• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1146-1151
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• 2003

Pneumatic servo valve is an electro-mechanical device which change electric signals to a proper pneumatic signals, that is, flowrate and pressure. In this study, a pneumatic servo valve was designed and each simulation was conducted on any variation in the flowrate depending upon the magnetic force of the linear force motor and the displacement of the spool. And permanent magnet was used as a material for the plunger of the servo valve. Thereby, a low electrical power consumption type coil was desinged. And a modeling for the coil design was conducted by using the magnetic circuit. also, the feasibility of the modeling was verified by using a commercial magnetic field analysis program. The designed and fabrication of the spool and sleeve, position sensor, servo controller and the dynamic characteristic verified by the experiment.

• Journal of Power System Engineering
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• v.8 no.3
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• pp.52-57
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• 2004

A new non-destructive inspection technique has been developed. One characteristic of the technique is that defects are visualized by laser ray. Magnetic domains and domain walls of a magneto-optical sensor(MO sensor) are varied by the magnetic flux leaked by defects, and the variations are observed by the reflected light of the laser ray. The information of defect can remotely be inspected by this technique in a real time. This paper describes the results estimated on the 2-dimensional surface defects and opposite-side defects in a ferromagnetic material and the natural surface defect in a clutch disk wheel. The light region of a visible image and the magnitude of a reflected light increases as the input current of the magnetizer increases. The natural surface defect, that has not the width of crack's open mouth, can be also visualized like as 2-dimensional artificial defects.

• Journal of the Korean Ceramic Society
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• v.32 no.3
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• pp.289-294
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• 1995

As the results of the study on the effects of mixing time for raw materials to the electric and magnetic properties of Mg-ferrite, the fraction of spinel phase after calcination and the geometry density of sintered Mg-ferrite increased from 30% to 100% and from 2.5g/cc to 4.25g/cc respectively due to mixing-homobenity of raw materials. The AC resistivity of grains decreased and lattice parameter, saturation magnetization increased due to the increase in Fe+2 of sintered body. conclusively the characteristic of powder after calcination had strong influence on the microstructure, electric, and magnetic properties in Mg-ferrite sintered body.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.171-173
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• 1994

Magnetic wedge is proposed for improving the motor performance and to reduce the ripple of air gap flux. Carter's coefficient plays very important role when the ampere turns or exciting current is calculated. In this paper, we calculate the Carter's coe. by FEM taking into account the magnetic anisotropy of magnetic wedge in simple manner and analyze the effect of the wedge. And we analyze the slot leakage flux according to the wedge property.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.705-710
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• 2002

Magnetostrictive materials are used low frequency sonar transmitter instead of piezoelectric materials. But it is difficult to analyze due to the nonlinearity and hysteresis of magnetostrictive materials. This paper deals with the program development for the finite element modeling of magnetostrictive tonpilz transducers and for analyzing their acoustic characteristics. To take into account the nonlinearity of magnetostrictive materials, the magnetic field calculation is separated form the displacement calculation, and a curve fitting is adopted for the nonlinear behavior of the magnetic and mechanical strain fields. At first, the magnetic field is obtained by using a commercial FEM software and the displacement of the transducer is calculated by plugging the obtained magnetic field into forcing term. To verity the accuracy of the developed program, a comparison is made with a commercial code, ATILA.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.901-903
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• 2001

This paper studies the influences of the magnetic radial forces on the vibrations of the Switched Reluctance Motor(SRM). The effects of changing the switching angle on the magnetic forces is analyzed by Finite Element Analysis. Theoretical and several experimental results explain clearly the origins of vibrations caused by radial magnetic forces and current.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.352-356
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• 2011

The isolation performance of a linear vibration isolator is limited to the ratio of stiffness to mass it supports. The stiffness of the isolator must be large enough to hold the weight. This results in the deterioration of the isolation performance. Recently, to overcome this fundamental limitation, the HSLDS(high-static-low-dynamic-stiffness) magnetic vibration isolator was introduced and its isolation characteristic was investigated theoretically. In this paper, the isolation performance of the HSLDS magnetic isolator is examined experimentally. Considerable amount of experiments are performed by carefully considering nonlinear characteristics. The experimental results verify the practical usability promisingly and agree with the theoretical studies, i.e. its performance is largely dependent on the key design parameter.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.2
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• pp.46-51
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• 2006

In this study, the electromagnetic characteristic of a flat-type two-dimensional proportional solenoid were analyzed by the magnetic reluctance method. The magnetic equivalent circuit equation for the solenoid was derived by modeling the reluctance of air gaps and magnetic structural components such as pole core, armature and yoke. It was solved iteratively because of the nonlinear magnetization properties of iron parts. The solutions showed good agreement with experimental data. Based on the magnetic equivalent circuit equation, the influence of design parameters on force-to-armature displacement curves was mathematically derived and experimentally verified. In this way, dominant design parameters could be analytically determined.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.22-24
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• 1997

The 4-pole LHSM was composed of the figure-of-eight shaped 3-phase armature windings. DC field windings, and the segmented secondary with the transverse bar track. The motor was designed on the base of the performance characteristic equations and the equivalent circuit model, with the coefficients of the magnetic shape. These coefficients were computed from the analytical expressions and examined from FEM analysis. The magnetic equivalent circuit of 3-D model of LHSM was obtained. and this concept provided the equivalent models for 2-D FEM analysis. Therefore, the airgap field, the lift and thrust force were calculated and compared with the results of magnetic equivalent circuit method.

• Investigative Magnetic Resonance Imaging
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• v.22 no.3
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• pp.200-203
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• 2018

Metronidazole is an antimicrobial agent widely used for the treatment of anaerobic infection or antibiotics-associated diarrhea. It is generally thought to be safe, but can induce reversible toxic encephalopathy in the case of excessive or cumulative over-dose. Metronidazole-induced encephalopathy generally demonstrates the characteristic features of typical lesion location and bilaterality on magnetic resonance imaging (MRI). We report a case of metronidazole-induced encephalopathy with the involvement of asymmetric white matter. To our knowledge, only a few cases have been reported with respect to white matter lesion characteristics on MRI with diffusion-weighted images.