1,720,964 research outputs found
Do dolphins benefit from nonlinear mathematics when processing their sonar returns?
No full textAn interview with author Tim Leighton about the paper
Bubble acoustics: from seas to surgeries
No full textIn 2004 Professor Tim Leighton founded the University of Southampton Centre for Ultrasonics and Underwater Acoustics. A member of the Institute of Sound and Vibration Research (ISVR) for over 10 years, he looks at how research on sound in liquids is proving to be a very fertile area, from biomedical applications and environmental monitoring, to looking at how whales and dolphins use sound to fish
Ultrasound in air: Today's guidelines have an insufficiently solid basis for today's exposures
No full textToday we see a proliferation of technology that purports to use the low ultrasonic frequency range (~20-40 kHz) in air for a wide variety of purposes: pest deterrents; through-air electrical charging; haptic feedback; acoustic spotlights; etc. These exposures are in addition to the inadvertent exposures of humans to ultrasound in air from cleaning baths, dental treatments etc. that have occurred for decades. New forms of exposure might possibly occur in future as more technology is introduced into homes, workplaces and classrooms. Whilst the vast majority of humans have not reported ill effects from this, some have, although there have not been the resources for widespread testing of the validity of these claims. However the dozens of national and international guidelines for such exposures are not currently adequate for the task of offering guidance for public exposures, since they are based on a very sparse dataset (of observations of primarily adult males), and all but one are for occupational exposure, and so cannot cover the un-monitored exposures of, say, infants taken into public location by adults who potentially have different susceptibilities to possible adverse effects
An acoustical hypothesis for the spiral bubble nets of humpback whales and the implications for whale feeding
No full textEfficacy of up and down-chirps for two-pulse sonar techniques
No full textTwin-Inverted Pulse Sonar (TWIPS) and Biased Pulse Summation Sonar (BiaPSS) were inspired by a video of dolphins using bubble nets to hunt. There are a number of animals that have been observed to use the chirp (a sweep in sine waves of shifting frequency) in echolocation. This talk will present the difference in efficacy of the sonar techniques, mentioned above, when using upwards and downwards sweeping chirps as sonar signals. These techniques have been simulated and experimentally tested with a number of bubble size distributions (BSD). This includes simulations using the results of BSD measurements by Farmer and Vagle (1989). Further, another two-pulse technique will be outlined, proposed as a means to overcome the limitation on detection range, owing to the inter-pulse delay in TWIPS and BiaPSS
Chirp sub-bottom profiler source signature design and field testing
No full textChirp sub-bottom profilers are marine sonar systems which use a highly repeatable source signature to facilitate the acquisition of correlated data with decimetre vertical resolution in the top 20–30 m of sediments. Source signatures can be readily developed and implemented, but an applicable methodology for assessing resolution and attenuation characteristics of these wide-band systems did not exist. Methodologies are developed and applied to seven contrasting source signatures which occupy the same frequency band, but differ in their Envelope and Instantaneous Frequency functions. For the Chirp source signatures tested, a Sine-Squared envelope function is shown to produce seismic data with the optimum resolution and penetration characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Ultrasonic activated stream cleaning of a range of materials
No full textDespite decades of routine use (starting from the industrial setting but now also with domestic products available), ultrasonic cleaning faces technical challenges that have never been overcome, and the root of many of these lies with an understanding of the interaction between the bubble population and the sound field. Ultrasonically Activated Stream (UAS) technology is designed to produce ultrasonic cleaning, and in this paper it does so for scenarios for which an ultrasonic cleaning bath would be unsuitable, e.g., removing key contaminants (such as biofilms) from delicate substrates (tissues, etc.), without damaging that substrate
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