One of the instruments onboard the China Seismic Electromagnetic Satellite （CSES） is the Low Energy Particle Detector （LEPD）. The primary objective of LEPD is to provide measurements of the fluxes, energy spectra ...One of the instruments onboard the China Seismic Electromagnetic Satellite （CSES） is the Low Energy Particle Detector （LEPD）. The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth＇s magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity-count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via GPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes （cylinder, truncated cone and rectangle） was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336±0.036 m cm2·sr for 10 MeV proton and 8.211±0.032 m cm2·sr for 8 MeV electron.展开更多
Geometric factor is the key parameter for inversion of particle spectrum in space particle detection. Traditional geometric factor is obtained through the method of numerical calculation with the actual structure of t...Geometric factor is the key parameter for inversion of particle spectrum in space particle detection. Traditional geometric factor is obtained through the method of numerical calculation with the actual structure of the detector as the input condition. The degree of accuracy for data inversion is reduced since traditional geometric factor fails to take into account the physical process of interaction between the particle and substance as well as the influence of factors such as the particle interference between different energy channels on the measurement result. Here we propose an improved geometrical factor calculation method, the concept of which is to conduct actual structural modelling of the detector in the GEANT4 program, consider the process of interaction between the particle and substance, obtain the response function of the detector to particles of different energy channels through the method of Monte Carlo simulation, calculate the influence of contaminated particle on the geometrical factor, and finally get the geometrical factors for different energy channels of the detector. The imrpoved geometrical factor obtained through the method has carried out inversion for the data of high energy protons detector on China's FY-3 satellite, the energy spectrum after which is more in line with the power law distribution recognized by space physics. The comparison with the measured result of POES satellite indicates that the FY-3 satellite data are in good accordance with the satellite data, which shows the method may effectively improve the quality of data inversion.展开更多
The large dynamic range and high performance of temperature and humidity profile lidar made it a popular tool for monitoring the atmospheric environment.In this study,we carried out an accurate analysis of the key com...The large dynamic range and high performance of temperature and humidity profile lidar made it a popular tool for monitoring the atmospheric environment.In this study,we carried out an accurate analysis of the key components of the lidar system,including lasers,the emitting and receiving light paths,and photodetectors.We combined the validation of simulations with experimental testing,and then the applicability indicators and necessary conditions in accordance were suggested.For the frequency stability of the laser,when the wavelength shift is less than 0.15%,the measurement accuracy of the system can be guaranteed to be less than 5%.The degree of near-field signal distortion will be significantly impacted by the size of the geometric factor’s transition zone.The introduced measurement error is less than 2%when the deviation angle of the emission axis is less than 0.1 mrad.It has been tested that selecting a low-sensitivity detector can help to improve the sensitivity of temperature detection since this channel is sensitive to the detector’s nonlinearity.To enhance lidar’s detection capabilities and direct the lidar system design process,it is beneficial to analyze the precision of the key components.展开更多
The pure Mg with columnar crystals was prepared by directional solidification,and the effect of process parameters on the crystal orientation and tensile properties was studied.Moreover,the microstructure evolution du...The pure Mg with columnar crystals was prepared by directional solidification,and the effect of process parameters on the crystal orientation and tensile properties was studied.Moreover,the microstructure evolution during tensile deformation was analyzed by electron backscatter diffraction(EBSD)technology.Furthermore,the slip within adjacent grains and grain boundary strain were discussed using the bicrystal model theory.The results show that the microstructure of the pure Mg at a pulling rate of 200μm/s is columnar polycrystal with growth orientation concentrated in<022ˉ5>,and no transverse grain boundaries can be seen.In addition,the Schmid factors(SFs)of basalslips in columnar crystals are higher than 0.43 under tensile stress.Moreover,the geometric compatibility factor of slip systems on both sides of grain boundaries is greater than 0.7,showing good strain coordination ability of grain boundaries.Therefore,the elongation of the directionally solidified pure Mg is as high as 53%at room temperature.展开更多
Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. S...Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.展开更多
Structure-from-Motion(SfM)techniques have been widely used for 3D geometry reconstruction from multi-view images.Nevertheless,the efficiency and quality of the reconstructed geometry depends on multiple factors,i.e.,t...Structure-from-Motion(SfM)techniques have been widely used for 3D geometry reconstruction from multi-view images.Nevertheless,the efficiency and quality of the reconstructed geometry depends on multiple factors,i.e.,the base-height ratio,intersection angle,overlap,and ground control points,etc.,which are rarely quantified in real-world applications.To answer this question,in this paper,we take a data-driven approach by analyzing hundreds of terrestrial stereo image configurations through a typical SfM algorithm.Two main meta-parameters with respect to base-height ratio and intersection angle are analyzed.Following the results,we propose a Skeletal Camera Network(SCN)and embed it into the SfM to lead to a novel SfM scheme called SCN-SfM,which limits tie-point matching to the remaining connected image pairs in SCN.The proposed method was applied in three terrestrial datasets.Experimental results have demonstrated the effectiveness of the proposed SCN-SfM to achieve 3D geometry with higher accuracy and fast time efficiency compared to the typical SfM method,whereas the completeness of the geometry is comparable.展开更多
With the help of the modified geometrical factor theory, the Marquardt method was used to calculate the true electrical parameters of the formation from array induction logs. The inversion results derived from the ass...With the help of the modified geometrical factor theory, the Marquardt method was used to calculate the true electrical parameters of the formation from array induction logs. The inversion results derived from the assumed model and some practical cases show that the rebuilt formation profile determined by 2-ft resolution array induction logs is reasonable when the formation thickness is greater than 1 m, which thus indicates that the inversion method is reliable and can provide quantitative information for the discrimination of oil/gas or water zone.展开更多
Road deaths,injuries and property damage places a huge burden on the economy of most nations.Wyoming has one of the highest truck-related fatality rates among the states in the US.The high crash rates observed in the ...Road deaths,injuries and property damage places a huge burden on the economy of most nations.Wyoming has one of the highest truck-related fatality rates among the states in the US.The high crash rates observed in the state is as a result of many factors mainly related to the challenging mountainous terrain in the state,which places extra burden on truck drivers in terms of requiring higher levels of alertness and driving skills.The difficult geometry of roads characteristic of mountainous terrain in terms of steep grade lengths adds extra risks of fatalities or injuries occurring as a result of a crash.These risks are more pronounced for truck-related crashes due to their weight and sizes.As part of the measures to reduce the incidence of truck-related crashes on mountainous areas,the Wyoming Department of Transportation(WYDOT)initiated a study to investigate causes of truck crashes on downgrade areas of Wyoming.Several studies have investigated the contributory factors to severe injury crashes but the focus has mostly been on level sections.This study analyzed the contributory geometric factors of truck crashes on downgrades by estimating three crash prediction negative binomial models.These models took into account the injury severity of the crashes.The results indicate that downgrade length,shoulder width,horizontal curve length,number of lanes,number of access points and truck traffic on the highway all impact truck-related crashes and injury frequencies ondowngrades in Wyoming.The results of this study will be helpful to future downgrade road design policy aimed at reducing downgrade truck related crashes.展开更多
文摘One of the instruments onboard the China Seismic Electromagnetic Satellite （CSES） is the Low Energy Particle Detector （LEPD）. The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth＇s magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity-count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via GPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes （cylinder, truncated cone and rectangle） was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336±0.036 m cm2·sr for 10 MeV proton and 8.211±0.032 m cm2·sr for 8 MeV electron.
基金supported by the National Natural Science Foundation of China(Grant No.41204119)the Space Science Strategic Pioneer Program of CAS(Grant No.XDA04060804)
文摘Geometric factor is the key parameter for inversion of particle spectrum in space particle detection. Traditional geometric factor is obtained through the method of numerical calculation with the actual structure of the detector as the input condition. The degree of accuracy for data inversion is reduced since traditional geometric factor fails to take into account the physical process of interaction between the particle and substance as well as the influence of factors such as the particle interference between different energy channels on the measurement result. Here we propose an improved geometrical factor calculation method, the concept of which is to conduct actual structural modelling of the detector in the GEANT4 program, consider the process of interaction between the particle and substance, obtain the response function of the detector to particles of different energy channels through the method of Monte Carlo simulation, calculate the influence of contaminated particle on the geometrical factor, and finally get the geometrical factors for different energy channels of the detector. The imrpoved geometrical factor obtained through the method has carried out inversion for the data of high energy protons detector on China's FY-3 satellite, the energy spectrum after which is more in line with the power law distribution recognized by space physics. The comparison with the measured result of POES satellite indicates that the FY-3 satellite data are in good accordance with the satellite data, which shows the method may effectively improve the quality of data inversion.
基金supported by the National Key R&D Program of China(Nos.2022YFC3700400 and 2022YFC3704000).
文摘The large dynamic range and high performance of temperature and humidity profile lidar made it a popular tool for monitoring the atmospheric environment.In this study,we carried out an accurate analysis of the key components of the lidar system,including lasers,the emitting and receiving light paths,and photodetectors.We combined the validation of simulations with experimental testing,and then the applicability indicators and necessary conditions in accordance were suggested.For the frequency stability of the laser,when the wavelength shift is less than 0.15%,the measurement accuracy of the system can be guaranteed to be less than 5%.The degree of near-field signal distortion will be significantly impacted by the size of the geometric factor’s transition zone.The introduced measurement error is less than 2%when the deviation angle of the emission axis is less than 0.1 mrad.It has been tested that selecting a low-sensitivity detector can help to improve the sensitivity of temperature detection since this channel is sensitive to the detector’s nonlinearity.To enhance lidar’s detection capabilities and direct the lidar system design process,it is beneficial to analyze the precision of the key components.
基金Projects(51775099,51675092)supported by the National Natural Science Foundation of ChinaProjects(E2021501019,E2022501001,E2022501006)supported by the Natural Science Foundation of Hebei Province,China。
文摘The pure Mg with columnar crystals was prepared by directional solidification,and the effect of process parameters on the crystal orientation and tensile properties was studied.Moreover,the microstructure evolution during tensile deformation was analyzed by electron backscatter diffraction(EBSD)technology.Furthermore,the slip within adjacent grains and grain boundary strain were discussed using the bicrystal model theory.The results show that the microstructure of the pure Mg at a pulling rate of 200μm/s is columnar polycrystal with growth orientation concentrated in<022ˉ5>,and no transverse grain boundaries can be seen.In addition,the Schmid factors(SFs)of basalslips in columnar crystals are higher than 0.43 under tensile stress.Moreover,the geometric compatibility factor of slip systems on both sides of grain boundaries is greater than 0.7,showing good strain coordination ability of grain boundaries.Therefore,the elongation of the directionally solidified pure Mg is as high as 53%at room temperature.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 51490675 and 11572300)the Natural Science Foundation of Shandong Province (NSFSD) (No. ZR2015EM025)the Fundamental Research Fund for Central Universities (Ocean University of China)
文摘Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.
基金National Natural Science Foundation of China(No.41701534)Open Fund of State Key Laboratory of Coal Resources and Safe Mining(No.SKLCRSM19KFA01)+1 种基金Ecological and Smart Mine Joint Foundation of Hebei Province(No.E2020402086)State Key Laboratory ofGeohazard Prevention and Geoenvironment Protection(No.SKLGP2019K015)
文摘Structure-from-Motion(SfM)techniques have been widely used for 3D geometry reconstruction from multi-view images.Nevertheless,the efficiency and quality of the reconstructed geometry depends on multiple factors,i.e.,the base-height ratio,intersection angle,overlap,and ground control points,etc.,which are rarely quantified in real-world applications.To answer this question,in this paper,we take a data-driven approach by analyzing hundreds of terrestrial stereo image configurations through a typical SfM algorithm.Two main meta-parameters with respect to base-height ratio and intersection angle are analyzed.Following the results,we propose a Skeletal Camera Network(SCN)and embed it into the SfM to lead to a novel SfM scheme called SCN-SfM,which limits tie-point matching to the remaining connected image pairs in SCN.The proposed method was applied in three terrestrial datasets.Experimental results have demonstrated the effectiveness of the proposed SCN-SfM to achieve 3D geometry with higher accuracy and fast time efficiency compared to the typical SfM method,whereas the completeness of the geometry is comparable.
文摘With the help of the modified geometrical factor theory, the Marquardt method was used to calculate the true electrical parameters of the formation from array induction logs. The inversion results derived from the assumed model and some practical cases show that the rebuilt formation profile determined by 2-ft resolution array induction logs is reasonable when the formation thickness is greater than 1 m, which thus indicates that the inversion method is reliable and can provide quantitative information for the discrimination of oil/gas or water zone.
文摘Road deaths,injuries and property damage places a huge burden on the economy of most nations.Wyoming has one of the highest truck-related fatality rates among the states in the US.The high crash rates observed in the state is as a result of many factors mainly related to the challenging mountainous terrain in the state,which places extra burden on truck drivers in terms of requiring higher levels of alertness and driving skills.The difficult geometry of roads characteristic of mountainous terrain in terms of steep grade lengths adds extra risks of fatalities or injuries occurring as a result of a crash.These risks are more pronounced for truck-related crashes due to their weight and sizes.As part of the measures to reduce the incidence of truck-related crashes on mountainous areas,the Wyoming Department of Transportation(WYDOT)initiated a study to investigate causes of truck crashes on downgrade areas of Wyoming.Several studies have investigated the contributory factors to severe injury crashes but the focus has mostly been on level sections.This study analyzed the contributory geometric factors of truck crashes on downgrades by estimating three crash prediction negative binomial models.These models took into account the injury severity of the crashes.The results indicate that downgrade length,shoulder width,horizontal curve length,number of lanes,number of access points and truck traffic on the highway all impact truck-related crashes and injury frequencies ondowngrades in Wyoming.The results of this study will be helpful to future downgrade road design policy aimed at reducing downgrade truck related crashes.
