No description available.

No description available.

Une onde acoustique plane propagée dans un guide couplée à des parois vibrantes, siège d'ondes transversale ou de flexion, donne un ensemble d'ondes dans le fluide et dans la structure. Les ondes dans le fluide sont évanescentes, propagatives, ou encore propagatives avec un amortissement. Il n'est pas besoin que l'ensemble soit dissipatif pour en arriver là car les résultats proviennent d'interférences destructives on constructives. Un amortissement dans la structure donne un système cette fois-ci dissipatif et ajoute ses effets à la dissipation mais pas de façon classique puisqu'il s'agit ici d'ondes couplées acoustique/structure. En présence d'un flux stationnaire et uniforme la capacité d'une paroi vibrante à produire de l'atténuation acoustique se réduit. Les opérateurs en jeu, les méthodes pour les résoudre dont celle des éléments finis donnent accès à des prédictions. Elles sont confrontées à des résultats expérimentaux. Sans écoulement, les prédictions font sens. En revanche, avec écoulement, il n'en est pas de même et le mémoire tentera d'analyser les raisons. En conclusion technologique, une atténuation d'une quinzaine de décibels en moyenne sur une gamme de fréquences de quelques centaines de Hz centrées dans les médiums (500Hz) est envisageable avec une paroi mince qui n'encombre pas le guide. / A plane acoustic wave propagated in a duct some walls of which are vibrating due to transversal or flexural waves gives rise to a set of various waves within the fluid and the structure. Within the fluid, the waves are evanescent, propagatives or propagatives with decreasing amplitudes. There is no need for the global operator to be dissipative for such a result since it is arising from destructive or constructive interferences. When the structural damping exists, as in the real life, it adds its effect to the coupling but not in a classical way as coupled acoustic/structure waves are at play rather than pure acoustic or structural waves. Now in presence of a convection of the fluid that bears the acoustic wave (a stationary and uniform flow), the attenuation is reduced sligtly at the very low Mach numbers, and significantly at higher Mach numbers. As far as technological conclusions are sought, an averaged acoustic attenuation of around fifteen dB in a frequency range of some hundreds Hz centered at 500Hz can be obtained with this system very light and needing almost no room.

O canal acústico é um sistema de sinalização de longo alcance eficiente que pode ser especialmente efetivo para animais com hábitos crepusculares/noturnos. O lobo-guará é um canídeo ameaçado com hábitos crepusculares/noturnos que, no senso comum, é visto como uma espécie solitária. De fato, seria melhor definida como uma espécie gregária, uma vez que macho e fêmea dividem o mesmo território e a distância espacial entre eles varia de acordo com o período reprodutivo da fêmea. O aulido do lobo-guará é uma vocalização de longa distância que funciona como um mecanismo para aumentar a distância espacial entre coespecíficos, bem como para permitir casais de encontrarem um ao outro. Variações individuais nesta vocalização foram relatadas, mas a possibilidade de que elas possam ser percebidas e usadas pela espécie nunca foi testada. Deve-se esperar que essas variações individuais possam ser percebida, pois somente neste cenário seria plausível para o aulido ter a dupla função mencionada acima. Se esta variabilidade individual não é percebida pelos coespecíficos, a eficiência desta vocalização a longas distâncias seria comprometida, já que o ouvinte não seria capaz de identificar se o remetente é o seu parceiro reprodutivo ou um possível rival. Em nosso estudo usamos playbacks para testar se essas variações individuais podem ser percebidas por lobos em cativeiro e concluimos que eles podem. Pelo que conhecemos, esta é a primeira vez se demonstra que o lobo-guará é capaz de discriminar entre aulidos emitidos por diferentes indivíduos / The acoustic channel is an efficient long-distance signaling system that may be especially effective for animals with crepuscular/nocturnal habits. The maned wolf is a threatened canid with crepuscular/nocturnal habits that is thought to be a solitary species in common sense. As a matter of fact, it would be better defined as a gregarious species, since male and female share the same wide territory and the spatial distance between them varies according to the females reproductive period. The maned wolfs extended-bark is a long-distance vocalization that functions as a mechanism to increase spatial distance among conspecifics as well as to enable pair-mates to find each other. Individual variations in this vocalization have been reported, but the possibility that they can be perceived and used by the species has never been tested. One should expect these individual variations to be perceived by the species, since only in this scenario it would be plausible for the extended-bark to have the dual function stated above. If this individual variability is not perceived by conspecifics, the efficiency of this vocalization at long distances, at least for the hypothesized functions, would be compromised, as the hearer would not be able to identify if the sender is its reproductive partner or a possible rival. In our study we used playbacks to test if these individual variations can be perceived by captive wolves and have concluded that they can. To our knowledge, this is the first time it has been demonstrated that the maned wolf is capable of discriminating among extended-barks of different individuals

Le lion de mer Australien a un cycle de reproduction non-annuel et asynchrone entre les colonies.Contrairement aux autres pinnipèdes, ce système unique offre l’opportunité aux mâles de se reproduiredans plusieurs sites lors d’une saison de reproduction. L’accès des mâles à plusieurs sites dereproduction pourrait contrecarrer le fort degré de structure génétique de population chez les femellesdûe à une fidélité extrême au site de reproduction. J'ai utilisé deux méthodes indépendantes maiscomplémentaires, moléculaire et acoustique, afin d’étudier la structure de la population et le systèmede reproduction. Pour l'analyse moléculaire, j'ai développé une banque de microsatellites spécifiques àl'espèce. Ces marqueurs ont été utilisés pour examiner le flux génétique des mâles dans les différentescolonies de reproduction, le succès reproducteur, et les taux de paternité inter- et intra-colonies. Deplus, j'ai mesuré la variation géographique dans les cris des mâles, ce qui représente une approchealternative pour mesurer les convergences/divergences entre colonies. J'ai montré que si les mâlesprésentent une certaine dispersion entre colonies, elle est limitée à une courte échelle en dépit del’opportunité des mâles de se reproduire dans différents sites. Les analyses acoustiques des cris demâles ont révélé des variations géographiques significatives entre colonies, qui ne reflètent pas lastructure génétique. Les analyses de paternité indiquent un faible taux de polygynie, la majorité desmâles ne produisant qu’un ou deux jeunes par saison. Des stratégies alternatives de reproduction(nomade ou sédentaire) sont présentes dans cette espèce, certains mâles se déplaçant activement entredifférentes colonies proches. Le système de reproduction unique du lion de mer Australien semblefortement influer à la fois les modalités de dispersion, mais aussi la structure de population et lesystème de reproduction. / The Australian sea lion has a non-annual and asynchronous breeding cycle across geographically closecolonies. In contrast to other pinnipeds, this unique reproductive system provides the opportunity formales to breed in different colonies during one breeding cycle. Male mating success across differentcolonies could counteract the high degree of structure driven by extreme site fidelity in females. I usedtwo, independent but complementary methods, molecular and acoustic to investigate their populationstructure and mating system. For molecular analysis I developed a species-specific microsatellitelibrary. These markers were used to examine the extent and rate of male mediated gene-flow acrossbreeding colonies but also to determine the breeding success and paternity both within and acrossspatially close colonies. Also, I investigated the geographical variation in male barking call. Thisrepresents an alternative approach to measure boundaries and relationships between colonies. Malesexhibit dispersal; however, this is limited to remarkably small scale in regards to the high potential fordispersal and opportunity to breed in different colonies. Acoustic analyses of the male barking callsrevealed significant geographical variation across sites; however this observed acoustic variation didnot reflect the genetic structure. Paternity analyses revealed that males display relatively modest ratesof polygyny with the majority of successful males siring only one or two pups per breeding cycle. Thepresence of alternative mating strategies (roaming vs staying) is apparent in this species with somemales actively moving and breeding between close colonies. It appears that the unique breedingbiology of Australian sea lion influences dispersal patterns, population structure and mating system.

O canal acústico é um sistema de sinalização de longo alcance eficiente que pode ser especialmente efetivo para animais com hábitos crepusculares/noturnos. O lobo-guará é um canídeo ameaçado com hábitos crepusculares/noturnos que, no senso comum, é visto como uma espécie solitária. De fato, seria melhor definida como uma espécie gregária, uma vez que macho e fêmea dividem o mesmo território e a distância espacial entre eles varia de acordo com o período reprodutivo da fêmea. O aulido do lobo-guará é uma vocalização de longa distância que funciona como um mecanismo para aumentar a distância espacial entre coespecíficos, bem como para permitir casais de encontrarem um ao outro. Variações individuais nesta vocalização foram relatadas, mas a possibilidade de que elas possam ser percebidas e usadas pela espécie nunca foi testada. Deve-se esperar que essas variações individuais possam ser percebida, pois somente neste cenário seria plausível para o aulido ter a dupla função mencionada acima. Se esta variabilidade individual não é percebida pelos coespecíficos, a eficiência desta vocalização a longas distâncias seria comprometida, já que o ouvinte não seria capaz de identificar se o remetente é o seu parceiro reprodutivo ou um possível rival. Em nosso estudo usamos playbacks para testar se essas variações individuais podem ser percebidas por lobos em cativeiro e concluimos que eles podem. Pelo que conhecemos, esta é a primeira vez se demonstra que o lobo-guará é capaz de discriminar entre aulidos emitidos por diferentes indivíduos / The acoustic channel is an efficient long-distance signaling system that may be especially effective for animals with crepuscular/nocturnal habits. The maned wolf is a threatened canid with crepuscular/nocturnal habits that is thought to be a solitary species in common sense. As a matter of fact, it would be better defined as a gregarious species, since male and female share the same wide territory and the spatial distance between them varies according to the females reproductive period. The maned wolfs extended-bark is a long-distance vocalization that functions as a mechanism to increase spatial distance among conspecifics as well as to enable pair-mates to find each other. Individual variations in this vocalization have been reported, but the possibility that they can be perceived and used by the species has never been tested. One should expect these individual variations to be perceived by the species, since only in this scenario it would be plausible for the extended-bark to have the dual function stated above. If this individual variability is not perceived by conspecifics, the efficiency of this vocalization at long distances, at least for the hypothesized functions, would be compromised, as the hearer would not be able to identify if the sender is its reproductive partner or a possible rival. In our study we used playbacks to test if these individual variations can be perceived by captive wolves and have concluded that they can. To our knowledge, this is the first time it has been demonstrated that the maned wolf is capable of discriminating among extended-barks of different individuals

Ultrasound acoustic energy transfer (UAET) is an emerging contactless technology that offers the capability to safely and efficiently power sensors and devices while eliminating the need to replace batteries, which is of interest in many applications. It has been proposed to recharge and communicate with implanted medical devices, thereby eliminating the need for invasive and expensive surgery and also to charge sensors inside enclosed metal containers typically found in automobiles, nuclear power plants, space stations, and aircraft engines. In UAET, energy is transferred through the reception of acoustic waves by a piezoelectric receiver that converts the energy of acoustic waves to electrical voltage. It has been shown that UAET outperforms the conventional CET technologies that use electromagnetic waves to transfer energy, including inductive coupling and capacitative coupling. To date, the majority of research on UAET systems has been limited to modeling and proof-of-concept experiments, mostly in the linear regime, i.e., under small levels of acoustic pressure that result in small amplitude longitudinal vibrations and linearized piezoelectricity. Moreover, existing models are based on the "piston-like" deformation assumption of the transmitter and receiver, which is only accurate for thin disks and does not accurately account for radiation effects. The linear models neglect nonlinear effects associated with the nonlinear acoustic wave propagation as well as the receiver's electroelastic nonlinearities on the energy transfer characteristics, which become significant at high source strengths. In this dissertation, we present experimentally-validated analytical and numerical multiphysics modeling approaches aimed at filling a knowledge gap in terms of considering resonant acoustic-piezoelectric structure interactions and nonlinear effects associated with high excitation levels in UAET systems. In particular, we develop a reduced-order model that can accurately account for the radiation effects and validate it by performing experiments on four piezoelectric disks with different aspect ratios. Next, we study the role of individual sources of nonlinearity on the output power characteristics. First, we consider the effects of electroelastic nonlinearities. We show that these nonlinearities can shift the optimum load resistance when the acoustic medium is fluid. Next, we consider the nonlinear wave propagation and note that the shock formation is associated with the dissipation of energy, and as such, shock formation distance is an essential design parameter for high-intensity UAET systems. We then present an analytical approach capable of predicting the shock formation distance and validate it by comparing its prediction with finite element simulations and experimental results published in the literature. Finally, we experimentally investigate the effects of both the nonlinearity sources on the output power characteristics of the UAET system by considering a high intensity focused ultrasound source and a piezoelectric disk receiver. We determine that the system's efficiency decreases, and the maximum voltage output position drifts towards the source as the source strength is increased. / Doctor of Philosophy / Advancements in electronics that underpinned the development of low power sensors and devices have transformed many fields. For instance, it has led to the innovation of implanted medical devices (IMDs) such as pacemakers and neurostimulators that perform life-saving functions. They also find applications in condition monitoring and wireless sensing in nuclear power plants, space stations, automobiles and aircraft engines, where the sensors are enclosed within sealed metal containers, vacuum/pressure vessels or located in a position isolated from the operator by metal walls. In all these applications, it is desired to communicate with and recharge the sensors wirelessly. Such a mechanism can eliminate the need for invasive and expensive surgeries to replace batteries of IMDs and preserve the structural integrity of metal containers by eliminating the need for feed through wires. It has been shown that ultrasound acoustic energy transfer (UAET) outperforms conventional wireless power transfer techniques. However, existing models are based on several assumptions that limit their potential and do not account for effects that become dominant when a higher output power is desired. In this dissertation, we present experimentally validated numerical and theoretical investigations to fill those knowledge gaps. We also provide crucial design recommendations based on our findings for the efficient implementation of UAET technology.