Based on the results of force measurement experiment in a low speed wind tunnel, the effect of asymmetrical leading-edge sweep angle on aerodynamic load was investigated with the common-swift’s wing model. The wing m...Based on the results of force measurement experiment in a low speed wind tunnel, the effect of asymmetrical leading-edge sweep angle on aerodynamic load was investigated with the common-swift’s wing model. The wing model was divided into three segments, i.e., arm wing, hand wing<SUB>in</SUB> and hand wing<SUB>out</SUB>, and the roll moment produced by the variation of asymmetrical change of wing segment’s leading-edge sweep angle was analyzed.展开更多
Deserts,which have high surface albedo and wide area,are important components of the earth system.It is very important for the research of surface radiation and energy balance to understand the anisotropic scattering ...Deserts,which have high surface albedo and wide area,are important components of the earth system.It is very important for the research of surface radiation and energy balance to understand the anisotropic scattering of desert areas.The emergence and development of multi-angle remote sensing made possible the inversion of the anisotropic scattering of desert areas at the regional or global scale.Firstly,this paper explored the accuracy of the inversion of asymmetry factor using the Hapke model and the simulated single-and multi-phase MISR data.Based on the results,the asymmetry factor of representative surface of desert areas in northwestern China was retrieved.The values of the asymmetry factor retrieved from MISR data were compared with the values retrieved from the laboratory data.The results showed that the single-phase MISR data could be used for the inversion of asymmetry parameter of desert areas.The sign of the asymmetry parameter for the laboratory measurements was positive,which suggests that the surface of laboratory samples is forward scattering.The sign of the asymmetry parameter for MISR data was negative;that is,it is backscattering.The values of the asymmetry parameters retrieved from MISR data were related to the character of the land surface.At Loulan,where the surface was smoother than other sites,retrieved values exhibited the largest negative values of asymmetry factor,suggesting the strongest backscattering.The sand dune area of the Kumtag Desert,which has the greatest roughness,had only slightly negative asymmetry factor values.These findings indicated that at the sensor scale,a rough surface(e.g.,dunes) does not necessarily mean more backscattering than a smooth surface.This finding has significant implications for empirical methods(e.g.,using the normalized index of backward-scattered radiance minus forward-scattered radiance as an indicator of surface roughness),which should be used carefully for analyzing surface roughness from the remote sensing data.展开更多
The angle compensation method is adopted to detect sloshing waves by laser diffraction, in the case that the wavelength of the sloshing waves is much greater than that of the incident light. The clear diffraction patt...The angle compensation method is adopted to detect sloshing waves by laser diffraction, in the case that the wavelength of the sloshing waves is much greater than that of the incident light. The clear diffraction pattern is observed to be of asymmetry, involving orders, position and interval of the diffraction spots that are discovered during the light grazing incidence. It is found that the larger the angle of incidence is, the more obvious the asymmetry is. The higher the negative diffraction orders are, the smaller the intervals between spots are. On the contrary~ in the positive region, the higher the diffraction orders are, the larger the spot intervals are. The positive interval is larger than that of the same negative diffraction order. If the incident angle reaches 1.558 rad in the experiment, all positive diffraction orders completely vanish. Based on the mechanism of phase modulation and with the Fourier transform method, the relations between the incident angle and position, interval spaces, and orders of diffraction spots are derived theoretically. The theoretical calculations are compared with the experimental data, and the comparison shows that the theoretical calculations are in good agreement with the experimental measurement.展开更多
Existing traffic flow models give little consideration on vehicle sizes. We introduce the solid angle into car-following theory, taking the driver’s perception of the leading vehicle’s size into account. The solid a...Existing traffic flow models give little consideration on vehicle sizes. We introduce the solid angle into car-following theory, taking the driver’s perception of the leading vehicle’s size into account. The solid angle and its change rate are applied as inputs to the novel model. A nonlinear stability analysis is performed to analyze the asymmetry of the model and the size effect of the leading vehicle, and the modified Korteweg–de Vries equation is derived. The solid angle model can explain complex traffic characteristics and provide an important basis for modeling nonlinear traffic phenomena.展开更多
基金Supported by the National Natural Science Foundation of China (Grant No. 10425207)
文摘Based on the results of force measurement experiment in a low speed wind tunnel, the effect of asymmetrical leading-edge sweep angle on aerodynamic load was investigated with the common-swift’s wing model. The wing model was divided into three segments, i.e., arm wing, hand wing<SUB>in</SUB> and hand wing<SUB>out</SUB>, and the roll moment produced by the variation of asymmetrical change of wing segment’s leading-edge sweep angle was analyzed.
基金supported by National Natural Science Foundation of China (Grant No.40930103)National High-tech Research & Development Programme of China (Grant No.2009AA12Z134)National Natural Science Foundation of China (Grant No.40701125)
文摘Deserts,which have high surface albedo and wide area,are important components of the earth system.It is very important for the research of surface radiation and energy balance to understand the anisotropic scattering of desert areas.The emergence and development of multi-angle remote sensing made possible the inversion of the anisotropic scattering of desert areas at the regional or global scale.Firstly,this paper explored the accuracy of the inversion of asymmetry factor using the Hapke model and the simulated single-and multi-phase MISR data.Based on the results,the asymmetry factor of representative surface of desert areas in northwestern China was retrieved.The values of the asymmetry factor retrieved from MISR data were compared with the values retrieved from the laboratory data.The results showed that the single-phase MISR data could be used for the inversion of asymmetry parameter of desert areas.The sign of the asymmetry parameter for the laboratory measurements was positive,which suggests that the surface of laboratory samples is forward scattering.The sign of the asymmetry parameter for MISR data was negative;that is,it is backscattering.The values of the asymmetry parameters retrieved from MISR data were related to the character of the land surface.At Loulan,where the surface was smoother than other sites,retrieved values exhibited the largest negative values of asymmetry factor,suggesting the strongest backscattering.The sand dune area of the Kumtag Desert,which has the greatest roughness,had only slightly negative asymmetry factor values.These findings indicated that at the sensor scale,a rough surface(e.g.,dunes) does not necessarily mean more backscattering than a smooth surface.This finding has significant implications for empirical methods(e.g.,using the normalized index of backward-scattered radiance minus forward-scattered radiance as an indicator of surface roughness),which should be used carefully for analyzing surface roughness from the remote sensing data.
基金Supported by the Open Research Fund of State Key Laboratory of Transient Optics and Photonics of Chinese Academy of Sciences under Grant No SKLST201508the China Postdoctoral Science Foundation Funded Project under Grant No 2015M580945the Government of Chaoyang District Postdoctoral Research Foundation
文摘The angle compensation method is adopted to detect sloshing waves by laser diffraction, in the case that the wavelength of the sloshing waves is much greater than that of the incident light. The clear diffraction pattern is observed to be of asymmetry, involving orders, position and interval of the diffraction spots that are discovered during the light grazing incidence. It is found that the larger the angle of incidence is, the more obvious the asymmetry is. The higher the negative diffraction orders are, the smaller the intervals between spots are. On the contrary~ in the positive region, the higher the diffraction orders are, the larger the spot intervals are. The positive interval is larger than that of the same negative diffraction order. If the incident angle reaches 1.558 rad in the experiment, all positive diffraction orders completely vanish. Based on the mechanism of phase modulation and with the Fourier transform method, the relations between the incident angle and position, interval spaces, and orders of diffraction spots are derived theoretically. The theoretical calculations are compared with the experimental data, and the comparison shows that the theoretical calculations are in good agreement with the experimental measurement.
基金National Key R&D Program of China(Grant No.2018YFB1601000).
文摘Existing traffic flow models give little consideration on vehicle sizes. We introduce the solid angle into car-following theory, taking the driver’s perception of the leading vehicle’s size into account. The solid angle and its change rate are applied as inputs to the novel model. A nonlinear stability analysis is performed to analyze the asymmetry of the model and the size effect of the leading vehicle, and the modified Korteweg–de Vries equation is derived. The solid angle model can explain complex traffic characteristics and provide an important basis for modeling nonlinear traffic phenomena.
