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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 3006-3018 
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Cross correlation measurements of the longitudinal velocity fluctuations in fully developed pipe flow have been performed with a reference hot-wire probe at a distance y+1 =100 from the wall for five different y+2 locations (namely, 50, 100, 200, 400, and 600) of a second probe with zero longitudinal separation but nonzero transverse separations. The pipe flow Reynolds number is 69 000 based on the pipe radius and the centerline velocity. The covariant (Co) and quadrature (Quad) correlations, which have been determined for each of the seven frequencies ω+ used to constrain the longitudinal wavenumber k+x, have been Fourier transformed with the transverse wavenumber k+z, y+1, y+2, and ω+ as the independent variables. The data presented in this form enable similarity to be examined in terms of waves of different sizes and inclinations. By using a similarity variable k+y+, where k+=[k+2x k+2z]1/2, the relative phases determined from the Co and Quad correlations and the wave intensity function for various wave angles have been shown to collapse. These results support the similarity hypothesis that the phase and intensity of the turbulance components is scaled by wave size k+ and distance from the wall y+. The dimension over which a turbulence structure retains its coherence has been deduced from the correlation data for various wave angles. Two estimates for the lifetime of turbulence structures have been derived, one from the phase-shifting effects of shear contained in the relative phase data, and the other from spectral sheet thickness data. Their significance and implications have been discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 180 (1957), S. 1072-1072 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Table 1 Weight average molecular weight x 10~3(26 ± 2) Intrinsic viscosity 100 cm.3 sol./gm. (25-0) Influence of rate of shear on viscosity at low ionic strength Sodium alginate Magnesium alginate (I) Magnesium alginate (II) 110 ± 20 1,250 ± 300 350 ± 100 9-34 ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    [s.l.] : Nature Publishing Group
    Nature 195 (1962), S. 1091-1092 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] High-speed photographic methods were used to observe a cleavage rhomb of calcite to which was applied a shear stress. Crossed polaroids in the optical system cause the twin lamellae to show up as bright areas while the parent crystal remains dark (apart from surface scratches). Stopped twins which ...
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The facultative hemiparasitic angiosperm Rhinanthus minor was grown on 11 different host species, and in the absence of a host. The height of R. minor parasitising the legume Trifolium pratense exceeded that of unattached plants by more than an order of magnitude, with performance on grasses and non-legume dicotlyedonous hosts between these two extremes. Light saturated rates of photosynthesis in R. minor on different hosts ranged from 1. 5 to 22. 5 μmol g−1 dry weight min−1, and were positively correlated with growth. Foliar nitrogen concentrations in the parasite exceeded those of the hosts. The former were positively related to light saturated rates of photosynthesis, and inversely related to photosynthetic nitrogen use efficiency. There was no relationship between leaf nitrogen concentration and water use efficiency in R. minor. The data are discussed in relation to studies of nitrogen and water use in mistletoes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 2 (1967), S. 233-237 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Tensile tests at 20° C have been carried out on seventy-three sapphire whiskers and on seventeen silicon nitride whiskers. The sapphire whiskers were of 〈0001〉, 〈1¯120〉, 〈10¯10〉, and 〈10¯11〉 orientations, while the silicon nitride whiskers were 〈0001〉, 〈11¯20〉, and 〈10¯13〉. Tensile strengths were in the range 45 to 1500 kg/mm2, and deformation was found to be purely elastic. The tensile strength data have been analysed and fitted to empirical equations describing the effect of size on strength for different orientations. These empirical equations have been used to deduce possible fracture nucleation mechanisms. It is concluded that, in the case of 〈0001〉 sapphire whiskers, fracture nucleation may be due to dislocation pile-ups or interactions, while in the other cases a Griffith flaw mechanism is probably applicable.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 2 (1967), S. 301-302 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 2 (1967), S. 347-353 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Tensile tests at 20
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 13 (1977), S. 77-83 
    ISSN: 1573-2673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird experimentell demonstriert, das die statistische Verteilung von Bruchbildungstellen in einer Scheibe, die auf einer Fläche unter zweidimensionaler Spannung steht, mit den Berechnungen der Weibull'schen Theorie für spröde Materialien übereinstimmt. Die maximale Wahrscheinlichkeit einer Bruchbildung tritt nicht in der Scheibenmitte auf, obwohl es sich hier um die Stelle der maximalen Zugspannung handelt. Die Ergebnisse bilden eine markante Demonstration des Grössen/Festigkeitseffektes in halbsproden Materialien.
    Kurzfassung: Résumé On a démontré, moyennant une experimentation, que la repartition statistique de points d'amorcement de fractures, sur un disque qu'on soumet à des contraintes biaxes sur une de ses faces, accord bien avec une notion Weibull de points faibles. La probabilité maximale de fracture ne se produit pas au centre du disque, bien que ce soit à ce point que la force de traction est maximale. Les resultats montrent d'une façon frappante l'effet du rapport “cote-resistance” sur les materiaux dits “semi-fragiles”.
    Notizen: Abstract It is demonstrated experimentally that the statistical distribution of fracture initiation points in a disc which is subjected to biaxial tension on one face is consistent with predictions of a Weibull weakest link theory. The maximum probability of fracture initiation does not occur at the disc centre even though this is the point of maximum tensile strain. The results form a striking demonstration of the size-strength effect in semi-brittle materials.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials science 4 (1969), S. 15-20 
    ISSN: 1573-4803
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract Tensile tests have been carried out on 124 sapphire whiskers at temperatures in the range 350 to 1810° C. The effects of crystallographic orientation, growth process, purity and surface perfection have been investigated. The strength-temperature-dependences of different categories of whisker are compared with that to be expected for a Griffith fracture mechanism, and it is shown that such a mechanism may apply up to ∼1000° C to A-type (〈hk.o〉) whiskers grown by the wet-hydrogen process [1]. Chemically-polished whiskers of this type show a strength-temperature-dependence more consistent with a dislocation-induced fracture mechanism. There is some evidence that chemically-polished C-type (〈0001〉) whiskers grown by a chloride oxidation process [2] behave in the same manner. For other categories of whisker there are insufficient data to ascribe fracture mechanisms.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Monatshefte für Chemie 98 (1967), S. 887-890 
    ISSN: 1434-4475
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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