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지하철 7호선 차륜의 구름 및 미끄럼 접촉으로 인한 피로손상 예측 연구
이희섭(Lee Hee-Sub),주세민(Joo Se-Min),김호경(Kim Ho-Kyung),권석진(Kwon Seok-Jin) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월
Since the train wheel supports the whole weight of train carriage as an important mechanical component which moves on the rail, the damage to wheel surface occurs due to exfoliation, abrasion, depression and micro-cracking, while its interaction with rail eventually leads to wear during operation. The interaction between several parameters could be a reason for the damage. But, in this study, we tried to identify the economical and optimal period of rail re-profiling for operation by investigating the life span of the train wheel and estimate its safety through estimating fatigue damage on the train wheel surface in consideration of the effect of friction coefficient of rolling and sliding on the contact surface between the wheel and rail during operation. Therefore, a fatigue damage analysis model was embodied by applying stress which occurs during rolling contact with rail, using the material properties and the analysis of operating data, which were obtained through tensile tests on the sample extracted from a train wheel of Subway Line 7. It also has analyzed the effect of friction on fatigue damage in wheel during its rolling and sliding.
80kW급 고분자 전해질 연료전지의 공기공급계(터보 블로워) 개발
이희섭(Lee, Hee-Sub),김창호(Kim, Chang-Ho),이용복(Lee, Yong-Bok) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.06
Blower as an air supply system is one of the most important BOP (Balance of Plant) system fur FCV(Fuel Cell Vehicle). For generating and blowing compressed air, the motor of air blower consumes maximum 25% of net power and fuel cell demands a clean air. Considering the efficiency of whole FCV, low friction lubrication of high speed rotor is needed. For the purpose of reducing electrical power and supplying clean air to Fuel cell, oil-free air foil bearings are applied at the each side of brushless motor (BLDC) as journal bearings which diameter is 50mm. The normal power of driving motor has 1.7kW with the 30,000rpm operating range and the flow rate of air has maximum 160 SCFM. The impeller of blower was adopted a mixed type of centrifugal and axial which has several advantages for variable operating condition. The performance of turbo-blower and parameters of air foil bearings was investigated analytically and experimentally. From this study, the performance of the blower was confirmed to be suitable far 80kw PEM FC.
PEM 연료전지용 복합재 분리판의 제작비용 비교: 압축성형과 기계식 가공
이희섭(Lee, Hee-Sub),추원식(Chu, Won-Shik),강윤철(Kang, Yun-Cheol),강혁진(Kang, Hyuk-Jin),안성훈(Ahn, Sung-Hoon) 한국신재생에너지학회 2006 한국신재생에너지학회 학술대회논문집 Vol.2006 No.11
The fuel cell is one of the promising environment-friendly energy sources for the next generation. The fuel cell provides good energy efficiency above 40% without pollution or noise. Different fuel cell types are usually distinguished by the kind of electrolyte. Among these, the proton exchange membrane fuel cell (PEMFC) has advantages of high power density. low operating temperature, relatively quick start-up, and rapid response to varying loads. The bipolar plate is a major component of the PEM fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding with design of experiments (DOE) to evaluate moldability. The cost for compression molding of graphite-composite bipolar plate was compared with machining cost to make the same bipolar plate.
이희섭(Lee, Hee-Sub),김성근(Kim, Sung-Geun),안성훈(Ahn, Sung-Hoon),전의식(Jeon, Ui-Sik),안상열(Ahn, Sang-Yeoul),안병기(Ahn, Byung-Ki) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.11
The bipolar plate is a major component of the PEM fuel cell stack, which takes a large portion of stack cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. To achieve desired electric properties, specimens made with different mixing ratio, processing pressure and temperature were tested. To increase mechanical strength, one or two layer of woven carbon fabric were added to the original graphite and resin composite. Thus, the composite material is consisted of the three phases: graphite particles, epoxy resin, and carbon fabric. By increasing mixing ratio, fabricated pressure and process temperature, electric conductivity was improved. The results of tensile test showed that the tensile strength of two-phase graphite composite was about 5MPa, and that of three-phase composite was increased to 54MPa.
참치 자숙액의 항산화 활성에 감마선 조사가 미치는 영향
이희섭(Hee-Sub Lee),김현주(Hyun-Joo Kim),최종일(Jong-il Choi),김재훈(Jae-Hun Kim),김진규(Jin-Gyu Kim),전병수(Byung-Soo Chun),안동현(Dong-Hyun Ahn),정영진(Young-Jin Chung),김영지(Yeung-Ji Kim),변명우(Myung-Woo Byun),이주운(Ju-Woon Lee 한국식품영양과학회 2008 한국식품영양과학회지 Vol.37 No.6
수산 가공 폐기물중 하나인 참치 자숙액을 이용하여 천연기능성 소재 개발을 하기 위해 참치 자숙액 에탄올 추출물에 감마선 조사(0, 50 kGy)를 하여 전자공여능을 확인하고, FRAP, UWLA, Rancimat 등을 사용하여 항산화 활성 변화에 관하여 알아보았다. 감마선 조사한 참치 자숙액의 전자공여능 및 hydroxyl 라디칼 소거능 측정 결과 감마선 조사에 의해 각각 16.17% 및 10.38% 증가하였고, 산화안정지수 및 FRAP value 또한 각각 23% 및 26% 증가하였다. β-carotene bleaching assay를 이용하여 항산화지수를 측정한 결과 감마선 조사에 의해 항산화지수가 증가하는 경향을 보였다. 이러한 결과로 미루어 볼 때 참치 자숙액 자체가 가지고 있는 항산화 활성 및 산화안정성을 감마선 조사 기술을 사용하여 증진시켜 식품 및 공중보건산물의 첨가제로서의 이용이 가능할 것이라 사료된다. This study was conducted to examine the effect of a gamma irradiation on the antioxidant activity of ethanol extract from cooking drips of Thunnus thynnus (ECT). The electron donating ability against 1,1-diphenyl-2-picryl-hydrazyl (DPPH), authentic hydroxyl radical scavenging activity by Ultra Weak Luminescence Analyzer, oxidative protection factors by Racimat method, ferric reducing antioxidant power (FRAP), and β -carotene bleaching activity were measured as indices of antioxidant activity. All of the results shown that irradiation increased the antioxidant activity of ECT. These results suggested that ECT could be used as an antioxidative component in food and gamma irradiation could enhance these antioxidative properties.
고분자전해질 연료전지 분리판용 복합재의 전기적/기계적 특성
이희섭(Hee-Sub Lee),김성근(Sung-Geun Kim),안성훈(Sung-Hoon Ahn),전의식(Ui-Sik Jeon),안상열(Sang-Yeoul Ahn),안병기(Byung-Ki Ahn) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
Fuel cell is one of promising environment-friendly energy sources for the next generation. The bipolar plate is a major component of the PEM fuel cell stack, which takes a large portion of the stack cost. In this study, as the alternative materials of bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding. P-15 particles were mixed with epoxy resin to provide electric conductivity and structural properties. To find out the most suitable electric properties, graphite composites were fabricated with different mixing ratio, processing pressure and temperature. By increasing mixing ratio and fabricated pressure, electric conductivity was improved due to the smaller gap between the particles. In addition, by increasing process temperature, the electric conductivity was also improved probably by the excited molecular activities and resulting low viscosity of the epoxy resin for better fill of the gaps. The results of mechanical test showed that the tensile strength of graphite composite was about 5㎫.
허영수,이희섭,Huh, Young-Soo,Lee, Hee-Sub 대한소아외과학회 1995 소아외과 Vol.1 No.1
Neuroblastoma is the most common solid malignancy in childhood. However, a neuroblastoma presenting as bilateral and multifocal is very rare. A male newborn weighing 2.7 kg was born by normal vaginal delivery at 39 weeks' gestation to a 27-year-old mother who had a normal pregnancy. He was in good condition at birth but presented palpable masses in the both upper abdomen and both side of the neck. Ultrasound examination showed the lesions to be $3{\times}3cm$ sized calcified mass in right suprarenal area and $5{\times}3cm$ sized homogenous mass in left suprarenal area. The abdominal mass was also examined by computed tomography with similar findings. With the impression of bilateral neuroblastoma or metastatic spread, the laparotomy was performed on the 13th day of life. Frozen section of biopsy of the left neck mass was obtained, which showed neuroblastoma. Intraoperative findings revealed bilateral adrenal masses which were distinct and anatomically separate. Bilateral adrenalectomy was accomplished and the initial postoperative course was uneventful. The patient was discharged for hopeless and expired at age 45 days. We present bilateral adrenal neuroblastoma considered to be simultaneous occurrence rather than metastases from one site to another.
허영수,이희섭,김근우,Huh, Young-Sao,Lee, Hee-Sub,Kim, Geun-Woo 대한소아외과학회 1996 소아외과 Vol.2 No.1
Esophageal atresia(EA) with a double tracheoesophageal fistula(TEF) is rare. It accounts for only 0.7% of all cases of EA and TEF. A male newborn weighing 2860g was born by normal vaginal delivery at 41 weeks' gestation to a 27-year-old mother who had a normal pregnancy. But immediately developed recurrent choking and respiratory distress. Feeding tube was inserted and chest X ray showed the feeding tube coiled in the proximal pouch(T-2 level). With a preoperative diagnosis of EA and distal TEF, the thoracotomy was performed on the third day of life. At thoracotomy, TEF was proved to be a double fistula. Both fistulas were divided and an esophageal anastomosis was performed. The postoperative course was uncomplicated until the eighth postoperative day when a minor anastomotic leak. The patient was discharged at 103 days of age.