As humans and robots work closer together than ever,anthropomorphic robotic arms with intuitive human-robot interaction interfaces have drawn massive attention to improving the quality of robot-assisted manipulation.I...As humans and robots work closer together than ever,anthropomorphic robotic arms with intuitive human-robot interaction interfaces have drawn massive attention to improving the quality of robot-assisted manipulation.In pursuit of this,we designed a dedicated 7-degrees-of-freedom(DoF)anthropomorphic robotic arm having three compact differential joints and a head-mounted gaze tracker enabling head-pose-tracked 3D gaze estimation.Moreover,two key challenges were addressed to achieve accurate robot-assisted manipulation of the object indicated by the direction of human gaze.First,a novel predictive pupil feature was proposed for 3D gaze estimation.Differing from most existing features subjected to the common paraxial approximation assumption,the proposed novel predictive pupil feature considered the light refraction at two corneal surfaces with a more realistic eye model,significantly improving the 3D gaze estimation accuracy when the eyeball rotates at large angles.Second,a novel optimization-based approach was developed to efficiently compensate for the posture errors of the designed 7-DoF anthropomorphic robotic arm for accurate manipulation.Compared with the existing Jacobian-based or optimization-based approaches with nominal joint values as iteration initial,the proposed approach computed the optimal iteration initial and realized faster convergence for real-time posture error compensation.With the posture error compensation in real time and 3D gaze estimated accurately,the human can command accurate robot-assisted manipulation using his eyes intuitively.The proposed system was successfully tested on five healthy subjects.展开更多
Using a θ-θ X ray diffractometer the structure of liquid hypoeutectic Al Fe alloy at 675℃ and its change with different thermal histories are investigated . Liquid Al is used as a reference system. It is found that...Using a θ-θ X ray diffractometer the structure of liquid hypoeutectic Al Fe alloy at 675℃ and its change with different thermal histories are investigated . Liquid Al is used as a reference system. It is found that a pre peak appears on the small angle part of the structure factor of the nonsuperheated hypoeutectic Al Fe alloy, but disappears after superheating whereas the structure factors of liquid Al hardly change with the different thermal histories, and no pre peak can be observed on them. The appearance of a pre peak is a mark of the intermediate range order (IRO). The pre peak is taken as the correlation between Fe atoms on the IRO length scale. Assume that the crystalline structure is the first order approximation of the liquid structure. A model structure is constructed. The basic unit is a cube formed by 8 Al atoms on its corner and one Fe atom occupying its center. The translation of such a unit along its fourbody diagonals by the length of a diagonal can meet the requirement of the Fe_Fe distance and gives a DO 3 like structure. If the vacancy among the units is filled with fcc like Al cells, the composition of the entity is about Al 7Fe, close to that of the metastable phase Al 6Fe from rapid solidification. It is speculated that there are Al 6Fe like clusters in the liquid hypoeutectic Al Fe alloy.展开更多
Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles ca...Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.展开更多
In this article the grant number 2021YFE0107900 relating to National Key R&D Program of China for Dr.Hanghui Chen was omitted.The original article has been corrected.
基金supported by the National Natural Science Foundation of China(Grant Nos.52027806,52435005,92248304,52075191).
文摘As humans and robots work closer together than ever,anthropomorphic robotic arms with intuitive human-robot interaction interfaces have drawn massive attention to improving the quality of robot-assisted manipulation.In pursuit of this,we designed a dedicated 7-degrees-of-freedom(DoF)anthropomorphic robotic arm having three compact differential joints and a head-mounted gaze tracker enabling head-pose-tracked 3D gaze estimation.Moreover,two key challenges were addressed to achieve accurate robot-assisted manipulation of the object indicated by the direction of human gaze.First,a novel predictive pupil feature was proposed for 3D gaze estimation.Differing from most existing features subjected to the common paraxial approximation assumption,the proposed novel predictive pupil feature considered the light refraction at two corneal surfaces with a more realistic eye model,significantly improving the 3D gaze estimation accuracy when the eyeball rotates at large angles.Second,a novel optimization-based approach was developed to efficiently compensate for the posture errors of the designed 7-DoF anthropomorphic robotic arm for accurate manipulation.Compared with the existing Jacobian-based or optimization-based approaches with nominal joint values as iteration initial,the proposed approach computed the optimal iteration initial and realized faster convergence for real-time posture error compensation.With the posture error compensation in real time and 3D gaze estimated accurately,the human can command accurate robot-assisted manipulation using his eyes intuitively.The proposed system was successfully tested on five healthy subjects.
文摘Using a θ-θ X ray diffractometer the structure of liquid hypoeutectic Al Fe alloy at 675℃ and its change with different thermal histories are investigated . Liquid Al is used as a reference system. It is found that a pre peak appears on the small angle part of the structure factor of the nonsuperheated hypoeutectic Al Fe alloy, but disappears after superheating whereas the structure factors of liquid Al hardly change with the different thermal histories, and no pre peak can be observed on them. The appearance of a pre peak is a mark of the intermediate range order (IRO). The pre peak is taken as the correlation between Fe atoms on the IRO length scale. Assume that the crystalline structure is the first order approximation of the liquid structure. A model structure is constructed. The basic unit is a cube formed by 8 Al atoms on its corner and one Fe atom occupying its center. The translation of such a unit along its fourbody diagonals by the length of a diagonal can meet the requirement of the Fe_Fe distance and gives a DO 3 like structure. If the vacancy among the units is filled with fcc like Al cells, the composition of the entity is about Al 7Fe, close to that of the metastable phase Al 6Fe from rapid solidification. It is speculated that there are Al 6Fe like clusters in the liquid hypoeutectic Al Fe alloy.
基金H.C.is supported by the National Natural Science Foundation of China under project number 11774236the Ministry of Science and Technology of China under project number SQ2020YFE010418+3 种基金Open Grant of State Key Laboratory of Low Dimensional Quantum Physics at Tsinghua UniversityG.L.is supported by NSF of China(Grant No.11874263)the Sino-German mobility program(M-0006)Shanghai Technology Innovation Action Plan 2020-Integrated Circuit Technology Support Program(Project No.20DZ1100605).
文摘Oxide heterostructures exhibit many intriguing properties.Here we provide design principles for inducing multiple topological states in(001)(AMO_(3))_(1)/(AM′O_(3))_(1)oxide superlattices.Aided by first-principles calculations and model analysis,we show that a(SrMO_(3))_(1)/(SrM′O_(3))_(1)superlattice(M=Nb,Ta and M′=Rh,Ir)is a strong topological insulator with Z_(2)index(1;001).More remarkably,a(SrMoO_(3))1/(SrIrO_(3))_(1)superlattice exhibits multiple coexisting topological insulator(TI)and topological Dirac semi-metal(TDS)states.The TDS state has a pair of type-II Dirac points near the Fermi level and symmetry-protected Dirac node lines.The surface TDS Dirac cone is sandwiched by two surface TI Dirac cones in the energy-momentum space.The non-trivial topological properties arise from the band inversion between d orbitals of two dissimilar transition metal atoms and a particular parity property of(001)superlattice geometry.Our work demonstrates how to induce non-trivial topological states in(001)perovskite oxide heterostructures by rational design.
文摘In this article the grant number 2021YFE0107900 relating to National Key R&D Program of China for Dr.Hanghui Chen was omitted.The original article has been corrected.
