• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.245-250
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• 1999

일반적으로 초음파현미경에서 획득한 초음파 영상은 단일 동작주파수를 사용하여 획득하였으며, 분해능은 동작주파수와 초음파변환기에 의해 결정되는 공간주파수 대역에 의하여 제한되어 졌다. 본 연구에서는 초음파현미경에서 동작주파수를 변화시키면서 획득한 영상들을 합성하여 공간주파수의 축 방향 대역을 확장시킨 개선된 고체 내부의 진폭영상을 얻는 방법에 대하여 연구하였다. 실험에서는 동작주파수가 5MHz이고 비대역폭이 $35\%$인 초음파변환기를 사용하여 초음파현미경 시스템을 구성하였고, 이러한 처리를 위해서는 진폭과 위상영상 데이터가 필요하기 때문에 진폭과 위상을 동시에 획득할 수 있도록 검출기로서 쿼드러춰 검출기를 사용하였다. 시편으로는 알루미늄을 선택하였고, 시료의 표면으로부터 깊이를 다르게 하여 내부에 4개의 원형결함을 제작하였다. 실험결과 단일 주파수를 사용한 경우에는 결함의 형태는 나타났으나, 고체 내부 결함의 깊이와 영상 강도의 변화가 비례하여 나타나지 않는 반면에, 개선된 영상에서는 깊이 변화에 대해서 영상 강도의 변화가 비례하여 출력되었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1229-1235
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• 1991

본 연구에서는 음향파의 입사각을 횡파임계각도 이상으로 하여 횡파를 발생시키고 이를 이용하여 종래방식보다 고체 내부에 존재하는 미소결함의 검출한계를 개선시키는 방법을 연구분석하였다. 실험을 위하여 중심주파수3MHz인 반사형 음향현미경 시스템을 구성하였고 서로 다른 깊이에 임의의 결함을 갖는 시료를 제작하였으며 defocus 깊이를 변화시키면서 실험하였다. 실험결과 고체내부 Rayleigh파장의 3배정도 깊이에 존재하는 1mm 크기의 결함을 검출할 수 있었다.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.399-402
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• 1999

본 연구에서는 표면 거칠기가 존재하는 시편의 내부 탐상 시 내부 영상에 중첩되는 표면에 의한 영향을 제거하여 영상을 개선시키는 방법을 연구하였다. 이러한 방법은 표면을 위상계로 간주하고, 내부영상을 위해 다포커싱할 때 디포커싱 거리만큼 위상지연을 시켜 내부영상에서 대수격으로 때어줌으로서 영상을 개선시켰다. 실험을 위하여 쿼드러줘 검출기를 사용하여 초음과현미경을 구성하였고 이때 중심주파수가 5MHz이고 비대역폭이 $35\%$인 초음파변환기률 사용하였다. 시편으로는 100원 주화를 사용하였으며 한 단면에 표면 거칠기가 존재하도록 가공하였다. 실험결과 개선 전의 영상과 비교하여 큰트라스트가 2배 이상의 향상됨을 알 수 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.181-184
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• 2009

In this study, flow visualization method to simulate internal flows of solid rocket motor in a water tunnel is introduced. The tunnel provides excellent visualization of vortex flows and has been used to propellant grain design of the solid rocket motor. A water tunnel is suggested for the research and the visualization test using dye, hydrogen bubble generator and PIV has been studied and discussed.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.480-484
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• 2007

일반적으로 x선 CT는 물체 투과율이 짧기 때문에 대형 산업공정 내부의 영상진단 시 대상체는 금속으로 구성되어 있으며 내부는 액체, 고체, 기체 등 고밀도 물질이 포함되어 있어 계측이 어렵다. 따라서 본 논문에서는 물체 투과율이 x선에 비해 긴 감마선을 사용하였다. 대형 산업공정 내부의 단면영상을 재구성하기 위하여 반복적인 영상재구성 방법의 가중치 함수를 비교하였다. 실험 결과를 통하여 감마 CT 영상에서 빔 통과 여부에 따른 가중치 함수보다 빔 길이나 면적에 의한 가중치 함수로 복원할 경우, 원 영상과 유사함을 확인하였다.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.176-180
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• 2001

In this paper, we have studies the images have been reconstructed by using combination of images which has been acquired by the variation of operating frequency. When inner images has been reconstructed, inner image has been superposition by surface state effect. In this case, image enhancement the phase object and enhance the contrast of inner image. In the result of the specimen for the round defect with 2mm diameter, for the types of the depth are 1.5mm, 2mm, 2.5mm, and 3mm, it has been show that the shape of defect has better than before this processing and phase contrast grow large twice. And we have constructed the acoustic microscope by using quadrature detector that is able simultaneously to acquired the amplitude and phase of the reflected signal. Father more we have studied the reconstruction method of the amplitude and phase images and the enhancement method of the defect images' contrast.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.426-433
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• 2002

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. In this experiment, there are two kinds of specimens, one is a reference block haying 1/4T, 1/2T, 3/4T side drilled holes as main run piping material 111 the steam generator in NPP(Neuclear Power Plant)s and the another is a part of a hemisphere type specimen having about 1-2㎜ distance gap. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously Further more ore have studied the reconstruction method of the amplitude and phase images and the enhancement method of the defect images contrast.

• The Journal of Information Technology
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• v.5 no.2
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• pp.69-80
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• 2002

Conventionally, we have used an acoustic microscope at single operating frequency. The resolution and quality of the measured images are determined by transducer of the microscope. In this paper, we have studied Vertical Resolution Enhancement with Acoustic Reflection Microscope using combining bases of support for SFR(Spatial Frequency Response). Increased Vertical resolution can be obtained by taking three-dimensional images at more that one frequency and numerically combining the results. As results of the experiment, we could get enhanced images with the rate of contrast in proportion to the changing rate of depth.

• The Journal of the Acoustical Society of Korea
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• v.22 no.5
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• pp.408-417
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• 2003

In this paper, we have studied the enhancement of the acoustic image by combining bases of support for SFR (Spatial Frequency Response) taken at multi-frequencies. The scanning acoustic microscope system have been constructed using the quadrature detector that is able to measure the amplitude and phase of the reflected signal simultaneously. Both real and quadrature components of reflected signal have been acquired at 4.4 ㎒ to 5.6 ㎒ reliably and accurately. In this experimental result, better depth resolution can be obtained by numerically combining images taken at several different frequencies. Image intensity have been better about 3.4 times at multi-frequency than one at a single frequency.

• The Journal of the Acoustical Society of Korea
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• v.16 no.3
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• pp.51-56
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• 1997

In this paper, we studied the configuration and depth measurement method of the crack in the interior of solid with scanning laser acoustic microscope. Precision measurement method of crack depth is required in SLAM because that system reconstructs the shadow image to the transmission coefficient. We proposed this method that used geometrical structure to the shadow area of SLAM images obtained from oblique incidence and the mode conversion of ultrasound in specimen and then experimented it. For this experiment, we fabricated various specimens which had the vertical line-crack with different depth and made the wedge as 20$^{\circ}$ for oblique incidence. Experimental results showed that the shadow area of SLAM images were proportional to the depth of crack. Measured depth error to the crack was less than 6% compared with practical crack depth.