碳含量对脱β层硬质合金组织和性能的影响

本文通过一步烧结法制备了三种不同含碳量的WC-Ti(C,N)-(Ti,W)C-(Ta,Nb)C-Co脱β层硬质合金,通过扫描电镜(SEM),电子探针微区分析仪(EPMA)分析合金的微观组织和成分分布,以及测定维氏硬度HV30,断裂韧性KIC等性能指标,研究碳含量对其微观组织和物理力学性能的影响,研究结果表明:在三个合金的表层均形成了缺Ti,Ta,Nb的立方相,而富Co粘结相的脱β层。微量的C含量变化对合金的组织和性能产生重要的影响,合金的脱β层厚度和WC的平均晶粒度均随着C含量的增加而增大。随着碳含量的增加,维氏硬度HV30降低,断裂韧性KIC增加。     

LED背光源热设计研究

在分析LED背光源热设计已有解决方案的基础上,指出已有的解决方案虽然从客观上缓解了LED背光源热设计问题,但却增加了LED背光源的生产成本。同时本文还指出最根本解决LED热设计的方案还需要从LED本身的光效上来考虑,也就是说,如何提高LED本身的发光效率依然是LED背光源热设计的关键。     

A review of CCFL phenomenon

Counter current flow limitation CCFL is an important phenomenon for numerous engineering applications and safety of light water reactors. In particular, the possible occurrence of CCFL in the hot-leg of a PWR during SBLOCA or LOCA accidents is of special interest for nuclear safety research. A review of the related literature has made in order to present the most important studies about the phenomenon and to reach common general understanding of the different factors that govern CCFL. Eventually this will allow explaining contradictions among different explanations provided by different authors. Most important factors were geometrical characteristics, liquid superficial velocity, and physical properties. The review shows that despite numerous experimental works, many scaling and geometrical effects are still not fully understood. For Instance there exist no consistent explanation of the channel diameter and inclined riser length effect upon results. The same can be stated-though to a minimum extent – for the inclination angle while channel length (or channel to diameter ratio) effect was clear and consistent. Since most experimental work was done in down-scaled hot-leg simulators, it becomes interesting to build a coherent knowledge about these effects and to explain arising contradictions in order to safely extrapolate results to full-scale hot-leg. The review has shown that many differences were simply due to geometrical effects, this leads to the need to “standardize” experimental data according to geometrical parameters. This should results in a better understanding of the phenomenon and corresponding scaling effects. Additionally, important variables such as: pressure drop, void fraction and shear stress were also investigated and discussed. A compilation of CCFL data was built and analyzed. Since the new simulation trends tend to use CFD codes where geometrical and spatial deviations are excluded by using 3D modeling, emphasis was placed upon introducing correlations for onset of CCFL out of collected data. Existing correlations for interfacial shear stress friction factor and the void fraction as a function of gas superficial velocity were also gathered and briefly discussed. The effect of condensation, physical parameters, and hysteresis upon CCFL was also introduced.     

细管径冷阴极荧光灯（CCFL）的开发

本文介绍了冷阴极荧光灯的特点，冷阴极荧光灯高辉度，高效率，低耗电，长寿命，管径细。主要用于液晶显示的背景照明，扫描仪光源，装饰照明。     

LCD背光源中金属反射罩对CCFL亮度的影响

研究了LCD背光源中金属反射罩对CCFL亮度的影响。通过测量金属反射罩与CCFL间不同距离时CCFL的亮度,以及不同温度下的CCFL亮度,分析了对亮度造成影响的原因,找到了金属反射罩对CCFL亮度影响的规律。     

液晶电视CCFL控制电路的设计技巧

液晶显示器(LCD)正成为电视的主流显示技术。LCD电视通常需要背光源产生可视的影像,因此背光源的设计就成为关键。由于LCD电视是消费品,CCFL工作在高压的状态下,在选用电路的时候不但要考虑成本,还要考虑其可靠性。驱动多个CCFL灯管时所要面对的关键的挑战是:挑选最佳的驱动架构、多灯驱动、脉冲调光、保护电路的设计。     

基于OZ9938 LCD背光高压板工作原理解析与检测

背光高压电源板为液晶显示器CCFL提供电源,由于工作在高电压大电流,因而背光高压板的故障率在液晶显示器故障中占有较大的比例,由于机型种类繁多,以及缺乏相关的技术资料,使我们对背光板高压板的检测带来了一定的困难。该文结合被广泛应用的OZ9938所构成LCD显示器背光高压典型电路,分析和总结了背光逆变高压电路的工作原理与检测的方法。     

Experimental investigation and CFD validation of countercurrent flow limitation (CCFL) in a large-diameter PWR hot-leg geometry

ABSTRACT

Countercurrent flow limitation (CCFL) is a phenomenon that consists of several flow patterns occurring simultaneously which produces a complex gas/liquid interface and interfacial momentum transfer, thus making it one of the most challenging two-phase flow configurations for computational fluid dynamics (CFD) validation. Numerous experimental investigations have been carried out in recent years regarding this, but most of those investigations were performed in small-diameter pipes or in non-pipe geometries (rectangular cross sections). A review of these experimental investigations has shown that the scale and geometry of the test section has a large impact upon the onset and characteristics of the CCFL. In order to provide a better understanding of this phenomenon in an actual pressurized water reactor (PWR) hot-leg geometry at a relatively large-diameter and scale, a test facility with a ～1/3.9 scale and a 190 mm inner diameter was constructed. Experiments were carried out at atmospheric pressure using water and air. High-speed recording was used to acquire high-quality images of the air/water interface. CCFL mechanisms, flow patterns, and the limits of the onset of CCFL and deflooding were experimentally identified. CFD simulations of two representative cases were carried out and assessed against experimental results. The analysis of the CFD simulations has provided insights into the improvements necessary for the accurate simulation of CCFL in large-scale geometries.     

Trans‐admittance control for eliminating the temperature effect of piezoelectric transformer in the CCFL backlight module

A half‐bridge (HB) resonant inverter for driving a cold cathode fluorescent lamp (CCFL) backlight module with a piezoelectric transformer (PT) is analyzed in this paper. The resonant inductance of the HB inverter is expressed as a function of the load current, the load resistance and the PT circuit parameters. Also, the trans‐admittance of the PT‐CCFL combination network is measured to track the operating frequency for the HB resonant inverter, which may be varied due to the temperature rise of PT. The lamp driving current and power can thus remain almost constant in a wide temperature range. Experiments show that the observed results match the theoretical analyses. Copyright © 2008 John Wiley & Sons, Ltd.     

LED用于LCD背光源的前景展望

随着液晶显示(LCD)模组不断向更亮、更轻、更薄、尺寸更大的方向发展，对背光源的要求也就越来越高，本文介绍了目前LCD的背光源：冷阴极荧光灯(CCFL)、电致发光(EL)和发光二极管(LED)背光源，特别是LED背光源及其相关动态，通过LED与CCFL和EL的比较，预测LED将成为LCD理想的背光源。