• 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.

• 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 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• Journal of the Korean Magnetics Society
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• v.19 no.1
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• pp.35-42
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• 2009

Among the next generation memory, MRAM (Magnetic Random Access Memory) is worthy of notice for substituting the preexisting memory thanks to its non-volatile property and other advantages. Recently perpendicular MRAM and spin transfer torque MRAM techniques are under active investigation to realize a high density and low power consumption. As a result, there are increasing of patents applications for high density, low current density for magnetization switching and high thermal stability. In this paper, we analyze the trend of patent applications and registrations about MRAM and propose a direction of future investigation.