对星形-多角形电路等效变换的研究

运用简便方法推导得出无源星形电路与多角形电路相互等效变换的公式,证明一个多角形(或不完备多角形)电路存在唯一的等效星形电路.举例说明了星形-多角形电路等效变换的应用.介绍了不完备多角形与星形电路的等效变换方法,以及把含源星形电路、多角形电路中的等效电源与无源星形电路、多角形电路分开的方法.     

一阶RC电路时间常数测量的难点及解决方案

RC电路是最基本的一阶动态电路,在电路中由于受电阻和电容元件参数的限制,电路的时间常数通常很小,测量过程难于实现.本文对RC电路进行了改进型设计,提高了RC电路时间常数值,使测量过程得以实现。     

用电势分析法解一段含源电路和复杂电路

在高中物理电路问题的教学中,经常用部分电路欧姆定律和全电路欧姆定律配合求解简单电路问题,但在求解一段含源电路和复杂电路问题时,采用这种方法往往无能为力。笔者在教学中尝试引入求解这类问题的有效方法——电势分析法,从而解决了上述困难,提高了学生对电路规律的认识.     

忆阻电路降维建模与特性分析

通过对蔡氏忆阻电路的数学建模分析,提出了忆阻电路动力学建模的降维问题.以包含两个磁控忆阻器的忆阻电路为例,进行了忆阻电路降维建模,由此建立了一个三维系统模型.基于该模型,分析了忆阻电路的平衡点和稳定性,研究了电路参数变化时忆阻电路的动力学特性.进一步,对包含两个磁控忆阻器的忆阻电路常规模型的分析结果和其降维模型的分析结果进行了比较.结果表明:忆阻电路降维模型的维数只与电容器的数量和电感器的数量有关,而与忆阻器的数量无关;当电路参数变化时忆阻电路存在分岔模式共存等非线性现象;降维建模降低了系统建模复杂度,有利于系统的动力学特性分析,但消除了忆阻器内部状态变量的初始条件对忆阻电路动力学特性的影响.     

忆阻元件与RLC以及二极管串并联电路的特性研究

对第四类基本电路元件:忆阻元件与RLC以及二极管串并联电路特性进行了研究,分别建立了两种电路的数学模型,并进行了仿真研究,分析了电路中的电容、电感、电阻等参数对电路特性的影响,得出了相关的结论.     

对四端蛛网电阻网络等效电路的研究

对电阻不相等的2×4阶蛛网电路,应用星形电路与多角形电路的等效互换方法和构建等效条件方法,将其等效为最简单的电路.计算了该电路A_1—A_4端钮之间的等效电阻,并用Multisim 12中的万用表对原电路和等效电路的A_1—A_4端钮之间的等效电阻进行了仿真测量.结果是理论计算与仿真测量结果一致.分析了3×4阶蛛网电阻网络的等效电路问题.这项研究的目的是把电阻不相等的四端蛛网电阻网络等效化简为在四端星形电路外端钮之间接有1~2个电阻的电路,以利于分析计算.介绍了对电路等效的一种新方法,即应用星形电路与多角形电路等效互换方法和构建等效条件方法,可以解决含有一般星形电路或多角形电路的等效化简问题.     

分段线性混沌电路的综合方法研究

本文研究了分段线性混沌电路的一种电路综合方法.首先根据电路系统的特征值参数,确定非线性元件参数和线性一端口电路的导纳.然后根据导纳函数确定与之对应的一端口电路形式.在电路综合过程中,本文采用两类基本导纳函数的并联形式实现一端口电路,可以始终使所用电感和电容为正值,所用负电阻共地,便于混沌电路的实现.最后给出了混沌系统电路综合的实例. 关键词： 混沌电路 综合 分段线性     

基于J-TEXT 装置的光耦合隔离放大器设计与分析

基于反馈技术设计了一款带宽2.7MHz、高线性度、低传输延时的光耦合隔离放大器,仿真分析了 I-V 转换电路补偿电容对电路频率特性的影响,并选择了合适的电路参数。将部分寄生参数考虑在内,建立了电路数学模型,仿真、测试与理论分析相结合研究了电路的线性度与频率特性。基于J-TEXT 装置静电探针悬浮电位测量系统验证了电路在系统中的可用性。     

适用于毫米波带状束行波放大器的光子晶体栅慢波电路研究

提出了一种适用于毫米波及THz波行波放大器的光子晶体栅慢波电路,即横向分布光子晶体栅慢波电路,并提出了分析和设计此类光子晶体栅慢波电路的方法.通过计算光子晶体TE极化的带隙和在带隙内将光子晶体栅慢波电路等效为矩形栅波导慢波电路,从而,光子晶体栅慢波电路的设计得以分为两步独立进行,从而简化了光子晶体栅慢波电路的设计.对横向分布光子晶体栅慢波电路进行了设计和计算,结果表明,与矩形栅波导慢波电路相比,横向分布光子晶体栅慢波电路可以降低工作电压并增加带宽,从而可以降低成本. 关键词： 行波放大器 光子晶体 毫米波 慢波电路     

一种高压电源谐振升压倍压电路

提出了一种高压电源谐振升压倍压电路,该电路由LC谐振电路与整流电路组成。对该电路的工作模式和稳态输出特性进行了分析;建立了该电路的数学模型:以归一化的形式定量描述了稳态输出电压与电流的增益、短路特性和开路特性、输出纹波与电压降、以及器件上的电应力,并分析了电路品质因数、归一化频率和电容比对输出特性的影响;对该电路进行了仿真与实验研究,仿真结果与实验结果具有很好的一致性,验证了数学模型的正确性。与C-W电路的对比研究结果表明:所提出的电路具有输出电压稳定、输出纹波小、短路特性好以及响应速度快的优点,满足高压小电流的应用需求。     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.