Visual simultaneous localization and mapping (SLAM) provides mapping and self-localization results for a robot in an unknown environment based on visual sensors, that have the advantages of small volume, low power con...Visual simultaneous localization and mapping (SLAM) provides mapping and self-localization results for a robot in an unknown environment based on visual sensors, that have the advantages of small volume, low power consumption, and richness of information acquisition. Visual SLAM is essential and plays a significant role in supporting automated and intelligent applications of robots. This paper presents the key techniques of visual SLAM, summarizes the current research status, and analyses the new trends of visual SLAM research and development. Finally, specific applications of visual SLAM in restricted environments, including deep space and indoor scenarios, are discussed.展开更多
First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile ...First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile stress is applied.Their ground states are all T phase.The biaxial tensile stress at the phase transition point of the double-layer VX_(2) is larger than that of the single-layer VX_(2).The direct band gaps can be also manipulated by biaxial tensile stress as they increases with increasing tensile stress to a critical point and then decreases.The Neel temperature(´TN)of double-layer VX_(2) are higher than that of single-layer.As the stress increases,the TN of all materials tend to increase.The magnetic moment increases with the increase of biaxial tensile stress,and which become insensitive to stress after the phase transition points.Our research provides a method to control the electronic and magnetic properties of VX_(2) by stress,and the single-layer and double-layer VX_(2) may have potential applications in nano spintronic devices.展开更多
The Moderate Resolution Imaging Camera(MoRIC)onboard the orbiter of China’s Tianwen-1 Mars mission aims to map the surface of Mars globally and to explore its topography and geomorphology.This camera’s wide field of...The Moderate Resolution Imaging Camera(MoRIC)onboard the orbiter of China’s Tianwen-1 Mars mission aims to map the surface of Mars globally and to explore its topography and geomorphology.This camera’s wide field of view can be used to overlap adjacent images sufficiently for topographic reconstruction.This study aimed to assess the topographic mapping potential of MoRIC images via a systematic accuracy analysis of MoRIC stereo mapping based on theoretical calculation and experimental validation.Experimental analyses were conducted using digital elevation models(DEMs)based on MoRIC images covering the Zhurong rover landing area and Mars Chart 11 region.Comparisons between these DEMs and reference DEMs revealed that the elevation accuracy of the former was approximately one ground sampling distance of the MoRIC image,which is consistent with the theoretical accuracy.Based on these results,MoRIC can be used to effectively map the Martian surface via stereo photogrammetry.These results serve as a useful guideline for topographic mapping based on MoRIC images and their application in various streams of research.展开更多
This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions.Photogrammetric mapping techniques were used to produce topographic products ...This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions.Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing,and to produce centimeter-resolution topographic products in near real-time after landing.Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing.During surface operations,visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images.The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning,science target selection and scientific investigations.A GIS-based digital cartography system was also developed to support rover teleoperation.展开更多
In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlatio...In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlation effect,we predicted the ground-state structure of CrTe to be NiAs-type(space group P63/mmc)structure at ambient pressure,consistent with the experimental observation.Moreover,we found two extra meta-stable Cmca and R3m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure.The Cmca structure is a layered antiferromagnetic metal.The cleaved energy of a single layer is 0.464 J/m^(2),indicating the possible synthesis of CrTe monolayer.The R3m structure is a ferromagnetic half-metal.When external pressure is applied,the ground-state structure of CrTe transitions from P63/mmc structure to R3m structure at a pressure of 34 GPa,then to Fm3m structure at 42 GPa.We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.展开更多
基金The National Key Research and Development Program of China (2016YFB0502102)The National Natural Science Foundation of China (41471388).
文摘Visual simultaneous localization and mapping (SLAM) provides mapping and self-localization results for a robot in an unknown environment based on visual sensors, that have the advantages of small volume, low power consumption, and richness of information acquisition. Visual SLAM is essential and plays a significant role in supporting automated and intelligent applications of robots. This paper presents the key techniques of visual SLAM, summarizes the current research status, and analyses the new trends of visual SLAM research and development. Finally, specific applications of visual SLAM in restricted environments, including deep space and indoor scenarios, are discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.11904312 and 11904313)the Project of Hebei Educational Department,China(Grant Nos.ZD2018015 and QN2018012)the Natural Science Foundation of Hebei Province,China(Grant No.A2019203507).
文摘First-principles calculations and Monte Carlo simulations reveal that single-layer and double-layer VX_(2)(X=Cl,Br)can be tuned from antiferromagnetic(AFM)semiconductors to ferromagnetic(FM)state when biaxial tensile stress is applied.Their ground states are all T phase.The biaxial tensile stress at the phase transition point of the double-layer VX_(2) is larger than that of the single-layer VX_(2).The direct band gaps can be also manipulated by biaxial tensile stress as they increases with increasing tensile stress to a critical point and then decreases.The Neel temperature(´TN)of double-layer VX_(2) are higher than that of single-layer.As the stress increases,the TN of all materials tend to increase.The magnetic moment increases with the increase of biaxial tensile stress,and which become insensitive to stress after the phase transition points.Our research provides a method to control the electronic and magnetic properties of VX_(2) by stress,and the single-layer and double-layer VX_(2) may have potential applications in nano spintronic devices.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the National Key Research and Development Program of China(Grant No.2021YFA0716100)the National Natural Science Foundation of China(Grant Nos.42172265 and 41771488).
文摘The Moderate Resolution Imaging Camera(MoRIC)onboard the orbiter of China’s Tianwen-1 Mars mission aims to map the surface of Mars globally and to explore its topography and geomorphology.This camera’s wide field of view can be used to overlap adjacent images sufficiently for topographic reconstruction.This study aimed to assess the topographic mapping potential of MoRIC images via a systematic accuracy analysis of MoRIC stereo mapping based on theoretical calculation and experimental validation.Experimental analyses were conducted using digital elevation models(DEMs)based on MoRIC images covering the Zhurong rover landing area and Mars Chart 11 region.Comparisons between these DEMs and reference DEMs revealed that the elevation accuracy of the former was approximately one ground sampling distance of the MoRIC image,which is consistent with the theoretical accuracy.Based on these results,MoRIC can be used to effectively map the Martian surface via stereo photogrammetry.These results serve as a useful guideline for topographic mapping based on MoRIC images and their application in various streams of research.
基金This work was supported by the National Natural Science Foundation of China[grant number 41671458,41590851,41941003,and 41771488].
文摘This paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions.Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing,and to produce centimeter-resolution topographic products in near real-time after landing.Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing.During surface operations,visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images.The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning,science target selection and scientific investigations.A GIS-based digital cartography system was also developed to support rover teleoperation.
基金This work was supported by the National Natural Science Foundation of China(Nos.11904312 and 11904313),the Project of Hebei Educational Department,China(Nos.ZD2018015 and QN2018012),the Natural Science Foundation of Hebei Province of China(No.A2020203027),the Doctor Foundation Project of Yanshan University(No.BL19008),and the Scientific Research Foundation of the Higher Education of Hebei Province,China(No.BJ2020015).The numerical calculations in this paper have been done on the supercomputing system in the High Performance Computing Center of Yanshan University.
文摘In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlation effect,we predicted the ground-state structure of CrTe to be NiAs-type(space group P63/mmc)structure at ambient pressure,consistent with the experimental observation.Moreover,we found two extra meta-stable Cmca and R3m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure.The Cmca structure is a layered antiferromagnetic metal.The cleaved energy of a single layer is 0.464 J/m^(2),indicating the possible synthesis of CrTe monolayer.The R3m structure is a ferromagnetic half-metal.When external pressure is applied,the ground-state structure of CrTe transitions from P63/mmc structure to R3m structure at a pressure of 34 GPa,then to Fm3m structure at 42 GPa.We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.
