• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.213-216
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• 2006

The magnetic levitation effect a high Tc superconductor beneath the toroidal permanent magnet was examined by means of a improved magnetic seesaw method. Magnetic effects associated with penetration and pinning in superconductor. One of these was focussing of magnetic field by superconductor and the other was magnetic levitation. The existence of equilibrium was shown to be related to hysteresis observed in the force separation for a toroidal permanent magnet and superconductor. Obtained results indicate that magnetic levitation effect in the present case was mainly due to diamagnetic effect.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1421-1423
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• 2003

The relationship between magnetic properties of BiPbSrCaCuo superconductor and externally applied magnetic field was studied to develop a magnetic field polarity sensor. The behavior was related to the magnetic flux trapped in the superconductor, which penetrates through the material by the external magnetic field. Some portion of the superconductor was changed to a normal state by the trapped magnetic flux. Electrical characteristics of the superconductor with trapped magnetic flux were extremely sensitive to the external magnetic field and showed different responses depending on the direction of the magnetic field.

• 대한기계학회논문집A
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• 제34권11호
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• pp.1643-1648
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• 2010

비자성체의 자기연마 공정에서는 공작물 표면에 발생하는 자속밀도가 매우 낮아 자기연마입자에 작용하는 절삭력이 현저히 낮아진다. 따라서 공작물 반대편에 전자석을 설치하여 공작물 표면의 자속밀도를 효과적으로 증가 시킬 수 있다. 본 연구에서는 전자석 배열 테이블을 비자성체의 자기연마에 활용하기 위해 전자석 배열에 따른 자속밀도 및 극성변화에 대한 시뮬레이션 및 실험적 검증을 수행하였다. 그 결과 전자석이 같은 극성을 가질 때 보다 중심부분 전자석을 기준으로 주변 전자석이 반대의 극성을 가질 때 중심부분의 전자석에서 가장 높은 자속밀도를 가지는 것을 확인할 수 있었다.

• Current Applied Physics
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• 제18권11호
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• pp.1426-1430
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• 2018

High magnetic field effects on the microstructure and magnetic properties of $BaFe_{12}O_{19}$ hexaferrites synthesized hydrothermal method have been investigated. The obtained results indicate that the lattice constant decreases gradually as the magnetic field strength increases, which may be attributed to the lattice distortion resulted from the high magnetic field. Polycrystalline $BaFe_{12}O_{19}$ samples prepared under magnetic field strength at zero and 5 T are single phase. It is found that application of external magnetic field during synthesis can induce orientated growth of the hexaferrite crystals along the easy magnetic axis. The magnetic properties can be effectively regulated by an application of high magnetic fields. It is observed that the $BaFe_{12}O_{19}$ prepared under a 5 T magnetic field exhibits a higher room-temperature saturation magnetization (66.3 emu/g) than that of the sample (43.6 emu/g) obtained without magnetic field. The results can be explained as the enhanced crystalline, improvement of $Fe^{3+}$ ions occupancy and the oriented growth induced by the external magnetic field. The growing orientation of particles gives rise to increased coercivity due to the enhancement in shape anisotropy. It is expected that an application of magnetic field during the formation of magnetic nanoparticles could be a promising technique to modify magnetic properties with excellent performance.

• 한국정밀공학회지
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• 제21권8호
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• pp.34-42
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• 2004

A new polishing technique for three dimensional micro/meso-scale parts is suggested using a micro quill and a magnetic chain structure. The principle of this method is to polish the target surface with the collected magnetic brushes at a micro tool by the non-uniform magnetic field generated around the tool. In a typical magnetic abrasive finishing process magnetic particles and abrasive particles are unbonded each other. But, to finish the three dimensional small parts bonded magnetic abrasive have to be used. Bonded magnetic abrasives are made from direct bonding, and their polishing characteristics are also examined. Alumina, silicon carbide and diamond micro powders are used as abrasives. Base metal matrix is carbonyl iron powder. It is found that bonded magnetic abrasives are superior to unbonded one by experiment. finally, the polished surface roughness is evaluated by atomic force microscope.

• 제어로봇시스템학회논문지
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• 제19권4호
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• pp.290-298
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• 2013

Geomagnetic is refracted by building's wall and pillar. Therefore refracted geomagnetic is able to be used as feature point. In a specific space, a mobile device that is equipped with magnetic sensor array measures 3-axis magnetic field for each point. Magnetic field map is acquired by collecting the every sample point in the magnetic field. The measured magnetic field must be calibrated, because each magnetic sensor has a distortion. For this reason, sensor distortion model and sensor calibration method are proposed in this paper. Magnetic field that is measured by mobile device matches magnetic field map. Result of the matching is used for position estimation. This paper implements hardware system for position estimation method using magnetic field map.

• 한국기계가공학회지
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• 제7권2호
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• pp.38-44
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• 2008

In the present paper, we theoretically analyze the flow of magnetic fluids in a circular pipe with a vertical magnetic field and investigate the magnetic response by the external magnetic field. Theoretical study through the governing equation derived by Siliomis is carried out with numerical analysis by the Gauss Elimination Method. Using polar and magnetic effect parameters, theoretical equations and distributions for the velocity, apparent viscosity as the magnetic response are shown. Especially, in the region of strong magnetic field the specific property is appeared by finding a critical magnetic effect parameter for a polar effect parameter.

• 한국전기전자재료학회논문지
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• 제16권5호
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• pp.429-434
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• 2003

The magnetic field sensor was fabricated with superconducting ceramics of BiPbSrCaCuO system. The sensor at liquid nitrogen temperature showed the increase of electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor was changed from zero to a value more than 100 $\mu\textrm{V}$ by the applied magnetic field. The change of electrical resistance depended on magnetic field. The sensitivity of this sensor was 2.9 $\Omega$/T. The sensing limit was about 1.5${\times}$10$\^$-5/ T. The increase of electrical resistance by the magnetic field was ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material. Considering the observed properties of the superconductor with trapped magnetic flux, a magnetic sensor was fabricated to detect simultaneously both the intensity and the direction of the magnetic field.

• Journal of Magnetics
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• 제20권1호
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• pp.62-68
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• 2015

This paper presents an experimental technique to accurately separate a permanent magnetic field and an induced one from the total magnetic fields generated by a steel ship, through compensating for the Earth's magnetic field. To achieve this, an Earth's magnetic field simulator was constructed at a non-magnetic laboratory, and the field separation technique was developed, which consisted of five stages. The proposed method was tested with a scaled model ship, and its permanent and induced magnetic fields were successfully extracted from the magnetic field created by the ship. Finally, based on the separated permanent magnetic field data, the permanent magnetization distribution on the hull was predicted by solving an inverse problem. Accordingly, the permanent magnetic fields generated by the ship can easily be calculated at any depth of water.

• Journal of Power Electronics
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• 제19권3호
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• pp.794-802
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• 2019

Magnetic geared motors are driven using the same operating principle as conventional synchronous motors in which a magnetic gear is embedded. The magnetic geared motor is structurally similar to a magnetic gear. However, by applying currents to the stator coil, the high-speed rotor is rotated by a magnetic field and the low-speed rotor is rotated according to the gear ratio. In this paper, the operational principle of a magnetic geared motor and the magnetic flux density in its inner and outer air gaps are described. Then the magnetic flux density in the two air gaps is used to express a method for calculating the electrical and mechanical output. Results obtained with the analytical calculation method are compared with those of the finite element analysis. Finally, a prototype is used to verify the results of the analytical calculation and FEA.