• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.397-401
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• 1995

ESPI(Electronic Speckle Pattern Interfermetry) is an optical technique to measure surface deforamtion of engineering components and materials in industrial ares. This optical method is capable of providing full-field results with high spatial resolution, high speed and is the non-contact technique. One of important application aspects using electronic speckle pattern interferometry is to generate contours of a diffuse object in order to provide data for 3-D shape analysis and topography measurement. The contouring method by modified dual-beam speckle pattern interferometry is proposed. We introduce a shift of the illumination beams through optical fiber in order to obtain the contour fringe patterns. The speckle pattern correlation technique is suitable for providing measurement range from millimeters to several centimeters. The complete geometric analysis of the contoretical and experimental results are obtained.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.67-79
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• 1997

100GHz와 150GHz 대역의 두 수신기를 한 개의 냉각기로 운용하여 두 대역을 동시에 관측하기 위한 이중채널 수신기의 준광학계를 설계하였다. 준광학계를 위하여 가우시안 빔에 대한 일반적인 해석을 하였다. 이를 이용하여 대덕전파망원경인 카세그레인 안테나의 초점에 형성된 빔이 각 준광학 소자들을 통해서 믹서 전단에 있는 휘드혼에 최적 빔 결합되도록 준광학소자들 사이의 빔 파라미터를 결정하였다.

• 전자공학회논문지A
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• 제28A권5호
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• pp.361-369
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• 1991

The optics and the signal processor of dual beam laser Doppler velocimeter(LDV) was fabricated. By using the dual beam and the forward scattering, the optics part of LDV was fabricated. And the signal processor of LDV was designed by the frequency counter type using new 11:6 period timing device in order to remove error signals, and was made of the reference clock of a 500 MHz ECL oscillator. Doppler frequencies from 10KHz to 70MHz can be measured using the signal processor. In the accuracy of the period counting part, from 1.81x10**-4% to 1.27% is estimated, and in the accuracy of the validation logic part, from 0.78% to 14.78% is estimated.

• Journal of Welding and Joining
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• 제31권6호
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• pp.71-76
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• 2013

Gas nitriding is a surface hardening process where nitrogen is introduced into the surface of a ferrous alloy. During fusion welding of nitrided carbon steel, the nitride inside weld metal is dissolved and generates nitrogen gas, which causes porosities - blow holes and pits. In this study, several laser welding processes such as weaving welding, two-pass welding, dual beam welding and laser-arc hybrid welding were investigated to elongate the weld pool to enhance nitrogen gas evacuation. The surface pits were successfully eliminated with elongated weld pool. However blowholes inside the weld metal were effective reduced but not fully disappeared.

• Structural Engineering and Mechanics
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• 제75권2호
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• pp.133-144
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• 2020

This investigation is to study the effect of gravitational field and diffusion on a microstretch thermoelastic medium heating by a non-Gaussian laser beam. The problem was studied in the context of the dual-phase-lag model. The normal mode analysis is used to solve the problem to obtain the exact expressions for the non-dimensional displacement components, the micro-rotation, the stresses, and the temperature distribution. The effect of time parameter, heat flux parameter and gravity response of three theories of thermoelasticity i.e. dual-phase-lag model (DPL), Lord and Shulman theory (L-S) and coupled theory (CT) on these quantities have been depicted graphically for a particular model.

• 한국전자파학회논문지
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• 제11권7호
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• pp.1247-1257
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• 2000

옵셋 안테나 (offset-fed dish antenna)를 분석한다. DBS 수신안테나로서 널리 사용되는 옵셋 안테나는 비대칭, 개방형 구조 때문에 해석이 어렵다. 본 논문에서는 푸리에 변환 방법과 Physical Optics를 이용하여 옵셋 반사판과 피드 혼 개구면으로부터의 방사 전계에 대한 정확한 성공적으로 유도하였다. 또한 반사판의 지경, 촛점거리, 단면 등 모든 다양한 구조적 환경에서 해석할 수 있도록 여러 구조 인자를 가진 해를 도출하였다. 이를 이용하여 한 개의 반사판에 어려 개의 혼을 배치시킨 다중 빔 안테나를 분석하고, 특히 동경 116$^{\circ}$의 무궁화위성 (중계기출력 59dBW)과 동경 139$^{\circ}$로 계획되어 있는 Orion 위성 (중계기출력 54dBW)로부터 동시에 수신할 수 있는 안테나를 고찰한다.

• 대한기계학회논문집
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• 제12권3호
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• pp.566-574
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• 1988

본 연구에서는 LDV의 수광계를 비임의 진행방향에 수직한 방향으로 위치시켜 분무액적에 의한 반사 산란성분을 수광하여 검출되는 신호의 가시도에 의해 액적크기 를 측정함과 동시에 도플러변화 주파수로부터 속도를 측정하고, 이 방법의 신뢰도를 충돌식 포진법에 의하여 측정한 결과와 비교하므로써 평가하여, 관측각 90˚의 측방 산란형 LDV에 의한 분무액적의 크기와 속도의 동시측정에 관한 유용성을 살펴보고자 한다.

• 한국정밀공학회지
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• 제26권11호
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• pp.55-61
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• 2009

The wall thinning defect of nuclear power pipe is mainly occurred by the affect of the flow accelerated corrosion (FAC) of fluid. This type of defect becomes the cause of damage or destruction of in carbon steel pipes. Therefore, it is very important to measure defect which is existed not only on the welding part but also on the whole field of pipe. This study use dual-beam Shearography, which can measure the out-of-plane deformation and the in-plane deformation by using another illuminated laser beam and simple image processing technique. And this study proposes Infrared thermography, which is a two-dimensional non-contact nondestructive evaluation that can detect internal defects from the thermal distribution by the inspection of infrared light radiated from the object surface. In this paper, defect of nuclear power pipe were, measured using dual-beam shearography and infrared thermography, quantitatively evaluated by the analysis of phase map and thermal image pattern.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1994년도 제6회 학술발표회 논문개요집
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• pp.41-42
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• 1994

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.714-721
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• 2005