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Investigation of charge management using UV LED device with a torsion pendulum for TianQin
摘要： TianQin is a Chinese space-based observatory concept with three drag-free spacecraft orbiting the earth to observe gravitational-waves in the millihertz range. Electrical charge is inevitably accumulating on its isolated test masses which are used as the mirrors for interferometers to measure gravity variation. Charge management system based on ultraviolet (UV) light is developed to reduce the charge-induced noises acting on the test mass in space gravitational experiments such as GP-B, LISA, LISA Pathfinder and TianQin mission. The UV LED is a new UV light source with some advantages relative to mercury lamps, such as smaller size, lighter weight, lower power consumption and higher efficiency. For these reasons, ground-based tests for the combination of UV LED and inertial sensor are essential. This paper presents the development of a charge management system based on a UV LED, its application to a torsion pendulum system with a TianQin-like test mass, and assesses the charge-management performance of the system. The experimental results indicate that the isolated test mass can be charged positively or negatively through UV illumination. It demonstrates that the charging and discharging rates can both reach higher than 105 e/s, as well as spectral measurement of the pendulum charge resulting in a white noise level equivalent to ～ 5 × 105 e/Hz1/2, satisfying the TianQin requirement.
关键词： gravitational-waves,UV LED,torsion pendulum,charge management,TianQin
更新于2025-09-23 15:21:01
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High-quality nanodisk of InGaN/GaN MQWs fabricated by neutral-beam-etching and GaN regrowth: Towards directional micro-LED in top-down structure
摘要： A nanodisk array of blue InGaN/GaN multiple quantum wells was made using neutral beam etching (NBE) followed by GaN regrowth. The NBE-fabricated nanodisk presented a vertical and highly smooth sidewall surface where the InGaN well layers were easily distinguished even with a scanning electron microscope. A high interface quality without any voids or obvious defects was obtained between the nanodisk and the regrown-GaN layer. The nanodisk after regrowth presented a smaller blueshift of photoluminescence emission energy (12 meV) and a substantially higher and almost constant internal quantum efficiency of ~50% over three orders of magnitude of excitation laser power when compared to the nanodisk before regrowth. This study shows that the process of NBE nanodisk etching followed by GaN regrowth represents a promising step forward in the development of truncated cone-shaped directional micro-LEDs with a buried active region in a top-town structure.
关键词： Regrowth,InGaN/GaN MQWs,Directional micro-LED,Nanodisk,Neutral beam etching
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE 3rd International Conference on Cloud Computing and Internet of Things (CCIOT) - Dalian, China (2018.10.20-2018.10.21)] 2018 IEEE 3rd International Conference on Cloud Computing and Internet of Things (CCIOT) - Study on LED Color Mixing for Stage Lighting Based on Locus Fitting of Blackbody
摘要： Aiming at overcoming the defects of basic lighting color rendering for LED stage lighting, this paper establishes a new mixing light method with RGBW four-color mixing model. Compared with traditional tricolor light mixing model, it uses the mixing light of white as the fourth input, with the three-basic color of red, green and blue to obtain a new mixing method. Then the original coefficients of RGBW are optimized after adjusting the two parameters of relative spectral power distribution and illuminance of mixing light for locus fitting of blackbody. Finally, better color rendering of white light can be acquired. By the MATLAB simulation and field testing, experimental results have shown that the proposed method will achieve ideal LED lighting performance, which is convenient for color management of lighting control system in modern theatre.
关键词： LED stage lighting,CRI,RGBW four-color mixing model,the blackbody locus fitting
更新于2025-09-23 15:21:01
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A discrete core-shell-like micro-light-emitting diode array grown on sapphire nano-membranes
摘要： A discrete core-shell-like micro-light-emitting diode (micro-LED) array was grown on a 100 nm-thick sapphire nano-membrane array without harmful plasma etching for chip singulation. Due to proper design for the sapphire nano-membrane array, an array of multi-faceted micro-LEDs with size of 4 μm × 16 μm was grown. threading dislocation density in the micro-LeD formed on sapphire nano-membrane was reduced by 59.6% due to the sapphire nano-membranes, which serve as compliant substrates, compared to GaN formed on a planar substrate. Enhancements in internal quantum efficiency by 44% and 3.3 times higher photoluminescence intensity were also observed from it. Cathodoluminescence emission at 435 nm was measured from c-plane multiple quantum wells (MQWs), whereas negligible emissions were detected from semi-polar sidewall facets. A core-shell-like MQWs were formed on all facets, hopefully lowering concentration of non-radiative surface recombination centers and reducing leakage current paths. This study provides an attractive platform for micro-LEDs by using sapphire nano-membrane.
关键词： internal quantum efficiency,photoluminescence,threading dislocation density,micro-LED,sapphire nano-membrane,core-shell-like,cathodoluminescence
更新于2025-09-23 15:21:01
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AIP Conference Proceedings [AIP Publishing 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019) - Bikaner, India (14a??15 October 2019)] 3RD INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC-2019) - Effect of polarization field and Auger recombination on internal quantum efficiency of InGaN/GaN blue LED
摘要： InxGa1-x N/GaN blue LEDs faces significant efficiency droop issue. The causes of efficiency droop are Shockley Read Hall recombination (SRH), Auger recombination (AR), carrier delocalization and electron leakage. The SRH, Auger and electron leakage are functions of carrier concentration and temperature. InGaN/GaN superlattice has polarization electric field at interface. In this work we explore effect of polarization electric field on efficiency droop. It is shown that polarization field enhances Auger coefficient resulting in more droop in internal quantum efficiency of blue LED. Thus, for improvement in efficiency, polarization field required to be minimized which requires growth of the material in m- plane instead of c-plane.
关键词： efficiency droop,polarization electric field,Auger recombination,blue LED,InGaN/GaN
更新于2025-09-23 15:21:01
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Effect of LED Radiation Pattern on BER Performance in Indoor Multipath MIMO-VLC System
摘要： The present paper investigates the impact of three radiation patterns of LED namely Lambertian, Batwing, Elliptical on the BER performance of 4 × 4 indoor multiple-input multiple-output (MIMO) visible light communication (VLC) system. The BER simulation has been done using LOS and LOS plus first reflection (L-R1) signals for ceiling-mounted and wall-mounted LEDs. For the case of ceiling-mounted LEDs, impulse response and BER have been computed using those radiation patterns at the centre and corner of a room (5 m × 5 m × 3 m). It has been found that LED having Elliptical radiation profile is more suitable for LOS signal when receiver is placed at the centre position whereas, Batwing radiation is suitable for L-R1 signal, both at the centre and corner positions. In the case of wall-mounted LEDs, impulse response and BER have been determined at the centre of the room using LOS and L-R1 signals. The results show that Batwing has least BER using LOS signal due to its wide radiation beam, but for L-R1 signal, the Elliptical profile having its narrow radiation beam has provided better BER performance. The present study shows that the BER in MIMO-VLC system not only depends on the transmitter and receiver position but also on the radiation patterns of LED and higher order reflection signals.
关键词： BER,MIMO,LED radiation pattern,VLC,Impulse response
更新于2025-09-23 15:21:01
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Interaction effect of LED color temperatures and light-protective additive packaging on photo-oxidation in milk displayed in retail dairy case
摘要： Effect of varied LED color temperatures on photo-oxidation in 2 % fat milk and protection efficiency of packaging with and without light-protective additives (LPA) under different color temperatures was firstly evaluated. Riboflavin (Rb) is one of the critical photo-sensitizers in 2 % milk when exposed to LED light. Higher color temperature with higher relative intensity of Rb absorbance region resulted in lower Rb and vitamin A retention, lower dissolved oxygen content, and higher TBARS value in milk packaged with non-LPA packaging. Yellow pigmented packaging that completely blocked the Rb absorbance region of all three LED color temperatures successfully reduced the rate of degradation of milk nutrients and flavor. TiO2-added packaging partially block the destructive light wavelength; higher level of TiO2 provided a longer protection on milk freshness. Combination of appropriate LED color temperature and LPA-packaging provided a cost-effective solution for minimizing photo-oxidation in retail dairy case.
关键词： color temperature,oxidation,freshness,milk,packaging,light wavelength,LED
更新于2025-09-23 15:21:01
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Effect of the Ce3+ concentration on laser-sintered YAG ceramics for white LEDs applications
摘要： This paper describes the laser sintering and luminescence properties of Y3Al5O12 (YAG) phosphors doped with different concentrations of Ce3+ and synthesized using the polymeric precursor method. The ceramics were sintered by a new laser sintering technique in which a CO2 laser is employed as the heating source. The resultant ceramics exhibited a homogeneous microstructure with narrow grain size distribution and high relative density. The introduction of Ce3+ ions led to luminescence quenching at a concentration above 0.5 mol% and a redshift of the emission spectrum band with increasing cerium concentration. The excitation spectrum showed two characteristic bands centered at 340 nm and 460 nm and a relative change in their intensity by change the Ce3+ concentration. The presence of a single valence (Ce3+) of cerium was determined by X-ray absorption near edge structure measurements.
关键词： laser sintering,ceramics,photoluminescence,LED,YAG
更新于2025-09-23 15:21:01
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Efficacy of ultraviolet light-emitting diodes (UV-LED) at four different peak wavelengths against Cryptosporidium parvum oocysts by inactivation assay using immunodeficient mice
摘要： As an alternative to using ultraviolet (UV) lamps, which are made with mercury that is toxic to the environment and human health, UV light-emitting diodes (UV-LEDs) are expected to be effective for inactivating microorganisms in water. Although UV-LEDs have been reported to be effective against bacteria and viruses, the effectiveness of UV-LEDs against Cryptosporidium parasites has not been fully evaluated. As we report here, we have developed an in vivo quantitative inactivation assay for C. parvum oocysts using immunodeficient mice. Using the assay, we evaluated the effectiveness of treatment by UV lamp (254 nm) at approximately 1000 μJ/cm2 (for 3 s at a distance of 95 mm) compared to inactivation by commercially available UV-LEDs (with peak wavelengths of 268, 275, 284, and 289 nm). The shed patterns of oocysts after treatment with 284- and 289-nm wavelength UV-LEDs were significantly delayed compared to that after treatment with a UV lamp. These findings provide the first suggestion that UV-LEDs are effective against these parasites, as assessed using commercially available 350-mA UV-LEDs under conditions of fixed exposure distance and time.
关键词： UV lamp,UV-LED,Cryptosporidium parvum,Inactivation assay,SCID mouse,Oocyst
更新于2025-09-23 15:21:01
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[IEEE 2018 Eighth International Conference on Instrumentation & Measurement, Computer, Communication and Control (IMCCC) - Harbin, China (2018.7.19-2018.7.21)] 2018 Eighth International Conference on Instrumentation & Measurement, Computer, Communication and Control (IMCCC) - Comment on "Impossible Differential Fault Analysis on the LED Lightweight Cryptosystem in the Vehicular Ad-Hoc Networks"
摘要： In January 2016, Li et al. introduced an impossible differential fault analysis on the LED cryptosystem. If one random nibble fault is injected into the preantepenultimate round of LED, 48 fault injections are required to recover the secret key. In this comment, we provide an improved scheme with theoretical analysis and experimental results. Under the same fault model, our analysis can reduce the key search space of LED to 27.92 on average with only ONE fault. The key extraction takes about 13.84 seconds on average.
关键词： fault analysis,security evaluation,LED
更新于2025-09-23 15:21:01