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Chinju, South Korea

Lee J.D.,Gyeongsang National University | An T.H.,Gyeongsangnamdo Institute of Science Education | Noh H.G.,Gyeongnam Science High School | Kim S.G.,Kwandong Middle School | Choi Y.R.,Samhyun Girs High School
Japanese Journal of Applied Physics | Year: 2010

The cobalt thin films were directly grown on n-Si(100) substrates in a non-aqueous electrolyte of 0.1M CoCl2 by using pulsed electrodeposition technique. In this paper, the growth, structural and magnetic properties of thin Co films have been investigated. Current transient experiments showed that Co nuclei in the early deposition stage forms through three dimensional (3D) instantaneous nucleation followed by diffusion-limited growth. From the atomic force microscopy (AFM) analysis, it has been found that the film surface consisted of cubic and distorted rectangularshaped nanocrystallites with the average size of about 140nm irrespective of the deposition voltage. X-ray diffraction (XRD) measurement indicated that Co was arranged with only a hexagonal close-packed (hcp) structure not involving face-centered cubic (fcc) Co or silicide phases. Vibrating sample magnetometer (VSM) measurements revealed that the easy magnetization axis of Co thin film is parallel to the film plane. © 2010 The Japan Society of Applied Physics. Source


Hwang J.,Korea Astronomy and Space Science Institute | Choi K.,Korea Astronomy and Space Science Institute | Lee J.,Korea Astronomy and Space Science Institute | Park Y.-D.,Korea Astronomy and Space Science Institute | Ha D.-H.,Gyeongnam Science High School
Journal of Astronomy and Space Science | Year: 2011

Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Mt. Bohyun Observatory to measure the Earth's magnetic field variations in South Korea. We, in 2007, installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we provide the preliminary and the first statistical analysis using the BOH magnetometer installed at Mt. Bohyun Observatory. By superposed analysis, we find that daily variations of H, D, and Z shows similar tendency, that is, about 30 minutes before the meridian (11:28) a minimum appears and the time after about 3 hours and 30 minutes (15:28) a maximum appears. Also, a quiet interval start time (19:06) is near the sunset time, and a quiet interval end time (06:40) is near the sunrise time. From the sunset to the sunrise, the value of H has a nearly constant interval, that is, the sun affects the changes in H values. Seasonal variations show similar dependences to the sun. Local time variations show that noon region has the biggest variations and midnight region has the smallest variations. We compare the correlations between geomagnetic variations and activity indices as we expect the geomagnetic variation would contain the effects of geomagnetic activity variations. As a result, the correlation coefficient between H and Dst is the highest (r = 0.947), and other AL, AE, AU index and showed a high correlation. Therefore, the effects of geomagnetic storms and geomagnetic substorms might contribute to the geomagnetic changes significantly. © The Korean Space Science Society. Source


Min K.S.,Kyungpook National University | Park A.H.,Gyeongnam Science High School | Shin J.W.,Kyungpook National University | Rowthu S.R.,Kyungpook National University | And 2 more authors.
Dalton Transactions | Year: 2010

Chiral copper(ii) complexes of the types [CuII(R/S-ppme) 3](ClO4)2 and [CuII(R/S-ppme) 2(SO4)] have been synthesized by reactions of Cu(ClO 4)2·6H2O and CuSO4· 5H2O with R/S-ppme in methanol under aerobic conditions (R/S-ppme = (R/S)-(±)-1-phenyl-N-(pyridine-2-ylmethylene)ethanamine). All complexes were isolated and characterized by X-ray crystallography and circular dichroism (CD): (Λ)-[CuII(R-ppme)3](ClO4) 2 (1), (Δ)-[Cu(S-ppme)3](ClO4) 2·H2O (2), (Δ)-[CuII(R-ppme) 2(SO4)]·4CH3OH (3), and (Λ)-[CuII(S-ppme)2(SO4)]·4CH 3OH (4). 1 and 2 with ClO4 - anions are formed as tris(R/S-ppme) copper(ii) complexes, while 3 and 4 with SO4 2- are formed as bis(R/S-ppme) copper(ii) complexes. The structures of 1 with R-ppmes and 4 with S-ppmes show the same absolute configurations (Λ). In contrast, 2 with S-ppmes and 3 with R-ppmes exhibit Δ configurations. In the electron paramagnetic resonance (EPR) spectra of 1 and 3, both compounds demonstrate z-axis elongated structures. The CD spectra of 1 and 2 show Cotton effects in an enantiomeric pattern; those of 3 and 4 also display the same effects. © 2010 The Royal Society of Chemistry. Source


Ahn C.W.,Korea Basic Science Institute | Ha M.G.,Korea Basic Science Institute | Hong K.S.,Korea Basic Science Institute | Lee D.J.,Korea Electrotechnology Research Institute | And 8 more authors.
Defect and Diffusion Forum | Year: 2010

The surface conditions of LiFePO4 powder were modified by adding AlF3 and Al2O3 by using the sol-gel process to improve its electrochemical properties. The surface of LiFePO4 powders was partially covered with nano-sized AlF3 and Al 2O3, which is confirmed by using a transmission electron microscope image. The states of coated Al materials were examined by using X-ray photoelectron spectrometer results. The nano-sized AlF3- and Al 2O3-coated LiFePO4 powders showed no difference in the bulk structure compared with the pristine one. However, the AlF 3- and Al2O3-coating on LiFePO4 powders improved the overall electrochemical properties such as the discharge capacity, the cyclability, and the rate capability compared with those of a pure LiFePO4. Such enhancements were attributed to the presence of a stable AlF3 and Al2O3 layer which acts as an interfacial stabilizer on the surface of LiFePO4 powders. © (2010) Trans Tech Publications. Source


Bae D.S.,Gyeongnam Science High School | Lee D.-H.,Gyeongnam Science High School | Eim D.E.,Gyeongnam Science High School | Hu S.-E.,Gyeongnam Science High School | And 4 more authors.
Molecular Crystals and Liquid Crystals | Year: 2013

New fluorene based light emitting polymer, poly[(4-(9,9-didecyl-9H-fluoren- 2-yl) phenyl)dimethyl(phenyl)silane] (PFDPS), was synthesized by palladium-catalzed Suzuki coupling reaction. The obtained copolymer was characterized by 1H-NMR, and IR-spectroscopy. The polymer showed good solubility in common organic solvents and weight average molecular weight of 16,300 with polydispersity index of 1.4. The maximum photoluminescence of the solution and film of the polymer was observed at 392 nm and 410 nm, respectively. The double-layered device with the configuration, ITO/PEDOT/PFDPS/LiF/Al structure has a turn-on voltage at about 5.5 V and maximum brightness of 9.40 cd/m2, and emitted violet light at 414 nm. Copyright © Taylor & Francis Group, LLC. Source

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