• 전기학회논문지
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• 제58권1호
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• pp.126-131
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• 2009

This study was carried out for the reliability of PD(Partial Discharge) pattern recognition. For the pattern recognition, the database for PD was established by use of self-designed insulation defects which occur and were mostly critical in GIS(Gas Insulated Switchgear). The acquired database was analyzed to distinguish patterns by means of PRPD(Phase Resolved Partial Discharge) method and stored to the form with to unite the average amplitude of PD pulse and the number of PD pulse as the input data of neural network. In order to prove the performance of genetic algorithm combined with neural network, the neural networks with trial-and-error method and the neural network with genetic algorithm were trained by same training data and compared to the results of their pattern recognition rate. As a result, the recognition success rate of defects was 93.2% and the neural network train process by use of trial-and-error method was very time consuming. The recognition success rate of defects, on the other hand, was 100% by applying the genetic algorithm at neural network and it took a relatively short time to find the best solution of parameters for optimization. Especially, it could be possible that the scrupulous parameters were obtained by genetic algorithm.

• 한국통신학회논문지
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• 제35권12B호
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• pp.1244-1250
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• 2010

본 논문에서는 고속으로 이동하는 표적을 탐지 및 레인징하기 위해서 높은 PRF(Pulse repetition frequency)로 동작하는 레이더의 신호처리 알고리즘을 제시한다. 제시된 방법은 준주기성(quasi-periodic) 펄스열을 사용하므로써 이동표적의 도플러 정보를 추정하고 이를 보상해서 코히어런트하게 레인지 프로세싱 하는 것으로 기존 방식과는 달리 도플러 프로세싱이 레인지 프로세싱에 선행되며 이를 통해서 SNR이 낮은 잡음 환경에서도 표적 탐지 및 레인징이 가능함을 보인다. 제시된 알고리즘을 수학적으로 유도하고 디지털 신호처리를 위한 도플러/레인징 샘플링 조건, 프로세싱 시간 및 도플러 오차가 성능에 미치는 영향에 대해 기술하고 시뮬레이션을 통해서 이를 검증한다.

• Journal of Magnetics
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• 제19권2호
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• pp.197-204
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• 2014

A transcranial magnetic stimulation device is a complicated appliance that employs a switching power device designed for discharging and charging a capacitor to more than 1 kV. For a simple transcranial magnetic stimulation device, this study used commercial power and controlled the firing angle using a Triac power device. AC 220V 60 Hz, the power device was used directly on the tanscranial magnetic stimulation device. The power supply device does not require a current limiting resistance in the rectifying device, energy storage capacitor or discharge circuit. To control the output power of the tanscranial magnetic stimulation device, the pulse repetition rate was regulated at 60 Hz. The change trigger of the Triac gate could be varied from $45^{\circ}$ to $135^{\circ}$. The AVR 182 (Zero Cross Detector) Chip and AVR one chip microprocessor could control the gate signal of the Triac precisely. The stimulation frequency of 50 Hz could be implemented when the initial charging voltage Vi was 1,000 V. The amplitude, pulse duration, frequency stimulation, train duration and power consumption was 0.1-2.2T, $250{\sim}300{\mu}s$, 0.1-60 Hz, 1-100 Sec and < 1 kW, respectively. Based on the results of this study, TMS can be an effective method of treating dysfunction and improving function of brain cells in brain damage caused by ischemia.

• 한국재료학회지
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• 제11권9호
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• pp.792-796
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• 2001

For electron beam lithography and SEM(scanning electron microscopy) applications, miniaturized electrostatic lenses called a microcolumn have been fabricated. In this paper, we report the fabrication technique for 20~30$\mu\textrm{m}$ apertures of electron lenses based on silicon and Mo membrane using an active Q-switched Nd:YAG laser. Experimental conditions of laser micromachining for silicon and Mo membrane are improved. The geometrical structures, such as the diameter and the preciseness of the micron-size aperture are dependent upon the total energy of the laser pulse train, laser pulse width, and the diameter of laser spot.

• 한국철도학회논문집
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• 제15권4호
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• pp.357-363
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• 2012

본 논문에서는 단상PWM컨버터 차량의 새로운 운전방식에 대해 기술하였다. 최근의 전기차량은 PWM 컨버터를 채택함으로써 그 이전의 차량들에 비하여 역률을 1.0에 가깝도록 유지할 수 있게 되었다. 그러나 이들 차량은 컨버터 제어방식의 비교적 간단한 수정을 통하여 진상 역률 영역에서의 운전이 가능한데, 이러한 특징은 차량 자체만으로는 큰 의미가 없을지 모르나 급전계통과 연계하여 검토하는 경우 선로의 무효전력 손실을 보상함으로써 급전선로의 유효전력 손실을 감소시키고 전압 분포를 개선하는 효과를 나타내게 된다. 이동형 보상장치가 될 수 있다는 특징으로 무효전력 보상을 위해 일반적으로 검토되는 SVC와 비교해도 장점을 가지게 된다. PWM컨버터차량의 진상운전 조건 및 관련식의 유도와 함께 이러한 방식을 적용하기 위한 새로운 역률 제어 알고리즘을 제시하였다. SIMULINK 모델을 사용한 모의를 통하여 제시된 방법의 실 적용 가능성을 검토하였으며 만족할 만한 결과를 얻을 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.319-322
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• 1990

Self-controlled permanent magnet synchronous motor (PMSM) has similar operating characteristics as seperately excited dc motor. It is favored in servo applications due to its improvement of efficiency and maintenance. This paper presents completely digitalized controller using microprocessor and voltage fed inverter. The speed control system for PMSM is implemented. To control the motor speed, the control system regulates the magnitude of Inverter output voltage by regular-sampled PWM method to generate sinusoidal PWM wave with microprocessor. And to keep the range of inverter switching frequency, it varies the number of pulse train according to the speed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.352-356
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• 1997

This paper present the design of a novel neural-network (NN) based pulse-width modulation (PWM) techniques for a three-level power converter of electric trains along with nonlinear mapping of essential switching patterns and fault tolerance, which are inherent characteristics of NNs. Considering the importance of safety, power factor and harmonics of electric train power converters, two-level type and three-level type of power converters using NNs are precisely investigated and compared in computer simulation. A computer simulation shows that a new current control scheme provides an improved performance over a fixed-band hysteresis current control in many aspects.

• 전자공학회논문지D
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• 제35D권8호
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• pp.53-61
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• 1998

Dynamic characteristics of widely tunable SGDBR/SSGDBR laser diodes integrated with an electroabsorption modulator is inestigated using an improved large-signal timef-domain model. First, wide tunning properties of a SGDBR laser diode and a SSGDBR laser diode are analyzed respectively and compared with each other. And, intensity-modulation characteristics of a SGDBR laser diode incorprating an electroabsorption modulator are investigated. It is shown that an external modulation has the lower frequency chirp by 1/20 for almost same extinction ratios than a direct modulation, and a nearly transform-limited pulse train can be generated using the optical gating of an electroabsorption modulator.

• 한국자동차공학회논문집
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• 제25권3호
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• pp.273-286
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• 2017

We develop an inspection method for bearing faults with a rapid change in the rotation speed and present indexes for the pass/fail inspection. At the end of line, impulse noises generated by the operation of machines and conveyors may distort the inspection results. In this paper, we present robust inspection indexes for bearing faults under impulse noises, by taking into account fault signals having pulse train. Using logistic regression, we optimize the pass/fail criterion for each index and evaluate the performance of the inspection indexes based on the total error rate.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.153-158
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• 2004

The security system using optical fiber is a system, circulating infrared rays laser pulse on the optical fiber which is attached on the security fence to prevent invasion, which can show invasion position with visible and audible signal on the situation monitor if an invader cut or pull the security fence with minuteness of 10m. The optical fiber can be also applied for the bed structure stability monitoring system of high speed train as well as security system. To apply this system for high speed railroad bed structures, this system will give an alarm if it detect excessive tension, shrinkage, deflection which is beyond the limit of structure, that will prevent serious railroad accident. In this paper, we like to propose that applying this system for security and structure stability can improve confidence and stability on operation of railways