A new nonautonomous version of Chua's circuit: Experimental observations

In this study, a novel nonautonomous version of autonomous Chua's circuit is presented. The proposed nonautonomous version of Chua's circuit was designed by placing a sinusoidal source to the inner structure of the nonlinear resistor, namely, Chua's diode. The circuit's chaotic dynamics have been investigated by PSpice simulations and laboratory experiments.     

Fault diagnosis for analog circuits based on chaotic signal excitation

A fault diagnosis method for analog circuit is proposed in this paper. An all-purpose amplifier is taken as the typical circuit under test (CUT). The chaotic signal, which is generated by an improved Chua's circuit, is employed as the excitation signal of CUT. The algorithm for phase-space reconstruction of chaotic time series is a combination algorithm of multiple autocorrelation and Γ-test. The circuit state is estimated based on detecting the geometric change of Chua's attractor with a data-mining approach. For the purpose of information fusion, another eight features are extracted from the testing data to comprehensively determine the CUT states. A discussion is made for comparing the effectiveness of each feature according to the testing results.     

Circuit state analysis using chaotic signal excitation

A new testing method for analog circuit is proposed in this paper. A low-pass Butterworth filter is taken as the typical system under test (SUT) since the analog circuits in different types of electronic systems can be regarded as the low-, band- or high-pass active (passive) filters. The chaotic signal, which is generated by an improved Chua's circuit, is employed as the excitation signal of SUT. The SUT is a “narrowband” system compared with the bandwidth of input signal, whose state is analyzed with an error-tracking approach. The experimental result depicts that this testing method can efficiently detect the change of the circuit parameter. Besides, another eight features are extracted from the output signal of SUT for analyzing the SUT states. A discussion is made for comparing the effectiveness of each feature according to the testing results.     

Examination of chaotic behaviours using bond graph model

In this paper, modelling and simulation of Chua's chaotic oscillator, which exhibits rich chaotic behaviours, are presented by using the bond graph model. Up to now modelling of Chua's chaotic oscillator using bond graph model is not yet developed. The non-linear resistor in the circuit is modelled in this contribution by linear time-invariant components and ideal switches using piecewise linearization approach. The bond graph model of all the circuit including switches is then generated. Simulations are provided via the computer program called as BOMAS using the obtained bond graph model. Finally, Chua's circuit is verified experimentally. It is shown that all experimental and simulation results well agree with the chaotic behaviours of Chua's circuit.     

软件MATLAB在电力电子实践教学中的仿真应用

本文介绍了仿真软件MATLAB/SIMULINK的强大功能,详细地阐述了它在电力电子实践教学中的作用,并以三相桥式全控整流电路建模与仿真为例来说明。对学生掌握和理解电路的电能变换和控制原理相当有用。     

特示理论对直接知觉论的启示

美国心理学家詹姆士·吉布森开创的生态心理学被认为是一种直接的知觉理论范式,理论基础在于特示（specification）问题。特示主张,任何能量列阵（光、声音、作用力等）的结构都是特定物理事实的结果,因而能量列阵能够特定地指示该物理事实。如果特示关系是成立的,就意味着信息的形成外在于知觉过程,继而,知觉就是对外在形成信息的探索和拾取（information pickup）。对生态学进路知觉理论的批判、发展,必须以特示关系成立与否为理论源头。     

一种低噪声低失调电容读出电路

针对差分式电容传感器,提出了一种结构简单的低噪声、低失调电容读出电路.该电路由2相非交叠时钟控制,且对电路的寄生电容不敏感,可直接将传感器电容的变化量转化为电压信号输出.相关双采样(CDS, correlated double sampling)技术有效降低了电路的低频噪声和失调电压的影响,提高了读出电路的分辨率和动态范围.读出电路在0.35μm 2P4M标准CMOS工艺下设计流片,芯片面积为0.7mm×1.8mm,5V电源电压.电路工作在1MHz的时钟频率下,实现了0.4aF/√Hz的电容分辨率和118dB的动态范围.     

具有缓冲功能的三值极性变换GaAs电路

从三值ＧａＡｓ逻辑输出级电路的等效开关模型出发,探索了适用于指导ＧａＡｓ极性变换电路的设计。设计的电路已用ＰＳＰＩＣＥ程序予以模型,结果表明,它们具有正确的逻辑功能与理想的瞬态特性。     

Hopf bifurcation and synchronization of a five-dimensional self-exciting homopolar disc dynamo using a new fuzzy disturbance-observer-based terminal sliding mode control

Having found hidden hyperchaos in a 5D self-exciting homopolar disc dynamo, we study the existence of a Hopf bifurcation, which leads to unstable limit cycles bifurcating from a stable equilibrium. Hidden chaos with only stable equilibria can be observed from the Hopf bifurcation: a typical way to enable hidden attractors to be located. We then provide a new fuzzy controller, and a fast fuzzy disturbance observer, based on terminal sliding mode control for synchronization of the hyperchaotic system. Fuzzy inference is considered to weaken the chattering phenomena. Using Lyapunov stability theory, the stability of the closed-loop system is proved. Finally, simulations of synchronization are illustrated to show the efficient performance of the designed control method via external disturbances and dynamic uncertainties.     

基于PICmicro系列单片机的超声波测距仪设计

利用微处理机控制单元（MCU microprocessor control unit）控制的超声波测距仪系统,由PIC16F877单片机、超声波发射电路、超声波接收放大电路及显示电路组成。通过MCU控制时间计数,计算超声波自发射至接收的往返时间,从而得到实测距离。此系统具有易控制、工作可靠、测距准确度高和流程清晰等优点。     

Stability and Hopf bifurcation analysis of an eco-epidemiological model with delay

In this paper, an eco-epidemiological model with time delay is considered. The asymptotical stability of the three equilibria, the existence of stability switches about both the disease-free planar equilibrium and the positive equilibrium are investigated. It is found that Hopf bifurcation occurs when the delay τ passes through a critical value. Some explicit formulae determining the stability and the direction of the Hopf bifurcation periodic solutions bifurcating from Hopf bifurcations at the positive equilibrium are obtained by using the normal form theory and center manifold theory. Some numerical simulations for justifying the theoretical analysis are also provided. Finally, biological explanations and main conclusions are given.     

Secure chaotic communication based on extreme multistability

Extreme multistability is the coexistence of a large number of attractors which can be reached by varying initial conditions. In this paper we show how this fascinating phenomenon can be used for secure communication. The main advantage of the communication system based on extreme multistability over a conventional chaos-based communication system is its exceptionally high security. The proposed system consists of two identical six-order oscillators; one in the transmitter and another one in the receiver, each exhibiting the coexistence of a large number of chaotic attractors. The oscillators are synchronized using a private channel through one of the system variables, while the information is transmitted via a public channel through another variable. The information is encrypted by varying the initial condition of one of the state variables in the transmitter using a chaotic map, adhering message packages in a staggered form to the coexisting attractors within the same time series of another state variable, which leads to switching among the coexisting chaotic attractors. To ensure communication security, the duration of the packages is shorter than synchronization time, so that synchronization attacks are ineffective.     

The theory of the telephone receiver

The equations connecting the winding current and diaphragm motion of a telephone receiver under impressed simple harmonic electromotive and mechanical forces are formulated under: (I) The Maxwell flux theory; (2) the magnetizing-winding theory; (3) the Ampèrean resistanceless fixed molecular circuit theory of permanent magnetism; and (4) a general molecular orbital theory of ferromagnetism. On the latter theory it is found that the coupling coefficients M and N in the equations in question are in general different, in counter-distinction to the other three theories as hitherto formulated. The flux theory is shown not to be inconsistent with this result when certain dynamical phase relations are introduced into the static flux-magnetomotive force formula (Ohm's Law analog) always employed in this theory. The Ampèrean rigid circuit theory is criticized as an inadequate dynamical representation of ferromagnetism. The magnetizing-winding theory (dynamical) is reproduced in slightly generalized form.     

Parasitic tolerant designs of sampled data filters using switched capacitors and unity gain amplifiers

New and systematic procedures are presented for realizing sampled data filter (SDF) functions using switched capacitors (SCs) and unity gain amplifiers (UGAs). The procedures are attractive and simple to implement. Any SDF, recursive or non-recursive and of any order, can be realized using the methods presented. The designs of biquadratic SDFs is discussed in detail. The resulting realizations possess the property that the numerator and denominator coefficients of the SDF functions can be controlled by independent capacitance ratios. This makes the filters attractive for adaptive applications. The sensitivity properties of the resulting filters are analyzed and guidelines given for obtaining low sensitivity realizations. A method is also suggested to make the filters relatively insensitive to the parasitic capacitances in the circuit. Finally, a step by step procedure, easily implemented in a computer, is given. Starting from the given analog filter specifications, the method yields a design that has very low sensitivity, uses minimum total capacitance and is tolerant of the various parasitic capacitances in the circuit. Experimental results show very good agreement with the theoretical analysis.     

低功耗二甲醚复合燃料浓度检测仪的设计

本文描述了一种以MSP430微控器为核心的二甲醚复合燃料浓度检测仪,仪器具有浓度显示、报警和事件记忆等功能。为了降低系统功耗,采用了非关键部分分时工作机制,设计了敏感元件闭环限流电路,并给出了试验结果。实际应用证明该仪器功耗低、性能可靠、操作简便。     

电路分析中对受控源处理方法的探讨

受控源具有多样性、复杂性和特殊性,含受控源的电路分析会涉及到受控源的等效变换和处理方法,受控源的等效变换时,可根据实际情况,对控制量进行变异或不变异;应用电路定理列写电路方程时,既可将受控源当作电源,也可将受控源当作负载.     

An instrument for measuring short intervals of time

This paper describes a meter for measuring short intervals of time. Full scale deflections of 0.001, 0.1 and 1.0 second can be obtained by the use of a selector switch. This meter will indicate the length of time a contact remains closed, or the interval of time between the closing of one circuit and the opening of another. The device has a linear acale for any chosem range. It measures time by the charge which flows to a condenser during the interval. The charge is found by reading the potential difference 0n the condenser with a sensitive vacuum-tube voltmeter.The theory of the circuit and its advantage over other devices for the same purpose are discussed.     

Knowledge diffusion, market segmentation and technological catch-up: The case of the telecommunication industry in China

This paper examines the growth of technological capability in the telecommunication industry in China. We apply a modified version of Lee and Lim's [Lee, K., Lim, C., 2001. The technological regimes, catch-up and leapfrogging: findings from the Korean industries. Research Policy, vol. 30.] model of technological learning and catching-up. Using the three cases of the Shanghai Bell, the CIT-led R&D consortium, and indigenous companies such as Huawei, we analyze how the catching-up in the telecommunication industry occurred. We find that the important factors in the catch-up are the strategy of “trading market for technology,” the knowledge diffusion from Shanghai Bell both to the R&D consortium and to Huawei, and industrial promotion by the government. As a condition for successful catch-up, the paper points out that the technological regime of the telephone switches is featured by a more predictable technological trajectory and a lower cumulativeness. These conditions and strategies helped the Chinese firms to achieve a stage-skipping catch-up, namely, by skipping the stage of analogue electronic switches to jump to digital electronic switches.     

可调光大功率LED驱动器的研究与设计

介绍一种非隔离的单级功率因素校正恒流可调光大功率LED驱动电源。输入级采用CL滤波电路和填谷电路,有效地抑制了噪声和纹波干扰,提高了功率因素。通过电源管理芯片BP2808控制buck型降压拓扑,能使LED稳定地工作,并有效延长LED的使用寿命,并在开路、短路、过温等各种异常状态时保护驱动电源。利用红外遥控器发射红外信号,并通过51系列单片机接收处理红外信号和产生PWM波,能实现LED的调光。实验测试表明,该驱动电源性能可靠稳定,效率高,调光性能好。     

Frequency-coordinate vector diagram

From the standpoint of circuit synthesis as well as for a fundamental comprehension of circuit behavior, it is desirable to be able to visualize the response of a circuit over an extended frequency range by means of a geometrical construction. Mathematically, the response of a circuit can be expressed with the La Place transform theory as a function of the complex frequency variable, p = α + jωw, in which a is the decrement and ω is the “real” angular frequency. Physically, the nature of the real-frequency response is usually not discernible by casual inspection of the mathematical function. This paper develops a means of visualizing this frequency response readily through the construction of a vector diagram from the response function.