• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 66
  • 33
  • 26
  • 22
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 171
  • 69
  • 43
  • 29
  • 22
  • 21
  • 20
  • 18
  • 18
  • 17
  • 16
  • 16
  • 15
  • 15
  • 14
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Reificação de objetos concorrentes / Reification of concurrent objects

Menezes, Paulo Fernando Blauth January 1997 (has links)
Autômatos não-seqüenciais constituem um domínio semântico categorial do tipo não-intercalação para sistemas reativos, comunicantes e concorrentes.É baseado em sistemas de transições etiquetados, inspirado em "Redes de Petri são Monóides" de Meseguer e Montanari, onde as operações de sincronização e encapsulação são funtoriais e as reificações constituem uma classe de morfismos especiais. Do que se tem conhecimento, é o primeiro modelo de concorrência a satisfazer a composicionalidade diagonal, ou seja, onde as reificações compõem (verticalmente) e distribuem-se sobre a composição paralela (verticalmente). Adjunções entre autômatos não-seqüenciais, redes de Petri e autômatos seqüenciais são introduzidas estendendo a abordagem de Winskel, Nielsen e Sassone onde é proposta uma classificação formal para modelos de concorrência. Dos passos que envolvem a passagem de um modelo para outro, pode-se inferir que os autômatos não-seqüenciais são mais concretos do que as redes de Petri e os autômatos seqüenciais. Para experimentar o domínio semântico proposto, é dada semântica a uma linguagem concorrente, baseada nos objetos, denominada Náutilus. Trata-se de uma versão simplificada e revisada da linguagem de especificação orientada aos objetos GNOME, onde são introduzidos algumas facilidades especiais, inspiradas no domínio semântico, como a reificação e a agregação. Neste contexto, a composicionalidade diagonal é uma propriedade essencial para dar a semântica. / Nonsequential automata constitute a non-interleaving categorial semantic domain for reactive, communicating and concurrent systems. It is based on labeled transition systems, inspired by Meseguer and Montanari's "Petri Nets are Monoids", where synchronization and encapsulation operations are functorial and a class of morphisms stands for reification. It is, for our knowledge, the first model for concurrency which satisfies the diagonal compositionality requirement, i. e., reifications compose (vertical) and distribute over the parallel composition (horizontal). Adjunctions between nonsequential automata, Petri nets and sequential automata are provided extending the approach of Winskel, Nielsen and Sassone where a scene for a formal classification of models for concurrency is set. The steps of abstraction involved in moving between models show that nonsequential automata are more concrete than Petri nets and sequential automata. To experiment with the proposed semantic domain, a semantics for a concurrent, object-based language named Nautilus is given. It is a simplified and revised version of the object-oriented specification language GNOME, introducing some special features inspired by the semantic domain such as reification and aggregation. The diagonal compositionality is an essential property to give semantics in this context.
82

Reificação de objetos concorrentes / Reification of concurrent objects

Menezes, Paulo Fernando Blauth January 1997 (has links)
Autômatos não-seqüenciais constituem um domínio semântico categorial do tipo não-intercalação para sistemas reativos, comunicantes e concorrentes.É baseado em sistemas de transições etiquetados, inspirado em "Redes de Petri são Monóides" de Meseguer e Montanari, onde as operações de sincronização e encapsulação são funtoriais e as reificações constituem uma classe de morfismos especiais. Do que se tem conhecimento, é o primeiro modelo de concorrência a satisfazer a composicionalidade diagonal, ou seja, onde as reificações compõem (verticalmente) e distribuem-se sobre a composição paralela (verticalmente). Adjunções entre autômatos não-seqüenciais, redes de Petri e autômatos seqüenciais são introduzidas estendendo a abordagem de Winskel, Nielsen e Sassone onde é proposta uma classificação formal para modelos de concorrência. Dos passos que envolvem a passagem de um modelo para outro, pode-se inferir que os autômatos não-seqüenciais são mais concretos do que as redes de Petri e os autômatos seqüenciais. Para experimentar o domínio semântico proposto, é dada semântica a uma linguagem concorrente, baseada nos objetos, denominada Náutilus. Trata-se de uma versão simplificada e revisada da linguagem de especificação orientada aos objetos GNOME, onde são introduzidos algumas facilidades especiais, inspiradas no domínio semântico, como a reificação e a agregação. Neste contexto, a composicionalidade diagonal é uma propriedade essencial para dar a semântica. / Nonsequential automata constitute a non-interleaving categorial semantic domain for reactive, communicating and concurrent systems. It is based on labeled transition systems, inspired by Meseguer and Montanari's "Petri Nets are Monoids", where synchronization and encapsulation operations are functorial and a class of morphisms stands for reification. It is, for our knowledge, the first model for concurrency which satisfies the diagonal compositionality requirement, i. e., reifications compose (vertical) and distribute over the parallel composition (horizontal). Adjunctions between nonsequential automata, Petri nets and sequential automata are provided extending the approach of Winskel, Nielsen and Sassone where a scene for a formal classification of models for concurrency is set. The steps of abstraction involved in moving between models show that nonsequential automata are more concrete than Petri nets and sequential automata. To experiment with the proposed semantic domain, a semantics for a concurrent, object-based language named Nautilus is given. It is a simplified and revised version of the object-oriented specification language GNOME, introducing some special features inspired by the semantic domain such as reification and aggregation. The diagonal compositionality is an essential property to give semantics in this context.
83

Modélisation par automate cellulaire des phénomènes diagénétiques des plateformes carbonatées. Calibration et paramétrisation à partir de deux cas d'études : l'Urgonien du Vercors (Crétacé inférieur, SE France) et les Calcaires Gris du Mont Compomolon (Lias, NE Italie). / Modelling of diagenetic overprints in carbonate platforms using gas automata. Calibration and definition of key parameters by data from two outcropping analogues : the Urgonian in Vercors (SE France) and in the Calcari Grigi of the Mont Comopomolon (NE Italy).

Planteblat, Caroline 05 June 2013 (has links)
Une fois déposé, un sédiment est affecté au cours de son enfouissement par un ensemble de processus, regroupé sous le terme diagenèse, le transformant parfois légèrement ou bien suffisamment pour le rendre méconnaissable. Ces modifications ont des conséquences sur les propriétés pétrophysiques qui peuvent être positives ou négatives, c'est-à-dire les améliorer ou bien les détériorer. Une voie alternative de représentation numérique des processus, affranchie de l'utilisation des réactions physico-chimiques, a été adoptée et développée en mimant le déplacement du ou des fluides diagénétiques. Cette méthode s'appuie sur le principe d'un automate cellulaire et permet de simplifier les phénomènes sans sacrifier le résultat et permet de représenter les phénomènes diagénétiques à une échelle fine. Les paramètres sont essentiellement numériques ou mathématiques et nécessitent d'être mieux compris et renseignés à partir de données réelles issues d'études d'affleurements et du travail analytique effectué. La représentation des phénomènes de dolomitisation de faible profondeur suivie d'une phase de dédolomitisation a été dans un premier temps effectuée. Le secteur concerne une portion de la série carbonatée de l'Urgonien (Barrémien-Aptien), localisée dans le massif du Vercors en France. Ce travail a été réalisé à l'échelle de la section afin de reproduire les géométries complexes associées aux phénomènes diagénétiques et de respecter les proportions mesurées en dolomite. De plus, la dolomitisation a été simulée selon trois modèles d'écoulement. En effet, la dédolomitisation étant omniprésente, plusieurs hypothèses sur le mécanisme de dolomitisation ont été énoncées et testées. Plusieurs phases de dolomitisation per ascensum ont été également simulées sur des séries du Lias appartenant aux formations du groupe des Calcaire Gris, localisées au nord-est de l'Italie. Ces fluides diagénétiques empruntent le réseau de fracturation comme vecteur et affectent préférentiellement les lithologies les plus micritisées. Cette étude a permis de mettre en évidence la propagation des phénomènes à l'échelle de l'affleurement. / Once deposited, sediment is affected by diagenetic processes during their burial history. These diagenetic processes are able to affect the petrophysical properties of the sedimentary rocks and also improve as such their reservoir capacity. The modelling of diagenetic processes in carbonate reservoirs is still a challenge as far as neither stochastic nor physicochemical simulations can correctly reproduce the complexity of features and the reservoir heterogeneity generated by these processes. An alternative way to reach this objective deals with process-like methods, which simplify the algorithms while preserving all geological concepts in the modelling process. The aim of the methodology is to conceive a consistent and realistic 3D model of diagenetic overprints on initial facies resulting in petrophysical properties at a reservoir scale. The principle of the method used here is related to a lattice gas automata used to mimic diagenetic fluid flows and to reproduce the diagenetic effects through the evolution of mineralogical composition and petrophysical properties. This method developed in a research group is well adapted to handle dolomite reservoirs through the propagation of dolomitising fluids and has been applied on two case studies. The first study concerns a mid-Cretaceous rudist and granular platform of carbonate succession (Urgonian Fm., Les Gorges du Nan, Vercors, SE France), in which several main diagenetic stages have been identified. The modelling in 2D is focused on dolomitisation followed by a dedolomitisation stage. For the second study, data collected from outcrops on the Venetian platform (Lias, Mont Compomolon NE Italy), in which several diagenetic stages have been identified. The main one is related to per ascensum dolomitisation along fractures. In both examples, the evolution of the effects of the mimetic diagenetic fluid on mineralogical composition can be followed through space and numerical time and help to understand the heterogeneity in reservoir properties.
84

On computer-aided design-space exploration for multi-cores / Exploration de l'espace de design assistée par ordinateur pour les systèmes multi-coeurs

Kempf, Jean-Francois 29 October 2012 (has links)
La complexité croissante des systèmes embarqués nécessite des formalismes de modélisation qui peuvent être simulés et analysés pour explorer l'espace des alternatives de conception. Cette thèse décrit le développement d'un formalisme de modélisation et des outils pour l'exploration de l'espace de design au plus tôt dans le flot de conception. Nous étendons le model-checking classique au pire cas pour les automates temporisés à l'analyse stochastique basée sur un raffinement des intervalles d'incertitude temporelle par des distributions sur les délais. D'une part, nous introduisons le formalisme des Duration Probabilistic Automata (DPA) à partir duquel nous pouvons réaliser de l'analyse ainsi que de l'optimisation. D'autre part nous présentons DESPEX (Design Space Explorer), un outil d'évaluation de performance de modèles de haut niveau des applications qui s'exécutent sur les plates-formes multi-coeurs. Nous montrons également son utilisation sur plusieurs cas d'étude. / The growing complexity of embedded systems calls for modeling formalisms that can be simulated and analyzed to explore the space of design alternatives. This thesis describes the development of a modeling formalism and tools for design space exploration at early design stage.We extend the classical worst-case model checking for timed automata to stochastic analysis based on a refinement of temporal uncertainty intervals into delay distribution. On one hand we introduce the formalism of Duration Probabilistic Automata (DPA) supporting analysis as well as optimization. On the other hand we provide DESPEX (DEsign SPace EXplorer), a tool for performance evaluation of high-level models of applications running on multi-core platforms. We also show its usage on several case studies.
85

Modelo de controle de acesso adaptativo

Cereda, Paulo Roberto Massa 30 May 2008 (has links)
Made available in DSpace on 2016-06-02T19:05:55Z (GMT). No. of bitstreams: 1 1996.pdf: 1191035 bytes, checksum: b157897bb46cbc27928eb487403c2e75 (MD5) Previous issue date: 2008-05-30 / Financiadora de Estudos e Projetos / Privacy has become an important aspect when modeling computational systems that have personal information and actions that deal with them. Control access models are used to provide security of such information. Some of these models, altough, are just applied to specific domains. It is proposed an access control model simple yet generic enough to comply with the security and privacy aspects of a system. The proposed model uses an adaptive automaton to perform the access control, and has a set of privacy commands, coded from a legislation or policy. These commands verify if a certain action in the systen may be characterized as a privacy violation. Moreover, the model may be used with auditing mechanisms to register actions in the system and guarantee the privacy. / A privacidade tornou-se um aspecto importante na modelagem de sistemas computacionais que envolvem informações pessoais e ações que as manipulam. Para garantir a segurança das informações, são utilizados modelos de controle de acesso. Alguns destes modelos tratam dos requisitos de privacidade, mas possuem aplicação apenas para domínios específicos. Este trabalho propõe um modelo de controle de acesso simplificado e genérico o suficiente para contemplar os requisitos de segurança e privacidade de um sistema. O modelo proposto utiliza um autômato adaptativo para realizar o controle de acesso, e possui um conjunto de comandos de privacidade, codificados a partir de uma legislação ou política, que verificam se uma determinada ação no sistema pode ser caracterizada como violação de privacidade. Além disso, o modelo permite a utilização de mecanismos de auditoria para registrar as ações no sistema e garantir a privacidade.
86

Reificação de objetos concorrentes / Reification of concurrent objects

Menezes, Paulo Fernando Blauth January 1997 (has links)
Autômatos não-seqüenciais constituem um domínio semântico categorial do tipo não-intercalação para sistemas reativos, comunicantes e concorrentes.É baseado em sistemas de transições etiquetados, inspirado em "Redes de Petri são Monóides" de Meseguer e Montanari, onde as operações de sincronização e encapsulação são funtoriais e as reificações constituem uma classe de morfismos especiais. Do que se tem conhecimento, é o primeiro modelo de concorrência a satisfazer a composicionalidade diagonal, ou seja, onde as reificações compõem (verticalmente) e distribuem-se sobre a composição paralela (verticalmente). Adjunções entre autômatos não-seqüenciais, redes de Petri e autômatos seqüenciais são introduzidas estendendo a abordagem de Winskel, Nielsen e Sassone onde é proposta uma classificação formal para modelos de concorrência. Dos passos que envolvem a passagem de um modelo para outro, pode-se inferir que os autômatos não-seqüenciais são mais concretos do que as redes de Petri e os autômatos seqüenciais. Para experimentar o domínio semântico proposto, é dada semântica a uma linguagem concorrente, baseada nos objetos, denominada Náutilus. Trata-se de uma versão simplificada e revisada da linguagem de especificação orientada aos objetos GNOME, onde são introduzidos algumas facilidades especiais, inspiradas no domínio semântico, como a reificação e a agregação. Neste contexto, a composicionalidade diagonal é uma propriedade essencial para dar a semântica. / Nonsequential automata constitute a non-interleaving categorial semantic domain for reactive, communicating and concurrent systems. It is based on labeled transition systems, inspired by Meseguer and Montanari's "Petri Nets are Monoids", where synchronization and encapsulation operations are functorial and a class of morphisms stands for reification. It is, for our knowledge, the first model for concurrency which satisfies the diagonal compositionality requirement, i. e., reifications compose (vertical) and distribute over the parallel composition (horizontal). Adjunctions between nonsequential automata, Petri nets and sequential automata are provided extending the approach of Winskel, Nielsen and Sassone where a scene for a formal classification of models for concurrency is set. The steps of abstraction involved in moving between models show that nonsequential automata are more concrete than Petri nets and sequential automata. To experiment with the proposed semantic domain, a semantics for a concurrent, object-based language named Nautilus is given. It is a simplified and revised version of the object-oriented specification language GNOME, introducing some special features inspired by the semantic domain such as reification and aggregation. The diagonal compositionality is an essential property to give semantics in this context.
87

Modelagem eletromecânica do coração com autômato celular e sistemas massa-mola

Campos, Ricardo Silva 15 February 2016 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-06-08T11:17:37Z No. of bitstreams: 1 ricardosilvacampos.pdf: 8528381 bytes, checksum: 29e3f07b2a4b4215d4e42d012e0f5df3 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-07-13T13:24:53Z (GMT) No. of bitstreams: 1 ricardosilvacampos.pdf: 8528381 bytes, checksum: 29e3f07b2a4b4215d4e42d012e0f5df3 (MD5) / Made available in DSpace on 2016-07-13T13:24:53Z (GMT). No. of bitstreams: 1 ricardosilvacampos.pdf: 8528381 bytes, checksum: 29e3f07b2a4b4215d4e42d012e0f5df3 (MD5) Previous issue date: 2016-02-15 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Este trabalho apresenta o simulador FisioPacer, que é um simulador que reproduz a propagação do pulso elétrico pelo tecido cardíaco e a sua deformação mecânica. Foi utilizado um autômato celular acoplado a um sistema massa-mola para que as simulações sejam realizadas rapidamente. Foi também utilizado um algoritmo genético para automaticamente determinar parâmetros do modelo de forma a reproduzir outros experimentos in silico e o comportamento de um ventrículo real. Com intuito de validar o modelo foram feitos setenta e dois experimentos e os resultados foram comparados com outro simulador robusto, baseado em equações diferenciais. As comparações mostraram que o FisioPacer reproduziu satisfatoriamente o comportamento do tecido, sendo até quinze mil vezes mais rápido. Além disto, foram simuladas as funcionalidades eletromecânicas de um ventrículo esquerdo a partir de dados de um paciente, obtidos via ressonância magnética. / This work proposes a computational heart model named FisioPacer, which aims to reproduce the electrical pulse propagation over the cardiac tissue and its mechanical deformation. In order to perform fast simulations, it was used a cellular automaton coupled with a mass-spring system. A genetic algorithm was also used to automatically adjust model parameters, in order to reproduce in silico experiments and a real left ventricle behavior. For the model validation, seventy two experiments were performed and the results were compared to another robust simulator, based on partial differential equations. The comparisons showed that the FisioPacer simulator could reproduce cardiac tissue electromechanics, with up to 15000-fold improvement in computational time. Furthermore, a real patient left ventricle was simulated, with data obtained via MRI.
88

Optimisation topologique des transferts de chaleur et de masse : application aux échangeurs de chaleur / Topological optimization of heat and mass transfer : application to heat exchangers

Marck, Gilles 21 December 2012 (has links)
Les transferts de chaleur et de masse sont deux phénomènes physiques à la base de nombreux systèmes thermiques employés dans des secteurs variés tels que l'industrie, le bâtiment ou encore les énergies renouvelables. Les présents travaux de recherche envisagent différentes méthodologies d'optimisation de configurations assurant le transfert de flux de chaleur, couplé ou non à un écoulement fluide, au sens topologique du terme. Les équations aux dérivées partielles décrivant les phénomènes physiques sont discrétisées avec la méthode des volumes finis. La première partie du manuscrit examine successivement trois classes différentes de méthodes: la théorie constructale, les automates cellulaires et les méthodes par pénalisation. Le même cas académique, portant sur le refroidissement d'un volume fini générant de la chaleur, est résolu au moyen de ces trois méthodes, ce qui permet ainsi de comparer les performances de chaque algorithme. Cette comparaison démontre l'ascendant des méthodes par pénalisation sur les deux premiers types, tant structurellement que quantitativement, et permet également d'établir des solutions basées sur des compromis dans le cadre d'optimisations multi-objectifs. Par conséquent, la seconde partie envisage l'application de cette approche à des configurations réalisant des transferts de chaleur conducto-convectifs en régime laminaire. L'utilisation de paramètres de pénalisation en conjonction avec les volumes finis requiert une régularisation de la dissipation visqueuse le long de l'interface fluide/solide. Une approche bi-objectif est développée visant à minimiser la puissance dissipée par le fluide, tout en maximisant l'énergie thermique récupérée sur le système. Les solutions obtenues adoptent des configurations non-triviales qui sont divisibles en quatre classes topologiques différentes. La thèse ouvre ainsi un nouveau champ d'investigation pour l'optimisation d'écoulements couplés à la problématique du transport de chaleur. / Heat and mass transfers are two physical phenomena at the base of many thermal systems involved in various fields, such as industries, buildings or renewable energies. The present researches tackle different optimization methodologies of structures subject to heat transfers, coupled with a fluid flow or not, in the topological sense of the term. The partial differential equations describing the physical phenomena are discretized thanks to the finite volume method. The first part of the thesis successively studies three different classes of approaches: constructal theory, cellular automaton, and the solid isotropic material with penalization method. The same academic case, aiming at the optimal cooling of a finite-size volume generating heat, is tackled by means of these three methods, allowing the comparison of the performances of each algorithm. This comparison shows that the method based on the material penalization performs better than the first two approaches, structurally and quantitatively, and also establishes solutions based on a trade-off in the frame multi-objective optimization. Consequently, the second part applies this method to configurations subject to heat and mass transfers with laminar flows. The use of penalization parameters in conjunction with the finite volume method requires a regularization of the viscous dissipation along the solid/fluid interfaces. A bi-objective approach is implemented in order to minimize the total power dissipated by the fluid, while maximizing the thermal energy recovered from the system. The solutions show non-trivial configurations that can be categorized in four different topological classes. The present researches open a new investigation field for fluid flows coupled with the problem of heat transport.
89

Equations in Self-Similar Groups

Groth, Thorsten 06 February 2018 (has links)
No description available.
90

Élaboration d'un modèle spatialisé pour favoriser le contrôle biologique de ravageurs de cultures par gestion du paysage agricole / A spatially explicit model to favour biological control of crop pest by managing the agricultural landscape.

Thierry, Hugo 23 November 2015 (has links)
La gestion agroécologique durable des paysages agricoles constitue un très fort enjeu social, écologique et économique. Favoriser les différents services écosystémiques que fournissent ces systèmes complexes, caractérisés par une forte variabilité spatio-temporelle liée aux activités anthropiques, est désormais crucial. Le travail développé dans cette thèse s’est focalisé sur les services de régulation des populations de ravageurs, en développant des modèles spatialisés destinés à identifier les interactions entre paysage et populations dans l’optique d’une gestion intégrée du paysage agricole. L’approche conceptuelle utilisée s’est appuyée sur une réflexion sur les choix de niveaux d’organisation et d’échelles spatio-temporelles pertinentes qui a conduit au développement de deux modèles imbriqués : un simulateur de paysages agricoles (ATLAS) reproduisant la variabilité spatio-temporelle des habitats et un automate cellulaire décrivant les dynamiques pluriannuelles d’un puceron des céréales : Rhopalosiphum padi. Une analyse statistique des résultats a permis d’identifier l’effet des différents paramètres du paysage (composition et climat) sur les densités de pucerons à différentes échelles spatiales au cours des saisons. Ont également été évalués les effets potentiels de différents scénarios de gestion plausibles au sein du paysage agricole étudié. Parmi nos résultats, nous identifions que le remplacement du maïs par le sorgho dans le sud-ouest de la France pourrait conduire à une augmentation des densités de R.padi au sein du paysage au printemps, période particulièrement sensible aux infestations. Nous replaçons ce travail dans le cadre plus large de la favorisation des services écosystémiques et apportons des premiers éléments de réflexion pour une gestion durable du paysage agricole; / Sustainable management of agricultural landscapes is a strong social, ecological and economic challenge. Favouring the different ecosystem services provided by these complex systems, characterized by a strong spatio-temporal variability linked to human activity, is by now crucial. The work developed in this thesis has focused on pest population regulation services, by developing spatialized models in order to identify the interactions between the landscape and populations in the context of an integrated management of the agricultural landscape. The conceptual approach we used is based on careful selection of the levels of organization and spatio-temporal scales which lead to the development of two embedded models: an agricultural landscape simulator (ATLAS) reproducing the spatial-temporal variability of habitats and a cellular automaton describing thepluriannual dynamics of a cereal aphid: Rhopalosiphum padi. A statistical analysis of the results highlighted the effects of different landscape parameters (composition and climate) on aphid densities at different spatial scales throughout the seasons. The potential effects of plausible management scenarios were also evaluated. Amongst our results, we identify the replacement of corn by sorghum in the south-western part of France to potentially lead to higher aphid densities within the landscape in spring, which is a season specifically sensible to infestations. We replace this work in the larger context of favouring ecosystem services and propose new ideas for a sustainable management of agricultural landscapes;

Page generated in 0.0356 seconds