Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhuj...Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhujiang River(Pearl River)Estuary,to investigate the short-term variation in suspended sediment concentrations(SSCs)and the relationship between the SSC and turbulent kinetic energy,bottom shear stress(BSS),and relative wave height.Based on extreme event analysis results,extreme events have a greater influence on turbulent kinetic energy than SSC.Although a portion of the turbulent kinetic energy dissipates directly into the water column,it plays an important role in suspended sediment motion.Most of the time,the wave-current interaction is strong enough to drive sediment incipience and resuspension.When combined,the wave-current interaction and wave-induced BSSs have a greater influence on suspended sediment transport and SSC variation than current-induced BSS alone.The relative wave height also has a strong correlation with SSC,indicating that the combined effect of water depth and wave height significantly impacts SSC variation.Water depth is mainly controlled by the tide on the beaches;thus,the effects of tides and waves should be conjunctively considered when analyzing the factors influencing SSC.展开更多
Under bilateral cooperation between the United States of America and the People's Republic of China, a series of research cruises were conducted over the western Pacific Ocean. It was found that a) the non-sea-sal...Under bilateral cooperation between the United States of America and the People's Republic of China, a series of research cruises were conducted over the western Pacific Ocean. It was found that a) the non-sea-salt sulfate aerosol particles are the major source of cloud condensation nuclei, b) the population of clouds and the total albedo are proportional to the concentration of condensation nuclei and consequently to the concentration of the non-sea-salt aerosol particles, and c) the amount of rainfall is inversely proportional to the concentration of non-sea-salt sulfate aerosol particles. It seems that anthropogenic sulfate aerosol particles affect the regional planetary albedo and climate and that the contribution from biogenically derived sulfate aerosol particles is of lesser importance.展开更多
In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentra...In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentration and geometry. Flame and pressure transducers were used to track the explosion front velocity. The flame speed (Sf) showed a slight downward trend while the methane concentration varied from 10% to 3% in the experimental channel. The peak overpressure (Pmax) dropped dramatically when compared with normal conditions. As well, the values of Pmax and Sf decreased when the methane concentration dropped from 8% to 6%. The flame speed in the channel, connected to a cylinder with a length varying from 0.5 to 2 m, was greater than that in the normal channel. The peak overpressure was also higher than that under normal conditions because of a higher flame speed and stronger pressure piling up. The values of Pmax and Sf increased with an increase in cylinder length. The research results indicate that damage caused by explosions can be reduced by decreasing the gas concentration, which should be immediately detected in roadways with large cross-sections because of the possibility of greater destruction caused by more serious explosions.展开更多
Sea ice conditions in the Bohai Sea of China are sensitive to large-scale climatic variations. On the basis of CLARA-A1-SAL data, the albedo variations are examined in space and time in the winter(December, January a...Sea ice conditions in the Bohai Sea of China are sensitive to large-scale climatic variations. On the basis of CLARA-A1-SAL data, the albedo variations are examined in space and time in the winter(December, January and February) from 1992 to 2008 in the Bohai Sea sea ice region. Time series data of the sea ice concentration(SIC), the sea ice extent(SIE) and the sea surface temperature(SST) are used to analyze their relationship with the albedo. The sea ice albedo changed in volatility appears along with time, the trend is not obvious and increases very slightly during the study period at a rate of 0.388% per decade over the Bohai Sea sea ice region.The interannual variation is between 9.93% and 14.50%, and the average albedo is 11.79%. The sea ice albedo in years with heavy sea ice coverage, 1999, 2000 and 2005, is significantly higher than that in other years; in years with light sea ice coverage, 1994, 1998, 2001 and 2006, has low values. For the monthly albedo, the increasing trend(at a rate of 0.988% per decade) in December is distinctly higher than that in January and February. The mean albedo in January(12.90%) is also distinctly higher than that in the other two months. The albedo is significantly positively correlated with the SIC and is significantly negatively correlated with the SST(significance level 90%).展开更多
GREENHOUSE gases such as CH<sub>4</sub> in the ancient atmospheric concentration can be reconstructed by extracting and analyzing the gases trapped in polar ice core bubbles. It is a new attempt to extract...GREENHOUSE gases such as CH<sub>4</sub> in the ancient atmospheric concentration can be reconstructed by extracting and analyzing the gases trapped in polar ice core bubbles. It is a new attempt to extract and analyze the CH<sub>4</sub> concentration in Dunde ice core for the study of mountain glacier. Samples were taken from the about 140-m ice core drilled in 1987 in Dunde ice cap in Qilian Mountain. The ice core has been well preserved in cold room. 12 samples were taken from the upper 95 m, and cut to 15 cm in length and 5cm in diameter. CH<sub>4</sub> concentrations were measured in CNRS Laboratory of Glaciology, Grenoble, France.展开更多
The study of atmospheric polycyclic aromatic hydrocarbons(PAHs) in northeastern Tibetan Plateau with fragile ecological environment and complex atmospheric circulation system is blank. To understand the characteristic...The study of atmospheric polycyclic aromatic hydrocarbons(PAHs) in northeastern Tibetan Plateau with fragile ecological environment and complex atmospheric circulation system is blank. To understand the characteristics and sources of persistent organic pollutants in the atmosphere of the northeastern Tibetan Plateau, we monitored levels in the central Qilian Mountain. From 2016 to 2017, we collected 45-pair(particle + gas) samples using active air samplers to investigate the sources, transport paths, and their influencing factors.Sources of PAHs were analysed with a source diagnostic model, and atmospheric transport paths were calculated. The concentration range for Σ15PAHs was 439–4666 pg/m^(3), and the average was 2015 pg/m^(3). The PAHs in central Qilian Mountain are mainly low molecular weight(LMW) PAHs. Winter concentrations of PAHs were higher than those in summer. The transport of PAHs is mainly affected by westerlies, and there are seasonal differences. Source analysis showed that PAHs mainly came from coal and biomass combustion and vehicle emissions, with seasonal differences. This study clarifies the concentration and seasonal variation of PAHs in the northern Tibetan Plateau, which is conducive to understanding the atmospheric transport process and fate of pollutants. The background site of Qilian Mountains located in the Silk Road economic belt has the value and significance of longterm observation of pollutants.展开更多
As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with ...As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with remarkable microstructures. After the basic governing equations are given and the reciprocal theorem is deduced, both the generalized variational prin- ciple and the generalized Hamilton principle for mixed boundary-initial value problems of micro- morphic thermoelectroelastodynamics in convolution form are established. Finally, as a primary application, steady state responses of an unbounded homogeneous isotropic micromorphic thermo- electroelastic body to external concentrated loads with mechanical, electric, and thermal origins are analyzed.展开更多
基金The National Key Research and Development Program of China under contract No.2016YFC0402603the Guangdong Provincial Department of Natural Resources Project under contract No.42090038the Guangdong Provincial Department of Ocean and Fisheries Project under contract No.42090033.
文摘Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes.Thus,a field measurement was conducted at the Heisha Beach,located on the west coast of the Zhujiang River(Pearl River)Estuary,to investigate the short-term variation in suspended sediment concentrations(SSCs)and the relationship between the SSC and turbulent kinetic energy,bottom shear stress(BSS),and relative wave height.Based on extreme event analysis results,extreme events have a greater influence on turbulent kinetic energy than SSC.Although a portion of the turbulent kinetic energy dissipates directly into the water column,it plays an important role in suspended sediment motion.Most of the time,the wave-current interaction is strong enough to drive sediment incipience and resuspension.When combined,the wave-current interaction and wave-induced BSSs have a greater influence on suspended sediment transport and SSC variation than current-induced BSS alone.The relative wave height also has a strong correlation with SSC,indicating that the combined effect of water depth and wave height significantly impacts SSC variation.Water depth is mainly controlled by the tide on the beaches;thus,the effects of tides and waves should be conjunctively considered when analyzing the factors influencing SSC.
文摘Under bilateral cooperation between the United States of America and the People's Republic of China, a series of research cruises were conducted over the western Pacific Ocean. It was found that a) the non-sea-salt sulfate aerosol particles are the major source of cloud condensation nuclei, b) the population of clouds and the total albedo are proportional to the concentration of condensation nuclei and consequently to the concentration of the non-sea-salt aerosol particles, and c) the amount of rainfall is inversely proportional to the concentration of non-sea-salt sulfate aerosol particles. It seems that anthropogenic sulfate aerosol particles affect the regional planetary albedo and climate and that the contribution from biogenically derived sulfate aerosol particles is of lesser importance.
基金provided by the National Natural Science Foundation of China (No.50574093)the Key Program of the National Nature Science of China (No.50534090)+2 种基金the National Basic Research and Development Program of China (No.2005CB221506)the National Science Foundation for Young Scholars of China (No.50804048)the National Key Technology Research and Development Program (Nos.2006BAK03B04 and 2007 BAK29B01)
文摘In order to investigate the effect of variation in the distribution of gas on explosion propagation characteristics in coal mines, experiments were carried out in two different channels with variation in gas concentration and geometry. Flame and pressure transducers were used to track the explosion front velocity. The flame speed (Sf) showed a slight downward trend while the methane concentration varied from 10% to 3% in the experimental channel. The peak overpressure (Pmax) dropped dramatically when compared with normal conditions. As well, the values of Pmax and Sf decreased when the methane concentration dropped from 8% to 6%. The flame speed in the channel, connected to a cylinder with a length varying from 0.5 to 2 m, was greater than that in the normal channel. The peak overpressure was also higher than that under normal conditions because of a higher flame speed and stronger pressure piling up. The values of Pmax and Sf increased with an increase in cylinder length. The research results indicate that damage caused by explosions can be reduced by decreasing the gas concentration, which should be immediately detected in roadways with large cross-sections because of the possibility of greater destruction caused by more serious explosions.
文摘Sea ice conditions in the Bohai Sea of China are sensitive to large-scale climatic variations. On the basis of CLARA-A1-SAL data, the albedo variations are examined in space and time in the winter(December, January and February) from 1992 to 2008 in the Bohai Sea sea ice region. Time series data of the sea ice concentration(SIC), the sea ice extent(SIE) and the sea surface temperature(SST) are used to analyze their relationship with the albedo. The sea ice albedo changed in volatility appears along with time, the trend is not obvious and increases very slightly during the study period at a rate of 0.388% per decade over the Bohai Sea sea ice region.The interannual variation is between 9.93% and 14.50%, and the average albedo is 11.79%. The sea ice albedo in years with heavy sea ice coverage, 1999, 2000 and 2005, is significantly higher than that in other years; in years with light sea ice coverage, 1994, 1998, 2001 and 2006, has low values. For the monthly albedo, the increasing trend(at a rate of 0.988% per decade) in December is distinctly higher than that in January and February. The mean albedo in January(12.90%) is also distinctly higher than that in the other two months. The albedo is significantly positively correlated with the SIC and is significantly negatively correlated with the SST(significance level 90%).
文摘GREENHOUSE gases such as CH<sub>4</sub> in the ancient atmospheric concentration can be reconstructed by extracting and analyzing the gases trapped in polar ice core bubbles. It is a new attempt to extract and analyze the CH<sub>4</sub> concentration in Dunde ice core for the study of mountain glacier. Samples were taken from the about 140-m ice core drilled in 1987 in Dunde ice cap in Qilian Mountain. The ice core has been well preserved in cold room. 12 samples were taken from the upper 95 m, and cut to 15 cm in length and 5cm in diameter. CH<sub>4</sub> concentrations were measured in CNRS Laboratory of Glaciology, Grenoble, France.
基金supported by the Natural Science Foundation of China (No. 41971073)the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (No. 2019QZKK0106)。
文摘The study of atmospheric polycyclic aromatic hydrocarbons(PAHs) in northeastern Tibetan Plateau with fragile ecological environment and complex atmospheric circulation system is blank. To understand the characteristics and sources of persistent organic pollutants in the atmosphere of the northeastern Tibetan Plateau, we monitored levels in the central Qilian Mountain. From 2016 to 2017, we collected 45-pair(particle + gas) samples using active air samplers to investigate the sources, transport paths, and their influencing factors.Sources of PAHs were analysed with a source diagnostic model, and atmospheric transport paths were calculated. The concentration range for Σ15PAHs was 439–4666 pg/m^(3), and the average was 2015 pg/m^(3). The PAHs in central Qilian Mountain are mainly low molecular weight(LMW) PAHs. Winter concentrations of PAHs were higher than those in summer. The transport of PAHs is mainly affected by westerlies, and there are seasonal differences. Source analysis showed that PAHs mainly came from coal and biomass combustion and vehicle emissions, with seasonal differences. This study clarifies the concentration and seasonal variation of PAHs in the northern Tibetan Plateau, which is conducive to understanding the atmospheric transport process and fate of pollutants. The background site of Qilian Mountains located in the Silk Road economic belt has the value and significance of longterm observation of pollutants.
基金Project supported by the State Key Laboratory of Materials Processing and Die & Mould Technology (No. 2011-P01)the National Natural Science Foundation of China (No. 11072082)
文摘As a natural extension of the micromorphic continuum theory, the linear theory of micromorphic thermoelectroelasticity is developed to characterize the nano-micro scale behavior of thermoelectroelastic materials with remarkable microstructures. After the basic governing equations are given and the reciprocal theorem is deduced, both the generalized variational prin- ciple and the generalized Hamilton principle for mixed boundary-initial value problems of micro- morphic thermoelectroelastodynamics in convolution form are established. Finally, as a primary application, steady state responses of an unbounded homogeneous isotropic micromorphic thermo- electroelastic body to external concentrated loads with mechanical, electric, and thermal origins are analyzed.