• Journal of the Korean Society for Heat Treatment
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• v.33 no.3
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• pp.129-134
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• 2020

Due to excellent properties such as high specific strength and low density, application of magnesium alloys have been rapidly increased. However, magnesium alloy has a serious problem that is easily oxidized when exposed to high-temperature. For this reason, magnesium alloys have been generally used for SF6 gas such as protective cover gas in casting and melting, but it has been reported that this gas has a serious influence on global warming. Therefore, many researchers have been studied to improve the oxidation resistance of magnesium alloy. It was reported that addition of Be, Ca and CaO in magnesium alloy can improve the oxidation properties. In this study, the possibility of improving the oxidation resistance by adding CaO extracted from oyster shells was investigated. Oyster shells were completely decomposed into CaO and CO₂ by annealing. With the addition of CaO, a coexistence region of MgO + CaO was formed in the oxide layer and its thickness was also reduced.

• Restorative Dentistry and Endodontics
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• v.13 no.2
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• pp.307-322
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• 1988

The purpose of this study is to evaluate the pulpal responses to the base materials such as zinc oxide eugenol cement, calcium hydroxide, zinc phosphate cement, polycarboxylate cement and glass ionomer cement. The 100 caries free dog teeth were devided into 2 groups by remaining dentin thickness (Group A: 0.4-0.6 mm, Group B: 0.8-1.0 mm) and each group were devided into 5 subgroups. The intervals of observation period are 3days, 1 week, 2 weeks, 4 weeks and 8 weeks respectively after experiment. The specimens were fixed with 10% formalin and decalcifed in 5% nitric acid. All specimens were stained with Hematoxylin-Eosin and examined histopathologically. The results were as follows. 1. In group A, atropy or hyperplasia in odontoblasts were seen in zinc oxide eugenol cement, calcium hydroxide and zinc phosphate cement. No changes in odontoblasts were seen in polycarboxylate cement and glass ionomer cement. 2. In group A, increase of predentin were seen in all experimental materials. 3. In group A, vascular congestion were seen in all experimental materials and inflammation were seen on 3 days in zinc oxide eugenol cement, 8 weeks in zinc phosphate cement and hemorrage were seen on 3 days in zinc phosphate cement. 4. In group B, changes of odontoblasts were not seen all experimental materials. 5. In group B, increase of predentin and vascular congestion were seen in all experimental materials but inflammation were not seen.

• 대한치주과학회:학술대회논문집
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• 2002.11a
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• pp.31-32
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• 2002

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.24-25
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• 2015

To secure fundamental materials for the performance change in concrete structure damaged by fire, this study analyzed SEM and XRD of hardened cement depending on high temperature conditions. As a result, at more than 200℃, SEM and XRD were not observed because of dehydration of Ettringite; at more than 500℃, calcium hydroxide was rapidly decomposed; at more than 700℃, calcium oxide was found; at 1000℃, the highest peak point appeared.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.773-778
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• 2002

The variance characteristics of the calcium carbonate contents along to the concrete cover depth takes the prediction method of remaining service life of concrete. Calcium carbonate contents were measured by the Thermo Gravimetric/Differential Thermal Analysis method at three point, depth of 0.25cm, 0.75cm, 1.25cm from the surface of concrete. This prediction method contain some assumption that the chemical protection conferred on steel is through a passive protective oxide film which forms on steel in an environment at or above a pH of 10.5$^{4)}$ .

• The Journal of the Korean dental association
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• v.20 no.12 s.163
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• pp.1025-1028
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• 1982

1) The authors have had a case of crown fractured upper central incisor with open apex and non vital pulp. 2) The patient was 8 years old female. 3) Apical closure has been induced with the use of calcium hydroxide and gutta percha cone. 4) At nine month after filling with calcium hydroxide and gutta percha cone, apical closure was observed by radiograph. 5) Root canal was permanently filled gutta percha cone and zinc oxide eugenol by the lateral condensation technique.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.357-362
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• 1999

ZnO varistors containing cobalt, praseodymium and calcium oxides were prepared. The current-voltage charcteristics and microstructures of the specimens were investigated with respect to calcium addition and sintering temperature. The potential barrier heights and the carrier densities were estimated from C-V relations. The compatibility of Ag-Pd as an internal electrode for multilayer chip varistor was also examined.

• The Research Journal of the Costume Culture
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• v.19 no.3
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• pp.612-621
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• 2011

The process of making or cultivating indigo dyes is very cumbersome and complex. The dye extraction and dyeing methods using general plant dye, moth repellent dye, fast acting natural dye, and other dyes are very different. This research investigates the extraction of indigo dye and liquid dye extraction of polygonum(indigo) plants using calcium oxide water. While extracting indigo dye the concentration of purified indigo dye may be controlled by adjusting the pH level. Due to the various uses of dyes the adjustment of surface color must be considered. In regard to the change according to different concentrations of reducing agents, it was found that cotton fabrics and ramie fabrics show the highest color difference at 0.4% and 0.3% respectively. As the reduction temperature increases, the color difference increases as well. The maximum color difference was found to appear at $90^{\circ}C$. Cotton fabrics and ramie fabrics showed 70.55 and 67.01 respectively. The color difference increases as the concentration of dyes increases, but at a concentration of 300%, cotton fabrics was found to show 6.22PB in H value using the Munsell color system, containing purple and blue color. The pH of the polygonum dyes extracted through this experiment were adjusted by adding calcium oxide to the experimental water, without directly adding calcium oxide to the liquid polygonum extract. In a refine state, it was mixed with polygonum extract to extract a more refine and highly concentrated indigo dye. When lye and reducing agents are added to extracted indigo dye and sealed for long-term storage, it can be effective and easily used for dyeing.

• Journal of Powder Materials
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• v.26 no.6
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• pp.493-501
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• 2019

In this work, ultra-fine calcium oxide (CaO) powder derived from eggshells is used as the starting material to synthesize mineral trioxide aggregate (MTA). The prepared CaO powder is confirmed to have an average particle size of 500 nm. MTAs are synthesized with three types of fine CaO-based powders, namely, tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate (C3A). The synthesis behavior of C3S, C2S and C3A with ultra-fine CaO powder and the effects of C₃A content and curing time on the properties of MTA are investigated. The characteristics of the synthesized MTA powders are examined by X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), and a universal testing machine (UTM). The microstructure and compressive strength characteristics of the synthesized MTA powders are strongly dependent on the C3A wt.% and curing time. Furthermore, MTA with 5 wt.% C3A is found to increase the compressive strength and shorten the curing time.

• Korean Journal of Food Science and Technology
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• v.37 no.5
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• pp.844-849
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• 2005

Bacteriocidal effect of calcium oxide (CaO, scallop shell powder) on reduction of microorganism in sesame leaf was evaluated through comparison with chemical sanitizers such as chlorine, ethanol, and hydrogen peroxide. CaO showed 0.55-1.49, 0.85-2.56, 0.16-1.08, 0.30-1.14, and $0.19-1.07\;log_{10}$ CFU/g reductions of total aerobic bacteria, total coliforms, Escherichia coli, Listeria monocytogenes, and Salmonella typhimurium respectively, indicating possible use of CaO as effective natural sanitizer.