The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Oleg A. Godin - One of the best experts on this subject based on the ideXlab platform.

  • Generation of acoustic-gravity waves by a submerged Monopole Source located near the water-air interface
    OCEANS'11 MTS IEEE KONA, 2011
    Co-Authors: Iosif M. Fuks, Oleg A. Godin
    Abstract:

    Powerful underwater explosions and certain natural Sources, such as underwater landslides, generate very low-frequency waves in water and air, for which both fluid buoyancy and compressibility simultaneously serve as restoring forces. In this paper, analysis of sound transmission through air-water interface is extended to acoustic-gravity waves (AGWs). It is found that, as for sound, the interface becomes anomalously transparent for sufficiently shallow compact Sources of AGWs. The increase of wave power flux into air due to diffraction effects can reach several orders of magnitude. Physical mechanisms responsible for the anomalous transparency are discussed. Excitation of an interface wave by an underwater Source is shown to be an important channel of AGW transmission into atmosphere, which has no counterpart in the case of sound.

  • anomalous transparency of water air interface for low frequency sound
    Physical Review Letters, 2006
    Co-Authors: Oleg A. Godin
    Abstract:

    Sound transmission through a water-air interface is normally weak because of a strong mass density contrast. We show that the transparency of the interface increases dramatically at low frequencies. Almost all acoustic energy emitted by a sufficiently shallow Monopole Source under water is predicted to be radiated into air. Increased transparency at lower frequencies is due to the increasing role of inhomogeneous waves. For Sources symmetric with respect to a horizontal plane, transparency is further increased by a destructive interference of direct and surface-reflected waves under water. The phenomenon of anomalous transparency has significant geophysical and biological implications.

  • Anomalous transparency of the water/air interface for low‐frequency sound
    The Journal of the Acoustical Society of America, 2006
    Co-Authors: Oleg A. Godin
    Abstract:

    Sound transmission through water/air interface is normally weak because of a stark density contrast between the two media. For a Monopole sound Source, at depth larger than a wavelength, the ratio R of the acoustic power transmitted into the air to the total emitted acoustic power is a small quantity of the order of the ratio of impedances of air and water. Acoustic transparency of the interface is shown to rise dramatically at low frequencies, where depth of the Monopole Source is small compared to the wavelength, with R increasing by up to 36 dB. Under certain conditions, almost all of the acoustic energy emitted by a low‐frequency Monopole Source underwater is predicted to be radiated into the air rather than into the water. Physically, higher transparency at lower frequencies is due to increasing role of inhomogeneous waves emitted by the Source and a destructive interference of fields in water due to the actual and image Sources. The anomalous transparency of the water/air interface may have significant implications for generation of low‐frequency acoustic noise in the air by bubbles collapsing underwater and for acoustic monitoring and detection of powerful underwater explosions for the purposes of the Comprehensive Nuclear Test Ban Treaty.

Grigol Gogoberidze - One of the best experts on this subject based on the ideXlab platform.

  • Spectrum of infrasound radiation from supercell storms
    Quarterly Journal of the Royal Meteorological Society, 2011
    Co-Authors: Mariam Akhalkatsi, Grigol Gogoberidze
    Abstract:

    We consider the generation of acoustic waves by turbulent convection and perform spectral analysis of a Monopole Source of sound related to the heat production by condensation of moisture. A quantitative explanation of the correlation between intensity of infrasound generated by supercell storms and later tornado formation is given. It is shown that low lifting condensation level (LCL) and high values of convective available potential energy (CAPE), which are known to favor significant tornadoes, also lead to a strong enhancement of supercell's low frequency acoustic radiation.

  • Spectrum of infrasound radiation from supercell storms
    Quarterly Journal of the Royal Meteorological Society, 2011
    Co-Authors: Mariam Akhalkatsi, Grigol Gogoberidze
    Abstract:

    We consider the generation of acoustic waves by turbulent convection and perform spectral analysis of a Monopole Source of sound related to the heat production by condensation of moisture. A quantitative explanation of the correlation between intensity of infrasound generated by supercell storms and later tornado formation is given. It is shown that low lifting condensation level (LCL) and high values of convective available potential energy (CAPE), which are known to favour significant tornadoes, also lead to a strong enhancement of a supercell's low-frequency acoustic radiation. Copyright © 2011 Royal Meteorological Society

Mariam Akhalkatsi - One of the best experts on this subject based on the ideXlab platform.

  • Spectrum of infrasound radiation from supercell storms
    Quarterly Journal of the Royal Meteorological Society, 2011
    Co-Authors: Mariam Akhalkatsi, Grigol Gogoberidze
    Abstract:

    We consider the generation of acoustic waves by turbulent convection and perform spectral analysis of a Monopole Source of sound related to the heat production by condensation of moisture. A quantitative explanation of the correlation between intensity of infrasound generated by supercell storms and later tornado formation is given. It is shown that low lifting condensation level (LCL) and high values of convective available potential energy (CAPE), which are known to favor significant tornadoes, also lead to a strong enhancement of supercell's low frequency acoustic radiation.

  • Spectrum of infrasound radiation from supercell storms
    Quarterly Journal of the Royal Meteorological Society, 2011
    Co-Authors: Mariam Akhalkatsi, Grigol Gogoberidze
    Abstract:

    We consider the generation of acoustic waves by turbulent convection and perform spectral analysis of a Monopole Source of sound related to the heat production by condensation of moisture. A quantitative explanation of the correlation between intensity of infrasound generated by supercell storms and later tornado formation is given. It is shown that low lifting condensation level (LCL) and high values of convective available potential energy (CAPE), which are known to favour significant tornadoes, also lead to a strong enhancement of a supercell's low-frequency acoustic radiation. Copyright © 2011 Royal Meteorological Society

V. Mariani Primiani - One of the best experts on this subject based on the ideXlab platform.

Graziano Cerri - One of the best experts on this subject based on the ideXlab platform.

  • theoretical radiated emission prediction of an aperture array by reverberation chamber field sampling
    International Symposium on Electromagnetic Compatibility, 2020
    Co-Authors: A. De Leo, Graziano Cerri, P. Russo, Mariani V. Primiani
    Abstract:

    This paper reports the application of a theoretical model designed to predict the electromagnetic field radiated by a piece of equipment under test through an array of apertures on its metallic chassis. The simulated scenario is a reverberation chamber where the electric field is measured close to its walls. At this scope the multipole Monopole Source stirring technique is considered because of the presence of the antennas onto the chamber’s walls. The results are successfully compared to the emissions in free space, and a wideband frequency analysis is performed. Finally, the effect of a random numeric noise on the module and on the phase of the electric field samples is analyzed.

  • Shielding Effectiveness Measurement in a Multiple Monopole Source Stirred Reverberation Chamber
    2020 XXXIIIrd General Assembly and Scientific Symposium of the International Union of Radio Science, 2020
    Co-Authors: A. De Leo, Graziano Cerri, Paola Russo, V. Mariani Primiani
    Abstract:

    This paper reports the measurement of the shielding effectiveness of a metallic enclosure. The experimental environment is a reverberation chamber where the multiple Monopole Source stirring technique is implemented. The results are compared to the measurements in the same environment, by using a traditional mechanical stirring technique and to the anechoic scenario using numerical simulations.

  • A Novel Emission Test Method for Multiple Monopole Source Stirred Reverberation Chambers
    IEEE Transactions on Electromagnetic Compatibility, 2020
    Co-Authors: A. De Leo, Graziano Cerri, Paola Russo, V. Mariani Primiani
    Abstract:

    This letter presents a novel method for predicting the electromagnetic field radiated by an equipment under test (EUT) in free space. The method is based on the knowledge of the electric field values close to the metallic walls of a reverberation chamber where the device is placed. From these field samples, a set of equivalent Sources is retrieved. The equivalent Sources likewise produce in free space the same field radiated by the EUT.

  • Design and Experimental Validation of a Stochastic Diffractor for a Multiple Monopole Source Stirring Reverberation Chamber
    2020 XXXIIIrd General Assembly and Scientific Symposium of the International Union of Radio Science, 2020
    Co-Authors: A. De Leo, Graziano Cerri, Paola Russo, Gabriele Gradoni, V. Mariani Primiani
    Abstract:

    This paper deals with the use of stochastic diffractors in a reverberation chamber to improve the stirring of the electromagnetic field. In particular, the stirring technique is achieved by varying the feeding of an array of Monopole antennas mounted on the chamber’s walls.

  • Calibration of a Reverberation Chamber for Radiated Emission Measurements by Wall Mounted Antennas
    2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring), 2019
    Co-Authors: Graziano Cerri, P. Russo, Mariani V. Primiani
    Abstract:

    This paper reports a novel technique to estimate the total averaged power emitted by a device under test placed inside the working volume of a reverberation chamber in a radiated emission test. The electromagnetic field inside the chamber is stirred by the application of the multiple Monopole Source stirring in receiving mode, that is a particular way to implement the Source stirring technique; in this scenario an array of Monopole antenna is placed onto the chamber walls and sequentially connected to the measurement system to get the stirring action. The procedure for the radiated emission estimation requires that chamber has to be calibrated by a set of measurements. In the paper the calibration results are compared to the prediction of the analytical model, developed to predict the chamber's performances.