Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for ca...Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for carrier tunneling to control the interface emission is still a mystery.Herein,the low-refractive HfO_(2)with a proper energy band configuration is em-ployed as the buffer layer in achieving ZnO-microwire/HfO_(2)/GaN heterojunctional light-emitting diodes(LEDs).The optic-ally pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO_(2)layer.As a result,the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet(UV)emission is en-hanced.To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN,the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO_(2)film causing blue shift and interface emission enhancement.Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs.展开更多
This study analyzed the potential impact of the increased oil volatility on the industries and the global economy. Specifically, it separated the oil price fluctuations into positive and negative components, and model...This study analyzed the potential impact of the increased oil volatility on the industries and the global economy. Specifically, it separated the oil price fluctuations into positive and negative components, and modeled the return of industry portfolios with them. Next, the sensitivity of the airline industry to oil price was investigated to gauge the effectiveness of their hedging strategies, with the hope that the methodology can be extended to other industries. In addition, this paper explored the macroeconomic impact of oil price movements by examining the benchmarks such as GDP and CPI.展开更多
Taking bovine nasal bone as a raw material,the sodium chondroitin sulfate was extracted by enzymolysis-ion adsorption-alcohol precipitation method,and the enzymolysis process was optimized.After single factor experime...Taking bovine nasal bone as a raw material,the sodium chondroitin sulfate was extracted by enzymolysis-ion adsorption-alcohol precipitation method,and the enzymolysis process was optimized.After single factor experiments,the response surface analysis was performed by software Design-Expert 8.0,and the optimal enzymolysis conditions were as follows:the trypsin concentration of 0.8%,the pH value of 9.0,the enzymolysis temperature at 52℃,and the enzymolysis time of 2.0 h.With this combination of conditions,the concentration of sodium chondroitin sulfate extract reached 11.3 g/L,the bovine nasal bone yield was 35%,and the finished product content was 92.5%,which provided guidance for industrial production.展开更多
van der Waals heterostructures(vdWHs)based on two-dimensional(2D)materials without the crystal lattice matching constraint have great potential for high-performance optoelectronic devices.Herein,a WS_(2)/InSe vdWH pho...van der Waals heterostructures(vdWHs)based on two-dimensional(2D)materials without the crystal lattice matching constraint have great potential for high-performance optoelectronic devices.Herein,a WS_(2)/InSe vdWH photodiode is proposed and fabricated by precisely stacking InSe and WS_(2)flakes through an all-dry transfer method.The WS_(2)/InSe vdWH forms an n–n heterojunction with strong built-in electric field due to their intrinsic n-type semiconductor characteristics and energy-band alignments with a large Fermi level offset between WS_(2)and InSe.As a result,the device displays excellent photovoltaic behavior with a large open voltage of 0.47 V and a short-circuit current of 11.7 nA under 520 nm light illumination.Significantly,a fast rising/decay time of 63/76μs,a large light on/off ratio of 105,a responsivity of 61 mA/W,a high detectivity of 2.5×10^(11) Jones,and a broadband photoresponse ranging from ultraviolet to near-infrared(325–980 nm)are achieved at zero bias.This study provides a strategy for developing high-performance self-powered broadband photodetectors based on 2D materials.展开更多
Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to ...Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to retrieve tropospheric NO_(2),SO_(2),and HCHO from the ozone monitoring instrument(OMI),with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere.We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005-2017,especially in heavily polluted regions.We found significant decreasing trends in NO_(2) and SO_(2) since 2011 over most regions,despite varying temporal features and turning points.In contrast,an overall increasing trend was identified for tropospheric HCHO over these regions in recent years.Furthermore,generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls.Our results indicated that although meteorological parameters,such as wind,water vapor,solar radiation and temperature,mainly dominated the day-to-day and seasonal fluctuations in air pollutants,anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO_(2),SO_(2),and HCHO in the past 13 years.Generally,recent declines in NO_(2) and SO_(2) could be attributed to emission reductions due to effective air quality policies,and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound(VOC)emissions.展开更多
Ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS)observations were operated from 02 to 21 December 2018 in Leshan,southwest China,to measure HONO,NO_(2) and aerosol extinction vertical dis...Ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS)observations were operated from 02 to 21 December 2018 in Leshan,southwest China,to measure HONO,NO_(2) and aerosol extinction vertical distributions,and these were the first MAX-DOAS measurement results in Sichuan Basin.During the measurement period,characteristic ranges for surface concentration were found to be 0.26-4.58 km^(−1) and averaged at 0.93 km^(−1) for aerosol extinction,0.49 to 35.2 ppb and averaged at 4.57 ppb for NO_(2) and 0.03 to 7.38 ppb and averaged at 1.05 ppb for HONO.Moreover,vertical profiles of aerosol,NO_(2) and HONO were retrieved from MAX-DOAS measurements using the Heidelberg Profile(HEIPRO)algorithm.By analysing the vertical gradients of pollutants and meteorological information,we found that aerosol and HONO are strongly localised,while NO_(2) is mainly transmitted from the north direction(city center direction).Nitrogen oxides such as HONO and NO_(2) are important for the production of hydroxyl radical(OH)and oxidative capacity in the troposphere.In this study,the averaged value of OH production rate from HONO is about 0.63 ppb/hr and maximum value of ratio between OH production from HONO and from(HONO+O_(3))is>93%before12:00 in Leshan.In addition,combustion emission contributes to 26%for the source of HONO in Leshan,and we found that more NO_(2) being converted to HONO under the conditions with high aerosol extinction coefficient and high relative humidity is also a dominant factor for the secondary produce of HONO.展开更多
Two-photon fluorescence (TPF) ellipsoid formed by a focused femtosecond laser into luminescent media serves as a fundamental pixel for TPF spatiotemporal imaging. Visualizing spatiotemporal evolution of the TPF ellips...Two-photon fluorescence (TPF) ellipsoid formed by a focused femtosecond laser into luminescent media serves as a fundamental pixel for TPF spatiotemporal imaging. Visualizing spatiotemporal evolution of the TPF ellipsoid itself in a selected luminescent medium is important for correctly reconstructing and interpreting spatiotemporal information of imaged targets. Here, we report a new spatiotemporal sectioning technique with a luminescent CsPbBr_(3) nanosheet and visualize the spatiotemporal evolution of TPF ellipsoid along the axial direction. Time-resolved axial lengths of TPF ellipsoids turn out to broaden nonlinearly with a turning point at about 600 ps. By comparison experiments, observed phenomena are attributed to photocarrier trapping and TPF photon recycling processes within CsPbBr_(3) nanosheets. The spatiotemporal sectioning technique is expected to be widely applicable, which will ignite a plethora of investigations and applications utilizing TPF ellipsoid.展开更多
基金Ths work was supported by NSFC(11734005.62075041,61821002)Na tional Key Research and Development Program of China(2018YFA0209101,2017YFA0700500).
文摘Interface emission from heterojunction is a shortcoming for electroluminescent devices.A buffer layer introduced in the heterojunctional interfaces is a potential solution for the challenge.However,the dynamics for carrier tunneling to control the interface emission is still a mystery.Herein,the low-refractive HfO_(2)with a proper energy band configuration is em-ployed as the buffer layer in achieving ZnO-microwire/HfO_(2)/GaN heterojunctional light-emitting diodes(LEDs).The optic-ally pumped lasing threshold and lifetime of the ZnO microwire are reduced with the introduced HfO_(2)layer.As a result,the interface emission is of blue-shift from visible wavelengths to 394 nm whereas the ultraviolet(UV)emission is en-hanced.To regulate the interface recombination between electrons in the conduction band of ZnO and holes in the valence band of GaN,the tunneling electrons with higher conduction band are employed to produce a higher tunneling current through regulation of thin HfO_(2)film causing blue shift and interface emission enhancement.Our results provide a method to control the tunneling electrons in heterojunction for high-performance LEDs.
文摘This study analyzed the potential impact of the increased oil volatility on the industries and the global economy. Specifically, it separated the oil price fluctuations into positive and negative components, and modeled the return of industry portfolios with them. Next, the sensitivity of the airline industry to oil price was investigated to gauge the effectiveness of their hedging strategies, with the hope that the methodology can be extended to other industries. In addition, this paper explored the macroeconomic impact of oil price movements by examining the benchmarks such as GDP and CPI.
基金Supported by the Open Project of Hunan Provincial University Innovation Platform(15K066)
文摘Taking bovine nasal bone as a raw material,the sodium chondroitin sulfate was extracted by enzymolysis-ion adsorption-alcohol precipitation method,and the enzymolysis process was optimized.After single factor experiments,the response surface analysis was performed by software Design-Expert 8.0,and the optimal enzymolysis conditions were as follows:the trypsin concentration of 0.8%,the pH value of 9.0,the enzymolysis temperature at 52℃,and the enzymolysis time of 2.0 h.With this combination of conditions,the concentration of sodium chondroitin sulfate extract reached 11.3 g/L,the bovine nasal bone yield was 35%,and the finished product content was 92.5%,which provided guidance for industrial production.
基金supported by the National Natural Science Foundation of China (U21A20496,61922060,62205235,62204157,61805172,12104334,62174117,and 61905173)the Graduate Innovation Project of Shanxi Province (2020BY117)+9 种基金the Key Research and Development (International Cooperation)Program of Shanxi Province (201803D421044)the Natural Science Foundation of Shanxi Province (20210302123154 and 20210302123169)Research Project Supported by Shanxi Scholarship Council of China (2021-033)Research Project Supported by Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering (2021SX-FR008 and 2022SX-TD020)Introduction of Talents Special Project of Lvliang City (Rc2020206,Rc2020207)Transformation Cultivation Project of University Scientific and Technological Achievements of Shanxi Province (2020CG013)the Key Research and Development Program of Shanxi Province (202102150101007)the support from the Research Grants Council,University Grants Committee,Hong Kong,General Research Fund (12303920)SZ-HK-Macao Science and Technology Plan Project (SGDX2020110309540000)Guangdong Basic and Applied Basic Research Fund (2022A1515010020)。
基金the National Natural Science Foundation of China(Nos.11734005,61821002,62075041,12004069,and 62204157)the National Key Research and Development Program of China(Nos.2018YFA0209101 and 2017YFA0700500)the Fundamental Research Funds for the Central Universities(No.2242021k10009).
文摘van der Waals heterostructures(vdWHs)based on two-dimensional(2D)materials without the crystal lattice matching constraint have great potential for high-performance optoelectronic devices.Herein,a WS_(2)/InSe vdWH photodiode is proposed and fabricated by precisely stacking InSe and WS_(2)flakes through an all-dry transfer method.The WS_(2)/InSe vdWH forms an n–n heterojunction with strong built-in electric field due to their intrinsic n-type semiconductor characteristics and energy-band alignments with a large Fermi level offset between WS_(2)and InSe.As a result,the device displays excellent photovoltaic behavior with a large open voltage of 0.47 V and a short-circuit current of 11.7 nA under 520 nm light illumination.Significantly,a fast rising/decay time of 63/76μs,a large light on/off ratio of 105,a responsivity of 61 mA/W,a high detectivity of 2.5×10^(11) Jones,and a broadband photoresponse ranging from ultraviolet to near-infrared(325–980 nm)are achieved at zero bias.This study provides a strategy for developing high-performance self-powered broadband photodetectors based on 2D materials.
基金supported by the National Natural Science Foundation of China(11734005,61821002,62075041,61704024,and 62204157)the National Key Research and Development Plan of China(2017YFA0700503 and 2018YFA0209101)。
基金supported by grants from the National Natural Science Foundation of China(Nos.41722501,91544212,51778596,41575021,41875043,and 41977184)the National Key Research and Development Program of China(Nos.2018YFC0213104,2017YFC0210002,and 2016YFC0203302)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102 and DQGG0205)the Major Projects of High Resolution Earth Observation Systems of National Science and Technology(05-Y30B01-9001-19/20-1).
文摘Abundances of a range of air pollutants can be inferred from satellite UV-Vis spectroscopy measurements by using the unique absorption signatures of gas species.Here,we implemented several spectral fitting methods to retrieve tropospheric NO_(2),SO_(2),and HCHO from the ozone monitoring instrument(OMI),with radiative simulations providing necessary information on the interactions of scattered solar light within the atmosphere.We analyzed the spatial distribution and temporal trends of satellite-observed air pollutants over eastern China during 2005-2017,especially in heavily polluted regions.We found significant decreasing trends in NO_(2) and SO_(2) since 2011 over most regions,despite varying temporal features and turning points.In contrast,an overall increasing trend was identified for tropospheric HCHO over these regions in recent years.Furthermore,generalized additive models were implemented to understand the driving forces of air quality trends in China and assess the effectiveness of emission controls.Our results indicated that although meteorological parameters,such as wind,water vapor,solar radiation and temperature,mainly dominated the day-to-day and seasonal fluctuations in air pollutants,anthropogenic emissions played a unique role in the long-term variation in the ambient concentrations of NO_(2),SO_(2),and HCHO in the past 13 years.Generally,recent declines in NO_(2) and SO_(2) could be attributed to emission reductions due to effective air quality policies,and the opposite trends in HCHO may urge the need to control anthropogenic volatile organic compound(VOC)emissions.
基金supported by grants from the National Key Research and Development Program of China(Nos.,2018YFC0213104,2018YFC0213201,2016YFC0203302 and 2017YFC0210002)the Anhui Science and Technology Major Project(No.18030801111)+4 种基金the National Natural Science Foun-dation of China(Nos.41722501,91544212,51778596,41575021 and 41977184)the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA23020301)the National Key Project for Causes and Control of Heavy Air Pollution(Nos.DQGG0102-03 and DQGG0205)the National High-Resolution Earth Observation Project of China(Nos.05-Y30B01-9001-19/20-3)the Civil Aerospace Technology Advance Research Project,No.Y7K00100KJ.
文摘Ground-based multi-axis differential optical absorption spectroscopy(MAX-DOAS)observations were operated from 02 to 21 December 2018 in Leshan,southwest China,to measure HONO,NO_(2) and aerosol extinction vertical distributions,and these were the first MAX-DOAS measurement results in Sichuan Basin.During the measurement period,characteristic ranges for surface concentration were found to be 0.26-4.58 km^(−1) and averaged at 0.93 km^(−1) for aerosol extinction,0.49 to 35.2 ppb and averaged at 4.57 ppb for NO_(2) and 0.03 to 7.38 ppb and averaged at 1.05 ppb for HONO.Moreover,vertical profiles of aerosol,NO_(2) and HONO were retrieved from MAX-DOAS measurements using the Heidelberg Profile(HEIPRO)algorithm.By analysing the vertical gradients of pollutants and meteorological information,we found that aerosol and HONO are strongly localised,while NO_(2) is mainly transmitted from the north direction(city center direction).Nitrogen oxides such as HONO and NO_(2) are important for the production of hydroxyl radical(OH)and oxidative capacity in the troposphere.In this study,the averaged value of OH production rate from HONO is about 0.63 ppb/hr and maximum value of ratio between OH production from HONO and from(HONO+O_(3))is>93%before12:00 in Leshan.In addition,combustion emission contributes to 26%for the source of HONO in Leshan,and we found that more NO_(2) being converted to HONO under the conditions with high aerosol extinction coefficient and high relative humidity is also a dominant factor for the secondary produce of HONO.
基金This work was supported by the National Natural Science Foundation of China(Nos.11734005,61704024,61821002,and 62075041)Natural Science Foundation of Jiangsu Province(No.BK20170696)+1 种基金the National Key Research and Development Program of China(Nos.2017YFA0700500 and 2018YFA0209101)Fundamental Research Funds for the Central Universities(No.2242021K10009).Q.N.C.gratefully acknowledges the support of Southeast University through Zhishan Young Scholar Fund.The authors thank Dr.Haibo Ding for insightful discussion.
文摘Two-photon fluorescence (TPF) ellipsoid formed by a focused femtosecond laser into luminescent media serves as a fundamental pixel for TPF spatiotemporal imaging. Visualizing spatiotemporal evolution of the TPF ellipsoid itself in a selected luminescent medium is important for correctly reconstructing and interpreting spatiotemporal information of imaged targets. Here, we report a new spatiotemporal sectioning technique with a luminescent CsPbBr_(3) nanosheet and visualize the spatiotemporal evolution of TPF ellipsoid along the axial direction. Time-resolved axial lengths of TPF ellipsoids turn out to broaden nonlinearly with a turning point at about 600 ps. By comparison experiments, observed phenomena are attributed to photocarrier trapping and TPF photon recycling processes within CsPbBr_(3) nanosheets. The spatiotemporal sectioning technique is expected to be widely applicable, which will ignite a plethora of investigations and applications utilizing TPF ellipsoid.
