• Polymer Science and Technology
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• v.13 no.6
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• pp.825-832
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.204-209
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• 1998

핵연료 펠렛이 장입되어 있는 원전연료봉 피복관은 핵분열성 물질의 외부 유출에 대한 일차 방호벽 역할을 하므로 원전의 안전성을 위해서는 피복관의 구조건전성 확보가 매우 중요하다. 고온, 고압의 운전 조건 속에서 연료봉 피복관은 산화막이 생성 상장하여 연료봉을 취성 파괴시킬 가능성이 있으므로 이를 가동중에 비파괴적으로 측정할 수 있는 방법을 개발할 필요가 있다. 산화막이 존재하는 지르칼로이 피복관에 대한 음파의 공명산란을 이론적으로 모델링하고 수치해석을 수행하였다. 산화막이 피복된 원통형 쉘의 공명산란에서 공명 원주파의 전파 특성은 산화막의 존재 여부와 그 두께 증가에 따라 크게 변화한다. 수치 해석 결과 제 1차 반대칭 (A$_1$) 원주파의 특정 부분파의 경우에는 산화막의 존재에도 불구하고 위상속도가 일정한 특이성을 보였다. 이러한 위상속도 특성을 실험을 통하여 확인하였으며 이 현상을 이용하여 산화막의 두께를 측정할 수 있는 새로운 비파괴 평가 방법을 제안하였다.

• Journal of the Korean Magnetics Society
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• v.23 no.2
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• pp.37-42
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• 2013

The out-of-plane and in-plane angular dependence of ferromagnetic resonance field was measured in NiFe thin films fabricated by magnetron sputtering. The effective magnetization was obtained from the out-of-plane angular dependence of ferromagnetic resonance field, which was well agreed with calculated one. The decrease of effective magnetization with NiFe thickness was due to the surface anisotropy constant of $K_s=-0.23\;erg/cm^2$. The in-plane uniaxial anisotropy fields were obtained from the in-plane angular dependence of ferromagnetic resonance field. The easy axis of in-plane uniaxial anisotropy field was rotated to the reverse direction of applied magnetic field during sample fabrication, which was explained by the antiferromagnetic NiFeO layer at sample surface.

• Journal of KIISE:Software and Applications
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• v.27 no.8
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• pp.815-826
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• 2000

This study is for the segmentation and volume calculation of the white matter and gray matter from brain MRI. In general, the volume of white and gray matter is reduced by contraction of each components in the case of mental retardation which are Alzheimer's disease and Down's syndrome. As results, it is useful for diagnostic and early detection for various mental retardation through the tracing of variation for its volume from the brain MRI. But, until now, it was very difficult to calculate the partial volume of each components existing in some thickness, because MR image was represented by single gray value after scanning by MR scanner. Accordingly, new segmentation algorithm proposed in this paper is to calculate the partial volume of the white and gray matter existing in some thickness through the analysis of the blurred gray value, and is to determine the threshold for segmentation of white and gray matter, and is to calculate the volume of each segmented component. And finally, proposed algorithm was applied the models which was created manually, and then acquired results was compared with that of original model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1785-1790
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• 2010

To study the vortex induced vibrations the wind tunnel and the two story shear building were designed and built. The wind tunnel was designed to generate the wind speed up to 24 m/s, and the building was designed to have the two lowest natural frequencies within the range of the vortex frequencies generated by the wind tunnel. The resonance behaviors by the locking-on phenomena were observed during the wind tunnel tests of the shear building with the cylinder attached. From the locking-on phenomena observed it is found that the effects of the amplitudes and the frequencies of the cylinders should be considered on the forces generated by the vortex shedding.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.405-412
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• 1999

Meta! Halide Discharge(]\1HD) Iamps have good color rendition, long life and good focusing capability but h have flickers bv acoustic resonances. We have designed the electronic ballast for reducing acoustic resonances in high pressure discharge tube. The ballast consists of main two parts, the first part is a half-bridge inverter to make a square wave form a and the st'Cond part is a flyback converter to combine the low frequency and high frequency component. As a r result of this study, we conclude that MHD lamps of 70 watt 따c very well light(D without acoustic resonance p phenomena by the elestronic ballast.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.1-8
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• 2002

The electronic ballast have much more shaking of arc than magnetic ballast because of acoustic resonance phenomenon. but it has used mare than before. In this paper, we made metal halide lamp modeling by modifying modeling of mercury lamp. To avoid acoustic resonance phenomenon, We calculated acoustic resonance frequency band. We proposed design of LCC circuit. Also, electronic ballast simulator for metal halide lamp was developed by simulink LCC parameters of inverter was decided on the basis of simulation results. After development of prototype ballast, it was verified the characteristics of simulator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.507-508
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• 2010

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.57-63
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• 2001

Tensor 하면 최근 3D로 white matter내의 섬유질을 멋있게 그려내는 diffusion tensor를 연상합니다. 하지만 여기서 다룰 tensor는 수학적 연산자(operator)입니다. NMR 혹은 MRI에서 스핀을 vector로 표시하고, 이 vector 스핀이 90도 rf pulse에 의해서 z축에서 x-y Plane으로 rotation되는 것을 vector diagram으로 나타냅니다. 그런데 이 vector notation으로는 스핀에 일어나는 여러 현상들을 수식적으로 모델 하는데 한계가 있습니다. 그래서 도입된 모델이 product operator와 tensor operator입니다 (1, 2, 3). 한 예로 우리가 다루는 proton NMR 신호가 single quantum인데 23Na 등에는 multiple quantum 신호가 생기게 되며 이는 vector로는 나타낼 수가 없으며 tensor로 분석이 가능합니다 (4, 5).

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.171-174
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• 1999

Methyl acetate의 초음파 흡수측정을 0.2-10MHz의 주파수 범위, 은도 5-30에 걸쳐 광회절 초음파 공명법을 사용하여 행하였다. 그 결과, cis와 trans에 의한 완화는 단일 완화현상을 보였고 그 스책트럼으로 부터 완화 주파수와 완화강도를 결정하였다. 완화 주파수의 온도 의존성으로부터 활성화 에너지(${\Delta}H^{#}$)=6.6 kcal/mol을, 완화강도의 온도 의존성에서 엔탈피차(${\Delta}H$)=3.4 kcal/mol을 각각 구하였다.