• Journal of Magnetics
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• v.18 no.2
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• pp.105-110
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• 2013

The design model and key parameters of the material design for the control of induced magnetic flux at the near-field and efficient power transfer in a modified wireless power transfer (WPT) system with a large air gap of wireless electric vehicles were investigated through analytical simulations for magnetic vector and time-domain transient analysis. Higher saturation magnetic core with low core loss induced a stronger vertical magnetic field by the W-type primary coil in the WPT system with a gap of 20 cm at 20 kHz, which is shown from the vector potentials of the magnetic induction. The transient analysis shows that the higher magnetic fluxes through the pick-up cores lead to a linear increment of the alternating voltage with a sinusoidal waveform in the non-contact energy transfer system.

• Progress in Superconductivity
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• v.13 no.3
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• pp.146-150
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• 2012

We solve the momentum resolved d-wave Eliashberg equation employing the magnetic excitation spectrum from the inelastic neutron scattering on the LSCO superconductors reported by Vignolle et al. The magnetic excitation spectrum exhibits 2 peaks: a sharp incommensurate peak at 18 meV at momentum (${\pi}$, ${\pi}{\pm}{\delta}$) and (${\pi}{\pm}{\delta}$, ${\pi}$) and another broad peak near 40~70 meV at momentum (${\pi}$, ${\pi}$). Above 70 meV, the magnetic excitation spectrum has a long tail that is shaped into a circle centered at (${\pi}$, ${\pi}$) with ${\delta}$. The sign of the real part of the self-energy is determined by the momentum position of the peaks of the magnetic excitation spectrum and bare dispersion. We will discuss the effects of the each component of the magnetic excitation spectrum on the self-energy, the pairing self-energy.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.42-48
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• 1991

The basic soft magnetic characteristics of a typical Fe based amorphous $Fe_{80}B_{15}Si_{5}$ alloy were measured with pulse metheod. Quantitative relations between magnetostriction, anisotropy energy, reluctivity were investigated. The relative contribution factor of magnetostrictive and uniaxial anisotropy energy to the reluctivity were calculated. The internal stress and induced anisotropy were estimated. A tension applied to the long axis of the sample greatly enhanced induced anisotropy.

• Journal of Magnetics
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• v.17 no.1
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• pp.19-26
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• 2012

This paper deals with the performance analysis and estimation of the electrical parameters of a permanent magnet synchronous generator (PMSG) for hydrokinetic energy conversion applications using vortex induced vibration (VIV). The analytical solutions for the magnetic fields produced by permanent magnets (PMs) and stator winding currents are obtained using a 2D polar coordinate system and a magnetic vector potential. An analytical expression for the 2D permeance is also derived, which takes into account stator skew effects. Based on these magnetic field solutions and the 2D permeance function, electrical circuit parameters such as the backemf constant and the air-gap inductance are obtained analytically. The performances of the PMSG are investigated using the estimated electrical circuit parameters and an equivalent circuit (EC). All analytical results are validated extensively using 2D finite element (FE) analyses. Experimental measurements for parameters such as the back-emf and inductance are also presented to confirm the analyses.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3506-3511
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• 2007

The energy harvesting using smart materials has been extensively investigated to supply electric power to wireless sensor systems. In this paper, the energy harvesting using eddy current was studied with the integrated magnetic cantilever beam system. If a large conductive metal plate moves through a magnetic field which intersects perpendicularly to the sheet, the magnetic field will induce small rings of current which will actually create internal magnetic fields opposing the change. This eddy current that was induced in the coiled conductive sheet from the mechanical vibration was converted to chemical energy by charging batteries. The experimental results show that the eddy current generated the electric power up to max 31.2mW. Additionally the vibration reduction of the mechanical cantilever beam was observed by the energy dissipation in the electro-magnetic coupled system. The present result shows that the vibration level of the first natural frequency was reduced up to 7.7dB

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.261-269
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• 1998

Induced anisotropy with the energy of $6{\times}10^4\; J/m^3$ is obtained in amorphous Sm-Fe based thin films which are fabricated by rf magnetron sputtering under a magnetic field of 500~600 Oe. Compared with conventional thin films, the anisotropic thin films exhibit a similar "saturation" magnetostriction, but show a very large anisotropy in magnetorstiction which is of significant practical importance due to increased strain at a particular direction. It is shown from a systematic investigation over a wide composition range for binary Sm-Fe alloys that anisotropy is also induced, though small, during a normal sputtering procedure due to the stray field, and the largest anisotropy is observed in the composition range of 25~30 at.% Sm. Furthermore, induced anisotropy is also found to be formed by magnetic annealing, but the anisotropy energy is much smaller than that by magnetic sputtering. This may be because the volume diffusion by which atoms move during magnetic annealing to from induced anisotropy is much slower than the surface diffusion which is expected to be a dominant factor during magnetic sputtering.puttering.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.162-162
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• 2013

Magnetic properties of 3d transition metals were determined by exchange interaction between magnetic ions that was characterized by the exchange integral. Bulk Mn material is one of transition metals that have been well known as an anti-ferromagnetic material due to an anti-parallel spin with negative exchange integral. Here we report on the MBE growth of Mn on $BaTiO_3$ (001) substrate and induced ferromagnetism. The bcc ${\alpha}$-Mn single crystal film has been grown on $BaTiO_3$ (100) substrate. The XRD and Raman results indicated that the structural phase transitions of $BaTiO_3$ substrate induced a lattice distortion at the interface. Consequently, the grown Mn film exhibits ferromagnetism with strong saturation magnetization of 495 emu/$cm^3$ at 320 K. The electrical resistivity of the Mn film strongly depended on the crystal structure of $BaTiO_3$ substrate.

• Corrosion Science and Technology
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• v.3 no.5
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• pp.222-225
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• 2004

A portable RF HTS SQUID-based susceptometer was applied to the measurement of fatigue behavior for type 316L(N) stainless steel containing 0.04% to 0.15% nitrogen content. Strain-controlled low cycle fatigue (LCF) tests were conducted at RT and $600^{\circ}C$ in air an atmosphere, and the magnetic moments were measured after the fatigue test using HTS SQUID. The magnetic moment of an as-received sample is higher than that of a fatigued sample in all the temperature ranges irrespective of the nitrogen content. The fatigue life decreased with an increasing test temperature up to $500^{\circ}C$, but increased at $600^{\circ}C$. The change of the magnetic moments by LCF test is attributed to the stress induced micro defects.

• Applied Science and Convergence Technology
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• v.23 no.1
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• pp.1-13
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• 2014

Semiconductor quantum structures are often characterized by their energy gaps which are modified by the quantum size effect. Energy levels in semiconductors can be realized by optical transitions within confined structures. Photoluminescence spectroscopy in magnetic fields at low temperatures has proved to be a powerful technique for investigating the electronic states of quantum semiconductor heterostructures and offers a complimentary tool to electrical transport studies. In this review, we examine comprehensive investigations of magneto-excitonic and Landau transitions in a large variety of undoped and doped quantum-well structures. Strong magnetic fields change the diamagnetic energy shift of free excitons from quadratic to linear in B in undoped single quantum well samples. Two-dimensional electron gas induced by modulation doping shows pronounce quantum oscillations in integer quantum Hall regime and discontinuous transition at ${\nu}=1$. Such discontinuous transition can be explained as the formation of spin waves or Skyrmions.

• Journal of Magnetics
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• v.21 no.2
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• pp.266-272
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• 2016

Transcranial magnetic stimulation devices has been used mainly for diagnostic purposes by measuring the functions of the nervous system rather than for treatment purposes, and has a problem of considerable energy fluctuations per repeated pulse. The majority of strokes are caused by ischemia and result in brain tissue damage, leading to problems of the central nervous system including hemiparesis, dysfunction of language and consciousness, and dysfunction of perception. Control is difficult and the size is large due to the difficulty of digitalizing the energy stored in a capacitor, and there are many heavy devices. In addition, there are many constraints when it is used for a range of purposes such as head and neck diagnosis, treatment and rehabilitation of nerve palsy, muscle strengthening, treatment of urinary incontinence etc. Output stabilization and minimization of the energy variation rate are required as the level of the transcranial magnetic stimulation device is dramatically improved and the demand for therapeutic purposes increases. This study developed a compact, low cost transcranial magnetic stimulation device with minimal energy variation of a high repeated pulse and output stabilization using a real time capacitor charge discharge voltage. Ischemia was induced in male SD rats by closing off the common carotid artery for 5 minutes, after which the blood was re-perfused. In the cerebrum, the number of PARP reactive cells after 24 hours significantly decreased (p < 0.05) in the TMS group compared to the GI group. As a result, TMS showed the greatest effect on necrosis-related PARP immuno-reactive cells 24 hours after ischemia, indicating necrosis inhibition, blocking of neural cell death, and protection of neural cells.