It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the mi...It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.展开更多
Unmanned aerial vehicles(UAVs)attract increasing attention in the transportation community due to their low cost,wide view cover-age and rapid deployment.Previous studies mainly focus on extracting traffic parameters ...Unmanned aerial vehicles(UAVs)attract increasing attention in the transportation community due to their low cost,wide view cover-age and rapid deployment.Previous studies mainly focus on extracting traffic parameters from aerial videos with air-borne cameras in planar movements.Less focus is paid to extracting traffic parameters from the UAV-like videos recorded with multi-dimensional cam-era movement.To address this issue,we propose an adapted framework for obtaining traffic parameters with the UAV camera moving at different dimensions.First,the framework introduces a temporally robust global motion compensation model to compensate for UAV camera movements and obtains a stabilized traffic scenery background.Second,the kernelized correlation filter is integrated into the proposed framework to accurately track vehicles.Third,we introduce the Hough line detection to find reference markings in videos and map the image length from video to physical length in the real world.Fourth,we estimate microscopic traffic parameters,including individual vehicle speed,time headway and space headway in a traffic stream.We testify the proposed framework perfor-mance on three different videos that are collected under the interference of different camera movements.The experimental results show that the proposed method achieves an accuracy of 96.98%and 96.94%,respectively.展开更多
The distinct element method（DEM） incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the...The distinct element method（DEM） incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stressestrain relationship and failure pattern of rocks.展开更多
SeeBand is an interactive tool for extracting microscopic material parameters by fitting temperaturedependent thermoelectric transport properties using Boltzmann transport theory.With real-time comparison between elec...SeeBand is an interactive tool for extracting microscopic material parameters by fitting temperaturedependent thermoelectric transport properties using Boltzmann transport theory.With real-time comparison between electronic band structures and transport data,it analyzes the Seebeck coefficient,resistivity,and Hall coefficient.Neural-network-assisted guesses and efficient fitting routines enable high-throughput processing of large datasets.SeeBand accelerates material design by allowing electronic band structure models to be derived directly from a single sample’s transport measurements.展开更多
基金Projects(51474251,51874351)supported by the National Natural Science Foundation,China。
文摘It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.
基金supported by the National Natural Sci-ence Foundation of China(Grant Nos.52331012,52472347 and 52071200)opening project of State Key Laboratory of Maritime Technology and Safety,Open Fund of Chongqing Key Laboratory of Green Logistics Intelligent Technology(Chongqing Jiaotong University)(No.KLGLIT2024ZD001).
文摘Unmanned aerial vehicles(UAVs)attract increasing attention in the transportation community due to their low cost,wide view cover-age and rapid deployment.Previous studies mainly focus on extracting traffic parameters from aerial videos with air-borne cameras in planar movements.Less focus is paid to extracting traffic parameters from the UAV-like videos recorded with multi-dimensional cam-era movement.To address this issue,we propose an adapted framework for obtaining traffic parameters with the UAV camera moving at different dimensions.First,the framework introduces a temporally robust global motion compensation model to compensate for UAV camera movements and obtains a stabilized traffic scenery background.Second,the kernelized correlation filter is integrated into the proposed framework to accurately track vehicles.Third,we introduce the Hough line detection to find reference markings in videos and map the image length from video to physical length in the real world.Fourth,we estimate microscopic traffic parameters,including individual vehicle speed,time headway and space headway in a traffic stream.We testify the proposed framework perfor-mance on three different videos that are collected under the interference of different camera movements.The experimental results show that the proposed method achieves an accuracy of 96.98%and 96.94%,respectively.
基金funded by the National Basic Research Programs of China(Grant Nos.2011CB013504 and 2014CB046901)the National Funds for Distinguished Young Scientists of China(Grant No.51025932)the National Nature Science Foundation of China(Grant No.41372272)
文摘The distinct element method（DEM） incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stressestrain relationship and failure pattern of rocks.
基金supported by the Japan Science and Technology Agency (JST) programs MIRAI, No. JPMJMI19A1. The authors thank Nikolas Reumann for fruitful discussions regarding the theoretical framework of SeeBand. We thank the anonymous reviewers for their constructive feedback, which significantly improved both the manuscript and the SeeBand softwareThe authors acknowledge TU Wien Bibliothek for financial support through its Open Access Funding Programme.
文摘SeeBand is an interactive tool for extracting microscopic material parameters by fitting temperaturedependent thermoelectric transport properties using Boltzmann transport theory.With real-time comparison between electronic band structures and transport data,it analyzes the Seebeck coefficient,resistivity,and Hall coefficient.Neural-network-assisted guesses and efficient fitting routines enable high-throughput processing of large datasets.SeeBand accelerates material design by allowing electronic band structure models to be derived directly from a single sample’s transport measurements.
