大功率GaN基LED的提取效率

影响GaN基LED效率的主要因素是内量子效率和提取效率. 蓝光GaN基的LED内量子效率可达70%以上， 紫外GaN基LED可达80%，进一步改善的空间较小. 而传统大面积结构GaN基LED由于全反射和吸收等原因，外提取效率只有百分之几，提高空间很大. 本文从几何和物理光学角度分析了影响GaN基LED外提取效率的因素，针对全反射、吸收、横向光波导等问题总结了现有的各种提高GaN基LED提取效率的手段及其优缺点.     

故障自治系统的构想

本文提出了一种故障自治系统的基本构想:即根据系统先验信息和某些状态或参数的观 测,计算滤波残差和故障特征矩阵,构造能分离故障的投影算子(DPO).由故障探测分离逻 辑判断系统运行是否正常,分离确立故障发生的P位,补偿由故障所造成的影响,使系统具有 启动诊断治理故障的能力. 本文给出了DPO算子产生的方法,论证了存在的充要条件.为了减少计算量和保持滤 波器在系统运行正常时的最佳性和在有故障时对不期望变化的灵敏性,本文提出了一种故障 开关滤波器.数字计算结果显示了这些方法的有效性.     

SDB／MCT新型功率器件的研究

本文探讨了新型功率器件ＭＣＴ（ＭＯＳ控制晶闸管）的电参数设计和工艺设计，通过计算机模拟，采用ＳＤＢ（硅片直接键合）材料，在实验室制成了ＮＭＣＴ样品。测试结果表明，在－１２Ｖ的栅偏压下能在５μｓ内关断４２Ａ／ｃｍ＾２的阳极电流。     

Development of a detector for liquid chromatography based on aerosol chemiluminescence on porous alumina

This paper describes a novel aerosol chemiluminescence-based detector, which can be coupled to liquid chromatography for the determination of the chemicals with weak optical absorbance in the UV-visible region. This aerosol chemiluminescence (CL)-based detector, in which HPLC effluent is converted to aerosol and then generated CL emission on the surface of porous alumina, is composed of three main processes: nebulization of HPLC effluent, CL emission on surface of porous alumina material, and optical detection. To demonstrate the utility of the aerosol chemiluminescence detector, some compounds such saccharides, poly(ethylene glycol)s, amino acids, and steroid pharmaceuticals are determined by the present aerosol chemiluminescence detection method. Compared with an evaporative light scattering detector, the proposed detector shows the following features: (a) extensive CL emissions on porous alumina by many compounds tested, which leads to the potential application for the determination of volatile and nonvolatile chemicals with or without UV-visible absorbance; (b) a CL mechanism based on the catalytic oxidation of analytes, not on the light scattering, which suggests the present detector be free from the interference of the inorganic and nonvolatile mobile-phase modifiers. The CL characteristics and effect of different parameters, such as temperature and nebulizer gas flow rate, were also discussed in this paper. Furthermore, this aerosol chemiluminescence-based detector was successfully applied to the determination of raffinose, glucose, sucrose, maltose, and alpha-lactose.     

垂直结构GaN基LEDs热压键合应力损伤分析

热压键合是垂直结构LED制备的关键工艺步骤,通过TEM,PL,Raman等测试手段,探讨热压键合造成的应力损伤、GaN材料缺陷、LED内量子效率以及反向漏电间的内在联系,研究以键合引起的应力诱导垂直结构GaN基LED光电特性的退化机制,探讨应力损伤对垂直结构GaN基LED光电特性的影响.实验结果表明,热压键合过程会在GaN材料内产生GPa量级的残余应力,在量子限制strark效应作用下,GaN材料辐射复合效率发生明显退化;同时热压键合应力还会诱发GaN材料位错密度的增加,最终导致LED反向漏电增大.     

浇注式隔热型材的几个问题探讨

本文探讨了浇注式隔热型材所使用的隔热原胶的线膨胀系数、热变形温度、相容性及隔热型材的切桥宽度,并由此带来的隔热型材的问题。     

Light extraction efficiency enhancement of GaN-based light emitting diodes by a ZnO current spreading layer

preading layers are analyzed.     

Packaging technology of LEDs for LCD backlights

traditional package method of a yellow phosphor with a blue chip. However, its light efficiency needs to be further improved for the use of backlights for LCDs.     

Predistribution and local collaboration-based group rekeying for wireless sensor networks

When a sensor network is deployed in a hostile environment, an adversary may launch such attacks as eavesdropping the communications and compromising sensor nodes. Using the compromised nodes, he may inject false sensing reports or modify the reports sent by other nodes. To defend against these attacks, researchers have proposed symmetric group key-based schemes. In these schemes, however, if a large number of nodes are compromised, many (sub)group keys will be revealed. This greatly endangers the filtering schemes, making them very ineffective or even useless. To address this problem, we propose a family of predistribution and local collaboration-based group rekeying (PCGR) schemes, which update the compromised group keys to prevent the compromised nodes from understanding the communications between noncompromised nodes or injecting false data. These schemes are designed based on a simple while controversial idea – preload future group keys into sensor nodes before their deployment. To protect the preloaded keys from being disclosed by compromised nodes, we propose a novel technique that requires neighboring nodes to collaborate to derive the future group keys. To the best of our knowledge, our schemes are the first set of distributed group rekeying schemes for sensor networks without involving online key servers. Extensive analysis and simulations are conducted to evaluate the proposed schemes, and the results show that the proposed schemes can achieve a good level of security, outperform several previous group rekeying schemes, and significantly improve the effectiveness of false data filtering.     

Upconversion Luminescence in γ-AlON:Yb3+,Tm3+ Ceramic Phosphors

Upconversion emission properties of γ-AlON:Yb³⁺,Tm³⁺ phosphors were investigated under single-wavelength diode laser excitation of 980 nm. Blue (479 nm) and red (653 nm) emission bands were observed which correspond to the transitions of ¹G₄→³H₆ and ¹G₄→³F₄ of Tm³⁺ ions, respectively. The upconversion spectra show a concentration-dependent luminescence intensity, reaching its peak at a concentration of 1.2 mol% Yb and 0.5 mol% Tm. Pump power dependence of the upconversion emission intensity ( P – I ) revealed that a two-photon process was involved in the blue and red emissions.