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Ultra - Soft Magnetic Properties in Nanocrystalline Fe81B₁₁Nb7Cu₁ Alloy
Heebok Lee,Kyeong-Jae Lee,Yong-Kook Kim,Sung-Ho Yoon,Taik-Kee Kim,Seong-Cho Yu 한국자기학회 2000 Journal of Magnetics Vol.5 No.3
The extremely soft magnetic behaviors in the nanocrystalline Fe_(81)B₁₁Nb_7Cu₁ alloy annealed at 450 ℃ and 550 ℃ for 1 hour in a vacuum were investigated by means of the magnetoimpedance (MI) effect and the incremental permeability. Because the MI effect can be obtained only in ultra-soft magnetic materials, the improvement of magnetic softness by proper thermal treatment was carefully monitored by the MI effect for all annealed samples. The changes of the incremental permeability as a function of an external field were also measured to verify the magnetic softness along with the MI measurement.
Magnetoimpedance Effect in Nanocrystalline Fe91.5-xZr7BxCu₁Al0.5 (x = 2, 4, 6, 8) Alloys
Heebok Lee,Yong-Kook Kim,Taik-Kee Kim,Chong-Oh Kim,Seong-Cho Yu 한국자기학회 2002 Journal of Magnetics Vol.7 No.1
The magnetoimpedance of Fe_(91.5-x)Zr_7B_xCu₁Al_(0.5) (x = 2, 4, 6, 8) alloys has been measured to investigate the influence of structural changes in the nanocrystallization process after thermal treatment. Annealing was performed at temperatures of 350℃, 450℃, and 550℃ for 1 hour in a vacuum. Ultra soft magnetic behavior was observed in the samples annealed at 550℃. The magnetoimpedance ratio and the longitudinal permeability ratio coincided with the softness of the magnetic properties of the thermally treated samples.
Heebok Lee,Yong-Seok Kim,Seong-Cho Yu 한국자기학회 2002 Journal of Magnetics Vol.7 No.4
A new discovery of the super-giant magneto-impedance (SGMI) effect was found out in a LC-resonator consisted of a glass-coated amorphous Co_(83.2)B_(3.3)Si_(5.9)Mn_(7.6) microwire. The measurement was carried out at high frequency range from 100 ㎒ up to 1 ㎓ of an ac-current flowing along the wire and at varying axial dc-magnetic field in its range of ±120 Oe. The wires, about 16 ㎛ in diameter, were fabricated by a glass-coated melt spinning technique. The shape of the impedance curves plotted vs. a dc-field is changing dramatically with the frequency. The phase angle was also strongly dependent on this field. The external dc-magnetic field changes the circumferential permeability as well as the penetration depth, both in turn change the impedance of the sample. The drastic increments of SGMI at high frequency can be understood in terms of the LC-resonance phenomena. The sudden change of the phase angle, as large as 180°, evidenced the occurrence of the resonance at a given intensity of the external dc-field. The maximum ratio of SGMI reached in the experiment by precise tuning frequency equals 450,000% at the frequency of around 551.9075 ㎒.
Temperature dependence of magnetoimpedance effect in amorphous CO?? Fe₄NiB?? Si? ribbon
Lee, Heebok,Cho, W.S,Kim, C.O,Kim, T.K,Kim, Y.K 公州大學校 基礎科學硏究所 1998 自然科學硏究 Vol.7 No.-
The temperature dependence of the magnetoimpedance (MI) effect is important both for scientific study and for thermal stability of MI sensors. We have performed the measurement of MI effect in amorphous Co66Fe4 NiB14Si15 (Metglas 2714A) ribbon from a cryogenic chamber where the temperature of the sample can vary from 10 to 300 K. The ac current was fixed at 10 mA for all measured frequencies ranging from 100 kHz to 10 MHz. The magncioimpedancc ratio (MIR) was revealed the drastic increment as a function of MIR(T)=MIR(O)exp(cT2), where c is a constant. The measured MIR values at room temperature are usually 2-3 times larger than the data measured at 10 K for all measured frequencies. However, the shapes of the MIR curves are remained. This result shows the potential application of the MI effect for a temperature sensor.
시험 DFSS기법을 이용한 릴레이의 고장인자 영향도 분석
이희복(Heebok Lee),위신환(Shinhwan Wi),엄학용(Hakyong Eom),성기우(Kiwoo Sung),이용(Yong Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
Failure factors of the automotive relay are operating voltage, load voltage, temperature and chattering count. In order to analyze effects of failure factors for the relay, effects of them are solved through DFSS method. In this study, the effect of failure factors is analyzed under the same load. The final results are as follows; ⅰ) Experiment is designed by L? tables of orthogonal arrays. ⅱ) failure factors of four types are used as control factors. And 3 levels are used. ⅲ) The influence of failure factors is interpreted in the following orders; (1. Chattering count 2. Load voltage. 3. Temperature. 4. Operating voltage.) ⅳ) finally for these reason, influence of failure factors is analyzed and verified.
이희복(Heebok Lee),위신환(Shinhwan Wi),박상욱(Sangwook Park),김형민(Hyungmin Kim),이경택(Kyungteak Lee),김성우(Seongwoo Kim) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
Generally, failure of the automotive relay is considered as N.T.F (No Trouble Found) failure. Therefore, reason and mechanism of the failure should be solved by detailed analysis through development of failure reappearance test. In this study, failure root-cause analysis and field environmental analysis are performed for determining conditions of failure reappearance in automotive relay. And field failure of the relay is reproduced by using these conditions. The results show failure mode of the relay, an effect of switching velocity and a failure reappearance test under the failure mode and field conditions.