• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.36-40
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• 2003

The considered satellite is supposed to operate in the earth-point mode and sun-point mode in accordance with the mission requirements. The magnetic field correction is based on the orbit geometry using a set of measured magnetic field data from the three-axis-magnetometer and its algorithm excludes the earth’s magnetic field model. Moreover, the usefulness of the proposed method is investigated throughout the simulation of KOMPSAT-1.

• Investigative Magnetic Resonance Imaging
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• 제15권1호
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• pp.57-66
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• 2011

목적 : 0.35 Teslas의 저자장 자기공명영상 시스템에서 인체 조직의 물 성분 또는 지방 성분의 영상을 얻는데 있어서 주자장의 불균일도를 two-point Dixon 방법을 기반으로 보정하는 새로운 방법을 모색하였다. 대상 및 방법 : Two-point Dixon 방법을 사용하여 물과 지방의 위상이 동상일 때와 역상일 때의 영상들을 얻은 후 그 영상들로부터 위상과 크기의 위상 크기 결합 밀도 함수를 계산하고, 이를 통해 물과 지방의 영역을 분리하여 3차원 볼륨의 물 영역에서의 주자장의 불균일도 패턴을 분석하고 이를 반복적으로 보정하여 주자장의 불균일도를 개선하였다. 결과 : 제안한 영상 기법으로 인체의 여러 부위에서 주자장의 불균일도를 보정한 물과 지방 영상을 얻을 수 있었다. 삼차원 보정을 통하여 멀티 슬라이스 전체 영상에서 균일하게 물 또는 지방만의 영상을 얻을 수 있었다. 결론 : 위상-크기 결합 밀도 함수를 통하여 물과 지방의 영역을 분리할 수 있었고, 이를 이용하여 자장의 불균일도를 분석하고 보정할 수 있었다. 제안한 방법을 통해 주자장의 불균일도가 월등히 개선된 물 또는 지방 영상을 얻을 수 있었다.

• 한국자기공명학회논문지
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• 제24권3호
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• pp.66-69
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• 2020

In ultra-low field magnetic resonance imaging (ULF-MRI), the strength of a static magnetic field can be comparable to that of gradient field. On that occasion, the gradient field is accompanied by concomitant gradient field, which yields distortion and blurring artifacts on MR images. Here, we focused on the distortion artifact and derived the equations capable of correcting it. Its usefulness was confirmed through the corrections in both simulated and experimental images. This solution will be effective for acquiring more accurate images in low and/or ultra-low magnetic fields.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 Asia Navigation Conference
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• pp.29-36
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• 2004

The paper describes recent experimental results on the development of Digital Magnetic Compass (DMC), which can provide smart automatic correction functions to the magnetic interferences. The design methodology of magnetic sensing circuit with ring-core fluxgate sensor is represented. The performance results of the sensing circuits are discussed with error analysis by polynomial regressions. As test results, the sensing circuit filtered only the second harmonic signal that is proportional to the direction of earth's magnetic field, and it leads to the obtainment of bearing information. In addition, the total residual errors of DMC can be analyzed by the adoption of polynomial regressions. It shown that the possibility of high precise DMC, in the future.

• Journal of Magnetics
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• 제19권2호
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• pp.174-180
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• 2014

In this paper, a new and simple method is proposed to quickly estimate the induced electric field in the human child exposed to a 100 kHz-10 MHz magnetic field, for the sake of electromagnetic field (EMF) safety assessment. The quasi-static finite-difference time-domain (FDTD) method is used to calculate the induced electric fields in high resolution 3D human child models with various body size parameters, in order to derive the correction factor for the estimation equation. The calculations are repeated for various frequencies and incident angles of the magnetic field. Based on these calculation results, a new and simple estimation equation for the 99th percentile value of the body electric field is derived that depends on the body size parameters, and the incident magnetic field. The estimation errors were equal to or less than 5.1%, for all cases considered.

• 한국의학물리학회지:의학물리
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• 제31권4호
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• pp.189-193
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• 2020

An MR-based attenuation correction (MRAC) map plays an important role in quantitative positron emission tomography (PET) image evaluation in PET/magnetic resonance imaging (MRI) systems. However, the MRAC map is affected by the magnetic field inhomogeneity of MRIs. This study aims to evaluate the characteristics of MRAC maps of physical phantoms on PET/MRI images. Phantom measurements were performed using the Siemens Biograph mMR. The modular type physical phantoms that provide assembly versatility for phantom construction were scanned in a four-channel Body Matrix coil. The MRAC map was generated using the two-point Dixon-based segmentation method for whole-body imaging. The modular phantoms were scanned in compact and non-compact assembly configurations. In addition, the phantoms were scanned repeatedly to generate MRAC maps. The acquired MRAC maps show differently assigned values for void areas. An incorrect assignment of a void area was shown on a locally compact space between phantoms. The assigned MRAC values were distorted using a wide field-of-view (FOV). The MRAC values also differed after repeated scans. However, the erroneous MRAC values appeared outside of phantom, except for a large FOV. The MRAC map of the phantom was affected by phantom configuration and the number of scans. A quantitative study using a phantom in a PET/MRI system should be performed after evaluation of the MRAC map characteristics.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1984년도 하계학술회의논문집
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• pp.287-291
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• 1984

The electromagnetic wave scattered by an arbitrary-angled dielectric wedge is constructed by physical optics solution and its corrected field. Two models of correction source are obtained; one is multipole line source at tip of wedge and the other is correction electric and magnetic currents distributed along the interfaces of dielectric wedge. Calculated far-field patterns are presented and compared each other.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.143-146
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• 2000

Generally, two methods can be used to correct the undesirable magnetic field of MRI. One is active shimming method and the other is passive shimming. Passive shimming method uses many magnetized shims to correct the field. And it involves hardwared for supporting shim trays and a software to calculate a field map and optimaze the locations of the shims[1]. The software is the most important part of the passive shimming system. We made a prototype of the software and tested it in a virtual situation.

• Journal of Biosystems Engineering
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• 제33권1호
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• pp.58-62
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• 2008

The need for position information in agriculture is gradually increasing for precise control farm vehicle and effective manage farm land. Though geomagnetic sensor has a lot of merits in estimating heading angle of vehicle because of low costs and sensing ability of magnetic north, it is easy that sensor outputs are distorted in electro magnetic field environment. This study was conducted to develop geomagnetic compass which could be available in measuring relative position from reference point correcting output distorted by external electro magnetic field in a small scale field. Magnetic inducing sensor (PNI's Vector2X) which wound enamel coated copper coil on ferrite core in order to measure and correct earth magnetic field. Magnetic azimuth was corrected using the algorithm which estimated amount of magnetic distortion from the difference between each outputs of magnetic sensors that located on the cross shaped base. Developed auto-tuning magnetic sensor was showed less then 5% as bearing accuracy in the strong magnetic field.

• 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.