المؤلفون: Xie, Cui, Guo, Hao, Dong, Junyu

المصدر: IEEE Transactions on Geoscience & Remote Sensing; Jun2022, Vol. 60, p1-9, 9p

مصطلحات موضوعية: FRONTS (Meteorology), UNDERWATER acoustics, SOURCE code, ACOUSTIC wave propagation, MILITARY readiness, FOREST mapping

مصطلحات جغرافية: GULF of Mexico

مستخلص: Ocean fronts can cause the accumulation of nutrients and affect the propagation of underwater sound, so high-precision ocean front detection is of great significance to the marine fishery and national defense fields. However, the existing ocean front detection methods either have low detection accuracy or regard it as a binary classification problem to only detect where the ocean front occurs and cannot identify and distinguish various categories of ocean fronts with different behavior characteristics in different times and regions. In order to solve the above problems, we propose a semantic segmentation network called location and seasonality enhanced network (LSENet) for multiclass ocean fronts detection at pixel level. In this network, we first design a channel supervision unit (CSU) structure, which integrates the seasonal characteristics of the ocean front itself and the contextual information to improve the detection accuracy. We also introduce a location attention (LA) mechanism to adaptively assign attention weights to the fronts according to their frequently occurred sea area, which can further improve the accuracy of multiclass ocean front detection. Compared with other semantic segmentation methods and current representative ocean front detection method at Offshore China and Gulf of Mexico, the experimental results demonstrate convincingly that our method is more effective. The source code and datasets are released and publicly available via https://github.com/lliusha1155/LSENETTest. [ABSTRACT FROM AUTHOR]

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المؤلفون: Yao Xiao^1,2, Zhenglin Li¹ lzhl@mail.ioa.ac.cn, Jun Li³, Jiaqi Liu⁴, Karim G Sabra⁵

المصدر: Chinese Physics B. May2019, Vol. 28 Issue 5, p1-1. 1p.

مصطلحات موضوعية: *ACOUSTIC wave propagation, *EDDIES, *SOUND energy, *MESOSCALE eddies, *BAYS

مصطلحات جغرافية: GULF of Mexico, MEXICO

مستخلص: An automatic detection method is employed to identify and track eddies in the Gulf of Mexico. The physical parameters of the eddies, such as lifespan, radius, and distribution position are first examined and used to determine the spatio–temporal evolution of a strong warm eddy separated from the Mexico current. Then, the influence of this strong warm eddy on sound propagation during its lifespan are comprehensively analyzed with the parabolic equation and explained by using the normal mode and ray theories. Additionally, the influence of mesoscale eddies on the redistribution of total depth-integrated energy among the normal modes in the deep water is also discussed. The variation of arrival angle is investigated to explain the spreading acoustic energy caused by eddies. Overall, the results show that warm eddies can change the propagation paths and cause the convergence zone to broaden and approach the sound source. Moreover, the warm eddy can disperse sound energy and cause the total depth-integrated energy to incline to a lower normal mode. Throughout the whole of these three periods (eddy generating, eddy maturing, and eddy terminating), the fluctuation in the transmission loss is up to 30 dB (depending on the relative location of eddy center to the source). [ABSTRACT FROM AUTHOR]

المؤلفون: Xiang Xiao, Leaney, W. Scott

المصدر: Geophysics; Mar/Apr2010, Vol. 75 Issue 2, pS35-S49, 15p, 2 Diagrams, 16 Graphs

مصطلحات موضوعية: VERTICAL seismic profiling, ELASTIC wave propagation, IMAGING systems in geophysics, SALT flats, SHEAR waves

مصطلحات جغرافية: GULF of Mexico

مستخلص: To avoid the defocusing effects of propagating waves through salt and overburden with an inaccurate overburden velocity model, we introduce a vertical seismic profiling (VSP) local elastic reverse-time-migration (RTM) method for salt-flank imaging by transmitted P-to-S waves. This method back-projects the transmitted PS waves using a local velocity model around the well until they are in phase with the back-projected PP waves at the salt boundaries. The merits of this method are that it does not require the complex overburden and salt-body velocities and it automatically accounts for source-side statics. In addition, the method accounts for kinematic and dynamic effects, including anisotropy, absorption, and all other unknown rock effects outside of this local subsalt velocity model. Numerical tests on an elastic salt model and offset 2D VSP data in the Gulf of Mexico, using a finite-difference time-domain staggered-grid RTM scheme, partly demonstrate the effectiveness of this method over interferometry PS-PP transmission migration and local acoustic RTM. Our method separates elastic wavefields to vector P- and S-wave velocity components at the trial image point and achieves better resolution than local acoustic RTM and interferometric transmission migration. The analytical formulas of migration resolution for local acoustic and elastic RTM show that the migration illumination is limited by data frequency and receiver aperture, and the spatial resolution is lower than standard poststack and prestack migration. This new method can image salt flanks as well as subsalt reflectors. [ABSTRACT FROM AUTHOR]

: Copyright of Geophysics is the property of Society of Exploration Geophysicists and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: DeRuiter, Stacy L., Tyack, Peter L., Ying-Tsong Lin, Newhall, Arthur E., Lynch, James F., Miller, Patrick J. O.

المصدر: Journal of the Acoustical Society of America; Dec2006, Vol. 120 Issue 6, p4100-4114, 15p, 1 Chart, 19 Graphs

مصطلحات موضوعية: BAIT markers, ANIMAL tagging, SPERM whale, PULSE (Heart beat), RADIO wave propagation

مصطلحات جغرافية: GULF of Mexico

مستخلص: In 2002 and 2003, tagged sperm whales (Physeter macrocephalus) were experimentally exposed to airgun pulses in the Gulf of Mexico, with the tags providing acoustic recordings at measured ranges and depths. Ray trace and parabolic equation (PE) models provided information about sound propagation paths and accurately predicted time of arrival differences between multipath arrivals. With adequate environmental information, a broadband acoustic PE model predicted the relative levels of multipath arrivals recorded on the tagged whales. However, lack of array source signature data limited modeling of absolute received levels. Airguns produce energy primarily below 250 Hz, with spectrum levels about 20–40 dB lower at 1 kHz. Some arrivals recorded near the surface in 2002 had energy predominantly above 500 Hz; a surface duct in the 2002 sound speed profile helps explain this effect, and the beampattern of the source array also indicates an increased proportion of high-frequency sound at near-horizontal launch angles. These findings indicate that airguns sometimes expose animals to measurable sound energy above 250 Hz, and demonstrate the influences of source and environmental parameters on characteristics of received airgun pulses. The study also illustrates that on-axis source levels and simple geometric spreading inadequately describe airgun pulse propagation and the extent of exposure zones. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of the Acoustical Society of America is the property of American Institute of Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Chapman, Ross

المصدر: IEEE Journal of Oceanic Engineering; Jul2015, Vol. 40 Issue 3, p496-496, 1p

مصطلحات موضوعية: OCEAN engineering, SOUND wave scattering, SOUND reverberation, ACOUSTIC wave propagation

مصطلحات جغرافية: GULF of Mexico

مستخلص: Presents the introductory editorial for this issue of the publication. [ABSTRACT FROM PUBLISHER]

: Copyright of IEEE Journal of Oceanic Engineering is the property of IEEE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)