• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.60-67
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• 2019

To understand the low frequency instability(LFI) characteristics in hybrid rockets combustion, effects of equivalence ratio variations on the phase shift between pressure and heat release oscillations were investigated by using the direct numerical simulation. The change in the equivalence ratio of the main chamber was simulated by the temperature and composition variation of the combustion gas introduced into the post-combustion chamber. In the results, additional combustion appeared along with vortex generation at the backward step, and combustion pressure and heat release oscillations were observed as the vortex moved. In addition, the results confirmed that the phase difference between the pressure and heat release oscillation shifts because of the changes in the propagation velocity of pressure wave as the temperature of combustion gas changes.

• Journal of the Korean Magnetics Society
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• v.16 no.1
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• pp.14-17
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• 2006

[ $AIFeO_3$ ]has been studied by x-ray diffraction (XRD), vibrating sample magnetometer, Mossbauer spectroscopy. The crystal structure is found to orthorhombic with the lattice parameters being $a_0=4.983\;{\AA},\;b_0=8.554\;{\AA},\;c_0=9.239\;{\AA}$, Magnetic hysteresis curve for $AIFeO_3$ showed weakly ferromagnetic phase at room temperature and a asymmetric shape dependent on the direction of applied field at low temperature. The Curie temperature determined by the temperature dependence of magnetization is 250 K. Mossbauer spectra of $AIFeO_3$ have been taken from 4.2 K to 295 K. Isomer shift at room temperature are found to be $0.11\~0.32\;mm/s$, which is consistent with ferric state. The absorption lines widths become broader with increasing temperature, which is attributed to the Fe ions distribution of each cation site and anisotropy energy difference of each sublattice.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1382-1384
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• 1995

In order to study the structure of RF glow discharge driven at 13.56MHz in argon, the discharge voltage, current and phase shift between them will be measured over a wide range of discharge parameters(gas pressure between 1mTorr and 50mTorr with discharge power between 20mW and 200W). In this paper, the dc glow discharge characteristics and plasma parameters of both FTS and CPMS systems are studied experimentally. It is found that for CPMS system discharge is stablized under wider ranges of magnetic field and pressure than for FTS system. The plasma density and electron temperature of the plasma for these two systems are in the range of $10^{10}{\sim}7{\times}10^{11}[cm^{-3}]$ and $3.5{\sim}6.5$[eV], respectively.

• 한국전기화학회:학술대회논문집
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• 2005.07a
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• pp.317-322
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• 2005

[ $Pt/CeO_2$ ] 촉매에 Zr을 첨가하여 우수한 저온 수성가스전화반응의 활성을 가진 촉매를 만들었다. $Pt/ZrO_2-CeO_2$ 촉매는 $Pt/ZrO_2$나 $Pt/CeO_2$ 촉매에 비해 Ce와 Zr의 상호작용에 의한 시너지 효과로 인해 CO chemisorption으로 측정한 Pt area가 증가하고 담체에 Pt가 잘 분산되었다. 또한, Zr이 첨가된 $Pt/CeO_2$는 Ce의 redox 능력을 향상시켜 support의 reducibility를 향상시켰다. 담체에 고르게 잘 분산되고 support의 산소저장능력과 reducibility가 향상된 $3\;wt\%\;Pt/ZrO_2-CeO_2$ 촉매들은 반응물에 수소와 이산화탄소의 첨가 유무와 상관없이 $3\;wt\%\;Pt/ZrO_2$나 $3\;wt\%\;Pt/CeO_2$ 촉매보다 우수한 활성을 보였다.

• Nuclear Engineering and Technology
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• v.38 no.5
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• pp.405-410
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• 2006

Microstructural features and their related mechanical property changes in the 309L cladding and the heat affected zone (HAZ) of SA508 cl.3 steel were investigated through the use of TEM, tensile and small punch (SP) tests. The specimens were irradiated at 563 K up to the neutron fluences of $5.79{\times}10^{19}n/cm^2$ (>1MeV). The microstructure of the clad was mainly composed of a fcc ${\gamma}-phase$, a low percentage of bcc ${\delta}-ferrite$, and a brittle ${\sigma}-phase$. Along the weld fusion line there formed a heavy carbide precipitation with a width of $20{\sim}40{\mu}m$, showing preferential cracking during plastic deformation. The yield stress and ductile-to-brittle transition temperature (DBTT) of the irradiated clads increased. The origin of the hardening and the shift of the DBTT are discussed in terms of the irradiation-produced defect clusters of a fine size and brittle ${\sigma}-phase$.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.516-519
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• 1996

Sub-assembly in ship manufacturing is a sequence of filet joint welding of stiffeners on metal panels and the process is different depending on companies. In this paper, we introduce a new intelligent robotic system of the sub-assembly process in Samsung Heavy Industry, where one shift of 22m * 9m workspace includes one to ten panels and each panel includes up to 10 stiffeners. The inherent problems such as several hundreds of different panels, unstructured task environment and the large scale do not allow a fixed automation, but needs highly intelligent versatile automation. The robotic system is composed of four 14DOF macro-mini robots and a task recognition system. Application of this system has verified the task specification such as low temperature environment(-10.deg. C) and productivity is satisfied successfully.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.273-276
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• 2001

The origin of image-slicking in metal-insulator-metal type thin-film-diode(TFD) LCDs is the asymmetric current-voltage(I-V) characteristic of TFD element. we developed that MIM-LCDs have reduced-image-sticking and perfect symmetry characteristic. One-Time Post-Annealing (OPTA) heat treatment process was introduced to reduce the asymmetry and shift of the I-V characteristics, respectively. OPTA means that the whole layers of lower metal, insulator, and uuper metal are annealed at one time. The treatment temperatures and fabricated process of TFD element were under foot. Also, this low temperature fabricated process allows the application of plastic substrates.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.112-116
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• 2011

In this paper, a preconverter of MCFC for an emergence electric power supplier is numerically simulated to increase the hydrogen production from natural gas (methane). Commercial code is used to simulated the porous catalyst with user subroutine to model three dominant chemical reactions which are Stream Reforming(SR), Water-Gas Shift(WGS), and Direct Stram Reforming(DSR). To get 10% fuel conversion rate in preconverter. the required external heat flux is supplied from outer wall of preconverter. The calculated results show that very nonuniform temperature distribution and chemical reaction happen near the wall of preconverter. These phenomena can be explained by the low heat conductivity of porous catalyst and the endothermic reforming reaction.

• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1729-1732
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• 2002

The LB71350,(3S, 4R)-Epoxy-(5S)-[[N-(1-methylethoxy)carbonyl]-3-(methylsulfonyl)-L-valinyl]amino]-N-[2-methyl-(1R)-[(phenyl)carbonylpropyl-6-phenylhexanamide, is a novel HIV protease inhibitor. Its equilibrium solubility at room temperature was less than $40{\mu}g/mL.$ It was speculated that the low aqueous solubility might be due to the high crystalline lattice energy resulting from intermolecular hydrogen bonds. The present study was carried out to learn the solid-state characteristics of LB71350 using analytical methods such as NMR, FT-IR and XRD. $^{13}C$ Solid-state NMR, solution NMR, and FT-IR spectra of the various solid forms of LB71350 were used to identify the conformation and structure of the solid forms. The chemical shifts of $^{13}C$ solid-state NMR spectra suggest that the crystalline form might have 3 intermolecular hydrogen bondings between monomers.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.746-748
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• 2004

a-Si TFTs with field-effect mobility of 1.2 $cm^2$/V-s have been fabricated on plastic substrate. Pixel circuits on plastic for AMOLED were made with the same low-temperature fabrication process. The circuits compensate for $V_T$-shift, exhibit high output current, retain functionality and drive current level during long-time continuous operation.