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2 edition of Angular scatter and time scatter of acoustic signals underwater found in the catalog.

Angular scatter and time scatter of acoustic signals underwater

M. S. Ahmed

Angular scatter and time scatter of acoustic signals underwater

by M. S. Ahmed

  • 225 Want to read
  • 21 Currently reading

Published by University of Birmingham in Birmingham .
Written in English


Edition Notes

Thesis (Ph.D.) - University of Birmingham, Dept of Electronic and Electrical Engineering, 1984.

Statementby M. S. Ahmed.
ID Numbers
Open LibraryOL13826817M

In physics, backscatter (or backscattering) is the reflection of waves, particles, or signals back to the direction from which they is usually a diffuse reflection due to scattering, as opposed to specular reflection as from a mirror, although specular backscattering can occur at normal incidence with a attering has important applications in astronomy, photography, and. where S can be referred to as the spin (polarization) angular momentum and L the OAM. [11] The most well known twisted electromagnetic beam is the paraxial Laguerre-Gaussian beam. The fields for this type of beam include the azimuthal phase factor exp(ilφ) in addition to a cylindrically symmetric amplitude distribution, where φ is the azimuthal angle and l is an integer.

Underwater broadband acoustic scattering modelling based on FDTD Bibee, "Simulation of acoustic scattering from an aluminum cylinder near a roughinterface using the elastodynamic finite integration technique," Wave Motion Journal, vol. roughness straight away, is tested trough several anisotropic surfaces. In a longitudinal direction of ripples, the scatter-ing strength is mostly in the specular direction, whereas in the transversal direction of ripples, the scattering strength prediction shows high values for different angular Size: 2MB.

This document is a Book of Abstracts for the Underwater Acoustic Signal Processing Workshop SUBJECT TERMS Underwater acoustics, SONAR, signal processing, detection, classification, localization SECURITY CLASSIFICATION OF: LIMITATION OF NUMBER 19a. NAME OF RESPONSIBLE PERSON a. REPORT : Richard J Vaccaro. The signal is phase coherent allowing high time resolution. Figure 3 shows 12 hours of propagation measurements where the tidal modulation is clearly apparent in travel time associated with the direct path and surface scatter. Figure 3. Color image of horizontal propagation arrival time and intensity for 12 hours of data in Narragansett Bay.


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Angular scatter and time scatter of acoustic signals underwater by M. S. Ahmed Download PDF EPUB FB2

This book provides comprehensive coverage of the detection and processing of signals in underwater acoustics. Background material on active and passive sonar systems, underwater acoustics, and statistical signal processing makes the book a self-contained and valuable resource for graduate students, researchers, and active practitioners alike.

In some underwater applications, acoustic backscatter might have undesired consequences, such as reflect and/ or scatter the sonar signal, which has to t ravel again through the sea to arrive at a sonar determines the long distan ce angular propagation sector of the sonar signal.

The second part calculates. Principles and Applications. Outlines the basic physical phenomena governing underwater acoustical waves, including propagation, reflection, target scattering and noise in a rigorous and standardized mathematical framework.

Usually dispatched within 3 to 5 business days. Usually dispatched within 3 to 5 business : Springer-Verlag Berlin Heidelberg. Abstract: This paper contains theoretical and experimental results on the application of the time-reversal process to acoustic communications in order to improve data telemetry in the ocean.

A coherent underwater acoustic communication system must deal with the inter-symbol interference caused by the time-varying, dispersive, shallow-water ocean environment.

Signals and systems in Underwater Acoustics: listen through the ocean S ergio M. Jesus ([email protected]) Universidade do Algarve, PT Faro, Portugal 20 January Signals and Systems in Underwater Acoustics. Underwater acoustic signals can be either short in duration relative to the observation time (e.g., an air-gun pulse in a 1-min window) or extend through the analysis window (e.g., a communications signal in a ms window).

Propagation of the acoustic signals underwater was modelled with boundary conditions using the finite element method. These include the bathymetry (features of underwater terrain) of the deployment site and.

properties of the propagation media. The type of spreading of the acoustic signals, and their interaction with theCited by: 3. Introduction. Acoustic backscatter (ABS) measurement is a non-intrusive technique for the monitoring of suspended sediment particles in the water column and changing seabed characteristics (see Figures 1 and 2).

An acoustic backscatter instrumentation package comprises acoustic sensors, data acquisition, storage and control electronics, and data extraction and reduction software. Electron back scatter patterns (EBSP) were collected on a phosphor screen and processed using the software package CHANNEL5 (Oxford Instruments, Ltd.).

EBSD data were collected in a point-collection mode. Each EBSD has a mean angular deviation (MAD) of less than 1° and generally better than °. A bistatic ultrasound imaging system is demonstrated that uses two element linear phased array transducers oriented at an angle of 40 degrees to one another.

The system simultaneously acquires and displays in real time one conventional backscatter image and one “angular scatter” image formed using side-scattered echoes from the same B-mode sector : James C.

Lacefield, Olaf T. von Ramm. This short video covers the Scatterplot display features, including selecting signals, XY reversal, how to highlight capsules, and explore time relationships. AN ELECTRONICALLY-SCANNED RECEIVER USED TO STUDY ACOUSTIC SCATTERING PHENOMENA V.

WELSBY and B. GAZEY Department of Electronic and Electrical Engineering, University of Birmingham, Edgbaston, Birmingham, 15 (Great Britain) (Received: 9 April, ) SUMMARY The energy of an acoustic wave tends to become scattered in frequency, time and Cited by: 3.

Underwater acoustic channels are generally rec-ognized as one of the most difficult communica-tion media in use today. Acoustic propagation is best supported at low frequencies, and the band-width available for communication is extremely limited. For example, an acoustic system may operate in a frequency range between 10 and 15 kHz.

A time-dependent model of the acoustic intensity backscattered by the seafloor is described and compared with data from a calibrated, vertically oriented, echo-sounder operating at 33 and 93 kHz. Underwater Object Tracking Using Time Frequency Signatures of Acoustic Signals Digulescu Angela1, Candel Ion 2, Ioana Cornel2, Bucur Diana3, Petrut Teodor 1Faculty of Military Electronic and Information Systems, Military Technical Academy, Bucharest, Romania [email protected] 2Gipsa-lab, Grenoble Institute of Technology, Grenoble, France {,}@gipsa-lab Cited by: 5.

In the second edition of his book, Dr Lurton provides an updated and extended introduction to underwater acoustics, including coverage of the physical processes and their basic modeling, different underwater acoustic systems and their practical applications and a description and assessment of the various by: The experiments to evaluate the performance of underwater acoustic communication using the particle velocity and pressure signal were conducted on Octoin a shallow water region located at 34 48′ N, 47′ E, south of Korea.

The nominal water depth at the site is 59 m [Fig. 3(a)]. An omni-directional transducer (NEPTUNE, D) was used as a source, which was deployed at a depth of 31 Cited by: 1. Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems.

A stationary phase analysis of the Helmholtz–Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the Cited by: water depth varied from 8 m to 16 m. The acoustic backscat-ter images of the study sites before and after angular compen-sation are shown in Figure 1.

For the time when these two surveys were conducted, the SeaBat sonar system had not yet been calibrated, and. Scattering of the parametric-antenna acoustic field by spheroidal objects. rather long time. In [1, 2], the angular characteristics of.

Scattering of the Parametric-Antenna Acoustic Field. An Introduction to Acoustics S.W. Rienstra & A. Hirschberg Eindhoven University of Technology 28 Nov This is an extended and revised edition of IWDE Comments and corrections are gratefully accepted. This file may be used and printed, but for personal or educational purposes only.

c S.W. Rienstra & A. Hirschberg This again verifies the efficiency of the present HS-FEM for solving acoustic scattering problems.

Download: Download full-size image; Fig. The scattered acoustic pressure on the artificial boundary as a function of the wave number at the point with polar angle θ = 0: (a) The real part of the pressure. (b) The imaginary part of the by:   For scattering, acoustic wavelengths are of the order of obstacles and medium fluctuation dimensions.

Francisco Maria Grimaldi first described scattering of optical waves inin the opus Physicomathesis of lumine, but this principle was .