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Cathode 산소 공급조건에서 고분자막 내구평가 프로토콜의 가습/건조 시간 변화의 영향
임대현 ( Daehyeon Lim ),오소형 ( Sohyeong Oh ),정성기 ( Sunggi Jung ),정지홍 ( Jihong Jeong ),박권필 ( Kwonpil Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.1
PEMFC 고분자막의 내구성 향상을 위한 내구성 평가는 PEMFC 발전을 위해 매우 중요하므로 고분자막 내구성 평가 프로토콜(AST) 연구개발이 계속 되고 있다. 최근에 DOE의 고분자막 화학적/기계적 내구성 평가 AST가 개발되어 Nafion XL에 적용해 검토하였다. 평가시간을 단축시키기 위해 공기대신 산소를 Cathode 가스로 사용해 144시간만에 종료하였다. DOE AST가 가습 45초/건조 30초로 전압변화 횟수가 많아서 전극의 열화가 MEA 내구성에 더 많은 영향을 미쳤다. 그래서 가습 60초/건조 300초로 1사이클 시간을 길게하고 가습시간 대비 건조시간도 길게 하여 고분자막을 더 열화시키게 하였고, 240시간에 종료하였다. 고분자막 내구성 평가를 위한 DOE AST가 전극 열화도 동반됨을 확인하였다. Since the durability evaluation for improving the durability of PEMFC polymer membranes is very important for the development of PEMFC, research and development of the polymer membrane durability evaluation protocol (AST) continues. Recently, DOE's polymer membrane chemical/mechanical durability evaluation AST was developed and applied to Nafion XL for review. In order to shorten the evaluation time, oxygen was used as a cathode gas instead of air, and it was finished in 144 hours. Since DOE AST has a large number of voltage changes with 45 seconds of humidification and 30 seconds of drying, the degradation of the electrode has more influence on the MEA durability. Therefore, one cycle time was lengthened with 60sec of wet/300sec of dry, and the drying time was made longer than the humidification time to further deteriorate the polymer membrane, and it was finished in 240 hours. It was confirmed that the DOE AST for evaluation of the durability of the polymer membrane was accompanied by electrode degradation.
임대현(Dae Hyun Lim),손병관(Byong Kwan Son),고은영(Eun Young Ko),김정희(Jung Hee Kim) 대한소아알레르기호흡기학회 2002 소아알레르기 및 호흡기학회지 Vol.12 No.2
Barnes syndrome(thoracolaryngopelvic dysplasia)is an exceedingly rare clinical entity originally described in 1969. The diagnosis is made by clinical and radiologic findings including thoracic dystrophy, a small contracted pelvis and laryngeal and subglottic stenosis. It has many anatomic variances which are considered as the feature of autosomal dominant inheritance with variable penetrance. This syndrome is distinguished from the better known autosomal recessive Jeune syndrome(asphyxiating thoracic dystrophy)by the presence of laryngeal stenosis, the absence of iliac spurs in infancy, and later the absence of renal involvement or shortenings of the limbs. We report a Barnes syndrome with small thoracic cavity, subglottic stenosis and the absence of iliac spurs in pelvic bone with the review of the literature.
화학적/기계적 열화 병행방법에 의한 PEMFC 고분자막 내구성 평가
임대현 ( Daehyeon Lim ),오소형 ( Sohyeong Oh ),정성기 ( Sunggi Jung ),정지홍 ( Jihong Jeong ),박권필 ( Kwonpil Park ) 한국화학공학회 2021 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.59 No.3
고분자 전해질 연료전지(Proton Exchange Membrane Fuel Cell, PEMFC) 내구성 향상을 위해서 고분자막의 내구성을 짧은 시간에 정확히 평가하는 것은 중요하다. 최근에 미국 에너지부(Department of Energy, DOE)에서 고분자막의 화학적 내구성과 기계적 내구성을 결합해 평가하는 프로토콜을 보고하였다. 이 프로토콜은 개회로전압(Open Circuit Voltage, OCV) 유지 상태에서 가습/건조를 반복함으로써 화학적/기계적 열화를 고분자막에 가한다. OCV 변화 반복에 따른 전극 열화의 영향을 많이 받고 평가시간이 장시간인 점들이 이 프로토콜의 문제점이다. 본 연구에서 DOE 프로토콜의 다른 조건들은 그대로 두고 양극(Cathode) 가스로 공기 대신 산소를 사용함으로써 내구평가 시간을 408시간에서 144시간으로 단축시킬 수 있었다. 전압변화 사이클 횟수를 1/3로 감소시킴으로써 전압변화 사이클에 의한 전극열화는 종료 시점에서 공기에 비해 산소 사용 시 1/12로 감소시켜서, 고분자막 내구 평가를 보다 정확히 할 수 있게 하였다. In order to improve the PEMFC (Proton Exchange Membrane Fuel Cell) durability, it is important to accurately evaluate the durability of the membrane in a short time. Recently, DOE (Department of Energy) reported a protocol that combines the chemical and mechanical durability of membranes to evaluate them effectively. This protocol applies chemical/mechanical deterioration to the membrane by repeating wet/dry while OCV (Open Circuit Voltage) holding. The problem of this protocol is that it is highly affected by electrode degradation due to change cycles in OCV and that the evaluation time is long. By using oxygen instead of air as the cathode gas while leaving the other conditions of the DOE protocol as it is, the durability evaluation time could be reduced from 408 hours to 144 hours. By reducing the number of voltage change cycles to 1/3, the electrode degradation due to the voltage change cycle was reduced to 1/12 when oxygen was used compared to air at the end, thereby enabling more accurate evaluation of polymer membrane durability.
임대현 ( Lim Dae Hyun ),정찬일 ( Jung Chan Ill ),이규일 ( Lee Gyu Il ),지광습 ( Zi Goangseup ) 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.22 No.1
The purpose of this study is to develop a durable packaging concrete using silica - based LCD waste glass. In order to verify the performance of the waste glass mixed pavement concrete, four types of concrete mixture were classified into general concrete, fly ash concrete, LCD concrete and LCD + fly ash concrete. The performance of the durable concrete pavement was tested for compressive strength, alkali - silica reaction, freezing - thawing, saltation and abrasion resistance. The purpose of this study was to develop a high - performance pavement concrete manufacturing technology using LCD waste glass powder.
천식에서 Matrix Metalloproteinase-9의 역할
임대현 ( Dae Hyun Lim ) 대한소아알레르기호흡기학회 2006 소아알레르기 및 호흡기학회지 Vol.16 No.1
Variable airway obstruction, increased bronchial hyperresponsiveness, allergic inflammatory reaction and airway remodeling are main characteristics of asthma. Matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases(TIMPs) do play important roles to pathogenesis and pathology of asthma via influence on the function and migration of inflammatory cells as well as extracellular matrix(ECM) deposition and degradation. MMP-9 is the predominant MMP in asthma and chronic obstructive pulmonary disease(COPD), and its expression is enhanced when asthma patients have spontaneous exacerbations or in response to local instillation of allergen in the airway. As acute inflammation of asthma resolves, MMP-9 levels return to normal. TIMPs bind MMPs in a 1 : 1 fashion. Thus, an increase in the molar ratio of MMP/TIMP can favor tissue injury, while the reverse ratio could be associated with increased fibrosis. Glucocorticosteroids could downregulate MMPs and enhance TIMPs. Even though it is clear that stimulated allergic inflammation in airway is associated with increased expression of MMPs, whether specific inhibitors of MMPs could reduce airway structural changes and facilitate orderly healing in asthma is still unknown. [Pediatr Allergy Respir Dis(Korea) 2006;16:12-22]