• 전기학회논문지
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• 제62권1호
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• pp.43-48
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• 2013

In this paper, magnetic buoyancy force on nonmagnetic solid object submerged in magnetic liquid was simulated and measured. For the evaluation of the force, a multi-physics approach of hydrostatic equilibrium considering magnetic body force as well as gravity is presented. The magnetic body force should be regarded as an additional forcing term in the momentum equation of hydrodynamics. It is also shown that the virtual air-gap based Kelvin's force formula is a useful method for the calculation of force distribution in the magnetic liquid. The experimental result which was performed by a load-cell measurement system agreed quantitatively well with the numerical one.

• 한국주조공학회지
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• 제17권1호
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• pp.76-84
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• 1997

An investigation of the effects of transverse magnetic field on melt convection and macrosegregation in vertical Bridgman growth of Te doped InSb was carried out by means of microstructure observation, the measurement of Te distribution by Hall measurement, electrical resistivity measurement and X-ray analysis. Prior to the experiments, interface stability, convective instability and suppression of convection by magnetic field were examined. A thermosolutal convection in the Te doped InSb melt occurred in the examined growth condition without magnetic field. The effective distribution coefficient, $K_{eff}$, was about 0.35 without magnetic field, 0.45 with magnetic field of 2kG, and 0.7 at 4kG. It was found that the stronger the applied magnetic field was, the more the convection was suppressed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.7-8
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• 2009

Non-contact critical current measurement apparatus was developed using hall probe which measures the magnetic field distribution across the width of superconducting tape. The hall probe consists of 7 independent hall sensors which lie in a line 600 ${\mu}m$. The difference between maximum and minimum magnetic field in the magnetic filed distribution is a main parameter to determine the critical current. As preliminary research, we calculated the magnetic field intensity at the middle sensor, which is a minimum magnetic field and generated by the circular shielding current modeled by Bean model. We confirmed that there are some parameters that affect on the minimum magnetic field; the distance between superconducting layer and hall sensor, the width of superconducting tape, and the critical current distribution across the width of superconducting tape. Among these parameters, the distance between superconducting layer and hall sensor highly influences on the minimum magnetic field.

• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 2002년도 제20회 학술발표회
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• pp.5-5
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• 2002

• 한국지반환경공학회 논문집
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• 제12권11호
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• pp.71-77
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• 2011

최근 들어 자기이방성센서를 이용한 비파괴응력계측기법은 강교나 강관 등의 건설 분야에서 적용되어지고 있다. 또한 터널건설현장에서 이용되는 강지보재에 대해서도 적용한 사례가 있다. 본 연구에서는 일본에서 개발된 자기이방성센서와 스트레인 게이지를 이용하여 국산 강재인 SS400에 적합한 응력감도곡선을 도출하기 위해 강재하중재하실험을 수행하였다. 또한 자기이방성센서를 이용한 비파괴 응력계측기법의 적용성을 평가하기 위하여 추가 강재하중재하실험과 수치해석을 실시하였다. 본 연구의 결과, 계측위치에 따라 자기이방성센서에서 측정된 출력전압과 스트레인 게이지로 측정된 응력의 평균을 이용하여 국산 강재인 SS400에 적합한 응력감도곡선을 도출하였다. 그리고 추가 강재하중재하실험과 수치해석을 비교한 결과, 자기이방성센서의 오차범위가 약 20MPa 정도임을 알 수 있었다. 자기이방성센서를 강재의 응력상태를 파악할 목적으로 사용할 경우, 강재의 항복응력의 레벨(245MPa)을 고려하면 공학적으로 충분한 정확도를 가지고 있다고 판단된다. 특히 자기이방성센서는 계측 센서가 부착되어 있지 않은 강구조물에서 잔류응력을 고려한 현재상태의 응력을 용이하게 파악할 수 있으며, 강구조물의 유지관리에 편리하게 적용이 가능함을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권8호
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• pp.4227-4240
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• 2019

In this paper, we present our proposed magnetic induction based wireless communication system. The proposed system is designed to perform communication as well as distance measurement in underground environments. In order to improve the communication quality, we propose and implement the adaptive channel compensation technique. Based on the fact that the channel may be fast time-varying, we keep track of the channel status each time the data is received and accordingly compensate the channel coefficient for any change in the channel status. By using the proposed compensation technique, the developed platform can reliably communicate over distances of 10m while the packet error rate is being maintained under 5%. We also implement the distance measurement block that is useful for various applications that should promptly estimate the location of nearby nodes in communication. The distance between two nodes in communication is estimated by generating a table describing pairs of the magnetic signal strength and the corresponding distance. The experiment result shows that the platform can estimate the distance of a node located within 10m range with the measurement error less than 50cm.

• 한국전기전자재료학회논문지
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• 제30권4호
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• pp.253-257
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• 2017

Nowadays, it is increasingly important to detect whether cables are live for the operator's safety if there is a sudden power failure. It is especially hard to detect the electrical field of an underground line because of shielding. This paper on detection of live-line states in cables studied the detection characteristics of the change in the magnetic field and axis as the frequency, voltage, and distance at the same load are changed using 3 axes. A search coil type was used as a magnetic field sensor with non-contact. We found that magnetic fields decrease proportionally to the square of the distance and the decrease of rated voltage with load effected to magnetic field. The magnetic field was detected by 3-axis sensors given correct proximity, but appeared as noise components beyond a distance of 2 cm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.685-686
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• 2015

This paper describes design results of the measurement system to test the properties of broadband AC magnetic field sensors used in weapon system. This measurement system consists of 3-axis helmholtz coil, signal generator, signal amplifier, sensor data acquisition unit and measurement & analysis controller including the operating software. This system is able to measure various properties of AC magnetic field sensor such as sensitivity, linearity and dynamic response in the frequency of 1 Hz to 10 kHz. The performance of this system was verified by measuring and analyzing the property of a MAG 639, standard magnetic field sensor of bartington instruments, with this developed system.

• Journal of Magnetics
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• 제8권4호
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• pp.160-163
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• 2003

In magnetic flux measurement, output voltage drift of electronic integrator is an essential problem. In this work, we have developed a new kind of Miller type integrator using a sample and hold amplifier. Input bias current was measured and this value was hold in the sample and hold amplifier, after that input bias current of Miller integrator was compensated automatically using the value which holds in the sample and hold amplifier. Developed flux-meter shows the drift of flux-meter are smaller than 10$^{-5}$ Wb/min in full scale of 10$^{-2}$, and we could also measure multi-channel magnetic flux simultaneously.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.318-326
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• 2009

A simple method for measuring magnetic flux and induced current in magnetic nerve stimulation for urinary incontinence treatment is proposed. Unlike electric nerve stimulation, direct measurement of the induced current in magnetic nerve stimulation is impossible. Since induced currents stimulate nerves or muscles in magnetic nerve stimulation, measuring induced current is very important in validating stimulation efficacy and securing safety. The magnetic flux measuring system is composed of 6 layers with pick-up coils of 7 by 7 in each layer, and the induced current measuring system is composed of 6 layers with 7 concentric circular coils in each layer. The proposed method can be used in the design or performance test of a magnetic nerve stimulator for many clinical applications such as urinary incontinence treatment, activation of peripheral nerves, and transcranial magnetic stimulation.