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  • Articles  (702)
  • Articles: DFG German National Licenses  (702)
  • Life and Medical Sciences  (505)
  • thermal conductivity  (197)
  • 1990-1994  (393)
  • 1985-1989  (309)
  • 1940-1944
  • Physics  (702)
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  • Articles  (702)
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  • Articles: DFG German National Licenses  (702)
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  • 1
    Electronic Resource
    Electronic Resource
    Implications of estimated and measured thermal conductivity for oceanic heat flow studies (1991)
    Springer
    Marine geophysical researches 13 (1991), S. 311-329 
    Details
    ISSN: 1573-0581
    Keywords: thermal conductivity ; heat flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Heat flow data provide constraints on the thermal structure and evolution of the oceanic lithosphere. Because precise determination of the heat flux requires that both the thermal gradient and the thermal conductivity be well determined we have examined the thermal conductivities used in a new Pacific Basin heat flow data set. ∼43% of the ∼1600 heat flow determinations rely on values estimated by various methods, rather than directly measured. Although the measured and estimated conductivities have comparable means, the measured conductivities have a standard deviation ∼50% larger than the estimated, suggesting that the estimated values underestimate the actual variation. We investigate the limitations of using such estimates by examining factors controlling the variations of measured conductivity values. We find that the variation between the closest adjacent sites increases with increasing separation, such that sites within 200 km are on average noticeably closer in conductivity than sites further apart. Contributing to this effect may be the variation of conductivity with lithology (with mean conductivity highest for carbonate oozes, intermediate for deep-sea clays, and least for siliceous oozes) and a possible trend of decreasing conductivity with increasing seafloor depth. Tests with the measured data suggest that the best method for estimating conductivity is using the mean value measured within 200 km. The mean of a larger geographical region is a somewhat poorer predictor, and using the oceanwide mean and the value at the nearest site are poorer still. Approximately 29% of the estimated values were not based on measurements from a reference site. For most others, the reference site was the nearest measurement from the same cruise, typically a large distance away. For those sites where conductivity was not measured, 78% had measured conductivity within 200 km and were reestimated using the local mean, whereas the remaining 22% were reestimated using the regional mean. The resulting change in the estimated conductivity averaged ∼9% using the local mean and ∼6% using the regional mean. We suggest that such a procedure be used to improve the utility of the heat flow data set, as an alternative to discarding the large fraction of the available data that does not incorporate measured conductivities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366281
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrodynamic correlation functions of hard-sphere fluids at short times (1989)
    Springer
    Journal of statistical physics 57 (1989), S. 595-629 
    Details
    ISSN: 1572-9613
    Keywords: Neutron scattering function ; shear viscosity ; bulk viscosity ; thermal conductivity ; Green-Kubo integrand ; hard-sphere fluid ; short-time expansion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The short-time behavior of the coherent intermediate scattering function for a fluid of hard-sphere particles is calculated exactly through ordert 4, and the other hydrodynamic correlation functions are calculated exactly through ordert 2. It is shown that for all of the correlation functions considered the Enskog theory gives a fair approximation. Also, the initial time behavior of various Green-Kubo integrands is studied. For the shear-viscosity integrand it is found that at densitynσ3=0.837 the prediction of the Enskog theory is 32% too low. The initial value of the bulk viscosity integrand is nonzero, in contrast to the Enskog result. The initial value of the thermal conductivity integrand at high densities is predicted well by Enskog theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01022824
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  • 3
    Electronic Resource
    Electronic Resource
    Large single-crystal growth of RBa2Cu3O7−x by the flux method (R=Y and rare earths) (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1679-1683 
    Details
    ISSN: 0392-6737
    Keywords: Thermodynamic properties ; thermal conductivity ; Methods of crystals growth and purification ; Phase diagrams of other materials ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In this work the thermal conditions required for single-crystal growth in RBa2Cu3O7−x systems (R=Y or rare earths apart from Ce and Tb) have been systematically revised in order to improve the size of crystals obtainable by the flux method. Large single crystals of NdBCO, SmBCO and EuBCO have been actually obtained and characterized by XRD, oxygen content and electrical resistivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462159
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  • 4
    Electronic Resource
    Electronic Resource
    Anisotropic thermal and mechanical properties of bulk high-T c Bi-based superconductors (1994)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1863-1869 
    Details
    ISSN: 0392-6737
    Keywords: Thermodynamic properties ; thermal conductivity ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Superconducting powders with nominal composition Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Ox were prepared by two different routes: by solid-state reaction of the respective oxides and carbonates and by pyrolysis of organic precursors. Highly dense superconducting specimens characterized by textured microstructure were prepared by hot pressing. The thermal-expansion coefficients of different typologies of samples were measured by dilatometric tests in both directions parallel and perpendicular to the pressure application direction. Structural rearrangements occurring during thermal treatments were studied. As regards mechanical characterization, microhardness, flexural strength and fracture toughness were evaluated and related to the microstructure anisotropic degree of the sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02462186
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  • 5
    Electronic Resource
    Electronic Resource
    The peak in the thermal conductivity of Cu-O superconductors: Electronic or phononic origin? (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 323-329 
    Details
    ISSN: 1572-9605
    Keywords: High-T c superconductors ; thermal conductivity ; scattering rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The thermal conductivityК of hole-doped Cu-O plane high-T c perovskites exhibits a dramatic increase belowT c which results in a pronounced peak nearT c /2. The origin of this peak was initially thought to arise from an enhancement in the mean-free path of phonons as the charge carriers undergo condensation. Indeed, excellent fits to the data can be obtained with physically reasonable parameters using the conventional theory of lattice conduction in superconductors. In contrast, a recently observed sharp decrease in the quasiparticle scattering rate of YBCO single crystals belowT c has motivated proposals for an electronic origin of the thermal conductivity peak. We shall critically examine experimental evidence and highlight relative advantages and shortcomings of the two contrasting interpretations. Furthermore, we shall draw attention to recently available data on the relaxation time of out-of-equilibrium carriers in Cu-O superconductors obtained using pump-probe femtosecond laser studies and what new light they shed on the controversy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724562
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal conductivity of high-T c superconductors (1990)
    Springer
    Journal of superconductivity 3 (1990), S. 337-389 
    Details
    ISSN: 1572-9605
    Keywords: High-Transition-temperature superconductors ; thermal conductivity ; single crystal ; Mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract This paper reviews existing data on the thermal conductivity of high-T c superconductors. Included are discussions of pristine polycrystalline high-T c ceramics, single crystal specimens, and high-T c materials structurally modified by substitution or by radiation damage. The thermal conductivity of high-T c superconductors is compared with that of conventional superconductors, and dramatic differences are found between the two families. Mechanisms of thermal conductivity applicable to high-T c perovskites are discussed and implications for theories of high-T c superconductivity are noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617463
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal conductivity of high-T c crystals: Dependence on magnitude and orientation of magnetic field, and effect of Zn doping (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 331-335 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductors ; thermal conductivity ; magnetic field effects ; single crystals ; order parameter ; doping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present precise measurements of in-plane thermal conductivity for superconducting single crystals of YBa2Cu3O7−x (YBCO) withT c =92 and 60 K, Bi2Sr2CaCu2O8 (BSCCO), and of Zn-doped YBCO. Magnetization and thermal conductivity data obtained with the same 90-K YBCO crystal demonstrate a close relationship between the magnetic thermal resistivity and the internal magnetic fieldB in a superconductor in the mixed state. For all superconductors studied here, the magnetic thermal resistivity is a sublinear function of magnetic field. The origins of the nonlinearity are discussed. Angular dependences of the magnetic thermal resistivity have been shown to depart from the anisotropic 3D superconductor model and are in quantitative agreement with a quasi-2D model. Implications for spatial modulation of the order parameter are made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00724563
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal conductivity and electrical resistivity of the T′ phase and the T phase in 2-1-4 oxide superconductors (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 813-817 
    Details
    ISSN: 1572-9605
    Keywords: 2-1-4 Oxide Superconductors ; thermal conductivity ; electrical resistivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The temperature dependences of the thermal conductivity,κ(T), and the electrical resistivity,ρ(T), of sintered samples of Nd1.85Ce0.15CuO4−y (NCCO) and Pr1.85Ce0.15CuO4−y (PCCO) with the T′ phase, and La1.85Sr0.15CuO4−y (LSCO) and La1.935Ca0.065CuO4−y (LCCO) with the T phase, have been measured. The superconducting transition temperatureT con , of NCCO, PCCO, LSCO, and LCCO were 26.4, 23.0, 37.1, and 8.8 K, respectively. The enhancement ofκ(T) below justT con such as seen in 1-2-3 oxide superconductors was not clearly observed.κ(T) for the samples of NCCO and PCCO showed a pronounced maximum such as that of sapphire crystal around 30 and 40 K, respectively. For these samples of NCCO and PCCO, it has been shown that the analysis based on the various phonon scattering mechanisms is in good agreement with our experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320875
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  • 9
    Electronic Resource
    Electronic Resource
    Transport phenomena in a plane shock wave (1991)
    Springer
    Journal of statistical physics 64 (1991), S. 429-436 
    Details
    ISSN: 1572-9613
    Keywords: Shock wave ; Boltzmann equation ; Mott-Smith theory ; nonpolynomial closure ; transverse temperature ; viscosity ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract With the use of the nonpolynomial closure 1/ν z in the Mott-Smith approximation of the solution of the Boltzmann equation, we obtain a value of the density gradient in the limit of a very weak shock wave that is close to the correct value. For the determination of the transverse temperature gradient we calculated theν x 2 /ν z moment of the Mott-Smith collision integral. The effective values of viscosity and thermal conductivity in the limit of a very weak shock wave were calculated for inverse-power potentials and found to agree almost exactly with the Chapman-Enskog values. Such a comparison can serve as a criterion for the evaluation of different bimodal theories. Various bimodal theories give different values of viscosity and thermal conductivity, but all of them give 33 % too high a value of the Eucken ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01057885
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  • 10
    Electronic Resource
    Electronic Resource
    The thermal conductivity of ethane in the critical region (1989)
    Springer
    International journal of thermophysics 10 (1989), S. 409-415 
    Details
    ISSN: 1572-9567
    Keywords: critical region ; ethane ; thermal conductivity ; thermal diffusivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of ethane in the critical region has been measured isochorically at densities up to 1.76 times the critical density and at temperatures down to 0.13 K above the critical temperature. The measurements were performed with a thermal conductivity apparatus based on the parallelplate method. The experimental accuracy was 0.5 to 5%, depending on the distance to the critical point. The experimental results agree well with a recently developed crossover theory for the thermal diffusivity of fluids in the critical region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133537
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