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  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Effect of size on levitation force in a magnet/superconductor system (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3318-3322 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We consider a model system consisting of an infinitely long magnetic dipole line placed symmetrically above an infinitely long superconducting strip. Using the Meissner effect of superconductors, we derive analytical expressions of the levitation forces acting on the dipole line. At lowest-order approximation, we discuss the possible application of our model system to estimate the upper limit of the levitation forces in some magnetic bearing systems. In one example, the model correctly calculated the vertical vibration frequency of an experimental superconducting bearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361232
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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
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Low friction in high temperature superconductor bearings (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1132-1134 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of drag in rotating permanent magnet/high temperature superconductor magnetic bearings is reported. The effects of magnet asymmetry, atmospheric resistance, and eddy currents are discussed. One of the bearings achieved a rotational speed of 200 000 RPM and a low speed coefficient of friction of 8.1×10−6, values that have technological significance for flywheel energy storage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106367
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  • 9
    Electronic Resource
    Electronic Resource
    Environmental Geology and the marine dimension (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 1 (1989), S. 0 
    Details
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: This paper reviews the role of environmental geology, and the practice of environmental geology mapping, in the context of the geological, geophysical and geochemical factors which are relevant to human activity and safety.It is concluded that informed planning policies for the offshore areas are necessary. These would allow mutually acceptable and sensible exploitation of all natural resources, engineering and military developments and recreational uses, and would also take account of natural and man-made hazards to such activities. The policies would follow from multidisciplinary, systematic, environmental studies involving international cooperation.The imperative for the earth-science practitioner to remain sensitive to the requirements of the users of such information is recognized, as is the need to communicate unambiguously. It is concluded that geologists should look increasingly from the past to the future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3121.1989.tb00427.x
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  • 10
    Electronic Resource
    Electronic Resource
    Occlusion of armoured tubes (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Anaesthesia 44 (1989), S. 0 
    Details
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2044.1989.tb09288.x
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