• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.664-667
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• 2011

In this paper, threshold voltage characteristics have been analyzed as one of short channel effects occurred in double gate(DG)MOSFET to be next-generation devices. The Gaussian function to be nearly experimental distribution has been used as carrier distribution to solve Poisson's equation, and threshold voltage has been investigated according to projected range and standard projected deviation, variables of Gaussian function. The analytical potential distribution model has been derived from Poisson's equation, and threshold voltage has been obtained from this model. Since threshold voltage has been defined as gate voltage when surface potential is twice of Fermi potential, threshold voltage has been derived from analytical model of surface potential. Those results of this potential model are compared with those of numerical simulation to verify this model. As a result, since potential model presented in this paper is good agreement with numerical model, the threshold voltage characteristics have been considered according to the doping profile of DGMOSFET.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.2
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• pp.128-137
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• 1999

Recently the pelionnance of CO2 arc welding machine has been advanced significantly through the adoption of i invelter circuit topology. which made it possible to improve welding perfonnances such as spatter generation and bead s state. But the conventional inverter arc welding machine generates constant output voltage which cause much spatter g generation dUling short-circuit and arc start time because it is unable to control output current instantaneously. So this p paper representes wavefCnm controlled inverter arc welding machine which control the wavefonn of welding current and t thus to suppress the spatter generation. And the system designed in this paper is the digital controller using single chip m microprocessor of 80C196KC. As a result of perfonnance test for this system, the spatter generation is reduced and s shOlt-circuit time period is stabilized compared to conventional one. And more by using switched mode rectifier for A AC/DC power convelter. unity power factor is maintained and low order halmonic spectrum is supressed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.1-11
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• 2009

In this paper, a new 1 kW power amplifier with high efficiency and high stability in a RF generator is designed and fabricated for plasma applications. The efficiency of power amplifier is improved by using class-E amplifier that consists of one push-pull MOSFET and high current drive IC instead of class-C amplifier composed of several single ended MOSFET. Switchable damper that allows selecting three different modes of amplifiers for considering efficiency and stability is added into the amplifier for plasma applications. Stable region of an early electronic discharge section is extended to VSWR of 4.5:1 compared to conventional VSWR of 3.8:1 through using switchable damper. The dimension of the amplifier is also reduced to 30 % of conventional amplifier. The 80 % efficiency of power amplifier with switchable damper is obtained the output power of 1 kW in operating frequency of 13.56 MHz. In comparison of conventional power amplifier for plasma applications, 13 % efficiency is improved.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.12-21
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• 2004

Error control is one of major concerns in many electronic systems. Experience shows that most malfunctions during system operation are caused by transient faults, which often mean abnormal signal delays that may result in violations of circuit element timing constraints. This paper presents a novel CMOS-based concurrent timing error detector that makes a flip-flop to sense and then signal whether its data has been potentially corrupted or not by a setup or hold timing violation. Designed circuit performs a quiescent supply current evaluation to determine timing violation from the input changes in relation to a clock edge. If the input is too close to the clock time, the resulting switching transient current in the detection circuit exceeds a reference threshold at the instant of the clock transition and an error is flagged. The circuit is designed with a $0.25{\mu}m$ standard CMOS technology at a 2.5 V supply voltage. The validity and effectiveness are verified through the HSPICE simulation. The simulation results in this paper shows that designed circuit can be used to detect setup and hold time violations effectively in clocked circuit element.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.55-62
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• 2006

This paper presents experimental evaluation of an insect-mimicking flapping-wing device actuated by a unimorph piezoceramic actuator. Length of each rod and hinge point in the linkage/amplification system are carefully chosen such that the resulting wing motion can mimic clapping of wings in a real insect at the end of upstroke. In addition to this, a pair of corrugated wings are fabricated mimicking zig-zag cross section of a real insect wing. Thanks to the two additional implementation, the improved flapping wing device can generate a larger lift force than the previous model even though area of the new wing is about 50% less than that of the previous wing. In this work, effects of the wing clapping, the wing corrugation, and the input wave form on the lift force generation have been also experimentally investigated. Finally, the vortex generated by the flapping device has been captured by a high speed camera, showing that vortices are produced during up- and down-strokes.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.38-48
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• 2014

In this paper, a design of Signal Processing Analog Front-End IC for Automotive Piezo-Resistive Type Pressure Sensor is presented. In modern society, as the car turns to go from mechanical to electronic technology, the accuracy and reliability of electronic parts required importantly. In order to improve these points, Programmable Gain Amplifier (PGA) amplifies the received signal in accordance with gain for increasing the accuracy after PRT Sensor is operated to change physical pressure signals to electrical signals. The signal amplified from PGA is processed by Digital blocks like ADC, CMC and DAC. After going through this process, it is possible to determine the electrical signal to physical pressure signal. As processing analog signal to digital signal, reliability and accuracy in Analog Front-End IC is increased. The current consumption of IC is 5.32mA. The die area of the fabricated IC is $1.94mm{\times}1.94mm$.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.345-346
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• 2008

최근에 콘덴서 뱅크에서 자주 일어나는 고장의 유형은 콘덴서의 내부절연파괴, 리액터의 소손이 주를 이루고 있다. 그중에서 콘덴서 셀의 절연파괴가 수대에서 십 수대까지 동시에 발생하기도 한다. 이러한 현상의 대부분은 차단기의 투입 시 서지전압과 전류에 의해 서서히 진행 혹은 갑작스런 고장으로 진행되고 있다. 이중에서 저항기의 절연열화가 진행되면 차단기 투입 시 순간적인 절연파괴를 일으켜 급준파의 전류를 더 급준하게 만들면서 콘덴서나 리액터의 열화를 더욱 더 가중시키며 순간적으로 저항기의 역할을 못하게 되어 안정상태를 더욱 해치는 역할을 수행하게 된다. 이 논문에서는 콘덴서 뱅크와 중성점 저항기의 특성을 분석하고 중성점 저항기의 절연성능을 보강하여 전, 후의 서지전류 특성을 비교함으로써 실제 계통에서 중성점 저항기의 절연열화가 콘덴서 뱅크에 미치는 영향에 대해서 알아보고자 한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.231-239
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• 1999

An improved version of current-regulated delta modulator (CRDM) is investigated for the output cunent control of v voltage-source inverters that have transformer-coupled series resonant load and are operated at the resonant frequency. Conventional CRDM has not only CUlTent offset problem but also transformer flux saturation problem when i it is applied to induction heating systems that have transformel-coupled loads. To cope with these problems, the effect of flux saturation is analysed, and simple method to av이d the problem is proposed. And integral type of CRDM is a adopted to remove the cunent offset. The boundaries of integrator gain for stable operation is calculated using the c concept of sliding mode controL The validity of proposed strategy is vel퍼ed through simulations and prototype e experiments.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.1-8
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• 2006

The purpose of this study is to experimentally analysis the eletrokinetic phenomena and remediation characteristics developed during the application of electrokinetic remediation technique to unsaturated soils contaminated by heavy metals. In the laboratory a series of column tests are performed on degree of saturation for shooting range soil. The test results indicated that Pb is mainly removed under unsaturated conditions by electromigration within diffuse double layer, and if the initial containment concentration is below cation exchange capacity and equals to adsorption per unit soil solid weight, the remedial efficiency decreases with the decreasing of transport efficiency due to the changes in the degree of saturation in the electric gradient of 1V/cm.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.335-342
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• 2004

This paper describes a trans-admittance scanner for breast cancer detection. A FPGA-based sinusoidal waveform generator produces a constant voltage. The voltage is applied between a hand-held electrode and a scan probe placed on the breast. The scan probe contains an 8x8 array of electrodes that are kept at the ground potential. Multi-channel precision digital ammeters using the phase-sensitive demodulation technique were developed to measure the exit current from each electrode in the array. Different regions of the breast are scanned by moving the probe on the breast. We could get trans-admittance images of resistor and saline phantoms with an anomaly inside. The images provided the information on the depth and location of the anomaly. In future studies, we need to improve the accuracy through a better calibration method. We plan to test the scanner's ability to detect a cancer lesion inside the human breast.