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      • KCI등재

        패시브 타입 공랭식 연료전지 성능향상을 위한 캐소드 채널 폭 비율에 대한 수치해석적 연구

        이재승,이남민,임기성,최재유,주현철 한국유체기계학회 2020 한국유체기계학회 논문집 Vol.23 No.1

        In general, a passive air cooled proton exchange membrane fuel cell (PEMFC) operates under an excessive amount of air flow and low humidification conditions, indicating effective control of stack temperature and membrane hydration is of paramount importance for achieving high and stable performance. In this study, we numerically investigate the effects of cathode bipolar plate flowfield design on temperature and water distributions inside a passive air cooled PEMFC. The three-dimensional (3D) non-isothermal PEMFC model is applied to various PEMFC geometries where three different flowfield designs with different ratio and dimensions of air supply channel and cooling channels are taken into account. Simulation results show that the flowfield design with narrow air supply channel and/or wide cooling channel exhibits superior water management performance whereas the effect of oyxgen depletion is minimal due to sufficiently a large amount of air supply conditions. This study clearly demonstrates that the membrane dehydration issue in a passive type air cooled PEMFC can be mitigated by proper design of cathode flowfield.

      • SCOPUSKCI등재

        열간단조된 $\gamma$-TiAl 합금의 이방성에 관한 연구

        이재승,박노진,김성진,김승언,오명훈,Lee, Jae-Seung,Park, No-Jin,Kim, Seong-Jin,Kim, Seung-Eon,O, Myeong-Hun 한국재료학회 2000 한국재료학회지 Vol.10 No.9

        본 논문에서는 Ti-48.5at%Al-0.96at%Mo 조성을 갖는 $\gamma$-TiAl 합금은 항온 단조 및 후속 조직제어 열처리 시 발달하는 집합조직의 변화에 관해 연구하였다. 특히, 동적 재결정 후 조직제어 열처리 온도와 시간의 증가에 따라 발생하는 lamellar volume fraction 과 집합조직 변화에 주목하여 관찰하였다. 동적 재결정 후 집합조직은 ND$\perp${302) 선분과, TD$\perp${100) 및 이에 비해 상대적으로 다소 약한{111) 성분들이 발달하였으며, 열처리 온도와 시간이 증가함에 따라 lameller volume fraction 은 증가했고 동일한 성분의 집합조직도 점차 강하게 발달함을 알 수 있었다. 하지만 상온인장시험 결과는 lameller volume fraction이 증가할수록 낮은 상온 연신을 보였는데, 이는 준 층상조직을 갖는 $\gamma$-TiAl합금의 상온인장특성이 집합조직의 영향보다는 lameller volume fractio과 같은 미세조직 특성에 더욱 강하게 영향을 받기 때문인 것으로 판단된다. The texture evolution during isothermal forging and subsequent heat treatment in Ti-48.5at%Al-0.6at%Mo alloy was investigated. Especially, in the present study, research interest was focused on the interrelation between lamellar volume fraction and textures varied with the change of heat-treated time and temperature. It was found that texture components having ND┴{302) and TD$\perp${100} with minor TD$\perp${111} were developed by isothermal forging. In addition, when the followed heat-treatment time and temperature increased from $1330^{\circ}C$/10h to $1350^{\circ}C$/20h respectively, both the lamellar volume fraction and the intensity of textures mentioned above also gradually increased. However, the tensile elongation at room temperature decreased oppositely, as the lamellar volume fraction increased. These results suggested that tensile properties of $\gamma$-TiAl with the nearly lamellar microstructure at room temperature were affected more strongly by the microstructural features such as lamellar volume fraction rather than by textures.

      • KCI등재

        환자의 재현성을 위한 고정장치(Vac-lok) 제작과 방사선치료에서 유용성 평가

        이재승,김경희,정규환,권대철,구은회,박철우,임인철,동경래,정운관,Lee, Jae-Seung,Kim, Gyoung-Hee,Jeong, Kyu-Hwan,Kweon, Dae-Cheol,Goo, Eun-Hoe,Park, Cheol-Woo,Im, In-Chul,Dong, Kyung-Rae,Chung, Woon-Kwan 대한방사선방어학회 2011 방사선방어학회지 Vol.36 No.1

        방사선치료에서 특수한 체형을 갖거나 특별한 자세가 요구되는 환자에게 적용할 수 있으며 환자의 위치결정 및 조사영역 내에서 표적체적의 위치 재현성을 향상시킬 수 있는 고정 장치(Vac-lok)를 제작하고 그 유용성을 검증하였다. EVA 합성수지와 1.5 mm 바이오 비드폼을 이용하여 제작된 Vac-lok의 기능적, 형태적 검사를 시행하고 모형 및 환자의 상대적 재현성을 분석하였다. 전 방사선치료 기간 동안 제작된 Vac-lok의 기능적 검사에서 미소한 진공 압력의 변화는 있었으나 무시할 정도로 작았다. 모형의 상대적 재현성은 기존 상품화된 제품보다 재현성이 향상되었으며 평균 4% 미만의 오차를 보였다. 또한 환자의 상대적 재현성에서 전후 또는 측면방향에서 다소 오차가 증가하였으나 최대 ${\pm}\;2.3$ mm 미만이었다. 결론적으로 방사선치료의 한계 오차를 ${\pm}\;3$ mm 미만이라 할 때 임상적으로 충분하게 사용 가능하였고 재현성의 향상과 특수한 환자에게 맞춤형 고정 장치를 가격이 저렴하면서 신속하게 제공할 수 있을 것으로 사료된다. We manufactured the Vac-lok that can be applied to patient of special body shape and need to special set-up position and evaluated the usefulness in the radiation therapy. The manufacture Vac-lok, It was used EVA resin and biobeadform of a diameter 1.5 mm. carried out the test of functionality, structural and analyzed the relative reproducibility of phantoms and patients. During the total period of radiation therapy, Vacuum pressure bring variety to a very small amount in the test of functionality of the manufacture Vac-lok. But It was a negligible quantity. The manufacture Vac-lok improved the relative reproducibility of phantoms than the existing Vac-lok and tolerance has a confidence less than 4% error. Also, relative reproducibility of patient increased error than phantom in the antero-posterior and lateral plan. However, the maximum set-up error was less than ${\pm}\;2.3$ mm. In conclusion, If tolerance set-up error of radiotherapy is less than ${\pm}\;3$ mm, the manufacture Vac-lok was enough possible to use and improvement of reproducibility, considering supply with the Vac-lok made to measure of special patient that produced at a low price and without delay.

      • KCI등재
      • KCI등재

        독일에서 병역거부와 민간봉사

        이재승 민주주의법학연구회 2001 민주법학 Vol.20 No.1

        Die ju¨ngsteren Bestrafungen der Zeugen Jehovas wegen des Ungehorsams der Anordnungen durch einen koreanischen Milita¨rgerichtshof riefen die politische O¨ffentlichkeit fu¨r die Einfu¨hrung des Zivildienstes fu¨r die Kriegsdienstverweigerer aus Gewissensgru¨ nden hervor. In diesem Zusammenhang versuchte der vorligende Aufsatz eine Skizze u¨ber Kriegsdienstverweigerung und Zivildienst in Deutschland Zu machen. Nach dem Zusammenbruch des dritten Deutschen Reiches verbreitete sich die neue Hoffnung auf den dauerhaften Weltfrieden. Endlich fand der pazifistische Geist seinen vagen Niederschlag in Art. 4 Abs. 3(das Recht auf Kriegsdiens-tverweigerung) und Art. 26 Abs. 1(Verbot des Angriffskrieges) des Grundgesetzes. Aber mit dem 7. Gesetz zur A¨nderung des Grundgesetz vom 18.03.1956 wurden die allgemeine Wehrpflicht und Ersatzdient fu¨r die anerkannten Kriegsdienstverweigerer in der Bundesrepublik Deutschland eingefu¨hrt. Deswegen wurde die heftige Debatte u¨ber die Kompatibilita¨t zwischen dem Kriegsdienstverweigerungsrecht und der allgemeinen Wehrpflicht oder Ersatzdienstpflicht gefu¨hrt. Von §1 Kriegsdientverweigerungsgesetz(KDVG) wird nicht die situationsabha¨ngige Kriegsdienstverweigerung, sondern nur die absolute und prinzipielle als berechtigte Kriegsdienstverweigerung anerkannt. Nach der Rechtsprechung darf als Kriegsdienstverweiger anerkannt werden, nur wer eigene Beteiligung an jedem Krieg zwischen Deutschland und irgend einem anderen Staat ablehnt. Aber die u¨berwiegende Meinung in der Literatur folgt der Rechtsprechung nicht. Nach der Rechtsprechung umfassen Art. 4 Abs. 3 GG und §1 KDVG kein Recht auf Verweigerung des Zivildienstes aus Gewissensgru¨nden d.h. Totalverweigerung oder Doppelverweigerung. Wegen §53(Dienstflucht) Zivildienstgesetz wird mit Freiheitsstrafe bestraft, wer den Zivildienst verweigert. Aber fu¨r die deutschen Wehrpflichtigen wird die Zivildienstleistung als eine Allta¨glichkeit rezeptiert. In der Tat werden neun von zehn Antragstellern als berechtigte Kriegsdienstverweiger anerkannt. Fast jeder dritte von den erfaßten Wehrpflichtigen leistet den Zivildienst zum Allgemeinwohl im sozialen Bereich.

      • SCOPUSKCI등재

        만성 바이러스 간염 환자에서 간조직 내 아연의 농도

        이재승,강대환,문지현,송근암,조몽,양응석,주형준,서경덕,김정렬 대한간학회 2001 Clinical and Molecular Hepatology(대한간학회지) Vol.7 No.2

        Background and Aims - Zinc is an essential, mostly intracellular, trace element which participates in many oxidative or deoxidative reactions and in a protective action on liver cell activity. Plasma zinc levels are known to decrease in patients with liver disease including chronic viral hepatitis. The aim of this study was to reveal whether hepatic zinc concentrations have a correlation with grades of necroinflammation or stages of fibrosis in the patients with chronic viral hepatitis. Methods - This study consisted of 50 subjects (43 chronic hepatitis B, 4 chronic hapatitis C, and 3 cirrhosis). Each specimen of liver tissue was classified with the grade of lobular inflammation, portal/periportal inflammation, and stage of fibrosis according to Scheuer`s method. Hepatic zinc concentration was determined by ICP-Atomic Emission Spectrometry. Results: The mean hepatic zinc concentration in the 50 chronic viral hepatitis patients was 233.66㎍/g dry weight of liver tissue. The hepatic zinc levels were significanty correlated with the grades of portal/periportal inflammation (rs=-0.385, p=0.006), and grades of lobular inflammation(rs=-0.342, p=0.015). The stages of fibrosis were also negatively related (rs=-0.423, p=0.002). The zinc concentrations differed significantly among grades of lobular inflammation (p=0.013) and among stages of fibrosis (p=0.044). Conclusions- Hepatic zinc concentrations showed negative correlation with grades of portal/periportal inflammation, lobular inflammation, and stage of fibrosis in the patients of chronic viral hepatitis. These results suggest that decreased hepatic zinc concentration might be associated with severe hepatic injury and reflect decreased protective activity on liver cell injury.(Korean J Hepatol 2001;7:147-152)

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