• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05a
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• pp.96-99
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• 2004

The combination of mechano-chemical activation and Self-propagating High-temperature Synthesis (SHS) has widened the possibilities for both methods. For YBCO systems the investigation showed that a short-term mechano-chemical activation of initial powders before SHS leads to single-phase and ultra-fine products. A new technique for preparation ultra-fine high-temperature superconductors of YBCO composition with a grain size d ＜1 ${\mu}{\textrm}{m}$ is developed. The specific feature of the technique is formation of the YBa$_2$Cu$_3$O$_{7-{\delta}}$ crystalline lattice directly from an X-ray amorphous state arising as a result of mechanical activation of the original oxide mixture. The technique allows the stage of formation of any intermediate reaction products to be ruled out. X-ray and magnetic studies of ultra-fine high temperature superconductors (HTS) are carried out. Dimension effects associated with the microstructure peculiarities are revealed. A considerable enhancement of inter-grain critical currents is found to take place in the ultra-fine samples.fine samples.

• Electrical & Electronic Materials
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• v.5 no.1
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• pp.8-13
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• 1992

일련의 Al/Tb-Fe-Co 다층박막 시편이 DC마그네트론 스퍼터링에 의해 제조되었다. 이 박막들은 (xA/yB)n의 형태이고 여기서 x와 y는 각각 Al 및 Tb-Fe-Co 박막의 두께를 나타내고 n은 각 박막의 수를 나타낸다. 각 박막의 두께는 2~40nm이다. Al과 Tb-Fe-Co박막의 두께변화에 따른 다층박막의 자기적 성질이 vibration sample magnetometry(VSM)에 의해 측정되었다. 이들 다층박막은 동일한 스퍼터링조건에서 제조되고 수평 자기적 이방성 특성을 보이고 있는 단층 Tb-Fe-Co박막을 기준시편으로 하여 자기적 성질이 비교되었다. 다층박막 시스템에서는 현저한 계면 또는 박막두께의 효과가 발견되었으며 이들 효과에 의해 단층박막의 수평자기체가 다층박막에서는 강한 수직자기체로 변화되는 것을 알 수 있고, 또한 Al과 Tb-Fe-Co합금 경계구역에 스퍼터링에 따른 약 2nm두께의 dead layer가 존재함이 입증 되었다.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1264-1266
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• 2005

This paper analyzes static and transient response characteristics of a permanent magnet type stepping motor with claw poles using three-dimensional finite element method. The outer diameter of the stepping motor to be analyzed is approximately 6 mm. In this paper we analyzes only 2 poles of the stepping motor, which has 10 magnetic poles made up of NdFeB material, using periodic boundary condition. We clarify transient response and static torque charateristics using Maxwell 3D and Matlab Simulink.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.990-992
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• 2005

This paper presents a new magneto-thermal finite element analysis for predicting the temperature rise of the EHV GIS bus bar. The power losses of a bus bar calculated by the magnetic field analysis are used as the input data to predict the temperature rise for the thermal analysis. The heat-transfer coefficients on the boundaries are analytically calculated by applying the Nusselt number considering material constant and model geometry for the natural convection. The temperature distribution in a bus bar by coupled magneto-thermal finite element analysis shows good agreement with the experimental data.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.28-30
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• 1998

In this paper, voltage source FEA considering hysteresis characteristics for a simple electrical system is presented because most electrical machines is used under the voltage sources. The magnetization dependent hysteresis model is used for this analysis and the magnetic materials considered in this simulation are iron core and semi-hard material. For a sinusoidal voltage sourece, we got acceptible current wave form which is calculated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.92-93
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• 2013

In this study, Shock Absorption performance of Magneto-rheological elastomer(MRE) is identified through the drop impact test. Magneto-rheological materials are divided into two groups by MR fluid in fluid state and MR elastomer in solid state like rubber. The stiffness characteristics of Magneto-rheological material can be changed as magnetic field is applied. The impact loads in MR elastomer were measured under weight of impactor. Experiment results are shown through the experiments to confirm the effect of shock absorption of MR elastomer. Thus, the MR elastomer can be applied to shock absorber used in area that shock occurs.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.221-222
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• 2012

2000년 미국에서 국가나노기술개발 전략을 발표한 이래로 현재 한국, 일본, 유럽연합, 독일, 중국, 대만 등 전 세계 60여개 국가들은 나노기술을 미래 국가 경쟁력을 결정하는 핵심요소로 인식하고, 나노국가기술개발 전략을 수립하고 경쟁하고 있다. 한국은 제 1기 나노기술종합발전계획(2001.7)과 제 2기 나노기술종합발전계획(2005.12)의 수립, 추진을 통하여 지난 10여 년 동안 나노기술연구개발, 첨단 연구시설 구축, 나노전문 인력양성, 나노기술산업화 등의 분야에서 괄목할 만한 많은 성과들을 이룩해 왔다. 특히 한국은 나노기술 경쟁구도에 있어 분기점으로 될 것으로 예상되는 2015년에 나노기술 3대 강국 진입을 목표로 설정하고, 정부의 적극적인 투자와 연구자들의 헌신적인 노력이 경주되고 있다. 최근 스마트폰 등, 이동통신기 대량보급과 함께 나노소재는 암 치료나 생체재료분야의 연구개발이 활성화되고 있다. 본고에서는 최근의 나노자성도금의 특성을 중심으로 기술하였다.

• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.663-665
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• 1992

The superconducting $YBa_2Cu_4O_8$ was synthesized in oxygen condition at 1 atm. The starting material with 1 : 2 : 4 composition was obtained by pyrolysis of EDTA complex, which was converted to 1-2-3 phase during densification, followed by the 1-2-4 phase recovery at $810^{\circ}C$ . The phase presents were identified by XRD, TG, DTA and AC magnetic susceptibility. Our data indicated that considerable amounts of 1-2-4 phase formed but with the 1 : 2 : 3 phase or possibly 2-4-7 as visible. As the P($O_2$) increased with temperature, impurity peak, CuO ($2{\Theta}$ = 38.8), gradually decrease, and we conclude that the 1-2-4 phase is predominant bulk superconductor under the high oxygen pressure.

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.206.1-206.1
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• 2008

• Advances in nano research
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• v.5 no.4
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• pp.313-336
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• 2017

This article investigates vibration behavior of magneto-electro-elastic functionally graded (MEE-FG) nanobeams embedded in two-parameter elastic foundation using a third-order parabolic shear deformation beam theory. Material properties of MEE-FG nanobeam are supposed to be variable throughout the thickness based on power-law model. Based on Eringen's nonlocal elasticity theory which captures the small size effects and using the Hamilton's principle, the nonlocal governing equations of motions are derived and then solved analytically. Then the influences of elastic foundation, magnetic potential, external electric voltage, nonlocal parameter, power-law index and slenderness ratio on the frequencies of the embedded MEE-FG nanobeams are studied.