• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.806-809
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• 1988

The frequency response characteristics of a bimorph type PZT piezoelectric transducer was investigated. In this study, function generator which generates short burst signal, plane reflection plate and oscilloscope were used to measure the characteristics of piezoceramic ultrasonic transducer. The resonant frequency of a bimorph type piezoceramic transducer which is acquired by using Tone-Burst Method had good agreement with the measured results from spectrum analyzer.

• 조명전기설비학회논문지
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• 제26권5호
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• pp.85-90
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• 2012

In this paper, it was investigated experimentally that diameter and polarity variation of corona wire electrode affected to ozone generation of the ozone generator using a wire-to-plate type electrode. The change in the diameter(D) of the corona wire electrode has a great effect upon ozone generation, higher influence appears in the positive corona discharge than the negative corona discharge. In the case of D=0.50[mm], maximum ozone generation and power efficiency could be obtained. However, in the case of smaller D than this, the ozone generation and efficiency decreases slowly and in the case of larger D, the ozone generation decreases rapidly. It means performance decline as an ozone generator. Therefore, ozone generation and power efficiency would increase through simple optimization of the corona electrode specification.

• 대한기계학회논문집B
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• 제33권10호
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• pp.757-766
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• 2009

In the present study, the effect of delta-wing vortex generators(DWVG) on the local heat transfer of the plate fin-oval tube was experimentally analyzed for Reynolds numbers for 2000, 2500 and 3200. The local heat transfer coefficient of the fin surface for four type DWVGs was measured by the naphthalene sublimation technique. As the results, the distribution of the heat transfer coefficient at rear of DWVGs showed longitudinal contours for common flow down DWVGs and wavy contours for common flow up DWVGs. The distribution showed many cell type contours at near wall and downstream for all DWVGs. Compared to case without DWVGs in present experimental tests, all DWVGs showed the best enhancement of heat transfer at Re=2000. Of 4 cases of DWVGs, D type showed the best enhancement of heat transfer.

• 대한기계학회논문집B
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• 제29권10호
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• pp.1139-1147
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• 2005

The shape optimal design of the plate-fin type heat sink with vortex generator is performed to minimize the pressure loss subjected to the desired maximum temperature numerically. Evaluation of the performance function, in general, is required much computational cost in fluid/thermal systems. Thus, global approximate optimization techniques have been introduced into the optimization of fluid/thermal systems. In this study, Kriging method Is used to obtain the optimal solutions associated with the computational fluid dynamics (CFD). The results show that when the temperature .rise is less than 40 K, the optimal design variables are $B_1=2.44\;mm,\;B_2=2.09\;mm$, and t=7.58 mm. Kriging method can dramatically reduce computational time by 1/6 times compared to SQP method so that the efficiency of Kriging method can be validated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.321-321
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• 2010

In this paper, we propose a novel type shaft-less ring type ultrasonic motor. A traveling wave rotary type ultrasonic motor is selected as a base model. The newly designed stator has two piezoelectric ceramic rings which are bonded in sandwich shape as traveling wave generator. So, we can expect to produce higher torque. The proposed model has the rotor structure that coupled with the stator provokes the pressure, this model do not install the separate plate any spring device. We used the finite element method to verify the operation principle and to compute the vibration mode of proposed model.

• 한국항행학회논문지
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• 제20권6호
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• pp.556-561
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• 2016

논문은 ISM 밴드 응용분야에 사용되는 13.35 MHz, 5 kW RF 제너레이터의 구현에 대한 내용이다. 이 제너레이터의 구성은 드라이브증폭기와 LDMOS 1.25 kW 트랜지스터를 클래스 AB 푸쉬풀 증폭기로 구현한 모듈을 바탕으로 4개의 모듈을 윌킨슨 형태의 전송선로 변환기를 이용하여 결합하는 구조를 갖고 있다. 이 제너레이터는 선형성보다는 높은 출력과 효율을 얻는 것이 중요하며, 트랜지스터에서 발생하는 열은 워터 쿨링에 의한 수냉식 방법을 선택하여 외부로 배출하였다. 또한, 결합기와 저역통과 필터의 결합 그리고 출력 및 반사 신호를 검출하는 보호회로를 삽입하였다. 이렇게 구현된 RF 제너레이터는 포화 전력레벨 5.33 kW 출력에서 79 %의 효율을 얻었다.

• 한국의학물리학회지:의학물리
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• 제13권2호
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• pp.69-73
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• 2002

본 연구는 제작된 평행평판형 검출기에서 두 전극간의 거리에 따른 극성효과의 정도를 확인하기 위하여 실행되었다. 개발된 전리함의 극성효과를 측정하기 위하여 평행평판형 전리함의 윗면과 아래 면의 전극에 극성을 바꾸어가며 방사선을 조사하고 그에 의하여 생성된 전하를 측정하여 두 양을 비교하였다. 실험은 두 전극간의 거리가 3, 6, 10 mm 일 때 각각의 명목상 체적이 0.9, 1.9, 3.1 cc인 평행평판형 전리함에 대하여 실행하였다. 조사된 방사선은 6, 10 MV 광자선과 4, 6, 9, 12, 16 MeV의 전자선이며, SSD는 100 cm 이었고, 조사면 크기는 광자선의 경우는 10$\times$10 ㎤ 이고 전자선의 경우는 10$\times$10 $\textrm{cm}^2$을 사용하였으며, 측정점은 최대선량점이고, 선량률은 240 MU/min 으로 하였다. 평행평판형 전리함의 극성의 변환은 평행평판형 전리함의 윗면 즉, 방사선이 입사되는 면의 전극이 (+)극을 갖고 아래 면이 (-)극을 갖는 positive와 방사선이 입사되는 면의 전극이 (-)극을 갖고 아래 면이 (+)극을 갖게 되는 negative 측정으로 시행하였다. 실험결과는 광자선의 경우는 0.5 % 이내의 극성효과를 나타냈고, 전자선의 경우는 1% 에서 3.5% 까지 나타났으며, 높은 에너지를 갖는 16 MeV 전자선의 경우가 다른 에너지의 전자선의 경우 보다 극성효과의 영향이 적음을 알 수 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.262-265
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• 2009

This study was carried out to evaluate the clear day operating performances for the decentralized desalination system with the solar thermal system and the photovoltaic power system. In a clear day, we used a solar thermal system as heat source of the single-stage fresh water generator with plate-type heat exchangers and a photovoltaic power system as electric source for hydraulic pumps. The demonstration system generation was designed and installed at Jeju-island in 2006. The system was comprised of the desalination unit with daily fresh water capacity designed as $2m^3$, a $120m^3$ evacuated tubular solar collector to supply the heat, a $6m^3$ heat storage tank, and a 5.2kW photovoltaic power generation to supply the electricity of hydraulic pumps for the heat medium fluids. In a clear day, solar irradiance daily averaged was measured $518W/m^3$, the daily fresh water yield showed that about 565 liter.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권12호
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• pp.624-630
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• 2001

The trend of the regulations on environmental issues are getting tight. Responding to this trend new technologies such as moving electrodes, wide pitch and pulsed power supply are also introduced in the electrostatic precipitator(EP) systems. The introduction of wide pitch and moving electrodes enhances the system performance of the EPs by improving air-flow and by improving the ash reentrainment on rapping. The power supplies for the EPs developed up to date include thyristor-based dc or intermittent type, SMPS(switching mode power supply) type and the pulsed-power supply type. The use of the pulsed ones is known to improve dust-collecting efficiency of high resistivity ash and reduces back corona occurrence in the collecting plate. There are two kinds of pulsed-power supplies; one with pulsed transformers and the other with direct dc switching devices. The latter uses rotary spark gap switches or semiconductor switches. Both have the merits and demerits: the spark gap switches are simple and robust but has short life time, hence, high maintenance cost, whereas the semiconductor switches have long life time but are costly. In this study, A high voltage power supply with superimposing voltage pulse on dc source was developed for EPs. This study describes circuit topology, operating principle of the scheme, and analysis of experimental results on Dong-Hae Power Plant. The pulsed power supply consists of a variable dc power supply with ratings of 60kV, 800mA and pulse generator which is made of high voltage thyristor-diode switch strings, an LC resonant tank and a blocking inductor. The pulse generator generates variable pulse-voltage up to 70kV using a high frequency resonant inverter with a variable dc source. Two prototypes were built and tested on 250MW DongHae power plant to verify the possibility of the commercial use and the normal operation in the transient states.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.109-109
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• 2009

This paper represented driving characteristic of a thin-type ultrasonic motor by fabricating and utilizing two kinds of drivers which could generate sinusoidal wave, square wave, respectively. A thin brass plate was used as a cross shaped vibrator and sixteen ceramic plates were attached on upper and bottom side of the brass plate. From the thin stator, elliptical displacements of the four contact tips were obtained. Speed, torque, and current were measured by applying sinusoidal waves through driving equipment such as function generator, power amplifier: to measure characteristic of the motor. As a result, the speed and the torque changed linearly at either driving frequency of 88.6 ~ 87.6[kHz] or voltage of 24~36[V]. Two-drivers which generate sinusoidal waves and square waves were designed respectively, and then were compared through some experiments in order to be put to practical use. In conclusion, the drivers had similar characteristic of speed-torque at similar frequency and voltage. It was able to control the motor linearly by using the driver generating square wave among two-drivers. Besides, it also was possible to make the drivers smaller.