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  • 1
    Online Resource
    Online Resource
    Genitrix
    Wiley ; 1967
    In:  The Modern Language Journal Vol. 51, No. 3 ( 1967-03), p. 181-
    Details
    In: The Modern Language Journal, Wiley, Vol. 51, No. 3 ( 1967-03), p. 181-
    Type of Medium: Online Resource
    ISSN: 0026-7902
    URL: Article
    DOI: 10.2307/323678
    RVK:
    EA 1000
    RVK:
    EQ 1000 � EA 4100
    Language: Unknown
    Publisher: Wiley
    Publication Date: 1967
    detail.hit.zdb_id: 2016414-2
    SSG: 7,11
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  • 2
    Online Resource
    Online Resource
    Demonstration of a quasi-monostatic autonomous underwater vehicle based high duty cycle active sonar
    Acoustical Society of America (ASA) ; 2019
    In:  The Journal of the Acoustical Society of America Vol. 145, No. 1 ( 2019-01-01), p. EL90-EL96
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 145, No. 1 ( 2019-01-01), p. EL90-EL96
    Abstract: The feasibility of resolving target returns within receive signals collected by a continuously transmitting quasi-monostatic, broadband, autonomous underwater vehicle (AUV) based sonar is explored. Theoretical studies supported by experimental results suggest that it is possible to capture the source-to-receiver coupling response and target scattering with sufficient fidelity during the continuous transmission to enable detection and (potentially) classification processing. Demonstrations focused upon the detection of a bottomed target object at sea using transmit signals with duty cycles of 60% and 100% indicate that such an approach is feasible for a representative AUV-based side looking sonar system operating in shallow water.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.5088029
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2019
    detail.hit.zdb_id: 1461063-2
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  • 3
    Online Resource
    Online Resource
    Bistatic, above-critical angle scattering measurements of fully buried unexploded ordnance (UXO) and clutter
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 132, No. 5 ( 2012-11-01), p. 3076-3085
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 132, No. 5 ( 2012-11-01), p. 3076-3085
    Abstract: Laboratory grade bistatic scattering measurements are conducted in order to examine the acoustic response of realistic fully buried unexploded ordnance (UXO) from above-critical angle insonification, between 2 and 40 kHz. A 127 mm diameter rocket UXO, a 155 mm diameter artillery shell, a natural rock of approximately the same size, and a cinder block are fully buried in water-saturated medium grained sand (mean grain diameter, 240 μm) at depths of 10 cm below the water–sediment interface. A two-dimensional array of bistatic scattering measurements is generated synthetically by scanning a single hydrophone in steps of 3 cm over a 1 m × 1 m patch directly above the targets at a height of 20 cm above the water–sediment interface. Three-dimensional volumetric acoustic images generated from the return waveforms reveal scattering components attributed to geometric and elastic scattering, as well as multiple-scattering interactions of returns between the sediment–water interface and the buried objects. The far-field target strength of the objects is estimated through extrapolation of the angular spectrum. Agreement is found between experimental data and simulated data generated from a finite-element-based, three-dimensional time-harmonic model (2–25 kHz). Separation of the measured UXO from the clutter objects is demonstrated through exploitation of structural-acoustics-based features.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4757098
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
    detail.hit.zdb_id: 1461063-2
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  • 4
    Online Resource
    Online Resource
    Identifying buried unexploded ordnance with structural acoustics based numerically trained classifiers: Laboratory demonstrations
    Acoustical Society of America (ASA) ; 2014
    In:  The Journal of the Acoustical Society of America Vol. 136, No. 4_Supplement ( 2014-10-01), p. 2112-2112
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 136, No. 4_Supplement ( 2014-10-01), p. 2112-2112
    Abstract: Strategies for the automated detection and classification of underwater unexploded ordnance (UXO), based upon structural acoustics derived features, are currently being transitioned to autonomous underwater vehicle based sonar systems. The foundation for this transition arose, in part, from extensive laboratory investigations conducted at the Naval Research Laboratory. We discuss the evolution of structural acoustic based methodologies, including research into understanding the free-field scattering response of UXO and the coupling of these objects, under varying stages of burial, to water-saturated sediments. In addition to providing a physics-based understanding of the mechanisms contributing to the scattering response of objects positioned near the sediment–water interface, this research supports the validation of three-dimensional finite-element-based models for large-scale structural–acoustics problems. These efforts have recently culminated with the successful classification of a variety of buried UXO targets using a numerically trained relevance vector machine (RVM) classifier and the discrimination of these targets, under various burial orientations, from several objects representing both natural and manmade clutter. We conclude that this demonstration supports the transition of structural acoustic processing methodologies to maritime sonar systems for the classification of challenging UXO targets. [Work supported by ONR and SERDP.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4899605
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2014
    detail.hit.zdb_id: 1461063-2
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  • 5
    Online Resource
    Online Resource
    Measurements and modeling of acoustic scattering from targets in littoral environments
    Acoustical Society of America (ASA) ; 2014
    In:  The Journal of the Acoustical Society of America Vol. 136, No. 4_Supplement ( 2014-10-01), p. 2111-2111
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 136, No. 4_Supplement ( 2014-10-01), p. 2111-2111
    Abstract: Broadband laboratory and at-sea measurements systems have been built by NRL to quantify the acoustic target strength of objects sitting on or in the bottom of littoral environments. Over the past decade, these measurements and the subsequent modeling of the target strength have helped to develop an understanding of how the environment, especially near the bottom interface, impacts the structural acoustic response of a variety of objects. In this talk we will present a set of laboratory, at-sea rail and AUV based back scatter, forward scatter, and propagation measurements with subsequent analysis to understand the impact of the littoral environment. Simple targets such as spheres, along with UXO targets will be discussed. The analysis will be focused on quantifying the changes to target strength as a result of being near the bottom interface. In addition to the traditional backscatter or monosatic target strength, we focus upon efforts to investigate the multi-static scattering from targets. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4899601
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2014
    detail.hit.zdb_id: 1461063-2
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  • 6
    Online Resource
    Online Resource
    Acoustic identification of buried underwater unexploded ordnance using a numerically trained classifier (L)
    Acoustical Society of America (ASA) ; 2012
    In:  The Journal of the Acoustical Society of America Vol. 132, No. 6 ( 2012-12-01), p. 3614-3617
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 132, No. 6 ( 2012-12-01), p. 3614-3617
    Abstract: Using a finite element-based structural acoustics code, simulations were carried out for the acoustic scattering from an unexploded ordnance rocket buried in the sediment under 3 m of water. The simulation treated 90 rocket burial angles in steps of 2°. The simulations were used to train a generative relevance vector machine (RVM) algorithm for identifying rockets buried at unknown angles in an actual water/sediment environment. The trained RVM algorithm was successfully tested on scattering measurements made in a sediment pool facility for six buried targets including the rocket at 90°, 120°, and 150°, a boulder, a cinderblock, and a cinderblock rolled 45° about its long axis.
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4763997
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2012
    detail.hit.zdb_id: 1461063-2
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  • 7
    Online Resource
    Online Resource
    Acoustic imaging and structural acoustic analysis of laboratory measurements of scattering from buried targets above critical grazing angles
    Acoustical Society of America (ASA) ; 2011
    In:  The Journal of the Acoustical Society of America Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2341-2341
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 130, No. 4_Supplement ( 2011-10-01), p. 2341-2341
    Abstract: A broadband (3-40 kHz) compact range measurement technique has been developed to obtain the acoustic scattering from buried unexploded ordnance and objects simulating natural and man-made clutter. The targets—two 5 in. rockets with 0, 30, and 60 deg pitch angles, a large rock, and cinder blocks with 0 and 45 deg roll—are buried 10 cm beneath the surface of a water-saturated sandy bottom with a mean grain size of 240 μm. A 2D synthetic array is generated at a height of 20 cm above the sediment–water interface with an element spacing of 3 cm (25 kHz Nyquist). Waveforms collected on the synthetic array are processed to extract the structural acoustic response of the buried targets. A Relevance Vector Machine algorithm applied to the scattered data for target identification, which shows that the target features separate even as the receiver array size is considerably decreased. Similar results are presented for numerical simulations of the bistatic returns for the buried 5 in. rocket and a rock of comparable size. [Work supported by ONR and SERDP.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3654366
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2011
    detail.hit.zdb_id: 1461063-2
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  • 8
    Online Resource
    Online Resource
    Processing techniques applied to underwater target echoes and their relationships.
    Acoustical Society of America (ASA) ; 2009
    In:  The Journal of the Acoustical Society of America Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2608-2608
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 125, No. 4_Supplement ( 2009-04-01), p. 2608-2608
    Abstract: Interest in acoustic scattering from underwater unexploded ordnance (UXO) has been increasing because of the growing need for sonar technology able to detect submerged UXO and to efficiently separate these detections from those due to natural and man-made clutter. Recent efforts range from laboratory and numerical studies seeking to understand the basic structural acoustic echo formation processes and the environmental effects on them to field exercises determining how well a particular detection/identification technology performs. This paper discusses several important scattering-based constructs, which have been utilized in both the basic UXO studies and the technology exercises as well. They include: (1) σ(ω, θ), the frequency/angle-dependent scattering cross section; (2) standard imagery, oftentimes implemented with synthetic aperture arrays; (3) reflection tomography imaging; and (4) supersonic imaging using holographic techniques. Without a clear appreciation for the differences among the constructs, it is difficult to properly relate the results of the various studies. We have measured the broadband scattering from several underwater UXO targets using laboratory, rail-based, and AUV systems and processed the data using the above constructs. The use of a common, high quality UXO scattering data base in this process helps clarify the differences and relationships among the constructs. [Work supported by SERDP and ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.4783932
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2009
    detail.hit.zdb_id: 1461063-2
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  • 9
    Online Resource
    Online Resource
    Sound penetration into unconsolidated sand: Quantifying and predicting acoustic scattering from proud, half buried and fully buried targets in both the laboratory and littoral environments using direct measurements of sound speed in the sandy bottom.
    Acoustical Society of America (ASA) ; 2010
    In:  The Journal of the Acoustical Society of America Vol. 128, No. 4_Supplement ( 2010-10-01), p. 2294-2294
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 128, No. 4_Supplement ( 2010-10-01), p. 2294-2294
    Abstract: The impact of unconsolidated sandy bottoms on sound propagations and scattering from targets of interest is quantified with a series of experiments in both the laboratory and in littoral environments. In the laboratory, the sound speed and attenuation is well quantified and a series of proud, partially buried and fully buried scattering measurements from a variety of targets is discussed. The compressional sound speed and dispersion is important in understanding the propagation of sound into and out of sandy bottoms and the impact of scattering from buried targets both above and below the critical angle. The compressional sound speed and dispersion are important to understand and model the unconsolidated sandy bottom and to predict the impedance loading and impact to scattering signatures from targets. We will detail several laboratory and field measurements of the compressional sound speed and scattering from buried targets. Also, we will show measurements and predictions of scattering from targets in various states of burial. Propagation models will be used to predict sound propagation and scattering in the sandy bottom and will be compared to measurements of sound propagating through the sandy bottom at close and long ranges. [Work supported by ONR.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.3508056
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 2010
    detail.hit.zdb_id: 1461063-2
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  • 10
    Online Resource
    Online Resource
    Local admittance fluctuations and the scattering from a cylindrical shell with many internal oscillators
    Acoustical Society of America (ASA) ; 1997
    In:  The Journal of the Acoustical Society of America Vol. 102, No. 5_Supplement ( 1997-11-01), p. 3072-3072
    Details
    In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 102, No. 5_Supplement ( 1997-11-01), p. 3072-3072
    Abstract: The angular and spectral scattering patterns from local admittance fluctuations, assumed to be caused by the presence of mechanical, dumbbell oscillators attached more or less randomly in the interior of a cylindrical shell, are predicted numerically and compared to the experimental measurements reported by Bucaro et al. [Proc. ASME, Noise Control and Acoustics Division, NCA 22, 87–92 (1996)] and Photiadis et al. [J. Acoust. Soc. Am. 101, 895–899 (1997)] . The numerical results are shown to be in reasonable agreement with what is observed experimentally. It is suggested that scattering contributions from such local admittance fluctuations can be a significant component in the midfrequency scattering patterns of submerged targets of interest. [Work supported by the Office of Naval Research.]
    Type of Medium: Online Resource
    ISSN: 0001-4966 , 1520-8524
    URL: Article
    DOI: 10.1121/1.420129
    RVK:
    EQ 1000
    Language: English
    Publisher: Acoustical Society of America (ASA)
    Publication Date: 1997
    detail.hit.zdb_id: 1461063-2
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