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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

A COMPARISON OF SOIL NITROGEN AVAILABILITY ALONG HILLSLOPES FOR A PREVIOUSLY MINED RECLAIMED WETLAND AND TWO NATURAL WETLANDS IN FORT MCMURRAY, ALBERTA

Thorne, Chelsea 11 1900 (has links)
In situ measurements of soil nitrogen dynamics is a potential method for evaluating the health of constructed wetlands following oil sands mining. The objective of this study is to measure and compare the soil nitrogen availability of a reclaimed fen (Sandhill fen) with a nutrient-rich reference fen (Poplar fen) and a nutrient-poor reference fen (Pauciflora fen) in the Athabasca oil sands region of northern Alberta. Total Nitrogen (TN), Nitrate (NO3-) and Ammonium (NH4+) supply rates were determined along wetland hillslope transects using Western Ag Innovations Plant Root Simulator (PRSTM) probes at all three sites in 2014. Net N mineralization, net nitrification and net ammonification were determined simultaneously using the buried polyethylene bag sampling method. Overall, TN supply rates were greatest at the poor fen and least at the constructed Sandhill fen. In contrast, mineralization was greatest at the rich fen but again least at the Sandhill fen. Mineralization at the Sandhill fen was controlled evenly by ammonification and nitrification, whereas the two natural sites were controlled by ammonification. Relatively low N supply rates and mineralization at the Sandhill fen were likely due to lower soil organic matter and limited soil moisture in these newly constructed substrates. Spatial differences along the hillslopes also varied among sites. The Sandhill fen had higher TN supply rates at the upslope positions but no significant differences in net N mineralization rates along the hillslopes. The rich fen also had higher TN supply rates at the upslope but greatest mineralization rates downslope. These results highlight the importance of N storage and transport processes and offer insight into the N status of a constructed fen. / Thesis / Master of Science (MSc)
12

dissertation.pdf

Apostolia Topaloudi (14193239) 30 November 2022 (has links)
<p>Complex disorders are caused by multiple genetic, environmental, and lifestyle factors, and their interactions. Most human diseases are complex, including many psychiatric, autoimmune, neurodegenerative, and cardiovascular disorders. Understanding their genetic background is an essential step toward developing effective preventive and therapeutic interventions for these disorders. In this dissertation, we present an overview of state-of-the-art methodology that is used to help elucidate the genetic basis of complex diseases and apply these methods to understand the genetic background of different complex disorders. First, we carried out a GWAS for myasthenia gravis (MG), a rare autoimmune disorder, and detected a novel risk locus, AGRN, which encodes a protein, involved in neuromuscular junction activation. Additionally, we observed significant genetic correlation between MG and ADs, and variants with pleiotropic effects. Second, we explored the genetic and phenotypic relationships among 11 different autoimmune disorders (ADs), using GWAS results o to calculate polygenic risk scores (PRS) and performing a PRS- phenome-wide association study (PheWAS) analysis with 3,281 phenotypes available in the UK Biobank. We observed associations of ADs PRS with phenotypes in multiple categories, including lifestyle, biomarkers, mental and physical health. We also explored the shared genetic components among the ADs, through genetic correlation and cross-disorder meta-analysis approaches, where we</p> <p>identified pleiotropic variants among the correlated ADs. Finally, we performed a meta-analysis GWAS of Tourette Syndrome (TS) followed by post-GWAS analyses including biological annotation of the results, and association tests of TS PRS with brain volumes. We detected a novel locus, NR2F1, associated with TS, supported by eQTL and Hi-C data. TS PRS was significantly associated with right and left thalamus volumes and right putamen volume. Overall, our work demonstrates the power of GWAS and related methods to help disentangle the genetic basis of complex disease and provides important insights into the genetic basis of the specific disorders that are the focus of our studies.</p>
13

Investigation of Momentum and Heat Transfer in Flow Past Suspensions of Non-Spherical Particles

Cao, Ze 11 March 2021 (has links)
Investigation of momentum and heat transfer between the fluid and solid phase is critical to the study of fluid-particle systems. Dense suspensions are characterized by the solid fraction (ratio of solid volume to total volume), the particle Reynolds number, and the shape of the particle. The behavior of non-spherical particles deviates considerably from spherical particle shapes which have been studied extensively in the literature. Momentum transfer, to first-order, is driven by drag forces experienced by the particles in suspension, followed by lift and lateral forces, and also through the transmission of fluid torque to the particles. The subject of this thesis is a family of prolate ellipsoidal particle geometries of aspect ratios (AR) 2.5, 5.0 and 10.0 at nominal solid fractions (φ) between 0.1 and 0.3, and suspensions of cylinders of AR=0.25. The nominal particle Reynolds number (Re) is varied between 10 to 200, representative of fluidized beds. Fluid forces and heat transfer coefficients are obtained numerically by Particle Resolved Simulations (PRS) using the Immersed Boundary Method (IBM). The method enables the calculation of the interstitial flow and pressure field surrounding each particle in suspension leading to the direct integration of fluid forces acting on each particle in the suspension. A substantial outcome of the research is the development of a new drag force correlation for random suspensions of prolate ellipsoids over the full range of geometries and conditioned studied. In many practical applications, especially as the deviation from the spherical shape increases, particles are not oriented randomly to the flow direction, resulting in suspensions which have a mean preferential orientation. It is shown that the mean suspension drag varies linearly with the orientation parameter, which varies from -2.0 for particles oriented parallel to the flow direction to 1.0 for particles normal to the flow direction. This result is significant as it allows easy calculation of drag force for suspension with any preferential orientation. The heat transfer coefficient or Nusselt number is investigated for prolate ellipsoid suspensions. Significantly, two methods of calculating the heat transfer coefficient in the literature are reconciled and it is established that one asymptotes to the other. It is also established that unlike the drag force, at low Reynolds number the suspension mean heat transfer coefficient is very sensitive to the spatial distribution of particles or local-to-particle solid fractions. For the same mean solid fraction, suspensions dominated by particle clusters or high local solid fractions can exhibit Nusselt numbers which are lower than the minimum Nusselt number imposed by pure conduction on a single particle in isolation. This results from the dominant effect of thermal wakes at low Reynolds numbers. As the Reynolds number increases, the effect of particle clusters on heat transfer becomes less consequential. For the 0.25 aspect ratio cylinder, it was found that while existing correlations under predicted the drag forces, a sinusoidal function F_(d,θ)=F_(d,θ=0°)+(F_(d,θ=90°)-F_(d,θ=0°) )sin⁡(θ) captured the variation of normalized drag with respect to inclination angle over the range 10≤Re≤300 and 0≤φ≤0.3. Further the mean ensemble drag followed F_d=F_(d,θ=0°)+1/2(F_(d,θ=90°)-F_(d,θ=0°)). It was shown that lift forces were between 20% to 80% of drag forces and could not be neglected in models of fluid-particle interaction forces. Comparing the pitching fluid torque to collision torque during an elastic collision showed that as the particle equivalent diameter, density, and collision velocities decreased, fluid torque could be of the same order of magnitude as collisional torque and it too could not be neglected from models of particle transport in suspensions. / Doctor of Philosophy / Momentum and heat exchange between the fluids (air, water…) and suspensions of solid particles plays a critical role in power generation, chemical processing plants, pharmaceuticals, in the environment, and many other applications. One of the key components in momentum exchange are the forces felt by the particles in the suspension due to the flow of the fluid around them and the amount of heat the fluid can transfer to or from the particles. The fluid forces and heat transfer depend on many factors, chief among them being the properties of the fluid (density, viscosity, thermal properties) and the properties of the particles in the suspension (size, shape, density, thermal properties, concentration). This introduces a wide range of parameters that have the potential to affect the way the fluid and particles behave and move. Experimental measurements are very difficult and expensive to conduct in these systems and computational modeling can play a key role in characterization. For accuracy, computational models have to have the correct physical laws encoded in the software. The objective of this thesis is to use very high-fidelity computer models to characterize the forces and heat transfer under different conditions to develop general formulas or correlations which can then be used in less expensive computer models. Three basic particle shapes are considered in this study, a sphere, a disk like cylindrical particles, and particles of ellipsoidal shapes. More specifically, Particle Resolved Simulations of flow through suspensions of ellipsoids with aspect ratio of 2.5, 5, 10 and cylinders with aspect ratio of 0.25 are performed. The Reynolds number range covered is [10, 200] for ellipsoids and [10, 300] for cylinders with solid fraction range of [0.1, 0.3]. New fluid drag force correlations are proposed for the ellipsoid and cylinder suspensions, respectively, and heat transfer behavior is also investigated.
14

Early adversity, psychosis risk and brain response to faces

Lieslehto, J. (Johannes) 30 October 2018 (has links)
Abstract Schizophrenia and other psychotic disorders are severe and disabling mental disorders that break out during early adulthood, often when a person is in his/her early 20s. Furthermore, functional decline in many cognitive areas, including the ability to communicate in social interactions and impaired facial expression recognition, is typical to patients with schizophrenia. Understanding the risk factors of psychosis is essential as these disorders may be more amenable to treatment in their early stages. However, recognition of those at the highest risk of psychosis is challenging as no definitive biomarkers are available. Functional MRI is a promising tool that can potentially identify neural signals relating to the individual’s risk of psychosis onset. Psychotic disorders are etiologically heterogeneous disorders — both environmental and genetic factors have been linked to the onset of psychotic disorders. The most influential risk factor for a psychotic disorder is familial risk with genetic loading. The present study examines whether familial risk of psychosis (FR), the polygenic risk score for schizophrenia (PRS) and early adversity associate with brain response to faces. We used fMRI to measure blood oxygen level dependent (BOLD) response to faces. Our study showed that FR associated with deviant prefrontal cortex BOLD responses. In addition, we detected that interregional BOLD signal and grey matter volume varied as a function of PRS; the lowest functional and structural covariance was detected in individuals with high PRS. We also detected that early adversities associated with brain response to faces and that this association varied as a function of glucocorticoid receptor gene expression. Our findings indicate that the above risk factors of psychosis associate with brain response to faces. / Tiivistelmä Skitsofrenia ja muut psykoosisairaudet ovat vakavia mielenterveyden häiriöitä, jotka puhkeavat usein nuorella aikuisiällä. Eräs tyypillinen piirre psykoosisairauksille on vaikeus tunnistaa muiden ihmisten kasvonilmeitä. Psykoosisairauksien riskitekijöiden ymmärtäminen on tärkeää, sillä hoito tehoaa parhaiten sairastumisen alkuvaiheessa. Suurimmassa psykoosivaarassa olevien henkilöiden tunnistaminen on kuitenkin haastavaa, sillä luotettavia tautiin liittyviä biomarkkereita ei ole saatavilla. Toiminnallinen magneettikuvaus (fMRI) on lupaava työkalu, jolla saattaa olla tulevaisuudessa käyttöarvoa psykoosivaaraan liittyvien aivomuutosten tunnistamisessa. Etiologialtaan psyykoosisairaudet ovat heterogeenisiä: sekä ympäristö että perinnölliset tekijät vaikuttavat yksilön sairastumisriskiin. Voimakkain riskitekijä on suvullinen psykoosialttius. Tässä osajulkaisuväitöskirjassa tutkitaan suvullisen psykoosialttiuden, skitsofrenian polygeenisen riskipisteen (PRS) sekä varhaisten vastoinkäymisten yhteyttä aivojen kasvonilmeitä tulkitsevaan järjestelmään. Tutkimuksessa on hyödynnetty fMRI-kuvausta kasvonilmestimuluksen aikana. Tutkimuksessamme suvullinen psykoosialttius oli yhteydessä etuotsalohkon fMRI-signaalimuutoksiin. Tämän lisäksi havaitsimme, että kasvonilmejärjestelmän fMRI-signaalin ja harmaan aineen kovarianssi oli yhteydessä PRS:ään: matalin aivoalueiden välinen korrelaatio havaittiin henkilöillä, joiden PRS oli korkea. Havaitsimme myös, että varhaiset vastoinkäymiset ovat yhteydessä kasvonilmeiden aikaansaamiin aivovasteisiin. Tämä assosiaatio oli myös yhteydessä glukokortikoidireseptorin geenin ilmentymiseen. Väitöskirjan löydökset viittaavat siihen, että edellä mainitut psykoosin riskitekijät ovat yhteydessä kasvonilmeitä tulkitsevaan järjestelmään.
15

Termes et relations sémantiques en corpus spécialisés : rapport entre patrons de relations sémantiques (PRS) et types sémantiques (TS)

Bodson, Claudine January 2004 (has links)
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.
16

Creators' organisations as actors in copyright policy : mapping the complexity of stakeholder behaviour, dynamics and differences

Kostova, Nevena Borislavova January 2017 (has links)
A basic tenet and challenge of copyright law is the need to balance the interests of a range of stakeholders, from authors and performers to publishers, producers, broadcasters, intermediaries, service providers and the general public. To ensure that this balancing act takes place, policymakers involve organisations representing these stakeholders in the development of policy and the drafting of legislation in several ways, including through meetings, public consultations, and stakeholder dialogues. However, the process by which stakeholders steer the course and substance of copyright law and policy, their behaviour, as well as the varying extent to which they impact and characterise the copyright policy framework, have rarely been the specific focus of empirical research in IP. The present thesis examines creators’ organisations (COs) as participants and shapers of copyright policy. Through a socio-legal study into the workings of The Society of Authors, the Authors’ Licensing and Collecting Society, the Musicians’ Union, and the Performing Right Society on several contemporary policy issues, the thesis observes how two types of organisations: trade unions and collective management organisations, across the music and publishing industries, engage in policy work. Through in-depth analysis of primary data obtained from interviews with CO representatives as well as documentary data (public consultation responses, policy briefings, press releases, reports, academic studies, and more), the thesis captures and discusses differences in the behaviour of these actors and argues that these differences are not fully understood by policymakers. It illustrates how factors such as an organisation’s mandate, resources, membership composition, political power, and self-concept, influence an organisation’s policy proactivity. Some actors may be more concerned with influencing the copyright policy agenda itself, while others primarily seek to shape its outcomes. The thesis also identifies power dynamics and imbalances between the COs and argues that some actors are in a better position to effectively participate in policy compared to others. Furthermore, it discusses the effects of the plurality of actors with varying interests and priorities, as well as the competition of policy issues that this provokes. In this context, the thesis illustrates the complex structure of the copyright policy environment and, in particular, the role of umbrella organisations and ad-hoc coalitions in the furtherance of a particular policy issue or position. It concludes that as a result of complex stakeholder dynamics, power imbalances, and policymakers’ insufficient understanding of these phenomena, certain creators’ issues will not surface onto copyright policy agendas and will thus remain unaddressed by copyright law. The thesis further concludes that complex stakeholder dynamics challenge the objective of developing evidence-based policy and render the copyright policy process unclear and its outcomes unpredictable. Given the disparity of views and positions on many copyright law issues, policymakers often attempt to shape law and policy outcomes as a compromise between different stakeholder interests. However, this does not always produce sound or appropriate results for copyright law.
17

Estudio combinado de marcadores fenotípicos y genotípicos para la evaluación del riesgo individualizado a desarrollar cáncer de mama

Triviño Pardo, Juan Carlos 13 June 2024 (has links)
[ES] El cáncer de mama es uno de los tumores más frecuentes en la población femenina, estableciéndose una prevalencia global en los países occidentales alrededor del 12,5%, es decir, aproximadamente una de cada ocho mujeres padecerá cáncer de mama a lo largo de su vida. En la lucha por la reducción del impacto de esta enfermedad en la sociedad y en las entidades sanitarias públicas, en los últimos años se han desarrollado diferentes propuestas, siendo la estratificación de la población general uno de dichos métodos. Estos sistemas de estratificación permiten clasificar a la población general en función del riesgo a padecer cáncer de mama de manera individual usando diferentes variables genéticas, fenotípicas o ambientales. En la presente tesis, partiendo de una cohorte caso - control retrospectivo, basado en población española femenina, se aplicarán diferentes modelos matemáticos utilizando variables genéticas, fenotípicas y combinando ambas. Estos modelos permitirán la estratificación de la población general femenina en función del riesgo individual a padecer cáncer de mama esporádico. En un primer estudio se evaluaron las variables genéticas como factor discriminante en la cohorte caso - control estudiado. Estas variables son variantes genéticas puntuales denominados SNPs (single nucleotide polymorphism). Estas variantes fueron seleccionadas mediante estudios GWAs (genome-wide association study) basados en cohortes casos-control, asociados a cáncer de mama esporádico y usando miles de mujeres de población general Caucásica. Estas alteraciones, estadísticamente significativas y asociadas a fenotipo, tienen escaso efecto funcional, poca penetrancia, son relativamente frecuentes en la población y con asociación individual a un riesgo bajo o moderado a padecer cáncer de mama. En la presente tesis, se utilizaron inicialmente 121 de estos SNPs descritos anteriormente y combinados mediante modelos "polygenic risk score" (PRS) para evaluar su poder discriminante en función del riesgo individual a padecer cáncer de mama esporádico en una cohorte caso-control representativa de la población española. En un segundo estudio se evaluaron las variables fenotípicas como factores discriminantes de la cohorte caso- control estudiado. Los factores de riesgo fenotípicos seleccionados se obtuvieron a partir de bibliografía científica mayoritariamente de población española y son; la densidad mamaria, el estatus de menopausia, la edad de la mujer, la edad de menarquia, edad el primer hijo nacido vivo y los posibles antecedentes familiares. En un tercer estudio se evaluó la significancia y el poder discriminante utilizando un modelo logístico que combina las variables genéticas agrupadas mediante un PRS, las variables fenotípicas, y la interacción de algunas de estas variables. Se evaluó la posible utilidad del modelo para la clasificación de la cohorte representativa de la población española en función del riesgo individual a padecer cáncer de mama esporádico. En la presente tesis se presenta un modelo matemático que combina factores genéticos y fenotípicos de riesgo a padecer cáncer de mama esporádico. En este estudio se demuestra la sinergia y la ausencia de colinealidad entre este tipo de variables, permitiendo obtener una capacidad discriminante entre las mujeresque desarrollaron cáncer de mama esporádico durante los siguientes cinco años después de la toma de los datos y mujeres sanas que no lo desarrollaron. Esta capacidad discriminante obtenida mediante estos modelos combinados de los factores de riesgo es mayor que la obtenida usando modelos basados solo en los factores de riesgo individuales. También permite, como prueba de concepto, valorar su posible utilidad en un sistema de cribado mediante la clasificación de la población general en diferentes categorías en función de su riesgo a padecer cáncer de mama esporádico / [CA] El càncer de mama és un dels tumors més freqüents en la població femenina, establintse una prevalença global als països occidentals al voltant del 12,5%, és a dir, aproximadament una de cada huit dones patirà càncer de mama al llarg de la seua vida. En la lluita per la reducció de l'impacte d'aquesta malaltia en la societat i en les entitats sanitàries públiques, en els últims anys s'han desenvolupat diferents propostes, sent l'estratificació de la població general un d'aquests mètodes. Aquests sistemes d'estratificació permeten classificar a la població general en funció del risc a patir càncer de mama de manera individual usant diferents variables genètiques, fenotípiques o ambientals. En la present tesi, partint d'una cohort case - control retrospectiu, basat en població espanyola femenina, s'aplicaran diferents models matemàtics utilitzant variables genètiques, fenotípiques i combinant ambdues. Aquests models permetran l'estratificació de la població general femenina en funció del risc individual a patir càncer de mama esporàdic. En un primer estudi es van avaluar les variables genètiques com a factor discriminant en la cohort case - control estudiat. Aquestes variables són variants genètiques puntuals denominats SNPs (single nucleotide polymorphism) . Aquestes variants van ser seleccionades mitjançant estudis GWAs (genome-wide association study) basats en cohorts casos-control, associats a càncer de mama esporàdic i usant milers de dones de població general Caucàsica. Aquestes alteracions, estadísticament significatives i associades a fenotip, tenen escàs efecte funcional, poca penetrancia, són relativament freqüents en la població i amb associació individual a un risc baix o moderat a patir càncer de mama. En la present tesi, es van utilitzar inicialment 121 d'aquests SNPs descrits anteriorment i combinats mitjançant models polygenic risk score (PRS) per a avaluar el seu poder discriminant en funció del risc individual a patir càncer de mama esporàdic en una cohort cas-control representativa de la població espanyola En un segon estudi es van avaluar les variables fenotípiques com a factors discriminants de la cohort case- control estudiat. Els factors de risc fenotípics seleccionats es van obtindre a partir de bibliografia científica majoritàriament de població espanyola i són; la densitat mamària, l'estatus de menopausa, l'edat de la dona, l'edat de menarquia, edat el primer fill nascut viu i els possibles antecedents familiars. En un tercer estudi es va avaluar la significança i el poder discriminant utilitzant un model logístic que combina les variables genètiques agrupades mitjançant un PRS, les variables fenotípiques, i la interacció d'algunes d'aquestes variables. Es va avaluar la possible utilitat del model per a la classificació de la cohort representativa de la població espanyola en funció del risc individual a patir càncer de mama esporàdic. En la present tesi es presenta un model matemàtic que combina factors genètics i fenotípics de risc a patir càncer de mama esporàdic. En aquest estudi es demostra la sinergia i l'absència de colinealidad entre aquesta mena de variables, permetent obtindre una capacitat discriminant entre les dones que van desenvolupar càncer de mama esporàdic durant els següents cinc anys després de la presa de les dades i dones sanes que no ho van desenvolupar. Aquesta capacitat discriminant obtinguda mitjançant aquests models combinats dels factors de risc és major que l'obtinguda usant models basats només en els factors de risc individuals. També permet, com a prova de concepte, valorar la seua possible utilitat en un sistema de garbellat mitjançant la classificació de la població general en diferents categories en funció del seu risc a patir càncer de mama esporàdic. / [EN] Breast cancer is one of the most common tumours in the female population, with a global worldwide incidence around 12.5%, that is, this means there is a 1 in 8 chance will suffer breast cancer throughout the live. In the investigation to reduce the impact of this disease on society and public health entities, in last years, different proposals have been developed, where the stratification of the general population being one of these methods. These stratification systems allow the general population to be classified based on the risk of suffering from breast cancer individually using different genetic, phenotypic or environmental variables. Was started from a retrospective case-control cohort based on the Spanish female population, different mathematical models will be applied using genetic and phenotypic variables and combining both of them. These models will allow the stratification of the general female population based on the individual risk of suffering sporadic breast cancer. In a first study, genetic variables were evaluated as a discriminating factor. These variables are genetic punctual variants called SNPs (single nucleotide polymorphism). These variants were selected using GWA (genome-wide association study) studies based on case-control cohorts, associated with sporadic breast cancer and using thousands of women from the general Caucasian population. These alterations, statistically significant and associated with phenotype, present modest functional effect, low penetrance, modest risk to development breast cancer and are relatively frequent in the general population. In this study, 121 of these previously described SNPs were initially used and combined using "polygenic risk score" (PRS) models to evaluate their discriminating capacity based on the individual risk of suffering sporadic breast cancer in a representative case-control cohort of the Spanish population. In a second part of the study, the phenotypic variables are evaluated as discriminating factors of the case-control cohort studied. The selected phenotypic risk factors were obtained from scientific literature, mainly from the Spanish population, and are: breast density, menopause status, age of the woman, age of menarche, age of first live birth and family history. In a third study, the significance and discriminant capacity were evaluated using a logistic model that combines the genetic variables grouped through a PRS score, the phenotypic variables, and the interaction of some of these variables. The possible usefulness of the model was evaluated for the classification of the representative cohort of the Spanish population based on the individual risk of suffering sporadic breast cancer. In this thesis, a mathematical model is presented where combines genetic and phenotypic risk factors for sporadic breast cancer. This study demonstrates the synergy and absence of collinearity between this type of variables, allowing obtaining a discriminant capacity between women who developed sporadic breast cancer during the following five years after data collection and healthy women. This discriminant capacity obtained using these combined models are greater than that obtained using models based only on the individual risk factors. It also allows, as a proof of concept, to assess its possible usefulness in a screening system by classifying the general population into different categories based on their risk of suffering sporadic breast cancer. / Triviño Pardo, JC. (2024). Estudio combinado de marcadores fenotípicos y genotípicos para la evaluación del riesgo individualizado a desarrollar cáncer de mama [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/205177
18

Analyse symbolique de systèmes infinis basée sur les automates: Application à la vérification de systèmes paramétrés et dynamiques

Touili, Tayssir 21 November 2003 (has links) (PDF)
Nous nous intéressons dans cette thèse au model-checking des systèmes infinis, notamment<br />les systèmes paramétrés et les programmes récursifs parallèles. Nous présen\-tons un cadre<br />uniforme pour la vérification algorithmique de ces systèmes. Ce cadre est basé sur la <br />représentation des ensembles de configurations par des automates de mots ou d'arbres, et la<br />représentation des relations de transition des systèmes par des règles de réécritures de mots<br />ou de termes. Le problème de la vérification est ensuite réduit au calcul des ensembles des<br />accessibles dans ce cadre. Les contributions de cette thèse sont les suivantes:<br /><br />1- Définition d'une technique d'accélération générale. Nous proposons une méthode basée sur <br />des techniques d'extrapolation sur les automates, et nous étudions la puissance de cette approche.<br />2- Techniques de model-checking régulier pour la vérification des réseaux paramétrés avec des <br />topologies linéaires et arborescentes. En particulier, nous considérons les réseaux modélisés <br />par des systèmes de réécriture comprenant des semi-commutations, c-à-d. des règles de la forme ab -> ba,<br />et nous exhibons une classe de langages qui est effectivement fermée par ces systèmes.<br />3- Modélisation et vérification des programmes récursifs parallèles. Dans un premier temps, <br />nous étudions les modèles PRS qui sont plus généraux que les systèmes à pile, les réseaux de Petri,<br />et les systèmes PA; et nous proposons des algorithmes qui calculent les ensembles des accessibles <br />de (sous-classes de) PRS en considérant différentes sémantiques. <br /><br />Dans une autre approche, nous considérons des modèles basés sur des automates à pile communicants<br />et des systèmes de réécritures à-la CCS, et nous proposons des méthodes de vérification de ces modèles<br />basées sur le calcul d'abstractions des langages des chemins d'exécutions. Nous proposons un cadre<br />algébrique générique permettant le calcul de ces abstractions.
19

Antény pro oblasti (sub)milimetrových vln / (Sub)millimeter-Wave Antennas

Pítra, Kamil January 2014 (has links)
Disertační práce se zabývá návrhem a optimalizací kruhově polarizované anténa pro oblast terahertzových kmitočtů. V práci se věnuji zjednodušené teorii terahertzového zdroje a návrhu vhodné antény pro tento zdroj. Návrh je zaměřen na dosažení kruhové polarizace z lineárně polarizovaných antén. Abych potlačil šíření povrchové vlny na elektricky tlustém dielektrickém substrátu, věnuji se návrhu a optimalizaci specifických periodických struktur. Návrh těchto struktur je poměrně komplikovaný, protože neexistuje přímočarý vztah mezi vlastnostmi struktur s elektromagnetickým zádržným pásmem (EBG) a geometrií buňky. Abych vhodně koncentroval vyzařovanou energii do úzkého svazku, věnuji se návrhu a optimalizaci částečně odrazného plochy (PRS), které působí jako planární čočka pro terahertzovou anténu.
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Phonons in 1-D Graphene Nanoribbons Probed with Raman Spectroscopy : Unraveling Fundamental Properties in 9-atom-wide Graphene Nanoribbons

Victor Labordet Alvarez, Angel January 2023 (has links)
This report employs advanced Raman spectroscopy techniques to investigate the fundamental properties of 9-AGNRs comprehensively. It is divided into two main sections addressing distinct aspects of 9-AGNR behavior. In the first section, Polarization Raman spectroscopy (PRS) probes phonon mode symmetries in 9-AGNRs. Our analysis reveals deviations from predicted symmetries, suggesting the presence of lattice defects. We also investigate specific phonon modes (G, D, and RBLM), providing insights into lattice integrity. The second section employs temperature-dependent Raman spectroscopy to explore the thermal properties of 9-AGNRs. This dynamic analysis quantifies vibrational mode responsiveness to temperature variations using the Grüneisen parameter (χ). Comparisons across various carbon-based materials uncover distinct sensitivities and stabilities. This research advances our understanding of 9-AGNR properties, with implications for nanomaterial science and potential applications. / Denna rapport använder avancerade Raman spektroskopitekniker för att på ett omfattande sätt undersöka de grundläggande egenskaperna hos 9-AGNRs. Den är uppdelad i två huvudsektioner som tar upp distinkta aspekter av 9-AGNR beteende. I det första avsnittet sonderar Polarisation Raman spektroskopi (PRS) fononlägessymmetrier i 9-AGNRs. Vår analys avslöjar avvikelser från förutsagda symmetrier, vilket tyder på närvaron av gitterdefekter. Vi undersöker också specifika fononlägen (G, D och RBLM), vilket ger insikter om gitterintegritet. Den andra sektionen använder temperaturberoende Raman-spektroskopi för att utforska de termiska egenskaperna hos 9-AGNRs. Denna dynamiska analys kvantifierar vibrationslägets känslighet för temperaturvariationer med hjälp av Grüneisen-parametern (χ). Jämförelser mellan olika kolbaserade material avslöjar distinkta känsligheter och stabiliteter. Denna forskning främjar vår förståelse av 9-AGNR-egenskaper, med implikationer för nanomaterialvetenskap och potentiella tillämpningar.

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