Optimized power simulation of AlGaN/GaN HEMT for continuous wave and pulse applications

An optimized modeling method of 8 × 100 μm AlGaN/GaN-based high electron mobility transistor (HEMT) for accurate continuous wave (CW) and pulsed power simulations is proposed. Since the self-heating effect can occur during the continuous operation, the power gain from the continuous operation significantly decreases when compared to a pulsed power operation. This paper extracts power performances of different device models from different quiescent biases of pulsed current-voltage (I-V) measurements and compared them in order to determine the most suitable device model for CW and pulse RF microwave power amplifier design. The simulated output power and gain results of the models at V_gs = -3.5 V, V_ds = 30 V with a frequency of 9.6 GHz are presented.     

面向智能家居的数据库中间件软件设计

文章旨在将不同无线网络、不同通信格式的设备结合起来,从而构建一个面向智能家居的异构网络控制系统。针对不同协议、不同厂家的无线设备难以互通互联、统一控制的问题,本文提出了一种基于Web的中间件软件架构。该中间件进行数据格式转换的同时还能结合Web界面控制设备呈现给用户。上层控制端通过对数据库的操作来实现对不同通信网络智能家居设备的控制和联动。异构无线网络-ARM网关-数据库中间件-控制端的架构能够使用户在避免接触底层硬件系统和软件编程的情况下,快速组网灵活控制智能家居设备,增强了智能家居的系统的易用性。     

基于GSM模块的光线检测系统设计

开关量信号采样是工业过程领域中一种常见的数据采集技术。本系统由单片机控制系统、显示模块、发送模块和光线检测模块等组成,采用AT89S51单片机作为系统的控制器,实现对开关量信号的采集和处理,并通过TC35 GSM模块发送处理后的信息。系统工作正常,运行稳定。     

4G移动通信的特点及关键技术分析

近年来我国网络通信技术取得了较快的发展,特别是人们对网络通信速度要求不断提升的新形势下,2G和3G通信技术越来越无法满足人们对高水平通信技术的要求,在这种情况下,4G通信技术应运而生。4G通信技术不仅传输效率较为稳定上,而且传播速度非常快捷,具有人性化和智能化的结构,能够更好的为人们提供高水平的通信服务。4G移动通信技术有效的满足了人们对技术更新和功能体验的要求,成为当前移动通信的主流技术。     

掺铈石英闪烁光纤的伽马传感特性研究

提出了基于溶胶-凝胶(Sol-Gel)法制备掺铈石英闪烁光纤,将其作为辐射传感头,搭建了对伽马辐射敏感的光纤传感系统。通过改变溶胶-凝胶中铈元素掺杂浓度,分别拉制出Ce与Si的摩尔分数分别为0.14%和0.22%的闪烁石英光纤。利用137Cs伽马辐射源,研究了闪烁光纤涂覆层、铈元素掺杂浓度及闪烁光纤长度等参量对辐射传感特性的影响。     

High‐Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self‐Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self‐assembled monolayer (SAM)‐based doping on the performance of WSe₂‐ and MoS₂‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p‐doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm² V^?1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^?1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^?1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^?1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6‐fold in the OTS/WSe₂ devices and ≈24.5‐fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air‐exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD‐based electronic/optoelectronic applications.     

TD-SCDMA网络重要性浅谈

在国内4G快速发展的背景下,3G网络逐步被取代以承载移动宽带用户的数据流量,因而国内涌现了很多认为3G网络如TD-SCDMA已过时的观点,本文通过对中国移动现网用户的数据承载、自主知识产权技术积累、国内外通信体制的博弈、国内4G的发展和人才培养等方面进行分析,显示了TD-SCDMA仍发挥着重要的作用。     

电感耦合等离子体原子发射光谱法测定钛合金中钨、铌、钽

采用电感耦合等离子体原子发射光谱法（ICP-AES）法测定钛合金中W,Nb,Ta元素的含量。样品采用盐酸、氢氟酸和硝酸溶解,并对仪器工作参数和试验条件进行了优化试验,确定了仪器最佳工作条件,考察了钛合金基体和共存元素对待测元素的影响,确定了各待测元素谱线为W207．911nm,Nb309．418nm,Ta240．063nm。选定的待测元素分析线不受合金基体和共存元素的干扰,通过基体匹配消除基体的影响。加标回收率在98％104％之间,测定结果的相对标准偏差为0．3％～2．4％（n=8）,方法的检出限为0．003-0．013μg／mL。进行了标准物质对照试验,试验结果与标准值相符。     

离子色谱法测定甲醇和噻吩中硫、氯含量

建立了测定工业用甲醇和噻吩中硫、氯含量的离子色谱检测方法。样品经(700±25)℃灼烧后,残留物用蒸馏水洗涤,利用离子色谱仪进行分析。甲醇和噻吩中硫、氯检测结果的相对标准偏差为1.04%~1.26%,加标回收率为99.2%~101.2%。该方法操作简单,精密度和准确度高,可用于大部分可燃性有机化合物中硫、氯含量的检测。     

Amperometric detection of nitrite based on Dawson-type vanodotungstophosphate and carbon nanotubes

A nitrite sensor based on Dawson vanodotungstophosphates α₂-K₇P₂VW₁₇O₆₂·18H₂O (P₂W₁₇V) and carbon nanotubes (CNTs) was prepared by electrostatic layer-by-layer self-assembly technique. The sensor {PEI/PSS/[PDDA/P₂W₁₇V-CNTs]_n} was characterized by UV–vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS). The electron transfer and sensing ability of this sensor were explored using cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) technology. The results show that the incorporation of CNTs and P₂W₁₇V into the composite film endowed the modified electrode with fast transfer rate and high electrocatalytic activity towards oxidation of nitrite. This nitrite sensor with 10 bilayers has a broad linear range of 5 × 10⁻⁸ to 2.13 × 10⁻³ M, a low detection limit of 0.0367 μM (S N⁻¹ = 3), a high sensitivity of 0.35 mA mM⁻¹ NO₂⁻, an excellent anti-interference property in the presence of other potential interfering species and a good stable. It was successfully employed for determination of nitrite in real towards.