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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>
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, 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.
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>
Multi-centennial-scale changes in East Asian typhoon frequency during the mid-Holocene
Katsuki, Kota,Yang, Dong-Yoon,Lim, Jaesoo,Lee, Jin-Young,Asahi, Hirofumi,Han, Min Elsevier 2017 Palaeogeography, palaeoclimatology, palaeoecology Vol.476 No.-
<P><B>Abstract</B></P> <P>This study reconstructs a record of typhoon frequency over the Korean Peninsula during the mid-Holocene using mineral components and diatom assemblages in deposits of Lagoon Hyangho, located on the east coast of the peninsula. The lagoon deposits confirm the occurrence of cyclical, multi-centennial scale episodes of low salinization induced by typhoon-derived heavy rain. Although shifts in typhoon frequency broadly follow El Niño/Southern Oscillation (ENSO) conditions during the Holocene, evidence from the typhoon-induced deposits in Hyangho Lagoon suggests that the path of the polar westerly jet controls the effect of ENSO on multi-centennial-scale typhoon patterns across the mid-latitude region of East Asia. The influence of ENSO is limited when the westerly jet passes through low latitudes. Fluctuations in solar activity play a key role in regulating movement of the westerly jet. Multi-centennial scale changes in typhoon frequency in mid-latitude East Asia are, therefore, influenced by changes in solar activity and ENSO conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Typhoon records for the mid-Holocene are reconstructed using lagoon sediments. </LI> <LI> Typhoon frequency in East Asia is synchronous with changes in solar irradiance. </LI> <LI> The effect of ENSO on typhoon paths is regulated by westerly jet stream conditions. </LI> </UL> </P>
Development of rapid mixing fuel nozzle for premixed combustion
Katsuki Masashi,정진도,김장우,황승민,김승모,안철주 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.3
Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel.
Properties of sedimentary clays for Karatsu ware
KATSUKI, Hiroaki,KAWAHARA, Akihiko,KAMOCHI, Nobuaki,PEE, Jae-Hwan,CHO, Woo-Seok,KIM, Hyung-Tae CERAMIC SOC OF JAPAN 2014 JOURNAL- CERAMIC SOCIETY JAPAN Vol.122 No.1428
<P>Four sedimentary clays for Karatsu ware which were geologically derived from the weathered sandstone and granite were mined and used in this study. The chemical composition, mineral composition and morphology of minerals were investigated by XRF, XRD, SEM and TEM analysis. The mineral composition of normative alpha-quartz, feldspar and kaolin of two clays were 43.1, 4.7, and 44.3, and 52.1, 21.3, and 27.0, respectively. These clays had lower content of feldspar and higher content of kaolin than those of clays prepared from some sandstone for Karatsu ware. Average size of coarse particles in four clays was 22-28 mu m and maximum particle size were 188-290 mu m, and these sizes were similar to those of clays prepared from sandstone. It was suggested that the decomposition of feldspar to sericite and kaolin was promoted by the weathering and hydrolysis of sandstone or granite. (C) 2014 The Ceramic Society of Japan. All rights reserved.</P>