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  • Quality control  (2)
  • 78.90. + t  (1)
  • 81.60.Bn  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Physical and material aspects in using visible laser pulses of nanosecond duration for ablation (1996)
    Springer
    Applied physics 63 (1996), S. 123-131 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 79.20.DS ; 81.90. + c ; 78.90. + t
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Interaction phenomena of 50 ns copper vapour laser pulses (λ = 511/578 nm) with matter are investigated. The basic ablation process is classified into four fundamental classes. On basis of this classification processing results are connected with specific material properties like the brittleness, the viscosity of the melt or the optical properties. Knowing these properties a prognosis of the expected fundamental process is possible. In order to generate a geometrically defined structure via ablation in a given material-specific process, strategies have to be developed. Typical examples for process strategies are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01567639
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  • 2
    Digitale Medien
    Digitale Medien
    Laser nitriding of iron: Nitrogen profiles and phases (1995)
    Springer
    Applied physics 61 (1995), S. 1-5 
    Details
    ISSN: 1432-0630
    Schlagwort(e): 61.80.Ba ; 52.75.-d ; 81.60.Bn ; 76.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Armco iron samples were surface nitrided by irradiating them with pulses of an excimer laser in a nitrogen atmosphere. The resulting nitrogen depth profiles measured by Resonant Nuclear Reaction Analysis (RNRA) and the phase formation determined by Conversion Electron Mössbauer Spectroscopy (CEMS) were investigated as functions of energy density and the number of pulses. The nitrogen content of the samples was found to be independent of the number of pulses in a layer of 50 nm from the surface and to increase in depths exceeding 150 nm. The phase composition did not change with the number of pulses. The nitrogen content can be related to an enhanced nitrogen solubility based on high temperatures and high pressures due to the laser-induced plasma above the sample. With increasing pulse energy density, the phase composition changes towards phases with higher nitrogen contents. Nitrogen diffusion seems to be the limiting factor for the nitriding process.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01538202
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  • 3
    Digitale Medien
    Digitale Medien
    The World Health Organization and International Atomic Energy Agency second interlaboratory comparison study in 16 countries on quality performance of nuclear medicine imaging devices (1988)
    Springer
    European journal of nuclear medicine 13 (1988), S. 495-501 
    Details
    ISSN: 1619-7089
    Schlagwort(e): Quality control ; Gamma camera ; Scanner
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Sixteen European countries participated in this WHO-IAEA intercomparison for which transmission CAP (College of American Pathologists) thyroid and IAEA-WHO liver phantoms were used. A total of 257 laboratories submitted 428 image evaluation reports. Overall results showed differences in performance between the various countries but similarities in performance for two gamma camera subgroups defined by year of manufacture, before and after 1980. A unique review of current European liver imaging practice is presented in terms of technical parameters, imaging conditions and evaluation procedures, and quality control procedures. The WHO-IAEA intercomparison demonstrated the need to establish new, or to improve the existing, quality control programmes in certain countries. However, the large number of participating laboratories, 257 compared with 70 in the previous WHO study, (Volodin et al. 1985), shows that these international studies are serving a useful purpose in promoting quality control in nuclear medicine imaging laboratories.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00256623
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  • 4
    Digitale Medien
    Digitale Medien
    External quality control of gamma cameras —results of an inter-laboratory comparison study in Austria (1990)
    Springer
    European journal of nuclear medicine 16 (1990), S. 23-28 
    Details
    ISSN: 1619-7089
    Schlagwort(e): Quality control ; Gamma camera ; Interlaboratory comparison ; ROC-curve ; Emission phantom
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Some 28 nuclear medicine departments out of a total of 40 participated in a nationwide Austrian interlaboratory comparison of the imaging quality of gamma cameras. The participation was voluntary, and confidentiality of the individual results was guaranteed. The survey was completed within 2 months, employing instructors to administrate the tests. An emission phantom simulating a flood field with non-uniformities was imaged by 43 cameras, and 54 images were evaluated. The test images were read by the participants using a graded rating scale to indicate the probability of the presence of a non-uniformity in the various parts of the image. The rating data were used to construct individual ROC curves for each image. The area under the ROC curve was used as the ranking parameter for image quality. The results show a spread of the ROC areas between 0.6 and 0.99, with a median of 0.81. A correlation was found between the year of installation and the ROC area obtained from the gamma camera, indicating improvements of performance in more recent cameras, which accounts for part of the variation of the ROC areas. The remaining variations are due to differences in the performance of the gamma cameras. Feedback was provided to the participants by describing individual performance with respect to the true structure of the phantom and by comparing this performance with that of the group. A questionnaire accompanying the test phantom yielded information about the practice of routine quality control and about details of the acquisition and analysis of images. The survey demonstrated the feasibility and usefulness of interlaboratory comparisons of this type even for a small number of participants. The feedback was found by the participants to be helpful and stimulated awareness of the importance of quality control.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01566008
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