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The Global ETD Search service is a free service for researchers
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Showing 101 to 110 of 111 (0.025 seconds)Spelling suggestions: "subject:"[een] DISPLACEMENTS"" "subject:"[enn] DISPLACEMENTS""
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A method for correcting a moving heat source in analyses with coarse temporal discretizationPartzsch, Marian, Beitelschmidt, Michael, Khonsari, Michael M. 04 November 2019 (has links)
The numerical simulation of a moving heat source from a fixed point observer is often done by discretely adjusting its position over the steps of a thermal transient analysis. The efficiency of these simulations is increased when using a coarse temporal discretization whilst maintaining the quality of results. One systematic error source is the rare update of a nonconstant moving heat source with regard to its magnitude and location. In this work, we present an analysis of the error and propose a correction approach based on conserving the specified heat from a continuous motion in analyses with large time-step sizes. Deficiencies associated with the correction in special motion situations are identified by means of performance studies and the approach is extended accordingly. The advantages of applying the proposed correction are demonstrated through examples.
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[pt] MODELAGEM NUMÉRICA DE PROBLEMAS GEOTÉCNICOS DE GRANDES DEFORMAÇÕES MEDIANTE O MÉTODO DO PONTO MATERIAL / [en] NUMERICAL MODELING OF GEOTECHNICAL PROBLEMS OF LARGE DEFORMATIONS USING THE MATERIAL POINT METHODFABRICIO FERNANDEZ 18 May 2021 (has links)
[pt] Os problemas geotécnicos e geológicos envolvem a descrição do comportamento de materiais tais como solo e rocha e sua eventual interação com fluidos e estruturas. Em geral, a evolução desses problemas é caracterizada por grandes deformações e deslocamentos, descontinuidades, heterogeneidades e um comportamento constitutivo complexo. A abordagem deste tipo de problemas requer técnicas numéricas que levem em conta essas características, sem apresentar inconvenientes numéricos associados à distorção
dos elementos como acontece no método dos elementos finitos (FEM). A presente tese desenvolve um algoritmo computacional baseado no método do ponto material (MPM) para aproximar a solução das equações governantes dos fenômenos mencionados. O algoritmo é baseado numa formulação
dinâmica tridimensional do contínuo, considerando grandes deformações. Os amortecimentos de Rayleigh o local não viscoso são incorporados para modelar problemas dinâmicos e quase-estáticos. A geração dinâmica das poro-pressões é formulada assumindo o meio poroso saturado e um ponto material para discretizar a mistura. Diversas técnicas de suavização das pressões são avaliadas em problemas de impacto sobre meios saturados. Diferentes modelos constitutivos são implementados para modelar tanto a
formação da superfície de ruptura e o processo de escoamento da massa de solo durante as instabilidades, quanto a gênese, evolução e quantificação de zona de falhas nos processos geológicos. Para a abordagem da discretização de problemas de escala geológica de grande número de partículas usando o MPM, uma metodologia é proposta e verificada com a discretização do deslizamento do Daguangbao, na China. Visando à diminuição do tempo computacional, o algoritmo é implementado segundo o paradigma de programação paralela. / [en] Geotechnical and geological problems involve the description of the
behavior of materials such as soil and rock, and their eventual interaction
with fluids and structures. In general, the evolution of these problems is characterized by large deformations and displacements, discontinuities, heterogeneities and complex constitutive behavior. Addressing these problems requires numerical techniques that take these characteristics into account,
without numerical drawbacks associated with element distortion as occurs in the finite element method (FEM). In this thesis is developed a computational algorithm based on the material point method (MPM) to approximate the solution of the governing equations to the mentioned phenomena. The algorithm is based on a three-dimensional dynamic formulation of the continuum considering large deformations. Rayleigh damping and non-viscous local damping are incorporated to model dynamic and quasi-static problems.
The dynamic generation of pore pressures is formulated assuming the saturated porous medium and a single material point to discretize the mixture. Different techniques are evaluated to mitigate spurious pressure in impact problems on saturated media. Different constitutive models are implemented
to model the failure surface and the soil mass flow process during slope instabilities, as well as the genesis, evolution and failure zone quantification in geological processes. To address the discretization of large-scale
geological problems using MPM, a methodology is proposed and validated with the discretization of the Daguangbao landslide, in China. In order to decrease the computational time, the algorithm is implemented according to the parallel programming paradigm.
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Structural Investigations of the Italian Trap Allochthon, Redington Pass, Pima County, ArizonaBenson, Gregory Scott January 1981 (has links)
Italian Trap Allochthon is a rare upper-plate exposure of Paleozoic metasedimentary and Precambrian to Tertiary crystalline tectonites in the Santa Catalina-Rincon metamorphic core complex. Elsewhere in the complex, metasedimentary tectonite is usually restricted to an autochthononous position. The internal structures of the allochthon consist of numerous low-angle faults, tear faults, and overturned asymmetric and upright folds. Close association of the low-angle faults and asymmetric folds, and vergence of the folds, indicates that these folds were formed during westward transport along the low-angle faults. The structures of the allochthon are truncated and rotated to the northeast by a listric (?) normal fault. The probable shape of the fault surface, together with the northeastward rotation of the internal structures, suggests translation of the allochthon from the northeast to the southwest. The fact that metasedimentary tectonites are found in upper- plate position indicates that the listric (?) normal faulting post-dates the metamorphism of the Paleozoic and Mesozoic strata. Metamorphism in turn was part of the development of the Santa Catalina-Rincon metamorphic core complex. It is inferred that the Italian Trap Allochthon was emplaced in the final stages of profound regional extension which prevailed during the mid-Tertiary in southern Arizona.
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Géante éolienne offshore (GEOF) : analyse dynamique des pales flexibles en grandes transformations / Large scale offshore wind turbines (GEOF) : dynamic analysis of flexible blades undergoing large displacements and large rotationsBoujelben, Abir 15 November 2018 (has links)
L’objectif de ce travail porte sur le développement d’un modèle d’interaction fluide-structure adapté à la dynamique des éoliennes de grandes tailles avec des pales flexibles qui se déforment de manière significative sous l’effet de la pression exercée par le vent. Le modèle développé est basé sur une approche efficace d’IFS partitionnée pour un fluide incompressible et non visqueux en interaction avec une structure flexible soumise a des grandes transformations. Il permet de fournir une meilleure estimation de la charge aérodynamique et de la réponse dynamique associée du système (pales, mat, attachements, câbles) avec un temps de calcul raisonnable et pour des simulations sur des longues périodes. Pour la modélisation structurale, un élément fini de type solide 3D est développé pour l’étude dynamique des pales d’éolienne soumises à des grands déplacements et des grandes rotations. Une amélioration du comportement en flexion est proposée par l’introduction des degrés de liberté en rotation et l’enrichissement du champ de déplacements afin de décrire plus précisément la flexibilité des pales. Cet élément solide est apte de capter des modes de hautes fréquences qui peuvent s’avérer néfastes pour la stabilité du calcul. Deux techniques sont donc proposées pour les contrôler : la régularisation de la matrice masse et le développement des schémas d’intégration robustes de conservation et de dissipation d’énergie. Les chargements aérodynamiques sont modélisés en utilisant la Panel Method. Il s’agit d’une méthode aux frontières, relativement rapide par rapport à la CFD mais suffisamment précise pour calculer la distribution de la pression exercée sur la pale. Les modèles fluide et structure interagissent via un algorithme de couplage partitionné itératif dans lequel des considérations particulières sont prises en compte dans le contexte des grandes transformations. Dans un effort visant à instaurer un indicateur de fatigue dans la méthodologie proposée, des câbles précontraints sont introduits reliant le mat de l’éolienne au support. Une nouvelle formulation complémentaire en termes de contraintes est ainsi développée pour l’analyse dynamique des câbles 3D en comportement élasto-visco-plastique. Chaque méthode proposée a été d’abord validée sur des cas tests pertinents. Par la suite, des simulations numériques d’éoliennes avec des pales flexibles sont effectuées en vue d’affiner la compréhension de leur comportement dynamique et l’intérêt que la flexibilité des pales peut apporter à leur fonctionnement. / In this work, a numerical model of fluid-structure interaction is developed for dynamic analysis of giant wind turbines with flexible blades that can deflect significantly under wind loading. The model is based on an efficient partitioned FSI approach for incompressible and inviscid flow interacting with a flexible structure undergoing large transformations. It seeks to provide the best estimate of true design aerodynamic load and the associated dynamic response of such system (blades, tower, attachments, cables). To model the structure, we developed a 3D solid element to analyze geometrically nonlinear statics and dynamics of wind turbine blades undergoing large displacements and rotations. The 3D solid bending behavior is improved by introducing rotational degrees of freedom and enriching the approximation of displacement field in order to describe the flexibility of the blades more accurately. This solid iscapable of representing high frequencies modes which should be taken under control. Thus, we proposed a regularized form of the mass matrix and robust time-stepping schemes based on energy conservation and dissipation. Aerodynamic loads are modeled by using the 3D Vortex Panel Method. Such boundary method is relatively fast to calculate pressure distribution compared to CFD and provides enough precision. The aerodynamic and structural parts interact with each other via a partitioned coupling scheme with iterative procedure where special considerations are taken into account for large overall motion. In an effort to introduce a fatigue indicator within the proposed framework, pre-stressed cables are added to the wind turbine, connecting the tower to the support and providing more stability. Therefore, a novel complementary force-based finite element formulation is constructed for dynamic analysis of elasto-viscoplastic cables. Each of theproposed methods is first validated with differents estexamples.Then,several numerical simulations of full-scale wind turbines are performed in order to better understand its dynamic behavior and to eventually optimize its operation.
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Towards detection of user-intended tendon motion with pulsed-wave Doppler ultrasound for assistive hand exoskeleton applicationsStegman, Kelly J. 31 August 2009 (has links)
Current bio-robotic assistive devices have developed into intelligent and dexterous machines. However, the sophistication of these wearable devices still remains limited by the inherent difficulty in controlling them by sensing user-intention. Even the most commonly used sensing method, which detects the electrical activity of skeletal muscles, offer limited information for multi-function control. An alternative bio-sensing strategy is needed to allow for the assistive device to bear more complex functionalities. In this thesis, a different sensing approach is introduced using Pulsed-Wave Doppler ultrasound in order to non-invasively detect small tendon displacements in the hand. The returning Doppler shifted signals from the moving tendon are obtained with a new processing technique. This processing technique involves a unique way to acquire raw data access from a commercial clinical ultrasound machine and to process the signal with Fourier analysis in order to determine the tendon displacements. The feasibility of the proposed sensing method and processing technique is tested with three experiments involving a moving string, a moving biological beef tendon and a moving human hand tendon. Although the proposed signal processing technique will be useful in many clinical applications involving displacement monitoring of biological tendons, its uses are demonstrated in this thesis for ultrasound-based user intention analysis for the ultimate goal of controlling assistive exoskeletal robotic hands.
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Comment le phénomène du déplacement environnemental est-il perçu par les pays industrialisés ? Observations empiriques en Italie à partir des glissements de terrain à Sarno et à Cerzeto / How is the phenomenon of the environmental movement perceived by industrialized countries? Empirical observations in Italy from landslides in Sarno and CerzetoGuadagno, Eleonora 20 June 2014 (has links)
Cette recherche interroge la perception du phénomène des déplacés environnementaux dans les pays industrialisés à partir de l'observation de deux catastrophes en Italie. L'analyse de la gestion environnementale et de la vulnérabilité dans le contexte italien, ainsi qu'une étude qualitative sur la couverture médiatique, les discours politiques et le vécu des déplacements environnementaux causés par deux coulées de boue à Sarno (en 1998) et à Cerzeto (en 2005), ont révélé les limites de l'usage de ce concept. De plus, cette recherche a montré que ces déplacements se produisent également dans des pays industrialisés, contrairement aux débats théoriques, aux discours politiques et aux représentations médiatiques actuels, qui se focalisent sur les contextes géographiques spécifiques des pays en développement. Les raisons expliquant les différences dans les discours sur ce même phénomène sont ici enquêtées, avec des instruments propres à la géographie et à la science politique. Les resultats de l'analyse révèlent un dessein politique qui vise à instrumentaliser le débat dans le but de renforcer le déséquilibre des pouvoirs politiques dans les pays industrialisés et entre ces derniers et les pays en développement. / This research investigates how the environmentally induced displacement phenomenon is perceived in the Global North on the basis of the evidence gathered in in two Italian catatsrophes. An analysis on the environmental resources management and the vulnerability in Italy has been associated with a study over media coverage, political discourses and personal experiences about environmentally induced displacements following the two landslides in Sarno (1998) and Cerzeto (2005), highlighting the limits of the use of this concept. Moreover, this research illustrated how, contrarily to the current debate, the phenomenon is likely to occur both in the Global North and Global South contexts. The theoretical, political and media discourses and representations seem to be, in fact, mostly focused on specific geographical areas of the Global South. The motivations behind these different descriptions and narratives on the same concept are investigated, through geographical and political science tools. The findings of this research reveal a political agenda exploiting the debate to reinforce the power unbalance within the Global North and between the Global North and the Global South. / La presente ricerca analizza la percezione del fenomeno dei profughi ambientali nel Paesi del Nord a partire dall'osservazione di due casi italiani. L'analisi della gestione ambientale e della vulnerabilità in Italia, associata ad uno studio qualitativo sul trattamento mediatico, i discorsi politici e l'esperienza personale inerente al fenomeno dei profughi ambientali causati dalle frane di Sarno (1998) e Cerzeto (2005), ha messo in evidenza i limiti della definizione di questo concetto. Inoltre, lo studio dimostra in che modo il fenomeno si produca anche nel Nord del Mondo, contrariamente al dibattito teorico, ai discorsi politici e alle rappresentazioni mediatiche correnti che tendono a focalizzarsi su specifiche aree geografiche del Sud, utilizzando una narrativa mono-causale e deterministica. Le motivazioni che spiegano le diverse concettualizzazioni di uno stesso fenomeno sono qui analizzate, attraverso degli strumenti propri alla geografia e alla scienza politica. I risultati di questo studio rivelano un disegno politico che mira a strumentalizzare il dibattito in modo da rinforzare l'asimmetria di potere nei Paesi del Nord e tra questi e i Paesi del Sud.
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Aide au tolérancement tridimensionnel : modèle des domaines / Three-dimensional tolerancing assistance : domains modelMansuy, Mathieu 25 June 2012 (has links)
Face à la demande de plus en plus exigeante en terme de qualité et de coût de fabrication des produits manufacturés, la qualification et quantification optimal des défauts acceptables est primordial. Le tolérancement est le moyen de communication permettant de définir les variations géométriques autorisé entre les différents corps de métier intervenant au cours du cycle de fabrication du produit. Un tolérancement optimal est le juste compromis entre coût de fabrication et qualité du produit final. Le tolérancement repose sur 3 problématiques majeures: la spécification (normalisation d'un langage complet et univoque), la synthèse et l'analyse de tolérances. Nous proposons dans ce document de nouvelles méthodes d'analyse et de synthèse du tolérancement tridimensionnel. Ces méthodes se basent sur une modélisation de la géométrie à l'aide de l'outil domaine jeux et écarts développé au laboratoire. La première étape consiste à déterminer les différentes topologies composant un mécanisme tridimensionnel. Pour chacune de ces topologies est définie une méthode de résolution des problématiques de tolérancement. Au pire des cas, les conditions de respect des exigences fonctionnelles se traduisent par des conditions d'existence et d'inclusions sur les domaines. Ces équations de domaines peuvent ensuite être traduites sous forme de système d'inéquations scalaires. L'analyse statistique s'appuie sur des tirages de type Monte-Carlo. Les variables aléatoires sont les composantes de petits déplacements des torseur écarts défini à l'intérieur de leur zone de tolérance (modélisée par un domaine écarts) et les dimensions géométriques fixant l'étendue des jeux (taille du domaine jeux associé). A l'issue des simulations statistiques, il est possible d'estimer le risque de non-qualité et les jeux résiduels en fonction du tolérancement défini. Le développement d'une nouvelle représentation des domaines jeux et écarts plus adapté, permet de simplifier les calculs relatifs aux problématiques de tolérancement. Le traitement local de chaque topologie élémentaire de mécanisme permet d'effectuer le traitement global des mécanismes tridimensionnels complexes avec prise en compte des jeux. / As far as the demand in quality and cost of manufacturing increase, the optimal qualification and quantification of acceptable defects is essential. Tolerancing is the means of communication between all actors of manufacturing. An optimal tolerancing is the right compromise between manufacturing cost and quality of the final product. Tolerancing is based on three major issues: The specification (standardization of a complete and unequivocal language), synthesis and analysis of the tolerancing. We suggest in this thesis some new analysis and synthesis of the three-dimensional tolerancing. These methods are based on a geometric model define by the deviations and clearances domains developed on the laboratory. The first step consists in determining the elementary topology that composes a three-dimensional mechanism. For each kind of these topologies one resolution method is defined. In worst case, the condition of functional requirement respect is traduced by existence and inclusions conditions on the domains. Then these domains equations can be translated in inequalities system of scalar. The statistical analysis uses the Monte-Carlo simulation. The random variables are the small displacements components of the deviation torsor which is defined inside its tolerance area (model by a deviations domain) and the geometrics dimensions which set the extent of clearance (size of the clearance domain). Thanks to statistical simulation, it is possible to estimate the non-quality rate in regards to the defined tolerancing. The development of a new representation of clearances and deviations domains most suitable, allows us to simplify the calculation for tolerancing problems. The local treatment of elementary topology makes enables the global treatment of complex three-dimensional mechanisms with take into account of clearances.
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Pre-Existing Film Music Re:sourced : Technical Aspects and Narratological Implications of Audible Diegetic Transitions in Joker and Other Films / Förflyttning av tidigare existerande filmmusik : Tekniska aspekter och narratologiska implikationer av hörbara diegetiska övergångar i Joker och andra filmerDanstål Skiöld, Martin January 2023 (has links)
This thesis concerns itself with a phenomenon found in film music that can be described as audible diegetic transitions. In short, an audible diegetic transition occurs when film music shifts from one implied musical placement to another by changing its presented sound quality. This occurs predominantly through the employment of music that is pre-existing in relation to the release of the film where the music is utilised. These audible diegetic transitions are categorised as aural displacements and transaural displacements which are both anchored in previous research concerning stable musical placements. In order to answer the research questions regarding technical aspects and narratological implications, the thesis is centred around a film music analysis. The demarcation of said analysis uses pre-existing songs from the film Joker (Philips, 2019) as its main focus. In order to provide a colourful and meaningful discussion the selected material also contains a variety of examples from other films. The analysis shows that the selected audible diegetic transitions can provide narratological implications both for a film as a whole and for a specific scene or sequence in any film. In Joker specifically, the audible diegetic transitions arguably contain the narratological implication of adding to the retrospective and unreliable narration, which is important for the story of the film. The thesis also argues that the technical aspects of the analysed audible diegetic transitions can be condensed into being either diegetic to commentary, or vice versa. Diegetic music is, in this context, defined as music that is implied as being heard in the acoustic space of the story-world, whereas commentary music is an umbrella term defined as music that is not implied being heard in the acoustic space of the story-world. The analysis shows that these transitions can transpire either instantly or gradually with the change of sound quality from being either narrow or wide. These technical aspects contribute in understanding the narratological implications of said audible diegetic transition by categorising them as either emotive or grounding. Both of these narratological implications can be concluded and described as swift enforcers of the relationship between the one consuming the film and the characters, or locations, of the film they are consuming. Audible diegetic transitions figuratively breach the fourth wall that is the screen.
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Numerical Investigation of Rock Support ArchesRentzelos, Theofanis January 2019 (has links)
The Garpenberg mine, owned by the Boliden Mining group, has established a trial area at Dammsjön orebody in order to examine the possibility of increasing the productivity of the mine. The mine uses the rill mining method with a current rill height of 15 m. In order to increase the productivity, the mine is examining the possibility of increasing the height of the rill. The trial area is located at 882 m depth surrounded by dolomite on the hangingwall and quartzitic rock on the footwall side. Rock support arches have been installed, in addition to the regular support pattern, to test their effectiveness on stabilizing the ground around the drifts. The arches have been installed in every 6 m and every 3 m in different parts of the test area. Rock samples from the trial area were brought to the university laboratory for testing. The data gathered from the laboratory tests along with the data from the monitoring of the trial area were used to develop a calibrated numerical model. A three-dimensional (3-D) model was therefore created, by using the FLAC3D numerical code. After the calibration of the model a parametric study was conducted for different rill heights and different arch spacing to investigate the performance of the arches. Specifically, the case of no arch installation along with the cases of an installed arch every 6 m and 3 m were tested, for the rill heights of 15 m, 20 m, 25 m and 30 m. The study concluded that the arches assisted in reducing the ground convergence in the production drift. The results also showed that the total height of the rill bench yields regardless of its height. After the yielding, the rockmass can no longer support itself and caves under its own weight. The larger the rill height, the larger the volume of loose rock that has to be supported and thus, higher the convergence. Furthermore, it was also observed that, significant amount of convergence in the production drift occurred during the drifting of the top drive and less during the stoping of the rill bench. This indicates that, the timely installation of the arches is an important criterion for their performance.
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Settling-Time Improvements in Positioning Machines Subject to Nonlinear Friction Using Adaptive Impulse ControlHakala, Tim 31 January 2006 (has links) (PDF)
A new method of adaptive impulse control is developed to precisely and quickly control the position of machine components subject to friction. Friction dominates the forces affecting fine positioning dynamics. Friction can depend on payload, velocity, step size, path, initial position, temperature, and other variables. Control problems such as steady-state error and limit cycles often arise when applying conventional control techniques to the position control problem. Studies in the last few decades have shown that impulsive control can produce repeatable displacements as small as ten nanometers without limit cycles or steady-state error in machines subject to dry sliding friction. These displacements are achieved through the application of short duration, high intensity pulses. The relationship between pulse duration and displacement is seldom a simple function. The most dependable practical methods for control are self-tuning; they learn from online experience by adapting an internal control parameter until precise position control is achieved. To date, the best known adaptive pulse control methods adapt a single control parameter. While effective, the single parameter methods suffer from sub-optimal settling times and poor parameter convergence. To improve performance while maintaining the capacity for ultimate precision, a new control method referred to as Adaptive Impulse Control (AIC) has been developed. To better fit the nonlinear relationship between pulses and displacements, AIC adaptively tunes a set of parameters. Each parameter affects a different range of displacements. Online updates depend on the residual control error following each pulse, an estimate of pulse sensitivity, and a learning gain. After an update is calculated, it is distributed among the parameters that were used to calculate the most recent pulse. As the stored relationship converges to the actual relationship of the machine, pulses become more accurate and fewer pulses are needed to reach each desired destination. When fewer pulses are needed, settling time improves and efficiency increases. AIC is experimentally compared to conventional PID control and other adaptive pulse control methods on a rotary system with a position measurement resolution of 16000 encoder counts per revolution of the load wheel. The friction in the test system is nonlinear and irregular with a position dependent break-away torque that varies by a factor of more than 1.8 to 1. AIC is shown to improve settling times by as much as a factor of two when compared to other adaptive pulse control methods while maintaining precise control tolerances.
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