No description available.

No description available.

Motivés par les développements récents dans le domaine des nanosciences, nous étudions les propriétés statistiques et thermodynamiques des systèmes mésoscopiques. En particulier, nous nous concentrons sur les résultats connus sous le nom de théorèmes de fluctuation. Ces relations donnent des prédictions sur le comportement de différents quantités dynamiques dans des situations loin de l'équilibre, tout en tenant compte des fluctuations de l'évolution temporelle. La première partie de notre étude est consacrée aux relations existants entre les fluctuations et la théorie de la réponse. Nous commençons par dériver une relation fonctionnelle pour les systèmes quantiques forcés dans le temps qui généralise l'égalité de Jarzynski et dont l'expansion en l'intensité du forçage permet de retrouver les résultats de la réponse linéaire. Nous poursuivons ensuite ces considérations en nous intéressant aux états stationnaires de non-équilibre. Ceci est réalisé dans le cadre des processus stochastiques, dans lequel nous dérivons une relation de fluctuation pour les courants de non-équilibre traversant le système. Cette relation lie explicitement les fluctuations aux forces thermodynamiques, ce qui nous permet de développer ses conséquences au niveau de la théorie de la réponse non-linéaire. De cette manière, nous obtenons de nouvelles relations liant fluctuations et coefficients de réponse dans le régime non-linéaire. Dans la deuxième partie de ce travail, nous développons une connexion récente liant l'irréversibilité au désordre dynamique. Nous présentons des résultats expérimentaux montrant que la production d'entropie s'exprime comme la différence de deux quantités mesurant la brisure de symétrie sous renversement du temps au niveau du désordre temporel. Nous étudions ensuite les conséquences de cette relation dans le contexte de l'énergétique du traitement de l'information. En particulier, nous présentons une généralisation du principe de Landauer pour l'effaçage d'information. De la même manière, nous relions la dissipation à la génération d'information par les entités biologiques.

Ion beam erosion of solid surfaces is known to produce a variety of surface morpholo- gies, such as pits, mounds or crests. Very often self-organized patterns composed of highly correlated arrays of dots or ripples at sub-micrometer and nanometer length scale could be obtained. Ion beam erosion patterning have demonstrated the poten- tial to tailor related surface properties for optoelectronic and spintronic applications, such as modulated photoemission induced by quantum con¯nement of nanodots and magnetic anisotropy induced by nanoripples. On the other hand, one considerable practical importance and e®ect of ion beam erosion is that of surface smoothing of nanometer features, during etching or ¯lm deposition coincident with energetic species. In my dissertation, systematic investigations of ripple formation and smooth- ing during low energy Ar+ ion erosion of sapphire surfaces using synchrotron grazing incidence small angle x-ray scattering and atomic force microscopy are performed. It is found in the pattern formation that the wavelength of ripples can be varied over a remarkably wide range by changing the ion incidence angle. The ion induced viscous °ow smoothing mechanism explains the general trends of the ripple wavelength at low temperature and incidence angles larger than 30±. The behavior at high temper- atures suggests relaxation by surface di®usion. However, strong smoothing is inferred from the observed ripple wavelength near normal incidence, which is not consistent with either surface di®usion or viscous °ow relaxation. Furthermore, a real-time x- ray scattering experiment is presented showing that ion smoothing of a pre-patterned surface near normal incidence is consistent with the e®ect of a collision-induced lat- eral current. Quantitative agreement is obtained using ion-collision simulations to compute the magnitude of the surface current. The results lead to predictions for the surface morphology phase diagram as a function of ion beam energy and incidence angle that substantially agree with experimental observations. The ion-induced lat- eral current smoothing model is applicable to many surfaces that become amorphous but maintain the stoichiometry of bulk materials during ion bombardment.

No description available.

No description available.

Many who study complex systems believe that the complexity we observe in the world around us is frequently the product of a large number of interactions between components following a simple rule. However, the task of discerning the rule governing the evolution of any given system is often quite difficult, requiring intuition, guesswork, and a great deal of expertise in that domain. To circumvent this issue, researchers have considered the inverse problem where one searches among many candidate rules to reveal those producing interesting behavior. This approach has its own challenges because the search space grows exponentially and interesting behavior is rare and difficult to rigorously define. Therefore, the contribution of this work includes tools and techniques for searching for dimer automaton rules that exhibit self-organization (the transformation of disorder into structure in the absence of centralized control). Dimer automata are simple, discrete, asynchronous rewriting systems that operate over the edges of an arbitrary graph. Specifically, these contributions include a number of novel, surprising, and useful applications of dimer automata, practical methods for measuring self-organization, advanced techniques for searching for dimer automaton rules, and two efficient GPU parallelizations of dimer automata to make searching and simulation more tractable. / Ph. D.

Communication applications have diverse network service requirements. For instance, <em>Voice over IP</em> (VoIP) demands short end-to-end delay, whereas <em>File Transfer Protocol</em> (FTP) benefits more from high throughput than short delay. However, the Internet delivers a uniform best-effort service. As a result, much research has been conducted to enhance the Internet to provide service differentiation. Most of the existing proposals require additional access-control mechanisms, such as admission control and pricing, which are complicated to implement and render these proposals not incrementally deployable. <em>Incentive-compatible Differentiated Scheduling</em> (ICDS) provides incentives for applications to choose a service class according to their burst characteristics without additional access-control mechanisms. <br /><br /> This thesis investigates the behaviour of ICDS with different types of traffic by analysis and extensive simulations. The results show some evidences that ICDS can achieve its design goal. In addition, this thesis revises the initial ICDS algorithm to provide fast convergence for TCP traffic.

Esta pesquisa apresenta um estudo de caso cujo objetivo é descrever os saberes produzidos no processo de auto-organização de grupos de mulheres da Rede Xique-Xique de Comercialização Solidária, nos municípios de Mossoró, Upanema, Governador Dix-Sept Rosado, Baraúna, Grossos, Tibau e Apodi, no estado do Rio Grande do Norte. Trata-se de uma análise sócio histórica e econômica das categorias discursivas de termos como \'mulheres\', \'trabalho, \'família\' e \'história\', assim como da capacidade de transformação social que estes saberes apresentam. A pesquisa de campo foi guiada essencialmente pelo método da observação participante, com procedimentos aplicados pelo método biográfico, mais especificamente pela história de vida. Sobre a coleta dos dados, foram realizadas 11 entrevistas individuais com as mulheres dos grupos auto-organizados; uma entrevista com a coordenadora do CF8 e uma entrevista coletiva, na qual estavam presentes mulheres participantes de seis grupos da região. Além das entrevistas, foram realizadas visitas aos grupos produtivos, participação em reuniões e seminários promovidos pela Rede Xique-Xique ou instituições parceiras. Para analisar todos os dados registrados, as entrevistas foram transcritas e categorizadas. A análise foi realizada a partir do objetivo apresentado e da referenciação das categorias supracitadas, com o auxílio do Software NVivo10. Nesse sentido, foi possível descrever e apreender que o processo de auto-organização dessas mulheres permite a construção de um ato comunicativo entre estas, que por sua vez possibilita a produção de saberes. Esse ato comunicativo torna-se emancipatório na medida em que se caracteriza como uma prática constante de autorreflexão a respeito dos efeitos da organização produtiva autogerida e contribui assim com a transformação de vida dessas mulheres. Sobre a estrutura textual do presente trabalho, a dissertação está dividida em três capítulos. O primeiro capítulo trata da descrição dos aspectos sócio históricos do estado do Rio Grande do Norte e sua relação constitutiva com a ação atual da Rede Xique-Xique. O capítulo dois descreve a estrutura de princípios ou pilares que sustentam a prática da Rede: agroecologia, economia solidária e feminismo. No capítulo três, com base nas categorias discursivas propostas, analiso as histórias de vidas das mulheres entrevistadas durante o trabalho de campo. Por fim, as considerações finais são apresentadas. / This research presents a case study which aims to describe the knowledge produced in the process of self-organizing groups of women Xique-Xique Network Marketing Partnership located in Mossoró, Upanema, Governador Dix-Sept Rosado, Baraúna, Grossos, Tibau e Apodi in the state of Rio Grande do Norte. It is a historical and socioeconomic analysis of the discursive categories of terms such as \'women\', \'work\', \'family\' and \'history\', as well as the ability to social transformation this knowledge presents. The field research was guided essentially by the method of participant observation with procedures applied by the biographical method, more specifically the history of life. On data collection, 11 individual interviews with women of self-organized groups were conducted; interview with the coordinator of the CF8 and a press conference, in which women from six groups in the region were present. Besides the interviews, visits to productive groups, participation in meetings and seminars sponsored by Xique-Xique Network or partner institutions were conducted. To analyze all the recorded data, the interviews were transcribed and using NVivo10, categorized. The analysis was based on the discursive and historical referencing of the above categories. Thus, it was possible to describe and understand that the process of self-organization of these women allows the construction of a communicative act between them, which in turn enables the production of knowledge. This communicative act becomes emancipatory in that it is characterized as a constant practice of self-reflection about the effects of self-managed productive organization and thus contributes to the transformation of these women\'s lives. On the textual structure of the present paper, it is divided into three chapters. The first chapter presents the description of the historical and social aspects of the state of Rio Grande do Norte and its constitutive relationship with the Xique-Xique Network current action. Chapter two describes the structure of principles that support the practice of the group: agroecology, economic solidarity and feminism. In chapter three, based on the discursive categories proposed, I analyze the life histories of the women interviewed during the field work. Finally, the concluding remarks are presented.

A emergência de estruturas espaço-temporais auto-organizadas em sistemas químicos abertos e afastados do estado de equilíbrio termodinâmico resulta da cooperação entre os processos de reação e transporte de espécies ativas e tem se tornado uma área de intensa atividade nos últimos anos. Auto-organização dinâmica na interface sólido/líquido durante a eletrodeposição de Cu-Sn em regime oscilatório é o tema central do presente trabalho. O sistema estudado consistiu da co-eletrodeposição de cobre e estanho sobre eletrodo de ouro policristalino na presença do surfactante Triton X-100. Instabilidades temporais na forma de oscilações de corrente sob controle potenciostático resultantes da presença de uma região de resistência diferencial negativa no perfil voltamétrico têm sido experimentalmente observadas nesse sistema. Acompanhando essas oscilações de corrente há uma deposição intercalada em multicamadas de diferentes composições (basicamente Cu e CuSn), espessuras e morfologias. Especificamente foram estudadas neste trabalho a variedade dinâmica (i.e., o formato e escala de tempo das oscilações de corrente) e a estrutura e composição dos eletrodepósitos formados. Esse estudo tomou como base o mapeamento das regiões de instabilidade no plano (resistência externa, Rext) x (voltagem aplicada, U) sob diferentes concentrações das espécies eletroativas. Curvas de polarização foram obtidas por meio de experimentos quasi-estacionários de varredura catódica a baixas velocidades. De posse do conhecimento da localização das regiões nas quais oscilações de corrente foram observadas, experimentos estacionários foram realizados, e a morfologia e composição dos depósitos foram investigadas ex-situ por meio de microscopia eletrônica de varredura (MEV) e EDX, respectivamente. / The study of the dynamics self-organization on the solid/liquid interface during the co-electro deposition of copper and tin in the presence of adsorbed surfactant was carried out. Temporal instabilities in form of current oscillations under potentiostatic control resulted from the presence of a negative differential resistance in the voltametric profile has been reported in this system. The electro deposits obtained by this oscillatory regimen exhibit layer-by-layer structure with different compositions of Cu-Sn alloys. In the present work current density (j) versus potential(U) curves and j versus time (t) curves were recorded for the co-electro depositions under a series of external resistances (Rext) and polarization potentials. The characterization of the films were carried out by scanning electron microscope (SEM) and energy dispersive x-ray (EDX) analysis. The results confirm that for different values of external resistance and polarization potentials different compositions of the electro deposited Cu-Sn alloys were obtained.