分布式放大器的变阻抗实现

从普通分布式放大器的基本原理出发，指出了存在的问题；从等电压传输概念出发，给出了一种新的阶梯型变阻抗分布式放大器的工作原理，提出了传输线视在匹配的概念。变阻抗放大器的性能在很多方面优于普通分布式放大器。     

一种磁耦合谐振线圈结构阻抗测量装置设计

提出了一种基于矢量伏安法测量原理的便携式阻抗测量装置,并分析了磁耦合谐振式无线电能传输中耦合线圈结构阻抗测量电路的设计原理,通过单片机系统控制AD5933阻抗转换器测量待测谐振耦合结构的阻抗,利用串口通讯协议实现LabVIEW软件和单片机系统的相互通讯。实验结果表明,耦合线圈工作在谐振态下,阻抗测量值与理论阻抗值相对误差为2%,成本较低,便于携带,能够满足大部分耦合线圈设计需求。     

探讨含受控源电路的过渡过程

通过实例探讨利用三要素法、解微分方程法和复频域分析法求解含受控源电路的过渡过程。提出在分析、求解含受控源电路的过渡过程时,应视具体情况而采用适当的方法.     

视译在口译中的基础性作用及训练技巧

视译作为口译的一种特殊形式,具有不同于其他口译的传译机制和训练技巧,对交替传译和同声传译有基础性作用.但是在我国,由于口译理论体系及教学体制还不够完善,视译训练还没有得到足够的认识.本文从视译训练模式和技巧分析等方面提出了视译学习和培训的有效途径.     

电桥法测量阻抗刍议

介绍了四臂电桥、变量器电桥、双T电桥测量阻抗的原理，总结了三种电桥的优缺点。为了实现阻抗的高精度测量，提出了在不同的频率范围内，应选用不同的电桥法。在阻抗的实际测量中，具有指导性作用。     

敦煌壁画与西方绘画出现焦点透视的分析

针对西方传统的线性透视--焦点透视法的出现时间,提出并论述了我国在盛唐时期(公元713年左右)和中唐期间,敦煌壁画莫高窟、榆林窟同样出现了焦点透视法,足足比西方早700年.不相同的是二者在绘画上,各自选择了视向不同的焦点透视法.敦煌壁画更是采用了多视向的焦点透视法.敦煌壁画盛唐时期和西方采用的线性透视,他们都不自觉地注意到客观中存在着透视现象,又以他们特有的方式去处理,通过其敏锐的视觉特点及审美天性暗示着这一点.     

西方基础教育改革阻抗研究及其启示

西方基础教育改革在其推进过程中,各国学者认识到了改革阻抗问题的客观存在,分析了权力阻抗、心理阻抗、价值阻抗、社会阻抗等阻抗因素,提出了阻抗的消解策略。对这些研究及其策略加以借鉴与反思,会更有效地推动我国基础教育改革的顺利进行。     

谈钢琴教学中的视奏和背奏

在钢琴教学中如何处理好视奏与背奏的关系是教师与学生经常遇到的问题.笔者认为,首先通过读谱、慢视奏训练,提高视奏的准确性;而后进行快视奏的训练,提高视觉反应的敏锐性和演奏的连贯性与完整性.在慢、快视奏的基础上,从理解乐曲思想内容、风格等方面入手,将视觉背谱法、听觉背谱法、触觉背谱法、基础理论背谱法有机地结合起来,能较好地克服上述问题,达到预目的.     

超磁致伸缩平面扬声器阻抗特性研究

对超磁致伸缩平面扬声器的阻抗特性进行了实验研究和等效电路分析,通过恒流法测试其阻抗特性。结果表明:超磁致伸缩平面扬声器的阻抗随着频率的变化趋势类似于高损耗电感,不存在动圈式扬声器阻抗特性的低频谐振峰。还讨论了与之相配接的功率放大器的幅频均衡问题。     

小波分析在矩量法中的应用

将小波分析同矩量法相结合,首先,讨论了周期小波在电磁散射问题中的应用,并指出随着目标电尺寸的增大,该方法产生一个庞大而病态的阻抗矩阵,结果大量的计算机资源因此而耗费。其次,提出周期小波的两种改进算法,其中物理光学预处理算法改善了阻抗矩阵的病态性,降低了矩阵维数,提高了计算速度。     

负反馈电路近似计算方法的统一

对集成运算放大器和分立元件放大器组成的负反馈电路的不同计算方法进行剖析,实现了用统一的方法进行分析计算。     

Wavelet network based predistortion method for wideband RF power amplifiers exhibiting memory effects

RF power amplifiers (PAs) are usually considered as memoryless devices in most existing predistortion techniques. Nevertheless, in wideband communication systems, PA memory effects can no longer be ignored and memoryless predistortion cannot linearize PAs effectively. After analyzing PA memory effects, a novel predistortion method based on wavelet networks (WNs) is proposed to linearize wideband RF power amplifiers. A complex wavelet network with tapped delay lines is applied to construct the predistorter and then a complex backpropagation algorithm is developed to train the predistorter parameters. The simulation results show that compared with the previously published feed-forward neural network predistortion method, the proposed method provides faster convergence rate and better performance in reducing out-of-band spectral regrowth.     

Gender Differences on the Use of Amplifiers in Academic Writings

This study aims to investigate the use of amplifiers in term of gender and disciplinary groups in academic research arti cles,which is based on the British Academic Written English Corpus(BAWE).18 amplifiers were examined across two dimen sions:gender and disciplinary groups.The results show amplifiers are more common in males’ academic writings than in those of females in general,amplifiers are used more often in AH discipline.However,not all amplifiers show significant gender differ ences between men and women.Six words show a significant difference between male and female writers:pretty,by far,perfect ly,quite,a great deal,totally,which are used more often by males.However,the interesting is in LS discipline,most amplifiers are used more often by female than male writers and males tend to use by far more frequently than females.     

非线性液晶光信号放大器

提出了非线性液晶光信号放大器的原理、结构和系统,理论分析了光信号放大器的实验结果。研究表明,这种光信号放大器,由液晶光敏介质组成,这种光敏介质,能够接收已调制的信号光波和泵波,并能用于光传输系统。     

计算机控制的PWM放大器的设计

在我国,多数伺服系统以交磁电机扩大机作为功率放大器,该文对采用PWM功率放大器的新伺服系统进行定性和定量分析及设计,以PWM功率放大器替代伺服系统中普遍使用的电机扩大机,从局部上改变伺服系统的结构,提高整个系统的技术含量和各项性能指标.     

基于多级BP神经网络的EIT阻抗变化位置的确定

Electrical impedance tomography (EIT) is a new computer tomography technology, which reconstructs an impedance (resistivity, conductivity) distribution, or change of impedance, by making voltage and current measurements on the object's periphery. Image reconstruction in EIT is an ill-posed, non-linear inverse problem. A method for finding the place of impedance change in EIT is proposed in this paper, in which a multilevel BP neural network (MBPNN) is used to express the non-linear relation between the     

反馈放大器教学探讨

提出了一种判断反馈放大器组态的方法和步骤。依此可以直观而准确地判断出反馈放大器的组态。同时，还可以在此基础上进一步定性分析负反馈对放大器性能的影响。     

电阻抗图象重建的新正则化方法

Image reconstruction in elecrical impedance tomography(EIT)is a highly ill-posed inverse problem,Regularization techniques must be used in order to solve the problem,In this paper,a new regularization method based on the spatial filtering theory is proposed.The new regularized reconstruction for EIT is independent of the estimation of impedance distribution,so it can be implemented more easily than the maxiumum a posteriori(MAP) method.The regularization level in our proposed method varies spatially so as to be suited to the correlation character of the object‘s impedance distribution.We implemented our regularization method with two dimensional computer simulations.The experimental results indicate that the quality of the reconstructed impedance images with the descibed regularization method based on spatial filtering theory is better than that with Tikhonov method.     

基于直接寻找法的电阻抗断层成像

Solution to impedance distribution in electrical impedance tomography （EIT） is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. Tikhonov regularization with some prior information is a sound regnlarization method for static electrical impedance tomography under the condition that some true impedance distribution information is known a priori. This paper presents a direct search method （DSM） as pretreatment of image reconstruction through which one not only can construct a regularization matrix which may locate in areas of impedance change, but also can obtain an initial impedance distribution more similar to the true impedance distribution, as well as better current modes which can better distinguish the initial distribution and the true distribution. Simulation results indicate that, by using DSM, resolution in the center area of the measured object can be improved significantly.     

一种负反馈放大器的计算方法

电压增益、输入电阻、输出电阻是放大电路的三项指标，一般用微变等效电路法计算，但是在负反馈放大器中，由于引入反馈支路，用微变等效电路法计算上述指标很困难。本文给出一种消去反馈支路的方法，使负反馈放大器的计算得以简化。