• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2338-2340
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• 1999

In this paper measurements of AE (Acoustic Emission) signals caused by corona discharge were performed to analyze the electrical deterioration in oil. We also examined the relationship between discharge magnitude and peak-to-peak value of AE signals to diagnose the deterioration of liquid dielectrics. From these results, Vpp(peak to peak value) of AE signals was proportional to corona discharge magnitude. The main frequency band of AE signals in oil appeared to 130[kHz].

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.861-864
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• 2006

냉장고에 적용된 BLDC Fan Motor에 있어서 공진소음의 원인에 대하여 연구하였다. 연구에 있어서 종래의 가진 방법을 적용하기 곤란한 구조를 가진 소형 Fan & Rotor System의 동 특성 실험에서 전자 가진법 및 Microphone을 이용한 고유진동수 계측방법을 사용하고 그 타당성을 보였으며 연구결과, Pan과 Rotor System의 비틀림 고유진동수와 Fan의 굽힘 고유진동수가 BLDC Motor의 Commutating Torque Ripple에 의한 가진 주파수와 일치하여 공진이 발생하는 것으로 분석 되었으며 이와 관련된 주요 인자를 분석하고 대안을 제시하였다.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.567-571
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• 2004

The 2-dimensional unsteady flows on and around the cambered airfoils were computed by applying LES with the deductive dynamic SGS model. The unsteady flow field were used as inputs to compute the far-field sounds and directivity patterns from rotating blades by a hybrid approach that exploits Farassat's formula. The BEM (Boundary Element Method) was applied to predict the frequency characteristics from the rotating blades for the cases of even- and uneven-pitched fans. The BEM results suggested that the unevenly pitched fan have less pronounced discrete peaks at BEF frequencies, which was confirmed by the experiment.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1364-1368
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• 1999

Langasite( La3Ga5SiO14) is suitable for new piezoelectric properties. Langasite can be applied for communication de-vices due to intermediate piezoelectric properties which are similar to those of quartz and LiTaO3 in its acoustic cha-racteristics. In this study Langasite( La3Ga5SiO14) single crystals were successfully grown by using self-designed Czo-chralski system. From the results of optical properties it was found that crystals having a high quality and higher optical transmittance were grown at atmosphere of 1 to 30 vol% of oxygen content.

• Proceedings of the Acoustical Society of Korea Conference
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• 1996.06a
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• pp.51-54
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• 1996

동해 중부 연안(수심: 200 m)에서 해수 중 주위잡음을 측정하는 동안 태평양 흰줄무늬 돌고래(pacific white-sided dolphin, 학명: Lagenorhynchus obliquidens)의 발생음을 수신하였으며 그 음향 특성을 분석하였다. 그 결과 얻어진 결론을 요약하면 다음과 같다. 첫째, 돌고래 발생음의 파형은 임펄스의 형태로서 그것의 전체 길이는 0.25~60.50 ms였고, 처음에 음(-)의 방향으로 작은 진폭을 보였으며, 그 후 작은 진폭으로 빠르게 감쇠진동하고 있는 형태를 나타내었다. 둘째, 돌고래 발생음의 주파수 스펙트럼은 약 18~90kHz의 광범위한 성분을 포함하고 있었다. 셋째, 돌고래 발생음의 스펙트럼 레벨 피크는 주파수 범위 35~55 kHz에서 나타났으며, 이것은 돌고래의 발생음이 없는 경우 해수 중 주위잡음의 레벨에 비하여 약 30~40 dB 높게 나타났다.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.154-155
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• 2001

파장가변 광 필터는 WDM 광전송 시스템에 필요로 하는 핵심 부품중의 하나이다. 특히 LiNbO$_3$의 음향광학효과를 이용하는 AOTF(Acousto-Optic Tunable Filter)는 150nm 이상의 파장 가변 범위, 1.5nm 이하의 파장 통과대역폭, 수 $\mu\textrm{s}$ 정도의 비교적 빠른 스위칭 속도, 그리고 여러 파장 채널을 동시에 선택할 수 있는 장점들을 보유하고 있음에도 불구하고 표면 음향파(SAW： SurFace Acoustic Wave) 구동에 필요한 RF 파워와 부 모드(sidelobe)가 비교적 크다는 단점 때문에 실용화에 많은 제약을 받아왔다. (중략)

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1457-1459
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• 1994

A surface acoustic wave(SAW) sensor for the detection of odorants has been constructed by depositing various phospholipids and fatty acids onto the surface of the SAW device. Applying the Langmuir-Blodgett technique, it was possible to deposit the optimal number of layers which was found to be between 10 and 20. Menthone, amylacetate, acetoin, and other organic gases showed different affinities to the coated lipids. An explanation is given for different odorant affinities based on the monolayer properties of phospholipids.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1580-1582
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• 1994

In this study, when AC voltage is applied to block type treeing specimen which is fabricated with polyethylene which dielectric characteristics is excellent, from initial tree to final breakdown, Using acoustic emission method. we take statistically on parameter, which is skewness. We experimented on quenching condition and illustrated skewness locus plane so that studied interrelation of life expectation and parameter.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.177-180
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• 1997

A new excitation method of switched reluctance moor drive is described in this paper. This motor produces reluctance torque by mutual action between tyro phases as well as conventional self reluctance torque. The change of self inductance and mutual inductance are used to produce torque. This paper suggests the operational principle, the mechanism of torque product and the driving characteristics of Switched Reluctance Motor with 2 phase excitation against conventional SRM experimentally. The energy conversion ratio is increased because the next phase is excited after one phase is already excited. Acoustic noise of SRM with 2 phase excitation is decreased than that of conventional SRM due to the mechanism of torque production.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1014-1019
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• 2003

It seems inevitable for residential buildings to be high-rise and allocated near traffic roads due to the overcrowding in urban area. Acoustic environment in those area has been seriously deteriorated by the increase of traffic vehicles. Commonly used sound barriers have a limitation in controlling noise due to diffraction noise of sound barrier. Hence sound barrier is not effective to attenuate noise especially for the residential units in high level. This work aims at evaluating noise reduction according to the tunnel section shape by using 1/5 scale model. We carried out a number of field measurements for 1/5 scale model of Noise Barrier Tunnel with various sectional shape. The results from predictions and the measurement show generally good agreement.