• Title/Summary/Keyword: Linear current source

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Development of Multi-Purpose Variable Polarization Imaging System for Clinical Diagnosis (임상 진단용 다목적 가변 편광 영상장치 개발)

  • Bae, Young-Woo;Jung, Byung-Jo
    • Journal of Biomedical Engineering Research
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    • v.28 no.2
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    • pp.265-270
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    • 2007
  • Polarization imaging systems have been widely used to selectively characterize skin lesions. Nevertheless, current systems are used in single-mode due to the limitations of a fixed polarization mode and a single-working distance of light source, in which uniform light distribution is achieved on target area. To address such limitations, we developed a variable polarization imaging system based on multi-working distance of light source for various clinical diagnoses. In this study, we characterize the imaging system and present experiment results demonstrating its clinical usefulness. The imaging system consists of a CCD color camera, linear polarization filters, and a single-layered LED ring light source which provides uniform light distribution at multi-working distances. The first polarizer was placed on the light source and the second polarizer placed on objective lens provides continuous linear polarization angle from $0^{\circ}\;to\;90^{\circ}$. The clinical efficacy of the imaging system was investigated by acquiring and analyzing clinical images of skin wrinkle and dental plaque. With the experiments, we verified the potential usefulness of the imaging system for other clinical applications.

Characteistics of a CMOS Differential Input-Stage Using a Source-Coupled Backgate Pair (Source-Coupled Backgate쌍을 이용한 CMOS 차동입력단의 특성)

  • Kang, Wook;Lee, Won-Hyeong;Han, Woo-Jong;Kim, Soo-Won
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.28A no.1
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    • pp.40-45
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    • 1991
  • It is well known that the conventional differential source-coupled pair uses gates as its input terminals. This input pair provids a high open-loop gain, a large CMRR, and a good PSRR. For these reasons, the input pair has been used widely as an input stages of the differential amplifiers, but a narrow linear input range of this structurelimits its application in the area of some analog circuit design. A novel CMOS source-coupled backgate pair is proposed in this paper. The bulk of MOSFET is exploited and input devices are biased to operate in ohmic region. With this topology, the backgate pair of the wide linear input range and variable transconductance can be obtained. This backgate input differential stage is realized with the size of W/L=50/25 MOSFETs. The results show the nonlinear error is less than $\gamma$1% over 10V full-scale range for the bias current of 200$\mu$A with 10V single power-supply.

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Controller Optimization Algorithm for a 12-pulse Voltage Source Converter based HVDC System

  • Agarwal, Ruchi;Singh, Sanjeev
    • Journal of Electrical Engineering and Technology
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    • v.12 no.2
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    • pp.643-653
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    • 2017
  • The paper presents controller optimization algorithm for a 12-pulse voltage source converter (VSC) based high voltage direct current (HVDC) system. To get an optimum algorithm, three methods namely conventional-Zeigler-Nichols, linear-golden section search (GSS) and stochastic-particle swarm optimization (PSO) are applied to control of 12 pulse VSC based HVDC system and simulation results are presented to show the best among the three. The performance results are obtained under various dynamic conditions such as load perturbation, non-linear load condition, and voltage sag, tapped load fault at points-of-common coupling (PCC) and single-line-to ground (SLG) fault at input AC mains. The conventional GSS and PSO algorithm are modified to enhance their performances under dynamic conditions. The results of this study show that modified particle swarm optimization provides the best results in terms of quick response to the dynamic conditions as compared to other optimization methods.

An Improved Control Approach for DSTATCOM with Distorted and Unbalanced AC Mains

  • Singh, Bhim;Solanki, Jitendra
    • Journal of Power Electronics
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    • v.8 no.2
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    • pp.131-140
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    • 2008
  • This paper presents a new control approach of DSTATCOM (distribution static compensator) for compensation of reactive power, unbalanced loading and harmonic currents under unbalanced non-sinusoidal ac mains. The control of DSTATCOM is achieved using Adaline based current estimator based on LMS algorithm to maintain source currents real and undistorted. The dc bus voltage of voltage source converter (VSC) working as DSTATCOM is maintained at constant voltage using a proportional-integral (PI) controller. The DSTATCOM system alongwith proposed control scheme is modeled in MATLAB to simulate the behavior of the system. The practical implementation of the DSTATCOM is carried out using dSPACE DS1104 R&D controller having TMS320F240 as a slave DSP. Simulated and implementation results are presented to demonstrate the effectiveness of the DSTATCOM with Adaline based control to meet the severe load perturbations with different types of loads (linear and non-linear) under distorted and unbalanced AC mains.

An Algorithm for Applying Multiple Currents Using Voltage Sources in Electrical Impedance Tomography

  • Choi, Myoung-Hwan;Kao, Tzu-Jen;Isaacson, David;Saulnier, Gary J.;Newell, Jonathan C.
    • International Journal of Control, Automation, and Systems
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    • v.6 no.4
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    • pp.613-619
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    • 2008
  • A method to produce a desired current pattern in a multiple-source EIT system using voltage sources is presented. Application of current patterns to a body is known to be superior to the application of voltage patterns in terms of high spatial frequency noise suppression, resulting in high accuracy in conductivity and permittivity images. Since current sources are difficult and expensive to build, the use of voltage sources to apply the current pattern is desirable. An iterative algorithm presented in this paper generates the necessary voltage pattern that will produce the desired current pattern. The convergence of the algorithm is shown under the condition that the estimation error of the linear mapping matrix from voltage to current is small. Simulation results are presented to illustrate the convergence of the output current.

Observation of saturation transfer characteristics in solution processed vertical organic field-effect transistors (VOFETs) with high leakage current

  • Sarjidan, M.A. Mohd;Shuhaimi, Ahmad;Majid, W.H. Abd.
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1415-1421
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    • 2018
  • Unlike ordinary organic field-effect transistors (OFETs), saturation current is hardly to be found in vertical OFETs (VOFETs). Moreover, the fabrication process of patterned sourced for VOFETs is quite complex. In this current work, a simple solution processed VOFET with directly deposited intermediate silver source electrode has been demonstrated. The VOFET exhibits a high leakage current that induces an inversion polarity of its transistor behavior. Interestingly, a well-defined saturation current was observed in the linear scale of transfer characteristic. The VOFET operated with high-current density > $280mA/cm^2$ at $V_d=5V$. Overview potential of the fabricated device in display application is also presented. This preliminary work does open-up a new direction in VOFET fabrication and their application.

CONVERTER DESIGN AND CONTROL OF PIEZOELECTRIC ACTUATORS IN SLIDING MODE OPERATION

  • Palis F.;Heller D.
    • Proceedings of the KIPE Conference
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    • 2001.10a
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    • pp.785-789
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    • 2001
  • Piezoelectric actuators are characterized by non-linear dynamics and high frequency oscillations of the piezocrystal. Both properties have to be taken into consideration when optimizing real time systems. Taking benefit of the almost linear behaviour between charge and strain, current source fed piezoelectric actuators are given preference for high dynamic applications. Here special emphasis is put on current sources for multi-actuator systems and the controller design for optimal system integration of the actuator. It is shown that sliding mode operation of the converter system offers good possibilities to guaranty high accuracy and dynamics of the actuators system. The presented multi-actuator system is used for positioning and vibration damping in flexible mechanical systems.

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Fiber-Optic Current Sensor Using a Faraday Rotator Glass Fiber Sensor Coil (Faraday Rotator Glass 광섬유 전류센서)

  • 김기혁;송민호
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.18 no.4
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    • pp.28-33
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    • 2004
  • We developed a fiber-optic CT for large current monitoring in power systems. We used a FRG fiber sensor coil to suppress CT output degradation caused by linear birefringence, and different optical sources were used to compare their noise characteristics. From the experiments, we obtained output variation less than $\pm$0.4(%) when the sensor coil suffered mechanical perturbations, and the ASE source showed -23(㏈) less noise in the output than singlemode laser diode.

Design of the Detection Circuitry for the Characteristics of Micromachined Vibrating Gyroscope (미세가공 진동형 자이로스코프의 특성 감지 회로의 설계에 관한 연구)

  • U, Yeong-Sin;Byeon, Gwang-Gyun;Seo, Il-Won;Seong, Man-Yeong
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.10
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    • pp.687-692
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    • 1999
  • A new technique to measure low level capacitance variations of the gyroscope is proposed and verified by computer simulation. It is based on the new CV(capacitance-voltage) converter circuit biased by dc current source and the peak detector without low pass filter. The CV converter biased by dc current source provides good signal-to-noise ratio and this setup of the detection circuitry without low pass filter makes it possible to provide short settling time, that is, higher speed of measurement and wide operation range if only a few parameters are adjusted. The key parameters that affect the performance of the detection circuitry are illustrated and computer simulation results are presented. The demonstrated detection circuitry shows linear response from 10 fF to 130 fF at 10 kHz and shows good linearity.

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Nonlinear Motion Responses of a Moored Ship beside Quay (안벽에 계류된 선박의 비선형 운동응답)

  • 이호영;임춘규;유재문;전인식
    • Journal of Ocean Engineering and Technology
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    • v.17 no.4
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    • pp.8-15
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    • 2003
  • When a typoon sets into harbour, a moored ship shows erratic motions and even mooring line failure may occur. such troubles may be caused by harbour resonance phenomena, resulting in large motion amplitudes at low frequency, which is close ti the natural frequency of th moored ship. The nonlinear motions of a ship moored to quay are simulated under external forces due to wave, current including mooring forces in time domain. The forces due to waves are obtained from source and dipole distribution method in the frequency domain. The current forces are calculated by using slow motion maneuvering equation in the horizontal plane. The wind forces are calculated from the empirical formula of ABS and the mooring forces of ropes and fenders are modeled as linear spring.