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김영학,Kim, Y.H. 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.2
본 논문에서는 Co를 주성분으로 하는 아몰퍼스 자성 와이어를 동축케이블의 신호선으로 하는 자계센서를 제작하여 외부자계에 대한 특성을 측정하였다. 측정된 임피던스의 주파수의존성에는 전송선로의 공진특성이 반영되었으며 인가자계가 없을 때, 1/4 파장에 해당하는 주파수가 250 MHz에서 나타났다. 측정 주파수대역에서는 표피효과에 의한 저항성분이 임피던스를 거의 결정하였으며 또한 외부자계가 $0\;Oe{\sim}1\;Oe$ 사이에서 임피던스는 자성 아몰퍼스와이어의 투자율의 변화에 의해 크게 변화하였다. 0.1 Oe 부근에서 150 MHz의 ${\Delta}Z/{\Delta}H$가 $300{\Omega}/Oe$이라는 매우 큰 값이 얻어져 Co를 주성분으로 하는 자성와이어를 동축케이블형 자계센서로 사용하는 경우 센서로서 매우 유용함을 알 수 있었다. Co-based amorphous magnetic wire with a diameter of $125{\mu}m$ and a length of 40 mm was used as an inner conductor of a coaxial cable to construct a magnetic sensor. Sensor characteristics was measured up to 3 GHz with applied up to 60 Oe by using network analyzer. Frequency dependence of impedance for this sensor was very close to the impedance resonant pattern of transmission line and 250 MHz was obtained as a 1/4 wavelength without external magnetic field. Large impedance change was measured in the magnetic field range between 0 Oe and 1 Oe, which was influenced by permeability change of magnetic amorphous wire. Because ${\Delta}Z/{\Delta}H$ value of $300{\Omega}/Oe$ was obtained at 0.1 Oe, this coaxial cable with amorphous wire can be useful as a magnetic sensor.
허진,김영학,신광호,사공건,Hur, J.,Kim, Y.H.,Shin, K.H.,Sa-Gong, G. 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.1
Magneto-Impedance(MI) sensor is a highly sensitive sensor, which was able to detect a weak geomagnetic field. It also has a merit to be able to build in the low power system. In this study, their magnetic permeability and anisotropy field(H$\sub$k/) as a function of some different thickness of sputtered amorphous CoZrNb films with zero-magnetostriction and soft magnetic property are investigated. In order to make a uniaxial anisotropy, film was subjected to the post annealing in a static magnetic field with 1KOe intensity at 250, 300, and 320$^{\circ}C$ respectively for 2 hours. Magnetic properties of films are measured by using a M-H loop tracer. Magnetic permeability of a film is measured over the frequency range from 1 ㎒ to 750㎒. By thickening a CoZrNb film relatively, magnetic permeability and impedance are examine to design the. MI sensor which drives at 50㎒, and thereof fabricated the MI sensor which drives at the 50㎒.
3차 재결정에 의한 극박 방향성 규소강판의 결정립 크기와 자벽수와의 관계
김영학(Y. H. Kim),荒井賢一(K. I. Arai) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.3
The relationship between grain size and number of magnetic domain walls for tertiary recrystallized ultra thin 3% Si-Fe strips was investigated. It was found that the strips with different grain size can be produced by controlling the inserting speed of sample in annealing furnace. Though grain size of the stirip became smaller than 1㎜, B_8 of high value above 1.95T was obtained. But Hc increased with decaying the grain size. The magnetic domains and losses of the ultra thin grain oriented silicon steel with smaller grain size were observed. The eddy current losses of the strips were decreased with decreasing the grain size in high frequency range because strips with smaller grain have narrower magnetic domain wall spacings. But Hysteresis losses of the strips with smaller grain have high value in low frequency range. Therefore the iron loss of ultra thin grain oriented silicon steel could be controlled by the grain size. It was clarified that the minumum tatal loses depended on the exciting frequency and grain size.
김영학(Y. H. Kim),荒井賢一(K. I. Arai) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
This paper discussed on the observation of dynamic domain patterns using Lorentz SEM in the frequency region of 50 ㎐-10 ㎑. The observed dynamic domain patterns were compared with the simulated ones. The observation method is characterized by using the slight difference between the exciting frequency and the multiples of the scannning frequency of SEM.
김영학(Y. H. Kim),송재성(J. S. Song) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.3
This paper discussed on the impedance analysis of the planar air core inductors having spiral pattern and meander pattern. The width and distance of conductor, and number of turns were varied. As the width of conductor increased, both resistance and inductance decreased and there existed an maximum value in Q for spiral pattern. But Q increased with increasing width of conductor in meander pattern. In spiral pattern, there existed a distance between conductors where inductance became constant and Q became maximum, while the distance between conductors must be as large as possible to obtain large Q because the mutual inductance of meander pattern inductor has negative sign due to opposite current direction at adjacent conductor. Resistance and inductance increased with increasing the number of turns. There existed maximum Q at certain number of turns in spiral pattern. But Q became small in the meander pattern because increase of resistance was larger than increase of inductance with increasing number of turns.
비정질 와이어를 센서헤드로 이용한 금속의 미세결함 검출
김영학(Y. H. Kim),신광호(K. H. Shin) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.5
Ac magnetic field was changed in the vicinity of a flaw because of the distribution of eddy current within a conductor, when the magnetic field was applied to a conductor having a flaw. The flaw detection was performed by using Co-based amorphous wire sensor head. The wire has almost 0 magneto-striction and high permeability. An comparative uniform magnetic field was applied to a 1 ㎜ thick copper plate and a 25 ㎛ thick aluminum sheet conductor using spiral typed coil. The size of the coil has 40 ㎜×40 ㎜ outer width and 8 ㎜× 8 ㎜ inner width. The copper plate and the aluminum sheet has 0.5 ㎜ and 0.1 ㎜ wide gap, respectively. The frequency range of applied field was 100 ㎑-600 ㎑. The induced voltage difference of 2.5 ㎷ was obtained in the maximum voltage and minimum one measured across the gap of the 1㎜ thick conductor. In the case of aluminum sheet, 0.4 ㎷ was obtained. From this results, the effectiveness of Co-based amorphous wire was confirmed in the ECT technique.