• Advances in nano research
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• v.11 no.6
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• pp.581-593
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• 2021

This model is proposed to describe the buckling behavior of Carbon Nanotubes (CNTs) embedded in an elastic medium taking into account the combined effects of the magnetic field, the temperature, the nonlocal parameter, the number of walls. Using Eringen's nonlocal elasticity theory, thin cylindrical shell theory and Van der Waal force (VdW) interactions, we develop a system of partial differential equations governing the buckling response of CNTs embedded on Winkler, Pasternak, and Kerr foundations in a thermal-magnetic environment. The pre-buckling stresses are obtained by applying airy's stress function and an adjacent equilibrium criterion. To estimate the nonlocal critical buckling load of CNTs under the simultaneous effects of the magnetic field, the temperature change, and the number of walls, an optimization technique is proposed. Furthermore, analytical formulas are developed to obtain the buckling behavior of SWCNTs embedded in an elastic medium without taking into account the effects of the nonlocal parameter. These formulas take into account VdW interactions between adjacent tubes and the effect of terms involving differences in tube radii generally neglected in the derived expressions of the critical buckling load published in the literature. Most scientific research on modeling the effects of magnetic fields is based on beam theories, this motivation pushes me to develop a cylindrical shell model for studying the effect of the magnetic field on the static behavior of CNTs. The results show that the magnetic field has significant effects on the static behavior of CNTs and can lead to slow buckling. On the other hand, thermal effects reduce the critical buckling load. The findings in this work can help us design of CNTs for various applications (e.g. structural, electrical, mechanical and biological applications) in a thermal and magnetic environment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.1
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• pp.1-10
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• 1996

A numerical study was conducted on the effects of the cusp magnetic field in 8" silicon single crystal grwoth by Czochralski method. For a damping effects simulation by magnetic field, low reynolds number ${\kappa} - {\varepsilon}$ model was adopted. Symmetrci cusp magnetic field has a effect of damping streamline crystal, is lowerd with the increasing cusp magnetic field intensity. The uniformity of the oxygen concentration was improved. The asymmetirc cusp magnetic field increased the oxygen concentration however, oxygen concentration distribution in the radial direction was remained uniform. Suitable combination of symmetric and asymmetric cusp magnetic fields could give uniform and low oxygen concentration in the axial direction.tion.

• Current Applied Physics
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• v.18 no.11
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• pp.1201-1204
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• 2018

The effect of electric current pulses on a sub-100 nm magnetic bubble state in a symmetric Pt/Co multilayer was directly observed using a full-field transmission soft X-ray microscope (MTXM). Field-induced evolution of the magnetic stripe domains into isolated bubbles with their sizes down to 100 nm was imaged under varying external magnetic fields. Electric current pulses were then applied to the created magnetic bubbles, and it was observed that the bubbles could be either created or annihilated by the current pulse depending on the strength of applied magnetic field. The results suggest that the Joule heating plays a critical role in the formation and/or elimination of the bubbles and skyrmions. Finally, the schematic phase diagram for the creation and annihilation of bubbles is presented, suggesting an optimized scheme with the combination of magnetic field and electric current necessary to utilize skyrmions in the practical devices.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.93-95
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• 2011

In this study we tried to measure the effect of magnetic field on the dielectric properties of $BaTiO_3-MgFe_2O_4$ soft magnetic composite. Composites with different weight percents of ferroelectric and ferromagnetic phases were subjected to magnetic field in the order of 0 to 450 Oe and the variation of the dielectric properties was observed. The Variation of dielectric polarization was discussed in terms of Maxwell-Wagner type polarization in particulate composites.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.2
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• pp.37-41
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• 1989

The purpose of this paper is to estimate the effect of wobble and nonconcentricity of tubes or rods in eddy current test with encircling test coils. Because the eddy current induced in a sample is related to the total magnetic flux linkages, the information about magnetic field distribution in a coil is important. In theoretical study, magnetic field distribution in a single turn coil was calculated and variation of impedance according to the difference of sample positions was presumed. Magnetic field intensity at inside of a solenoidal coil was measured and compared with the theoretical estimation. In experiment, impedance loci of a coil encircling an aluminum rod were measured at different sample positions. The effect of crack positions was examined at same sample positons.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.1
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• pp.27-31
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• 2014

Magnetic fields (MF) generated both on board the vehicle and along the guideway provide levitation and propulsion forces. High speed maglev trains adopt electromagnet or superconducting magnet to realize levitation and propulsion functions. However, stray fields existing in passenger compartment and regions surrounding the vehicle and guideway have effect on passengers and environment. To investigate stray magnetic field effect, model of Transrapid and MLX are studied.

• Journal of Magnetics
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• v.16 no.3
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• pp.259-262
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• 2011

Compared to acupuncture, the pulsed magnetic field (PMF) stimulus is a useful tool for treatment of many physical conditions and health maintenance due to its advantages as a noninvasive and nontoxic medical treatment. The purpose of this study was to investigate the effect of PMF stimulus direction at PC9 on the alpha activity of electroencephalogram (EEG) and vascular aging calculated from photoplethysmograph (PPG). It can be concluded that the direction of PMF stimulus affects the increase of alpha activity of EEG and PPG, indicating the vascular stiffness and the sclerosis level of blood vessels weakly relevant to the direction of PMF stimulus.

• Tribology and Lubricants
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• v.13 no.2
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• pp.52-59
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• 1997

An experimental study is presented for the characteristics of the high temperature superconductor as an application of the repulsive type magnetic bearing. A ring shaped YBCO type superconductor and Neodium permanent magnets are employed for the experiment. For the case of field cooling, superconductor shows strong repulsive force, which is due to the Meissner effect, as the gap between the superconductor and the magnet gets closer. The repulsive force variation with respect to the gap change shows hysterisis characteristics. The area of the loop of the hysterisis curve represents the dissipation of energy, which reveals that the magnetic bearing with superconductor has large damping. The effect of the initial gap and the magnetic flux density on the repulsive force is analyzed experimentally and the static stiffness variation is calculated from the measured repulsive force variation. The relative sliding velocity between the superconductor and the magnet has little effect on the repulsive force which is quite different from the usual sliding element bearing. As the initial gap for the field cooling becomes larger, the maximum repulsive force at the minimum gap increases and approaches to the value for the case of zero field cooling.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.36-40
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• 2010

In recent society, the electricity is so essential for the human lives. Lots of modern people take many cultural benefits owing to the development of the power systems, the cell phone, the electrical appliances, and etc. However, the problems related to the electromagnetic field generate as the side effects. Examples are the fault in the electric machinery due to the electromagnetic coupling, the fault in the communication devices due to the electromagnetic field around the power line equipments, and the effect upon the human beings due to the electromagnetic field, and etc. In this paper, we induce the vector equation about the magnetic field based on Biot-Savart law. We calculate the magnetic field at the surface of the high speed train with this induced equation and the current in the high speed railroad catenary wire. Finally, we calculate the magnetic field in the high speed train considering the material property like the permeability, the conductivity, and so on.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.6
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• pp.309-315
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• 1999

Coupling loss is generated by the time-varying external magnetic field in the normal matrix of the multi-filamentary HTS tape. This paper calculates the coupling loss in the HTS tape. Analytic calculation of the coupling loss cannot consider the effect of the different shapes and the arrangement of the filaments. Numerical calculation by using finite element method and analytic calculation of the coupling loss have been done in this paper and results of two calculations have been compared. Transverse magnetic field and longitudinal magnetic field were considered as the external field.