• 한국세라믹학회지
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• 제45권10호
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• pp.594-599
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• 2008

Hydroxyapatite(HA) was prepared from waste tuna bone, and its sintering property and dissolution behavior were investigated. Tuna bone derived-HA powder consisted of mainly HA and small amount of MgO. Porous HA ceramics with sintered density of 79% was obtained by pressureless sintering at $1200^{\circ}C$. Meanwhile, HA ceramics prepared by hot pressing at $1000^{\circ}C$ showed dense microstructure with sintered density of 95%. Immersion test revealed that both porous and dense HA ceramics were stable in liquid environment without distinct evidence of surface dissolution. It may be assumed that the presence of Mg in tuna bone-derived HA may improve dissolution resistance of HA.

• 호남수학학술지
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• 제37권1호
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• pp.41-52
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• 2015

It is well known that the area U of the triangle formed by three tangents to a parabola X is half of the area T of the triangle formed by joining their points of contact. Recently, it was proved that this property is a characteristic one of parabolas. That is, among strictly locally convex $C^{(3)}$ curves in the plane $\mathbb{R}^2$ parabolas are the only ones satisfying the above area property. In this article, we study strictly locally convex curves in the plane $\mathbb{R}^2$. As a result, generalizing the above mentioned characterization theorem for parabolas we present some conditions which are necessary and sufficient for a strictly locally convex $C^{(3)}$ curve in the plane to be an open part of a parabola.

• 대한수학회논문집
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• 제11권3호
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• pp.673-680
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• 1996

It is proved that $K(c_0,Y)$ is an M-ideal in $L(c_0,Y)$ if Y is a closed subspace of $c_0$. And a new direct proof of the fact that $K(L_1[0,1],\ell_1)$ is not an M-ideal in $L(L_1[0,1],\ell_1)$ is given.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.280.1-280.1
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• 2008

• KSBB Journal
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• 제27권1호
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• pp.21-27
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• 2012

Five yeast strains were isolated from traditional Makgeollies, Makgeollies were made by isolated yeasts after cultivation, and then property changes of Makgeollies were analyzed according to yeasts, storage temperatures and storage periods. Average pHs were shown to be 3.22~3.88 and statistically changed according to yeasts used, storage temperatures and storage periods. Total acidities were statistically changed according to storage periods. Amino-type nitrogen contents were in the ranges of 0.009~0.245% and statistically changed according to storage temperatures especially at 18 and $25^{\circ}C$ for 15 days. Average alcohol concentrations were in the ranges of 7.5~18.5% and reduced until 10 days and increased for 15 days according to yeasts used and storage periods. Consequently, Makgeollies, made by isolated yeast strains originated from traditional Makgeollies, revealed that alcohol concentrations and amino-type nitrogen contents were changed but pHs and total acidities were not dramatically changed according to yeasts used. It suggests that development of various Makgeollies would be possible using isolated yeast strains in this study, and optimal storage condition of ready-made Makgeollies to maintain its original property turned out to be at $4^{\circ}C$ for 5 days. Especially, Makgeolli made by F strain showed the best quality on its property, therefore Makgeolli which maintains its property stably until 10 days when stored at $4^{\circ}C$ could be made using this strain.

• 전기학회논문지
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• 제63권2호
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• pp.250-256
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• 2014

In this study, we deposited and investigated ${\mu}c$-Si:H thin films prepared by Plasma Enhanced Chemical Vapor Deposition(PECVD) system. To deposition silicon thin films, we controlled $SiH_4$ gas concentration, RF input power, and heater temperature. According to the experiments, the more $SiH_4$ gas concentration increased, deposition rate also increased but crystalline property decreased at the same conditions. In the RF input power case, deposition rate and crystalline property increased together when the input power increased from 100[W] to 300[W]. If RF input power was 300[W], deposition rate has reached saturation point. In the heater temperature, deposition rate increased when heater temperature increased. Crystalline property maintained a certain level until heater temperature was $250[^{\circ}C]$. And then it was a suddenly increased. Multistep method has been proposed to improve the quality of ${\mu}c$-Si:H thin film. $SiH_4$ gas was injected with a time interval. According to the experiments, crystallite ratio improve about 20~60[%] and photo conductivity increased up to six times.

• 센서학회지
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• 제15권2호
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• pp.120-126
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• 2006

Physicochemical and electrical properties for hydrogen gas sensors based on Pd-deposited $WO_3$ thin films were investigated as a function of Pd thickness, annealing temperature, and operating temperature. $WO_3$ thin films were deposited on an insulating material by thermal evaporator. XRD, FE-SEM, AFM, and XPS were used to evaluate the crystal structure, microstructure, surface roughness, and chemical property, respectively. The deposited films were grown $WO_3$ polycrystalline with rhombohedral structure after annealing at $500^{\circ}C$. The addition effect of Pd is not the crystallinity but the suppression of grain growth of $WO_3$. Pd was scattered an isolated small spherical grain on $WO_3$ thin film after annealing at $500^{\circ}C$ and it was agglomerated as an irregular large grain or diffused into $WO_3$ after annealing at $600^{\circ}C$. 2 nm Pd-deposited $WO_3$ thin films operated at $250^{\circ}C$ showed good response and recovery property.

• 한국표면공학회지
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• 제29권6호
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• pp.666-672
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• 1996

The optical property of CdTe thin film is important for applications such as the compound semiconductor type solar cells. CdTe films are prepared by RF sputtering at various substrate temperature between $25^{\circ}C$ and $300^{\circ}C$, then, annealed in argon gas environment at $400^{\circ}C$. The annealing process of the thin film caused variation in the film structure and the composition of films. The deformation of CdTe thin film was observed by X-ray diffractometry. After annealing, the grain size increased and the portion of the non-crystalline CdTe reduced. Futhermore, the structure of sputtered CdTe film grown at the substrate temperature more than $250^{\circ}C$ was enhanced in the (111) direction of zincblend structure. There was a discrepancy, in the spectroscopic ellipsometer spectrum, between the single crystal CdTe and the sputtered CdTe thin films, especially in the region over 3.2eV. An oxidation layer was found on the CdTe thin film by spectroscopic ellipsometry analysis.

• 한국주조공학회지
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• 제27권2호
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• pp.83-87
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• 2007

Aluminum plates of the same materials as the foam were attached by the casting process inserting the foam as a core to investigate the tensile property of open cell foams. Tensile properties of the open cell 6063 aluminum alloy foam of $10{\sim}30$ PPI were measured before and after heat treatment. Densities of test specimens were between 0.14 and $0.29g/cm^3$. Tensile strength of the 6063 aluminum foam after heat treatment showed little change. C values were in the range of $0.41{\sim}0.87$ for as cast foams and $0.11{\sim}0.27$ for T6 heat treated foams in the eq. of ${\sigma}^* _{pl}/{\sigma}_{ys}=C({\rho}/{\rho}_s)^{1.5}$, and increased with increase in the cell size.

• Kyungpook Mathematical Journal
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• 제55권4호
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• pp.909-931
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• 2015

This paper presents some new paranormed sequence spaces $X(r,s,t,p;{\Delta})$ where $X{\in}\{l_{\infty}(p),c(p),c_0(p),l(p)\}$ defined by using generalized means and difference operator. It is shown that these are complete linear metric spaces under suitable paranorms. Furthermore, the ${\alpha}$-, ${\beta}$-, ${\gamma}$-duals of these sequence spaces are computed and also obtained necessary and sufficient conditions for some matrix transformations from $X(r,s,t,p;{\Delta})$ to X. Finally, it is proved that the sequence space $l(r,s,t,p;{\Delta})$ is rotund when $p_n$ > 1 for all n and has the Kadec-Klee property.