基于监督学习的日冕暗化检测与提取算法

日冕物质抛射(CME)是空间灾害天气的重要驱动源,而日冕暗化(dimming)被认为是CME初发的主要表征,对理解和预测CME具有重要作用.基于极紫外成像望远镜(EIT)和大气成像仪(AIA)的观测数据,实现了图像中日冕暗化现象的检测与提取.通过分析差分图中与暗化现象相关的图像统计特征,采用Adaboost分类算法检测暗化现象的发生,进而分割出日冕暗化区域.实验表明,提出的算法较现有算法能更准确有效地检测和提取日冕暗化区域,为分析日冕暗化特性提供了研究基础.     

Effects of frequency dimming electronic ballast on a high‐pressure mercury thallium iodide discharge

This study focuses on the behavior of a cylindrical metal halide discharge lamp powered by frequency‐controlled electronic ballast. Half‐bridge electronic ballast was designed and achieved.     

LED PWM dimming linearity investigation

LED PWM dimming application for large scale LED video displays is analyzed. The need for short light pulse duration is outlined. PWM dimming with short driving pulses is investigated experimentally. The LED response time skew introduces the nonlinearity for PWM dimming. For LED response time skew estimation, a method is suggested that has been successfully applied to measure some of today’s market representative LEDs. PWM dimming nonlinearity can be forecasted using the estimated skew. For a particular driving configuration, it is indicated that LED PWM dimming fails to satisfy the required 14 bit output coding together with the image refresh frequency of 400 Hz. A rough investigation demonstrates that the skew is quite stable. Therefore, the nonlinearity correction for the PWM pulse durations shorter than the skew value should be possible.     

Human visual sensitivity based optimal local backlight dimming methodologies under different viewing conditions

An adaptive local backlight dimming algorithm is proposed considering human visual sensitivities under various viewing conditions. Local dimming amount is maximized based on contrast sensitivity function and local image characteristics to minimize perceived luminance and contrast losses maintaining image qualities. Average luminance, contrast and spatial frequency are evaluated as local image characteristics. As dimming based on local characteristics has blocking artifacts, a compensation method using edge luminance difference is proposed considering human responses. The proposed algorithms reduce backlight power consumption by 39.69% on average, with an average SSIM of 0.995. It can be increased by 5.66% with varying viewing conditions, resulting in a 45.35% power consumption reduction on average. The outperformances of the proposed algorithm in power consumption reduction and maintaining image quality are verified with various image quality metrics compared to recent dimming algorithms.     

LED调光控制技术在飞机导光板照明中的应用

描述了LED技术在飞机驾驶舱照明控制系统中的应用情况,针对目前民用飞机驾驶舱导光板照明普遍采用的LED电压调光技术和单纯PWM调光技术的不足,提出了改进的LED调光技术方案。新型方案利用组合调光技术和数字调光技术,弥补了传统LED调光技术的不足,并对不同的LED调光控制方案进行了分析,最后提出了LED调光技术的发展方向。     

基于ATmega128的调光控制器方案设计

现有的模拟调光控制器大多采用拉杆、旋钮、开关等对模拟信号进行变换,控制精度不高,体积较大,且只能实现对灯具的通断控制。本文结合PC上位机、ATmega128单片机及AD7226芯片实现一种高精度的模拟调光控制器,通过上位机的调光控制软件可以对灯具实现多种灯光效果的变换。     

基于高边电流检测驱动LED

研究了一种采用高边电流检测的滞环控制LED恒流驱动芯片。基于0．5um5V／18V／40VCDMOS．工艺,运用HSPICE工具对电路进行仿真,仿真结果显示：在4．5V～28V电源电压范围内,-40℃～＋l25℃工作温度范围内,电路可为LED提供恒定的350mA驱动电流,LED驱动电流为滞环变化的三角波,最大误差为6．2％。通过调节外部信号DIM的占空比可以调节LED的亮度。     

Power savings and enhancement of gray‐scale capability of LCD TVs with an adaptive dimming technique

Abstract— The luminance of a backlight unit for an LCD TV is adaptively and locally dimmed along with the input video signal in order to reduce the power consumption and also to improve the picture quality. By adopting the zero‐dimensional (0D), 1D, and 2D adaptive dimming techniques, a sample movie having 8.0% post‐gamma average picture levels (APL) could be displayed using 83%, 71%, and 50% of the original backlight power, respectively. For an adoption of the 2D dimming, an LED backlight is preferable. The adaptive‐dimming technique also allows the differential aging characteristics between the LED components and temperature dependence of color and luminance to be overcome. From simulations of a reduction in power consumption, it was found that 40 × 40 pixels is a unit of the local dimming, 30 frames for the sampling period, 24 dimming steps, and an equal‐signal‐step method for determining the dimming factor have been found to be appropriate. The gray‐scale capability of low‐luminance images can also be improved by dimming the backlight luminance and expanding the input signal. By using an LCD TV having an 8‐bit capability, an 11‐bit‐equivalent gray‐scale expression was experimentally proven.     

混合型调光电子镇流器的研究

介绍了一种新型的荧光灯调光控制方式，即通过占空比调制和频率调制相结合的方式控制荧光灯的输出功率。首先，基于与功率相关的荧光灯模型，通过基波近似的方法得到了控制方程，得出了荧光灯的调光特性；然后，以一个半桥式串联谐振并联负载电路为例，给出了设计步骤及仿真、实验结果。     

单级PFC恒流驱动及蓝牙调光技术的研究

LED 智能照明系统逐渐应用到室内照明,具有智能控制、高效节能、绿色的特点。国内 LED 智能照明系统仍不完善,存在不易控制、能源浪费、功率因数低、谐波干扰大等问题,使得 LED 照明的优势没有很好的体现出来,并阻碍其推广。对智能调光控制技术进行研究,设计单级 PFC 反激式恒流驱动电路和蓝牙调光方案,Android 智能手机作为客户端以蓝牙无线技术传输调光控制信号,对 LED 恒流驱动电路进行开关、调光控制实现智能照明,具有便捷可靠、电源转换效率和功率因数高、电流总谐波低的性能。