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  • 1
    Electronic Resource
    Electronic Resource
    X-Ray Diffraction Studies on LaBa2Cu3O x Cuprates with Iron Substitution (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 215-219 
    Details
    ISSN: 1572-9605
    Keywords: LaBa2Cu3−y Fe y O x with 0.00≤y≤1.5 ; Rietveld analysis ; structural phase transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract LaBa2Cu3−y Fe y O x ceramic samples with y = 0.00−1.50 are synthesized by the solid-state reaction technique. Rietveld analysis for X-ray diffraction is performed on these iron-doped samples. A BaCuO2 impurity phase and a ceramic cuprate phase coexist in each sample. An orthorhombic-to-tetragonal (OT) phase transition occurs in the doping range of 0.03≤y≤0.06, and a tetragonal-to-orthorhombic (TO) one occurs in the doping level of 0.10≤y≤0.25. There is a jump in the structural parameters due to the iron doping. The occupancy of oxygen at the O(4) site, which is in the La plane at z = 1/2, increases with increase in iron content. These results may relate to the iron preferential occupancy for the Cu(1) site at the lower doping level, and for Cu(2) sites at the higher doping level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022667414272
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear Response of High- T c Superconductors with Small Current Density (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 199-201 
    Details
    ISSN: 1572-9605
    Keywords: Anderson pinning model ; nonlinear response ; relaxation phenomena ; small current density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract By using the Anderson pinning model and considering the reversal transition probability of the magnetic flux bundle, we use the consistent theory to derive the three relaxation phenomena with small current density consisting of the relaxation of the fixed external field, the scanning rate $$\dot H$$ of the external field, and the ac response with driving frequency ν of the external field, respectively. We also explain the corresponding physical phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022611329293
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  • 3
    Electronic Resource
    Electronic Resource
    Orientation Distribution of Grain Planes in Polycrystal Ag/Bi-2223 Tape (2000)
    Springer
    Journal of superconductivity 13 (2000), S. 441-446 
    Details
    ISSN: 1572-9605
    Keywords: Bi2223 tapes ; grain orientation ; critical current density ; microstructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract For polycrystalline Ag/Bi-2223 tapes, the preferential orientation of grains is a very important issue. The platelike grains in the tapes are generally believed in a high-order alignment. However, microstructural observation by SEM shows that the grain alignment is far from perfect. Theoretically, upper critical field, H c2, for H parallel to ab plane and c axis was calculated form the relation of M(H). However, the ratio of H c2 (H//ab) to H c2(H//c) depends on the angle (θ) between the ab plane of grains and the broad surface of the tapes. Based on the ratio, the orientation distribution of grains is obtained. The results show that grains in Ag/Bi-2223 tapes can grow with ab plans at any angle between 75° 〉 θ 〉 −75°, but no grain can grow with its ab plane perpendicular to the tape broad surface. The overall distribution is that: 〉90% grains orient in the angle range of |θ| 〈 ± 75°, about 5% grains at ±75° ≤|θ| ≤ ±85°, and no grains at |θ| 〉 ±85°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007711310818
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  • 4
    Electronic Resource
    Electronic Resource
    Role of free carriers in the application of optically detected magnetic resonance for studies of defects in silicon (1991)
    Springer
    Applied physics 53 (1991), S. 130-135 
    Details
    ISSN: 1432-0630
    Keywords: 76.70.Hb ; 72.20.Jv ; 71.55.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The influence of free carriers on optically detected magnetic resonance (ODMR) signals for defects in silicon is discussed. The presence of free carriers induces a strong background signal in the ODMR spectrum due to carrier heating effects in a microwave field. This background signal often obscures a possible detection of a defect-related magnetic resonance signal and is therefore highly undesirable. To avoid this problem, a delayed ODMR (D-ODMR) technique is employed. On the other hand, the presence of free carriers provides a medium for a possible ODMR detection of nonradiative defects. This is realized by a shunt pass of carrier recombination at such defects, which competes with the radiative carrier recombinations detected optically, and gives rise to negative ODMR signals for the defects responsible for the nonradiative recombination. Typical examples from recent studies of these different cases of defects in silicon are demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323872
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  • 5
    Electronic Resource
    Electronic Resource
    Natural convection in partitioned enclosed spaces of solar collector (1990)
    Springer
    Heat and mass transfer 25 (1990), S. 59-67 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Die zweidimensionale, stetige, laminare freie Konvektion in unterteilten Kammern von Solarkollektoren wurde numerisch untersucht. Die Wärmeübertragung entlang dieser Kammern wurde betrachtet. Ein iteratives Finite-Differenzen-Schema wurde angewandt um die Gleichungen, welche das Strömungsfeld beschreiben, zu lösen. Der Einfluß der Rayleigh-Zahl, der thermische Leitfähigkeit, des Kammerwinkels, des Neigungswinkels und der Längenverhältnisse auf die örtlichen und durchschnittlichen Wärmeübertragungskoeffizienten des Solarkollektors wurde diskutiert. Der Bereich der Rayleigh-Zahl erstreckte sich bis zu 5 × 104, das Verhältnis der thermischen Leitfähigkeit betrug 4.5 und 30, der Kammerwinkel lag zwischen 10° und 170°, der Neigungswinkel zwischen 10° und 90° und das Längenverhältnis variierte zwischen 0.2 und 10. Die Ergebnisse beinhalten, daß die konvektive Wärmeübertragung sehr stark durch das Längenverhältnis der Kammern beeinflußt wird.
    Notes: Abstract The two-dimensional, steady, laminar natural convection phenomena in partitioned enclosure of solar collector has been studied numerically. Heat conduction along the partition is considered. An iterative finite-difference scheme is employed to solve the governing equations in the flow field. The effects of Rayleigh number, thermal conductivity ratio, partition angle, tilt angle, and aspect ratio on both the local and average heat transfer coefficients of the solar collector have been discussed. The range of Rayleigh number tested was up to 5 × 104, the thermal conductivity ratio of 4.5 and 30, partition angle from 10 deg to 170 deg, tilt angle from 10 deg to 90 deg, and aspect ratio varied between 0.2 and 10. The results indicate that the convective heat transfer is strongly affected with the aspect ratio of the enclosures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01592353
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  • 6
    Electronic Resource
    Electronic Resource
    An improved procedure for determining oxygen content in high-T ccopper oxides (1996)
    Springer
    Journal of superconductivity 9 (1996), S. 551-554 
    Details
    ISSN: 1572-9605
    Keywords: Iodometric titration ; superconductor ; indicator ; oxygen content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We present an improved double titration method for high-T c superconductors, in which the major step is adding KSCN as an indicator of the end point after the starch end point. By adding it, a greater amount of Na2S2O3 solution can be added after the starch end point, at least 0.12 ml. We found that adding KSCN can lead to precise measuring results and reduce the experimental error. The oxygen contents of two series of superconductors were determined by this approach. For YBa2Cu3O y , the errors are Δp∼0.003 and Δy∼0.005, which are lower than that of other reports.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00723530
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  • 7
    Electronic Resource
    Electronic Resource
    An Equation for Calculating Nitrogen Density from Measurements of Dielectric Constants (1998)
    Springer
    International journal of thermophysics 19 (1998), S. 215-225 
    Details
    ISSN: 1572-9567
    Keywords: density ; dielectric constant ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new equation for determining the density of nonpolar substances based on measurements of dielectric constants is presented. Applying the new equation to nitrogen at a density from 1 to 30 mol·L−1, the mean deviation of the results calculated from the equation is of the order of 10−4, which is the same as the uncertainty of the experimental data. Owing to its analytical form, the derived equation can be applied to indicate the density of nonpolar substances with a densitometer, without adding error to the experimental uncertainty. This equation is also capable of determining the mean polarizabilities and molecular diameters, which agree well with results from other investigators. We suggest that the equation derived here can be applied to some other nonpolar substances as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021459304637
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