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서대철,이덕희,이정주,남수우,주웅용,Seo, Dae-Cheol,Lee, Duck-Hee,Lee, Jung-Ju,Nam, Soo-Woo,Choo, Wung-Yong 대한기계학회 1997 大韓機械學會論文集A Vol.21 No.5
In this study, the stress-strain relations of steels have been calculated as a function of microstructural morphologies of each phase by use of FEM program(i.e. ABAQUS). The mechanical behavior of low carbon steels is affected by the microstructural factors such as yield ratio, volume fraction, shape and distribution of each phase and so on. The effects of shape, volume fraction and yield ratio of each phase on the mechanical behavior were analyzed by using unit cell and whole specimen size models. Results obtained are summarized as follows. As the yield ratio of hard phase to that of soft phase and volume fraction of hard phase were increased, stress level of flow curves were increased. It was found that in whole specimen size model, as the particle size was decreased, higher stress level was shown. Lastly the relationship between microstructure and tensile properties was examined by using the steels with various microstructural morphologies.
서대철 ( Seo Dae Cheol ),권용석 ( Kwon Yong Seok ),권일범 ( Kwon Il Bum ) 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.22 No.1
This paper presents the measurement of earth anchor tension using fiber optic OFDR sensor. Fiber optic OFDR sensor was configurated with tunable laser source, APD with polarization beam splitter and high speed DAQ system. Strains of pressure plate and anchor head were measured and compared using strain gage and fiber optic OFDR sensor. Fiber optic OFDR sensor signal showed linear increase in both tension and compression direction as tensional force increase. This results shows the capability of fiber optic OFDR sensor for monitoring earth anchor tension.
서대철(Dae-Cheol Seo),권일범(Il-Bum Kwon),윤동진(Dong-Jin Yoon),이승석(Seung-Suk Lee),이정율(Jung-Ryul Lee) 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.1
음향방출법은 압력용기 구조에서 존재하는 결함이나 누출을 탐지하거나 모니터링 하는데 유용한 도구로 부상하였다. 본 연구에서는 브레그 격자에 근거한 음향방출센서 시스템이 개발되었다. 다양한 길이의 센싱부를 포함하는 다양한 형태의 광섬유 브레그 격자센서가 제작되었고 PZT 펄서와 연필심 파괴를 이용하여 시험되었다. 두 가지 형태의 센서부착법이 사용되었다. 첫째는 광섬유 브레그 격자센서가 접착제를 이용하여 표면에 완전히 부착되는 방법이고 둘째는 센서의 한쪽 부분만 표면에 부분적으로 고정하고 다른 쪽은 외팔보와 같이 작동하도록 하는 방법이다. 이렇게 함으로써 센싱부의 길이에 비례하는 고유진동수를 갖는 광섬유 브레그 격자센서를 구성할 수 있다. 본 연구에 사용된 센서 시스템의 최종 목적은 원자력발전소 상부 관통관의 균열이나 누출을 탐지하는 온라인 모니터링 시스템에 사용하는 것이다. Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect or monitor preexisting defects and leaks in the vessel structures. A Bragg grating based acoustic emission sensor system is developed. Various type of fiber Bragg grating sensor including the variable length of sensing part was fabricated and prototype sensor system was tested by using PZT pulser and pencil lead break sources. Two types of sensor attachment were used. First, the fiber Bragg grating sensor was attached fully to the surface using bonding agent. Second one is that one part of fiber was attached to the surface partly by bonding and the other part of fiber will be act as a cantilever. That is, the resonant frequency of the fiber Bragg grating sensor will depend on the length of sensing part. The final goal of the sensor system is to provide on-line monitoring of cracks or leaks in reactor vessel head penetration of nuclear power plants.
하악골에 발생한 동정맥 기형의 혈관 색전술에 의한 치험례
이승호(Seung-Ho Lee),서대철(Dae-Cheol Seo),장현호(Hyun-Ho Chang),이부규(Bu-Kyu Lee) 대한구강악안면외과학회 2003 대한구강악안면외과학회지 Vol.29 No.6
Mandibular arteriovenous malformations(AVM) are relatively rare and potentially life threatening lesions. Surgical treatment consists of wide resection of the mandible, which is difficult and potentially hazardous due to significant blood loss during surgery. Therefore, some authors advocate that transvenous embolization may be a safer and more effective method in the treatment of mandibular AVM. We report a treatment case of mandibular AVM in a 9-year-old-girl for episodes of spontaneous bleeding for 6 days using by selective transarterial embolization ,direct puncture embolization and microcoil embolization.
미세채널 내 정재초음파 장 형성 및 미세입자 거동 관찰
조승현(Seung Hyun Cho),서대철(Dae-Cheol Seo),안봉영(Bongyoung Ahn),김기복(Ki-Bok Kim),김용일(Yong-Il Kim) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Using ultrasonic standing waves, the position of micro particles submerged or flowing in fluid can be manipulated. Due to the acoustic radiation force of ultra sounds, particles are forced to move to pressure nodes or antinodes of standing wave field. In this work, ultrasonic standing wave field was generated in a micro water channel of a few millimeter width and the behavior of the submerged particles was observed. The standing wave field generation system was established using an immersible ultrasonic transducer. The system is valid in a frequency range between 2.0 ㎒ and 2.5 ㎒. Particles in consideration were SiC powder of a few micrometer diameters. It was observed that the particle in water moves to pressure nodal lines in the standing field. The effect of the channel thickness and operating frequency on the particle behavior was also investigated.