• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.279-284
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• 2017

Mechanical properties of titanium alloy can be improved by controlling microstructure through heat treatment. In this study, Ti-3Al-8V-6Cr-4Mo-4Zr metastable beta titanium alloy, was controlled for excellent mechanical property and sound formability through various high temperature heat treatment and aging conditions and the optimum heat treatment conditions were determined. The specimens were heat-treated at $950^{\circ}C$, followed by various aging treatments from $430^{\circ}C$ to $500^{\circ}C$ for 1 to 24 h. As aging temperature and holding time increased, hardness increased by ${\beta}^{\prime}$ phase formation and precipitation of secondary ${\alpha}$ phase in ${\beta}$ matrix. However, the optimum aging temperature and holding time for mechanical properties were at $450{\sim}470^{\circ}C$ for 8~16 hr. Hardness values of the specimen aged at $450^{\circ}C$ for 8 h were found to be the highest. These results can be effectively applied to fabrication of spring with better formability and mechanical property.

• Journal of Microbiology and Biotechnology
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• v.28 no.5
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• pp.697-706
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• 2018

Lactobacillus pentosus K1-23 was selected from among 25 lactic acid bacterial strains owing to its high inhibitory activity against several pathogenic bacteria, including Escherichia coli, Salmonella typhimurium, S. gallinarum, Staphylococcus aureus, Pseudomonas aeruginosa, Clostridium perfringens, and Listeria monocytogenes. Additionally, among 13 strains of Aureobasidium spp., A. pullulans NRRL 58012 was shown to produce the highest amount of ${\beta}$-glucan ($15.45{\pm}0.07%$) and was selected. Next, the optimal conditions for a solid-phase mixed culture with these two different microorganisms (one bacterium and one yeast) were determined. The optimal inoculum sizes for L. pentosus and A. pullulans were 1% and 5%, respectively. The appropriate inoculation time for L. pentosus K1-23 was 3 days after the inoculation of A. pullulans to initiate fermentation. The addition of 0.5% corn steep powder and 0.1% $FeSO_4$ to the basal medium resulted in the increased production of lactic acid bacterial cells and ${\beta}$-glucan. The following optimal conditions for solid-phase mixed culture were also statistically determined by using the response surface method: $37.84^{\circ}C$, pH 5.25, moisture content of 60.82%, and culture time of 6.08 days for L. pentosus; and $24.11^{\circ}C$, pH 5.65, moisture content of 60.08%, and culture time of 5.71 days for A. pullulans. Using the predicted optimal conditions, the experimental production values of L. pentosus cells and ${\beta}$-glucan were $3.15{\pm}0.10{\times}10^8CFU/g$ and $13.41{\pm}0.04%$, respectively. This mixed culture may function as a highly efficient antibiotic substitute based on the combined action of its anti-pathogenic bacterial and immune-enhancing activities.

• Korean Journal of Materials Research
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• v.24 no.4
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• pp.214-220
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• 2014

In this research, a precipitation method was used to synthesize ${\beta}-Ga_2O_3$ powders with various particle morphologies and sizes under varying precipitation conditions, such as gallium nitrate concentration, pH, and aging temperature, using ammonium hydroxide and ammonium carbonate as precipitants. The obtained powders were characterized in detail by XRD, SEM, FT-IR, and TG-DSC. From the TG-DSC result, GaOOH phase was transformed to ${\beta}-Ga_2O_3$ at around $742^{\circ}C$, and weight loss percent was about 14 % when $NH_4OH$ was used as a precipitant. Also, ${\beta}-Ga_2O_3$ formed at $749^{\circ}C$ and weight loss percent was about 15 % when $(NH)_2CO_3$ was used as a precipitant. XRD results showed that the obtained $Ga_2O_3$ had pure monoclinic phase in both cases. When $(NH)_2CO_3$ was used as a precipitant, the particle shape changed and became irregular. The range of particle size was about $500nm-4{\mu}m$ based on various concentrations of gallium nitrate solution with $NH_4OH$. The particle size was increased from $1-2{\mu}m$ to $3-4{\mu}m$ and particle shape was changed from spherical to bar type by increasing aging temperature over $80^{\circ}C$.

• KSBB Journal
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• v.11 no.4
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• pp.438-444
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• 1996

Using recombinant Vaccinia virus(vSC8) that express ${\beta}$-galactosidase, a model heterologous protein, conditions for virus and protein production were investigated in tissue culture flask. As host animal cells HeLa and HeLa S3 were used. It was demonstrated that cells infected during the exponential growth phase gave higher protein yield than those infected during the stationary growth phase and calf serum concentration after virus infection did not significantly alter protein yield. Pretreatment of cell layer with hypotonic solution enhanced the virus infectivity. Optimum cell growth and recombinant protein production was achieved at $37^{\circ}C$. But, during 2 hours of virus infection period incubation temperature must be lowered to 20∼$30^{\circ}C$ for maximum recombinant protein yield. To enhance virus replication, the effects of adrenal glucocorticoid hormone (Dexamethasone) and silkworm hemolymph were evaluated. Only dexamethasone increased about 20% of ${\beta}$-galactosidase yield in HeLa S3 cells when added with 10-7∼10-5M concentration 24 hours before infection.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.349-355
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• 1994

Superrsolution of an optical imaging system, which resolves $\epsilon_O$ (half width of the square top amplitude impulse function) less than the Rayleigh's resolution limit $\epsilon_R$, is theoretically treated by using the diffraction theory, and an experimental system is proposed. Initially superresolution is stated as an inverse problem, and an integral equation is derived as a function of parameter $\beta$, which is positive. The integration is numerically carried out for the given aperture and those given values of $\beta$, which is 1, 5, 10, 15, and 20. 1/2$\times$FWHM's of the amplitude impulse functions are meassured for the cases of diffrent value of {J and in the case of $\beta=5$, the half-width already approaches to $\epsilon_O=0.1$,urn, which is, in the case of the present work, one fifth of the Rayleigh's resolution limit. It is found both the pupil function and the phase of the Huygens wave are to be modified, and theories of the pupil function modulation plate and the phase modulation hologram plate are also presented. The result obtained may be useful in ultrafine optical lithography.graphy.

• Food Science of Animal Resources
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• v.30 no.6
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• pp.923-929
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• 2010

Colostral whey prepared from colostrum (pooled from first six post-partum milkings) was heated for 10 min at $100^{\circ}C$ Heated colostral whey was incubated with 1% enzymes (protein equivalent basis) for 15, 30, 60, 90, and 120 min at $50^{\circ}C$. Papain, pepsin, trypsin, and alcalase produced different degrees of hydrolysis (DH), 10.66%, 12.42%, 10.83%, and 25.31%, respectively, at an incubation time of 120 min. The SDS-PAGE reveals that significant amounts of bovine serum albumin (BSA), ${\beta}$-lactoglobulin (${\beta}$-LG), and ${\alpha}$-lactalbumin (${\alpha}$-LA) survived papain digestion. In contrast, pepsin completely removed BSA but not ${\beta}$-LG present in heated colostral whey. Alcalase completely eliminated BSA, ${\beta}$-LG, and ${\alpha}$-LA. This differential hydrolysis was confirmed by reversed-phase HPLC analysis. Using ion-exchange chromatography, fraction-1 (F-1) was obtained from alcalase hydrolysate at a NaCl gradient concentration of 0.25 M. Reversed-phase HPLC chromatograms of alcalase F-1 showed numerous small peaks, which probably indicate that a variety of new peptides were produced. Iron content of alcalase F-1 was 28.94 ppm, which was the highest among all enzyme fractions, whereas iron content of colostral whey was 36.56 ppm. Main amino acids contained in alcalase F-1 were Thr (15.45%), Glu (14.12%), and Ser (10.39%). Therefore, alcalase can be used to generate good iron-binding peptides in heated colostral whey, and the resulting iron-binding peptides could be suitable as a value-added food ingredient for food supplements.

• Korean Journal of Materials Research
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• v.12 no.4
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• pp.317-323
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• 2002

Effect of V and Sb content on characteristics of ${\beta}\;to\;{\alpha}$ phase transformation in Zr-0.84Sn alloy has been studied using optical microscopy and transmission electron microscopy. As V content increased, the ${\beta}{\to}{\beta}+{\alpha}$ transformation temperature was lowered, thus allowing the width of $\alpha$-lath in air-cooled Zr-0.86Sn-0.40V alloy to be fine. The width of ${\alpha}$-lath in air-cooled Zr-0.84Sn-xSb, however, was rarely changed with Sb content. The ${\beta}\;to\;{\alpha}$ transformed microstructures of water-quenched Zr-0.84Sn, Zr-0.84Sn-0.10V and Zr-0.84Sn-0.19V alloys were mainly slipped martensite. On the other hand, those of wafter-quenched Zr-0.86Sn-0.40V and Zr-0.85Sn-0.05Sb alloys were predominantly twinned martensite. In case of water-quenched Zr-0.85Sn-0.12Sb and Zr-0.84Sn-0.17Sb alloys, basketweave structure was observed. The transition of slipped martensite to twinned martensite in Zr-0.84Sn-xV alloys and the transition of twinned martensite to basketweave structure in Zr-0.84Sn-xSb alloys were due to the decrease of $M_s$ temperature.

• Archives of Pharmacal Research
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• v.21 no.5
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• pp.503-507
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• 1998

Percutaneous absorption and model membrane variations of melationin (MT) in aqueous-based propylene glycol and $2-hydroxypropyl-{\beta}-cyclodextrin $vehicles were investigatted. the excised hairless mouse skin (HMS) and two synthetic ethylene vinyl acetate (EVA) and microporous polyethylene (MPE) were selected as a model membrane. the solubility of MT was determined by phase equilibrium study. the vertical $Franz{\circledR}$ type cell was used for diffusion study. The concentration of MT was determined using reverse phse HPLC system. The MT solubility was the highest in a mixture of PG and $2-HP{\beta}CD$. The percutaneous absorption of MT through excised HMS increased as the solubility increased. However, the permeability coefficient decreased and then slightly increased in mixture of PG and $2-HP{\beta}CD$. On the other hand, both flux and permeability coefficient through EVA membrane decreased as the solubility increased. No MT was detected over 12 h after starting diffusion through MPE membrane. The flux of MT was dependent on the type of membrane selected. Flux of MT was greatest in excised HMS followed by EBA and MPE membrane. Flux of MT through EVA membrane was 5-20 times lower when compared to excised HMS. Interestingly, volumes of donor phase when MPE membrane was used, significantly increased during the study period. the HMS might be applicable to expect plasma concentration of MT in human subjects based on flux and pharmacokinetic parameters as studied previously. the current studies may be applied to deliver MT transdermally using aqueous-based vehicles and to fabricate MT dosage forms.

• Polymer(Korea)
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• v.28 no.5
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• pp.361-366
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• 2004

The poling characteristics of PVDF (poly(vinylidene fluoride)) film was investigated by measuring the electric voltage generated by the external load for the distributed tactile sensor applications. The poling conditions for the PVDF films were controlled by changing temperature and electric field, and the resulting crystal structure of the $\beta$-phase crystal was confirmed by FT-IR, DSC, and XRD experiments. The $\beta$-phase crystal was increased with the poling temperature and poling voltage, and subsequently the permittivity of the Poled PVDF films was increased. Finally, the prototype tactile sensor was tested by a 8 $\times$ 8 may circuit exhibiting high voltage signal for the highly poled PVDF films.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5A
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• pp.634-640
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• 2000

This paper proposes a new extended decision directed-decision estimated phase recovery algorithm based on maximum likelihood parameter estimation for OQPSK. In this scheme, comparing conventional one, the data dependent noise of phase recovery loop is reduced by inserting filter with 2 taps to in-phase and quadrature-phase channel respectively before phase detector. The proposed scheme is compared to conventionalscheme and OQPSK in aspect to BER(Bit Error Rate) and phase error according to the roll-off factor of baseband filter, the output back-offs of nonlinear satellite channel, and loop bandwidth.