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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 9 (1999), S. 71-82 
    ISSN: 1434-6036
    Keywords: PACS. 36.20.-r Macromolecules and polymer molecules - 61.10.-i X-ray diffraction and scattering - 82.70.Gg Gels and sols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl metacrylate (EGDMA) was investigated in solution at different molar ratios R = [EGDMA]/[MMA] between 0 and 0.05. Initially mainly linear PMMA was formed with weight average molar mass 7.5 g/mol independent of R. At larger reaction extents branched polymers were formed and the systems gelled. The scattering intensity rose initially with the reaction extent, but reached a plateau value at larger reaction extents. The plateau value increased strongly with R. Dynamic light scattering showed the appearance of a slow relaxation not observed in linear PMMA solutions. The data can be interpreted by assuming that the excess scattering originates from the branching points and relaxes through self diffusion of the branched particles. The results agree with predictions of the percolation model for gelation and Rouse dynamics. Viscosity measurements corroborate this interpretation. Measurements on a progressively diluted sample quenched close to the gel point again showed quantitative agreement with the percolation model for gelation.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Cross sections for stripping and dissociation of deuterons interacting with Be targets in the 100–2300 MeV energy range have been measured. Comparisons with model calculations suggest a dominant contribution of the stripping process. It is also shown that the deuteron break-up cross section exhibits the same energy dependence as the nucleon-nucleon cross section.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 12 (1999), S. 91-97 
    ISSN: 1434-6036
    Keywords: PACS. 82.70.Gg Gels and sols - 83.80.Jx Chemically reactive materials - 64.60.Ak Renormalization-group, fractal, and percolation studies of phase transitions - 02.70.Lq Monte-Carlo and statistical methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: 3d lattice Monte-Carlo simulations were done to obtain the mass distribution (N(m)) and pair correlation function (g(r)) of percolating clusters. We give analytical expressions of the external cut-off functions of N(m) at the z-average mass and of g(r) at the radius of gyration. The simulation results were compared with experimental results on gel forming systems reported in the literature. The comparison shows that the experimental results are compatible with the simulation results. However, more experiments are needed before we can be confident that the percolation model is a good model for the sol-gel transition.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 14 (1997), S. 1275-1277 
    ISSN: 1573-904X
    Keywords: X-ray scattering ; human stratum corneum ; electroporation, high voltage pulses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 90 (1996), S. 139-159 
    ISSN: 1573-2878
    Keywords: Nonlinear parameter estimation ; associative memory ; adaptive training ; linear associative memory matrix ; weighted cost function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The method of linear associative memory (LAM), a notion from the field of artificial neural nets, has been applied recently in nonlinear parameter estimation. In the LAM method, a model response, nonlinear with respect to the parameters, is approximated linearly by a matrix, which maps inversely from a response vector to a parameter vector. This matrix is determined from a set of initial training parameter vectors and their response vectors, and can be update recursively and adaptively with a pair of newly generated parameter response vectors. The LAM advantage is that it can yield a good estimation of the true parameters from a given observed response, even if the initial training parameter vectors are far from the true values. In this paper, we present a weighted linear associative memory (WLAM) for nonlinear parameter estimation. WLAM improves LAM by taking into account an observed response vector oriented weighting. The basic idea is to weight each pair of parameter response vectors in the cost function such that, if a response vector is closer to the observed one, then this pair plays a more important role in the cost function. This weighting algorithm improves significantly the accuracy of parameter estimation as compared to a LAM without weighting. In addition, we are able to construct the associative memory matrix recursively, while taking the weighting procedure into account, and simultaneously update the ridge parameter α of the cost function further improving the efficiency of the WLAM estimation. These features enable WLAM to be a powerful tool for nonlinear parameter simulation.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2945-2946 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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