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박현,박진환,하효민,전호환,이인원,Park Hyun,Park Jin-Hwan,Ha Hyo-Min,Chun H.H.,Lee In-Won 해양환경안전학회 2006 海洋環境安全學會誌 Vol.12 No.1
유기도막의 방식성능은 도막의 수지성분과 안료의 화학적 특성에 의존한다 전자는 부식인자의 침투를 차단 및 지연시키는 역할을 하며, 후자는 침투된 부식인자들에 의해 일어나는 부식반응을 억제하는 기능을 갖고 있다. 또한 도막 자체의 영향 외에, 외부 환경에 의해서 다르게 나타난다. 본 연구에서는 교류 임피던스 법을 이용하여 유속과 그에 따른 유동 전단응력에 의한 도막의 열화거동을 조사하였다. 실험기 사용된 도막의 두께는 $70{\mu}m$에서 $140{\mu}m$까지 변화시켰다. 두꺼운 도막($140{\mu}m$) 에서는 유속이 증가함에 따라 물 흡수량의 감소와 높은 임피던스 특성을 나타내었다. 그러나 얇은 도막($90{\mu}m$) 에서는 유속이 증가함에 따라 도막의 파괴가 진행되고 있음을 확인할 수 있었다. 도막에 가해지는 전단응력이 증가할수록, 즉 선박의 운항속도가 증대될수록 도막의 열화에 의하여 방식성능이 떨어짐을 확인할 수 있었다. Analysis has been made of the anti-corrosive property of organic coating under the shear stress of the flow by means of AC impedance method. Marine anti-corrosive painted panels were placed in the water channel with varying flow rate, thereby experiencing varying flow shear stress on the surfaces. The velocities of the salt water were ranged from 1.48 to 5.2 m/s and the coating thickness of from $70{\mu}m\;to\;140{\mu}m$. For all coating thicknesses investigated, the poorer anti-corrosive property and the lower adhesion strength have been found for the higher shear stress. It has been found that the shear stress accelerates the aging of organic marine coatings.
J. H. Park,이춘식,박현서,J. H. Lee,J. Y. Kim,K. B. Lee,권영관 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.1
We have measured the cross sections of the 16O(n,3He)14C and the 16O(n,t)14N reactions above neutron thresholds up to 18.1 MeV in an activation experiment. H2O (water) as an 16O target was irradiated with semi-monoenergetic neutrons generated from the 9Be(p,n)9B reaction with 20-MeV protons. The neutron flux was obtained with the aid of previous study by Uwamino et al. The 14C and the tritium activities were measured by using a liquid scintillation counting (LSC) method. The cross sections of 16O(n,3He)14C and 16O(n,t)14N measured by using the LSC method for water were 52 ± 16 mb and 0.25 ± 0.11 mb, respectively. While the present value for the cross section of 16O(n,t)14N agrees within a factor of four with previous values measured by using the same LSC method at similar neutron energies, the present value for the cross section of 16O(n,3He)14C turns out to be about 200 times as large as the previous accelerator mass spectrometry (AMS) value obtained by Imamura et al. This large discrepancy may be attributed to the loss of 14C atoms during the sample preparation in the AMS method. To further investigate such disagreement, we conducted both LSC and AMS measurements by using C3D6O (d-acetone) liquid targets which are easily combustible for extracting CO2 for the AMS measurements. The 14C yield of the LSC method also turned out to be 80 times as large as that of the AMS method. The reliability of the AMS method could be challenged by that of the neutron-activation measurements in view of the fact that the AMS method involves complex sample preparation, such as combustion and cryogenic trapping of CO2.
PEMFC 용 Pt 담지 촉매의 Pt 담지비에 따른 성능변화
조용훈(Y. H. Cho),조윤환(Y. H. Cho),박현서(H. S. Park),성영은(Y. E. Sung) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
This study focuses on a determination of amount of Pt in the Pt/C for catalysts of polymer electrolyte membrane fuel cells (PEMFC). PEMFC offer low weight and high power density and being considered for automotive and stationary power applications. The PEMFC behavior is quite complex is influenced by several factors, including catalysts and structure of electrode and membrane type. Catalyst of electrode is important factor for PEMFC. One of the obstacles preventing polymer electrolyte membrane fuel cells from commercialization is the high cost of noble metals to be used as catalyst, such as platinum. To effectively use these metals, they have to be will dispersed to small particles on conductive carbon supports. The optimal amount of Pt in Pt/C was investigated by using polarization curves in single cell with H₂/O₂ operation.