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.     

低阶煤煤层气富集模式初探

通过对美国粉河盆地以及我国铁法盆地煤层气富集规律的解剖,总结出影响低阶煤煤层气富集的关键因素是封堵,而构造、岩性和水动力是形成煤层气封堵的主要因素。同时提出了5种不同的煤层气富集模式,即背斜模式、构造—水动力模式、构造—岩性模式、岩性—水动力模式和岩性模式。     

Thermal and mechanical properties of epoxy composites reinforced by a natural hydrophobic sand

If a low weight percentage of crude fine fillers can improve properties of polymer materials directly without complicated chemical treatment process involved, it will be significant for many industrial applications. Our previous study indicated that a kind of Cancun natural sand could be an effective filler material for polymer composites. In this current work, the epoxy composites reinforced by this kind of natural sand particles were prepared and thermal and mechanical properties of the composites containing up to 5 wt % of the sand particles were characterized. Results showed that the highest flexural strength appears in the epoxy composite containing 1 wt % sand particles. A damage model was used to interpret the flexural properties, which showed an acceptable agreement with the experimental results. The glass transition temperature, high temperature storage modulus, and dimensional stability of the sand/epoxy composites monotonically increased with the addition of the sand particles. The sand particle/epoxy composites also displayed a noticeable enhancement in thermal conductivity. Theoretical analysis showed that in addition to conduction, other heat transport mechanisms played roles in the improved heat transmission through the composites. As a natural porous micron-scale material, Cancun sand has the potential for applications in cost-effective composites with enhanced mechanical and thermal properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

高酸性气田压力容器无损检测

通过对压力容器四种常规无损检测方法进行分析对比,阐述了高酸性气田压力容器对接接头的无损检测方法和比例,在满足国内外现行标准规范的前提下,应加大超声波检测比例,对接触高酸性气体介质的焊缝内表面进行100%磁粉检测或渗透检测,最大限度地检测出焊缝内表面或近表面裂纹,确保高酸性气田地面建设工程的安全。     

K终端可靠度分解算法中多边形→链简化定理的完善

无向网络K终端可靠度的分解算法中,包括多边形→链简化在内的等可靠度简化和分解定理结合,可以降低算法的复杂度。本文完善了边随机无向网络和混合随机无向网络的4#,6#,7#型多边形→链简化定理。计算机编程验证了其正确性。     

饮用水氯化中氯仿形成的动力学模式

以黄腐酸（ＦＡ）为卤仿前驱物质，分别测定不同投氯量、ＴＯＣ水平、温度以及ｐＨ值对ＣＨＣｌ３形成速率的影响，确定出ＣＨＣｌ３形成的动力学模式。该模式可用于预测投氯后的管网水中ＣＨＣｌ３的形成量，以便采取必要措施保证饮用水符合国家规定ＣＨＣｌ３〈６０μｇ／Ｌ的标准。     

添加尖晶石对氧化锌压敏电阻性能的影响

通过添加尖晶石（Ｚｎ７Ｓｂ２Ｏ（１２））改性研制出电位梯度为１００Ｖ／ｍｍ左右，压敏电压在８２～１５０Ｖ，通流容量可达１６００Ａ／ｃｍ２，漏电流＜２μＡ系列压敏电阻器，从而满足了国内电话交换机行业对８２Ｖ、１００Ｖ、１２０Ｖ、１５０Ｖ压敏电阻器的电性能要求。从工艺的角度解释了尖晶石对氧化锌瓷晶粒的作用原理，并分析了尖晶石的微观结构及粒度对瓷片电性能的影响。     

通过对一个旧战例的回顾看构筑物倒塌的抢险救援

通过北京火车站站前广告牌倒塌的抢险救援,阐述了构筑倒塌抢险救援的程序、方法及注意的问题。     

LD泵浦的Nd∶YAG腔内倍频激光器及其模式

用KTP晶体研制成LD泵浦的YAG腔内倍频激光器,得到0.532μm连续绿色线偏振激光输出,阈值泵浦功率为41mW,输出功率为1.4mW,斜效率为1.7％。研究了泵浦光对倍频激光横模的影响。     

浅议计算机信息安全所面临的威胁以及防范技术

伴随计算机互联网技术的普及和发展,人们在网络中得到便利的同时,也因为网络的自由和开放给我们的信息安全代理一定的威胁。本文针对网络信息安全的几个方面出发,结合现在网络信息安全的实际状况以及将来的发展趋势,有针对性的提出了信息安全所面临的威胁以及针对此威胁的一些防范措施。