• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.24-28
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• 2008

Eddy current are induced when a nonmagnetic, conductive material is moving as the result of being subjected to the magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and conductor. Using this concept, eddy current damping can be used as a form of viscous damping. This paper investigated analytically and experimentally the characteristics of an eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of the eddy current damping is developed from electromagnetics and is verified from Maxwell program and experiments. From these comparisons, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies. In order to improve the prediction of the characteristics of an eddy current damping, the induced magnetic flux densities have to be considered in following researches.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1482-1484
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• 1996

To apply Magnetic wedges to the motor, comparing with not applying, showes its performance change of efficiency increse, reduction of temperature rise, harmonics, and magnetic noise. The motor specification and test condition are 37kW-4P-380V-60Hz,squirrel-cage, three phase induction motor with semiclosed type slots. The result of load test to compare with nonmagnetic wedges showed 1.5% increment of efficiency at 100% load and $8.0^{\circ}C$ decrement of temperature rise at stator coil. And for developing the magnetic wedge matrial, its manufacturing process was setting and TG-DTA, optical microscope, SEM, bending strength and permeability were investigated into the material made of through the process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.635-636
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• 2005

최근에 미국이나 러시아를 중심으로 가공승전선의 승전효율을 증대시키고자 하는 연구가 활발히 이루어지고 있으며 어느 정도 성과를 거두고 있다. ACSR가공송전선에서 교류전류의 흐름에 의하여 코어 (Core)에 자기장이 발생되어 투자율이 증가되고 이로 인하여 알루미늄층에서 전류밀도의 재 분포, skin effect 등으로 인하여 전력손실이 발생된다. 본 연구에서는 기존의 ACSR가공송전선의 코어 (Core)인 고탄소강선 대신에 비자성이면서 고강도인 새로운 강선을 코어재료로 채택한 ACNR(Aluminum Conductor Nonmagnetic Steel Reinforced)가공송전선을 개발하여 전력손실을 감소시켰다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.629-630
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• 2005

ACSR(Aluminum Conductor Steel Reinforced)가공송전선은 교류전류의 흐름에 의하여 코어 (Core)부에 자기장이 발생되어 전력손실을 발생시킨다. 이로 인한 전력손실을 최소화 하는 방법으로는 코어의 재질을 자성체인 고탄소강선 대신에 비자성강으로 교체하는 방법이 있다. 본 연구에서는 기존의 고탄소강선 대신에 고강도 비자성강을 코어(Core)에 적용한 ACNR(Aluminum Conductor Nonmagnetic Steel Reinforced) 가공송전선을 개발하였다. ACNR 가공송전선의 전기적 특성시험에서 약 9%정도의 손실저감효과를 나타내었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.249-255
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• 2017

Using a magnetic separation process, pond ash generated in thermoelectric power plants was separated into magnetic materials and nonmagnetic materials in order to make it into a raw material of geopolymers and unburned carbon; screening characteristics according to the particle sizes and magnet strength levels of the pond ash were observed. Based on the results of magnetic separation into fine particle (0.15~0.84 mm) and rough particle (0.84~2.4 mm) pond ash using 3000 G magnets, the weight fraction and ignition loss of nonmagnetic materials were found to be higher than those of magnetic materials, regardless of the particle size. In the case of fine particle pond ash, when the magnet strength was increased from 3000 G to 10000 G, even those materials that were weakly magnetic were separated into magnetic materials, leading to drastic increases in the weight fraction of magnetic materials, such that the ignition loss accounted for 66.9 % (22.8 wt%) of the entire ignition loss of 32.6 wt%, despite of the low ignition loss. Based on the results of measurement of the compressive strength levels of geopolymers made of magnetic-separated rough particle pond ash, the compressive strength of geopolymers made of magnetic materials containing small amounts of unburned carbon was found to be 20 MPa.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.184-190
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• 2010

Recently, the polishing process using magnetorheological fluids(MR fluids) has been focused as a new ultra-precision polishing technology for micro and optical parts such as aspheric lenses, etc. This method uses MR fluid as a polishing media which contains required micro abrasives. In the MR polishing process, the surface roughness and material removal rate of a workpiece are affected by the process parameters, such as the properties of used nonmagnetic abrasives(particle material, size, aspect ratio and density, etc.), rotating wheel speed, imposed magnetic flux density and feed rate, etc. The objective of this research is to predict MRR according to the polishing conditions based on the multiple regression analysis. Three polishing parameters such as wheel speed, feed rates and current value were optimized. For experimental works, an orthogonal array L27(313) was used based on DOE(Design of Experiments), and ANOVA(Analysis of Variance) was carried out. Finally, it was possible to recognize that the sequence of the factors affecting MRR correspond to feed rate, current and wheel speed, and to determine a combination of optimal polishing conditions.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.233-236
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• 2002

A conceptual design of single phase high Tc superconducting (HTS) 1MVA transformer was presented in this paper. The rated voltages of each sides of the transformer are 22.9kV /6.6kV respectively. Double pancake windings of BSCCO-2223 HTS tape and the room temperature shell type core are adopted. The HTS tapes of windings are going to be cooled down to 65K by sub-cooled liquid nitrogen. A cryostat made of nonmagnetic and nonconducting material with a bore is going to be used in order to locate the core out of the cryostat. This conceptual design will be modified and a fabrication of the machine is going to be based on the presented design in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1873-1876
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• 2003

Magneto-rheological polishing is a new technology used in precision polishing. It utilizes magneto-rheological fluid. nonmagnetic polishing abrasive, aqueous carrier fluids in magnetic field to remove material from a part surface. Silicon micro channel as work piece is fixed in the slurry which is made of MR fluid and CeO$_2$(10 vol%) abrasive particles. And permanent magnet rotate in the slurry to transfers magnetic force to abrasive particles by increasing yield strength of MR fluid. so, the obtained bottom surface roughness of micro channel by experiment reduced to Ra 0.010 $\mu\textrm{m}$ Rmax 0.103 $\mu\textrm{m}$ and finwall surface roughness of micro channel reduced to Ra 0.018 $\mu\textrm{m}$ Rmax 0.468 $\mu\textrm{m}$. At optimum conditions of variables, the workpiece as silicon micro channel have about 24 times smaller surface roughness than before polishing.

• Journal of Magnetics
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• v.13 no.4
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• pp.128-131
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• 2008

We have investigated the electronic structures and magnetic properties of both undoped and doped bcc Ni using the full-potential linearized augmented plane wave (FLAPW) band method. A ferromagnetic ground state is obtained at the equilibrium volume of bcc Ni. When the system is under strain, the nonmagnetic ground state is stabilized. When the Ni is doped with V, the $Ni_{16-x}V_x$ material loses its magnetic properties when x > 2. We have also discussed the possible superconducting properties of $Ni_{16-x}V_x$.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1016-1021
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• 1997

Magneto resistance properties in spin-valve sandwiches with various thickness of nanmagnetic layer in contact with the ferromagnetic NiFe film were investigated. The NiFe layer in contact with the NiO film was pinned by strongly exchange-biased coupling and the free NiFe layer at the film surface induced a sharp change in the magnetoresistance at -5~15Oe due to small coercivity. The NiO/NiFe/Cu/NiFe film showed a magnetoresistance ratio in the range of 2.3~2.9% and a field sensitivity above 2.2%/Oe with various of nonmagnetic layer. The NiO/NiFe/Cu/NiFe film of the field sensitivity above 2.2%/Oe suggests stang possibility of magnetic sensor matter.