As an important development direction of pure electric vehicle drive system,the distributed drive system has the advantages of compact structure,high transmission efficiency,and flexible control,but there are some ser...As an important development direction of pure electric vehicle drive system,the distributed drive system has the advantages of compact structure,high transmission efficiency,and flexible control,but there are some serious problems such as high performance requirements to the drive motors,complex control strategies,and poor reliability.To solve these problems,a two motors dual-mode coupling drive system has been developed at first,which not only has the capacity of two-speed gear shifting,but also can automatically switch between the distributed drive and the centralized drive by means of modes change control.So,the performance requirements to the drive motors can be reduced,the problem of abnormal running caused by the fault of unilateral distributed drive systems also can be resolved by replacing the drive mode with centralized drive.Then,the system parameters primary and the optimum matching under the principle of efficiency optimization have been carried out,which makes the drive system achieve predetermined functions and meet the actual demands of different operating statuses.At last,the economic comparison of a pure electric vehicle installation with a dual-mode coupling drive sytem,a single-motor centralized drive system or a dual-motor distributed drive system in the simulation conditions has been completed.Compared with other systems,the driving range of the electric vehicle driven by the designed system is significantly increased,which proves the better efficiency and application value of the system.展开更多
The single-shaft parallel hybrid powertrain with the automatic mechanical transmission(AMT)is an efficient hybrid driving system in the hybrid electric bus(HEB),while the electromechanical coupling driving control bec...The single-shaft parallel hybrid powertrain with the automatic mechanical transmission(AMT)is an efficient hybrid driving system in the hybrid electric bus(HEB),while the electromechanical coupling driving control becomes a complicated question to find a transient optimal control method to distribute the power between the engine and the electric machine(EM).This paper proposes an innovative control method to deal with the complicated transient coupling driving process of the electromechanical coupling driving system,considering the accelerating condition and the cruising condition mostly in the city driving cycle of HEB.The EM might be operated at driving mode or generating mode to assist the diesel engine to work in its high-efficiency area.Therefore,the adaptive torque tracking controller has been brought forward to ensure that the EM implements the demand torque as well as compensate the torque fluctuation of diesel engine.The d?q axis mathematical model and back stepping method are employed to deduce the adaptive controller and its adaptive laws.Simulation results demonstrate that the proposed control scheme can make the output torque of two power sources respond rapidly to the demand torque from the powertrain in the given driving condition.The proposed method could be adopted in the real control of HEB to improve the efficiency of the hybrid driving system.展开更多
The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals....The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals.Despite tremendous efforts in engineering synthetic cold-atom,as well as electronic and photonic lattices to explore orbital physics,thus far high orbitals in an important class of materials,namely,higher-order topological insulators(HOTIs),have not been realized.Here,we demonstrate p-orbital corner states in a photonic HOTI,unveiling their underlying topological invariant,symmetry protection,and nonlinearity-induced dynamical rotation.In a Kagome-type HOTI,we find that the topological protection of p-orbital corner states demands an orbital-hopping symmetry in addition to generalized chiral symmetry.Due to orbital hybridization,nontrivial topology of the p-orbital HOTI is“hidden”if bulk polarization is used as the topological invariant,but well manifested by the generalized winding number.Our work opens a pathway for the exploration of intriguing orbital phenomena mediated by higher-band topology applicable to a broad spectrum of systems.展开更多
The uplift of eastern Tibet,Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked,but in obscure ways.Sedimentology,geochronology,clumped isotope thermometry,and fossil ...The uplift of eastern Tibet,Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked,but in obscure ways.Sedimentology,geochronology,clumped isotope thermometry,and fossil leaf-derived numerical climate data from the Relu Basin,eastern Tibet,show at~50–45 Ma the basin was a hot(mean annual air temperature,MAAT,~27℃)dry desert at a low-elevation of 0.6±0.6 km.Rapid basin rise to 2.0±0.9 km at 45–42 Ma and to 2.9±0.9 km at 42–40 Ma,with MAATs of~20 and~16℃,respectively,accompanied seasonally varying increased annual precipitation to>1500 mm.From~39 to 34 Ma,the basin attained 3.5±1.0 km,near its present-day elevation(~3.7 km),and MAAT cooled to~6℃.Numerically-modelled Asian monsoon strength increased significantly when this Eocene uplift of eastern Tibet was incorporated.The simulation/proxy congruence points to a distinctive Eocene Asian monsoon,quite unlike that seen today,in that it featured bimodal precipitation and a winter-wet regime,and this enhanced biodiversity modernisation across eastern Asia.The Paleogene biodiversity of Asia evolved under a continually modifying monsoon influence,with the modern Asian monsoon system being unique to the present and a product of a long gradual development in the context of an ever-changing Earth system.展开更多
Conventional microscopes designed for submicron resolution in biological research are hindered by a limited field of view,typically around 1 mm.This restriction poses a challenge when attempting to simultaneously anal...Conventional microscopes designed for submicron resolution in biological research are hindered by a limited field of view,typically around 1 mm.This restriction poses a challenge when attempting to simultaneously analyze various parts of a sample,such as different brain areas.In addition,conventional objective lenses struggle to perform consistently across the required range of wavelengths for brain imaging in vivo.Here we present a novel mesoscopic objective lens with an impressive field of view of 8 mm,a numerical aperture of 0.5,and a working wavelength range from 400 to 1000 nm.We achieved a resolution of 0.74μm in fluorescent beads imaging.The versatility of this lens was further demonstrated through high-quality images of mouse brain and kidney sections in a wide-field imaging system,a confocal laser scanning system,and a two-photon imaging system.This mesoscopic objective lens holds immense promise for advancing multi-wavelength imaging of large fields of view at high resolution.展开更多
基金supported by the National Key Technology R&D Program of the Ministry of Science and Technology(Grant No.2013BAG14B01)the Shandong Provincial Natural Science Foundation of China(Grant No.ZR2012EEL08)China Postdoctoral Science Foundation Funded Project(Grant No.2013M530608)
文摘As an important development direction of pure electric vehicle drive system,the distributed drive system has the advantages of compact structure,high transmission efficiency,and flexible control,but there are some serious problems such as high performance requirements to the drive motors,complex control strategies,and poor reliability.To solve these problems,a two motors dual-mode coupling drive system has been developed at first,which not only has the capacity of two-speed gear shifting,but also can automatically switch between the distributed drive and the centralized drive by means of modes change control.So,the performance requirements to the drive motors can be reduced,the problem of abnormal running caused by the fault of unilateral distributed drive systems also can be resolved by replacing the drive mode with centralized drive.Then,the system parameters primary and the optimum matching under the principle of efficiency optimization have been carried out,which makes the drive system achieve predetermined functions and meet the actual demands of different operating statuses.At last,the economic comparison of a pure electric vehicle installation with a dual-mode coupling drive sytem,a single-motor centralized drive system or a dual-motor distributed drive system in the simulation conditions has been completed.Compared with other systems,the driving range of the electric vehicle driven by the designed system is significantly increased,which proves the better efficiency and application value of the system.
基金supported by the National Natural Science Foundation of China(Grant No.51275557)the National Science-technology Support Plan Projects of China(Grant No.2013BAG14B01)
文摘The single-shaft parallel hybrid powertrain with the automatic mechanical transmission(AMT)is an efficient hybrid driving system in the hybrid electric bus(HEB),while the electromechanical coupling driving control becomes a complicated question to find a transient optimal control method to distribute the power between the engine and the electric machine(EM).This paper proposes an innovative control method to deal with the complicated transient coupling driving process of the electromechanical coupling driving system,considering the accelerating condition and the cruising condition mostly in the city driving cycle of HEB.The EM might be operated at driving mode or generating mode to assist the diesel engine to work in its high-efficiency area.Therefore,the adaptive torque tracking controller has been brought forward to ensure that the EM implements the demand torque as well as compensate the torque fluctuation of diesel engine.The d?q axis mathematical model and back stepping method are employed to deduce the adaptive controller and its adaptive laws.Simulation results demonstrate that the proposed control scheme can make the output torque of two power sources respond rapidly to the demand torque from the powertrain in the given driving condition.The proposed method could be adopted in the real control of HEB to improve the efficiency of the hybrid driving system.
基金the National Key R&D Program of China(2022YFA1404800)the National Natural Science Foundation of China(12134006,12274242)+4 种基金the Natural Science Foundation of Tianjin(21JCJQJC00050)the QuantiXLie Center of Excellence,a project co-financed by the Croatian Government and the European Union through the European Regional Development Fund the Competitiveness and Cohesion Operational Programme(KK.01.1.1.01.0004)the 66 Postdoctoral Science Grant of Chinathe NSERC Discovery Grantthe Canada Research Chair Programs.
文摘The orbital degrees of freedom play a pivotal role in understanding fundamental phenomena in solid-state materials as well as exotic quantum states of matter including orbital superfluidity and topological semimetals.Despite tremendous efforts in engineering synthetic cold-atom,as well as electronic and photonic lattices to explore orbital physics,thus far high orbitals in an important class of materials,namely,higher-order topological insulators(HOTIs),have not been realized.Here,we demonstrate p-orbital corner states in a photonic HOTI,unveiling their underlying topological invariant,symmetry protection,and nonlinearity-induced dynamical rotation.In a Kagome-type HOTI,we find that the topological protection of p-orbital corner states demands an orbital-hopping symmetry in addition to generalized chiral symmetry.Due to orbital hybridization,nontrivial topology of the p-orbital HOTI is“hidden”if bulk polarization is used as the topological invariant,but well manifested by the generalized winding number.Our work opens a pathway for the exploration of intriguing orbital phenomena mediated by higher-band topology applicable to a broad spectrum of systems.
基金supported by the National Natural Science Foundation of China Basic Science Center for Tibetan Plateau Earth System(41988101)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0708)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20070301)the National Natural Science Foundation of China-Natural Environment Research Council of the United Kingdom Joint Research Program(41661134049 and NE/P013805/1)the National Natural Science Foundation of China(41941016)。
文摘The uplift of eastern Tibet,Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked,but in obscure ways.Sedimentology,geochronology,clumped isotope thermometry,and fossil leaf-derived numerical climate data from the Relu Basin,eastern Tibet,show at~50–45 Ma the basin was a hot(mean annual air temperature,MAAT,~27℃)dry desert at a low-elevation of 0.6±0.6 km.Rapid basin rise to 2.0±0.9 km at 45–42 Ma and to 2.9±0.9 km at 42–40 Ma,with MAATs of~20 and~16℃,respectively,accompanied seasonally varying increased annual precipitation to>1500 mm.From~39 to 34 Ma,the basin attained 3.5±1.0 km,near its present-day elevation(~3.7 km),and MAAT cooled to~6℃.Numerically-modelled Asian monsoon strength increased significantly when this Eocene uplift of eastern Tibet was incorporated.The simulation/proxy congruence points to a distinctive Eocene Asian monsoon,quite unlike that seen today,in that it featured bimodal precipitation and a winter-wet regime,and this enhanced biodiversity modernisation across eastern Asia.The Paleogene biodiversity of Asia evolved under a continually modifying monsoon influence,with the modern Asian monsoon system being unique to the present and a product of a long gradual development in the context of an ever-changing Earth system.
基金supported by National Key R&D Program of China(grant no.2022YFC2404201)the Chinese Academy of Sciences Project for Young Scientists in Basic Research(grant no.YSBR067).
文摘Conventional microscopes designed for submicron resolution in biological research are hindered by a limited field of view,typically around 1 mm.This restriction poses a challenge when attempting to simultaneously analyze various parts of a sample,such as different brain areas.In addition,conventional objective lenses struggle to perform consistently across the required range of wavelengths for brain imaging in vivo.Here we present a novel mesoscopic objective lens with an impressive field of view of 8 mm,a numerical aperture of 0.5,and a working wavelength range from 400 to 1000 nm.We achieved a resolution of 0.74μm in fluorescent beads imaging.The versatility of this lens was further demonstrated through high-quality images of mouse brain and kidney sections in a wide-field imaging system,a confocal laser scanning system,and a two-photon imaging system.This mesoscopic objective lens holds immense promise for advancing multi-wavelength imaging of large fields of view at high resolution.
