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  • 1
    Electronic Resource
    Electronic Resource
    SHEAR-WAVE VELOCITY ESTIMATION FROM FULL SONIC WAVEFORM BY THE EXTENDED-LATTICE PREDICTOR (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 38 (1990), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: One of the basic parameters of the rock formation surrounding a fluid-filled borehole to be estimated is the shear-wave velocity. In the present contribution a novel method for carrying out this estimate, based on the use of linear prediction techniques, is proposed. It is assumed that the shape and energy content of each wave can be accurately modelled by an ARMA (Auto Regressive Moving Average) impulsive process and by an appropriate delay. The overall seismogram is then considered to be a multiple impulsive ARMA process and the estimation is carried out by using the residual at the output of an extended version of the Burg lattice predictor. The resulting algorithm is very effective as illustrated by several examples performed on synthetic and real seismograms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1990.tb01856.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    SYNTHESIS OF ACOUSTIC WELL-LOGGING WAVEFORMS ON AN IRREGULAR GRID (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 34 (1986), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The need for synthetic seismograms arises in several acoustic well-logging contexts. We propose a numerical algorithm for computing the seismograms, characterized by a very reduced computational cost. Unlike previous contributions appearing in the technical literature, the proposed algorithm is based on a non-uniform sampling step and on linear interpolation for computing the integrals involved in the synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1986.tb00519.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Efficient Minimisation of the KL Distance for the Approximation of Posterior Conditional Probabilities (1997)
    Springer
    Neural processing letters 5 (1997), S. 47-55 
    Details
    ISSN: 1573-773X
    Keywords: conditional probabilities estimate ; Kullback–Leibler distance ; MLP classifier training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The minimisation of a least mean squares cost function produces poor results in the ranges of the input variable where the quantity to be approximated takes on relatively low values. This can be a problem if an accurate approximation is required in a wide dynamic range. The present paper approaches this problem in the case of multilayer perceptrons trained to approximate the posterior conditional probabilities in a multicategory classification problem. The use of a cost function derived from the Kullback–Leibler information distance measure is proposed and a computationally light algorithm is derived for its minimisation. The effectiveness of the procedure is experimentally verified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009605310499
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    Paper (German National Licenses)
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