滤波器在单相PWM整流器中的应用

为消除混叠在PWM单相整流器交流电流反馈信号中的高次谐波分量和直流电压控制外环中的2次谐波分量,在交流电流反馈通道中设置低通滤波器,并使用陷波滤波器衰减直流2次谐波分量;通过在建立电流控制系统模型中发现的内环低通滤波器可有效消除混叠的高次谐波信号的方法保障系统稳定,而对截止频率过高将引起反馈信号相移,改变系统中低频特性,进而影响系统稳定性,则给出了滤波器参数的设定要求;采用直流环节中的陷波滤波器,相比低通滤波器不仅易于在计算精度有限的底层控制芯片中实现,同时更有效消除2次谐波分量,保障系统的高输入功率因数和低谐波分量,同时拥有良好的动态特性。相关仿真分析及搭建4.5kVAPWM整流器样机平台的实验结果验证了以上推论。     

Development of gated fiber detectors for laser-induced strong electromagnetic pulse environments

With the development of laser technologies,nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of at...     

Untraceable Analysis of Scalable RFID Security Protocols

Wireless Personal Communications - In order to support robust implementation of IoT, many schemes have been done to provide privacy, anonymity, scalability and customizability. Ray et al.’s...     

用单端矢量网络分析仪测试手机RF电路的差分散射参数

本文以声表的测试为例,说明了采用单端矢量网络分析仪测试手机射频(RF)电路的差分散射参数的原理及方法,其中包含物理三端口的散射参数和模式三端口网络散射参数。     

基于AHP和改进模糊理论的某艇C3I系统效能评估

在AHP与模糊理论结合的方法对系统效能进行评估基础上,通过对模糊理论中隶属度计算方法进行改进,克服了一般模糊理论计算中隶属度转换过程中存在的对目标影响不起作用的冗余数据也参与运算的缺点.同时C3I系统效能评估为指挥人员及科研人员对舰艇作战能力了解有了初步依据.     

High-Q microresonators on 4H-silicon-carbide-oninsulator platform for nonlinear photonics

The realization of high-quality (Q) resonators regardless of the underpinning material platforms has been a ceaseless pursuit, because the high-Q resonators pro...     

Thickening and Rheological Properties of Crystalline Polyester Used in Low Pressure Sheet Molding Compounds

Low pressure sheet molding compound (LPMC,1.0-3.0 MPa,95-103 ℃) is a new kind of thermosetting material with crystalline polyester as a physical thickenner.LPMC is different from conventional SMC using an earth oxide thickening agent (e.g.MgO) as chemical thickenner,it relies on the physical thickening of crystalline polyester.Crystalline polyester resin is the key material to mold LPMC parts.Currently there was no report about the thickening mechanism of crystalline polyester in LPMC.In this article,crystalline polyester resins,whose melting points were between 45 ℃ and 89 ℃,were synthesized by a two-step esterification.The melt points of crystalline polyesters are controlled by regulating the mol ratio of the two glycols and the two acids.And by means of varying the content of crystalline polyester resin,the thickening effect on resin paste is investigated.In addition,the thickening mechanism of crystalline polyester in LPMC was investigated by FTIR and DSC analysis.The effects of the diameters and viscosity of crystalline polyester on the rheological property and fiber distribution of LPMC sheets were studied,too.Results show that the thickening effect is excellent when the weight content of crystalline polyester resin is 3%.And there exists three kinds of functions acting in the process of thickening:swelling,hydrogen bonds and induction crystallization.During the preparing process of resin paste in LPMC,the temperature of resin paste must be kept at 90 ℃.In addition,crystalline polyester make LPMC have a perfect fluid property.When the viscosity of LPMC sheet is beyond 1 kPa s,the fiber orientation is not obvious.But when the viscosity of LPMC sheet is about 500 Pa s,the fiber shows a certain degree of orientation.Moreover the study of physical and chemical thickening mechanism of crystalline polyester and the rheological discipline of LPMC sheets in the hot mould will provide the researchers and enterprises with theory guidance.     

本钢新1号高炉生产创新实践

对本钢新1号高炉2010年恢复炉况期间的一些生产经验和创新进行了总结。新1号高炉通过加强原燃料管理、合理的装料制度、调整送风制度及强化炉前管理等措施,高炉冶炼强度达到一个较高的水平,2010年12月份达到日产过万的良好成绩。     

耦合渐变槽线天线及其和差波束的矩量法分析

本文阐述一种新型渐变槽线天线（ＴＳＡ）结构,耦合渐变槽线天线ＣＴＳＡ。单片的ＣＴＳＡ除可降低副瓣电平,提高增益,改善Ｅ面Ｈ面波束的对称外,还可通过与之配合的平面印刷奇偶模双工器馈电,同时实现和差波束。本文应用空间域矩量法（ＭｏＭ）建立了分析各种ＴＳＡ结构的数值模型;该方法在没有介质基片的情况下是严重的,本文集中讨论简化ＭｏＭ中阻抗矩阵积分运算的各种技术,有效地减小了计算量,并获得较高的精度。计算结     

Performances of carbon nanotube field effect transistors with altered channel length

The influence of channel length on the performances of carbon nanotube field effect transistors(CNT-FETs) has been studied.Buffered oxide etching was used to remove approximately a 60 nm layer from the original 100 nm silicon dioxide layer,to thin the dielectric layer of the back gate.Channel length of the CNT-FETs was changed along with the etching process.The dependence of drain-source current on gate voltage was measured to analyze the performance of the CNT-FETs,including the transconductance,carrier mo...