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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>
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>
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, K.,Seto, K.,Nomura, R.,Maekawa, K.,Khim, B.K. Academic Press in association with the Estuarine a 2009 Estuarine, coastal and shelf science Vol.81 No.2
Diatom assemblages of the surface and in core sediment samples from Lake Saroma (Japan) were examined for the purpose of evaluating anthropogenic effect on the coastal environmental changes. Before the first inlet excavation, the lake's water quality and ecology were controlled by water exchange with the Okhotsk Sea as well as lake-level variation. However, large-scale ecological modification occurred, mainly due to artificial excavation and shellfish industrial farms. A distinct record of the succession of the dominant diatom taxa was preserved in core sediments. Low-oxygen water was prevalent in the lake in 1929, before the first inlet excavation. Immediately after the first inlet excavation, the low-oxygen water in the western basin of the lake began to disappear, in a trend that became increasing transparent, which has been attributed to an increasing rate of water exchange. However, the lacustrine environment of bottom sediments resumes deterioration 20years after since the first artificial excavation: the resultant deposition of river-mouth materials into the deep basin caused eutrophication and environmental disturbance of the lake bottom. At the same time, the eutrophication of surface water became intensified with the onset of intense scallop culturing beginning in 1966. Increasing organic loads deposited onto the bottom layer in the form of excreta from the scallop nursery led to more oxygen deficiency and the elution of nitrogen and phosphorus from the sediment, which again brought about eutrophication of the surface layer. Such environmental change was reflected in a decrease of benthic diatom taxa and an increase of planktonic taxa, trends which have continued until today. Particularly, the numbers of diatom assemblage have been decreasing all over the lake during the last 10years, which suggests that Lake Saroma's present-day deterioration and eutrophication will continue or become even worse.
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.