• 한국자기학회지
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• 제5권6호
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• pp.963-967
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• 1995

Ni/Cu 인공초격자의 계면에 얇은 NiFeCo와 NiFe층을 삽입시 Ni/Cu 인공초격자의 자기 저항 거동에 미치는 영향에 관해 연구하였다. NiFe층이 Ni/Cu 인공초격자의 계면에 삽입된 경우 6%의 자기저항과 50 Oe의 포화자장을 보였으며 이때의 자기저항곡선은 hysteresis를 거의 보이지 않았다. NiFeCo층이 삽입된 경우는 자기저항값은 7%를 보였으나 포화자장과 hysteresis가 많이 증가하였다. 교류자장원을 이용한 동적자기저항을 측정한 결과 bias 자장하에서 자기저항의 증가폭이 NiFe층을 삽입한 경우가 NiFeCo를 삽입한 경우보다 컸으며 이는 hysteresis가 작았기 때문으로 해석된다.

• Journal of Magnetics
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• 제18권1호
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• pp.26-29
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• 2013

$Mn_xFe_{3-x}O_4$ powders have been fabricated by using sol-gel methods; their crystallographic and magnetic properties were investigated by using X-ray diffraction, scanning electron microscopy, M$\ddot{o}$ssbauer spectroscopy, and vibrating sample magnetometer. The $Mn_xFe_{3-x}O_4$ ferrite powders annealed at $500^{\circ}C$ had a single spinel structure regardless of the $Mn^{2+}$-doping amount and their lattice constants became larger as the $Mn^{2+}$ concentration was increased. Their Mossbauer spectra measured at room temperature were fitted with 2 Zeeman sextets due to the tetrahedral and octahedral sites of Fe ions, which made them ferrimagnetic. The magnetic behavior of $Mn_xFe_{3-x}O_4$ powders showed that the $Mn^{2+}$-doping amount made their saturation magnetization increase, but there were no severe effects on their coercivities. The saturation magnetization of the $Mn_xFe_{3-x}O_4$ powder varied from 38 emu/g to 70.0 emu/g and their minimum coercivity was 111.1 Oe.

• Journal of Magnetics
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• 제19권3호
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• pp.210-214
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• 2014

The effects of manganese substitution on the crystallographic and magnetic properties of Li-Zn-Cu ferrite, $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$ ($0.0{\leq}x{\leq}0.8$), were investigated. Ferrites were synthesized via a conventional ceramic method. We confirmed the formation of crystallized particles using X-ray diffraction, field emission scanning electron microscopy and $M{\ddot{o}}ssbauer$ spectroscopy. All of the samples showed a single phase with a spinel structure, and the lattice constants linearly decreased as the substituted manganese content increased, and the particle size of the samples also somewhat decreased as the doped manganese content increased. All the $M{\ddot{o}}ssbauer$ spectra can be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites, and one doublet. The cation distribution was determined from the variation of the $M{\ddot{o}}ssbauer$ parameters and of the absorption area ratio. The magnetic behavior of the samples showed that an increase in manganese content led to a decrease in the saturation magnetization, whereas the coercivity was nearly constant throughout. The maximum saturation magnetization was 73.35 emu/g at x = 0.0 in $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$.

• 대한기계학회논문집A
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• 제24권5호
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• pp.1166-1174
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• 2000

In this paper, we introduce a positioner based on magnetic levitation to eliminate the friction which is the most severe effect to limit high resolution on the micro level. Differently from existing electromagnetic device, the proposed positioner consists of air core solenoid and permanent magnet. Although the combination produces small magnetic force, it is suitable for realizing micro motion repeatedly without the accumulation of error because there is no hysteresis caused by ferromagnetic materials, no eddy current loss, no flux saturation. First, the approximate modeling of stiffness and damping effects between the magnetic elements is made and verified experimentally. Then, we have formulated the dynamic equation of one d.o.f magnetic levitation positioner using linear perturbation method and discussed the necessity of optimization for the chief design parameters to maximize the stability performance.

• Journal of Magnetics
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• 제14권3호
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• pp.104-107
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• 2009

The effects of the magnetic property variation on current-induced magnetization switching in magnetic tunnel junction with perpendicular magnetic anistoropy (PMA) and the soft magnetic polarization-enhancement layers (PELs) inserted between the layers with PMA and the MgO layer was studied. A micromatnetic model was used to estimate the switching time of the free layer by different applied current densities, with changing saturation magnetization ($M_s$) of the PELs, interlayer exchange coupling between PMA layers and PELs. The switching time could be significantly reduced at low current densities, by increasing $M_s$ of PELs and decreasing interlayer exchange coupling.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.253-257
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• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• Advances in concrete construction
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• 제5권2호
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• pp.87-99
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• 2017

After passing through a magnetic field, the physical quality of water improves, and magnetic water (MW) is produced. There are many investigations on the effects of magnetic field on water that shows MW properties like saturation and memory effect. This study investigates the fresh and hardened properties of concrete mixed with MW, which contains silica fume (SF) and superplasticizer (SP). The test variables included the magnetic field intensity for producing MW (three kinds of water), SF content replaced cement (0 and 10 percent), water-to-cementitious materials ratio (W/CM=0.25, 0.35 and 0.45) and curing time (7, 28 and 90 days). The results of this study show that MW had a positive impact on the workability and compressive strength of concrete. By rising the intensity of the magnetic field which was used for producing MW, its positive influence on both workability and compressive strength improved. MW had greater positive impacts on samples containing SP that did not have SF. Moreover, the best compressive strength improvements of concrete achieved as W/CM ratio decreased.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.9-13
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• 2004

This paper proposes a modified current differential relay for Y-$\Delta$ transformer protection. The relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. A method to estimate the circulating component of the delta winding current is proposed. To cope with the remanent flux, before saturation, the core-loss current is calculated and used to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Test results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation because the exciting current was successfully compensated. The relay correctly discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

• 한국자기공명학회논문지
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• 제6권2호
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• pp.94-102
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• 2002

An interesting recent application of intermolecular NOE experiment is the saturation transfer difference NMR(STD-NMR) method that is useful in screening compound libraries to identify bio-active ligands. This technique also identifies the group epitopes of the bound ligand in a reversibly forming protein-ligand complex. We present here a complete relaxation and conformational exchange matrix (CORCEMA) theory (Moseley et al., J. Magn. Reson. B, 108, 243-261 (1995)) applicable for the STD-NMR experiment. Using some ideal model systems we have analyzed the factors that influence the STD intensity changes in the ligand proton NMR spectrum when the resonances from some protons on the receptor protein are saturated. These factors will be discussed and some examples of its application in some model systems will be presented. This CORCEMA theory for STD-NMR and the associated algorithm are useful in a quantitative interpretation of the STD-NMR effects, and are likely to be useful in structure-based drug design efforts. They are also useful in a quantitative characterization of protein-protein (or protein-nucleic acid) contact surfaces from an intermolecular cross-saturation NMR experiment.

• 한국자기학회지
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• 제4권2호
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• pp.135-141
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• 1994

스퍼터방식으로 제조한 FeZrCrN 미결정박막의 질소 유입량의 변화와 Cr 첨가량 변화에 따라 연자기특성과 내반응성 및 내식성을 조사하였다. 질소 유립량 증가에 따라 포화자속밀도는 감소하고 적 절한량(질소 유입량 3%)의 질소가 유입 되었을 때 열처리후에도 이방성 분산 감소효과 등에 의하여 우수 한 연자기특성이 출현 하였으며, 이때 보자력은 0.4 Oe, 투자율은 5 MHz에서 2600 정도를 나타내었다. FeZrN 박막에 Cr을 7.5 at.% 정도 첨가하였을때 포화자속밀도는 12.5kg까지 감소하였지만 양호한 연자기 특성이 그대로 유지되었고 Cr 첨가에 의해 현저한 내식성의 향상과 집합 glass와의 내반응성의 개선이 있었다.