• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.675-676
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• 2006

This paper shows the temperature rise of the high voltage GIS bus bar. The temperature rise in GIS bus bar is due to Joule's losses in the conductor and the induced eddy current in the tank. The power losses of a bus bar calculated from the magnetic field analysis are used as the input data for the thermal analysis to predict the temperature. The required analysis is a couple-field Multiphysics that accounts for the interactions between three-dimensional AC harmonic magnetic and fluid fields. The heat transfer calculation using the fluid analysis is done by considering the natural convection and the radiation from the tank to the atmosphere. Consequently, because temperature distributions by couple-field Multiphysics (coupled magnetic-fluid) have good agreement with results of temperature rise test, the proposed couple-field Multiphysics technique is likely to be used in a conduction design of the single-pole and three pole-encapsulated bus bar in CIS..

• Journal of the Korean Magnetics Society
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• v.24 no.4
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• pp.97-100
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• 2014

We have studied electronic and magnetic structure of Mn-dimer molecule using OpenMX method based on density functional method. The calculated density of states shows that the four O atoms split $e_g$ and $t_{2g}$ energy levels. The energy splitting by the crystal field is smaller than bulk MnO with cubic structure, because of small coordination number of atoms. Total energy with antiferromagnetic spin configuration is lower than that of ferromagnetic configurations. Calculated exchange interaction J between Mn atoms is one order larger than that of the other Mn-O magnetic molecules. That comes from the direct exchange interaction between Mn 3d orbitals and the super-exchange interactions caused by strong ${\sigma}$-bonding of Mn-O orbitals.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.7-7
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• 2003

Heteromagnetic nanostructures, which consist of two or more different layers such as nonmagnet, insulator, ferromagnet, antiferromagnet, and superconductor, have been widely used in current and likely future spintronics devices. Their many intriguing magnetic properties are originated from a variety of magnetic interactions at relevant length scales at or near interfaces and between different constituent layers as well as laterally different regions in chemical and magnetic heterogeneity. The fundamental properties can thus differ along depth and laterally in the film plane, depending on their relevant coupling length scales. The entire properties may be characterized by interface properties and/or the depth-varying properties of the individual constituent layers, and lateral inhomogeneity as well. It is a challenge to investigate both depth-varying properties and lateral heterogeneity in such heteromagnetic nanostructures. In this talk, soft x-ray magneto-optical effect as a nanometer scale probe of a variety of heteromagnetic structures is presented and its related noble techniques are introduced. For instances, magnetization vector imaging to investigate vector spin configurations in the film plane is presented, as well as the Kerr rotation, ellipticity, and intensity measurements as a depth sensitive probe on the atomic scales.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.137-141
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• 2005

The CMR properties and magnetic properties of sulphospinels $Zn_xFe_{1-x}Cr_2S_4$ have been explored by X-ray diffraction, magnetoresistance measurement, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structures in the range of x=0.05, 0.1, 0.2 are cubic at room temperature. Magnetoresistance measurement indicates that these system is semiconducting below about 160 K. The temperature of maximum magnetoresistance is almost consistent with Curie temperature. The Zn substitutions for Fe occur to increase the Jahn-Teller relaxation and the electric quadrupole shift. CMR properties could be explained with Jahn-Teller effect, and half-metallic electronic structure, which is different from both the double exchange interactions of manganite La-Ca-Mn-O system and the triple exchange interactions of chalcogenide $Cu_xFe_{1-x}Cr_2S_4$.

• Korean Journal of Materials Research
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• v.28 no.10
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• pp.539-543
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• 2018

We report the structural, morphological and magnetic properties of the $Ni_{70}Mn_{30}$ alloy prepared by Planetary Ball Mill method. Keeping the milling time constant for 30 h, the effect of different ball milling speeds on the synthesis and magnetic properties of the samples was thoroughly investigated. A remarkable variation in the morphology and average particle size was observed with the increase in milling speed. For the samples ball milled at 200 and 300 rpm, the average particle size and hence magnetization were decreased due to the increased lattice strain, distortion and surface effects which became prominent due to the increase in the thickness of the outer magnetically dead layer. For the samples ball milled at 400, 500 and 600 rpm however, the average particle size and hence magnetization were increased. This increased magnetization was attributed to the reduced surface area to volume ratio that ultimately led to the enhanced ferromagnetic interactions. The maximum saturation magnetization (75 emu/g at 1 T applied field) observed for the sample ball milled at 600 rpm and the low value of coercivity makes this material useful as soft magnetic material.

• Journal of The Korean Astronomical Society
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• v.45 no.5
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• pp.127-138
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• 2012

We explore how wave-particle interactions affect diffusive shock acceleration (DSA) at astrophysical shocks by performing time-dependent kinetic simulations, in which phenomenological models for magnetic field amplification (MFA), Alfv$\acute{e}$nic drift, thermal leakage injection, Bohm-like diffusion, and a free escape boundary are implemented. If the injection fraction of cosmic-ray (CR) particles is ${\xi}$ > $2{\times}10^{-4}$, for the shock parameters relevant for young supernova remnants, DSA is efficient enough to develop a significant shock precursor due to CR feedback, and magnetic field can be amplified up to a factor of 20 via CR streaming instability in the upstream region. If scattering centers drift with Alfv$\acute{e}$n speed in the amplified magnetic field, the CR energy spectrum can be steepened significantly and the acceleration efficiency is reduced. Nonlinear DSA with self-consistent MFA and Alfv$\acute{e}$nic drift predicts that the postshock CR pressure saturates roughly at ~10 % of the shock ram pressure for strong shocks with a sonic Mach number ranging $20{\leq}M_s{\leq}100$. Since the amplified magnetic field follows the flow modification in the precursor, the low energy end of the particle spectrum is softened much more than the high energy end. As a result, the concave curvature in the energy spectra does not disappear entirely even with the help of Alfv$\acute{e}$nic drift. For shocks with a moderate Alfv$\acute{e}$n Mach number ($M_A$ < 10), the accelerated CR spectrum can become as steep as $E^{-2.1}$ - $E^{-2.3}$, which is more consistent with the observed CR spectrum and gamma-ray photon spectrum of several young supernova remnants.

• The Journal of the Korea Contents Association
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• v.19 no.7
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• pp.538-545
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• 2019

The purpose of this study was to analyze the change of body temperature and pain by application of Gaussian magnetic for the elderly delayed muscle pain. For the purpose, we selected 15 elderly women(age;$69.47{\pm}1.60$) and conducted repeated experiments. The Gaussian magnetic field area was divided into three areas (1000G, 1500G, 2000G). The applying arbitrarily manufactured magnetic field wristbands changes of body heat and pain before and after wearing Gaussian magnetic were measured and collected data were analyzed using SPSS 19.0. To examine the pre-and post-treatment differences by treatment areas, we conducted paired t-test. Group differences and interaction effects were analyzed using two-way ANOVA and Duncan post hoc tests. The significance level was set to ${\alpha}=.05$. The results are as follows. The change of body heat by the Gaussian magnetic field area showed significant differences in all three groups(P<.05). There were also significant differences in the results of group interactions and in the delayed muscle pain scale between groups(P<.05). The area with the largest difference appeared in the area of 1500G field. The 1000G-1500G Gauss field is considered to be the most ideal magnetic field for body heat and muscle pain changes. In conclusion, the Gaussian magnetic field of 1000G-1500G may affect body temperature and muscle pain in the elderly, and may have a significant impact on the quality of life in old age.

• Journal of Astronomy and Space Sciences
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• v.7 no.2
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• pp.113-123
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• 1990

Two dimensional electrostatic model was used to investigate the interactions between beam electron and neutral plasma. It was found that results heavily depend on the beam density. When the beam electron density is lower than the ambient plasma beam density, many beam electrons exhibit vortex structure through beam-plasma interactions and can propagate into the ambient plasma easily from the injection area. On the other hand, when the beam density larget than that of the neutral ambient plasma, it was found that most of the beam electrons constitute return current and ion with much larger mass than that of the electron can be accelerated according to the magnetic field strength. Furthermore, as external field strength varies, it was found that propagation and interaction of the beam can show large dependence on it.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.515-518
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• 1995

We have studied the magnetization in fields up to 1T at 5K, the saturation magnetization dependence on temperature and the temperature dependence of AC-susceptibility at very low fields (5mOe to 50mOe) of glassy $Fe_{91-x}Zr_{7}B_{2}Ni_{x}$ (x = 0, 5, 10, 15) alloys. The temperature dependence of the magnetization follows the predictions of spin wave excitations with long wavelengths. At zero Ni concentration there is a clear competition between ferromagnetic and antiferromagnetic interactions giving rise to spin-glass behaviour. The addition of Ni drastically modifies the magnetic properties: the antiferromagnetic exchange coupling is reduced and finally disappears, the spin wave stiffness increases from 39.5 to $87.3\;meV{\AA}^{2}$ and To increases from 230 K to 478 K. We develop a simple model to quantify the competing interactions and to relate the antiferromagnetically coupled Fe moments to the Ni concentration. We find that the initial susceptibility increases with increasing Ni content along with a decrease of the temperature dependence.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.253-259
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• 2005

[$(tacn)_4Fe_4O_2(OH)_4]_2{\cdot}8Br{\cdot}9H_2O$ (tacn = 1,4,7-triazacyclononane), a tetranuclear iron(III) complex was synthesized by the hydrolysis of (tacn)FeCl3 and crystallizes in the orthorhombic space group, Pca2(1), with cell parameters, a = 37.574(3) $\AA$, b = 16.9245(12) $\AA$, c = 14.2830(11) $\AA$, V = 9082.9(12) ${\AA}^3$. [$(tacn)_4Fe_4O_2(OH)_4]^{4+}$ cations approach S4 point symmetry containing an adamantane skeleton. Four Fe(III) atoms have distorted octahedral environments with two hydroxo and an oxo bridges. Two [$(tacn)_4Fe_4O_2(OH)_4]^{4+}$ clusters having different Fe…Fe distances are connected to each other by the networked hydrogen bonds. The electrochemical behavior reveals irreversible three cathodic and two anodic peaks. Magnetic properties are characterized by antiferromagnetic (AF) interactions between Fe(III) ion spins. However, the low-lying states are still magnetic and exhibit a blocking behavior and a magnetic hysteresis at low temperatures.