• Title/Summary/Keyword: Spin density

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Statistical Analysis of Interacting Dark Matter Halos: On two physically distinct interaction types

  • An, Sung-Ho;Kim, Juhan;Moon, Jun-Sung;Yoon, Suk-Jin
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.28.1-28.1
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    • 2021
  • We present a statistical analysis of dark matter halos with interacting neighbors using a set of cosmological simulations. We classify the neighbors into two groups based on the total energy (E12) of the target-neighbor system; flybying neighbors (E12 ≥ 0) and merging ones (E12 < 0). First, we find a different trend between the flyby and merger fractions in terms of the halo mass and large-scale density. The flyby fraction highly depends on the halo mass and environment, while the merger fraction show little dependence. Second, we measure the spin-orbit alignment, which is the angular alignment between the spin of a target halo (${\vec{S}}$ ) and the orbital angular momentum of its neighbor (${\vec{L}}$). In the spin-orbit angle distribution, the flybying neighbors show a weaker prograde alignment with their target halos than the merging neighbors do. With respect to the nearest filament, the flybying neighbor has a behavior different from that of the merging neighbor. Finally, we discuss the physical origin of two interaction types.

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Wavelet Encoded MR Imaging (웨이블릿 부호화 자기공명영상)

  • Kim, Eung-Kyeu;Lee, Soo-Jong
    • Proceedings of the IEEK Conference
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    • 2005.11a
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    • pp.343-346
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    • 2005
  • In this study, a basic concept of wavelet encoding and its advantages over Fourier based phase encoding application. Wavelet encoding has been proposed as an alternative way to Fourier based phase encoding in magnetic resonance imaging. In wavelet encoding, the RF pulse is designed to generate wavelet-shaped excitation profile of spins. From the resulting echo signals, the wavelet transform coefficients of spin distribution are acquired and an original spin density is reconstructed from wavelet expansion. Wavelet encoding has several advantages over phase encoding. By minimizing redundancy of the data acquisition in a dynamic series of images, we can avoid some encoding steps without serious loss of quality in reconstructed image. This strategy may be regarded as data compression during imaging. Although there are some limitations in wavelet encoding, it is a promising scheme in a dynamic imaging.

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Al-doped ZnO via Sol-Gel Spin-coating as a Transparent Conducting Thin Film

  • Nam, Gil-Mo;Kwon, Myoung-Seok
    • Journal of Information Display
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    • v.10 no.1
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    • pp.24-27
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    • 2009
  • A simple nonalkoxide sol-gel route for depositing an Al-doped ZnO thin film on a glass substrate was derived in this study. The initial Al dopant concentration in the sol-gel preparation varied and ranged from 0 to 5%. The sol-gel-derived thin films showed c-plane preferred crystallization of their hexagonal phase, with nanosized grain structures. First and second post-heat-treatments were carried out to improve the film’s electrical resistivity. The carrier density and the Hall mobility were measured and discussed to explain the electrical resistivity. The optical transmittance within the visible range showed compatible properties, which indicates the possible use of A1-doped ZnO as a transparent electrode in flat panel displays.

The spin of spiral galaxies in different environments

  • Cervantes-Sodi, Bernardo
    • The Bulletin of The Korean Astronomical Society
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    • v.35 no.1
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    • pp.81.2-81.2
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    • 2010
  • The origin of galactic angular momentum is commonly explained as a result of tidal torques of neighbouring protogalaxies on the forming galactic halo. In this context, the environment plays a preponderant role establishing the total angular momentum of present day galaxies. For the last four decades, most of the observational studies focused their attention on the spatial orientation of galaxies in filaments, groups or clusters, leaving behind the magnitude of the angular momentum. We have implemented a simple model to account for the spin of disk galaxies that allow us to obtain an estimate for any galaxy requiring a minimum of information. Applying this method to a sample of galaxies extracted from the Sloan Digital Sky Survey, we have been studying angular momentum distributions of galaxies in different environments. In this talk I will present some results for galaxies immersed in different environments, spanning three orders of magnitude in environmental density, galaxies having nearby companions and clustered galaxies.

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Giant Perpendicular Magnetic Anisotropy of a Fe(001) Surface: A Density Functional Study

  • Odkhuu, D.;Rhim, S.H.;Yun, Won Seok;Hong, S.C.
    • Proceedings of the Korean Magnestics Society Conference
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    • 2013.12a
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    • pp.29-29
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    • 2013
  • We predict agigantic perpendicular magnetocrystalline anisotropy (MCA) in Fe (001) capped by 5d transition metal (TM) overlayers by using first principles calculations. Analysis of atom-by-atom contribution to MCA reveals that gigantic MCA as large as 11 meV/TM originates not from Fe atoms but from the 5d TMs through the strong spin-orbit coupling. More specifically, it is the hybridization between TM and Fe d orbitals that also induces non-negligible magnetic moments in TM. Furthermore, spin-channel decompositions of MCA matrix with and without the presence of Fe substrate identify the electronic origin of the perpendicular MCA that the down-down channel contribution plays the most crucial role for the sign changes of MCA of TM overlayers upon the hybridization with Fe-3d.

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Electrical Properties of (Pb, LaITiO$_3$ Thin Films fabricated by Sol-Gel Processing (Sol-Gel 법에 의한 (Pb, La)TiO$_3$ 박막의 전기적 특성)

  • 구본혁;박정흠;장낙원;마석범;박창엽
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1997.11a
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    • pp.48-51
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    • 1997
  • (Pb. La)TiO$_3$ thin films were fabricated by sol-gel Processing and spin-coated on the Pt substrate. The spin-coated PLT films were sintered at 75$0^{\circ}C$ for 5min by rapid thermal ann La content dependence of the electrical properties of the PLT thin films are discussed. Wit La mole% from 20 to 36mo1e%. the dielectric constant of the PLT thin films decreased f 570. P-E hysteresis loops changed from ferroelectric to paraelectric. and the charge storage charging time decreased. The Curie Point decreased with increasing La content. The leak density also decreased and La 36mo1% species shows mood characteristics less than 10- electric field 500 (KV/cm) Because of the broad range of composition-controlled ferroelectric PLT thin films are suitable for memory application.

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The Effects of Media on the Intramolecular Photocycloaddition of 3-(3-Butenyl)cyclohex-2-enone

  • 노태희;최균선;박종욱
    • Bulletin of the Korean Chemical Society
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    • v.19 no.5
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    • pp.501-503
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    • 1998
  • In this work, we applied the 1D $11^B$ nutation NMR method for the analysis of the local structural environments in powdered borosilicates $(SiO_2-B_2O_3)$. Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density ma trix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D $11^B$ nutation NMR experiment. The $11^B$ NMR parameters, quadrupole coupling constants $(e^2qQ/h)$ and asymmetry parameters (η), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

$^{11}B $Nutation NMR Study of Powdered Borosilicates

  • 우애자;한덕영;양경화
    • Bulletin of the Korean Chemical Society
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    • v.19 no.5
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    • pp.519-524
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    • 1998
  • In this work, we applied the 1D 11B nutation NMR method for the analysis of the local structural environments in powdered borosilicates (SiO2-B2O3). Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density matrix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D 11B nutation NMR experiment. The 11B NMR parameters, quadrupole coupling constants (e2qQ/h) and asymmetry parameters (η), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

Electronic and Magnetic Structures of Ba2MReO6 (M=Mn, Fe, Co, and Ni)

  • Park, J.H.;Kwon, S.K.;Min, B.I.
    • Journal of Magnetics
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    • v.12 no.2
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    • pp.64-67
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    • 2007
  • Electronic structures of ordered double perovskites $Ba_2MReO_6$ (M=Mn, Fe, Co, and Ni) are investigated by using the linearized muffin-tin orbitals band method in the local spin-density approximation (LSDA) and the LSDA+U method. The half-metallic ferrimagnetic ground states are obtained for M=Fe and Ni in the LSDA+U, whereas the insulating ground state is obtained for M=Mn in the LSDA+U incorporating the spinorbit interaction. For M= Co, the antiferromagnetic ground state is stabilized in the LSDA+U by invoking the structural distortion.

Magnetism in α-RuCl3 : Dependence on Coulomb Interaction and Hund's Coupling

  • Gong, Hoshin;Kim, Kyoo;Ji, Sungdae;Kim, Bongjae;Min, B.I.
    • Journal of the Korean Physical Society
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    • v.73 no.11
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    • pp.1691-1697
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    • 2018
  • Employing the density functional theory, we have investigated the roles of Coulomb and Hund's interactions in the electronic and magnetic properties of newly discovered ${\alpha}-RuCl_3$ having the $R{\overline{3}}$ symmetry, which is in close proximity of the Kitaev system. We show that both the size and the direction of local magnetic moment are highly dependent on Coulomb and Hund's interactions, and the spin and orbital parts show different behaviors. The validity of the so-called $j^{eff}$ picture is accessed upon interaction parameters, and the explicit roles of Hund's interaction in the local electronic structures and magnetic properties are discussed.