,CAS(No.CERAE202004)。
文摘New particle formation(NPF)events are an increasingly interesting topic in air quality and climate science.In this study,the particle number size distributions,and the frequency of NPF events over Hefei were investigated from November 2018 to February 2019.The proportions of the nucleation mode,Aitken mode,and accumulation mode were 24.59%,53.10%,and 22.30%,respectively,which indicates the presence of abundant ultrafine particles in Hefei.Forty-six NPF events occurred during the observation days,accounting for 41.82%of the entire observation period.Moreover,the favorable meteorological conditions,potential precursor gases,and PM_(2.5)range of the NPF events were analyzed.Compared to non-NPF days,the NPF events preferentially occurred on days with lower relative humidity,higher wind speeds,and higher temperatures.When the PM_(2.5) was 15–20,70–80,and105–115μg/m^(3),the frequency of the NPF events was higher.Nucleation mode particles were positively related to atmospheric oxidation indicated by ozone when PM_(2.5) ranged from 15 to 20μg/m^(3),and related to gaseous precursors like SO_(2) and NO_(2) when PM_(2.5)was located at 70-80 and 105–115μg/m^(3).On pollution days,NPF events did not directly contribute to the increase in the PM_(2.5) in the daytime,however,NPF events would occur during the night and the growth of particulate matter contributes to the nighttime PM_(2.5) contents.This could lead to pollution that lasted into the next day.These findings are significant to the improvement of our understanding of the effects of aerosols on air quality.
基金Supported by the National Basic Research Program of China(Grant No.2003CB214607)the Development Project of Changjiang River Scholars and the Innovation Research Team in University(Grant No.IRT0559)
文摘The Helan Mountain lies in the northwest margin of Ordos Basin and its uplift periods have close relations with the tectonic feature and evolution of the basin.There are many views on the uplift time of Helan Mountain,which is Late Triassic and Late Jurassic.It is concluded by the present strata,magmatic rock and hot fluid distribution that the Helan Mountain does not uplift in Late Triassic to Middle Jurassic but after Middle Jurassic.Through the research of the sedimentary strata and deposit rate in Yinchuan Graben which is near to the Helan Mountain,it is proved that the Helan Mountain uplifts in Eocene with a huge scale and in Pliocene with a rapid speed.The fission track analysis of apatite and zircon can be used to determine the precise uplift time of Helan Mountain,which shows that four stages of uplifting or cooling:Late Jurassic to the early stage of Early Cretaceous,mid-late stage of Early Cretaceous,Late Cretaceous and since Eocene.During the later two stages the uplift is most apparent and the mid-late stage of Early Cretaceous is a regional cooling course.Together with several analysis ways,it is considered that the earliest time of Helan Mountain uplift is Late Jurassic with a limited scale and that Late Cretaceous uplift is corresponding to the whole uplift of Ordos Basin,extensive uplift happened in Eocene and rapid uplift in Pliocene.
基金supported by the National Natural Science Foundation of China (40701196, 40890051, 40525004 and 40599423)the West Light Foundation of the Chinese Academy of Sciences,the Special Foundation of President of the Chinese Academy of Sciences
文摘As a consequence of recent global warming and its social impact, regional climate change is attracting an increasing amount of attention from scientists. A May-July temperature proxy extending back to 1836 was developed from tree-ring width of Chinese pine (Pinus tabulaeformis Carr.) found in the middle Lüliang Mountains, northern China. Correlations with climatic data from six nearby meteorological stations range from -0.58 to -0.65, indicating a strong response of tree-ring index to May-July mean temperatures, which were subsequently reconstructed. The reconstruction captures 45% (F=38.474, P<0.001) of the regional variance in the instrumental data over the calibration period 1955-2003. Reconstructed warm and cold periods were verified by additional temperature reconstructions based on tree-ring data from northern China. In addition, the reconstruction was significantly corre-lated with May-July mean temperatures from 13 other meteorological stations in northern China, suggesting that our reconstruction is also representative of north-central China. The warming trend during the second half of the 20th century is seen in the reconstruction, but only the 1994-2002 mean temperature seems unprecedented over the whole reconstructed period.
基金the National Natural Science Foundation of China (40890051)the One-hundred Talents Program of the Chinese Academy of Sciences (KZCX2-YWQ1-01)SKLLQG Foundation
文摘A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendroc hronological techniques. Based on the results of correlation function analysis, the total precipitation from the previous August to current July was reconstructed for 1771-2008 AD with an explained variance of 49.3%. The reconstruction correlated well with the dryness/wetness series derived from historical documents, as well as the precipitation reconstruction of the Chifeng-Weichang region. There were eight intervals with greater precipitation than the average (associated with the strong East Asian summer monsoon) and seven intervals lower than the average (weak monsoon). A power spectrum analysis showed that there were 120 a, 80 a, 8 a and 2 a periodicities.
