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Selective oxygen species for the oxidative coupling of methane
Kim, Ilho,Lee, Gihoon,Na, Hyon Bin,Ha, Jeong-Myeong,Jung, Ji Chul Elsevier 2017 Molecular catalysis Vol.435 No.-
<P>Herein, we attempt to identify selective oxygen species for the oxidative coupling of methane using lanthanum-based perovskite catalysts (LaXO3, X = Al, Fe, or Ni), which are well-known not only as stoichiometric materials with simple and definite structures but also as materials with outstanding catalytic activities in various methane conversion reactions. The catalytic activities of LaXO3 in the presence or absence of oxygen clearly demonstrated that surface lattice oxygen species are responsible for the selective conversion of methane. More importantly, electrophilic (LaAlO3), moderate (LaFeO3), and nucle-ophilic (LaNiO3) lattice oxygen species selectively catalyze the oxidative coupling of methane to C-2 hydrocarbons, the direct partial oxidation of methane to carbon monoxide, and the methane combustion to carbon dioxide, respectively. In addition, adsorbed oxygen species originating from gas-phase oxygen play roles both in converting methane to CO. and in filling surface lattice oxygen vacancies, which are caused by the reaction of lattice oxygen and methane. Finally, we concluded that electrophilic lattice oxygen species and the facile filling of surface lattice oxygen vacancies by gas-phase oxygen are key factors for the systematic design of efficient catalysts for the oxidative coupling of methane. (C) 2017 Elsevier B.V. All rights reserved.</P>
아스팔트 혼합물의 골재 간극률 예측을 위한 기계학습 프레임워크
박혜민,나일호,김현환,지봉준,Hyemin Park,Ilho Na,Hyunhwan Kim,Bongjun Ji 한국지반신소재학회 2024 한국지반신소재학회 논문집 Vol.23 No.1
The Voids in the Mineral Aggregate (VMA) within asphalt mixtures play a crucial role in defining the mixture's structural integrity, durability, and resistance to environmental factors. Accurate prediction and optimization of VMA are essential for enhancing the performance and longevity of asphalt pavements, particularly in varying climatic and environmental conditions. This study introduces a novel machine learning framework leveraging ensemble machine learning model for predicting VMA in asphalt mixtures. By analyzing a comprehensive set of variables, including aggregate size distribution, binder content, and compaction levels, our framework offers a more precise prediction of VMA than traditional single-model approaches. The use of advanced machine learning techniques not only surpasses the accuracy of conventional empirical methods but also significantly reduces the reliance on extensive laboratory testing. Our findings highlight the effectiveness of a data-driven approach in the field of asphalt mixture design, showcasing a path toward more efficient and sustainable pavement engineering practices. This research contributes to the advancement of predictive modeling in construction materials, offering valuable insights for the design and optimization of asphalt mixtures with optimal void characteristics.
다짐온도에 따른 변형강도 변화를 통한 아스팔트 콘크리트의 철도노반 적용성 평가
박지용(Ji-Yong Park),최광수(Kwang-Soo Choi),이성진(Sung-Jin Lee),김성운(Sungun Kim),나일호(Ilho Na),김광우(Kwang W. Kim) 한국철도학회 2012 한국철도학회 학술발표대회논문집 Vol.2012 No.10
아스팔트 콘크리트 철도노반은 여러 가지 장점 때문에 선진국에서는 많이 적용되고 있어 국내에서도 철도에 적용성 연구가 필요하다. 아스팔트 포장은 소성변형 발생의 우려가 커 사전에 강도시험 등을 통해 공용성 확인이 필요하며, 철도용 아스팔트 콘크리트도 같은 맥락에서 소성변형에 대한 평가가 필요하다. 이에 본 연구에서는 변형강도(SD)를 사용하여 가열 아스팔트(HMA) 콘크리트와 준고온 아스팔트(WMA) 콘크리트의 소성변형 저항성을 평가하여 적정다짐온도를 추정하였다. 연구 결과 일반 아스팔트 혼합물은 HMA 135℃, WMA 105℃ 이상, PMA에서는 HMA155℃, WMA 125℃ 이상이 적정 다짐온도로 확인되었다. Since asphalt concrete is widely used for railroad base in advanced countries due to many advantages, the preliminary research for its applicability is necessary in Korea. Asphalt concrete is prone to deform (rut) in hot environment, and therefore, the rut resistance of asphalt concrete for railroad is also need to be evaluate. The rut resistance of hot-mix asphalt (HMA) concrete and warm-mix asphalt (WMA) concrete was evaluated to determine optimum compaction temperature (OCT) using deformation strength (SD). The results showed that OCT values of normal asphalt HMA and WMA were 135℃ and 105℃ , respectively, and those of polymer-modified HMA and WMA were 155℃ and 125℃, respectively.