• 지구물리
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• 제7권1호
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• pp.11-21
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• 2004

The variation of geomagnetic field and absolute magnetic field at the geomagnetic observatory of King Sejong Station has been measured with 3-component ring core fluxgate magnetometer, proton magnetometer and D-I magnetometer. With data obtained from King Sejong Station during 2003, thediurnal and annual variations of geomagnetic field were researched and compared with those at other observatories. The deviation of daily variation of magnetic field in antarctica decreased gradually during winter season due to sun effect. The rates of componental annual variation of magnetic field at King Sejong Station were calculated using the least-square method under the assumption that the annual variation of magnetic field is linear. The rates are -55.93 nT/year in horizontal intensity, -0.87 min./year in declination, 58.30 nT/year in vertical intensity, and -69.85 nT/year in total intensity of magnetic field. A remarkable variation was caused by the magnetic storms occurred on 29~30 October, which were so powerful that the variation was observed in mid latitudes as well as high latitudes. The values of variation are generally 1500 2000 nT in Antarctica including King Sejong Station, 350 500 nT in East Asia. The measurement of absolute magnetic field shows that ring core fluxgate magnetometer has relatively large error range under cold temperature.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1656-1662
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• 2010

Automatic train control systems are divided into ATC, ATP and ATS systems etc. The ATP and ATS systems offer discontinuous information for train control. While the ATC systems provide continueous information for train control. There is a method for offering continuous information by AF track circuits. Magnetic fields are formed by current through rails in the AF track circuit systems. So, the continuous information is received by the magnetic fields on a on-board antenna. Coating materials on rails are researched to decrease defects such as head check, shelling, corrugation, squats and so on in Germany. Currently, a coating method of rail construction is proposed by using the ceramics in Korea. When deciding physical characteristic of ceramics, researches are required about variation of flux density by the ceramics. In case that the flux density is much lower than existing value, the information for train control is not transmitted to the on-board antenna. In this paper, inductance on rails is calculated and a model is presented about variation of the magnetic field intensity in the AF track circuit. Standard permeability of ceramics is proposed by analyzing the variation of magnetic field intensity. It is demonstrated by using Maxwell and Matlab program.

• 한국자기학회지
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• 제20권2호
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• pp.45-51
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• 2010

비파괴검사는 탐지물체에 물리적 손상을 가하지 않고 내부 정보를 파악할 수 있어 다양한 분야에서 이용되고 있다. 그 중 전자기를 이용한 물체의 형상추정방법의 경우 역 유한요소법을 이용하여야 하지만 이는 비선형성이 강하고 수치계산이 복잡하고 측정 센서의 개수가 미지수의 개수보다 훨씬 적어 정확한 결과를 얻는데 어려움이 있다. 본 논문에서는 탐지물체에 의한 자기장 변화 신호만을 이용하여, 물체의 시스템 내 각 센서별 위치에서 물체와 등가면적의 원의 비교를 통해 비교적 간편하게 자성물체의 부피를 판정하고 형상추정을 위한 다양한 보정과정을 거쳐 탐지물체의 형상판정이 가능한 알고리즘을 제안하고 검증하였다.

• 한국자기학회지
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• 제24권3호
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• pp.90-96
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• 2014

요골동맥의 움직임에 따라 손목의 "관" 위치에 놓인 영구자석이 요동함으로 자기장의 변화를 생성하였다. 맥동에 의존하는 자기장을 감지하는 홀소자가 구비된 집게형맥진기의 출력신호인 맥진파형 특성을 분석하였다. 유한요소법으로 전산모사한 자기장 파형과 실제 맥진 파형의 시간 특징점들은 거의 일치하였다. 한 개의 원통 소형 영구자석의 자기장 분포의 변화를 감지하는 홀소자 집게형맥진기 시뮬레이터를 제작하여 재현성과 유효성 있는 한방진단기기로 활용하는 기틀을 마련하였다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.172-175
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• 2001

AC loss which is generated in an HTS wire varies with the direction of the external magnetic field. This paper calculates the AC loss in an HTS tape, where effects of the perpendicular direction of the magnetic field are considered. Brandt equation is used to calculate the loss by perpendicular magnetic field. In the calculation, current densities are varied along the variation of the magnitude of the external magnetic field. Results of calculation are compared with those of the conventional method.

• 대한전기학회논문지
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• 제34권10호
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• pp.384-388
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• 1985

In this paper, an attempt is made to derive the variation equatios of the discharge current and the luminous flux for flourescent lamp subjected to a transverse magnetic field. As the field increases, so do the electric field, the electron temperature, and the luminous flux, while the current decreases. The theory is in a reasonable agreement with the experimental results, taking account of many approximations and restrictions.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.137-141
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• 2006

선박용 디지털 컴퍼스를 사용하는 경우 선박의 진방위를 획득하기 위해서는 고정밀도의 자차와 편차가 필요하다. 편차는 지구자장의 주 자장과 경년변화에 대한 구면 지구 조화 모델을 이용한 WMM(World Magnetic Model)으로 예측 가능하였고, 자차는 포아송 방정식을 적용한 자차계수 합성과 분석 방법을 적용한 방법을 이용하여 획득 가능하였다. 실습선 '새누리호' 항해 중 디지털 컴퍼스에 편차와 자차를 가해준 결 과 정확한 진방위 획득이 가능하였다.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.99-105
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• 2011

This paper is about the design of 3-axis magnetic sensor module which detects parking and moving vehicle. For the sensor module, MR Sensor from Honeywell of which maximum measurement range is ${\pm}2$[G] is used. It also consisted of amplifier and sensor filter and fabricated $30{\times}50$[mm] PCB. Fabricated sensor module produced helmholtz coil of which the length is 1.2[m] of 3-axis to know the performance. It installed sensor module at the center and measured the detected magnetic field. In result, 3-axis were detected as 0.2~0.3[mG] and the drift of the fluctuation of magnetic field was stabilized at 0.03[mG] unit. For the performance evaluation of the vehicle detection, after the entry and parking of the vehicle, variation of magnetic field was measured as 0.323~0.695[G] which the average 0.5[G] of the earth magnetic field was the center and the range of variation was confirmed as 0.37[G]. Therefore, the designed magnetic sensor can be used as the vehicle detection sensor module.

• 전기학회논문지
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• 제60권3호
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• pp.552-559
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• 2011

There is a method for offering continuous information by AF track circuits. Magnetic fields are formed by current through rails in the AF track circuit systems. So, the continuous information is received by the magnetic fields on a on-board antenna. Coating materials of spray on rails are researched to decrease defects such as head check, shelling, corrugation, squats and so on in Germany. Currently, a coating method of rail construction is proposed by using the ceramics in Korea. When deciding physical characteristic of the coating material of spray, researches are required about variation of flux density and resistivity by using the coating material of spray. In case that the flux density is much lower than existing value, the information for train control is not transmitted to the on-board antenna. In this paper, inductance on rails is calculated and a model is presented about variation of the magnetic field intensity and resistivity in the AF track circuit. Standard permeability of the coating material of spray is proposed. Also, standard resistivity of the coating material of spray is presented by analyzing short current.

• Tribology and Lubricants
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• 제13권2호
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• pp.52-59
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• 1997

An experimental study is presented for the characteristics of the high temperature superconductor as an application of the repulsive type magnetic bearing. A ring shaped YBCO type superconductor and Neodium permanent magnets are employed for the experiment. For the case of field cooling, superconductor shows strong repulsive force, which is due to the Meissner effect, as the gap between the superconductor and the magnet gets closer. The repulsive force variation with respect to the gap change shows hysterisis characteristics. The area of the loop of the hysterisis curve represents the dissipation of energy, which reveals that the magnetic bearing with superconductor has large damping. The effect of the initial gap and the magnetic flux density on the repulsive force is analyzed experimentally and the static stiffness variation is calculated from the measured repulsive force variation. The relative sliding velocity between the superconductor and the magnet has little effect on the repulsive force which is quite different from the usual sliding element bearing. As the initial gap for the field cooling becomes larger, the maximum repulsive force at the minimum gap increases and approaches to the value for the case of zero field cooling.