• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.482-488
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• 1995

The phase transformation temperature from $\theta$- to $\alpha$-alumina was lowered from 1214$^{\circ}C$ to 114$0^{\circ}C$ in DSC by treating ${\gamma}$-alumina obtained by calcination of boehmite at $700^{\circ}C$ for 2hrswith $\alpha$-Al2O3 seeds (d50=0.36${\mu}{\textrm}{m}$) and 3wt% of the alumina sol. $\alpha$-Al2O3 seeds seemed to lower to the transformation temperature and the alumina sol suppressed the high temperature agglormeration. The effect was increased as the amount of the sol was increased, which was supported by TEM and particle size distribution. For an example, spherical ${\gamma}$-alumina powder with d50=0.54${\mu}{\textrm}{m}$ was prepared by treating the ${\gamma}$-alumina with 9 wt% of the alumina sol and 3wt% of the $\alpha$-Al2O3. It sintered to 99% of the theoretical density at 150$0^{\circ}C$ for 2hrs. and it had relatively homogeneous microstructure with 2~3${\mu}{\textrm}{m}$ sized grains.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.43.1-43.1
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• 2017

A three-dimensional (3D) $Ly{\alpha}$ radiative transfer code is developed to study the Wouthuysen-Field effect, which couples the 21 cm spin temperature of neutral hydrogen and the $Ly{\alpha}$ radiation field, and the escape fraction of $Ly{\alpha}$ from galaxies. The Monte Carlo code is capable of treating arbitrary 3D distributions of $Ly{\alpha}$ source, neutral hydrogen and dust densities, gas temperature, and velocity field. It is demonstrated that the resonance-line profile at the center approaches to the Boltzmann distribution with the gas temperature. A plane-parallel ISM model, which is appropriate for the neutral ISM of our Galaxy, is used to calculate the $Ly{\alpha}$ radiation field strength as a function of height above the galactic plane. We also use a two-phase, clumpy medium model which is composed of the cold and warm neutral media (WNM). It is found that the $Ly{\alpha}$ radiation field is strong enough to thermalize the 21 cm spin temperature in the WNM to the gas kinetic temperature. The escape fraction of $Ly{\alpha}$ is found to be a few percent, which is consistent with the $Ly{\alpha}$ observations of our Galaxy and external galaxies.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.5
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• pp.271-277
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• 2004

Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at ${\beta}$-temperature ($1020^{\circ}C$) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanst$\ddot{a}$tten structure was observed on the furnace-cooled sample. The relationship between ${\alpha}$-Widmanst$\ddot{a}$tten and ${\beta}$-phase was the {0001}${\alpha}$//{110}${\beta}$, <11$\bar{2}$0>//<111>. The ${\beta}$-phase in Widmanst$\ddot{a}$tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as ${\beta}_{Zr}$ phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.

• Journal of Adhesion and Interface
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• v.2 no.2
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• pp.11-19
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• 2001

The phase-transfer catalyzed radical polymerization of styrene was carried out using tricaprylylmethylammonium chloride as a phase-transfer catalyst in a two-phase system of an aqueous $Na_2S_2O_8$ solution and toluene at $60^{\circ}C$ under nitrogen atmosphere. The initial rate of radical polymerization was expressed as the combined terms of concentrations of quaternary onium cation and peroxydisulfate anion in the aqueous phase rather than the fed concentrations of catalyst and $Na_2S_2O_8$. The observed initial rate of radical polymerization was used to analyze the radical polymerization mechanism with a cycle phase-transfer initiation step in the heterogeneous liquid-liquid system. The viscosity average molecular weight of polystyrene was inversely proportional to concentration of $Na_2S_2O_8$ expressed as $[Q^+]([S_2O{_8}^{2-}]{\alpha}_2)^{1/2}$ derived by the radical polymerization mechanism.

• Korean Journal of Materials Research
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• v.19 no.6
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• pp.305-312
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• 2009

The effects of Quenching and Partitioning (Q&P) and Annealed Martensite (AM) heat treatment on the microstructure and tensile properties were investigated for 0.24C-0.5Si-1.5Mn-1Al steels. The Q&P steels were annealed at a single phase ($\gamma$) or a dual phase (${\gamma}+{\alpha}$), followed by quenching to a temperature between $M_s$ and $M_f$. Then, enriching carbon was conducted to stabilize the austenite through the partitioning, followed by water quenching. The AM steels were intercritically annealed at a dual phase (${\gamma}+{\alpha}$) temperature and austempered at $M_s$ and $M_s{\pm}50^{\circ}C$, followed by cooling in oil quenching. The dual phase Q&P steels showed lower tensile strength and yieldyield strength than those of the single phase Q&P steels, and tThe elongation for the dual phase Q&P steel was partitioning 100s higher than that of that for the single phase Q&P steels as the partitioning time was less than 100s up to partitioning 100s. For AM steels, the tensile/yield strength decreased and the total elongation increased as the austempering temperature increased. The stability of the retained austenite controlled the elongation for Q&P steels and the volume fraction of the retained austenite controlled the elongation for AM steels.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.322-326
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• 1999

In this study, cold-rolling and appropriate annealing was adopted for the grain refining of Cu-26.65Zn-4. 05Al-0.31Ti(wt%) shape memory alloy. For the cold deformation of this alloy the ducti1e $\alpha$-phase must be contained. After heat treatment at $550^{\circ}C$ the $(\alpha+$\beta)$-dual phase with 40vol.% $\alpha$-phase was obtained which could be rolled at room temperature. This alloy was cold rolled into a final thickness of 1.0mm with total reduction degrees of 70% and 90%. The rolled sheets were betanized at $800^{\circ}C$ for various times, then quenched into ice water. The grain size of co]d rolled samples were $60~80\mu\textrm{m}$ which is much smaller comparing with the hot-rolled samples. And the 90% rolled sample showed smaller grain size than the case of the 70% rolled one. The small grain size had influence on the phase transformation temperatures and stabilization of the austenitic phases.

• Clinical and Experimental Reproductive Medicine
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• v.29 no.4
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• pp.337-343
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• 2002

Objectives: To investigate the distribution of $ER{\alpha}$, $ER{\beta}$, c-fos and c-jun in the uterine myoma and myometrium in oder to know how the tamoxifen cause the growth of myoma. Methods: Myoma and myometrial tissue were obtained from the postmenopausal women treated with tamoxifen in the patients with breast cancer and in the premenopausal patients, who were undergoing myoma of uterus from 1998 through 2000. The espression of each gene was quantitated with quantitative RT-PCR. Results: The expression of $ER{\alpha}$ was slightly increased in the myoma than the myometrium in the proliferative phase, and was slightly decreased in the myometrium than the myoma in the secretory phase. However it was not significant statistically. In the postmemopausal women treated with tamoxifen, $ER{\alpha}$ was expressed in all myoma and myome1rial tissues and the expression was not statistically significant. The expression ofER~ was slightly increased in the myome1rium than the leiomyoma in the proliferative and secretory phase, but it was not significant statistically. In the postmemopausal women treated with tamoxifen, the expression of ER~ was significantly incresed in the myome1rium than the leiomyoma. The expression of c-fos was significantly increased in the myome1rium than the leiomyoma in the proliferative and secretory phase. In the postmemopausal women treated with tamoxifen, the expression of c-fos was slightly increased in the leiomyoma than the myomelrium, however, it was not statistically significant. Conclusion: Tamoxifen may cause the growth of leiomyoma by $ER{\alpha}$ with AP-l pathway reducing the counteraction of 6$ER{\beta}$ to $ER{\alpha}$.

• Korean Journal of Materials Research
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• v.21 no.10
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• pp.563-567
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• 2011

We report the structural characterization of $Bi_xZn_{1-x}O$ thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, $Bi_xZn_{1-x}O$ thin films with various Bi contents (x = 0~13.17 atomic %) were prepared. X-ray diffraction (XRD) measurements revealed the formation of Bi-oxide phase in (Bi)ZnO after increasing the Bi content. However, it was impossible to determine whether the formed Bi-oxide phase was the monoclinic structure ${\alpha}-Bi_2O_3$ or the tetragonal structure ${\beta}-Bi_2O_3$ by means of XRD ${\theta}-2{\theta}$ measurements, as the observed diffraction peaks of the $2{\theta}$ value at ~28 were very close to reflection of the (012) plane for the monoclinic structure ${\alpha}-Bi_2O_3$ at 28.064 and the reflection of the (201) plane for the tetragonal structure ${\beta}-Bi_2O_3$ at 27.946. By means of transmission electron microscopy (TEM) using a diffraction pattern analysis and a high-resolution lattice image, it was finally determined as the monoclinic structure ${\alpha}-Bi_2O_3$ phase. To investigate the distribution of the Bi and Bi-oxide phases in BiZnO films, elemental mapping using energy dispersive spectroscopy equipped with TEM was performed. Considering both the XRD and the elemental mapping results, it was concluded that hexagonal-structure wurtzite $Bi_xZn_{1-x}O$ thin films were grown at a low Bi content (x = ~2.37 atomic %) without the formation of ${\alpha}-Bi_2O_3$. However, the increased Bi content (x = 4.63~13.17 atomic %) resulted in the formation of the ${\alpha}-Bi_2O_3$ phase in the wurtzite (Bi)ZnO matrix.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1063-1069
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• 1997

For me1t-spun Fe-Nd-C alloys, variation of phase development and magnetic properties with the variety of alloy compositions and production conditions were investigated. To find out whether hard magnetic $Fe_{14}Nd_2C$ is crystallized direct1y from the melt by rapid quenching, the phase development of the as-spun ribbons spun at various speed was a1so studied. For the ribbons spun at 10m/s, ${\alpha}-Fe$ was the primary crystallization phase followed by the secondary $Fe_{17}Nd_2C$. At 20m/s ${\alpha}-Fe$ was suppressed so that the primary $Fe_{17}Nd_2C$ coexisted with the secondary ${\alpha}-Fe$ and the amorphous phase. Above 30m/s the ribbons were a1most amorphous, and the amorphization was complete at 40m/s. $Fe_{14}Nd_2C$ therefore was not found in as-spun state but obtained after heat treating the ribbons. The effective temperature range ($700{\sim}900^{\circ}C$) in which $Fe_{14}Nd_2C$ can be obtained was wider than that of a cast alloy. An alloy made with the wheel speed of 20 or 30m/s yielded higher coercivities after heat treatment. In iron-rich Fe-Nd-C, the composition range in which a high coercivity (more than 10kOe) is expected is narrow, i.e., 77~78 Fe and 7~8 C(at.%).

• Food Science and Biotechnology
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• v.14 no.1
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• pp.131-136
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• 2005

The selective extraction behavior of lactoferrin (Lf) from whey protein mixture was examined using reverse micelles formed by the cationic surfactant, cetyldimethylammonium bromide (CDAB). The major whey proteins, including ${\beta}$-lactoglobulin, ${\alpha}$-lactalbumin and bovine serum albumin, were solubilized from aqueous phase to organic phase while Lf was recovered in the aqueous phase. The solubilization behaviors of the proteins were manipulated by the process parameters such as the pH and salt concentration of the aqueous phase and the surfactant concentration in the organic phase. Efficient forward extraction was achieved with sodium borate buffer (50 mM, pH 9) containing 50 mM KCl and organic phase containing 100 mM CDAB. Based on SDS-PAGE and densitometry, about 96% of the initial Lf remained in the aqueous phase after forward extraction. The dialyzed Lf fully maintained its bacteriostatic activity against E. coli O157:H7.