• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.215-218
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• 1994

Dielectric properties of $(Sr_{l-x}{\cdot}Ca_x)_mTiO_3+0.006Nb_2O_5$($0.05{\leq}x{\leq}0.2$, 0.996$N_2$) were painted on the surface with CuO paste, and then annealed at $1100^{\circ}C$ for 2hr. Grain size increased with increasing substitutional contents of Ca up to 15[mol%], but decreased with further substitution. In the specimens with $10{\sim}15[mol%]$ of Ca and m=1, excellent dielectric properties were obtained as follows; dielectric constant <25000, dielectric loss($tan{\delta}[%]$) <0.3[%] and capacitance change rate with temperature <${\pm}10[%]$, respectively. All the specimens in this study exhibited dielectric relaxation with frequency as a function of the temperature. The dispersive frequency was over $10^6[Hz]$.

• The Journal of Engineering Research
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• v.6 no.2
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• pp.23-32
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• 2004

Metals, ceramics and polymers are widely used as bioimplant materials. However, Ti and Ti alloys are widely used because of its high strength to weight ratio and good biocompatibility when implanted in the body. In this experiment, Ti alloys of Grade-4 (gr4), 0.2 wt % Fe, 0.5 wt % Fe and 2 wt % Fe were studied for their surface morphology and HAp forming ability on the metal substrate for different treatments. Intially, the samples were mechanically polished on silicone carbide paper (No.-2000). The polished samples were treated with 5M NaOH solution at $60^{\circ}C$ for 24 hours. The NaOH treated samples were washed gently with distill water and dried at $40^{\circ}C$ for 1 day. The dried samples were heated in air at $600^{\circ}C$ for 1 hour. The surface morphology of these samples were studied using SEM. The SEM studies showed network of pores in all samples. These samples were immersed in stimulated body fluids (SBF) kept at $36.5^{\circ}C$ for different periods over the length of 1 to 14 days. The apatite formation was confirmed on all Ti-alloys using EDAX.

• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.258-262
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• 2000

$YMnO_3$thin films are deposited on Si(100) and $Y_2O_3/Si(100)$ substrate by radio frequency sputtering. The deposition condition of oxygen partial pressure and annealing temperature have significant influences on the preferred orientation of $YMnO_3$film and the size of memory window. The results of x-ray diffraction show that the film deposited in the oxygen partial pressure of 0% is highly oriented along c-axis after annealing at $870^{\circ}C$ for 1 hr in oxygen ambient. However, the films deposited on Si and $Y_2O_3/Si$ in the oxygen partial pressures of 20% show $Y_2O_3$ peak, the excess $Y_2O_3$ in the $YMnO_3$film suppresses the c-axis oriented crystallization. Especially memory windows of the $Pt/YMnO_3/Y_2O_3/Si$ capacitor are 0.67~3.65 V at applied voltage of 2~12 V, which is 3 times higher than that of the film deposited on $Y_2O_3/Si$ in 20% oxygen (0.19~1.21 V) at the same gate voltage because the film deposited in 0% oxygen is well crystallized along c-axis.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.527-534
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• 1992

Raney nickel was used as catalyst in the hydrogen electrode for an alkaline fuel cell. The hydrogen electrode manufactured with the Raney nickel catalyst which was sintered at $700^{\circ}C$ was found to have the highest electrode performance. Using the Raney nickel powder of average particle size $90{\AA}$ for the electrode, the current density which had been measured was $450mA/cm^2$ at $80^{\circ}C$ using 6N KOH solution as an electrolyte. The effects of PTFE addition were investigated with CO-chemisorption, polarization curves and Tafel slope. CO-chemisorption had shown the optimum value when the Raney nickel was mixed with 5wt% of PTFE, but from the current density and Tafel slope at porous Raney nickel electrode, the appropriate value of PTFE addition was 10wt%. Recommendable Ni and Al portion for Raney nickel was 60 : 40 and loading amount was $0.25g/cm^2$. Also the influence of pressing pressure for manufacturing catalytic layer and for junction with gas diffusion layer was examined. The morphology of catalyst surface was investigated with SEM. The influence of reactivation time and heat-treatment temperature were also studied.

• Korean Journal of Food Science and Technology
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• v.34 no.6
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• pp.1067-1072
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• 2002

Peroxidase was used as a standard enzyme to determine optimum blanching conditions of Flammulina velutipes and Lyophyllum ulmarium. Crude peroxidase extracted from raw mushrooms had maximum activity at $10{\sim}15^{\circ}C$ and pH 5.5 (50 mM, potassium phosphate buffer) using substrates of $H_2O_2$ and p-Phenylendiamine. Thermal inactivation of the crude peroxidase followed the first-order kinetics. The activation energy and z value of the crude peroxidase for F. velutipes were 59.58 kcal/mol and $9.0^{\circ}C$, whereas were 43.05 kcal/mol and $12.4^{\circ}C$ for L. ulmarium, respectively. On the basis of thermal kinetics parameters obtained, the optimum blanching conditions for F. velutipes and L. ulmarium were 1 min at $70^{\circ}C$ and 5 min at $80^{\circ}C$, respectively. Activation energies and z values of peroxidases extracted from heat-treated mushrooms were 7.97 and 6.55 kcal/mol, and $59.8^{\circ}C\;and\;74.1^{\circ}C$ for F. velutipes and L. ulmarium, respectively.

• Korean Journal of Food Science and Technology
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• v.32 no.6
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• pp.1396-1402
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• 2000

The effects of Coptis chinensis Franch(CCF) extract on the growth, acid production, cell adherence and glucosyltransferase(GTase) activity of Streptococcus mutans JC-2 were investigated. Methanol extract from CCF showed a strong inhibitory effect on the growth of S. mutans. The minimal inhibition concentration(MIC) of the methanol extract was determined as $130\;{\mu}g/mL$, whereas MIC of water extract was $200\;{\mu}g/mL$. MICs of berberine and palmatine were $50\;{\mu}g/mL$ and $110\;{\mu}g/mL$, respectively, showing stronger antimicrobial activities than the extracts of CCF. Antimicrobial activities of methanol extract, berberine and palmatine were not decreased by heating at $121^{\circ}C$ for 15 min, suggesting that the antimicrobial components including berberine and palmatine are heat-stable. Acid production of S. mutans was decreased by methanol and water extracts, berberine and palmatine. The activity of GTase was inhibited by methanol extract, berberine and palmatine at $300\;{\mu}g/mL$ with 23.2%, 46.1% and 17.1%, respectively, but was not inhibited by water extract. The water extract and palmatine at sub-MICs inhibited the adherence of S. mutans to glass surface by 59.2% and 41.7%, respectively. These results suggest that CCF extracts have anticariogenic effects and could be used as an anticariogenic food additive.

• Korean Journal of Food Science and Technology
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• v.32 no.2
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• pp.349-355
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• 2000

This study was conducted to enhance the storage stability of fermented shrimp with different salt contents using a high hydrostatic pressure. The effects of the magnitude of pressure and treatment time on the microorganisms of the fermented shrimp were investigated. The highest microbial counts with respect to the salt levels were observed at 18% salt, showing $3.4{\times}10^5\;CFU/g$ for general bacteria, $6.4{\times}10^4\;CFU/g$ for halophilic bacteria, $4.2{\times}10^5\;CFU/g$ for yeast and $3.0{\times}10^4\;CFU/g$ for halophilic yeast. The degree of sterilization increased with the magnitude of pressure and treatment time, and the sterilization could be analyzed by the first order reaction kinetics. The sterilization rate constants $(k_p)$ of the halophilic bacteria was lower than that of general bacteria. The $log(k_p)$ increased linearly with pressure and the slope of the regression line of the halophilic bacteria was greater than that of general bacteria, indicating that the sterilization of the halophilic bacteria was more dependent on the pressure. High hydrostatic pressure treatment was an effective non-thermal sterilization method for the salted and fermented shrimp, and the optimum treatment condition was for 10 min at 6,500 atm.

• Korean Journal of Food Science and Technology
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• v.32 no.2
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• pp.461-468
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• 2000

To investigate the antigenotoxicity of Korean mistletoe using Comet assay, the crude extract was divided into 4 fractions, i.e. fraction I (MW range over 14,000), fraction II $(8,000{\sim}14,000)$, fraction III $(3,500{\sim}8,000)$, and fraction IV (below 3,500) by molecular weight fractionation. In the non-tumoral 3T3 cells, fraction IV could reduce DNA damage induced by MNNG in a dose dependent pattern while fraction I and III which were known to contain lectins and viscotoxins, respectively, did not show the activity. By heat treatment, the antigenotoxic activity of faction IV, though was gradually diminished according to heating time, was found to be maintained significantly. From the Sephadex G-25 gel filtration chromatography, a more purified fraction responsible for the activity of faction IV was obtained from the latter part of total elute. Therefore, it was concluded that the antigenotoxic components of Korean mistletoe were water soluble substances of MW below 1,000 and there is a possibility of utilization as a material of functional foods for chemoprevention.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.3
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• pp.452-459
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• 2016

Nutritional compositions, volatile compounds, and sensory attributes of grilled and fast-chilled mackerel (Scomber japonicus) were analyzed in order to examine its practical utilization as a food resource compared to commercial frozen mackerel. In the proximate analysis, lipid contents were $27.3{\pm}2.7%$ in grilled and fast-chilled mackerel. Palmitic acid was the most predominant fatty acid (20.68% and 18.88%), and the percentages of polyunsaturated fatty acid were higher than 40% in both. No benzopyrene was found in the grilled mackerel, and even grilling was employed at $260^{\circ}C$. For chemical stabilities, para-anisidine value (8.56 vs. 9.26) and acid value (2.96 vs. 3.35) in grilled mackerel were improved compared to those of commercial mackerel. Moreover, color index of grilled mackerel, a physiological property, showed greater lightness than commercial mackerel. Lastly, analysis of volatile compounds by gas chromatographic analysis and sensory tests by trained panels demonstrated higher potential for grilled mackerel as a highly marketable product compared to commercial mackerel. Taken altogether, the above results provide important preliminary results for utilization of grilled and fast-chilled mackerel as a quality food.

• Journal of Chitin and Chitosan
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• v.23 no.4
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• pp.228-233
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• 2018

We isolated microorganisms from soil, which is sampled at forest, Kyeonbuk, Korea, as cellulolytic microorganisms. The isolated strains were identified by analysis of 16S rRNA gene from the starins. The result, four kinds of Bacillus subtilis, one kind of Bacillus amyloliquefaciens, and one kind of Bacillus cereus were identified. Among these strains, Bacillus subtilis was selected due to its high cellulase activity and this strain was named as Bacillus subtilis CNS. The optimum pH and temperature of the cellulase from Bacillus subtilis CNS was pH 5.0 and $40^{\circ}C$, respectively. In the investigation of pH and temperature stability, the cellulase from Bacillus subtilis NSC stabled pH 4.0~6.0 range and until $40^{\circ}C$ for 30 min perfectly. In the enzyme activity for various cellulosic substrate, cellulase from Bacillus subtilis CNS showed the highest activity for CM-cellulose. And, the enzyme activities for alkali swollen cellulose, Alpha-cellulose, Sigmacell-cellulose, and Avicel were approximately 31%, 8%, 8% and 4% of activity for CM-cellulose, respectively. In the degradation of CM-cellulose, the 0.26 U/ml and 0.52 U/ml of cellulase showed 0.43 and 0.76 U/ml activity for CM-cellulose after the reaction of 120 min, respectively.