• Title/Summary/Keyword: Flow contour

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A Method of Segmentation and Tracking of a Moving Object in Moving Camera Circumstances using Active Contour Models and Optical Flow (Active contour와 Optical flow를 이용한 카메라가 움직이는 환경에서의 이동 물체의 검출과 추적)

  • 김완진;장대근;김회율
    • Proceedings of the IEEK Conference
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    • 2001.06d
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    • pp.89-92
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    • 2001
  • In this paper, we propose a new approach for tracking a moving object in moving image sequences using active contour models and optical flow. In our approach object segmentation is achieved by active contours, and object tracking is done by motion estimation based on optical flow. To get more dynamic characteristics, Lagrangian dynamics combined to the active contour models. For the optical flow computation, a method, which is based on Spatiotempo-ral Energy Models, is employed to perform robust tracking under poor environments. A prototype real tracking system has been developed and applied to a contents-based video retrieval systems.

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Numerical simulations of convergent-divergent nozzle and straight cylindrical supersonic diffuser

  • Mehta, R.C.;Natarajan, G.
    • Advances in aircraft and spacecraft science
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    • v.1 no.4
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    • pp.399-408
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    • 2014
  • The flowfields inside a contour and a conical nozzle exhausting into a straight cylindrical supersonic diffuser are computed by solving numerically axisymmetric turbulent compressible Navier-Stokes equations for stagnation to ambient pressure ratios in the range 20 to 34. The diffuser inlet-to-nozzle throat area ratio and exit-to-throat area ratio are 21.77, and length-to-diameter ratio of the diffuser is 5. The flow characteristics of the conical and contour nozzle are compared with the help of velocity vector and Mach contour plots. The variations of Mach number along the centre line and wall of the conical nozzle, contour nozzle and the straight supersonic diffuser indicate the location of the shock and flow characteristics. The main aim of the present analysis is to delineate the flowfields of conical and contour nozzles operating under identical conditions and exhausting into a straight cylindrical supersonic diffuser.

NUMERICAL SIMULATION OF MULTIPHASE FLOW USING LEVEL CONTOUR RECONSTRUCTION METHOD (Level Contour Reconstruction 방법을 이용한 다상유동 수치해석)

  • Shin, Seung-Won
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.193-200
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    • 2009
  • Recently, there have been efforts to construct hybrids among the existing methodologies for multiphase flow such as VOF, Level Set, and Front Tracking with the intention of facilitating simulations of general three-dimensional problems. As one of the hybrid method, we have developed the Level Contour Reconstruction Method (LCRM) for general three-dimensional multiphase flows including phase change. The main idea was focused on simplicity and a robust algorithm especially for the three-dimensional case. It combines characteristics of both Front Tracking and Level Set methods. While retaining an explicitly tracked interface using interfacial elements, the calculation of a vector distance function plays a crucial role in the periodic reconstruction of the interface elements in the LCRM method to maintain excellent mass conservation and interface fidelity. In addition, compact curvature formulation is incorporated for the calculation of the surface tension force thereby reducing parasitic currents to a negligible level.

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Enhanced Gradient Vector Flow in the Snake Model: Extension of Capture Range and Fast Progress into Concavity (Snake 모델에서의 개선된 Gradient Vector Flow: 캡쳐 영역의 확장과 요면으로의 빠른 진행)

  • Cho Ik-Hwan;Song In-Chan;Oh Jung-Su;Om Kyong-Sik;Kim Jong-Hyo;Jeong Dong-Seok
    • Journal of KIISE:Software and Applications
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    • v.33 no.1
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    • pp.95-104
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    • 2006
  • The Gradient Vector Flow (GVF) snake or active contour model offers the best performance for image segmentation. However, there are problems in classical snake models such as the limited capture range and the slow progress into concavity. This paper presents a new method for enhancing the performance of the GVF snake model by extending the external force fields from the neighboring fields and using a modified smoothing method to regularize them. The results on a simulated U-shaped image showed that the proposed method has larger capture range and makes it possible for the contour to progress into concavity more quickly compared with the conventional GVF snake model.

DEVELOPMENT OF AN ORTHOGONAL DOUBLE-IMAGE PROCESSING ALGORITHM TO MEASURE BUBBLE VOLUME IN A TWO-PHASE FLOW

  • Kim, Seong-Jin;Park, Goon-Cherl
    • Nuclear Engineering and Technology
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    • v.39 no.4
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    • pp.313-326
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    • 2007
  • In this paper, an algorithm to reconstruct two orthogonal images into a three-dimensional image is developed in order to measure the bubble size and volume in a two-phase boiling flow. The central-active contour model originally proposed by P. $Szczypi\'{n}ski$ and P. Strumillo is modified to reduce the dependence on the initial reference point and to increase the contour stability. The modified model is then applied to the algorithm to extract the object boundary. This improved central contour model could be applied to obscure objects using a variable threshold value. The extracted boundaries from each image are merged into a three-dimensional image through the developed algorithm. It is shown that the object reconstructed using the developed algorithm is very similar or identical to the real object. Various values such as volume and surface area are calculated for the reconstructed images and the developed algorithm is qualitatively verified using real images from rubber clay experiments and quantitatively verified by simulation using imaginary images. Finally, the developed algorithm is applied to measure the size and volume of vapor bubbles condensing in a subcooled boiling flow.

An Automatic Extraction of Blood Flow Contour from Cardiac MRI (심장 MRI 영상에서 혈류 윤곽선의 자동 추출)

  • Lee, Hyeong-Jik;Jo, Sang-Hyeon;Choe, Heung-Mun
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.37 no.5
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    • pp.56-62
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    • 2000
  • In this paper, an automatic extraction of the blood flow contour from cardiac MRI is proposed. By using the GVF snake which has wider capture range than the conventional snake, and by automatically generating the initial points along the outside of the contour of the zero GVF field in the edge image of the cardiac MRI, the blood flow contour can be automatically extracted, even when the contours have boundary concavities due to the papillary muscles, without any manual initialization of the experts. Experiments are conducted on the various real cardiac MRIs including noise and papillary muscles, and the proposed method is proved to be efficient in automatic extraction of the blood contours even if they have the boundary concavities.

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A Study on Biased Flow Region Using PIV Technique (PIV기법을 이용한 편향흐름 발생영역 규명)

  • Na, Jeong-Heon;Kwon, Sun-Hong
    • Journal of Ocean Engineering and Technology
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    • v.13 no.1 s.31
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    • pp.105-112
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    • 1999
  • This research is an experimental investigation of the region of the Biased Flow. This experiment was carried out in a circulating water channel, and the results are analyzed by using the PIV technique. The results are presented in velocity vector field, velocity contour and vorticity contour. The results were compared with those of Zdravkovich which were carried out in a wind tunnel. These results will be very useful to verify numerical codes.

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Contour Integral Method for Crack Detection

  • Kim, Woo-Jae;Kim, No-Nyu;Yang, Seung-Yong
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.6
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    • pp.665-670
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    • 2011
  • In this paper, a new approach to detect surface cracks from a noisy thermal image in the infrared thermography is presented using an holomorphic characteristic of temperature field in a thin plate under steady-state thermal condition. The holomorphic function for 2-D heat flow field in the plate was derived from Cauchy Riemann conditions to define a contour integral that varies according to the existence and strength of a singularity in the domain of integration. The contour integral at each point of thermal image eliminated the temperature variation due to heat conduction and suppressed the noise, so that its image emphasized and highlighted the singularity such as crack. This feature of holomorphic function was also investigated numerically using a simple thermal field in the thin plate satisfying the Laplace equation. The simulation results showed that the integral image selected and detected the crack embedded artificially in the plate very well in a noisy environment.

Application of Geostatistical Methods to Groundwater Flow Analysis in a Heterogeneous Anisotropic Aquifer (불균질.이방성 대수층의 지하수 유동분석에 지구통계기법의 응용)

  • 정상용;유인걸;윤명재;권해우;허선희
    • The Journal of Engineering Geology
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    • v.9 no.2
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    • pp.147-159
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    • 1999
  • Geostatistical methods were used for the groundwater flow analysis in a heterogeneous anisotropic aquifer. This study area is located at Sonbul-myeon in Hampyong-gun of Cheonnam Province which is a hydrogeological project area of KORES(Korea Resources Cooperation). Linear regression analysis shows that the topographic elevation and groundwater level of this area have very high correlation. Groundwater-level contour maps produced by ordinary kriging and cokringing have large differences in mountain areas, but small differences in hill and plain areas near the West Sea. Comparing two maps on the basis of an elevation contour map, a groundwater-level contour map using cokriging is more accurate. Analyzing the groundwater flow on two groundwater-level contour maps, the groundwater of study area flows from the high mountain areas to the plain areas near the West Sea. To verify the enffectiveness of geostatistical methods for the groundwater flow analysis in a heterogeneous anisotropic aquifer, the flow directions of groundwater were measured at two groundwater boreholes by a groundwater flowmeter system(model 200 $GeoFlo^{R}$). The measured flow directions of groundwater almost accord with those estimated on two groundwater-level contour maps produced by geostatistical methods.

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The Study of Pre-processing Algorithm for Improving Efficiency of Optical Flow Method on Ultrasound Image (초음파 영상에서의 Optical Flow 추적 성능 향상을 위한 전처리 알고리즘 개발 연구)

  • Kim, Sung-Min;Lee, Ju-Hwan;Roh, Seung-Gyu;Park, Sung-Yun
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.47 no.5
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    • pp.24-32
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    • 2010
  • In this study, we have proposed a pre-processing algorithm newly developed for improving the tracking efficiency of the optical flow method. The developed pre-processing algorithm consists of a median filter, binarization, morphology, canny edge, contour detecting and an approximation method. In order to evaluate whether the optical flow tracking capacity increases, this study applied the pre-processing algorithm to the Lucas-Kanade(LK) optical flow algorithm, and comparatively analyzed its images and tracking results with those of optical flow without the pre-processing algorithm and with the existing pre-processing algorithm(composed of median filter and histogram equalization). As a result, it was observed that the tracking performance derived from the LK optical flow algorithm with the pre-processing algorithm, shows better tracking accuracy, compared to the one without the pre-processing algorithm and the one with the existing pre-processing algorithm. It seems to have resulted by successful segmentation for characteristic areas and subdivision into inner and outer contour lines.