Rheological effect on thermocapillary flow of a liquid film jet painted on a moving boundary

In the present paper, a liquid (or melt) film of relatively high temperature ejected from a vessel and painted on the moving solid film is analyzed by using the second-order fluid model of the non-Newtonian fluid. The thermocapillary flow driven by the temperature gradient on the free surface of a Newtonian liquid film was discussed before. The effect of rheological fluid on thermocapillary flow is considered in the present paper. The analysis is based on the approximations of lubrication theory and perturbation theory. The equation of liquid height and the process of thermal hydrodynamics of the non-Newtonian liquid film are obtained, and the case of weak effect of the rheological fluid is solved in detail.     

光电耦合器封装及相关失效机理

与一般的半导体器件相比,光电耦合器的工作原理、结构和封装设计独具特色。光耦的失效机理除与单独的LED、三极管相同外,还有它独有的失效机理。在简单介绍光耦的工作原理与封装结构的基础上,重点分析了几种与光耦封装有关的失效机理:导光胶或反射胶工艺控制不佳导致胶开裂、起皮;光耦内部材料间热膨胀系数不匹配,内部电连接开路;内部沾污产生腐蚀;塑料和内部有机胶吸潮发生"爆米花效应";外部电路异常导致光耦失效。并针对各种失效机理提出了改进措施。     

Dy3+ emission in M5(PO4)3F (M = Ca, Ba) phosphor

Ultrafine M₅(PO₄)₃F:Dy³⁺ (M = Ca, Ba) phosphors were prepared via combustion process using metal nitrates as precursors. The formation of crystalline phosphate was confirmed by X-ray diffraction pattern. The PL excitation spectra show the excitation peaks observed at 250 to 400 nm due to f → f transition of Dy³⁺ ion, which are useful for solid-state lighting purpose (mercury free excitation). The PL emission of Dy³⁺ ion by 348 nm excitation gave an emission at 489 nm (blue), 582 nm (yellow) and 675 nm (red). All the characteristics of BYR emissions like BGR indicate that Dy doped Ca₅(PO₄)₃F and Ba₅(PO₄)₃F phosphors are good candidates that can be applied in solid-state lighting phosphor (mercury free excited lamp phosphor) and white light LED.      

二维空间紫外LED阵列实现单光斑辐照固化系统的设计

新型大功率紫外LED具有电光转化效率高、光谱纯度高和体积小等优点,但单管LED功率仍很难满足光固化的要求,针对单光斑辐照要求,提出采用空间阵列UV-LED排布实现能量累加的方案。该方案通过单管LED聚光系统与集成阵列系统综合设计实现了各单元单光斑辐照度在辐照面上的合成,最终得到的光斑辐照度分布均匀、尺寸合理,阵列系统后工作距离长,完全满足现场应用的具体指标要求。通过外围电子线路控制阵列LED的电流强度及通断状态可实现光斑辐照度在(1000～1800) mW/cm²可调,光斑尺寸为1cm²,后工作距离为10cm。     

金属有机化学气相沉积外延技术生长GaN基半导体发光二极管和激光二极管(Ⅰ)

文章评论性地介绍了金属有机化学气相外延技术（MOCVD）生长氮化物半导体GaN和InGaN以及激子局域化效应、量子束缚斯塔克效应对它们的光学性能的影响，详细比较了这两种效应对GaN基半导体发光二极管和激光二极管特性的影响，特别是量子束缚斯塔克效应以显著不同的方式影响着发光二极管和激光二极管的性能；文章还讨论了在A面蓝宝石衬底上生长GaN的情况．     

未来的照明光源--白光LED技术及其发展

白光是黑白和彩色摄像机的照明光源，可以替代白炽灯、荧光灯和高压气体放电灯等传统光源。介绍了白光LED技术的原理、特点、发展方向。     

基于旋转二维发光二极管阵列的体三维显示系统

利用发光二极管 (LED)的高速发光特性 ,以旋转的二维发光二极管阵列为显示载体 ,通过时分寻址电路快速显示三维形体的二维截面序列。受调制的离散二维图像信息 ,因视觉暂留而形成深度效应 ,将被整合感知为一幅连续的三维图像。成功实现了具有 4 915 2个体像素 ,尺寸为14 4 .6mm× 110mm的柱体空间内的三维显示 ,图像具有双目视差、调节、会聚等常规视差信息 ,能提供真实的深度暗示 ,可同时从任意角度直接观察。论述了系统的显示原理及图像编码分解方法 ,分析和讨论了显示质量与体像素优化选取、起始位置显示信息的关联程度     

液晶显示器NVIS高亮LED背光源研究

提出了一种满足液晶显示器NVIS的高亮LED背光设计方法。介绍了白灯LED+OGB LED背光阵列优化设计,降低混光距离比、提高均匀度的方法,并通过试差法,对配色后测量结果进行分析,求出最佳配色方案;模拟与实验结果表明,该设计方法完全能够满足夜航要求。     

新型高精度高效率LED照明驱动电路的实现

提出并设计了一种高精度、高效率LED照明驱动电路.采用平均电流控制模式代替峰值电流的控制模式;同时,采用低阶低侧的Buck拓扑结构,使输出驱动电流的精度误差控制在1％之内.整体电路的转换效率最高可达96％以上,输出驱动电流为350 mA,可驱动8个1W的HBLED灯.该设计基于CSMC 0.5μm 40 V BCD工艺,版图尺寸约为1.4 mm×1.4 mm.通过流片验证了设计的可行性.     

Design and Simulation of High-power LED Array Packaging

Thermal management is one of the key technologies for high-power Light emitting diode（LED） entering into the general illuminating field. Successful thermal management depends on optimal packaging structure and selected packaging materials. In this paper, the aluminum is employed as a substrate of LED, 3×3 array chips are placed on the substrate, heat dissipation performance is simulated using finite element analysis（FEA） software, analyzed are the influences on the temperature of the chip with different convection coefficient, and optical properties are simulated using optical analysis software. The results show that the packaging structure can not only effectually improve the thermal performance of high-power LED array but also increase the light extraction efficiency.