scholarly journals Measurements of acoustic scattering from zooplankton and oceanic microstructure using a broadband echosounder

2009 ◽  
Vol 67 (2) ◽  
pp. 379-394 ◽  
Author(s):  
Andone C. Lavery ◽  
Dezhang Chu ◽  
James N. Moum
Keyword(s):  
High Frequency ◽  
System Performance ◽  
Pulse Compression ◽  
Acoustic Scattering ◽  
Single Frequency ◽  
Frequency Range ◽  
Range Resolution ◽  
Continuous Frequency ◽  
Processing Techniques ◽  
Signal Processing Techniques

Abstract Lavery, A. C., Chu, D., and Moum, J. N. 2010. Measurements of acoustic scattering from zooplankton and oceanic microstructure using a broadband echosounder. – ICES Journal of Marine Science, 67: 379–394. In principle, measurements of high-frequency acoustic scattering from oceanic microstructure and zooplankton across a broad range of frequencies can reduce the ambiguities typically associated with the interpretation of acoustic scattering at a single frequency or a limited number of discrete narrowband frequencies. With this motivation, a high-frequency broadband scattering system has been developed for investigating zooplankton and microstructure, involving custom modifications of a commercially available system, with almost complete acoustic coverage spanning the frequency range 150–600 kHz. This frequency range spans the Rayleigh-to-geometric scattering transition for some zooplankton, as well as the diffusive roll-off in the spectrum for scattering from turbulent temperature microstructure. The system has been used to measure scattering from zooplankton and microstructure in regions of non-linear internal waves. The broadband capabilities of the system provide a continuous frequency response of the scattering over a wide frequency band, and improved range resolution and signal-to-noise ratios through pulse-compression signal-processing techniques. System specifications and calibration procedures are outlined and the system performance is assessed. The results point to the utility of high-frequency broadband scattering techniques in the detection, classification, and under certain circumstances, quantification of zooplankton and microstructure.

scholarly journals Design of Biphase Sequences using PSA for Radar Applications

2019 ◽  
Vol 8 (4) ◽  
pp. 4396-4401
Keyword(s):  
Pulse Compression ◽  
Search Algorithm ◽  
Phase Coding ◽  
Range Resolution ◽  
Frequency Coding ◽  
Development Procedure ◽  
Radar Applications ◽  
Processing Techniques ◽  
Signal Processing Techniques ◽  
High Range

Pulse compression is widely used method to get high range resolution in radar applications. This can be achieved when transmitted pulse is modulated either using phase coding or frequency coding. In phase coding technique, it can be bi-phase or poly phase.Bi-phase coding is preferred method due to its simplicity in generation and needs less signal processing techniques. This paper wepropose a new algorithm called Progressive Search Algorithm (PSA) for the optimization of biphase sequences for radar applications. It is devised that the new algorithm is capable of optimizing the sequences with low autocorrelation sidelobes. The convergence rate of PSA isvery fast compared to the other existing algorithms such as PSO and SGO. The development procedure and its efficiency with respect to the PSO and SGO is also presented in this work.

CHARACTERIZATION OF STOCHASTIC PROPAGATION AND SCATTERING VIA GABOR AND WAVELET TRANSFORMS

1994 ◽  
Vol 02 (03) ◽  
pp. 345-369 ◽  
Author(s):  
L. H. SIBUL ◽  
L. G. WEISS ◽  
T. L. DIXON
Keyword(s):  
Wavelet Transforms ◽  
Acoustic Scattering ◽  
Time Intervals ◽  
First Order ◽  
Spreading Function ◽  
Time Variations ◽  
Processing Techniques ◽  
Signal Processing Techniques ◽  
Methods Numerical

An application to remote acoustic sensing that remains unexploited is measuring acoustic scattering and spreading effects with wideband, coherent signal processing techniques. Such techniques allow distributed objects, such as a layer of scatterers due to bubbles or biological particles, and first order time variations in an ocean channel to be estimated. This paper presents narrowband and wideband methods for characterizing stochastic propagation and acoustic scattering in a time-varying ocean in terms of spreading functions. It is shown that the Gabor transform is the natural transform for estimating the narrowband spreading function, and the wavelet transform is the natural transform for estimating the wideband spreading function. Both techniques of characterization use a correlator processing structure in a monostatic transmitter/receiver configuration to estimate the spreading function. The narrowband and wideband spreading functions characterize the distribution of scatterers in range and velocity (time and frequency) in a propagation channel. It is shown that the wideband formulation follows directly from a physical derivation. Moreover, wideband processing removes many of the narrowband restrictions and allows first order time variations, caused by inhomogeneities and relative motion in the ocean channel, to be processed. In addition, wideband techniques allow for increased time intervals and, therefore, increased energy transmission when the transmitter is peak-power-limited. Thus, weak scatterers that may have been unidentified with narrowband techniques may be identified with the wideband methods. Numerical examples for wideband characterization of a distributed scatterer are presented.

scholarly journals The CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Research Collaborative

2020 ◽  
Vol 47 (4) ◽  
pp. 551-556 ◽  
Author(s):  
Francis Bernard ◽  
Clare Gallagher ◽  
Donald Griesdale ◽  
Andreas Kramer ◽  
Mypinder Sekhon ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
High Resolution ◽  
High Frequency ◽  
Genomic Analysis ◽  
High Frequency Signal ◽  
Cerebral Physiology ◽  
Processing Techniques ◽  
Signal Processing Techniques

ABSTRACT:In traumatic brain injury (TBI), future integration of multimodal monitoring of cerebral physiology and high-frequency signal processing techniques, with advanced neuroimaging, proteomic and genomic analysis, provides an opportunity to explore the molecular pathways involved in various aspects of cerebral physiologic dysfunction in vivo. The main issue with early and rapid discovery in this field of personalized medicine is the expertise and complexity of data involved. This brief communication highlights the CAnadian High-Resolution Traumatic Brain Injury (CAHR-TBI) Research Collaborative, which has been formed from centers with specific expertise in the area of high-frequency physiologic monitoring/processing, and outlines its objectives.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

HIGH FREQUENCY OHMIC LOSSES IN TERAHERTZ FREQUENCY RANGE CW KLYNOTRONS

2017 ◽  
Vol 76 (10) ◽  
pp. 929-940 ◽  
Author(s):  
Yu. S. Kovshov ◽  
S. S. Ponomarenko ◽  
S. A. Kishko ◽  
A. A. Likhachev ◽  
S. A. Vlasenko ◽  
...  
Keyword(s):  
High Frequency ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range ◽  
Ohmic Losses
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