First-principles calculations of the crystal structures, phase transition, and elastic properties of EuS have been carried out with the plane-wave pseudopotential density functional theory method. The calculated value...First-principles calculations of the crystal structures, phase transition, and elastic properties of EuS have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values are in very good agreement with experimental data as well as some of the existing model calculations. The dependence of the elastic constants, the aggregate elastic modulus, and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson's ratio, Debye temperature, and the compressional and shear elastic wave velocities with pressure have been investigated for the first time. Through the quasi-harmonic Debye model, the thermal expansions, heat capacities, Grneisen parameters and Debye temperatures dependence on the temperature and pressure are obtained in the pressure range from 0 GPa to 60 GPa and temperature range from 0 K to 800 K.展开更多
The South Asia High (SAH) is the dominant feature of the circulation in the upper troposphere and lower stratosphere (UTLS) during the boreal summer, and the upper tropospheric anticyclonic circulation extends int...The South Asia High (SAH) is the dominant feature of the circulation in the upper troposphere and lower stratosphere (UTLS) during the boreal summer, and the upper tropospheric anticyclonic circulation extends into the lower stratosphere. The preferred locations of the center of the SAH occur in two different regions, and the center can be located over the Iranian Plateau or over the Tibetan Plateau. This bimodality has an impact on the distribution of chemical constituents in the UTLS region. We analyzed water vapor (H20), carbon monoxide (CO), and ozone (03) data derived from the Aura Microwave Limb Sounder (MLS) and total column ozone data from the Ozone Monitoring Instrument (OMI). For the Iranian Plateau mode of the SAH, the tropospheric tracers exhibited a positive anomaly over the Iranian Plateau and a negative anomaly over the Tibetan Plateau, whereas the stratospheric tracer exhibited a negative and a positive anomaly over the Iranian Plateau and the Tibetan Plateau, respectively. For the Tibetan Plateau mode, however, the distribution of the anomaly was the reverse of that found for the chemical species in the UTLS region. Furthermore, the locations of the extrema within the anomaly seemed to differ across chemical species. The anomaly extrema for H20 occurred in the vicinity of the SAH ridgeline, whereas CO and O3 exhibited a northward shift of 4-8 degrees. These impacts of the variation in the SAH on the chemical constitutes in the UTLS region can be attributed in part to the dynamical structure delineated by the tropopause field and the temperature field at 100 hPa.展开更多
This study proposes a method to derive the climatological limit thresholds that can be used in an operational/historical quality control procedure for Chinese high vertical resolution(5–10 m)radiosonde temperature an...This study proposes a method to derive the climatological limit thresholds that can be used in an operational/historical quality control procedure for Chinese high vertical resolution(5–10 m)radiosonde temperature and wind speed data.The whole atmosphere is divided into 64 vertical bins,and the profiles are constructed by the percentiles of the values in each vertical bin.Based on the percentile profiles(PPs),some objective criteria are developed to obtain the thresholds.Tibetan Plateau field data are used to validate the effectiveness of the method in the application of experimental data.The results show that the derived thresholds for 120 operational stations and 3 experimental stations are effective in detecting the gross errors,and those PPs can clearly and instantly illustrate the characteristics of a radiosonde variable and reveal the distribution of errors.展开更多
During Yushu Earthquake,a large number of rescuers flocked to the mountainous quake areas. Under such a very specific circumstance,a high incidence of acute altitude illness was observed in rescuers who rapidly travel...During Yushu Earthquake,a large number of rescuers flocked to the mountainous quake areas. Under such a very specific circumstance,a high incidence of acute altitude illness was observed in rescuers who rapidly traveled from near sea level to an altitude of 4 000 m. It is evident that acute altitude illness leads to a significant human and economic toll,and also seriously influences the mountain rescue operation. So what does this teach us about mountain rescue in Yushu? Professor Wu Tianyi and many other authors collected shining points of the experiences and drew the lessons from the Yushu Earthquake into this special issue in Engineering Sciences which is like to thread pearl beads for a necklace. What readers learn from this special issue will have implications for the health and well-being of all high altitude populations all over the world.展开更多
Zoige Wetland is one of the largest plateau wetlands in the world. This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8....Zoige Wetland is one of the largest plateau wetlands in the world. This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8.7 and ArcGIS9.0. It is the first comparative analysis of a system of rapidly changing wetland with landscape patterns in Zoige, using 3 classified landsat Thematic Mapper images of 1977, 1994 and 2001. The classified images were used to generate wetland distributing maps, and shape index (S), diversity index (H), dominance index (D), evenness index (E), fragmentation index (F) and fractal dimension (Fd) were calculated and analyzed spatiotemporally across pure grazing area in Zoige for each landscape type and in different periods (before 1977, during 1977-1994 and 1994-2001), as well as the driving forces of natural and anthropogenic. The study shows that for a comprehensive understanding of the shapes and trajectories of the shrinking and desertificated land expansion of the wetland, a spatiotemporal landscape metrics analysis in different periods is an improvement than only with landscape changing rates. This type of analysis can also be used to infer underlying social, economic, and political processes that drive the observed wetland forms. The results indicate that wetland patterns can be changed over relatively short periods of time. The total area of lake reduced by 164.86 km^2, grassland extended by 141.74 km^2, semi-marsh extended by 105.94 km^2, marsh reduced by 86.00 km^2 the number of landscape patches reduced by 56, and their average area decreased by 2.68 km^2, the successions within lake, marsh, semi-marsh and grassland were found obviously. S decreased stepwise: D and F increased but H decreased: The changing rate after 1994 was 2.3 to 2.9 times greater than that before. The change of the wetland landscape patterns resulted in the interaction between socio-ceenomic and natural forces of positive and negative aspects; and natural factors affected as assistant aspect. Some important human activities in this period led to the change of the landscape patterns in this region directly. Some measurements made by government and NGO delayed the converting process partly.展开更多
Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytop...Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl α=99.76±24.01 μg/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being I 423 ind/m^2 and 8.71 g/m^2 in XL and 4 249 ind/m^2 and 8.60 g/m^2 in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffrneisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes.展开更多
The fixture layout is crucial to assure the product quality in a multistation assembly process (MAP). A well-designed fixture layout will make the final product's variability be insensitive to the fixture variation...The fixture layout is crucial to assure the product quality in a multistation assembly process (MAP). A well-designed fixture layout will make the final product's variability be insensitive to the fixture variation inputs. As the basis of the fixture layout design, the design criterion plays an important role in the effectiveness of a solution and the optimization efficiency. In this paper, an effective and efficient design criterion is proposed for the fixture layout with a fixed reference point (FRP) in an MAP. First of all, a state space model for the individual port's variation propagation and accumulation is developed, which is the mathematical foundation of the proposed criterion. Then, based on this model, a novel design criterion used to evaluate the performance of the fixture layout is proposed for the fixture layout with an FRP. Finally, a method extracted from the proposed design criterion is developed for quick fixture layout design. A four-station assembly process is used to validate the effectiveness and efficiency of the proposed models and methods.展开更多
The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of...The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually,it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere;the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening.展开更多
This study aims to assess the hydrological effects of four herbs and four shrubs planted in a selfestablished test area in Xining Basin of northeastern Qinghai-Tibet Plateau, China. The RainfallIntercepting Capability...This study aims to assess the hydrological effects of four herbs and four shrubs planted in a selfestablished test area in Xining Basin of northeastern Qinghai-Tibet Plateau, China. The RainfallIntercepting Capability(RIC) of the herbs and shrubs was evaluated in rainfall interception experiment at the end of the third, fourth and fifth month of the growth period in 2007. The leaf transpiration rate and the effects of roots on promoting soil moisture evaporation in these plants were also assessed in transpiration experiment and root-soil composite system evaporation experiment in the five month's growth period. It is found that the RIC of the fourstudied herbs follows the order of E. repens, E. dahuricus, A. trachycaulum and L. secalinus; the RIC of the four shrubs follows the order of A. canescens, Z. xanthoxylon, C. korshinskii and N. tangutorum. The RIC of all the herbs is related linearly to their mean height and canopy area(R^2 ≥ 0.9160). The RIC of all the shrubs bears a logarithmic relationship with their mean height(R^2 ≥ 0.9164), but a linear one with their canopy area(R^2 ≥ 0.9356). Moreover, different species show different transpiration rates. Of the four herbs, E. repens has the highest transpiration rate of 1.07 mg/(m^2·s), and of the four shrubs, A. canescens has the highest transpiration rate(0.74 mg/(m^2·s)). The roots of all the herbs and shrubs can promote soil moisture evaporation. Of the four herbs, the evaporation rate of E. repens root-soil composite system is the highest(2.14%), and of the four shrubs,the root-soil composite system of A. canescens has the highest evaporation rate(1.41%). The evaporation rate of the root-soil composite system of E. dahuricus and Z. xanthoxylon bears a second-power linear relationship with evaporation time(R^2 ≥ 0.9924). The moisture content of all the eight root-soil composite systems decreases exponentially with evaporation time(R^2 ≥ 0.8434). The evaporation rate and moisture content of all the plants' root-soil composite systems increases logarithmically(R^2 ≥ 0.9606) and linearly(R^2 ≥ 0.9777) with root volume density. The findings of this study indicate that among the four herbs and four shrubs, E. repens and A. canescens possess the most effective hydrological effects in reducing the soil erosion and shallow landslide in this region.展开更多
Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in t...Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in the Qinghai-Tibet Plateau is dominated by freeze-thaw erosion.In this research,freezing–thawing process of the soil samples collected from the Qinghai–Tibet Plateau was carried out by laboratory experiments to determinate the volume variation of soil as well as physical and mechanical properties, such as porosity, granularity and uniaxial compressive strength, after the soil experiences various freeze–thaw cycles.Results show that cohesion and uniaxial compressive strength decreased as the volume and porosity of the soil increased after experiencing various freeze–thaw cycles, especially in the first six freeze–thaw cycles.Consequently, the physical and mechanical properties of the soil were altered.However, granularity and internal friction angle did not vary significantly with an increase in the freeze–thaw cycle.The structural damage among soil particles due to frozen water expansion was the major cause of changes in soil mechanical behavior in the Qinghai–Tibet Plateau.展开更多
Permafrost in China includes high latitude permafrost in northeastern China, alpine permafrost in northwestern China and high plateau permafrost on the Tibetan Plateau. The high altitude permafrost is about 92% of the...Permafrost in China includes high latitude permafrost in northeastern China, alpine permafrost in northwestern China and high plateau permafrost on the Tibetan Plateau. The high altitude permafrost is about 92% of the total permafrost area in China. The south boundary or lower limit of the seasonally frozen ground is defined in accordance with the 0 ℃ isothermal line of mean air temperature in January, which is roughly corresponding to the line extending from the Qinling Mountains to the Huaihe River in the east and to the southeast boundary of the Tibetan Plateau in the west. Seasonal frozen ground occurs in large parts of the territory in northern China, including Northeast, North, Northwest China and the Tibetan Plateau except for permafrost regions, and accounting for about 55% of the land area of China. The southern limit of short-term frozen ground generally swings south and north along the 25° northern latitude line, occurring in the wet and warm subtropic monsoon climatic zone. Its area is less than 20% of the land area of China.展开更多
Objectives:This study seeks to understand the experiences of nurses who resigned because of limited available career development opportunities and of the possible reasons for their resignation.Methods:Semi-structured ...Objectives:This study seeks to understand the experiences of nurses who resigned because of limited available career development opportunities and of the possible reasons for their resignation.Methods:Semi-structured interviews were conducted with nine clinical nurses who experienced limitations in the development of their careers and consequently left their jobs to elicit their feelings and reasons for leaving.The content analysis was used to analyze the interview data.Results:Two themes and four subthemes relating to the experiences and attributions of former nurses were identified.Nurses who experienced career plateau were disappointed with the current work and uncertainty about the future.The attribution of career plateau lies in unsatisfied personal needs and the absence of organizational support.Conclusions:Nurses had strong career plateau experiences before they left,and it caused a series of negative feelings in their practice.Establish a clear career development path and multi-dimensional support from the organization may be helpful to reduce the occurrence of career plateau,thus increasing the retention of nurses.展开更多
The Wangdonggou Watershed on the Loess Plateau in China was selected as the study area to develop a model for soil erosion assessments. Using the data collected at 20 sampling sites all tentatively selected indicators...The Wangdonggou Watershed on the Loess Plateau in China was selected as the study area to develop a model for soil erosion assessments. Using the data collected at 20 sampling sites all tentatively selected indicators were assessed against their corresponding erosion intensity through a correlation analysis. Eight highly correlated indicators were then chosen for the soil erosion assessment. In addition, threshold limits to delineate the class size for these indicators and weights to rank them were determined. Next, a grading model incorporating the selected indicators class rating and their associated weights was developed and verified by an on site evaluation of the soil erosion intensity in the study area. Results of the verification showed that the overall accuracy of the indicator system for assessing soil erosion in the Loess Plateau gully regions could reach 85%.展开更多
This paper first summarizes that traditional EFL teaching considers target language isolatedly beyond its culture. It, therefore, stresses the interdependence of language and culture. It analyzes the existing problems...This paper first summarizes that traditional EFL teaching considers target language isolatedly beyond its culture. It, therefore, stresses the interdependence of language and culture. It analyzes the existing problems and their predominant causes in basic EFL teaching, and discusses the possible solutions to be taken to solve such problems. It suggests that there is culture-based instruction for high achievement in classroom acquisition of the target culture. It deems undoubtedly that the systematic permeation of cross-cultural communication aiming at developing cross-cultural awareness is one of the most effective steps toward cultural appropriateness in authentic communication.展开更多
Jiroft region is one of the most historical cities, placed in the southeastern of Iranian plateau. Its history dates back to the second millennium B.C. The ancient history of Jiroft and its proximity to the River ofHa...Jiroft region is one of the most historical cities, placed in the southeastern of Iranian plateau. Its history dates back to the second millennium B.C. The ancient history of Jiroft and its proximity to the River ofHalil Roud have attracted archeologists during the recent decades. So far various historical works have been unearthed from the region of which marble ones are especially noteworthy. Basically, marble works were used more commonly in central plateau of Iran than other ones. The marble works discovered in Jirofl region are only comparable with those from the recently excavation at Shahr-I Sokhta in Zabol. The scientific examination of such works may pave way to identify their internal structures and to compare them in terms of their provenance. The present study will focus on the characterization of marbles discovered in Konar Sandal, Jiroft. In addition to petro graphical studies, XRD and XRF investigations were used to identify the crystalline structures as well as balk chemical composition of the discovered marbles. The obtained results revealed that the major constituents of the discovered marbles in Jiroft were Ca and CaO. The structure of discovered marbles had orderly compact patterns resulted mainly from metamorphism conditions. This structure is actually Unsimilar to those from Shahr-I Sokhta.展开更多
Chitosan (CS) was successfully modified in supercritical carbon dioxide ( scCOz ) by grafting method to enhance its water solubility. In this work, a three.arm star-like fluorinated polymer was synthesized by atom...Chitosan (CS) was successfully modified in supercritical carbon dioxide ( scCOz ) by grafting method to enhance its water solubility. In this work, a three.arm star-like fluorinated polymer was synthesized by atom transfer radical polymerization ( ATRP ) method and applied as a surfactant in supereriticul carbon dioxide (scCO2 ). Then 2-acrylamido-2-methyl propane sulfonie acid (AMPS) was grafted onto CS (CS-g-PAMPS) in H2O/scCO2 inverse emulsion. The effects of mass ratio of water and surfactants (Rw/s ) and pressure of scCO2 on the grafting reaction were investigated. The grafting rate, partide size, and dispersity in water of CS-g-PAMPS varied greatly as Rw/s and pressure of scCO2 changed. It could be found that the value of Rw/s at 12 and the pressure of scCO2 at 30 MPa were the optimum conditions for the grafting reaction. CS-g-PAMPS prepared in this reaction system has higher grafting rate, smaller particle sizes, and better dispersity in water than those prepared via conventional methods.展开更多
Poly[ 2, 2-(m.phenylene) -5, 5-bibenzimidazole] (mPBI) were synthesized by mixing 3, 3', 4, 4'-tetraaminobiphenyl and isophthallc acid in 1 -butyl-3 -methyUmidazolinm chloride ( E BMIM] CI). Intrinsic viscosit...Poly[ 2, 2-(m.phenylene) -5, 5-bibenzimidazole] (mPBI) were synthesized by mixing 3, 3', 4, 4'-tetraaminobiphenyl and isophthallc acid in 1 -butyl-3 -methyUmidazolinm chloride ( E BMIM] CI). Intrinsic viscosity of mPBI polymers was 0.67 dL/g which was measured in 96% sulfuric acid. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance ( 1H-NMR ), and thermogravimetric analysis (TGA). The effects of polymerization conditions on the intrinsic viscosity of mPBI were investigated. It showed that the molecular weight of polymer mainly depended on pre-reaction time and reaction temperature. Comparison of structure and properties of mPBI synthesized in ionic liquids(ILs) and polyphosphoric acid was also reported. It indicates that the ionic liquids are a kind of good solvents in synthesis process of m_PBI and ionic liquids mainly affect molecular weight of mPBL展开更多
In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected mon...In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected monthly over 1 year in the Min River, eastern Tibetan Plateau, and analyzed for trace element composition. The dissolved trace elements exhibited different relationships with increasing discharge compared with major elements.The elements analyzed can be divided into three groups according to their behavior in response to changing discharge:(1) elements that showed weak positive correlation with discharge, e.g. Cu, V, and Ba;(2) elements that exhibited weak negative correlation with discharge,including Rb, Sr, Pb, Sb, Zn, Cr, Cd, and U; and(3) elements that displayed no significant correlation with variation in discharge, e.g. Ti, Fe, Co, Ni, and As. Cu was strongly affected by anthropogenic activities and flushed into the river with increasing discharge. Ba has a strong solubility in the terrestrial environment, dissolved quickly,and was released into the river. The positive relationship between V concentration and discharge may be attributed to secondary reactions, such as precipitation and adsorption on oxides and aluminosilicate clays. Conservative behavior had an impact on the geochemical behavior of Sr and Rb across hydrologic variation. Pb, Zn, Sb, Cd, and Cr underwent a mild dilution effect connected with anthropogenic activities. The chemostatic behavior of U was regulated by carbonate dissolution and biological uptake.In addition, higher temperatures enhanced biotic activities,affecting the concentrations of Fe and Ni. The relationship between power law slopes and coefficient of variation for discharge and solute concentration suggests that concentrations of trace elements vary significantly with increasing discharge compared with major elements. Silicate mineral weathering had less effect on the fluvial solutes with increasing discharge. Mining activity may exert an additional control on concentration–discharge dynamics of anthropogenic trace elements.展开更多
The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the stru...The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al-O and Si-O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition.展开更多
基金V. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.40804034 and No.11304141), the Natural Science Foundation of the Education Department of Henan Province of China (No.2011B140014), the Program for the Science and Technology Department of Henan Province of China (No. 112102310641), and the Program for Innovative Research Team (in Science and Technology) in University of Henan Province (No.13IRTSTHN020).
文摘First-principles calculations of the crystal structures, phase transition, and elastic properties of EuS have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values are in very good agreement with experimental data as well as some of the existing model calculations. The dependence of the elastic constants, the aggregate elastic modulus, and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson's ratio, Debye temperature, and the compressional and shear elastic wave velocities with pressure have been investigated for the first time. Through the quasi-harmonic Debye model, the thermal expansions, heat capacities, Grneisen parameters and Debye temperatures dependence on the temperature and pressure are obtained in the pressure range from 0 GPa to 60 GPa and temperature range from 0 K to 800 K.
基金supported by the National Basic Research Program of China (Grant No.2010CB428602)the National Natural Science Foundation of China (Grant No.40830102)
文摘The South Asia High (SAH) is the dominant feature of the circulation in the upper troposphere and lower stratosphere (UTLS) during the boreal summer, and the upper tropospheric anticyclonic circulation extends into the lower stratosphere. The preferred locations of the center of the SAH occur in two different regions, and the center can be located over the Iranian Plateau or over the Tibetan Plateau. This bimodality has an impact on the distribution of chemical constituents in the UTLS region. We analyzed water vapor (H20), carbon monoxide (CO), and ozone (03) data derived from the Aura Microwave Limb Sounder (MLS) and total column ozone data from the Ozone Monitoring Instrument (OMI). For the Iranian Plateau mode of the SAH, the tropospheric tracers exhibited a positive anomaly over the Iranian Plateau and a negative anomaly over the Tibetan Plateau, whereas the stratospheric tracer exhibited a negative and a positive anomaly over the Iranian Plateau and the Tibetan Plateau, respectively. For the Tibetan Plateau mode, however, the distribution of the anomaly was the reverse of that found for the chemical species in the UTLS region. Furthermore, the locations of the extrema within the anomaly seemed to differ across chemical species. The anomaly extrema for H20 occurred in the vicinity of the SAH ridgeline, whereas CO and O3 exhibited a northward shift of 4-8 degrees. These impacts of the variation in the SAH on the chemical constitutes in the UTLS region can be attributed in part to the dynamical structure delineated by the tropopause field and the temperature field at 100 hPa.
基金supported by the National Innovation Project for Meteorological Science and Technology grant number CMAGGTD003-5the National Key R&D Program of China grant number2017YFC1501801。
文摘This study proposes a method to derive the climatological limit thresholds that can be used in an operational/historical quality control procedure for Chinese high vertical resolution(5–10 m)radiosonde temperature and wind speed data.The whole atmosphere is divided into 64 vertical bins,and the profiles are constructed by the percentiles of the values in each vertical bin.Based on the percentile profiles(PPs),some objective criteria are developed to obtain the thresholds.Tibetan Plateau field data are used to validate the effectiveness of the method in the application of experimental data.The results show that the derived thresholds for 120 operational stations and 3 experimental stations are effective in detecting the gross errors,and those PPs can clearly and instantly illustrate the characteristics of a radiosonde variable and reveal the distribution of errors.
基金"973"National Key Basic Research and Development Program(No.2012CB518202)
文摘During Yushu Earthquake,a large number of rescuers flocked to the mountainous quake areas. Under such a very specific circumstance,a high incidence of acute altitude illness was observed in rescuers who rapidly traveled from near sea level to an altitude of 4 000 m. It is evident that acute altitude illness leads to a significant human and economic toll,and also seriously influences the mountain rescue operation. So what does this teach us about mountain rescue in Yushu? Professor Wu Tianyi and many other authors collected shining points of the experiences and drew the lessons from the Yushu Earthquake into this special issue in Engineering Sciences which is like to thread pearl beads for a necklace. What readers learn from this special issue will have implications for the health and well-being of all high altitude populations all over the world.
基金supported by China Scholarship, the Chinese Academy of Sciences (KSCXI-07, KSCX2-01-09)the Ministry of Science & Technology of China (2004BA606A-05)Sichuan provincial training foundation for Science & Technology leader ,Sichuan youth foundation.
文摘Zoige Wetland is one of the largest plateau wetlands in the world. This paper provides a dynamic analysis of spatial and temporal patterns of the wetland in Zoige, Eastern Qinghai-Tibetan Plateau, supported by ERDAS8.7 and ArcGIS9.0. It is the first comparative analysis of a system of rapidly changing wetland with landscape patterns in Zoige, using 3 classified landsat Thematic Mapper images of 1977, 1994 and 2001. The classified images were used to generate wetland distributing maps, and shape index (S), diversity index (H), dominance index (D), evenness index (E), fragmentation index (F) and fractal dimension (Fd) were calculated and analyzed spatiotemporally across pure grazing area in Zoige for each landscape type and in different periods (before 1977, during 1977-1994 and 1994-2001), as well as the driving forces of natural and anthropogenic. The study shows that for a comprehensive understanding of the shapes and trajectories of the shrinking and desertificated land expansion of the wetland, a spatiotemporal landscape metrics analysis in different periods is an improvement than only with landscape changing rates. This type of analysis can also be used to infer underlying social, economic, and political processes that drive the observed wetland forms. The results indicate that wetland patterns can be changed over relatively short periods of time. The total area of lake reduced by 164.86 km^2, grassland extended by 141.74 km^2, semi-marsh extended by 105.94 km^2, marsh reduced by 86.00 km^2 the number of landscape patches reduced by 56, and their average area decreased by 2.68 km^2, the successions within lake, marsh, semi-marsh and grassland were found obviously. S decreased stepwise: D and F increased but H decreased: The changing rate after 1994 was 2.3 to 2.9 times greater than that before. The change of the wetland landscape patterns resulted in the interaction between socio-ceenomic and natural forces of positive and negative aspects; and natural factors affected as assistant aspect. Some important human activities in this period led to the change of the landscape patterns in this region directly. Some measurements made by government and NGO delayed the converting process partly.
基金Supportted by a Key Project grant,CAS (KSCX1-SW-13-04)the National Natural Science Foundation of China (No.30470205)
文摘Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl α=99.76±24.01 μg/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being I 423 ind/m^2 and 8.71 g/m^2 in XL and 4 249 ind/m^2 and 8.60 g/m^2 in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffrneisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes.
基金National Nature Science Foundation of China(No.71201025)Specialized Research Fund for the Doctoral Program of Higher Education,China(No.20110092120007)Jiangsu Key Laboratory of Equipments Detection and Control,China(No.JSKLEDC201215)
文摘The fixture layout is crucial to assure the product quality in a multistation assembly process (MAP). A well-designed fixture layout will make the final product's variability be insensitive to the fixture variation inputs. As the basis of the fixture layout design, the design criterion plays an important role in the effectiveness of a solution and the optimization efficiency. In this paper, an effective and efficient design criterion is proposed for the fixture layout with a fixed reference point (FRP) in an MAP. First of all, a state space model for the individual port's variation propagation and accumulation is developed, which is the mathematical foundation of the proposed criterion. Then, based on this model, a novel design criterion used to evaluate the performance of the fixture layout is proposed for the fixture layout with an FRP. Finally, a method extracted from the proposed design criterion is developed for quick fixture layout design. A four-station assembly process is used to validate the effectiveness and efficiency of the proposed models and methods.
基金supported by the NSF(EAR 9803484)to M.EllisA.Densmore,and NSFC(40372084)SZD0408 and EYTP to Li Yong
文摘The eastern margin of the Tibetan Plateau is marked by an extremely steep mountain front with relief of over 5 km. This topography,coupled with abundant Mesozoic thrusts within the margin,explains why tectonic maps of the India-Asia collision typically show the eastern margin as a major thrust zone. Actually,it does not like that. Field observations suggest that the margin is better characterized as a zone of NNE-directed dextral shear with extensive strike-slip faulting and secondary thrusting. The high relief and steep gradients are partially explained by erosional unloading of an elastic lithosphere;the pre-erosion inherited topography may be the inherited Mesozoic thrust belt landscape modified by a component of Cenozoic tectonic shortening.
基金financially supported by the National Natural Science Foundation of China (Grant Nos.41572306,41162010)Natural Science Foundation of Qinghai Province (Grant No.2014ZJ-906)+2 种基金Hundred Talents Program in Chinese Academy of Sciences (Grant No.Y110091025)Scientific and Technologic Support Plan of Qinghai Province (2015-SF-117)Ministry of Education 'Innovative Team Development Scheme' (IRT_17R62)
文摘This study aims to assess the hydrological effects of four herbs and four shrubs planted in a selfestablished test area in Xining Basin of northeastern Qinghai-Tibet Plateau, China. The RainfallIntercepting Capability(RIC) of the herbs and shrubs was evaluated in rainfall interception experiment at the end of the third, fourth and fifth month of the growth period in 2007. The leaf transpiration rate and the effects of roots on promoting soil moisture evaporation in these plants were also assessed in transpiration experiment and root-soil composite system evaporation experiment in the five month's growth period. It is found that the RIC of the fourstudied herbs follows the order of E. repens, E. dahuricus, A. trachycaulum and L. secalinus; the RIC of the four shrubs follows the order of A. canescens, Z. xanthoxylon, C. korshinskii and N. tangutorum. The RIC of all the herbs is related linearly to their mean height and canopy area(R^2 ≥ 0.9160). The RIC of all the shrubs bears a logarithmic relationship with their mean height(R^2 ≥ 0.9164), but a linear one with their canopy area(R^2 ≥ 0.9356). Moreover, different species show different transpiration rates. Of the four herbs, E. repens has the highest transpiration rate of 1.07 mg/(m^2·s), and of the four shrubs, A. canescens has the highest transpiration rate(0.74 mg/(m^2·s)). The roots of all the herbs and shrubs can promote soil moisture evaporation. Of the four herbs, the evaporation rate of E. repens root-soil composite system is the highest(2.14%), and of the four shrubs,the root-soil composite system of A. canescens has the highest evaporation rate(1.41%). The evaporation rate of the root-soil composite system of E. dahuricus and Z. xanthoxylon bears a second-power linear relationship with evaporation time(R^2 ≥ 0.9924). The moisture content of all the eight root-soil composite systems decreases exponentially with evaporation time(R^2 ≥ 0.8434). The evaporation rate and moisture content of all the plants' root-soil composite systems increases logarithmically(R^2 ≥ 0.9606) and linearly(R^2 ≥ 0.9777) with root volume density. The findings of this study indicate that among the four herbs and four shrubs, E. repens and A. canescens possess the most effective hydrological effects in reducing the soil erosion and shallow landslide in this region.
基金funded by the National Natural Science Foundation of China(Grant No.41401611,41301072)China Postdoctoral Science Foundation(Grant No.2014M560817,2015T81069)the Open Project Program of the State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201208)
文摘Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in the Qinghai-Tibet Plateau is dominated by freeze-thaw erosion.In this research,freezing–thawing process of the soil samples collected from the Qinghai–Tibet Plateau was carried out by laboratory experiments to determinate the volume variation of soil as well as physical and mechanical properties, such as porosity, granularity and uniaxial compressive strength, after the soil experiences various freeze–thaw cycles.Results show that cohesion and uniaxial compressive strength decreased as the volume and porosity of the soil increased after experiencing various freeze–thaw cycles, especially in the first six freeze–thaw cycles.Consequently, the physical and mechanical properties of the soil were altered.However, granularity and internal friction angle did not vary significantly with an increase in the freeze–thaw cycle.The structural damage among soil particles due to frozen water expansion was the major cause of changes in soil mechanical behavior in the Qinghai–Tibet Plateau.
文摘Permafrost in China includes high latitude permafrost in northeastern China, alpine permafrost in northwestern China and high plateau permafrost on the Tibetan Plateau. The high altitude permafrost is about 92% of the total permafrost area in China. The south boundary or lower limit of the seasonally frozen ground is defined in accordance with the 0 ℃ isothermal line of mean air temperature in January, which is roughly corresponding to the line extending from the Qinling Mountains to the Huaihe River in the east and to the southeast boundary of the Tibetan Plateau in the west. Seasonal frozen ground occurs in large parts of the territory in northern China, including Northeast, North, Northwest China and the Tibetan Plateau except for permafrost regions, and accounting for about 55% of the land area of China. The southern limit of short-term frozen ground generally swings south and north along the 25° northern latitude line, occurring in the wet and warm subtropic monsoon climatic zone. Its area is less than 20% of the land area of China.
基金The study was supported by a grant from the nursing research subproject of China Health Human Resources Training Program(RFA:2019-HLYJ-001),which did not influence the study results and publishing.
文摘Objectives:This study seeks to understand the experiences of nurses who resigned because of limited available career development opportunities and of the possible reasons for their resignation.Methods:Semi-structured interviews were conducted with nine clinical nurses who experienced limitations in the development of their careers and consequently left their jobs to elicit their feelings and reasons for leaving.The content analysis was used to analyze the interview data.Results:Two themes and four subthemes relating to the experiences and attributions of former nurses were identified.Nurses who experienced career plateau were disappointed with the current work and uncertainty about the future.The attribution of career plateau lies in unsatisfied personal needs and the absence of organizational support.Conclusions:Nurses had strong career plateau experiences before they left,and it caused a series of negative feelings in their practice.Establish a clear career development path and multi-dimensional support from the organization may be helpful to reduce the occurrence of career plateau,thus increasing the retention of nurses.
基金supported by the State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, China (No. 10501-88) the National High Technology Research and Development Program of China (863 Program) (No. 2001AA245041).
文摘The Wangdonggou Watershed on the Loess Plateau in China was selected as the study area to develop a model for soil erosion assessments. Using the data collected at 20 sampling sites all tentatively selected indicators were assessed against their corresponding erosion intensity through a correlation analysis. Eight highly correlated indicators were then chosen for the soil erosion assessment. In addition, threshold limits to delineate the class size for these indicators and weights to rank them were determined. Next, a grading model incorporating the selected indicators class rating and their associated weights was developed and verified by an on site evaluation of the soil erosion intensity in the study area. Results of the verification showed that the overall accuracy of the indicator system for assessing soil erosion in the Loess Plateau gully regions could reach 85%.
文摘This paper first summarizes that traditional EFL teaching considers target language isolatedly beyond its culture. It, therefore, stresses the interdependence of language and culture. It analyzes the existing problems and their predominant causes in basic EFL teaching, and discusses the possible solutions to be taken to solve such problems. It suggests that there is culture-based instruction for high achievement in classroom acquisition of the target culture. It deems undoubtedly that the systematic permeation of cross-cultural communication aiming at developing cross-cultural awareness is one of the most effective steps toward cultural appropriateness in authentic communication.
文摘Jiroft region is one of the most historical cities, placed in the southeastern of Iranian plateau. Its history dates back to the second millennium B.C. The ancient history of Jiroft and its proximity to the River ofHalil Roud have attracted archeologists during the recent decades. So far various historical works have been unearthed from the region of which marble ones are especially noteworthy. Basically, marble works were used more commonly in central plateau of Iran than other ones. The marble works discovered in Jirofl region are only comparable with those from the recently excavation at Shahr-I Sokhta in Zabol. The scientific examination of such works may pave way to identify their internal structures and to compare them in terms of their provenance. The present study will focus on the characterization of marbles discovered in Konar Sandal, Jiroft. In addition to petro graphical studies, XRD and XRF investigations were used to identify the crystalline structures as well as balk chemical composition of the discovered marbles. The obtained results revealed that the major constituents of the discovered marbles in Jiroft were Ca and CaO. The structure of discovered marbles had orderly compact patterns resulted mainly from metamorphism conditions. This structure is actually Unsimilar to those from Shahr-I Sokhta.
基金National Natural Science Foundation of China(No.20674017)Shanghai Key Laboratory Project of China(No.08DZ2230500)
文摘Chitosan (CS) was successfully modified in supercritical carbon dioxide ( scCOz ) by grafting method to enhance its water solubility. In this work, a three.arm star-like fluorinated polymer was synthesized by atom transfer radical polymerization ( ATRP ) method and applied as a surfactant in supereriticul carbon dioxide (scCO2 ). Then 2-acrylamido-2-methyl propane sulfonie acid (AMPS) was grafted onto CS (CS-g-PAMPS) in H2O/scCO2 inverse emulsion. The effects of mass ratio of water and surfactants (Rw/s ) and pressure of scCO2 on the grafting reaction were investigated. The grafting rate, partide size, and dispersity in water of CS-g-PAMPS varied greatly as Rw/s and pressure of scCO2 changed. It could be found that the value of Rw/s at 12 and the pressure of scCO2 at 30 MPa were the optimum conditions for the grafting reaction. CS-g-PAMPS prepared in this reaction system has higher grafting rate, smaller particle sizes, and better dispersity in water than those prepared via conventional methods.
基金Natural Science Foundation of Shanghai,China(No.09ZR1401500)
文摘Poly[ 2, 2-(m.phenylene) -5, 5-bibenzimidazole] (mPBI) were synthesized by mixing 3, 3', 4, 4'-tetraaminobiphenyl and isophthallc acid in 1 -butyl-3 -methyUmidazolinm chloride ( E BMIM] CI). Intrinsic viscosity of mPBI polymers was 0.67 dL/g which was measured in 96% sulfuric acid. The polymer was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance ( 1H-NMR ), and thermogravimetric analysis (TGA). The effects of polymerization conditions on the intrinsic viscosity of mPBI were investigated. It showed that the molecular weight of polymer mainly depended on pre-reaction time and reaction temperature. Comparison of structure and properties of mPBI synthesized in ionic liquids(ILs) and polyphosphoric acid was also reported. It indicates that the ionic liquids are a kind of good solvents in synthesis process of m_PBI and ionic liquids mainly affect molecular weight of mPBL
基金financially supported by the National Key R&D Program of China (Grant No. 2016YFA0601002)National Natural Science Foundation of China (Grant Nos. 41372376,41422303,41571130072,41561134017)
文摘In order to better understand the relative importance of hydrologic variation and anthropogenic disturbance and their complex interactions within the trace elemental geochemical cycle, water samples were collected monthly over 1 year in the Min River, eastern Tibetan Plateau, and analyzed for trace element composition. The dissolved trace elements exhibited different relationships with increasing discharge compared with major elements.The elements analyzed can be divided into three groups according to their behavior in response to changing discharge:(1) elements that showed weak positive correlation with discharge, e.g. Cu, V, and Ba;(2) elements that exhibited weak negative correlation with discharge,including Rb, Sr, Pb, Sb, Zn, Cr, Cd, and U; and(3) elements that displayed no significant correlation with variation in discharge, e.g. Ti, Fe, Co, Ni, and As. Cu was strongly affected by anthropogenic activities and flushed into the river with increasing discharge. Ba has a strong solubility in the terrestrial environment, dissolved quickly,and was released into the river. The positive relationship between V concentration and discharge may be attributed to secondary reactions, such as precipitation and adsorption on oxides and aluminosilicate clays. Conservative behavior had an impact on the geochemical behavior of Sr and Rb across hydrologic variation. Pb, Zn, Sb, Cd, and Cr underwent a mild dilution effect connected with anthropogenic activities. The chemostatic behavior of U was regulated by carbonate dissolution and biological uptake.In addition, higher temperatures enhanced biotic activities,affecting the concentrations of Fe and Ni. The relationship between power law slopes and coefficient of variation for discharge and solute concentration suggests that concentrations of trace elements vary significantly with increasing discharge compared with major elements. Silicate mineral weathering had less effect on the fluvial solutes with increasing discharge. Mining activity may exert an additional control on concentration–discharge dynamics of anthropogenic trace elements.
基金Project(2005CB623701) supported by the Major State Basic Research and Development Program of ChinaProject(50874118) supported by the National Nature Science Foundation of ChinaProject(2007B52) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China
文摘The bulk electronic structure of kaolinite (001) plane was studied with quantum mechanical calculations. The CASTEP parameterization of ultrasoft pseudopotentials without core corrections was used to optimize the structure of kaolinite bulk and slab models. The results show that Fermi energy of kaolinite (001) plane is 3.05 eV, and the band gap is 4.52 eV. The partial density of states (PDOS) of kaolinite (001) plane indicates that Al-O and Si-O bonds on the mineral surface are highly polar. The oxygen atoms of hydroxyl groups in surface layer are capable of forming hydrogen bond with the head group of cationic collectors. The properties of dodecylamine (DDA) cation were also calculated by density function theory (DFT) method at B3LYP/6-31G (d) level for illuminating the flotation processes of kaolinite. Besides the electrostatic attraction, the mechanism between kaolinite and DDA is found to be hydrogen bonds under acidic condition.