Optical and electrical characteristics of GaN vertical light emitting diode with current block layer

A GaN vertical light emitting diode(LED)with a current block layer(CBL)was investigated.Vertical LEDs without a CBL,with a non-ohmic contact CBL and with a silicon dioxide CBL were fabricated.Optical and electrical tests were carried out.The results show that the light output power of vertical LEDs with a non-ohmic contact CBL and with a silicon dioxide CBL are 40.6%and 60.7%higher than that of vertical LEDs without a CBL at 350 mA,respectively.The efficiencies of vertical LEDs without a CBL,with a non-ohmic contact CBL and with a silicon dioxide CBL drop to 72%,78%and 85.5%of their maximum efficiency at 350 mA,respectively. Moreover,vertical LEDs with a non-ohmic contact CBL have relatively superior anti-electrostatic ability.     

双束质子辐照降低快速晶闸管通态压降的研究

在分析晶闸管通态压降产生的机理的基础上, 从协调开关时间与通态压降关系入手提出了采用双束质子辐照晶闸管。对ＫＫ２００Ａ 半成品晶闸管进行能量３．５ＭｅＶ 和５．０ＭｅＶ 注量为２．５×１０１１ｐ／ｃｍ ２ 的单束质子辐照晶闸管所得的晶闸管的电学参数与先用５．０ＭｅＶ 后用３．５ＭｅＶ 能量注量都为２．５×１０１１ｐ／ｃｍ ２ 的双束质子辐照的晶闸管所得的电学参数进行了对比, 发现双束质子辐照不仅能有效地缩短晶闸管的开关时间, 而且在降低快速晶闸管的通态压降方面比单束质子辐照的晶闸管优越     

E1—VC4的SDH集成化系统设计

介绍一种SDH系统专用集成电路的设计,它可以从VC4信号中任意上下分插出多达21个E1信号,包括E1的线路编解码及数字解同步器,码速调整及去调整,VC12开销的终结及生成,TU12的指针调整及解释,VC4的合成及分解,电路设计既充分考虑ITU－T的标准,又结合实际系统设计,克服了以前电路的缺点,具有规模大,功能完善,性能优越的特点。     

全光通信网技术

本文对全光网的概念和关键技术做了简要说明，并介绍了具有代表性的全光网络，最后对各个网络的技术进行了比较，并同了全光网发展的一些主要障碍。     

350MW机组超速预防功能和甩负荷试验

介绍由美国西屋公司进口３５０ＭＷ机组控制系统的超速预防功能和机组甩负荷控制功能,及利港电厂３号机组的甩负荷试验情况。     

低压环境下放气系统压降特性分析

针对低压环境下放气系统的结构设计，建立了基于开口放气系统的容器压力变化公式，并结合实验结果对带长细导管的放气系统的压力变化规律进行了系数修正，理论计算和实验结果对比表明，在低压环境下，理论推导公式具有较好的准确性。将该公式与放气系统放气过程的多维流场模拟结合，可达到简化计算过程，缩短计算时间目的。     

海洋条件下U型管内倒流特征压降数值模拟

自然循环工况下立式倒 U 型管蒸汽发生器内单相流体存在倒流现象,增大了自然循环流动阻力,减少了有效换热面积,对核动力装置的安全运行造成不利影响。针对该问题,利用 Fluent 软件研究了海洋条件下 U 型管内倒流特征压降的变化规律。结果表明,横摇和起伏特征压降的周期与横摇和起伏运动的周期相同,而纵摇特征压降的变化周期为纵摇周期的一半。横摇和纵摇特征压降波动振幅随横摇和纵摇周期的减小而增大,随横摇和纵摇振幅的增大而增大,起伏特征压降的振幅与起伏周期无关,随起伏加速度振幅的增大而增大。横摇对特征压降的影响最大,起伏次之,纵摇最小。     

落锤试验撞击粒状HMX炸药变形及点火过程数值模拟（英）

利用AUTODYN软件对落锤撞击粒状HMX炸药过程进行二维数值模拟.基于应力和塑性功的计算值,通过塑性功转化热能的原理,估算了颗粒中产生的温升.样品HMX颗粒为圆形几何形状,假设颗粒具有弹塑性变形特性.颗粒堆放形式有规则排布和不规则排布两种情形.通过设定的落高和由自由落体公式计算出落锤的初始速度.针对落高分别为33,40,50,60 cm的情况,及样品颗粒材料不同屈服应力值(0.26,0.13 GPa)进行计算,得到落锤撞击颗粒时的温升变化.结果表明,规则排布产生温度较低(37.2℃),而不规则排布产生温度较高(142.9℃).在不规则排布当中,颗粒的局部塑性变形功可以导致较高的温升,从而引起颗粒点火.同时考虑到HMX的屈服应力值的不确定性,取较小屈服应力值(0.13 GPa)进行温升计算,而其他计算条件相同,得到的温升值仅为83.2℃,比0.26 GPa时低59.7℃.     

Thermal-hydraulic performance of novel louvered fin using flat tube cross-flow heat exchanger

Experimental studies were conducted to investigate the air-side heat transfer and pressure drop characteristics of a novel louvered fins and flat tube heat exchangers. A series of tests were conducted for 9 heat exchangers with different fin space and fin length, at a constant tube-side water flow rate of 2.8 m³/h. The air side thermal performance data were analyzed using the effectiveness-NTU method. Results were presented as plot of Colburn j factor and friction factor f against the Reynolds number in the range of 500–6500. The characteristics of the heat transfer and pressure drop of different fin space and fin length were analyzed and compared. In addition, the curves of the heat transfer coefficients vs. pumping power per unit heat transfer area were plotted. Finally, the area optimization factor was used to evaluate the thermal hydraulic performance of the louvered fins with differential geometries. The results showed that the j and f factors increase with the decrease of the fin space and fin length, and the fin space has more obvious effect on the thermal hydraulic characteristics of the novel louvered fins. __________ Translated from Journal of Shanghai Jiaotong University, 2007, 41(3): 380–383 [译自: 上海交通大学学报]     

数码手榴弹引信研究与设计

通过引入三轴加速度传感器和单片机,解决现行手榴弹由于延期时间不准确而导致的早爆和迟爆,以及手榴弹未扔出安全范围起爆对操作手引起意外伤亡的问题,提出了一种新型手榴弹引信——数码手榴弹引信的设计方案与研究思路。