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1
Lundin, Emelie. "Flax in flux : Dress flax in a state of flux". Thesis, Konstfack, Textil, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-7773.
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2
Reed, Patrick Edward. "Flux". Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1489496995093965.
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3
Thomas, Paul David. "Transit flux /". Connect to this title online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1124727663.
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Thomas, Paul. "Transit: Flux". Bowling Green State University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1124727663.
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5
Roessler, Heather. "Existential Flux". CSUSB ScholarWorks, 2018. https://scholarworks.lib.csusb.edu/etd/745.
Testo completoAbstract (sommario):
My wok is a place for meditation (through play and ritual) to grapple with ideas around what it means to be alive. I explore my own history, psychology and the nature of things, to better understand myself. I create because of the need to build a familiarity with the unknown and the uncomfortable and to accept that which is out of my control. While seeking to understand and learn from my own personal confrontations with death, I also find my own form of spirituality.
Losing my hold on graspable things, as time and change tend to bring, witnessing the dualities in nature ever-shifting; I must accept that nothing stays the same nor remains… not even me.
6
Baggaley, Andrew William. "Flux Rope Dynamo". Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515055.
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7
Gillespie, Sarah E. "Landscapes in Flux". Thesis, Southern Illinois University at Edwardsville, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1556913.
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8
Kuharik, Christian Bernard. "In constant flux". Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=2787.
Testo completoAbstract (sommario):
Thesis (M.F.A.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains iv, 29 p. : col. ill. + video clip. Includes an injection system video clip. Vita. Includes abstract. Includes bibliographical references (p. 17).
9
Horn, Thomas J. "Comparison of heat flux standards for calibrating heat flux gages at elevated temperatures and high heat flux levels". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063032/.
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10
Chambefort, Françoise. "Mimèsis du flux, exploration des potentialités narratives des flux de données". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCC004.
Testo completoAbstract (sommario):
Art du flux, data art, l’art numérique s’approprie les flux de données. Le rapport au réel et au temps qui s’y joue semble propice à la narration, pourtant les œuvres intègrent rarement des récits. Choisissant la voie de la recherche création, cette thèse explore les potentialités narratives des flux de données. Articulant les approches techniques, sémiotiques, sociales et esthétiques, la réflexion se nourrit, outre les sciences de l’information et de la communication, de disciplines variées telles que l’informatique, la philosophie, la sociologie, les sciences cognitives et la narratologie. L’œuvre Lucette, Gare de Clichy a été créée spécifiquement pour répondre à la question de recherche. La structure de l’œuvre a été déclinée en une version écran et une version performance. Elle est étudiée depuis sa création jusqu’à sa réception par le public. L’installation de Jonathan Fletcher Moore Artificial Killing Machine est analysée en parallèle. Dans un premier temps, l’objet de recherche – le récit fondé sur un flux de données en temps réel - est défini et le concept de moulins à données est forgé pour désigner ce type d’œuvres. Quatre hypothèses sont ensuite formulées et vérifiées successivement. Si les moulins à données sont à même de configurer une représentation de type narratif, ils doivent pour cela s’affranchir de la logique de l’action. Le récit de fiction est alors mis en mouvement par le réel. La métaphore qui relie les données du réel à la fiction provoque une oscillation de l’attention du spectateur entre le comparé et le comparant. Cette métaphore-switch possède la capacité de renforcer le sens qu’elle véhicule. Les moulins à données sont ainsi à même de faire ressentir la contingence de la vie telle que l’éprouve une personne vulnérable, ballotée entre temps objectif et temps subjectifSometimes called stream art or data art, digital art seizes data streams as its raw materials. Choosing a path of creative research, this thesis explores the story-telling potentialities of data streams. Structured around technical, social, semiotic and aesthetic approaches, its thinking draws on various fields of study : information and communication sciences, but also computer sciences, cognitive sciences, philosophy, sociology and narratology. The work Lucette, Gare de Clichy was especially designed to answer the researched question. The conformation of the work allowed for two different versions of it : a screen version and a performance. It is studied in all its stages, from its creation process to the public's response to it. Jonathan Fletcher Moore's installation, Artificial Killing Machine, is also analyzed. First, our object of research - stories made from a real-time data stream - is defined and the concept of data mills is crafted to refer to this type of work. Then four hypothesis are formulated and individually verified. If data mills are to be able to form a narrative representation, they must free themselves from the logic of action. Thus can fiction become powered by reality. The metaphor that links the data originated in reality and the crafted fiction generates in the viewer a shifting of focus between what is compared and what compares. This switching-metaphor has the power to reinforce the meaning it carries. Data mills are therefore able to convey the contingency of life as experienced by a vulnerable individual, tossed back and forth between objective and subjective time
11
Yang, Jun. "Effect of non-uniform axial heat-flux distribution on critical heat flux". Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26816.
Testo completoAbstract (sommario):
An experimental study of the effect of axial flux distribution (AFD) on critical heat flux (CHF) was conducted in directly heated tubes at the Freon-equivalent CANDU reactor conditions of interest. CHF measurements were obtained on test sections with four nonuniform AFD profiles as well as a uniform AFD profile using HFC-134a as a test fluid. Each of the non-uniform AFD test sections had a stepped cosine heat flux profile with approximately 16 heat flux steps. The test conditions covered a pressure range of 1662 to 2389 kPa, a mass flux range of 2827 to 4648 kg m-2 s -1 and an inlet quality range of -0.909 to -0.002.
The results showed that the AFD has a strong effect on CHF at high dryout qualities. (Abstract shortened by UMI.)
12
Bondehagen, Diane. "Passive flux meter for measuring groundwater and contaminant flux in bioactive environments". [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011390.
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13
Koers, Simon. "Type IIA Flux Compactifications". Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-104745.
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14
Sarkis, Matthieu. "Compactifications hétérotiques avec flux". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066074/document.
Testo completoAbstract (sommario):
Nous étudions différents aspects liés aux compactifications hétérotiques avec torsion. Nous définissons et calculons le genre elliptique vêtu associé aux compactifications Fu-Yau, et exploitons ce résultat pour calculer les corrections de seuil à une boucle de différents couplages BPS-saturés dans l’action effective de supergravité à quatre dimen- sions. Enfin nous nous intéressons à des solutions supersymétriques non-compactes qui généralisent, entre autres, les solutions hétérotiques connues sur le conifoldWe study various aspects of heterotic compactifications with torsion. We de- fine and compute the dressed elliptic genus associated to Fu-Yau compactifications, and use this result to compute one-loop threshold corrections to various BPS-saturated cou- plings in the four-dimensional effective supergravity action. Finally, we study non-compact supersymmetric solutions which generalize, among others, the known heterotic solutions on the conifold
15
Dimitrov, Pavel. "Flux invariants for shape". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19679.
Testo completoAbstract (sommario):
This thesis focuses on a particular class of representations of visual form, those based on the Blum skeleton [6]. We shall argue that such a representation has a number of desirable properties, which any good shape descriptor should possess. We shall begin this discussion in Section 1.1 but will keep it on a relatively high level leaving the details to Chapter 2. We shall then, in Section 1.2, review some of the previous work on skeletonization and identify the major computational difficulties encountered in the past. Finally, in Section 1.3, we shall briefly discuss how the method presented in this thesis deals with those issues and we shall identify the contributions of this work.
16
MacTaggart, David. "Theoretical magnetic flux emergence". Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1692.
Testo completoAbstract (sommario):
Magnetic flux emergence is the subject of how magnetic fields from the solar interior can rise and expand into the atmosphere to produce active regions. It is the link that joins dynamics in the convection zone with dynamics in the atmosphere. In this thesis, we study many aspects of magnetic flux emergence through mathematical modelling and computer simulations. Our primary aim is to understand the key physical processes that lie behind emergence. The first chapter introduces flux emergence and the theoretical framework, magnetohydrodynamics (MHD), that describes it. In the second chapter, we discuss the numerical techniques used to solve the highly non-linear problems that arise from flux emergence. The third chapter summarizes the current literature. In the fourth chapter, we consider how changing the geometry and parameter values of the initial magnetic field can affect the dynamic evolution of the emerging magnetic field. For an initial toroidal magnetic field, it is found that its axis can emerge to the corona if the tube’s initial field strength is large enough. The fifth chapter describes how flux emergence models can produce large-scale solar eruptions. A 2.5D model of the breakout model, using only dynamic flux emergence, fails to produce any large scale eruptions. A 3D model of toroidal emergence with an overlying magnetic field does, however, produce multiple large-scale eruptions and the form of these is related to the breakout model. The sixth chapter is concerned with signatures of flux emergence and how to identify emerging twisted magnetic structures correctly. Here, a flux emergence model produces signatures found in observations. The signatures from the model, however, have different underlying physical mechanisms to the original interpretations of the observations. The thesis concludes with some final thoughts on current trends in theoretical magnetic flux emergence and possible future directions.
17
House, Thomas. "Aspects of flux compactification". Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421529.
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18
Madani, Ramin. "The proton flux probe". Thesis, Manchester Metropolitan University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400940.
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Mann, Peter Douglas. "Nonlinear flux transport dynamos". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610712.
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20
Mohammadi, Neda. "Urban Spatiotemporal Energy Flux". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/89611.
Testo completoAbstract (sommario):
Urban energy systems are often studied in a very similar way in the sense that the characteristics of the underlying physical infrastructure are weighted as the main determinants of energy use predictions, while the behavior of the human population in relation to this systemthe so-called ``energy consumers''in time and urban spaces is effectively neglected. The spatial and temporal variations in infrastructure-population interactivity greatly complicate urban energy systems; the unremitting growth in population and advances in technology mean that the dynamic interrelationship between the population and urban environment will continue to grow exponentially, resulting in increasing uncertainties, unreliable predictions and poor management decisions given the inadequacy of existing approaches. In this dissertation, I explore the interdependencies of spatiotemporal fluctuations of human mobility as an indicator for human activities and energy use in urban areas in three main studies. First, I show that the fluctuations of intra-urban human mobility and energy use have an underlying structure across both time and space, and that human mobility can indeed be used as a predictor for energy use in both dimensions. Second, I examine how one of the dominant drivers of this structure, namely individuals' location-based activities, influence patterns in energy supply and demand across building types (i.e. residential and commercial buildings) and show how variations in the human mobility networks of two distinct urban populations (the so-called returners and explorers) can explain fluctuations in energy use. Third, I introduce an integrated approach for predicting urban energy use across time and space by incorporating these interdependencies. Generating predictive models that capture the spatiotemporal variations in these determinants in urban settings, as suggested in this research, will contribute to our understanding of how variations in urban population activities for particular times and locations influence can be applied to estimate energy use patterns in surrounding areas.PHD
21
Nel, Wynand. "Impact of pole shape and proportions on flux leakage in switched-flux generators". abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433347.
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22
Henderson, Alistair. "Predicting Ignition Time Under Transient Heat Flux Using Results from Constant Flux Experiments". University of Canterbury. Civil Engineering, 1998. http://hdl.handle.net/10092/8273.
Testo completoAbstract (sommario):
This project investigated if ignition could be mathematically predicted when a material is subjected to a transient heat flux.
Six timbers commonly used in New Zealand for construction and indoor furnishing timbers were tested in a cone calorimeter at the University of Canterbury. The experiments were run at 50, 35, 20 and 15 kW/m2 incident heat flux. The sample surface temperature and heat release data was collected for each test. From the ignition time data a value for thermal inertia was calculated and using specific heat data from the literature the thermal properties of each material was inserted into a One Dimensional Heat Transfer Model.
A second series of tests were conducted on each of the materials tested at constant flux. These new tests involved subjecting the sample to a transient heat flux based on t² fire growth curves. Again surface temperature and heat release data was obtained from the tests.
The one dimensional heat transfer model was used to attempt to predict the surface temperature profile and the ignition time when the test conditions were entered into it.
It was found that the predicted surface temperature profile generally matched the shape of the measured temperature profile. However the model was unsuccessful in accurately predicting the ignition time in either the constant or transient flux conditions.
It is considered that accurate values for the thermal conductivity and the specific heat would be required before the ignition time and temperature profile could be accurately modelled.
23
Fillion, Gilles. "Flux line cutting and flux pinning phenomena in hollow cylinders of type II superconductors". Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4673.
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Daigmorte, Hugo. "Analyse des interactions entre flux synchrones et flux asynchrones dans les réseaux temps réel". Thesis, Toulouse, ISAE, 2019. http://www.theses.fr/2019ESAE0003/document.
Testo completoAbstract (sommario):
Les systèmes embarqués complexes (avions, satellites, drones...) contiennent de plus en plus de calculateurs. Désormais ce sont des dizaines voire des centaines de calculateurs qui communiquent à travers un réseau partagé. Une fonction est réalisée par la collaboration d'un ensemble de calculateurs qui s'échangent un nombre croissant d'informations. Dans un contexte de temps réel embarqué, il faut non seulement garantir que ces informations échangées sont correctes mais il faut aussi garantir qu'elles vérifient leurs contraintes temporelles. Du point de vue du réseau cela signifie qu'une information doit être échangée en respectant les délais qui lui sont imposés. Ceci implique de pouvoir borner le temps de traversée du réseau de chaque message afin de vérifier qu'il arrive dans les temps. Or les systèmes embarqués étant de plus en plus complexes et le nombre d'informations échangées étant en constante augmentation, cette borne est de plus en plus difficile à calculer. De plus il est important que cette borne soit le moins pessimiste possible afin d'éviter que le système soit surdimensionné. L'objectif de ce travail est de mettre en place un modèle capable de calculer ces bornes.Afin d'y parvenir nous nous sommes basés sur la méthode d'analyse du Calcul Réseau.Ce travail s'est en particulier attardé sur la modélisation des interactions qui existent entre les messages synchrones et les messages asynchrones. Les modèles présentés dans ce manuscrit prennent en compte les dates d'émission sur le réseau des messages synchrones lors du calcul des bornes supérieures de temps de traversée des messages asynchrones.Les principales contributions apportées par ce manuscrit sont :1. la présentation d'une nouvelle façon d'envisager l'utilisation des dates d'émission sur le bus CAN : la synchronisation faible.Ainsi que la modélisation complète d'un tel système et enfin l'évaluation du gain apporté par cette solution.2. une modélisation complète du réseau TTEthernet permettant d'évaluer finement l'impact des flux synchrones sur le tempsde traversée des flux asynchrones.3. une présentation de l'utilisation de la synchronisation dans le réseau TSN ainsi qu'un modèlecomplet permettant d'analyser cette nouvelle technologieComplex embedded systems (planes, satellites, drones ...) contain more and more calculators. From now on, these are tens or even hundreds of calculators that communicate through a shared network. A function is achieved by the collaboration of a set of devices that exchange a growing number of information. In an embedded real-time context, it must be ensured that these informations exchanged are correct but it must also be ensured that they verify their temporal constraints. From the network point of view, this means that informations must be exchanged respecting their deadlines. This implies being able to upper bound the traversal time of the network of each message in order to verify that it arrives in time. However, as embedded systems are more and more complex and as the amount of information exchanged is constantly increasing, this bound is increasingly difficult to compute. Furthermore, it is important that this upper bound to be the least pessimistic possible to avoid an oversized system.The goal of this work is to develop new methods of analysis in order to be able to compute these bounds.In order to achieve this, we used the Network Calculus method of analysis.This work focuses on the modeling of interactions between synchronous messages and asynchronous messages.The models presented in this work take into account the transmission dates on the network of synchronous messageswhen calculating the upper bounds of traversal time of the asynchronous messages.The main contributions are:1. the presentation of a new way of considering the use of the dates of emission on the CAN bus: the weak synchronization.As well as the complete modeling of such a system and finally the evaluation of the gain provided by this solution.2. a complete modeling of the TTEthernet network allowing to evaluate the impact of the synchronous flows on the traversal time of the asynchronous flows.3. a presentation of the use of synchronization in the TSN network and a complete model for analyzing this new technology
25
Guinaudeau, Camille. "Structuration automatique de flux télévisuels". Phd thesis, INSA de Rennes, 2011. http://tel.archives-ouvertes.fr/tel-00646522.
Testo completoAbstract (sommario):
L'augmentation du nombre de documents multimédias disponibles rend nécessaire la mise en place de méthodes de structuration automatique capables de faciliter l'accès à l'information contenue dans les documents, tout en étant suffisamment génériques pour pouvoir structurer des documents tout-venants. Dans ce cadre, nous proposons deux types de structuration, linéaire et hiérarchique, s'appuyant sur les transcriptions automatiques de la parole prononcée dans les documents. Ces transcriptions, indépendantes du type des documents considérés, sont exploitées par le biais de méthodes issues du traitement automatiques des langues (TAL). Les deux techniques de structuration, ainsi que la phase de segmentation thématique sur laquelle elles reposent, donnent lieu à plusieurs contributions originales. Tout d'abord, la méthode de segmentation thématique employée, originellement développée pour du texte écrit, est adaptée aux particularités des transcriptions automatiques de vidéos professionnelles - erreurs de transcription, faible nombre de répétitions de vocabulaire. Le critère de cohésion lexicale sur lequel elle se fonde est, en effet, sensible à ces spécificités, ce qui pénalise fortement les performances de l'algorithme. Cette adaptation est mise en place, d'une part grâce à la prise en compte, lors du calcul de la cohésion lexicale, de connaissances linguistiques et d'informations issues de la reconnaissance automatique de la parole et du signal (relations sémantiques, prosodie, mesures de confiance), et d'autre part grâce à des techniques d'interpolation de modèles de langue. À partir de cette étape de segmentation thématique, nous proposons une méthode de structuration thématique linéaire permettant de mettre en relation des segments abordant des thématiques similaires. La méthode employée, fondée sur une technique issue du domaine de la recherche d'information, est adaptée aux données audiovisuelles grâce à des indices prosodiques, qui permettent de favoriser les mots proéminents dans le discours, et des relations sémantiques. Finalement, nous proposons un travail plus exploratoire examinant différentes pistes pour adapter un algorithme de segmentation thématique linéaire à une tâche de segmentation thématique hiérarchique. Pour cela, l'algorithme de segmentation linéaire est modifié - ajustement du calcul de la cohésion lexicale, utilisation de chaines lexicales - pour prendre en compte la distribution du vocabulaire au sein du document à segmenter. Les expérimentations menées sur trois corpora composés de journaux télévisés et d'émissions de reportages, transcrits manuellement et automatiquement, montrent que les approches proposées conduisent à une amélioration des performances des méthodes de structuration développées.
26
Poli, Jean-Philippe. "Structuration automatique de flux télévisuels". Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2007. http://tel.archives-ouvertes.fr/tel-00207960.
Testo completoAbstract (sommario):
Dans le cadre du dépôt légal de la télévision, nous proposons une méthode de structuration automatique des flux télévisuels afin de procéder au catalogage des émissions.La stabilité des grilles de programmes nous permet d'en proposer une modélisation statistique basée sur un modèle de Markov contextuel et un arbre de régression. Entraîné sur les grilles de programmes des années précédentes, ce modèle permet de pallier l'imprécision des guides de programmes (EPG, magazines). En rapprochant ces deux sources d'informations, nous sommes en mesure de prédire les séquences d'émissions les plus probables pour un jour de l'année et d'encadrer la durée des émissions.
A partir de ces grilles de programmes prédites et d'un ensemble de règles indiquant les éléments
caractéristiques d'une transition entre deux genres de programmes (images monochromes, silences ou logos), nous sommes en mesure de localiser ces ruptures à l'aide de d´etections effectuées localement dans le flux.
27
Brière, Normand. "Représentation hiérarchique de flux lumineux". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/NQ43702.pdf.
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28
Sheffield, Randolph J. "High heat flux spray cooling". Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17881.
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29
Gross, Richard Edward. "Numerical simulations of flux pinning". Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243012.
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30
Rands, Marc Lawrence. "Nutrient flux in intracellular symbiosis". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306705.
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31
Amreiz, Hassan Musa. "Transverse flux switched reluctance motors". Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270782.
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32
Schofield, Andrew John. "Flux phases for correlated fermions". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282101.
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33
Goodier, Ewan Roderick Tearlach. "Reluctance machines with flux assistance". Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30207.
Testo completoAbstract (sommario):
This thesis presents three reluctance machines with flux assistance. These machines provide alternative novel geometries that provide high efficiencies with a reduction in the ampere turns in the armature windings for torque production, lowering armature winding switching losses and reducing the power electronic rating. The Dual Stack Variable Reluctance Machine is a switched reluctance variant of the homopolar inductor alternator topology. The Single Stack Variable Reluctance Machine is a simplification of the Dual Stack machine. Both machines use a toroidal field winding to provide additional flux. The methods of connecting armature coils on each stator pole to utilise the armature flux and the choice of power electronic circuitry are important. Testing shows that such machines favour unipolar excitation with single coil per pole for the armature windings. Use of the field winding in series with the armature windings improves torque production. The Dual Stack Variable Reluctance Machine can have the mechanical angular displacement between the two stator stacks varied to provide an improved back emf waveshape for smoother torque production. The Single Stack Variable Reluctance Machine has parasitic and axial air gaps that pose interesting design issues (e.g. end thrust). Magnets can be placed in steel sections where flux is unidirectional. An ideal candidate for magnet insertion is the Flux Switching Motor. A Permanent Magnet Flux Switching Motor has been built that replaces the field windings with ferrite magnets. The Permanent Magnet Flux Switching Motor achieves efficiencies of over 80%. It adds no additional cost to the fan application as cost savings in lower temperature rated thermoplastics offsets the cost of magnets. A prototyping circuit incorporating a novel micro-processor program to alter the commutation timings as the machine operates has been designed to allow fast optimisation of each machine for minimum input power.
34
Greenland, Christopher. "Flux Measurements at Lake Erken". Thesis, Uppsala universitet, Luft-, vatten- och landskapslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-440331.
Testo completoAbstract (sommario):
Turbulent fluxes govern the exchange of momentum, heat and moisture between the Earth’s surface and the overlying air. Computations of these fluxes are crucial, particularly over lakes and seas because most of the earth’s surface consists of water. One of the most common methods of calculating turbu- lent fluxes is the bulk method, where the fluxes are expressed with exchange coefficients. With more knowledge of these coefficients, the fluxes can be determined with a higher accuracy. Consequently, the turbulence structure and the exchange of moisture, momentum and heat between the surface and the overlying air can be better understood. The goal of this study was to compute the neutral exchange co- efficients for drag (CDN), heat (CHN) and moisture (CEN) and investigate their dependency on various atmospheric conditions, based on four years of measurements from Lake Erken, located about 70 km east of Uppsala. The coefficients were evaluated against the wind speed, stratification and time over water TOW (the time that the air is above the water before it reaches the tower). A special analysis was done by studying the variation of the coefficients with the wind speed during the UVCN-regime. Another analysis was done to see if the coefficients may have been influenced by non-local processes, e.g. advection from the surroundings. Additionally, normalized standard deviations for the temperature and humidity were evaluated for different stabilities. The results were compared with estimations by the COARE3.0 algorithm (for the dependency on the wind speed and the stability) in a previous report and other earlier studies. The results indicated that the neutral exchange coefficients were higher and more dispersed during near neutral stratification and low TOWs. The normalized standard deviations also increased during neutral conditions. The explanation for this could be related to the presence of the UVCN-regime or non-local effects such as advection or entrainment from the surroundings. The wind speed had no ob- vious impact on the coefficients. However, the drag coefficient was larger and more spread out in the wind speed range 1-3 m/s. In comparison to earlier studies, the exchange coefficients were higher and scattered to a greater extent. This may be because of a strong UVCN-regime, sustainable non-local influences, relatively steeper waves than open-sea conditions or outliers in the data.
35
Beller, Philip. "FLUX : Rethinking two-wheel mobility". Thesis, Umeå universitet, Designhögskolan vid Umeå universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171771.
Testo completoAbstract (sommario):
This project has investigated how to reshape two-wheel mobility in a more functional driven way, without losing the thrill of riding a motorcycle. The intitial cue was offered by the current rise of electric powertrains in the market. The opportunity of finding new spaces in the existing motorcycle architecture that could increase it's functionality and safety served as inspiration for this project. By achieving these steps this project wishes to envision a product that can attract new audiences whilst making two-wheel mobility more accessible. The process involved a variety of techniques that range from concept creation to 3D visualisation. During the ideation phase digital and analogue sketching techniques were combined after benchmarking existing products and visualising through animations possible solutions. In a later step the design was refined using digital painting in addition to polygon modelling. It has been helpful to evaluate the product in VR through various steps of the process, this provided a better understanding of the volumes and enabled a more accurate design of certain components. The result of the project is Flux. Combining unusual materials, like silicone, with a new layout offered the possibility of creating a simple yet advanced solution that provides various benefits to riding in everyday life. These benefits range from an enhanced cargo capability to an easier way to swap or recharge the batteries. In addition, it features some seamlessly integrated technology improvements that are vowed to make riding safer, without compromising on the experience.
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Leclercq, Stéphanie. "Flux de métaux en manche". Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-97.pdf.
Testo completoAbstract (sommario):
L'etude presentee entre dans le cadre du programme europeen marine science and technology et concerne les transferts d'eau, de matieres en suspension et de contaminants de l'ocean atlantique vers la mer du nord. A partir d'un echantillonnage effectue pendant une periode de 1 an sur le transect cherbourg-ile de wight, et grace a des techniques analytiques spectroscopiques (icp/aes, gfaas) et electrochimiques adaptees (dpsav) et nouvelles au laboratoire (swcsv), nous avons pu etudier la distribution spatio-temporelle des elements majeurs (fe, al, ca, mg, ti) et des metaux-traces (cu, pb, zn, cd, v, cr, mn). Le caractere oceanique des eaux est peu affecte sur le transect, exception faite au nord ou une double influence anthropique est mise en evidence. Nous montrons que des reactions d'adsorption sur les oxyhydroxides de fer et sur caco#3, d'assimilation / regeneration par le phytoplancton, de complexation par les substances humiques peuvent expliquer le comportement biogeochimique de certains des metaux traces etudies. Exception faite pour cd et cr(vi), cette forte influence anthropique perturbe l'observation du role biochimique de certains metaux-traces (cu, zn). L'etude de la speciation de la phase particulaire confirme l'adsorption de mn et de pb dans la phase biodisponible, et le calcul des coefficients de distribution k#d permet de classer l'affinite des elements pour cette phase selon l'ordre pb > v > zn > cd, cr. Enfin, l'utilisation d'un modele mathematique 2d de l'hydrodynamisme en manche a permis de calculer les flux annuels des metaux transitant vers la mer du nord. Les flux de contaminants, importants l'hiver, apparaissent geres plus par les flux d'eau que par les concentrations des elements.
37
Currano, Joseph A. "Heat flux-based emissivity measurement". College Park, Md.: University of Maryland, 2007. http://hdl.handle.net/1903/7397.
Testo completoAbstract (sommario):
Thesis (M.S.) -- University of Maryland, College Park, 2007.Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Edwards, John. "Magnetic flux based transformer model /". [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16945.pdf.
Testo completo
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Straub, Andreas. "Flux Trapping in Superconducting Pellets". PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4535.
Testo completoAbstract (sommario):
This research concerns the effects on samples of nominal composition Bil.8Pb0.2Sr2Ca2cu30y which were exposed to hot, dense argon in a ballistic compressor. The investigations were concentrated on two specimens which were exposed to hot, dense argon at about 1800 K (peak pressure 330 atm) and 1500 K (peak pressure 230 atm), respectively. Sample Bi #1 showed a completely melted surface structure after triple exposure in the ballistic compressor at 1800 K while the surface of sample Bi #7 was just partly melted after double exposure at 1500 K. Changes in flux trapping capability and qualitative Meissner effect were investigated in addition to the properties described by Duan, et al. ( 17, 18, 3 2] , who reported changes in critical temperature, crystal structure, surface morphology and composition after exposure of samples to hot, dense argon. After triple exposure in the ballistic compressor at a temperature of approximately 1800 K, sample Bi #1 showed an enhanced Meissner effect on the exposed side compared to the unexposed side of the pellet, while no difference in Meissner effect was found between the exposed and the unexposed side of sample Bi #7. EDS analysis showed that both samples are inhomogeneous in chemical surface composition. Oxygen loss due to exposure to hot, dense argon could not be demonstrated. X-ray analysis indicated that the melted surface layer of sample Bi # 1 after triple exposure to hot, dense argon contains smaller crystals than before exposure in the ballistic compressor. Tc measurements gave varying results which are explainable by the chemical inhomogeneity of the specimens. An increase in the amount of trapped flux due to exposure of the samples to hot, dense argon could not be demonstrated
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Proto, Yann. "Geometry of heterotic flux compactifications". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS125.
Testo completoAbstract (sommario):
Cette thèse explore des développements récents dans l'étude des compactifications avec flux de la théorie des cordes hétérotique. Nous nous concentrons principalement sur les compactifications Minkowski en quatre dimensions avec supersymétrie d'espace-temps, dont les géométries six-dimensionnelles sous-jacentes sont, en présence de torsion, des variétés non-kählériennes à structure SU(3). Nous développons plusieurs méthodes pour analyser ces compactifications à la fois du point de vue de la supergravité et de la surface d'univers. Nous étudions des flots en géométrie non-kählérienne qui jouent un rôle central dans l'étude des équations de Hull-Strominger, et élucidons leurs propriétés de supersymétrie. Nous présentons une classe d'orbifolds qui admettent une description en termes de modèles sigma linéaires avec torsion à supersymétrie (0,2), et obtenons de nouveaux exemples de fonds hétérotiques avec flux. Enfin, nous explorons les implications de la T-dualité de Narain dans l'espace des modules des vides hétérotiques avec torsion, et trouvons des preuves de changement de topologie et de dualités Kähler/non-KählerThis thesis delves into recent developments in the study of flux compactifications of the heterotic string theory. We primarily focus on four-dimensional Minkowski compactifications with spacetime supersymmetry, whose underlying six-dimensional geometries are, in the presence of torsion, non-Kähler SU(3) structure manifolds. We develop several methods to analyze these compactifications from both supergravity and worldsheet perspectives. We investigate geometric flows in non-Kähler geometry that play a central role in the study of the Hull-Strominger equations, and elucidate their supersymmetry properties. We present a class of orbifold backgrounds that can be described using torsional linear sigma models with (0,2) worldsheet supersymmetry, and obtain new examples of heterotic flux backgrounds. Finally, we explore the implications of Narain T-duality for the moduli space of torsional heterotic vacua, and find evidence for topology change and Kähler/non-Kähler dualities
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Thompson, Jordan Lee. "Direct Measurement of Boiling Water Heat Flux for Predicting and Controlling Near Critical Heat Flux". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23091.
Testo completoAbstract (sommario):
A novel method for measuring heat flux of boiling water is designed and built to study critical heat flux (CHF) and observe the response of a heat flux sensor when CHF occurs. A high temperature heat flux sensor is embedded in the wall of a pipe to get a direct measurement of the surface heat flux and sensor temperature. By submerging the pipe in water and applying a controlled heat flux to the inside diameter over the area where the sensor is located, boiling is created on the outer surface while measuring the heat flux. The heat flux is gradually increased up to CHF and the heat flux response is observed to determine if the heat flux sensor could sense CHF when it occurred. The heat flux sensor is able to consistently measure the value for CHF, which is approximately 510 kW/m" for this system. It is also observed during the experiments that the heat flux response undergoes an inflection of the heat transfer coefficient at a consistent temperature just before reaching CHF. This observed inflection caused the heat flux response to deviate from its cubic relationship with the temperature and drastically increase for a very small change in temperature. This inflection response can be used as an indication for approaching CHF and can also be used to approximate its value without prior knowledge of when it occurs.Master of Science
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Santos, Filipe Terra Nova dos. "Reversed flux patches on the archeomagnetic field". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-31052018-092934/.
Testo completoAbstract (sommario):
Archeomagnetic field models may provide important insights to the geodynamo. Here we investigate the existence and mobility of reversed flux patches (RFPs) in an archeomagnetic field model. We introduce topological algorithms to define, identify, and track RFPs. In addition, we explore the relations between RFPs and dipole changes and apply robustness tests to the RFPs. In contrast to previous definitions, patches that reside on the geographic equator are adequately identified based on our RFPs definition. Most RFPs exhibit a westward drift and migrate toward higher latitudes. Undulations of the magnetic equator and RFPs oppose the axial dipole moment (ADM). Filtered models show a tracking behavior similar to the nonfiltered model, and surprisingly new RFPs occasionally emerge. The advection and diffusion of RFPs have worked in unison to yield the decrease of the ADM at recent times. The absence of RFPs in the period 550-1440 A.D. is related to a low in intermediate degrees of the geomagnetic power spectrum. We thus hypothesize that the RFPs are strongly dependent on intermediate spherical harmonic degrees 4 and above. Filtered models and comparison with the GUFM1 model suggest that RFPs are robust features of the geomagentic field for the last millennia.Modelos do campo arqueomagnético podem fornecer importantes informações sobre o geodínamo. Nesta dissertação, estudou-se a existência e a mobilidade de lóbulos de fluxo reverso (RFPs, em inglês) no campo arqueomagnético. Testes de robustez foram aplicados para diferentes modeles. Além disso, foram exploradas as relações entre RFPs e as variações do momento do dipolo axial (ADM, em inglês). Para tanto, foram desenvolvidos algoritmos topológicos para definir, identificar e mapear os RFPs em modelos do campo arqueomagnético (modelo CALS3k.4b e modelo GUFM1). O equador magnético foi usado para definir a polaridade ao invés do equador geográfico. Uma vez que cada ponto da grade de 1 grau x 1 grau de latitude/longitude é associado com um hemisfério magnético e uma polaridade (normal ou reversa), o passo seguinte é identificar os picos de lóbulos de fluxo reverso. No passo final de identificação um critério de intensidade é imposto para evitar lóbulos que possuem intensidade muito baixa. Para mapear lóbulos de fluxo reverso no tempo, foi codificado um algoritmo que calcula a distancia de cada lobulo para todos os lóbulos do próximo intervalo de tempo. Diferentemente das definições anteriores, lóbulos que residem no equador geográfico são adequadamente identificados com a nova definição de RFPs. A maioria dos RFPs exibe deriva para Oeste e mais de 75% deles migram em direção a altas latitudes. Ondulações do equador magnético e RFPs resultam de campo com momento oposto ao ADM. Modelos filtrados apresentam resultados de mapeamento semelhantes aos de modelos não-filtrados, e em alguns casos, surgem nos modelos filtrados novos RFPs. Resultados dos modelos CALS3k.4b e GUFM1 para o período de 1840 AD até 1990 AD mostram concordância para o mapeamento de lóbulos de fluxo reverso com maiores similaridades para os filtros mais fortes. Os resultados desta dissertação são compatíveis com a ideia que a advecção e a difusão de RFPs tem operado em conjunto causando o decréscimo do ADM nos últimos séculos. A ausência de RFPs no período de 550-1440 AD sendo relacionada a baixos valores nos graus intermediários do espectro de potencia. Dessa forma, sugere-se que os RFPs são fortemente dependentes dos harmônicos esféricos de graus 4 e acima. Modelos filtrados e comparações com o modelo GUFM1 sugerem que lóbulos de fluxo reverso são feições robustas do campo magnético terrestre nos últimos milênios.
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Calisto, Hugo Miguel Filipe. "Transient transpiration radiometer : development of a heat flux sensor for high aggressivity environments". Doctoral thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12457.
Testo completoAbstract (sommario):
Doutoramento em Engenharia MecânicaThe development of a new instrument for the measurement of convective and radiative is proposed, based on the transient operation of a transpiration radiometer. Current transpiration radiometers rely on steady state temperature measurements in a porous element crossed by a know gas mass flow. As a consequence of the porous sensing element’s intrinsically high thermal inertia, the instrument’s time constant is in the order of several seconds. The proposed instrument preserves established advantages of transpiration radiometers while incorporating additional features that broaden its applicability range. The most important developments are a significant reduction of the instrument’s response time and the possibility of separating and measuring the convective and radiative components of the heat flux. These objectives are achieved through the analysis of the instrument’s transient response, a pulsed gas flow being used to induce the transient behavior.
Propõe-se o desenvolvimento de um novo instrumento para medição de fluxos de calor convectivos e radiativos, baseado na operação de um radiómetro de transpiração em regime transitório. Os radiómetros de transpiração atuais baseiam-se em medições de temperatura em regime estacionário num elemento poroso atravessado por um caudal mássico gasoso conhecido. Como consequência da inércia térmica intrinsecamente elevada do elemento sensível poroso, a constante de tempo do instrumento é da ordem dos segundos. O instrumento proposto preservará as vantagens estabelecidas dos radiómetros de transpiração incorporando características adicionais que alargarão a gama de aplicabilidade. As novas características mais importantes serão uma redução significativa do tempo de resposta do instrumento e a possibilidade de medir separadamente as componentes radiativa e convectiva do fluxo de calor. Estes objetivos serão conseguidos através da análise da resposta transitória do instrumento, utilizando-se um caudal pulsado de gás para induzir o comportamento transitório.
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Viller-Hamon, Isabelle. "Flux financiers, flux d'informations et reseaux internationaux : l'agence havas et le jeu des echanges, 1850-1914". Paris 3, 2000. http://www.theses.fr/2000PA030175.
Testo completoAbstract (sommario):
Les agences de presse se constituent en europe au xixeme siecle : l'agence havas en 1832, a paris ; la continental telegraphen compagnie en 1849 a berlin et la reuter's telegram company en 1851 a londres. Les << trois grandes >> s'assurent des 1859 le monopole des nouvelles et la mise en place de reseaux de transmission internationaux. Le developpement des activites de bourse a partir des annees 1850 appelle la constitution de services agenciers specialises dont la fiabilite et la rapidite assurent la bonne marche des affaires et la connexion des marches boursiers europeens. Les dimensions commerciales des activites agencieres impliquent des attitudes specifiques, se traduisant par une certaine propension a menager les susceptibilites. Le cas des relations entre abonnes financiers et l'agence havas montre tout particulierement les multiples degres d'influence agissant sur les structures agencieres. Flux et reseaux agenciers sont l'empreinte de preoccupations geopolitiques et geoeconomiques. Rapidite et discretion des informations financieres temoignent de la meme facon de l'interference entre milieux financiers et agenciers.
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Tassew, Wondesen. "Photovoltaic concentration at ultra-high flux /". [Beersheba, Israel] : Ben-Gurion University of the Negev, 2006. http://aranne5.lib.ad.bgu.ac.il/others/TassewWondesen.pdf.
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Chiky, Raja. "Résumé de flux de données ditribués". Phd thesis, Télécom ParisTech, 2009. http://pastel.archives-ouvertes.fr/pastel-00005137.
Testo completoAbstract (sommario):
Ces dernières années, sont apparues de nombreuses applications, utilisant des données en nombre potentiellement illimité, provenant de façon continue de capteurs distribués afin d'alimenter un serveur central. Les données sont utilisées à des fins de surveillance, de supervision, de déclenchement d'alarmes en temps réel, ou plus généralement à la production de synthèses d'aide à la décision à partir de plusieurs flux. Le volume des données collectées est généralement trop grand pour être entièrement stocké. Les systèmes de gestion de flux de données (SGFD) permettent de gérer facilement, et de façon générique les flux de données : les données sont traitées au fil de l'eau sans les archiver. Toutefois, dans certaines applications, on ne souhaite pas perdre complètement l'ensemble des flux de données afin de pouvoir analyser les données du passé et du présent. Il faut donc prévoir un stockage de l'historique du flux. Nous considérons dans cette thèse, un environnement distribué décrit par une collection de plusieurs capteurs distants qui envoient des flux de données numériques et unidimensionnelles à un serveur central unique. Ce dernier a un espace de stockage limité mais doit calculer des agrégats, comme des sommes ou des moyennes, à partir des données de tout sous-ensemble de capteurs et sur un large horizon temporel. Deux approches sont étudiées pour construire l'historique des flux de données :(1) Echantillonnage spatial en ne considérant qu'un échantillon aléatoire des sources qu'on observe dans le temps ; (2) Echantillonnage temporel en considérant toutes les sources mais en échantillonnant les instants observés de chaque capteur. Nous proposons une méthode générique et optimisée de construction de résumés à partir de flux de données distribués : A partir des flux de données observés à une période de temps t -1, nous déterminons un modèle de collecte de données à appliquer aux capteurs de la période t. Le calcul des agrégats se base sur l'inférence tatistique dans le cas de l'échantillonnage spatial et sur l'interpolation dans le cas de l'échantillonnage temporel. A notre connaissance, il n'existe pas de méthodes d'interpolation qui estiment les erreurs à tout instant et qui prennent en compte le flux de données ou courbe à interpoler et son intégrale. Nous proposons donc deux approches : la première se base sur le passé des courbes pour l'interpolation (approche naive) ; et la seconde utilise à un processus stochastique pour modéliser l'évolution des courbes (approche stochastique).
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Manson, Gaël. "Délinéarisation automatique de flux de télévision". Phd thesis, Université Rennes 1, 2010. http://tel.archives-ouvertes.fr/tel-00512675.
Testo completoAbstract (sommario):
Les flux de télévision sont structurés : ils sont en effet composés de programmes successifs (journaux, films, magazines, etc.) et entrecoupés par des inter-programmes (publicités, bandes annonces, parrainages, etc.). Dès que les flux sont diffusés sur les ondes, ils perdent malheureusement toute information de structure. La problématique de la délinéarisation automatique est de retrouver la structure des flux TV, avec en particulier le début précis et la fin précise de chaque programme, à partir des signaux audiovisuels reçus et des métadonnées éventuellement fournies par les chaînes TV. Cette thèse présente un système complet de délinéarisation automatique rigoureusement évalué sur quatre semaines de flux TV réels, pour deux chaînes de télévision différentes. Les travaux se basent sur la propriété de répétition des inter-programmes. Cette propriété est exploitée à travers la détection de toutes les répétitions d'un flux grâce à une technique de clustering des images clés du flux. Ces répétitions servent à la création de segments qui sont ensuite classés en segments de programme ou en segments d'inter-programme suivant les caractéristiques des répétitions et les relations entre les segments. Pour cela, le système utilise la programmation logique inductive. Une fois les segments classés, les segments de programme appartenant à un même programme sont étiquetés et réunifiés grâce aux métadonnées éventuelles. En l'absence de métadonnées, les segments de programme d'un même programme peuvent être seulement réunifiés grâce à des similarités visuelles.
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Gauwin, Olivier. "Flux XML, Requêtes XPath et Automates". Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2009. http://tel.archives-ouvertes.fr/tel-00421911.
Testo completoAbstract (sommario):
Ces dernières années, XML est devenu le format standard pour l'échange de données. Les documents XML sont généralement produits à partir de bases de données, durant le traitement de documents, ou au sein d'applications Web. L'échange de données en flux est fréquemment utilisé lors de l'envoi de données volumineuses par le réseau. Ainsi le transfert par flux est adéquat pour de nombreux traitements XML.Dans cette thèse, nous étudions des algorithmes d'évaluation de requêtes sur des flux XML. Notre objectif est de gérer efficacement la mémoire, afin de pouvoir évaluer des requêtes sur des données volumineuses, tout en utilisant peu de mémoire. Cette tâche s'avère complexe, et nécessite des restrictions importantes sur les langages de requêtes. Nous étudions donc les requêtes définies par des automates déterministes ou par des fragments du standard W3C XPath, plutôt que par des langages plus puissants comme les standards W3C XQuery et XSLT.
Nous définissons tout d'abord les Streaming Tree Automata (STAs), qui opèrent sur les arbres d'arité non bornée dans l'ordre du document. Nous prouvons qu'ils sont équivalents aux Nested Word Automata et aux Pushdown Forest Automata. Nous élaborons ensuite un algorithme d'évaluation au plus tôt, pour les requêtes définies par des STAs déterministes. Bien qu'il ne stocke que les candidats nécessaires, cet algorithme est en temps polynomial à chaque événement du flux, et pour chaque candidat. Par conséquent, nous obtenons des résultats positifs pour l'évaluation en flux des requêtes définies par des STAs déterministes. Nous mesurons une telle adéquation d'un langage de requêtes à une évaluation en flux via un nouveau modèle de machines, appelées Streaming Random Access Machines (SRAMs), et via une mesure du nombre de candidats simultanément vivants, appelé concurrence. Nous montrons également qu'il peut être décidé en temps polynomial si la concurrence d'une requête définie par un STA déterministe est bornée. Notre preuve est basée sur une réduction au problème de la valuation bornée des relations reconnaissables d'arbres.
Concernant le standard W3C XPath, nous montrons que même de petits fragments syntaxiques ne sont pas adaptés à une évaluation en flux, sauf si P=NP. Les difficultés proviennent du non-déterminisme de ce langage, ainsi que du nombre de conjonctions et de disjonctions. Nous définissons des fragments de Forward XPath qui évitent ces problèmes, et prouvons, par compilation vers les STAs déterministes en temps polynomial, qu'ils sont adaptés à une évaluation en flux.
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Malhi, Yadvinder Singh. "Sensible heat flux from heterogeneous surfaces". Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357894.
Testo completoAbstract (sommario):
This thesis describes the collection, analysis and interpretation of data on sensible heat transfer into the atmosphere from three sparsely vegetated sites: a vineyard and legume crop in Spain, and a savannah bush site in Niger. The viability of using measurements of the variance of air temperature to determine sensible heat flux is investigated. Monin-Obukhov similarity theory is reviewed, with particular emphasis on its limitations and asymptotes. The physical interpretation and relative magnitudes of zero-plane displacement and roughness length for heat and momentum transfer are examined. A heat flux measurement system based on measuring fluctuations of temperature is developed, and its results compared with eddy correlation measurements in both Spain and Niger. The surface temperatures of the various components of a sparsely vegetated surface are compared with the area-averaged radiometric temperature. It is shown that, for sparsely vegetated surfaces, this radiometric surface temperature may be much lower than the "aerodynamic" surface temperature required by similarity theory. Values of Z_0h, the roughness length for heat transfer, are calculated for all three sites. These are found to be smaller than for uniform vegetation, and to vary with wind speed by several orders of magnitude. A review of the physics of heat and momentum transfer is undertaken to explain this phenomenon. It is demonstrated that Z_0h is a function of both heat and momentum transfer, and that it can be expected to vary with wind speed. This effect is masked for uniform vegetation, but is amplified for sparse vegetation by the relatively low efficiency of heat transfer. This explains the observed behaviour of Z_Oh on the three field sites. Historical measurements of Z_0 and Z_0h over a variety of surfaces are reviewed and reinterpreted in terms of heat and momentum transfer properties.
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Silva, Claudio Mudado. "Flux prediction in high-shear microfiltration". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0010/NQ59095.pdf.
Testo completo