Design of switched-capacitor filters using non-ideal op amps

A general synthesis procedure is given for the realization of switched-capacitor filters in the z-domain. The method uses biphased switches, capacitors and non-ideal op amps with finite gain-bandwidth product. The design includes at the outset the effects of the op amp gain-bandwidth product. Two examples are given which have been verified by a computer program.     

Modeling switched circuits based on wavelet decomposition and neural networks

In this paper, switched circuits are modeled based on wavelet decomposition and neural network. Also describes the usage of wavelet decomposition and neural network for modeling and simulation of nonlinear systems. The switched circuits are piecewise-linear circuits. At each position of switch the circuit is linear but when considered all switching positions of the circuit it becomes nonlinear. An important problem which arises in modeling switched circuit is high structural complexity. In this study, wavelet decomposition is used for feature extracting from input signals and neural network is used as an intelligent modeling tool. Two performance measures root-mean-square (RMS) and the coefficient of multiple determinations (R²) are given to compare the predicted and computed values for model validation. The evaluated R² value is 0.9985 and RMS value is 0.0099. All simulations showed that the proposed method is more effective and can be used for analyzing and modeling switched circuits. When we consider obtained performance, we can easily say that the proposed method can be used efficiently for modeling any other nonlinear dynamical systems.     

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.     

Chip in a lab: Microfluidics for next generation life science research

Microfluidic circuits are characterized by fluidic channels and chambers with a linear dimension on the order of tens to hundreds of micrometers. Components of this size enable lab-on-a-chip technology that has much promise, for example, in the development of point-of-care diagnostics. Micro-scale fluidic circuits also yield practical, physical, and technological advantages for studying biological systems, enhancing the ability of researchers to make more precise quantitative measurements. Microfluidic technology has thus become a powerful tool in the life science research laboratory over the past decade. Here we focus on chip-in-a-lab applications of microfluidics and survey some examples of how small fluidic components have provided researchers with new tools for life science research.     

A microfluidic platform for studying the effects of small temperature gradients in an incubator environment

Studies on the effects of variations in temperature and mild temperature gradients on cells, gels, and scaffolds are important from the viewpoint of biological function. Small differences in temperature are known to elicit significant variations in cell behavior and individual protein reactivity. For the study of thermal effects and gradients in vitro, it is important to develop microfluidic platforms which are capable of controlling temperature gradients in an environment which mimics the range of physiological conditions. In the present paper, such a microfluidic thermal gradient system (μTGS) system is proposed which can create and maintain a thermal gradient throughout a cell-seeded gel matrix using the hot and cold water supply integrated in the system in the form of a countercurrent heat exchanger. It is found that a uniform temperature gradient can be created and maintained in the device even inside a high temperature and high humidity environment of an incubator. With the help of a hot and cold circuit controlled from outside the incubator the temperature gradient can be regulated. A numerical simulation of the device demonstrates the thermal feature of the chip. Cell viability and activity under a thermal gradient are examined by placing human breast cancer cells in the device.     

Adaptive iterative learning control for MIMO nonlinear systems performing iteration-varying tasks

The present work aims to develop a novel adaptive iterative learning control(AILC) method for nonlinear multiple input multiple output (MIMO) systems that execute various control missions with iteration-varying magnitude-time scales. In order to reduce the variations of the systems, this work proposes a series of time scaling transformations to normalize the iteration-varying trial lengths. An AILC scheme is then developed for the transformed control systems on a uniform trial length, which is shown to be capable of ensuring the asymptotic convergence of the tracking error. In other words, the proposed AILC algorithm is able to relax the constraint in conventional ILC where the control task must remain the same in the iteration domain. Additionally, the basic assumption in classic ILC that the control system must repeat on a fixed finite period is also removed. The convergence analysis of the AILC is derived rigorously according to the composite energy function (CEF) methodology. It is shown that the newly developed learning control strategy works well for control plants with either time-invariant or time-varying parametric uncertainties. To show the effectiveness of the AILC, three examples are illustrated in the end. Meanwhile, the proposed learning method is also implemented to a traditional X–Y table system.     

Characteristics of small grid-controlled hot-cathode mercury arcs or thyratrons

The principle of the grid-controlled arc or thyratron is briefly described and the norminal ratings as regards filament current, maximum plate current etc. of four important thyratrns are given in table form. Methods of measuring the grid current, critical grid potential, etc., with D.C. power supply are given along with the results obtained on the General Electric Company thyratrons FG-₁₇, FG-₂₇ and FG-₆₇. Characteristics obtained with A.C. power supply are also shown for these thyratrons and some of the relative advantages of the “phase-shift” and the “critical potential” methods of control are discussed when used in connection with photoelectric cell circuits. The A.C. measurements seem to show that a time of 10^?3 second is required to start a thyratron. An amplifier circuit is shown by which it is theoretically possible to control a thyratron circuit using an input current to the amplifier of 10^?11 ampere.     

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。     

Thoria as a cathode emitter

This paper outlines the cathode characteristics of thoria which lead to its selection in certain cases where the barium-strontium oxide cathode is unsuitable. Dependable values of pulsed thermionic emission of 4 amps/cm.² at 1600° C. and 14 or 15 amps/cm.² at 1800° C. are available.The decay of emission with time is much less rapid than with barium-strontium oxides, the time constants being of the order of one-tenth of 1 second. Maximum d-c. emission, that is, equilibrium emission after decay, is found to be between 1 and 5 amps/cm.². Although when compared to barium-strontium oxide the activation phenomena are not prominent, it is found that the same essential pattern exists. For use in pulsed applications the life of a thoria coated cathode is determined by its evaporation rate. At 1800° C. where 14 amps/cm.² is available the coating disappears at the rate of 1 mil thickness in about 300 hours.     

一种电流型PWM控制芯片的设计

本文借助Hspice和Cadence等EDA设计工具设计了一种电流模式的PWM控制电路芯片。重点研究了其中的核心模块电路:基准电压、PWM比较器、误差放大器(EA)、振荡电路、驱动电路和一系列保护电路。仿真结果表明设计的基准电压源具有较小的温度系数,能够在较宽的电源电压下正常工作,整体应用电路能够有效地调控工作。     

基于RT器件的数据选择器和D锁存器设计

以共振隧穿二极管(resonant tunneling diode)和三端共振隧穿器件RTD/HEMT为基本单元,设计了一个全新的1-of-2数据选择器,并以该数据选择器为核心电路,实现了基于RT器件的D锁存器,SPICE仿真结果验证了设计的正确性,为利用RT器件设计时序电路提供了一个简单有效的设计方法.本文所设计的电路具有量子器件的低功耗、高速等优点.     

Off-line isolated handwritten Thai OCR using island-based projection with n-gram model and hidden Markov models

Many traditional works on off-line Thai handwritten character recognition used a set of local features including circles, concavity, endpoints and lines to recognize hand-printed characters. However, in natural handwriting, these local features are often missing due to rough or quick writing, resulting in dramatic reduction of recognition accuracy. Instead of using such local features, this paper presents a method called multi-directional island-based projection to extract global features from handwritten characters. As the recognition model, two statistical approaches, namely interpolated n-gram model (n-gram) and hidden Markov model (HMM), are proposed. The experimental results indicate that the proposed scheme achieves high accuracy in the recognition of naturally-written Thai characters with numerous variations, compared to some common previous feature extraction techniques. Another experiment with English characters also displays quite promising results.     

A spectral theoretic approach to fault analysis in linear sequential circuits

A stepwise fault analysis procedure for the class of digital circuits known as Linear Sequential Circuits (LSC) is presented where the LSC is defined over a finite field. The development of a spectral theory for this class of systems provides a mechanism for exploiting the LSC's memory. This, in general, allows fewer test inputs than would be required for fault analysis of a memoryless circuit of similar complexity.     

人工基因线路的研究进展和未来挑战

基因线路是生命体对自身生命过程控制的动态调控系统。在工程化的设计原理的指导下,人工基因线路是对天然基因调控线路进行简单化处理和重新编程,以及引入自然界不存在的人造法则。人工基因线路由遗传开关、生物振荡器、逻辑门等组成,以执行诸多调控功能。多种多样的人工基因线路设计与构建,不仅极大地促进了人们对生命调控基本规律的认识,也进一步丰富了人们对天然的生物系统进行改造、再创的手段,并为医药健康、农业环境和工业发酵等领域的实际需求提供了全新解决方案。虽然在过去20年里,人们在人工基因线路领域取得了丰硕的研究成果,但是细胞体内蕴含着的众多复杂生化反应和信号传导途径,为设计和组装具有更加高级功能的基因线路带来了挑战。相应地,如何实现微小细胞内复杂基因线路的可预测设计组装,如何保障基因线路在复杂的体内外环境下发挥稳健的功能,将成为未来几年人工基因线路研究的关键核心问题和势必克服的重大挑战。     

WCCA分析中电感电容的PSpice建模优化

基于PSpice的最坏情况电路分析(WCCA)是检视器件和电路可靠性的有效工具,速一高级仿真应用对器件模型的准确度做出了很高的要求.为了提高WCCA仿真结果的真实性,保证电路极限分析的可信度,本文对电感电容的传统建模方式加以改进,提出了一种以元件内部拓扑结构为基础的建模方法,并通过一个电路仿真实例验证了这种模型构建方式的准确性和实用性.     

一种50M采样速率CMOS采样/保持电路

介绍了一种高性能CMOS采样/保持电路，在0.35-μm工艺、3.3-V电源和18-mW功耗下，实现了50-MHz采样频率，输入直到奈奎斯特频率仍能达到10位精度的要求。电路采用全差分结构、底极板采样、栅压自举开关技术、增益自举的折叠共源共栅跨导核心运算放大器和钳制共模电平的电平控制放大器。     

Extended dissipative analysis for uncertain T–S fuzzy system with time-varying delay and randomly occurring gain variations

This paper is concerned with the non-fragile dynamic output feedback control for uncertain T–S fuzzy systems with time-varying delay and randomly occurring gain variations (ROGVs). Considering the imperfect premise matching that the T–S fuzzy model and the fuzzy controller do not have the same membership function, the purpose is to enhance the robustness of the system and the flexibility of the controller design. By adjusting the free weight matrix in the concept of extended dissipative, H_∞, $L_2-L_{\infty },$ passive and (Q, S, R)-dissipative performance are solved in a unified framework. Stochastic phenomenon ROGVs is considered to describe the impact of the controller gain variations in the system, which is designed into two sequences of random variables and obey the Bernoulli distribution. Based on Lyapunov–Krasovskii functional (LKF) and integral inequality technique, some less conservative sufficient conditions are obtained to guarantee the close-loop system is asymptotically stable and extended dissipative. By solving the linear matrix inequalities (LMIs), a non-fragile dynamic output feedback controller can be developed. The advantage and effectiveness of the proposed design method can be illustrated by several numerical examples.     

Event-triggered control for active vehicle suspension systems with network-induced delays

This paper presents a novel event-triggered H_∞ static output-feedback control for active vehicle suspension systems with network-induced delays. The proposed control schema introduces an event-triggering mechanism in the suspension system such that the communication resources can be significantly saved. By applying some improved slack inequalities and an augmented Lyapunov–Krasovskii functional (LKF), a new design condition expressed in the form of linear matrix inequalities (LMIs) is developed to derive the desired event-triggered controller. The obtained algorithm is then employed to solve the static output-feedback control gain. Compared with the traditional sampled-data H_∞ control scheme, the proposed controller is able to provide an enhanced disturbance attenuation level while saving the control cost. Finally, comparative simulation results are provided to show the performance of the proposed event-triggered controller.