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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 56 (1991), S. 1337-1340 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 87 (2004), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Pb(Zn1/3Nb2/3)0.20(Zr0.50Ti0.50)0.80O3 ceramics of pure perovskite structure were prepared by the two-stage method with the addition of 0–3.0 wt% MnO2 and their piezoelectric properties were investigated systematically. The MnO2 addition influences in a pronounced way both the crystal structure and the microstructure of the materials. The materials are transformed from the tetragonal to the rhombohedral structure, and the grain size is enhanced when manganese cations are added. The distortion of crystal structure for samples with MnO2 addition can be explained by the Jahn–Teller effect. The values of electromechanical coupling factor (kp) and dielectric loss (tan δ) are optimized for 0.5-wt%-MnO2-doped samples (kp= 0.60, tan δ= 0.2%) and the mechanical quality factor (Qm) is maximized for 1.0-wt%-MnO2-doped samples (Qm= 1041), which suggests that oxygen vacancies formed by substituting Mn3+ and Mn2+ ions for B-site ions (e.g., Ti4+ and Zr4+ ions) in the perovskite structure partially inhibited polarization reversal in the ferroelectrics. The ceramics with 0.50–1.0 wt% MnO2 addition show great promise as practical materials for piezoelectric applications.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3512-3514 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave properties of spin-cast YBa2Cu3O7−x thin films on LaAlO3 substrates were investigated. The films, prepared with carboxylate solution precursors and by reactive liquid phase sintering mechanism, showed dense epitaxial structure and good electrical properties. The surface resistance, measured at a frequency of 10 GHz, was 0.47 mΩ at 5.4 K and 3.1 mΩ at 77 K. The results indicate that this technique can be used to fabricate superconducting thin films for microwave applications at low cost and with wide area coverage.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1282-1284 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general methodology is developed for simulating complicated reacting flow problems. This method combines the large-eddy simulation (LES) technique with the existing probability density function (PDF) approach for turbulent reacting flows and provides a closed form representation for all terms that are involved in the simulations. Some other issues related to this problem are also discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 956-959 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown how to construct amplitude mapping closures for molecular diffusion in a multispecies turbulent flow. The mappings are an extension of an earlier single-species mapping and they retain the property of an asymptotic approach to Gaussian states. The closure, in conjunction with a suitable closure for turbulent advection, is expected to be useful in treating multispecies diffusion as part of a single-point pdf modeling of chemically reactive flows.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2062-2069 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It is shown how to implement, via a Monte Carlo method, a single-scalar mapping closure for diffusion when chemical reactions or other processes are present. The mixing term in the one-point probability density function (pdf) equation of the scalar is closed via a mapping. The chemical term, closed in the pdf formulation, is treated exactly. To isolate each process, a fractional step technique is used. The methodology is the same if more processes are present. As an example, the pdf equation of one scalar reacting with itself in a statistically homogeneous forced turbulent flow is solved. Comparisons with computed direct numerical simulation data are excellent.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1625-1632 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The joint probability density function (pdf) of a scalar and its gradient are investigated. Under isotropic conditions, a relation is derived between this pdf and the joint pdf of a scalar and its x derivative. Physical properties of the scalar derivative are analyzed quantitatively to show that its pdf conditional on a given scalar value is close to a Gaussian distribution. The conditional pdf of the scalar derivative is then expanded according to the Gram–Charlier expansion. The coefficients of this expansion are evaluated using direct numerical simulation (DNS) of stationary turbulent scalar fields. Results obtained from a number of simulations support the assumption of a near-Gaussian distribution for the scalar derivative. Finally, the intermittency of the scalar gradient is discussed.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1028-1035 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amplitude mapping closure of Kraichnan [Bull. Am. Phys. Soc. 34, 2298 (1989); Phys. Rev. Lett. 63, 2657 (1989)] is used for statistical description of the mixing process by Fickian diffusion of a stochastically distributed scalar variable. This closure is invoked in the context of an evolution equation for the single-point probability density function (pdf) of the scalar from initially symmetric binary and trinary states. In the binary case, a simple recipe is provided for the time scaling relation which is very useful in model implementation. In the trinary case, it is shown that after a fixed elapsed time, the pdf relaxes to a distribution similar to that of the binary mixing. The magnitude of this time is independent of the initial extent of departure from a binary state; however, the rate of evolution toward an asymptotic Gaussian state depends on the level of the departure. In both cases, the closure predictions for the scalar flatness factor and the correlation of the mean square scalar–scalar gradients agree well with those obtained by direct numerical simulations (DNS). However, some features of the results are different from those of earlier DNS of mixing in stationary turbulence. These differences are likely attributed to inadequacy of the amplitude mapping closure at the single-point level in accounting for the effects of turbulence stretching.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 511-513 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The probability density function (pdf) of a passive scalar in homogeneous turbulence is studied using the mapping closure model recently developed by Kraichnan and co-workers. An analytical solution for the mapping equation is derived. This solution preserves the boundedness of the scalar fields and yields the pdf's that relax to Gaussian distributions, in agreement with experiments and numerical simulations.
    Type of Medium: Electronic Resource
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