Teses / dissertações sobre o tema "Multi-field approach"
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1
Sustar, Tomaz. "A solution approach to non-linear multi-field problems". Thesis, Swansea University, 2002. https://cronfa.swan.ac.uk/Record/cronfa42573.
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In this work a solution approach for non-linear multi-filed problems is presented. The approach is based on co-operative usage of several advanced techniques inside a single environment instead of combining several different systems. The objective of this work is to demonstrate the applicability of advanced computational techniques to complex numerical problems and to present advantages of a co-operative solution environment in the development of finite elements. The solution environment, implemented in Mathematica, consists of a symbolic code generator - AceGen, a package of prearranged modules for the automatic creation of the interfaces between the generated code and specific finite element environment - Computational Templates and a model finite element environment called Finite Element Driver. Within the scope of this work the ANSI C version of Finite Element Driver - CDriver was developed and used for numerical evaluation throughout the work. The CDriver is fully integrated with Mathematica and it provides high numerical efficiency to the environment. The solution approach is demonstrated on magneto-thermo-mechanical problem of inductive heat treatment. First the high abstract formulation level, which is required for efficient symbolic description, was introduced. Following the general formulation the models of individual magnetic, thermal and displacement fields were derived. After the individual fields model were verified the magneto-thermal and magneto- thermo-mechanical problems were formulated and derived. Both non-linear multi- filed models were verified using analytical solutions and numerical convergence tests. Different multi-filed solution strategies were applied to numerical examples and their performance issues were studied using the magneto-thermo-mechanical model. Finally the large scale numerical example of inductive heat treatment was solved.
2
Dai, Zhenwen, e 戴振文. "A Markov random field approach for multi-view normal integration". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4308588X.
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Dai, Zhenwen. "A Markov random field approach for multi-view normal integration". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4308588X.
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4
Davis, Matthew Harris. "A Bond Valence-Based Force Field: A Multi-Body Approach". BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3796.
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The typical form for a molecular mechanics force field consists of a foundation of pair-wise terms to describe bonded and non-bonded atomic interactions, with multi-body correction terms to deal with the limitations of pair-wise terms. I present here the first attempts of a molecular mechanics model that is founded on multi-body terms, which are based on the Bond Valence Model (Brown, 2002) and recent developments in the Vectorial Bond Valence Model (Bickmore et al., 2013a; Harvey et al., 2006). I calibrated these models on pressure vs. energy curves for a set of SiO2 polymorphs. The average deviation for the best-fit iteration, with only six adjustable parameters was ±1.98 kcal/mol.
5
Hagelbäck, Johan. "A Multi-Agent Potential Field based approach for Real-Time Strategy Game bots". Licentiate thesis, Blekinge Tekniska Högskola, Avdelningen för programvarusystem, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00428.
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Computer games in general and Real-Time Strategy (RTS) games in particular provide a rich challenge for both human- and computer controlled players, often denoted as bots. The player or bot controls a large number of units that have to navigate in partially unknown dynamic worlds to pursue a goal. Navigation in such worlds can be complex and require much computational resources. Typically it is solved by using some sort of path planning algorithm, and a lot of research has been conducted to improve the performance of such algorithms in dynamic worlds. The main goal of this thesis is to investigate an alternative approach for RTS bots based on Artificial Potential Fields, an area originating from robotics. In robotics the technique has successfully been used for navigation in dynamic environments, and we show that it is possible to use Artificial Potential Fields for navigation in an RTS game setting without any need of path planning. In the first three papers we define and demonstrate a methodology for creating multi-agent potential field based bots for an RTS game scenario where two tank armies battle each other. The fourth paper addresses incomplete information about the game world, referred to as the fog of war, and show how Potential Field based bots can handle such environments. The final paper shows how a Potential Field based bot can be evolved to handle a more complex full RTS scenario. It addresses resource gathering, construction of bases, technological development and construction of an army consisting of different types of units. We show that Artificial Potential Fields is a viable option for several RTS game scenarios and that the performance, both in terms of being able to win a game and computational resources used, can match and even surpass those of traditional approaches based on path planning.
6
Asseburg, Christian. "A Bayesian approach to modelling field data on multi-species predator prey-interactions". Thesis, St Andrews, 2006. https://research-repository.st-andrews.ac.uk/handle/10023/174.
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7
Hagelbäck, Johan. "A multi-agent potential field based approach for real-time strategy game bots /". Karlskrona : Department of Systems and Software Engineering, School of Engineering, Blekinge Institute of Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00428.
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8
RAMASWAMY, EASWAR SINGANELLORE. "AN APPROACH TOWARDS HDL MODEL GENERATION FOR THE MULTI-TECHNOLOGY FIELD PROGRAMMABLE GATE ARRAY". University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1139339547.
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9
Engels, Philipp Simon [Verfasser], Alexander [Gutachter] Hartmaier e Ingo [Gutachter] Steinbach. "A multi-phase-field simulation approach incorporating finite, elasto-plastic deformations / Philipp Simon Engels. Gutachter: Alexander Hartmaier ; Ingo Steinbach". Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1102525499/34.
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10
Uusitalo, Tim. "A first approach in applying Artificial Potential Fields in Car Games". Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2480.
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In car racing simulation games, finishing first is the main goal. To reach that goal, it is required to go around a racing track, competing against other cars aiming for the same goal. Implementing a bot for doing so may have its difficulties, although using a technique called multi-agent systems combined with artificial potential field, let- ting the agents take care of subtasks like keeping the car on the track, minimize how much the car turns in a curvature and basics in navigation around the track, has showed that artificial potential fields very well fit the problem of driving a car in simulated car racing in a competitive way.Mobiltelefon: 0707422666
11
De, Nicola Antonio. "Development of molecular models of interfaces using a multi-scale hybrid particle-field approach: application to composite materials and biomembranes". Doctoral thesis, Universita degli studi di Salerno, 2014. http://hdl.handle.net/10556/1444.
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2012-2013The rule of the interface in systems including polymer composites and block-‐ copolymer interacting with biomembrane has been investigated by computational approach. In particular, for the polymer composite investigation, a system composed of PMMA embedding a silica nanoparticle of 3 nm (diameter), and an analogue system made of MMA and silica nanoparticle have been simulated. The structuration of both, PMMA and MMA close to the surface of the nanoparticle have been evaluated and calculated. As main results we found a stronger structuration of PMMA close to the nanoparticle respect to the MMA bulk. Pluronics based formulations are among the most successful nanomedicines and block-‐copolymer micelles including drugs are undergoing phase I/II studies as anticancer agents. Using coarse-‐grained models, molecular dynamics simulations of large-‐scale systems, modeling Pluronic micelles interacting with DPPC lipid bilayers, on the μs timescale have been performed. Simulations show, in agreement with experiments, a release of Pluronic chains from the micelle to the bilayer. This release changes the size of the micelle, moreover the presence of drug molecules inside the core of the micelle has a strong influence on this process. The picture emerging from the simulations is that the micelle stability is a result of an interplay between drug/micelle core and block-‐copolymer/bilayer interactions. The equilibrium size of the drug vector shows a strong dependency on the hydrophobicity of the drug molecules embedded into the core of the micelle. In particular, the radius of the micelle shows an abrupt increase in a very narrow range of drug molecule hydrophobicity. [edited by author]
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12
Keller, Michel. "Development of a multi-scale approach using chemical kinetics and reactive force field molecular dynamics to model soot formation and oxidation". Thesis, Institut polytechnique de Paris, 2019. http://www.theses.fr/2019IPPAE005.
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La présente étude décrit la mise au point d'une approche multi-échelles pour la modélisation des processus pendant la formation et l'oxydation précoce de la suie. Pour ce faire, des calculs cinétiques détaillés et macroscopiques en phase gazeuse sont utilisés, à l'aide de Chemkin, pour modéliser la combustion dans un réacteur fermé hétérogène dans des conditions diverses. Afin d'étudier l'impact de la température, du mélange de carburant et du rapport d'équivalence, une gamme de ces trois paramètres a été analysée. A partir des résultats des calculs de cinétique de réaction, des molécules pertinentes pour la formation de suie, appelées précurseurs de suie, ont été extraites et selon certains critères introduits dans des boîtes de simulation pour modéliser la formation de liaisons entre les molécules de précurseurs de suie par modélisation de la dynamique moléculaire du champ de force réactif. Afin d'obtenir la meilleure description de ces processus, trois champs de forces réactives sont évalués et comparés aux calculs ab initio. L'effet des paramètres de simulation utilisés dans l'approche de modélisation moléculaire du champ de force réactive, comme la température et le pas de temps, sur la précision des calculs est étudié et analysé pour confirmer les conditions optimales de modélisation. Les impacts de la température, du mélange de combustible et du rapport d'équivalence des calculs de Chemkin se traduisent par les compositions des précurseurs de suie et l'influence des différentes compositions a été étudiée sur le taux et la structure des molécules nouvellement formées. Les structures qui en résultent se comparent bien aux résultats expérimentaux précédemment rapportés. En outre, le taux de formation de liaison entre les précurseurs de suie est en corrélation linéaire avec la température à laquelle les précurseurs de suie sont produits, tandis que le combustible et le rapport d'équivalence n'ont pas d'incidence directe sur le taux de réaction. Les structures de croissance générées sont regroupées : 1) hydrocarbures polycycliques directement liés, 2) aliphatiquement liés et 3) hydrocarbures polycycliques péricondensés. On constate que la quantité de molecules aliphatiquement liés augmente avec la quantité de contenu aliphatique du mélange de carburant. De plus, un schéma de réaction est présenté montrant les voies de réaction les plus représentatives pour former des structures de croissance dans chaque classe de grumeaux et leur interconversion éventuelle. L'impact des différences structurelles dans les structures générées par la formation de liaisons entre les précurseurs de suie, sur leur cinétique d'oxydation est testé. Pour ces quatre oxydants différents, ce sont des radicaux oxygène, des radicaux hydroxyle, des radicaux hydroperoxyle et des radicaux méthoxy, qui sont introduits et les réactions modélisées. On constate que deux des oxydants introduits se décomposent et interagissent largement et ne réagissent donc pas avec les structures de suie naissantes formées. Pour les deux autres oxydants, la cinétique des réactions d'oxydation avec les structures de suie naissantes est étudiée. On peut montrer que la cinétique est différente pour les espèces qui possèdent une chaîne latérale aliphatique par rapport à celles qui n'en possèdent pas. Enfin, les énergies d'activation des réactions d'oxydation sont estimées, en traçant la constante de vitesse sur la température inverse. Les énergies d'activation trouvées se comparent bien aux expériences et autres études de modélisation de la littérature. Le présent travail - qui applique une approche combinée de calculs cinétiques macroscopiques en phase gazeuse et de simulations de champ de force atomique réactive - offre une bonne alternative pour obtenir des différences structurelles de suie naissante pour une large gamme de conditions thermodynamiques et des mécanismes de réaction détaillés pour les processus de formation et d'oxydation des suiesIn the present study bond formation reactions between soot precursors and their role in the soot inception process is investigated. The soot precursors were generated in macroscopic detailed gas-phase kinetic calculations and according to certain criteria introduced in simulation boxes to model bond formation between soot precursor molecules with reactive force field molecular dynam-ics modeling. The impacts of temperature, fuel mixture and equivalence ratio have been investigated on the rate and structure of the newly formed molecules. The resulting structures compare well to previously reported experimental results. Furthermore, the bond formation rate between PAH is found to be linearly correlated with the temperature at which the PAH precursors are generated, while fuel and equivalence ratio do not have a direct impact on the reaction rate. The generated growth structures are lumped in: 1) directly linked, 2) aliphatically linked and 3) pericondensed polycyclic hydrocarbons. It is found that the amount of aliphatically linked PAH increases with the amount of aliphatic content of fuel mixture. Finally, a reaction scheme is presented displaying the most representative reaction pathways to form growth structures in each lumping class and their eventual intercon-version. The present work – that applies a combined approach of macroscopic gas-phase kinetic calculations and atomistic reactive force field simulations – offers a good alternative to obtain structural differences of nascent soot for a broad range of thermodynamic conditions and detailed reaction mechanisms for soot inception process
13
Danisman, Betul. "Spinodal Instabilities In Symmetric Nuclear Matter Within A Density-dependent Relativistic Mean-field Approach". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613473/index.pdf.
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The nuclear matter liquid-gas phase transition is expected to be a signal of nuclear
spinodal instabilities as a result of density fluctuations. Nuclear spinodal
instabilities in symmetric nuclear matter are studied within a stochastic relativistic
density-dependent model in semi-classical approximation. We use two
parameterization for the Lagrange density, DDME1 and TW sets. The early
growth of density fluctuations is investigated by employing relativistic Vlasov
equation based on QHD and discussed the cluster size of the condensations
from the early growth of density correlation functions. Expectations are that
hot nuclear matter behaves unstable around &rhob &asymp
&rho
0/4 (below the saturation density) and at low temperatures. We therefore present our results at low temperature T=1 MeV and at higher temperature T=5 MeV, and also at a lower initial baryon density &rho
b = 0.2 &rho
0 and a higher value &rho
b = 0.4 &rho
0 where unstable behavior is within them. Calculations in density-dependent model are compared with the other calculations obtained in a relativistic non-linear model and in a Skyrme type nonivrelativistic model. Our results are consistent with them. Qualitatively similar results show that the physics of the quantities are model-independent. The size of clusterization is estimated in two ways, by using half-wavelength of the most unstable mode and from the width of correlation function at half maximum. Furthermore, the average speed of condensing fragments during the initial phase of spinodal decomposition are determined by using the current density correlation functions.
14
Freitas, Halley H. Eisner. "Leveling the Playing Field: a Multi-method Approach to Examine the Student Achievement Gap among High Poverty Middle Schools in Southern Arizona". Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228133.
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This dissertation contributes to the educational literature by providing new research on the achievement gap in the Southwest. For this study, a sequential mixed-methods approach was employed. The quantitative research assessed which factors influenced academic achievement among a 2012 high school graduating class (N=2,238) through analyses using correlation, ANOVA and HLM. Additionally, qualitative themes from 15 in-depth ethnographic teacher interviews and 116 teacher surveys from low income schools were triangulated with the quantitative findings to describe the multiple, interconnected factors that affected student achievement from the teacher's viewpoint. The low income schools in this study were defined as `hardship schools' because they had a high percentage of free and reduced lunch participants, a high minority population, low academic achievement, and frequent turnover in the administrative staff. The findings indicated that a statistically significant academic gap existed between high and low income schools. However, the longitudinal student standardized scores from elementary (5th grade) to high school (10th grade) revealed that the gap did not widen over time between high and low income students. Although students from low income schools lacked social capital and other resources available to their wealthier peers, they were still able to make equivalent academic growth, albeit at a lower performance level. It was argued that a pivotal reason that the gap did not widen was due to a dedicated teacher cadre that chose to work in low income middle schools. These teachers expressed a high level of self efficacy and cultural competency and identified with the students and the surrounding community. Their sense of identification came from one of three sources: similar ethnic background, including Latino culture and language; similar socio-economic upbringing, including poverty and the hardships associated with being an economic underclass; and/or cultural competency, where curiosity and love of diversity is emphasized. This identification helped teachers level the playing field by relating to students and making learning relevant to their environment.
15
Bergkvist, Markus, e Tobias Olandersson. "Machine learning in simulated RoboCup". Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik och datavetenskap, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3827.
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An implementation of the Electric Field Approach applied to the simulated RoboCup is presented, together with a demonstration of a learning system. Results are presented from the optimization of the Electric Field parameters in a limited situation, using the learning system. Learning techniques used in contemporary RoboCup research are also described including a brief presentation of their results.
16
Er, Nuray. "Nuclear Spinodal Instabilities In Stochastic Mean-field Approaches". Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610834/index.pdf.
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Nuclear spinodal instabilities are investigated in non-relativistic
and relativistic stochastic mean-field approaches for charge
asymmetric and charge symmetric nuclear matter. Quantum statistical
effect on the growth of instabilities are calculated in
non-relativistic approach. Due to quantal effects, in both symmetric
and asymmetric matter, dominant unstable modes shift towards longer
wavelengths and modes with wave numbers larger than the Fermi
momentum are strongly suppressed. As a result of quantum statistical
effects, in particular at lower temperatures, amplitude of density
fluctuations grows larger than those calculated in semi-classical
approximation.
Relativistic calculations in the semi-classical limit are compared
with the results of non-relativistic calculations based on
Skyrme-type effective interactions under similar conditions. A
qualitative difference appears in the unstable response of the
system: the system exhibits most unstable behavior at higher baryon
densities around $rho_{B}=0.4 rho_{0}$ in the relativistic
approach while most unstable behavior occurs at lower baryon
densities around $rho_{B}=0.2 rho_{0}$ in the non-relativistic
calculations.
17
Páez, Avilés Cristina. "Innovation on Nanoscience: Processes and Ecosystems of Innovation with a multi-KET approach to foster Technology Transfer and Commercialization of Nanotechnologies in the Field of Healthcare". Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/401502.
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Transferring nanotechnology into marketable products and services is still considered a major challenge. In Europe, this issue has been identified as a weakness, not only for nanotechnology, but also for the other five Key Enabling Technologies (KETs), strategic for the economic growth of the region. In this regard, the current European Funding Programme Horizon 2020 is making great efforts with their action lines in order to prioritize the industrial implementation of KETs, and in this manner, address major economic and societal needs. This initiative is also fostering the cross-fertilization of KETs, since it has been determined that the sum of individual technologies increases the potential for innovation, optimizes technological development, and allows the creation of new markets. This thesis has been developed on the basis of this scenario. The aim is to analyse innovation and technology transfer challenges for the successful commercialization of nanotechnologies by emphasizing the process of cross-fertilization of KETs. The research is focused on healthcare due to the great impact that nano-scale is having on this field. For this reason, the present work has considered two approaches: from a technological perspective and from a management perspective. The analysis is comprised of a state-of-the-art and theoretical framework review, followed by a multiple case-study approach where several nano-enabled sensor-based devices are analysed at diverse levels of technological maturity. In addition, an empirical study of European nano-related innovation projects was undertaken in order to determine which projects’ characteristics are influencing the creation of technological diversity; a critical element for the long-term success of an emergent technology. Finally, project leaders were interviewed in order to gain insights about the managerial strategies that are boosting the process of cross-fertilization of KETs.
Findings have shown that a multi-disciplinary, collaborative and integrated community of innovators is necessary for the effective transference and commercialization of multi-KET nanotechnologies. Additionally, the degree of multi-disciplinary projects was identified as significantly contributing to the creation of technological diversity. Furthermore, higher levels of cross-fertilization were found in market and customer-oriented projects, with actors strongly
motivated to search for ideas from broad informal networks, and where technological knowledge is moderately heterogeneous. Lastly, it has been found that the cross-fertilization of KETs is boosted by actors with a high involvement of nanotechnologies in their industries. With these outcomes, this thesis has sought to contribute to the analysis of the successful transference and commercialization of multi-KET nanotechnologies in the field of healthcare by understanding the processes and ecosystems of innovation.
The outcomes of this thesis have sought to contribute to the analysis of the successful transference and commercialization of multi-KET in the field of nanotechnologies applied to healthcare by understanding the processes and ecosystems of innovation. Accordingly, it is aimed to contribute to the reduction of the gap between research and the marketplace and to expand the knowledge of current interest regarding innovation ecosystems of emergent technologies, regional systems of innovation and strategic innovation management.La transferència de productes i serveis basats en la nanotecnologia representa un gran repte. A Europa, aquest fet ha estat identificat com a punt dèbil, no només per a les nanotecnologies si no també per a les altres cinc tecnologies facilitadores transversales (KETs per les seves sigles en anglès), considerades estratègiques pel creixement econòmic de la regió. En aquest sentit, l’actual programa marc Europeu Horitzó 2020 està redirigint les seves línies d’acció per a prioritzar la implementació de les KETs i, d’aquesta manera, poder fer front a les necessitats econòmiques i socials més imperatives d’Europa. Aquesta iniciativa també pretén fomentar la fertilització creuada de les KETs, ja que s’ha establert que la suma de tecnologies individuals incrementa el potencial d’innovació, optimitza el desenvolupament de tecnologies i permet la creació de nous mercats. Sobre aquesta base es desenvolupa aquest treball d’investigació, el qual té la finalitat d’analitzar els reptes relacionats amb la innovació i la transferència tecnològica per a assolir amb èxit la comercialització de les nanotecnologies, posant de relleu el procés de fertilització creuada de les KETs en el camp de la salut. Amb aquesta finalitat, s’han considerat dues aproximacions: d’una banda una perspectiva tecnològica i, de l’altra, una perspectiva de gestió de la innovació. Els resultats obtinguts fan aportacions per l’anàlisi i identificació dels reptes que cal afrontar per a una favorable transferència i comercialització de les nanotecnologies multi-KET en el camp de la salut mitjançant la comprensió dels processos i ecosistemes d’innovació i, d’aquesta manera, contribuir a la reducció de la separació entre el laboratori i el mercat. Finalment també es pretén ampliar el coneixement sobre temàtiques d’interès actual respecte els ecosistemes d’innovació de les tecnologies emergents, els sistemes regionals d’innovació i la gestió estratègica de la innovació tecnològica.
18
Bazin, Clément. "Numerical and experimental studies of two-phase flows interacting with a bundle of tubes". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAX106.
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Les générateurs de vapeur (GV) des centrales nucléaires sont composés de faisceaux de tubes soumis à des écoulements diphasiques eau-vapeur. Les vibrations liées à cette interaction peuvent induire des dommages (fatigue et usure par frottement et chocs) pouvant entraîner de graves conséquences pour la sûreté nucléaire.Dans le cadre de la prévention des risques vibratoires des tubes de GV des études expérimentales sont réalisées à l'aide de faisceaux analytiques de tubes droits soumis à un écoulement transverse diphasique.En parallèle, il est également important de développer un outil de simulation numérique permettant d'accéder à des données et des informations difficilement mesurables.L'objectif de cette thèse est donc de simuler l’interaction entre un fluide diphasique et une structure rigide (tube unique ou faisceau de tubes), à l'aide du code NEPTUNE_CFD. Ces simulations doivent permettre de reproduire le chargement mécanique exercé par le fluide sur les tubes. La modélisation employée dans cette thèse repose sur un modèle à deux-fluides - trois-champs, comprenant un champ liquide continu, un champ de gaz dispersé, composé de bulles peu déformées, et un champ hybride dispersé-continu pour tenir compte des bulles très déformées et des poches de gaz. La première partie de ce travail s'est concentrée sur la validation du couplage diphasique-turbulence liquide ainsi que sur la modification et l'adaptation de la modélisation pour mieux prendre en compte la présence d'une structure immergée. De nouvelles modélisations pour la force de dispersion turbulente, les termes sources de coalescence et fragmentation, la masse ajoutée et le critère d'activation du champ continu ont été proposées. Dans la deuxième partie de ce travail, nous avons simulé l’écoulement diphasique autour d’un tube unique fixe, afin d'en extraire une physique sous-jacente et d'identifier ses limites et lacunes. Enfin, dans la dernière partie de ce travail, nous avons simulé l’interaction d’un écoulement diphasique avec un faisceau de tubes rigides. Les résultats numériques ont été comparés aux mesures expérimentales. Cette approche nous a permis de justifier l'intérêt de notre modélisation, de trouver des similitudes entre les résultats numériques et expérimentaux, tout en proposant des pistes d'améliorationThe steam generators (SG) in nuclear power plants are made up of bundles of tubes subjected to two-phase water-steam flows. Vibrations related to this interaction can cause damage (fatigue, wear due to friction and shocks) that can lead to serious consequences for nuclear safety.In the context of preventing vibrational risks in SG tubes, experimental studies are conducted using analytical bundles of straight tubes subjected to transverse two-phase flow. In parallel, it is also important to develop a numerical simulation tool to access data and information that are difficult to measure.The goal of this work is to simulate the interaction between a two-phase fluid and a rigid structure (single tube or bundle of tubes) using the NEPTUNE_CFD code. These simulations aim to reproduce the mechanical loading exerted by the fluid on the tubes. The modeling used in this work is based on a two-fluid - three-field model, including a continuous liquid field, a dispersed gas field made up of slightly deformed bubbles, and a dispersed-continuous hybrid field to account for highly deformed bubbles and gas pockets. The first part of this work focused on the validation of the two-phase liquid-turbulence coupling as well as the modification and adaptation of the modeling to better account for the presence of an immersed structure. New models for turbulent dispersion force, source terms of coalescence and break-up, added mass, and the activation criterion of the continuous field were proposed. In the second part of this work, we simulated the two-phase flow around a fixed single tube to extract underlying physics, and identify its limitations and shortcomings. Finally, in the last part of this work, we simulated the interaction of a two-phase flow with a bundle of rigid tubes. The numerical results were compared to experimental measurements. This approach allowed us to justify the relevance of our modeling, find similarities between numerical and experimental results, while also suggesting areas for improvement
19
Smedslund, Katja. "Les violences conjugales à l'égard des femmes en Europe : analyse socio-politique contemporaine et perspectives d'action dans l'Union Européenne". Paris 3, 2008. http://www.theses.fr/2008PA030127.
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Suite à une prise de conscience internationale au travers notamment des conférences mondiales des Nations-Unies sur les femmes, marqué par le tournant de la Conférence de Pékin en 1995, la question des violences conjugales à l’égard de femmes dans l’Union européenne et de son éradication se pose comme un enjeu de société actuel et complexe. Cette prise de conscience européenne s’opère plus spécifiquement à partir la fin des années 90 et concerne l’ensemble des instances européennes notamment à travers les travaux de l’UE, du Conseil de l’Europe (l���ensemble des pays de l’UE étant membres du Conseil de l’Europe) et du Lobby Européen des Femmes. Un des outils les plus importants mis en oeuvre au niveau l’Union européenne en 1997, le programme Daphné, fait clairement état d’une approche pluridisciplinaire dans une perspective européenne. L’ensemble de ces travaux nécessite au préalable une étude approfondie de l’ampleur du phénomène, de son périmètre et de ses causes profondes reliées à une violence de genre afin de permettre une analyse critique des politiques européennes et nationales de lutte mises en oeuvre. Cette approche permettra de s’interroger à travers une dimension sociopolitique sur l’importance des politiques pluridisciplinaires et sur la possibilité et la pertinence d’une harmonisation européenne des politiques et législations pour lutter efficacement contre ce fléau de grande ampleurFollowing international awareness through United Nations World Conferences on Women, marked by the turn of the Beijing Conference in 1995, the issue of intimate partnership violence against women in the European Union and its eradication arises as a complex and current challenge to the society. This European awakening takes place more specifically starting from the end of the Nineties and concerns all European bodies in particular through the works of the EU, the Council of Europe (all EU countries being members of the Council of Europe) and the European Women Lobby. One of the most important tools implemented at the European Union level in 1997, the program Daphne, clearly gives a report on a multi-field approach from the European point of view. The whole of this work requires, to begin with, a thorough study of the width of the phenomenon, its perimeter and its major causes related to gender violence in order to allow a critical analysis of the implemented European and national policies against intimate partnership violence. This approach will allow us, through a sociopolitical dimension, to reflect upon the importance of multi-field measures and the possibility and the relevance of a European harmonization of the policies and legislations to fight efficiently against this huge plague
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Lv, Duchao. "A Multi-Scale Simulation Approach to Deformation Mechanism Prediction in Superalloys". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469009668.
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Ducroix, Alice. "Multi-scale dynamics of water inside boehmite : a NMR approach". Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS575.pdf.
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Dans plusieurs domaines de la chimie, les catalyseurs occupent une place importante puisqu’ils assurent une réaction plus rapide, une meilleure sélectivité et réduisent l’utilisation de matières premières. L’industrie s’est récemment tournée vers les catalyseurs hétérogènes dont la récupération est plus facile. Ces catalyseurs sont constitués d’un support poreux et de sites actifs répartis en surface à travers la porosité du support. Pour optimiser pleinement le support, de récentes études ont abordé la question de l’accessibilité des molécules aux sites réactionnels. Cela passe notamment par la compréhension de la mobilité des solvants et du trafic moléculaire dans le milieu poreux. Le support catalytique hétérogène par excellence est l’alumine γ, obtenue par calcination topotactique de la boehmite. La texture et les propriétés poreuses sont principalement héritées de la boehmite, en particulier de l’organisation des agglomérats et des agrégats. Cette organisation est principalement obtenue lors des étapes de mise en forme (peptisation) et d’extrusion lors du procédé d’obtention de l’alumine. Le transport et la dynamique multi-échelle à l’intérieur de la boehmite seront étudiés au cours de ces deux étapes, notamment comment les molécules de solvant (ici l’eau) se déplacent à l’intérieur de ce matériau et quels mécanismes pilotent la dynamique. Afin d’étudier cette dynamique, des suspensions de boehmite avec différentes textures initiales seront obtenues par dialyse et stress osmotique et les extrudés par une voie industrielle usuelle. Le transport autour de l’interface des agrégats et des parois des pores (échelle nanométrique) sera étudié par Résonance Magnétique Nucléaire à champ cyclé sur une échelle de temps de la nanoseconde à la microseconde. La diffusion a été suivie à la surface de ces objets et s’est avérée être régie par une forte interaction avec la surface, en particulier la courbure de surface. Il a notamment été trouvé un temps de séjour important (≈ 8μs) des molécules d’eau à la surface et un coefficient de diffusion de surface lent (< 3. 10-10 m2/s). À l’échelle du micron, la dynamique est étudiée par RMN à gradient de champ pulsé sur une échelle de temps de la milliseconde à la seconde. La diffusion semble être gouvernée par la structure topologique résultant de l’organisation complexe des agrégats et des agglomérats (connectivité des pores, anisotropie, etc.)For several domains of chemistry, catalyst take up a significant place since they ensure a quicker reaction, a better selectivity and reduce the use of raw material. Industry has recently turned to heterogeneous catalyst whose recovery is easier. These catalysts consist of a porous support and active sites distributed on the surface through the support porosity. To fully optimized the support, recent studies have tackled the issue of accessibility of molecules to the reaction sites. This one includes the comprehension of solvent mobility and molecular traffic in the porous medium. The heterogeneous catalytic support par excellence is γ-alumina, obtained by a topotactic calcination of boehmite. Texture and porous properties are then mostly inherited from boehmite, especially from the organization of agglomerates and aggregates. This organization is mostly obtained during the kneading, (peptization) and the extrusion steps of the boehmite-to-alumina process. Transport and multi-scale dynamics inside boehmite will then be investigated during these two steps particularly how solvent molecules (here water) move inside this material and what mechanisms drive the dynamics . To study this dynamics, boehmite suspensions with different initial textures will be obtained through dialysis and osmotic stress and extrudates from the traditional industrial route. Transport around the interface of aggregates and pore walls (nanometric scale) will be studied by Field Cycling Nuclear Magnetic Resonance on a ns-µs time scale. Diffusion was followed at the surface of such objects and was found to be governed by a strong interaction with the surface and especially the surface curvature. A consequent residence time (≈ 8µs) of water molecules at the surface and a rather slow surface diffusion coefficient (< 3. 10-10 m2/s) was exhibited. At the micron scale, dynamics is investigated by Pulsed Field Gradient NMR on a millisecond to second time scale. Diffusion seems to be driven by the topological structure imposed by the complex organization of aggregates and agglomerates (connected pore, anisotropy, etc.)
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Demange, Gilles. "Mise en oeuvre d'une approche multi-échelles fondée sur le champ de phase pour caractériser la microstructure des matériaux irradiés : application à l'alliage AgCu". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015ECAP0048/document.
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Anticiper l’évolution de la microstructure d’un matériau en condition d’usage est d’une importance cruciale pour l’industrie. Cette maîtrise du vieillissement nécessite une compréhension claire des mécanismes sous-jacents, qui agissent sur une large gamme d’échelles spatiales et temporelles. Dans cette optique, ce travail de thèse a choisi d’appliquer la méthode de champ de phase qui, en raison du saut d’échelle qu’elle réalise naturellement, est un outil intensivement employé dans le domaine des matériaux, pour prédire l’évolution en temps long de la microstructure. L’enjeu de l’étude a été d’étendre cette méthode à un système porté loin de l’équilibre thermodynamique, en particulier en présence d’irradiation. Nous avons ainsi adopté le formalisme du mélange ionique, introduit par Gras-Marti pour décrire le mélange balistique au sein d’une cascade de déplacements. Par l’utilisation conjointe d’un schéma numérique et d’une approche analytique, il nous a été possible d’établir le diagramme de phase générique d’un matériau irradié. Nous avons ensuite étudié le vieillissement de l’alliage binaire test AgCu sous irradiation, par l’utilisation conjointe de la méthode du champ de phase et d’approches atomistiques, dans une démarche multi-échelles. En fixant les paramètres de contrôle que sont le flux d’irradiation et la température, il nous a ainsi été possible de prédire la taille,la concentration ainsi que la distribution spatiale des nodules de cuivre produits sous irradiation dans cet alliage. La connaissance de ces informations a permis de simuler un diagramme de diffraction en incidence rasante, directement comparable aux diagrammes expérimentauxIt is of dramatic matter for industry to be able to predict the evolution of material microstructure under working conditions. This requires a clear understanding of the underlying mechanisms, which act on numerous space and time scales. Because it intrinsically performs a scale jump, we chose to use a phase field approach, which is widely used amidst the condensed matter community to study the aging of materials. The first challenge of this work was to extend this formalism beyond its thermodynamic scope and embrace the case of far from equilibrium systems when subjected to irradiation. For that purpose, we adopted the model of ion mixing, developed by Gras Marti to account for ballistic exchanges within a displacements cascade. Based on a numerical scheme and ananalytical method, we were able to describe the generic microstructure signature for materials under irradiation.We then applied this formalism to the particular case of the immiscible binary alloy AgCu.With the joined use of the phase field approach and atomistic methods, we managed to predict how the temperature and the irradiation flux tailor the main microstructure features such as the size, the concentration and the distribution of copper precipitates. This eventually allowed us to simulate a diffraction pattern in grazing incidence, which is directly comparable to experimental ones
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Le, Guillou Fanny. "Approche systémique de la haie, pour passer de sa multifonctionnalité à la conception de plans de gestion". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC003.
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La haie bocagère, au travers des nombreuses fonctions qu’elle possède, intervient dans les problématiques engendrées par le changement climatique actuel. Cependant, l’évolution radicale du paysage agraire au cours du XXe siècle a conduit à un arasement massif des haies ces 60 dernières années. Bien que ses intérêts économiques, écologiques et socio-culturels soient avérés, ils ne sont pas reconnus par tous les acteurs et la dégradation du bocage se poursuit. Les conséquences de cette disparition font peu à peu prendre conscience de la nécessité de préserver les haies. Des initiatives apparaissent à diverses échelles et une forte demande d’outils de diagnostic et d’évaluation qualitative émerge. Or, il y a un manque de cohérence territoriale de ces initiatives et un manque de données permettant la caractérisation précise de la haie.Notre recherche s’attèle à l’étude systémique des rôles de la haie et de sa place dans l’espace sur le territoire bas-normand à partir d’une démarche multi-échelle afin de comprendre les raisons de la dégradation toujours à l’œuvre et de proposer des solutions. Cette étude vise à proposer des outils de caractérisation de la haie, de façon à intégrer une vision systémique des services rendus par cette dernière afin de développer des plans de gestion multifonctionnels transposables. Trois approches complémentaires permettent d’aboutir à cet outil. Pour commencer, un modèle systémique est réalisé à partir de la bibliographie à la fois dense, pluridisciplinaire et très éclatée. Puis, une approche quantitative visant à caractériser l’évolution et les fonctionnalités des linéaires, estimer les capacités de production et analyser l’organisation spatiale des réseaux des haies est mise en place. Enfin, une approche qualitative permettant de recueillir la parole des acteurs (populations et gestionnaires) pour mieux appréhender la place des haies dans le paysage rural actuel est réalisée. Pour terminer, les résultats de ces approches ont été utilisés pour l’élaboration du modèle Ger’haies, un modèle sous Système Multi-Agent destiné à être employé comme outil de médiation pour la mise en place de PGMH sur le territoire d’une collectivitéHedgerow, across its many functions, takes action in the problems generated by the current climate change. However, the radical agricultural landscape evolution during the 20th century led to massive removal of hedgerows in the past 60 years. Although its economic, ecological and socio-cultural interests are proved, they are not recognised by all the actors and the hedgerow density keep decreasing. The consequences of this disappearance gradually raise awareness of the need to preserve hedgerows. Some initiatives appears at various scales with an increasing demand for diagnostic tools and qualitative evaluation. Yet, the territorial cohesion is missing and there is a lack of data to precisely characterise the hedge.Our research gets on with the systemic study of roles and functions of hedgerow and its place in space on the bas-normand territory from a multi-scale approach in order to understand the reasons of deterioration still at work and suggest solutions. This study aims to propose tools to characterise the hedge, so as to integrate a systemic vision of the services in order to develop multifunctional management plans that can be spatially transposed. Three complementary approaches lead to this tool. The first purpose of this work is to realise a systemic model from a substantial, multidisciplinary and very fragmented bibliography. Then, a quantitative approach has been set up to characterise the evolution and functionality of the hedgerows, estimate production capacities and analyse the spatial organisation of hedgerow networks. In a third step, a qualitative approach is carried out to collect the actor perception (populations and managers) and to better understand the place of hedges in the current rural landscape. Finally, the results of these approaches have been used to develop the Ger'haies model, an agent-based model intended to be used as a mediation tool for the establishment of PGMH on a municipal territory
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Demeyère, Caroline. "Gouvernance publique et collaboration gouvernements-associations dans l’action publique : approche ethnographique des dynamiques relationnelles dans le champ des politiques d’égalité entre les femmes et les hommes (1981-2020)". Thesis, Paris 10, 2020. http://www.theses.fr/2020PA100068.
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Cette thèse propose d’étudier la collaboration entre acteurs gouvernementaux et associations pour la conduite de l’action publique, conçue comme un processus de transformation des modalités relationnelles conduit par les pratiques des acteurs et leurs interactions. Un cadre théorique néo-institutionnaliste centré sur les concepts de Champ d’action stratégique, de travail institutionnel et d’interactions est mobilisé afin d’articuler le niveau micro des pratiques collaboratives, la collaboration émergeant à l’échelle inter-organisationnelle et le niveau macro de la gouvernance publique. La méthodologie adoptée est une ethnographie organisationnelle, avec une immersion de trois années dans un champ réunissant acteurs publics et associatifs autour des politiques publiques d’égalité entre les femmes et les hommes dans une région française. La doctorante a utilisé une double entrée académique et associative pour observer les dynamiques relationnelles entre acteurs gouvernementaux et associatifs. Elle a occupé des responsabilités administratives et exercé des activités bénévoles dans une association de formation à l’égalité professionnelle. Elle a aussi été membre d’une structure de collaboration ouverte entre l’État et des acteurs de l’Économie sociale et solidaire dont l’objet est de promouvoir l’égalité entre les femmes et les hommes par et dans la vie associative. L’enquête combine une perspective longitudinale rétrospective en retraçant l’évolution des relations gouvernements-associations depuis les premières politiques publiques régionales en 1981 et une étude de la collaboration gouvernements-associations comme processus en cours de 2016 à 2020. Trois résultats sont exposés. Premièrement, il existe une diversité de stratégies associatives et gouvernementales adoptées à l’égard de la collaboration, explicables par les positions des acteurs au sein des champs et les impacts organisationnels de la collaboration. Nous en proposons une typologie. Deuxièmement, la gouvernance d’une collaboration doublement encastrée dans la logique hiérarchique et la logique de marché soulève des difficultés et des paradoxes pour les acteurs. Nous décrivons le travail qu’ils mettent en œuvre pour articuler la collaboration aux logiques préexistantes dans l’environnement institutionnel. Troisièmement, l’avènement d’un paradigme collaboratif de l’action publique distinct du New Public Management apparaît conditionné à une transformation du rôle, des responsabilités et des modes de fonctionnement des acteurs publics, des outils de gestion des relations gouvernements-associations et des modes de financement de l’action publique. L’éthique du management public collaboratif à construire devrait être centrée sur la valorisation et la préservation des différences des partenaires associatifs et la redéfinition de la dialectique consensus/conflitThis thesis proposes to study the collaboration between governments and non-profit organizations in policy-making, conceived as a process in which existing intersectoral relationships are transformed by the actors' practices and their interactions. A neo-institutionalist theoretical framework, focusing on the concepts of Strategic Action Field, institutional work and interactions, is used to articulate the micro-level of collaborative practices with collaboration emerging at a meso-level, and with public governance at a macro-level. The adopted methodology is an organizational ethnography, with a 3-year immersion in a field bringing together public and non-profit actors around gender equality public policy making in a French region. The doctoral student has used a double academic and non-profit position to observe relational dynamics between governmental and non-profit actors. She has held administrative responsibilities and has volunteered in a professional equality training association. She was also a member of an open collaboration structure between the State and the Social and Solidarity Economy actors whose aim is to promote equality between women and men through and in associative life. The study combines a retrospective longitudinal perspective by tracing the evolution of government-association relations from the first regional public policies in 1981 with a study of government-association collaboration as an ongoing process between 2016 and 2020. Three results are exposed. First, there is a diversity of associative and governmental strategies adopted with regards to collaboration, explained by the positions of actors within the fields and the organizational impacts of collaboration. A typology of these strategies is proposed. Secondly, the governance of collaboration is doubly embedded in a hierarchical and a market logic, which raises difficulties and paradoxes for the actors. Their work to articulate collaboration with preexisting logics in their institutional environment is described. Thirdly, the advent of a collaborative paradigm of public action separate from New Public Management appears to be conditioned by the transformation of public actors’ role, responsibilities and working methods, of intersectoral relationships management tools, and of public policies funding. The construction of a collaborative public management ethic should focus on valuing and preserving the diversity and differences of associative partners and on the redefinition of the consensus/conflict dialectic
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Völker, Benjamin [Verfasser]. "Phase-field modeling for ferroelectrics in a multi-scale approach / von Benjamin Völker". 2010. http://d-nb.info/1010373668/34.
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Adolph, Inga Winny. "Remote sensing large-scale surface structures in the Wadden Sea. Application of satellite SAR data (TerraSAR-X) to record spatial distribution and dynamics of habitats and geomorphic structures for monitoring and long-term ecological research". Doctoral thesis, 2021. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-202104064249.
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The Wadden Sea off the coast of the southern North Sea is the largest coherent area of tidal flats worldwide. As a highly productive ecosystem it is of global importance, e.g. as nursery for fish and as a feeding and resting area for 10 – 12 million migratory birds following the East Atlantic Flyway. The outstanding ecological significance of this region corresponds to a high level of protection by EU directives and national law and by inscription as UNESCO World Heritage Site, all of which requires regular monitoring and assessment. Apart from the ecological aspects, the Wadden Sea is also of great importance for coastal protection. To survey the extensive, often inaccessible tidal area, remote sensing is essential and while mainly airborne techniques have been carried out for decades, now high-resolution satellite-borne sensors open up new possibilities relevant for monitoring and long-term ecological research. Especially satellite synthetic aperture radar (SAR) sensors offer a high availability of acquisitions as they operate largely independently of daylight and weather. The aim of the studies presented here was to explore the use of data from the TerraSAR-X satellite to record geomorphological structures and habitats for Wadden Sea Monitoring. More than 100 TerraSAR-X acquisitions from 2009 to 2016 were analyzed to distinguish various and variable surface types continuously influenced by tidal dynamics in the main study area, the tidal flats near the island of Norderney.
Visual image interpretation supported by extensive in-situ verification proved to be a suitable and unsophisticated approach which is unspecific enough to identify mussel beds, fields of shell-detritus, gully structures, mud fields, and intertidal bedforms in the upper flats of the East Frisian Islands. The method proved to be robust against changes in geometry of acquisition and environmental influences. Several time series of TerraSAR-X data enabled to follow inter-annual and seasonal dynamics as well as event effects (Adolph et al. 2018). The high-frequency TerraSAR-X data revealed novel evidence of an intertidal bedform shift in an easterly direction during the study period. To this aim, an unsupervised ISODATA classification of textural parameters was developed to vectorize and compare the bedforms positions in a GIS (Adolph et al. 2017a). The same intertidal bedform area was chosen as test-site for comparison of different remote sensing methods, namely airborne lidar, satellite-based radar (TerraSAR-X) and electro-optical sensors (RapidEye) (Adolph et al. 2017b).
High-resolution SAR data offer a relevant component for Wadden Sea Monitoring and Research, as they provide reliable, regular data with a high repetition rate. In particular, habitats with noticeable surface roughness, specific structures and textures are well reflected. Geomorphic Structures and their dynamics can be observed indirectly via detection of residual water trapped within. A comprehensive concept for Wadden Sea Monitoring however, requires automatized classifications and an integrative, multi-sensor approach (SAR, LIDAR, multi-spectral data, drones) in which different and complementary information, coverage and resolutions (spatial and temporal) contribute to an overall picture.
The studies were carried out as part of the joint research project “Scientific monitoring concepts for the German Bight” (WIMO), jointly funded by the Ministry of Environment, Energy and Climate Protection (NMU) and the Ministry of Science and Culture (NMWK) of the Federal State of Lower Saxony. The findings have been published in Geo-Marine Letters 37/2 (2017) and in Remote Sensing 10/7 (2018).