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Molecular Beam Epitaxy Grouth of $\textrm{LaAlO}_3$ Thin Film by a Pulsed laser Deposition Technique
김인선,허남회,박용기,Kim, In-Seon,Heo, Nam-Hoe,Park, Yong-Gi Materials Research Society of Korea 1999 한국재료학회지 Vol.9 No.1
We have developed a laser molecular beam epitaxy system for the layer-by-layer growth of oxide thin films. Using this system, we could grow and control oxide thin films of LaAlO$_3$in a molecular layer epitaxy mode on the atomically flat SrTiO$_3$ substrate with a LaAlO$_3$single crystal target. Very clear RHEED oscillations were observed during to growth of a LaAlO$_3$ film for a long period under the optimized conditions of substrate temperature at $650^{\circ}C$, oxygen pressure at 1$\times$10\ulcorner torr, and an incident laser fluence of 4.6J/$\textrm{cm}^2$. The height of mono-layer-LaAlO$_3$ film grown during one period of RHEED intensity oscillation was 3.8$\AA$.
2.25Cr강 보일러 튜브재료의 고온입계균열 발생 거동
유근봉(Keun Bong Yoo),허남회(Nam Hoe Heo),장중철(Jung Chel Jang),김재훈(Jae Hoon Kim) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Recently, a premature failure of boiler tubes or pipes has frequently occurred at several domestic power plants and most of the fracture type was intergranular. It has been well known that the elevated temperature intergranular cracking in heat-resistant steels occurs through the combination of closely spaced voids at the grain boundaries oriented normal to the tensile stress. However, what the mechanism of low ductility intergranular fracture induced by the tensile stress is are still obscure. In this study, we analyzed the behavior of the elevated temperature intergranular cracking in 2.25Cr-1.5W heat-resistant steels through stress-rupture test. We used the SEM(Scanning Electron Microscope) and AES(Auger Electron Spectroscopy) to investigate the fracture surface and segregation behavior.
이재승,이호진,이강봉,허남회,Lee, Jae Seung,Jung, Dong J.,Lee, Ho Jin,Lee, Gang Bong,Heo, Nam Hoe,Jang, Ho G. Korean Chemical Society 2000 Bulletin of the Korean Chemical Society Vol.21 No.10
[Fe II Fe III $BPLNP(OAc)_2](BPh_4)_2$ (1), a new model for the reduced form of the purple acid phosphatases, has been synthesized by using a dinucleating ligand, 2,6-bis[((2-pyridylmethyl)(6-methyl-2-pyridylmethyl)ami-no)methyl]-4-nitrophenol (HBPLNP) . Complex 1 has been studied by electronic spectral, NMR, EPR, SQUID, and electrochemical methods. Complex 1 exhibits two strong bands at 498 nm $(\varepsilon=$ 2.6 ${\times}10^3M-^1cm-^1)$ and 1363 nm $(\varepsilon=$ 5.7 ${\times}10^2M-^1cm-^1)$ in $CH_3CN.$ These are assigned to phenolate-to-FeIII and intervalence charge-transfer transitions, respectively. NMR spectrum of complex 1 exhibits sharp isotropically shifted resonances, which number is half of those expected for a valence-trapped species, indicating that electron transfer between FeⅡ and FeⅢ centers is faster than NMR time scale at room temperature. Complex 1 undergoes quasireversible one-electron redox processes. The $FeIII_2/FeIIFeIII$ and $FeIIFeIII/FeII_2$ redox couples are at 0.807 and 0.167 V ver-sus SCE, respectively. It has Kcomp = 5.9 ${\times}$10 1s(acetato) ligand combination sta-bilizes a mixed-valence FeIIFeIII complex in the air. Interestingly, complex 1 exhibits intense EPR signals at g = 8.56, 5.45, 4.30 corresponding to mononuclear high-spin FeⅢ species, which suggest a very weak magnetic coupling between the iron centers. Magnetic susceptibility study shows that there is a very weak antiferromag-netic coupling (J = $-0.78cm-^1$, H = $-2JS_1${\times}$S_2)$ between FeII and FeIII centers. Thus, we can suggest that complex 1 has a very weak antiferromagnetic coupling between the iron centers due to the electronic effect of the nitro group in the bridging phenolate ligand.
공기구동밸브 스템 손상 원인분석을 통한 구조 신뢰성 향상
박치용(Chi-yong Park),이경수(Kyoung-soo Lee),김완재(Wan-Jae Kim),허남회(Nam-Hoe Heo) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
The air operated isolation valve in the power plant is used to stop pipe flow from heat exchange to steam turbine. If an isolation valve would be abruptly closed due to failure of its component such as stem, shaft and others, the plant could be shut down by the safety operation system. In this paper, firstly, we carried out the failure analysis for failed stem of an air operated valve, which are included macro and micro investigation for failure component and surfaces, root cause analysis for damaged component and establishment of failure scenario. Next, numerical analysis also were performed for investigation of effects for four failure factors, which were selected by root cause analysis. Finally, modified design and maintenance methodology were proposed for structural reliability improvement of air operated isolation valve.