A zinc oxide ZnO field emitter-based backlight unit for liquid crystal display with a gated structure is fabricated by screen-printing processes.The measured anode field emission current density reaches 0.62 mA/cm2 wh...A zinc oxide ZnO field emitter-based backlight unit for liquid crystal display with a gated structure is fabricated by screen-printing processes.The measured anode field emission current density reaches 0.62 mA/cm2 when the applied gate voltage is 570 V.Part of the anode current is contributed by the secondary electron emission which is excited from the MgO layer inside the gate apertures on the gate plate. The average emission current density and luminance are 0.47 mA/cm2 and 1 250 cd/m2 respectively with a fluctuation of about 10% during the 1 000 min measurement.By a finite element method calculation the gated structure shows a good electron beam focusing property. The driving performance of the backlight unit is characterized by SPICE simulation tools and measured by the oscilloscope. Stable field emission line-by-line scanning and fast response characteristics of the backlight unit indicate its promising application in the liquid crystal displays.展开更多
We have developed a compact photoelectron imaging facility, including an anion source with dissociative photoelectron attachment to molecules, a linear time-of-flight mass spec-trometry （TOFMS）, and an orthogonal hi...We have developed a compact photoelectron imaging facility, including an anion source with dissociative photoelectron attachment to molecules, a linear time-of-flight mass spec-trometry （TOFMS）, and an orthogonal high-resolution threshold photoelectron velocity map imaging spectrometer （VMI）. Intense and cold cluster anions were prepared in photoelectron- attachment processes upon pulsed UV laser ablation of metal target. Combining this anion source with TOFMS-VMI, the achieved mass resolution is about 200, and the electron ki- netic energy resolution is better than 3%, i.e., 30 meV for 1 eV electrons. More importantly, low-energy photoelectron imaging spectra for CH3S- and S2- at 611.46 nm are obtained. In both cases, the refined electron affinities are determined to be 1.86264-0.0020 eV for CH3S and 1.67444-0.0035 eV for S2, respectively. Preliminary results suggest that the apparatus is a powerful tool for estimating precise electron affinities values from threshold photoelectron imaging spectroscopy.展开更多
The development of single-component white emitters for white light-emitting diodes(WLEDs)remains challenging.Herein,a rare earth-free white light-emitting composite is developed by assembling blue-emitting carbon dots...The development of single-component white emitters for white light-emitting diodes(WLEDs)remains challenging.Herein,a rare earth-free white light-emitting composite is developed by assembling blue-emitting carbon dots(CDs)and yellow-emitting Cs_(2)InCl_(5)·H_(2)O:Sb^(3+)metal halide crystals via a facile liquid-liquid diffusion-assisted crystallization approach.The encapsulation mechanism is then analyzed.Depending on the ratios of blue/yellow emitters,these luminescent composites exhibit white light emission with tunable cold and warm hues.The composites also possess prominent ultraviolet resistance,thermal tolerance,and good stability at about 200°C.By employing such“CDs in metal halide”composites as a converter,a WLED is successfully fabricated with a high color rendering index of 93.6,benefiting from the assembled blue and yellow broadband emission.With this strategy,the developed composites show great promise in next-generation WLED lighting.展开更多
Daytime radiative cooling with high solar refection and mid-infrared emission offers a sustainable way for cooling without energy consumption.However,so far sub-ambient daytime radiative coolers typically possess whit...Daytime radiative cooling with high solar refection and mid-infrared emission offers a sustainable way for cooling without energy consumption.However,so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications.Although various colored radiative cooling designs have been pursued previously,multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to signifcant thermal load.Here,we demonstrate that photoluminescence(PL)based colored radiative coolers(PCRCs)with high internal quantum effciency enable sub-ambient full-color cooling.As an example of experimental demonstration,we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence.The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet–visible sunlight into emitted light to minimize the solar-heat generation,and cellulose acetate based nanofbers as the underlayer that strongly refect sunlight and radiate thermal load.As a result,the green,yellow and red colors of PCRCs achieve temperatures of 5.4–2.2℃ below ambient under sunlight(peak solar irradiance>740 Wm),respectively.With the excellent cooling performance and scalable process,our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.展开更多
The global demand for resource sustainability is growing. Thus, the development of single-source, environment-friendly colloidal semiconductor nanocrystal （NC） phosphors with broadband emission spectra is highly des...The global demand for resource sustainability is growing. Thus, the development of single-source, environment-friendly colloidal semiconductor nanocrystal （NC） phosphors with broadband emission spectra is highly desirable for use as color converters in white light-emitting diodes （WLEDs）. We report herein the gram-scale synthesis of single-source, cadmium-free, dual-emissive Mn-doped Zn-Cu-In-S NCs （d-dots） by a simple, non-injection, low-cost, one-pot approach. This synthesis method led to the formation of NCs with continuously varying compositions in a radial direction because each precursor had a different reactivity. Consequently, the d-dots exhibited two emission bands, one that could be attributed to Mn emission and a second that could be ascribed to the band edge of the Zn-Cu-In-S NCs. The emission peaks assigned to band edge were tunable by modifying the particle size and composition. The prepared d-dots also exhibited the characteristic zero self-absorption, a quantum yield of 46%, and good thermal stability. Combining a commercial blue light-emitting diode （LED） chip with optimized d-dots as color converters gave a high color rendering index of up to 90, Commission Internationale de l＇eclairage color coordinates of （0.332, 0.321）, and a correlated color temperature of 5,680 K. These results suggest that cadmium-free, thermally stable, single-phase d-dot phosphors have potential applications in WLEDs.展开更多
An acoustic emission （AE） linear location system was proposed, which employed fiber Bragg gratings （FBGs） as AE sensors. It was demonstrated that the FBG wavelength could be modulated as the static case when the g...An acoustic emission （AE） linear location system was proposed, which employed fiber Bragg gratings （FBGs） as AE sensors. It was demonstrated that the FBG wavelength could be modulated as the static case when the grating length was much shorter than the AE wavelength. In addition, an improved AE location method based on the Gabor wavelet transform （WT） and threshold analysis was represented. The method was testified through AE linear location experiments based on a tunable narrow-band laser interrogation system using ultra-short FBG sensors as AE sensors. Results of the experiments showed that 86% of the linear location errors were less than 10mm.展开更多
Using the acoustic emission locating technology to monitor the health of the structure is important for ensuring the continuous and healthy operation of the complex engineering structures and large mechanical equipmen...Using the acoustic emission locating technology to monitor the health of the structure is important for ensuring the continuous and healthy operation of the complex engineering structures and large mechanical equipment. In this paper, four fiber Bragg grating(FBG) sensors are used to establish the sensor array to locate the acoustic emission source. Firstly, the nonlinear locating equations are established based on the principle of acoustic emission, and the solution of these equations is transformed into an optimization problem. Secondly, time difference extraction algorithm based on the phase transform(PHAT) weighted generalized cross correlation provides the necessary conditions for the accurate localization. Finally, the genetic algorithm(GA) is used to solve the optimization model. In this paper, twenty points are tested in the marble plate surface, and the results show that the absolute locating error is within the range of 10 mm, which proves the accuracy of this locating method.展开更多
基金The National Basic Research Program of China(973 Program)(No.2013CB328803)the National Natural Science Foundation of China(No.51002031)+1 种基金the Ph.D.Programs Foundation of Ministry of Education of China(No.20100092120022)the National High Technology Research and Development Program of China(863 Program)(No.2012AA03A302,2013AA011004)
文摘A zinc oxide ZnO field emitter-based backlight unit for liquid crystal display with a gated structure is fabricated by screen-printing processes.The measured anode field emission current density reaches 0.62 mA/cm2 when the applied gate voltage is 570 V.Part of the anode current is contributed by the secondary electron emission which is excited from the MgO layer inside the gate apertures on the gate plate. The average emission current density and luminance are 0.47 mA/cm2 and 1 250 cd/m2 respectively with a fluctuation of about 10% during the 1 000 min measurement.By a finite element method calculation the gated structure shows a good electron beam focusing property. The driving performance of the backlight unit is characterized by SPICE simulation tools and measured by the oscilloscope. Stable field emission line-by-line scanning and fast response characteristics of the backlight unit indicate its promising application in the liquid crystal displays.
文摘We have developed a compact photoelectron imaging facility, including an anion source with dissociative photoelectron attachment to molecules, a linear time-of-flight mass spec-trometry （TOFMS）, and an orthogonal high-resolution threshold photoelectron velocity map imaging spectrometer （VMI）. Intense and cold cluster anions were prepared in photoelectron- attachment processes upon pulsed UV laser ablation of metal target. Combining this anion source with TOFMS-VMI, the achieved mass resolution is about 200, and the electron ki- netic energy resolution is better than 3%, i.e., 30 meV for 1 eV electrons. More importantly, low-energy photoelectron imaging spectra for CH3S- and S2- at 611.46 nm are obtained. In both cases, the refined electron affinities are determined to be 1.86264-0.0020 eV for CH3S and 1.67444-0.0035 eV for S2, respectively. Preliminary results suggest that the apparatus is a powerful tool for estimating precise electron affinities values from threshold photoelectron imaging spectroscopy.
基金supported by the National Natural Science Foundations of China (51961145101)Guangzhou Science & Technology Project (202007020005)+3 种基金the Project Supported by Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme (GDUPS, 2018) for Prof. Bingfu Leithe National Key R&D Program of China (2020YFB0407902)Guangdong Provincial Science & Technology Project (2021A0505050006 and 2021B0707010003)Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams (2021KJ122)。
文摘The development of single-component white emitters for white light-emitting diodes(WLEDs)remains challenging.Herein,a rare earth-free white light-emitting composite is developed by assembling blue-emitting carbon dots(CDs)and yellow-emitting Cs_(2)InCl_(5)·H_(2)O:Sb^(3+)metal halide crystals via a facile liquid-liquid diffusion-assisted crystallization approach.The encapsulation mechanism is then analyzed.Depending on the ratios of blue/yellow emitters,these luminescent composites exhibit white light emission with tunable cold and warm hues.The composites also possess prominent ultraviolet resistance,thermal tolerance,and good stability at about 200°C.By employing such“CDs in metal halide”composites as a converter,a WLED is successfully fabricated with a high color rendering index of 93.6,benefiting from the assembled blue and yellow broadband emission.With this strategy,the developed composites show great promise in next-generation WLED lighting.
基金jointly supported by the National Key Research and Development Program of China(2021YFA1400700,2020YFA0406104,and 2017YFA0205700)the National Natural Science Foundation of China(52002168,12022403,11874211,61735008,62134009,and 62121005)+4 种基金Science Foundation of Jiangsu(BK20190311)Key Science and Technology Innovation Programme of Shandong Province(2019JZZY020704)Excellent Research Programme of Nanjing University(ZYJH005)the Fundamental Research Funds for the Central Universities(021314380214,021314380190,021314380140,and 021314380150)support from the XPLORER PRIZE。
文摘Daytime radiative cooling with high solar refection and mid-infrared emission offers a sustainable way for cooling without energy consumption.However,so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications.Although various colored radiative cooling designs have been pursued previously,multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to signifcant thermal load.Here,we demonstrate that photoluminescence(PL)based colored radiative coolers(PCRCs)with high internal quantum effciency enable sub-ambient full-color cooling.As an example of experimental demonstration,we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence.The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet–visible sunlight into emitted light to minimize the solar-heat generation,and cellulose acetate based nanofbers as the underlayer that strongly refect sunlight and radiate thermal load.As a result,the green,yellow and red colors of PCRCs achieve temperatures of 5.4–2.2℃ below ambient under sunlight(peak solar irradiance>740 Wm),respectively.With the excellent cooling performance and scalable process,our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.
基金This work was supported by the National Natural Science Foundation of China （Nos. 21373097 and 51072067） and the National Basic Research Program of China （No. 2011CB935800）.
文摘The global demand for resource sustainability is growing. Thus, the development of single-source, environment-friendly colloidal semiconductor nanocrystal （NC） phosphors with broadband emission spectra is highly desirable for use as color converters in white light-emitting diodes （WLEDs）. We report herein the gram-scale synthesis of single-source, cadmium-free, dual-emissive Mn-doped Zn-Cu-In-S NCs （d-dots） by a simple, non-injection, low-cost, one-pot approach. This synthesis method led to the formation of NCs with continuously varying compositions in a radial direction because each precursor had a different reactivity. Consequently, the d-dots exhibited two emission bands, one that could be attributed to Mn emission and a second that could be ascribed to the band edge of the Zn-Cu-In-S NCs. The emission peaks assigned to band edge were tunable by modifying the particle size and composition. The prepared d-dots also exhibited the characteristic zero self-absorption, a quantum yield of 46%, and good thermal stability. Combining a commercial blue light-emitting diode （LED） chip with optimized d-dots as color converters gave a high color rendering index of up to 90, Commission Internationale de l＇eclairage color coordinates of （0.332, 0.321）, and a correlated color temperature of 5,680 K. These results suggest that cadmium-free, thermally stable, single-phase d-dot phosphors have potential applications in WLEDs.
基金The authors gratefully acknowledge the financial support for this work from the Natural Science Foundation of China （Grant No. 61074163） and the Natural Science Foundation of Shandong Province, China （Grant No. ZR2011FQ025）.
文摘An acoustic emission （AE） linear location system was proposed, which employed fiber Bragg gratings （FBGs） as AE sensors. It was demonstrated that the FBG wavelength could be modulated as the static case when the grating length was much shorter than the AE wavelength. In addition, an improved AE location method based on the Gabor wavelet transform （WT） and threshold analysis was represented. The method was testified through AE linear location experiments based on a tunable narrow-band laser interrogation system using ultra-short FBG sensors as AE sensors. Results of the experiments showed that 86% of the linear location errors were less than 10mm.
基金supported by the National Natural Science Foundation of China(No.41472260)the Fundamental Research Funds of Shandong University(No.2016JC012)the Young Scholars Program of Shandong University(No.2016WLJH30)
文摘Using the acoustic emission locating technology to monitor the health of the structure is important for ensuring the continuous and healthy operation of the complex engineering structures and large mechanical equipment. In this paper, four fiber Bragg grating(FBG) sensors are used to establish the sensor array to locate the acoustic emission source. Firstly, the nonlinear locating equations are established based on the principle of acoustic emission, and the solution of these equations is transformed into an optimization problem. Secondly, time difference extraction algorithm based on the phase transform(PHAT) weighted generalized cross correlation provides the necessary conditions for the accurate localization. Finally, the genetic algorithm(GA) is used to solve the optimization model. In this paper, twenty points are tested in the marble plate surface, and the results show that the absolute locating error is within the range of 10 mm, which proves the accuracy of this locating method.
