Imaging in the solar blind ultraviolet(UV)region offers significant advantages,including minimal interference from sunlight,reduced background noise,low false-alarm rate,and high sensitivity,and thus has important app...Imaging in the solar blind ultraviolet(UV)region offers significant advantages,including minimal interference from sunlight,reduced background noise,low false-alarm rate,and high sensitivity,and thus has important applications in early warning or detection of fire,ozone depletion,dynamite explosions,missile launches,electric leakage,etc.However,traditional imaging systems in this spectrum are often hindered by the bulkiness and complexity of conventional optics,resulting in heavy and cumbersome setups.The advent of metasurfaces,which use a two-dimensional array of nano-antennas to manipulate light properties,provides a powerful solution for developing miniaturized and compact optical systems.In this study,diamond metalenses were designed and fabricated to enable ultracompact solar-blind UV imaging.To prove this concept,two representative functionalities,bright-field imaging and spiral phase contrast imaging,were demonstrated as examples.Leveraging diamond's exceptional properties,such as its wide bandgap,high refractive index,remarkable chemical inertness,and high damage threshold,this work not only presents a simple and feasible approach to realize solar-blind imaging in an ultracompact form but also highlights diamond as a highly capable material for developing miniaturized,lightweight,and robust imaging systems.展开更多
In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describ...In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describes a novel front-surface high-temperature deformation measurement technique,which adopts ultraviolet 3D digital image correlation(UV 3D-DIC)to observe and measure the high-temperature deformation fields on front surfaces directly heated by quartz lamps.Compared with existing blue light DIC techniques,the established UV 3D-DIC,which combines UV CCD camera,active UV illumination and bandpass filter imaging,can effectively suppress the strong disturbing light emitted by the quartz lamps and the heated sample itself during heating process.Two experiments were carried out to verify the robustness and accuracy of the developed technique:(1)direct observation of front surfaces of a hypersonic thermal structure sample heated from room temperature to 1050℃,and(2)front-surface thermal stain and coefficient of thermal expansion(CTE)measurement of an Inconel 718 sample up to 800℃.The well matched strain and CTE results with literature data show that UV 3D-DIC system is an effective technique for front-surface deformation measurement and has great potential in characterizing deformation response of hypersonic materials and structures subjected to transient aerodynamic heating.展开更多
Global images of auroras obtained by cameras on spacecraft are a key tool for studying the near-Earth environment.However,the cameras are sensitive not only to auroral emissions produced by precipitating particles,but...Global images of auroras obtained by cameras on spacecraft are a key tool for studying the near-Earth environment.However,the cameras are sensitive not only to auroral emissions produced by precipitating particles,but also to dayglow emissions produced by photoelectrons induced by sunlight.Nightglow emissions and scattered sunlight can contribute to the background signal.To fully utilize such images in space science,background contamination must be removed to isolate the auroral signal.Here we outline a data-driven approach to modeling the background intensity in multiple images by formulating linear inverse problems based on B-splines and spherical harmonics.The approach is robust,flexible,and iteratively deselects outliers,such as auroral emissions.The final model is smooth across the terminator and accounts for slow temporal variations and large-scale asymmetries in the dayglow.We demonstrate the model by using the three far ultraviolet cameras on the Imager for Magnetopause-to-Aurora Global Exploration(IMAGE)mission.The method can be applied to historical missions and is relevant for upcoming missions,such as the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.展开更多
Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigatio...Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigation of a typical 750 kV AC substation located in Lanzhou with ultraviolet imager(UVI) demonstrated that the corona discharge of some insulators is serious due to the improper structure design and installation,so research on porcelain insulators used in substation is needed.The three-dimensional finite element method(FEM) 750 kV AC substation calculation model was established to calculate electric field and voltage distribution of insulators,and the voltage distribution curves along insulators which are classified by type and suspension location were obtained using a novel FEM method which can effectively reduce the calculation amount without losing accuracy,meanwhile,the effect of the grading ring for improving voltage distribution of insulators was studied by adjusting the structure parameters of grading ring. Consequently,an optimization structure of rings was proposed by improving the voltage distribution of insulator string and reducing the electric strength of grading ring for the purpose of restricting corona noise,and the onsite observations by UVI showed that the newly manufactured and installed grading ring could obviously avoid the occurrences of corona discharge which validates the optimization design.This paper proposed an effective method combining UVI observation and FEM calculation to study voltage-sharing characteristics of porcelain insulators,and the results can provide experiences and references for the design of 750 kV AC substation.展开更多
There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their ...There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their practical applications are greatly limited by their slow response speed as well as low specific detectivity.Here,the successful fabrication of two-/three-dimensional(2D/3D)graphene(Gr)/PtSe2/β-Ga_(2)O_(3)Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated.Benefitting from the high-quality 2D/3D Schottky junction,the vertically stacked structure,and the superior-quality transparent graphene electrode for effective carrier collection,the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W,a large on/off current ratio of~105,along with an ultra-high ultraviolet(UV)/visible rejection ratio of 1.8×104.More importantly,it has an ultra-fast response time of 12µs and a remarkable specific detectivity of~1013 Jones.Finally,an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga_(2)O_(3)Schottky junction photodetector,demonstrating its great potential application in DUV imaging systems.展开更多
Two-dimensional organic semiconductor single crystals(2D OSSCs)have great potential for use in highperformance optoelectronic devices.However,challenges associated with controlling complex fluid dynamics and molecular...Two-dimensional organic semiconductor single crystals(2D OSSCs)have great potential for use in highperformance optoelectronic devices.However,challenges associated with controlling complex fluid dynamics and molecular mass transfer during solution-based processes hinder large-scale high-quality production.To address this issue,we developed a nanoconfinement-driven approach for controlling molecular crystallization,improving isotropic molecular mass transfer in fluids,and regulating the morphology of the 2D molecular film.Using a dual-solvent strategy,we created a stable nanoscale extended evaporation meniscus that modulates molecular nucleation and growth dynamics,thereby facilitating the direct shift from one-dimensional to two-dimensional crystals.Dual solvents are essential for generating and maintaining nanoscale wet films during meniscal recession,which is crucial for 2D crystal engineering.Mechanistic studies revealed that adhesion in a dual-solvent system is vital for meniscus formation while disjoining pressure maintains its stability.We also systematically evaluated several[1]benzothieno[3,2-b][1]benzothiophenes(BTBTs)bearing various alkyl chains,which revealed how molecular interactions affect morphology during printing.Organic-field-effect transistors fabricated using 2D OSSCs have significantly higher carrier mobilities than those with striped structures.Moreover,the highly ordered 2D C8-BTBT single-crystal thin film exhibited high sensitivity to polarized ultraviolet light,boasting a dichroic ratio of 2.80 and demonstrating exceptional imaging capabilities for polarized ultraviolet light.展开更多
基金National Key Research and Development Program of China(2022YFB3608604)National Natural Science Foundation of China(U21A2070,62374150,62074011,(62134008,62474165)+2 种基金Natural Science FoundationofHenan(242300421216)Science and Technology Major Project of Henan Province(231100230300)Beijing Nova Program(Z201100006820096).
文摘Imaging in the solar blind ultraviolet(UV)region offers significant advantages,including minimal interference from sunlight,reduced background noise,low false-alarm rate,and high sensitivity,and thus has important applications in early warning or detection of fire,ozone depletion,dynamite explosions,missile launches,electric leakage,etc.However,traditional imaging systems in this spectrum are often hindered by the bulkiness and complexity of conventional optics,resulting in heavy and cumbersome setups.The advent of metasurfaces,which use a two-dimensional array of nano-antennas to manipulate light properties,provides a powerful solution for developing miniaturized and compact optical systems.In this study,diamond metalenses were designed and fabricated to enable ultracompact solar-blind UV imaging.To prove this concept,two representative functionalities,bright-field imaging and spiral phase contrast imaging,were demonstrated as examples.Leveraging diamond's exceptional properties,such as its wide bandgap,high refractive index,remarkable chemical inertness,and high damage threshold,this work not only presents a simple and feasible approach to realize solar-blind imaging in an ultracompact form but also highlights diamond as a highly capable material for developing miniaturized,lightweight,and robust imaging systems.
基金supported by the National Natural Science Foundation of China(Nos.11602011,11872009,and 11632010)the National S&T Major Project of China(No.ZX069)+1 种基金the Aeronautical Science Foundation of China(No.2016ZD51034)the Postdoctoral Science Foundation of China(No.2017M610029)。
文摘In thermal-structural testing of hypersonic materials and structures,deformation measurement on the front surface of an object directly heated by quartz lamps is highly necessary and very challenging.This work describes a novel front-surface high-temperature deformation measurement technique,which adopts ultraviolet 3D digital image correlation(UV 3D-DIC)to observe and measure the high-temperature deformation fields on front surfaces directly heated by quartz lamps.Compared with existing blue light DIC techniques,the established UV 3D-DIC,which combines UV CCD camera,active UV illumination and bandpass filter imaging,can effectively suppress the strong disturbing light emitted by the quartz lamps and the heated sample itself during heating process.Two experiments were carried out to verify the robustness and accuracy of the developed technique:(1)direct observation of front surfaces of a hypersonic thermal structure sample heated from room temperature to 1050℃,and(2)front-surface thermal stain and coefficient of thermal expansion(CTE)measurement of an Inconel 718 sample up to 800℃.The well matched strain and CTE results with literature data show that UV 3D-DIC system is an effective technique for front-surface deformation measurement and has great potential in characterizing deformation response of hypersonic materials and structures subjected to transient aerodynamic heating.
基金supported by the Research Council of Norway under contracts 223252/F50 and 300844/F50the Trond Mohn Foundation。
文摘Global images of auroras obtained by cameras on spacecraft are a key tool for studying the near-Earth environment.However,the cameras are sensitive not only to auroral emissions produced by precipitating particles,but also to dayglow emissions produced by photoelectrons induced by sunlight.Nightglow emissions and scattered sunlight can contribute to the background signal.To fully utilize such images in space science,background contamination must be removed to isolate the auroral signal.Here we outline a data-driven approach to modeling the background intensity in multiple images by formulating linear inverse problems based on B-splines and spherical harmonics.The approach is robust,flexible,and iteratively deselects outliers,such as auroral emissions.The final model is smooth across the terminator and accounts for slow temporal variations and large-scale asymmetries in the dayglow.We demonstrate the model by using the three far ultraviolet cameras on the Imager for Magnetopause-to-Aurora Global Exploration(IMAGE)mission.The method can be applied to historical missions and is relevant for upcoming missions,such as the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)mission.
文摘Considering the complex environment in 750 kV AC substation,porcelain insulators have particular electric field and voltage distribution in comparison with those used in AC transmission line,meanwhile,the investigation of a typical 750 kV AC substation located in Lanzhou with ultraviolet imager(UVI) demonstrated that the corona discharge of some insulators is serious due to the improper structure design and installation,so research on porcelain insulators used in substation is needed.The three-dimensional finite element method(FEM) 750 kV AC substation calculation model was established to calculate electric field and voltage distribution of insulators,and the voltage distribution curves along insulators which are classified by type and suspension location were obtained using a novel FEM method which can effectively reduce the calculation amount without losing accuracy,meanwhile,the effect of the grading ring for improving voltage distribution of insulators was studied by adjusting the structure parameters of grading ring. Consequently,an optimization structure of rings was proposed by improving the voltage distribution of insulator string and reducing the electric strength of grading ring for the purpose of restricting corona noise,and the onsite observations by UVI showed that the newly manufactured and installed grading ring could obviously avoid the occurrences of corona discharge which validates the optimization design.This paper proposed an effective method combining UVI observation and FEM calculation to study voltage-sharing characteristics of porcelain insulators,and the results can provide experiences and references for the design of 750 kV AC substation.
基金the National Natural Science Foundation of China(Nos.U2004165,51702017,and 11974016)the Natural Science Foundation of Henan Province,China(No.202300410376)Research Grants Council of Hong Kong,China(No.GRF 152093/18E PolyU B-Q65N).
文摘There is an emerging need for high-sensitivity solar-blind deep ultraviolet(DUV)photodetectors with an ultra-fast response speed.Although nanoscale devices based on Ga_(2)O_(3)nanostructures have been developed,their practical applications are greatly limited by their slow response speed as well as low specific detectivity.Here,the successful fabrication of two-/three-dimensional(2D/3D)graphene(Gr)/PtSe2/β-Ga_(2)O_(3)Schottky junction devices for high-sensitivity solar-blind DUV photodetectors is demonstrated.Benefitting from the high-quality 2D/3D Schottky junction,the vertically stacked structure,and the superior-quality transparent graphene electrode for effective carrier collection,the photodetector is highly sensitive to DUV light illumination and achieves a high responsivity of 76.2 mA/W,a large on/off current ratio of~105,along with an ultra-high ultraviolet(UV)/visible rejection ratio of 1.8×104.More importantly,it has an ultra-fast response time of 12µs and a remarkable specific detectivity of~1013 Jones.Finally,an excellent DUV imaging capability has been identified based on the Gr/PtSe2/β-Ga_(2)O_(3)Schottky junction photodetector,demonstrating its great potential application in DUV imaging systems.
基金supported by the National Natural Science Foundation of China(22175185,52293470,52321006,T2394480,and T2394484)the National Key R&D Program of China(2018YFA0703200)+1 种基金the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202005)the CAS-VPST Silk Road Science Fund 2022(121111KYSB20210006).
文摘Two-dimensional organic semiconductor single crystals(2D OSSCs)have great potential for use in highperformance optoelectronic devices.However,challenges associated with controlling complex fluid dynamics and molecular mass transfer during solution-based processes hinder large-scale high-quality production.To address this issue,we developed a nanoconfinement-driven approach for controlling molecular crystallization,improving isotropic molecular mass transfer in fluids,and regulating the morphology of the 2D molecular film.Using a dual-solvent strategy,we created a stable nanoscale extended evaporation meniscus that modulates molecular nucleation and growth dynamics,thereby facilitating the direct shift from one-dimensional to two-dimensional crystals.Dual solvents are essential for generating and maintaining nanoscale wet films during meniscal recession,which is crucial for 2D crystal engineering.Mechanistic studies revealed that adhesion in a dual-solvent system is vital for meniscus formation while disjoining pressure maintains its stability.We also systematically evaluated several[1]benzothieno[3,2-b][1]benzothiophenes(BTBTs)bearing various alkyl chains,which revealed how molecular interactions affect morphology during printing.Organic-field-effect transistors fabricated using 2D OSSCs have significantly higher carrier mobilities than those with striped structures.Moreover,the highly ordered 2D C8-BTBT single-crystal thin film exhibited high sensitivity to polarized ultraviolet light,boasting a dichroic ratio of 2.80 and demonstrating exceptional imaging capabilities for polarized ultraviolet light.
