Search results for "acoustics"
showing 10 items of 984 documents
High-pressure x-ray-absorption study of GaSe
2002
The III-VI layered semiconductor InSe has been studied by high-pressure single crystal x-ray absorption spectroscopy up to a maximum pressure of 14 GPa. The In-Se distance has been measured in both the low- pressure layered phase and the high-pressure NaCl phase. The bond compressibility in the layered phase is lower than the ``a'' crystallographic parameter compressibility, which implies an increase of the angle between the In-Se bond and the layer plane. Under plausible hypothesis, a description of the evolution of the whole structure with pressure is given. In particular, the intralayer distance is observed to increase with increasing pressure. A plausible precursor defect and a simple m…
Influence of the MgO barrier thickness on the lifetime characteristics of magnetic tunnelling junctions for sensors
2016
Magnetic tunnelling junctions increasingly enter the market for magnetic sensor applications. Thus, technological parameters such as the lifetime characteristics become more and more important. Here, an analysis of the lifetime characteristics of magnetic tunnelling junctions using the Weibull statistical distribution for CoFeB/MgO/CoFeB junctions is presented. The Weibull distribution is governed by two parameters, the characteristic lifetime η of the population and the shape parameter β, which gives information about the presence of an infant mortality. The suitability of the Weibull distribution is demonstrated for the description of dielectric breakdown processes in MgO-based tunnelling…
A Nonisovelocity Geometry-Based Underwater Acoustic Channel Model
2018
This paper proposes a new geometry-based shallow underwater acoustic (UWA) channel model allowing for nonisovelocity ocean conditions. The fact that the isovelocity assumption does not hold in many real-world scenarios motivates the need for developing channel models for nonisovelocity UWA propagation environments. Starting from a geometrical model, we develop a stochastic channel model for a single-input single-output (SISO) vehicle-to-vehicle UWA channel assuming that the ocean surface and bottom are rough and that the speed of sound varies with depth. The effect of the nonisovelocity condition has been assessed regarding its influence on the temporal autocorrelation function, the frequen…
Environmentally‐induced noise dampens and reddens with increasing trophic level in a complex food web
2019
Stochastic variability of key abiotic factors including temperature, precipitation and the availability of light and nutrients greatly influences species’ ecological function and evolutionary fate. Despite such influence, ecologists have typically ignored the effect of abiotic stochasticity on the structure and dynamics of ecological networks. Here we help to fill that gap by advancing the theory of how abiotic stochasticity, in the form of environmental noise, affects the population dynamics of species within food webs. We do this by analysing an allometric trophic network model of Lake Constance subjected to positive (red), negative (blue), and non‐autocorrelated (white) abiotic temporal …
The tropical African genus Morgenia (Orthoptera, Tettigoniidae, Phaneropterinae) with emphasis on the spur at the mid tibia
2018
The authors revised the genus Morgenia Karsch, 1890 which now consists of eight species, of which three are here newly described (Morgeniaplurimaculata Massa & Moulin, sp. n., M.angustipinnata Massa, sp. n., and M.lehmannorum Heller & Massa, sp. n.). Six of the eight species occur in the Tri National Sangha (TNS) comprising Dzanga-Sangha Special Reserve and Dzanga Ndoki National Park (Central African Republic), whose high biodiversity has been recently highlighted. In particular the genus is characterised by the presence of a more or less long spur at the inner mid tibia, different in each species; in M.modulata, it moved lower down into a new position at about ¼ of tibia, w…
Decoding Group Vocalizations: The Acoustic Energy Distribution of Chorus Howls Is Useful to Determine Wolf Reproduction
2016
Population monitoring is crucial for wildlife management and conservation. In the last few decades, wildlife researchers have increasingly applied bioacoustics tools to obtain information on several essential ecological parameters, such as distribution and abundance. One such application involves wolves (Canis lupus). These canids respond to simulated howls by emitting group vocalizations known as chorus howls. These responses to simulated howls reveal the presence of wolf litters during the breeding period and are therefore often used to determine the status of wolf populations. However, the acoustic structure of chorus howls is complex and discriminating the presence of pups in a chorus i…
Paraplangia sinespeculo, a new genus and species of bush-cricket, with notes on its biology and a key to the genera of Phaneropterinae (Orthoptera: T…
2018
Madagascar is a well-known hotspot of biodiversity. However, many Orthoptera, and especially the Tettigonioidea, belong to little-studied groups. Here we describe a new genus and species of bush-cricket reared from field-collected eggs.Paraplangiasinespeculogen. nov., sp. nov. belongs to Phaneropterinae and shares diagnostic characteristics with members of the tribe Amblycoryphini and its African subtribe Plangiina stat. nov.Paraplangia, which has a chromosome number of 31 X0, differs from other African members of the tribe and subtribe such asEurycoryphaandPlangia, which both have 29 X0. In addition to morphology, we describe the male calling song, female acoustic response, and mating beha…
Are mussels able to distinguish underwater sounds? Assessment of the reactions of Mytilus galloprovincialis after exposure to lab-generated acoustic …
2016
This study examined the effects of lab-generated acoustic signals on the behaviour and biochemistry of Mediterranean mussels (Mytilus galloprovincialis). The experiment was carried out in a tank equipped with a video-recording system using six groups of five mussels exposed to five acoustic treatments (each treatment was replicated three times) for 30 min. The acoustic signals, with a maximum sound pressure level of 150 dB rms re 1 μPa, differed in frequency range as follows: low (0.1–5 kHz), mid-low (5–10 kHz), mid (10–20 kHz), mid-high (20–40 kHz) and high (40–60 kHz). The exposure to sweeps did not produce any significant changes in the mussels' behaviour. Conversely, the specimens expos…
Crocodile egg sounds signal hatching time.
2008
Summary Crocodilians are known to vocalize within the egg shortly before hatching [1,2]. Although a possible function of these calls — inducing hatching in siblings and stimulating the adult female to open the nest — has already been suggested, it has never been experimentally tested [1–5]. Here, we present the first experimental evidence that pre-hatching calls of Nile crocodile ( Crocodylus niloticus ) juveniles are informative acoustic signals which indeed target both siblings and mother.
Response to: The metabolic cost of whistling is low but measurable in dolphins
2020
Costs of sound production have been investigated only sparsely in cetaceans, despite recent efforts to understand how increasing anthropogenic noise affects these animals that rely extensively on sound for communication and foraging. Theoretical estimates suggest that metabolic costs of whistling