• KSTLE International Journal
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• 제2권2호
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• pp.114-119
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• 2001

The distribution of magnetic flux density of electro-magnetic chucks may clarify the clamping characteristics, which is strongly related to the machining efficiency and machining accuracy in surface grinding machine. Therefore the distribution of the normal and the tangential components of magnetic flux density have been analyzed theoretically. It appears that the normal component of magnetic flux density increases and the tangential component of magnetic flux density increases as the ratio of the separator width to the pitch, e/p decreases. The results seem to increase the stability and uniformity of normal component of magnetic flux density for the decreased e/p.

• Journal of Magnetics
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• 제11권4호
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• pp.160-163
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• 2006

We have prepared crystalline Ag nanoparticles with an average size of 4 nm in diameter by using an inductively coupled plasma reactor equipped with the liquid nitrogen cooling system. Our magnetic data show that the nano-sized effect of Ag nanoparticles on the magnetic properties is ferromagnetic, instead of a diamagnetic component of the Ag bulk and a superparamagnetic component of magnetic nanoparticles. We have also studied the magnetic properties of Ag-Cu nanocomposites with an opposite concentration profile between surface and core. These comparisons indicate that the ferromagnetic component strongly depends on the surface of Ag nanoparticles, while the paramagnetic component is strongly affected by the outer oxide layer, with the background of a diamagnetic component from the core of Ag.

• 천문학회지
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• 제49권2호
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• pp.59-64
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• 2016

In this study, we investigate the kinetic properties of magnetic decreases observed in the solar wind at ~1 AU using the Cluster observations. We study two different magnetic decreases: one with a short observation duration of ~2.5 minutes and stable structure and the other with a longer observation duration of ~40 minutes and some fluctuations and substructures. Despite the contrast in durations and magnetic structures, the velocity space distributions of ions are similar in both events. The velocity space distribution becomes more anisotropic along the direction parallel to the magnetic field, which differs from observations obtained at high heliographic latitudes. On the other hand, electrons show different features from the ions. The core component of the electrons shows similar anisotropy to the ions, though the anisotropy is much weaker. However, while ions are heated in the magnetic decreases, the core electrons are slightly cooled, especially in the perpendicular direction. The halo component does not change much in the magnetic decreases from the ambient solar wind. The strahl component is observed only in one of the magnetic decreases. The results imply that the ions and electrons in the magnetic decreases can behave differently, which should be considered for the formation mechanism of the magnetic decreases.

• 한국지능시스템학회논문지
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• 제16권3호
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• pp.297-302
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• 2006

본 논문에서는 지구자계를 이용하여 3축 자계센서의 수직성분자계를 간편하게 보정할 수 있는 방법과 장치를 제안한다. 자계센서의 출력은 설치각도 및 이득오차에 의한 출력 오프셋을 포함하고 있다. 따라서 자계센서를 사용하기에 앞서 보정이 필요하다. 자계센서의 보정은 무자계 공간에서 이루어져야 하나 지구자계를 이용하면 간단하게 자계센서의 출력 오프셋을 보정할 수 있다. 그리고 보정을 위한 장치를 설계하였다. 제안하는 방법과 장치는 실험을 통하여 실용성을 검증하였다.

• 자원리싸이클링
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• 제28권3호
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• pp.53-58
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• 2019

폐납축적지 재활용 공정에서 발생한 납드로스는 비소 등의 유해물질을 함유하고 있어 적절한 처분이 요구되고 있다. 본 연구에서는 볼밀과 믹서밀로 분쇄한 납드로스를 대상으로 자력선별을 실시하여 비소 성분을 농축하고자 하였다. 볼밀에 의해 $150{\mu}m$ 이하로 분쇄된 시료를 대상으로 10000 G와 2000 G의 자석봉으로 순차적 자력선별을 실시한 결과, 10000 G의 비자착물에서는 비소성분이 검출되지 않아 유해물질이 제거된 산물을 확보가능하였다. 추가적인 2000 G 자력선별의 자착물에는 비소가 18.87 %까지 농축되는 것을 확인하였다. 또한 볼밀 분쇄시 $300{\mu}m$ 이상인 분쇄산물을 대상으로 믹서밀로 $150{\mu}m$ 이하로 분쇄하고 4000 G와 2000 G의 자석봉으로 순차적인 자력선별을 실시한 결과 2000 G의 자착물에 비소가 21.021 %로 농축된 것이 확인되었다. 비소는 XRD 결과에서 $Fe_2As$로 존재하는 것을 확인하였으며, 분쇄와 자력선별에 의해 비소 성분이 원시료의 0.6 %에서 21.021 %까지 농축되는 것을 확인하였다.

• 응용통계연구
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• 제34권2호
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• pp.127-139
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• 2021

독립성분분석은 혼합 데이터로부터 독립된 신호들을 분리해내는 대표적인 통계적 방법론이며, 그룹 독립성분분석은 독립성분분석을 여러 개체에 적용할 수 있도록 확장한 방법론이다. 그룹 독립성분분석은 기능적 자기 공명 영상 데이터에 활용되어 의학적으로 유의미한 결과를 줌이 알려져있다. 그러나 자기 공명 영상 스캔에서 흔히 일어나는 이상치가 포함되어 있는 경우, 기존의 그룹 독립성분분석은 그 효과가 떨어짐이 알려져있다. 본 연구에서는 ROBPCA 기반의 로버스트한 그룹 독립성분분석 방법론을 제안하였다. 시뮬레이션과 실제 자료 분석을 통해 제안한 방법과 기존 방법을 비교하였고, 그 결과 제안한 방법론의 로버스트성을 입증했다.

• 지구물리와물리탐사
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• 제3권2호
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• pp.48-52
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• 2000

저주파수 전자탐사 관로 탐지기 개발 및 현장 운용시의 지침을 마련하기 위해 3차원 유한요소법을 이용해서 수평 자기 쌍극자 송신원에 의한 도전성 지하 매설 관로의 전자기 반응을 계산하고 그 특성을 분석하였다. 단일 관로의 전자기 반응은 수평 자기장 및 수직 자기장의 수평 차분치 모두 관로 직상부에서 최대값을 나타낸다. 반응 곡선에서 최대값의 1/2이 되는 위치의 폭은 수평 자기장의 경우 수직 자기장의 수평 차분치보다 2배 정도 넓으며, 이는 수직 자기장의 수평 차분치가 관로 위치 분해능이 높은 것을 의미한다. 그리고 관로의 심도 계산식이 관로의 직상부에서만 정의되기 때문에 분해능이 높은 수직 자기장의 수평 차분치를 측정하는 것이 관로 심도 결정시 유리할 것이다. 서로 2 m 떨어진 이중 관로의 전자기 반응은 수직 자기장의 수평 차분의 경우 송신기 하부 및 인접 관로의 상부 모두에서 반응 곡선의 피크가 보인다. 이에 반해 수평 자기장의 경우는 인접 관로에 의한 자기장은 송신기 하부 관로에 의한 자기장에 의해 상쇄되어 송신기 하부 관로에 의한 피크만 나온다. 이로 미루어 볼 때 지하에 다수의 관로가 인접하여 매설되어 있는 상황에서는 수직 자기장의 수평 차분을 측정함으로써 다수 관로의 탐지도 가능할 것으로 보인다. 그리고 반응 곡선의 폭을 비교할 때, 단일 관로에서와 마찬가지로 분해능은 수직 자기장의 수평 차분치를 측정하는 것이 수평 자기장을 측정하는 것에 비해 뛰어난 것으로 판단된다.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.538-548
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• 2003

We studied effects by Re$_2$O$_3$(R=Dy, Gd, Ho) addition on the properties of Mn-Zn ferrite. The doping concentration range from 0.05 wt% to 0.25 wt%. All samples were prepared by standard fabrication of ceramics. With increasing the rare earth oxides, specific density and initial permeability increased on the whole. But, the tendencies such as upper result had the measured value on limitation and characteristics saturated or decreased properties after that. In case of excessive addition of additive beyond some level, initial permeability properties of ferrite have gone down in spite of anomalous grain. With increasing the content of additive, both the real and imaginary component of complex permeability and the magnetic loss (tan$\delta$) increased. Because the increased rate of real component had higher than imaginary component, magnetic loss increased none the less for increasing the real component related with magnetic permeability. But, the magnetic loss of ferrite doped with the rare earth oxides was lower than that of Mn-Zn ferrite at any rate. The small amount of present rare earth oxides in Mn-Zn ferrite composition led to enhancement of resistivity in bulk, and more so in the grain boundary. It was seem to be due to the formation of mutual reaction such as between iron ions and rare earth element ions.

• 한국세라믹학회지
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• 제49권2호
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• pp.185-190
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• 2012

The purpose of this study was to examine a possibility that fly ash could be used as raw material for carbonation by conducting the experiment on magnetic separation and hydration of fly ash that contained a large amount of CaO composite. Wet magnetic separation experiment was performed to remove the component of magnetic substance that contained fly ash, which aimed at increasing the content of CaO in the non-magnetic domain. The selected fly ash was used for hydration experiment before the TG-DTA, XRF and XRD analyses were made to confirm the Ca component that could be carbonated. Then, the fly ash was turned to a hydrate that was favorable to dissociation of $Ca^{2+}$ ion. As a result, the magnetic separation enabled detecting the content of CaO component by up to 61 wt% in the non-magnetic domain. Since the hydrate was confirmed, it is believed that the fly ash can be used as raw material for carbonation.

• 수산해양기술연구
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• 제34권2호
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• pp.144-158
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• 1998

In order to study basic information on the developed electro-magnetic compass, experiments were carried out on board M. S. KAYA at the pier of Dong Kuk Steel Mill in Pusan and the Korean southern sea using a three-axis magnetic sensor from Jan. 21, 1995 to Feb. 14, 1996. The obtained results were as follows : 1. The amount of old metal on the pier was about 27,290tons~57,440tons with an average of 40,560tons, the artificial local disturbance at the pier was min. 27.1$\mu$T, max. 66.5$\mu$T, ave. 433$\mu$T for the horizontal component and min. -27.0$\mu$T, max. 45.1$\mu$T, ave. 3.7$\mu$T for the vertical component. Its direction of horizontal component was 305$^{\circ}$ with the ship's head up bearing at 225$^{\circ}$. 2. The ship's magnetic distribution on the starboard side on berthing at the pier was 17.4$\mu$T for the horizontal component and -6.2$\mu$T for the vertical component. On the ship's port side, it was 19.8$\mu$T for the horizontal component and 4.1$\mu$T for the vertical component. On the ship's starboard side at sea, the ship's magnetic distribution was 19.2$\mu$T for the horizontal component and 3.2$\mu$T for the vertical component. On the ship's port side, the readings were 22.0$\mu$T for the horizontal component and -1.8$\mu$T for the vertical component. The directions of these readings were nearly starboard side. 3. On the pier, the secular change of the artificial local disturbance decreased 8.3$\mu$T from 61.0$\mu$T to 52.7$\mu$T for the horizontal component and decreased 7.1$\mu$T from 8.9$\mu$T M 1.8$\mu$T for the vertical component. On the starboard side from its berth, the ship, s magnetic distribution increased 2.6$\mu$T from 14.8$\mu$T to 17.4$\mu$T for the horizontal component and increased -0.1$\mu$T from -6.1$\mu$T to -6.2$\mu$T for the vertical component. On the ship's port side from its berth, it increased 7.1$\mu$T from 12.7$\mu$T to 19.8$\mu$T for the horizontal component and increased 10.2$\mu$T from -6.1$\mu$T to 4.1$\mu$T for the vertical component. 4. While at sea, on the ship's starboard side, the Secular change of the ship's magnetic distribution increased 3.9$\mu$T from 15.3$\mu$T to 19.2$\mu$T for the horizontal component and increased 2.0$\mu$T from -5.2$\mu$T to -3.2$\mu$T for the vertical component. On the port side, the changes increased 11.4$\mu$T from 10.6$\mu$T to 22.0$\mu$T for the horizontal component and increased 4.9$\mu$T from -6.7$\mu$T to -1.8$\mu$T for the vertical component. Upon berthing at the pier, the deviation of the secular change increased westerly 1 degree W~ 2.5$^{\circ}$ W from 3.5$^{\circ}$ W~ 5$^{\circ}$ W M 6W with the ship's head up bearing at 225$^{\circ}$. While at sea, these increased westerly 2$^{\circ}$ ~ 3$^{\circ}$ from the Northeast to the South and increased easterly 1$^{\circ}$ ~ 8$^{\circ}$ from the Southwest to the North. 5. While at port, within 1 mile between the ship and berth of the pier, as we approached the pier, the westerly deviation increased and when we departed the pier easterly deviation increased. When approaching the pier, the deviation was smaller than the deviation when the ship was departing from the pier. When approaching the bearing at 225$^{\circ}$ with the ship's head up bearing, the varies of deviation was smaller than the varies when the ship's head up bearing was departing from it.