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Reduced order model of three-dimensional Euler equations using proper orthogonal decomposition basis
Jun, Sang-Ook,Park, Kyung-Hyun,Kang, Hyung-Min,Lee, Dong-Ho,Cho, Maeng-Hyo The Korean Society of Mechanical Engineers 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.2
This study seeks to validate the accuracy and the efficiency of the aerodynamic reduced order model (ROM). In doing this, snapshot data are generated from the full system analysis of a fighter wing problem. From an eigensystem analysis of these snapshots, the basis vector reproducing the behavior of the full system is obtained. The span length, sweep angle, dihedral angle, and spar and rib thickness representing the wing configuration are determined as the input variables. The constructed ROM is applied to the fighter wing problem while varying the input conditions for validation. Subsequently, a comparison of the reduced system with the full system confirmed that the aerodynamic performance is within 4% error and that the <TEX>$L_2$</TEX> norms are <TEX>$10^{-6}$</TEX> order of the entire flow field. Therefore, the ROM is able to capture the variation of the aerodynamic performance with respect to the input variables. Though there are structural input variables which influence the aerodynamic performance indirectly, the ROM can reproduce the flow field of the full system. Additionally, even if the ROM incurs a high computational cost to generate snapshots, it can represent the behavior of the full system efficiently once the reduced order model is constructed.
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Kim, Sung-Kwan,Hong, Sung-Ahn,Son, Ho-Jin,Han, Won-Sik,Michalak, Artur,Hwang, Son-Jong,Kang, Sang Ook The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.16
<P>A highly electrophilic cationic Pd<SUP>II</SUP> complex, [Pd(MeCN)<SUB>4</SUB>][BF<SUB>4</SUB>]<SUB>2</SUB> (<B>1</B>), brings about the preferential activation of the B–H bond in ammonia-borane (NH<SUB>3</SUB>·BH<SUB>3</SUB>, AB). At room temperature, the reaction between <B>1</B> in CH<SUB>3</SUB>NO<SUB>2</SUB> and AB in tetraglyme leads to Pd nanoparticles and formation of spent fuels of the general formula MeNH<SUB><I>x</I></SUB>BO<SUB><I>y</I></SUB> as reaction byproducts, while 2 equiv. of H<SUB>2</SUB> is efficiently released per AB equiv. at room temperature within 60 seconds. For a mechanistic understanding of dehydrogenation by <B>1</B>, the chemical structures of spent fuels were intensely characterized by a series of analyses such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid state magic-angle-spinning (MAS) NMR spectra (<SUP>2</SUP>H, <SUP>13</SUP>C, <SUP>15</SUP>N, and <SUP>11</SUP>B), and cross polarization (CP) MAS methods. During AB dehydrogenation, the involvement of MeNO<SUB>2</SUB> in the spent fuels showed that the mechanism of dehydrogenation catalyzed by <B>1</B> is different from that found in the previously reported results. This AB dehydrogenation derived from MeNO<SUB>2</SUB> is supported by a subsequent digestion experiment of the AB spent fuel: B(OMe)<SUB>3</SUB> and <I>N</I>-methylhydroxylamine ([Me(OH)N]<SUB>2</SUB>CH<SUB>2</SUB>), which are formed by the methanolysis of the AB spent fuel (MeNH<SUB><I>x</I></SUB>BO<SUB><I>y</I></SUB>), were identified by means of <SUP>11</SUP>B NMR and single crystal structural analysis, respectively. A similar catalytic behavior was also observed in the AB dehydrogenation catalyzed by a nickel catalyst, [Ni(MeCN)<SUB>6</SUB>][BF<SUB>4</SUB>]<SUB>2</SUB> (<B>2</B>).</P> <P>Graphic Abstract</P><P>This work provides a comprehensive experimental study on the mechanism of AB dehydrogenation with the [Pd(MeCN)<SUB>4</SUB>][BF<SUB>4</SUB>]<SUB>2</SUB> (<B>1</B>) catalyst. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5dt00599j'> </P>
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Tensile Bond Characteristics between Underwater Coating Materials and Concrete Substrate
Min Ook Kim(김민욱),Yeonung Jeong(정연웅),Sung-Hoon Kang(강성훈),Juhyuk Moon(문주혁),Jin-Hak Yi(이진학) 한국해안해양공학회 2018 한국해안해양공학회 논문집 Vol.30 No.6
본 연구에서는 해양·항만 콘크리트 구조물의 보수작업을 위한 수중코팅제의 부착 특성을 조사하기 위하여 실험적 연구를 수행하였다. 고려된 실험변수는 코팅제의 종류, 코팅대상 모재의 표면 거칠기, 도포 작업환경(육상 혹은 수중)으로 부착 강도는 Pull-off 방식으로 측정하였다. 코팅제의 부착 강도는 각 수중코팅제의 도포 작업 완료 24시간 후에 ASTM C1583 규정에 따라 측정하였다. 또한, 콘크리트 모재와 코팅제 간의 부착파괴 거동(코팅제, 계면, 콘크리트 모재)을 육안으로 관찰하였으며 측정된 부착 강도 수치에 근거하여 각 실험요인의 비교분석을 수행하였다. 실험결과, 수중에서 도포한 코팅제의 부착 강도가 육상의 경우에 비해 감소하는 경향을 보였으며 수중환경에서는 부착 강도에 미치는 모재 표면 거칠기의 영향이 육상의 경우에 비하여 미비하였다. 마지막으로 수중코팅제의 선정, 사용 시에 유의할 점에 대하여 설명하였다. In this study, we investigated the tensile bond characteristics of underwater coating materials, in order to obtain useful information in support of repair work for marine and coastal concrete structures. Test variables included type of underwater coating, surface conditions of the concrete substrate, and environmental conditions. Pull-off tensile bond strength was measured at 24 h after applying underwater coatings to concrete substrates, in compliance with the procedures specified in ASTM C1583. Failure modes (coating, interface, and parent concrete) for each coating were identified through visual inspection, and comparisons were made based on measured bond strength. The tensile bond strength decreased underwater compared to that under dry conditions, while no significant effect of surface roughness on the measured bond strength was observed in underwater tests. Key aspects that need to be considered regarding selection and use of underwater coating materials for marine and coastal concrete structures were discussed.
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Growth of TiO2 nanorods on a Ta substrate by metal-organic chemical vapor deposition.
Lee, Kang Suk,Hyun, Jae-Sung,Seo, Hyun Ook,Kim, Young Dok,Boo, Jin-Hyo American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.5
<P>TiO2 nanorods were successfully grown on Tantalum (Ta) substrates using titanium tetra isopropoxide (TTIP) as a single precursor without any carriers or bubbling gases. For characterization of the TiO2 structures, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were employed. For substrate temperatures below 800 degrees C, a rough film structure without nanorods could be found. However, at a sample temperature of 800 degrees C, nanorod structures with a respective diameter and length of 0.1 approximately 0.2 microm and 0.7 approximately 1.5 microm, respectively, could be synthesized. The nanorods exhibited a rutile phase with a 2:1 stoichiometry of O:Ti, identified using XRD and XPS. When the growth temperature exceeded 800 degrees C, agglomeration of the nanorods was identified.</P>
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