• 전기학회논문지
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• 제63권2호
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• pp.245-249
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• 2014

Wireless power transfer (WPT) system is very attractive because it removes power cables from home appliances, office equipments and battery chargers for electric vehicles. In this paper, non-radiative WPT systems studied recently are claimed to be technologically or theoretically identical in operation irrespective of the number of coils. Especially, 2-coil and 3-coil systems are compared in detail. It is also shown that multiplicity of coils does not increase power transfer capability.

• 전기학회논문지
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• 제66권8호
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• pp.1222-1229
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• 2017

In this paper, a wireless power transfer system with semi-random magnetic flux is studied. Directions of semi-random magnetic flux are changing almost randomly which can induce voltages at coils irrelevantly to coil's posture. So, very convenient charging is possible. Semi-random magnetic flux can be generated by a coil system which has three coils perpendicular to each other and carrying currents with different frequencies. A prototype for charging mobile devices is constructed and tested, and the proposal is verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.235-237
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• 2006

In this paper, the previous 2-D gradient coil design method using loop current elements is extended to 3-D or multi-layer structures which is useful for various MRI applications including MR microscopic imaging where relatively large space may be available for the implementation of the gradient coils. Either the power consumption or the stored energy (thus, inductance), or the combination of the two can be minimized with a set of chosen target field constraints. Complete 3-D design equations for the optimization as well as inductance or resistance calculation are derived. An effective coil shape correction method for a curved current pattern is also developed. The design method can also be easily extended to the active shielding structure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.77-80
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• 2008

In this paper the electromagnetic shunt damper was newly employed for vibration suppression of the flexible structures. The electromagnetic shunt damper consists of a coil and a permanent magnet. The ends of the coil were connected to the RLC shunt circuit. The numerical solutions of resonant frequency of the shunt circuits were calculated by using Pspice. The vibration and damping characteristics of the flexible beams with the electromagnetic shunt damper were investigated by tuning the circuit parameters. Also, the effect of the magnetic intensity on the shunt damping was studied with the variation of the gap between the aluminum beam and the permanent magnet. Present results show that the magnet shunt damper can be successfully applied to reduce the vibration of the flexible structures.

• 전기학회논문지
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• 제57권2호
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• pp.314-319
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• 2008

In this paper, the electric field distribution induced inside the brain during Transcranial Magnetic Stimulation(TMS) has been thoroughly investigated in terms of tissue heterogeneity and anisotropy as well as different head models. To achieve this, first, an elaborate head model consisting of seven major parts of the head has been built based on the Magnetic Resonance(MR) image data. Then the Finite Element Method(FEM) has been used to evaluate the electric field distribution under different head models or three different conductivity conditions when the head model has been exposed to a time varying magnetic field achieved by utilizing the Figure-Of-Eight(FOE) stimulation coil. The results show that the magnitude as well as the distribution of the induced field is significantly affected by the degree of geometrical asymmetry of head models and conductivity conditions with respect to the center of the FOE coil.

• 산업기술연구
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• 제20권B호
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• pp.125-130
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• 2000

Heat dissipation technology using flow resonant phenomenon is a kind of new concept in heat transfer area. A vibration exciter is needed to generate air turbulence which has the natural shedding frequency of heat system. A mechanical vibrating device for the air flow oscillation is introduced, which is driven by a moving coil actuator. An analytical dynamic model for this mechanical vibration exciter is presented and its validity is verified by the comparison with experimental data. Values of some unknown system parameters in the analytic model are estimated through the system identification approach. Based on this mathematical model, a high bandwidth vibration phase, it turns out the high modal resonant characteristics of vibrating plate are the major barrier against obtaining a high bandwidth vibration exciter.

• 센서학회지
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• 제20권4호
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• pp.249-253
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• 2011

This paper describes the fabrication and characteristics of vibration-driven electromagnetic energy harvester without spring to use at low frequency like a human body motion. The implemented energy harvester consists of NdFeB magnets, copper coil. The optimization of induced voltage was done by the various widths of coil, number of the turns, size of fixed and moving magnets and thicknesses of the cylinder. The fabricated energy harvester is capable of producing up to 15.0 $V_{pp}$ for basic model and 28.80 $V_{pp}$ for improved model at 5.0 Hz resonance frequency and 0.75 g acceleration level. The basic model and improved model are provided a maximum power of 6.375 mWand 25.831 mW at 1 KHz of load resistance in rectifier circuit.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.445-446
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• 2012

Recently the interest in wireless power transfer have been studied. ECR (Electromagnetic Coupled Resonance) device, depending on the size of the frequency characteristics of the structure, increasing in volume and larger volume of wireless power transmission device to make use of ECR is a big barrier. So to solve this problem for ECR device miniaturization and high efficiency has been actively studied. In this paper, the size of the device for ECR IM (Impedance Matching) by applying a one-turn coil circuit, remove the device in the form of ECR Network Analyzer measured by removing the one-turn coil has demonstrated the possibility of the device in the form of ECR.

• Investigative Magnetic Resonance Imaging
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• 제18권1호
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• pp.52-58
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• 2014

목적: 임상용 MRI에서 마우스 종양의 pH 측정을 위한 $^1H-^{31}P$ RF 코일 시스템을 개발하고 팬텀을 이용하여 pH 값의 정확도를 시험하고자 한다. 대상과 방법: 마우스 종양 연구를 위한 표면형 $^1H$ 및 $^{31}P$ radio frequency (RF) 코일을 개발하였다. 두 코일을 서로 수직이 되도록 설치하여 두 코일간의 상호인덕턴스를 0으로 하였다. 다양한 pH 값을 가진 팬텀으로부터 $^{31}P$ MR 스펙트럼을 얻어 Henderson-Hasselbalch equation을 이용하여 pH를 구하였다. $^{31}P$ 스펙트럼으로부터 얻은 pH값은 pH meter를 사용하여 직접 구한 pH값과 비교한다. 결과: $^1H-^{31}P$ RF 코일 상호간 coil coupling (S12)은 각각 -73.0, -62.3 dB로 충분히 분리 되었다. 균일한 팬텀으로부터 얻은 $^1H$ 영상의 signal-to-noise ratio (SNR)는 약 300 이상이며, in vivo 고해상도 마우스 영상을 얻을 수 있었다. $^1H$ 신호가 분리된 $^{31}P$ MR 스펙트럼으로부터 얻은 pH값은 pH meter로 직접 측정하여 얻은 값과 약 97% 상관관계를 가졌다. 결론: 본 연구에서 개발한 임상 MRI 장비용 $^1H-^{31}P$ RF 코일 시스템으로부터 정확한 pH를 구할 수 있었다. 본 코일 시스템은 31P 이외의 다른 핵 MRS 혹은 MRI에 적용 가능할 것으로 기대된다.

• 한국방사선학회논문지
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• 제15권7호
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• pp.975-982
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• 2021

본 연구는 체내의 식도용 스텐트와 일플란트에 많이 사용되는 티타늄 성분의 금속성 물질을 사용하여 구리와 black metal, polyester로 구성된 머리카락 보다 가늘게 제작된 mesh로 시험관을 부분적으로 RF를 차폐하여 주변에 위치한 자기공명영상용 팬텀에 미치는 영향을 평가하고자 하였다. 3T Achieva X-series의 Cardiac Coil을 사용하여 TR 500 ms, TE 20 ms, NEX 1, slice thickness 5 mm의 Spin Echo T1강조영상에서 field of view(FOV)에 따른 자기공명영상을 분석하였다. FOV 304 mm × 304 mm에서는 발생하지 않았던 aliasing artifact가 발생하지 않았지만 250 mm × 250 mm 과 170 mm × 170 mm에서는 발생되었다. FOV 170 mm × 170 mm에서 mesh를 사용하지 않은 경우는 SNR이 78.23으로 가장 낮았으며, mesh를 가운데 세워 분리한 경우에는 215.05, mesh로 완전히 차폐한 경우에는 366.44로 높게 측정되었다. 또한 mesh로 완전히 감싸고 차폐한 경우에는 aliasing artifact도 제거되었고, 영상의 왼쪽과 가운데, 오른쪽의 신호 대 잡음비가 높으면서 다른 조건과 비교하여 균질한 영상을 획득할 수 있었다. 결론적으로 mesh로 RF를 부분적으로 감싸고 차단하면 aliasing artifact를 제거할 수 있고, 작은 FOV를 사용하여 영상의 해상도와 균질성이 우수한 자기공명영상을 획득할 수 있을 것으로 사료된다.