Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode (...Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode (5.6-20 um), Aitken mode (20-100 um), and accumulation mode (100-560 um) particles, and total particles were 17500, 32000, 4000, and 53500 cm^-3, respectively. Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 um during the daytime. New particle formation events, which were connected to diurnal variation of nucleation mode particles, were observed in more than half of the observation days. The events often started around 10:00-11:00 Chinese Standard Time (CST) and ended up after 3-4 h. Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10:00 CST, and then decreased and became the lowest in the afternoon. Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission, and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.展开更多
Conceptual design, data model and key techniques of "Geo-engineer 3D assistant", an underground 3D GIS oriented to geology and mine application, were discussed. In particular, the importance of high-order sm...Conceptual design, data model and key techniques of "Geo-engineer 3D assistant", an underground 3D GIS oriented to geology and mine application, were discussed. In particular, the importance of high-order smoothing triangular pieces to surface's fine expression in geological modeling was emphasized. The contour mode is the most favorite mode of the three modes about surface expression: DEM, TIN and contour. Topology in underground 3D modeling with CAGD was compared. From the view of boundary and coboundary, which is soul of IS 19107 (Geographic information spatial schema), 3D underground topology was re-examined.展开更多
Understanding the mechanisms of the breakage of ore particles is important to predict the particle size distribution in size reduction operations.This paper aims to show the presence of common breakage modes in impact...Understanding the mechanisms of the breakage of ore particles is important to predict the particle size distribution in size reduction operations.This paper aims to show the presence of common breakage modes in impact breakage and ball milling of the cement clinker and chromite samples.For that purpose,narrow size fractions of the two samples were broken in a drop-weight tester or ball mill by changing the degree of applied energy.Then the resultant size distributions were evaluated to seek evidence for the common breakage modes.The results showed that increasing the breakage energy will produce a systematic change in the shapes of the size distributions,suggesting a sequential set of breakage modes.The breakage is initially due to tensile stresses at low breakage energies and compressive stresses at high breakage energies.Further studies should be done to assess if these breakage modes occur at sizereduction of different ores.展开更多
基金Project supported by the National Natural Science Foundation of China(No.20477020)the National Science Fund for Distinguished Young Scholars(No.20625722).
文摘Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode (5.6-20 um), Aitken mode (20-100 um), and accumulation mode (100-560 um) particles, and total particles were 17500, 32000, 4000, and 53500 cm^-3, respectively. Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 um during the daytime. New particle formation events, which were connected to diurnal variation of nucleation mode particles, were observed in more than half of the observation days. The events often started around 10:00-11:00 Chinese Standard Time (CST) and ended up after 3-4 h. Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10:00 CST, and then decreased and became the lowest in the afternoon. Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission, and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.
基金Project(A11024)supported by the Key Laboratory Fund of Geo-Informatics of State Bureau of Surveying and MappingProject(7771022)supported by the Basic Research Fund for Chinese Academy of Surveying and MappingProject(2010AA22202)supported by the National High-tech Research and Development Program of China
文摘Conceptual design, data model and key techniques of "Geo-engineer 3D assistant", an underground 3D GIS oriented to geology and mine application, were discussed. In particular, the importance of high-order smoothing triangular pieces to surface's fine expression in geological modeling was emphasized. The contour mode is the most favorite mode of the three modes about surface expression: DEM, TIN and contour. Topology in underground 3D modeling with CAGD was compared. From the view of boundary and coboundary, which is soul of IS 19107 (Geographic information spatial schema), 3D underground topology was re-examined.
文摘Understanding the mechanisms of the breakage of ore particles is important to predict the particle size distribution in size reduction operations.This paper aims to show the presence of common breakage modes in impact breakage and ball milling of the cement clinker and chromite samples.For that purpose,narrow size fractions of the two samples were broken in a drop-weight tester or ball mill by changing the degree of applied energy.Then the resultant size distributions were evaluated to seek evidence for the common breakage modes.The results showed that increasing the breakage energy will produce a systematic change in the shapes of the size distributions,suggesting a sequential set of breakage modes.The breakage is initially due to tensile stresses at low breakage energies and compressive stresses at high breakage energies.Further studies should be done to assess if these breakage modes occur at sizereduction of different ores.