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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical geology 25 (1993), S. 559-572 
    ISSN: 1573-8868
    Schlagwort(e): heterogeneity ; random permeability field ; anisotropy ; correlation length
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Mathematik
    Notizen: Abstract Aquifer properties, for example permeability and porosity, vary in space and may be characterized by their distributions. The property distribution is not totally random but shows some correlation structure. Because most of the values are not known, some rational method is required to generate credible aquifer distribution properties for inclusion in fluid transport models. This paper presents a numerically efficient method of generating geostatistical random fields, by the source Point Method (SPM). The SPM is a very efficient method and requires little computer time and relatively small data storage, as compared to other methods of generating random fields. In addition, the SPM is modified to include any desired amount of anisotropy in the property distribution of a system. By using conditional covariances, a formula for a two-dimensional anisotropic field is derived to prespecify the desired correlation length in any direction. Results show that for an anisotropic medium the correlation length can be pre-specified in any specific direction.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 1005-1008 
    ISSN: 1040-0397
    Schlagwort(e): Quadridentate dihydrogen perchlorate ; Macrocyclic membrane ; Zn2+ ions ; Baby foods ; Soft drinks ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A quadridentate dihydrogen perchlorate macrocyclic membrane is found to exhibit quite promising selectivity for Zn2+. It can be used to estimate zinc in the range 2.5 × 10-6 to 1.0 × 10-1 mol dm-3 (0.16 to 6.50 × 103 mg dm-3) with a near-Nernstian slope of ≍ 28 mV per decade of concentration. The working pH range of the sensor is 3.0 to 7.0. The polystyrene based membrane electrode is found to possess adequate stability and specific selectivity with a response time of 10 s. Most of the ions that interfere with Zn2+ electrode do not cause any significant disturbance with this assembly and the sensor can be used for more than three months in aqueous as well as in partially nonaqueous media. The utility of the membrane sensor has also been observed in solutions contaminated with detergent matter. The membrane sensor has also been used successfully to analyse some baby food products and soft drinks for the determination of Zn2+ ions.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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