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10 results on '"何志毅"'

1. 紫外LED散射通信信道特性与传输研究

Author

郭求实, 何宁, and 何志毅

Subjects
散射通信, 紫外光, 仰角, 透过率, 视场角, Applied optics. Photonics, TA1501-1820
Abstract

利用modtran大气传输模型对低空信道紫外光传输特性进行分析,研究了近地短距离传输的大气吸收和散射的数学模型。在实验室环境下,系统采用视场角为80°的紫外LED（发光二极管）发射,在传输距离为5～8m的情况下进行了模拟信号的散射传输测试。结果表明:利用一定的有效散射体,收发俯仰角从10°增加到65°时,能有效实现短距离紫外散射传输。散射体浓度过大对紫外光存在强烈的吸收作用,传输距离将减小,单个紫外LED发射功率低,实际通信应用中,可采用阵列LED来提高发射功率,增加传输距离。

Published
2013
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2. 电致发光器件的复合开关电路驱动技术.

Author

卯 龙, 何志毅, 郑 岩, and 郭士玉

Subjects
SWITCHING circuits, FLEXIBLE printed circuits, TRANSISTORS, THYRISTORS, SHORT-circuit currents, METAL oxide semiconductor field-effect transistors, ELECTROLUMINESCENCE
Abstract

Copyright of Chinese Journal of Liquid Crystal & Displays is the property of Chinese Journal of Liquid Crystal & Displays and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2022
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5. Efficiency Characteristic Analysis and Driving Scheme Design of Power LEDs

Author

覃雪玲 Qin Xue-ling, 何宁 He Ning, and 何志毅 He Zhiyi

Subjects
Materials science, business.industry, Electrical engineering, LED circuit, Electronic, Optical and Magnetic Materials, law.invention, Power (physics), Duty cycle, law, Signal Processing, Waveform, Quantum efficiency, Voltage droop, business, Instrumentation, Pulse-width modulation, Light-emitting diode
Abstract

Development of the research on power LEDs' quantum efficiency droop was investigated.Several LED products with different performance of high power operation were compared.Due to the improvement of the LEDs' efficiency dependence on the driving current,their operating current corresponding to the maximum efficiency are exceeding their rating values.Under this circumstance,a driving strategy by rectangular pulse is proposed.In the driving circuit,the MOSFET's gate was controlled by an intermittent waveform of PWM pulse series which is generated by modulating the rectangular pulses at lower frequency(200~800 Hz) on those at higher frequency(~40 kHz),whereby an approximately rectangular waveform at the lower frequency of the current pulses can be obtained by filtering the high frequency components.The peak current and duty ratio of the output drive to the loaded LED were correlated to maintain the constant drive current in average while the operating current was regulated to reach the maximum efficiency of the loaded LED.

Published
2012
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