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Two Cases of Immediate Stent Fracture after Zotarolimus-Eluting Stent Implantation
이필형,이승환,이종영,김영학,이철환,박덕우,박성욱,박승정 대한심장학회 2015 Korean Circulation Journal Vol.45 No.1
Drug-eluting stent (DES) implantation is currently the standard treatment for various types of coronary artery disease. However, previousreports indicate that stent fractures, which usually occur after a period of time from the initial DES implantation, have increased duringthe DES era; stent fractures can contribute to unfavorable events such as in-stent restenosis and stent thrombosis. In our present report,we describe two cases of zotarolimus-eluting stent fracture: one that was detected six hours after implementation, and the other casethat was detected immediately after deployment. Both anatomical and technical risk factors contributed to these unusual cases of immediatestent fracture.
경기 과학 고등학교 신입생 선발고사와 과학적성 검사의 예언 타당도에 관한 연구
이필형,이학동 韓國生物敎育學會 1993 생물교육 Vol.21 No.2
The purposes of this study are to present the problem of selective examination and the plan of improving them, and develop the instrument of selecting students as one of the most important factors which decide the success of education for the gifted of science at this time after 10 years' passage since this school was founded. The researcher verified the degree of predictive validity by adopting the selective examination and scientific aptitude test for new students as predictive variables and the scholastic examination and term-end examination during their school days as standard variables. The results of this study are summarized as follows: 1. It was shown that the prediction degree was higher in considering the results of selective examination and scientific aptitude test at the same time than in adopting the selective examination and scientific aptitude test respectively as predictive variables. From the results of this study, it was also found that the current entrance examination of science high school which resorted to only the selective examination to select students and imposed scientific aptitude test only to there was not suitable to selecting the students of high creativity and scientific talents. 2. It is suggested that the degree of validity and confidence should be made higher and that the standardizing of examination paper should be completed to select the gifted of science properly.
유동방향 변화에 따른 고분자 전해질 연료전지의 성능 및 전달특성에 대한 3차원 수치해석적 연구
이필형,한상석,황상순,Lee, Pil-Hyong,Han, Sang-Seok,Hwang, Sang-Soon 한국전기화학회 2008 한국전기화학회지 Vol.11 No.1
Many researches for effects of different flow configurations on performance of Proton Exchange Membrane Fuel Cell have extensively been done but the effects of flow direction at the same flow channel shape should be considered for optimal operation of fuel cell as well. In this paper a numerical computational methode for simulating entire reactive flow fields including anode and cathode flow has been developed and the effects of different flow direction at parallel flow was studied. Pressure drop along the flow channel and density distribution of reactant and products and water transport, ion conductivity across the membrane and I-V performance are compared in terms of flow directions(co-flow or counter-flow) using above numerical simulation method. The results show that the performance under counter-flow condition is superior to that under co-flow condition due to higher reactant and water transport resulting to higher ion conductivity of membrane. 고분자 전해질 연료전지의 성능향상을 위한 방법으로 유동채널의 형상을 변경한 많은 연구가 진행되어 왔으나 동일한 유동채널 형상에서 유동방향 변경에 따른 연구는 많이 진행되지 못하였다. 본 연구에서는 동일한 반응면적과 동일한 유동채널의 고분자 전해질 연료전지의 수소와 산소의 유동방향을 Co-flow에서 Counter-flow로 변경될 경우의 연료전지의 성능변화를 분석하기 위하여 연료극과 공기극이 포함된 3차원 수치해석모델을 개발하였다. 개발된 수치해석모델을 활용하여 Co-flow와 Counter-flow의 유동채널 내부의 압력손실, 반응물질의 농도분포, 고분자 전해질 막을 통한 Water Transport, 고분자 전해질 막의 이온전도도 및 I-V 성능곡선을 비교하였다. 그 결과 반응물질의 농도분포, Water Transport, 고분자 전해질 막의 이온전도도가 우수한 Counter-flow 유동조건에서의 성능이 Co-flow 유동조건에 비하여 더욱 우수하였다.
평행류와 Interdigitated 유로를 가진 교분자 전해질 연료전지(PEMFC)의 성능특성에 대한 수치해석
이필형,조선아,최성훈,황상순,Lee, Pil-Hyong,Cho, Son-Ah,Choi, Seong-Hun,Hwang, Sang-Soon 한국전기화학회 2006 한국전기화학회지 Vol.9 No.4
고분자 전해질 연료전지의 분리판의 유동채널 설계는 고전류밀도에서 발생하는 농도분극에 직접적인 영향을 줄 뿐 아니라 생성되는 물의 효과적인 전달을 위하여 매우 중요하다. 평행류 유로와 interdigitated 유로의 성능비교를 위하여 연료극과 공기극이 포함된 완전한 형태의 고분자 전해질 연료전지의 3차원 수치해석모델을 개발하였다. 수치해석모델을 사용하여 평행류 유동장과 interdigitated 유동장의 압력강하, 채널간의 물질전달, $H_2O$와 $O_2$의 농도 분포 그리고 i-V 성능을 비교하였다. 그 결과 물질전달에서 채널간의 대류에 의한 물질전할이 더욱 우수한 interdigitated 유동채널에서 성능이 더 높게 나타났으며 압력강하는 보다 크게 나타나 설계시 두가지 성능에 대한 상호보완이 필요함을 알 수 있었다. Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.