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Eco-friendly Self-cooling System of Porous Onggi Ceramic Plate by Evaporation of Absorbed Water
Katsuki, Hiroaki,Choi, Eun-Kyong,Lee, Won-Jun,Kim, Ung-Soo,Hwang, Kwang-Taek,Cho, Woo-Seok The Korean Ceramic Society 2018 한국세라믹학회지 Vol.55 No.2
Porous ceramic plates were prepared from Onggi clay and bamboo charcoal powder at 1100 and $1200^{\circ}C$ and their porous properties and water absorption, and the cooling effect of porous plates, were investigated to produce eco-friendly porous ceramics for a self-cooling system that relies on the evaporation of absorbed water. Porous properties were dependent on the particle size of charcoal powder pore forming additive and the firing temperature; properties were also found to be dependent on the total pore volume, average pore size and porosity, which had values of $0.103-0.243cm^3/g$, 0.81 - 2.56 mm and 20.9 - 38.2%, respectively, at $1100^{\circ}C$ and $0.04-0.18cm^3/g$, 0.33 - 2.03 mm and 10.8 - 30.9%, respectively, at $1200^{\circ}C$. Cooling temperature difference of flowing air parallel to surface of porous ceramic plates fired with two kinds of charcoal powder at $1100^{\circ}C$ was $3.5-3.6^{\circ}C$ at $26^{\circ}C$ and 60% of relative humidity in a closed box. Cooling temperature difference was dependent on the number of porous plates and the distance between porous plates. A simple and eco-friendly cooling system using porous ceramic plates fired from Onggi clay and charcoal powder was proposed.
Katsuki, Kota,Nakanishi, Toshimichi,Lim, Jaesoo,Nahm, Wook‐,Hyun Blackwell Scientific 2017 The island arc Vol.26 No.6
<P><B>Abstract</B></P><P>Detailed diatom records within core sediments from Maeho Lagoon along the Eastern coast of South Korea revealed that the ecological dynamics of the lagoon during the Holocene were associated with relative sea level and regional precipitation. Accelerator mass spectrometry (AMS) <SUP>14</SUP>C dating indicates that sediment accumulation began prior to 8300 cal. year BP, and that the lagoon formed around 8000 cal. year BP. The salinity level of the lagoon increased until 5000 cal. year BP, and then decreased. Long‐term trends in salinity were dependent upon changes in sea level: periods of high salinity in the lagoon were generally coincident with periods of high sea levels along the east coasts of Korea and Japan. On the other hand, multicentennial‐scale fluctuations in diatom assemblages and magnetic susceptibility (MS) suggest that a 400 year fluctuation in salinity was regulated by changes in precipitation in the area of this lagoon. Changes in the westerly jet stream, controlled by variation in solar irradiance, had an important influence on precipitation volume in South Korea, suggesting that the patterns of the westerly jet stream fluctuate on a 400 year cycle.</P>
Katsuki, Hiroaki,Choi, Eun-Kyoung,Lee, Won-Jun,Cho, Woo-Seok,Hwang, Kwang-Taek,Huang, Wenyan,Komarneni, Sridhar Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.16
<P><B>Abstract</B></P> <P>The effect of mixing process of FeCl<SUB>3</SUB> and NaOH solution on the formation of platy (hexagonal) α-Fe<SUB>2</SUB>O<SUB>3</SUB> was investigated at 160 and 180°C by the hydrothermal process. The crystal growth of platy α-Fe<SUB>2</SUB>O<SUB>3</SUB> was promoted at higher hydrothermal temperature, higher concentration of NaOH solution and by the addition of FeCl<SUB>3</SUB> solution to NaOH solution instead of the reverse addition. Platy crystals of α-Fe<SUB>2</SUB>O<SUB>3</SUB> showed dark red wine color while nanophase equiaxed crystals showed yellowish red color. The platy crystals of 3–6µm in average diameter kept their platy structure after heating at 900 and 1100°C in air due to their higher thermal stability towards sintering.</P>
Influence of alumina content in the raw clay on the sintering behavior of Karatsu ware
KATSUKI, Hiroaki,KIM, Jaegyeom,KIM, Seung-Joo,KIM, Jong-Young,PEE, Jae-Hwan,CHO, Woo-Seok Ceramic Society of Japan 2016 JOURNAL OF THE CERAMIC SOCIETY OF JAPAN - Vol.124 No.8
<P>In this paper, mineral and sintering properties of high alumina-containing clay (Yamase clay) derived from a weathered granite stone were investigated, and compared with those of low alumina-containing clay derived from a weathered sandstone (Hobashira clay) for the ancient Karatsu ware. Content of Al2O3 in Yamase clay was 30.8-33.1 mass%, and showed higher than that of Hobashira clay (13.1-15.8 mass%). Yamase and Hobashira clay had a mineral composition of kaolinite (64.3), alpha-quartz (10.6), muscovite (11.9), albite (10.3), and microcline (2.9 mass%), and kaolinite (12.9), alpha-quartz (52.9), muscovite (23.4), albite (6.9), and microcline (3.9 mass%), respectively, by the Rietveld analysis. Bulk densities of Yamase clay heated at 1200, 1300, and 1400 degrees C were 1.99, 2.15, and 2.35 g/cm(3), and Yamase clay had a higher refractoriness than Hobashira clay. After heating Yamase clay at 1300-1400 degrees C, the heated body was composed of fine needle-like mullite (49.8) and glass (50.2 mass%) without the bloating of the body. (C) 2016 The Ceramic Society of Japan. All rights reserved.</P>
Factors controlling typhoons and storm rain on the Korean Peninsula during the Little Ice Age
Katsuki, K.,Yang, D. Y.,Seto, K.,Yasuhara, M.,Takata, H.,Otsuka, M.,Nakanishi, T.,Yoon, Y.,Um, I. K.,Cheung, R. C. Springer Science + Business Media 2016 Journal of paleolimnology Vol.55 No.1
<P>Documenting multi-decadal typhoon and storm-rain variability is useful to prevent future typhoon and flood disasters. We present the history of typhoon and storm-rain activity in East Asia inferred from multi-proxy analyses of Lagoon Hwajin-po sediments along the eastern coast of Korea. Anthropogenic effects were enhanced in Lagoon Hwajin-po since ca. AD 1900, by increasing farming in the catchment. To avoid these human-induced effects, we reconstructed the history of typhoon and storm-rain activity only for the interval AD 1400-1900. The record indicates that typhoon frequency throughout the Korean Peninsula varied in response to the state of the El Nio/Southern Oscillation. Typhoon variability was likely modulated further by the state of the East Asia summer monsoon (EASM) pattern, associated with variation in the magnitude of solar irradiance. During periods of minimum solar activity, such as the early Maunder Minimum (AD 1650-1675), typhoons struck the east China coast and Korean Peninsula more frequently because of a strengthened EASM.</P>
Katsuki, Akihiko,Oki, Takuya The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
The quantity of alternating current (AC) leakage and the value of distortion factor in capacitor currents are discussed with regard to a new power component called variable capacitance device (VCD). This component has terminals for controlling its capacitance. Nonlinear dielectric characteristics are utilized in this device to vary the capacitance. When VCD operates in an AC circuit, the AC leakage from this device through direct current (DC) control voltage source increases according to the conditions of DC control voltage and so on. To solve this problem, we propose techniques for suppressing AC leakage. Although VCD has strong nonlinear characteristics, the current through the capacitor is not distorted significantly. The relations between AC leakage and the distortion in current waveforms are investigated. An application example for an AC power regulator is also introduced to evaluate the distortion in waveforms.