• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.125-130
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• 2008

If the properties of artificial lightweight aggregates produced by rotary kiln can be predicted by using a simulator equipped with a small electric furnace and a specially designed device for specimen movement, large amount of raw materials and plenty of test time can be saved to produce test products of lightweight aggregates. In this study a simulator for the accurate prediction of the artificial lightweight aggregates produced by rotary kiln was assembled by our own design and the properties of lightweight aggregates produced by both the simulator and rotary kiln were compared to speculate its usefulness. The average diameter of aggregates was 8 mm and atmosphere in the furnace was controlled by the amount of carbon powders. Specific gravity, absorption rate (%), black-core area in the cross-sectional view of both aggregates were measured and compared. Unlike oxydizing atmosphere, both specific gravity and absorption rate of the aggregates sintered at reducing atmosphere were increased with increasing carbon addition. It is concluded that the sintering atmosphere was the closest to that of the rotary kiln when the carbon addition was 0.7 g to make a reducing atmosphere in the furnace and the properties of both agreggates was also similar to each other.

• Agricultural and Biosystems Engineering
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• v.3 no.1
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• pp.10-17
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• 2002

Quality attributes of apple are greatly affected by the cooling rate and environmental conditions during storage. Studies were conducted to evaluate the effect of cooling rate on different quality attributes of apple. The effect of $O_2$ pulldown rate of the CA chamber on the quality of apple was also determined. Two methods were used viz. conventional CA procedure and rapid CA procedure. Apples stored by medium and slow cooling methods lost its flesh firmness significantly from an initial level of 4.55 kg to 2.83 kg and 2.27 kg, respectively on 35 days after storage whereas, in rapid cooling, the firmness level changed from 4.55 kg to 3.20 kg on 35 days after storage. At the end of 35 days of storage, titratable acidity decreased insignificantly from an initial value of 0.24l% to 0.239% in the case of rapid CA whereas in the case of conventional CA it dropped significantly to 0.215% from its initial level. The initial flesh firmness of 4.55 kg also changed significantly to 4.05 kg on 35 days after storage in conventional CA whereas in rapid CA it changed to 4.36 kg, which was found to be non-significant at 5% level of significance. Total soluble solids increased from an initial level of $12.43^{\circ}$Bx to $12.60^{\circ}C.$ Bx on 35 days after storage in rapid CA whereas it increased to $13.07^{\circ}$ Bx in conventional CA. Ascorbic acid content of apple juice decreased insignificantly from 6.67 mg/100 mL to 5.87 mg/100 mL on 35 days after storage in rapid CA whereas in conventional CA, it decreased significantly to 5.27 mg/100 mL from its initial level.

• Particle and aerosol research
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• v.14 no.4
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• pp.145-151
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• 2018

Rod shaped Potassium hexatitanate ($K_2Ti_6O_{13}$) was synthesized from colloidal mixture of $TiO_2$, KOH and graphene oxide (GO) by aerosol spray drying and post heat treatment. Firstly, $TiO_2-KOH-GO$ composites were fabricated by aerosol spray drying in argon atmosphere. The composites were then calcined to form a rod shaped morphology of potassium titanate (KTO) in the presence of graphene at $900^{\circ}C$ for 3 h in argon atmosphere. Finally, the rod shaped KTO was obtained after removal of graphene (GR) at $800^{\circ}C$ and 3 h in air atmosphere. Characterization of the synthesized $K_2Ti_6O_{13}$ was carried out using the XRD, BET and FE-SEM. The length and diameter of the synthesized $K_2Ti_6O_{13}$ could be controlled by weight fraction of GO in the aerosol precursor. The length of $K_2Ti_6O_{13}$ rod increased with decreasing its diameter as GO concentration increased. The aspect ratio of the synthesized $K_2Ti_6O_{13}$ rod was controlled from 5 to 13.

• Progress in Superconductivity
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• v.3 no.2
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• pp.168-171
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• 2002

We have demonstrated ramp-edge Josephson junctions using high temperature superconductors without depositing artificial barriers. We fabricated a surface barrier formed naturally during an ion beam etching process and the annealing under the oxygen atmosphere. The experimental results imply that the barrier natures such as the resistivity are varied by the annealing conditions and the ion milling conditions including the beam voltages. Thus, the ann eating and etching conditions should be optimized to obtain excellent junction properties. In optimizing the fabricating factors, the interface-controlled junctions showed resistively shunted junctions like current-voltage characteristics and an excellent uniformity. These junctions exhibited a spread ($1\sigma$) of $I_{c}$ is 10% fur chips containing 7 junctions at 50K.K.

• Journal of the Korean Society of Food Science and Nutrition
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• v.20 no.3
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• pp.214-219
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• 1991

The damaging effect of peroxidized lipid on amino acid was studied in rice bran by determining the free amino acid content in abiological system. The content of free amino acid in the rice bran stored in the controlled atomsphere of $35^{\circ}C$ with relative humidity of 65% for 180 days, increased during the first 60 days of storage, and then decreased as the lipid peroxidation proceeded. The content of free amino acid in the sample exposed to the air of $25-30^{\circ}C$ with relative humidity of 70-90% for 100 days decreased rapidly in the beginning period of the storage. The lipid oxidation developed much faster in the rice bran exposed to the air than in the rice bran stored in the controlled atmosphere. The correlation coefficients between the total content of free amino acid and degree of peroxidation for the samples of both conditions were above -0.8, which is significant(p<0.05). The changes in the concentration of serine, glutamic acid, proline, methionine, lysine, histidine, and arginine were significantly correlated with the degree of lipid oxidation(p<0.05) for the samples stored in the controlled atmosphere and the open air. It was observed that peroxidized lipid has damaging effects on protein in the bilogical system of rice bran.

• Journal of the Korean Ceramic Society
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• v.39 no.2
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• pp.199-203
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• 2002

To investigate an effect of sintering atmosphere on microstructure and properties of metallic particle dispersed ceramic based composites, the powder mixtures of $Al_2O_3$/Fe-Ni, synthesized by chemical solution process, were hot-pressed under different atmospheres such as hydrogen or argon gas and different sintering temperature. Hot-pressed composite in a hydrogen atmosphere exhibited less reaction phase of $FeAl_2O_4$ and enhanced mechanical properties than that in an argon atmosphere. Furthermore, decreasing hot-pressing temperature produced a refinement of ceramic matrix and metallic dispersion particles as well as improvement of mechanical properties. The change of mechanical properties in the composites with different sintering conditions was explained by microstructural characteristics relating to reaction phase formation.

• Journal of Powder Materials
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• v.24 no.1
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• pp.41-45
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• 2017

The effects of the heat treatment temperature and of the atmosphere on the dehydrogenation and hydrogen reduction of ball-milled $TiH_2-WO_3$ powder mixtures are investigated for the synthesis of Ti-W powders with controlled microstructure. Homogeneously mixed powders with refined $TiH_2$ particles are successfully prepared by ball milling for 24h. X-ray diffraction (XRD) analyses show that the powder mixture heat-treated in Ar atmosphere is composed of Ti, $Ti_2O$, and W phases, regardless of the heat treatment temperature. However, XRD results for the powder mixture, heat-treated at $600^{\circ}C$ in a hydrogen atmosphere, show $TiH_2$ and TiH peaks as well as reaction phase peaks of Ti oxides and W, while the powder mixture heat-treated at $900^{\circ}C$ exhibits only XRD peaks attributed to Ti oxides and W. The formation behavior of the reaction phases that are dependent on the heat treatment temperature and on the atmosphere is explained by thermodynamic considerations for the dehydrogenation reaction of $TiH_2$, the hydrogen reduction of $WO_3$ and the partial oxidation of dehydrogenated Ti.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.2 s.245
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• pp.170-176
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• 2006

A spark discharge aerosol generator using air as a carrier gas has successfully been applied to silver nanoparticle production. The spark discharge between two silver electrodes, which was periodically obtained by discharging the capacitor, produced sufficient high temperatures to evaporate a small fraction of the silver electrodes. The silver vapor was subsequently supersaturated by rapid cooling and condensed to silver nanoparticles by nucleation and condensation. The morphology of the generated particles observed by transmission electron microscope was spherical. The element composition of the nanoparticles was silver, which was determined by energy dispersive X-ray spectroscopy. The crystal phase of the particles spark-generated under air atmosphere was composed of silver and silver oxides phase, which was determined by Xray diffraction analysis. While the nanoparticles generated under nitrogen atmosphere had only silver phase. This XRD data indicates that some fraction of the evaporated silver vapor could be oxidized in air atmosphere by the reaction with oxygen. A stable operation of the spark discharge generator has been achieved. The size and concentration of the particles can be easily controlled by altering the repetition frequency, capacitance, gap distance and flow rate of the spark discharge system.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.2
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• pp.1-7
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• 2001

In order to form a uniform oxidation layer of spinel phase on Kovar which helps the strong bonding in Kovar-to-glass sealing, the humidified $N_2/H_2$ was used as an oxidation atmosphere. The oxidation of Kovar was controlled by diffusion mechanism and the activation energy was 31.61 kacl/mol at 500~$800^{\circ}C$. After oxidation at $600^{\circ}C$, the external oxidation layer was below 0.5 $\mu \textrm{m}$ thick. According to TEM analysis, oxidized Kovar was spinel its lattice parameter of 7.9 $\AA$. Oxidation of under $600^{\circ}C$ and in a humidified $N_2/H_2$ atmosphere, Kovar was found to be appropriate for the Kovar-to-glass sealing.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.270-275
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• 2009

Lotus-type porous nickel with cylindrical pores was fabricated by unidirectional solidification under an Ar gas atmosphere using the thermal decomposition method of the compounds such as sodium hydroxide, calcium hydroxide, calcium carbonate, and titanium hydride. The decomposed gas does form the pores in liquid nickel, and then, the pores become the cylindrical pores during unidirectional solidification. The decomposed particles from the compounds do play a rule on nucleation sites of the pores. The behavior of pore growth was controlled by atmosphere pressure, which can be explained by Boyle's law. The porosity and pore size decreased with increasing Ar gas pressure when the pores contain hydrogen gas decomposed from calcium and sodium hydroxide and titanium hydride, ; however it they did not change when the pores contain containing carbon dioxide decomposed from calcium carbonate. These results indicate that nickel does not have the solubility of carbon dioxide. Lotus-type porous metals can be easily fabricated by the thermal decomposition method, which is superior to the conventional fabrication method used to pressurized gas atmospheres.