• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2009년도 학술대회 초록집
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• pp.139-143
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• 2009

• 비파괴검사학회지
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• 제9권2호
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• pp.25-36
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• 1989

This essay is a general review of the application of ultrasonic NDE techniques to the performance assessment and characterization of composite materials. A brief review of ultrasonic input-output characterization of a composite plate by shear waves is presented. A theoretical development of ultrasonic wave propagation in isotropic and anisotropic media excited, respectively, by a circular transducer and an oscillatory point source is summarized. Some experimental results are described in which ultrasonic velocity and attenuation measurements give insight into material degradation of fatigued composite laminates. Ultrasonic determination of the elastic constants of a composite plate and an experimental attempt at ultrasonic testing of an isotropic plate containing a crack are also included. A recent effort for the characterization of viscoelastic materials using the ultrasonic NDE technique is outlined. Finally, the reliability of ultrasonic NDE is briefly touched upon.

• Smart Structures and Systems
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• 제18권5호
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• pp.911-930
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• 2016

The main purpose of this paper is to study the effects of initial stress, gravity, anisotropy and porosity on the propagation of shear wave (SH-waves) in a fiber-reinforced layer placed over a porous media. The frequency equations in a closed form have been derived for SH-waves by applying suitable boundary conditions. The frequency equations have been expanded and approximated up to $2^{nd}$ order of Whittaker's function. It has been observed that the SH-wave velocity decreases as width of fiber-reinforced layer increases. However, with the increase of initial stress, gravity parameter and porosity, the phase velocity increases. The results obtained are in perfect agreement with the standard results investigated by other relevant researchers.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2002년도 정기총회 및 학술대회
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• pp.57-62
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• 2002

전송선로와 저장공간의 제약을 극복할 수 있는 영상압축기술이 발달함에 따라 인터넷과 멀티미디어 통신이 비약적으로 발전할 수 있었으며, 앞으로도 보다 높은 효율의 압축기술이 요구되고 있다. 현재 영상압축표준은 대부분 블록 DCT(Discrete Cosine Transform)를 기반으로 하고 있지만, 압축 이전에 영상을 블록으로 나누어 처리하게 되므로 블록효과가 발생하게 된다 본 논문에서는 이러한 블록효과를 제거하기 위해 확산을 이용한 방법을 제시한다. 확산의 정도를 자유로이 조절할 수 있는 새로운 형태의 이방성 확산 방정식을 제안하여 이를 블록효과를 제거하는데 적용한다. 이는 평탄한 영역에서의 경계에 대해서는 등방성 확산으로, 그렇지 않은 영역에 대해서는 경계에 수직인 방향으로만 확산이 일어나는 이방성 확산으로 자유로이 조절하여 적용할 수 있는 장점이 있다. 이를 이용하여 원 영상정보의 손실을 최소화하기 위해 영역에 따라 확산속도와 방향을 적응적으로 조절할 수 있는 알고리즘을 제안하고 기존의 블록효과 제거 알고리즘과 비교 실험을 통하여 제안한 알고리즘의 성능을 평가한다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1999년도 KOBA 방송기술 워크샵 KOBA Broadcasting Technology Workshop
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• pp.29-34
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• 1999

We present a practical method for removing biotches and restoring their mission data. To detect blotches, we employ a robust approach of local analysis of spatiotemporal anisotropic brightness continuity Our approach uses first-order spatiotemporal directional derivatives to select the smoothest direction for each examined pixel, and puts out the incorruption probability that he examined pixel may not be corrupted by blotches. As the restoration filter, were employ a spatiotemporal fuzzy filter whose response is adaptively controlled according to a fuzzy rule defined by the incorruption probability. The fuzzy filter is composed of the two different filter of the identity filter and the spatiotemporal directional-weighted-mean filter, and will put out an intermediate value between the original input brightness and the directional-weighted-mean brightness. We design the fuzzy rule in advance by a standard supervised learning fuzzy rule in advance by a standard supervised learning method. The computer simulations are presented.

• 지질공학
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• 제28권4호
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• pp.727-740
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• 2018

불포화대 매질은 지하수면 상부층으로서 지하수에 의해 포화되어 있지 않거나 불연속적으로 포화되어 있는 층으로 정의된다. 불포화대의 특성은 토양층 하부로부터 지하수면까지 유동하는 오염물질의 저감에 영향을 미친다. 최근 지하수오염도 평가에서는 불포화대 매질의 이방성 및 불균질성을 고려하지 않고 투수성을 나타내는 가중치를 주는 문제점이 있다. 지질학적 매질들은 다양한 범위의 투수성을 갖는다. 표준화된 입도를 대상으로 투수성을 나타내는 가중치로 오염취약도 작성에 적용한다면 불포화대 지질특성을 고려하여 작성한 오염취약도보다 과대하게 작성될 것이다. 본 연구에서는 이방성의 불균질 불포화대의 투수특성을 알아보기 위하여 복수의 불포화층을 고려한 실내 칼럼실험을 실시하였으며, 이를 바탕으로 현장 시추자료에서 얻어진 불포화대 매질의 특성에 의한 평균 투수계수로 환산하여 기존의 불포화대의 가중치를 적용한 지하수오염취약도와 불포화대 매질특성을 고려한 지하수오염취약도를 비교한 결과 불포화대 매질특성을 고려한 지하수오염취약도가 현장의 수질 측정결과와 잘 일치한다.

• Journal of International Society for Simulation Surgery
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• 제1권1호
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• pp.37-40
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• 2014

Purpose For living donor liver transplantation, liver segmentation is difficult due to the variability of its shape across patients and similarity of the density of neighbor organs such as heart, stomach, kidney, and spleen. In this paper, we propose an automatic segmentation of the liver using multi-planar anatomy and deformable surface model in portal phase of abdominal contrast-enhanced CT images. Method Our method is composed of four main steps. First, the optimal liver volume is extracted by positional information of pelvis and rib and by separating lungs and heart from CT images. Second, anisotropic diffusing filtering and adaptive thresholding are used to segment the initial liver volume. Third, morphological opening and connected component labeling are applied to multiple planes for removing neighbor organs. Finally, deformable surface model and probability summation map are performed to refine a posterior liver surface and missing left robe in previous step. Results All experimental datasets were acquired on ten living donors using a SIEMENS CT system. Each image had a matrix size of $512{\times}512$ pixels with in-plane resolutions ranging from 0.54 to 0.70 mm. The slice spacing was 2.0 mm and the number of images per scan ranged from 136 to 229. For accuracy evaluation, the average symmetric surface distance (ASD) and the volume overlap error (VE) between automatic segmentation and manual segmentation by two radiologists are calculated. The ASD was $0.26{\pm}0.12mm$ for manual1 versus automatic and $0.24{\pm}0.09mm$ for manual2 versus automatic while that of inter-radiologists was $0.23{\pm}0.05mm$. The VE was $0.86{\pm}0.45%$ for manual1 versus automatic and $0.73{\pm}0.33%$ for manaual2 versus automatic while that of inter-radiologist was $0.76{\pm}0.21%$. Conclusion Our method can be used for the liver volumetry for the pre-surgery planning of living donor liver transplantation.

• The Journal of the Acoustical Society of Korea
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• 제17권2E호
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• pp.47-52
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• 1998

An analysis of dynamic responses is carried out on monoclinic anisotropic system due to a buried harmonic line source. The load is in the form of a normal stress acting along an arbitrary axis on the plane of symmetry within the orthotropic materials: In case that the line load is acting along the symmetry axis normal to the plane of symmetry, plane wave equation is coupled with verital shear wave and longitudinal wave. However, if the line load is acting along an arbitrary axis normal to the plane of symmetry, plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in a reference coordinate system, where the line load is coincident with a symmetry axis of the orthotropic material. Then the equation of motion is transformed into one with respect to general coordinate system with azimuthal angle by using transformation tensor. Plane wave solutions of monoclinic systems are derived for infinite media. Finally complete solutions for the plane harmonic wave are obtained by calculating the inverse of the integral transforms, in which bulk wave poles are avoided by deforming the contour of the integration to the complex plane. Numerical results for examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• 지질공학
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• 제3권3호
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• pp.231-239
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• 1993

본 연구에서는 지층속도가 이방성의 일종인 횡적등방성을 갖는 지역에서의 시추공 간 탄성파 주시자료를 역산하여 속도 이상대를 규명하는 연구를 시행하였다. 등방성 및 횡적등방성이 모형지층에 대해 파선추적법으로 합성 탄성파 주시를 구한 후, 이 주시자료에 대해 이방성을 고려한 ART 역산법과 이방성을 고려하지 않은 일반적인 ART 연산법에 의해 속도 분포를 구해본 결과, 이방성을 고려한 ART법에 의하면 이방성 및 등방성 지층의 속도분포가 잘 결정되었으며 일반적 ART법에 의하면 등방성 지층의 속도는 잘 결정되나 이방성 지층의 속도에는 오차가 많이 발생하였다. 따라서 지층의 이방성 또는 횡적등방성에 대한 사전 정보가 없을 때에는 이방성을 고려한 ART법을 적용하는 것이 좋을 것이다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2540-2543
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• 2008

Liquid crystal displays (LCD's) are continuously coated with some chemicals in the clean room of a factory. Spreading of these chemicals is causing serious problems both in controlling clean room quality as well as to the workers inside the factory. It is required to alleviate or properly control the offensive odor which is mainly composed of propylene glycol mono ethyl acetate, novolak resin and photo active compound. The control strategy employed is to bleed the offensive odor gas out the clean room. A full scale 3D CFD model was created with anisotropic porous media, chemical species transport with no volumetric reaction, and thermal diffusion with propane gas (tracer gas) to simulate the odor spreading. A segregated implicit solver with standard k-$\varepsilon$ model is employed. The detailed CFD analysis made it possible to develop an effective method of ventilating the coater room and optimizing their capacities.