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  • Engineering  (2)
  • rare earths  (2)
  • 1990-1994  (4)
  • 1935-1939
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  • 1
    ISSN: 1436-5073
    Keywords: rare earths ; terbium oxide ; inductively coupled plasma atomic emission spectrometry (ICP-AES)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Inductively coupled plasma atomic emission spectrometry (ICP-AES) was employed to determine Y, Sm, Eu, Gd, Dy, Ho and Er in high purity terbium oxide. Terbium oxide was dissolved in 0.5 mol/l HNO3 and nebulized into the plasma generated by a 56 MHz RF generator at 1.5 kW output power. Using a Jobin-Yvon 1-m Czenry-Turner high resolution, high dispersion scanning monochromator, lines mutually interference-free as well as free of interference from the matrix Tb were chosen for the seven analytes. A set of standards containing the analytes in the concentration range 0.01–1.0 gmg/ml with 1 mg/ml Tb was used for calibration. It was necessary to apply background correction to the gross analyte line intensities in order to obtain linear calibration plots for the analytes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-5073
    Keywords: yttrium oxide ; rare earths ; inductively coupled plasma-atomic emission spectrometry (ICP-AES)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Traces of heavy rare earth elements (Eu-Lu) were determined in high purity yttrium oxide by inductively coupled plasma atomic emission spectrometry. The yttrium oxide samples were dissolved in nitric acid and the solutions analyzed with a plasma produced by a 56 MHz RF generator at an output power of 1.5 kW. Using a high resolution sequential monochromator, interference-free spectral lines for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu could be found for calibration. The detection limits for the above elements have been found to be slightly higher in the presence of yttrium matrix, than in aqueous solution. This could be attributed to background enhancements due to the presence of yttrium. The mean RSD of the method varied between 2.3% and 6.3% in the concentration range 0.01 and 0.5 μg/ml. The percentage recovery ranged from 84 to 106 for the different rare earth elements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 17 (1993), S. 975-993 
    ISSN: 0271-2091
    Keywords: Navier-Stokes equations ; Mass and momentum balance ; Non-orthogonal control volume ; Gauss-Legendre quadrature ; Pressure correction ; Flow over bluff bodies ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical method for predicting viscous flows in complex geometries has been presented. Integral mass and momentum conservation equations are deploved and these are discretized into algebraic form through numerical quadrature. The physical domain is divided into a number of non-orthogonal control volumes which are isoparametrically mapped on to standard rectangular cells. Numerical integration for unsteady mementum equations is performed over such non-orthogonal cells. The explicitly advanced velocity components obtained from unsteady momentum equations may not necessarily satisfy the mass conservation condition in each cell. Compliance of the mass conservation equation and the consequent evolution of correct pressure distribution are accomplished through an iterative correction of pressure and velocity till divergence-free condition is obtained in each cell. The algorithm is applied on a few test problems, namely, lid-driven square and oblique cavities, developing flow in a rectangular channel and flow over square and circular cylinders placed in rectangular channels. The results exhibit good accuracy and justify the applicability of the algorithm.This Explicit Transient Algorithm for Flows in Arbitrary Geometry is given a generic name EXTRAFLAG.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 1473-1484 
    ISSN: 0271-2091
    Keywords: Bluff body ; Wake ; Vortex shedding ; Unsteady periodic flow ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The structure of confined wakes behind a square cylinder in a channel is investigated via the numerical solution of the unsteady Navier-Stokes equations. Vortex shedding behind the cylinder induces periodicity in the flow field. Details of the phenomenon are simulated through numerical flow visualization. The unsteady periodic wake can be characterized by the Strouhal number, which varies with the Reynolds number and the blockage ratio of the channel. The periodicity of the flow is, however, damped in the downstream region of a long duct. This damping may be attributed to the influence of side walls on the flow structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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