• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.599-606
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• 1998

Since the discovery of ceramic superconductor the various theoretical developments has progressed but there are no definitive description about the superconducting transition mechanism. In special, both the double transition and the various magnetic phase transition add to the complication of the understanding of HTSC. In this paper, we presented the idea of the two-step mechanism for the superconducting transition in view of the condensation model of electron fluid for superconductivity. And these concepts are successfully applied to the double transition and the magnetic phase diagram of various types of superconductivity. Therefore, both the double transition and magnetic phase transition should be the touchstone of general theory for superconductivity.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.1053-1058
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• 1989

This paper presents the preliminary studies on measurements of dynamic torque in the rotating shaft by utilizing the magnetic lattice. The intensity of torque can be detected as the phase differences between two magnetic sinusoidal signals recorded on magnetic tapes wound on the shaft. This research describes, from the data concerning with phase differences including noise, a method of signal processing to estimate the true value of the torque.

• Journal of Magnetics
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• v.16 no.4
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• pp.403-407
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• 2011

Metal-insulator type, nano-granular soft magnetic films have been reviewed from the viewpoint of high frequency magnetic materials. The formation of nano-granular structure is related to the magnitude of heat of formation of intergranule materials. Variation of the ratio of granule phase to intergranule phase in the film is found to produce various characteristics in the magnetic properties of the film. The HRTEM observation reveals that neighboring granules in the film with above 60 at.% Co, contact at considerable points and the films show soft magnetic properties which are explainable in terms of the random anisotropy model for nano-crystalline materials. Addition of Ni group elements in Co-O based films enhances their anisotropy field up to 400 Oe and they exhibit excellent frequency response of permeability. Also, large electromagnetic noise suppression effect is demonstrated as one of their potential applications.

• Journal of Magnetics
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• v.18 no.4
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• pp.405-411
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• 2013

The structural, magnetic and magnetocaloric properties of $CoMn_{1-x}Cr_xGe$ (x=0.05-0.125) have been investigated by using electron microscopy, x-ray diffraction, calorimetric and magnetic measurements. In this study, our aim is to justify the magnetocaloric effect by tuning the structural and magnetic transition temperature with Cr doping on CoMnGe pure system. The substitution of Cr for Mn leads to a decrease of both structural and magnetic transition temperatures. However, structural and magnetic transition temperatures do not close to each other. From magnetization measurement, we calculate that isothermal entropy change associated with magnetic transition can be as high as 3.82 J $kg^{-1}K^{-1}$ at 302 K in a field of 7 T. Meanwhile, structural phase transition contribution to isothermal entropy change is calculated as 5.85 J $kg^{-1}K^{-1}$ at 322 K for 7 T.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.115-121
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• 2014

The intrinsic simplicity, ruggedness, and simple power electronic drive requirement of a Switched Reluctance Motor(SRM) make it possible to use in many commercial adjustable speed application. The simple magnetic circuit results in a high efficiency drive and low temperature rise, and the drive system provides a good drive characteristics. This paper is provides two phase 4/3 SRM that is similar to two phase 6/3 SRM as aspect to magnetic structure. Although 6/3 SRM does not experience any flux reversal as the flux is in the same direction whether phase A or B is excited, but two phase 4/3 SRM experiences a flux reversal in small part of stator yoke. The flux reversal in two phase 4/3 SRM could be relieved by an adjustment of stator yoke structure. The magnetic analysis and design considerations of the two phase 4/3 SRM have been obtained by the finite element method analysis (FEM).

• Journal of Biomedical Engineering Research
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• v.22 no.3
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• pp.303-309
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• 2001

It is well known that the electrical impedance of biological tissues is very sensitive to their temperature. In this paper, we have analyzed the effects of temperature change on the phase of magnetic resonance images obtained with external current injection. It has been found that the local phase in the current injected magnetic resonance image can be changed noticeably when local temperature change appears at a part of the tissue. At the experiments with a 0.3 Tesla MRI system, we observed the local phase changes at the phantom images when the phantom temperature was varied between 25 -45$^{\circ}C$. We think that the current injection MRI technique can be used for in-vivo monitoring of the temperature inside biiological tissues if the relation between the local temperature and phase can be quantified.

• Investigative Magnetic Resonance Imaging
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• v.19 no.3
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• pp.200-204
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• 2015

Image findings of hepatic lymphoma have been reported as variable, ranging from single or multiple small nodules to diffuse infiltrative patterns. On MRI, most hepatic lymphomas show T1 low signal intensity, T2 high signal intensity. Dynamic imaging reveals a hypointense appearance in the arterial phase, followed by delayed enhancement in the portal venous and transitional phase. In the hepatobiliary phase using a hepatocyte-specific contrast agent (which have recently aided in increasing the access to the focal liver lesions), hepatic lymphoma is known to exhibit low signal intensity. We report a case of hepatic lymphoma, which shows iso-signal intensity on hepatobiliary phase, using gadoxetic acid (Gd-EOB-DTPA).

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1678-1680
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• 1998

The purpose of this study is to obtain optimum arrangement of phase conductors in minimizing magnetic field from overhead transmission lines. Data of the transmission lines rated 345 kV of the KEPCO(Korea Electric Power Company)'s system were used. For a three phase-double circuit transmission line, low-reactance arrangement is optimum in minimizing magnetic fields. For a three phase-four circuit, optimum phase arrangement is a-b-c-b-a-c(lower two circuits, clockwise)/b-c-a-c-a-b(upper two circuits, clockwise).

• Journal of the Korean Magnetic Resonance Society
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• v.21 no.2
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• pp.63-66
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• 2017

The $^{14}N$ NMR spectra for $(NH_4)_2SO_4$ crystals were obtained near the phase transition temperature $T_C=223K$, and were found to precisely reflect the symmetry change in the crystal at this first-order phase transition. Changes in the resonance frequencies near $T_C$ were attributed to the structural phase transition. In the ferroelectric and paraelectric phases, two inequivalent NH4 groups were distinguished in the $^{14}N$ NMR spectra. The two types, $NH_4$(1) and $NH_4$(2), have slightly different local environments. Consequently, we conclude that the phase transition is caused by the change in the environment of the $^{14}N$ nuclei in the $NH_4$ groups, rather than by the $SO_4$ groups.

• Journal of Magnetics
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• v.2 no.1
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• pp.1-6
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• 1997

The magnetic and magnetostrictive properties of melt-spun ribbons of the alloys (R0.33Fe0.67)1-xBx (R=Tb0.3Dy0.7 and 0$\leq$x$\leq$0.06) are ivestigated as a function of wheel speed during melt-quenching. The saturation magnetiation of the alloys with a crystalline phase ranges from 70 to 80 emu/g and does not vary substantially with the B content. The saturation magnetization of an amorphous phase, which is formed at the condition of thigh wheel speed and high B content, is reduced significantly, however. The coercive force is minimum at x= 0.02 and increases monotonously with the further increase of B content when the microstructure mainly consists of a crystalline phase, but again it is reduced significantly by the formation of an amorphous phase. The low field sensitivity of magnetostriction with magnetic field is found to be good for the alloys with x$\leq$0.04 over a wide range of wheel speed. This magnetostrictive behavior is in contrast with that observed previously for Dy-Fe and Tb-Fe based alloys and is thought to be due to low intrinsic magnetocrystalline anisotropy of the compound.