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  • 1
    Digitale Medien
    Digitale Medien
    XTL-SIZE: a computer program for crystal-size-distribution calculation from X-ray diffraction line broadening (1990)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 23 (1990), S. 136-137 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A computer program has been written for the determination of crystal-size distribution in a direction perpendicular to an (hkl) crystal plane, from a digitized XRD peak. It implements an information theory approach devised by Guérin, Alvarez, Rebollo Neira, Plastino & Bonetto [Acta Cryst. (1986), A42, 30–35] and Alvarez, Bonetto, Guérin, Plastino & Rebollo Neira [Powder Diffr. (1987), 2, 220–224]. The program has a fully automated operation mode and owing to the very restricted amount of input data this program is specially suited to users with a limited knowledge of crystal-size-determination methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0021889889011775
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  • 2
    Digitale Medien
    Digitale Medien
    Statistical inference and crystallite size distributions (1986)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 42 (1986), S. 30-35 
    Details
    ISSN: 1600-5724
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: An information theory approach is devised in order to obtain crystallite size distributions from X-ray line broadening. The method is shown to be superior to those based on Fourier expansions, as illustrated by numerical examples and a realistic situation. The powder model of Warren and Averbach is considered, in which the sample is thought of as a 'column-like' structure of unit cells perpendicular to the diffraction plane. Errors in excess of 100% arise as a result of truncating the diffraction peak. It is shown that, with the present approach, the corresponding figure is reduced to 5%, which confirms the power of information theory, and makes this method especially convenient in those cases in which there are large overlaps between the tails of two diffraction peaks.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0108767386099944
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  • 3
    Digitale Medien
    Digitale Medien
    Measuring system for obtaining concentration profiles in supported catalysts using electron-probe microanalysis. Influence of standards (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 24 (1995), S. 3-8 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A system based on the EDAX 9100 analyser was developed to obtain concentration profiles. Even though the system can be used on any type of flat specimens, in this study it was used for measuring the tungsten (W) concentration on rough spherical specimens of the W-γ-Al2O3 supported catalyst. The concentration gradient of the active component from the periphery to the centre of the particle is often an important factor in determining catalyst performance. The purpose was to determine the concentration profile of W along the radius of a sphere with a large enough number of experimental points to draw accurate information in a short time. In this way, a considerable number of impregnated spheres can be analysed, and average results can be calculated and taken as representative values of the population under study. The method developed provides highly satisfactory results, making it very useful for the systematic study of this type of specimen. Obviously, the use of this system can be extended to metallurgical and mineralogical specimens.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300240103
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  • 4
    Digitale Medien
    Digitale Medien
    Deconvolution problems and information theoryWork partially supported by the Argentine National Research Council (CONICET) and the Buenos Aires Scientific Commision (CIC). (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 17 (1988), S. 47-52 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A method is derived, using information theory and the maximum entropy principle, for treating deconvolution problems. The approach is particularly suitable for the determination of instrumental effects in spectral lines. The technique is illustrated by recourse to numerical examples. A comparison is made with alternative methods. Although realistic situations are restricted to the correction of x-ray diffraction profiles (instrumental width), the formalism applies for any spectral technique.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300170204
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  • 5
    Digitale Medien
    Digitale Medien
    Intensity for cubic particles in x-ray fluorescence analysis (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 14 (1985), S. 2-7 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: Particle size effects constitute a major source of error in the x-ray fluorescence of granular material. Different models have been proposed to account for the influence of particle size on the characteristic x-ray intensity leaving the sample. Important points in these models are the granular distribution from each grain. Berry et al. proposed a model which is in reasonable agreement with experimental values. In this work, fluorescent intensity calculations for a cubic particle with different geometries were carried out. The intensity values obtained through this model were compared with the Berry et al. model. There is better agreement with the experimental values when the expression obtained is used in order to find the total fluorescent intensity using heterogeneous samples consisting of fluorescent and non-fluorescent components of particle size d.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300140103
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  • 6
    Digitale Medien
    Digitale Medien
    Measuring the dead time of an x-ray spectrometer by means of the first- and second-order reflections method (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 13 (1984), S. 44-45 
    Details
    ISSN: 0049-8246
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: The dead time of a Philips PW 1410 x-ray fluorescence spectrometer with a photon detector has been calculated employing intensities of first- and second-order reflections. The spread of the values obtained can be considered very satisfactory in the light of the experimental difficulties inherent in this method.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/xrs.1300130109
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