• Title/Summary/Keyword: Multiplicative Algebraic Reconstruction Technique

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Tomographic Reconstruction of Two-Phase Flows

  • Ko, Han-Seo;Kim, Yong-Jae
    • Journal of Mechanical Science and Technology
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    • v.17 no.4
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    • pp.571-580
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    • 2003
  • Tomography has been investigated to observe bubble behaviors in two-phase flows. A bubbly flow and an annular flow have been reconstructed by tomography methods such as an algebraic reconstruction technique (ART) and a multiplicative algebraic reconstruction technique (MART) . Computer synthesized phantom fields have been used to calculate asymmetric density distributions for limited cases of 3, 5, and 7 projection angles. As a result of comparison of two tomography methods, the MART method has shown a significant improvement in the reconstruction accuracy for analysis of the two-phase flows.

Comparison and Analysis of Tomography Methods for Reconstruction of Three-dimensional Density Distributions in Two-phase Flows (2상유동장 내 3차원 밀도 분포 재건을 위한 토모그래피 기법의 성능 비교 분석)

  • Ko, Han-Seo;Kim, Yong-Jae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.22 no.5
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    • pp.545-556
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    • 2002
  • Bubble behaviors in two-phase flows have been analyzed by tomography methods such as an algebraic reconstruction technique (ART) and a multiplicative algebraic reconstruction technique (MART). Initially, a bubbly flow and an annular flow have been investigated by cross-sectional view using computer synthesized phantoms. Two tomography methods have been compared to obtain more accurate results of the two-phase flows. Then, reconstruction of three-dimensional density distributions of phantoms with two and three bubbles have been accomplished by the MART method which provided the better results for the two-dimensional reconstructions accurately to analyze the bubble behaviors in the two-phase flow.

Analysis of Density Distribution for Unsteady Butane Flow Using Three-Dimensional Digital Speckle Tomography

  • Ko, Han-Seo;Park, Kwang-Hee;Kim, Yong-Jae
    • Journal of Mechanical Science and Technology
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    • v.18 no.7
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    • pp.1213-1221
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    • 2004
  • Transient and asymmetric density distributions have been investigated by three-dimensional digital speckle tomography. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and transient. The speckle movements between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields have been reconstructed from the deflection angles by a real-time multiplicative algebraic reconstruction technique (MART).

Experimental Analysis of Unsteady Bubble Behaviors Using Three-Dimensional Tomography

  • Ko, Han-Seo;Kim, Yong-Jae
    • Journal of the Korean Society for Nondestructive Testing
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    • v.25 no.6
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    • pp.431-438
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    • 2005
  • Bubble behaviors in a circular tube have been analyzed numerically and experimentally by a three-dimensional tomography method, Initially, a multiplicative algebraic reconstruction technique (MART) which showed better results for previous studies of numerical simulations has been performed to confirm the accuracy of the three-dimensional reconstruction for the two-phase flow using a computer-synthesized phantom, Then, bubble behaviors have been investigated experimentally by the three-dimensional MART method using real projected data captured simultaneously by a laser and three CCD cameras for three angles of view, Also, the transient reconstructions have been attempted to analyze the real-time oxygen-bubble movements in water by the interval of 1/30 second.

Analysis of Density Distribution for Hydrogen Flow Using Three-dimensional Digital Speckle Tomography (3차원 디지털 스페클 토모그래피를 이용한 수소 유동의 밀도 분포 분석)

  • Ahn, S.S.;Ko, H.S.
    • Transactions of the Korean hydrogen and new energy society
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    • v.16 no.3
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    • pp.253-261
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    • 2005
  • 석유 연료 고갈 해결 및 온실 효과 가스 배풀 저감을 위한 방안으로 제시되는 수소는 다양한 에너지 저장체로 사용되어 질 수 있으나 안전성에 대한 연구가 요구되어진다. 따라서, 일반적인 저장 형태인 고압 저장 탱크에서 누출이 되었을 경우 분사되는 수소의 거동에 대한 연구가 이루어져야하며 이를 바탕으로 한 보완책이 제시되어야 한다. 이번 연구에서는 누설 시 확산되는 수소의 밀도를 실제 거동과 유사한 3차원 컴퓨터 영상장으로 합성한 후 ART(algebraic reconstruction technique) 및 MART(multiplicative ART)를 기반으로 한 3차원 디지털 스페클 토모그래피 기법을 개발하여 재건하고 분석하였다.

Development of Signal Processing Technique of Digital Speckle Tomography for Analysis of Three-Dimensional Density Distributions of Unsteady and Asymmetric Gas Flow (비정상 비대칭 기체 유동의 3차원 밀도 분포 분석을 위한 디지털 스펙클 토모그래피 기법의 신호 처리 기술 개발)

  • Baek, Seung-Hwan;Kim, Yong-Jae;Ko, Han-Seo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.2
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    • pp.108-114
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    • 2006
  • Transient and asymmetric density distributions of butane flow have been investigated from laser image signals by developed three-dimensional digital speckle tomography. Moved signals of speckles have been captured by multiple CCD images in three angles of view simultaneously because the flows were asymmetric and transient. The signals of speckle movements between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays fur density gradients. The three-dimensional density fields have been reconstructed from the fringe shift signal which is integrated from the deflection angle by a real-time multiplicative algebraic reconstruction technique (MART).

Development of Three-dimensional Tomography Technique for Analysis of Impinging Jet (충돌 제트 분석을 위한 3차원 토모그래피 기법 개발)

  • Kim Yong-Jae;Ahn Seong Soo;Ko Han Seo
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.34-35
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    • 2004
  • Three dimensional density distributions of impinging and eccentric flames have been investigated by digital speckle tomography. The flames have been ignited by a mixture of butane and air from a circular nozzle and impinged against a plate located at the upper side of the burner exit. For comparison with experimental data, computer synthesized phantoms of impinging and eccentric flames have been reconstructed by a developed three-dimensional multiplicative algebraic reconstruction technique (MART). The advanced reconstruction in the stagnation flow region involved the sharp change of the flow direction and pressure gradient has been developed using a cross-correlation method and new scanning technique for the speckle displacement.

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Development of Combined Optical System for Analysis of Impinging Butane Flame (충돌 부탄 화염의 분석을 위한 복합 광학 계측 기법 개발)

  • Baek, Seung-Hwan;Ahn, Seong-Soo;Ko, Han-Seo
    • 한국가시화정보학회:학술대회논문집
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    • 2005.12a
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    • pp.69-73
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    • 2005
  • Three-dimensional density distributions of an impinging and eccentric flame have been analyzed numerically and experimentally by a combined optical system with a digital speckle tomography. The flame has been ignited by premixed butane/air from air holes and impinged vertically against a plate located at the upper side of tile burner nozzle. In order to compare with experimental data, computer synthesized phantoms of impinging and eccentric flames have been made and reconstructed by a developed three-dimensional multiplicative algebraic reconstruction technique (MART). A new scanning technique has been developed for the analysis of speckle displacements to investigate wall jet regions of the impinging flame including sharp variation of the flow direction and pressure gradient. The reconstructed temperatures have been compared with a temperature photography by an infrared camera and results of numerical analysis using a finite-element method.

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Analysis of Unsteady and Asymmetric Flows Using Digital Speckle Tomography with Developed Integration Method (개발된 적분법을 포함하는 디지털 스펙클 토모그래피 기법을 이용한 비정상 비대칭 유동 분석)

  • Baek, Seung-Hwan;Kim, Yong-Jae;Ko, Han-Seo
    • 유체기계공업학회:학술대회논문집
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    • 2006.08a
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    • pp.517-518
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    • 2006
  • Transient and asymmetric density distributions have been investigated by three-dimensional digital speckle tomography with a novel integration method. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and unsteady. The speckle movements which have been formed by a ground glass between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. A novel integration method has been developed to obtain projection data from the deflection angles for the speckle tomography.'The three-dimensional density fields have been reconstructed from the accurate projection values by a real-time multiplicative algebraic reconstruction technique (MART) with the developed integration method.

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Analysis of Density Distribution for Butane Using Three-dimentional and Real-time Digital Speckle Tomography (3차원 실시간 디지털 스페클 토모그래피를 이용한 부탄 밀도 분포 분석)

  • Go, Han-Seo;Park, Gwang-Hui;Kim, Yong-Jae
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1789-1794
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    • 2003
  • Transient and asymmetric density distributions have been investigated by digital speckle tomography. Multiple CCD images captured movements of speckles in three angles of view simultaneously because the flows were asymmetric and transient. The speckle movements between no flow and downward butane flow from a circular half opening have been calculated by a cross-correlation tracking method so that those distances can be tranferred to deflection angles of laser rays for density gradients. The three-dimensional density fields have been reconstructed from the fringe shift by a real-time multiplicative algebraic reconstruction technique (MART).

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