• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 87
  • 59
  • 26
  • 17
  • 10
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 241
  • 241
  • 60
  • 54
  • 48
  • 39
  • 39
  • 29
  • 28
  • 24
  • 22
  • 19
  • 19
  • 19
  • 19
  • 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.
221

Modeling and simulation of hybrid systems and cell factory applications

Assar Cuevas, Rodrigo 21 October 2011 (has links)
Les fonctions biologiques sont le résultat de l'interaction de beaucoup de processus, avec différents objectifs, complexités, niveaux de hiérarchie, et changements de conditions que modifient le comportement de systèmes. Nous utilisons des équations différentielles ou dynamiques plus générales, et systèmes stochastiques de transition pour décrire la dynamique de changements des modèles. La composition, réconciliation et réutilisation des modèles nous permettent d'obtenir des descriptions de systèmes biologiques complètes et compatibles et leur combiner. Notre spécification de systèmes hybrides avec BioRica assure l'intégrité de modèles, et implémente notre approche. Nous appliquons notre approche pour décrire in-silico deux systèmes: la dynamique de la fermentation du vin, et des décisions cellulaires associées à la formation de tissu d'os. / The main aim of this thesis is to develop an approach that allows us to describe biological systems with theoretical sustenance and good results in practice. Biological functions are the result of the interaction of many processes, that connect different hierarchy levels going from macroscopic to microscopic level. Each process works in different way, with its own goal, complexity and hierarchy level. In addition, it is common to observe that changes in the conditions, such as nutrients or environment, modify the behavior of the systems. So, to describe the behavior of a biological system over time, it is convenient to combine different types of models: continuous models for gradual changes, discrete models for instantaneous changes, deterministic models for completely predictable behaviors, and stochastic or non- deterministic models to describe behaviors with imprecise or incomplete information. In this thesis we use the theory of Composition and Hybrid Systems as basis, and the BioRica framework as tool to model biological systems and analyze their emergent properties in silico.With respect to Hybrid Systems, we considered continuous models given by sets of differential equations or more general dynamics. We used Stochastic Transition Systems to describe the dynamics of model changes, allowing cofficient switches that control the parameters of the continuous model, and strong switches that choose different models. Composition, reconciliation and reusing of models allow us to build complete and consistent descriptions of complex biological systems by combining them. Compositions of hybrid systems are hybrid systems, and the refinement of a model forming part of a composed system results in a refinement of the composed system. To implement our approach ideas we complemented the theory of our approach with the improving of the BioRica framework. We contributed to do that giving a BioRica specification of Hybrid Systems that assures integrity of models, allowing composition, reconciliation, and reuse of models with SBML specification.We applied our approach to describe two systems: wine fermentation kinetics, and cell fate decisions leading to bone and fat formation. In the case of wine fermentation, we reused known models that describe the responses of yeasts cells to different temperatures, quantities of resources and toxins, and we reconciled these models choosing the model with best adjustment to experimental data depending on the initial conditions and fermentation variable. The resulting model can be applied to avoid process problems as stuck and sluggish fermentations. With respect to cell fate decisions the idea is very ambitious. By using accurate models to predict the bone and fat formation in response to activation of pathways such as the Wnt pathway, and changes of conditions affecting these functions such as increments in Homocysteine, one can analyze the responses to treatments for osteoporosis and other bone mass disorders. We think that here we are giving a first step to obtain in silico evaluations of medical treatments before testing them in vitro or in vivo.
222

Nonlinear and Hybrid Feedbacks with Continuous-Time Linear Systems / Rétroactions non linéaires et hybrides avec systèmes linéaires à temps continu

Cocetti, Matteo 21 May 2019 (has links)
Dans cette thèse, nous étudions la rétroaction de systèmes linéaires invariants dans le temps reliés entre eux par trois blocs non linéaires spécifiques : un opérateur de lecture/arrêt, un mécanisme de réinitialisation de commutation et une zone morte adaptative. Cette configuration ressemble au problème de Lure étudié dans le cadre de stabilité absolue, mais les types de non-linéarités considérés ici ne satisfont pas (en général) une condition sectorielle. Ces blocs non linéaires donnent lieu à toute une série de phénomènes intéressants, tels que des ensembles compacts d’équilibres, des ensembles hybrides oméga-limites et des contraintes d’état. Tout au long de la thèse, nous utilisons le formalisme des systèmes hybrides pour décrire ces phénomènes et analyser ces boucles. Nous obtenons des conditions de stabilité très précises qui peuvent être formulées sous forme d’inégalités matricielles linéaires, donc vérifiables avec des solveurs numériques efficaces. Enfin, nous appliquons les résultats théoriques à deux applications automobiles. / In this thesis we study linear time-invariant systems feedback interconnected with three specific nonlinear blocks; a play/stop operator, a switching-reset mechanism, and an adaptive dead-zone. This setup resembles the Lure problem studied in the absolute stability framework, but the types of nonlinearities considered here do not satisfy (in general) a sector condition. These nonlinear blocks give rise to a whole range of interesting phenomena, such as compact sets of equilibria, hybrid omega-limit sets, and state constraints. Throughout the thesis, we use the hybrid systems formalism to describe these phenomena and to analyze these loops. We obtain sharp stability conditions that can be formulated as linear matrix inequalities, thus verifiable with numerically efficient solvers. Finally, we apply the theoretical findings to two automotive applications.
223

Thermohydraulischer Lineargenerator – Basis für einen dieselelektrohydraulischen Hybrid

Hänel, Frank, Seifert, Robert, Kunze, Günter, Hofmann, Wilfried 21 April 2022 (has links)
Auf dem Gebiet der mobilen Arbeitsmaschinen und Nutzfahrzeuge zeigen aktuelle Arbeiten weltweit ein verstärktes Interesse an leistungsverzweigten Antriebskonzepten auf Basis elektrischer und hydraulischer Hybridlösungen. Die Kombination beider Technologien verspricht wartungsarme, energieeffiziente Antriebssyteme mit hoher Steuer- und Regelbarbeit sowie hoher Kraftdichte. Die primär erzeugte mechanische Antriebsleistung der Wärmekraftmaschine kann meist für die Arbeitsprozesse und zur Versorgung zugehöriger Hilfsfunktionen nicht direkt verwendet werden. Diese muss je nach Anforderungen gewandelt bzw. angepasst oder bedarfsgerecht mittels zusätzlichen, wiederaufladbaren Speichern bereitgestellt werden. Solche hybriden Lösungsansätze führen jedoch gegenüber konventionellen Antrieben zu einer steigenden Komplexität sowie einem erhöhten technischen Aufwand. Nach dem Stand der Technik erfolgt die Erzeugung hydraulischer und elektrischer Leistung mit Hilfe mindestens dreier Komponenten: Verbrennungsmotor, Hydraulikpumpe und Generator. Für künftige antriebstechnische Innovationen ist daher aus funktionellen und energetischen Gründen ein einfaches, preiswertes Primäraggregat zur gleichzeitigen, bedarfsgerechten Bereitstellung hydraulischer und elektrischer Leistung wünschenswert, welches unnötige Umwandlungsverluste vermeidet und zusätzlich Kosten spart. Das Forschungsprojekt „Theoretische Grundlagen zur Verknüpfung von thermohydraulischer und thermoelektrischer Leistungswandlung in einem Aggregat – Thermohydraulischer Lineargenerator“ befasst sich mit einer belastbaren Abschätzung der technischen Realisierbarkeit und des technischen Aufwands eines derartigen neuen Antriebskonzeptes mit frei wählbarer Bereitstellung hydraulischer und elektrischer Leistung auf Basis des Freikolbenprinzips. Die grundlegenden Untersuchungen widmen sich der Kopplung zweier unterschiedlicher Leistungswandlungen, einer stabilen Prozessführung sowie der Analyse und Bewertung der physikalischen Prozessgrößen in Bezug auf eine zukünftige Auslegung eines Prototyps. Der Beitrag erklärt das Grundkonzept, zeigt den aktuellen Stand des Projekts auf und stellt die zum gegenwärtigen Zeitpunkt vorliegenden Ergebnisse vor.
224

Electrical, thermomechanical and sorption properties of hybrid organic-inorganic systems based on urethane oligomers and silicates / Propriétés électriques, thermomécaniques et de sorption de systèmes hybrides organique-inorganique basés sur des oligomères uréthane et silicates

Iurzhenko, Maksym 25 November 2009 (has links)
L'objectif de cette recherche est d'établir des mécanismes de formation de la structure des systèmes hybrides organique-inorganique à base des oligomères uréthane et silicates en fonction de la réactivité de la composant organique, d'identifier l'impact de l'organisation structurelle du OIS obtenue sur leurs propriétés électriques et thermomécaniques, de sorption et de l'activité du capteur. La signification pratique des résultats est la détermination de l'impact de la réactivité composant organique sur la structure des systèmes hybrides polymère organique-inorganique avec la possibilité d'obtenir des matériaux avec des propriétés spéciales prévisibles. Les résultats peuvent être utilisés comme base scientifique pour comprendre l'interconnexion de la structure, les propriétés et les moyens de leur régulation en direction de systèmes hybrides polymère organique-inorganique. La sensibilité très élevée pour les différents types de solvants, qui, combiné avec une haute sélectivité, a été révélé pour les systèmes de synthèse, la possibilité de leur utilisation pratique en tant que matières capteur existe. / The aim of the research is to establish mechanisms of structure formation of hybrid organic-inorganic systems based on urethane oligomers and silicates, depending on reactivity of organic component, to identify the impact of structural organization of OIS obtained on their electrophysical and thermomechanical properties, sorption and sensor activity.The practical significance of the results is the determination of the impact of organic component reactivity on the structure of hybrid organic-inorganic polymer systems with the possibility of obtaining of the materials with predictable special properties. The results can be used as scientific basis for understanding the interconnection of structure, properties and ways of their directional regulation of hybrid organic-inorganic polymer systems. Whereas, the extremely high sensitivity to different types of solvents, which combined with the high selectivity, was revealed for the synthesized systems, the possibility of their practical use as sensor materials exists.
225

Safe Controller Design for Intelligent Transportation System Applications using Reachability Analysis

Park, Jaeyong 17 October 2013 (has links)
No description available.
226

[pt] ESTIMAÇÃO DE HORIZONTE FINITO APROXIMADA E CONTROLE PREDITIVO DE SISTEMAS CHAVEADOS APLICADOS A MANIPULADORES ROBÓTICOS FLEXÍVEIS / [en] SWITCHING RECEDING-HORIZON APPROXIMATE ESTIMATION AND CONTROL OF A FLEXIBLE JOINT ROBOTIC MANIPULATOR

LARA CANDIDO ALVIM 30 October 2023 (has links)
[pt] Os avanços da Robótica nas últimas décadas permitem um aumento nas gamas de aplicações de manipuladores robóticos em diversos setores da indústria. Isto, impacta diretamente a interação Homem-Robô (HRI), resultando em um aumento de tarefas que requerem compartilhamento de ambiente de trabalho, desempenho de segurança e a habilidade de detecção de contato do manipulador robótico. Consequentemente, métodos de controle capazes de prever contato, controlar força ou trajetória para evitar danos durante colisões se tornam cada vez mais necessários seja por questões de segurança ou de desempenho. Separando a dinâmica de um manipulador de um único elo em dois modos, sendo eles modo de controle de posição (modo livre) e modo de controle de torque (modo de contato), a primeira parte desta dissertação, lida com o problema de estimação de estados para detecção do modo ativo através da implementação do método de Estimação de Estados de Horizonte móvel com Redes Neurais (NNMHSE). A efetividade do método de estimação proposto é avaliada através da comparação dos estados e modos gerados pelo MHSE e dos estimados pela Rede Neural. Este método apresentou baixos valores de RMSE, altos valores de R(2), e uma redução do tempo de processamento do algoritmo de estimação. A segunda parte desta dissertação lida com o problema de controle de posição e força chaveado para um manipulador robótico não linear, aplicando Controle Preditivo Baseado em Modelo (MPC). O algoritmo MPC chaveado implementado mostrou-se capaz de controlar efetivamente ambos os modos do sistema apresentando baixo erro na predição, aproximadamente 2 por cento no modo de controle de posição e 0.5 por cento no modo de controle de torque, mesmo considerando alterações cíclicas nos modos. Ambos os métodos provam ser adequados para controle de manipuladores robóticos colocalizados com seres humanos ou em ambientes desestruturados por meio da detecção do modo de operação e do controle chaveado posição-torque. / [en] The advances in Robotics in recent decades allow a growing range of robotic manipulator applications in various industry sectors. This directly impacts Human-Robot Interaction (HRI), increasing tasks that require a shared work environment, safety performance, and the contact detection ability of the robotic manipulator. Consequently, control methods capable of predicting contact, and controlling force or trajectory to avoid damage during collisions become increasingly necessary either for safety or performance reasons. Separating the dynamics of a single-link manipulator into two modes, namely position control mode (free mode) and torque control mode (contact mode), the first part of this dissertation deals with the estimation problem of states for active mode detection through the implementation of the Moving Horizon State Estimation with Neural Networks (NNMHSE) method. The effectiveness of the proposed estimation method is evaluated by comparing the states and modes generated by the MHSE and those estimated by the Neural Network. This method showed low RMSE values, high values of R(2), and a reduction in the processing time of the estimation algorithm. The second part of this dissertation deals with the position and force switching problem for a non-linear robotic manipulator, applying Model-Based Predictive Control (MPC). The implemented switched MPC algorithm effectively controlled both modes of the system, presenting low prediction error, approximately 2 percent in position control mode and 0.5 percent in torque control mode, even considering cyclical changes in the modes. Both methods prove to be suitable for controlling co-located robotic manipulators with humans or in unstructured environments through operation mode detection and position-torque switching control.
227

Dispositivos adaptativos cooperantes: formulação e aplicação. / Cooperative adaptive devices : design and implementation.

Santos, José Maria Novaes dos 26 November 2014 (has links)
Com a crescente complexidade das aplicações e sistemas computacionais, atualmente tem se tornado importante o uso de formalismos de várias naturezas na representação e modelagem de problemas complexos, como os sistemas reativos e concorrentes. Este trabalho apresenta uma contribuição na Tecnologia Adaptativa e uma nova técnica no desenvolvimento de uma aplicação para execução de alguns tipos de jogos, (General Game Playing), cuja característica está associada à capacidade de o sistema tomar conhecimento das regras do jogo apenas em tempo de execução. Com esse trabalho, amplia-se a classe de problemas que podem ser estudados e analisados sob a perspectiva da Tecnologia Adaptativa, através dos Dispositivos Adaptativos Cooperantes. A aplicação desenvolvida como exemplo neste trabalho introduz uma nova ótica no desenvolvimento de aplicações para jogos gerais (GGP) e abre novos horizontes para a aplicação da Tecnologia Adaptativa, como a utilização das regras para extração de informação e inferência. / The complexity of computer applications has grown so much that several formalisms of different kinds became important nowadays. Many systems (e.g. reactive and concurrent ones) employ such formalisms to represent and model actual complex problems. This work contributes to the field of Adaptive Technology, and proposes a new approach for developing general game playing system, whose feature is the capability to play a game by acknowledging the game rules only at run time. This work expands the set of problems that can be studied and analyzed under the Adaptive Technology perspective, by means of cooperating adaptive devices. The developed application used a new approach for general game playing development bringing and widens the application field of Adaptive Technology with subjects related to information extraction and inference based in the devices rules.
228

Tecnologia adaptativa aplicada a sistemas híbridos de apoio à decisão. / Adaptative tecnology applied to hybrid decision support systems.

Okada, Rodrigo Suzuki 11 March 2013 (has links)
Este trabalho apresenta a formulação de um sistema híbrido de apoio à decisão que, através de técnicas adaptativas, permite que múltiplos dispositivos sejam utilizados de forma colaborativa para encontrar uma solução para um problema de tomada de decisão. É proposta uma estratégia particular para o trabalho colaborativo que restringe o acesso aos dispositivos mais lentos com base na dificuldade encontrada pelos dispositivos mais rápidos para solucionar um problema específico. As soluções encontradas por cada dispositivo são propagadas aos demais, permitindo que cada um deles agregue estas novas soluções com o auxílio de técnicas adaptativas. É feito um estudo sobre aprendizagem de máquina mediante incertezas para verificar e minimizar os impactos negativos que uma nova solução, possivelmente errônea, possa ter. O sistema híbrido proposto é apresentado numa aplicação particular, utilizando testes padronizados para compará-lo com os dispositivos individuais que o compõem e com sistemas híbridos de mesma finalidade. Através destes testes, é mostrado que dispositivos consolidados, mesmo que de naturezas distintas, podem ser utilizados de maneira colaborativa, permitindo não só calibrar um compromisso entre o tempo de resposta e a taxa de acerto, mas também evoluir de acordo com o histórico de problemas processados. / This work presents a formulation of a hybrid decision-making system that employs adaptive techniques as a way to coordinate multiple devices in order to make a collaborative decision. The strategy proposed here is to restrict the use of slower devices, based on how difficult the specific problem is - easier problems may be solved on faster devices. Each device is able to learn through solutions given by the others, aggregating new knowledge with the aid of adaptive techniques. In order to evaluate and minimize the negative impact those new solutions may have, a study concerning machine learning under uncertainty is carried out. A particular application of this system has been tested and compared, not only to each individual device that is part of the system itself, but to similar hybrid systems as well. It is shown that even devices of distinct natures may be reused in a collaborative manner, making it possible to calibrate the trade-off between hit rate and response time, and to evolve according to the input stimuli received as well.
229

Dispositivos adaptativos cooperantes: formulação e aplicação. / Cooperative adaptive devices : design and implementation.

José Maria Novaes dos Santos 26 November 2014 (has links)
Com a crescente complexidade das aplicações e sistemas computacionais, atualmente tem se tornado importante o uso de formalismos de várias naturezas na representação e modelagem de problemas complexos, como os sistemas reativos e concorrentes. Este trabalho apresenta uma contribuição na Tecnologia Adaptativa e uma nova técnica no desenvolvimento de uma aplicação para execução de alguns tipos de jogos, (General Game Playing), cuja característica está associada à capacidade de o sistema tomar conhecimento das regras do jogo apenas em tempo de execução. Com esse trabalho, amplia-se a classe de problemas que podem ser estudados e analisados sob a perspectiva da Tecnologia Adaptativa, através dos Dispositivos Adaptativos Cooperantes. A aplicação desenvolvida como exemplo neste trabalho introduz uma nova ótica no desenvolvimento de aplicações para jogos gerais (GGP) e abre novos horizontes para a aplicação da Tecnologia Adaptativa, como a utilização das regras para extração de informação e inferência. / The complexity of computer applications has grown so much that several formalisms of different kinds became important nowadays. Many systems (e.g. reactive and concurrent ones) employ such formalisms to represent and model actual complex problems. This work contributes to the field of Adaptive Technology, and proposes a new approach for developing general game playing system, whose feature is the capability to play a game by acknowledging the game rules only at run time. This work expands the set of problems that can be studied and analyzed under the Adaptive Technology perspective, by means of cooperating adaptive devices. The developed application used a new approach for general game playing development bringing and widens the application field of Adaptive Technology with subjects related to information extraction and inference based in the devices rules.
230

Tecnologia adaptativa aplicada a sistemas híbridos de apoio à decisão. / Adaptative tecnology applied to hybrid decision support systems.

Rodrigo Suzuki Okada 11 March 2013 (has links)
Este trabalho apresenta a formulação de um sistema híbrido de apoio à decisão que, através de técnicas adaptativas, permite que múltiplos dispositivos sejam utilizados de forma colaborativa para encontrar uma solução para um problema de tomada de decisão. É proposta uma estratégia particular para o trabalho colaborativo que restringe o acesso aos dispositivos mais lentos com base na dificuldade encontrada pelos dispositivos mais rápidos para solucionar um problema específico. As soluções encontradas por cada dispositivo são propagadas aos demais, permitindo que cada um deles agregue estas novas soluções com o auxílio de técnicas adaptativas. É feito um estudo sobre aprendizagem de máquina mediante incertezas para verificar e minimizar os impactos negativos que uma nova solução, possivelmente errônea, possa ter. O sistema híbrido proposto é apresentado numa aplicação particular, utilizando testes padronizados para compará-lo com os dispositivos individuais que o compõem e com sistemas híbridos de mesma finalidade. Através destes testes, é mostrado que dispositivos consolidados, mesmo que de naturezas distintas, podem ser utilizados de maneira colaborativa, permitindo não só calibrar um compromisso entre o tempo de resposta e a taxa de acerto, mas também evoluir de acordo com o histórico de problemas processados. / This work presents a formulation of a hybrid decision-making system that employs adaptive techniques as a way to coordinate multiple devices in order to make a collaborative decision. The strategy proposed here is to restrict the use of slower devices, based on how difficult the specific problem is - easier problems may be solved on faster devices. Each device is able to learn through solutions given by the others, aggregating new knowledge with the aid of adaptive techniques. In order to evaluate and minimize the negative impact those new solutions may have, a study concerning machine learning under uncertainty is carried out. A particular application of this system has been tested and compared, not only to each individual device that is part of the system itself, but to similar hybrid systems as well. It is shown that even devices of distinct natures may be reused in a collaborative manner, making it possible to calibrate the trade-off between hit rate and response time, and to evolve according to the input stimuli received as well.

Page generated in 0.051 seconds