Rare-earth-doped GaN: growth, properties, and fabrication of electroluminescent devices

A review is presented of the fabrication, operation, and applications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs emit light due to impact excitation of the rare earth (RE) ions by hot carriers followed by radiative RE relaxation. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The deposition of GaN:RE layers is carried out by solid-source molecular beam epitaxy, and a plasma N/sub 2/ source. Growth mechanisms and optimization of the GaN layers for RE emission are discussed based on RE concentration, growth temperature, and V/III ratio. The fabrication processes and electrical models for both dc- and ac-biased devices are discussed, along with techniques for multicolor integration. Visible emission at red, green, and blue wavelengths from GaN doped with Eu, Er, and Tm has led to the development of flat-panel display (FPD) devices. The brightness characteristics of thick dielectric EL (TDEL) display devices are reviewed as a function of bias, frequency, and time. High contrast TDEL devices using a black dielectric are presented. The fabrication and operation of FPD prototypes are described. Infrared emission at 1.5 /spl mu/m from GaN:Er ELDs has been applied to optical telecommunications devices. The fabrication of GaN channel waveguides by inductively coupled plasma etching is also reviewed, along with waveguide optical characterization.     

Novel waveguide structures for enhanced fiber grating devices

An emerging class of fiber waveguide structures is being used to increase the functionality of fiber gratings, enabling new devices critical to the performance of next generation light-wave communications systems. These devices rely on advances in the fabrication of optical fiber waveguides, which go beyond the conventional doped silica design and fall into two general categories: 1) local modifications to the waveguide after fabrication and 2) fibers drawn with modified claddings that include nonsilica regions throughout their length. This paper provides a comprehensive review of emerging fiber waveguide structures that enhance the functionality of optical fiber grating devices. Two examples of technologies that fall into the first category are thin metal films deposited onto the cladding surface, which can be used for thermal tuning and infusion of nonsilica materials into the air regions, which change the waveguide structure and can provide enhanced tunability. The second category is typified by air-silica microstructured optical fibers, which contain air-voids that run along the length of the fiber. These fibers have unique cladding mode properties that can be exploited in fiber grating based devices     

一种新型的变频器件群时延特性测量方法

群时延作为衡量变频器件相位线性的主要指标,对于变频系统来说更是重中之重,对射频器件测量中具有重要地位的群时延测量问题进行了研究。首先介绍了群时延的定义及概念,然后从群时延的测量原理入手,逐步讲明了利用PNA型矢量网络分析仪的标量混频器+相位(SMC)模式测量变频器件群时延的方法及适用性,最后利用实验对该新型群时延测量方法与传统测量方法结果进行对比。结果表明,利用标量混频器+相位模式测量变频器件的变频损耗与群时延与利用矢量混频器模式测量得到的结果较为一致,变频损耗测量误差在0.5dB以内,群时延测量误差在皮秒量级,证明了该方法的正确性及准确度。且无论从测试复杂性、稳定性与溯源性上均优于传统的矢量混频器法,因此该测试方案可广泛应用于变频器件的变频损耗与群时延测量。     

PVP及其共聚物凝胶电解质的制备与应用

采用自由基溶液聚合方法.合成出不同分子量和微观结构的聚4-乙烯基吡啶(PVP)及其共聚物,通过与交联剂的化学交联反应固化液体电解质制备了凝胶电解质,将其应用于染料敏化太阳电池.研究发现,分子量小的凝胶电解质电池具有较好的光电转换性能,与纯液体电解质电池相比,短路电流(ISC)、开路电压(V∝)、填充因子(FF)、光电转换效率(η)分别达到液体电解质电池的50.9%、98.1%、93.2%、46.4%.     

Electrodeposited iridium oxide for neural stimulation and recordingelectrodes

Iridium oxide films formed by electrodeposition onto noniridium metal substrates are compared with activated iridium oxide films (AIROFs) as a low impedance, high charge capacity coating for neural stimulation and recording electrodes. The electrodeposited iridium oxide films (EIROFs) were deposited on Au, Pt, PtIr, and 316 LVM stainless steel substrates from a solution of IrCl₄, oxalic acid, and K ₂CO₃. A deposition protocol involving 50 potential sweeps at 50 mV/s between limits of 0.0 V and 0.55 V (versus Ag|AgCl) followed by potential pulsing between the same limits produced adherent films with a charge storage capacity of >25 mC/cm². Characterization by cyclic voltammetry and impedance spectroscopy revealed no differences in the electrochemical behavior of EIROF on non-Ir substrates and AIROF. The mechanical stability of the oxides was evaluated by ultrasonication in distilled water followed by dehydration and rehydration. Stability under charge injection was evaluated using 200 μs, 5.9 A/cm² (1.2 mC/cm²) cathodal pulses. Loss of iridium oxide charge capacity was comparable for AIROFs and the EIROFs, ranging from 1% to 8% of the capacity immediately after activation or deposition. The EIROFs were deposited and evaluated on silicon microprobe electrodes and on metallized polyimide electrodes being developed for neural recording and stimulation applications     

Novel on-chip fully monolithic integration of GaAs devices with completely fabricated Si CMOS circuits

We monolithically integrated polycrystalline GaAs metal-semiconductor-metal (MSM) photoconductive switches with a completely fabricated Si-CMOS amplifier and obtained a properly functional optical receiver, without altering the Si circuit performance. To our knowledge, this is the first time a fully monolithic on-chip integration has been achieved.     

配电网故障区段定位的互补松弛约束新模型与算法

研究快速高容错性馈线故障区段辨识技术对于提升配电网运行安全可靠性具有重要作用。基于故障电流信号并联叠加特性和逼近关系理论,首次提出代数建模机制下馈线故障区段定位的互补松弛约束模型,其优势为:克服了逻辑模型对群体智能算法的依赖,可采用数值稳定性好的梯度算法求解;利用互补松弛约束条件将非线性整数规划模型转化为具有光滑特性的非线性规划模型,降低了决策求解复杂性;无需对配电网进行分层解耦,即可实现单一和多重故障区段的有效辨识。为有效求解互补松弛故障定位模型,基于模型等价转换思想和松弛因子压缩策略,提出具有全局收敛特性的交互式优化决策算法。仿真算例验证新方法可实现配电网馈线单一或多重故障区段的准确高容错性辨识,且数值稳定性好、故障定位效率高。     

A many-particle quantum-trajectory approach for modeling electron transport and its correlations in nanoscale devices

Electron transport in mesoscopic systems is analyzed in terms of quantum (Bohm) trajectories associated to wave-function solutions of a many-particle (effective-mass) Schrödinger equation. Many-particle Bohm trajectories can be computed from single-particle Schrödinger equations. As an example, electron correlations for a triple-barrier tunneling system with electron-electron interactions are computed. Simulated noise results for interacting electrons that tunnels through triple barriers are presented. The approach opens a new path for studying electron transport and quantum noise in nanoscale systems, beyond the “Fermi liquid” paradigm.     

汽轮机低压缸排汽焓在线计算新模型的研究及应用

针对现有汽轮机低压缸排汽焓在线计算模型的缺点,提出一种排汽焓在线计算新模型.通过对不同容量汽轮机组的额度工况点和特定机组的不同工况点进行实例计算,结果表明:该计算模型不必对汽轮机回热系统和低压缸湿蒸汽区进行计算,计算模型简单,计算量小;所需测点少,测点积累误差小,计算精度高.     

并联补偿装置运行中的异常现象及对策

并联补偿装置投运时发生的异常现象与很多因素有关 ,如 :接线方式、分组容量、配套装置选型、运行方式及电力系统谐波分量等。现就近年运行中较易发生的问题加以分析并提出对策。1　合闸涌流产生的过电压1 .1　现象、危害及原因分析不带串联电抗器的电容器组 ,在投运合闸瞬间 ,相关的计量仪表或保护用电流互感器二次回路中 ,往往发生绝缘闪络或仪表、继电器损坏 ,这是电容器合闸涌流产生的过电压造成的。因为一组电容器合闸涌流的幅值和频率都可高达电容器组额定电流的数十倍 ,而电流互感器次级所接仪表和继电器多为感性、感抗大频率高。幅…     

Heterojunction and heterodimensional devices for optoelectronics

This article features a few optical sensory devices with basic properties that are changed by the presence of a two-dimensional electron gas (2DEG). A photodetector based on ohmic contact to the 2DEG is first presented in which variation of the 2DEG concentration and the (transverse) electric field that causes this confinement radically changes the device behavior. Next, the same device architecture is used but two Schottky contacts replace the ohmic ones, resulting, as expected, in a vastly different device behavior     

电网谐波检测新方法及其实现

提出一种基于电磁变换原理的谐波检测新方法,该方法可以解决非正弦三相不平衡系统中电压和电流以谐波分量的检测问题。计算机仿真与单片机检测系统的硬件实现证明了该方法的有效性。     

现代新型传感器技术及应用(下)

4　新型电流传感器4 1　光电电流传感器 (OCT)光电电流传感器的原理是利用磁致旋光效应 ,即法拉第效应 (Faradayeffect) ,法拉第效应测量电流原理见图 7。图 7　法拉第效应测量电源原理图当一束平面线偏振光通过置于磁场的、透明的磁光材料 (如铅玻璃等 )时 ,偏振光在外磁场作     

复杂网络中最短路径算法的研究及应用

本文将复杂网络中最短路径算法引入到交通网络领域中,将标号改正算法应用于交通网络路径分析.首先讨论了标号算法的基本结构;然后分析了标号设定算法和标号改正算法的实现过程、复杂度、运行特点和适用性,进而选择了标号设定和标号改正算法中公认的几种优秀算法--基于逼近桶结构、改进四叉堆的Dijkstra算法(DIKBA与DIKQH)以及Pallottino算法(TWO-Q),并结合交通网络邻接链表结构予以实现;最后采用城市交通网络数据,对几种算法的实际运行效率进行了对比实验.实验结果表明:标号改正算法和标号设定算法优点各异;由于交通网络中路径算法的应用越来越强调动态性和网络适用性,而且标号改正算法较之标号设定算法具有更大的适用范围,因此其在交通网络路径分析中具有极大的应用潜力.     

聚天冬氨酸及其复配对白铜(B30)缓蚀作用的电化学研究

采用交流阻抗法和极化曲线法,研究了两种环境友好型水处理药剂聚天冬氨酸和钨酸钠的单一配方及其复配对模拟水中白铜(B30)的缓蚀效果.研究表明:聚天冬氨酸和钨酸钠各自的单一配方对于B30均具有一定的缓蚀效果,其中聚天冬氨酸在浓度为15 mg/L时对B30的缓蚀效果最佳,钨酸钠在浓度为10 mg/L时缓蚀效果最佳.在缓蚀剂总浓度为20 mg/L时,聚天冬氨酸与钨酸钠配比为6∶1、3∶1、1∶3和1∶6时对B30具有明显的缓蚀效果,其中以配比为6∶1时最佳且具有缓蚀协同效应,缓蚀率达94.52%.     

高压电能计量装置远程校验与监测系统及其应用

针对目前电力系统高压电能计量装置技术监督管理中存在的一些问题,本文介绍了一种计量装置远程校验与监测系统并已在益阳电厂安装应用.该系统可以在线监测计量装置二次回路的电力技术参数、电能表的精度、TV二次压降、TV和TA的二次负荷等,并结合网页数据库实现了数据的共享.这种新技术可以解决目前电能计量管理中的诸多不足,大大提高了计量管理的工作效率和技术水平,为电能计量管理带来了技术进步.     

新型Cuk电路及其在光伏系统中的应用

虽然Cuk变换器传输效率较高,但因其高频化所产生的开关损耗和电磁干扰(Electromagnetic Interference.简称EMI)等问题不容忽视.在对隔离式Cuk电路进行理论分析的基础上,构建了带零电压开通软开关隔离式Cuk电路的硬件电路.研究了在不同占空比、开关频率和负载条件下该电路的传输效率,并根据光伏电池的特性将该电路应用于光伏发电的最大功率追踪(Maximum Power Point Tracking,简称MPPT)系统.实验结果证明了软开关在提高Cuk电路传输效率方面的作用及其在光伏系统应用中的优势.     

新型中压配电线载波通信技术及其应用

基于虚拟载波帧测技术的多虚拟逻辑网络组、增强型自适应模拟前端、自适应多频段收发、多耦合方式等关键技术,能够满足不同应用需求.通过新型中压配电线数字载波通信装置(PLC-075)在城市小区配电自动化和中小型水电站信息采集的具体应用案例证明,该装置能够有效和可靠地解决配电自动化系统中压配电线传输特性的动态变化、突发干扰、组网通信和实时性等难题,有着广阔的应用前景.     

Extraction and modeling methods for FET devices

The proposed method is based on spline functions, takes into account thermal and noise effects, allows a scaling of different FET device geometries, and is available in commercial CAD software like Agilents Series IV or ADS