• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• 제15권3호
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• pp.1-6
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• 2019

The basalt fiber, which is found to be non-toxic and harmless to the human body, is expected to become a trend for industrial fibers as they have better properties of non-combustion, heat-resistant, soundproof, absorbent, moistureproof, wear-resistant, corrosion resistant, lightweight, and high strength properties. Thus, in this study, we analyzed the chemical compositions of basalt produced at seven sites on Jeju Island for making a high value inorganic insulation material. The results showed that the MgO content of basalt collected from the eastern part of Jeju Island was higher than 7.5 percent, while that of the western region was less than 6 percent.

• Korean Journal of Materials Research
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• 제29권4호
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• pp.241-251
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• 2019

There are several manufacturing techniques for developing thermionic cathodes for vacuum ultraviolet(VUV) ionizers. The triple alkaline earth metal emitters(Ca-Sr-Ba) are formulated as efficient and reliable thermo-electron sources with a great many different compositions for the ionizing devices. We prepare two basic suspensions with different compositions: calcium, strontium and barium. After evaluating the electron-emitting performance for europium, gadolinium, and yttrium-based cathodes mixed with these suspensions, we selected the yttrium for its better performance. Next, another transition metal indium and a lanthanide metal neodymium salt is introduced to two base emitters. These final composite metal emitters are coated on the tungsten filament and then activated to the oxide cathodes by an intentionally programmed calcination process under an ultra-high vacuum(${\sim}10^{-6}torr$). The performance of electron emission of the cathodes is characterized by their anode currents with respect to the addition of each element, In and Nd, and their concentration of cathodes. Compared to both the base cathodes, the electron emission performance of the cathodes containing indium and neodymium decreases. The anode current of the Nd cathode is more markedly degraded than that with In.

• Nutrition Research and Practice
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• 제6권1호
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• pp.21-27
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• 2012

Pumpkins have considerable variation in nutrient contents depending on the cultivation environment, species, or part. In this study, the general chemical compositions and some bioactive components, such as tocopherols, carotenoids, and ${\beta}$-sitosterol, were analyzed in three major species of pumpkin ($Cucurbitaceae$ $pepo$, $C.$ $moschata$, and $C.$ $maxima$) grown in Korea and also in three parts (peel, flesh, and seed) of each pumpkin species. $C.$ $maxima$ had significantly more carbohydrate, protein, fat, and fiber than $C.$ pepo or $C.$ $moschata$ (P<0.05). The moisture content as well as the amino acid and arginine contents in all parts of the pumpkin was highest in $C.$ $pepo$. The major fatty acids in the seeds were palmitic, stearic, oleic, and linoleic acids. $C.$ $pepo$ and $C.$ $moschata$ seeds had significantly more ${\gamma}$-tocopherol than $C.$ $maxima$, whose seeds had the highest ${\beta}$-carotene content. $C.$ $pepo$ seeds had significantly more ${\beta}$-sitosterol than the others. Nutrient compositions differed considerably among the pumpkin species and parts. These results will be useful in updating the nutrient compositions of pumpkin in the Korean food composition database. Additional analyses of various pumpkins grown in different years and in different areas of Korea are needed.

• Proceedings of the KWS Conference
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• 대한용접접합학회 1993년도 특별강연 및 춘계학술발표 개요집
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• pp.82-84
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• 1993

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.861-862
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• 2004

• Journal of Periodontal and Implant Science
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• 제2권1호
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• pp.6.2-6.2
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• 1972

• Proceedings of the KWS Conference
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• 대한용접접합학회 1997년도 특별강연 및 추계학술발표 개요집
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• pp.128-132
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• 1997

• Proceedings of the KWS Conference
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.241-244
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• 2001

• Proceedings of the KWS Conference
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.195-197
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• 2001

• Journal of the Korean Ceramic Society
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• 제37권2호
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• pp.158-163
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• 2000

Six different SiC ceramics with SiO2-Re2O3 (Re=Yb, Er, Y, Dy, Gd, Sm) as sintering additives have been fabricated by hot-pressing the SiC-Re2Si2O7 compositions at 1850$^{\circ}C$ for 2 hr under a pressure of 25 MPa. The room temperature strneth and the fracture toughness of the hot-pressed ceramics were characterized and compared with those of the ceramics sintered with YAG (Y3Al5O12). Five SiC ceramics (Re=Yb, Er, Y, Dy, Gd) investigated herein showed sintered densities higher than 94% of theoretical. Tthe SiC-Re2Si2O7 compositions showed lower strength and comparable toughness to those from SiC-YAG composition, owing to the chemical reaction between SiO2 and SiC during sintering. SiC ceramics fabricated from a SiC-Y2Si2O7 composition showed the best mechanical properties of 490 MPa and 4.8 MPa$.$m1/2 among the compositions investigated herein.