Domain reversal and current transport property in BiFeO3 films

The electrical properties and domain reversal in BiFeO₃ ferroelectric films were studied using sandwiched heterostructures and piezoresponse force microscopy. A robust polarization state was observed, combined with a switchable domain pattern and a remanent polarization of approximately 100 μC cm^?2. In addition, domain reversal was explored using scanning probe microscopy. The results show that dipoles could be reversed along the direction of the electric field under a negative tip bias, leading to carrier gathering near the domain walls. The enhanced conductivity near the domain walls was owing to the discontinuous polarization boundary conditions. In addition, typical diode-like current transport properties are sensitive to various temperature conditions, which is attributed to the Schottky barriers at the contact interface. These findings extend the current understanding of domain texture reversal in ferroelectric films and shed light on their potential applications for future ferroelectric random-access memory operations over a wide temperature range.     

2400系列数字源表在二极管测试中的应用

本文章将介绍Kethley2400系列数字源表在二极管测试中的应用及相应的编程算法。     

Polarisation behaviour of diode lasers with frequency selective feedback

The paper reviews recent results obtained with diode lasers used in external hybrid cavities with frequency selective feedback. Such cavities attract continuing interest for several reasons. They generate a tunable single laser mode with very low linewidths (usually a few tens of kilohertz). Very wide discrete tunable ranges over 100 nm for Fabry-Perot type and over 200 nm for quantum well lasers are achieved. They can be made to oscillate in a tunable mode having the desired polarization state,TE orTM and, in some cases, simultaneously atTE andTM. This is done by designing a cavity that increases strongly theTM/TE intensity ratio and by using coatings on one laser facet that greatly lower bothTE andTM reflectivities. High-speed polarization switching in the gigahertz range is possible by inserting passive or active polarization selecting elements in the cavity. For all these reasons hybrid external cavities are attractive for applications in optical metrology, spectroscopy and optical communications. Moreover, the external cavity configuration allows the study of physical mechanisms in the laser diode by inducing on purpose phenomena that would have been otherwise impossible to achieve with free-running lasers.     

微密封真空微电子二极管

本文介绍了一种微密封真空微电子二极管的工艺及实验结果。     

半导体耦合腔激光器的波长调谐与频率调制特性分析

本文将激光射器与调制器的直接耦合和耦合槽的影响综合考虑，用散射矩阵法及两步等效反射率法，对沟槽耦合腔激光器的波长调谐和频率调制特性进行了分析，数学处理简单，物理图象清晰。     

非接触式掌纹图像采集光源的设计*

通过波段选择和均匀光源设计,本文提出一种新的非接触式掌纹图像采集光源。根据人体皮肤对光谱的吸收比和人体血液对光谱的共振散射的研究,发现430nm波长的光波照射下,采集到的手掌图像相比其它波段光波照射时掌纹纹理更加突出。通过对发光二极管（LED）的发光特性,LED形状的选择、多个LED间距与排列方式的研究,最终得到光照度均匀的光源。结果表明：在该光源下采集到的非接触手掌图像对比度高,手掌纹线突出且无亮斑影响的高质量手掌图像,为提取准确的掌纹特征提供了便利。     

Cryogenic thermometry with a common diode: Type BAS16

Cryogenic test experiments often require a large number of temperatures to be monitored. In order to reduce cost, we investigated the feasibility of low-cost common diodes. We chose the Philips BAS16 diode in a type SOT23 package. By means of Stycast 2850FT, these diodes were glued into alumina holders. In total, 20 sensors were assembled and tested. With an excitation current of 100 μA and considering a temperature range from 50 K to room temperature, a quadratic least-squares-fit was obtained: T = 486.1 − 363.7V − 38.3V². All sensors agreed with this fit within an error of 1.3 K.     

Effect of interactions between voltage and current harmonics on the net harmonic current produced by single phase non-linear loads

The effect of the interaction between both load voltage and current harmonics on the net harmonic current produced by different types of single phase non-linear loads is investigated. Two types of loads are considered: the fluorescent lamps' load and single phase diode bridge rectifiers' load. Studies are done on each load alone and then on the combination of both. The electromagnetic transient program has been used to model these loads. The computer simulations are supported by laboratory testing. The main conclusion of this work is that neglecting the interactions between both voltage and current harmonics will result in incorrect estimation of the harmonic current produced by these loads. Also it is concluded that using a combination of different types of loads can result in a reduction of the current and voltage distortions.     

高效率的BOOST型功率因数校正预调节器

有源功率因数校正(PFC)通常采用Boost变换器，在低压90V输入时，其输出电压调节在380V，此时变换器效率最低。该文提出一种变输出电压的控制方式，其输出电压随着输入电压的变化而变化。这种方法可以缩短开关管的导通时间，减小流经开关管的电流有效值，从而降低其导通损耗，提高变换器的效率。分析了Boost PFC变换器的损耗分布和控制方法。最后在一台1200W的原理样机上进行实验验证，还对比快恢复二极管和SiC二极管的关断特性，给出实验结果。     

母差保护出现的问题及处理过程

本文介绍了220kV金砂变电站Ⅱ期扩建工程投运中220kV母差保护出现的问题及处理过程,指出了继电保护 设计、安装、调试、维护工作的重要性,对每个环节都需要认真处理。