동해 남부해역 해저단층 및 해저사면사태 연구

유동근(Donggeun Yoo),손문(Moon Son),이정민(Jeongmin Lee),Roger Urgeles 대한지질학회 2019 대한지질학회 학술대회 Vol.2019 No.10

영상 클레스별 중요 특징 가중에 의한 영상 검색 방법

유동근 ( Donggeun Yoo ),박채훈 ( Chaehoon Park ),최유경 ( Yukyung Choi ),권인소 ( In So Kweon ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1

이 논문에서는 영상 검색(image retrieval) 및 영상 부류(image categorization)을 위하여 영상을 기술할 때 영상의 클레스(class)별로 서로 다른 주요 특징량(feature)에 가중치를 주는 방법론을 제안한다. 기존에 연구되어온 영상의 특징량 벡터에 가중치를 주는 방식은 모든 영상 클레스에 대하여 동일하게 가중치를 적용하기 때문에 영상이 클레스별로 서로 다른 특징량이 중요하다는 성질을 이용할 수 없다. 영상이 클레스별로 서로 다른 특징량이 중요하다는 성질을 이용하기 위하여 영상의 클레스별로 특징량 벡터에 서로 다른 가중치 벡터(weight vector)를 학습하였다. 그 후 질의 영상(query image)이 입력되면, 기존의 영상 검색 프레임워크(framework)를 통해 데이터베이스(database)로 부터 미리 정의된 서브 클레스(sub-class)의 수에 해당하는 영상부 집합(subset)을 만들었다. 그리고 영상 부 집합의 특징량 벡터들에 클레스별로 각각 학습된 가중치 벡터를 적용하여 특징량 벡터들 간의 거리를 다시 계산하여 리 랭킹(re-ranking)하였다. 이 방법론을 UKBench Dataset 에 적용하여 실험을 해보았으며 가중치를 주기 전과 비교 하였을 때 더 높은 정확도를 보였다.

고분자전해질 연료전지에서 고분자 막과 전극의 철 이온 오염 및 산 세척 효과

유동근 ( Donggeun Yoo ),박민정 ( Minjeong Park ),오소형 ( Sohyeong Oh ),박권필 ( Kwon-pil Park ) 한국화학공학회 2022 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.60 No.1

In the process of long-term use of PEMFC (Proton Exchange Membrane Fuel Cells), chemical degradation of membrane electrode assembly (MEA) occurs due to corrosion of stack elements and contamination of supply gas. In this study, we investigated whether chemically degraded MEA can be recovered by acid washing. The performance was measured and compared in a PEMFC cell after contamination with iron ions and washing with an aqueous sulfuric acid solution. The performance was reduced by about 25% by 0.5 ppm iron ion contamination, and 97.1% performance recovery was possible by washing of 0.15 M sulfuric acid. The membrane resistance was increased due to iron ion contamination of the polymer membrane, and the ionic conductivity was restored by washing the iron ions from the membrane while minimizing the loss of the electrode catalyst by washing with a low-concentration sulfuric acid aqueous solution. The possibility of solving the decrease in durability caused by chemical contamination of PEMFC MEA by the acid washing was confirmed.

우리나라 해양지질

유동근(Donggeun Yoo),정대교(Daekyo Cheong) 대한지질학회 2018 대한지질학회 학술대회 Vol.2018 No.10

PEMFC 고분자 막의 전기화학적 열화과정에서 OCV 감소 및 회복 거동을 통한 비가역적 열화 연구

유동근 ( Donggeun Yoo ),박권필 ( Kwon-pil Park ) 한국화학공학회 2022 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.60 No.2

It is very important to analyze the OCV change behavior during the open circuit potential holding (OCV holding) process, which accelerates the evaluation of the electrochemical durability of the PEMFC membrane. In this study, an empirical formula using the experimental data of three MEAs with different durability was created and compared. The durability evaluation time of the reinforced membrane MEA without radical scavenger inside the membrane was 383 h, and the durability evaluation time of the reinforced membrane MEA with radical scavenger inside the membrane was 1,000 and 1,650 h, respectively. The degradation of the membrane was divided into the reversible degradation that can be recovered by activation and the irreversible degradation that is not recovered. The irreversible degradation of the membrane was indicated by an increase in hydrogen permeability, and the change in hydrogen permeability was similar to the irreversible degradation constant c of all three MEAs. The initiation of irreversible deterioration without recovery is indicated by an increase in hydrogen permeability, and the OCV is not recovered due to an increase in hydrogen permeability, so the slope of the OCV recovery line (ORL) decreases, which can be confirmed by an increase in the constant c value of the empirical formula.

Cathode 개방형 고분자연료전지 스택 내구성 평가

유동근 ( Donggeun Yoo ),김현석 ( Hyeonsuck Kim ),오소형 ( Sohyeong Oh ),박권필 ( Kwon-pil Park ) 한국화학공학회 2022 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.60 No.1

Cathode open-type PEMFC (Proton Exchange Membrane Fuel Cells) stacks, which are widely used in small transport-type PEMFC, have a problem with poor durability. Through the accelerated durability test of the 13-cell PEMFC stack, we tried to find the cause of the degradation of the stack and to contribute to the improvement of the durability of the cathode open stack. A hydrogen/air boundary is formed during start-up/shut-down (SU/SD) due to the structural problem of the cathode open stack in which the cathode is open to the atmosphere and it is difficult to maintain airtightness, thereby deteriorating the cathode. In this study, it was possible to evaluate the durability in a relatively short time by reducing the 54% of the initial performance by repeating SU/SD 1,800 times on the cathode open stack. After dismantling the stack, each cell was divided into two and the performance was analyzed. Overall, the anode outlet MEA, which facilitates air inflow, showed more severe electrode deterioration than the inlet MEA, confirming that the hydrogen/air boundary formation during SU/SD is the main cause of degradation.

고분자전해질 연료전지에서 박막의 화학적 내구성 평가

오소형,유동근,정성기,정지홍,박권필,Sohyeong Oh,Donggeun Yoo,Sunggi Jung,Jihong Jeong,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

PEMFC 고분자 막의 전기화학적 가속 열화에 미치는 평가조건들의 영향

오소형,유동근,배석주,채선규,박권필,Sohyeong Oh,Donggeun Yoo,Suk Joo Bae,Sun Geu Chae,Kwonpil Park 한국화학공학회 2023 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.61 No.3

In order to improve the durability of the proton exchange membrane fuel cell (PEMFC), it is important to accurately evaluate the durability of the polymer membrane in a short time. The test conditions for chemically accelerated durability evaluation of membranes are high voltage, high temperature, low humidity, and high gas pressure. It can be said that the protocol is developed by changing these conditions. However, the relative influence of each test condition on the degradation of the membrane has not been studied. In chemical accelerated degradation experiment of the membrane, the influence of 4 factors (conditions) was examined through the factor experiment method. The degree of degradation of the membrane after accelerated degradation was determined by measuring the hydrogen permeability and effluent fluoride ion concentration, and it was possible to determine the degradation order of the polymer membrane under 8 conditions by the difference in fluoride ion concentration. It was shown that the influence of the membrane degradation factor was in the order of voltage > temperature > oxygen pressure > humidity. It was confirmed that the degradation of the electrode catalyst had an effect on the chemical degradation of the membrane.

PEMFC에 사용되는 강화막과 비강화막의 Fenton 반응에 의한 열화 비교

오소형 ( Sohyeong Oh ),유동근 ( Donggeun Yoo ),이미화 ( Mihwa Lee ),박지상 ( Jisang Park ),박권필 ( Kwon-pil Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.4

In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with e- PTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.

울릉분지 남서부 심해저 퇴적층에 분포하는 천부 가스의 지화학 및 지구물리 특성

이영주(Young-Joo Lee),유동근(Donggeun Yoo),김일수(Il-Soo Kim),류병재(Byong-Jae Ryu) 대한자원환경지질학회 2003 자원환경지질 Vol.36 No.3

울릉분지 남서부 심해저 퇴적층에 분포하는 천부 가스의 특성을 파악하기 위해서 피스톤 코아시료를 채취하고 공기층 가스 기법으로 퇴적물 내에 함유된 가스를 포집하여 탄화수소 가스?l 함량, 성분 및 탄소 동위원소 분석을 실시하였다. 또한 가스의 함량과 시추 코아 퇴적물이 연관성 및 특성을 파악하기 위해서 가스를 함유하는 퇴적물에 대해서 유기 지화학 분석을 실시하였다. 그리고 가스를 함유하는 퇴적물의 탄성파 특성을 살펴보았다. 퇴적물에서는 탄화수소 가스가 0.01%에서 11.255까지 검출되었다. 단위 퇴적물내의 탄화수소 가스의 양을 젖은 퇴적물의 부피를 기준으로 정량적으로 곗나하면 0.1에서 87.4ml/L wet sediment를 나타냈다. 분석된 탄화수소 가스의 성분은 주로 메탄으로 분석 시료에서 2개 시료를 제외하고는 메탄의 함유비가 98% 이상을 나타냈으며 32개 분석 시료 중에서 15개 구간에서는 메탄만이 검출되었다. 채취된 시료의 메탄 가스의 탄소 동위원소 비(δ13C)는 -94.31‰ 에서 -55.50‰ 까지의 밤위를 나타내서 분석된 가스의 기원은 메탄 생성 박테리아에 의한 생물 기원 가스인 것으로 판명된다. 연구 지역의 퇴적물내의 탄화수소 가스의 함량은 지역에 따라서 차이를 보인다. 퇴적물내의 가스의 함량은 퇴적물의 지화학적 특성과 퇴적물의 입도와는 뚜렷한 상관 관계를 보이지 않았다. 단지 탄성파 단면상에서 이상대를 나타내는 곳에서는 가스의 함량이 많은 것으로 나타났다. 탄성파 단면상에 보이는 이상대는 현장의 온도 압력 조건에서 공극수에 탄화수소 가스가 과포화 된 곳으로 다른 조건이 만족된다면 가스 하이드레이트를 형성하기에 적합한 것으로 해석한다. Deep sea core samples were taken in the southwestern part of the Ulleung Basin in order to characterize the proper-ties of shallow gases in the sediment. Amount of shallow gases in the sediments were calculated by head space tech-niques, and chemical and isotopic compositions of hydrocarbon gases were analyzed. Geochemical analyses were carried out on the gas bearing sediments to find out relationship between natural gas contents and organic characteris-tics of the sediments. Seismic characteristics of shallow gases in the sediments were also examined in this study. The amount of the hydrocarbon gases in the sediments range from 0.01% to 11.25%. Calculation of volume of gas per vol-ume of wet sediment varies from 0.1 to 82.0 ml HC/L wet sediment. Methane consists 98% of the total hydrocarbon gases except for two samples. Based on the methane content and isotopic composition(δ13C: -94.31‰∼-55.50‰), the hydrocarbon gases from the sediments are generated from bacterial activities of methanogenic microbes. Contents of hydrocarbon gases are variable from site to site. Volume of shallow gases in the sediments shows no apparent trends vs. either characteristics of organic matter or particle sizes of the sediments. Gas concentration is high in the area of seis-mic anomalies such as blanking zone or chimney structures in the section. Physicochemically the pore water and the formation water systems are saturated with gases in these areas. Concentration of hydrocarbon gases in the sediments in these area shows favorable condition for generation of gas hydrate, as far as the other conditions are satisfied.