• Resources Recycling
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• v.18 no.5
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• pp.12-18
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• 2009

The 20% Pt/C catalysts were synthesized using the chemical reduction method for polymer electrolyte fuel cell cathode and were heat-treated in the temperature range from 300 to $600^{\circ}C$. The oxygen reduction reaction of the catalysts was evaluated using the electrochemical measurement. The oxygen reduction reaction of the heat-treated Pt/C at $300^{\circ}C$ had high catalytic activity and the oxygen reduction reaction current of that was 2 times than that of non-heat treatment catalyst. It is considered that the change of the crystallinity and particle size by heat treatment could increase the catalytic activity.

• Composites Research
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• v.25 no.6
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• pp.172-177
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• 2012

For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed ${\alpha}$-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine ${\beta}$-SiC particle and the structure was changed to dense material. The amount of fine ${\beta}$-SiC particle was gradually increased as carbon content increase. According to mixed composite, it's mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.

• Journal of Veterinary Clinics
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• v.7 no.1
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• pp.429-438
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• 1990

The cytochemical characteristics of the hematopoietic cells in blood and bone marrow from 3 clinically healthy dogs were examined using a battery of cytochemical stains. Alkaline phosphotase activity was demonstrated in eosinophilic series and occassionally in progranulocytes. A variety of cells exhibited acid phosphatase activity, but tartrate-resistant acid phosphatase activity was seen only in eosinophilic series. Peroxidase activity was observed in myeloblasts to segmented cells of granulocytic series and in monocytes. ${\alpha}$-naphthyl acetate esterase activity was found in monocytes and occassionally in lymphocytes. Naphthyl-AS-D-chloroacetate esterase marked neutrophilic series from myeloblasts to segmented cells. ${\beta}$-Glucuronidase activity was detected in a variety of cells except the cells of erythrocytic series. Periodic acid Schiff stain-positive granules were demonstrated in the neutrophilic and eosinophilic series from myelocytes to segmented cells and in monocytes and occassionally in lymphocytes. Sudan black B stain-positive granules marked granulocytic series from myeloblasts to segmented tells and monocytes.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.659-663
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• 2016

The efficiency of a heterogeneous ruthenium zirconia catalyst ($Ru(OH)_x/ZrO_2$) was demonstrated to the selective oxidative transformation of alkenes or alkynes. The scissions of C-C double bonds to aldehydes and triple bonds to diketones or carboxylic acids were carried out with (diacetoxyiodo)benzene as an oxidant under dichloromethane (5 mL)/water (0.5 mL) solvent system at $30^{\circ}C$ for wide range of substrates. The $Ru(OH)_x/ZrO_2$composite showed higher catalytic activity and selectivity than other ruthenium-based homogeneous or heterogeneous catalysts for the scission reaction. The catalyst exhibited a high mechanical stability, and no leaching of the metal was observed during the reaction. These features ensured the reusability of the catalyst for several times for the oxidative cleavage of unsaturated hydrocarbons.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.215-221
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• 2016

The subjects of this study were 64 young children aged 12 to 36 months old and their mothers and teachers. The attachment Q-set and an instrument for teachers' responsivity were used. Data were analyzed using SPSS 18.0, and Cronbach's and Pearson's r were calculated. The results were as follows. Teachers' consistency, warmth, and sensitivity were significantly correlated with the children's attachment to teachers. In addition, teachers' warm and sensitive responses were related to the children's attachment to mothers. Teachers' warm, sensitive, and responsive characteristics are emphasized for quality interactions between young children and teachers, since they contribute to the children's secure attachment to their mothers as well as teachers.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.375-380
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• 2003

In this study. we have intended to control the properties of surface reaction zone generated between pure titanium and oxide investment moulds. Commercially pure titanium was centrifugally casted and silica$.$alumina based phosphate bonded investment was used as the mould material. The effect of cooling methods after casting on the surface reaction zone and mechanical properties of casts were investigated. The resulting casts showed the multilayered surface reaction zone regardless of cooling method. Especially. water cooling method produced the titanium casts with thinner surface reaction zone. weaker strength. and higher elongation properties compared to air cooling. It can thus be known that the resulting casts had satisfactory mechanical properties as dental materials. From these results, the cooling rate dependence of interfacial and mechanical properties can be attributed to the diffusion of oxygen from casting environment, which control the reaction of titanium and mould.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.561-567
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• 2004

The influence of ultrasound frequency, dissolved gases, and initial concentration on the decomposition of sodium dodecylbenzene sulfonate(DBS) aqueous solution was investigated using ultrasound generator with 200 W ultrasound power. The decomposition rates at three frequencies(50, 200, and 600 kHz) examined under argon atmosphere were highest at 200 kHz. The highest observed decomposition rate at 200 kHz occurred in the presence of oxygen followed by air and argon, helium, and nitrogen. The effect of initial concentration of DBS on the ultrasonic decomposition was decreased with increasing initial concentration and would depend upon the formation of micelle in aqueous solution. It appears that the ultrasound frequency, dissolved gases, and initial concentration play an important role on the sonolysis of DBS. Sonolysis of DBS mainly take place at the interfacial region of cavitation bubbles by both OH radical attack and pyrolysis to alkyl chain, aromatic ring, and headgroup.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.644-649
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• 2011

Polyaniline/$SiO_2$ catalyzed one-pot mannich reaction of acetophenone, aromatic aldehydes and aromatic amines are carried out in ethanol to afford various ${\beta}$-amino ketones. The various wt% of polyaniline were supported on pure silica synthesized by using chemical oxidative method. The catalyst prepared has been characterized by means of thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR). Solvent stability of catalyst was tested using UV-Visible spectroscopy. This protocol has several advantages such as high yield, simple work up procedure, non-toxic, clean, easy recovery and reusability of the catalyst.

• Journal of the Korean Institute of Gas
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• v.27 no.1
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• pp.78-85
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• 2023

Fixed-bed reactor Computational Fluid Dynamics (CFD) simulation of methanol steam reforming reaction was performed using the intrinsic kinetic data of the copper-impregnated hydrotalcite catalyst. The activation energy of the copper hydrotalcite catalyst obtained from the previous study results was 97.4 kJ/mol, and the pre-exponential was 5.904 × 10¹⁰. Process simulation was performed using the calculated values and showed a similar tendency to the experimental results. And the conversion rate according to the change of the reaction temperature (200 - 450 ℃) and the molar ratio of methanol and water was observed using the intrinsic kinetic data. In addition, mass and heat transfer phenomena analysis of a commercial reactor (I.D. 0.05 - 0.1m, Length 1m) was predicted through axial 2D Symmetry simulation using the power law model of the above kinetic constants.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.8
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• pp.986-996
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• 2017

In this study, we optimized fermentation conditions for burdock vinegar by response surface methodology. We confirmed the fermentation characteristics and major components of burdock vinegar. Alcohol fermentation of burdock extract added with 15% apple concentrates for vinegar production was performed. Consequently, 6.4% alcohol was produced after 5 days of fermentation. Central composite design was applied to investigate the effects of two independent variables, fermentation time (5~17 days; X1) and fermentation temperature ($26{\sim}34^{\circ}C$; X2), on fermentation of burdock vinegar. Fermentation conditions were optimized using characteristics of fermentation broth as a dependent variable. Acetic acid contents of dependent variables were 3.85~4.73% during acetic acid fermentation. The correlation coefficient ($R^2$) of the derived equation from the response surface regression for acetic acid contents was 0.9850 with significance level of 1%. Arctiin contents of all fermentation samples were 0.37~0.50 mg/100 mL, with an $R^2$ value of 0.8380 and significance level of 5%. We elicited a regression equation for each variable and superimposed the optimum area of fermentation conditions for characteristics and effective constituent contents of the fermentation broth. The predicted values for the optimum fermentation conditions for burdock vinegar were at $31^{\circ}C$ and 16 days.