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직접메탄올연료전지에서 메탄올 크로스오버에 미치는 인자 연구
현민수,김상경,임성엽,이병록,백동현,정두환,Hyun, Min-Soo,Kim, Sang-Kyung,Lim, Seong-Yop,Lee, Byung-Rock,Peck, Dong-Hyun,Jung, Doo-Hwan 한국전기화학회 2008 한국전기화학회지 Vol.11 No.1
직접메탄올연료전지의 운전 변수에 따른 메탄올 크로스오버를 메탄올 농도센서를 이용하여 정량적으로 측정하였으며 실제 셀 운전 시 메탄올크로스오버 저감의 측면에서 유리한 운전조건을 분석하였다. 메탄올 농도, 전극 양단의 압력차, 전류의 크기, 온도, stoichiometry등을 변화시켜 diffusion, convection, electro-osmosis의 메커니즘별 기여도와 실제 전지 운전 조건의 영향을 함께 분석하였다. 이상의 세 가지 메커니즘 중에서 농도 차이에 의한 diffusion이 가장 큰 영향을 미쳤으며 electro-osmosis에 의한 영향은 고농도에서만 관찰할 수 있었다. The amount of methanol crossover was measured with changing the operating condition by using a liquid methanol concentration sensor. Appropriate operating condition was discussed in terms of methanol crossover. Mechanism of methanol crossover was classified into three items which are diffusion, convection and electro-osmosis. Contribution of each mechanism to methanol crossover and the effect of operating condition were analyzed with varying methanol concentration, pressure difference between anode and cathode, current, temperature, and stoichiometry of anode fuel. Among the three mechanisms diffusion affected mostly and electro-osmosis effect was observed only under high methanol concentration.
장기운전에 의한 직접메탄올 연료전지 스택의 성능 열화 분석
김상경 ( Sang Kyung Kim ),현민수 ( Min Soo Hyun ),이병록 ( Byung Rok Lee ),정두환 ( Doo Hwan Jung ),백동현 ( Dong Hyun Peck ),임성엽 ( Seong Yop Lim ) 한국화학공학회 2011 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.49 No.6
5-cell DMFC stack was fabricated and operated with the load of 4 A for 4000 hrs. After 4000 hrs operation peak power density of the stack reduced by 27.3%. Two of the five cells did now show performance degradation, the performance of other two was reduced by 40% and the performance of the other decreased by 60%. The amount of performance degradation of each cell by long-term operation did not correlate with the position in the stack. Platinum particle size in the anode catalyst layer of the MEA with the strongest degradation increased and the increase was severer on the position of methanol inlet than on the position of methanol outlet. However, platinum particle size in the cathode catalyst layers did not changed for all the MEA`s. Ruthenium crossover from the anode catalyst layer to the cathode catalyst layer through the membrane was observed after 4,000 hrs operation by SEM-EDX and it occurred for all MEA`s regardless of the degree of performance degradation. Atomic ratio of ruthenium to platinum in the cathode catalyst layer was the highest in the MEA with the strongest performance degradation.
흉통의 양상에 따라 분류한 불안정형 협심증 환자의 임상적 소견의 비교
김명수,김성구,정호석,온영근,신원용,김철현,최태명,현민수,권영주 순천향의학연구소 2001 Journal of Soonchunhyang Medical Science Vol.7 No.1
Background and aims : The clinical syndrome unstable angina pectoris that encompasses a variety of symptoms and clincal presentations of transient episode of myocardial ischemia, was devided to several subgroups. Also, it has variable pathophysiologic factors to cause myocardial ischemia. According to clincal presentation, coronary angiographic finding and prognostic factor, the result of unstable angina pectoris is variable. In fact, there were a few data reported on the prognosis of wide spectrum of patients with unstable angina. However, the precise risk of subgroups according to classitication has not been established because it was difficult to compare between studies. We classified unstable angina pectoris by clinical nature of chest pain, and performed to establish and compare the clinical presentations, coronary angiographic findings, treatement and prognosis of patients with unstable angina within subgroups of classification. Methods : Retrospenctive data for 164 unstable angina pectoris patients admitted to the Internal Cardiology Division of Soon Chun Hyang University Hospital from May 1996 to July 1999 was analyzed. The patients were classified into one of the following categories: Class I, new onset of severe angina; Class II, acceleration of previous chronic stable angina; Class III, angina at rest. Clinical presentations, echocardiographic findings, coronary angiographic findings, treatment and prognosis were compared. Results : From the total 164 patients, the subjects of classes were as follows : Class I, 46 cases (28.1%); Class II, 74 cases (45.1%); Class III, 44 cases (26.8%). In view of age distribution, the 7th decade had the highest incidence, and then, 6th, 8th decades were followed. There was no baseline differences among the 3 classes with respect to gender, number of risk factors. Significantly, class II showed more severe findings in abnormal Q wave 15 cases (20.8%), total occclusive lesion 10 cases (20.8%) and three vessel coronary disease 11 cases (22.9%) than other classes. The change of ST segment was significantly apparent (p<0.02) among class I 28 cases (60.8%), class III 26 cases (59.0%), comparing with class II 30 cases (40.5%). Class III had the higher incidence of one vessel coronary artery disease than class I and III. The heparin treatment was performed in 99 cases (60.1%). The incidence of nonfatal myocardial infarction was much more in class I and III, each 4 cases (8.7%, 9.8%) than in class II 1 cases (1.4%). In-Hospital death was occurred in class I and II, each 1 case. Conclusion : The patients with the acclerated angina from chronic stable angina had more severe coronary artery disease than other classes, but they had better in-hospital prognosis.
급성 심근경색 초기에 도플러 심초음파를 이용한 좌심실 이완기 기능의 평가
신원용,김주성,김철현,이광희,최태명,현민수,김성구,권영주 순천향의학연구소;Soonchunhyang Medical Research Institute 2000 Journal of Soonchunhyang Medical Science Vol.6 No.1
Background : Congestive heart failure after acute myocardial infarction relate to left ventricular systolic sysfunction. Also, left ventricular diastolic function contribute to heart failure. The aims of this study were, firstly to characterize left ventricular diastolic function by transmitral flow velocity, and secondly to study the significance of Doppler measurements in relation to the development of heart failure in the early phase of myocardial infarction. Method : Pulsed Doppler echocardiography of transmitral flow was assessed in 34 patients with acute myocardial infarction. According to the Doppler transmitral flwo velocity profile, the study patients were assigned to the three groups: normal filling pattern (DT > 140ms, IVRT < 100ms), relaxation abnormality (DT > 140ms, IVRT ≥ 100ms), pseudonormal or restrictive pattern (DT ≤ 140ms). Also, on the basis of the presence of heart failure during first week of hospitalization, the patients were divided into two groups: patients with no sign of heart failure (Killip class Ⅰ) and heart failure (Killip class Ⅱ-Ⅳ). Results : Of the 34 patients studied, 10(29%) were normal filling pattern, 17(50%) abnormal relaxation and 7(21%) were restrictive patterns. The left ventricular ejection fraction(EF, 40 ±6%) of restrictive pattern was significantly lower than that of normal filling pattern of abnormal relaxation(p < 0.01). And, the IVRT, DT, E/A and left ventricular EF were reduced in patients with heart failure(14 patients) compared to no sign of heart failure(20 patients)(p<0.05). Of the patients with heart failure, IVRT and left ventricular EF were reduced in patients with DT≤140 ms compared to DT> 140ms(p=0.001). Conclusion : Left ventricular diastolic dysfunction is present early after onset of symptoms of acute myocardial infarction. Assessment of left ventricular diastolic function complements measurements of systolic function in the evaluation of cardiac function. DT, IVRT, E/A and left ventricular EF are useful predictors for development of congestive heart failure following acute myocardial infarction.
대퇴골 골절 수술 중에 발생한 급성 폐색전증을 Urokinase로 치료한 증례 보고
이상윤,김순임,박형빈,현민수 대한마취과학회 2000 Korean Journal of Anesthesiology Vol.39 No.3
A massive pulmonary embolism occurring during surgery is a fatal complication. Therefore, early detection and subsequent treatment of pulmonary emboli are important clinical challenges. In this report, an acute pulmonary embolism associated with cardiac arrest occurred during the surgical reduction of a femur fracture. It was diagnosed by echocardiography and treated with urokinase successfully. Therefore, we recommend the use of urokinase for the treatment of a intraoperative massive pulmonary embolism.