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  • 1
    Digitale Medien
    Digitale Medien
    Vortex pair annihilation in Taylor wavy-vortex flow (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 7-9 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have made precision measurements of the vortex pair size and wavy mode amplitude of vortices in wavy Taylor–Couette vortex flow. These results are compared to a model advanced by Park and Crawford to account for expulsion of vortex pairs as the Reynolds number is increased in the wavy-vortex regime.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.865129
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  • 2
    Digitale Medien
    Digitale Medien
    Cryogenic separation of methane from other hydrocarbons in air (1974)
    s.l. : American Chemical Society
    Environmental science & technology 8 (1974), S. 671-673 
    Details
    ISSN: 1520-5851
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Energietechnik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/es60092a004
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  • 3
    Digitale Medien
    Digitale Medien
    Feasibility study of condensation flue gas cleaning (CFGC) system (1978)
    s.l. : American Chemical Society
    Environmental science & technology 12 (1978), S. 1183-1188 
    Details
    ISSN: 1520-5851
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Energietechnik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/es60146a010
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  • 4
    Digitale Medien
    Digitale Medien
    Thermal excitation of waves on quantized vortices (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 498-504 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We consider the problem of the thermal excitation of vortex waves on quantized vortex lines and rings. We discover that this problem, which has been largely neglected in the past, apparently presents a "free energy catastrophe'' above about 1.85 K; that is, if one naively proceeds to compute the thermally induced vortex waves on rings or lines, the entropy of the waves becomes so large that the free energy of vortices is driven negative, and superfluidity could not exist. Various mechanisms for eliminating this problem are considered; it appears to be necessary to consider the relevant system to be the vortex plus the bath in order to avoid double counting of states. We comment on the relevance of this calculation to the problem of thermally induced nucleation of vortices.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.865113
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  • 5
    Digitale Medien
    Digitale Medien
    An experiment to investigate the superfluid transition in a confined planar geometry (1998)
    Springer
    Journal of low temperature physics 113 (1998), S. 441-446 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present a progress report on our investigation of finite size effects on the superfluid transition. In our experiment, the helium is confined between the parallel plates of a carefully constructed capacitor. We measure the dielectric constant as a function of temperature, from which we can calculate the thermal expansivity. We discuss some of the following important features of our experiment: The capacitor, built in collaboration with the Chex experiment, gives us a simple, well defined planar geometry, extremely flat surfaces, and a sub-micron gap. A low temperature audio-frequency preamp improves the sensitivity of the capacitance measurement. A high resolution paramagnetic salt thermometer, also from Chex, enables us to work extremely close to the lambda point. We also present a novel design for a simple low temperature burst disc that is part of our apparatus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022548011314
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  • 6
    Digitale Medien
    Digitale Medien
    Scattering and binding of rotons (1974)
    Springer
    Journal of low temperature physics 15 (1974), S. 1-27 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The interaction of rotons is studied by a direct examination of their orbital dynamics. It is found that upon representing rotons as point dipoles in the superfluid, obeying the Landau dispersion relation, negative energy states occur, some of which are stable and some unstable. The binding energy and effective mass of these states are found, but are too large to agree with experiment. Improvements in the Hamiltonian are explored which recognize the actual dispersion curve as well as higher moments in the interaction. Both modifications lead to binding energy and effective mass in better agreement with experiment. Scattering is also examined, and one finds that a representative roton-roton cross section may be obtained in the dipole approximation, again using Landau dispersion. The scattering cross section is shown to be in satisfactory agreement with neutron linewidths in the roton-dominated region, as well as the roton contribution to the shear viscosity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00655620
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  • 7
    Digitale Medien
    Digitale Medien
    Calculation of frequency- and velocity-dependent mutual friction parameters in helium II (1987)
    Springer
    Journal of low temperature physics 66 (1987), S. 263-276 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We argue that the range of experimental conditions for which the mutual friction coefficientsB andB′ are used today is great enough that one should include the frequency and the velocity dependence of these two parameters. We provide both an algorithm and the data necessary for obtainingB andB′ as a function of frequency and velocity at the saturated vapor pressure according to the Hall and Vinen theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00682257
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  • 8
    Digitale Medien
    Digitale Medien
    The interaction of rotons in HeII (1992)
    Springer
    Journal of low temperature physics 89 (1992), S. 417-420 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have investigated the scattering of rotons as motivated by recent experiments with crossed roton beams. We assumed an excitation mediated interaction between rotons and used 2nd order perturbation theory to calculate scattering cross-sections as a function of total roton momentum. Comparison of experiment to quantum mechanical and classical theories is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00694053
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  • 9
    Digitale Medien
    Digitale Medien
    Onset of vorticity in a rotating annulus of helium II (1993)
    Springer
    Journal of low temperature physics 91 (1993), S. 81-103 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present measurements of the critical angular velocity for the onset of vorticity in a rotating annulus. The measurements of the critical velocity were made over a temperature range from 1.5 to 2.165 K, and are consistently lower than theoretical predictions by about 20%. Nor do our results agree within experimental uncertainty with previous measurements of the critical velocity in an annulus. It appears that the discrepancies can be explained by the presence and growth of high concentrations of residual vorticity which prevent the system from achieving the lowest free energy state. We find that vorticity perpendicular to the axis of rotation grows as the angular velocity is increased and that the axial mutual friction coefficientB″ is 0.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00132090
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  • 10
    Digitale Medien
    Digitale Medien
    The appearance of vortices in the flow of helium II between rotating cylinders (1987)
    Springer
    Journal of low temperature physics 67 (1987), S. 185-193 
    Details
    ISSN: 1573-7357
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We argue that the appearance of quantized vortices in laminar Taylor-Couette flow of helium II is a problem for which free energy minimization should give valid results even in the presence of dissipation. We (approximately) reduce the problem to an equivalent problem in solid-body rotation, for which the solution for the low-lying states has been obtained by Fetter. We then use approximations to the solution for solid-body rotation to predict the appearance of vortices for the general Taylor-Couette problem. These results compare moderately well with the existing data, which now seem relatively incomplete.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00681828
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