• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제3권6호
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• pp.231-236
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• 2014

의료 초음파 영상에서 조영제의 전이시간과 조영효과 변화 곡선 특성에 대한 파라미터는 각종 소화기 질환을 진단하는 중요한 인자가 된다. 이러한 진단인자들에 대한 육안판별의 어려움을 극복하기 위하여 파라미터 영상의 자동 생성 기법을 구현할 수 있는데 이 과정에서 마이크로 버블형태의 노이즈와 호흡에 의한 흔들림 현상은 추출된 영상의 신뢰도를 저하 시킨다. 이에 본 연구에서는 MRF(Markov Random Field) 모델을 기반으로 하는 최적화 기법을 적용하여 파라미터 영상을 개선하는 방법을 고찰하며, 호흡에 의한 영상의 흔들림을 보정하기 위한 영상추적 기법을 제시한다. 세부적으로 초음파 동영상 원시 데이터로부터 호흡주기 추출 기법을 구현하였으며, 추출된 주기를 기반으로 모멘텀 요소와 동적 가중치를 반영하는 ROI(Region of Interest) 추적 알고리즘을 적용하였다. 또한 영상 개선 기법에 적용되는 Gibbs 샘플러의 에너지 함수를 정의하고 실제 간질환 진단 데이터를 대상으로 영상 개선 효과를 실험적으로 평가하였다.

• 대한조선학회논문집
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• 제60권1호
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• pp.31-37
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• 2023

In the present study, a method of performing cavitation erosion test directly on the anodized surface of the rudder model is proposed, not applying ink or paint on its surface. An image processing technique is newly developed to quantitatively evaluate the erosion damages on the rudder model surface after erosion test. The preprocessing saturation image, image smoothing, adaptive hysteresis thresholding and eroded area detection algorithms are in the image processing program. The rudder cavitation erosion tests are conducted in the rudder deflection angle range of 0° to -4°, which is used to maintain a straight course at the highest speed of the targeted navy ship. In the case of the conventional flat-type full-spade rudder currently being used in the target ship, surface erosion can occur on the model rudder surface in the above rudder deflection angle range. The bubble type of cavitation occurs on rudder surface, which is estimated to be the main reason of erosion damage on the rudder surface.

• 한국전산유체공학회지
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• 제20권2호
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• pp.96-102
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• 2015

In this study, the green water phenomena on rectangular shaped structure is numerically simulated by STAR-CCM+ to investigate the flow pattern including the velocity profiles in bubbly water flow. 5 phases of the formation of green water in front of and over the rectangular shaped structure is simulated at the design condition which is scaled down by 1:125 from FPSO operating in GOM. All numerical results are compared with the experimental results performed in a two dimensional wave flume. The water deformation due to the green water are obtained by the high speed CCD camera with employing the shadow graphy technique, which is allowed to take the bubbly water flow into images. A series of image taken by shadow graphy technique is analyzed with MQD method to calculate the velocity in bubbly water flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.306-311
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• 2001

Effect of boundary layer thickness on the flow characteristics around a rectangular prism has been investigated by using a PIV(Particle Image Velocimetry) technique. Three different boundary layers(thick, medium and thin)were generated in the Atmospheric Boundary Layer Wind Tunnel at Pusan National University. The thick boundary layer having 670mm thickness was generated by using spires and roughness elements. The medium thickness of boundary layer$(\delta=270mm)$ was the natural turbulent boundary layer at the test section with fully long developing length(18m). The thin boundary layer with 36.5mm thickness was generated by on a smooth panel elevated 70cm from the wind tunnel floor. The Reynolds number based on the free stream velocity and the height of the model was $7.9{\times}10^3$. The mean velocity vector fields and turbulent kinetic energy distribution were measured and compared. The effect of boundary layer thickness is clearly observed not only in the length of separation bubble but also in the reattachment points. The thinner boundary layer thickness, the higher turbulent kinetic energy peak around the model roof. It is strongly recommended that the height ratio between model and approaching boundary layer thickness should be a major parameter.

• 한국의류산업학회지
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• 제16권5호
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• pp.689-697
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• 2014

This study aims to analyze the representation forms of bloggers' personal style on the fashion blogs and enlighten their values which can be actively applied to design and marketing in fashion industry. Image representation of fashion bloggers is reflected by the characteristics in the digital environment, which are the creative manipulation of expression and the production of virtual and fantastic images by taking advantage of the composite medium such as images, music, videos, articles, etc. Also real time updates in blog indicate the latest trends in terms of the representation of image as the actual currency. The study conducted case studies of 5 women's personal fashion blogs through the verification of a variety of global fashion media and blog ranking sites: Style Bubble, Style Rookie, The Cherry Blossom Girl, The Blond Salad, and Fashion Toast. Research findings are as follows. First, the application of creative design elements is indicated as symbolic items, self-made designs, DIY, and various mix and match emphasizing design elements such as color, patterns, proportion, etc. Second, the virtual representation is very highlighted on the story telling applied by film like production or digital effect. Third, the commercial application with mainly sponsored wardrobe and designer collaboration indicates promoting a updated trend as well as a specific brand or designer to make their business profits.

• 대한기계학회논문집B
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• 제25권11호
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• pp.1527-1534
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• 2001

Phase averaged velocity fields in the near wake region behind a square cylinder have been (successfully) obtained using randomly sampled PIV data sets. The Reynolds number based on the flow velocity and the vertex height was 3,900. To identify the phase information, we examined the magnitude of circulation and the center of peak vorticity. The center of vorticity was estimated from lowpass filtered vorticity contours (LES decomposition) adopting a sub-pixel searching algirithm. Due to the sinusoidal nature of firculation which is closely related to the instantaneous vorticity, the location of peak voticity fits well with a sine curve of the circulation magnitude. Conditionally-averaged velocity fields represent the barman vortex shedding phenomenon very well within 5 degrees phase uncertainty. The oscillating nature of the separated shear layer and the separation bubble at the top surface are clearly observed. With the hot-wire measurements of Strouhal frequency, we found thats the convection velocity changes its magnitude very rapidly from 25 to 75 percent of the free stream velocity along the streamwise direction when the flow passes by the recirculation region.

• 대한방사선기술학회지:방사선기술과학
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• 제20권1호
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• pp.39-42
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• 1997

This study was done at 45 medical facilities located in Seoul. The purpose of study is twofold. First, this is to investigate usually who extmines patients for UGI and how many films are used for the examination. Secondly, this is to evaluate image qualities of UGI in terms of representation of lesser curvatures, amount of Ba and air and other criteria for the exam. The results are as follows : 1. In most cases, the UGI is examined by the Dr(67%), by the RT(22%), and together(11%). 2. The total films used ranged from 5 sheets(42%) to 7 sheets(18%). 3. The amount of Ba given to Pt. was mostly $200{\sim}300\;ml$(60%) and gastrografin was used $3{\sim}4\;g$(86.6%) for the examination. 4. For the evaluation of qualities, lack of representation of lesser curvature was 86.7%, lack of Ba and air and bubble formation was 62%, 46.7% and 42.2% respectively.

• 대한조선학회논문집
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• 제45권1호
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• pp.42-53
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• 2008

The two dimensional PIV (particle image velocimetry) measurement technique is applied to water flow in a narrow cavitation tunnel. The nearly homogeneous and isotropic turbulent flows are generated by the honeycomb installed in the tunnel and visualized with a PIV technique. The velocities in the measurement plane at the tunnel centerline 184cm downward from the honeycomb were measured and calculated by an image correlation technique. The turbulent properties are evaluated and each term in the turbulent kinetic energy equation is calculated for the conditions with different internal pressures. Lowering the internal pressure gives an effect on the turbulent flow due to growing bubbles which are resolved in the water. The turbulent kinetic energy in the measurement plane is decayed much slower than those of other research results carried out with wind tunnels. With decreasing the tunnel internal pressures the turbulent intensities are increased about 1.5 times and the anisotropic tendency is also increased.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제4권7호
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• pp.297-300
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• 2015

의료 진단 초음파영상에서 조영제의 전이시간과 확산패턴의 형태는 질환 및 병변을 분석하는 중요한 파라미터로 고려된다. 조영증강 초음파영상 분석과 관련한 기존의 대부분의 연구에서 대상 영역의 평균 명도 변화곡선을 기반으로 파라미터값을 추출한다. 그런데 이러한 명도 데이터는 조영제의 마이크로 버블 효과로 인하여 그 값이 왜곡될 수 있다. 이에 본 논문에서는 조영증강 초음파 진단 파라미터의 추출 과정에서 그 정확도를 개선하기 위하여 명도값의 변화뿐만 아니라, 조영제의 영향을 반영하는 픽셀에 대한 밀도 정보를 보완적으로 활용하는 방법을 제안한다. 제안된 기법은 간 질환 진단 과정에서 병변의 윤곽선 추출과 병변의 특성분석을 위하여 조영제의 확산시점과 속도를 보다 정확하게 판별할 수 있게 한다. 실제 임상 데이터를 사용한 실험결과를 통하여, 제안된 방법이 파라미터 영상 생성기법에서 개선된 결과를 생성할 수 있음을 보인다.

• 정보과학회 논문지
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• 제42권7호
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• pp.910-918
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• 2015

본 논문에서는 조영증강 초음파영상의 분석과정에서 육안판별의 한계를 극복하기 위한 파라미터 가시화기법을 소개하고, 이 과정에서 영상의 왜곡과 노이즈를 보정하기 위한 방법론을 제시한다. 초음파영상에서 조영제의 전이형태에 대한 동적패턴은 간질환 진단에서 의미있는 파라미터가 되는데, 전이시간 정보와 조영증강 패턴을 정적인 단일영상으로 표현함으로써 급속도로 진행되는 동영상에서 정확한 정보를 효과적으로 판별할 수 있게 한다. 진단파라미터 데이터의 신뢰도를 저하시키는 요인으로 호흡에 의한 흔들림현상과 마이크로 버블에 의한 노이즈를 들 수 있다. 이에 대한 대안으로 영상의 움직임추적을 위한 다단계 알고리즘과 마르코프 랜덤 필드 모델에 기반한 영상개선기법을 제안한다. 실제 임상데이터를 사용한 실험결과를 통하여, 제안된 방법의 유용성을 실험적으로 고찰한다.