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  • 1
    In: Artificial Intelligence, Elsevier BV, Vol. 213 ( 2014-08), p. 1-41
    Type of Medium: Online Resource
    ISSN: 0004-3702
    RVK:
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 1468341-6
    detail.hit.zdb_id: 218797-8
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  • 2
    Online Resource
    Online Resource
    Elsevier BV ; 2016
    In:  Artificial Intelligence Vol. 233 ( 2016-04), p. 84-121
    In: Artificial Intelligence, Elsevier BV, Vol. 233 ( 2016-04), p. 84-121
    Type of Medium: Online Resource
    ISSN: 0004-3702
    RVK:
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2016
    detail.hit.zdb_id: 1468341-6
    detail.hit.zdb_id: 218797-8
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  • 3
    Online Resource
    Online Resource
    JSTOR ; 1984
    In:  Twentieth Century Literature Vol. 30, No. 1 ( 1984-21), p. 1-
    In: Twentieth Century Literature, JSTOR, Vol. 30, No. 1 ( 1984-21), p. 1-
    Type of Medium: Online Resource
    ISSN: 0041-462X
    RVK:
    Language: Unknown
    Publisher: JSTOR
    Publication Date: 1984
    detail.hit.zdb_id: 2067117-9
    SSG: 7,25
    SSG: 7,12
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  • 4
    Online Resource
    Online Resource
    Elsevier BV ; 2010
    In:  Artificial Intelligence Vol. 174, No. 15 ( 2010-10), p. 1172-1221
    In: Artificial Intelligence, Elsevier BV, Vol. 174, No. 15 ( 2010-10), p. 1172-1221
    Type of Medium: Online Resource
    ISSN: 0004-3702
    RVK:
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2010
    detail.hit.zdb_id: 1468341-6
    detail.hit.zdb_id: 218797-8
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  • 5
    Online Resource
    Online Resource
    Elsevier BV ; 2014
    In:  Artificial Intelligence Vol. 216 ( 2014-11), p. 233-274
    In: Artificial Intelligence, Elsevier BV, Vol. 216 ( 2014-11), p. 233-274
    Type of Medium: Online Resource
    ISSN: 0004-3702
    RVK:
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 1468341-6
    detail.hit.zdb_id: 218797-8
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  • 6
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2000
    In:  The Journal of the Acoustical Society of America Vol. 108, No. 1 ( 2000-07-01), p. 223-234
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 108, No. 1 ( 2000-07-01), p. 223-234
    Abstract: To focus ultrasonic waves in an unknown inhomogeneous medium using a phased array, one has to calculate the optimal set of signals to be applied on the transducers of the array. In the case of time-reversal mirrors, one assumes that a source is available at the focus, providing the Green’s function of this point. In this paper, the robustness of this time-reversal method is investigated when loss of information breaks the time-reversal invariance. It arises in dissipative media or when the field radiated by the source is not entirely measured by the limited aperture of a time-reversal mirror. However, in both cases, linearity and reciprocity relations ensure time reversal to achieve a spatiotemporal matched filtering. Nevertheless, though it provides robustness to this method, no constraints are imposed on the field out of the focus and sidelobes may appear. Another approach consists of measuring the Green’s functions associated to the focus but also to neighboring points. Thus, the whole information characterizing the medium is known and the inverse source problem can be solved. A matrix formalism of the propagation operator is introduced to compare the time-reversal and inverse filter techniques. Moreover, experiments investigated in various media are presented to illustrate this comparison.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2000
    detail.hit.zdb_id: 1461063-2
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  • 7
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2004
    In:  The Journal of the Acoustical Society of America Vol. 115, No. 5_Supplement ( 2004-05-01), p. 2468-2468
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 115, No. 5_Supplement ( 2004-05-01), p. 2468-2468
    Abstract: Time reversal arrays are becoming common tools whether for detection, tomography or communication. These applications require the measurement of the response from the array to one or several receivers. The most natural way to record different impulse responses between several points is to generate pulses successively from each emitting point and directly record all the impulse responses on the recording points. However, this method is very time consuming and inefficient in terms of signal-to-noise ratio. Hence, in this work, we propose an original way of sending continuous signals simultaneously from all the sources, recording all the pressure fields on the receivers and processing them in order to extract the exact impulse responses by matched filter. To this end, the signals are adapted to the environment and, more specifically, to highly dispersive media. These adaptive instant records signals (AIRS) are used experimentally to detect targets using the time reversal operator decomposition method. The quality of the 15×15 transfer functions acquired simultaneously, and therefore, the detection capability is demonstrated in shallow water in the presence of bottom absorption and reverberation. Finally, the connection of AIRS with CDMA and FDMA that are two coding techniques used in telecommunication is shown.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2004
    detail.hit.zdb_id: 1461063-2
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  • 8
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2003
    In:  The Journal of the Acoustical Society of America Vol. 113, No. 4_Supplement ( 2003-04-01), p. 2211-2211
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 113, No. 4_Supplement ( 2003-04-01), p. 2211-2211
    Abstract: The decomposition of the time reversal operator (DORT) method applies to active detection and focusing of acoustic waves using arrays of transmitters and receivers. This method allows detection and selective focusing on scatterers through complex media. It consists in the construction of the invariants of the time reversal process, that are also the singular vectors of the array response matrix. The DORT method is particularly interesting for detection in inhomogeneous media when the acoustic properties are poorly known. However, if an estimate of the medium’s Green function is available, images of the medium can be formed by backpropagation of the dominant eigenvectors. For the detection of defect in scattering media like titanium, the method is useful to separate the echo of a defect from the microstructure contribution and thus to reduce speckle noise. We will also see that the time reversal operator can be interpreted as a pseudocovariance matrix like those encountered in classical array signal processing. And as shown by Anthony J. Devaney [J. Acoust. Soc. Am. 110, 2617 (2001)], nonlinear estimators like MUSIC can be applied to achieve high resolution. These different points will be illustrated through several experimental results.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2003
    detail.hit.zdb_id: 1461063-2
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  • 9
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 2007
    In:  The Journal of the Acoustical Society of America Vol. 122, No. 2 ( 2007-08-01), p. 761-768
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 122, No. 2 ( 2007-08-01), p. 761-768
    Abstract: A rigid 24-element source-receiver array in the 10–15kHz frequency band, connected to a programmable electronic system, was deployed in the Bay of Brest during spring 2005. In this 10- to 18-m-deep environment, backscattered data from submerged targets were recorded. Successful detection and focusing experiments in very shallow water using the decomposition of the time reversal operator (DORT method) are shown. The ability of the DORT method to separate the echo of a target from reverberation as well as the echo from two different targets at 250m is shown. An example of active focusing within the waveguide using the first invariant of the time reversal operator is presented, showing the enhanced focusing capability. Furthermore, the localization of the scatterers in the water column is obtained using a range-dependent acoustic model.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2007
    detail.hit.zdb_id: 1461063-2
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  • 10
    Online Resource
    Online Resource
    Acoustical Society of America (ASA) ; 1998
    In:  The Journal of the Acoustical Society of America Vol. 103, No. 5 ( 1998-05-01), p. 2403-2410
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 103, No. 5 ( 1998-05-01), p. 2403-2410
    Abstract: The time-reversal process is applied to focus pulsed ultrasonic waves through the human skull bone. The aim here is to treat brain tumors, which are difficult to reach with classical surgery means. Such a surgical application requires precise control of the size and location of the therapeutic focal beam. The severe ultrasonic attenuation in the skull reduces the efficiency of the time reversal process. Nevertheless, an improvement of the time reversal process in absorbing media has been investigated and applied to the focusing through the skull [J.-L. Thomas and M. Fink, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43, 1122–1129 (1996)]. Here an extension of this technique is presented in order to focus on a set of points surrounding an initial artificial source implanted in the tissue volume to treat. From the knowledge of the Green’s function matched to this initial source location a new Green’s function matched to various points of interest is deduced in order to treat the whole volume. In a homogeneous medium, conventional steering consists of tilting the wave front focused on the acoustical source. In a heterogeneous medium, this process is only valid for small angles or when aberrations are located in a layer close to the array. It is shown here how to extend this method to aberrating and absorbing layers, like the skull bone, located at any distance from the array of transducers.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    RVK:
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1998
    detail.hit.zdb_id: 1461063-2
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