• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.232-236
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• 2000

CoSm thin films with a Cr underlayer have received continuous attention as a potential material for a high density longitudinal magnetic recording media. In this study the Ax gas sputtering pressure effects on the magnetic properties of CoSm thin films, which were fabricated by using a dc magnetron sputtering machine, were investigated. The magnetic switching volume is especially important parameter to understand the thermal stability of the written information, magnetization reversal process and media noise. Therefore, in this paper the effects of sputtering pressure on the magnetic switching volume of CoSm thin films grown on Cr underlayer with the same sputtering conditions was studied. As the Ar sputtering pressure during sputtering of the CoSm magnetic layer increases from 5 to 30 mTorr, the measured switching volumes decreased from 9.0 to 5.2$\times$10$^{-18}$ cm$^3$. The calculated diameter of switching unit from V＊ was less than 22 nm, which satisfies the Sharrock's requirement on the thermal stability of the high density longitudinal magnetic recording media.

• Journal of Magnetics
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• v.14 no.3
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.265-270
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• 1995

An implementation scheme of the magnetic nerve stimulator using a switching mode power supply is proposed. By using a switching mode power supply rather than a conventional linear power supply for chArging high voltage cApacitors, the weight and size of the magnetic net've stimulator can be considerably reduced. Maximum output voltage of the developed magnetic nerve stimulator using the switching mode power supply is 3,000 volts and switching time is about 100 msec Experimental results of human nerve stimulations using the developed stimulator are presented.

• 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.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.68-69
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• 2002

Magnetic tunnel junctions은 최근 자기저항용 재료나 MRAM용 소자로 사용하기 위한 연구가 활발하게 진행되고 있다. Magnetic tunnel junction을 저자계, 저전력용 소자로 사용되기 위해서는, 작은 switching field 값과 uniform한 switching field 분포를 가져야 한다. Micromagnetic simulation을 통하여 free layer의 두께와 포화 자화 값이 감소함에 따라서 switching field가 감소함을 알 수 있었다. 본 연구에서는 얇은 free layer를 사용하여 magnetic tunnel junction을 제조하고, 얇은 free layer가 자기저항에 미치는 영향에 대하여 알아보았다. (중략)

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.24-26
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• 1998

A new high frequency switching drive method using IGBT is proposed for non-magnetic induction heating system. Using this method, the switching and conduction losses of the switching devices can be reduced. In addition, since IGBT cosl is lower than MOS-FET one, the system cosl can be remarkably pared down. The prototype induction heating system with 1.2㎾ power consumption is builted and tested to verify the operation of the proposed high frequency switching drive method.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.5-11
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• 2003

A simulation model for radial magnetic bearings is presented. The model incorporates hysteresis, saturation and eddy current effects. A simple magnetization model that describes hysteresis and saturation is proposed. Eddy currents are taken into consideration by assuming that they are generated by single-turn fictitious coils wrapped around each magnetic flux path. The dynamic equations describing the simulation model can easily incorporate the operation of switching power amplifier. A simulation of a typical 8-pole radial magnetic bearing produces switching waveforms very similar to the experimental observation.

• International Journal of Railway
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• v.8 no.1
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• pp.10-14
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• 2015

Due to the characteristics of the vehicle structure, the magnetic levitation train has a confined bottom space thus a study on miniaturization and weight reduction of auxiliary power unit is essential. This auxiliary power unit is an essential device used for illumination, air conditioning, heating and air brake equipment excluding the motor. The previous auxiliary power unit for magnetic levitation train has used the hard switching having a high switching frequency with heavy loss in order to reduce the size of filter reactor and transformer but the reduction in volume was not significant. In this paper, by reducing the loss, reducing the size of the cooling unit and by increasing the switching frequency using the soft switching of resonant converter, it has miniaturized and reduced the weight of filter reactor and transformer which occupy significant space in the auxiliary power unit. This study has verified the performance of 50KVA grade prototype through simulated interpretation and analysis, and compared the size and weight of auxiliary power unit of the previous magnetic levitation train.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1639-1649
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• 2016

This paper presents a family of soft-switching DC-DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.516-522
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• 2009

The dimmable magnetic ballast which applies the variable inductor needs a switching process for the dimming process, and it consists of mechanical relays because of costs and reliabilities. However, it is hard to operate with correct timing in mechanical relay, so relays reduce their own life time in inductive applications. Moreover this creates a destructive problem at the switching process. The life time reduction of relays means the life time reduction of the ballast. Thus, in this paper, we described the problem at the witching process in the dimmable magnetic ballast with a variable inductor, which consists of relays and the soft AC switching method in order to solve the problems. As result, we achieved the improvement of the life time and reliability of the ballast.