• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.374-386
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• 2019

A process for nitrogen doping of TiO₂ ceramics was developed, whereby polycrystalline titania particles were prepared at 450-1000℃ with variation of the firing schedule under N₂ atmosphere. The effect of nitrogen doping on the polycrystallites was investigated by X-ray diffraction (XRD) and Raman analysis. The microstructure of the TiO₂ ceramics changed with variation of the firing temperature and the firing atmosphere (N₂ or O₂). The microstructural changes in the nitrogen-doped TiO₂ ceramics were closely related to changes in the Raman spectra. Within the evaluated temperature range, the nitrogen-doped titania ceramics comprised anatase and/or rutile phases, similar to those of titania ceramics fired in air. Infiltration of nitrogen gas into the titania ceramics was analyzed by Raman spectroscopy and XRD analysis, showing a considerable change in the profiles of the N₂-doped TiO₂ ceramics compared with those of the TiO₂ ceramics fired under O₂ atmosphere. The nitrogen doping in the anatase phase may produce active sites for photocatalysis in the visible and ultraviolet regions.

• 한국지구과학회:학술대회논문집
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• 2005.02a
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• pp.115-125
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• 2005

Carbon isotopic composition of a stream (Odaecheon Stream) monitored over 7 months from July 2004 to January 2005 in Gangweon Province ranges from -9.24 to -4.69‰. Strong negative correlation between ${\delta}^{13}C_{DIC}$ and water temperature suggests that temperature is a dominant factor controlling ${\delta}^{13}C_{DIC}$ in the Odaecheon Stream. The variation pattern of ${\delta}^{13}C_{DIC}$ was thought to be caused by fractionation of C isotope between stream water and atmosphere and more fractionation at reduced temperature. More fractionation of C isotope between stream water and atmosphere at reduced temperature resulted in increase of ${\delta}^{13}C_{DIC}$ of stream water in winter compared to summer. Photosynthesis and respiration of aqueous biota seem to affect little in ${\delta}^{13}C_{DIC}$ as indicated by little variation of dissolved oxygen and reverse variation pattern of Eh in the stream and scarce aqueous biota in stream water. pH seems to be controlled by $CO_2{2}$ exchange between stream water and atmosphere. During summer more $CO_2{2}$ exchange between stream water and atmosphere resulted in decrease in pH value.

• Journal of Korea Foundry Society
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• v.30 no.2
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• pp.55-59
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• 2010

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• v.10 no.1
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• pp.265-268
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• 2005

• Korean journal of applied entomology
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• v.54 no.1
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• pp.17-23
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• 2015

A complete control on quarantine insect pests is required for exporting domestic apples to other countries. To this end, a controlled atmosphere and heat treatment system (CATTS) has been developed as a post-harvest treatment. This study determined the CATTS conditions to control completely two lepidopteran insect pests, the smaller tea tortrix moth, Adoxophyes paraorana and the peach pyralid moth, Dichocrocis punctiferalis, which exhibit different feeding behviors. In both species, the fifth instar larvae were the most tolerant developmental stage to the heat treatment. Under CATTS conditions with 15% $CO_2$ and 1% $O_2$ for 1 h heat treatment at $46^{\circ}C$, the fifth instar larvae of A. paraorana exhibited a complete lethality, while those of D. punctiferalis underwent 88% mortality. To control completely the fifth instar larvae of D. punctiferalis, 2 h heat treatment required under the same atmosphere condition. These CATTS treatment effects were confirmed against over 3,000 fifth instar larvae of each species infesting apples. This study demonstrates that the longer exposure to CATTS conditions is required for the complete disinfestation of the internal apple feeder compared to the non-internal apple feeder.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.865-870
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• 2003

The effects of storage atmosphere on the physicochemical and organoleptic properties of Asian pears (Pyrus pyrifolia Nakai cv. Niitaka) were investigated. The pears were stored at $0^{\circ}C$ for up to 8 months under CA conditions (3 kPa $O_2$＋1 kPa $CO_2$, 1 kPa $O_2$+5 kPa $CO_2$, 1 kPa $O_2$+1 kPa $CO_2$) controlled by a static system or air (21 kPa $O_2$+0 kPa $CO_2$). CA conditions retarded the loss of weight, flesh firmness, organoleptic properties (appearance, aroma, sweetness, texture), and the development of injuries in the fruits during storage. Low $O_2$ plus high $CO_2$ conditions maintained the highest flesh firmness. In addition, low $O_2$ reduced injuries more than the other conditions. Skin color (lightness, chroma, hue), soluble solids, titratable acidity, pH and vitamin C were unaffected by storage atmosphere.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.116-125
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• 2018

Color shade variation was investigated in zirconia dental blocks, prepared using commercial powders. As a reference color-shade block we used the color indexes of A2, A3.5, A4 and B3, according to the VITA classical color scale. The zirconia powders for color shade blocks showed colors of white, yellow, pink and grey, respectively, after firing at $1530^{\circ}C$. The zirconia powders were mixed according to the recipe of color shade blocks and shaped at lower pressure using a uniaxial hydrostatic press. The shaped sample was inserted into a vinyl pack and sealed in a vacuum form machine. The shaped block samples were reshaped at 450 bar using an isostatic cold press and fired at $1530^{\circ}C$ for three hours. In order to investigate the atmospheric color variation with firing temperature, the A2, A3.5, A4 and B3 sintered blocks were fired between $700^{\circ}C$ and $1300^{\circ}C$ under controlled atmosphere of $pN_2$ and $pO_2$. The surface color picture was taken using a smart phone camera and compared with the results obtained using the VITA classical color scale. Quantitative color index value, CIELAB, was measured using a color-meter. Above $800^{\circ}C$, the color darkness greatly increased with the increase of the reduction temperature and keeping time.

• Food Science and Biotechnology
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• v.18 no.6
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• pp.1379-1385
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• 2009

Quality changes of the slices processed from 'Niitaka' Asian pears (Pyrus pyrifolia) stored at $0^{\circ}C$ for up to 4 months under controlled atmosphere (CA, 1% $O_2+1%\;CO_2$) and normal air have been investigated for 4 days at $10^{\circ}C$. Respiration rate of the slices was retarded by pre-slicing storage for 4 months in CA. Electrolyte leakage was lower in the slices from pears stored for short-term than long-term and under CA than air. L and a values of the slices from whole pears stored under CA were maintained higher and lower, respectively as compared to the other. Levels of acetaldehyde and ethanol in the slices were increased by CA and long-term storage of whole pears. Content of ascorbic acid and counts of total aerobic microbes in the slices were not affected by storage conditions of whole pears. These results show that storage atmospheres and durations of whole pears affected quality changes of the slices and the conditions of pre-slicing storage should be considered as an important factor for optimizing fresh-cut procedures.

• Horticultural Science & Technology
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• v.19 no.2
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• pp.145-148
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• 2001

This research was conducted to find out whether controlled atmosphere(CA) can maintain Satsuma Mandarin fruit fresh longer compared to cold storage. Fruit harvested in Nov. 1998 at Jeju Province were stored in three different CA condition including cold storage. The CA treatments consisted of combinations of 3%, 5% and 10.9% $CO_2$ with 1% and 3-3.9% $O_2$, respectively. Weight and firmness were maintained higher in static CA chambers than in the cold storage. Soluble solid content in fruit of cold storage increased until 2 months of storage and thereafter sharply decreased, whereas that of CA-stored fruit increased slowly throughout the storage period of 120 days. Citric acid decreased obviously in all the treatments with a partially longer retention in CA chambers during storage. Sensory evaluation clearly showed that CA could extend market period of Satsuma Mandarin fruit.

• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.388-393
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• 2018

Sublimation of $Bi_2O_3$-based materials is an important degradation issue for the long-term applications of many electronic devices. A series of $SnO_2$-doped $Bi_2O_3$ materials (SBO), was synthesized, densified, and then tested in air or strong reducing atmosphere. The $SnO_2$-doping effects and sublimation kinetics of the SBO materials were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and precise mass loss measurement. The results show that formation of $Bi_2Sn_2O_7$ phase greatly retards the mass loss of SBO. The SBO samples show a surface sublimation in an energy of $52.6kJ{\cdot}mol^{-1}$. However, the sublimation is also controlled by surface microstructure as the amount of vaporizing species (the Bi or gaseous Bi-oxides) is more than 0.1 mass%. The evaporation is retarded on the rough surface and the mechanism of surface evaporation is changed to diffusional control.