Variation in advertisement call structure of whistling frogs, Litoria ewingi, was studied among breeding sites in the vicinity of Christchurch on the East coast and Harihari on the West coast of the South Island. Males vocalized in breeding choruses throughout the year and females moved toward and appeared to evaluate calls of territorial males before initiating amplexus. Acoustic interactions between neighbours led to modification of call structure and timing, and wrestling matches between males were frequent. I quantified call structure for 1623 calls of 168 individuals using 24 call parameters. Most temporal characteristics were significantly correlated with the caller's body temperature and dominant frequency was negatively correlated with body size. These results are consistent with the prediction of temperature-dependent metabolic rates in a poikilotherm's nervous system. I compared call structure among the study populations using both multivariate and univariate analyses. Advertisement call structure showed highly significant variation among populations for most call variables. The greatest difference occurred between the West and East coast populations, and a clinal trend occurred in the East coast populations on a microgeographic scale. Variation among East coast populations in some variables was comparable to the scale of variation between coasts. These results suggest that whistling frogs exhibit natal philopatry. I obtained repeated recordings for 21 individuals and examined variation in call structure within and among individuals using nested multivariate analyses of variance. Highly significant variation occurred both within and among individuals for most call characters, but certain call characters were more variable among individuals. This suggests that whistling frog advertisement calls are individually distinctive.

The black-bellied tree duck (Dendracygna autumnal is) 1 is one of eight tree ducks (whistling ducks) in the genus Dendracygna . This group shares enough characteris tics--reticulated tarsus and symmetrical syrinx structure, among others--with the swans and geese Ia warrant a cam man subfamily, Anserinae of the waterfowl family Anatidae. De Iacour and Mayr ( 1945) make a tribal distinction, however, between the tree ducks (Dendracygnini) and the swans and geese (Anserini) based, in part, an differences in size, vertebrae number, and downy plumage . These same authors remark that the tree ducks are the leas t known of the waterfowl largely because there are no life history studies for any of the species. Of the two species found in the continental United States, the fulvous (_Q . bicolor) and black-bellied tree ducks , the ecology of the last named seemed singularly unknown.

Variation in advertisement call structure of whistling frogs, Litoria ewingi, was studied among breeding sites in the vicinity of Christchurch on the East coast and Harihari on the West coast of the South Island. Males vocalized in breeding choruses throughout the year and females moved toward and appeared to evaluate calls of territorial males before initiating amplexus. Acoustic interactions between neighbours led to modification of call structure and timing, and wrestling matches between males were frequent. I quantified call structure for 1623 calls of 168 individuals using 24 call parameters. Most temporal characteristics were significantly correlated with the caller's body temperature and dominant frequency was negatively correlated with body size. These results are consistent with the prediction of temperature-dependent metabolic rates in a poikilotherm's nervous system. I compared call structure among the study populations using both multivariate and univariate analyses. Advertisement call structure showed highly significant variation among populations for most call variables. The greatest difference occurred between the West and East coast populations, and a clinal trend occurred in the East coast populations on a microgeographic scale. Variation among East coast populations in some variables was comparable to the scale of variation between coasts. These results suggest that whistling frogs exhibit natal philopatry. I obtained repeated recordings for 21 individuals and examined variation in call structure within and among individuals using nested multivariate analyses of variance. Highly significant variation occurred both within and among individuals for most call characters, but certain call characters were more variable among individuals. This suggests that whistling frog advertisement calls are individually distinctive.

Les diaphragmes utilisés comme organes de perte de charge à l'intérieur des tuyauteries de centrales électriques ont été mis en cause dans la création de sifflement. Les conséquences de ces phénomènes sont des niveaux de bruit et de vibration pouvant dépasser les valeurs admissibles. L'objectif de la thèse est d'étudier le sifflement sur la base d'expérimentations et de calculs numériques afin de proposer des outils de compréhension et de prédiction. Un résultat de la thèse correspond à l’identification expérimentale et numérique des conditions d’amplification acoustique au niveau de diaphragmes, phénomène nécessaire au sifflement. Les expériences montrent que les plages de sifflement, exprimées sous la forme d’un nombre de Strouhal fonction de l’épaisseur du diaphragme et de la vitesse dans l’orifice, s’étendent de 0,2 à 0,4 et de 0,7 à 0,9 et sont indépendantes du nombre de Reynolds. Le potentiel de sifflement de diaphragmes est également caractérisé à l’aide de simulations numériques. Deux approches sont utilisées avec des calculs U-RANS incompressibles et des simulations LES compressibles. Il apparaît que la simulation numérique permet de reproduire l’effet d’amplification acoustique à l’origine du sifflement, pour des pas de discrétisation spatial au coin amont de l’orifice suffisamment petit. Un autre résultat de la thèse est la définition des paramètres contrôlant les caractéristiques du sifflement en présence de réflexions acoustiques. Une analyse de stabilité linéaire prédit l’apparition d’un sifflement et sa fréquence. L’amplitude de sifflement est maximum pour un nombre de Strouhal autour de 0,25 et augmente avec le taux de réflexion autour du diaphragme. / Orifices used as pressure drop devices in pipes of power plants can cause tonal noise. The consequences of whistling are noise and vibration levels higher than what is acceptable. The purpose of the present works is to study the whistling phenomenon with experiments and numeric in order to propose comprehension and prediction tools. One of the results of the study is the experimental and numerical identification of the acoustic amplification conditions at the orifice, which is a necessary phenomenon for whistling. The experiments show that the whistling ranges, expressed in a Strouhal number function of the orifice thickness and the flow velocity inside the orifice, lie between 0.2 and 0.4 and between 0.7 and 0.9 and that they are independent of the Reynolds number. The whistling ability of orifices has also been defined with numerical simulations. Two approaches are used, the first consisting of incompressible U-RANS calculations, the second based on compressible LES. The numerical simulations are able to capture the acoustic amplification at the orifice, for a spatial discretization small enough at the upstream edge of the orifice. Another result of the study is the definition of the parameters controlling the whistling features when acoustic reflections are present. A linear stability analysis is able to predict the whistling frequency, and it is shown that the whistling amplitude is maximum at a Strouhal number of 0.25 and that it increases with the global reflection surrounding the orifice.

Man-made nest boxes are surrogate nest sites widely used by waterfowl managers in North America to propagate free-ranging Wood Ducks (Aix sponsa) and other cavity-nesting waterfowl. I monitored 129 and 174 nest boxes in 2020 and 2021, respectively, at Noxubee National Wildlife Refuge and York Woods, Mississippi. I evaluated site-specific biotic and abiotic factors that were potentially influential on nest survival of Wood Ducks and general nesting ecology and apparent nest success of Black-bellied Whistling Ducks (Dendrocygna autumnalis) and Hooded Mergansers (Lophodytes cucullatus). Daily survival rate of Wood Ducks was negatively influenced by increasing encroaching vegetation at Noxubee NWR and varied by year at York Woods. Across both sites and years, Black-bellied Whistling Duck and Hooded Merganser nest success averaged 59% and 77%, respectively. I also evaluated eggshell breaking strength (EBS) between all three species, where EBS was highest in Hooded Mergansers, followed by Black-bellied Whistling Ducks and Wood Ducks.

New methodologies and concepts for developing compact and energy efficient automotive exhaust systems have been studied. This originates in the growing concern for global warming, to which road transportation is a major contributor. The focus has been on commercial vehicles—most often powered by diesel engines—for which the emission legislation has been dramatically increased over the last decade. The emissions of particulates and nitrogen oxides have been successfully reduced by the introduction of filters and catalytic converters, but the fuel consumption, which basically determines the emissions of carbon dioxides, has not been improved accordingly. The potential reduction of fuel consumption by optimising the exhaust after-treatment system (assuming fixed after-treatment components) of a typical heavy-duty commercial vehicle is ~4%, which would have a significant impact on both the environment and the overall economy of the vehicle. First, methodologies to efficiently model complex flow duct networks such as exhaust systems are investigated. The well-established linear multiport approach is extended to include flow-acoustic interaction effects. This introduces an effective way of quantifying amplification and attenuation of incident sound, and, perhaps more importantly, the possibility of predicting nonlinear phenomena such as self-sustained oscillations—whistling—using linear models. The methodology is demonstrated on T-junctions, which is a configuration well known to be prone to self-sustained oscillations for grazing flow past the side branch orifice. It is shown, and validated experimentally, that the existence and frequency of self-sustained oscillations can be predicted using linear theory. Further, the aeroacoustics of T-junctions are studied. A test rig for the full determination of the scattering matrix defining the linear three-port representing the T-junction is developed, allowing for any combination of grazing-bias flow. It is shown that the constructive flow-acoustic coupling not only varies with the flow configuration but also with the incidence of the acoustic disturbance. Configurations where flow from the side branch joins the grazing flow are still prone to whistling, while flow bleeding off from the main branch effectively cancels any constructive flow-acoustic coupling. Two silencer concepts are evaluated: first the classic Herschel-Quincke tube and second a novel modified flow reversal silencer. The Herschel-Quincke tube is capable of providing effective attenuation with very low pressure loss penalty. The attenuation conditions are derived and their sensitivity to mean flow explained. Two implementations have been modelled using the multiport methodology and then validated experimentally. The first configuration, where the nodal points are composed of T-junctions, proves to be an example where internal reflections in the system can provide sufficient feedback for self-sustained oscillation. Again, this is predicted accurately by the linear theory. The second implementation, with nodal points made from Y-junctions, was designed to allow for equal flow distribution between the two parallel ducts, thus allowing for the demonstration of the passive properties of the system. Experimental results presented for these two configurations correlate well with the derived theory. The second silencer concept studied consists of a flow reversal chamber that is converted to a resonator by acoustically short-circuiting the inlet and outlet ducts. The eigenfrequency of the resonator is easily shifted by varying the geometry of the short circuit, thus making the proposed concept ideal for implementation as a semi-active device. Again the concept is modelled using the multiport approach and validated experimentally. It is shown to provide significant attenuation over a wide frequency range with a very compact design, while adding little or no pressure loss to the system. / QC 20110208

Thesis (MA (Afrikaans and Dutch))--University of Stellenbosch, 2006. / In fulfilment of the degree of Magister in Creative Writing: Afrikaans, a novel titled Kielhaal (Keelhaul) is presented in which the main character figures as an abject hero. It is accompanied by a formal essay titled “Die abjekte held in Steppenwolf, Fight Club en A Whistling Woman” (“The abject hero in Steppenwolf, Fight Club and A Whistling Woman”). The essay researches the application of the abject hero in literary texts.

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Dans la Chine du IIIè siècle, les mutations politiques et intellectuelles considérables survenues après l’effondrement des Han favorisent l’éveil d’une conscience inédite de l’individu, ainsi que l’émergence de nouvelles tendances philosophiques (le néo-taoïsme de l’Étude du Mystère) et l’apparition d’une activité artistique en rupture avec la tradition qui s’est imposée durant quatre siècles d’hégémonie confucéenne. La musique, qui occupe une place d’élection dans la vie des lettrés, voit évoluer le statut et la pratique auxquels elle était jusqu’alors confinée, l’outil moralisateur au service de la concorde sociale s’affirmant désormais comme une distraction libre et privée, affranchie de ses finalités politiques et civilisatrices. Notre travail prend pour objet les conceptions de la musique qui ont vu le jour dans ce contexte de l’avènement esthétique et d’une valorisation sans précédent des émotions individuelles. En nous concentrant plus particulièrement sur Ruan Ji 阮籍 (210-263) et Ji Kang 嵇康 (223-262), figures de proue de la pléiade des Sept Sages de la Forêt de Bambous et éminents poètes, philosophes et musiciens, nous avons cherché à étudier la réflexion esthétique qui s’élabore dans leurs écrits autour des questions de l’origine et la nature de la musique, de ses fonctions morales et sociales, de son utilisation politique ou macrobiotique, de ses vertus éthiques ou diététiques, ou encore de son lien aux émotions. L’analyse textuelle est complétée par celle de pratiques ou de gestes musicaux : le sifflement chez Ruan Ji, la cithare chez Ji Kang, qui donnent corps aux discours et illustrent leur mise en œuvre concrète dans la vie de ces auteurs. De sorte que l’esthétique ne se définit plus seulement comme un discours, mais aussi comme un ethos, et que l’effort d’affranchissement de la musique est contemporain d’une d’émancipation des sujets mêmes de l’expérience esthétique. / In third-century China, the huge political and intellectual mutations occurring after the collapse of the Han dynasty result in the awakening of a new self-consciousness of man and the emergence of new philosophical trends (the so called Dark Learning), or also an artistic activity breaking off with four centuries of Confucian orthodoxy. Music, which occupies a privileged position in the life of literati, evolves as well, as far as its traditional status and practice are both concerned. No more considered a tool of moralization for the sake of civilized order or social harmony, it becomes a private and free distraction, emancipated from political or any other pragmatic purpose. The conceptions of music appearing in this context of nascent aesthetics provide the subject matter of our research. Focusing on Ruan Ji 阮籍 (210-263) and Ji Kang 嵇康 (223-262), two leading figures of the well-known literati group “the Seven Sages of the bamboo grove” who were also famous poets, thinkers and musicians, we attempt to examine their aesthetic thought throughout their main writings on music, concerning issues such as the origins and nature of music, its moral or social functions, its political or macrobiotic use, its ethical or dietetic virtues, and also its relation to man’s emotions. The textual analysis is completed by the study of musical practices or gestures (Ruan Ji’s whistling, Ji Kang’s playing the zither), that illustrate the effective application of their ideas in concrete life. Therefore, aesthetics does not only consist in a mere discourse, but becomes a kind of ethos, in which the emancipation of music is inseparable from that of the individual himself, through his aesthetic experience.