Efficiency improvement of near-ultraviolet InGaN LEDs using patterned sapphire substrates

The use of conventional and patterned sapphire substrates (PSSs) to fabricate InGaN-based near-ultraviolet (410 nm) light-emitting diodes (LEDs) was demonstrated. The PSS was prepared using a periodic hole pattern (diameter: 3 /spl mu/m; spacing: 3 /spl mu/m) on the (0001) sapphire with different etching depths. From transmission-electron-microscopy and etch-pit-density studies, the PSS with an optimum pattern depth (D/sub h/=1.5 /spl mu/m) was confirmed to be an efficient way to reduce the thread dislocations in the GaN microstructure. It was found that the output power increased from 8.6 to 10.4 mW, corresponding to about 29% increases in the external quantum efficiency. However, the internal quantum efficiency (@ 20 mA) was about 36% and 38% for the conventional and PSS LEDs, respectively. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the PSS. Finally, better long-time reliability of the PSS LED performance was observed.     

中小企业创业资源的形成机制研究

创业资源是创业的基础,创业过程的规律性和市场配置资源的基础作用影响和决定中小企业创业资源的内在功能和形成方式。对中小企业资源的形成机制进行了分析探讨,并分析了它们之间的内在关系。     

虚拟仪器在教学中的应用

主要介绍了Multisim2001中虚拟仪器库中函数发生器、示波器的使用方法及功能；并在Multisim2001环境中仿真单管放大电路、桥式整流滤波电路。由调试结果，分析了其在教学中应用的可行性。     

遥读遥测式表层型核子水分-密度仪

为减少放射源对仪器操作人员辐射的影响,对表层型核子水分-密度仪进行了改进,研制出遥读遥测式表层型核子水分-密度仪.并对该仪器的测量方法和在工程施工现场的应用作了简要介绍.     

巧点火锅鸳鸯谱

北风起．火锅热。户外寒气逼人，屋内热气腾腾．鲜红的肉片。翠生生的青菜．在或红或白滚烫的锅中上下飞舞，仅是这灵动的姿态就让人禁受不住媚惑，抬手、举箸．一番狼吞虎咽，于是热气从心底缓缓升起，寒冷顿时一扫而空。[编者按]     

MOS RF reliability subject to dynamic voltage stress-modeling and analysis

Dynamic stress on MOSFETs with 900-MHz inverter-like waveforms as well as static (or dc) stress were evaluated experimentally. It showed that the degradation due to dynamic stress is less than that of dc stress for our test transistors. A compact model is used to evaluate the degradation in radio frequency performances, such as transconductance, cutoff frequency, linearity, and noise figure. A class-AB power amplifier is presented as an example to demonstrate the effect of dynamic stress on RF circuit performance.     

超宽带通信技术及其在军事通信方面的应用

本文给出了超宽带(Ultra-wide Bandwidth:UWB)系统的信号表示形式,分析了其具体含义、信号特点及UWB通信系统的性能,结合当前军事通信的特点及发展趋势,介绍了超宽带脉冲通信在军事通信领域的应用现状及前景。     

单面滑模法施工在船坞工程中的应用

舟山马峙岛船坞工程位于舟山普陀区马峙岛,该工程包括混凝土底板、坞墙、水泵房、廊道等主体结构.其中坞墙为直立式C30薄壁墙（单面模板）,坞墙总计80块,单块坞墙高度为11.8m、宽度15m、混凝土体积在90～110m^3左右,具有模板用量大、工期紧张的特点.根据现场施工条件及类似结构施工经验,该坞墙采用单面滑模法施工.