Ionic self-assembled multilayers (ISAMs) can be formed by alternately dipping a substrate in anionic and cationic polyelectrolytes. Each immersion deposits a monolayer via electrostatic attraction, allowing for nanometer-scale control over film thickness. Additionally, ISAM films can be applied to arbitrary substrate geometries and can easily incorporate a variety of polymers and nanoscale organic or inorganic inclusions. The ISAM technique was used to tune and functionalize a rapid, sensitive fiber optic biosensor for textit{Brucella}, a family of bacteria that are detrimental to livestock and can also infect humans. The sensor was based on a turn-around point long period fiber grating (TAP-LPG). Unlike conventional LPGs, in which the attenuation peaks shift wavelength in response to environmental changes, TAP-LPGs have a highly sensitive single wavelength peak with variable attenuation. ISAMs were applied to a TAP-LPG to tune it to maximum sensitivity and to facilitate cross-linking of receptor molecules. Biotin and streptavidin were used to attach biotinylated hybridization probes specific to distinct species of textit{Brucella}. The sensor was then exposed to lysed cell cultures and tissue samples in order to evaluate its performance. The best results were obtained when using samples from textit{Brucella} infected mice, which produced a transmission change of 6.0 ± 1.4% for positive controls and 0.5 ± 2.0% for negative controls. While the sensor was able to distinguish between positive and negative samples, the relatively short dynamic range of the available fiber limited its performance. Attempts to fabricate new TAP-LPGs using a CO2 laser were unsuccessful due to poor laser stability. A second application of the ISAM technique was as a source of second-harmonic generation (SHG). SHG is a nonlinear optical process in which light is instantaneously converted to half its wavelength in the presence of intense electric fields. Localized surface plasmons (LSPs) in metal nanoparticles produce strong electric field enhancements, especially at sharp tips and edges, that can be used to increase SHG. Colloidally grown silver nanoprisms were deposited onto nonlinear ISAM films and conversion of 1064 nm Nd:YAG radiation to its 532 nm second-harmonic was observed. Little enhancement was observed when using nanoprisms with LSP resonance near 1064 nm due to their large size and low concentration. When using shorter wavelength nanoprisms, enhancements of up to 35 times were observed when they were applied by immersion, and up to 1380 times when concentrated nanoprisms were applied via dropcasting at high enough densities to broaden their extinction peak towards the excitation wavelength. A maximum enhancement of 2368 times was obtained when concentrated silver nanoprisms with LSP resonance around 900 nm were spincast with an additional layer of PCBS. / Doctor of Philosophy / Polyelectrolytes are long molecules composed of chains of charged monomers. When a substrate with a net surface charge is dipped into an oppositely charged polyelectrolyte solution, a single layer of molecules will be electrostatically deposited onto the substrate. Because the surface charge now appears to match the charge of the solution, no further deposition occurs. However, the process can be repeated by rinsing the substrate and immersing in a solution with the opposite charge. This technique forms ionic self-assembled multilayers (ISAMs), which can be assembled with nanometer-level control over thickness. The flexibility of polymer chemistry allows ISAMs to be formed from polyelectrolytes with a wide variety of properties. Additionally, the technique can easily incorporate other nanoscale materials, such as nanoparticles, clay platelets, and biological molecules, and has been investigated for applications ranging from dye-sensitized organic solar cells to drug delivery and medical implant coatings. This dissertation presents two applications of ISAM films. In one, ISAM films were used to tune and functionalize an optical biosensor for Brucella. Brucellosis primarily infects livestock, in which it causes significant reproductive problems leading to economic losses, but can also cause flu-like symptoms and more serious complications in humans. A rapid, sensitive test for Brucella is required to monitor herds and adjacent wild carriers, such as elk and bison. Optical biosensors, which operate by detecting changes due to the interaction between light and the stimulus, could satisfy this need. Long period fiber gratings (LPGs) are periodic modulations induced in the core of an optical fiber that cause transmitted light to be scattered at a resonant wavelength, resulting in attenuation. Conventional LPGs respond to changes in strain, temperature, or external refractive index by shifting their resonant wavelength. When special conditions are met, an LPG may exhibit a turn-around point (TAP), where dual peaks coalesce into a single peak with a constant wavelength but variable attenuation depth. TAP-LPGs are more sensitive than ordinary LPGs, and could be developed into inexpensive sensors with single-wavelength light sources and detectors. In this work, ISAMs were deposited onto an LPG to tune it near its TAP. Segments of single-stranded DNA, called hybridization probes, that were specific to individual species of Brucella were attached to the ISAM film before the sensor was exposed to lysed bacterial cultures. It was found that the sensor could distinguish between Brucella and other types of bacteria, but was less successful at distinguishing between Brucella species. The project was limited by the available TAP-LPGs, which had less dynamic range than those used in prior work by this group. Attempts were made to establish a new supply of TAP-LPGs by fabrication with a CO2 laser, but these efforts were unsuccessful due to poor laser stability. The second project discussed in this dissertation investigated ISAM films as a source of second-harmonic generation (SHG), a nonlinear optical process in which light is converted to half its fundamental wavelength in the presence of intense electric fields. Nonlinear ISAMs were constructed by choosing a polyelectrolyte with a hyperpolarizable side group in which SHG can occur. The SHG efficiency was increased by factors of several hundred to several thousand by the addition of silver nanoprisms. Metal nanoparticles can produce strong electric field enhancements, especially at their tips and edges, when incident light causes resonant collective oscillations in their electrons called localized surface plasmons (LSPs). It was found that while silver nanoprisms whose LSP resonant wavelength matched the fundamental wavelength were too dilute to produce noticeable enhancement, better results could be obtained by depositing shorter wavelength nanoprisms at sufficient density to broaden their extinction peak via interparticle interactions. The best enhancement observed was for a sample where concentrated silver nanoprisms with LSP resonance around 900 nm were dropcast onto an ISAM film and coated with an additional polymer layer, resulting in 2368 times more SHG than the plain ISAM film.

Tesis por compendio / Los juegos serios colaborativos tienen un impacto positivo en el comportamiento y el aprendizaje, pero siguen desarrollándose para plataformas tecnológicas tradicionales como videoconsolas y ordenadores de sobremesa o portátiles, los cuales han sido identificados como sub-óptimos para niños en diversos estudios. En su lugar, el uso de dispositivos móviles como tabletas y teléfonos inteligentes presenta diversas ventajas: son económicamente asequibles, están ampliamente distribuidos, y pueden ser transportados, lo cual permite la actividad física y poder iniciar un juego sin necesitar que los usuarios se trasladen a una localización fija, especialmente dedicada para tal fin. Además, combinar varios de estos dispositivos y coordinar la interacción entre ellos en lo que se denomina Entorno Multi-Pantalla (EMP) proporciona beneficios adicionales para la colaboración tales como una mayor escalabilidad, conciencia del espacio de trabajo, paralelismo y fluidez de las interacciones. La interacción en estos entornos multi-tableta es por tanto un aspecto crítico. Los dispositivos móviles están diseñados para ser interactuados mediante el toque de los dedos principalmente, lo cual es muy sencillo y directo, pero está normalmente limitado a la pequeña dimensión de las pantallas, lo que puede conllevar la oclusión de la pantalla y la infrautilización del espacio periférico. Por esta razón, esta tesis se centra en la exploración de otro mecanismo de interacción que puede complementar al táctil: interacciones tangibles alrededor del dispositivo. Las interacciones tangibles están basadas en la manipulación de objetos físicos, lo que presenta un valor adicional en la educación de los niños puesto que resuena con los manipulativos educativos tradicionales y permite la exploración del mundo físico. Por otra parte, la explotación del espacio que envuelve a las pantallas tiene diversos beneficios adicionales para actividades educativas colaborativas: reducida oclusión de la pantalla (lo cual puede incrementar la conciencia del espacio de trabajo), el uso de objetos tangibles como contenedores de información digital que puede ser transportada de forma continua entre dispositivos, y la identificación de un determinado estudiante a través de la codificación de su ID en un operador tangible (lo cual facilita el seguimiento de sus acciones y progreso durante el juego). Esta tesis describe dos enfoques distintos para construir juegos educativos colaborativos en EMPs utilizando interacciones tangibles alrededor de los dispositivos. Una, denominada MarkAirs, es una solución óptica aérea que no necesita ningún hardware adicional aparte de las tabletas excepto diversas tarjetas de cartón impresas. La otra, Tangibot, introduce un robot tangiblemente controlado y otro atrezo físico en el entorno, y se basa en tecnología RFID. Ambas interacciones son respectivamente evaluadas, y se observa que MarkAirs es usable y poco exigente tanto para adultos como para niños, y que se pueden realizar con éxito gestos de grano fino encima de las tabletas con ella. Además, al aplicarse en juegos colaborativos, puede ayudar a reducir la oclusión de las pantallas y la interferencia entre las distintas acciones de los usuarios, lo cual es un problema que puede surgir en este tipo de escenarios cuando solamente se dispone de interacciones táctiles. Se evalúa un juego educativo colaborativo con MarkAirs con niños de educación primaria, y se concluye que este mecanismo es capaz de crear experiencias de aprendizaje colaborativo y de presentar un valor añadido en términos de experiencia de usuario, aunque no en eficiencia. Con respecto a Tangibot, se muestra que controlar colaborativamente un robot móvil mediante unas palas tangibles con cierta precisión es factible para niños a partir de los tres años de edad, e incluso para personas mayores con un deterioro cognitivo leve. Además, proporciona una experiencia divertida / Collaborative serious games have a positive impact on behavior and learning, but the majority are still being developed for traditional technological platforms, e.g., video consoles and desktop/laptop computers, which have been deemed suboptimal for children by several studies. Instead, the use of handheld devices such as tablets and smartphones presents several advantages: they are affordable, very widespread, and mobile---which enables physical activity and being able to engage in a game without requiring users to gather around a fixed, dedicated, location. Plus, combining several of these devices and coordinating interactions across them in what is called a Multi-Display Environment (MDE) brings on additional benefits to collaboration like higher scalability, awareness, parallelism, and fluidity of the interaction. How to interact with these multi-tablet environments is therefore a critical issue. Mobile devices are designed to be interacted mainly via touch, which is very straightforward but usually limited to the small area of the displays, which can lead to the occlusion of the screen and the underuse of the peripheral space. For this reason, this thesis focuses on the exploration of another interaction mechanism that can complement touch: tangible around-device interactions. Tangible interactions are based on the manipulation of physical objects, which have an added value in childhood education as they resonate with traditional learning manipulatives and enable the exploration of the physical world. On the other hand, the exploitation of the space surrounding the displays has several potential benefits for collaborative-learning activities: reduced on-screen occlusion (which may increase workspace awareness), the use of tangible objects as containers of digital information that can be seamlessly moved across devices, and the identification of a given student through the encoding of their ID in a tangible manipulator (which facilitates the tracking of their actions and progress throughout the game). This thesis describes two different approaches to build collaborative-learning games for MDEs using tangible around-device interactions. One, called MarkAirs, is a mid-air optical solution relying on no additional hardware besides the tablets except for several cardboard printed cards. The other, Tangibot, introduces a tangible-mediated robot and other physical props in the environment and is based on RFID technology. Both interactions are respectively evaluated, and it is observed that MarkAirs is usable and undemanding both for adults and for children, and that fine-grained gestures above the tablets can be successfully conducted with it. Also, when applied to collaborative games, it can help reduce screen occlusion and interference among the different users' actions, which is a problem that may arise in such settings when only touch interactions are available. A collaborative learning game with MarkAirs is evaluated with primary school children, revealing this mechanism as capable of creating collaborative learning experiences and presenting an added value in user experience, although not in performance. With respect to Tangibot, we show how collaboratively controlling a mobile robot with tangible paddles and achieving certain precision with it is feasible for children from 3 years of age, and even for elderly people with mild cognitive impairment. Furthermore, it provides a fun experience for children and maintains them in a constant state of flow. / Els jocs seriosos col·laboratius tenen un impacte positiu en el comportament i l'aprenentatge, però continuen sent desenvolupats per a plataformes tecnològiques tradicionals com videoconsoles i ordinadors de sobretaula o portàtils, els quals han sigut identificats com sub-òptims per a xiquets en diversos estudis. D'altra banda, l'ús de dispositius mòbils com ara tabletes i telèfons intel·ligents presenta diversos avantatges: són econòmicament assequibles, estan àmpliament distribuïts i poden ser transportats, la qual cosa permet l'activitat física i poder iniciar un joc sense necessitat de què els usuaris es traslladen a una localització fixa i especialment dedicada per a eixa finalitat. A més, combinar diversos d'estos dispositius i coordinar la interacció entre ells en el que es denomina Entorn Multi-Pantalla (EMP) proporciona beneficis addicionals per a la col·laboració tals com una major escalabilitat, consciència de l'espai de treball, paral·lelisme i fluïdesa de les interaccions. La interacció amb estos entorns multi-tableta és per tant crítica. Els dispositius mòbils estan dissenyats per a ser interactuats mitjançant tocs de dit principalment, mecanisme molt senzill i directe, però està normalment limitat a la reduïda dimensió de les pantalles, cosa que pot ocasionar l'oclusió de la pantalla i la infrautilització de l'espai perifèric. Per aquesta raó, la present tesi se centra en l'exploració d'un altre mecanisme d'interacció que pot complementar al tàctil: interaccions tangible al voltant dels dispositius. Les interaccions tangibles estan basades en la manipulació d'objectes físics, cosa que presenta un valor addicional en l'educació dels xiquets ja que ressona amb els manipulatius tradicionals i permet l'exploració del món físic. D'altra banda, l'explotació de l'espai que envolta a les pantalles té diversos beneficis addicionals per a activitats educatives col·laboratives: reduïda oclusió de la pantalla (la qual cosa pot incrementar la consciència de l'espai de treball), l'ús d'objectes tangibles com a contenidors d'informació digital que pot ser transportada de forma continua entre dispositius, i la identificació d'un estudiant determinat a través de la codificació de la seua identitat en un operador tangible (cosa que facilita el seguiment de les seues accions i progrés durant el joc). Aquesta tesi descriu dos enfocaments distints per a construir jocs educatius col·laboratius en EMPs utilitzant interaccions tangibles al voltant dels dispositius. Una, denominada MarkAirs, és una solució òptica aèria que no precisa de cap maquinari addicional a banda de les tabletes, exceptuant diverses targetes de cartró impreses. L'altra, Tangibot, introdueix un robot controlat tangiblement i attrezzo físic addicional en l'entorn, i es basa en tecnologia RFID. Ambdues interaccions són avaluades respectivament, i s'observa que MarkAirs és usable i poc exigent tant per a adults com per a xiquets, i que es poden realitzar gestos de granularitat fina dalt de les tabletes amb ella. A més a més, en aplicar-se a jocs col·laboratius, pot ajudar a reduir l'oclusió de les pantalles i la interferència entre les distintes accions dels usuaris, problema que pot aparèixer en este tipus d'escenaris quan solament es disposa d'interaccions tàctils. S'avalua un joc educatiu col·laboratiu amb MarkAirs amb xiquets d'educació primària, i es conclou que aquest mecanisme és capaç de crear experiències d'aprenentatge col·laboratiu i de presentar un valor afegit en termes d'experiència d'usuari, tot i que no en eficiència. Respecte a Tangibot, es mostra que controlar conjuntament un robot mòbil mitjançant unes pales tangibles amb certa precisió és factible per a xiquets a partir de tres anys i inclús per a persones majors amb un lleu deteriorament cognitiu. A més, proporciona una experiència divertida per als xiquets i els manté en un estat constant de flow. / García Sanjuan, F. (2018). CREAME: CReation of Educative Affordable Multi-surface Environments [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/101942 / Compendio

Diese Dissertation untersucht ökonomische Sanktionen im Kontext der empirischen politischen Ökonomie. Obwohl sie aus drei unabhängigen Kapiteln besteht, ist das übergeordnete, verbindende Ziel dieser Forschungsarbeit ein Gesamtverständnis der Motivation und der Effekte von Sanktionen anzubieten, getragen von der generellen Idee der Wechselwirkungen zwischen ökonomischen Anreizen und politischen Zielen. Meine Forschung zeichnet die ökonomischen Restriktionen ab, mit denen sich die politischen Entscheidungsträger im Bereich der internationalen Beziehungen auseinandersetzen. / This dissertation explores economic sanctions in an empirical political economy context. While consisting of three independent papers, it aims at providing a holistic understanding of the motivation and effects of sanctions in particular, and the interplay between economic incentives and political goals in general. My research delineates the economic constraints that policymakers encounter in the field of international relations.

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the 'wrap around' technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission.

Cette thèse porte sur les artistes suédois et norvégiens en France de 1889 à 1908. Ces années ont traditionnellement été considérées comme une période de retour au pays et d’abandon de la France pour les artistes scandinaves qui se seraient tournés de nouveau vers Paris seulement en 1908 avec l’arrivée des élèves d’Henri Matisse. Une étude approfondie de leur présence aux Salons parisiens a été menée afin de constater que leur nombre ne baisse pas et que les départs des uns sont aussitôt comblés par l’arrivée d’autres artistes scandinaves. À travers l’examen de la taille et de l’activité de cette communauté d’artistes installés en France durant ces deux décennies, dites nationalistes, il s’avère que l’hypothèse du retour vers la Scandinavie dans les années 1890 est un mythe créé par une historiographie faussée. La plupart des artistes scandinaves expatriés en France de 1889 à 1908 menèrent des carrières couronnées de succès dans un environnement cosmopolite et international. Les raisons de la mauvaise interprétation de cette période de l’histoire de l’art scandinave ont été analysées à travers les ouvrages d’histoire de l’art anciens et actuels. D’autres investigations ont été entreprises, basées sur la correspondance de ces artistes principalement conservée à l’Académie Royale des Beaux-Arts de Suède et dans les archives d’Auguste Rodin, ainsi que sur l’étude de leur accueil critique en France. Elles démontrent que la colonie scandinave de Paris de ces années-là a été exclue des expositions organisées en France par leurs propres pays et que la carrière de ces artistes expatriés, ainsi que le rôle de la France, ont été minimisés dans l’histoire de l’art scandinave. / This dissertation is about the presence of Swedish and Norwegian artists in France during the years 1889 to 1908. Traditionally these years have been considered as a period when Scandinavian artists left France to return to their homelands and according to this traditional view, they only returned to Paris and French influence with the arrival of Henri Matisse’s students around 1908. A thorough study of their presence in the Parisian Salons has been conducted which determines that their numbers do not decrease and that the departure of certain Scandinavian artists was balanced by the arrival of others. By examining the size and the activity of this artistic community in France during these two so-called nationalistic decades, it appears in fact that the hypothesis about the return to Scandinavia in the 1890’s is a myth created by a distorted historiography. Most Scandinavian expatriate artists living in France between 1889 and 1908 led successful careers in a cosmopolitan and international environment. The reasons for the misinterpretation of this period in Scandinavian art history have been analysed using historical and current texts and art history handbooks. Further investigation based on the correspondence of these artists, kept chiefly by the Royal Swedish Academy of Fine Arts and in the archives of Auguste Rodin, as well as the study of their critical reception in France, have shown that the Parisian colony of Scandinavian artists has often been excluded from exhibitions organized in France by their home countries and that the career of these expatriate artists as well as the role of France during this period has been minimized in Scandinavian art history.

La dispersion atmosphérique de substances dangereuses est un évènement susceptible d’entrainer de graves conséquences. Sa modélisation est primordiale pour anticiper des situations accidentelles. L’objectif de ce travail fut de développer un modèle opérationnel, à la fois rapide et précis, prenant en compte la dispersion en champ proche sur un site industriel. L’approche développée s’appuie sur des modèles issus de l’intelligence artificielle : les réseaux de neurones et les automates cellulaires. L’utilisation des réseaux de neurones requiert l’apprentissage d’une base de données de dispersion : des simulations CFD k-ϵ dans ce travail. Différents paramètres sont évalués lors de l’apprentissage : échantillonnage et architecture du réseau. Trois méthodologies sont développées :La première méthode permet d’estimer la dispersion continue en champ libre, par réseaux de neurones seuls.La deuxième méthode utilise le réseau de neurones en tant que règle de transition de l’automate cellulaire pour le suivi de l’évolution d’une bouffée en champ libre.La troisième méthode sépare la problématique : le calcul de l’écoulement est effectué par les réseaux de neurones alors que le calcul de la dispersion est réalisé par la résolution de l’équation d’advection diffusion pour le suivi de l’évolution d’un nuage autour d’un obstacle cylindrique. La simulation de cas tests non-appris avec des simulations CFD permet de valider les méthodes développées. Les temps de calcul mis en œuvre pour réaliser la dispersion sont en accord avec la cinétique d’une situation de crise. L’application à des données réelles doit être développée dans la perspective de rendre les modèles opérationnels. / Atmospheric dispersion of hazardous materials is an event that could lead to serious consequences. Atmospheric dispersion is studied in particular in this work. Modeling of atmospheric dispersion is an important tool to anticipate industrial accidents. The objective of this work was to develop a model that is both fast and accurate, considering the dispersion in the near field on an industrial site. The approach developed is based on models from artificial intelligence: neural networks and cellular automata. Using neural networks requires training a database typical of the phenomenon, CFD k-ϵ simulations in this work. Training the neural network is carried out by identifying the important parameters: database sampling and network architecture. Three methodologies are developed:The first method estimates the continuous dispersion in free field by neural networks.The second method uses the neural network as a transition rule of the cellular automaton to estimate puff evolution in the free field.The third method divides the problem: the flow calculation is performed by the neural network and the calculation of the dispersion is realized by solving the advection diffusion equation to estimate the evolution of a cloud around a cylindrical obstacle. For the three methods, assessment of the generalization capabilities of the neural network has been validated on a test database and on unlearned cases. A comparison between developed method and CFD simulations is done on unlearned cases in order to validate them. Simulations computing time are low according to crisis duration. Application to real data should be developed to make these models operational.

Esta tese apresenta o estudo da transição para um escoamento tridimensional da esteira de um cilindro oscilando. Esta é a transição secundária do escoamento ao redor de um cilindro, sendo a primária a própria esteira de von Kármán. A investigação é realizada na mesma faixa de número de Reynolds (Re) que ocorre a transição da esteira de um cilindro fixo: 200 Re 400. O estudo envolve simulações numéricas diretas bi- e tridimensionais do escoamento incompressível ao redor de um cilindro oscilando usando o método dos elementos espectrais. A transição também é analisada através do estudo de estabilidade linear do escoamento. O método de Gaston Floquet é adequado para a análise de estabilidade a perturbações tridimensionais devido à periodicidade característica da esteira de von Kármán. Além disto, o método é mais geral e não é aplicado somente a equações autônomas com soluções periódicas: ele também pode ser usado em análises cujo campo base é estacionário como a análise da transição primária da esteira de um cilindro. Mostra-se que a transição da esteira para tridimensionalidade é influenciada pela oscilação do cilindro. As oscilações podem atrasar a transição quando em amplitudes baixas e com escoamento a um número de Reynolds até 260. Em outros casos, a transição é similar à observada no escoamento ao redor um cilindro fixo. Além disso, quando há mudança de padrões de desprendimento de vórtices devido às oscilações, desencadeiam-se modos instáveis diferentes dos observados na esteira de um cilindro fixo. A comparação dos resultados da análise de estabilidade de Floquet com simulações numéricas diretas e experimentos publicados mostra na maioria dos casos que, apesar de ser uma análise de estabilidade linear, muitas características da análise persistem além do limiar de estabilidade. As situações com discrepâncias são identificadas nesta tese, como padrão de desprendimento diferentes em simulações bi- e tridimensionais na mesma situação. As causa das discrepâncias são estudadas através das simulações numéricas diretas e considerações sobre o sistema linearizado e a abrangência da análise de estabilidade. Em adição, mostra-se que há um limiar de amplitude de oscilação acima do qual a dinâmica da esteira, e portanto a transição secundária, é afetada. Abaixo deste limiar, retoma-se o comportamento do escoamento ao redor de um cilindro fixo. / This thesis presents the investigation of the transition to a three-dimensional flow in the wake of an oscillating circular cylinder. This is the secondary transition of the flow around a circular cylinder, while the primary transition leads to the von Kármán wake. The investigative work is performed in the Reynolds number (Re) range which occurs the secondary transition of the wake o a circular cylinder: 200 Re 400. The study consists of two- and three-dimensional direct numerical simulations of the incompressible flow around an oscillating circular cylinder by means of the spectral/hp method. The transition is also analyzed through linear stability study of the flow. The Gaston Floquet method is an appropriate method for this linear stability analysis to three-dimensional perturbations due to the typical periodicity of the von Kármán wake. Furthermore, the Floquet method is of a general kind and it is not specifically applied to autonomous equation with periodic solutions: it can be employed in analysis with a stationary base flow like the primary transition of the wake of a circular cylinder. The thesis shows that the transition to a three-dimensional wake is affected by the cylinder oscillation. The oscillations can delay the transition when they have low amplitudes and the flow has Reynolds number below 260. In other situations, the transition is similar to that observed in the flow of a fixed circular cylinder. In addition, when there is a change in the vortex shedding pattern due to the oscillatory motion, the observed unstable modes are different than those in a wake of a fixed circular cylinder. The comparison of the results from the Floquet stabilty analysis with the ones from direct numerical simulations and published experiments shows that in most cases, despite the linearization for the stability analysis, many features of the analysis persist beyond the instability threshold. The discrepant features observed are specified in this thesis, e.g. vortex shedding patterns different in two- and three-dimensional simulations with the same parameters. The cause of the discrepancies are studied through direct numerical simulations and careful considerations on the linearized system and the range of the stability analysis. In addition, this thesis shows that there is a threshold amplitude of oscillation for which the wake dynamics, therefore the secondary transition, is affected. Below this threshold, the wake behaves the same way as in the flow around a fixed circular cylinder.

Silicon nanowire based multiple gate metal oxide field effect transistors(MG-MOSFET) appear as replacements for conventional bulk transistors in post 45nm technology nodes. In such transistors the short channel effect(SCE) is controlled by the device geometry, and hence an undoped (or, lightly doped) ultra-thin body silicon nanowire is used to sustain the channel. The use of undoped body also solves several issues in bulk MOSFETs e.g., random dopant fluctuations, mobility degradation and compatibility with midgap metal gates. The electrostatic integrity of such devices increases with the scaling down of the body thickness. Since the quantization of electron energy cannot be ignored in such ultra-thin body devices, it is extremely important to consider quantum effects in their threshold voltage models. Most of the models reported so far are valid for long channel double gate devices. Only Munteanu et al. [Journal of non-crystalline solids vol 351 pp 1911-1918 2005] have reported threshold voltage model for short channel symmetric double gate MOSFET, however it involves unphysical fitting parameters. Only Munteanu et al.[Molecular simulation vol 31 pp 839-845 2005] reported threshold voltage model for quad gate transistor which is implicit in nature. On the other hand no modeling work has been reported for other types of MG-MOSFETs (e.g., tri gate, cylindrical body)apart from numerical simulation results. In this work we report physically based closed form quantum threshold voltage models for short channel symmetric double gate, quad gate and cylindrical body gate-all-around MOSFETs. In these devices quantum effects aries mainly due to the structural confinement of electron energy. Proposed models are based on the analytical solution of two or three-dimensional Poisson equation and one or two-dimensional Schrodinger equation depending on the device geometries. Judicial approximations have been taken to simplify the models in order to make them closed form and efficient for large scale circuit simulation. Effort has also been put to model the quantum threshold voltage of tri gate MOSFET. However it is found that the energy quantization in tri gate devices are mainly due to electronic confinement and hence it is very difficult to develop closed form analytical equations for the threshold voltage. Thus in this work the modeling of tri gate devices have been limited to long channel cases. All the models are validated against the professional numerical simulator.

Undoped body multi gate (MG) Metal Oxide Semiconductor Field Effect Transistors (MOSFET) are appearing as replacements for single gate bulk MOSFET in forthcoming sub-45nm technology nodes. It is therefore extremely necessary to develop compact models for MG transistors in order to use them in nano-scale integrated circuit design and simulation. There is however a sharp distinction between the electrostatics of traditional bulk transistors and undoped body devices. In bulk transistor, where the substrate is sufficiently doped, the inversion charges are located close to the surface and hence the surface potential solely controls the electrostatic integrity of the device. However, in undoped body devices, gate electric field penetrates the body center, and inversion charge exists throughout the body. In contrast to the bulk transistors, depending on device geometry, the potential of the body center of undoped body devices could be higher than the surface in weak inversion regime and the current flows through the center-part of the device instead of surface. Several crucial parameters (e.g. Sub-threshold slope) sometimes become more dependable on the potential of body center rather than the surface. Hence the body-center potential should also be modeled correctly along with the surface-potential for accurate calculation of inversion charge, threshold voltage and other related parameters of undoped body multi-gate transistors. Although several potential models for MG transistors have been proposed to capture the short channel behavior in the subthreshold regime but most of them are based on the crucial approximation of coverting the 2D Poisson’s equation into Laplace equation. This approximation holds good only at surface but breaks down at body center and in the moderate inversion regime. As a result all the previous models fail to capture the potential of body center Correctly and remain valid only in weak-inversion regime. In this work we have developed semiclassical compact models for potential distribution for double gate (DG) and cylindrical Gate-All-Around (GAA) transistors. The models are based on the analytical solution of 2D Poisson’s equation in the channel region and valid for both: a) weak and strong inversion regimes, b) long channel and short channel transistors, and, c) body surface and center. Using the proposed model, for the first time, it is demonstrated that the body potential versus gate voltage characteristics for the devices having equal channel lengths but different body thicknesses pass through a single common point (termed as crossover point). Using the concept of “crossover point” the effect of body thickness on the threshold voltage of undoped body multi-gate transistors is explained. Based on the proposed body potential model, a new compact model for the subthreshold swing is formulated. Some other parameters e.g. inversion charge, threshold voltage roll-off etc are also studied to demonstrate the impact of body center potential on the electrostatics of multi gate transistor. All the models are validated against professional numerical device simulator.

Αντικείμενο της παρούσας εργασίας είναι η πρόβλεψη τόσο της κίνησης, αλληλεπίδρασης και παραμόρφωσης δύο φυσαλίδων λόγω μεταβολής της πίεσης στο περιβάλλον ιξώδες υγρό, όσο και της ανοδικής κίνησης μιας φυσαλίδας λόγω άνωσης σε ένα Νευτωνικό ή ιξωδοπλαστικό ρευστό. Για τη μοντελοποίηση των αλληλεπιδρώντων φυσαλίδων, αναπτύχθηκε μιας νέα ελλειπτική μεθόδος κατασκευής του υπολογιστικού πλέγματος προκειμένου να αντιμετωπιστούν επιτυχώς τα ιδιάζοντα σημεία (πόλοι) των φυσαλίδων και οι μεγάλες παραμορφώσεις των διεπιφανειών τους. Με τη μέθοδο αυτή η πύκνωση του πλέγματος περιορίζεται μόνο στις περιοχές που είναι αναγκαίο, μειώνοντας έτσι το υπολογιστικό κόστος και αυξάνοντας την ακρίβεια των υπολογισμών. Για την επίλυση των παρακάτω προβλημάτων χρησιμοποιήθηκε η μέθοδος των μικτών πεπερασμένων στοιχείων κατά Galerkin. Στην περίπτωση των αλληλεπιδρώντων φυσαλίδων έχει εξετασθεί η επίδραση του σχετικού μεγέθους τους, της συχνότητας και του εύρους μεταβολής της επιβαλλόμενης πίεσης και πότε οδηγούν σε έλξη ή άπωση των φυσαλίδων. Στην περίπτωση ελκτικής δύναμης, ακολουθείται η κίνηση και η παραμόρφωσή τους μέχρι του σημείου που έρχονται σε επαφή, όπου αυτό είναι εφικτό. Για τη μελέτη του προβλήματος της φυσαλίδας που ανέρχεται λόγω άνωσης, υποθέτουμε αξονική συμμετρία και μόνιμη κατάσταση. Σύγκριση των προβλέψεών μας για το σχήμα των φυσαλίδων και το πεδίο ροής γύρω τους με προηγούμενα θεωρητικά και πειραματικά αποτελέσματα για Νευτωνικά ρευστά έδειξε άριστη συμφωνία. Στην περίπτωση του ιξωδοπλαστικού ρευστού εξετάστηκαν λεπτομερώς οι παραμορφώσεις των φυσαλίδων σαν συνάρτηση των αριθμών Bingham, Bond και Αρχιμήδη και υπολογίσθηκαν οι συνθήκες υπό τις οποίες είναι δυνατή η παγίδευση της φυσαλίδας μέσα σε αυτό. / The present study deals with the numerical simulation of the motion, interaction and deformation of two bubbles due to variation of the pressure of the ambient Newtonian fluid, and the buoyancy-driven rise of a bubble in a Newtonian or a viscoplastic fluid. A new elliptic mesh generation method is developed in order to deal with the singular points (poles) of the bubbles and the large deformations of their surface. This method permits us to increase the mesh resolution only in the regions that is necessary, decreasing thus the computational cost and increasing the precision of our calculations. The following problems are solved using the mixed finite element/Galerkin method. In the case of the interacting bubbles the effect of their relative size, the frequency and the width of the imposed pressure is examined as well as the conditions that lead in attraction or repulsion of the bubbles. In the case that attractive forces exist, the motion and the deformation of the bubbles followed up to the point that they come in contact, whenever this is possible. In order to study the problem of the bubble that rises due to buoyancy, axial symmetry and steady flow is assumed. Our results for the shape of the bubbles and the flow around them are in very good agreement with previous theoretical and experimental results for Newtonian fluids. The deformations of the bubbles rising in a viscoplastic material are also examined for various values of the Bingham, Bond and Archimedes numbers and the conditions under which entrapment of a bubble is possible are determined.