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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
411

An investigation into the acoustic behaviour, ecology, biogeography, genetic relatedness and species limits within the Pauropsalta annulata Goding and Froggatt species complex (Hemiptera: Cicadidae)

Lindsay Popple Unknown Date (has links)
This thesis investigates aspects of the ecology, morphology, bioacoustics, genetic relatedness, biogeography and taxonomy of cicadas in the Pauropsalta annulata Goding and Froggatt species complex, across their entire eastern Australian geographical distribution. These cicadas seem to emerge at the same sites annually, although the exact duration of their life cycle is not known. They are wary and mobile insects, with individuals generally taking flight at the first sign of disturbance, which makes them challenging to record, capture and observe. The males produce distinctive calling songs that have a consistent rhythmic structure, which is critically important for attracting females. In most cases, the songs are biphasic, with a penetrating introductory or "buzzing" component that apparently functions in mate attraction and a strongly structured cueing or "lilting" component for mate localisation. Initially Pauropsalta annulata was thought to comprise a single species with some degree of geographically structured variation in its calling song. Consequently, various "song types" had been recognised, but their precise relationship to one another had never been investigated. Therefore the structure of their calling songs were compared statistically across individuals of three song types, and this revealed four discrete clusters that were demonstrated to be independent of one another and consistent in their calling song structure. Plotting the geographical distributions of these cicadas revealed that each of the P. annulata song types is independently distributed geographically, with areas of overlap that are relatively small. Calling song structure is consistent for each song type across extensive geographical space and this structure holds even into areas of sympatry. One song type showed consistent differences from the others in male genitalia structure, and female ovipositor length differs significantly among three of the other song types. Each song type was found to be strongly associated with a small number of tree species and these associations are maintained into areas of sympatry. The spatial ecological and morphological comparisons in song structure, plant associations and morphology made in this study demonstrate that the P. annulata song types actually represent a complex of cryptic species. Two of the song types appear to intergrade in areas of sympatric overlap in terms of calling songs, plant associations and morphology, and thus represent subspecies as defined in population genetics terms. The components of the male calling song were then investigated to determine their specific functions and thus how they could delimit species boundaries. Significant differences were found in dominant song frequency between three of the four species, and may contribute to differential mate attraction. Both components of the song of each species have the same dominant frequency. Consistent differences were also evident, among species and subspecies, in the rhythmic structure of the "lilting" component of the male calling song. This component contains repeated phrases and each one of these provides a cue to which the conspecific female may respond. Her response is timed for the brief silent interval between the phrases. At this point the calling song becomes a duet, which enables the male to locate the female, as he actively searches for her on the surrounding branches at this stage. The calling song is discussed in terms of random mating within gene pools of these cicadas and in terms of its role as part of their broader fertilisation mechanism. A molecular analysis of the P. annulata species complex was performed to examine the phylogenetic relationships across 12 species and four subspecies defined in this study, and estimate divergence times within the group. Individual specimens were sampled widely across the geographical distributions of the species and subspecies where possible to account for genetic variation across space. DNA sequences from two loci were amplified: mitochondrial CO1 ("barcoding region") and a large intron from the dynamin nuclear gene. Separate phylogenies were reconstructed for each locus using maximum parsimony procedures and Bayesian posterior sampling with implementation of a relaxed molecular clock. The phylogenies from both genes provided strong support for the monophyly of the P. annulata species complex, and nine of the species were monophyletic based on the CO1 gene. The remaining three emerged non-monophyletic. Based on a clock calibration of 0.0165s/s/myr, the monophyletic clades represented by extant P. annulata species diverged about 4.5-8.0 million years ago. Those species that emerged non-monophyletic had shallower divergences, with the exception of one species, which exhibited haplotype diversity that conferred up to 13.2% sequence divergence between allopatric populations in CO1. Dynamin produced a broadly similar phylogenetic pattern to that of CO1, but the relationships among individuals across the species and subspecies that emerged non-monophyletic differed substantially. This lack of congruence between the two genomes, in combination with the dominance of internal haplotypes in both loci, indicates an overall pattern of deep coalescence rather than interspecific hybridization. Therefore the molecular data do not provide an alternative definition of species limits in the P. annulata species complex, despite some emerging non-monophyletic in this analysis. Sound interpretation of the phylogenetic pattern discovered here would not have been possible without the acoustic, ecological and geographical investigations on species limits that preceded this work. To determine what biological and climatic factors influence the present day distributions of these cicadas, the distributions of two of the most closely related species in the P. annulata species complex were compared with the distributions of the tree species with which each is mainly associated. Because a large part of their life cycle is subterranean, soil texture, pH, electrical conductivity and force required for surface penetration were compared across sites where each of the cicadas occur in sympatry and allopatry. Finally, the influence of temperature and rainfall variables were investigated by testing 'predicted distribution' models (formed using positive distribution records) against negative records for both sets of variables, individually and in combination. The results show that the extent of the distribution of the cicada species is substantially less than that of the associated tree species. The geographical distributions of one of the species may be influenced more by rainfall, or a combination of temperature and rainfall, whereas the other species appears to be more influenced by temperature alone. Both species tolerate soils with a wide range of pH levels, electrical conductivity and forces required for surface penetration. They both showed a strong association with soils that had a silt loam texture, with only few records from sandy soils. However, none of the soils sampled where the cicadas occurred were heavy clays, which suggests that the physical properties of such soils may provide an unsuitable environment for the nymphal stages of the life cycle of these particular cicadas. The resolution of species limits within the P. annulata species complex allowed the redescription of Pauropsalta annulata Goding and Froggatt sensu stricto and the description of 11 new species belonging to the P. annulata species group, all from eastern Australia. Two of these species comprise two subspecies each, also all new. New distribution records and calling song data are documented for the allied species, P. ayrensis Ewart, which is redescribed to include the characters newly recognised in the present study as significant taxonomically with respect to Pauropsalta cicadas. The treatment includes comprehensive descriptions of the morphology and calling songs of the species and subspecies, and separate descriptive keys are provided for both sets of characters. The new taxa comprise P. artatus sp. nov., P. corymbiae sp. nov., P. decorus sp. nov., P. graniticus sp. nov., P. inversus inversus subsp. nov., P. i. laboris subsp. nov., P. notialis notialis subsp. nov., P. notialis incitatus subsp. nov., P. simplex sp. nov., P. subtropicus sp. nov, P. torrensis sp. nov. and P. tremulus sp. nov. Areas of hybridization between P. n. notialis subsp. nov. and P. n. incitatus subsp. nov. are also documented, together with their calling songs and morphology, which justifies their subspecific status. The P. inversus subspecies are allopatric, but consistently differ in the duration between phrases of the calling song. Finally, the results and conclusions are amalgamated into a critical reassessment of what defines species limits and the most appropriate approaches to investigating species limits in sexual organisms. Some historical discussions are revisited, such as the question of the reality of species and how species are perceived under the premises of neoDarwinism. The realism of species demands that species limits are most realistically defined in terms of their fertilisation mechanism, for this delimits the gene pool and thus the distribution of adaptations (the calling song of cicadas, for example).
412

A study of radio astronomy principles and SKA pathfinder system designs with pulsar science

Otto, Sunelle 14 March 2011 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The Square Kilometre Array (SKA) is an international project to build the world’s largest and most sensitive radio telescope interferometer. It will consist of thousands of antennas distributed over many kilometers, with the hosting country being either South Africa or Australia. Various pathfinders have been initiated to demonstrate the technologies needed to implement the SKA. The astronomy community has defined five Key Science Projects (KSP), which are the drivers for the SKA. The science goals determine the technical requirements needed to design SKA systems. Many years of planning and development are still needed in order to meet to the requirements of such a large and complex project. This thesis aims to present the various SKA pathfinder systems in terms of their application to the SKA key science projects, with main focus that of pulsar observations. In order to achieve this, a thorough overview of basic radio astronomy principles and techniques is presented, followed by a detailed look at the various pathfinders. Throughout the work, aspects of pulsar observations are given particular attention with the goal of designing optimal systems for the SKA. / AFRIKAANSE OPSOMMING: Die Square Kilometre Array (SKA) is ’n internasionale projek om die wêreld se grootste en mees sensitiewe radio teleskoop interferometer te bou. Dit sal bestaan uit duisende antennas versprei oor etlike kilometers, met die gasheer land óf Suid-Afrika óf Australië. Verskeie koersbepalers is geïnisieer om die tegnologie te demonstreer wat benodig is om die SKA te implementeer. Die astronomie gemeenskap het vyf sleutel wetenskap projekte (KSP) gedefinieër wat dien as die drywers vir die SKA. Die wetenskap doelwitte bepaal die tegniese vereistes wat nodig is om SKA stelsels to ontwerp. Talle jare van beplanning en ontwikkeling word steeds benodig om te voldoen aan die vereistes van so ’n groot en komplekse projek. Hierdie tesis het ten doel die aanbieding van verskeie SKA koersbepaler stelsels in terme van hulle aanwending tot die SKA sleutel wetenskap projekte, met hoof fokus op die van pulsar waarnemings. Om dit te behaal, word ’n deeglike oorsig van basiese radio astronomie beginsels en tegnieke aangebied, gevolg deur ’n gedetailleerde kyk na die verskeie koersbepalers. Regdeur die werk word spesifieke aandag gegee aan aspekte van pulsar waarnemings met die doel om optimale stelsels vir die SKA te ontwerp.
413

IP mobile multicast over next generation satellite networks : design and evaluation of a seamless mobility framework for IP multicast communications over a multi-beam geostationary satellite network

Jaff, Esua Kinyuy January 2016 (has links)
The inherent broadcast nature of satellites, their global coverage and direct access to a large number of subscribers give satellites unrivalled advantages in supporting IP multicast applications. A new generation of satellite systems that support regenerative on-board processors and multiple spot beam technology have opened new possibilities of implementing IP multicast communication over satellites. These new features enable satellites to make efficient use of their allocated bandwidth resources and provide cost effective network services but equally, create new challenges for mobile satellite terminals. IP mobility support in general and IP mobile multicast support in particular on mobile satellite terminals like the ones mounted on continental flights, maritime vessels, etc., still remain big challenges that have received very little attention from the research community. Up till now, there are no proposed mechanisms to support IP multicast for mobile receivers/sources in multi-beam satellite networks in open literature. This study explores the suitability of IP multicast mobility support schemes defined for terrestrial networks in a satellite environment and proposes novel schemes based on the concepts of Home and Remote subscription-based approaches, multiple interface and PMIPv6 protocol. Detailed analysis and comparison of results obtained from the proposed schemes, Mobile IP (MIP) Home and Remote subscription-based approaches (for terrestrial networks) when implemented on a reference multi-beam satellite network are presented. From these results, the proposed schemes outperform the MIP Home and Remote subscription-based approaches in terms of gateway handover latency, number of multicast packets lost and signalling cost over the satellite air interface.
414

Analysis of angular accuracy in the IFF Monopulse receiver

Bengtsson, Filip, Sköld, David January 2018 (has links)
This master thesis investigates how certain components error margin may affect the accuracy of a IFF monopulse receiver. The IFF monopulse receiver measures the angle of arrival of the incident signal by comparing sum and difference signals created in the receiver. The components of interest are phase shifters and attenuators, where both can give individual and different errors depending on the antenna steering angle. The project is conducted at Saab Aeronautics, based on a receiver in development for the Gripen E aircraft. The results of the thesis generated results showing that the angular accuracy decreases with the increase of steering angle. The angular deviation can for some cases be seen as sufficiently small for the receiver to work properly in the ideal case.
415

Essays on communication and information transmission / Essai sur la communication et la transmission d'informations

Schopohl, Simon 13 November 2017 (has links)
Cette thèse de doctorat traite de différentes questions concernant la communication et la transmission d’informations dans le cadre de la théorie des jeux. J’analyse différents dilemmes auxquels peut être confronté un joueur qui envoie des informations. Ces dilemmes correspondent aux questions suivantes: "Devrais-je investir dans un message vérifiable?", "Quand dois-je transmettre mon information?" et "Est-il préférable de ne pas envoyer mon information et uniquement de recueillir l’information des autres?". Cette thèse comprend une introduction et trois chapitres. L’introduction contient une motivation générale pour les trois problèmes que je présente dans cette thèse. Je donne une vue d’ensemble détaillée de tous les chapitres, j’examine la littérature relative au sujet et je la compare à mes résultats. / This Ph.D dissertation addresses different issues concerning communication and information transmission in a game theoretical framework. I analyze different dilemmas that a player who sends information has to deal with. These dilemmas correspond to the following questions: "Should I invest into a verifiable message?", "When should I pass my information?" and "Is it better if I do not send my information, but collect information from others?". This thesis includes an introduction and three chapters. The introduction contains a general motivation for the three different problems that I model in this thesis. I give a detailed overview of all the chapters, survey the related literature and compare it to my results.
416

Intelligent computing applications to assist perceptual training in medical imaging

Dong, Leng January 2016 (has links)
The research presented in this thesis represents a body of work which addresses issues in medical imaging, primarily as it applies to breast cancer screening and laparoscopic surgery. The concern here is how computer based methods can aid medical practitioners in these tasks. Thus, research is presented which develops both new techniques of analysing radiologists performance data and also new approaches of examining surgeons visual behaviour when they are undertaking laparoscopic training. Initially a new chest X-Ray self-assessment application is described which has been developed to assess and improve radiologists performance in detecting lung cancer. Then, in breast cancer screening, a method of identifying potential poor performance outliers at an early stage in a national self-assessment scheme is demonstrated. Additionally, a method is presented to optimize whether a radiologist, in using this scheme, has correctly localised and identified an abnormality or made an error. One issue in appropriately measuring radiological performance in breast screening is that both the size of clinical monitors used and the difficulty in linking the medical image to the observer s line of sight hinders suitable eye tracking. Consequently, a new method is presented which links these two items. Laparoscopic surgeons have similar issues to radiologists in interpreting a medical display but with the added complications of hand-eye co-ordination. Work is presented which examines whether visual search feedback of surgeons operations can be useful training aids.
417

Caractérisation et modélisation multiphysique de MEMS supraconducteurs pour une application en radioastronomie millimétrique / Multiphysic characterization and modelling of superconducting MEMS for radio astronomy applications

Allouch, Nouha 28 November 2011 (has links)
Des MEMS supraconducteurs ont été développés par l’IRAM pour des besoins instrumentaux dans les récepteurs hétérodyne large bande en millimétrique. Dans ce mémoire, la caractérisation de ces MEMS capacitifs par des mesures profilométriques, vibrométriques, aux rayons X , électriques et thermiques est présentée. Ils ont en outre été modélisés avec un modèle analytique électromécanique simple. Ce modèle est complété par un schéma équivalent haute fréquence semi-distribué facilement implantable dans le simulateur multiphysique COMSOL pour prendre en compte la supraconductivité. Ce travail a permis de déterminer quelles géométries de ces MEMS sont satisfaisantes pour une utilisation dans les récepteurs hétérodyne large bande en hyperfréquence. / Superconducting MEMS were developed by IRAM for millimetre wave heterodyne receivers improvements. In this report, the characterization of these capacitive MEMS is presented (profilometry, vibrometry, X rays, electric and thermal). They were described with a simple analytical electromechanical model which can be easily implemented with an equivalent high frequency circuit in the COMSOL multiphysic software to take into account the superconductivity. This work answers to the question of what are the MEMS geometries well suited for broadband heterodyne receivers requirements.
418

Dramaturgia do aqui e agora: presen?a, recep??o e sentido no corpo do ator

Toledo, Marina Madeira de 12 April 2013 (has links)
Made available in DSpace on 2014-12-17T14:00:17Z (GMT). No. of bitstreams: 1 MarinaMT_DISSERT.pdf: 1946161 bytes, checksum: fa78815b909d85267052422856f66700 (MD5) Previous issue date: 2013-04-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The actor is an actor during all the phases of creation and development of his character. (S) He goes beyond the moment of interpreting. In this sense, in her (his) daily life, the actor may use her (his) potential to extract from reality the necessary elements for the work of creation. This is a theoretical research which focus on the concept of presence in the actor s work, stretching the concept beyond the scene, encompassing different components such as the body, the word, the silence, the technique and the acting as the actor s stance in regards to his own reality. The objective of such stance is to integrate him (her) self in the environment, balancing his (hers) inner life with the outside life flow. To reach this objective, the research drew theoretical resources from the concept of presence in the actor s work according to BROOK, BARBA, GROTOWSKI and MNOUCHKINE and the studies on reception theory in ISER, 1996; GUMBRECHT, 2010. Thus, the dialogue between reader and actor high lights both as receivers in this work. A practical description of a street theater Kamch?tka show, featured by the Kamch?tka Company is used as an example of the research on the presence. The elements localized in this show are: play, listening, word, silence, meaning, relationship with here and now and the effects of the said presence / O ator n?o ? ator somente no momento da cena, ? ator em todas as etapas de cria??o e desenvolvimento de seu objeto est?tico. Nesse sentido, em seu cotidiano o ator pode procurar utilizar suas potencialidades para captar e traduzir da realidade o material para seu trabalho criativo. Esta pesquisa possui car?ter te?rico e aborda o conceito de presen?a no trabalho do ator, colocando-o como conceito para al?m da cena, n?o isolado de outros componentes entre eles o corpo, a palavra, o sil?ncio, a t?cnica, a representa??o como uma postura do ator para com sua realidade, a fim de integrar-se ao meio ambiente que o cerca, equilibrando seu conte?do interior com o conte?do exterior. Para tanto, utiliza como aporte te?rico encenadores que abordam o conceito de presen?a no trabalho do ator (BROOK; BARBA; GROTOWSKI; MNOUCHKINE) e os estudos da teoria da recep??o (ISER, 1996; GUMBRECHT, 2010), tra?ando um paralelo dial?gico entre as fun??es de leitor e ator, apontando ambos como receptores. Como exemplo pr?tico do estudo sobre a presen?a, ? feita aqui uma descri??o do espet?culo de teatro de rua Kamch?tka, realizado pela Companhia Kamch?tka, localizando nesse espet?culo os elementos: jogo, escuta, palavra, sil?ncio, sentido, rela??o com o aqui e agora e efeitos de presen?a; citados ao longo da disserta??o
419

AnÃlise de Sistemas OFDM Cooperativos AF com Amplificadores de PotÃncia NÃo Linearesâ / Analysis of Cooperative Systems OFDM AF with Nonlinear Power Amplifiers

Eder Jacques Porfirio Farias 26 July 2013 (has links)
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Cooperation diversity and orthogonal frequency division multiplexing (OFDM) are two key technologies for the modern wireless communication systems. The cooperative communication systems considered through this work use the OFDM technology and they are composed of: one transmitter with a nonlinear power amplifier (PA), one or more amplify-and-forward (AF) relays, also having a nonlinear PAs, and one destination node. In this dissertaion, it is initially proposed an optimal receiver, in the signal to noise ratio (SNR) sense, for a nonlinear cooperative AF system. The proposed receiver uses the maximum ratio combining (MRC) diversity technique to combine the received signas, assuming that both the source-destination and source-relay-destination links are available. In the sequel, closed-form expressions for the instantaneous SNR and outage probability of the considered system are developed. The outage analysis is then extended to the case of a multi-hop system, that is, with multiple serial relays. Finally, an outage analysis is also proposed for a nonlinear AF OFDM system using a Selection Combining receiver, considering two cases: one relay and multiple parallel relays. Numerical simulation results are presented through the work, evaluating the performance of the proposed receiver and theoretical expressions. / A diversidade cooperativa e a multiplexaÃÃo por divisÃo de frequÃncias ortogonais (Orthogonal Frequency Division Multiplexing - OFDM) sÃo duas das principais tecnologias para os sistemas de comunicaÃÃo sem fio modernos. Os sistemas de comunicaÃÃo cooperativos considerados neste trabalho de dissertaÃÃo utilizam a tecnologia OFDM e possuem: uma fonte com amplificador de potÃncia nÃo linear, um ou mais repetidores (relays) do tipo amplifica-e-encaminha (Amplify-and-Forward - AF), tambÃm com amplificadores de potÃncia (Power Amplifier - PA) nÃo lineares, e um nà destino. PropÃe-se inicialmente um receptor Ãtimo, no sentido da razÃo sinal ruÃdo (Signal-to-Noise Ratio - SNR) para um sistema OFDM cooperativo nÃo linear. Usando a tÃcnica de diversidade por combinaÃÃo de razÃo mÃxima (Maximal Ratio Combining - MRC) para tratar os sinais recebidos, o receptor proposto considera tanto as informaÃÃes oriundas do caminho direto (fonte-destino) como as provenientes do repetidor. Posteriormente, sÃo apresentadas expressÃes para o cÃlculo da SNR instantÃnea e da probabilidade de outage do sistema proposto. Fez-se ainda, uma proposta de expressÃo para o cÃlculo da probabilidade de outage do sistema considerando mÃltiplos relays em sÃrie. Por fim, propÃe-se expressÃes para o cÃlculo da probabilidade de outage do sistema utilizando receptor Selection Combining para um e para mÃltiplos relays dispostos paralelamente. Resultados de simulaÃÃo sÃo apresentados durante todo o trabalho, evidenciando o desempenho do receptor e das expressÃes propostas.
420

Análise da precisão e acurácia de pontos georreferenciados com a técnica do código suavizado pela fase da portadora utilizando GPS de simples freqüência / Precision and accuracy analysis of georeferencing points using the carrier-smoothed-code technique with GPS single frequency receiver (L1)

João Olympio de Araújo Neto 23 June 2006 (has links)
A presente dissertação teve como finalidade avaliar a precisão e a discrepância das coordenadas (acurácia) obtidas por meio das observações GPS, no modo estático rápido, medidas com receptores de uma freqüência, empregando-se a técnica de suavização do código C/A pela fase da portadora para diferentes comprimentos de linha base (20, 50, 75, 100, 150, 200 e 300 Km), a partir da estação de monitoramento contínuo da EESC/USP. Essa técnica obteve boa repercussão no Brasil, a partir do momento em que foi permitida sua utilização para fins de georreferenciamento de imóveis rurais, conforme a norma técnica do INCRA, que permite a utilização da suavização do código pela fase da portadora, desde que esta apresente acurácia com valores iguais ou inferiores a 50 cm. Atualmente, trabalhos com tal técnica estão sendo desenvolvidos e aceitos para compor o banco de dados do cadastro rural nacional. Pelos resultados obtidos nesta dissertação, foi possível avaliar que a aplicação dessa técnica não atende à exigência requerida em 100% das medições e, ao mesmo tempo, verificar a diferença entre a precisão do pós-processamento, indicada pelos softwares comerciais e a acurácia dos pontos medidos comparados com os pontos de controle estabelecidos para esse fim. / The present dissertation has as objective to evaluate precision and discrepancies of coordinates (accuracy) obtained through GPS observations, in a rapid static method, measured by single frequency, which applies carrier-smoothed-code for different baseline length (20, 50, 75, 100, 150, 200 and 300 km), since continuous monitoring station from EESC/USP. This technique obtained a good repercussion in Brazil, since when its use was legitimate in rural property georeferencing, according to INCRA\'s norma técnica (technical rule), which allows the use of carrier-smoothed-code in view of the fact that presents accuracy with equal or inferior values to 50 cm. Currently, works using such technique are developed and accepted in order to compound database of national rural survey in Brazil. Based on the obtained results it was possible to evaluate that the technique does not guaranteed to requested requirement in 100% of measurements, and at the same time to verify the difference between post-processing precision, indicated by commercial software, as well as measured point accuracy compared with points established for this purposed.

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