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Influence of continental outflow events on the aerosol composition at Cheju Island,South Korea
Park, John K.,Arimoto, Richard,Savoie, Dennis,Carmichael, Gregory R,Prospero, Joseph,Hong, Min-Sun,Ueda, Hiromasa,Murano, Kentaro,Chen, Li-Ling,Kim, Y. P.,Shim, Shang,Lee, Ho-geun,Song, Chul H.,Kang, 濟州大學校 基礎科學硏究所 1998 基礎科學硏究 Vol.11 No.1
The chemical composition of aerosols measured at Cheju Island, Korea, over the 3-year period March 1992 to February 1995 are presented and discussed, with a particular emphasis on the Pacific Exploratory Mission in the Western Pacific (PEM-West B) time period. Cheju Island is under the influence of continental outflow conditions nearly 70% of the year, and as a result the aerosol loading of sea salt as well as continental aerosol components is high. The 3-year mean values derived from the daily tape filters are non-sea-salt (nss) SO₄²?=6.8㎍/㎥, NO₃?=1.2㎍/㎥, Cl??=1.9㎍/㎥, Na+=1.7㎍/㎥, Ca²?=0.5㎍/㎥, NH₄?=1.3㎍/㎥, Mg²?=0.3㎍/㎥, and K+=0.4㎍/㎥. Sea-salt components show peak values in winter, while calcium, nitrate, potassium, and to a lesser extent, sulfate and ammonium, show higher values in the spring, and all species exhibit a pronounced minimum in summer. Trajectory and principal component analysis show that elevated levels of primary aerosols (both sea salt and soil-derived) occur with strong wind conditions associated with winter and spring, and high concentrations of non-sea-salt components are most strongly associated with springtime continental outflow events. During the PEM-West B period, nitrate and calcium are found to be ∼60% higher than the annual mean, sea-salt components ∼30% higher, and sulfate ∼10% higher. The aerosol data are combined with gaseous SO₂ concentrations, precipitation chemistry data and companion aerosol measurements taken at the same site, to provide further insights into the aerosol composition at Cheju. At Cheju, sulfate and ammonium are found mostly in the fine fraction (∼80 to 90%), while calcium and nitrate reside in the coarse size fraction. sulfate and nitrate are not associated with the primary aerosols, but rather become associated with the aerosol during the long-range transport process.
Preparation and Properties of Inverse Perovskite Mn3GaN Thin Films and Heterostructures
H. Tashiro,R. Suzuki,T. Miyawaki,K. Ueda,H. Asano 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Thin films and heterostructures of Mn3GaN with an inverse perovskite structure were grownepitaxially on SrTiO3 (001) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (001) (LSAT) substrates by ionbeam sputtering, and their structural and electrical properties have been investigated. Mn3GaNepitaxial thin films showed metallic behavior of temperature-dependent resistivity with a smallmaximum at 290-340 K. The maximum resistivity could be attributed to the magnetic transitionfrom antiferromagnetism to paramagnetism. It has been found that epitaxial heterostructuresformed by ferroelectric Ba0.7Sr0.3TiO3 and Mn3GaN layers exhibit a large magnetocapacitanceeffect of more than 2000% in an applied magnetic filed of 1.5 T.
Adsorption and Reaction of CO and NO on Ir(111) Under Near Ambient Pressure Conditions
Ueda, K.,Suzuki, K.,Toyoshima, R.,Monya, Y.,Yoshida, M.,Isegawa, K.,Amemiya, K.,Mase, K.,Mun, B. S.,Arman, M. A. Springer Science + Business Media 2016 Topics in catalysis Vol.59 No.5
<P>The adsorption and reaction of CO and NO on Ir(111) have been studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) together with low-energy electron diffraction, scanning tunneling microscopy, and mass spectroscopy (MS). Under both ultrahigh vacuum (UHV) and NAP conditions CO molecules occupy on-top sites of the Ir(111) surface at room temperature (RT) by forming two-dimensional clusters. Exposure to NO under UHV conditions at RT induces partially dissociative adsorption, while NAP NO exposure leads to a Ir(111) surface that is covered by molecular NO. We conducted in-operando NAP-XPS/MS observation of the NO + (CO)-C-13 reaction under a NAP condition as a function of temperature. Below 210 degrees C adsorption of NO is inhibited by CO, while above 210 degrees C the CO inhibition is released due to partial desorption of CO and dissociative adsorption of NO starts to occur leading to associative formation of N-2. Under the most active condition studied here the Ir surface is covered by a dense co-adsorption layer consisting of on-top CO, atomic N and O, which suggests that this reaction is not a NO-dissociation-limited process but a N-2/CO2 formation-limited process.</P>
Inversion of Magnetoresistance in La1−xSrxMnO3 /Nb-doped SrTiO3/CoFe Junctions
K. Ueda,K. Tozawa,H. Asano 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Magnetoresistance (MR) devices using degenerated oxide semiconductors, Nb-doped SrTiO3,(Nb-STO) as intermediate layers between two ferromagnets were fabricated and their magneticand transport properties were evaluated. Magnetic junctions using the trilayer films showed MRof 5% at 4.2 K, and the sign and the magnitude of the MR were changed depending on thethickness of Nb-STO layers. The origin of the inversion of the MR is not clear, however we considerspin injection from ferromagnetic electrodes to Nb-STO through Schottky tunnel barriers plays animportant role.
Epitaxial Growth and Physical Properties of Heusler/Perovskite Heterostructures
K. Kobayashi,N. Fukatani,H. Kawada,K. Ueda,K. Sakuma,H. Asano 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Multiferroic heterostructures of the ferromagnetic, half-metallic Heusler Fe2CrSi (FCS) and theferroelectric perovskite Ba0.7Sr0.3TiO3 (BSTO) have been formed by magnetron sputtering, andtheir magnetic and ferroelectric properties have been investigated. FCS/BSTO bilayer structureswere epitaxially grown on LaAlO3 substrates with epitaxial relationships of FCS (001)[110]//BSTO(001)[100]. Multiferroic properties with a remanent polarization of 10.6 µC/cm2 and a saturationmagnetization of 417 emu/cc were observed for the FCS/BSTO heterostructures at room temperature. These results suggest that the Heusler/perovskite epitaxial heterostructure is a promisingcandidate for fabricating multiferroic devices.
Ellipso-Microscopic Observation of Titanium Surface under UV-Light Irradiation
( K. Fushimi ),( K. Kurauchi ),( T. Nakanishi ),( Y. Hasegawa ),( M. Ueda ),( T. Ohtsuka ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.6
The ellipso-microscopic observation of a titanium surface undergoing anodization in 0.05 mol dm<sup>-3</sup> of H<sub>2</sub>SO<sub>4</sub> was conducted. During irradiation by ultra-violet (UV) light with a wavelength of 325 nm, the titanium surface allowed for the flow of a photo-induced current and showed up as a bright, patch-like image on an ellipso-microscopic view. The brightness and patch-pattern in the image changed with flowing photo-induced current. The changes in the brightness and the image corresponded to the formation and/or degradation of titanium oxide due to the photo-electrochemical reaction of the oxide. An in situ monitoring using the ellipso-microscope revealed that the film change was dependent on the irradiation light power, by UV-light increases the anodic current and results in the initiation of pitting at lower potentials as compared with the non-irradiated condition.
Reactively Sputtered MgAl2O4 Barrier Layers for Heusler Tunnel Junctions
K. Inagaki,N. Fukatani,K. Mari,H. Fujita,T. Miyawaki,K. Ueda,H. Asano 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
Epitaxial MgAl2O4 thin films were deposited on a lattice-matched Heusler alloy, Fe2CrSi,by reactive magnetron sputtering of an MgAl2 target in an Ar+O2 atmosphere. EpitaxialFe2CrSi/MgAl2O4 junctions were obtained by inserting an ultrathin MgAl2 interlayer, which workedas a protective layer for oxidization at the surface of the Fe2CrSi. The growth of MgAl2O4 was foundto be very sensitive to the MgAl2 thickness and the oxygen partial pressure during the deposition ofMgAl2O4. Both epitaxial growth and characteristics of the efficient tunneling barrier were obtainedin an Fe2CrSi/MgAl2O4 (3 nm)/CoFe tunneling device for MgAl2O4 thin films grown by reactivesputtering. The present epitaxial MgAl2O4 barrier deposited by reactive sputtering is expected torealize high performance spintronic devices.