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트리핑 와이어를 사용한 평판에서의 열전달 특성에 관한 실험적 연구
조우식(Woo-Sik Jo),조웅선(Woong Sun Cho),유성연(Seong-Yeon Yoo) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
The purpose of this research is to investigate how boundary layer separation by the tripping wire installed in front of the flat plate affects the transition from laminar to turbulent, and consequently heat transfer. Naphthalene sublimation technique is used to measure the average and local heat transfer coefficients on the flat plate, and two boundary conditions of the developed and developing flow are considered to evaluate the effects of flow boundary. The heat transfer data from the flat plate with tripping wire is compared with those of flat plate without tripping wire. The variation trend of local heat transfer coefficients from the plate with and without tripping wire is similar each other in case of the developing flow, but quite different for the developed flow. Average Sherwood number on the flat plate with tripping wire is much higher than those of the flat plate without tripping wire due to boundary layer separation.
경사진 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong Yeon Yoo),조우식(Woo Sik Jo),조웅선(Woong Sun Cho) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.5
본 연구의 목적은 평행 평판과 경사진 평판의 물질전달 특성을 비교하여 경사각에 따른 유동의 박리와 재부착이 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 평균물질전달계수는 주어진 측정면에 대하여 국소물질전달계수를 평균하여 구하였다. 평판의 경사각은 10°에서 -10°까지 5°간격으로 변화시켰으며 유동 속도는 2㎧에서 15㎧까지 변화시켰다. 양의 각으로 경사진 평판에서 국소 Sherwood 수는 경계층이 발달하면서 감소하는 경향을 보이고 있는며, 음의 각으로 경사진 평판의 경우는 재순환 와류의 박리점에서 최소값을 나타내고, 박리된 유동의 재부착점에서 최대값을 나타내었다. 평균 Sherwood 수는 음의 각과 양의 각 모두 평행 평판보다 낮았다. The purpose of this research is to investigate how the separated and reattached flow affect the mass transfer by comparing local mass transfer characteristics from the inclined flat plate with that of the parallel flat plate. The local mass transfer coefficients on the flat plate were measured using naphthalene sublimation technique, and the average mass transfer coefficients were calculated by averaging the local mass transfer coefficients on the measurement surface. Inclined angle of the flat plate was varied from -10° to 10° with 5° intervals, and the free-stream velocity was varied from 2㎧ to 15㎧. In case of the positive inclined angle, local Sherwood numbers decrease gradually because boundary layer thickness increases. On the other hand, the minimum value at the separation point of the recirculated flow and the maximum value at the reattachment point are observed for the negative inclined angle. Average Sherwood numbers for both positive and negative angle are lower than those of the parallel plate.
경사진 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong Yeon Yoo),조우식(Woo Sik Jo),조웅선(Woong Sun Cho) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.12
본 연구의 목적은 평행 평판과 경사진 평판의 물질전달 특성을 비교하여 경사각에 따른 유동의 박리와 재부착이 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 평판의 경사각은 10°에서 -10°까지 5°간격으로 변화시키고 유동 속도는 2㎧에서 15㎧까지 변화시켰다. 양의 각으로 경사진 평판에서 국소 Sherwood 수는 경계층이 발달하면서 감소하는 경향을 보이고 있는며, 음의 각으로 경사진 평판의 경우는 재순환 와류의 박리점에서 최소값을 나타내고, 박리된 유동의 재부착점에서 최대값을 나타내었다. 평균 Sherwood 수는 음의 각과 양의 각 모두 평행 평판보다 낮았다. The purpose of this research is to investigate how separated and reattached flow affects mass transfer, by comparing the local mass transfer characteristics on an inclined flat plate with those on a parallel flat plate. The local mass transfer coefficients for the flat plate were measured using the naphthalene sublimation technique; the inclined angle of the flat plate was varied from -10° to 10° at 5° intervals, and the free-stream velocity was varied from 2㎧ to 15㎧. At positive inclined angles, the local Sherwood numbers decreased gradually because the boundary-layer thickness increased. On the other hand, for negative inclined angles, the local Sherwood numbers assumed the minimum value at the separation point of the recirculation flow and the maximum value at the reattachment point. The average Sherwood numbers for both positive and negative inclined angles were lower than those in the case of the parallel plate.
트리핑 와이어를 사용한 평판에서의 국소물질전달 특성에 관한 실험적 연구
유성연(Seong-Yeon Yoo),조웅선(Woong-Sun Cho),조우식(Woo-Sik Jo) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3
본 연구의 목적은 평판의 선단에 설치된 트리핑 와이어에 의한 경계층 박리가 층류에서 난류로의 천이에 미치는 영향과 그 결과로 발생하는 물질전달에 미치는 영향을 규명하는 것이다. 나프탈렌승화법을 사용하여 평판에서의 국소물질전달계수를 측정하였으며, 유동 경계층의 효과를 평가하기 위해 발달된 유동과 발달하는 유동의 조건에서 트리핑 와이어가 설치된 평판에서의 국소물질전달계수를 설치되지 않은 평판에서의 값과 비교하였다. 발달하는 유동에서 국소물질전달계수가 변화하는 경향은 트리핑 와이어가 설치된 평판과 설치되지 않은 평판이 비슷하지만 발달된 유동에서는 상당히 다르게 나타났다. 평균 Sherwood 수는 경계층 박리로 인하여 트리핑와이어가 설치된 평판이 설치되지 않은 평판에 비해서 훨씬 높았다. The purpose of this research is to investigate how the boundary layer separation caused by a tripping wire installed in front of the flat plate affects the transition from laminar to turbulent flow, and consequently mass transfer. A naphthalene sublimation technique is used to measure the local mass transfer coefficients on the flat plate, and two boundary conditions for the developed and developing flow are considered to evaluate the effects of the flow boundary. The local mass transfer data for a flat plate with a tripping wire are compared with the data for a flat plate without a tripping wire. The variation trends of the local heat transfer coefficients for the plates with and without the tripping wire are similar to each other in the case of the developing flow, but are quite different for the developed flow. The average Sherwood number for the flat plate with a tripping wire is much higher than that without a tripping wire because of the boundary layer separation.
철도신호시스템의 Systematic failure와 Random failure에 대한 사례 연구
한찬희(Han Chan-Hee),안진(An Jin),조우식(Cho Woo-Sik) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
Hazard identification is most important in safety activity. But hazard identification is vague and wide extent, error(mistake) happens to safety activity. This paper defined breakdown that hazard by Systematic failure and Random failure. So, for the specification example, show that can achieve systematic analysis and management. This method is recommanded in EN50129. Applied this method to railway signal system in this paper.
S/W 안전성을 위한 분석기법 조합과 개발 프로세스 평가에 대한 연구
이영수(Young-Soo Lee),안진(Jin Ahn),하승태(Seung-Tea Ha),조우식(Woo-Sik Cho),한찬희(Chan-Hee Han) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
The goal of this thesis is to support safety and reliability characteristics of software intensive critical systems. The verification method developed is innovative from current state of the art in what concerns the verification viewpoint adopted: focusing on software faults, and not, like many other approaches purely on fulfilling functional requirements. As a first step and based on a number of well defined criteria a comparison was made of available literature in the area of static non formal non probabilistic software fault removal techniques. But, None of the techniques evaluated fulfilled all criteria set in isolation. Therefore a new technique was developed based on a combination of two existing techniques: the FMEA and FTA. These two techniques complement each other very well. It is possible to integrate both techniques with commonly used techniques at system level. The resulting new technique can be shown to combine nearly all aspects of existing fault removal techniques.
안전성활동의 추적성을 위한 초기 위험원 도출 기법에 대한 연구
한찬희(Han Chan-Hee),이영수(Lee Young-soo),안진(Ahn Jin),조우식(Cho Woo-Sik) 한국철도학회 2007 한국철도학회 학술발표대회논문집 Vol.- No.-
The primary purpose of the safety management is to prevent the loss of lives or physical damages arising from potential hazards in the railroad signaling system. Since such potential hazards may occur at any time during the system life cycle from design and development to maintenance, safety management activities have to be continuously taken in the course of the system life cycle. The identification of potential hazards is the early step of the safety management. However, such identification activities have to be continued during the system life cycle. Further, they have to be closely linked with system functions to prevent functional problems. This study provides a systematic approach to identification of potential hazards for their tracking and management during the system life cycle to assure the identification and definition of the most appropriate hazards.