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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.
421

Ανάλυση και αποτίμηση απόδοσης αμιγώς οπτικών δικτύων μεταγωγής ριπών

Πανταζής, Κωνσταντίνος 03 October 2011 (has links)
Σκοπός αυτής της διπλωματικής εργασίας είναι η ανάλυση και αξιολόγηση της απόδοσης των οπτικών δικτύων μεταγωγής ριπών με την μέθοδο της προσέγγισης μειωμένου φορτίου. Η μέθοδος αυτή είναι αρκετά ευέλικτη για να προσαρμοστεί σε ένα οπτικό δίκτυο μεταγωγής οπτικών ριπών το οποίο υιοθετεί 4 διαφορετικά είδη πολιτικών και οι οποίες είναι η JET, η κατάτμηση ριπής, όπως επίσης και δυο πολιτικές προτεραιοτήτων. Η ακρίβεια της μεθόδου επιβεβαιώνεται από την προσομοίωση και τέλος οι διάφορες πολιτικές συγκρίνονται μεταξύ τους. Το πρώτο κεφάλαιο αυτής της εργασίας έχει αφιερωθεί στο να εισάγει τον αναγνώστη σε βασικές έννοιες σχετικά με τις οπτικές ίνες και τα οπτικά δίκτυα από την πρώτη έως την τρίτη γενιά. Αναφέρεται στα τρία είδη οπτικής μεταγωγής που υπάρχουν και ακολούθως γίνεται μια σύγκριση αυτών των τεχνολογιών οπτικής μεταγωγής. Στο δεύτερο κεφάλαιο αυτής της εργασίας, γίνεται μια πιο ενδελεχής ανάλυση των δικτύων δρομολόγησης με οπτικές ριπές και παρουσιάζονται όλοι οι απαραίτητοι μηχανισμοί για την ύπαρξη και άρτια λειτουργία αυτών των δικτύων. Αναλυτικότερα, παρέχονται πληροφορίες για την επίλυση θεμάτων ανταγωνισμού και την σηματοδοσία την συναρμολόγηση των ριπών. Στη συνέχεια, στο τρίτο κεφάλαιο γίνεται η παρουσίαση της μεθόδου προσέγγισης μειωμένου φορτίου για κλασσικά τηλεφωνικά δίκτυα. Σκοπός είναι να αναλυθεί εκτενώς ο τρόπος με τον οποίο μπορεί να χρησιμοποιηθεί η μέθοδος αυτή σε οπτικά δίκτυα μεταγωγής οπτικών ριπών και τι απαραίτητες αλλαγές πρέπει να γίνουν για την κάθε πολιτική που εφαρμόζεται ξεχωριστά. Παράλληλα, για κάθε πολιτική παρέχονται πίνακες με αποτελέσματα όπως και γραφήματα για να γίνουν πιο κατανοητά τα αποτελέσματα της μεθόδου. Έπειτα, παρουσιάζονται τα συμπεράσματα της εργασίας όπως και διάφορες προτάσεις για το πώς μπορεί να αξιοποιηθεί η κάθε πολιτική με τον καλύτερο τρόπο. Τέλος στο τέταρτο κεφάλαιο παρατίθενται οι κώδικες των αναλυτικών μοντέλων για κάθε μια από τις πολιτικές που χρησιμοποιήθηκε σε γλώσσα προγραμματισμού C, έτσι ώστε αν θέλει ο αναγνώστης να έρθει σε επαφή και με το προγραμματιστικό περιβάλλον του δικτύου που υλοποιήθηκε. / The subject of this Diploma Thesis is the analysis and evaluation of the performance of Optical Burst Switching Networks by using the method of reduced load approximation. This method is flexible enough to be adjusted to the type of networks mentioned above which normally adopt four different kinds of policies, like the JET policy, the burst segmentation policy and also two policies of priorities. Thus, the main goal of this project is the confirmation of the accuracy of this method by performing the necessary simulations in order to compare these different policies. The first chapter of the project is dedicated to the task of making the reader familiar with the basic elements of the science of optical fibers and optical networks in general, all the way from the very first generation of them to the third one that is widely used at present. During this chapter, the three types of optical switching networks are described. These types are further examined next, during the second chapter, where a thorough analysis of network routing with optical bursts is performed. In addition, all the necessary mechanisms for the existence and well-functioning of these networks are presented. Specifically, a wide range of information related to the solving of competition issues and signaling for the assembly of the bursts, is given. Then, during the third chapter, the method of reduced load approximation is presented for the classic telephony networks. This method can be used in optical burst switching networks, and different variations of it are used, according to each separate policy that is followed. Result tables accompanied by the appropriate charts are supplied in order to clarify the results of this method. Next, the results of this Diploma Thesis are aggregated and accompanied by proposals about reclaiming each policy the best way. In the last chapter, the programming codes of each analytical model of these four optical networks policies, expressed in the programming language C, are supplied, giving the reader the chance to get in touch with the programming environment that was used in order to derive the optical network that was simulated.
422

Qualidade, desempenho operacional e custos de plantios, manual e mecanizado, de Eucalyptus grandis, implantados com cultivo mínimo do solo / Quality, operational performance and cost of eucalyptus grandis hand and machine planting, implemented with minimal tillage.

Vitor Augusto Graner Fessel 03 July 2003 (has links)
O método de plantio manual de mudas de árvores é predominante no Brasil. Para a redução dos custos com mão-de-obra, aumento de produtividade e qualidade operacional, o plantio manual deve ser substituído total ou parcialmente por operações mecanizadas. Com esse enfoque foram avaliadas as atividades de plantios manual e mecanizado de eucaliptos, bem como de preparo mecanizado do solo, em área pertencente a uma empresa florestal. O plantio manual foi feito por onze trabalhadores rurais, com o uso da transplantadora de acionamento manual. O plantio mecanizado foi realizado por uma máquina de transplantio de mudas, operada por um trabalhador rural e tracionada por um trator. Na área do estudo foram locadas duas parcelas amostrais, formando uma malha de setenta e cinco pontos amostrais para cada sistema de plantio. Os itens do preparo do solo avaliados foram a profundidade do sulco, o diâmetro dos torrões e o volume cilíndrico dos galhos de madeira sobre a faixa de sulcamento. O itens dos sistemas de plantio avaliados foram a presença de defeitos da operação, a distância entre plantas, a altura da parte aérea das mudas e a sobrevivência das plantas após um mês de idade. As ferramentas da qualidade total utilizadas foram os histogramas, o diagrama de causa e efeito, os gráficos de Pareto e de controle. As análises estatísticas dos resultados foram feitas pelo teste t e pelo teste de qui-quadrado Para avaliar o desempenho operacional do sistema manual estimou-se somente a capacidade de campo operacional. No sistema mecanizado foram estimadas as capacidades de campo efetiva e operacional. Nos dois sistemas de plantio foram estimados também os custos horários e operacionais das máquinas e da mão-de-obra. Entre os sistemas de plantio, a distância entre plantas foi diferente estatisticamente, com melhor distribuição das mudas no sistema manual. O número de defeitos por muda plantada foi semelhante estatisticamente entre os sistemas de plantio. Os principais defeitos do sistema manual foram as mudas plantadas com colo encoberto pelo solo e as mudas plantadas fora do centro do sulco, os quais representaram 72,8% do total. No sistema mecanizado, esses defeitos, somados às mudas não plantadas e mudas não firmes, representaram 76,7% do total. A altura da parte aérea foi diferente estatisticamente, tanto no plantio como um mês após. A sobrevivência das mudas efetivamente plantadas, após um mês de idade, foi semelhante estatisticamente. Concluiu-se, assim, que a qualidade em ambos os sistemas de plantio não variaram dentro de padrões aceitáveis pela empresa florestal. O tempo produtivo do sistema de plantio mecanizado foi igual a 48,2%, gerando uma capacidade de campo operacional 60,0% menor do que no sistema manual. Inferiu-se que o número médio de mudas plantadas por trabalhador por hora foi igual a 95 no sistema manual, enquanto que no sistema mecanizado foi igual a 205. O custo operacional estimado do sistema mecanizado foi 44,9% maior do que no sistema manual, fato devido a baixa capacidade de campo operacional observada no sistema mecanizado. / Hand planting of tree seedlings is the predominant method in Brazil. In order to reduce labor costs, increase productivity, and improve operational quality, hand planting should be totally or partially replaced by machine operations. Having this in mind, eucalyptus’ hand and machine planting activities were assessed, as well as those of mechanical tillage, in an area belonging to a forestation company. Hand planting had been carried out by 11 rural workers by using a planting tube. Machine planting had been carried out by using a seedling transplant machine, which was operated by a rural worker and pulled by a tractor. In the study area, two sampling parts were allocated, forming a web with 75 sampling points for each planting system. Tillage items that were assessed included furrow depth, stone diameter, and the cylindrical volume of wood branches on the furrow belt. Planting system items that were assessed included the presence of operation defects, distance between plants, height of the top portion of the seedlings, and plant survival after one month of age. Total quality tools included histograms, cause and effect diagram, control graphs, and Pareto's graphs. Statistical analyses of the results were performed by using test and qui-square test. To evaluate hand planting system’s operational performance, only the operational field capacity was estimated. As for the machine system, effective and operational field capacities were estimated. Labor and machine hourly costs, as well as the operational costs for both planting systems were assessed. When comparing planting systems, the distance between plants was statistically different, with hand planting system showing better seedling distribution. The number of defects per planted seedling was statistically similar for both planting systems. The major defects in the hand planting system were seedlings planted with soil-covered base and those planted out of the furrow center, which represented 72.8% of the total. With the machine system, these defects, in addition to non-planted and loose seedlings, represented 76.7% of the total. The height of the top portion was statistically different, both when planting and after one month. The survival of effectively planted seedlings after one month of age was statistically similar. Thus, we concluded that the quality of both planting systems did not vary within the standards that are acceptable for the forestation company. Machine planting system's productive time was 48.2%, and generated an estimated operational field capacity 60.0% less to that for the hand planting system. The average number of planted seedlings per worker by hour was inferred to be equal to 95 in the hand planting system, whereas it was equal to 205 in the machine system. The operational cost for the machine system was estimated to be 44.9% greater to that for the hand planting system, which is due to the low operational field capacity observed in the machine system.
423

Atenuação de cargas estáticas em modelo reduzido de linha de ancoragem de sistema offshore / Attenuation of statics forces in model reduced of mooring lines of offshore systems

Rocha, Cinthia Cristina Morais January 2014 (has links)
O desenvolvimento de pesquisas relativas ao comportamento das estruturas offshore são de fundamental importância para as atividades de exploração de petróleo a fim de permitir uma análise mais precisa do desempenho do sistema de ancoragem. Neste sentido, o presente trabalho tem como objetivo analisar o comportamento das linhas de ancoragem submetidas a esforços de tração bem como avaliar e quantificar a atenuação das cargas ao longo do trecho enterrado determinando assim as forças que efetivamente chegam à estaca torpedo. Inicialmente foram projetados e construídos os equipamentos, em modelo reduzido, para a realização dos ensaios experimentais de carregamento estático conduzidos na escala de 1:40. As argilas empregadas nos ensaios foram produzidas em laboratório com o objetivo de obter um solo com propriedades físicas similares à da argila típica do leito marinho, a partir da mistura caulim, bentonita e água, sendo definida a composição em massa seca de 85% de caulim, 15% de bentonita e teores de 100% de umidade para a mistura denominada como argila A, e 120% de umidade para a mistura referida como argila B. Após a caracterização geotécnica concluiu-se que a argila B se assemelha às condições de campo. A força que chega ao ponto de ancoragem, equivalente ao que seria o ponto de fixação da amarra ao torpedo, foi medida experimentalmente através de uma célula de carga para duas componentes (vertical e horizontal) instalada no piso do tanque. A catenária invertida formada pela amarra foi registrada em alguns pontos não visíveis através de um sensor por ultrassom. O carregamento da linha de ancoragem foi produzido para diferentes ângulos de incidência, em ciclos de carga e descarga. Os resultados mostram que, mesmo em uma abordagem estática, flutuações de carga na linha de ancoragem não são inteiramente transmitidas ao ponto de ancoragem (torpedo), sendo parcialmente absorvidas ao longo do trecho enterrado da amarra. A atenuação de carga na argila A foi de 24%, enquanto que a atenuação apresentada na argila B variou entre 14 %, 6% e tendendo a 0 nos ensaios realizados respectivamente nas alturas de solo de 72 cm, 48 cm e 24 cm. Verificou-se também que a qualidade dos critérios de similaridade inicialmente adotados foi satisfatória. / The research development on the behavior of offshore structures is fundamentaly important for the exploration of oil in order to allow a more precise analysis of the performance of offshore mooring systems. In this sense, the present work aims to analyze the behavior of embedded mooring lines subjected to tensile stresses and to evaluate and quantify the attenuation of loads along the stretch buried thus determining the forces that effectively reach the torpedo pile. Initially, the equipment were designed and built, in a reduced model, so the experimental tests of conducted static load on the scale of 1:40 could be conducted. The clays used in the tests were produced in the laboratory in order to obtain a soil with similar physical properties to the typical clay seabed, from mixing kaolin, bentonite and water, the composition being set on dry matter of 85% kaolin 15% bentonite content and 100% humidity for mixing clay called as A, and 120% humidity for mixing said clay as B. After geotechnical characterization, it was found that the clay B is similar to field conditions. The force that reaches the anchor point, equivalent to what would be the point of attachment of mooring the torpedo, was experimentally measured by a load cell for two components (vertical and horizontal) installed on the floor of the tank. The reverse catenary formed by the embedded mooring line was recorded in some not visible spots through an ultrasound sensor. The load of the anchor line has been produced for different incidence angles, in loading and unloading cycles. The results show that, even in a static approach, load fluctuations in the anchor line are not fully transmitted to the anchor point (torpedo). Partially absorbed along the stretch of mooring buried. The attenuation of the load on the clay A was 24%, while the attenuation shown in clay B ranged from 14%, 6% and approaches 0 in the tests performed respectively on the ground heights of 72 cm, 48 cm and 24 cm. It was also found that the quality of similarity criteria adopted initially was satisfactory.
424

Teoretický popis kolektivních excitací jader / Theoretical description of nuclear collective excitations

Repko, Anton January 2016 (has links)
Density functional theory is a preferred microscopic method for calculation of nuclear properties over the whole nuclear chart. Besides ground-state properties, which are calculated by Hartree-Fock theory, nuclear excitations can be described by means of Random Phase Approximation (RPA). The main objective of the present work is to give the RPA formalism for spherically symmetric nuclei, using the techniques of angular-momentum coupling. Various auxiliary topics, such as Hartree-Fock theory, Coulomb integral, center-of-mass corrections and pairing, are treated as well. RPA method is derived also for axially deformed nuclei. The derived formulae are then implemented in the computer code and utilized for calculation of some physical results. After thorough investigation of the precision aspects of the calculation, the following topics are treated as examples: toroidal nature of the low-energy (pygmy) part of the E1 resonance, giant resonances of various multipolarities in deformed nucleus 154Sm, and magnetic dipole (M1) transitions in deformed 50Cr. Powered by TCPDF (www.tcpdf.org)
425

Selfish, mobile genes in honeybee gut bacteria

Põlajev, Aleksei January 2018 (has links)
Transposons are selfish, mobile genetic elements, moving within the genome. The transposase genemakes this possible, as it codes for the enzyme that catalyzes the movement. In the case of bacteria,they can also move horizontally between individual bacteria, and sometimes even between species.By default, they are a burden for the host organism, coding for a protein that the host does not need.They also pose the risk of disabling the host’s crucial genes by inserting themselves into it.Transposons are under some pressure to benefit the host, to help propagate themselves moreeffectively. And some transposons have indeed evolved to benefit the host. Lactobacillus kunkeei is a bacterial species known to reside in honeybee guts. It is known for itsrole in honey preservation and wine spoilage. The genome of L. kunkeei is reduced because it is asymbiont, however it contains an unusually high amount of transposons in its genome. In this study, the transposase genes (transposon enzymes) found in L. kunkeei are studied andcategorized. The L. kunkeei have been extracted from honeybees (Apis mellifera). The honeybeesthemselves have been collected from the islands Åland and Gotland. This study focuses on the transposase genes that come in pairs, one after another in the genome.Transposase genes were identified using annotation software and orthology-based methods. Theannotation software provides numbering for the genes, which allows finding paired genes. Thepaired genes were categorized based on alignments and phylogenetic software. Pseudogenizedtransposons were identified based on length and/or clustering into triplets. A total of 766 paired transposase genes were found. The transposase genes were found to take up1.9% of the genome, on average. A low level of diversity has been found when performingalignments and generating phylogenetic trees. The positions of the transposase genes are generallyconserved within phylogenetic groups. Pseudogenization has been detected for some transposasegenes – 4.5 per genome, on average. All of the studied transposons belong to the IS3 family, whichis a family of Class I transposons.
426

Optimisation robuste et application à la reconstruction du réseau artériel humain / Robust optimization and application to the reconstruction of the human arterial system

El Bouti, Tamara 02 July 2015 (has links)
Les maladies cardiovasculaires représentent actuellement une des premières causes de mortalité dans les pays développés liées à l’augmentation constante des facteurs de risques dans les populations. Différentes études cliniques ont montré que la rigidité artérielle était un facteur prédictif important pour ces maladies.Malheureusement, il s’avère difficile d’accéder expérimentalement à la valeur de ce paramètre. On propose une approche qui permet de déterminer numériquement la rigidité artérielle d’un réseau d’artères à partir d’un modèle monodimensionnel personnalisé de la variation temporelle de la section et du débit sanguin des artères. L’approche proposée résout le problème inverse associé au modèle réduit pour déterminer la rigidité de chaque artère, à l’aide de mesures non invasives de type IRM, echotracking ettonométrie d’aplanation.Pour déterminer la robustesse du modèle construit vis à vis de ses paramètres, une quantification d’incertitude a été effectuée pour mesurer la contribution de ceux-ci, soit seuls soit par interaction, à la variation de la sortie du modèle, ici la pression pulsée. Cette étude a montré que la pression pulsée numérique est un indicateur numérique robuste pouvant aider au diagnostic de l’hypertension artérielle.Nous pouvons ainsi offrir au praticien un outil numérique robuste et peu coûteux permettant un diagnostic précoce et fiable des risques cardiovasculaires pour tout patient simplement à partir d’un examen non invasif / Cardiovascular diseases are currently the leading cause of mortality in developed countries, due to the constant increase in risk factors in the population. Several prospective and retrospective studies have shown that arterial stiffness is an important predictor factor of these diseases. Unfortunately, these parameters are difficult to measure experimentally. We propose a numerical approach to determine the arterial stiffness of an arterial network using a patient specificone-dimensional model of the temporal variation of the section and blood flow of the arteries. The proposed approach estimates the optimal parameters of the reduced model, including the arterial stiffness, using non-invasive measurements such MRI, echotracking and tonometry aplanation. Different optimization results applied on experimental cases will be presented. In order to determine the robustness of the model towards its parameters, an uncertainty analysis hasbeen also carried out to measure the contribution of the model input parameters, alone or by interaction with other inputs, to the variation of model output, here the arterial pulse pressure. This study has shown that the numerical pulse pressure is a reliable indicator that can help to diagnose arterial hypertension.We can then provide the practitioner a robust patient-specific tool allowing an early and reliable diagnosis of cardiovascular diseases based on a non-invasive exam
427

Limitações do critério de vazão ecológica do estado do Tocantins : o caso das PCHs Agrotrafo e Palmeiras

Brito, Rubens Pereira January 2010 (has links)
A pressão exercida sobre os recursos hídricos nas ultimas décadas, principalmente por setores como irrigação, abastecimento público, indústria e geração de energia tem sido um dos principais fatores para ampliar as bases de discussão sobre a importância da manutenção de uma parcela de água nos rios para garantir a sua integridade ecológica. Vazão ecológica foi o termo utilizado neste trabalho para definir a parcela a ser mantida nos cursos d’água, para esse fim. Dessa forma, este trabalho tem como objetivo avaliar as limitações do critério de vazão ecológica do Estado do Tocantins, tendo como estudo de caso as Pequenas Centrais Hidrelétricas - PCHs Agrotrafo e Palmeiras na bacia hidrográfica do rio Palmeiras-TO, a qual reúne condições adequadas para o escopo do trabalho, além de ser o único dos sete aproveitamentos hidrelétricos do rio Palmeiras a gerar energia a partir de um Trecho de Vazão Reduzida – TVR, é atualmente a bacia com maior vocação para a geração de energia no Estado. Para alcançar o objetivo proposto para o trabalho, a metodologia foi dividida em três etapas: a) levantamento das características das PCHs Agrotrafo e Palmeiras, b) levantamento da caracterização e limites de uso e manutenção de água na bacia, c) disponibilidade de informações hidrológicas a serem utilizadas. A partir da aplicação da metodologia foi possível identificar quatro categorias de limitações: i) limitações de ordem hidrológica, neste caso como a vazão de referência para outorga é um valor fixo com base na Q90, em determinadas épocas do ano, inclusive em período de cheia, a vazão natural é menor que a Q90; ii) limitações de ordem econômica, que indicam que caso o órgão outorgante estadual resolva seguir com rigor o que estabelece o critério de vazão ecológica, onde cada usuário tem direito de captar 25% de 75% da Q90 haveria uma drástica redução da energia a ser gerada em Agrotrafo e Palmeiras, podendo tornar o aproveitamento inviável economicamente; iii) limitações de ordem ambiental, considerando que a vazão ecológica com base em um valor fixo não leva em consideração aspectos da sazonalidade do regime de vazões, podendo haver um intenso desequilíbrio, principalmente no TVR, afetando hábitos alimentares e de migração espécies de peixes e organismos aquáticos, bem como comunidades ribeirinhas, aspectos paisagísticos e prática de esportes de corredeiras; e, iv) limitações de ordem legal ao não estabelecer uma solução operacional viável quando há disputa entre usuários, principalmente quanto à ordem de prioridade dos usos. / The pressure on the water resources in the last decades, mainly by sectors as irrigation, utility, industry and energy generation have been one of the main factors to enlarge the basis for discussion about the importance of maintaining a portion of water in rivers to ensure its ecological integrity. Ecological flow was the term used in this work to define that portion to be maintained in watercourses. That way, this work is aiming to evaluate the criteria limitations for ecological flow in Tocantins, taking as a case study on the Small Hydroelectric Centrals – “Agrotrafo” and “Palmeiras” in Palmeiras – TO river watershed, which meets appropriate conditions for the work scope, besides being the only one of seven hydropower recoveries in Palmeiras river, to generate energy from a reduced flow section – RFS, and nowadays it`s the watershed with greater vocation for energy generation in Tocantins. To achieve the proposed goal for the work, the methodology was divided into three stages: a) characteristics survey of SHC – “Agrotrafo” and “Palmeiras”; b) characterization survey, use limits and water maintenance in the watershed; c) availability of hydrologic information to be used. From the methodology application was possible to identify four limitations categories: i) hydrologic limitations, in this case as the flow reference for the grant is a fixed value based on “Q90”, at certain times of the year, including in flood times, the natural flow is less than “Q90”; ii) Economic limitations, indicating that if the state licensing agency decides to follow rigorously what establishes the criteria for ecological flow, where each user is entitled to capture 25% of 75% from “Q90” would be a drastic energy reduction to be generated in “Agrotrafo” and “Palmeiras”, can make use uneconomical; iii) Environmental limitations, considering that the ecological flow based on a fixed value does not consider flow regime seasonality, there may be an intense imbalance especially in RFS, affecting feeding habits and migration, fish species and aquatic organisms, as well as riparian communities, landscapes features and river sports; and iv) legal limitations by failing to establish a viable operational solution when there is contention among users, especially regarding the order of uses priority.
428

Análise elasto-plástica com não linearidade geométrica usando uma formulação Arbitrária Lagrangeana-Euleriana (ALE) / Elastoplastic analysis with geometric nonlinearity using an arbitrary lagrangian-eulerian (ALE) method

Lohse, Hermann Rigoberto Segovia January 2015 (has links)
Apresenta-se uma formulação de adaptação de malha para problemas com grandes deformações. A formulação Arbitrária Lagrangeana-Euleraina (ALE) permite manter a qualidade dos elementos finitos durante o processo de cálculo através de rearranjo ou movimento de malha independente do movimento material. Nas formulações Lagrangeanas a malha fica “colada” ao corpo durante toda a análise, logo quando este sofre grandes deformações diferenciais o mesmo se reproduz numa malha distorcida. A formulação ALE desacoplada consta de dois passos: O passo Lagrangeano onde são aplicados os incrementos de carga, a malha permanece “colada” à matéria durante a análise. E cada certo “tempo” o passo Euleriano onde “descola-se” a malha da matéria e efetua-se o movimento de malha que se ajusta melhor ao corpo deformado. São apresentados assim métodos de realocação da malha e transferência ou atualização das variáveis necessárias para, depois do passo Euleriano, continuar a análise com a nova malha sem grandes distorções dos elementos. Os problemas de grandes deformações e deslocamentos são acompanhados de não linearidades físicas e geométricas, assim, são abordados os métodos para o tratamento destas não linearidades. Trabalha-se com o elemento hexaédrico tri-linear com integração reduzida e controle dos modos espúrios que tem demostrado um bom comportamento frente a grandes não linearidades geométricas assim como para as não linearidades físicas. A formulação ALE tem ganhando seu espaço na mecânica dos sólidos, em problemas de conformação mecânica e impacto, devido às grandes deformações e na última década está abrindo-se passo na área da geomecânica tratando problemas recalque e penetração de fundações em solos. / This work presents remeshing techniques for finite element simulation and investigates their performance for large deformation problems. Lagrangian formulation generally results in excessive mesh distortion owing to its attachment to the material. Meanwhile, the Lagrangian- Eulerian (ALE) formulation alouds to keep the finite element quality through the arbitrarily rearrangement or movement of the mesh, to optimize the element’s shape. The decoupled Arbitrary Lagrangian-Eulerian approach consists in a sequence of Lagrangian and Eulerian steps. The mesh is “coupled” to the material during the Lagrangian steps. From step to step, mesh is decoupled from the system material (Eulerian step), the nodes corresponding to free boundaries are relocated using an analytical approach, remeshing is performed and finally the state variables are remapped. Rearrangements methods for the element’s node are presented, as well as the variables remapping algorithms at the new quadrature points, in order to continue with the finite element analysis without altering the element topology of the original mesh. Special attention is given to methods dealing with geometric and physical nonlinearities. A trilinear hexahedral element is used with reduced integration and hourglass control. This combination has shown well behavior in front of large geometric and physical nonlinearities. ALE formulation field has considerably grown in geotechnical research, especially in impact and mechanical extrusion problems. Over the last decade, geomechanic is dealing with settlement problems and foundation penetration in soils.
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Modélisation de liaisons flexibles amortissantes en élastomères pour la prédiction du comportement dynamique de systèmes complexes / Flexible and dissipative rubber mounts modelisation for the prediction of complex systems dynamic behavior

Morin, Benjamin 03 November 2016 (has links)
Dans le cadre de l’amortissement passif de structure, les élastomères sont employés dans les industries du transport sous la forme de liaisons amortissantes. Ces matériaux ont un comportement dépendant de la fréquence, de la température et de l’amplitude d’excitation. Les modèles numériques associés peuvent être coûteux en temps de calcul, notamment en phase d’optimisation. Le but de cette thèse est de proposer un modèle réduit efficace de ces liaisons amortissantes, qui prenne en compte la dissipation viscoélastique et les précharges non-linéaires dans les liaisons. La première partie de ce mémoire se concentre sur la représentation de la dissipation par le modèle réduit. Une loi de comportement viscoélastique, basée sur un modèle rhéologique identifié expérimentalement, est utilisée avec la méthode des éléments finis pour obtenir un modèle numérique des liaisons amortissantes. Un premier modèle réduit prédictif, prenant en compte la dissipation en est dérivé en utilisant une extension originale des méthodes de sous-structuration. La deuxième partie traite de l’influence des précharges statiques non-linéaires sur le comportement dynamique et la dissipation dans les liaisons. Pour cela, une loi de comportement hyper-visco-élastique linéarisée autour d’un état précontraint statique non-linéaire est développée. Les méthodes de sous-structuration introduites dans la première partie sont alors enrichies afin de tenir compte de la dissipation et les non-linéarités géométriques dans les liaisons. Finalement, ces modèles réduits à 2 nœuds permettent des gains en temps de calcul d’un facteur 50 à 100 et sont facilement utilisables par l’ingénieur en phase de conception. / In the context of passive damping, various mechanical systems from the space, aeronautic or auto-mobile industry use elastomer components (shock absorbers, silent blocks, flexible joints...).These materials have frequency, temperature and amplitude dependentcharacteristics. The associated numerical models may become computationally too expensive during an optimization process.The aim of this work is to propose an efficient reduced model of rubber devices that account for the viscoelastic damping and the non-linear pre-stress in the dampers.The first part of this thesis is about how to include the viscoelasticdamping in the reduced model. It starts by using a viscoelastic constitutive relation, based on experimental identification, within the frame of the finite element method to obtain a numerical model of the rubber dampers. A first efficient reduced model is then derived from this FE model by using an original extension of sub-structuring methods in the case of viscoelastic damping.In the second part, the influence of non-linear static pre-stress overthe dynamic behavior and the dissipation in the dampers is studied. An hyper-visco-elastic constitutive relation, linearized in the neighbourhood of a pre-stressed state, is developed. The sub-structuring methods presented in the first part are then upgraded to account for the damping and the geometrical non-linearities in the dampers. Finally, these 2-node reduced models give access to greatly reduced computation times (50 to 100 times faster) and are easy to use for the engineer.
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Aktiv anpassning till förändrade villkor : Fem kvinnors erfarenheter av kroniskt nedsatt funktionsförmåga och återskapande av ett meningsfullt liv

Prack, Berit January 2017 (has links)
Studiens övergripande syfte var att utveckla kunskap om kvinnors erfarenheter av att i vuxen ålder drabbas av och leva med kroniskt nedsatt fysisk funktionsförmåga. Utöver studiens beskrivande och kunskapsgenererande syfte och frågeställningar hade denna även en ambition att bidra till utvecklingen av forskningsområdet ”hälsa och livsstil”. Studien baserades på aktiva intervjuer med fem kvinnor som i vuxen ålder drabbats av nedsatt funktionsförmåga, på grund av kronisk sjukdom eller skada. Analysen skedde i flera steg som successivt gav en breddad och fördjupad förståelse av kvinnornas berättelser. I ett första steg genomfördes en tematisk analys av innehållet i kvinnornas berättelser. Den tematiska analysen sammanfattades av hur kvinnorna själva genom olika retoriska stilgrepp betonade särskilt viktiga delar av sina berättelser. Det andra steget av analysen belyste berättelserna utifrån tidigare forskning och den symboliska interaktionismens perspektiv. Att studiens resultat relaterades till tidigare forskning och ett teoretiskt sammanhang ökade dess överförbarhet ytterligare. Studiens resultat låg i linje med tidigare forskning, det bekräftade bl.a. tidens betydelse under omställningen till ett liv med nedsatt funktionsförmåga, där kontrollen över livet återskapades genom planering av tillvaron så att krafterna räckte till det som upplevdes som mest angeläget, eller genom att krympa tiden till ett här och nu, och ta en dag i sänder och avskärma sig från osäkerheten inför framtiden. Det fanns även fynd som gick utöver vad tidigare forskning rapporterat. De kvinnor som ingick i studien rekonstruerade ur tidigare erfarenheter en ny identitet, med en livsstil i balans mellan omgivningen och den faktiska funktionsförmågan. Förhållanden som bidrog till en hälsosam livsstil var organiseringen i stödjande nätverk, och engagemang i ideella organisationer i vilka kvinnorna kunde uppleva den medkänsla som de stundtals sade sig sakna i mötet med vårdgivare och myndigheter. De kvinnor som medverkade i studien framstod som mer aktiva och kreativa än som var vanligt bland kvinnor med nedsatt funktionsförmåga i tidigare studier. Kvinnorna i studien berättade hur de tog initiativ till, planerade och genomförde längre livsprojekt, som satsningar på studier och eget företagande, vilket inte rapporterats vara vanligt i tidigare studier. Några kvinnor visade sin självständighet genom att inte villkorslöst acceptera vårdapparatens och myndigheternas beslut, utan motsatte sig sådant som motverkade deras strävan att förverkliga personliga mål. Kvinnorna stärkte självkänslan och utvecklade alternativa livsstilar och identiteter genom att ta vara på tidigare erfarenheter och ur dem konstruera nya livsstilar, präglade av relativ hälsa och välmående. Det skedde t.ex. genom att utveckla ett idrottsintresse i gemenskap med andra inom handikappidrotten, eller genom att vårda ett fräscht och ungdomligt utseende och bekräftas genom att medverka som modell vid modevisningar. Studiens resultat har betydelse för att stärka unga kvinnor, som drabbats av nedsatt funktionsförmåga i vuxenålder, men även för yrkesverksamma som möter kvinnor i samma situation och deras anhöriga. / The overall objective of the study is to develop an understanding oft he women’s experiences of suffering from and living with chronically reduced physical ability in adulthood. In addition to the study’s descriptive and knowledge-building objective, it also aims at helping towards developing research in the field of “health and lifestyle”. The study is based on active interviews with five women who have suffered from reduced physical abilities in adulthood, due to chronic disease or injury. The analyses were conducted over two stages that gradually provided a more in-depth understanding of the women’s stories. The first stage was to thematically analyse the content of the women’s stories. The thematic analyses was summarised by how the women personally, through various methods, emphasised specifically important parts of their stories. The second stage of the analyses used previous research and symbolic interaction perspectives. The study’s compatibility increased via the results of previous research and theoretical context. The results of the study were compatible with previous research, confirming such things as the significance of time while adapting to a life of reduced physical ability, where control over one’s life was restored either through planning day-to-day life, giving the individual enough energy for the essentials in life, or by compressing time to the here and now, taking one day at a time and shying away from the uncertainties of the future. There were also findings that exceeded what previous research had reported on. The women who took part in the study mapped out their social rights, and reconstructed an identity from previous experiences, with a lifestyle in balance between the world around them and their own expectations of their reduced physical abilities. Circumstances that contributed to a healthy lifestyle were women’s organising in social network and engaging in non-profit organisations, were they could experience the compassion that they sometimes felt was lacking when interacting with caregivers or governmental authorities. The women that took part in the study appeared more active and creative than was usual among women with reduced physical abilities from other studies. The women in the study explained how they took the initiative, planned and carried out extensive life projects, like study initiatives and starting businesses, which was not as common in previous studies. Some women displayed their independence by not unconditionally accepting healthcare and government authorities’ decisions, but opposed such things that were counter intuitive to their desire to realise personal objectives. The women bolstered their selfesteem and developed alternative lifestyles and identities by using previous experience, from which they could form new lifestyles, characterised by relative good health and wellbeing. This happened either by developing an interest for team sports with other athletes with disabilities, or by maintaining a fresh and youthful appearance, confirmed by modelling for a fashion show. The results of the study are important for strengthening women with impaired functional ability in adulthood, but also for professionals who meet women in the same situation and their relatives.

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