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  • 1
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The erosion properties of brittle materials depend upon plastic deformation and crack generation at an impact or indented site. Vickers indentations have been used to investigate the plastic processes and crack systems in chemical vapour deposited zinc sulphide of different grain sizes. The hardness,H, and the “local” fracture toughnessK c, are dependent upon the grain size of the material. For small grain size material (〈50 Μm) the Vickers hardness was found to increase with decreasing grain size in accord with the Petch mechanism, i.e.H=H 0 +kd −1/2 wherek andH 0 are constants andd is the grain diameter. A maximum hardness of ca. 4 GPa has been observed for material with an average 0.5 Μm grain diameter. In large grain size material, hardness anisotropy within the grains causes significant experimental scatter in the hardness measurements because the plastic impression formed by the indenter (load 10 N and 100 N) is smaller than the grain diameter. The values ofK c obtained using an indentation technique show that for grain sizes less than 8 ΜmK c decreases with decreasing grain size. For materials with a grain size in the range 500 Μm to 8 Μm, well developed median cracks were not observed, however, the radius of the fracture zone was measured in order to estimate an “effective”K c. The “effective”K c was found to increase approximately linearly with the reciprocal root of the grain size. Consideration of the models for elastic/plastic impact and micromechanics of crack nucleation in conjuction with the variation ofK c andH, indicate that zinc sulphide with a mean grain size of 8 Μm will give the optimum solid particle and rain erosion resistance.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The analyses of density fields, nitrate and chlorophyll α concentrations, Lagrangian current measurements and remote sensing of sea surface temperatures demonstrated an island mixing effect for Monhegan Island (Gulf of Maine). The island's unique location within the westward flowing arm of a counterclockwise basin gyre and the bathymetry surrounding the island result in a combination of vertical mixing and upwelling to produce chlorophyll maxima on the north and south flanks of the island.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Manuscripta mathematica 35 (1981), S. 91-103 
    ISSN: 1432-1785
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we investigate the prediction (or best approximation) operator from a uniformly convex real Orlicz space to a subset of σ-lattice measurable functions. In particular, a counterexample to the monotoncity property, which holds in Lp spaces, is given. Also, a sufficient condition for monotonicity to hold is given. Finally, nested σ-lattices, as occur in isotonic regression, are considered.
    Type of Medium: Electronic Resource
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