• Korean Journal of Materials Research
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• v.25 no.12
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• pp.694-702
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• 2015

Nd-Fe-B permanent magnets have been used in a wide variety of applications because of their high magnetic flux density. So, demand for neodymium has been increasing in worldwide. In this study, an electrowinning process was performed in $LiF-NdF_3-Nd_2O_3$ high temperature molten salts. However, a corrosion resistant material for use in the molten salt must be found for stable operation because of the harsh corrosion environment of the electrowinning process. Therefore, for this paper, boron nitride(BN), aluminum nitride(AlN), and silicon nitride($Si_3N_4$) were selected as protective and structural materials in the high temperature electrolyte. To investigate the characteristics of BN, AlN, and $Si_3N_4$, in molten salts, materials were immersed in the molten salts for 24, 72, 120, and 192 hours. Also, surface condition and stability were investigated by SEM and EDS and corrosion products were calculated by HSC chemistry. As a result, among BN, AlN, and $Si_3N_4$, AlN was found to show the best protective material properties.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.140-142
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• 2006

Cogging torque is often a principal source of vibration, noise and difficulty of control in permanent-magnet brushless DC motors. Cogging torque can be minimized by sinusoidal air-gap flux density waveform because it is produced by the interaction of the rotor magnetic flux and angular variation in the stator magnetic reluctance. Therefore, this paper will present a design method of magnetization system of bonded isotropic neodynium-iron-boron(Nd-Fe-B) magnets in ring type with sinusoidal air-gap flux density distribution and low manufacturing cost. An analytical technique of magnetization makes use of two-dimensional finite element method(2D FEM) and Preisach model that expresses the hysteresis phenomenon of magnetic materials in order for accurate calculation.

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.143-147
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• 2013

This paper describes a low frequency driven electromagnetic energy harvester (EMEH) which consists of a thin flame resistant (FR-4) planar spring, NdFeB permanent magnets, and a copper coil. The FR-4 spring was fabricated using a desk computer numerical control (CNC) 3D modeling machine. Mathematical modeling and ANSYS finite element analysis (FEA) were used totheoretically investigate the mechanical properties of the spring mass system. The proposed EMEH generates a maximum power of 65.33 ${\mu}W$ at a resonance frequency of 8 Hz with an acceleration of 0.2 g (1 g = 9.8 $m/s^2$) and a superior normalized power density (NPD) of 77 ${\mu}W/cm^3{\cdot}g^2$.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.93-99
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• 2016

The present study aims to increase the amount of surface flux by changing the magnetic directions of a spherical magnet (NdFeB) consisting of four poles. For this purpose, the magnetic directions of quartile spherical slices constituting the spherical magnet are manipulated and their three-dimensional analyses are carried out by using finite-element method via Maxwell environment. The analysis of the magnetic quartile spheres with four different magnetic directions are compared to the each other, and then the quartile sphere with the best surface flux distribution is suggested for rotor structure. It is clear emphasized that the induced torque of the spherical motor, in which such a rotor is used, will be improved as well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.565-569
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• 2002

To improve the driving sensitivity of an optical pickup actuator for high density and high speed drive, we present a new actuator design using multipolar flux-density distribution by magnetic materials and Nd-Fe-B sintered magnets. We expect this actuator to use in 3-axis actuator for tilt compensation as well as conventional 2-axis actuator. The electromagnetic field analysis applying 3-D FEM was performed and several samples were actually tested. From comparing simulated data with experimental results, we verified the accuracy of the simulation and the superiority of the presented method.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.379-384
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• 2008

This paper examines permanent magnet eddy current couplings and brakes. Specifically, the effect of permanent magnet magnetization patterns on the magnetic field and force production is investigated. The eddy current couplings and brakes employ high energy-product neodymium-iron-boron (NdFeB) permanent magnets that act on iron-backed copper drums to provide torque transfer from motor to load without mechanical contact. A 2-dimensional finite element modeling is performed to predict the electromagnetic behavior and the torque-speed characteristics of permanent magnet type eddy current couplings and brakes under constant speed operation.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.880-882
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• 2001

A moving-coil-type linear oscillatory actuator is consisted of the NdFeB permanent magnets with high specific energy as the stator, a coil-wrapped nonmagnetic hollow rectangular structure and an iron core as a pathway for magnetic flux. The inductance of moving coil and the push/pull effect is obtained from the permeance model of LOA with the open magnetic circuit. The analytical method are verified using the 2D finite element method.

• Transactions of Materials Processing
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• v.10 no.6
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• pp.478-484
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• 2001

Tube Process (TP) is a process to produce permanent magnets using a deformable tube for densification of magnet powder. This process claims that it can accomplish both densification and anisotropication in one step forming. This process is distinguished from other processes since it uses a deformable copper tube for densification of magnet powder. In this paper, simulation has been carried out for tile Tube Process in a closed die considering the compressibility of powdered material, arbitrary curved shape and deformable body contact between Nd-Fe-B magnet powder and a copper tube. Results show that the finite element analysis of the Tube Process plays an important role in the stage of preform design.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.139-141
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• 2001

YBCO superconductors were prepared by top-seeded melt growth process using various numbers of seeds. The levitation forces and trapped magnetic fields of the top surfaces of the samples were measured using Nd-B-Fe permanent magnets It was found that the processing time was greatly reduced by multiple seeding, but the properties were decreased as the number of seeds was increased. The degradation of the properties is attributed to the presence of the nonsuperconducting phases at the grain boundaries as result of the entrapment of a residual melt at grain boundaries during melt processing.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.109.1-109
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• 2002

This paper presents a macro/micro flip chip mounting head system for precise force control. In the proposed macro/ micro system, the macro actuator is conventional do servomotor with a ball screw mechanism and the micro actuator is a voice coil motor(VCM) that consists of four NdFeB magnets and a winded moving coil. For force control, a sensitive strain-gauge force sensor is mounted in the micro actuator. Through harmonic motion between macro and micro actuator, we would like to get precise contact force control when small sized flip chip is mounted on flexible substrate in high speed. In order to show the effectiveness of the proposed macro/micro flip chip mounting head system, we com...