Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried out.The data used in the analysis were from the multilevel ultrasonic anemometer-th...Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried out.The data used in the analysis were from the multilevel ultrasonic anemometer-thermometers at 47 m,120 m,and 280 m levels on Beijing 325 m meteorological tower.The time series of 3D atmospheric velocity were analyzed by using conventional Fourier spectral analysis and decompose into three parts:basic mean flow(period > 10 min),gusty disturbances(1 min < period < 10 min)and turbulence fluctuations(period < 1 min).The results show that under weak mean wind condition:1)the gusty disturbances are the most strong fluctuations,contribute about 60% kinetic energy of eddy kinetic energy and 80% downward flux of momentum,although both the eddy kinetic energy and momentum transport are small in comparison with those in strong mean wind condition;2)the gusty wind disturbances are anisotropic;3)the gusty wind disturbances have obviously coherent structure,and their horizontal and vertical component are negatively correlated and make downward transport of momentum more effectively;4)the friction velocities related to turbulence and gusty wind are approximately constant with height in the surface layer.展开更多
Environmental impact evaluation system boundary of high-speed railway was defined based on the total life cycle theory,and the index system to evaluate the environmental impact of high-speed railway was established wi...Environmental impact evaluation system boundary of high-speed railway was defined based on the total life cycle theory,and the index system to evaluate the environmental impact of high-speed railway was established with the fuzzy analytic hierarchy method,and the matter-element evaluation model was established on the basis of the extension theory.By calculating its comprehensive interrelatedness,the evaluation rank of environment impacts of high-speed railway was determined.The numerical example shows that the model has vast prospect,which can not only expand the application areas of extension theory,but also change the traditional evaluation methods and provide new ideas and means for environmental impact evaluation of high-speed railway.展开更多
The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated t...The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope （SEM） and scanning probe microscopy （SPM）. It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical appli- cations.展开更多
Based on the Winkler model, a mechanic model was established with formulas derived concerned with the deformations before and after a roof breakage at places in front of and at the back of the working face. In accorda...Based on the Winkler model, a mechanic model was established with formulas derived concerned with the deformations before and after a roof breakage at places in front of and at the back of the working face. In accordance with the theory for rock beam breakage, the beam breaking position in front of the working face is specified. In addition, the formulas were developed for the velocity of the subsidence at observatory point A in front of the working face when the coal wall serves as the coordinate center and the advance distance at time t as the dynamic coordinate. In the application of the above-mentioned achievements to the practice of Xieqiao Mine and the mines of the Eastern Panji Company of Huainan Mining（Group） Co. Ltd., the results concerned with the velocity with which the roof stratum tends to subside before and after breakage as derived from the mechanic model are well compatible to the results based on in-situ observations and measurements.展开更多
Analytic predictions of mean velocity profile(MVP) and streamwise(x) development of related integral quantities are presented for flows in channel and turbulent boundary layer(TBL), based on a symmetry analysis of edd...Analytic predictions of mean velocity profile(MVP) and streamwise(x) development of related integral quantities are presented for flows in channel and turbulent boundary layer(TBL), based on a symmetry analysis of eddy length and total stress. Specific predictions include the relations for momentum Reynolds number(Reθ) with friction Reτ and streamwise Re_x: Re_θ≈ 3.27Re_τ,and Re_x/Re_θ = 4.94(lnRe_θ + 1.88)~2 + 1; the streamwise development of the friction velocity u_τ: U_e/u_τ≈ 2.22 lnRe_x + 2.86. 3.83ln(lnRe_x), and of the boundary layer thickness δ_e: x/δ_e ≈ 7.27 lnRe_x.5.18.12.52ln(lnRe_x), which are fully validated by recent reliable data.展开更多
基金supported by the national natural Science Foundation of China(40830103 and 41375018)the national Basic Research Program of China(2010CB951804)the Research Program of the Chinese Academy of Sciences(XDA10010403)
文摘Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried out.The data used in the analysis were from the multilevel ultrasonic anemometer-thermometers at 47 m,120 m,and 280 m levels on Beijing 325 m meteorological tower.The time series of 3D atmospheric velocity were analyzed by using conventional Fourier spectral analysis and decompose into three parts:basic mean flow(period > 10 min),gusty disturbances(1 min < period < 10 min)and turbulence fluctuations(period < 1 min).The results show that under weak mean wind condition:1)the gusty disturbances are the most strong fluctuations,contribute about 60% kinetic energy of eddy kinetic energy and 80% downward flux of momentum,although both the eddy kinetic energy and momentum transport are small in comparison with those in strong mean wind condition;2)the gusty wind disturbances are anisotropic;3)the gusty wind disturbances have obviously coherent structure,and their horizontal and vertical component are negatively correlated and make downward transport of momentum more effectively;4)the friction velocities related to turbulence and gusty wind are approximately constant with height in the surface layer.
基金Project(2011QNZT062)supported by the Fundamental Research Funds for Central Universities of China
文摘Environmental impact evaluation system boundary of high-speed railway was defined based on the total life cycle theory,and the index system to evaluate the environmental impact of high-speed railway was established with the fuzzy analytic hierarchy method,and the matter-element evaluation model was established on the basis of the extension theory.By calculating its comprehensive interrelatedness,the evaluation rank of environment impacts of high-speed railway was determined.The numerical example shows that the model has vast prospect,which can not only expand the application areas of extension theory,but also change the traditional evaluation methods and provide new ideas and means for environmental impact evaluation of high-speed railway.
基金Supported by Major State Basic Research Program of China ("973"Program,No. 2011CB610500)
文摘The degradation coefficient is proposed to evaluate the degradation degree of organic coatings by directly anaIyzing the Bode plots of the electrochemical impedance spectroscopy （EIS） data. This paper investigated the degradation of phenolic epoxy coating/tinplate system by EIS and the degradation coefficient value, which correlates well with the results of breakpoint frequency and variation of phase angle at 10 Hz. Furthermore, the degradation process was confirmed by scanning electron microscope （SEM） and scanning probe microscopy （SPM）. It is concluded that degradation coefficient can be used for the fast evaluation of degradation degree of organic coatings in practical appli- cations.
文摘Based on the Winkler model, a mechanic model was established with formulas derived concerned with the deformations before and after a roof breakage at places in front of and at the back of the working face. In accordance with the theory for rock beam breakage, the beam breaking position in front of the working face is specified. In addition, the formulas were developed for the velocity of the subsidence at observatory point A in front of the working face when the coal wall serves as the coordinate center and the advance distance at time t as the dynamic coordinate. In the application of the above-mentioned achievements to the practice of Xieqiao Mine and the mines of the Eastern Panji Company of Huainan Mining（Group） Co. Ltd., the results concerned with the velocity with which the roof stratum tends to subside before and after breakage as derived from the mechanic model are well compatible to the results based on in-situ observations and measurements.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11452002 and 11521091)
文摘Analytic predictions of mean velocity profile(MVP) and streamwise(x) development of related integral quantities are presented for flows in channel and turbulent boundary layer(TBL), based on a symmetry analysis of eddy length and total stress. Specific predictions include the relations for momentum Reynolds number(Reθ) with friction Reτ and streamwise Re_x: Re_θ≈ 3.27Re_τ,and Re_x/Re_θ = 4.94(lnRe_θ + 1.88)~2 + 1; the streamwise development of the friction velocity u_τ: U_e/u_τ≈ 2.22 lnRe_x + 2.86. 3.83ln(lnRe_x), and of the boundary layer thickness δ_e: x/δ_e ≈ 7.27 lnRe_x.5.18.12.52ln(lnRe_x), which are fully validated by recent reliable data.
