• Journal of Magnetics
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• v.18 no.3
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• pp.245-249
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• 2013

A finite element model was built for MnBi/${\alpha}$-Fe nanocomposite permanent magnets, and the demagnetization curves of the magnets were simulated by micro-magnetic calculation. The microstructure of the cubic model is composed of 64 irregular grains with an average grain size of 20 nm. With the volume fraction of soft magnetic phase (t vol. %) ranged from 5 to 20 vol. %, both isotropic and anisotropic nanocomposite magnets show typical single-phase permanent magnets behavior in their demagnetization curves, illustrating good intergranular exchange coupling effect between soft and hard magnetic phases. With the increase of volume fraction of soft magnetic phase in both isotropic and anisotropic magnets, the coercive force of the magnets decreases monotonically, while the remanence rises at first to a peak value, then decreases. The optimal values of maximum energy products of isotropic and anisotropic magnets are 84 and $200kJ/m^3$, respectively. Our simulation shows that the MnBi/${\alpha}$-Fe nanocomposite permanent magnets own excellent magnetic properties and therefore good potential for practical applications.

• Journal of The Korean Astronomical Society
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• v.44 no.3
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• pp.97-108
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• 2011

The photometric light curves of the W-type W UMa eclipsing contact binary system BB Pegasi have been found to be extremely asymmetric over all the observed 63 years in all wavelengths UBVR. The light curves have been characterized by occultation primary minima. Hence, the morphology of these light curves has been studied in view of these different asymmetric degrees. The system shows a distinct O'Connell effect, as well as depth variation. A 22.96 years of stellar dark spots cycle has been determined for the system. Almost the same cycle (22.78 yr) has been found for the depth variation of MinI and MinII. We also present an analysis of mid-eclipse time measurements of BB Peg. The analysis indicates a period decrement of $5.62{\times}10^{-8}$ day/yr, which can be interpreted in terms of mass transfer at a rate of $-4.38{\times}10^{-8}M_{\odot}$/yr, from the more to the less massive component. The O - C diagram shows a damping sine wave covering two different cycles of 17.0 yr and 12.87 yr with amplitudes equal to 0.0071 and 0.0013 day, respectively. These unequal durations show a non-periodicity which may be explained as a result of magnetic activity cycling variations due to star spots. The obtained characteristics are consistent with similar chromospherically active stars, when applying the Applegate's (1992) mechanism.

• Annals of Clinical Neurophysiology
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• v.13 no.1
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• pp.38-43
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• 2011

Background: In the brain, the dominant primary motor cortex (M1) has a greater hand representation area, shows more profuse horizontal connections, and shows a greater reduction in intracortical inhibition after hand exercise than does the non-dominant M1, suggesting a hemispheric asymmetry in M1 plasticity. Methods: We performed a transcranial magnetic stimulation (TMS) study to investigate the hemispheric asymmetry of paired associative stimulation (PAS)-induced M1 plasticity in 9 right-handed volunteers. Motor evoked potentials (MEPs) were measured in the abductor pollicis brevis (APB) muscles of both hands, and MEP recruitment curves were measured at different stimulation intensities, before and after PAS. Results: MEP recruitment curves were significantly enhanced in the dominant, but not the non-dominant M1. Conclusions: These results demonstrate that the dominant M1 has greater PAS-induced plasticity than does the non-dominant M1. This provides neurophysiological evidence for the asymmetrical performance of motor tasks related to handedness.

• Progress in Superconductivity
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• v.7 no.1
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• pp.22-27
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• 2005

We have studied the standardization of critical temperature measurements by using an ac susceptometer. Wire forms of NbTi, $Nb_{3}Sn$, and Bi-2223 superconductors were prepared to measure the temperature dependences of the magnetization. In order to study the optimum ac magnetic field and frequency, various amplitudes from 2 Oe to 10 Oe with frequencies from 11.3 Hz to 1033 Hz were applied to three specimens. Analytical comparison of the magnetic curves with the resistive curves was accomplished to investigate validity of using the new method.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.91-93
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• 2003

Disk type Single Phase SRM(Switched Reluctance Motor) can be used axial direction magnetic flux and radial direction magnetic flux. In this paper, the flux linkage was measured according as rotor positions of disk-tyre single phase SRM, which is designed and manufactured in previous research. From the measured data, we got the magnetization curves, inductance profile and Co-energy.

• Journal of the Korean Institute of Navigation
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• v.12 no.2
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• pp.23-32
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• 1988

This paper offers a method of magnetic compass adjustment for the vessel alongside the wharf using newly designed magnetic north former, which makes the same magnetic field-change as the turning vessel does. The characteristics of the magnetic north former was examined by observing the deviation curves of the magnetic compass installed on the compass deviascop at laboratory. The magnetic north former consists of A and B arms which hold the permanent bar magnets at the both ends of each arm. The arm is to rotae in the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal component of the earth's field. The B arm makes the artificial magnetic north around the magnetic compass for every ship's heading. The results of investigation are summarized as follows ; 1. The observation and correction of magnetic compass deviation can be done without swinging the ship, of the effect of D coefficient is negligible. 2. The residual deviation curve of the magnetic compass depends on the accuracy of deduced value of ship's multplier($\lambda$). 3. The errors due to the inaccuracy of deduced value of ship's multiplier change in the same way as the B and C coefficient do.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.83-85
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• 2007

In magnetic field analysis of electrical machines, hysteresis phenomena of B-H curves should be taken into account in order to obtain more accurate results. In this paper, the hysteresis modeling using the micromagnetics for the magnetic field analysis is investigated. In the micromagnetics, usually, it takes much CPU times. Therefore, the method for representing hysteresis phenomena by minimum modeling is investigated in order to applying it to the magnetic field analysis. First, the micromagnetics is described. Then, the method of minimum modeling is shown. Finally, the hysteresis curve obtained by the minimum modeling is demonstrated. The effect of parameters of micromagnetics on the shape of hysteresis curve is investigated.

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.102-103
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• 1998

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.130-131
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• 1998

• Proceedings of the Korean Magnestics Society Conference
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• 1994.03a
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• pp.90-91
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• 1994