• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.231-236
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• 2003

The $Al_{0.2}$CoF $e_{1.8}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample depending on annealing temperature have been investigated by means of x-ray diffraction, FE SEM, Mossbauer spetroscopy and vibrating sample magnetometry. The x-ray diffractions of all samples annealing temperature above 873 K clearly indicate the presence of spinel structure, the lattice constant decrease from 8.425 $\AA$ at 873 K to 8.321 $\AA$ at 1073 K, whereas the particle size rapidly increase from about 39 nm at 673 K to about 108 nm at 1073 K. The Mossbauer spectra annealed above 873 K could be fitted as the superposition of two sextets due to F $e^{3+}$ at A-site and B-site. The isomer shift (IS) and quadruple splitting (QS) values nearly constant with annealing temperature, whereas magnetic hyperfine field ( $H_{hf}$) of A-site slowly in crease and that of B-site fastly increases with increasing annealing temperature. The magnetic behaviour of powders shows that the saturation magnetization increase from 0.7 emu/g at 473 K to 72.1 emu/g at 1073 K while the coercivity decrease from 0.951 kOe at 673 K to 0.374 kOe at 1073 K with increasing annealing temperature.

• Membrane Journal
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• v.26 no.2
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• pp.97-107
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• 2016

This study was carried out to prepare a heterogeneous cation exchange membrane by mixing polyvinylidene fluoride (PVDF), commercial cation exchange resin and sulfonated poly(phenylene oxide)(SPPO) in order to propose an optimum condition for the preparation, and to compare its properties with commercial membrane. Study results show that the ion exchange capacity and electrical resistance were outstanding when the ratio of polymer matrix was less than 30% comparing between PVDF-IER, PVDF-SPPO and PVDF-SPPO-IER. The tensile strength was confirmed that seemed a hard look was five times greater compared to the commercial heterogeneous membrane, despite the weak durability of PVDF resin. Therefore, when chemical and mechanical properties are considered, the optimum mixing ratio between PVDF, IER and SPPO was 30 : 70, at which electric resistance was measured as $3{\sim}5{\Omega}{\cdot}cm^2$, ion exchange capacity as 0.6~1.0 meq/g, while mechanical strength was in a range of $12{\sim}15kgf/cm^2$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.2
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• pp.176-187
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• 1983

Volatile flavor components of garlic and factors which influence on its flavors were reviewed. Growth, storage and processing conditions influence on the flavor intensity of garlic. To intensify garlic flavors, it is desirable that sufficient sulfate nutrition be supplied to the soil of growing garlic and that the suggested proportions of mineral composition and water content be considered. And to maintain the flavor intensity of post harvested garlic, flavor losses taken place during over inter storage mainly due to respiration, sprout and decay, have to be minimized. Among the various storage methods, combination method of post harvest hot-air drying and low temperature ($0^{\circ}C$), low humidity (RH 70-75%) is useful. The flavor of processed garlic is very much decreased as compared with that of fresh, and the decreasing rate of flavors depends on processing method. The synthetic garlic flavors were obtained by three types based on intermediate thiosulfinate, S-alk(en) yl-$\small{L}$-cyteine sulfoxlde-alliinase fission products and $\small{L}$-5-alk (en)yl thiomethylhydantoin ${\pm}$ S-oxides. These synthetic garlic flavors may be promised to be applied to food additives.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.104-107
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• 2005

[ $TiN_x$ ] powder have been fabrication by making of reaction between titanium powder and $Si_3N_4$ bowl during a planetary milling. Milling times were maintained for 1 hour, 5 hours, and 10 hours, respectively. The XRD result showed existence of non-stoichiometric compound of $TiN_{0.26}$ after 5 hours milling and coexistence of TiN with $TiN_{0.26}$ after 10 hours milling. Particle size distribution was investigated by particle size analyzer and microstructure was analyzed by FE-SEM. The size of titanium was decreased with increasing the milling time and the mean size of $TiN_x$ after 10 hours milling was increased by 200 nm.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.513-517
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• 2013

This study focused on the synthesis of $Nb_xSrTi_{1-x}O_3$ photocatalysts which partially inserted Nb ions with excellent ability of fluorescence into the perovskite structured $SrTiO_3$ frameworks and their photocatalytic hydrogen productions from methanol/water splitting corresponding to the molar ratios of Ti and Nb. The characteristics of the synthesized $SrTiO_3$ and $Nb_xSrTi_{1-x}O_3$ powders were analyzed by X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS), and UV-Visible spectrometer. The hydrogen evolution from methanol/water photo-splitting was enhanced over $Nb_{0.05}SrTi_{0.95}O_3$ compared to those over $SrTiO_3$ and another $Nb_xSrTi_{1-x}O_3$; 4.9 mL of hydrogen gases was collected after 8 h when 0.5g of $Nb_{0.05}SrTi_{0.95}O_3$ catalyst was used in pH 10.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.407-411
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• 2015

Dense ceramic membranes have been prepared using the commercial perovsikite $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$, powders synthesized by the solid state reaction method. The as-synthesized powders were compressed into disks with 1.0 mm of thickness and the disk was sintered at $1,100^{\circ}C$ for 2 hr. The oxygen permeation flux of $Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}O_{3-{\delta}}$ membrane increased with the increasing temperature and oxygen partial pressure. The activation energy for oxygen permeation was increased with the increasing oxygen partial pressure. Oxygen permeation flux at $950^{\circ}C$ were measured at various flow rates of feed and sweep gas. It has been demonstrated that oxygen permeability increased at elevated flow rates of both gases, but the sweep gas is more influential.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.113-119
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• 2009

$^{57}Fe_xCu_{1-x}O$(x = 0.0, 0.02) powders were prepared by sol-gel method and their crystallographic and magnetic hyperfine properties have been studied using X-ray diffraction and $M{\ddot{o}}ssbauer$ spectroscopy (MS). The crystal structure of the samples is found to be monoclinic without any secondary phases and their lattice parameters increase with increasing annealing temperature ($T_A$), which is attributed to an increase in oxygen-vacancy content. MS measurements at room temperature indicate that $Fe^{3+}$ ions substitute $Cu^{2+}$ sites and ferromagnetic phase grow with increasing $T_A$. Magnetic hyperfine and quadrupole interactions of $^{57}Fe_{0.02}Cu_{0.98}O$ ($T_A=500^{\circ}C$) in the antiferromagnetic state at 17 K have been studied, yielding the following results: $H_{hf}=426.94\;kOe$, ${\Delta}E_Q=-3.67\;mm/s$, I.S.=0.32 mm/s, ${\theta}=65^{\circ}$, ${\phi}=0^{\circ}$, and ${\eta}=0.6$.

• The Journal of the Petrological Society of Korea
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• v.24 no.2
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• pp.77-90
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• 2015

The fission track registration techniques for accurate determinations of uranium in solid- and liquid-state geological materials were recommended and their applicability were examined. The determination of uranium can be achieved by optical counting of neutron-induced fission tracks of $^{235}U$ registered on solid-state track detectors under high magnification. In a dry registration method using powdered pellets of rocks (e.g., granite and coal) showing good uranium-affinity, it was not easy to decide an overall mean concentration over the total sample owing to track-clusters caused by frequent presence of uranium-bearing minerals. Separate scanning for homogeneous and track-clustered parts may be an alternative choice. Assuring the homogeneity over the whole sample, high reproducibilities were confirmed both from duplicate detections using mica and Lexan polycarbonate detectors and from multiple measurements at different thermal neutron fluences. The wet registration method using sealed quartz tubes is recommended to overcome the common heterogeneity in uranium concentrations of $10^1ppm$ and more. Adopting the wet registration, the uranium homogeneity was recovered below the $10^0ppm$ level and the lower detection limit was proved to reach without difficulty the $10^2ppb$ (i.e. $ng\;g^{-1}$) level.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.3
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• pp.103-109
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• 2020

The effect of La₂O₃ addition on the crystalline phase, microstructure, and dielectric properties of BaTiO₃ has been studied as a function of the amounts of La₂O₃. 0.3 mol% TiO₂-excess BaTiO₃ powder was synthesized by solid-state reaction, and then the powder compacts with various amounts of La₂O₃ were sintered at 1250℃ for 2 hours. Room temperature XRD showed changes in the lattice parameters and a decrease of tetragonality (c/a) as the amounts of La₂O₃ increased. It can be explained that the phase transition from tetragonal to cubic phase occurred because La³⁺ replaced Ba²⁺ site, which increased the instability of the tetragonal phase. As La₂O₃ was added over 0.1 mol%, the critical driving force for growth (Δg_c) increased over maximum driving force (Δg_max). As the result, the grain size decreased with La₂O₃ addition. Dielectric constant decreased as the amounts of La₂O₃ increased, which was analyzed with crystal structure and microstructure.

• Journal of Life Science
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• v.24 no.6
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• pp.633-641
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• 2014

This study investigated the antioxidant and antiobesity activity of extract powders from the following natural color resources: Polygonum indigo, Black locust, Cochineal, Catechu, Grape, Tesu flower, Henna, Chrysanthemum, Sandalwood Red, Himalayan Rhubarb, and Madder. Total phenol content was the highest in Catechu extract, at 348.25 mg/g. DPPH, ABTS radical scavenging activity and ferric reducing antioxidant power (FRAP) were also higher in Catechu extract. Bleaching inhibition activity in the ${\beta}$-carotene linoleic acid system was the highest in Black locust extract, as was ${\alpha}$-Glucosidase inhibition activity. ${\alpha}$-Amylase inhibition activity was the highest in Catechu extract. Trypsin inhibition activity of Black locust extract was greater than 60%, and ${\alpha}$- chymotrypsin inhibition activity of Catechu extract was greater than 40%. Lipase inhibition activity was the highest Black locust extract, at 52.73%. Viability of 3T3-L1 cells was not affected by treatment with extracts at concentrations of $1.25{\sim}25{\mu}g/ml$. Lipid accumulation in the 3T3-L1 cells was the lowest following treatment with Catechu extract, at 55.8%, and this extract also inhibited adipocyte differentiation. These results suggest that the Catechu and Black locust extracts have high antioxidant and antiobesity activities and can be useful ingredients in functional foods.