Dissertations / Theses on the topic 'Fluctuation de tension'

The change of the bandsaw tension force during wood cutting was investigated on the experimental installation created on the basis of the band saw machine. Experimental time dependen ce indicators of the tension force change in a narrow bandsaw during wood cutting were obtained. The influence ofthe pre-tension strain, the width of the saw blade and the cutting height on the pre-tension force change of the band saw was investigated.

A produção de petróleo em ambiente marítimo é feita através de plataformas, em geral flutuantes, conectadas aos reservatórios através de dutos, os chamados risers, responsáveis pelo transporte de petróleo bruto, gás ou água. Do ponto de vista estrutural, estes risers podem ser rígidos ou flexíveis, porém, independente do tipo empregado, com o aumento da profundidade, aumentam-se os esforços de tração sobre essas estruturas. Em águas profundas, essa desvantagem pode ser diminuída com a utilização de configurações mais complexas, dentre as quais se destaca a riser tower, que é foco do presente estudo. Este sistema é composto por vários dutos unidos ao longo de um tubo vertical único, sustentado por uma bóia de subsuperfície. Um grande atrativo desta configuração é a redução da fadiga devido às ondas, uma vez que a bóia e parte significativa dos risers rígidos verticais não sofrem efeitos relevantes das ondas de superfície. No entanto, dois problemas de interação fluido-estrutural persistem: um associado ao fenômeno de VIV Vibração Induzida pela Emissão de Vórtices no riser vertical e outro relativo ao VIM - Movimento Induzido pela Emissão de Vórtices na bóia. Devido ao fato da correnteza ser quase permanente, bem como das altas frequências passíveis de excitação, tem-se um número de ciclos de tensão bastante elevado, associados à flexão, o que pode ser importante no estudo de fadiga do material que compõe as referidas estruturas. De maneira mais completa, no que compete à fenomenologia das interações fluidoestruturais mencionadas, o presente trabalho propõe-se a estudar numérica e analiticamente a dinâmica transversal e longitudinal do conjunto formado pelo riser rígido e pela bóia de subsuperfície, particularmente focado nos efeitos da dinâmica sobre a vida útil do riser vertical.
The offshore oil production is performed with platforms, floating in most cases, which are connected to the well through pipes. These pipes are called risers and are responsible for the transport of crude oil, gas and water from seabed to the platform and vice-versa. From the structural standpoint, these risers can be rigid or flexible. However, independently of the type, the topside tension of these structures increases with the water depth. In deep water this disadvantage can be reduced by using more complex configurations, for example the riser tower, which is the focus of the current study. The riser tower is a system composed by pipes bundled around a central steel tube supported by a subsurface buoyancy tank. This configuration is attractive due to the reduction on waves fatigue since the buoy and most of the vertical risers length is not impacted by the effects of the surface waves. Nevertheless, two issues from the fluid-structural interaction still persist: one related to the VIV phenomena vortex-induced vibration on the vertical riser and the other associated to the VIM vortex induced motion on the buoyancy tank. Considering the almost permanent nature of the offshore currents associated to the high frequencies that can be excited, during the operational life, the riser is subjected to a large amount of stress cycles which are important for the evaluation of the structural integrity in terms of fatigue. In a more complete sense, considering the phenomenology of the fluid-structure interactions, the purpose of the present work is studying numerical and analytically the inline and cross-flow dynamics of the riser tower system especially focused on the impact of the dynamics on the vertical riser operational life.

Aujourd’hui, les « nanomatériaux » ouvrent des perspectives importantes dans diverses applications : énergie, aéronautique, automobile, etc. . . Un procédé relativement récent, la projection plasma de suspension, permet la formation de dépôt céramique finement voire nanostructuré avec de faibles épaisseurs (entre 5 µm et 10 µm). Néanmoins, la microstructure des dépôts obtenus passe par la compréhension d���un grand nombre de paramètres, et notamment l’injection de la suspension. Ces travaux ont particulièrement montré l’intérêt de l’injection et de la fragmentation de la suspension pour son traitement dans le plasma. L’injection de la suspension a été observée à l’aide d’un système optique qui permet de déclencher l’acquisition de l’image sur une valeur de tension d’arc de la torche. Ce système permet d’observer la trajectoire et la fragmentation de la suspension correspondante à un état instantané du jet de plasma. Cette étude a montré l’importance des fluctuations du jet de plasma sur la fragmentation et la trajectoire de la suspension. Il a été observé une grande différence de traitement de la suspension selon que l’on utilise un plasma Ar/H2 ou Ar/He. Le traitement des gouttes avec un plasma argon-hydrogène se fait de manière hétérogène, cette différence de traitement est due aux fluctuations de tension de la torche, et la porosité des dépôts formés en est directement liée. La diminution de ces instabilités avec un plasma Ar/He, par exemple, permet d’homogénéiser le traitement des gouttes de suspension. La diminution de la dispersion des trajectoires dans le plasma limite les particules infondues dans le dépôt, et par conséquent sa porosité. Ces travaux ont permis d’élaborer des dépôts de zircone avec une épaisseur de l’ordre de 10 µm et une faible porosité (~ 4%). Plusieurs dépôts denses (porosité de 4%) ont été formés que ce soit avec un plasma argon-hydrogène ou argon-hélium, à condition d’adapter l’injection de suspension avec les conditions plasmagènes de tir
Nanostructured coatings exhibits unique properties in various applications, such as aeronautics, energy, automotive, etc. . . Suspension Plasma Spraying (SPS) seems to be a promising technique to elaborate finely structured coatings with low thickness (between 5 µm to 10 µm). Nevertheless, SPS parameters which lead to control the microstructure of the deposit are not yet clearly identify, particularly for the injection of suspension. It has been shown that injection and fragmentation of the suspension into the plasma jet plays a key role in their further heat treatment. The injection of the suspension has been observed with a fast shutter camera coupled with a laser flash and triggered by a defined instantaneous voltage level of the plasma torch. Hence, the trajectories and fragmentations of the drops can be observed and correlated to an instantaneous plasma state. A particular attention is paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of arc root) and depending on the different spray parameters such as the plasma forming gas mixture and the suspension momentum. A significant difference has been highlighted between argon-hydrogen and argon-helium plasma, mainly due to their strong fluctuation particularities. The heterogeneity of drops treatment using argon-hydrogen plasma is due to arc voltage fluctuations, and the enhancement of the coating porosity has been observed in this case. The stabilization of the interaction plasma jet-suspension increases when using plasmas with low arc voltage instabilities like Ar-He. The reduction of the drops dispersion into the plasma flow decreases the rate of unmellted particles into the coating and thus it porosity. These works have also allowed the formation of zirconia coatings with low thicknesses (~10 µm) and dense structure (~ 4% of porosity). Different dense deposits have been elaborated using either argon-hydrogen or argon-helium plasma, when the interaction plasma-suspension is controlled and adapted

Thesis (Ph.D.)--Tufts University, 2002.
Adviser: L. H. Ford. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 161-165). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Recent research on particle size distributions and particle concentrations near a busy road cannot be explained by the conventional mechanisms for particle evolution of combustion aerosols. Specifically they appear to be inadequate to explain the experimental observations of particle transformation and the evolution of the total number concentration. This resulted in the development of a new mechanism based on their thermal fragmentation, for the evolution of combustion aerosol nano-particles. A complex and comprehensive pattern of evolution of combustion aerosols, involving particle fragmentation, was then proposed and justified. In that model it was suggested that thermal fragmentation occurs in aggregates of primary particles each of which contains a solid graphite/carbon core surrounded by volatile molecules bonded to the core by strong covalent bonds. Due to the presence of strong covalent bonds between the core and the volatile (frill) molecules, such primary composite particles can be regarded as solid, despite the presence of significant (possibly, dominant) volatile component. Fragmentation occurs when weak van der Waals forces between such primary particles are overcome by their thermal (Brownian) motion. In this work, the accepted concept of thermal fragmentation is advanced to determine whether fragmentation is likely in liquid composite nano-particles. It has been demonstrated that at least at some stages of evolution, combustion aerosols contain a large number of composite liquid particles containing presumably several components such as water, oil, volatile compounds, and minerals. It is possible that such composite liquid particles may also experience thermal fragmentation and thus contribute to, for example, the evolution of the total number concentration as a function of distance from the source. Therefore, the aim of this project is to examine theoretically the possibility of thermal fragmentation of composite liquid nano-particles consisting of immiscible liquid v components. The specific focus is on ternary systems which include two immiscible liquid droplets surrounded by another medium (e.g., air). The analysis shows that three different structures are possible, the complete encapsulation of one liquid by the other, partial encapsulation of the two liquids in a composite particle, and the two droplets separated from each other. The probability of thermal fragmentation of two coagulated liquid droplets is discussed and examined for different volumes of the immiscible fluids in a composite liquid particle and their surface and interfacial tensions through the determination of the Gibbs free energy difference between the coagulated and fragmented states, and comparison of this energy difference with the typical thermal energy kT. The analysis reveals that fragmentation was found to be much more likely for a partially encapsulated particle than a completely encapsulated particle. In particular, it was found that thermal fragmentation was much more likely when the volume ratio of the two liquid droplets that constitute the composite particle are very different. Conversely, when the two liquid droplets are of similar volumes, the probability of thermal fragmentation is small. It is also demonstrated that the Gibbs free energy difference between the coagulated and fragmented states is not the only important factor determining the probability of thermal fragmentation of composite liquid particles. The second essential factor is the actual structure of the composite particle. It is shown that the probability of thermal fragmentation is also strongly dependent on the distance that each of the liquid droplets should travel to reach the fragmented state. In particular, if this distance is larger than the mean free path for the considered droplets in the air, the probability of thermal fragmentation should be negligible. In particular, it follows form here that fragmentation of the composite particle in the state with complete encapsulation is highly unlikely because of the larger distance that the two droplets must travel in order to separate. The analysis of composite liquid particles with the interfacial parameters that are expected in combustion aerosols demonstrates that thermal fragmentation of these vi particles may occur, and this mechanism may play a role in the evolution of combustion aerosols. Conditions for thermal fragmentation to play a significant role (for aerosol particles other than those from motor vehicle exhaust) are determined and examined theoretically. Conditions for spontaneous transformation between the states of composite particles with complete and partial encapsulation are also examined, demonstrating the possibility of such transformation in combustion aerosols. Indeed it was shown that for some typical components found in aerosols that transformation could take place on time scales less than 20 s. The analysis showed that factors that influenced surface and interfacial tension played an important role in this transformation process. It is suggested that such transformation may, for example, result in a delayed evaporation of composite particles with significant water component, leading to observable effects in evolution of combustion aerosols (including possible local humidity maximums near a source, such as a busy road). The obtained results will be important for further development and understanding of aerosol physics and technologies, including combustion aerosols and their evolution near a source.

Mesures précises de la tension de surface, de l'énergie de gradin et de la vitesse de croissance pour l'orientation (0001), au voisinage de la transition rugueuse à t = 1,28 k; mise en évidence de la croissance par nucléation bidimensionnelle et de l'élargissement dynamique de la transition. Très bon accord avec les prévisions de la théorie critique qui apparente cette transition aux transitions de Kosterlitz-Thouless.

Large vacuum fluctuations of a quantum stress tensor can be described by the asymptotic behavior of its probability distribution. Here we focus on stress tensor operators which have been averaged with a sampling function in time. The Minkowski vacuum state is not an eigenstate of the time-averaged operator, but can be expanded in terms of its eigenstates. We calculate the probability distribution and the cumulative probability distribution for obtaining a given value in a measurement of the time-averaged operator taken in the vacuum state. In these calculations, we use the normal ordered square of the time derivative of a massless scalar field in Minkowski spacetime as an example of a stress tensor operator. We analyze the rate of decrease of the tail of the probability distribution for different temporal sampling functions, such as compactly supported functions and the Lorentzian function. We find that the tails decrease relatively slowly, as exponentials of fractional powers, in agreement with previous work using the moments of the distribution. Our results lead additional support to the conclusion that large vacuum stress tensor fluctuations are more probable than large thermal fluctuations, and may have observable effects.

L'ère des technologies CMOS fortement submicroniques et des circuits à hautes performances temporelles et énergétiques exige la réduction de l'impact sur les circuits : de la fluctuation du procédé de fabrication (P), de la tension d'alimentation (V) et de la température (T). Il est donc nécessaire de mettre en place des capteurs ou ring oscillateurs sur puce dédiés à la qualification intrinsèque des circuits intégrés en termes de PVT. Les capteurs seront activés pendant la phase de test des circuits ou pendant leur phase de fonctionnement normal, et les mesures seront converties en données numériques permettant de classifier les performances temporelles et énergétiques du système-sur-puce. Dans ce cadre, la présente thèse en milieu industriel a permis le développement de techniques et d'algorithmes de compensations post-fabrication en réduisant la consommation et/ou augmentant la vitesse du circuit. Précisément, les algorithmes validés au niveau silicium utilisent l'ajustement de la tension d'alimentation pour une compensation à gros-grain, ainsi que l'ajustement de la tension des substrats des transistors NMOS et PMOS pour une compensation à fin-grain
The new requirement for nanometer CMOS technologies enabling optimal speedand power performances is to increase the integrated circuits' robustness under thefluctuation of the PVT parameters: Process (P), Voltage (V), and Temperature (T). In thisway, identifying the exact process on a die per die basis using on-chip sensors or ringoscillators becomes a necessity. This hardware (sensors) is used to measure the intrinsicperformance of the silicon either during industrial test or while applications are running. Thesensors' data are converted to a digital format in order to classify parts at the manufacturingstage (speed binning). Within this context, the present thesis has focused on the developmentof post-manufacturing compensation algorithms in order to minimise power consumptionand/or maximise speed. More precisely, the algorithms validated at the silicon level combineboth the voltage scaling for large-grain tuning, and the body biasing for fine-grain tuning

La recharge de l'eau souterraine est un paramètre encore peu connu du bilan hydrologique. La connaissance des processus et l'estimation précise de la recharge de l'eau souterraine est une condition préalable à une gestion efficace et durable des eaux souterraines dans les régions arides et semi-arides. En plus la recharge de l'eau souterraine est considérée comme le paramètre le plus direct avec lequel le changement climatique peut affecter les ressources renouvelables des aquifères. Les présents travaux de thèse s'intéressent à la recharge de l'aquifère alluvial de la plaine du Haouz par les crues de l'oued Rheraya (rivière intermittente), qui descend des montagnes du Haut-Atlas et traverse la plaine du Haouz du sud vers le nord. Ces travaux ont deux objectifs principaux (i) d'abord simuler le régime hydrologique de l'oued Rheraya dont les crues sont à l'origine de la recharge de l'eau souterraine, et ensuite (ii) aborder la quantification de la recharge de l'eau souterraine du Haouz par ces crues dans la zone du piémont atlasique. La modélisation des débits de l'oued Rheraya dans le Haut-Atlas marocain (225 km², altitudes comprises entre 1030 m et 4165 m) est réalisée en prenant en compte la composante nivale. Pour cela, le modèle conceptuel global GR4J est appliqué sur la période 1989-2009 en y adjoignant le module CemaNeige qui simule la dynamique de la composante neigeuse de manière semi- distribuée. La fraction enneigée simulée se révèle corrélée avec celle extraite du produit neige MODIS durant la période 2000-2009 (R2 = 0,64). De plus, l'équivalent en eau de la neige simulé est cohérent avec celui mesuré par la station automatique au sommet de l'Oukaimeden durant la période 2004-2006 (R2 = 0,81). Enfin, nous obtenons une simulation des débits qui reproduit bien la très forte variabilité saisonnière et interannuelle. En conclusion, le régime hydrologique de l'oued Rheraya est pluvio-nival avec une distribution unimodale des débits dont le maximum en avril coïncide avec la fonte des neiges. L'étude de la recharge de l'eau souterraine est effectuée à travers l'analyse du suivi des fluctuations de l'eau souterraine sous le lit de l'oued Rheraya sur deux cycles hydrologiques 2014-2015 et 2015-2016.[...]
Groundwater recharge is a little known parameter in the water balance. Knowledge of processes and accurate estimation of groundwater recharge is a prerequisite for effective and sustainable management of groundwater resources. In addition, groundwater recharge is considered the most direct parameter by which climate change affects the renewable groundwater resources. The present PhD thesis focuses on the recharge of the alluvial aquifer of the Haouz plain by the floods of the Rheraya wadi (intermittent river), which descends from the High-Atlas Mountains and crosses the southern plain towards the North. This work has two main objectives: (i) simulating the hydrological regime of the Rheraya River whose floods are at the origin of the groundwater recharge, and (ii) Quantifying the groundwater recharge by the floods of the Rheraya in the zone of the High-Atlas piedmont. The runoff modeling of the Rheraya wadi in the High-Atlas (225 km², elevations ranging between 1030 and 4165 m.a.s.l.) takes into account the snow component. For this purpose, the GR4J conceptual and global model was applied over the period 1989- 2009, coupled with the CemaNeige module for semi-distributed snow dynamics. The daily snow coverage simulated by CemaNeige is in good agreement with that extracted from the MODIS snow product in the period 2000-2009 (R² = 0,64). In addition, the simulated daily snow water equivalent is consistent with that measured at the weather station of Oukaimeden (2004-2006, R² = 0,81). Finally, the runoff simulation reproduces quite well the strong seasonal and inter-annual variability. In conclusion, the hydrological regime of the Rheraya wadi is pluvio-nival with an unimodal distribution whose maximum in April is linked with snowmelt. The study of groundwater recharge is carried out through the analysis of the monitoring of groundwater fluctuations in the streambed of the Rheraya wadi, over two hydrological cycles 2014-2015 and 2015-2016.[...]

L'obbiettivo di questa tesi è lo studio delle fluttuazioni quantistiche dei modi tensoriali primordiali prodotti durante l'inflazione, con particolare attenzione alla possibilità di rilevare tali modi come onde gravitazionali di background. Una eventuale rilevazione confermerebbe ulteriormente la validità dei modelli inflazionari. Tuttavia, la densità di energia predetta per le onde gravitazionali di background è di gran lunga inferiore alla sensibilità degli attuali rivelatori. In questo lavoro noi andiamo oltre l'inflazione slow-roll standard e analizziamo nuovi modelli che ci permettono di amplificare le perturbazioni tensoriali su scale al di fuori dell'orizzonte. Introduciamo un meccanismo che sfrutta una fase transitoria di evoluzione non-attractor per amplificare i modi tensoriali. Procediamo poi con lo studio della fenomenologia del modello, dimostrando la possibilità di amplificare la densità di energia delle onde gravitazionali fino alle scale accessibili dai rivelatori LISA, aLIGO e PTA. Calcoliamo poi il numero di e-folds di fase non-attractor necessari per assicurare la rivelazione di tali onde. Successivamente, presentiamo un nuovo modello di bigravità, caratterizzato da un termine di accoppiamento tra un tensore privo di massa ed uno massivo. Presentiamo un'analisi dettagliata della dinamica dei due campi tensoriali, derivando vincoli che la massa del campo deve soddisfare per poter amplificare le fluttuazioni prive di massa. Infine, assumiamo che l'accoppiamento sia dominante per un certo numero di e-folds durante l'inflazione e diamo una stima di tale valore per i tre rivelatori sopracitati.

Dans l’industrie des semi-conducteurs, les puces électroniques, au cours de leur processus de fabrication, peuvent être revêtues d’un dépôt CVD et/ou PVD, réalisé dans des enceintes en quartz (bell jar). Après utilisation, ces dernières, recouvertes d’un dépôt « polluant », sont nettoyées dans une solution acide. Dans le but d’augmenter la durée de vie de ces enceintes et d’espacer les nettoyages, la société Edwards les protège d’un dépôt rugueux de zircone yttriée réalisé par projection plasma. Cependant, la porosité du dépôt protecteur entraîne une infiltration de la solution chimique de nettoyage jusqu’au quartz. Non seulement, le dépôt « polluant » est décapé, mais aussi le dépôt protecteur en zircone yttriée. L’objectif de cette thèse est de densifier le dépôt de zircone yttriée afin de le rendre imperméable à la solution chimique, permettant sa réutilisation en ne décapant que le dépôt « polluant ». La rugosité du dépôt doit, toutefois, rester élevée. La densification des dépôts va se faire à partir d’une optimisation des paramètres de projection - débit massique, pourcentage d’hydrogène, distance de tir,… - de la distribution granulométrique de la poudre, de la nature du gaz plasmagène (argon ou azote) et donc de la torche utilisée. Cette optimisation des conditions de tir est effectuée via l’étude des propriétés du plasma, telles que l’enthalpie et les fluctuations de tension aux bornes de la torche, et de leurs influences sur le traitement thermique des particules en vol, la formation des lamelles lors de leur écrasement et la construction des dépôts et leurs propriétés (en particulier leur porosité, rugosité et épaisseur)
In semiconductor industry, the electronic chips, during their manufacturing process, can be covered with CVD/PVD coatings, carried out inside bell jars. After use, these quartz chambers, layered with a contaminated coating, are cleaned inside an acid solution. In order to increase their time of life and the time between two cleanings, Edwards society masks the chambers with a rough yttria partially stabilized zirconia coating made by plasma spraying process. However, the chemical cleaning solution reaches the quartz substrate through the coating porosity. So, the protected coating is etched at the same time than the contaminated coating. The aim of this research work is to increase the coating density to make it cleanable, in order to remove only the contaminated layer. Nevertheless, the coating roughness must remain high. The coating densification is obtained by optimising the plasma spray parameters (mass flow rate, hydrogen percentage, stand-off distance…), the powder size distribution, the plasma gas mixture composition (argon or nitrogen) and so the plasma torch design. This optimisation of spray conditions is determined by studying plasma properties, such as its enthalpy and its voltage fluctuations, and their influences on the in-flight particle thermal treatment, the corresponding splat formation and the coating growth and properties (especially their porosity, roughness and thickness)

Aujourd’hui le challenge est de réaliser des combustibles de piles à combustibles à électrolyte solide de façon propre au moyen de l’électrolyse de l’eau à haute température. Les nanomatériaux ouvrent des perspectives intéressantes dans ce domaine. La projection thermique est un procédé au rendement intéressant qui permet de réaliser des matériaux nanostructurés d’épaisseurs variables. Ces travaux ont permis de réaliser deux couches de cet EHT par des procédés innovants que sont la projection thermique de suspensions pour l’électrolyte et la projection d’agrégats de particules nanométriques pour l’anode. Grâce à l’utilisation de la torche TriplexPro 200, dont les fluctuations de tension relatives ne dépassent pas les 20% et qui permet de découpler la vitesse et la température des particules, cette étude a permis d’élaborer des électrolytes dont la porosité totale est inférieure à 10% et des anodes qui ne présentent pas de décomposition de phase à haute température
Nowadays manufacturing fuel for solid oxide fuel cells by mean of steam water electrolysis is a real challenge. Nanomaterials should find their place in this way. And then plasma spraying, a process with high ratio, allows manufacturing such nanoscaled materials with varying thicknesses. In this study two of the three HTE layers were manufactured by suspension plasma spraying in the case of the electrolyte and by atmospheric plasma spraying of agglomerated nanoparticules in the case of the anode. Finally the use of the TriplexPro 200 torch, which fluctuations are lower than 20% and which allows decoupling velocity from surface temperature of the in-flight particles, gives the opportunity of manufacturing a gastight electrolyte layer and a second phase less anode layer

We perform Monte-Carlo simulations of a binary, strongly separated mixture of A- and B-type homopolymers with some amount of random AB copolymers added. The interface is analyzed and the interface tension is calculated using the model of capillary waves. We can clearly demonstrate that random copolymers are localized at real, fluctuating interfaces between incompatible polymer species and micellization is not favored over adsorption. Our study proves that random copolymers are potential candidates for compatibilization of polymer-polymer mixtures. By simulating random copolymers in a one-component bulk and comparing their free energy to the copolymers adsorbed at the two-phase interface we show that the adsorption is thermodynamically stable. We use scaling arguments developed for ideal and non-fluctuating interfaces to rationalize the simulation results and we calculate the reduction of interface tension with increasing amount of the adsorbed copolymers.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Geometry, topology and elasticity are found in various branchs of physics and they play important roles in the understanding of many physical phenomena. In this work, we present three diferent systems where we can see such importance. First, a quantum neutral particle, constrained to move on a conical surface, is used as a toy model to explore bound states due to both a inverse squared distance potential and a delta-function potential, which appear naturally in the model due the geometry and topology of the cone. In the second one, we propose a method for probing the effects of curved 3-space by using materials with large coefficients of thermal expansion. Studying their fluctuations can be naturally cast in terms of a nonflat background geometry. In the last one, we determine the elastic-mediated interaction between colloidal nanoparticles adsorbed on the surface of free-standing smectic films. In contrast with the short-range character of the elastic- mediated force between particles adsorbed on smectic films supported by a solid substrate, the effective force acquires a long-range character in free-standing films, thus playing an important role in the formation of self-assembly structures in these systems.
A geometria, topologia e elasticidade estão presentes em vários ramos da física, e desempemham papel fundamental no entendimento de vários fenômenos físicos. Nesse trabalho, apresentamos três sistemas distintos onde podemos ver esse papéis. No primeiro, uma partícula quântica neutra confinada a mover-se em uma superfície cônica é usada como modelo para explorar estados ligados devido a um potencial proporcional ao inverso do quadrado da distância e devido a um potencial tipo delta. Ambos potenciais aparecem naturalmente devido a geometria e topologia do cone. No segundo, propomos um método de sondar os efeitos de um espaço curvo tridimensional usando materiais de grande coeficiente de expansão térmica. Neste caso, os três ingredientes citados acima são importantes para o entendimento do problema. Por fim, determinamos a interação entre nanocolóides adsorvidos na superfície de um filme esmético livremente suspenso. Essa interação é mediada por deformações elásticas no filme esmético; ela é de longo alcance, o que é importante para a formação de estruturas coloidais auto organizadas na superfície de tal filme.

Ce travail consiste à caractériser la variabilité temporelle et spatiale des séries chronologiques de paramètres hydroclimatiques (pluies, débits) au niveau de trois grand bassins au Maroc ; (bassins de la Moulouya, du Sebou et du Tensift) et à chercher les liens entre cette variabilité hydrologique et les fluctuations climatiques matérialisées par différents indices climatiques, NAO, SOI, WMOI. L’approche d’étude est basée le traitement statistique des séries temporelles, liée aux dimensions temps et espace.Les grands bassins versants d'échelle continentale comme le Tensift, le Sebou et la Moulouya en climat méditerranéen sous influence océanique, intègrent sur des grandes surfaces la réponse hydrologique aux changements climatiques et environnementaux (fluctuations du climat, précipitations, débits) à de larges échelles spatiales et temporelles, mais également les modifications du milieu physique d’origine anthropique (changements d’occupation des sols, aménagements…), ce qui rend parfois difficile l’identification des liens entre la variabilité hydrologique et la variabilité climatique. Les principaux objectifs de ce travail sont de déterminer et de quantifier les relations entre la variabilité hydroclimatique et les fluctuations du climat à l’échelle de chaque bassin étudié et de ses principaux sous-bassins, via l'utilisation de méthodes d’analyses spectrales adaptées à l’étude des processus non stationnaires (analyse en ondelettes continues, analyse de la cohérence par ondelettes). Plusieurs modes de variabilités sont identifiés à partir de l’analyse par station (pluies et débits), du cycle annuel au mode 16-22 ans, cette analyse sera complétée par une analyse par maille, dont les données sont issues d’un fichier (SIEREM) couvrant la période 1940-1999, où on identifie des fréquences de 1an au 8-16 ans, distinguées sur des périodes différentes au niveau de chaque bassin, permettant ainsi une décomposition de la variabilité spatiale des signaux mis en évidence. Trois principales discontinuités sont identifiées en 1970, 1980 et 2000. La contribution des indices climatiques est assez importante elle est entre 55% et 80%
This work is to characterize the temporal and spatial variability of hydroclimatic time series (rainfall, flow) at three large basins in Morocco; (basins of the Sebou and Moulouya Tensift) and look links between the hydrologic variability and climate fluctuation materialized by various climate indices, NAO, SOI, WMOI. The approach to study is based on statistical analysis of time series, related to time and space dimensions.The great watershed of continental scale as Tensift, Sebou and Moulouya in Mediterranean climate under oceanic influence, integrate over large areas the hydrological response to climate and environmental changes (climate fluctuations, precipitation, flows) not only to large spatial and temporal scales, but also to changes in the physical environment anthropogenic (land use changes, developments ...), which sometimes makes difficult to identify the links between hydrological variability and climate variability. The main objective of this work is to determine and quantify the relationships between hydrological variability and climate fluctuations (regionalised precipitation, climate change indexes) across each studied basin and its main sub-basins, via using spectral analysis methods adapted to the study of non-stationary processes (continuous wavelet analysis, coherence analysis wavelet). Many modes of variability are identified from the station analysis (rainfall and flow rates), the annual cycle to 16-22 years, this analysis will be complemented by a grid analysis, the data come from a (SIEREM) file covering the period from 1940 to 1999, which will allow a better understanding of the spatial variability of signals set highlighted. Which is identified frequencies the 1 year 8-16 years, distinguished different time periods at each basin, three main discontinuities identified in 1970, 1980 and 2000. The contribution of climatic indices is important enough it is between 55% and 80%

Nach einem ausführlichem Überblick über den Kenntnisstand der Genetik und Neurowissenschaft von allgemeiner Intelligenz und einer methodischen Anmerkung zur Notwendigkeit der Berücksichtigung latenter Variablen in den kognitiven Neurowissenschaften am Beispiel einer Reanalyse publizierter Ergebnisse wir das am besten etablierte Gehirnkorrelat der Intelligenz, die Gehirngröße, aus evolutionsgenetischer Perspektive neu betrachtet. Schätzungen des Koeffizienten additiv-genetischer deuten an, dass es keine rezente direktionale Selektion auf Gehirngröße gegeben hat, was ihre Validität als Proxy für Intelligenz in evolutionären Studien in Frage stellt. Stattdessen deuten Korrelationen der Gesichtssymmetrie älterer Männer mit Intelligenz und Informationsverarbeitungsgeschwindigkeit an, dass organismusweite Entwicklungsstabilität eine wichtige Grundlage von unterschieden in kognitiven Fähigkeiten sein könnte. Im zweiten Teil dieser Arbeit geht es vornehmlich um die Alterung kognitiver Fähigkeiten, beginnend mit einem allgemeinen Überblick. Daten einer Stichprobe von über 130 Individuen zeigen dann, dass die Integrität verschiedener Nervenbahnen im Gehirn hoch korreliert, was die Extraktion eines Generalfaktors der Traktintegrität erlaubt, der mit Informationsverarbeitungsgeschwindigkeit korreliert. Der einzige Trakt mit schwacher Ladung auf diesem Generalfaktor ist das Splenium des Corpus Callosum, welches mit Veränderungen der Intelligenz über 6 Jahrzehnte korreliert und den Effekt des Bet2 adrenergischem Rezeptorgens (ADRB2) auf diese Veränderung mediiert, möglicherweise durch Effekte auf neuronale Komopensationsprozesse. Schließlich wird auf Basis neuer Analyseverfahren für Magnetresonanzdaten gezeigt, dass vermehrte Eiseneinlagerungen im Gehirn, vermutlich Marker für zerebrale Mikroblutungen, sowohl mit lebenslang stabilen Intelligenzunterschieden als auch mit der altersbedingten Veränderung kognitiver Fähigkeiten assoziiert sind.
After an extensive review of what is known about the genetics and neuroscience of general intelligence and a methodological note emphasising the necessity to consider latent variables in cognitive neuroscience studies, exemplified by a re-analysis of published results, the most well-established brain correlate of intelligence, brain size, is revisited from an evolutionary genetic perspective. Estimates of the coefficient of additive genetic variation in brain size suggest that there was no recent directional selection on brain size, questioning its validity as a proxy for intelligence in evolutionary analyses. Instead, correlations of facial fluctuating asymmetry with intelligence and information processing speed in old men suggest that organism-wide developmental stability might be an important cause of individual differences in cognitive ability. The second half of the thesis focuses on cognitive ageing, beginning with a general review. In a sample of over 130 subjects it has then been found that the integrity of different white matter tracts in the brain is highly correlated, allowing for the extraction of a general factor of white matter tract integrity, which is correlated with information processing speed. The only tract not loading highly on this general factor is the splenium of the corpus callosum, which is correlated with changes in intelligence over 6 decades and mediates the effect of the beta2 adrenergic receptor gene (ADRB2) on cognitive ageing, possibly due to its involvement in neuronal compensation processes. Finally, using a novel analytic method for magnetic resonance data, it is shown that more iron depositions in the brain, presumably markers of a history of cerebral microbleeds, are associated with both lifelong-stable intelligence differences and age-related decline in cognitive functioning.

碩士
國立成功大學
材料科學及工程學系
102
In this study, the reliability of yield strength (YS) and total elongation (TE) of friction stir process (FSP) 7075-T6 Al alloy were studied. Three different rotation speeds in the FSP were applied namely, 1230, 1450 and 1670 rpm. Transverse tensile test (TTT) and longitudinal tensile test (LTT) were performed, both YS and TE used as a raw data for reliability analysis using Weibull statistics. Tensile test result revealed both YS and TE have a tendency to decrease with increasing rotation speed. The cause of this event is simply due to voids inside the SZ area. In order to verify the establishment of void, scaning electron microscope (SEM) was used. The result showed that the size of the voids increases from 2.4µm to 9.2µm respectively from low to high rotation speed. Using Weibull, the three-parameter Weibull of YS and TE were analyzed. From low to high rotation speed. YS (TTT) failure rate found, that at low rotation speed such as 1230 rpm the typical graph was increasing failure rate, however at 1450 and 1670 rpm the typical graph were decreasing failure rate. YS (TTT) reliability found, that both m and x_o value affect the graph alteration and lead to 1230 rpm provide better performance than other rotation speed. TE (TTT) failure rate found, that for TE value 〈 19% 1230 rpm have lower failure rate value than 1450 rpm. However, if TE value 〉 19% or about 22% the 1450 rpm lower failure rate values than 1230 rpm. TE (TTT) reliability found, that m value affect the graph alteration. At this parameter we also found that at 1450 and 1230 rpm the graph line is overlap at 22% elongation which lead the reliabity into two section of TE value such as TE 〈 22% and TE 〉 22%. For TE value 〈 22% low rotation speed such as 1230 rpm has better reliability. However, for TE 〉22% rotation speed such as 1450 provide better reliability. YS (LTT) failure rate found, that all rotation speed had the same tendency that is increasing failure. YS (LTT) reliability found, that both m and x_o value affect the graph alteration and lead to 1230 rpm perform better than other rotation speed in terms of reliability. TE (LTT) failure rate found, that all rotation speed had the same tendency that is increasing failure rate. TE (LTT) reliability found, that m value affect the graph alteration that lead to low rotation speed such as 1230 rpm give a better value of reliabilty that other rotation speed. The data showed that through the Weibull statistical analysis, a failure model in this research revealed low rotation speed like 1230 rpm is reliable enough for further engineering application.