• Kyungpook Mathematical Journal
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• v.60 no.2
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• pp.349-359
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• 2020

We study perfect 2-colorings of regular graphs. In particular, we consider the 4-regular case. We obtain a characterization of perfect 2-colorings of toroidal grids.

• Journal of the Chungcheong Mathematical Society
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• v.18 no.2
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• pp.145-159
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• 2005

In this paper we introduced the concept of perfect folding defined on $E^2$ which equipped by perfect k-coloring of r-monohedral tillings. Then we studied the different cases of perfect foldings of 4-monohedral and 3-monohedral tillings of $E^2$. Also the permutations describe each folding are obtained.

• Journal of Conservation Science
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• v.26 no.2
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• pp.183-190
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• 2010

We fabricated urethane material based on properties of reversible and unfading for antic-ceramics restoration. This material with low viscosity was made hardness control possible that user want. And it have very strong adhesion and shear strength properties and is shown the best properties for pigment filling, anti-contractibility, coloring as like epoxy system materials. Particularly, the yellowing and ir-reversibility problem in epoxy restoration material were finally solved. So, there is guarantee in the eternity and stabilization of restoration for antic-celamics. And in order to show the reversible state of the restoration, we successfully dissolve this urethane materials in solvent after perfect restoring subsequently.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.2
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• pp.79-86
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• 2016

The late-maturing black rice cultivar Shinnongheugchal from Jeollabuk-do Agricultural Research and Extension Service was used as the plant material for estimating growth characters, quality and yield from the vegetation period to harvest age. This study was performed to select an optimum combination of nitrogen level and planting density for the maximum yield of Shinnongheugchal. The plant height, number of tillers, and SPAD index were higher when the combination of 70 hills per $3.3m^2$ and 13 kg/10 a nitrogen level was used at 30 days after transplanting. The heading date for the combination of 70 hills per $3.3m^2$ and 15 kg/10 a nitrogen level, and 80 hills per $3.3m^2$ and 15 kg/10 a nitrogen level was August 22. The heading date for the other combinations was August 21. The combination of 70 hills per $3.3m^2$ and 13 kg/10 a nitrogen level yielded the highest number of tillers at 40 days after flowering. Even though the lodging index was increased with increasing nitrogen levels, field lodging did not occur until harvest time. Seed nitrogen concentration in the combination of 70 hills per $3.3m^2$ and 13 kg/10 a nitrogen level showed a significant difference when compared with the other combinations. The black rice yield varied significantly, and the highest yield was observed in the combination of 70 hills per $3.3m^2$ and 13 kg/10 a nitrogen level. The yield was significantly correlated with seed nitrogen concentration. The maximum yield was estimated to be 14.67 kg/10 a nitrogen level by using the regression equation. On average, the coloring degree of the black rice was higher at planting density of 70 hills per $3.3m^2$ than at 80 hills per $3.3m^2$. The highest yield of perfect black rice was obtained using the combination of 70 hills per $3.3m^2$ and 13 kg/10 a nitrogen level. Our findings demonstrate that a nitrogen level of 13-14 kg/10 a can be used to obtain the maximum yield from Shinnongheugchal with yield, cyanidin 3-glucoside content, and perfect black rice yield as the standard.