• 한국산학기술학회논문지
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• 제13권11호
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• pp.5403-5408
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• 2012

본 논문에서는 신체 성분 분석을 위한 다주파수 생체전기 임피던스 분석법에 대하여 소개하고 이를 기반으로 다주파수 생체전기 임피던스 분석 시스템을 구현하고 그 과정 및 결과를 제시하였다. 시스템의 구성요소들을 다주파수 교류 신호 발생부, 위상 신호 검출부, 전압 신호 검출부, 제어부, 입 출력부, 전극부, 전원부로 구분하여 설명하고, 구체적으로 구현 기법을 소개하였다. 체성분 데이터의 임상적 의의를 검토하고자 세계 최고 수준의 기술을 적용하여 높은 재현도와 고정밀도의 데이터를 제공하는 전문가용 체성분 분석기로 측정한 데이터와 비교 검토하고 두 측정치간의 상관관계를 구한 결과 시스템에 의한 체성분 분석은 상당히 높은 재현성을 나타낸다고 할 수 있다.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.60-61
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• 2003

Theoretical considerations on a giant magneto-impedance (GMI) effect in amorphous ribbons (i.e., thin films) have been made in terms of the expressions of effective permeability and impedance derived in the frame of classical electrodynamics and ferromagnetism. The dependence of GMI effect on the external do magnetic field (H$\_$ext/) and the frequency of alternating current are simulated and discussed in the knowledge of energy conversion consisting of the current energy loss, the ferromagnetic energy consumption, and the magnetic energy storage in the film. The obtained results are summarized as follow: (a) As frequency f< 20 ㎒, the real part of effective permeability (${\mu}$′) changes slightly. The peak of the ${\mu}$′curve always locates at H$\_$ext/=H$\_$ani/ - the anisotropy field. However, the peak value of ${\mu}$′ tends to increase with increasing frequency in the frequency range of 11-20 ㎒. (b) In the frequency range, f= 21-23 ㎒, a negative peak additionally appears. Meanwhile, both the positive and negative peak values rapidly increase with increasing frequency and their peak positions shift towards a high H$\_$ext/. (c) The positive peak value of ${\mu}$′ starts to decrease at f= 29 ㎒ and its negative peak does so at about 35 ㎒. Then, both peaks keep such a tendency and their peak positions move to high H$\_$ext/, as increasing frequency. (d) The dependence of the imaginary part of effective permeability (${\mu}$") on the external dc magnetic field and the frequency of the alternating field indicates that there is only one peak involved in ${\mu}$" for the whole frequency range. (e) The impedance vs. magnetic field curves at various frequencies show that there is a critical value of frequency around f= 18-19 ㎒ where the transition between two frequency regimes occurs; the one (low frequency) in which ${\mu}$′ predominantly contributes to the GMI effect and the other (high frequency) in which ${\mu}$" determines the GMI effect.

• 한국멀티미디어학회논문지
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• 제19권7호
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• pp.1146-1153
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• 2016

The bioelectrical impedance (BI) at the inner forearms was measured using bioelectrical impedance measurement system (BIMS), which employs the multi-frequency and the two-electrode method. Experiments were performed as follows. First, while applying a constant alternating current of 800A to the inner region of the forearms, BI (Z) was measured at nineteen frequencies ranging from 5 to 500 kHz. The prediction marker (PM) was calculated for right and left forearm. The resistance (R) and the reactance (X_c) were simultaneously measured during impedance measurement. Second, a Cole-Cole plot (relationship between reactance and resistance) was obtained for left and right forearm, indicating the different characteristic frequencies (f_c). Third, the phase angle was obtained, indicating strong dependence on the applied frequency.

• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.572-577
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• 1996

Alternating current and direct current of pure, ball milled, and $Al_{2}$O$_{3}$ added ZnO were investigated by means of complex impedance measurement and voltage-current source measurement unit. The electrical conductivity of A1$_{2}$O$_{3}$ added ZnO samples increases when the content of A1$_{2}$O$_{3}$ is used within 1 at% and decreases when it's used more than that. The increase and decrease of electrical conductivity seem to be the donor effect of $Al_{2}$O$_{3}$ and the increase of the number of ZnO grains, respectively. Impedance spectrum seems to be one semircicle. The size of semicircle increase with increasing the A1$_{2}$O$_{3}$ contents. The calculated dielectric constant(at 50.deg. C) were about 70-140 at the peak of the semicircle. The semicircles seem not to be the resistance of ZnO grain as compared to that of 10 for pure ZnO.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.53-55
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• 2005

The signals of the eddy current testing(ECT) for the examination of the steam generator(SG) tubes in the nuclear power plant(NPP) determine the existence, size, and kind of defects using the variation of impedance signals when a testing coil, driven by alternating current, passes through the SG tube contains defects. The aim of this paper is building a database of the RPC probe signals on the basis of the sizes variation of defects and frequency variation of probe. In this paper 3-D numerical analysis of the ECT signals using the finite element method is performed. Through this study, it is shown variation of magnitude and phase of impedance according to variation of defect size and frequency. From the result of this paper, we can obtain the information which is useful in defect discrimination of SG tube in nuclear power plant.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.691-706
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• 2008

ATP(Automatic Train Protection) system in railway signaling system is the important one grasping the position and velocity of a train. The wayside transmitter of ATP system is installed between rails. In concrete slab track, the signal current using wayside transmitter of ATP system is influenced by reinforcing bars. The magnetic coupling between reinforcing bars and wayside transmitter of ATP system as a filter makes an input current distorted. So, it makes an alternating current signal with a desirable size not transmit to on-board system of a train. Way to decrease the distortion of an input current signal frequency is to avoid maximum induction current frequency. And the induction phenomenon between reinforcing bars insulated and wayside transmitter of ATP system does not occur. In this paper, we represent the model about wayside transmitter of ATP system and reinforcing bars on the concrete slab tracks, and calculated the parameters demanded for the model. Also, we demonstrated it through the Maxwell program. Furthermore, we calculated impedance on wayside transmitter used in KVB system and ERTMS/ETCS system which are a kind of ATP system, frequency response of induction current, using the Matlab, and demonstrated the validity of it, using the PSpice program.

• 한국정보통신학회논문지
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• 제19권6호
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• pp.1515-1524
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• 2015

최근 선박의 부식을 방지할 목적으로 전기적인 방식 장치를 이용하여 선체와 프로펠러의 부식을 방지하는 장치가 많이 이용되고 있는 추세이다. 그러나 전기적 방식 방법은 선체 내부의 전원장치에 의해 선체 주위의 해수로 전류를 방사하여 선체와 프로펠러가 부식이 되지 않는 상태로 인위적으로 만들어 주는 방법을 사용하는데, 해수에 방사되는 방식전류로 인하여 선체 외부에서 전자장 신호가 발생하게 된다. 본 논문에서는 선체 외부의 수중에서 발생하는 전자장 신호를 분석하고, 이에 대한 감소 대책에 대한 연구를 수행하는 것을 목표로 하였다. 기존의 축 접지 시스템에서는 축 전위가 100[mV] 이상 이며, 교류 전류 성분이 전체의 10% 이상을 차지하였으나, 본 논문에서는 방식전류내에서 교류전자장을 발생하는 교류 전류 성분과 축 전위가 각각 1% 와 2[mV]이내로 유지되게 하는 제어 시스템을 설계하고, 모의 실험을 통하여 그 성능을 입증하였다.

• Applied Microscopy
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• 제47권3호
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• pp.126-130
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• 2017

The dielectric relaxation characteristics of composites with different concentrations of carbon nanotubes loaded in an epoxy polymer matrix has been studied as a function of frequency over a wide range (1 Hz~10 MHz) at room temperature. Two characterization techniques were used in this work to measure and calculate the dimensionality parameters: small angle neutron scattering and impedance spectroscopy. The results obtained from both methods are in good agreement, indicating the reliability of the estimated fractal dimension, despite of the difference in the length scales accessed by the two techniques.

• 한국철도학회논문집
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• 제11권6호
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• pp.536-542
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• 2008

콘크리트 슬래브궤도에서 ATP시스템 지상자를 이용한 신호 전류는 철근에 의해 신호전류에 영향을 미칠 수 있다. 즉, 콘크리트 슬래브궤도에서 ATP시스템 지상자와 철근의 자기적 결합은 하나의 필터로 작용하게 되어 입력전류신호에 왜곡을 주게 된다. 그리고 결국 왜곡된 신호에 의해서 열차의 차상자에 잘못된 신호가 전송될 수 있다. 입력전류신호의 왜곡을 줄이기 위한 방법으로 철근에 유도되는 전류와 주파수를 구하여 해당 주파수를 ATP시스템의 지상자 주파수로 사용하지 않거나, 철근을 절연시켜 철근과 ATP시스템 지상자간에 유도현상을 억제할 수 있다. 본 논문에서는 콘크리트 슬래브궤도에서 ATP시스템의 지상자와 철근의 모델을 전기적으로 표현하였고, 모델에 요구되는 값들을 Maxwell 프로그램을 이용하여 구하였다. 또한 모델로부터 ATP시스템인 KVB시스템, ERTMS/ETCS시스템에서 사용하고 있는 지상자의 주파수에 대한 지상자의 임피던스 및 철근의 유도전류를 계산하였다. 이를 Matlab 및 PSpice 프로그램으로 타당성을 입증하였다.

• 비파괴검사학회지
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• 제35권4호
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• pp.258-267
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• 2015

Eddy current testing is widely used for inspecting steam generator tubing in nuclear power plants (NPPs). The inspection technique for steam generator tubing in NPPs should be qualified in accordance with examination guidelines. When the components of a qualified system such as eddy current tester, probe, and data analysis program, are changed, the equivalency of the modified system to the originally qualified system must be verified. The eddy current tester is the most important part of an eddy current testing system because it excites and transmits alternating currents to the probe, receives coil impedance of the probe and generates signals for anomalies. The Korea Hydro & Nuclear Power Co., Ltd. (KHNP) developed an eddy current testing system with an eddy current tester and data acquisition-analysis program for inspecting the steam generator tubing in NPPs; this system can be used for an array probe and as a bobbin and rotating probes. The equivalency assessment for the currently developed system was carried out, and we describe the results in this paper.