共查询到20条相似文献,搜索用时 78 毫秒
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固体照明——通过氮化物基发光二极管(LED)制造白光照明光源。自20世纪60年代初首只GaAsP红色发光二极管(LED)诞生以来,人类一直致力于固态光源技术的实现,经过40多年的努力,已实现了红、绿、黄、蓝光LED的生产应用,发光效率提高了近千倍。随着以氮化镓(GaN)为代表的第三代半导体的兴起,蓝绿光和白光二极管的研发成功,可取代白炽灯和日光的固体照明光源终于应运而生。1发展固体照明的必要性1998年美国照明用电630亿美元,约占能源消耗的20%,在发电过程中产生CO2废气1.12亿t;日本照明用电消耗民用能源20%;而全球照明消耗是2300亿美元,… 相似文献
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<正>近年来,在全球节能减排的大趋势下,白光发光二极管(LED)照明基于半导体封装技术和材料的发展呈现了快速增长的势头。与传统光源相比,LED照明具有寿命长、体积小、节能、高效、响应速度快、抗震、无污染等优点,被称为第4代照明光源或绿色光源。2014年诺贝尔物理学奖就颁给了因发明"高亮度蓝色发光二极管"的赤崎勇、天野浩和中村修二等3位科学家,是对原创技术的肯定,也是对照明市场发展方向的肯定。正是在市 相似文献
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《软包装商情》2017,(10)
UV-LED固化已经越来越被市场所采纳,成为了资本市场的新宠儿,该项技术也已成为国内外印刷领域的研究热点。UV-LED印刷固化技术具有节能、环保、绿色的特点。和传统的UV固化方式相比,能够减少80%-90%的耗电量,不产生臭氧,没有VOC(易挥发的有机物质)排放。其中,光源驱动的电路设计是UV-LED固化设备的关键技术之一。UV-LED光源驱动的电路需要有很高的稳定性,以提高固化设备的工作可靠性和使用寿命。单颗UV-LED芯片功率只有几瓦,不能满足固化功率要求,因此可采用多颗芯片阵列组成UV-LED集成光源系统。本文介绍的光源系统是由72颗LED芯片采用阵列排布方式构成的,重点介绍通过整流滤波、填谷电路直接驱动LED芯片的电路。该驱动电路不仅可满足LED光源系统固化功率的要求,还可根据固化系统的实际需求对芯片功率进行补偿及提升,使固化设备的工作可靠性和使用寿命得到提高。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献
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