In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in 1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence paramete...In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in 1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such as turbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculated and their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results are obtained and compared with others' results.展开更多
Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin, China.The characteristics of the turbu...Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin, China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat, uniform and open grassland,for a broad stability range(-22.12≤Z_L≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies. Under near neutral stratification,σ_u/u_*=1.20,σ_v/u_*=1.23 and σ_w/u_*=1.02.For Z_i/L≤ -0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Z_i/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law, and as Z_i/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.展开更多
Synthesis of TiO2 nanoparticles by the oxidation of titanium tetrachloride （TiCI4） in high-strength propane/air turbulent flame is investigated tentatively for mass production of TiO2 nanoparticles. Effects of react...Synthesis of TiO2 nanoparticles by the oxidation of titanium tetrachloride （TiCI4） in high-strength propane/air turbulent flame is investigated tentatively for mass production of TiO2 nanoparticles. Effects of reactor heat flux varying from 247 to 627 kJ/m^2 s, initial TiO2 number density from 2 × 10^20 to 1 × 10^21 m^ 3, and apparent residence time of TiO2 nanoparticles in reactor from 0.06 to 0.9 s, on particle morphology, phase composition, UV absorption and photoluminescence （PL） spectra are studied. The TiO2 nanoparticles synthesized, with mean size of 30-80 nm and futile mass fraction from 0.155 up to 0.575, exhibited a strong PL signal at the wavelength of 370-450 nm, with a wide peak signal at 400-420 nm, reflecting significant oxygen vacancies on the surface of the TiO2 nanoparticles.展开更多
基金This study is supported by the National Natural Science Foundation of China.
文摘In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in 1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such as turbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculated and their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results are obtained and compared with others' results.
基金the State Key Laboratory of Atmosphere Physics and Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences.
文摘Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin, China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat, uniform and open grassland,for a broad stability range(-22.12≤Z_L≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies. Under near neutral stratification,σ_u/u_*=1.20,σ_v/u_*=1.23 and σ_w/u_*=1.02.For Z_i/L≤ -0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Z_i/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law, and as Z_i/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter.
文摘Synthesis of TiO2 nanoparticles by the oxidation of titanium tetrachloride （TiCI4） in high-strength propane/air turbulent flame is investigated tentatively for mass production of TiO2 nanoparticles. Effects of reactor heat flux varying from 247 to 627 kJ/m^2 s, initial TiO2 number density from 2 × 10^20 to 1 × 10^21 m^ 3, and apparent residence time of TiO2 nanoparticles in reactor from 0.06 to 0.9 s, on particle morphology, phase composition, UV absorption and photoluminescence （PL） spectra are studied. The TiO2 nanoparticles synthesized, with mean size of 30-80 nm and futile mass fraction from 0.155 up to 0.575, exhibited a strong PL signal at the wavelength of 370-450 nm, with a wide peak signal at 400-420 nm, reflecting significant oxygen vacancies on the surface of the TiO2 nanoparticles.
