Papers by Yevgeniy Postrekhin
Review of Scientific Instruments, Nov 30, 2003
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Journal of Applied Physics, May 14, 2002
The angular dependence of the magnetic torque has been measured in cubic shaped YBaCuO samples. T... more The angular dependence of the magnetic torque has been measured in cubic shaped YBaCuO samples. The bulk sample was prepared by a seeded-melt growth process in which a small NdBaCuO seed was used to induce domain growth of YBaCuO. The sample had cubic shape so that its edges coincided with basic crystallographic directions. The measurements were conducted in static and dynamic modes. Under static mode, the angular dependencies of the torque have been obtained in a series of zero field cooled magnetic hysteresis measurements. Between each measurement at a specific angle, the sample was warmed up above critical temperature. Under dynamic mode, the magnetic field was increased up to a certain point and then the sample was turned around its axis continuously. It was found that the static torque was a sinusoidal function of the double angle between the external field and one of basic directions of the crystal structure. It also exhibited prominent anisotropy in relation to the crystal structure of the high-temperature superconductor. The dynamic torque-angle relation is not only a result of the anisotropic structure of the superconductor but also a result of the strong intrinsic pinning of this material. Based on Kogan's theory for the anisotropic superconductors and the Bean model approach, a physical model has been developed to describe the angular dependence of the magnetic torque.
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Superconductor Science and Technology, 2002
Seeded growth YBCO material samples, while not single crystals, nevertheless have a preferred ori... more Seeded growth YBCO material samples, while not single crystals, nevertheless have a preferred orientation of their crystal axes. This can be expected to lead to anisotropic behaviour of material properties such as the critical current density for this material. In this work, we report the exploration of this anisotropy of seeded growth YBCO materials by their magneto-mechanical response in the
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Superconductor Science and Technology, 2002
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IEEE Transactions on Magnetics, 2001
Page 1. 2874 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Drag Torque on Slowly Rota... more Page 1. 2874 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Drag Torque on Slowly Rotating High Temperature Superconductor in Non-Axisymmetric Magnetic Field Ki Bui Ma, Phillip M. Wu, Yevgeniy ...
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IEEE Transactions on Appiled Superconductivity, 1999
ABSTRACT
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IEEE Transactions on Appiled Superconductivity, 2001
ABSTRACT
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IEEE Transactions on Appiled Superconductivity, 2003
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IEEE Transactions on Appiled Superconductivity, 2001
The design of superconductor magnet bearings for high load applications such as flywheel kinetic ... more The design of superconductor magnet bearings for high load applications such as flywheel kinetic energy storage necessitates the use of large pieces of high quality high temperature superconductors. Limitations on the size of one continuous block of HTS materials that can be produced make it very attractive to use contiguous pieces of high quality HTS materials to provide the same large amount of HTS surface that can interact with magnets to give as high a levitation force. More often than not, the shape of such a composite piece is not symmetric about any axis of rotation. Variations in the drag torque are observed within each rotation cycle of the magnet above the composite HTS piece. The authors show that part of this drag torque variation originates from the nonaxisymmetric shape of the composite HTS piece. Implications of this drag torque variation on the power loss of superconductor magnet bearings made with composite HTS pieces are discussed
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Papers by Yevgeniy Postrekhin