• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.976-981
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• 1997

The magnetic susceptibilities of molybdenum ions with 4d1 electronic configuration in the octahedral crystal field were calculated on the basis of ligand field theory. The experimental magnetic susceptibilities for molybdenum ions, which are stabilized at the octahedral site in the perovskite lattice of Ba2ScMoⅤO6 and Sr2YMoⅤO6, were compared with the theoretical ones. We have tried to fit their temperature dependence of magnetic susceptibility with ligand field parameters, spin-orbit coupling constant ζSO, and orbital reduction parameter κ according to intermediate field coupling and strong field theory. Strong field coupling theory could not explain experimental curves without unrealistically large axial ligand field, since it ignores the mixing up between different state via spin-orbit interaction and ligand field. On the other hand, the intermediate field coupling theory could successfully reproduce experimental data in octahedral and trigonal ligand field. The fitting result demonstrates not only the fact that spin-orbit interaction is primarily responsible for the variation of magnetic behavior but also the fact that effective orbital overlap, enhanced by cubic crystal structure, reduces significantly orbital angular momentum as indicated by κ parameter.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.145-153
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• 2019

Modified couple stress formulation and first order shear deformation theory are used for magneto-electro-elastic bending analysis of three-layered curved size-dependent beam subjected to mechanical, magnetic and electrical loads. The governing equations are derived using a displacement field including radial and transverse displacements of middle surface and a rotation component. Size dependency is accounted based on modified couple stress theory by employing a small scale parameter. The numerical results are presented to study the influence of small scale parameter, initial electric and magnetic potentials and opening angle on the magneto-electro-elastic bending results of curved micro beam.

• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.262-266
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• 2001

The magnetic switching volume is known as an important parameter to understand the magnetization reversal process, thermal stability of the written information and media noise. This parameter is influenced significantly by the microstructure of the magnetic layer as well as underlayer. Therefore, we fabricated CoSm/Cr thin films with varying magnetic layer thickness under constant sputtering by using a dc magnetic sputtering machine. The magnetic layer thickness effect on the magnetic switching volume have been studied by the means of magnetic viscosity and dc demagnetization remanence curve mesurements. From these measurements, we found that the switching volumes increased with increasing the magnetic layer thickness, whereas the coercivity showed different behavior. These may be a result of the increased intergranular coupling and the larger volume fraction of the magnetic layer.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.322-322
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• 2000

This paper shows an application of H$_{\infty}$ control design for a magnetic suspension system which has strongly nonlinearity and parameter perturbation. The control design is evaluated by numerical simulations and experiments.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.395-401
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• 2014

Magnetic levitation systems using the attraction force of electromagnets have many constraints according to the variation of air gap and the nonlinearity of electromagnetic force and inductances. As a result of these constraints, the nonlinear control of a magnetic levitation system has been improved by the latest advanced processors and accurate measurement system which can overcome problems such as many constraints and nonlinearity. This paper concentrates on the modeling of a nonlinear magnetic levitation system and an application of an exponential reaching law based sliding mode controller using the exponential reaching law which is one of the most robust controllers against external unexpected disturbances or parameter fluctuations. Controllability of a magnetic levitation system using the sliding mode control algorithm and robustness against parameter fluctuations have been verified through the experimental results.

• Journal of Institute of Convergence Technology
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• v.11 no.1
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• pp.7-12
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• 2021

The magnetic gear, which amplifies the torque by filtering the magnetic field generated by the low-speed permanent magnet with a modulator, can exclude gear contact and can be effectively applied when there are environmental restrictions. In this paper, we discuss the magnetic force characteristics of a magnetic gear using a magnetic focusing array that replaces a general permanent magnet array magnetized in a radial direction along the circumferential direction. The torque increasing effect of the discussed array, known as an arrangement that increases the principal component by focusing a radial magnetic field, is compared with that of a general magnetic gear. In particular, in a magnetic gear using such an array, the sensitivity of torque according to variables is analyzed to see how various variables known as factors affecting torque have an effect.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.151-157
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• 2004

It is investigated quantitative relations between the magnetic storm magnitude and the solar wind parameters such as the Interplanetary Magnetic Field (hereinafter, IMF) magnitude (B), the southward component of IMF (Bz), and the dynamic pressure during the main phase of the magnetic storm with focus on the role of the interplanetary shock (hereinafter, IPS) in order to build the space weather fore-casting model in the future capable to predict the occurrence of the magnetic storm and its magnitude quantitatively. Total 113 moderate and intense magnetic storms and 189 forward IPSs are selected for four years from 1998 to 2001. The results agree with the general consensus that solar wind parameter, especially, Bz component in the shocked gas region plays the most important role in generating storms (Tsurutani and Gonzales, 1997). However, we found that the correlations between the solar wind parameters and the magnetic storm magnitude are higher in case the storm happens after the IPS passing than in case the storm occurs without any IPS influence. The correlation coefficients of B and $BZ_(min)$ are specially over 0.8 while the magnetic storms are driven by IPSs. Even though recently a Dst prediction model based on the real time solar wind data (Temerin and Li, 2002) is made, our correlation test results would be supplementary in estimating the prediction error of such kind of model and in improving the model by using the different fitting parameters in cases associated with IPS or not associated with IPS rather than single fitting parameter in the current model.

• Journal of the Korean Magnetics Society
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• v.25 no.3
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• pp.79-82
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• 2015

The design parameter study about the magnetic pulse forming is performed using finite element analysis with MAXWELL. The first case of design parameters is about the initial charging voltage and the capacitance and the second case of design parameters are about the winding turns and the spacing of electromagnetic coil. The 3D finite element model of electromagnetic forming system is created and the magnetic force is calculated. The effects of design parameters on the magnetic forming force are investigated.

• Journal of Magnetics
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• v.12 no.1
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• pp.21-26
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• 2007

Si-based electromagnetic noise suppressors on coplanar waveguide transmission lines incorporated with a $SiO_2$ dielectric layer and a nanogranular Co-Fe-Al-O magnetic thin film are reported. Unlike glass-based devices, large signal attenuation is observed even in the bare structure without coating the magnetic thin film. Much larger signal attenuation is achieved in fully integrated devices. The transmission scattering parameter ($S_{21}$) is as small as -90 dB at 20 GHz at the following device dimensions; the thicknesses of the $SiO_2$ and Co-Fe-Al-O thin films are 0.1 $\mu$m and 1 $\mu$m, respectively, the length of the transmission line is 15 mm, and the width of the magnetic thin film is 2000 $\mu$m. In all cases, the reflection scattering parameter ($S_{11}$) is below -10 dB over the whole frequency band. Additional distributed capacitance formed by the Cu transmission line/$SiO_2$/Si substrate is responsible for these characteristics. It is considered that the present noise suppressors based on the Si substrate are a first important step to the realization of MMIC noise suppressors.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.3
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• pp.257-268
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• 2014

The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity $u=u_0t$ in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).