基于BP神经网络模型的南方离子型稀土矿区开采遥感监测研究

离子型稀土开采带来了一系列生态环境问题,日 益引起人们的关注.以多时相Landsat遥感影像为数据源,通过波段提取、植被指数(Normalized Difference Vegetation Index,NDVI)、裸土指数(Bare Soil Index,BSI)和数字高程模型(Digital Elevation M...     

PVA/PVP共混交联膜的渗透蒸发分离性质(Ⅰ)

研究了4,4'-双叠氮芪-2,2'-二磺酸钠和戊二醛对聚乙烯吡咯烷酮(PVP)、聚乙烯醇(PVA)共混膜的交联及交联对共混膜分离恒沸点附近的乙醇/水混合物的影响.结果表明,膜的分离性质随着膜中PVP含量的增加而改变;采用混合型交联剂对PVA/PVP共混膜交联能明显改善膜的选择性.     

光磁混合存储动态测试系统中的聚焦伺服模块研究

介绍了光磁混合存储动态测试系统中聚焦伺服模块的设计和实现.伺服模块采用了双光束的方案,用独立的红光抽运(LD)作为伺服光源,构成独立的动态聚焦伺服单元,使伺服单元具有模块化、可移植的特点.它不仅适用于混合存储动态测试系统,还可用于卧式或立式、静态或动态的远场激光记录系统中.本文研究了聚焦模块中执行器压电陶瓷(PZT)的幅相频特性和非线性滞回效应,在控制算法方面,使用了PI算法闭环控制结合逆系统和逆非线性滞回模型进行校正,实现了高精度的动态聚焦伺服,在盘片转速为8 r/s时聚焦偏差在±130 nm内.利用该测试系统对有机材料作了动态记录测试,记录点大小和深度均匀一致.     

改进桥路型高温超导限流器的实验研究

本文介绍了单相基本桥型高温超导限流器的基本工作原理,及其参数变化对限流特性的影响.在此基础上研究应用于电力系统中的改进桥路型高温超导故障限流器实验室样机,正常工作情况,在电桥上引入直流偏置电流,不出现限流现象;短路故障情况,整流桥中的直流偏流影响限流效果,在桥路上引入限流电阻,使故障电流限制到预定的范围.研究了该限流器的工作原理,分析限流参数的变化对其限流特性的影响.实验表明,该限流器有很好的限流和重合闸能力,能显著减少暂态及稳态的故障电流。     

SbOx Thin Films Used for Write-Once Blue Laser Recording

SbOx thin films are deposited by reactive dc-magnetron sputtering from an antimony metal target in Ar＋O2 with the relative O2 content 7%. It is found that the as-deposited films can represent a two-component system comprising amorphous Sb and amorphous Sb2 O3. The crystallization of Sb is responsible for the changes of optical properties of the films. The results of the static test show that the SbOx thin films have good writing sensitivity for blue laser beams and the recording marks are very clear and circular. High reflectivity contrast of about 41% is obtained at a writing power 6mW and writing pulse width 300ns. In addition, the films show a good stability after reading 10000 times.     

The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology

The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology has been investigated deeply. The fabricated 1-nH spiral inductor on SiC substrate demonstrates a self-resonant frequency of 51.6 GHz, with a peak Q-fact of 12.14 at 22.1 GHz. From the S-parameters measurements, the exponential decay phenomenon is observed for L, Q-factor, and SRF with the air-bridge height decreasing, and an analytic expression is concluded to exactly fit the measured data which can be used to predict the performance of the spiral inductor. All the coefficients in the formula have specific meaning. By means of establishing the lumped model, the parasitic coupling capacitance of the air-bridge has been extracted and presents the exponential decay with the air-bridge heights decreasing which indicates that this capacitor is directly related to the coupling effect of the air-bridge. Through the electromagnetic field distribution simulation, the details of the electric field around the air-bridge have been presented which demonstrate the formation and the variation principles of the coupling effect.     

铝的多孔阳极氧化自组织过程结晶度依赖特性

电子束蒸发在硅衬底上的多晶铝膜多孔型阳极氧化得到的多孔列阵排布与体材料单晶铝氧化结果比较,有序度存在很大差异,导致这种差异的原因,除了氧化时间、应用电压、电解液等电化学参数外,新引入的结晶度将作为一重要因数影响自组织过程.结晶度的影响主要反映在晶粒间界区域相比于晶粒内部存在的铝原子浓度和阳极氧化反应速度涨落,这种涨落将通过干扰孔底电场的分布,对自组织过程产生微扰,由于微扰具有实时和随机性质,将使铝膜阳极氧化不再象体材铝那样,可以通过单一延长时间来最终改善孔排布的有序度.     

磁屏蔽感应型超导故障限流器的仿真研究

介绍了磁屏蔽感应型超导故障限流器 (SCFCL)的结构 ,分析了它的工作原理 ,并对一样机进行了仿真实验 ,获得了与该样机的实验近乎一致的结果。并通过仿真 ,研究了相关参数对限流效果的影响 ,从而为设计该 SCFCL提供了新的方法。     

Influence of surface states on deep level transient spectroscopy in AlGaN/GaN heterostructure

Deep level transient spectroscopy(DLTS) as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors(HEMTs) has been widely utilized.The DLTS measurements under different bias conditions are carried out in this paper.Two hole-like traps with active energies of E_v + 0.47 eV,and E_v + 0.10 eV are observed,which are related to surface states.The electron traps with active energies of E_c-0.56 eV are located in the channel,those with E_c-0.33 eV and E_c-0.88 eV are located in the AlGaN layer.The presence of surface states has a strong influence on the detection of electron traps,especially when the electron traps are low in density.The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.