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  • 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.
121

Large-Scale Simulations for Complex Adaptive Systems with Application to Biological Domains

Guo, Donghang 13 March 2008 (has links)
Modeling or simulating Complex Adaptive Systems (CASs) is both important and challenging. As the name suggests, CASs are systems consisting of large numbers of interacting adaptive compartments. They are studied across a wide range of disciplines and have unique properties. They model such systems as multicellular organisms, ecosystems, social networks, and many more. They are complex, in the sense that they are dynamical, nonlinear, and heterogeneous systems that cannot be simply scaled up/down. However, they are self-organized, in the sense that they can evolve into specific structures/patterns without guidance from outside sources. Modeling/Simulating CASs is challenging, not only because of the high complexity, but also because of the difficulty in explaining the underlying mechanism behind self-organization. The goal of this research is to provide a modeling framework as well as a simulation platform to advance the study of CASs. We argue that there are common principles behind self-organization processes of different systems across different domains. We explore, analyze, and perform experiments into these principles. We propose and implement modeling templates such as short-term and long-term adaptivity. We incorporate techniques from systems theory, employing computing paradigms, including multi-agent system and asynchronous message passing. We also consider an application from the biological domain to model and simulate under our framework, treating it as a CAS for validation purposes. / Ph. D.
122

Ion beam processing of surfaces and interfaces – Modeling and atomistic simulations

Liedke, B. 14 March 2012 (has links) (PDF)
Self-organization of regular surface pattern under ion beam erosion was described in detail by Navez in 1962. Several years later in 1986 Bradley and Harper (BH) published the first self-consistent theory on this phenomenon based on the competition of surface roughening described by Sigmund’s sputter theory and surface smoothing by Mullins-Herring diffusion. Many papers that followed BH theory introduced other processes responsible for the surface patterning e.g. viscous flow, redeposition, phase separation, preferential sputtering, etc. The present understanding is still not sufficient to specify the dominant driving forces responsible for self-organization. 3D atomistic simulations can improve the understanding by reproducing the pattern formation with the detailed microscopic description of the driving forces. 2D simulations published so far can contribute to this understanding only partially. A novel program package for 3D atomistic simulations called trider (TRansport of Ions in matter with DEfect Relaxation), which unifies full collision cascade simulation with atomistic relaxation processes, has been developed. The collision cascades are provided by simulations based on the Binary Collision Approximation, and the relaxation processes are simulated with the 3D lattice kinetic Monte-Carlo method. This allows, without any phenomenological model, a full 3D atomistic description on experimental spatiotemporal scales. Recently discussed new mechanisms of surface patterning like ballistic mass drift or the dependence of the local morphology on sputtering yield are inherently included in our atomistic approach. The atomistic 3D simulations do not depend so much on experimental assumptions like reported 2D simulations or continuum theories. The 3D computer experiments can even be considered as ’cleanest’ possible experiments for checking continuum theories. This work aims mainly at the methodology of a novel atomistic approach, showing that: (i) In general, sputtering is not the dominant driving force responsible for the ripple formation. Processes like bulk and surface defect kinetics dominate the surface morphology evolution. Only at grazing incidence the sputtering has been found to be a direct cause of the ripple formation. Bradley and Harper theory fails in explaining the ripple dynamics because it is based on the second-order-effect ‘sputtering’. However, taking into account the new mechanisms, a ‘Bradley-Harper equation’ with redefined parameters can be derived, which describes pattern formation satisfactorily. (ii) Kinetics of (bulk) defects has been revealed as the dominating driving force of pattern formation. Constantly created defects within the collision cascade, are responsible for local surface topography fluctuation and cause surface mass currents. The mass currents smooth the surface at normal and close to normal ion incidence angles, while ripples appear first at θ ≥ 40°. The evolution of bimetallic interfaces under ion irradiation is another application of trider described in this thesis. The collisional mixing is in competition with diffusion and phase separation. The irradiation with He+ ions is studied for two extreme cases of bimetals: (i) Irradiation of interfaces formed by immiscible elements, here Al and Pb. Ballistic interface mixing is accompanied by phase separation. Al and Pb nanoclusters show a self-ordering (banding) parallel to the interface. (ii) Irradiation of interfaces by intermetallics forming species, here Pt and Co. Well-ordered layers of phases of intermetallics appear in the sequence Pt/Pt3Co/PtCo/PtCo3/Co. The trider program package has been proven to be an appropriate technique providing a complete picture of mixing mechanisms.
123

Self-Assembling Robots

Groß, Roderich 12 October 2007 (has links)
We look at robotic systems made of separate discrete components that, by self-assembling, can organize into physical structures of growing size. We review 22 such systems, exhibiting components ranging from passive mechanical parts to mobile robots. We present a taxonomy of the systems, and discuss their design and function. We then focus on a particular system, the swarm-bot. In swarm-bot, the components that assemble are self-propelled modules that are fully autonomous in power, perception, computation, and action. We examine the additional capabilities and functions self-assembly can offer an autonomous group of modules for the accomplishment of a concrete task: the transport of an object. The design of controllers is accomplished in simulation using techniques from biologically-inspired computing. We show that self-assembly can offer adaptive value to groups that compete in an artificial evolution based on their fitness in task performance. Moreover, we investigate mechanisms that facilitate the design of self-assembling systems. The controllers are transferred to the physical swarm-bot system, and the capabilities of self-assembly and object transport are extensively evaluated in a range of different environments. Additionally, the controller for self-assembly is transferred and evaluated on a different robotic system, a super-mechano colony. Given the breadth and quality of the results obtained, we can say that the swarm-bot qualifies as the current state of the art in self-assembling robots. Our work supplies some initial evidence (in form of simulations and experiments with the swarm-bot) that self-assembly can offer robotic systems additional capabilities and functions useful for the accomplishment of concrete tasks.
124

Le cyclotriphosphazène en tant qu'agent directeur de la formation de réseaux poreux pi-conjugués / Cyclotriphosphazene as directing agent for pi-conjugated porous network formation

Reynes, Mathias 16 December 2010 (has links)
L'élaboration de réseaux poreux pi-conjugués par l'auto-organisation de molécules organiques, les cyclotriphosphazènes spirocycliques, a été explorée. L'étude de la stabilité des réseaux obtenus à partir du tris(o-phénylènedioxy)cyclotriphosphazène (TPP) conjointement à l'étude de la réactivité du N3P3Cl6 face à l'attaque nucléophile de différents dérivés du catéchol ont permis de définir de nouvelles cibles. Dans ce cadre, un nouveau composé, le tris(2,3-triphénylènedioxy)cyclotriphosphazène (TTPP) dans lequel le motif central est substitué par trois systèmes pi-conjugués étendus de type triphénylène a été synthétisé. Les tectons TTPP, de symétrie C3, présentent une orientation atypique des motifs aromatiques. Leur forme, analogue à celle d'une roue à aubes, leur permet d'engendrer à l'état cristallin des lacunes sous forme de deux types de nano-canaux de respectivement 6,1 Å et 8,4 Å de large et 10,7 Å et 12,4 Å de large, pouvant inclure des molécules de 1,2,4-trichlorobenzène. Ce matériau contient la plus grande porosité obtenu à partir de cyclotriphosphazènes spirocycliques à ce jour. La formation de réseaux poreux chiraux a également été réalisée à partir de tectons portant chacun trois motifs (S)-binol. Le (S,S,S)-tribinolcyclotriphosphazène ((S,S,S)-TBP) a ainsi pu être co-cristallisé avec des molécules d'o-xylène. Ainsi, des informations permettant de mieux comprendre la structure moléculaire de cyclotriphosphazènes portant des spirocycles à sept chaînons ont été obtenues. Enfin, les propriétés optoélectroniques des tectons ont été étudiées en solution. L'influence de l'agent directeur cyclotriphosphazène sur les propriétés optiques des chromophores a, en particulier, été abordée. / Elaboration of pi-conjugated networks through self-organization of spirocyclic cyclotriphosphazene molecules has been explored. The stability of the networks built from described tris(o-phenylenedioxy)cyclotriphosphazene (TPP) jointly with the study of the reactivity of N3P3Cl6 undergoing nucleophilic attack by catechol derivatives allowed to design new tectons. In this context, a new tris(2,3-triphenylenedioxy)cyclotriphosphazene (TTPP) compound embedding a central hub substituted by pi-conjugated triphenylene unit has been synthesized. TTPP tectons exhibits a particular shape with specific orientation of aromatic units. Their paddle-wheel like shape allows the elaboration of a porous network having two types of nano-tunnels of respectively 6.1 Å and 8.4 Å large and 10.7 Å and 12.4 Å large. This material has the biggest channel size described for network build from spirocyclic cyclotriphosphazenes and inclusion compounds with 1,2,4-trich lorobenzene molecules were made. Elaboration of chiral porous network from tectons constituted by three (S)-binol units has also been realized. Tribinolcyclotriphosphazene has been co-cristallized with o-xylene molecules. Thus, useful informations on seven-membered spirocyclic cyclotriphosphazene molecular structure have been obtained. Finally, tectons opto-electronic properties have been studied in solution. Influence of the cyclotriphosphazene directing agent on optical chromophore properties has been a particular matter of attention.
125

Hybrid colloidal molecules from self-assembly of viral rod-like particles / Molécules colloïdales par auto-assemblage de virus anisotropes et de nanoparticules métalliques

Wu, Cheng 06 September 2018 (has links)
Dans cette thèse, l’auto-assemblage en molécules colloïdales de virus en forme de filament, les bactériophages M13, est étudié. Comme première approche, l’affinité de la streptavidine pour la biotine ou un Strep-tag est utilisée et quantitativement comparée. Pour ce faire, des virus modifiés génétiquement, M13-AS, présentant des Strep-tag et des virus M13C7C chimiquement bioconjugués par de la biotine ont réagi via leur extrémité proximale avec des nanoparticules fonctionnalisées par de la streptavidine. Il en résulte la formation de molécules colloïdales en étoile, dont la valence ou nombre de virus par structure, peut être simplement contrôlée par l’excès molaire initial. Cependant, la stabilité de ces molécules colloïdales est limitée par la libération progressive et la dégradation de la streptavidine. Nous avons alors développé une seconde approche basée sur l’affinité soufre-métal, qui s’est avérée à la fois pratique expérimentalement et fiable. Grâce aux groupements disulfures présents sur les cystéines de la protéine P3, des nanoparticules métalliques peuvent se lier à l’extrémité des virus. Le caractère générique de cette méthode est vérifié en faisant varier la nature du métal des nanoparticules ainsi que la souche des virus, dont la sauvage. La valence des structures formées est déterminée en fonction de plusieurs paramètres, dont l’excès molaire initial, la taille des nanoparticules et la force ionique. Un modèle rendant compte des résultats expérimentaux a été élaboré, dont les principales variables sont la surface des nanoparticules et le diamètre effectif électrostatique des virus. Cette approche est étendue à la réalisation de diblocs colloïdaux hétéro bifonctionnels, utilisant les virus comme briques constitutives. Comme preuve de concept, des diblocs bicolores à base de virus sont obtenus par auto-assemblage et leur dynamique est étudiée à l’échelle du bloc élémentaire en microscopie optique de fluorescence. Ainsi, nous avons montré dans cette thèse la réalisation par auto-assemblage d’une nouvelle génération de molécules colloïdales, dont l’auto-organisation peut conduire à la formation de superstructures hiérarchiques hybrides de complexité croissante, potentiellement utiles en sciences des matériaux. / In this thesis, the self-assembly of rod-like viral particles, specifically the M13 bacteriophages, into colloidal molecules is studied. As the first method, the affinity of streptavidin to biotin or Strep-tag is used and quantitatively compared. In this case, both biologically engineered M13-AS displaying Strep-tags and chemically biotinylated M13C7C viruses have reacted with streptavidin activated nanoparticles via their functionalized proximal ends. This results in star-like colloidal molecules, whose valency – or number of viruses par structure – can be solely controlled by tuning the initial molar excess. However, the stability of these colloidal molecules is limited by streptavidin release and degradation. Thus, we develop the second method based on the sulfur—metal interactions, which is more convenient and reliable. Thanks to the exposed disulfide groups located at p3 proteins, metallic nanoparticles are able to bind to proximal ends of the M13 virus. The generic feature of this method is verified by using different metals and two virus strains including wt-M13. Afterwards, the control of the valency is explored by varying the initial molar excess, the nanoparticle size and the ionic strength. A quantitative model is built correspondingly, using the surface area of Au nanobead and the effective electrostatic diameter of the virus as variables, which accounts for the assembly of colloidal molecules with desired valencies. This method is further applied to assemble heterobifunctional diblocks by using filamentous viruses as building units. As a proof-of-concept experiment, bicolored diblocks are produced and tracked by each block simultaneously. Overall, we demonstrate the synthesis of a new generation of hybrid colloidal molecules, whose self-organization could serve as a promising means to create novel hierarchical biologic/inorganic superstructures that may find applications in materials science.
126

Proposition d’une architecture holonique auto-organisée et évolutive pour le pilotage des systèmes de production / Self-organized and evolvable holonic architecture for manufacturing control

Barbosa, José 19 February 2015 (has links)
Le monde des entreprises est profondément soumis à un ensemble de contraintes toujours plus exigeantes provenant d’une part des clients, exigeant des produits plus personnalisables, de qualité supérieure et à faible coût, et d’autre part des aléas internes auxentreprises, comprenant les pannes machines, les défaillances humaines, la fluctuation de la demande, les fréquentes variations de production. Cette thèse propose une architecture de contrôle de systèmes de production, basée sur les principes holoniques développées dans l’architecture ADACOR (ADAptive holonic COntrol aRchitecture), et l’étendant en s’inspirant des théories de l’évolution et en utilisant des mécanismes d’auto-organisation. L’utilisation des théories de l’évolution enrichit l’architecture de contrôle en permettant l’évolution de deux manières distinctes, en réponse au type et au degré de la perturbation apparue. Le premier mode d’adaptation, appelé auto-organisation comportementale, permet à chaque entité qui compose le système d’adapter dynamiquement leur comportement interne, gérant de cette façon de petites perturbations. Le second mode, nommé auto-organisation structurelle, traite de plus grandes perturbations, en permettant aux entités du système de ré-organiser leurs relations, et par conséquent modifier structurellement le système. L’architecture holonique auto-organisée de contrôle de systèmes de production proposée dans cette thèse a été validée sur une cellule de production flexible AIP-PRIMECA. Les résultats ont montré une amélioration des indicateurs clés de performance par rapport aux architectures de contrôle hiérarchiques et hétérarchiques. / The manufacturing world is being deeply challenged with a set of ever demanding constraints where from one side, the costumers are requiring products to be more customizable, with higher quality at lower prices, and on other side, companies have to deal on a daily basis with internal disturbances that range from machine breakdown to worker absence and from demand fluctuation to frequent production changes. This dissertation proposes a manufacturing control architecture, following the holonic principles developed in the ADAptive holonic COntrol aRchitecture (ADACOR) and extending it taking inspiration in evolutionary theories and making use of self- organization mechanisms. The use of evolutionary theories enrich the proposed control architecture by allowing evolution in two distinct ways, responding accordingly to the type and degree of the disturbance that appears. The first component, named behavioural self- organization, allows each system’s entity to dynamically adapt its internal behaviour, addressing small disturbances. The second component, named structural self-organization, addresses bigger disturbances by allowing the system entities to re-arrange their rela- tionships, and consequently changing the system in a structural manner. The proposed self-organized holonic manufacturing control architecture was validated at a AIP-PRIMECA flexible manufacturing cell. The achieved experimental results have also shown an improvement of the key performance indicators over the hierarchical and heterarchical control architecture.
127

Transformação de hábitos e sustentabilidade : a evolução de interpretantes na (auto) construção da cidade /

Moraes, Sônia C.B. January 2004 (has links)
Orientador: Lauro F. B. Silveira / Banca: Lucrecia D'Alessio Ferrara / Banca: Mariana C. Broens / Resumo: A vida do homem inserido em seu meio ambiente, que (nesse trabalho) é a cidade faz sua atuação dependendo de sua consciência do mundo.As cidades são sistemas dinâmicos onde se pode constatar indícios de auto-organização. O paradigma da auto-organização nos sistemas dinâmicos é desenvolvido nas Ciências Cognitivas, com paralelos na física, biologia, sociologia. A auto-organização nos sistemas dinâmicos caracteriza-se como um processo criativo no qual a estrutura anterior é transformada. Os processos emergentes numa nova forma caracterizam a criação, assim como a formação de interpretantes peirceanos. A semiótica peirceana, fazendo parte de sua extensa "arquitetura metafísica", trata da formação de interpretantes numa forma anterior e mais abrangente que a concepções dos processos de auto-organização e emergência A criatividade pode ser constatada na significação de um processo informacional que relaciona signos produzindo crenças. No contínuo da formação de hábitos visto através da semiótica, através da relação interpretante, signo e objeto constatamos um processo evolutivo e criativo que possibilita a mudança de crenças e conseqüente transformação de hábitos. Um entendimento possível da cidade é caracteriza-la enquanto um sistema dinâmico auto-organizado na qual ocorre a transformação da relação entre seus elementos, num processo sígnico criativo e evolutivo, onde existe a possibilidade de continuidade da vida. / Abstract: Life of man integrated into his environment, which (in this work) is the town, makes his action to depend on his awareness of the world. Towns are dynamic systems where self-organization signs may be found out. In the dynamic systems self-organization paradigm is developed in the cognitive sciences, with parallels in physics, biology and sociology.In the dynamic systems self-organization is characterized as a creative process in which the previous structure is transformed. Emerging processes in a new shape characterize creation just as peircean interpretants constitution. Peircean semiotics, as part of his large "metaphysical architecture" deals with interpretants construction in a previous and more comprehensive way than concepts of self-organization and emergence processes. Creativity may be found out in the significance of an informational process which relates signs resulting in beliefs.In the continuum of habits shaping seen through semiotics, by means of interpretant, sign and object relationship, an evolutionary and creative process is found out, which may cause changes in beliefs and therefore in habits.A possible way to understand a town is to characterize it as a self-organized dynamic system in which change of relationship among its elements occurs, within a signic process that is creative and evolutionary, where possibility of continuity of life exists. / Mestre
128

A dinâmica da sociocomunicação no ciberespaço : o impulso alquímico /

Oliveira, Walter Clayton de. January 2005 (has links)
Resumo: O Ciberespaço é uma teia colossal, um dispositivo de comunicação que associa características múltiplas e opostas. Ao desenvolver-se de forma espontânea, o Ciberespaço começa então a orientar-se para a comunicação. Não faltam hoje inúmeras comunidades de comunicação. Neste sentido, objetivamos com esta pesquisa, analisar a dinâmica da sociocomunicação, transferência e fluxo de informações de comunidades virtuais tomadas como sistemas sociais auto-organizados, no Ciberespaço. Através de incursões na literatura, fizemos uma análise teórica-descritiva do conceito de sociocomunicação e discutimos em que medida ele pode ser aplicado diante das inter-relações que emergem entre os indivíduos pertencentes às comunidades virtuais. Concluímos que, o Ciberespaço, assim definido, configura-se como um locus de extrema complexidade e difícil compreensão. A sua heterogeneidade é notória quando se percebe o grande número de ambientes de sociabilidade existentes, no interior dos quais se estabelecem as mais diversas e variadas formas de interação, tanto entre Homens, quanto entre Homens e máquinas e, inclusive, entre máquinas. Trata-se de um novo tipo de organização sociotécnica que facilita a mobilidade no e do conhecimento, as trocas de saberes, a construção coletiva do sentido, em que a identidade sofre uma expansão do eu baseada na diluição da corporeidade, ou seja, o que se perde em corpo ganha-se em rapidez e capacidade de disseminar o eu no espaço-tempo. Assiste-se, assim, a uma aceleração do metabolismo social. / Abstract: The Cyberspace is a colossal tissue, a communication device that associates multiple and opposed characteristics. When developing in a spontaneous way, the Cyberspace begins then to guide for the communication. Don't lack countless communication communities today. In this sense, we objectified with this research, to analyze the dynamics of the social communication, transfer and flow of information in virtual communities, took as self-organized social systems, in the Cyberspace. Through incursions in the literature, we made a theoreticaldescriptive analysis of the social communication concept and we discussed in what measure could be applied to the interrelations that emerge among the individuals belonging to the virtual communities. We conclude that, the Cyberspace, thus defined, is configured as one locus of extreme complexity and difficult understanding. Its heterogeneous is well-known when the great existing environment number is perceived of sociability, in the interior of which if they establish most diverse and varied interaction forms, as much between Men, how much between Men and machines and, also, between machines. One is about a new type of social technique organization that facilitates the mobility in and of the knowledge, the exchanges to know, the collective construction of the direction, where the identity suffers an expansion from based self in the dilution the body, or either, what it is lost in body gains in rapidity and capacity to spread self in the space-time. It is attended, thus, to an acceleration of the social metabolism. / Orientador: Silvana Aparecida Borsetti Gregório Vidotti / Coorientador: Fátima Cabral / Banca: José Augusto Chaves Guimarães / Banca: Oswaldo Francisco de Almeida Júnior / Mestre
129

Um estudo filosófico interdisciplinar do conceito de corpo /

Frastrone, Maria Guiomar Benuto. January 2009 (has links)
Orientador: Mariana Cláudia Broens / Banca: Alfredo Pereira Júnior / Banca: Gustavo Maia Souza / Resumo: Este trabalho tem por objetivo investigar alguns pressupostos e implicações filosóficas da noção cartesiana de corpo e contrapor esta concepção ao entendimento de que o corpo dos organismos é uma estrutura biológica com capacidades cognitivas que se atualiza evolutivamente de modo auto-organizado. Apoiados na teoria de sistemas complexos, tal como proposto por Souza (2000, 2004, 2007), Souza e Daminelli (2008), Guimarães (2000, 2004), Pereira Júnior (2004), caracterizamos o corpo como instância auto-organizada que se atualiza nas relações com o meio e entre suas estruturas constituintes. Defendemos também a hipótese, apoiados em Haselager (2004, 2007, Gonzalez (2004) e Broens (2004, 2007), que a estrutura corpórea, em contraste com os postulados dualistas - mais proeminente o cartesiano -, corresponde à atualização de padrões disposicionais cuja interação com o meio é de importância central para a cognição. Assim, entendemos que o corpo não pode ser reduzido a uma substância extensa sem nenhum papel cognitivo, como entendiam Descartes e muitos dualistas, ou, como parecem pressupor alguns cognitivistas tradicionais, a desempenhar, quando muito, um papel cognitivo secundário. Procuraremos ressaltar que, adotada uma perspectiva evolucionária, (1) o corpo deve ser entendido simultaneamente como produto e produtor de processos cognitivos na dinâmica auto-organizativa própria da vida e (2) a adoção desta perspectiva têm implicações importantes para a Filosofia da Mente / Abstract: This work aims at inquiring into some of the philosophical assumptions and implications of the Cartesian concept of body, seeking to contrast such view to the understanding that the body of organisms is a biological structure with cognitive capacities actualizing itself in an evolutive self-organized way. We rely on the theories of complex systems, such as those argued for by Souza (2000, 2004, 2007), Souza and Daminelli (2008), Guimarães (2000, 2004), Pereira Júnior (2004), and we seek to identify the body as a self-organized instance actualizing itself in the relations with the environment and in between its constitutive structures. Based on the works of Haselager (2004, 2007), Gonzales (2004) and Broens (2004, 2007), and in contrast to dualistic assumptions, mainly of a Cartesian character, we also defend the hypothesis that corporal structure corresponds to the actualization of dispositional patterns, of which the interaction with the environment is chiefly significant to cognition. So, we understand that the body cannot be reduced to a mere bundle of matter and made to occupy a secondary role, as traditional cognitivists defend. Our account acquires consistency when the body is seen as a source of knowledge grounded on a fluid and continuous evolutive history, being not only a mere result reached from logical processes coordinated by knowledge representations, as Haselager points out (2004). We stress the central role of the body in processes of acquisition of knowledge. Finally, we conclude that the body cannot be resumed to an extended substance with no cognitive role at all, as Descartes and many other dualistic thinkers assumed; or, as many traditional cognitivists seem to assume, that it has only a secondary role in cognition. We seek to reinforce that once an evolutive standpoint is taken, (1) the body must be understood at the same time both as producer ... (Complete abstract click electronic access below) / Mestre
130

Reações oscilatórias e a temperatura: dos efeitos em escala bulk ao monitoramento local / Oscillatory reactions and temperature: From bulk effects to the local monitoring

Zülke, Alana Aragón 21 November 2017 (has links)
Utilizando uma faixa de temperatura entre 5° a 45°C, observou-se duas regiões de diferentes tendências para com o aumento da temperatura durante as oscilações (eletro-oxidação galvanostática, mesma corrente normalizada aplicada) no sistema ácido fórmico sobre platina policristalina em meio ácido. Até 25°C, o comportamento cinético operou de modo convencional, do tipo Arrhenius, sendo que acima desse ponto crítico observou-se o fenômeno de (sobre)compensação de temperatura. O sistema foi caracterizado fazendo uso de técnicas eletroquímicas clássicas e espectroscopia de impedância eletroquímica tendo ficado evidente um ponto de inflexão a 25°C que marca uma quebra na tendência em todas as frequências do sistema (f, Hopf,Sosc) e taxa de envenenamento. Os resultados foram discutidos em termos do papel-chave das espécies de PtO, que acoplam quimicamente as dinâmicas rápidas/lentas. Fomos capazes de: (i) identificar a competição entre duas etapas de reação como responsáveis pelos dois domínios de temperatura; (ii) comparar as energias de ativação relativas dessas duas etapas; E ademais (iii) especulamos sobre o papel de uma determinada etapa de reação no conjunto de reações responsáveis pelo aumento do período oscilatório. Com ajuda de métodos deconvolutivos, reforçamos a hipótese de que as etapas por trás do drift possuem menor energia de ativação que as etapas LH durante tais dinâmicas. Também estão aqui discutidos experimentos de monitoramento de temperatura local durante as dinâmicas oscilatórias. Duas estratégias experimentais foram empregadas: uma utilizando eletrodos-termômetros a base de termistores e outra utilizando um micro calorímetro onde sensores piroelétricos monitoraram as oscilações na temperatura do eletrodo de trabalho, altamente em fase com as oscilações de potencial. Destacamos que ambas configurações foram capazes de acompanhar as diferenças de temperatura durante as dinâmicas oscilatórias (na faixa de 0,1~0,5mK por ciclo). Os resultados obtidos para a reconstrução dos fluxos de calor (ø) corroboram com o atual modelo mecanístico da eletro-oxidação oscilante de ácido fórmico em Pt em meio ácido. Observamos que as etapas de envenenamento do eletrodo são acompanhadas pelo aumento no ø enquanto a reativação do eletrodo é acompanhada pela diminuição no ø. / The oscillating electro-oxidation of formic acid on polycrystalline platinum in acidic media, as a model system, was employed to investigate the temperature effects on the coupling of fast and slow dynamics processes belonging to its oscillatory dynamics, i.e. the core oscillator (fast dynamics) and the slow term deactivation of surface caused by the oxygen place-exchange process. Using a temperature range from 5 to 45°C, we observed two disparate regions of tendencies upon temperature increment on the galvanostatic oxidation. The system exhibits conventional Arrhenius behavior for T up to 25°C and, on the other hand, T > 25° revealed the occurrence of temperature (over)compensation. The system was characterized by means of conventional electrochemical techniques and electrochemical impedance spectroscopy. Clearly, we observed an inflexion point at 25°C marked by a break on the tendency of oscillatory frequency ( f, hopf, Sosc) and poisoning rates. Results were discussed in terms of the key role of PtO species, which chemically couple slow and fast dynamics. In summary we were able to: (i) identify the competition between two reaction steps as responsible for the two temperature domains; (ii) compare the relative activation energies of these two steps; and (iii) suggest the role of a given reaction step on the period-increasing set of reactions involved in the oscillatory dynamics. In addition, we performed experiments to monitor the local temperature of the interface during oscillatory dynamics. Two experimental strategies were applied: low cost thermometers-electrodes and a more sophisticated experimental set up based on pyroelectric detection. It should be noted that both configurations were able to monitor temperature differences during oscillatory dynamics (in the range of 0.1 ~ 0.5mK per cycle). The results obtained for the reconstruction of the heat fluxes (ø) corroborate with the current mechanistic model of the oscillating electro-oxidation of formic acid in Pt in acidic medium. We observed that the poisoning stages of the electrode are accompanied by the increase in ø while the reactivation of the electrode is accompanied by the decrease in ø.

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