• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1298-1302
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• 2000

Electrorheological(HER) and magnetorheologica(MR) fluids have a unique ability to increase the dynamic yield stress of the fluid substantially when electric or magnetic field is applied. ER and MR fluid-based dampers are typically analyzed using Bingham-plastic shear flow analysis under Quasi-steady fully developed flow conditions. An alternative perspective, supported by measurements reported in the literature, is to allow for post-yield shear thinning and shear thickening. To model these, the constant post-yield plastic viscosity in Bingham model can be replaced with a power-law model dependent on shear strain rate that is known as the Herschel-Bulkley fluid model. The objective of this paper is to predict the damping forces analytically in a typical ER bypass damper for variable electric field, or yield stress using Herschel-Bulkley analysis.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.28-31
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• 1997

Experiments and design efforts have been made to improve performance of the levitation magnet. One pole of the pair-magnet is manufactured as a solid core without stagger and its test result gives a 5 % increment of levitation force. One effort is to make molding coil to protect it from vibration and precifitation due to outdoor usage. In addition, a permeant magnet embedded type has been designed and analyzed by using FEM program.

• Electrical & Electronic Materials
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• v.9 no.9
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• pp.891-899
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• 1996

A model for predicting the characteristics of elastic ferromagnetic materials having a moving gap was presented. Based on the model parameters concerning behavior of material, such as the instantaneous field intensity, attractive force between the poles, length of gap, and the induced current/ emf in the circuit can be determined from the numerical integrations of the governing equations derived. From the results of the model it is found that when dc emf is imposed on the circuit the current sharply rise and fall for very short duration then stabilize at extremely low level which depends mainly on elasticity, permeabilities and ratio of resistivity. Subsequently output emf is shown stabilized at constant value which depends on the previous parameters as well as the resistivity ratio of primary to secondary circuit after sufficient progress of time.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2151-2155
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• 1998

The traveling wave type ultrasonic motor(USM) has no electro-magnetic circuits( coil or core). The driving principle of the USM is based on high-frequency mechanical vibrations and frictional force. The USM, thus, is fed by two-phase high - frequency sinusoidal inverter using its series resonant parasitic components. For the using of series resonant type inverter, it should be needed to a USM parasitic capacitance and a proper inductor chosen. In this paper, the values of optimal inductance are designed and the efficiency of USM drives is achieved. The effectiveness of the proposed design is demonstrated by experiments.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1169-1181
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• 1994

Vibration isolation of mechanical systems, in general, is achieved through passive or active vibration isolators. Passive vibration isolator has an inherenrt performance limitation. Whereas, active vibration isolator provides significantly superior vibration-isolation performance at the cost of energy sources and sensors. Recently, in many cases, such as suspension system, precision machinery ... etc, active isolation system outweighs its limitation. Therefore, many studies, researches, and applications are carried out in this field. In this study, vibration-isolation characteristics of an active vibration control system using electromagnetic force actuator are investigated. Several control algorithms including optimal, feedforward are used for active vibration isolation. From the experimental results of each algorithm, effective control algorithms for this active vibration-isolation system are proposed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.3
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• pp.34-39
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• 2008

The purpose of this paper is characteristic analysis of multi-disk axial-gap pm motor for turbo compressor. The axial-gap permanent magnet motor has shown a growing interest in high-speed application for its high-efficiency, compact size and low vibration characteristics due to core-less structure. To achieve high-power, the axial-gap PM motor has multi-disk structure of stator and rotor disk. Because of its complicated magnetic flux path, it is not easy to calculate a dynamic characteristics using finite element analysis. In this paper, the simplified 2-D unfolded model to predict EMF characteristic is presented. To verify thesuggested 2-D unfolded model analysis of back-EMF characteristic was calculated and compared 3-D finite element. Finally the proposed method is verified by experimental results and shows good agreement with test results.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.49-51
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• 1999

This paper presents an efficient 2D finite element analysis(FEA) for brushless DC motor (BLDCM) taking into account the eddy current and lamination effect of stator. In BLDCM, the dynamic characteristic analysis considering the eddy current and driving circuit is applied for the accurate prediction of motor performance in high speed because the eddy current loss is proportional of square of the driving frequency. According to the variation of lamination number, the characteristics of electro magnetic force, torque, and eddy current loss are analyzed. From the results, it is known that the effect of the lamination of stator on the eddy current loss is verified.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1134-1136
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• 1996

A necessary and suficient conditions is proposed for feedback linearizable SISO systems with unknown constant parameters. It is shown that the systems which satisfy the proposed conditions can be transformed into a controllable linear system with unknown parameter and it can be stabilized using the nonlinear feedback linearizing controller. We also present the analysis and implementation of a nonlinear feedback linearizing control for an Electro-Magnetic Suspension (EMS) system. We show that an EMS system is nonlinear feedback linearizable and satisfies the proposed conditions, and hence that the proposed nonlinear feedback controller for an EMS system is robust against mass parameter perturbation and force disturbance.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.911-912
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• 2007

영구자석형 조작기(PMA)의 단점을 보완한 고전압 차단기용 전자석 조작기인 EMFA는 긴 스트로크를 가지는 차단기에도 사용이 가능하며, 특히 진공 차단기(VCB)용 조작기를 비롯하여, 가스 차단기(GCB)에 적용한 모델도 이미 개발되었다. 다양한 모델에 대한 설계 및 연구가 추가적으로 진행되고 있으나, 아직 설계 방법이 정형화되어 있지 않아 모델에 따라 그 형상이 달라지는 경우가 많다. 이러한 점을 개선하기 위해, 본 논문에서 EMFA의 설계 변수를 변화시켜 가며 나타나는 특성을 홀딩력과 자속밀도를 통해 분석하였다. 나아가 이를 바탕으로 설계 방법의 정형화에 대한 실마리를 제공하고자 한다. 해석에는 2차원 유한요소법을 이용하였고, 설계 변수는 조작기의 초기상태를 기준으로 설정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.314-314
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• 2012

The dilute magnetic semiconductors (DMS) have been developed to multi-functional electro-magnetic devices. Specially, the Si based DMS formed by ion implantation have strong advantages to improve magnetic properties because of the controllable effects of carrier concentration on ferromagnetism. In this study, we investigated the deep level states of Fe- and Co-ions implanted Si wafer during rapid thermal annealing (RTA) process. The p-type Si (100) wafers with hole concentration of $1{\times}10^{16}cm^{-3}$ were uniformly implanted by Fe and Co ions at a dose of $1{\times}10^{16}cm^{-2}$ with an energy of 60 keV. After RTA process at temperature ranges of $500{\sim}900^{\circ}C$ for 5 min in nitrogen ambient, the Au electrodes with thickness of 100 nm were deposited to fabricate a Schottky contact by thermal evaporator. The surface morphology, the crystal structure, and the defect state for Fe- and Co- ion implanted p-type Si wafers were investigated by an atomic force microscopy, a x-ray diffraction, and a deep level transient spectroscopy, respectively. Finally, we will discuss the physical relationship between the electrical properties and the variation of defect states for Fe- and Co-ions implanted Si wafer after RTA.