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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.
571

Coleta, reprodução e larvicultura do Pseudopimelodus mangurus e desenvolvimento embrionário do Pimelodus maculatus e Pseudopimelodus mangurus em diferentes temperaturas.

Arashiro, Dilberto Ribeiro January 2018 (has links)
Orientador: José Senhorini / Abstract: The aim of this study was to describe a procedure for sampling, reproduction, and first feeding of the Neotropical catfish Pseudopimelodus mangurus. Wild adult P. mangurus specimens were collected in the Mogi Guassu river, and subsequently, were induced to spawn in laboratory conditions. After hand-stripping the females, the average weight of the oocytes was 143 ± 1.66 g, having an average of 718 ± 49.802 oocytes g-1. The diameter of zygotes was about 1226.354 ± 47.719 µm nonhydrated to 1761.256 ± 26.412 µm after hydration. The fertilization rates were 98.00 ± 0.63%, and the hatching rate were 68.94 ± 11.83%. Three days after hatching, the larvae started exogenous feeding. First feedings were made with 6 different treatments, in which the best results arose with sequential feeding with artemia nauplii, Astyanax altiparanae, and Prochilodus lineatus larvae. This condition resulted in a growth rate of 2012.795 ± 44.891 µm by the tenth day of experiment, higher survival rate (65 ± 0.09%), and a lower cannibalism rate 14 ± 0.03% on the tenth day after exogenous feed. The data obtained in this study is important for reproductive biotechniques and mass production of the endangered catfish P. mangurus. / Mestre
572

Détection et localisation tridimensionnelle par stéréovision d’objets en mouvement dans des environnements complexes : application aux passages à niveau / Detection and 3D localization of moving and stationary obstacles by stereo vision in complex environments : application at level crossings

Fakhfakh, Nizar 14 June 2011 (has links)
La sécurité des personnes et des équipements est un élément capital dans le domaine des transports routiers et ferroviaires. Depuis quelques années, les Passages à Niveau (PN) ont fait l’objet de davantage d'attention afin d'accroître la sécurité des usagers sur cette portion route/rail considérée comme dangereuse. Nous proposons dans cette thèse un système de vision stéréoscopique pour la détection automatique des situations dangereuses. Un tel système permet la détection et la localisation d'obstacles sur ou autour du PN. Le système de vision proposé est composé de deux caméras supervisant la zone de croisement. Nous avons développé des algorithmes permettant à la fois la détection d'objets, tels que des piétons ou des véhicules, et la localisation 3D de ces derniers. L'algorithme de détection d'obstacles se base sur l'Analyse en Composantes Indépendantes et la propagation de croyance spatio-temporelle. L'algorithme de localisation tridimensionnelle exploite les avantages des méthodes locales et globales, et est composé de trois étapes : la première consiste à estimer une carte de disparité à partir d'une fonction de vraisemblance basée sur les méthodes locales. La deuxième étape permet d'identifier les pixels bien mis en correspondance ayant des mesures de confiances élevées. Ce sous-ensemble de pixels est le point de départ de la troisième étape qui consiste à ré-estimer les disparités du reste des pixels par propagation de croyance sélective. Le mouvement est introduit comme une contrainte dans l'algorithme de localisation 3D permettant l'amélioration de la précision de localisation et l'accélération du temps de traitement. / Within the past years, railways undertakings became interested in the assessment of Level Crossings (LC) safety. We propose in this thesis an Automatic Video-Surveillance system (AVS) at LC for an automatic detection of specific events. The system allows automatically detecting and 3D localizing the presence of one or more obstacles which are motionless at the level crossing. Our research aims at developing an AVS using the passive stereo vision principles. The proposed imaging system uses two cameras to detect and localize any kind of object lying on a railway level crossing. The cameras are placed so that the dangerous zones are well (fully) monitored. The system supervises and estimates automatically the critical situations by detecting objects in the hazardous zone defined as the crossing zone of a railway line by a road or path. The AVS system is used to monitor dynamic scenes where interactions take place among objects of interest (people or vehicles). After a classical image grabbing and digitizing step, the processing is composed of the two following modules: moving and stationary objects detection and 3-D localization. The developed stereo matching algorithm stems from an inference principle based on belief propagation and energy minimization. It takes into account the advantages of local methods for reducing the complexity of the inference step achieved by the belief propagation technique which leads to an improvement in the quality of results. The motion detection module is considered as a constraint which allows improving and speeding up the 3D localization algorithm.
573

Polarisation MIMO indoor wireless communications using highly compact antennas and platforms

Burge, Joseph January 2017 (has links)
In the indoor environment, multipath fading causes the received signal amplitude to fluctuate rapidly over space and frequency. Multiple-in multiple-out (MIMO) systems overcome this phenomenon through the use of multiple antennas on transmitters and receivers. This establishes multiple independent MIMO sub-channels between antenna pairs, which allows a theoretical increase in capacity which is linear with the number of antennas, while requiring no additional power or bandwidth expenditure. The capacity increase is reliant upon MIMO sub-channels being well decorrelated. Decorrelation may be achieved by separating antennas in space. On devices where space is limited, an alternative approach is to use antennas with orthogonal polarisations, which may be positioned closer together. Existing literature states that the performance of polarisation MIMO systems is typically inferior to that of spatial MIMO systems under diversity applications, but can be superior in multiplexing applications. These statements are based on the analysis of a statistical channel model, using channel conditions assumed to be typical of an ideal polarisation MIMO system. There is little existing literature which examines how close these assumptions are to a practical polarisation MIMO channel, or whether the above statements remain true of practical systems. This thesis presents a novel end-to-end, predominantly deterministic approach to the modelling of polarisation MIMO systems. A bespoke MIMO channel model is used to estimate capacity and error rate under diversity and spatial multiplexing applications in the indoor environment. The parameters of the channel model are obtained deterministically from a ray launching propagation model, using antenna patterns of orthogonally polarised small antenna systems positioned in the indoor environment. The individual differences in the channel gains and K-factors of each sub-channel are accounted for. Correlation is accounted for using a full correlation matrix, rather than the Kronecker model. Particular attention is paid to mutual coupling of closely spaced antennas. Using this analysis, it is shown that for practical antennas and systems conditions of the polarisation MIMO channel may differ from those assumed in literature. The effect of this in terms of channel capacity and system bit error rate is directly determined and presented. Performance of polarisation MIMO systems, using co-located and spatially separate orthogonally polarised antennas, is compared to that of spatial MIMO systems, which use co-polar antennas with limited spatial separation. Additionally, comparison is made between compact polarisation MIMO systems which use orthogonal linear polarised antennas and those using orthogonal circular polarised antennas. Further analysis examines the significant effect of objects in the antenna near-field regions. The effects of the presence of a metal case on antenna performance are presented, before its impact on the channel conditions and ultimately the resultant MIMO performance is shown.
574

[en] ANALYSIS OF THE INFLUENCE OF THERMOMECHANICAL COUPLING IN WAVE PROPAGATION IN ELASTIC-VISCOPLÁSTICAS BARS WITH DAMAGE / [pt] SIMULAÇÃO DE CARREGAMENTOS CÍCLICOS A ALTAS FREQUÊNCIAS EM BARRAS ELASTO-VISCOPLÁSTICAS

JOSÉ MARIA ANDRADE BARBOSA 12 March 2018 (has links)
[pt] Este trabalho apresenta uma técnica numérica. baseada no Método de Decomposição do Operador (Operator Splitting Method) e algorítimos sequenciais associados (product formula algorithm) para simular o fenômeno de propagação de ondas em barras elasto-viscoplásticas. Este método tem boas propriedades de estabilidade e preciaão mesmo quando um esquema explícito de baixa ordem é utilizado na integração temporal. Esta técnica numérica é usada para simular carregamentos cíclicos de alta frequência em barras de aço austenítico a altas temperaturas. / [en] The present work presents a numerical technique ( based on the Operator Split Method associated with product formula algorithm ) for simulating the wave propagation phenomenon in bars with any kind of elastic-viecoplastic oonstitutive equations. This method has very good properties of stability and precision even if explicit time evolution schemes are used. This numerical technique is used to simulate high frequency cyclic loadings in austenitic steel bars at high temperatures.
575

Complex phase space representation of plasma waves : theory and applications

Ratan, Naren January 2017 (has links)
This thesis presents results on the description of plasma waves in terms of wavepackets. The wave field is decomposed into a distribution of wavepackets in a space of position, wavevector, time, and frequency. A complex structure joining each pair of Fourier conjugate variables into a single complex coordinate allows the efficient derivation of equations of motion for the phase space distribution by exploiting its analytic properties. The Wick symbol calculus, a mathematical tool generalizing many convenient properties of the Fourier transform to a local setting, is used to derive new exact phase space equations which maintain full information on the phase of the waves and include effects nonlocal in phase space such as harmonic generation. A general purpose asymptotic expansion of the Wick symbol product formula is used to treat dispersion, refraction, photon acceleration, and ponderomotive forces. Examples studied include the nonlinear Schrödinger equation, mode conversion, and the Vlasov equation. The structure of partially coherent wave fields is understood in terms of zeros in the phase space distribution caused by dislocations in its complex phase which are shown to be correlated with the field entropy. Simulations of plasma heating by crossing electron beams are understood by representing the resulting plasma waves in phase space. The local coherence properties of the beam driven Langmuir waves are studied numerically.
576

The bending effect in turbulent flame propagation

Nivarti, Girish Venkata January 2017 (has links)
In the present thesis, the sensitivity of flame propagation to the turbulent motion of burning gases is investigated. The long-standing issue of the 'bending effect' is focused upon, which refers to the experimentally-observed inhibition of flame propagation velocity at high intensities of turbulence. Plausible mechanisms for the bending effect are investigated by isolating systematically the effects of turbulence intensity. By providing a novel perspective on this topic, the thesis addresses the fundamental limits of turbulent burning. The investigation employs Direct Numerical Simulation (DNS), which enables the basic conditions of burning to be controlled directly. A parametric DNS dataset is designed and generated by increasing turbulence intensity over five separate simulations. Effects of turbulent motion are isolated in this manner, such that the bending effect is reproduced in the variation of flame propagation velocity recorded. Subsequently, the validity of Damköhler's hypotheses is investigated to ascertain the mechanism of bending. Analysis of the DNS dataset highlights the significance of kinematic flame response in determining turbulent flame propagation. Damköhler's first hypothesis is found to be valid throughout the dataset, suggesting that the bending effect may be a consequence of self-regulation of the flame surface. This contradicts the dominant belief that bending occurs as a result of flame surface disruption by the action of turbulence. Damköhler's second hypothesis is found to be valid in a relatively limited regime within the dataset, its validity governed by flame-induced effects on the prescribed turbulent flow field. Therefore, this thesis presents turbulent flame propagation and the bending effect as emergent from the dynamics of a flame surface that retains its internal thermo-chemical structure. Finally, experimental validation is sought for the proposed mechanisms of bending. Comparisons have been initiated with measurements in the Leeds explosion vessel, based on which the widely accepted mechanism of bending was hypothesized twenty-five years ago. Modifications to the DNS framework warranted by this comparison have aided the development of novel computationally-efficient algorithms. The ongoing work may yield insights into the key mechanism of the bending effect in turbulent flame propagation.
577

Propagação do rambutanzeiro (Nephelium lapacceum L.) /

Pita Júnior, José Luiz. January 2010 (has links)
Orientador: Antonio Baldo Geraldo Martins / Banca: Carlos Ruggiero / Banca: Simone Rodrigues da Silva / Resumo: O rambutan é uma frutífera tropical pertencente à família Sapindaceae, com origem no Sudeste Asiático, especialmente Malásia. No Brasil, o cultivo está em expansão e distribuído em diferentes estados e com plantas de origem seminífera, gerando pomares desuniformes e início de produção tardio. Com a propagação vegetativa é possível antecipar a fase produtiva, e também corrigir o problema de plantas masculinas. O presente trabalho teve por objetivo avaliar a enxertia em fenda cheia ao longo do ano e, a influência da aplicação de AIB em três diferentes formas no enraizamento de estacas do rambutan. A enxertia foi conduzida de set/2008 à ago/2010 no ripado de fruticultura da FCAV/Unesp, no município de Jaboticabal/SP, local onde também realizou-se a estaquia em jan/2010. O delineamento foi inteiramente casualizado, com 10 plantas/parcela na enxertia e 10 estacas/parcela na estaquia e 4 repetições em ambos experimentos. Para a enxertia as avaliações foram: porcentagem de pegamento mensal e por época, número e altura das brotações emitidas por enxerto e número de folíolos dos enxertos, e para a estaquia foram: porcentagem de sobrevivência, calejamento, pegamento e número e comprimento médio de raízes. Com os resultados obtidos pode-se concluir que o agosto e novembro são os meses mais adequados para o pegamento da enxertia do rambutan. Agosto é o melhor mês do ano para o desenvolvimento das brotações e folíolos dos enxertos. A melhor época do ano para a realização da enxertia é a primavera. A forma de aplicação de AIB e suas respectivas doses não influenciam nenhuma das variáveis analisadas / Abstract: The rambutan is a tropical fruit belonging to the Sapindaceae family, which originated in Southeast Asia, especially Malaysia. In Brazil, the cultivation is expanding and distributed in different states and with plant material seminiferous generating non uniform orchards and production starting late. With vegetative propagation is possible to anticipate the productive phase, and also fix the problem of male plants. This study aimed to evaluate the cleft grafting during the year, and the influence of IBA application in three different ways on the rooting of the rambutan. The grafting was conducted in Sep/2008 ago/2010 ripped the fruit of FCAV / UNESP in Jaboticabal / SP, which is also where the cutting took place in Jan/2010. The design was completely randomized, with 10 plants per plot of grafting and 10 cuttings per plot in the cutting and 4 replications in both experiments. For grafting were evaluated: successful rate per month and season, number and height of emitted buds per stock and leaflet number of grafts, and the cuttings were: percentage of survival, callus, and fixation number and average length of roots . With these results we can conclude that the August and November are the months most suitable for the fixation of the grafted rambutan. August is the best month of the year for the development of shoots and leaves of the grafts. The best season for grafting is spring. The form of application of IBA and their doses do not influence any of the variables / Mestre
578

Propagation Modeling and LTE Network Performancein Real City Scenarios

Vestberg, Sebastian January 2018 (has links)
Maps of chosen areas in Chicago, San José, London and Shibuya, areimported from Open Street Map into matlab in order to run LTE networksimulations for various scenarios. Firstly, two path loss models arecompared, the empirically based WINNER model and a set of sitespecificmodel. Secondly, low load network simulations are runseparately at two different carrier frequencies, 700MHz and 2GHz, forcity specific base station deployments. Simulation results show thatuser performance is quite unique for each city and that deploymentstrategies and city environments are strongly influencing path gain,SINR and throughput. In general, user performance in UL issignificantly worse at 2GHz than at 700MHz, whereas DL performance isnot as affected by the change in carrier frequency.
579

Propagating Changes between Aligned Process Models

Weidlich, Matthias, Mendling, Jan, Weske, Mathias 28 February 2012 (has links) (PDF)
There is a wide variety of drivers for business process modelling initiatives, reaching from organisational redesign to the development of information systems. Consequently, a common business process is often captured in multiple models that overlap in content due to serving different purposes. Business process management aims at exible adaptation to changing business needs. Hence, changes of business processes occur frequently and have to be incorporated in the respective process models. Once a process model is changed, related process models have to be updated accordingly, despite the fact that those process models may only be loosely coupled. In this article, we introduce an approach that supports change propagation between related process models. Given a change in one process model, we leverage the behavioural abstraction of behavioural profiles for corresponding activities in order to determine a change region in another model. Our approach is able to cope with changes in pairs of models that are not related by hierarchical refinement and show behavioural inconsistencies. We evaluate the applicability of our approach with two real-world process model collections. To this end, we either deduce change operations from different model revisions or rely on synthetic change operations.
580

Etude micromécanique de l’endommagement anisotrope des géomatériaux hétérogènes / Micromechanical study of anisotropic damage for heterogeneous geomaterial

Bikong, Christian 12 December 2016 (has links)
La conception et l’exploitation du stockage des déchets radioactifs en milieu géologique nécessitent absolument que le comportement à long terme de la roche hôte soit caractérisé. Cette caractérisation doit tenir compte de l’hétérogénéité multi-échelle de la roche, qui affecte de façon significative ses propriétés et son comportement sous diverses sollicitations. Parmi les mécanismes de déformation observés expérimentalement la microfissuration joue un rôle important. Nous proposons dans cette thèse une approche micromécanique 3D pour l’endommagement anisotrope de l’argilite du Callovo-oxfordien sous sollicitations mécaniques. L’accent est mis sur l’endommagement différé par propagation subcritique des microfissures. La microstructure complexe du matériau hétérogène est repartie sur plusieurs échelles d’espace. Le comportement macroscopique est construit pour notre approche par homogénéisation non linéaire avec plusieurs étapes de changement d’échelle. Premièrement l’étude de l’endommagement différé est réalisée pour les états des microfissures ouvertes et des microfissures fermées lisses dans la matrice argileuse. Puis nous réalisons une étude complète du comportement mécanique à court terme et à long terme pour le cas des microfissures susceptibles de se propager avec frottement par glissement sur les lèvres des microfissures fermées. Les critères et les lois d’évolutions, pour l’endommagement et pour les déformations anélastiques, sont déterminés dans le cadre de la thermodynamique des processus irréversibles. Après analyse de leurs capacités prédictives, les modèles développés sont validés par comparaisons avec les données expérimentales. / To guarantee the performance and safety of a deep underground reposal for nuclear wastes, the long-term behavior of the rock host must be characterized. Generally the heterogeneity of the rock highly affects his properties. Therefore the long-term analysis of the rock behavior under different coupled loading conditions must be made for a heterogeneous material. From the experimental observations, microcracks growth plays an important role on the rock deformation. The objective of this thesis is to study, in the field of micromechanics, the induced anisotropic damage behavior of the Callovo-oxfordian claystone. We put for this study an emphasis on the delayed induced damage by subcritical crack growth. To take in to account the complex microstructure of the heterogeneous rock, the macroscopic nonlinear mechanic behavior is derived by nonlinear homogenization with multiple steps of separated scales. Firstly a model is built for the delayed anisotropic damage for the case of open microcrack and frictionless microcrack. Then a full study is performed for the instantaneous damage and delayed damage in the case of close microcracks with sliding friction. We take advantage of the frame of thermodynamics of irreversible process, for the writing of criterion and evolution law of the damage variables and the inelastic strain. Following the capacity analysis of all our built-model, a first validation is made by comparison with experimental data.

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