渐变传输线阻抗变换器的优化设计

报道了一种宽带优化设计渐变传输线阻抗变换器的新方法．详细地推导了有关公式,并提出了相应的数值算法,给出了设计实例     

浅析中波发射机馈线阻抗变换器的安装

我台原来的PSM电子管发射机，所使用的馈线为阻抗150Ω的笼式馈线，现在我台安装使用的DX200全固态中波发射机，输出阻抗为50Ω，而发射机馈线仍要使用150Ω的笼式馈线，两者阻抗不匹配，根本无法一起使用。所以，我们决定使用50Ω转换到150Ω的阻抗变换器。     

基于回转器电路的数字交流电桥的快速平衡

本文提出了一种数字电桥在大范围内的快速平衡方法,并且设计了该方法的硬件实现方案。通过使用通用阻抗变换器(GIC)作为可变阻抗,实现了电桥比例臂系数的程控调节。该方法充分利用了微处理器的强大计算能力和处理能力,原理简明,实现简单。仿真实验表明,该方法可以有效地实现电桥的自动平衡,电阻测量准确度优于0.2%,电容测量准确度优于2%,可基本满足一般工业测量要求。     

一种改进的超宽带平面巴伦

设计了一种改进的基于共面波导和带状线传输的超宽带平面巴伦.采用低介电常数材料作为介质基板,引入一段切比雪夫多节阻抗变换器,并改进了使共面波导两地等势的方式.这些措施有效地增加了工作带宽,降低了介质损耗.设计并制作了一种50Ω非平衡到100Ω平衡馈电转换的超宽带平面巴伦,在0.1~3GHz的频率范围内,测试得到的插入损耗小于1.5dB,输出端接匹配负载时电压驻波比小于2,实验结果和仿真结果吻合良好.     

大学生负诚信心理分析

本文通过对负诚信行为者的心理动机的调查,对大学生负诚信心理作一分析,并提出调整负诚信心理的一些见解.文章首先分析了负诚信行为的心理因素,接着分析负诚信心理本身,最后提出诚信建设要做到自律和他律的统一、个体和社会的统一.     

直接AC／AC变换器输出电压及电流纹波分析

为解决直接AC/AC交换器的输出纹波计算问题,本文建立了以DC/DC变换器结构为基础的六种AC/AC变换器的理想模型.利用这些理想模型,DC/DC变换器的一般分析方法可方便地引入到AC/AC变换器的分析中,然后,论文以Buck型AC/AC变换器为例,给出其电路输出纹波系数的计算公式.为了证明理论分析的正确性,搭建了实验电路,实验结果与理论计算得到了很好的吻合.     

双脊波导与微带线转换器的仿真设计

根据工程需要,设计了一种双脊波导与微带线转换器。双脊波导采用非标准形式,利用λ/4单节阻抗变换器实现双脊波导与微带线之间的阻抗匹配,在微带线与双脊波导连接处进行了阶跃电容补偿设计。经过计算和仿真优化,在毫米波32.5GHz～36.7GHz的频段范围内,反射优于-20dB。     

自适应粒子群算法在微波电路中应用

常规粒子群算法(SPSO)在优化过程中易陷入局部最优,本文分析了常规粒子群算法陷入局部最优的原因,提出采用一种自适应粒子群算法(APSO)避免陷入局部最优,改善算法的收敛性和精度。最后用自适应粒子群算法设计宽带阶梯阻抗变换器,结果表明,与常规粒子群算法相比,自适应粒子群算法全局速度快、成功率和精度也有显著提高。     

基于UCC3895软开关技术的通信电源的设计

本文介绍了移相全桥零电压开关（ZVS）变换器原理和基于UCC3895的新型通信AC/DC变换器的设计。实验结果证明基于该电路设计的新型AC/DC变换器性能稳定,效率达90%.EMC测试项目达标并已进入量产阶段。     

母语负迁移现象在英语句法中的研究

本文运用语言迁移理论、语言输入、输出理论等,对中式英语中出现的母语负迁移现象作了分析,并得出结论:中式英语的产生是由于学习者不了解或者不能够正确运用两种语言在句法结构上的差异所造成的.最后对减少母语负迁移提出了一些建议.     

An improved passivity-based control strategy for providing an accurate coordination in a AC/DC hybrid microgrid

This paper proposes an improved passivity-based control (PBC) technique to provide accurate coordination between AC and DC sides of a grid-tied AC/DC hybrid microgrid. The proposed PBC is based on the passive properties of the system and the energy exchange between the subsystems. To this end, three mathematical formulations for the converters are driven in the first step. Then, using the formulations, the impedance injection is applied to shape the error dynamics of all DC/DC and DC/AC converters. The DC link-connected DC/AC converter is used to help the AC side for maintenance of the power quality factors such as, the grid frequency and voltage magnitude in the presence of any unbalanced power load sharing. The first contribution of the paper is the part of impedance injection to the DC/AC converter, which aims to provide more decoupling and faster convergence rate for both the steady states and the dynamical conditions. Secondly, a Lyapunov function is defined for converters’ error dynamics that provide more accurate statement of the proposed damping injections. Besides, as an attractive control feature, decoupling properties of the suggested method are investigated. Then, through achieving several curves, various operating conditions of DC/DC and DC/AC converters under varying the system errors and proposed damping injections are evaluated as well. For the purpose of validation, the system under study is simulated in the MATLAB/SIMULINK software package against a variety of system errors and converters’ operational conditions.     

Theory and explicit formulas for the design of optimum non-reciprocal negative-resistance amplifiers

General relations for the design of negative–resistance amplifiers using tunnel diodes are derived. Using these relations, explicit formulas for the element values of an optimum non-reciprocal negative–resistance amplifier having Butterworth or Chebyshev transducer power-gain characteristics of arbitrary order are presented. In developing the theory and formulas, we allow the frequency-dependent load impedance, and also include the series parasitic inductance used in the equivalent circuit representation of a tunnel diode. Thus, the design of such amplifiers is reduced to simple arithmetic.     

变频器异常检测方法研究与仿真

提出了一种异常参数映射估计的变频器异常动态参数检测算法。提取变频器异常动态参数,建立动态参数与变频器部件之间的映射关系,对变频器动态参数进行非线性变换,计算变频器动态参数异常区间排除干扰。实验证明,这种检测方式能够提高变频器异常检测的准确率,能够准确检测故障部件。     

FR-A540变频器在采煤机中应用及故障机理分析

介绍了FR-540变频器在采煤机中的调速与控制电路,分析了FR-A540变频器故障机理,指出振动是导致故障的主要原因,给出了减振、防潮和散热措施,从而可进一步降低变频器故障率,为变频器应用与故障诊断提供帮助。     

计算机电源高效率DC/DC变换器分析

归纳和总结了3种计算机电源Dc/Dc变换器,并对其进行效率分析。重点介绍了高效率的有源箝位正激变换器和LLC谐振变换器。指出有源箝住正激变换器和LLC谐振变换器可大幅提高计算机电源效率。     

Discrimination between the human prostate normal cell and cancer cell by using a novel electrical impedance spectroscopy controlling the cross-sectional area of a microfluidic channel

The prostate biopsy method shows a high false negative result because the suspicious tissue considered as cancer is not confirmed during tissue sampling. Thus, repeated biopsy procedures and diagnostic errors in relation to prostate cancer frequently occur. The purpose of this research is to enhance the prostate cancer detection rate by using microfluidic electrical impedance spectroscopy (μEIS), which allows real-time measurement of the electrical impedance of a single human prostate normal cell and cancer cell. The μEIS was equipped with a movable flexible membrane, which is operated by pneumatic pressure to capture the single cell on the surface of sensing electrodes. The forced tight contact between the cell and electrodes makes it possible to measure the electrical characteristics of the cell with a high sensitivity. The μEIS discriminates well between normal human prostate cells (RWPE-1) and cancer cells (PC-3) at 8.7 kHz based on the electrical signal responses of the cells. The average difference rates of admittance magnitude and susceptance are 54.55% and 54.59%, respectively. The developed μEIS also shows high repeatability, which was verified by a deionized water test conducted before and after each cell assay; the maximum variance of both the impedance and admittance at 8.7 kHz was as small as 9.48%.     

新型双向开关型直接AC/AC变频变换器的研究与仿真

笔者研究了一种新型的直接AC/AC变换器[1],该变换器可以直接将低频电流变换为高频电流。而传统的变换器为达到这一功能须包含整流和高频逆变[2]环节,其中间环节所用的滤波电容更是价格高、体积大、寿命短,导致整个变换器成本高、效率低、控制复杂等问题的产生。本文对该新型变换器的双向开关[3]结构、能量注入式控制原理做了分析,并对其做了详细的仿真,实现了50HZ到1KHZ以及20KHZ的变频。     

基于单周控制有源箝位正激变换器的设计

参阅国内外大量文献,对正激变换器的工作原理、电路特性、存在的缺点进行了分析,在此基础上提出一种单周控制有源箝位正激变换器,在控制方面采用单周控制PWM技术来实现对电路的控制.理论分析和实验结果都验证了该控制方法及变换器电路的正确性,表明基于单周控制有源箝位正激变换器是一种有前途的技术.     

单相交流逆变器的设计研究

本文针对单相逆变器的设计提出了一种新的CVCF逆变器方案——内部模型法。这种方法能够非常清晰地反映逆变器的内部工作原理，能按照控制精度对逆变器的输出波形进行控制。在控制策略上寻求抑制逆变器的输出因负载的改变而导致系统输出变化的方法。这种CVCF逆变器的输出不仅可以直接接入负载，还可以并入交流电网。     

带隔离变压器的Cuk型有源功率因数校正的研究与设计

随着电力电子技术的发展,各种电力电子设备应用于电网,给电网带来谐波问题,各种谐波滤波器也应运而生,但这只是一种先污染后治理的被动办法,APFC是一种主动的办法,它用于开关电源前级整流器,输入电流为正弦波,不对电网产生污染。全文围绕一种新颖的基于隔离型Cuk变换器的有源功率因数校正电路的设计,从Cuk变换器的基本单元入手,分析了Cuk变换器的工作原理,在此基础上,确定了基于隔离型Cuk变换器APFC电路的基本拓扑。