• 지구물리와물리탐사
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• 제11권4호
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• pp.343-349
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• 2008

차량이 자력계를 끌면서 자기장을 측정하는 차량자력탐사시스템을 구성하였다. 이 때 측정된 벡터합으로서의 총자기장에는 차량 자체가 발생하는 자기장이 포함되어 있다. 이 자기장은 잡음으로 작용하므로, 이를 제거해야 한다. 이를 위하여, 차량을 한 지점에 세워 두고 주위에서 자기장을 측정한 것과 같은 효과를 내도록 상황을 설정하여 자기장을 측정하였다. 이렇게 한 경우, 측정 지역 내에 차량 외의 다른 이상체가 없다면, 지구자기장을 소거한 자기장은 모두 차량이 발생한 자기장이라고 여길 수 있다. 이처럼 차량이 발생한 것으로 여긴 자기장을 역산하여 차량이 가진 잔류자기와 유도 자기 각각에 대해서 자기모멘트의 크기와 방향을 추출하고자 하였는데, 그 결과는 성공이었다. 일단 잔류자기와 유도자기의 자기모멘트의 크기와 방향을 추출하고 나면, 그들에 의해서 특정한 지점에서 발생되는 자기장은 직접 계산된다. 이 결과는 앞으로 차량자력탐사시스템을 이용하여 자력탐사를 수행한 뒤 획득된 자료를 처리하는 과정에서 차량에 의한 잡음을 소거함에 이용될 수 있다.

• 한국구조물진단유지관리공학회 논문집
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• 제3권2호
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• pp.161-167
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• 1999

There is an increasing need for the estimation of foundation piles whose depths are unknown. Especially in repair and reinforcement works or in safety inspection and assessment to the big structures whose foundations are piles, the accurate information about the depth of foundation piles is one of the most important factors. A borehole magnetic tool has been developed and tested to meet this object. The fundamental base is that there usually exist many re-bars inside the foundation structure such as piles, and these re-bars are ferromagnetic materials which cause strong induced magnetic field comparable to the earth magnetic field. It utilizes flux-gate type magnetometer which measures 3-components of the magnetic field. Taking vertical derivatives of vertical component of the measured magnetic field, we can expect the error limit of estimating the depth of the pile end less than 20 cm in favorable condition. The maximum measurable distance is about 3 m to the pile from the borehole. The field data show that borehole magnetics is one of the most accurate, fast, and reliable methods for this object so far, as long as there is no magnetic materials such as deep located steel pipe or power cables close to the foundation piles.

• Journal of Magnetics
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• 제17권4호
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• pp.308-315
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• 2012

Experimental investigations of the magnetization, magnetostriction and magnetoelectric (ME) effects were performed on sandwich - type Metglas/PZT/Metglas laminate composites. The results have been analyzed by taking into account the demagnetization contribution. The study has pointed out that the magnetic flux concentration is strongly improved in piezomagnetic laminates with a narrower width leading to a significant enhancement of the ME effects. The piezomagnetic laminates with the optimal area dimension were integrated to form a 2-D geomagnetic device, which simultaneously can precisely detect the strength as well as inclination of the earth's magnetic field. In this case, a magnetic field resolution of better than $10^{-4}$ Oe and an angle precision of ${\pm}0.1^{\circ}$ were determined. This simple and low-cost geomagnetic-field device is promising for various applications.

• 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.

• 지구물리와물리탐사
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• 제23권1호
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• pp.55-60
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• 2020

직육면체 프리즘에 대한 중력, 자력, 중력 변화율 텐서 및 자력 변화율 텐서 반응식을 정리하였다. 직교 좌표계에서 직육면체 프리즘에 대한 삼중 적분으로 수직 중력을 유도하고, 직육면체의 축 방향 대칭성을 이용하여 순환 치환으로 두 개의 수평 중력 성분을 유도한다. 벡터 중력을 각 성분 별로 미분하여 중력 변화율 텐서를 유도한다. 포아송(Poisson) 관계식을 이용하면 일정한 방향으로 자화된 벡터 자력은 중력 변화율 텐서로부터 얻어진다. 벡터 자력을 각 방향으로 미분하여 최종적으로 자력 변화율 텐서를 유도하였다.

• 천문학회보
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• 제42권2호
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• pp.81.3-81.3
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• 2017

In this paper, we report a small-scale emerging island and double arc loops, which are associated with a M6.5 flare, in Active Region 12371. We investigate the spatial and temporal changes of both photospheric magnetic fields using SDO/HMI data and coronal magnetic structures obtained from nonliner force-free field (NLFFF) extrapolation. From the vector magnetograms, we find a small-scale emerging island near the main polarityy inversion line about three hours before the flare. The island has a strong shear angle, which is determined by difference between transverse component of observed field and potential field, of around 90 degrees. Furthermore, the NLFFF well reproduces a sigmoidal structure seen in SDO/AIA 94, which is consistent with the double arc loops configuration suggested by Ishiguro and Kusano (2017) who introduced a magnetic configuration showing the double arc instability. The observed emerging island is located among the double arc loops, which is also supproted by their model. Finally, there was an eruption (M6.5 flare) associated with the loops. We discuss a possible role of the double arc instability for the eruption.

• 천문학회보
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• 제36권1호
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• pp.33.1-33.1
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• 2011

The plasma sheet of the Earth's magnetosphere is a sheet of hot plasmas in the magnetotail region, dividing the two (northern and southern) lobes of the Earth's magnetic field. It is the key region that is often closely linked to various electromagnetic dynamics in the Earth's magnetosphere-ionosphere system. In particular, it is the region that is most crucial for substorms, which is one of the most dynamic phenomena in the Earth's magnetosphere. The question of substorm triggering remains highly controversial until today, and at the center of the controversy there are several critical physics issues of the plasma sheet. In this talk I will introduce some of the physics issues of the plasma sheet. The specific topics that this talk will cover are (i) the general properties of the plasma sheet, (ii) fast plasma jets and plasma transport problem, (iii) stability/instability problem, and (iv) effects of thin current sheet. I will also present some of our group's recent findings regarding these topics, as obtained by comprehensive analyses of various observational data. The level and content of this talk are designed to be comprehensible to not only space physicists but also the scientists in a related field such as solar and heliospheric physics.

• 지구물리와물리탐사
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• 제5권2호
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• pp.84-92
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• 2002

이 연구에서는 최근에 개발되어 적용성에 대한 시험이 진행되고 있는 $1\;kHz\~1\;MHz$ 주파수대역의 수평 자기쌍극자를 송신원으로 하여 전기장과 자기장을 측정하는 탐사법의 모델링 알고리듬을 개발하고자 하였다. 이를 위해 공간주파수 영역에서 수평 자기쌍극자를 송신원으로 하는 이차장 Maxwell 방정식을 구성하고 유한요소법을 이용하여 2.5차원 모델링 알고리듬을 구현하였다. 또한, 검증된 층서구조 반응결과와 비교하여 그 정확도를 검증하였다. 개발된 알고리듬을 이용하여 균질 반무한공간 내에 전도성 및 비전도성 고립이상체가 존재하는 2차원 모형에 대한 전기장, 자기장과 임피던스를 계산하였다. 계산된 전기장, 자기장과 임피던스의 거동에 대한 고찰 결과 고립이상체와 같이 2차원 구조에서 전기장과 임피던스가 자기장에 비해 이상체의 탐지에 효과적임을 보였다. 특히, 전기장을 자기장으로 나눈 값인 임피던스는 전기장의 공간 분해능을 가지면서 보다 안정된 결과를 보여 주었다. 따라서 자기장만을 측정하는 기존의 전자탐사법에 비해 전기장과 자기장을 모두 측정하는 탐사법이 천부에 존재하는 이상체의 탐지에 보다 효과적임을 알 수 있었다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.648-653
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• 2003

Optimized recovery of heavy minerals from the near shore sands of Korean Yellow Sea was investigated using physical processing technologies such as gravity concentration and magnetic separation. The head samples were subjected to the three stages effective separation; Head sample was first treated by a spiral separator to recover rough heavy mineral concentrates, which are contained minerals like ilmenite, zircon and rare earth minerals. Much higher beneficiation processes were subsequently taken by wilfley table and magnetic separation according to their magnetic field responses. Heavy minerals were effectively recovered by wilfley table and subsequent recleaning of heavy minerals by magnetic separations was conducted. Qualitative and relative-quantitative analyses of their constituent elements were doing using XRD and XRF.

• 천문학회보
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• 제44권2호
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• pp.41.1-41.1
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• 2019

The stability analysis of coronal magnetic structures is important for studying the initiation of solar flares and eruptions. In order to understand the flare onset process, we first reconstructed the 3D coronal magnetic structures of active region 12371 with an M6.5 flare using a nonlinear force-free field (NLFFF) model based on vector magnetic fields. The NLFFFs successfully produce the observed sigmoidal structure which is composed of two branches of sheared arcade loops. The stability analysis were examined for three representative MHD instabilities: the kink, the torus, and the double arc instabilities. Our stability analysis shows that the two branches of sheared arcade loops are quite stable against the kink and torus instabilities, but unstable against the double arc instability before the flare occurrence. Finally, we discuss a probable onset process of the M6.5 flare.