Thèses : « Local phenomenon »

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Kouchakzadeh, Salah. « The local scouring phenomenon at bridge abutments terminating in the floodplain zone ». Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/9915.

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This study examines the local scouring phenomenon associated with bridge abutments exposed to combined main-channel (MC) and floodplain (FP) flows. The principal goal of the study was to develop and validate, based on a comprehensive physical-model testing programme that considered different abutment shapes, an improved relationship for predicting maximum scour depth. A relationship was established among sediment size, flow depth and longitudinal channel slope for initiating the threshold condition of bed material movement. This relationship facilitated the selection of sediment size and channel bed slope for the various experiments, which were performed in a compound channel under interacting (combined MC and FP flows) and non-interacting (isolated FP flow) conditions. Clear-water approach-flow conditions were utilized throughout the testing programme. A flow visualization technique was employed to study the various patterns of the combining flows in the MC/FP junction regions. It determined both the flow deflection angle and the extent of the influence zone (a portion of the channel width beyond the abutment) whose discharge, $Q\sb{w}$, contributes to the scour development. Maximum scour depths produced under interacting conditions were observed to be 15% to 30% greater than those observed for non-interacting conditions. This important observation clearly demonstrated the need to properly account for compound-channel effects in the simulation exercise. The scour prediction relationship presented herein is based on a dimensional analysis of the relevant parameters and incorporates the data obtained from the laboratory studies performed in a compound channel using vertical-wall, wing-wall, semi-circular, and spill-through abutment shapes. The model indicates a very good agreement between predicted and observed maximum scour depths for bridge abutments terminating in the FP zone.

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Moench, Matthew. « An Investigation into Crowd Out Phenomenon in Local Churches : Combining Experimental and Survey Methodology ». Oberlin College Honors Theses / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1370857293.

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Pangle, Teresa Marie. « Medjugorje's Effects : A History of Local, State and Church Response to the Medjugorje Phenomenon ». Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1300755377.

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Vasilevskaya, Marina. « The phenomenon of federalism division of authorities, intrastate stability, and international behavior / ». Diss., Online access via UMI:, 2008.

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AL, SHAWWA Haya. « Italy’s new immigrant entrepreneurship : The paths of development of this new phenomenon ». Doctoral thesis, Università degli studi di Ferrara, 2012. http://hdl.handle.net/11392/2389434.

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This study explores the evolution of the phenomenon of new immigrant entrepreneurship, tracing its paths of development, in order to develop new lines of analysis, reflections, and hypothesis of relevant policies and procedures in the light of future trends. Over the last years, Italy and many other European countries have witnessed a profound evolution in the migration process, and a relentless growth of immigrant entrepreneurial initiatives, together with the economic transformations that have affected the world of employment and economic development opportunities. Until today, most academic research focused on the traditional term "migrant worker". This work intends to explore a different line of research: to study that portion of immigrants who choose to run their own businesses, becoming owners of small and medium enterprises (SMEs). It furthermore aims to understand the dynamics and characteristics of these enterprises, how they differ from native ones, analyzing the socio-economic relations that they create with the other economic players in the territory. This dissertation commences with a theoretical framework of international migration, which is followed by a focus on the Italian migratory background, aimed at understanding the roots and basis for this entrepreneurial leap. The following chapter provides an in-depth theoretical analysis of the "immigrant/ethnic entrepreneurship" phenomenon. It begins with a close examination of various definitions and distinctions, stating in particular the difference between "ethnic entrepreneurship" and "immigrant entrepreneurship". The following section focuses on the crucial transformations that occurred in the manufacturing sector and labor market history, particularly from the seventies until today, with the emergence of the post-Fordist system. It seeks to explain the reasons that motivated immigrants towards this entrepreneurial shift. This chapter is moreover enriched with an analysis of different theoretical approaches, which are mainly of a cultural and/or structural nature. The third chapter explores the dynamics of this phenomenon in Italy, theoretically and statistically. Non-trivial figures emerge that confirm the relevance of this new event, and that highlights the existence of a close link between immigrant entrepreneurship and economic development, but on the other side show how this is backed up by “specific” policy interventions which are rather weak. The final chapter focuses on the case study that carefully analyzes the evolution of business conduct of Chinese entrepreneurs in the textile, clothing and leather industry in the province of Ferrara, with the intent to connect the findings of this study with the theoretical approaches explored in chapter II. The main results clearly show that this case-study can be explained under the mixed embeddedness model, where the determinant elements of this phenomenon are a result of a blend of both cultural and structural factors. Moreover, findings give evidence to an initial phase of an “ethnic niche”. Further elements are explored such the employment context, the economic activities that take place, and all these dynamics intertwined and analyzed together within the territory. Furthermore, a significant fact emerges, the economic and financial crisis that hit the economy in late 2008, has affected to a similar extent both enterprises, Chinese-run and Italian-run ones. However, responses and reactions to such crisis were decisively different. Chinese-owned have shown a greater level of dynamism and flexibility, combined with an expansion of their economic activities within the sector. One of the main findings of this study provide evidence that this new phenomenon is playing a key role in the economy’s demand and supply. Public intervention is still considered weak in the time where future challenges and potentials of such businesses are expected to grow further.

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Shapcotte, Timothy Frank. « A biblical and functional response by the local church to the "adult children of dysfunctional families" phenomenon ». Theological Research Exchange Network (TREN), 1992. http://www.tren.com.

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Gårseth-Nesbakk, Levi. « Experimentation with accural accounting at central government level in Norway : how a global phenomenon becomes a local practice / ». Bodø, 2007. http://www.gbv.de/dms/zbw/566502046.pdf.

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Zerbinati, Stefania. « An empirical analysis of the phenomenon of EU funding in Italian and English local governments : a theory-building approach ». Thesis, University of Portsmouth, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247644.

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The majority of studies on European integration focus on the implementation of EU policies and regulations at the national or regional levels or on the influence of national and regional institutions in ED policy-making (Anderson, 1990; Tranholm-Mikkelsen, 1991; Geyer, 1996; Moravcsik, 1993; Marks, 1996; Majone, 1997). A smaller number of studies report on a series of changes appearing at local government level and connect them with a changing environment at the ED level and with the increasing importance of the EU funding programmes (Martin and Pearce, 1993: Goldsmith, 1993; John, 1996: Sutcliffe. 1997). However, the use of a top-down perspective has limited the findings of the previous research. The main objective of this thesis is to expand the knowledge on the phenomenon of ED funding within local governments, adopting a bottom-up approach, where changes appeared at the local government level, which were not included in EU directives, regulations and policy proposals, but represented a consequence of a changing order at the European arena. The research question asked in the study is: "Why do some local governments succeed and others fail in applying for EU funds?" Little empirical research has been conducted in order to understand the ED funding procedures followed by local government organisations, and how those procedures affected the organisations themselves and their employees. The study's objective is to build a theory exploring the process of competing for new types of funding within local government organisations. A theoretical framework is proposed at the beginning of the study which connects the phenomenon of EU funding with the presence of three important constructs: Europeanisation, networking and entrepreneurship. These constructs were explicitly measured in the interview protocol. From the analysis of the data, the constructs emerged as related to the success in ED funding within local governments through a causal relationship.

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Nelson, James. « Hillbilly Music & ; Early Live Radio Programming in Bowling Green & ; Glasgow, Kentucky : Country Music as a Local Phenomenon ». TopSCHOLAR®, 1994. https://digitalcommons.wku.edu/theses/3151.

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In this study, the author examines the development of country music in the area surrounding Bowling Green and Glasgow, Kentucky, from approximately 1930 to 1960 and its relation to the newly emerging medium of radio. Emphasis is placed on several performers whose careers were linked to the radio stations which began to broadcast in Bowling Green and Glasgow during the 1940s. In the past, country music scholarship has tended to focus on phonograph records as a source of material for study and as the primary means of musical transmission. As a result, the careers of many of the lesser known artists were overlooked simply because they never made a record. The writer looks at country music as a local phenomenon with live radio broadcasts and personal appearances as the primary mode of transmission. Data were collected from tape recorded interviews and written sources, including various archival sources - old newspapers, fan magazines, and assorted ephemera - and used to outline the careers of several performers associated with WLBJ and WKCT in Bowling Green and WKAY in Glasgow.

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Pekelharing, Elizelle Juaneé. « The phenomenon of the urban edge as a planning tool for compact cities : an international and local comparison / Elizelle Juaneé Pekelharing ». Thesis, North-West University, 2005. http://hdl.handle.net/10394/1000.

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Urban Growth Boundaries are one of the most popular urban containment tools worldwide. In South Africa, this has found expression in the recent (2001) implementation of the Gauteng Urban Edge. (Barker, 2004 [Email interview]). Many urban conurbations are experiencing severe symptoms of urban sprawl resulting from the development of industrial manufacturing cities in the 19thcentury,and mass transport modes that facilitated movement away from city centers during the 20th century .Today, major urbanized areas such as Boston, Chicago, San Francisco and London exhibit exhaustive urban sprawl. International experience: Policymakers responded to these experiences as early as 1947 when the Town and Country Planning Act in the United Kingdom suggested as policy objective, the containment of growth of major conurbations and large cities. The policy found expression in the implementation of greenbelts around these cities, which at the time proved to be the most effective form of containment policy. Since then, the concept of an urban growth boundary has become one of the most popular urban containment tools, and has been implemented in sprawled urban areas such as London, Copenhagen and the often cited example of Portland, Oregon. National experience: Deliberate government policies during the pre-1994 Apartheid regime effected that, South Africa, as a developing country, exhibit wide disparities between richer urban areas, and poorer rural settlements. As a result large numbers of the population migrates to city centers. The influx of people are usually accommodated on the (cheaper) periphery of the city, and consequently, all South African cities have one important feature in common - that urban growth has taken the form of dispersed residential accretion at the city edge. (Department of Development Planning and Local Government, 2002: 1). In response to National legislation, the Development Facilitation Act of 1995, which promotes urban densification and infill development, the Provincial Government of Gauteng drafted a spatial framework in 1999, which aimed to steer all spatial trends in Gauteng. One of the proposals in this Spatial Development Framework was to strive towards a more compact urban form. The process of delineating the Gauteng Urban Edge was initiated and the policy implemented in 2001. The purpose of this paper is to review and assess the origin of the Urban Edge and to finally draw some conclusions from this specific case study, on the lessons learnt from International case studies, concerning Urban Growth Management in South Africa. Focus of this study: . To integrate existing planning knowledge and approaches in order to answer to the research questions. . To gain and unlock new knowledge in the research area, to describe the current trends. . To integrate the theoretical founding and empirical realities mentioned, and to apply the knowledge and findings in the South African context. . To communicate professionally with Professional Planners, Scientists and the community, to stimulate further debate and to publish the results of the research.
Thesis (M.Art. et Scien.)--North-West University, Potchefstroom Campus, 2006.

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Ranke, Ingrid. « A Wind Farm as a Controversial Landscape Phenomenon : A qualitative study of local residents' attitudes towards wind power implementation in their neighborhood ». Thesis, Karlstads universitet, Institutionen för geografi, medier och kommunikation, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-33279.

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Wind power is often presented as a technique for energy production with many environmental benefits, especially since it does not emit any carbon dioxide. Most people are generally positive towards wind power. But when a wind farm is to be implemented on a local level, often resistance occurs. This study investigates how and why local perceptions of a wind farm differ. A qualitative method using interviews was chosen, and the focus has been on an area where a wind farm was planned. The results reveal that advocates have a users’ perspective on nature, while opponents have a conservation perspective. Advocates believe wind power can contribute to a better environment, while opponents believe that preserving natural areas is the best for the environment. Moreover, living in a calm landscape is part of the opponents’ identity, while the identities of the advocates, who often are active farmers, are connected to their ability to live from the land. Thirdly, whether a person recognizes the need for a change towards a renewable energy system or not also matters for the attitude. According to previous research, a person’s relationship to the landscape is of crucial importance for her/his attitude towards wind power implementation, and this is confirmed in the current study. Research also stresses that the visual impact of wind turbines is usually what creates most resistance, but this is not supported. The roles of information and citizen participation, which previous research found significant, are not confirmed as important either: Both were deficient, but this study cannot determine whether a better managed planning process would have made some of the interviewees more positive to it or not. Definitely, the claims from earlier research that Not-In-My-Back-Yard (NIMBY) motives are rarely the reason for resistance are supported.

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Lee, Barry Everett. « The Nashville Civil Rights Movement : A Study of the Phenomenon of Intentional Leadership Development and its Consequences for Local Movements and the National Civil Rights Movement ». Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/history_diss/16.

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The Nashville Civil Rights Movement was one of the most dynamic local movements of the early 1960s, producing the most capable student leaders of the period 1960 to 1965. Despite such a feat, the historical record has largely overlooked this phenomenon. What circumstances allowed Nashville to produce such a dynamic movement whose youth leadership of John Lewis, Diane Nash, Bernard LaFayette, and James Bevel had no parallel? How was this small cadre able to influence movement developments on local and a national level? In order to address these critical research questions, standard historical methods of inquiry will be employed. These include the use of secondary sources, primarily Civil Rights Movement histories and memoirs, scholarly articles, and dissertations and theses. The primary sources used include public lectures, articles from various periodicals, extant interviews, numerous manuscript collections, and a variety of audio and video recordings. No original interviews were conducted because of the availability of extensive high quality interviews. This dissertation will demonstrate that the Nashville Movement evolved out of the formation of independent Black churches and college that over time became the primary sites of resistance to racial discrimination, starting in the Nineteenth Century. By the late 1950s, Nashville’s Black college attracted the students who became the driving force of a local movement that quickly established itself at the forefront of the Civil Rights Movement. Nashville’s forefront status was due to an intentional leadership training program based upon nonviolence. As a result of the training, leaders had a profound impact upon nearly every major movement development up to 1965, including the sit-ins, the Freedom Rides, the March on Washington, the birth of SNCC, the emergence of Black Power, the direction of the SCLC after 1962, the thinking of Dr. Martin Luther King, Jr., the Birmingham campaign, and the Selma voting rights campaign. In addition, the Nashville activists helped eliminate fear as an obstacle to Black freedom. These activists also revealed new relationship dynamics between students and adults and merged nonviolent direct action with voter registration, a combination considered incompatible.

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Ledesma, Alonso René. « Study of the interaction between a liquid film and a local probe ». Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0105/document.

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L’interaction statique et dynamique entre une sonde locale et un film de liquide provoque la déformation de ce dernier. Ce phénomène a été décrit par des équations analytiques, qui ont été analysées et résolues numériquement. Les potentiels d’interaction sonde/liquide et liquide/substrat ont été déduits à partir de l’intégration des forces de dispersion. La différence de pression à travers l’interface air/liquide a été calculée avec une équation de Young-Laplace modifiée, qui prend en compte les effets de la gravité, de tension superficielle, ainsi que les potentiels d’interaction liquide/substrat et sonde/liquide. Pour le cas statique, l’équation modifiée de Young-Laplace en équilibre a été examinée. La théorie de la lubrification a été utilisé pour décrire l’évolution du film liquide, afin d’analyser le phénomène dynamique. Des simulations numériques de la forme de la surface d’équilibre et de l’évolution dynamique du film ont été réalisées. Des comportements stables et instables ont été discernés, et les résultats ont confirmé l’existence d’une distance de seuil, pour le cas statique, et d’une combinaison de paramètres d’oscillation, pour la situation dynamique, pour lesquelles le saut du liquide vers la sonde se produit. Une analyse théorique a confirmé l’existence de conditions critiques qui séparent les régimes de comportement. Ces conditions critiques indiquent le rôle des paramètres physiques et géométriques dans la stabilité du système. Pour le cas dynamique, les résultats préliminaires sont rapportés et une interprétation qualitative du phénomène est formulée. En outre, des expériences de spectroscopie AFM de force et amplitude ont été effectuées et comparées avec les résultats numériques
The static and dynamic interaction between a local probe and a liquid film provokes the deformation of the latter. This phenomenon has been described by means of analytical equations, which had been analyzed and numerically solved. Probe/liquid and liquid/substrate interaction potentials have been deduced from the integration of the dispersion forces. The pressure difference across the air/liquid interface has been calculated with a modified Young-Laplace equation, which takes into account the effects of gravity, surface tension, the liquid film/substrate and the probe/liquid interaction potentials. For the static case, the equilibrium modified Young-Laplace equation has been considered. The lubrication theory has been used to describe the liquid film evolution, in order to analyze the dynamic phenomenon. Numerical simulations of the equilibrium surface shape and the dynamic evolution of the film have been performed. Stable and unstable behaviors had been discerned, and results confirmed the existence of a threshold distance, for the static case, and a combination of oscillation parameters, for the dynamic situation, for which the jump of the liquid to contact the probe occurs. A theoretical analysis confirmed the existence of critical conditions separating the behavior regimes. This critical conditions indicate the role of the physical and geometric parameters in the system stability. For the dynamic case, preliminary results are reported and a qualitative interpretation of the phenomenon is formulated. In addition, AFM force and amplitude spectroscopy experiments had been performed and compared with the numerical results

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Ben, Elhaj Salah Sami. « Modélisation non-locale et stochastique de matériaux à fort gradient de propriétés par développement asymptotique ». Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2019. http://www.theses.fr/2019ESMA0018.

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Le but est de proposer un modèle macroscopique, déterministe et non-local, construit par transition d'échelle pour des matériaux hétérogènes à fort gradient de propriétés, constitués d’inclusions distribuées dans une matrice élastique suivant un processus stochastique ergodique. La méthode des développements asymptotiques, ici étendue dans un cadre aléatoire, est combinée avec une approche énergétique pour faire apparaître le second gradient de déplacement dans l'expression de l'énergie de déformation. Un premier modèle est ainsi obtenu et implique trois tenseurs d'élasticité homogénéisés fonctions du paramètre stochastique et des propriétés des phases. Contrairement à la littérature, il fait intervenir deux longueurs caractéristiques fortement reliées à la microstructure. La mise en œuvre numérique est réalisée pour deux types de microstructures tridimensionnelles de complexité morphologique croissante. Les premières sont virtuelles générées à partir d'un motif simple (une inclusion entourée de six petites) distribué aléatoirement. Les secondes sont des microstructures réelles d'Ethylène-Propylène-Diène Monomère obtenues par tomographie, contenant des clusters d'inclusions de structures complexes.Une seconde transition d'échelle à l'aide d'outils d'homogénéisation variationnelle stochastique dans le cas ergodique est réalisée afin d’obtenir un modèle homogène, exploitable en calculs de structures. Le passage à la limite sur le paramètre d’hétérogénéité émanant du développement asymptotique précédent est ainsi effectué par la méthode de Γ-convergence avec pour objectif de conserver un maximum d'information microstructurale. In fine, le modèle obtenu est macroscopique, non-local, déterministe et richement connecté à la microstructure. La non-localité s'exprime non seulement par le second gradient de déplacement mais aussi par la présence du champ de déplacement virtuel (mémoire) des inclusions. Le lien fort avec la microstructure s'exprime toujours par la présence du paramètre stochastique et des propriétés des phases, mais aussi par celle des fractions asymptotiques de la phase inclusionaire dans le matériau et dans les volumes morphologiques définis par les longueurs caractéristiques intervenant dans le modèle.Pour une future utilisation pratique du modèle, un élément fini non-local et enrichi avec des interpolations de type Hermite est implémenté dans le solveur élément fini FoXtroT de l'Institut Pprime. Il prend en compte le champ de déplacement virtuel (mémoire) des inclusions et les gradients des champs de déplacement macroscopique et virtuel. Les premiers résultats sur cet aspect inédit sont encourageants
The aim is to propose a macroscopic, deterministic and non-local model, constructed by scale transition for heterogeneous materials with high property gradients and containing a random distribution of inclusions. More precisely, the inclusions are distributed in an elastic matrix according to a stochastic ergodic process. Several non-local models exist in the literature, but they do not allow (or very little) to obtain non-local quantities and/or fields at the macroscopic scale from a scale-transition. Besides, it is often difficult to link the non-local parameters to the microstructure. To this aim, we developed a two-step approach.In the first stage, we combined the method of asymptotic developments with an energetic approach to reveal a second displacement gradient in the strain energy. The advanced model involves three homogenized elasticity tensors functions of the stochastic parameter and of the phase properties. As opposed to the literature, the model involves two characteristic lengths strongly linked to the microstructure. These lengths define two morphological representative elementary volumes on which full field simulations are performed in order to determine the macroscopic strain tensors at orders 0 and 1 involved in the formulation of the model. In order to test this first version of the model, numerical simulations were performed. The estimate of the classical part of the energy, coming from the local part of the fields, has been successfully compared to classical bounds for a composite bar consisting of a random distribution of two homogeneous and isotropic elastic materials. Then, numerical solving of the whole model including the non-local terms has been performed in the three-dimensional case. Two types of microstructures with increasing morphological complexity were used. The first ones are virtual microstructures generated from a given simple pattern randomly distributed throughout the structure and composed of a big inclusion circled by six identical small ones. The second are real microstructures of Ethylène-Propylène-Diène Monomère (EPDM) obtained by tomography and containing clusters of inclusions with complex structures.In order to obtain a macroscopic model that can be used for structure analysis, without any full field intermediate calculations, a second scale transition has been performed using stochastic variational homogenization tools in the ergodic case. More precisely, the Γ-convergence method has been used in order to have a convergence of energy rather than that of mechanical fields, aiming at keeping a strong microstructural content. In fine, the model is macroscopic, non-local, deterministic and strongly connected to the microstructure. Non-local effects are now accounted for by the presence of the second displacement gradient but also by the presence of the virtual (memory) displacement field of the inclusions. The link with microstructure is still manifest through the presence of the stochastic parameter and phase properties, but also by the presence of the asymptotic fractions of the inclusion phase in the material and in each of the morphological volumes defined by the model characteristic lengths. In order to prepare the use of the model for structure calculations, a non-local finite element enriched with Hermit-type interpolations was implemented in FoXtroT, the finite element solver of the Pprime Institute. This element takes into account the virtual (memory) displacement field related to inclusions as well as the gradients of the macroscopic and virtual displacement fields. The first numerical results on this aspect, to our knowledge never discussed in the literature, are promising

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Ramírez, Gonzales Andrea. « “¿Qué se dice de la moda sostenible para los protagonistas?”. Un análisis de la percepción de los actores de la moda sostenible local sobre su representación en los medios digitales peruanos ». Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/653928.

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Esta investigación está enfocada en entender la percepción de los personajes más recurrentes dentro de la atmósfera local de la moda sostenible (diseñadores, entidades y creadores de contenido) con respecto a la producción de contenidos sobre este tema en los medios digitales peruanos desde el inicio del 2020. Para esto, se consideraron los conceptos de la moda como un fenómeno social dentro de un grupo específico en el que interactúa el emisor y el receptor, la adaptación del periodismo de modas hacia el mundo digital, qué dificultades periodismo de modas enfrenta de acuerdo al espacio geográfico en el que se desarrolla y la producción de información sobre moda sostenible en las plataformas virtuales. La metodología para realizar este análisis es cualitativa.
This research is focused on understanding the perception of the most recurrent characters in the local atmosphere of sustainable fashion (designers, entities and content creators) regarding the production of content on this subject in peruvian digital media from the beginning of 2020. For this, the concepts of fashion were considered as a social phenomenon within a specific group in which the sender and the receiver interact, the adaptation of fashion journalism to the digital world, what difficulties fashion journalism faces from according to the geographic space in which it is developed and the production of information on sustainable fashion on virtual platforms. The methodology to carry out this analysis is qualitative.
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Borjan, Zoran. « Application of local functional theory to surface critical phenomena ». Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302201.

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Banwait, Barinder S. « On some local to global phenomena for abelian varieties ». Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/58400/.

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Houssat, Mohammed. « Nanocomposite electrical insulation : multiscale characterization and local phenomena comprehension ». Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30211.

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Dans le domaine de l'isolation électrique, il a été démontré que les matériaux hybrides organiques/inorganiques nanocomposites (NC) assurent une nette amélioration de leur fonctionnement à haute température/haute tension et permettent aux systèmes d'isolation électrique de renforcer leurs propriétés diélectriques. Récemment, il a été démontré que certaines modifications des propriétés électriques telles que la permittivité, la rupture diélectrique, la résistance aux décharges partielles ou la durée de vie étaient souvent attribuées à l'interphase nanoparticule/matrice, une région où la présence des nanoparticules modifie les propriétés de la matrice. De plus, des études récentes montrent qu'une fonctionnalisation de la surface des nanoparticules permet une meilleure dispersion dans la matrice hôte. Cette meilleure dispersion affecte la zone d'interphase et joue également un rôle majeur dans l'amélioration des propriétés des nanocomposites. Cependant, le rôle de l'interphase reste théorique et peu de résultats expérimentaux existent pour décrire ce phénomène. Par conséquent, en raison de l'échelle nanométrique de l'interphase, une caractérisation de ses propriétés demeure un défi. Au cours de cette thèse, deux études principales sont menées afin de mieux comprendre la relation structure-propriété dans les polymères nanocomposites. Tout d'abord, la microscopie à force atomique (AFM) est utilisée pour effectuer simultanément des mesures qualitatives et quantitatives de ces zones d'interaction dans le nanocomposite polyimide/nitrure de silicium (PI/Si3N4). Le mode Peak Force Quantitative Nano Mechanical (PF QNM) dérivé de l'AFM révèle la présence de l'interphase en mesurant les propriétés mécaniques (module de Young, déformation ou adhérence). Le mode microscopie à force électrostatique (EFM) est utilisé pour détecter et mesurer la permittivité locale de la matrice et de l'interphases. Par ailleurs, l'objectif de ce travail est de présenter l'effet de la fonctionnalisation de surface des nanoparticules de nitrure de silicium (Si3N4) sur les régions d'interphase. Ces résultats quantitatifs, à la fois mécaniques et électriques, permettent de comparer la dimension et les propriétés des interphase autour des nanoparticules traitées et non traitées. Par conséquent, cette nouvelle approche de caractérisation de cette zone confronte les résultats expérimentaux à des modèles théoriques. Un nouveau modèle basé sur les résultats expérimentaux obtenus est proposé. De plus, la deuxième partie de cette étude présente une caractérisation macroscopique des propriétés et de la rigidité diélectrique des films de polyimide pur, du nanocomposite avec des particules traitées et non traités. Les résultats révèlent le rôle de l'interphase sur la réduction du phénomène de polarisation de l'électrode (PE) dû aux mouvements ioniques surtout à haute température. Pour les nanoparticules non traitées, ces effets sont moins importants en raison de la formation d'agrégats. En revanche, une diminution nette de la PE est obtenue en fonctionnalisant la surface des nanoparticules avec le silane comme agent de couplage. Enfin, la rigidité diélectrique de l'ensemble des échantillons est mesurée et montre une augmentation considérable de la performance diélectrique des nanocomposites à haute température par rapport au PI pur
In the electrical insulation field, it was demonstrated that nanocomposite (NC) organic/inorganic hybrid materials assure a distinct improvement of their high temperature/high voltage functioning and allow the electrical insulation to strengthen its dielectric properties. Recently, it was shown that some modifications of the electrical properties such as permittivity, dielectric breakdown, partial discharges resistance or lifetime are often awarded to the nanoparticle/matrix interphase, a region where the presence of the nanoparticle changes the matrix properties. Moreover, recent studies show that the nanoparticle surface functionalization allows a better dispersion of the particles within the host matrix. This better dispersion affects the interphase zone and plays a major role in the nanocomposite properties improvement as well. However, the role of the interphase remains theoretical and few experimental results exist to describe this phenomenon. Accordingly, because of its nanometer scale, the interphase properties characterization remains a challenge. Two main studies are carried out, during this thesis work, that can provide a better understanding of structure-properties relationships in polymer nanocomposite. First, Atomic Force Microscopy (AFM) is employed to make at the same time qualitative and quantitative measurements of these interaction zones within Polyimide/Silicon Nitride (PI/Si3N4) nanocomposite. The Peak Force Quantitative Nano Mechanical (PF QNM) AFM mode reveals the presence of the interphase by measuring mechanical properties (Young modulus, deformation or adhesion). Electrostatic force microscope (EFM) mode is used in order to detect and measure the matrix and interphase local permittivity. Moreover, the aim of this work is to present the effect of the surface functionalization of silicon nitride (Si3N4) nanoparticles on the interphase regions. Mechanical and electrical quantitative results permit comparing the interphase dimension and properties between treated and untreated Si3N4 nanoparticles. As a result, this new approach to characterize the nanocomposite interphase zone using local measurements confronts experimental results with theoretical models. A new model based on the obtained experimental results is proposed. In addition, the second part of this study presents a macroscopic investigation on the dielectric properties and breakdown strength of neat polyimide, untreated and treated nanocomposite films. Results reveal the interphase role on the reduction of the electrode polarization (EP) phenomenon due to ionic movements especially at high temperatures. For untreated nanoparticles, these effects are less important due to the aggregate formation. In contrast, an EP drastic decrease is obtained by functionalizing the nanofiller surface with a silane coupling agent. Finally, the high temperature breakdown strength for all samples is investigated and shows a considerable increase of nanocomposites dielectric performance at high temperature compared to neat PI

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Idrizbegovic-Zgonic, Aida. « "Challenge of set frames" ». Doctoral thesis, Università degli studi di Trieste, 2009. http://hdl.handle.net/10077/3147.

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2007/2008
Exploration of current trends in the Contextual Architecture (urban setting), meanings of context and finding new ways to connect to the existing. The key issue is establishing a relationship between new building and its setting (frames) through contextual processes like local scenarios or phenomenon or negotiation with site. The principles of dialogue and tension are tools that allow us to establish the new contextual order.
XXI Ciclo
1976

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Acheampong, Ernest Yeboah. « Analyse socioéconomique du «phénomène de don en retour» : les footballeurs africains en Europe et l'aide à leurs communautés d'origine ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAS016/document.

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L’accroissement du déplacement des footballeurs professionnels de l’Afrique vers les ligues européennes, observé dès les années 1990, a transformé la migration du travail du football. En retour, cela a aussi eu un impact sur les revenus des footballeurs africains, leur statut social, et leur relation avec leurs communautés d’origine en termes de soutien socioéconomique. Cette recherche se focalise sur ce sujet en s’appuyant sur la compréhension de l’évolution du football professionnel africain, des itinéraires de migration des joueurs, afin d’expliquer le « phénomène de don en retour » (PDR) lié à la relation entretenue avec leurs communautés d’origine. Elle examine le rôle des facteurs économiques et non économiques qui orientent la manière dont les footballeurs africains donnent en retour à leurs familles, leurs proches, leurs communautés. Celui-ci peut être déterminé dans le but d’un retour sur investissement, par l’influence des valeurs communautaires, des normes, par l’intégration à des réseaux sociaux ou des réseaux institutionnalisés relatifs à l’émigration des footballeurs. En d’autres termes, l’analyse de leur don en retour doit être basée sur la combinaison de facteurs sociaux, culturels et économiques. Aussi, cette recherche mobilise une approche interdisciplinaire à partir du modèle théorique d’analyse de la socio-économie. La méthodologie de Weber contribue à le faire, par l’analyse de l’action de don en retour des footballeurs. Celui-ci est généralement considéré comme la contribution sociale des joueurs, et leurs communautés attendent de recevoir quelque chose de la part des joueurs professionnels africains émigrés ayant réussi financièrement. L’étude est basée sur une enquête qualitative auprès de trente-deux footballeurs professionnels africains incluant aussi des biographies et autobiographies d’autres footballeurs africains. Les résultats montrent que les comportements des footballeurs africains migrants, en termes de don en retour, dépendant de leurs justifications qui sont basées sur des logiques d’intérêt économique, social et culturel.La recherche révèle trois résultats majeurs :1) Une évolution spécifique du football africain et de la perception du football professionnel par les communautés. On identifie une périodisation en trois phases, montrant l’évolution des familles, des structures du football et des stratégies de migration : a) une vision controversée du football (années 1980) : football vs scolarisation ; b) une vision partagée du football (années 1990) : passage progressif d’une activité sociale à une activité professionnelle ; et 3) le football professionnel comme opportunité (années 2000).2) Trois types d’itinéraires migratoires de joueurs qui sont liés à leurs stratégies, aux réseaux mobilisés, et aux ressources disponibles : a) ressources collectives, b) réseaux formels, et c) les ressources individuelles.3) Une typologie du « phénomène de don en retour » (PDR) du footballeur africain migrant concernant les comportements socio-économiques : a) familial hybride, b) familial croisé proche, c) familial partagé, d) familial de l’ombre, qui influencent leurs types d’investissements dans les communautés. D’autre part, certains projets de joueurs tendent à soutenir le développement régional et national de leurs communautés. Toutefois, les joueurs migrants africains doivent gérer et protéger leur réputation et leurs ressources sportives en les utilisant intelligemment et en effectuant de bonnes actions pour leurs communautés, amis et autres au-delà du continent
The increase in movement of professional footballers from Africa to the European leagues as observed since the 1990’, has transformed the labour football migration. In return, this also impacted African footballers’ incomes, social status, and their relation to the communities of origin in terms of socio-economic support. This research focuses on this subject by drawing on the understanding of the evolution of African professional football, players migration itineraries, as to explain the ‘give back phenomenon’ (GBP) related to their relationship with the communities of origin. It examines the role of the economic and non-economic factors that orient African footballers’ ways of giving back to their families, relatives, and the communities. Their give back may be determined by the aim of return on investments, by the influence of communities’ values, norms, or by embeddedness in social networks or by the institutionalised networks related to footballers’ migration. In other words, the analysis of their giving back may be based on the combination of social, cultural and economic factors. Thus, this research mobilised multidisciplinary approach through the socio-economic theoretical model of analysis. Weber methodology helps to do so, in the analysis of footballers’ 'give back' action. This is generally considered as the players’ social contribution and their communities expect to receive something from financially successful professional African migrant players. The study’s qualitative survey was based on thirty-two interviews of professional players from Africa including, biographies and autobiographies. The results show that African migrant players’ behaviours in term of giving back depend on their justifications, which are based on economic interest, social or cultural logics.The research revealed three major outcomes:1) specific evolution of African football and communities’ perception of professional football. This identified one periodization, with three phases, showing families, football structures and migration strategies evolution: a) the controversial vision of football (the 1980s): football vs. school b) the shared vision of football (the 1990s): gradual shift from social activity to a professional activity, and c) football professionalism as an opportunity (the 2000s) 2) three types of players’ migration itineraries which are linked to their strategies, networks mobilised, and the resources available to them: a) collective resource-based, b) formal networks-based, and c) individual resource-based. 3) typology of 'GBP' based on African migrant players’ socio-economic behaviours was a) hybrid family, b) cross-closed family, c) shared family, and d) shadow family that influenced their type of investments in the communities. On another hand, some projects of players tend to support regional and national development in the communities. However, African player migrants have to manage and protect the fame, and sporting resources by using them intelligently to do good things for their communities, friends and others beyond the continent. In conclusion, the itineraries of players’ show the role of the communities in their migration projects. On another hand, the evolution of African football displays how players’ strategies changed with the structuration of African football and the attractiveness of the European football market. The co-determining of economic and non-economic factors relating to the ‘GBP’, justify the use of economic sociology theories. This research demonstrates that ‘GBP’ is not only based on the players’ economic interest but also the combination of social, cultural and economic elements

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Martínez, Garcia Eva. « Document-level machine translation : ensuring translational consistency of non-local phenomena ». Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/668473.

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In this thesis, we study the automatic translation of documents by taking into account cross-sentence phenomena. This document-level information is typically ignored by most of the standard state-of-the-art Machine Translation (MT) systems, which focus on translating texts processing each of their sentences in isolation. Translating each sentence without looking at its surrounding context can lead to certain types of translation errors, such as inconsistent translations for the same word or for elements in a coreference chain. We introduce methods to attend to document-level phenomena in order to avoid those errors, and thus, reach translations that properly convey the original meaning. Our research starts by identifying the translation errors related to such document-level phenomena that commonly appear in the output of state-of-the-art Statistical Machine Translation (SMT) systems. For two of those errors, namely inconsistent word translations as well as gender and number disagreements among words, we design simple and yet effective post-processing techniques to tackle and correct them. Since these techniques are applied a posteriori, they can access the whole source and target documents, and hence, they are able to perform a global analysis and improve the coherence and consistency of the translation. Nevertheless, since following such a two-pass decoding strategy is not optimal in terms of efficiency, we also focus on introducing the context-awareness during the decoding process itself. To this end, we enhance a document-oriented SMT system with distributional semantic information in the form of bilingual and monolingual word embeddings. In particular, these embeddings are used as Semantic Space Language Models (SSLMs) and as a novel feature function. The goal of the former is to promote word translations that are semantically close to their preceding context, whereas the latter promotes the lexical choice that is closest to its surrounding context, for those words that have varying translations throughout the document. In both cases, the context extends beyond sentence boundaries. Recently, the MT community has transitioned to the neural paradigm. The finalstep of our research proposes an extension of the decoding process for a Neural Machine Translation (NMT) framework, independent of the model architecture, by shallow fusing the information from a neural translation model and the context semantics enclosed in the previously studied SSLMs. The aim of this modification is to introduce the benefits of context information also into the decoding process of NMT systems, as well as to obtain an additional validation for the techniques we explored. The automatic evaluation of our approaches does not reflect significant variations. This is expected since most automatic metrics are neither context-nor semantic-aware and because the phenomena we tackle are rare, leading to few modifications with respect to the baseline translations. On the other hand, manual evaluations demonstrate the positive impact of our approaches since human evaluators tend to prefer the translations produced by our document-aware systems. Therefore, the changes introduced by our enhanced systems are important since they are related to how humans perceive translation quality for long texts.
En esta tesis se estudia la traducción automática de documentos teniendo en cuenta fenómenos que ocurren entre oraciones. Típicamente, esta información a nivel de documento se ignora por la mayoría de los sistemas de Traducción Automática (MT), que se centran en traducir los textos procesando cada una de las frases que los componen de manera aislada. Traducir cada frase sin mirar al contexto que la rodea puede llevar a generar cierto tipo de errores de traducción, como pueden ser traducciones inconsistentes para la misma palabra o para elementos que aparecen en la misma cadena de correferencia. En este trabajo se presentan métodos para prestar atención a fenómenos a nivel de documento con el objetivo de evitar este tipo de errores y así llegar a generar traducciones que transmitan correctamente el significado original del texto. Nuestra investigación empieza por identificar los errores de traducción relacionados con los fenómenos a nivel de documento que aparecen de manera común en la salida de los sistemas Estadísticos del Traducción Automática (SMT). Para dos de estos errores, la traducción inconsistente de palabras, así como los desacuerdos en género y número entre palabras, diseñamos técnicas simples pero efectivas como post-procesos para tratarlos y corregirlos. Como estas técnicas se aplican a posteriori, pueden acceder a los documentos enteros tanto del origen como la traducción generada, y así son capaces de hacer un análisis global y mejorar la coherencia y la consistencia de la traducción. Sin embargo, como seguir una estrategia de traducción en dos pasos no es óptima en términos de eficiencia, también nos centramos en introducir la conciencia del contexto durante el propio proceso de generación de la traducción. Para esto, extendemos un sistema SMT orientado a documentos incluyendo información semántica distribucional en forma de word embeddings bilingües y monolingües. En particular, estos embeddings se usan como un Modelo de Lenguaje de Espacio Semántico (SSLM) y como una nueva función característica del sistema. La meta del primero es promover traducciones de palabras que sean semánticamente cercanas a su contexto precedente, mientras que la segunda quiere promover la selección léxica que es más cercana a su contexto para aquellas palabras que tienen diferentes traducciones a lo largo de un documento. En ambos casos, el contexto que se tiene en cuenta va más allá de los límites de una frase u oración. Recientemente, la comunidad MT ha hecho una transición hacia el paradigma neuronal. El paso final de nuestra investigación propone una extensión del proceso de decodificación de un sistema de Traducción Automática Neuronal (NMT), independiente de la arquitectura del modelo de traducción, aplicando la técnica de Shallow Fusion para combinar la información del modelo de traducción neuronal y la información semántica del contexto encerrada en los modelos SSLM estudiados previamente. La motivación de esta modificación está en introducir los beneficios de la información del contexto también en el proceso de decodificación de los sistemas NMT, así como también obtener una validación adicional para las técnicas que se han ido explorando a lo largo de esta tesis. La evaluación automática de nuestras propuestas no refleja variaciones significativas. Esto es un comportamiento esperado ya que la mayoría de las métricas automáticas no se diseñan para ser sensibles al contexto o a la semántica, y además los fenómenos que tratamos son escasos, llevando a pocas modificaciones con respecto a las traducciones de partida. Por otro lado, las evaluaciones manuales demuestran el impacto positivo de nuestras propuestas ya que los evaluadores humanos tienen a preferir las traducciones generadas por nuestros sistemas a nivel de documento. Entonces, los cambios introducidos por nuestros sistemas extendidos son importantes porque están relacionados con la forma en que los humanos perciben la calidad de la traducción de textos largos.

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Engel, Maximilian. « Local phenomena in random dynamical systems : bifurcations, synchronisation, and quasi-stationary dynamics ». Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/57613.

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We consider several related topics in the bifurcation theory of random dynamical systems: synchronisation by noise, noise-induced chaos, qualitative changes of finite-time behaviour and stability of systems surviving in a bounded domain. Firstly, we study the dynamics of a two-dimensional ordinary differential equation exhibiting a Hopf bifurcation subject to additive white noise. Depending on the deterministic Hopf bifurcation parameter and a phase-amplitude coupling parameter called shear, three dynamical phases can be identified: a random attractor with uniform synchronisation of trajectories, a random attractor with non-uniform synchronisation of trajectories and a random attractor without synchronisation of trajectories. We prove the existence of the first two phases which both exhibit a random equilibrium with negative top Lyapunov exponent but differ in terms of finite-time and uniform stability properties. We provide numerical results in support of the existence of the third phase which is characterised by a so-called random strange attractor with positive top Lyapunov exponent implying chaotic behaviour. Secondly, we reduce the model of the Hopf bifurcation to its linear components and study the dynamics of a stochastically driven limit cycle on the cylinder. In this case, we can prove the existence of a bifurcation from an attractive random equilibrium to a random strange attractor, indicated by a change of sign of the top Lyapunov exponent. By establishing the existence of a random strange attractor for a model with white noise, we extend results by Qiudong Wang and Lai-Sang Young on periodically kicked limit cycles to the stochastic context. Furthermore, we discuss a characterisation of the invariant measures associated with the random strange attractor and deduce positive measure-theoretic entropy for the random system. Finally, we study the bifurcation behaviour of unbounded noise systems in bounded domains, exhibiting the local character of random bifurcations which are usually hidden in the global analysis. The systems are analysed by being conditioned to trajectories which do not hit the boundary of the domain for asymptotically long times. The notion of a stationary distribution is replaced by the concept of a quasi-stationary distribution and the average limiting behaviour can be described by a so-called quasi-ergodic distribution. Based on the well-explored stochastic analysis of such distributions, we develop a dynamical stability theory for stochastic differential equations within this context. Most notably, we define conditioned average Lyapunov exponents and demonstrate that they measure the typical stability behaviour of surviving trajectories. We analyse typical examples of random bifurcation theory within this environment, in particular the Hopf bifurcation with additive noise, with reference to whom we also study (numerically) a spectrum of conditioned Lyapunov exponents. Furthermore, we discuss relations to dynamical systems with holes.

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Leyval-Granger, Anne. « La communication des collectivites locales remarques juridiques sur un phenomene politique local ». Lyon 3, 1996. http://www.theses.fr/1996LYO33002.

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L'analyse de la communication des collectivites locales se heurte a divers obstacles en apparence de differentes natures. Elle souleve tout d'abord, des questions d'ordre juridique, technique, et pratique et ne saurait etre limitee a 1 une d'entre eux comme elle ne saurait etre reduite a une finalite communicationnelle structurante de la demande des usagers de la sphere publique. La tentation estpourtant grande chez les differents types d'experts et de professionnels de s'emparer du concept et de le mettre en application. Ainsi, les communicateurs, qu'ils soient presents au sein de la collectivite locale par l'intermediaire d'un departement de la communication dirige par un directeur de la communication, ou externes a la commune, au departement ou a la region, plaident-ils en faveur de strategies de seduction que les juristes denoncent comme un symptome d une communication balbutiante et mal definie. Or en matiere de politique locale, les acteurs interesses par la communication doivent etre par definition non pas consideres sous un caractere prive d'exercice d'une profession mais sous un caractere public de revelation et de reglementation des problemes collectifs. La seconde difficulte se traduit par la tendance moderne a mettre l'accent sur une conception technique de la communication des collectivites locales dominee par l'idee de transfert d'information au detriment de la signification et de l'interpretation. La communication des collectivites territoriales n'est plus alors qu'une forme particuliere, un systeme partiel parmi tant d'autres qui respecteraient les memes principes et participeraient des memes facteurs de la communication. L'ultime ecueil reside dans le developpement et l'influence grandissante des politiques de communication des communes, des departements et des regions qui regit aujourd'hui les relations entre gouvernants et gouvernes a l'echelle locale au detriment d'une veritable communication de proximite originelle de l'echange au sein de l'espace public social. La communication des collectivites locales se presente en effet, comme une activite limite par le legislateur, couteuse dont les resultats ne sont ni qualifies ni quantifies. Au total, les differents obstacles decrits a l'analyse de la communication des collectivites locales presentent un point commun : qu'il s'agisse de la definition du concept, qui fluctue entre un cadre jurid

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Dupuis, Romain. « Surrogate models coupled with machine learning to approximate complex physical phenomena involving aerodynamic and aerothermal simulations ». Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0017/document.

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Les simulations numériques représentent un élément central du processus de conception d’un avion complétant les tests physiques et essais en vol. Elles peuvent notamment bénéficier de méthodes innovantes, telle que l’intelligence artificielle qui se diffuse largement dans l’aviation. Simuler une mission de vol complète pour plusieurs disciplines pose d’importants problèmes à cause des coûts de calcul et des conditions d’opérations changeantes. De plus, des phénomènes complexes peuvent se produire. Par exemple, des chocs peuvent apparaître sur l’aile pour l’aérodynamique alors que le mélange entre les écoulements du moteur et de l’air extérieur impacte fortement l’aérothermie autour de la nacelle et du mât. Des modèles de substitution peuvent être utilisés pour remplacer les simulations haute-fidélité par des approximations mathématiques afin de réduire le coût de calcul et de fournir une méthode construite autour des données de simulations. Deux développements sont proposés dans cette thèse : des modèles de substitution utilisant l’apprentissage automatique pour approximer des calculs aérodynamiques et l’intégration de modèles de substitution classiques dans un processus aérothermique industriel. La première approche sépare les solutions en sous-ensembles selon leurs formes grâce à de l’apprentissage automatique. En outre, une méthode de reéchantillonnage complète la base d’entrainement en ajoutant de l’information dans des sous-ensembles spécifiques. Le deuxième développement se concentre sur le dimensionnement du mât moteur en remplaçant les simulations aérothermiques par des modèles de substitution. Ces deux développements sont appliqués sur des configurations avions afin de combler l’écart entre méthode académique et industrielle. On peut noter que des améliorations significatives en termes de coût et de précision ont été atteintes
Numerical simulations provide a key element in aircraft design process, complementing physical tests and flight tests. They could take advantage of innovative methods, such as artificial intelligence technologies spreading in aviation. Simulating the full flight mission for various disciplines pose important problems due to significant computational cost coupled to varying operating conditions. Moreover, complex physical phenomena can occur. For instance, the aerodynamic field on the wing takes different shapes and can encounter shocks, while aerothermal simulations around nacelle and pylon are sensitive to the interaction between engine flows and external flows. Surrogate models can be used to substitute expensive high-fidelitysimulations by mathematical and statistical approximations in order to reduce overall computation cost and to provide a data-driven approach. In this thesis, we propose two developments: (i) machine learning-based surrogate models capable of approximating aerodynamic experiments and (ii) integrating more classical surrogate models into industrial aerothermal process. The first approach mitigates aerodynamic issues by separating solutions with very different shapes into several subsets using machine learning algorithms. Moreover, a resampling technique takes advantage of the subdomain decomposition by adding extra information in relevant regions. The second development focuses on pylon sizing by building surrogate models substitutingaerothermal simulations. The two approaches are applied to aircraft configurations in order to bridge the gap between academic methods and real-world applications. Significant improvements are highlighted in terms of accuracy and cost gains

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Almquist, Martin. « Efficient Simulation of Wave Phenomena ». Doctoral thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-310124.

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Wave phenomena appear in many fields of science such as acoustics, geophysics, and quantum mechanics. They can often be described by partial differential equations (PDEs). As PDEs typically are too difficult to solve by hand, the only option is to compute approximate solutions by implementing numerical methods on computers. Ideally, the numerical methods should produce accurate solutions at low computational cost. For wave propagation problems, high-order finite difference methods are known to be computationally cheap, but historically it has been difficult to construct stable methods. Thus, they have not been guaranteed to produce reasonable results. In this thesis we consider finite difference methods on summation-by-parts (SBP) form. To impose boundary and interface conditions we use the simultaneous approximation term (SAT) method. The SBP-SAT technique is designed such that the numerical solution mimics the energy estimates satisfied by the true solution. Hence, SBP-SAT schemes are energy-stable by construction and guaranteed to converge to the true solution of well-posed linear PDE. The SBP-SAT framework provides a means to derive high-order methods without jeopardizing stability. Thus, they overcome most of the drawbacks historically associated with finite difference methods. This thesis consists of three parts. The first part is devoted to improving existing SBP-SAT methods. In Papers I and II, we derive schemes with improved accuracy compared to standard schemes. In Paper III, we present an embedded boundary method that makes it easier to cope with complex geometries. The second part of the thesis shows how to apply the SBP-SAT method to wave propagation problems in acoustics (Paper IV) and quantum mechanics (Papers V and VI). The third part of the thesis, consisting of Paper VII, presents an efficient, fully explicit time-integration scheme well suited for locally refined meshes.

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Derivaux, Jean-Francois. « Stochastic thermodynamics of transport phenomena and reactive systems : an extended local equilibrium approach ». Doctoral thesis, Universite Libre de Bruxelles, 2020. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/308809.

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Avec les progrès de la technologie, il est désormais devenu possible de manipuler des faibles quantités d’objets nanométriques, voire des objets uniques. Observer une réaction chimique de quelques centaines de molécules sur des catalyseurs, étudier le travail exercé lors du déploiement d’un brin d’ADN unique ou mesurer la chaleur émise par un unique électron dans un circuit électrique constituent aujourd’hui des actes expérimentaux courants. Cependant, à cette échelle, le caractère aléatoire des processus physiques étudiés se fait plus fortement ressentir. Développer une théorie thermodynamique à ces échelles nécessite d'y inclure de manière exhaustive ces fluctuations.Ces préoccupations et les résultats expérimentaux et théoriques associés ont mené à l’émergence de ce que l’on appelle aujourd’hui la thermodynamique stochastique. Cette thèse se propose de développer une approche originale à la thermodynamique stochastique, basée sur une extension de l'hypothèse d'équilibre local aux variables fluctuantes d'un système. Cette théorie offre de nouvelles définitions des grandeurs thermodynamiques stochastiques, dont l'évolution est donnée par des équations différentielles stochastiques (EDS).Nous avons choisi d'étudier cette théorie à travers des modèles simplifiés de phénomènes physiques variés; transport (diffusif) de chaleur ou de masse, transport couplé (comme la thermodiffusion), ainsi que des modèles de réactions chimiques linéaires et non-linéaires. A travers ces exemples, nous avons proposé des versions stochastiques de plusieurs grandeurs thermodynamiques d'intérêt. Une large part de cette thèse est dévolue à l'entropie et aux différents termes apparaissant dans son bilan (flux d'entropie, production d'entropie ou dissipation). D'autres exemples incluent l'énergie libre d'Helmholtz, la production d'entropie d'excès, ou encore les efficacités thermodynamiques dans le transport couplé.A l'aide de cette théorie, nous avons étudié les propriétés statistiques de ces différentes grandeurs, et plus particulièrement l'effet des contraintes thermodynamiques ainsi que les propriétés cinétiques du modèle sur celles-là. Dans un premier temps, nous montrons comment l'état thermodynamique d'un système (à l' équilibre ou hors d'équilibre) contraint la forme de la distribution de la production d'entropie. Au-delà de la production d'entropie, cette contrainte apparaît également pour d'autres quantités, comme l'énergie libre d'Helmholtz ou la production d'entropie d'excès. Nous montrons ensuite comment des paramètres de contrôle extérieurs peuvent induire des bimodalités dans les distributions d'efficacités stochastiques.Les non-linéarités de la cinétique peuvent également se répercuter sur la thermodynamique stochastique. En utilisant un modèle non-linéaire de réaction chimique, le modèle de Schlögl, nous avons calculé la dissipation moyenne, non-nulle, engendrée par les fluctuations du système. Les non-linéarités offrent aussi la possibilité de produire des bifurcations dans le système. Les différentes propriétés statistiques (moments et distributions) de la production d'entropie ont été étudiées à différents points avant, pendant et après la bifurcation dans le modèle de Schlögl.Ces nombreuses propriétés ont été étudiées via des développements analytiques supportés par des simulations numériques des EDS du système. Nous avons ainsi pu montrer la fine connexion existant entre les équations cinétiques du système, les contraintes thermodynamiques et les propriétés statistiques des fluctuations de différentes grandeurs thermodynamiques stochastiques.
Over the last decades, nanotechnology has experienced great steps forwards, opening new ways to manipulate micro- and nanosystems. These advances motivated the development of a thermodynamic theory for such systems, taking fully into account the unavoidable fluctuations appearing at that scale. This ultimately leads to an ensemble of experimental and theoretical results forming the emergent field of stochastic thermodynamics. In this thesis, we propose an original theoretical approach to stochastic thermodynamics, based on the extension of the local equilibrium hypothesis (LEH) to fluctuating variables in small systems. The approach provides new definitions of stochastic thermodynamic quantities, whose evolution is given by stochastic differential equations (SDEs).We applied this new formalism to a diverse range of systems: heat or mass diffusive transport, coupled transport phenomena (thermodiffusion), and linear or non-linear chemical systems. In each model, we used our theory to define key stochastic thermodynamic quantities. A great emphasis has been put on entropy and the different contributions to its evolution (entropy flux and entropy production) throughout this thesis. Other examples include also the stochastic Helmholtz energy, stochastic excess entropy production and stochastic efficiencies in coupled transport. We investigated how the statistical properties of these quantities are affected by external thermodynamic constraints and by the kinetics of the system. We first studied how the thermodynamic state of the system (equilibrium \textit{vs.} non-equilibrium) strongly impacts the distribution of entropy production. We then extended those findings to other related quantities, such as the Helmholtz free energy and excess entropy production. We also analysed how some external control parameters could lead to bimodality in stochastic efficiencies distributions.In addition, non-linearities affect stochastic thermodynamics quantities in different ways. Using the example of the Schlögl chemical model, we computed the average dissipation of the fluctuations in a non-linear system. Such systems can also undergo a bifurcation, and we studied how the moments and the distribution of entropy production change while crossing the critical point.All these properties were investigated with theoretical analyses and supported by numerical simulations of the SDEs describing the system. It allows us to show that properties of the evolution equations and external constraints could strongly reflect in the statistical properties of stochastic thermodynamic quantities.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Finkbiner, Amy. « Global phenomena from local rules [electronic resource] : peer-to-peer networks and crystal steps / ». College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/7682.

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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Mathematics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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MULLER-GERKING, JOHANNES. « La dynamique cerebrale comme phenomene non-lineaire : une etude quantitative de potentiels de champ local ». Paris 6, 1996. http://www.theses.fr/1996PA066302.

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La question de la presence de dynamiques non-lineaires et de chaos au sein du cerveau reste irresolue. Des resultats recents indiquent que la revendication initiale de basse dimensionalite a ete faussee par des tests statistiques incomplets. Ici, nous avons applique une analyse rigoureuse a des donnees neuroelectriques controlees precisement et possedant une signification comportementale. L'activite fonctionnelle du cerveau semble etre liee aux potentiels de champs locaux synchronises, ce qui motive notre choix de donnees. La recherche de structures non-lineaires dans ces donnees est motivee de plus par des proprietes surprenantes de quelques systemes dynamiques deterministes. Comme la methode de la reconstruction de l'espace de phases a partir de donnees scalaires permet de conclure a une dynamique deterministe seulement en cas de systeme chaotique simple, nous ne pouvons que chercher la presence de non-linearites, c'est-a-dire des relations temporelles qui depassent celles obtenues pour des processus lineaires autoregressifs (arma). Nous presentons des tests statistiques pour la detection de non-linearites. Les resultats principaux de cette these sont bases sur l'examen d'episodes synchrones dans des potentiels de champs locaux enregistres au sein du systeme visuel de chats et de pigeons actifs. Notre propos etait d'examiner dans ces conditions ideales si des non-linearites apparaissaient simultanement a l'emergence de synchronisations neuronales. Nos resultats indiquent effectivement des traces de non-linearites faibles. Une etude plus detaillee nous convainc que les tentatives de les caracteriser ne nous permettront pas de mieux comprendre les proprietes dynamiques de ces systemes biologiques extremement compliques. Nous concluons qu'il est peu probable de trouver du chaos de basse dimension dans le cerveau et qu'aujourd'hui il faut preferer, pour l'analyse des donnees cerebrales, des statistiques lineaires avancees. Ces methodes sont moins exigeantes concernant la quantite et la qualite des donnees, et fournissent des informations sur des relations temporelles qui restent inexploitees a present

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Loday-Richaud, Michèle. « Classification meromorphe locale des systemes differentiels lineaires meromorphes : phenomene de stokes et applications ». Paris 11, 1991. http://www.theses.fr/1991PA112124.

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On se pose la question du calcul effectif des invariants meromorphes des systemes differentiels lineaires a coefficients meromorphes. Question double: que calculer? comment le calculer? la premiere question est theorique: dans la classification cohomologique due a sibuya et malgrange le classifiant se ramene a un ensemble de cohomologie non abelienne, muni d'une structure canonique de variete algebrique affine. Nous construisons une structure lineaire affine naturelle en caracterisant chaque classe de cohomologie par une cochaine particuliere dite cochaine fondamentale (theoreme d'isomorphisme avec le produit des groupes de stokes). Cette cochaine est unique et obtenue par un algorithme explicite a partir de n'importe quelle cochaine; elle caracterise le phenomene de stokes. Les invariants a calculer sont alors les composantes dans une base de cet espace lineaire, base que nous precisons. Mentionnons qu'une version abstraite, non constructive, du meme theoreme de structure a ete etablie independamment par babbitt et varadarajan a partir d'arguments dus a deligne. Comme consequence de la construction ci-dessus nous etablissons une correspondance simple entre cette classification et celle par le pi-un sauvage de ramis. Nous retrouvons et ce par des arguments algebriques, les proprietes galoisiennes des bonnes matrices de stokes et la multisommabilite des solutions. La deuxieme question est algorithmique et numerique: il s'agit d'evaluer des quantites essentiellement transcendantes. On se contente donc de calculs numeriques approches mais neanmoins porteurs d'informations. Nous decrivons la methode par resommation qui, sauf dans les cas simples, pose encore des problemes de stabilite numerique (j. Thomann, f. Richard-jung). Et nous proposons une methode dite infinitesimale qui, sauf en dimension deux, ne conduit pas toujours au calcul de tous les invariants mais qui est numeriquement tres stable. Les v

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Granados, Corsellas Albert. « Local and global phenomena in piecewise-defined systems : from big bang bifurcations to splitting of heteroclinic manifolds ». Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/131282.

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In the first part, we formally study the phenomenon of the so-called big bang bifurcations, both for one and two-dimensional piecewise-smooth maps with a single switching boundary. These are a special type of organizing centers consisting on points in parameter space with co-dimension higher than one from which an infinite number of bifurcation curves emerge. These separate existence regions of periodic orbits with arbitrarily large periods. We show how a mechanism for their occurrence in piecewise-defined maps is the simultaneous collision of fixed (or periodic) points with the switching boundary. For the one-dimensional case, the sign of the eigenvalues associated with the colliding fixed points determines the possible bifurcation scenarios. When they are attracting, we show how the two typical bifurcation structures, so-called period incrementing and period adding, occur if they have different sign or both are positive, respectively. Providing rigorous arguments, we also conjecture sufficient conditions for their occurrence in two-dimensional piecewise-defined maps. In addition, we also apply these results to first and second order systems controlled with relays, systems in slide-mode control. In the second part of this thesis, we discuss global aspects of piecewise-defined Hamiltonian systems. These are piecewise-defined systems such that, when restricted to each domain given in its definition, the system is Hamiltonian. We first extend classical Melnikov theory for the case of one degree of freedom under periodic non-autonomous perturbations. We hence provide sufficient conditions for the persistence of subharmonic orbits and for the existence of transversal heteroclinic/homoclinic intersections. The crucial tool to achieve this is the so-called impact map, a regular map for which classical theory of dynamical systems can be applied. We also extend these sufficient conditions to the case when the trajectories are forced to be discontinuous by means of restitution coefficient simulating a loss of energy at the impacts. As an example, we apply our results to a system modeling the dynamical behaviour of a rocking block. Finally, we also consider the coupling of two of the previous systems under a periodic perturbation: a two and a half degrees of freedom piecewise-defined Hamiltonian system. By means of a similar technique, we also provide sufficient conditions for the existence of transversal intersections between stable and unstable manifolds of certain invariant manifolds when the perturbation is considered. In terms of the rocking blocks, these are associated with the mode of movement given by small amplitude rocking for one block while the other one follows large oscillations of small frequency. This heteroclinic intersections allow us to define the so-called scattering map, which links asymptotic dynamics in the invariant manifolds through heteroclinic connections. It is the essential tool in order to construct a heteroclinic skeleton which, when followed, can lead to the existence of Arnold diffusion: trajectories that, in large time scale destabilize the system by further accumulating energy.

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Zordan, Marco. « Non-linear analysis of CFS hybrid structural building systems in presence of local and global damage phenomena ». Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/322426.

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The use of cold-formed steel (CFS) members enabled, in recent years, the development of a new light constructional solution for residential buildings: the light gauge steel buildings. These structures combine rapidity and simplicity of erection with a good structural performance. In addition, their lightness makes them very attractive for seismic areas. From a structural point of view, the building is a system composed of shear-walls and floor-systems that interact between them in the mechanism of force transfer. In the seismic context, the forces that arise on floors are transferred to the shear-walls that act as a bracing system, transferring the horizontal forces to the foundation. Generally, the steel-frame, made of CFS members, has walls and floor systems sheathed with panels of various materials, such as steel sheets, OSB panels or gypsum fibreboards: i.e. the structure is hybrid. The performance is hence affected by the response features of the various materials, of the connections and the individual components. This makes the prediction of the structural response very difficult and complex. To further complicate the subject, the presence of cyclic actions causes other nonlinear phenomena such as the pinching effect that is very common in these structures. Such a complex behaviour of CFS profiles, sub-assemblages and the whole system, makes it difficult to adopt a purely theoretical approach for their design. Therefore, a mixed approach that combines experimental tests and numerical simulations is usually adopted. As to the key structural components, many studies about the shear-walls are available in the literature, while little attention was paid to the behaviour of the floor diaphragms. Moreover, the attempts to get an insight into the overall building response were even fewer. In any case, the complexity of these sub-systems and of their interaction in the whole building system makes it difficult to predict the responses of specific configurations. In this framework, the University of Trento was involved in a research project aimed to develop an innovative industrialized housing system made of CFS members. With the aim to have a holistic comprehension of the performance of these building systems, a suitable number of experimental tests and numerical simulations were performed ranging from the single component to the entire building. In detail, the CFS members may be considered the main components of these systems, therefore their axial and bending behaviours were first tested and then investigated through detailed numerical simulations. Their characterization was also needed for developing reliable models of sub-assemblies. The steel-deck and gypsum fibreboards are essential parts of the floor diaphragms and shear walls studied, therefore experimental tests for evaluating their shear behaviour were carried out considering both monotonic and cyclic loading protocols. With the aim to characterize the in-plane behaviour of shear walls, the results of an experimental study carried out in Trento were considered. These results represent the background for the development of numerical analyses enabling the calibration and validation of the models. Like the walls, the floor-systems were deeply studied both from the experimental and the numerical point of view. The experimental tests enable appreciating the in-plane shear responses of different configurations, also providing the background to the calibration of FE models. The complexity of these systems required a particular modelling approach based on layers and on the numerical characterization of the floor components. Eventually, since the evaluation of the seismic performance of this new solution is the main goal of the project, three different building models were developed and analysed. The models refer to three different building archetypes representative of three solutions of buildings that differs from the type and number of shear-walls used as the bracing system. The eigen analysis, push-over analysis and the time-history analysis (THA) are the main tools used in the study enabling the evaluation of the vibration properties, the deformation capacity and seismic response of the structure. Besides, multi-stripe analyses (MSAs) were carried out with the aim to evaluated fragility functions providing the probability of failure given an intensity measure that describes the seismic event. The developed models are too complex to be used in everyday design analysis. However, they allowed set up simplified design methods that can be of great help to designers. In conclusion, the thesis aims at providing a contribution to the knowledge of the response of cold formed steel structures in light residential buildings. This contribution expands the present state-of-the-art, pointing out the role of the various components as well as the critical issues.

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Buchholz, Marcel [Verfasser], Markus [Akademischer Betreuer] Braden et Liu Hao [Akademischer Betreuer] Tjeng. « Local Symmetry and Domain Patterns : Ordering Phenomena in Transition-Metal Oxides / Marcel Buchholz. Gutachter : Markus Braden ; Liu Hao Tjeng ». Köln : Universitäts- und Stadtbibliothek Köln, 2013. http://d-nb.info/1038380359/34.

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Cavinato, Cristina. « Caractérisation des micro-mécanismes de déformation et de rupture de la paroi d’anévrisme aortique ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEM003.

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La paroi de l'aorte thoracique ascendante présente une microstructure complexe et hétérogène qui peut être sujette à la pathologie d'anévrisme, une dilatation irréversible associée à un remodelage dégénératif de la microstructure. Ce dernier entraîne une modification du comportement mécanique du tissu, dont les conséquences les plus graves sont la rupture ou la dissection.L'objectif de cette thèse est d'aborder l’hypothèse scientifique suivante : les phénomènes qui se produisent au niveau de la structure fibreuse microscopique de collagène et d'élastine sont impliqués ou même responsables de la réponse mécanique macroscopique des anévrismes de l'aorte thoracique ascendante, notamment proche de la rupture. Une méthodologie expérimentale a permis d’allier, en une approche unifiée, un essai mécanique de gonflement ex vivo, un dispositif optique de mesure haute résolution de l'épaisseur des échantillons, un dispositif de corrélation d’images numériques pour la mesure de champs de déplacement, un microscope confocal biphotonique. Des analyses spécifiques aux patients ont été réalisées sur des échantillons d'aorte animale et humaine, en particulier des anévrismes de l'aorte thoracique ascendante humaine, d'un état non chargé jusqu’à rupture. Les relations entre l’état mécanique local et la morphologie microstructurale des composants fibreux de la couche aortique externe, l'adventitia généralement considérée comme la barrière ultime avant rupture, ont été étudiées. Les contributions majeures consistent en des observations des structures fibreuses en réponse au scénario de chargement, jusqu'à rupture, et des liens quantitatifs avec l'état mécanique et les données cliniques
The wall of the ascending thoracic aorta retains a complex heterogeneous microstructural organization which can be subjected to aneurysms, irreversible dilatations associated with degenerative remodeling processes of the microstructure. The latter results in an altered mechanical behavior of such key tissue whose utmost consequences are rupture or dissection.The following hypothesis is addressed: the phenomena which occur at the microscopic fibrous structure of collagen and elastin are involved or even responsible for the macroscopic mechanical response of ascending thoracic aortic aneurysms, in particular when close to rupture. Towards an improved understanding of the structure-to-mechanics relationship, an experimental methodology enabled the consistent coupling of several test benches: a mechanical inflation test, an optical device for high resolution measurements of the specimen thickness, a image correlation set-up for full-field displacement measurements and a two-photon microscopy bench. Patient-specific analyses were conducted on ex-vivo specimens of animal and human thoracic aortae, in particular human ascending thoracic aortic aneurysms, up to rupture. The analyses focus on the relationship between local mechanical state and microstructural morphology of the principal fibrous components of the outer aortic layer, usually seen as ultimate resistive barrier before rupture. The connection between these data and fundamental information inherent to clinics or morphometry are analyzed. The resulting contribution consists of advanced observations of the fibrous recruitment and reactions to the loading scenario and quantitative links with mechanics and clinics

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Hernandez, Gonzalez Edna Magdalena. « High spatial resolution investigation of spin crossover phenomena using scanning probe microscopies ». Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30081/document.

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Récemment, un grand nombre d'objets de taille nanométrique, incluant les nanoparticules, les films minces, les dispositifs nanostructurés, présentant des phénomènes de commutation impliquant différents états de spin, ont été développé pour des applications dans le domaine des capteurs et des systèmes nanophotoniques, nanoélectroniques et nanomécaniques. En effet, Ces nanomatériaux à conversion de spin présentent une dépendance en taille des propriétés physico-chimiques très intéressantes. Même si l'origine du phénomène de conversion de spin est purement moléculaire, le comportement macroscopique de ces systèmes à l'état solide est fortement influencé par les interactions intermoléculaires élastiques. On s'attend donc à ce que les propriétés coopératives et, de manière plus générale, le diagramme de phase, soient très dépendantes de la taille du système. Au-delà de la stabilité des phases, les cinétiques de transformation dépendent également de la taille du système. Dans ce contexte, des interactions élastiques fortes conduisent dans de nombreux cas à des transitions de type premier ordre accompagnées par une séparation de phase hétérogène. Les détails du mécanisme de la dynamique spatio-temporelle associée à la transition de spin restent encore inexplorés. L'ensemble de ces phénomènes observés dans les matériaux à transition de spin demande des méthodes de caractérisation possédant une capacité d'imagerie d'une grande résolution spatiale afin d'aller au-delà des techniques de microscopie optique en champ lointain habituellement employées. Par conséquence, l'objectif global de cette thèse de doctorat est de développer de nouvelles approches qui permettent de détecter le phénomène de transition de spin avec une résolution spatiale nanométrique. Pour observer la transition de spin thermique dans les films minces, nous avons utilisé pour la première fois la microscopie optique en champ proche (NSOM en Anglais) ainsi que la microscopie à force atomique (AFM en Anglais) en conjonction avec des dispositifs originaux de chauffage à l'échelle du nanomètre, conçus à partir de nanofils et fonctionnant par effet Joule. En utilisant ces techniques, le changement de l'état de spin a pu être observé avec une résolution sub-longueur d'onde au travers des changements des propriétés mécanique et optique des matériaux. Le NSOM en mode illumination, utilisé soit en luminescence ou en mode réflexion fournit un signal utile pour la détection du changement d'état de spin mais ne permet en revanche qu'une quantification limitée du phénomène en raison de l'instabilité des échantillons (photoblanchiment, ...) . D'un autre côté, les différents modes mécaniques AFM, incluant la spectroscopie à force rapide et l'analyse multifréquentielle, ont permis des mesures quantitatives et reproductibles avec une résolution nanométrique. En particulier, nous avons été capable de mesurer pour la première fois l'augmentation du module d'Young (env. 25-30%) observée lors de la transition de l'état Haut Spin vers l'état Bas Spin et nous avons utilisé cette propriété pour réaliser une imagerie quantitative de la transition de spin. Des mesures AFM ont été faites sur des monocristaux à transition de spin. Nous avons montré que les transferts thermiques entre la sonde et l'échantillon peuvent être utilisés pour manipuler la nucléation et la propagation des phases Haut et Bas Spin dans des cristaux. Par ailleurs, ces interactions sonde-échantillon rendent difficiles l'imagerie AFM de ces phénomènes. Néanmoins, les changements d'ordre topographique de la surface au cours de la transition de spin peuvent être observés et discutés en conjonction avec les résultats de spectroscopie Raman (cartographie) et microscopie optique en champ lointain. L'ensemble de ces résultats ouvre de nouvelles possibilités d'étude et de contrôle/manipulation de ces objets bistables à l'échelle du nanomètre
Recently a variety of nanoscale objects, including nanoparticles, thin films and nanometric assemblies, exhibiting molecular spin-state switching phenomena have been developed for applications in sensors, nanophotonic, nanoelectronic and nanomechanical systems. These spin crossover nanomaterials have been also reported to exhibit interesting size-dependent properties. Indeed, even if the origin of the spin crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly influenced by elastic interactions between the molecules. These cooperative properties and, in general, the phase diagram are expected to depend strongly on the size of the material. Beyond the phase stability, the transformation kinetics is likely to display also size dependence. Indeed, the strong elastic interactions in these materials lead, in many cases, to first-order phase transitions and phase separation phenomena. Details of the associated spatio-temporal dynamics of spin crossover systems remain largely unexplored. All these size dependent and spatially heterogeneous phenomena in spin crossover materials call for appropriate characterization methods with high spatial resolution imaging capability, but to date only far-field optical microscopy has been used to this aim. Hence, the overall objective of this PHD thesis was to develop new approaches allowing to trigger and detect the spin crossover phenomenon with nanometric spatial resolution. For the detection of the thermally induced spin crossover in thin films, we used for the first time Near-Field Scanning Optical Microscopy (NSOM) and Atomic Force Microscopy (AFM) in conjunction with an original nano-heater device, based on Joule-heated metallic nanowires. Using these techniques the spin-state change in the films was inferred with sub-wavelength resolution through the associated optical and mechanical property changes of the material. Apertured NSOM used either in luminescence or reflectivity mode provided useful signal for detecting the spin-state switching phenomena, but rather limited quantification was possible due to sample stability issues (photobleaching, etc). On the other hand, AFM mechanical modes, including fast force spectroscopy and multifrequency analysis, allowed for quantitative and well-reproducible measurements with nanometric resolution. In particular, we have measured for the first time the increase of the Young's modulus (ca. 25-30 %) when going from the high spin to the low spin state and used this property for quantitative imaging of the spin transition. AFM measurements were also performed on spin crossover single crystals. We have shown that probe-sample thermal interactions can be used to manipulate the nucleation and propagation of the high spin and low spin phases in the crystals. On the other hand, these interactions make for difficulties for the AFM imaging of these phenomena. Nevertheless changes of the surface topography during the spin transition can be observed and discussed in conjunction with far-field optical microscopy and Raman spectroscopy data. The ensemble of these results open up new possibilities for the investigation and manipulation of these bistable objects at the nanoscale

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Savio, Daniele. « Nanoscale phenomena in lubrication : From atomistic simulations to their integration into continuous models ». Phd thesis, INSA de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-00961197.

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The modern trends in lubrication aim at reducing the oil quantity in tribological applications. As a consequence, the film thickness in the contact zone decreases significantly and can reach the order of magnitude of a few nanometres. Hence, the surface separation is ensured by very few lubricant molecules. Atomistic simulations based on the Molecular Dynamics method are used to analyze the local behavior of these severely confined films. A particular attention is paid to the occurrence of wall slip: predictive models and analytical laws are formulated to quantify and predict this phenomenon as a function of the surface-lubricant pair or the local operating conditions in a contact interface. Then, the coupling between Molecular Dynamics simulations and macroscopic models is explored. The classical lubrication theory is modified to include slip effects characterized previously. This approach is employed to study an entire contact featuring a nano-confined lubricant in its center, showing a severe modification of the film thickness and friction. Finally, the lubricant quantity reduction is pushed to the limits up to the occurrence of local film breakdown and direct surface contact. In this scenario, atomistic simulations allow to understand the relationship between the configuration of the last fluid molecules in the contact and the local tribological behavior.

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Romero, Hamers Adolfo. « STUDY OF THE THERMAL STRATIFICATION IN PWR REACTORS AND THE PTS (PRESSURIZED THERMAL SHOCK) PHENOMENON ». Doctoral thesis, Editorial Universitat Politècnica de València, 2014. http://hdl.handle.net/10251/36536.

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In the event of hypothetical accident scenarios in PWR, emergency strategies have to be mapped out, in order to guarantee the reliable removal of decay heat from the reactor core, also in case of component breakdown. One essential passive heat removal mechanism is the reflux condensation cooling mode. This mode can appear for instance during a small break loss-of-coolant-accident (LOCA) or because of loss of residual heat removal (RHR) system during mid loop operation at plant outage after the reactor shutdown. In the scenario of a loss-of-coolant-accident (LOCA), which is caused by the leakage at any location in the primary circuit, it is considered that the reactor will be depressurized and vaporization will take place, thereby creating steam in the PWR primary side. Should this lead to ¿reflux condensation¿, which may be a favorable event progression, the generated steam will flow to the steam generator through the hot leg. This steam will condense in the steam generator and the condensate will flow back through the hot leg to the reactor, resulting in counter-current steam/water flow. In some scenarios, the success of core cooling depends on the behaviour of this counter-current flow. Over several decades, a number of experimental and theoretical studies of counter-current gas¿liquid two-phase flow have been carried out to understand the fundamental aspect of the flooding mechanism and to prove practical knowledge for the safety design of nuclear reactors. Starting from the pioneering paper of Wallis (1961), extensive CCFL data have been accumulated from experimental studies dealing with a diverse array of conditions A one-dimensional two field model was developed in order to predict the counter-current steam and liquid flow that results under certain conditions in the cold leg of a PWR when a SBLOCA (small break loss of coolant accident) in the hot leg is produced. The counter-current model that has been developed can predict the pressure, temperature, velocity profiles for both phases, also by taking into account the HPI injection system in the cold leg under a counter-current flow scenario in the cold leg. This computer code predicts this scenario by solving the mass, momentum and energy conservation equations for the liquid and for the steam separately, and linking them by using the interfacial and at the steam wall condensation and heat transfer, and the interfacial friction as the closure relations. The convective terms which appear in the discretization of the mass and energy conservation equations, were evaluated using the ULTIMATE-SOU (second order upwinding) method. For the momentum equation convective terms the ULTIMATE-QUICKEST method was used. The steam-water counter-current developed code has been validated using some experimental data extracted from some previously published articles about the direct condensation phenomenon for stratified two-phase flow and experimental data from the LAOKOON experimental facility at the Technical University of Munich.
Romero Hamers, A. (2014). STUDY OF THE THERMAL STRATIFICATION IN PWR REACTORS AND THE PTS (PRESSURIZED THERMAL SHOCK) PHENOMENON [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36536
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CORDELIER, SYLVAIN. « Mecanismes de defense des plantes contre les agents pathogenes : etude du phenomene de resistance locale acquise chez le tabac ». Université Louis Pasteur (Strasbourg) (1971-2008), 2000. http://www.theses.fr/2000STR13146.

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La resistance locale acquise (lar) est un mecanisme de defense essentiel permettant a une plante, en combinaison avec la reaction d'hypersensibilite (hr), de restreindre les agents pathogenes au site d'attaque. La hr se caracterise par la mort des cellules vegetales et par la liberation d'un ou plusieurs signaux diffusant a courte distance pour induire le phenomene lar. Une resistance systematique acquise (sar) s'etablit egalement dans la plante entiere. Nous montrons que les phenomenes lar et sar se distinguent aux niveaux moleculaire et biologique. Le modele experimental implique l'infiltration dans des feuilles de tabac d'un eliciteur fongique induisant hr, lar et sar. Des etudes de perte de fonction suggerent que les cellules en etat de lar liberent le signal sar et que des signaux differents induisent lar et sar. L'identification du (ou des) signal lar est l'objectif principal de ce travail. Une combinaison d'approche pharmacologique, utilisant des inhibiteurs de la biosynthese de l'ethylene, et genetique, utilisant des tabacs transgeniques insensibles a l'ethylene, indique que l'ethylene apparait comme un signal important pour l'expression d'un sous-ensemble de reponses de defense au cours du phenomene lar et qu'un autre signal agirait comme signal lar diffusible. Des suspensions cellulaires de tabac traitees avec un eliciteur fongique constituent le modele utilise pour l'isolement du signal lar. Ces cellules liberent un signal presentant des proprietes caracteristiques d'un signal lar. Cette recherche a permis la determination de la structure chimique d'une molecule originale, inductrice de reponses de defense, et la caracterisation d'une fraction renfermant une activite biologique presentant certaines des proprietes typiques d'un signal lar. L'analyse par spectrometrie de masse et par resonance magnetique nucleaire devoile quelques elements de la structure chimique du signal lar potentiel.

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Chupin, Sylvain. « Comportement local et performances électriques d'une pile à combustible à membrane : vers un outil de diagnostic ». Thesis, Université du Québec à Trois-Rivières, 2009. http://www.theses.fr/2009INPL098N/document.

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Le travail de thèse présenté ici apporte des éléments de compréhension sur l'influence de la gestion de l'eau et de la gestion thermique d'une PEMFC sur ses performances électriques. Un modèle bidimensionnel représentant les transferts de matière et de chaleur dans l'épaisseur d'une cellule élémentaire et le long des canaux d'alimentation est mis en place. Une partie spécifique de l'étude concerne la modélisation microscopique des agglomérats réactionnels et l'influence de l'eau présente dans ces zones actives sur les performances électriques locales et globales de la pile. Dans l'optique de réaliser un modèle pouvant s'intégrer à un système de contrôle, les transports couplés de l'eau liquide et vapeur, de la chaleur et des charges sont résolus analytiquement. Quelles que soient les conditions de fonctionnement, le modèle permet de calculer quel est l'état interne de la pile en terme d'hydratation, de production de courant et de chaleur. Le diagnostic de l'état interne de la pile en fonction des conditions opératoires permet de connaître précisément comment adapter les paramètres d'alimentation de la pile pour obtenir des performances électriques optimales. Les distributions locales d'eau, de courant et de température sont présentées en fonction de la stratégie d'alimentation en gaz de la pile et de l'orientation du circuit de régulation thermique. Une partie consacrée au diagnostic de fonctionnement d'une pile illustre en quoi l'utilisation du modèle et la connaissance de l'état interne de la pile apporte des informations primordiales lors de l'utilisation d'une pile à combustible
The present work contributes to the understanding of water management and thermal management of a PEM fuel cell influences on the electrical performances. A bidimensional model representing mass and heat transfer in the cell thickness and along distribution channels is done. A specific part of the study concerns a microscopic representation of reactive agglomerates. This part presents the impact of the liquid water presence on local and global current densities. In te vein of integrating this model in a total fuel cell control system, simplifications have been done and coupled mass, heat and charge transfers are solved analytically. For any operating condition, the model gives a complete view of the hydric, thermal and electric inner situation of the cell. This diagnosis of the inner state of the cell leads to find the operating conditions giving to the optimal electric performances. Water, current and temperature distributions are presenting for different gas feeding strategies and different thermal management configurations. A specific part is dedicated to illustrate how this local diagnosis of the cell state can be used to estimate its global electric performances

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Cunsolo, Alessandro. « Relaxation phenomena in the THz dynamics of simple fluids probed by inelastic X-ray scattering ». Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10166.

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La dynamique a l'echelle atomique de differents exemples de fluides simples a ete etudiee dans le domaine de tres hautes frequences (thz) en utilisant la technique de la diffusion inelastique des rayons x avec une resolution de l'ordre du mev. L'etude experimentale est structuree naturellement en trois parties. Dans la premiere, le cas de la dynamique des fluides simples est traite, avec pour exemple, le neon tres au dela du point critique. Dans ce cas, le dynamique attendue doit etre proche de celle du cas simple des fluides a spheres dures, ou les interactions consistent en collisions mutuelles entre particules. La deuxieme partie concerne l'etude de la dynamique de systemes plus complexes, elle est illustree par l'exemple du neon cette fois en phase liquide. L'objectif de cette analyse est de differencier les effets lies aux interaction a plusieurs corps typiques des liquides, par rapport a l'etat supercritique. Dans la derniere partie, nous abordons l'etude de la dynamique des liquides pour lesquels existent des interactions spatiales a longue distance entre molecules. Le liquide choisit est l'eau en phase liquide. Pour ces trois etudes, un interet particulier a ete accorde a la caracterisation des phenomenes de relaxation. Plus specifiquement, nous montrons comment les phenomenes de relaxation evoluent avec le degre de connectivite croissant des systemes. Nous nous interessons a deux larges classes de phenomenes de relaxation : microscopiques et structurales. Les relaxations structurales sont liees a des processus cooperatifs par lesquels la structure locale, apres avoir ete perturbee par une fluctuation spontanee de densite, se rearrange vers une nouvelle position d'equilibre. Les relaxations microscopiques, d'un autre cote, ne sont pas cooperatives, elles impliquent une vibration atomique ayant une echelle de temps de l'ordre de 10 1 3s et ne dependent pratiquement pas de la temperature. Les premieres dominent les phenomenes observes dans l'eau, tandis que dans le cas du neon supercritique ou liquide, ce sont les relaxations microscopiques qui sont observees.

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Del, Sorbo Dario. « An entropic approach to magnetized nonlocal transport and other kinetic phenomena in high-energy-density plasmas ». Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0336/document.

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Les simulations hydrodynamiques pour la physique de haute densité d'énergie ainsi que pour la fusion par confinement inertiel exigent une description détaillée de flux d'énergie. Le mécanisme principal est le transport électronique, qui peut être un phénoméne non local qui doit être décrit avec des modèles de Fokker-Planck, stationnaires et simplifiés dans les codes hydrodynamiques à grande échelle. Mon travail thèse est consacré au développement d'un nouveau modèle de transport non local basé sur l'utilisation d'une méthode de fermeture entropique pour la résolution des premiers moments de l'équation de Fokker-Planck agrémentée d'un opérateur de collision dédié. Une telle fermeture permet une bonne résolution des fortes anisotropies de la fonction de distribution électronique dans les régimes où le développement d'instabilités électrostatiques à petite échelle le requiert. Ce modèle aux moments (M1) est comparé avec succès au modèle de Schurtz, Nicolaï et Busquet (SNB), référent dans le domaine du transport électronique non local. Ce modèle, basé sur l'hypothèse d'une faible anisotropie de la fonction de distribution sous-jacente induisant une relation de fermeture polynomiale (P1), utilise un opérateur de collision simplifié dont nous avons proposé une amélioration. Après avoir considéré plusieurs configurations typiques de transport de chaleur, nous avons montré que le modèle M1 ultidimensionnel peut prendre naturellement en compte des effets d'un plasmas magnétisés sur le transport électronique. De plus, ce modèle permet de calculer des fonctions de distribution utiles aux études cinétiques comme la stabilité du plasma dans la zone de transport. Nous confirmons avec notre modèle que le transport d'énergie électronique peut fortement modifier l'amortissement des ondes de Langmuir et des ondes acoustiques ; contrairement aux modèles non locaux simplifiés, M1 décrit les modifications de la fonction de distribution et l'amortissement des ondes du plasma. La structure du modèle permet également de prendre en compte naturellement des champs magnétiques autogénérés, qui jouent un rôle crucial dans des simulations multidimensionnelles. Ces champs magnétiques pourraient également être étudiés pour concentrer l'énergie dans les schémas d'ignition. Enfin, nous montrons que le modèle M1 reproduit les résultats de la théorie locale élaborée par Braginskii pour tous les niveau de magnétisation et propose de nouveaux résultats pour le régime non local. Ce travail constitue une première validation de l'utilisation des fermetures entropiques, dans les régimes de faibles anisotropies, qui va s'ajouter aux tests dans les régimes fortement anisotropes
Hydrodynamic simulations in high-energy-density physics and inertial con nement fusion require a detailed description of energy uxes. The leading mechanism is the electron transport, which can be a nonlocal phenomenon that needs to be described with quasistationary and simplified Fokker-Planck models in large scale hydrodynamic codes. My thesis is dedicated to the development of a new nonlocal transport model based on a fast-moving-particles collision operator and on a first moment Fokker-Planck equation, simplified with an entropic closure relation. Such a closure enables a better description of the electron distribution function in the limit of high anisotropies, where small scale electrostatic instabilities could be excited. This new model, so called M1, is successfully compared with the well known nonlocal electron transport model proposed by Schurtz, Nicolaï and Busquet, using different collision operators, and with the reduced Fokker-Planck model, based on a small-anisotropies polynomial closure relation (P1). Several typical configurations of heat transport are considered. We show that the M1 entropic model may operate in two and three dimensions and is able to account for electron transport modifications in external magnetic fields. Moreover, our model enables to compute realistic electron distribution functions, which can be used for kinetic studies, as for the plasma stability in the transport zone. It is demonstrated that the electron energy transport may strongly modify damping of Langmuir and ion acoustic waves, while the simplified nonlocal transport models are not able to describe accurately the modifications of the distribution function and plasma wave damping. The structure of the M1 model allows to naturally take into account self-generated magnetic fields, which play a crucial role in multidimensional simulations. Moreover, magnetic fields could also be used for the focusing of energetic particles in alternative ignition schemes. The M1 model reproduces the results of the local transport theory in plasma, developed by Braginskii, in a broad range of degrees of magnetization and predicts new results in the nonlocal regime. This work constitutes a first validation of the entropic closure assumption in the weakly-anisotropic regime. It can be added to the existing tests, in the strongly-anisotropic regimes

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El, May Mohamed. « Étude de la tenue en fatigue d'un acier inoxydable pour l'aéronautique en milieu marin corrosif ». Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0012/document.

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Ces travaux ont pour objectif l'identification et la compréhension de l'effet de la corrosion aqueuse sur la durée de vie en fatigue à grand nombre de cycles (HCF) d'un acier inoxydable martensitique utilisé dans des applications aéronautiques. Tout d'abord, l'effet géométrique des défauts de corrosion sur la limite de fatigue à 10^7 cycles à l'air a été étudié avec quatre tailles différentes de piqûres de corrosion. A partir de ces résultats, une nouvelle approche volumique non locale de modélisation numérique a été proposée pour prendre en compte une géométrie réelle d'un défaut de corrosion issu des analyses en microtomographie X. Ensuite, les phénomènes de couplage chargement cyclique/corrosion ont été identifiés par des essais de fatigue à grande durée de vie (entre 10^5 et 10^7 cycles) dans une solution aqueuse à 0,1 M NaCl (à pH = 6) pour deux rapports de charge (R = -1 et 0,1). Le comportement électrochimique du film passif a été étudié in situ au cours des essais de fatigue-corrosion par le suivi du potentiel libre de corrosion et des mesures d'impédance électrochimique. Les observations des mécanismes d'amorçage de fissures et des mesures électrochimiques in-situ ont permis d'identifier un scénario d'amorçage de fissures de fatigue. Ce scénario implique des processus de rupture locale du film passif (induite par le chargement cyclique) et de corrosion assistée par le chargement cyclique. Finalement un modèle analytiquede prévision de la durée de vie en fatigue dans un milieu aqueux corrosif a été proposé à partir des résultats expérimentaux
This study addresses the effects of corrosion on the high cycle fatigue (HCF)strength of a martensitic stainless steel used in aeronautic applications. First, the geometry of corrosion pits on the fatigue strength in air at 10^7 cycles were studied with four different pit sizes. A new non-local fatigue criterion was proposed to simulate real shapes of pits as identified by X-ray microtomography. Corrosion fatigue synergy phenomena was studied by HCF tests (between 10^5 and 10^7 cycles) in a 0.1 M NaCl aqueous solution (pH = 6) with two load ratios (R = -1 and 0.1). Next, the electrochemical behavior of the passive film was investigated during in situ corrosion fatigue tests by free potential measurements and electrochemical impedance spectroscopy (EIS). Based on fractography analysis and electrochemical test results, corrosion fatigue crack initiation mechanisms were investigated. A scenario of fatigue crack initiation was proposed based on physical evidence. This scenario implied combined processes of local passive film rupture (induced by the cyclic loading), stress-assisted corrosion and enhanced pitting development. Local passive film ruptures were the main cause of the corrosion fatigue crack initiation. Finally, a analytical model for corrosion fatigue crack initiation was proposed based

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Issa, Suleiman al [Verfasser], Rafael [Akademischer Betreuer] Macián-Juan, Eckart [Akademischer Betreuer] Laurien et David [Akademischer Betreuer] Aumiller. « Experimental investigation and CFD validation of two-phase phenomena related to nuclear safety research during LOCA accidents / Suleiman Al Issa. Gutachter : Eckart Laurien ; David Aumiller ; Rafael Macián-Juan. Betreuer : Rafael Macián-Juan ». München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1066363587/34.

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Shih-Hsien, Peng, et 彭思顯. « The Local Scouring Phenomenon of Free Overfall Flow ». Thesis, 1994. http://ndltd.ncl.edu.tw/handle/37939767681426637470.

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Huang, Jun-Rong, et 黃俊榮. « Phenomenon of Local Contact Electrification studied by Scanning Probe Microscopy ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/60580671286480182697.

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碩士
東海大學
物理學系
98
Contact electrification (CE) is the transfer of charge between two surfaces that are brought into contact, with or without friction and applied potential, they will exchange charge because of the work function difference or additional potential between metal to copolymer. The details of how CE happens on the nanometer scale are still not understood. So we study the interactional behavior of local surface charge between metal and polymer using the SPM probe (Cr/Pt coating). We used SPM probe to rub the polymer by changed tip bias and tip speed, and then used electrostatic force microscopy (EFM) to detect the charge distribution. We found that the contact charges must be decayed when the tip speed increased. But the contact charges increased with the tip bias. We almost found no CE occurs at the polymer in some particular tip bias and speed. It implies that the surface potential of probe were equal to copolymer’s. In this study, the EFM shows the CE in the nanometer scale, and the contact charges have relations with tip bias (electric field) and tip speed (friction).

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Hu, Li-Ren, et 胡力仁. « The Use of Local Volatility Model for Solving Volatility Smile Phenomenon ». Thesis, 2001. http://ndltd.ncl.edu.tw/handle/84423832537221614190.

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碩士
國立臺灣大學
財務金融學研究所
89
We try to utilize the theory that was developed by Dupire in 1994,then use the price information of European equity call options with different strikes and maturities to evaluate other type of options. The crux for implementing this theory is to find out the local volatilities generated by options prices in the market. Therefore, we propose a new idea to achieve it. By the practical study of Natenberg in 1994, he uncovered that there is one specific variable can perfectly describe the volatility smile pattern even in different maturities. With this stable relationship, we can easily extract the local volatilities from market. Then we use the local volatilities to verify the correctness of the model and to price other options by Black-Merton-Scholes’ backward partial differential equation. We find that using implied volatilities for delta hedging and pricing other options in B/S model under volatility smile phenomenon will lead to a huge error. Hence, from practitioners’ point of view, the local volatility model is more suitable.

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Majumdar, Pinaki. « Mott-Hubbard Phenomena : Studies Within The Local Approximation ». Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1589.

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Kung, David T. « Local smoothing phenomena for operators failing the cinematic curvature condition ». 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.

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SU, Ling-Yu, et 蘇玲玉. « The Phenomena of Fewer Children and Local Government Welfare Expenditures-the Case of Taiwanese Local Governments ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/y9wkgg.

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碩士
國立高雄應用科技大學
財富與稅務管理研究所碩士在職專班
101
Taiwan had the lowest fertility rate in the world in 2010. The total fertility rate was 0.9. The population growth rate is expected to be negative in 2023. To investigate the determinants of the declining fertility rates, we estimate a fixed-effect panel data model by using crude birth rates of 23 local governments in Taiwan during the period of 2001 to 2010. Our empirical results show that per capita social welfare expenditure is positively correlated to crude fertility rates. Moreover, female labor participation rates and violence criminal rates are negatively correlated. To increase the fertility rates, we suggest the local government raise social welfare expenditure, provide comprehensive child care services and maintain the social order.

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(9825509), Noel Patson. « Methods for revealing patterns of non-local order in complex collective phenomena ». Thesis, 2001. https://figshare.com/articles/thesis/Methods_for_revealing_patterns_of_non-local_order_in_complex_collective_phenomena/20341497.

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This topic arose from research done in Computing Special Topic 85333 and Math- ematics Special Topic 84333 [25]. An overview of quantum chaology [15, 16, 17] and structural complexity [20, 21, 22] was made with respect to how they describe global behaviour. Computer experimentation was used in an attempt to determine if there were any scaling properties in the distribution of prime numbers so as to find some patterns [26] that may be connected with non -local order as predicted by struc- tural complexity. The connections between the zeta function from number theory to quantum chaology [15] were also under investigation to in order to develop more tools for computational experiments. Following this research, there was a proposal by my supervisor Victor Korotkich to test his conjecture that the eigenvalue spectrum of matrices [13] associated with the dynamics of a robot soccer team would be a solid invariant that may serve as a global characteristic. The proposal was put forward for me to realise within a Masters of Applied Science topic. This required setting up a virtual simulation and computation laboratory using a combination of mathematics, statistics and programming. The laboratory had to be developed from scratch since this was the first time robot soccer team dynamics had been investigated in this way. It is analogous to the approach physicists take when searching for a theoretical particle. Because the methodology was new, the development of the new instrument (sim- ulators downloaded from the Internet, mathematical software and statistical analysis software) needed to be mastered and synthesised into something effective to detect the conjectured invariant. Once detected, adjustments to parameters were needed so that a clearer pattern could be discerned. The adjustments are analogous to the changing of lens and focussing required on a microscope to get better resolution. The data produced by robot soccer simulators was processed to test the conjecture. Nonparametric statistical analysis was applied to gain an understanding of the patterns that were found in the distribution of eigenvalues and eigenvalue spacings and create an experimental methodology to analyse this type of data. The computer simulation laboratory was set up to implement and test the technique. According to the statistical evidence it seems that each robot soccer team has an invariant in its collective dynamics. Several robot soccer simulators were found on the Internet. These simulators were evaluated as to whether they were able to be modified so as to extract the robot soccer teams' coordinates during a game, whether the teams strategies could be modified and whether they were suitable for use in the experiments. Features of the UNIX operating system, C++ (an implementation of the C++ programming language developed for the UNIX operating system) and JAVA compilers and languages also had to be studied in order to modify and run these simulators. The data produced by these simulators needed to be processed to test the conjec- ture. Because of the size of matrices (429 by 429) that arose by applying this approach, the MATLAB programming environment was used to evaluate and organise the data for statistical analysis. This data was then processed using the SPSS statistical pack- age and Excel spreadsheet software. Much reading and comprehension was gained in the advanced statistics topic of nonparametric analysis to gain understanding of the patterns that were found in the distribution of eigenvalues and eigenvalue spacings and create an experimental methodology to analyse this type of data. To present the results that were found, many features of MATLAB, postscript format, Excel, SPSS and aTEX needed to be understood. All the understanding, skills, software analysis programs, and statistical techniques synthesise together as a virtual computer laboratory s from which many other experiments can be performed. Here a powerful synergism has arisen that may be adapted and applied to understanding the dynamics of other systems. The laboratory has been successful in confirming the existence of the conjectured invariant using solid scientific methods. This study belongs to a new area of fundamental research and has already shown promising results which have been presented at the 12th Australian Joint Conference on Artificial Intelligence AI'99 and the International Conference "With Fuzzy Logic in the New Millennium". That the research is significant is demonstrated by the publication of the results by Springer-Verlag in their Lecture Notes on Artificial Intelligence [49] series and acceptance for publication in their Studies in Fuzziness and Soft Computing [51] series.

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Tibério, Miguel Alexandre Branco. « Study of localized transport phenomena of Cu2O ». Master's thesis, 2019. http://hdl.handle.net/10362/96276.

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Cu2O is a p-type semiconductor with a wide range of applications in optoelectronics, namely solar cells. Performance limitations have been previously ascribed to an inhomogeneous local conductivity: notably highly conductive grain boundaries compared to the grains. In this work, pol-ycrystalline Cu2O thin-films fabricated by reactive sputter deposition were studied. In addition, Cu2O particles with cubic and octahedral shapes were produced from solution. The facets of cubic particles have a (100) orientation, whereas octahedral particles have facets with (111) orientation. Electrical modes of atomic force microscopy were used to study the localized transport mecha-nisms of the differently prepared Cu2O samples. Remarkably, the thin-film Cu2O samples of this work all showed more conductive grains compared to the grain boundaries. The results were an-alyzed in conjunction with structural, chemical, optical and morphological information.

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Thèses sur le sujet « Local phenomenon »

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