High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared...High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared source structure based on an electron-phonon coupling and emitting mechanism.A series of electrical characterizations including carrier mobility[11,361.55 cm^(2)/(V.s)],pulse current(30 ms response time),and cycling stability(2000 cycles)modulated by polarized film was provided.展开更多
Separating wood and leaf components in tree point clouds is one of the key tasks for achieving automated forest inventory and management.To obtain accurate wood-leaf separation results,traditional methods typically re...Separating wood and leaf components in tree point clouds is one of the key tasks for achieving automated forest inventory and management.To obtain accurate wood-leaf separation results,traditional methods typically rely on large amounts of annotated point cloud data to train supervised semantic segmentation networks.However,point wise annotation is not only extremely labor-intensive but also time-consuming and costly,which greatly limits the widespread application and adoption of supervised learning methods in wood-leaf separation tasks.To eliminate the dependence on annotated point clouds,this study explores the feasibility of wood-leaf separation under completely unsupervised conditions.To this end,we propose an unsupervised semantic segmentation network that is capable of directly extracting wood and leaf components in 3D point clouds.The network adopts a sparse convolutional neural network as the backbone and incorporates two custom-designed modules:the dual point attention(DPA)module and the point cloud feature convolutional integrator(PFCI)module,for enhanced feature fusion and extraction.Semantic classification is then achieved by generating pseudolabels via super point clustering.Based on large-scale public datasets containing coniferous and broadleaf forests,in addition to our self-constructed dataset,our proposed network achieved an overall accuracy(oAcc)of 67.583%,a mean clas-sification accuracy(mAcc)of 50.249%,and a mean intersection over union(mIoU)of 38.512%,and in wood and leaf separation at the tree level,it attained an oAcc of 80.856%,a mAcc of 64.013%,and a mIoU of 49.695%.Across both the forest and tree scenarios,our network outperforms the current state-of-the-art methods,namely,GrowSP and PointDC.Ablation experiments further confirm that each of the proposed modules contributes significantly to improving the segmentation accuracy,and in addition,our segmentation network demonstrates strong robustness even under high occlusion rates and exhibits excellent generalization capability.展开更多
The unique structure of zero-dimensional(0D)perovskite-analogues has attracted a great amount of research interest in recent years.To date,the current compositional library of 0D perovskites is largely limited to the ...The unique structure of zero-dimensional(0D)perovskite-analogues has attracted a great amount of research interest in recent years.To date,the current compositional library of 0D perovskites is largely limited to the lead-based Cs4PbX6(X=Cl,Br,and I)systems.In this work,we report a new synthesis of lead-free 0D Cs3BiX6(X=Cl,Br)perovskite-analogue nanocrystals(NCs)with a uniform cubic shape.We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs3BiCl6 NCs at low temperatures.This feature originates from a self-trapped exciton mechanism.In situ thermal stability studies show that Cs3BiX6 NCs remain stable upon heating up to 200°C without crystal structural degradation.Moreover,we demonstrate that the Cs3BiX6 NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions.Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials,leading toward their future optoelectronic applications.展开更多
A hollow-core fiber based on photonic quasicrystal arrays is theoretically proposed for high-quality light wave propagation with high polarization maintaining performance and low nonlinearity.This fiber,called hollow-...A hollow-core fiber based on photonic quasicrystal arrays is theoretically proposed for high-quality light wave propagation with high polarization maintaining performance and low nonlinearity.This fiber,called hollow-core photonic quasicrystal fiber(HC-PQF),can simultaneously realize a high birefringence that reaches 1.345×10^-2 and a small nonlinear coefficient of 1.63×10^-3 W^-1·km^-1 at a communication wavelength of 1.55μm due to the air-filled core and unique quasiperiodic fiber structure.To further demonstrate the controllability of the nonlinear coefficient and the application of sensor and polarization-maintaining fiber,the nonlinearity is investigated by filling different inert gases in the fiber core while the birefringence keeps a high order of 10-2.In the wavelength rangeλ∈[1.53μm,1.57μm],the dispersion is near zero and flattened.The HC-PQF is expected to be used for applications in optical communication,high power pulse transmission,polarization beam splitters,etc.展开更多
In the fields of light manipulation and localization,quasiperiodic photonic crystals,or photonic quasicrystals[PQs],are causing an upsurge in research because of their rotational symmetry and long-range orientation of...In the fields of light manipulation and localization,quasiperiodic photonic crystals,or photonic quasicrystals[PQs],are causing an upsurge in research because of their rotational symmetry and long-range orientation of transverse lattice arrays,as they lack translational symmetry.It allows for the optimization of well-established light propagation properties and has introduced new guiding features.Therefore,as a class,quasiperiodic photonic crystal fibers,or photonic quasicrystal fibers[PQFs],are considered to add flexibility and richness to the optical properties of fibers and are expected to offer significant potential applications to optical fiber fields.In this review,the fundamental concept,working mechanisms,and invention history of PQFs are explained.Recent progress in optical property improvement and its novel applications in fields such as dispersion control,polarization-maintenance,supercontinuum generation,orbital angular momentum transmission,plasmon-based sensors and filters,and high nonlinearity and topological mode transmission,are then reviewed in detail.Bandgap-type air-guiding PQFs supporting low attenuation propagation and regulation of photonic density states of quasiperiodic cladding and in which light guidance is achieved by coherent Bragg scattering are also summarized.Finally,current challenges encountered in the guiding mechanisms and practical preparation techniques,as well as the prospects and research trends of PQFs,are also presented.展开更多
基金Natural Science Foundation of Shanxi Province(20210302123056)Shanxi Provincial Key Research and Development Project(202102040201007,202203021223005)National Natural Science Foundation of China(52275577,52205609).
文摘High-performance infrared emitters hold substantial importance in modern engineering and physics.Here,we introduce graphene/PZT(lead zirconate titanate)heterostructure as a new platform for the development of infrared source structure based on an electron-phonon coupling and emitting mechanism.A series of electrical characterizations including carrier mobility[11,361.55 cm^(2)/(V.s)],pulse current(30 ms response time),and cycling stability(2000 cycles)modulated by polarized film was provided.
基金This work was supported by the Scientific Research Program of Hunan Provincial Department of Education(No.22B0258)Natural Science Foundation of Hunan Province(No.2024JJ5649).
文摘Separating wood and leaf components in tree point clouds is one of the key tasks for achieving automated forest inventory and management.To obtain accurate wood-leaf separation results,traditional methods typically rely on large amounts of annotated point cloud data to train supervised semantic segmentation networks.However,point wise annotation is not only extremely labor-intensive but also time-consuming and costly,which greatly limits the widespread application and adoption of supervised learning methods in wood-leaf separation tasks.To eliminate the dependence on annotated point clouds,this study explores the feasibility of wood-leaf separation under completely unsupervised conditions.To this end,we propose an unsupervised semantic segmentation network that is capable of directly extracting wood and leaf components in 3D point clouds.The network adopts a sparse convolutional neural network as the backbone and incorporates two custom-designed modules:the dual point attention(DPA)module and the point cloud feature convolutional integrator(PFCI)module,for enhanced feature fusion and extraction.Semantic classification is then achieved by generating pseudolabels via super point clustering.Based on large-scale public datasets containing coniferous and broadleaf forests,in addition to our self-constructed dataset,our proposed network achieved an overall accuracy(oAcc)of 67.583%,a mean clas-sification accuracy(mAcc)of 50.249%,and a mean intersection over union(mIoU)of 38.512%,and in wood and leaf separation at the tree level,it attained an oAcc of 80.856%,a mAcc of 64.013%,and a mIoU of 49.695%.Across both the forest and tree scenarios,our network outperforms the current state-of-the-art methods,namely,GrowSP and PointDC.Ablation experiments further confirm that each of the proposed modules contributes significantly to improving the segmentation accuracy,and in addition,our segmentation network demonstrates strong robustness even under high occlusion rates and exhibits excellent generalization capability.
基金support from Brown University startup funds and the National Science Foundation(OIA-1538893)K.H.-K.is supported by the U.S.Department of Education GAANN research fellowship(P200A150037)。
文摘The unique structure of zero-dimensional(0D)perovskite-analogues has attracted a great amount of research interest in recent years.To date,the current compositional library of 0D perovskites is largely limited to the lead-based Cs4PbX6(X=Cl,Br,and I)systems.In this work,we report a new synthesis of lead-free 0D Cs3BiX6(X=Cl,Br)perovskite-analogue nanocrystals(NCs)with a uniform cubic shape.We observe a broad photoluminescence peak centered at 390 nm for the 0D Cs3BiCl6 NCs at low temperatures.This feature originates from a self-trapped exciton mechanism.In situ thermal stability studies show that Cs3BiX6 NCs remain stable upon heating up to 200°C without crystal structural degradation.Moreover,we demonstrate that the Cs3BiX6 NCs can transform into other bismuth-based perovskite-analogues via facile anion exchange or metal ion insertion reactions.Our study presented here offers the opportunity for further understanding of the structure-property relationship of 0D perovskite-analogue materials,leading toward their future optoelectronic applications.
基金supported by the National Natural Science Foundation of China(No.61405058)the Natural Science Foundation of Hunan Province(No.2017JJ2048)the Fundamental Research Funds for the Central Universities(No.531118040112)。
文摘A hollow-core fiber based on photonic quasicrystal arrays is theoretically proposed for high-quality light wave propagation with high polarization maintaining performance and low nonlinearity.This fiber,called hollow-core photonic quasicrystal fiber(HC-PQF),can simultaneously realize a high birefringence that reaches 1.345×10^-2 and a small nonlinear coefficient of 1.63×10^-3 W^-1·km^-1 at a communication wavelength of 1.55μm due to the air-filled core and unique quasiperiodic fiber structure.To further demonstrate the controllability of the nonlinear coefficient and the application of sensor and polarization-maintaining fiber,the nonlinearity is investigated by filling different inert gases in the fiber core while the birefringence keeps a high order of 10-2.In the wavelength rangeλ∈[1.53μm,1.57μm],the dispersion is near zero and flattened.The HC-PQF is expected to be used for applications in optical communication,high power pulse transmission,polarization beam splitters,etc.
基金supported by the Changsha Municipal Natural Science Foundation(No.kq2202295)the Scientific Research Foundation of Hunan Provincial Education Department(Nos.22B0273 and 21A0013)+1 种基金the National Natural Science Foundation of China(Nos.61405058 and 62075059)the Natural Science Foundation of Hunan Province(Nos.2017JJ2048 and 2020JJ4161)。
文摘In the fields of light manipulation and localization,quasiperiodic photonic crystals,or photonic quasicrystals[PQs],are causing an upsurge in research because of their rotational symmetry and long-range orientation of transverse lattice arrays,as they lack translational symmetry.It allows for the optimization of well-established light propagation properties and has introduced new guiding features.Therefore,as a class,quasiperiodic photonic crystal fibers,or photonic quasicrystal fibers[PQFs],are considered to add flexibility and richness to the optical properties of fibers and are expected to offer significant potential applications to optical fiber fields.In this review,the fundamental concept,working mechanisms,and invention history of PQFs are explained.Recent progress in optical property improvement and its novel applications in fields such as dispersion control,polarization-maintenance,supercontinuum generation,orbital angular momentum transmission,plasmon-based sensors and filters,and high nonlinearity and topological mode transmission,are then reviewed in detail.Bandgap-type air-guiding PQFs supporting low attenuation propagation and regulation of photonic density states of quasiperiodic cladding and in which light guidance is achieved by coherent Bragg scattering are also summarized.Finally,current challenges encountered in the guiding mechanisms and practical preparation techniques,as well as the prospects and research trends of PQFs,are also presented.
