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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic levitation and stiffness in melt-textured Y-Ba-Cu-O (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2089-2091 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic levitation and stiffness have been measured in several systems composed of a permanent magnet elastically suspended above a stationary melt-textured sample of Y-Ba-Cu-O. The levitation force and vertical stiffness have been calculated on the basis of magnetization measurements of the same system, and the calculated results showed excellent agreement with the experimental measurements. Based on the force and magnetization measurements, it is predicted that the same Y-Ba-Cu-O material configured in a geometry suitable for magnetic bearings could produce a levitation pressure of 100–400 kPa at 20 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351595
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  • 2
    Electronic Resource
    Electronic Resource
    Levitation force and magnetic stiffness in bulk high-temperature superconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4358-4360 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Levitation forces between a small permanent magnet and a disk of bulk high-temperature superconductor at 77 K were measured as a function of vertical separation for disks of composition Y-Ba-Cu-O, Ag/Y-Ba-Cu-O, (Pb,Bi)-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O. The forces were highly hysteretic; however, for all samples, on the initial descent of the magnet toward the disk, the force was unique, independent of magnet speed, and varied approximately as the negative exponential of the separation distance. Magnetic stiffness, associated with minor hysteresis loops, was found to be approximately proportional to the levitation force, and nearly independent of magnet configuration and superconductor composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344927
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  • 3
    Electronic Resource
    Electronic Resource
    Amplitude and frequency dependence of hysteresis loss in a magnet-superconductor levitation system (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2097-2100 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using an electromagnetically controlled mechanical pendulum, we measured the energy loss for different amplitudes in a magnetic levitation system that contained high temperature superconductors (HTSs). Two procedures were followed to measure losses at 77 K for frequencies of 93.8 mHz to 80 Hz. In the first procedure, the distance between the permanent magnet and the HTS levitator was the same as that during (field) cooling. In the second procedure, the magnet was lowered (after cooling) closer to the HTS levitator before the measurements were performed. The experimental data show that these two procedures give essentially the same results at the same distance despite different cooling (and magnetization) histories for melt-textured YBaCuO levitators, and the frequency-independent energy loss is a power-law function of amplitude. We attribute the energy loss to magnetic hysteresis in the superconductor. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360187
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  • 4
    Electronic Resource
    Electronic Resource
    Low friction in mixed-mu superconducting bearings (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 6833-6838 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Individual magnetic steel rotors were levitated by combining the attractive force between permanent magnets and the steel with the repulsive force between high-temperature superconductors and the steel. The free spindown of several rotors was observed, and the effective coefficient of friction for the bearing was calculated as a function of geometry. Low-speed coefficients of 〈10−8 were observed, and the velocity dependence of MnZn ferrite rotors suggest that coefficients of 〈10−6 are attainable at bearing rim velocities of 100 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360444
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  • 5
    Electronic Resource
    Electronic Resource
    Stable levitation of steel rotors using permanent magnets and high-temperature superconductors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 577-580 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Individual freely spinning magnetic steel rotors were levitated by combining the attractive force between permanent magnets and the rotor with the repulsive force between high-temperature superconductors and the steel. The levitation force and stiffness of several configurations are presented, and the application of this levitation method to high-speed bearings is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357115
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  • 6
    Electronic Resource
    Electronic Resource
    Amplitude dependence of magnetic stiffness in bulk high-temperature superconductors (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2942-2944 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic stiffness has been measured in several vibratory systems composed of a permanent magnet elastically suspended above a stationary high-temperature superconductor at 77 K. For Y-Ba-Cu-O, Ag/Y-Ba-Cu-O, (Pb-Bi)-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O sintered disks, both the vertical and horizontal magnetic stiffnesses increase strongly as the magnet's oscillation decays, down to amplitudes of 1 μm. Vertical stiffness is about twice as strong as horizontal stiffness, and both are much stronger than the gradient of the levitation force for large monotonic changes in magnet height over the superconductor. These results are not deducible from contemporary magnetization measurements, and elastic pinning of flux lines are believed to contribute significantly to the stiffness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104205
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic surface-pressure instrumentation for rods in parallel flow (1982)
    Springer
    Experimental mechanics 22 (1982), S. 31-36 
    Details
    ISSN: 1741-2765
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Methods employed and experience gained in measuring random fluid-boundary-layer pressures on the surface of a small-diameter cylindrical rod subject to dense, nonhomogeneous, turbulent, parallel flow in a relatively noise-contaminated flow loop are described. Emphasis is placed on identification of instrumentation problems; description of transducer construction and mounting; and the pretest calibration required to achieve instrumentation capable of reliable data acquisition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02325701
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