• 한국세라믹학회지
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• 제47권5호
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• pp.394-400
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• 2010

This study examined the effects of particle size on characteristics of cement by controlling the particle size of commercial cement. Through a size adjustment, the cement has increasing more of particles that are less than $10{\mu}m$ in size so the initial reaction time has been shortened as a result of improvement in the early hydration reaction. Additionally, it showed a great characteristics of strength from the early age and the initial hydration heat has been increased as well. In the upper and middle parts cements, the initial hydration reaction rate contribution is high with the $10{\mu}m$ compared to original cement. So the initial hydration reaction rate is improved and as a result, it also showed relatively high hydration heat as well. Additionally, adiabatic temperature also showed an increase rate in the results.

• 한국전기전자재료학회논문지
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• 제14권2호
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• pp.152-157
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• 2001

For the fabrication of YBa$_2$Cu$_3$O$_{x}$ thick film using diffusion process between $Y_3$BaCuO$_{5}$ and BaO+CuO, each material was selected as substrate and doping material. In this paper, we investigated the characteristic of YBa$_2$Cu$_3$O$_{x}$ thick film due to both addition of CeO$_2$into substrate and initial particle size of doping material. Through X-ray diffraction patterns and SEM photographs, the variation of composition and thickness of the formed phase was observed. It was from the experiment obtained that the addition of CeO$_2$into $Y_2$BaCuO$_{5}$ substrate and the initial particle size of doping material play important part in promoting the reaction between substrate and doping material.aterial.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2005년도 춘계학술발표회 및 정기총회 2권1호(통권2호)
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• pp.125-132
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• 2005

Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and it happens large deformation phenomenon. And also there are highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different. Therefore, in this study, to find the structural shape after large deformation caused by Initial stress, we need the shape analysis considering geometric nonlinear ten And the geodesic line on surface of initial equilibrium shape and the cutting pattern generation using the geodesic line is introduced.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.225-228
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• 1997

YBa$_2$Cu$_3$O$_{x}$ samples with different amounts of $Y_2$BaCuO$_{5}$ were prepared by MPMG (Melt Powder Melt Growth) method. The effects on the size of initial particles and Ag addition for $Y_2$BaCuO$_{5}$ distribution in YBa$_2$Cu$_3$O$_{x}$ were invesgated. The samples prepared by the melting process usually have large grains up to several ㎣ and precipitates of $Y_2$BaCuO$_{5}$. The distribution of the $Y_2$BaCuO$_{5}$ particles in the samples depends on the size of initial particles and the amounts of Ag addition.Ag addition.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.843-846
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• 2004

Pt nanoparticles loaded on alumina through an impregnation at room temperature was prepared using $K_2PtCl_4$ and acrylic acid as capping material. Transmission electron microscopy showed that the deposited Pt particles indicate ca. 80% cubic shapes with a narrow distribution of 8-10 nm in size. Propylene hydrogenation over the catalyst has been carried out to evaluate their catalytic performance by the values of activation energy. It is determined from the initial rate, reaction order, and rate constant and is found to be $9.7{\pm}0.5$ kcal/mol. This value has been discussed by comparing to those of encapsulated- and truncated octahedral Pt nanoparticles deposited on alumina, respectively, to study influence of the particle size and shape, and capping material used on the activation energy.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.136-139
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• 2002

Previous valves have initial gap problem, high voltage or high pressure problem. In this paper, various micro valves with free floating structure have been fabricated and tested to solve the initial gap and high pressure problems. The paper presents how to etch Parylene-C which is a valve cap material without A1 mask layer. The maximum flow-rate of fabricated micro valve is$118{\mu\ell}$/min with $370{\mu}m$ orifice size and the leakage at the initial and reverse pressure is not observed.

• 한국안전학회지
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• 제7권3호
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• pp.66-72
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• 1992

An experimental study was carried out to analyse the explosion characteristics of flammable gas-air mixtures. Used flammable gases were hydrogen, methane, acethylene, ethylene and pro-pane, explosion Pressure, explosoin pressure rising rate, and flame propagation velocity were measured experimentaly. The maximum explosion pressure and rising rate of flammmalbe gas air mixtures were appeared at the range of slightly higher concentration than the stoichiometric concentration. Initial pressure before explosion was controlled from 0.6 to 2.0kg/cm absolutly. Explosion pressure was increased with increment of the initial pressure, and the relationship between initial pressure and explosion pressure was Pe = KPi. The effect of vessel size on explosion characteristics was also analysed In this experiment. Explosion pressure was increased with in-creasing the vessel size, otherwise explosion pressure rising rate was decreased. When we locate a dummy material in vessel explosion pressure was decreased with increasing the dummy volume but exlosion pressure rising rate was increased.

• 한국전기전자재료학회논문지
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• 제11권5호
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• pp.384-393
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• 1998

A mixed powder of electrolyte and matrix support materials with a proper proportion was used for the fabrication of an electrolyte matrix sheet. The purpose of this study is to reduce the large change in MCFC cell thickness occurring in the initial start-up period when separate sheets of electrolyte and support are used. A focus was put on how small the carbonate particles could be made. The particle size of the carbonate powder was controlled by ball milling and the distribution was measured using a particle size analyser. The thickness change was reduced to 20% by this approach, which could be compared to 27% observed in a conventional cell. The thickness changes of electrolyte matrix have linear relation sizes of carbonate powders.

• 소성∙가공
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• 제20권7호
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• pp.491-497
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• 2011

This work describes a method for determining material parameters included in recrystallization and grain growth models of metallic materials. The focus is on the recrystallization and grain growth models of Ni-Fe based superalloy, Alloy 718. High temperature compression test data at different strain, strain rate and temperature conditions were chosen to determine the material parameters of the model. The critical strain and dynamically recrystallized grain size and fraction at various process conditions were generated from the microstructural analysis and strain-stress relationships of the compression tests. Also, isothermal heat treatments were utilized to fit the material constants included in the grain growth model. Verification of the determined material parameters is carried out by comparing the average grain size data obtained from other compression tests of the Alloy 718 specimens with the initial grain size of $59.5{\mu}m$.

• 대한의용생체공학회:의공학회지
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• 제34권3호
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• pp.117-122
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• 2013

Hyaluronic acid(HA) microbeads were synthesized by dropping the sodium hyaluronate(Streptococcus) solutions in NaOH into a solution mixture of divinyl sulfone(DVS) in 2-methyl-1-propanol, followed by stirring, cleaning and drying process at room temperature. The initial experimental conditions are crosslinking time(CLTi) of 5 h, crosslinking temperature(CLTe) of room temperature, injection air pressure(IAPr) of 5 psi, and DVS concentration( DVSc) of 0.2 vol%, respectively. Then, parametric studies were performed by varying the parameters to investigate the morphology, the porosity, the swelling ratio and the size of the beads. The microbead size pattern was not regular to function of the degree of crosslink. It was observed that the swelling ratio, the degree of crosslink, and the pore size can be controlled by adjusting the CLTi, CLTe and DVSc. Among the parameters investigated, the smallest bead size can be achieved by varying the CLTi parameter. The lowest swelling ratio, as an indication of the highest degree of crosslink, can be obtained by varying CLTe.