Dissertations / Theses on the topic 'Distribution Shift'
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Zennaro, Fabio. "Feature distribution learning for covariate shift adaptation using sparse filtering." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/feature-distribution-learning-for-covariate-shift-adaptation-using-sparse-filtering(67989db2-b8a0-4fac-8832-f611e9236ed5).html.
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This thesis studies a family of unsupervised learning algorithms called feature distribution learning and their extension to perform covariate shift adaptation. Unsupervised learning is one of the most active areas of research in machine learning, and a central challenge in this field is to develop simple and robust algorithms able to work in real-world scenarios. A traditional assumption of machine learning is the independence and identical distribution of data. Unfortunately, in realistic conditions this assumption is often unmet and the performances of traditional algorithms may be severely compromised. Covariate shift adaptation has then developed as a lively sub-field concerned with designing algorithms that can account for covariate shift, that is for a difference in the distribution of training and test samples. The first part of this dissertation focuses on the study of a family of unsupervised learning algorithms that has been recently proposed and has shown promise: feature distribution learning; in particular, sparse filtering, the most representative feature distribution learning algorithm, has commanded interest because of its simplicity and state-of-the-art performance. Despite its success and its frequent adoption, sparse filtering lacks any strong theoretical justification. This research questions how feature distribution learning can be rigorously formalized and how the dynamics of sparse filtering can be explained. These questions are answered by first putting forward a new definition of feature distribution learning based on concepts from information theory and optimization theory; relying on this, a theoretical analysis of sparse filtering is carried out, which is validated on both synthetic and real-world data sets. In the second part, the use of feature distribution learning algorithms to perform covariate shift adaptation is considered. Indeed, because of their definition and apparent insensitivity to the problem of modelling data distributions, feature distribution learning algorithms seems particularly fit to deal with covariate shift. This research questions whether and how feature distribution learning may be fruitfully employed to perform covariate shift adaptation. After making explicit the conditions of success for performing covariate shift adaptation, a theoretical analysis of sparse filtering and another novel algorithm, periodic sparse filtering, is carried out; this allows for the determination of the specific conditions under which these algorithms successfully work. Finally, a comparison of these sparse filtering-based algorithms against other traditional algorithms aimed at covariate shift adaptation is offered, showing that the novel algorithm is able to achieve competitive performance. In conclusion, this thesis provides a new rigorous framework to analyse and design feature distribution learning algorithms; it sheds light on the hidden assumptions behind sparse filtering, offering a clear understanding of its conditions of success; it uncovers the potential and the limitations of sparse filtering-based algorithm in performing covariate shift adaptation. These results are relevant both for researchers interested in furthering the understanding of unsupervised learning algorithms and for practitioners interested in deploying feature distribution learning in an informed way.
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Ingram, Douglas Russell. "Starlight correlated with damped Lyman alpha absorbers /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5435.
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Nodet, Pierre. "Biquality learning : from weakly supervised learning to distribution shifts." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASG030.
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Le domaine de l'apprentissage avec des faiblesses en supervision est appelé apprentissage faiblement supervisé et regroupe une variété de situations où la vérité terrain collectée est imparfaite. Les étiquettes collectées peuvent souffrir de mauvaise qualité, de non-adaptabilité ou de quantité insuffisante. Dans ce mémoire nous proposons une nouvelle taxonomie de l'apprentissage faiblement supervisé sous la forme d'un cube continu appelé le cube de la supervision faible qui englobe toutes les faiblesses en supervision. Pour concevoir des algorithmes capables de gérer toutes supervisions faibles, nous supposons la disponibilité d'un petit ensemble de données de confiance, sans biais ni corruption, en plus de l'ensemble de données potentiellement corrompu. L'ensemble de données de confiance permet de définir un cadre de travail formel appelé apprentissage biqualité. Nous avons examiné l'état de l'art de ces algorithmes qui supposent la disponibilité d'un petit jeu de données de confiance. Dans ce cadre, nous proposons un algorithme basé sur la repondération préférentielle pour l'apprentissage biqualité (IRBL). Cette approche agnostique du classificateur est basée sur l'estimation empirique de la dérivée de Radon-Nikodym (RND), pour apprendre un estimateur conforme au risque sur des données non fiables repesées. Nous étendrons ensuite le cadre proposé aux décalages de jeu de données. Les décalages de jeu de données se produisent lorsque la distribution des données observée au moment de l'apprentissage est différente de celle attendue au moment de la prédiction. Nous proposons alors une version améliorée d'IRBL, appelée IRBL2, capable de gérer de tels décalages de jeux de données. Nous proposons aussi KPDR basé sur le même fondement théorique mais axé sur le décalage de covariable plutôt que le bruit des étiquettes. Pour diffuser et démocratiser le cadre de l'apprentissage biqualité, nous rendons ouvert le code source d'une bibliothèque Python à la Scikit-Learn pour l'apprentissage biqualité : biquality-learnThe field of Learning with weak supervision is called Weakly Supervised Learning and aggregates a variety of situations where the collected ground truth is imperfect. The collected labels may suffer from bad quality, non-adaptability, or insufficient quantity. In this report, we propose a novel taxonomy of Weakly Supervised Learning as a continuous cube called the Weak Supervision Cube that encompasses all of the weaknesses of supervision. To design algorithms capable of handling any weak supervisions, we suppose the availability of a small trusted dataset, without bias and corruption, in addition to the potentially corrupted dataset. The trusted dataset allows the definition of a generic learning framework named Biquality Learning. We review the state-of-the-art of these algorithms that assumed the availability of a small trusted dataset. Under this framework, we propose an algorithm based on Importance Reweighting for Biquality Learning (IRBL). This classifier-agnostic approach is based on the empirical estimation of the Radon-Nikodym derivative (RND), to build a risk-consistent estimator on reweighted untrusted data. Then we extend the proposed framework to dataset shifts. Dataset shifts happen when the data distribution observed at training time is different from what is expected from the data distribution at testing time. So we propose an improved version of IRBL named IRBL2, capable of handling such dataset shifts. Additionally, we propose another algorithm named KPDR based on the same theory but focused on covariate shift instead of the label noise formulation. To diffuse and democratize the Biquality Learning Framework, we release an open-source Python library à la Scikit-Learn for Biquality Learning named biquality-learn
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Chen, Xiaojun. "Multiple Scattering from Bubble Clouds." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/36.
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Multiple scattering effects from bubble clouds are investigated in this study. A high performance, general purpose numerical tool for multiple scattering calculations is developed. This numerical tool is applied in three computational scenarios in this study. The total scattering cross section of a bubble cloud is investigated. Numerical results indicate that the resonant frequency of the bubble cloud is much lower than that of a single bubble. The variation of resonant frequency of multiple scattering is also studied. It is found that the resonant frequency decreases as the number of bubbles increases, or as the void fraction of the bubble cloud decreases. Phase distributions of bubble oscillations in various multiple scattering scenarios are presented. It is found that, at resonance, the bubbles synchronize to the same phase, which is indicative of the lowest mode of collective oscillation. At wave localization, half of the bubbles oscillate at phase 0 while the other half oscillate at phase Pi. An intuitive interpretation of this behavior is given.
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Ho, Yo-Bin. "Modeling the distribution and shift of Chinese Americans in the United States : an analysis by trend surface expansion /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487861796820923.
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Brodén, Daniel. "Analysis of Demand Response Solutions for Congestion Management in Distribution Networks." Thesis, KTH, Industriella informations- och styrsystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138575.
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According to the 20-20-20 targets set by the European Union, 50 percent of the Swedish electricity share is to be provided by renewable energy sources by 2020. The Smart Grid Gotland (SGG) project has emerged as a response to this target. The project aims at demonstrating a proof of concept on how smart grid solutions can be used to integrate large quantities of renewable energy sources in an existing network. The outcomes of the project are intended to pave the way for future renewable energy integration projects in Sweden. The Thesis focuses on one of the technical objectives of the SGG project, i.e. to increase the hosting capacity of wind power on Gotland from 195 MW to 200 MW by using Demand-Response (DR) from households and industries. DR consist of shifting peak-loads to peakproduction hours. The integration of additional wind power causes a risk of exceeding the transmission capacity of the power export cable between Gotland and the Swedish mainland. The approach considered for this Thesis is to use an Ancillary Service (AS) toolbox scheme based on multi-agent systems. The AS toolbox consist of flexibility tools such as DR on long-term, short-term, a battery energy storage system and a wind curtailment scheme. The DR activity includes space heating and domestic hot water consumption from detached houses on Gotland. The simulation results indicate that 1900 household participants are sufficient to balance the additional 5 MW for worst case scenarios. Furthermore, it is shown that the DR participation from industries contributes in some cases to a reduction of 700 household participants. The findings helped conclude that using an AS toolbox solution on Gotland is fully possible from a technical perspective. However, barriers that stand against its realisation are of economical nature and need to be investigated in future studies.
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Figueiredo, Cláudia Cerqueira de Souza Machado Vieira. "Repartição funcional do rendimento no Brasil : uma abordagem setorial." Master's thesis, Instituto Superior de Economia e Gestão, 2019. http://hdl.handle.net/10400.5/19042.
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Mestrado em Economia Internacional e Estudos EuropeusNeste trabalho faz-se uma análise da evolução da repartição funcional do rendimento no período contemporâneo Brasileiro, entre 2000 e 2016. A alteração da parte do trabalho no rendimento gerado na economia (VAB ou PIB), o chamado labour share, resulta da combinação de duas tendências importantes, a saber, a evolução da produtividade do trabalho e a do salário médio. Por sua vez, a alteração global (ou média) destas variáveis resulta das tendências verificadas em cada setor da economia em causa, cada um com as suas peculiaridades. Depois de um breve enquadramento teórico e revisão da literatura relevante, para a análise empírica da evolução do caso brasileiro será dada atenção à imputação do rendimento misto a "salários" e "lucros". Com isto pretende-se observar as relações existentes entre a evolução da participação do trabalho na economia e as transformações registadas na estrutura produtiva. Faz-se ainda a aplicação de uma análise shift-share, através da qual é possível distinguir/quantificar o chamado efeito "intra-sectorial" ou "within" (evolução do labour share de cada setor) do efeito "inter-setorial" ou "between" (ou de mudança estrutural, i.e., alterações no peso relativo de cada setor).
This paper analyzes the evolution of the functional distribution of income in the contemporary Brazilian period between 2000 and 2016. The change in the share of labor in the income generated in the economy (GVA or GDP), the so-called labor share, results from the combination of two important trends, namely the evolution of labor productivity and that of the average wage. In turn, the overall (or average) change in these variables results from trends in each sector of the economy concerned, each with its own peculiarities. After a brief theoretical framework and review of the relevant literature, for the empirical analysis of the evolution of the Brazilian case, attention will be given to the imputation of mixed income to "wages" and "profits". With this it is intended to observe the existing relations between the evolution of the participation of the work in the economy and the transformations registered in the productive structure. A shift-share analysis is also applied, whereby it is possible to distinguish / quantify the so-called "intra-sectoral" or "within" effect (evolution of each sector's labor share) from the "inter-sectoral" or "inter-sectoral" effect. "Between" (or structural change, ie, changes in the relative weight of each sector).
info:eu-repo/semantics/publishedVersion
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Ryckebusch, Gaëlle. "Analysis of Demand-Response Participation Strategies for Congestion Management in an Island Distribution Network." Thesis, KTH, Industriella informations- och styrsystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169220.
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The Master Thesis is part of the Smart Grid Gotlandproject. This project aims at implementing smart grid solutionson the island of Gotland in order to be able to efficientlyintegrate large quantities of renewable energy production.In situations of high wind power production and lowconsumption, energy export problems may occur betweenGotland and the mainland. A novel approach to manageanticipated congestions, compared to traditional gridreinforcements, consists of using flexibility from demandresponse(DR) resources. However, such an approach presentschallenges as it requires both technical and economic considerations.This Master Thesis proposes and analyses twomarket-based strategies applied to detached houses for dayaheadcongestion management. The strategies are implementedin an Ancillary Service toolbox developed in theMATLAB programming environment.The first strategy involves using a dynamic network tariffwhile the second uses spot price optimization. Simulationsare performed for seasonal worst-case congestion scenarioswhile satisfying comfort and economic constraints ofthe DR participants. A sensitivity analysis is carried out toassess the impact of different spot price profiles and windpower production prognosis errors on the results.Results show that congestions are managed with a feasiblenumber of participants, but that their savings are negligiblefor both strategies (between 2 and 40 SEK/participant).Moreover, using a dynamic network tariff strategy impliesa DSO cost in the range of 1700-89000 SEK. These resultsapply for a 3-days congestion period, which is estimated tooccur 5-6 times a year if the maximum hosting capacity isincreased by 5 MW.To conclude, an AS toolbox with economic constraintsis feasible for Gotland conditions with a reasonable numberof DR participants. However, the simple cost-benefitanalysis that was carried out showed that the AS toolboxapproach was still much more costly than traditional gridreinforcement.
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Slove, Davidson Jessica. "The plasticity and geography of host use and the diversification of butterflies." Doctoral thesis, Stockholms universitet, Zoologiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-69573.
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Our world is changing rapidly and factors like urbanisation, changed agricultural practices and climate change are causing losses in butterfly diversity. It is therefore of importance to understand the source of their diversity. Given the remarkable diversity of herbivorous insects compared to their non-herbivorous sister groups, changes in host use have been implicated as a promoter of speciation. This thesis looks at geographical aspects of host range evolution and the plasticity of host use. We show that butterflies in the subfamily Nymphalinae that feed on a wide range of host plants have larger geographic ranges than species with narrower host ranges. Although tropical butterflies appear to be more specialised than temperate species, this effect is lost when controlling for the differences in geographic range. Geographic variation in host plant use within Polygonia faunus, related to morphologically distinct subspecies, did not show any genetic differentiation. This suggests that the observed variation in host plant use is a plastic response to environmental differences. Reconstructing host use for the Polygonia-Nymphalis and Vanessa group shows that plasticity is also important for understanding host use at the level of butterfly genera. Using unequal transition costs and including larval feeding ability revealed that frequent colonisations of the same plant genus can often be explained by non-independent processes, such as multiple partial losses of host use, recolonisation of ancestral hosts, and parallel colonisations following a preadaptation for host use. These processes are further reflected in the conservative use of host plant orders within the butterfly family Nymphalidae. Few taxa feed on more than one host plant order, and these expansions occur at the very tips of the tree, which we argue is evidence of the transient nature of generalist host use. These insights improve our understanding of how host range evolution may promote diversification.At the time of the doctoral defence,the following papers were unpublished and had a status as follows: Paper 3: Submitted; Papers 4 and 5: Manuscripts
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Fisco, Dana. "Reef Fish Spatial Distribution and Benthic Habitat Associations on the Southeast Florida Reef Tract." NSUWorks, 2016. http://nsuworks.nova.edu/occ_stuetd/408.
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The Florida Reef Tract (FRT) extends from the tropical Caribbean up the southeast coast of Florida into a temperate environment where tropical reef assemblages diminish with increasing latitude. This study used data from a three-year comprehensive fishery-independent survey to quantify reef fish spatial distribution along the Southeast FRT and define where the assemblage shifts from tropical to temperate. A total of 1,676 reef fish visual census samples were conducted to assess the populations on a stratified-random selection of sites of marine hardbottom habitats between the Miami River and St. Lucie inlet. Multivariate analyses were used to investigate differences in assemblages among sites. Depth (m), general habitat (reef or hardbottom), and slope (high or low) strata were examined to explain the dissimilarities between assemblages. A general trend of cold-tolerant temperate fish dominated the northern assemblages and more tropical species dominated further south. Seven reef fish assemblage biogeographic regions were determined. In shallow habitats the data clustered in three spatial regions: One south of Hillsboro inlet, one in Northern Palm Beach south of Lake Worth inlet, and one north of Lake Worth inlet. The assemblage in deep habitats mainly split in close proximity to the Bahamas Fracture Zone south of Lake Worth Inlet. The presence of reef habitat aided in splitting the southern assemblage regions from the northern all-hardbottom assemblage regions in both the shallow and deep habitats. Substrate relief was significantly correlated with the differences in the northernmost deep assemblages but did not appear to affect the remainder of the shallow and deep assemblages. This bioregional study creates a baseline assessment of reef fish assemblages of the Southeast FRT for future analyses.
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Agnolini, Sébastien. "Contributions à l'étude et à la réalisation d'un système de distribution quantique de clef par codage en phase." Paris 6, 2007. https://pastel.archives-ouvertes.fr/pastel-00003416.
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Cette thèse propose une étude et une réalisation expérimentale d’un système de distribution quantique de clef utilisant le protocole BB84 par codage en phase sur un photon unique, aux longueurs d’onde des télécommunications optiques ( = 1,5µm). La génération des photons uniques est assurée par un laser de type ILM dont les impulsions optiques sont fortement atténuées afin qu’elles ne contiennent pas plus d’un photon (en moyenne 0,1 photon par bit). La modulation QPSK satisfaisant à des choix de base et de symbole indépendants est assurée par l’utilisation de modulateurs Mach-Zehnder à doubles électrodes. Différentes méthodes de détection cohérente (hétérodyne, homodyne, super-homodyne) sont proposées et comparées. Les évolutions successives de notre système nous amènent à proposer aujourd’hui un système de cryptographie quantique à une voie optique utilisant un codage DQPSK (Differential Quadrature Phase Shift Keying).
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Dadalto, Câmara Gomes Eduardo. "Improving artificial intelligence reliability through out-of-distribution and misclassification detection." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASG018.
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Cette thèse explore l'intersection cruciale entre l'apprentissage automatique (IA) et la sécurité, visant à résoudre les défis liés au déploiement de systèmes intelligents dans des scénarios réels. Malgré des progrès significatifs en IA, des préoccupations liées à la confidentialité, à l'équité et à la fiabilité ont émergé, incitant à renforcer la fiabilité des systèmes d'IA. L'objectif central de la thèse est de permettre aux algorithmes d'IA d'identifier les écarts par rapport au comportement normal, contribuant ainsi à la sécurité globale des systèmes intelligents.La thèse commence par établir les concepts fondamentaux de la détection des données hors distribution (OOD) et de la détection des erreurs de classification dans le chapitre 1, fournissant une littérature essentielle et expliquant les principes clés. L'introduction souligne l'importance de traiter les problèmes liés au comportement non intentionnel et nuisible en IA, en particulier lorsque les systèmes d'IA produisent des résultats inattendus en raison de divers facteurs tels que des divergences dans les distributions de données.Dans le chapitre 2, la thèse introduit une nouvelle méthode de détection de données hors distribution basée sur la distance géodésique Fisher-Rao entre les distributions de probabilité. Cette approche unifie la formulation des scores de détection pour les logits du réseau et les espaces latents, contribuant à une robustesse et une fiabilité accrues dans l'identification des échantillons en dehors de la distribution d'entraînement.Le chapitre 3 présente une méthode de détection des données hors distribution non supervisée qui analyse les trajectoires neuronales sans nécessiter de supervision ou d'ajustement d'hyperparamètres. Cette méthode vise à identifier les trajectoires d'échantillons atypiques à travers diverses couches, améliorant l'adaptabilité des modèles d'IA à des scénarios divers.Le chapitre 4 se concentre sur la consolidation et l'amélioration de la détection hors distribution en combinant efficacement plusieurs détecteurs. La thèse propose une méthode universelle pour combiner des détecteurs existants, transformant le problème en un test d'hypothèse multivarié et tirant parti d'outils de méta-analyse. Cette approche améliore la détection des changements de données, en en faisant un outil précieux pour la surveillance en temps réel des performances des modèles dans des environnements dynamiques et évolutifs.Dans le chapitre 5, la thèse aborde la détection des erreurs de classification et l'estimation de l'incertitude par une approche axée sur les données, introduisant une solution pratique en forme fermée. La méthode quantifie l'incertitude par rapport à un observateur, distinguant entre prédictions confiantes et incertaines même face à des données difficiles. Cela contribue à une compréhension plus nuancée de la confiance du modèle et aide à signaler les prédictions nécessitant une intervention humaine.La thèse se termine en discutant des perspectives futures et des orientations pour améliorer la sécurité en IA et en apprentissage automatique, soulignant l'évolution continue des systèmes d'IA vers une plus grande transparence, robustesse et fiabilité. Le travail collectif présenté dans la thèse représente une avancée significative dans le renforcement de la sécurité en IA, contribuant au développement de modèles d'apprentissage automatique plus fiables et dignes de confiance, capables de fonctionner efficacement dans des scénarios réels divers et dynamiquesThis thesis explores the intersection of machine learning (ML) and safety, aiming to address challenges associated with the deployment of intelligent systems in real-world scenarios. Despite significant progress in ML, concerns related to privacy, fairness, and trustworthiness have emerged, prompting the need for enhancing the reliability of AI systems. The central focus of the thesis is to enable ML algorithms to detect deviations from normal behavior, thereby contributing to the overall safety of intelligent systems.The thesis begins by establishing the foundational concepts of out-of-distribution (OOD) detection and misclassification detection in Chapter 1, providing essential background literature and explaining key principles. The introduction emphasizes the importance of addressing issues related to unintended and harmful behavior in ML, particularly when AI systems produce unexpected outcomes due to various factors such as mismatches in data distributions.In Chapter 2, the thesis introduces a novel OOD detection method based on the Fisher-Rao geodesic distance between probability distributions. This approach unifies the formulation of detection scores for both network logits and feature spaces, contributing to improved robustness and reliability in identifying samples outside the training distribution.Chapter 3 presents an unsupervised OOD detection method that analyzes neural trajectories without requiring supervision or hyperparameter tuning. This method aims to identify atypical sample trajectories through various layers, enhancing the adaptability of ML models to diverse scenarios.Chapter 4 focuses on consolidating and enhancing OOD detection by combining multiple detectors effectively. It presents a universal method for ensembling existing detectors, transforming the problem into a multi-variate hypothesis test and leveraging meta-analysis tools. This approach improves data shift detection, making it a valuable tool for real-time model performance monitoring in dynamic and evolving environments.In Chapter 5, the thesis addresses misclassification detection and uncertainty estimation through a data-driven approach, introducing a practical closed-form solution. The method quantifies uncertainty relative to an observer, distinguishing between confident and uncertain predictions even in the face of challenging or unfamiliar data. This contributes to a more nuanced understanding of the model's confidence and helps flag predictions requiring human intervention.The thesis concludes by discussing future perspectives and directions for improving safety in ML and AI, emphasizing the ongoing evolution of AI systems towards greater transparency, robustness, and trustworthiness. The collective work presented in the thesis represents a significant step forward in advancing AI safety, contributing to the development of more reliable and trustworthy machine learning models that can operate effectively in diverse and dynamic real-world scenarios
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Ji, Ming Chao. "Molecular relaxation dynamics of Anthracene cations studied in an electrostatic storage ring." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10051.
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Les molécules hydrocarbures aromatiques polycycliques (HAP) sont à l'heure actuelle considérées comme probablement responsables des bandes d'émission infrarouge non identifiées du milieu interstellaire (MIS). La dynamique de refroidissement des molécules HAP est essentielle pour estimer leur photo-stabilité, leur durée de vie et les distributions de taille dans le MIS. Au cours des dernières années, les expériences s'appuyant sur le stockage électrostatique d'ions moléculaires ou d'agrégats sont devenus des outils puissants pour étudier leur refroidissement dans une large gamme de temps allant de la microseconde à quelques secondes. En général, l'étude des courbes de déclin associées aux processus de dissociation dans le cas des cations ou bien de détachement d'électrons dans le cas des anions fournit des informations sur l'évolution de l'énergie interne des ions stockés. Dans ce travail de thèse, le refroidissement de cations d'anthracène a été étudié dans un anneau de stockage électrostatique compact, le Mini-Ring, jusqu'à 8 ms. Les courbes de déclin spontané provenant de la dissociation par émission de fragment C2H2 ou H neutres montrent trois régions distinctives. Ces trois régions indiquent différents régimes de refroidissement en fonction du temps de stockage, la dissociation domine pour les temps inférieurs à 1 ms, l'effet de l'émission radiative entre alors en compétition avec la dissociation puis domine au-delà de 3 msThe polycyclic aromatic hydrocarbon (PAH) molecules have been considered as possible carrier of the unidentified infrared emission bands from the interstellar medium (ISM) for about thirty years. The cooling dynamics of the PAH molecules which is essential to estimate their photostability and therefore their lifetime and size distributions in the ISM, has attracted numerous theoretical and experimental studies. In recent years, electrostatic storage devices (ESD) became powerful tool to investigate the cooling regime of molecules and clusters in a large time range from microseconds to seconds. Generally speaking, the decay of the emitted neutral yields due to dissociation of molecular cations or electron detachment of anions in such experiments carries information on the internal energy of the stored molecular ions. In this thesis work, the cooling regimes of anthracene cations are studied by following the time evolution of the internal energy distribution (IED) of the stored anthracene cations. A spontaneous neutral yield curve obtained from the stored molecular ions as a function of the storage time shows three distinguishable regions. The three regions indicate different cooling regimes at corresponding storage time range, i.e., the dissociation mechanism of the molecule dominates at storage time t < 1 ms, quenching of the dissociation by radiative cooling processes occurs during 1 < t < 3 ms and radiative cooling governs at t > 3 ms
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Kwan, Kermit S. Jr. "The Role of Penetrant Structure on the Transport and Mechanical Properties of a Thermoset Adhesive." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30666.
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In this work the relationships between penetrant structure, its transport properties, and its effects on the mechanical properties of a polymer matrix were investigated. Although there is a vast amount of data on the diffusion of low molecular weight molecules into polymeric materials and on the mechanical properties of various polymer-penetrant systems, no attempts have been made to inter-relate the two properties with respect to the chemical structure of the diffusant. Therefore, two series of penetrants - n-alkanes and esters - were examined in this context, with the goal of correlating molecular size, shape, and chemical nature of the penetrant to its final transport and matrix mechanical properties. These correlations have been demonstrated to allow quantitative prediction of one property, given a reasonable set of data on the other parameters.
A series of n-alkanes (C6-C17) and esters (C5-C17) have been used to separate the effects of penetrant size and shape, from those due to polymer-penetrant interactions, in the diffusion through a polyamide polymeric adhesive. These effects have been taken into account in order to yield a qualitative relationship that allows for prediction of diffusivity based upon penetrant structural information. Transport properties have been analyzed using mass uptake experiments as well as an in-situ FTIR-ATR technique to provide detailed kinetic as well as thermodynamic information on this process.
The phenomenon of diffusion and its effects on the resulting dynamic mechanical response of a matrix polymeric adhesive have been studied in great detail using the method of reduced variables. The concept of a diffusion-time shift factor (log aDt) has been introduced to create doubly-reduced master curves, taking into account the effects of temperature and the variations in the polymer mechanical response due to the existence of a low molecular weight penetrant.Ph. D.
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Bourgeaud, Luana. "Histoire évolutive et potentiel adaptatif : une approche éco-évolutive de la vulnérabilité des espèces aux changements climatiques." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30263.
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Comprendre les processus influençant la distribution géographique des espèces est un des objectifs en écologie et il revêt actuellement un intérêt particulier puisque le changement climatique causé par les activités humaines entraine la redistribution des espèces à la surface du globe. Dans ce contexte, nous avons exploré la dynamique temporelle de la niche climatique (ensemble des exigences climatiques d'une espèce) dans le but de déterminer la capacité des espèces à faire face aux changements climatiques. Pour cela, nous nous sommes intéressés aux taux de changements de niches climatiques passés qui décrivent les changements de niches climatiques survenus au cours de l'histoire évolutive des espèces faisant alors l'hypothèse que les changements climatiques passés pourraient refléter les changements climatiques actuels. Suite à la reconstruction d'une phylogénie datée pour 12616 espèces de poissons, nous avons compilé des données climatiques et de distributions afin d'estimer pour chaque espèce les taux de changements de niches climatiques passés. Dans un premier projet, nous avons étudié les facteurs influençant les taux de changements de niches climatiques passés dans les milieux aquatiques. Nous avons en particulier confirmé que les taux de changements de niches climatiques passés sont plus forts vers les latitudes les plus hautes. Nous avons également discuté des différences entre les écosystèmes marins et d'eau douce. Dans un deuxième projet, nous avons corrélé les taux de changements de niches climatiques avec des mesures de déplacements d'aires de distribution contemporains. Nous avons montré que les taux de changements de niches climatiques sont positivement associés aux déplacements d'aires de distribution contemporains chez les poissons marins. Nos résultats suggèrent que l'influence des taux de changements de niches climatiques passés et plus généralement de l'histoire évolutive des espèces sur leurs réponses aux changements climatiques actuels doit être explorée plus amplement pour définir comment ce domaine pourra informer la conservation de la biodiversitéUnderstanding the processes influencing the geographical distribution of species is one of the main aims in ecology and is of particular interest since climate change caused by human activities is currently leading to the geographical redistribution of species. In this context, we explored the temporal dynamics of the climatic niche (the set of climatic requirements of a species) in an attempt to determine species' ability to cope with climate change. To do this, we investigated historical rates of climatic niche change which describe past climatic niche changes that occurred over the course of species evolutionary history assuming that past climatic changes reflect current climate change. Following the reconstruction of a dated phylogeny for 12,616 fish species, we compiled climate and distribution data to estimate historical rates of climatic niche change. In a first project, we studied the factors influencing historical rates of climatic niche change in aquatic environments. In particular, we confirmed that historical rates of climatic niche change are greater at higher latitudes. We also discussed the differences between marine and freshwater ecosystems. In a second project, we correlated historical rates of climatic niche change with measures of contemporary range shifts. We showed that historical rates of climatic niche change are positively associated with contemporary range shifts in marine fish. Our results suggest that the influence of historical rates of climatic niche change and more generally of species evolutionary history on their response to current climate change needs to be further explored to determine how it can inform biodiversity conservation
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Ousmen, Ahmad. "Détermination du sens clinique d'un changement pour les questionnaires de qualité de vie relative à la santé en cancérologie." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCE001/document.
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En cancérologie, la qualité de vie relative à la santé (QdV) est considérée comme second critère de jugement principal dans les essais cliniques en l’absence d’effet sur la survie globale. L’interprétation des scores de QdV et d’une différence de scores cliniquement pertinente entre deux temps de mesure est un problème majeur en QdV. Cette différence peut être significative d’un point de vue statistique sans être cliniquement significative du point de vue du patient. La différence minimale cliniquement importante (DMCI) a ainsi été définie comme la plus petite différence de score de QdV qui serait considérée comme ayant un sens clinique pour le patient. L’analyse longitudinale de la QdV est complexe, en particulier en raison de l’occurrence de l’effet « Response Shift » qui est susceptible de biaiser les résultats d’analyse longitudinal et en particulier les résultats de la DMCI. Dans ce contexte, le premier objectif de ce travail de thèse est une revue de la littérature concernant la détermination de la DMCI selon les méthodes les plus couramment utilisées : les méthodes basées sur l’ancre et les méthodes basées sur la distribution. Deuxièmement, calculer la DMCI par les méthodes basées sur l’ancre et la distribution en appliquant différents critères de distribution et plusieurs ancres différentes. L’objectif est de comparer les résultats obtenus par les différentes méthodes et de les comparer également avec les résultats obtenus par les études antérieures. Enfin, étudier l’impact de l’occurrence de l’effet Response Shift sur la détermination de la DMCI pour les questionnaires de QdV en cancérologieIn oncology, the health-related quality of life (HRQOL) is generally considered as a second endpoint in the clinical trials. The interpretation of the results of the longitudinal analysis of such data must be made in both statistical and clinical point of view in order to produce meaningful results for both patients and clinicians. The main objective is to assess the impact of the treatment on patient’s HRQOL level over time. The minimal clinically important difference (MCID) was defined as the smallest change between two scores in a treatment outcome that a patient would identify as important. Indeed, the longitudinal analysis of HRQOL remains complex, particularly due to the potential occurrence of a Response Shift effect characterizing the process of adaptation of the patient in relation to the illness and its treatment. Hence, the first objective of this work is a literature review concerning the determination of the MCID by the most commonly used methods: anchor-based and distribution-based methods. Secondly, calculating the MCID using anchor-based and distribution-based methods by applying different distribution criteria and several different anchors. The objective is to compare the results obtained by the different methods and to compare them to others obtained by previous studies. Finally, studying the impact of the Response Shift effect on the determination of MCID for the HRQOL questionnaires in cancer research using several data corresponding to different therapeutic situations and cancer locations
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Falck, Lina, and Moa Thörlind. "YouTube och Musikbranschen : En studie i hur artisters användande av YouTube som marknadsföringskanal ser ut i en allt mer digital musikbransch." Thesis, Linnéuniversitetet, Institutionen för marknadsföring (MF), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-35919.
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Denna uppsats syfte är att analysera hur musikartister använder sig av YouTube som marknadsföringsverktyg, samt vilken betydelse YouTube har för dessa artisters marknadsföring. En kvalitativ och induktiv metod har tillämpats, medan ett antal intervjuer samt en innehållsanalys genomförts som grund till det empiriska materialet. Detta för att få en inblick i musikbranschens syn på ämnet, samt även ge en objektiv bild av hur plattformen används som marknadsföringsverktyg. Slutligen menade studien att ge artister och andra arbetande inom musikbranschen, en bild av hur användandet av denna marknadsföringskanal kan förbättras för att skapa en mer effektiv marknadsföring. Den teoretiska referensramen har utgått från tidigare teorier kring YouTubes betydelse, roller och potential inom musikartisters marknadsföring. Teorier kring YouTubes möjliggörande för artister att upptäckas av A&R personer eller nya fans, YouTubes påverkan på musikvideons roll som marknadsföringsmedel, samt teorier kring plattformens påverkan på maktbalansen inom branschen har legat som grund. Även teorier kring ett nytt fokus på opinion leaders; vem och när, samt teorier gällande relationsmarknadsföring, kommunikation, feedback och sampling har tillämpats. Slutligen har teorier kring YouTubes negativa aspekter, såsom svårigheter att sticka ut och illegal spridning setts till. I redogörelsen av det empiriska materialet ingår svar från de intervjuer som genomförts med musikartister samt nyckelpersoner inom branschen. Här redogörs även resultatet från den innehållsanalys som genomförts av de intervjuade artisternas respektive YouTube-kanaler. I analysen sammankopplas den teoretiska referensramen med det empiriska materialet i en diskussion och analys. Detta för att jämföra tidigare teorier med branschens nuvarande syn på forskningsfrågan samt artisternas faktiska användande av plattformen. Även för att belysa vad musikartisterna har för möjligheter att förbättra sin marknadsföring via YouTube, för en mer framgångsrik marknadsföring. De slutsatser som uppsatsen sedan mynnar ut i menar att YouTube har utvecklats till en stark marknadsföringskanal för musikartister. Plattformen är av stor betydelse för musikartisters exponeringsmöjligheter, men det krävs dock andra marknadsföringsaktiviteter för att klipp ska hittas av A&R avdelningar och nya fans. Musikvideon har en fortsatt viktig roll för artisternas exponeringsmöjligheter. YouTube skapar en möjlighet till relationsbyggande mellan artister och fans, men denna möjlighet utnyttjas ej till fullo av artisterna. Feedback via kommentarsfält skulle dock kunna nyttjas för större grad av lärande, samt för starkare relationsbyggande. En nackdel är att YouTube dock tycks vara illegal spridning av material, samt minskad kontroll över eget material. Makten över kreativiteten tycks med YouTube ha flyttats mer mot artisterna själva, men de stora aktörernas nätverk och resurser tycks dock fortsatt viktiga för att ge möjligheter att sticka ut i det enorma mediaflödet.This paper aims to analyze how music artists use YouTube as a marketing tool, and the importance YouTube has for these artists' marketing. A qualitative and inductive approach was used, while a number of interviews and a content analysis conducted as the basis for the empirical material. This to get an insight into the music industry's views on the topic, and also give an objective picture of how the platform is used as a marketing tool. Finally, the study is meant to give artists and others working in the music industry a picture of how the use of this marketing channel can be improved to create a more effective marketing. The theoretical framework was based on earlier theories of YouTube's importance, roles and potential in music artists' marketing. Theories on how YouTube enables artists to be discovered by A & R people or new fans, YouTube's impact on the music video's role as a marketing medium, and theories about the platform's impact on the balance of power within the industry has been the foundatioin. Theories about a new focus on opinion leaders; whom and when, as well as theories on relationship marketing, communication, feedback and sampling have also been applied. Finally, theories of YouTube's negative aspects, such as difficulties to stand out and illegal distribution has been looked into. In the account of the empirical material responses from the interviews with music artists and key people in the industry are included, as well as the results from the content analysis conducted by the interviewed artists' respective YouTube channels. In the analysis the theoretical framework is linked to the empirical material in a discussion and analysis. This is to compare previous theories with the industry's current opinions on the research question and the performers' actual usage of the platform, also to illustrate how music artists could improve their marketing through YouTube for more successful marketing. The conclusions of the essay is of the opinion that YouTube has evolved into a powerful marketing channel for music artists. The platform is of great importance for music artists interms of opportunities of exposure, but additional marketing activities are however required gor the material to be found by A & R departments and new fans. The music video has a continued important role for artists' exposure opportunities. YouTube creates an opportunity to build relationships between artists and fans, but this opportunity is generally not utilized fully by the artists. Feedback via the comment field could be utilized for greater levels of learning, and for stronger relationship building. One negative aspect of YouTube is that it can be considered as a way to illegaly distribute content, and it does add to reduced control over the artists own material. The creative authority seems with YouTube have moved more towards the artists themselves rather than their labels or management, but networks and resources available to the major labels seem to remain important to provide opportunities to be able stand out in the masses f available media on YouTube.
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Delava, Émilie. "Impacts du réchauffement climatique sur la distribution géographique des insectes et mise en place des adaptations locales : cas d'un parasitoïde de drosophiles dans le sud-est de la France." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10315.
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Prédire les réponses de la biodiversité aux changements climatiques anthropiques est devenu un champ de recherche avec des enjeux scientifiques et sociétaux majeurs. Mon travail de thèse a consisté à évaluer les impacts du réchauffement climatique sur un parasitoïde de drosophiles, Leptopilina boulardi, à une petite échelle géographique, le sud-est de la France. L'objectif était non seulement d'examiner l'évolution de la distribution du parasitoïde en réponse à une hausse des températures qu'il fallait préciser à cette échelle géographique, mais aussi d'appréhender les adaptations mises en place dans la zone de progression de l'espèce. Dans un premier temps, l'analyse de données d'échantillonnages et de données météorologiques m'ont permis de mettre en évidence une rapide expansion de l'aire de répartition du parasitoïde vers le nord, à un taux moyen de 90km/décennie, simultanément à une augmentation moyenne de la température de 1,57°C ces 30 dernières années, dans l'aire d'étude. Après avoir identifié les principaux facteurs environnementaux, structurant la répartition spatiale de L. boulardi, j'ai modélisé sa distribution potentielle dans le sud-est de la France, sous conditions climatiques actuelles et pour 2050, pour deux scénarios d'émission de CO2. En 2050, la distribution géographique de L. boulardi devrait considérablement s'étendre vers le nord sous l'effet des changements climatiques. Ensuite, en mesurant plusieurs traits d'histoire de vie selon 4 régimes thermiques fluctuants, j'ai montré que les populations de L. boulardi situées en limite d'aire de répartition sont génétiquement différenciées de celles situées dans l'aire centrale de répartition. Le fait que les populations marginales aient une valeur sélective plus importante à faible température suggère une adaptation locale des parasitoïdes dans la zone de progression de l'aire de répartition. La dernière partie de ce travail de thèse a pour objectif de mieux comprendre le processus de colonisation de L. boulardi. Pour cela, j'ai entrepris le développement de marqueurs RAD-sequencing sur 15 populations de cette espèce, distribuées le long d'un cline de latitude dans le sud-est de la France. Les nombreuses données issues du séquençage Illumina me permettront de connaître la structuration génétique de ces populations. L'ensemble de ces résultats obtenus au cours de ma thèse révèlent la force avec laquelle les changements climatiques peuvent impacter les espèces, principalement celles de haut niveau trophique, en provoquant des changements très rapide de distribution et des modifications génotypiques et phénotypiques permettant une meilleure adaptation localePredicting biodiversity responses to anthropogenic climate change has become a field of research with major scientific and societal issues. The main goal of my thesis was to evaluate the impacts of global warming on a Drosophila parasitoid, Leptopilina boulardi, at a small geographical scale, the South-East of France. The aim was not only to examine the change in the distribution of the parasitoid in response to rising temperatures, but also to understand the adaptations associated with this change. First, the analysis of insect sampling and meteorological data allowed me to demonstrate a rapid expansion of the parasitoid range to the north with an average rate of 90km/decade as well as a simultaneous temperature increase of 1.57°C on average over the past 30 years in the studied area. Following the identification of the main environmental factors structuring the spatial distribution of L. boulardi, I fitted a model predicting its potential distribution in the south-east of France, under the current climate and in 2050, for two CO2 emission scenarios. In 2050, the geographical distribution of L. boulardi should significantly extend northward as a result of climate change. Then, by measuring several life history traits under four fluctuating temperature regimes, I have shown that populations of L. boulardi located on the border of the range are genetically differentiated from those in the central range. The fact that marginal populations have a greater fitness at low temperature suggests local adaptation of parasitoids in the area of progression of range. The last part of this thesis aimed to better understand the process of colonization of L. boulardi. For this, I undertook the development of RAD-sequencing markers to genotype 15 populations of this species distributed along a cline of latitude in the southeast of France. Numerous data from Illumina sequencing will allow me to characterize the genetic structure of the populations. All the results obtained in my thesis highlight the force with which climate change may impact species, in particular those of high trophic level, causing rapid changes in distribution along with genotypic and phenotypic changes underlying local adaptation
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Elkington, Ruari B. "The education market for documentary film: Digital shifts in an age of content abundance." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/98494/4/Ruari_Elkington_Thesis.pdf.
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This research examines the education market for documentary film at a time of digitally mediated content abundance. How can an expanded acknowledgment of cineliteracy within the education market for screen content contribute to sustainability of the Australian documentary sector through improved distribution and educational outreach practices? Engaging with international case studies of film festivals, foundations and charities both in the UK and US allows for observations around best practice to be considered for a local context.
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Guio, Patrick. "Etude de paramètres ionosphériques à l'aide des raies de plasma électroniques observées à Eiscat." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10253.
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Ce travail présente une étude des raies de plasma observées à l'aide du radar à diffusion incohérente EISCAT. Le travail est centré sur deux points. Tout d'abord, la conception d'une expérience raies de plasma pour le radar EISCAT, avec une résolution spatiale améliorée. Puis, la comparaison de données raies de plasma acquises avec le radar EISCAT avec une théorie améliorée sur l'intensité et le décalage Doppler en fréquence des raies de plasma. Pour améliorer la résolution spatiale, nous avons conçu la première expérience raies de plasma mettant en oeuvre la technique du code alternatif. Cette expérience a été tournée avec succès avec une résolution spatiale de 3 km au lieu de 40-50 km obtenu avec les techniques conventionnelles. Parce qu'il est très difficile de construire un modèle cohérent de la fonction de distribution des vitesses des électrons satisfaisant tous les intervalles d'énergies pertinents, nous avons construit une représentation adéquate de la distribution des vitesses des électrons en séparant la distribution en deux populations : la thermique et la suprathermique. La population thermique est représentée par la fonction de Spitzer qui tient compte de l'effet d'un champ électrique et/ou d'un gradient de température. La population suprathermique est déduite du flux angulaire d'énergie calculé grâce à un modèle numérique du transport des électrons. Un code numérique a été développé pour calculer la fonction diélectrique et la fonction réduite de distribution des vitesses pour toutes distributions des vitesses à deux dimensions dont nous avons besoin pour modéliser l'intensité et le décalage Doppler en fréquence des raies de plasma. Nous avons pu reproduire les caractéristiques de l'intensité et du décalage Doppler en fréquence des raies de plasma avec des données mesurées avec le radar VHF EISCAT. En particulier, nous avons identifié deux pics étroits dans la distribution des vitesses des suprathermiques comme la signature de la photo-ionisation de N_2 et O. Ces pics ont été observés sur les données. L'effet d'un gradient de température - qui produit une correction importante au décalage Doppler des raies de plasma - a été pris en compte plus précisement que précédemment en calculant numériquement les intégrales singulières, au lieu d'utiliser les premiers termes d'une expansion en séries comme auparavant. C'est important car cela a permis pour la première fois à un modèle de reproduire précisément l'intensité et le décalage Doppler des raies de plasma mesurés par une expérience EISCAT.
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Steige, Kim A. "Cis-regulatory variation and divergence in Capsella." Doctoral thesis, Uppsala universitet, Evolutionsbiologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-268953.
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Cis-regulatory changes in e.g. promoters or enhancers that affect the expression of a linked focal gene have long been thought to be important for adaptation. In this thesis, I investigate the selective importance and genomic correlates of cis-regulatory variation and divergence in the genus Capsella, using massively parallel sequencing data. This genus provides an opportunity to investigate cis-regulatory changes in response to polyploidization and mating system shifts, as it harbors three diploid species, the outcrosser Capsella grandiflora and the selfers Capsella orientalis and Capsella rubella, as well as the tetraploid Capsella bursa-pastoris. We first identify cis-regulatory changes associated with adaptive floral evolution in connection with the recent switch to self-fertilization in C. rubella and show that cis-regulatory changes between C. rubella and its outcrossing close relative C. grandiflora are associated with differences in transposable element content. Second, we show that variation in positive and purifying selection is important for the distribution of cis-regulatory variation across the genome of C. grandiflora. Interestingly, the presence of polymorphic transposable elements is strongly associated with cis-regulatory variation in C. grandiflora. Third, we show that the tetraploid C. bursa-pastoris is of hybrid origin and investigate the contribution of both parental species to gene expression. We show that gene expression in the tetraploid is partly explained by cis-regulatory divergence between the parental species. Nonetheless, within C. bursa-pastoris there is a great deal of variation in homeolog expression. In summary, this thesis explores the role of cis-regulatory changes for adaptive morphological changes in connection to a shift in mating system, the role of cis-regulatory divergence between progenitor species for an allopolyploid as well as the impact of positive and purifying selection on cis-regulatory variation within a species.
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Bodén, Andreas. "The anode and the electrolyte in the MCFC." Doctoral thesis, KTH, Kemiteknik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4382.
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A goal of the Swedish government is to increase the usage of renewable fuels and biomass-based fuels. Fuel cells, and especially the MCFC, are useful for these types of fuels. The Swedish market may benefit from the MCFC in two ways: increased efficiency of the biofuels and also utilisation of produced heat in district heating. Most of the commercial MCFC systems today are optimised for use with methane. The possibility to utilise biomass in Sweden makes it important to study how the MCFC may be adapted or optimised for good performance and low degradation with gas produced from biomass or other renewable fuels. This thesis is focused on methods that may be used to investigate and evaluate MCFC electrodes and electrolytes with renewable fuels i.e. CO2-containing gases. The methods and results are both experimental and mathematically modelled. The objectives of this thesis are to better understand how the performance of the anode is dependent on different fuels. Anode kinetics and the water-gas shift reaction have been investigated as well as the possibility to increase cell lifetime by increasing the initial electrolyte amount by having the anode as a reservoir. The effect of segregation of cations in the electrolyte during operation has also been studied. It was found that if the gas composition at the current collector inlet is in equilibrium according to the water gas-shift reaction the gas composition inside the electrode is almost uniform. However, if the gas is not in equilibrium then the concentration gradients inside the current collector have a large effect on the gas composition inside the electrode. The conversion of the gas in the gas flow channels according to the water-gas shift reaction depends on the gas flow rate. For an anode used in a gas mixture of humidified hydrogen and carbon dioxide that are not in equilibrium some solubility of Ni in a (Li/Na)2CO3 mixture was found. To have the anode act as an electrolyte reservoir to prolong cell lifetime the anode pore size should be carefully matched with that of the cathode and a bimodal pore-size distribution for the anode is preferable to have as good performance as possible for as large electrolyte filling degree interval as possible. Modelling results of segregation of cations in the electrolyte during operation indicate that the electrolyte composition changes during operation and that the lithium ions are enriched at the anode for both types of electrolyte used for the MCFC. The electrolyte composition changes are small but might have to be considered in long-time operation. The results from this thesis may be used to better understand how the MCFC may be used for operation with renewable fuels and how electrodes may be designed to prolong cell lifetime.Ett av den svenska regeringens mål är att öka användandet av förnyelsebara bränslen och bränslen från biomassa. Bränsleceller och framförallt MCFC är användbara för dessa typer av bränslen. Den svenska marknaden kan dra fördelar av MCFC på två sätt; ökad bränsleutnyttjandegrad och utnyttjande av producerad värme för fjärrvärme. De flesta kommersiella MCFC-systemen idag är optimerade för användning av metan. Möjligheten att använda biomassa på den svenska marknaden gör det viktigt att studera hur MCFC kan anpassas eller optimeras för bra prestanda och låg degradering för användning med gas från biomassa eller andra förnyelsebara bränslen. Fokus i denna avhandling är på metoder som kan användas för att undersöka och utvärdera MCFC-elektroder och -elektrolyter med förnyelsebara bränslen, dvs. gaser innehållande CO2. Metoderna och resultaten är både experimentella och matematiskt modellerade. Målet med denna avhandling är att bättre förstå hur anodens prestanda beror på användningen av olika bränslen. Anodens kinetik och vattengasskiftreaktionen har studerats liksom möjligheten att förlänga cellens livstid genom att öka den initiala mängden elektrolyt medelst användning av anoden som reservoar. Effekten av segregation av katjoner i elektrolyten under last har också undersökts. Om gassammansättningen är i jämvikt enligt vattengasskiftreaktionen vid inloppet till strömtilledaren kommer gassammansättningen att vara nära uniform inuti elektroden. Om ingående gas inte är i jämvikt kommer stora koncentrationsgradienter uppkomma i strömtilledaren och påverka gassammansättningen i elektroden. Omsättningen med avseende på vattenskiftreaktionen av gasen i flödeskanalen verkar vara beroende av gasens flödeshastighet. För en anod som används i en uppfuktad blandning av vätgas och koldioxid som inte är i jämvikt befanns det att Ni har en viss löslighet i (Li/Na)2CO3. För att kunna använda anoden som reservoar för elektrolyt för att förlänga livstiden för MCFC skall anodens porstorleksfördelning överensstämma med katodens och ha en bimodal porstorleksfördelning för att ge en tillräckligt god prestanda i ett så stort elektrolytfyllnadsgradsintervall som möjligt. Modelleringsresultat för segregering av katjoner i elektrolyten under drift visar att litiumjoner anrikas i anoden för båda typerna av elektrolyt som används i MCFC. Elektrolytkoncentrationsförändringarna är små men kan behövas tas i beaktande vid långa driftstider. Denna avhandlings resultat kan användas för att bättre förstå hur MCFC skall anpassas för drift med förnyelsebara bränslen och hur elektroder kan utformas för att förlänga livstiden.
QC 20100630
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Gallo, Diego Sanchez. "Arquitetura de IPTV com suporte à apresentação deslocada no tempo baseada em distribuição peer-to-peer." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-18112009-092103/.
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Com o aumento da concorrência sofrido pelas operadoras de telecomunicações frente à entrada de diversas empresas de outros ramos no mercado de comunicação, como, por exemplo, os Provedores de Serviço de Internet (ISPs - Internet Service Providers) através da oferta de serviços de voz sobre IP, tais operadoras viram-se obrigadas a diversificar sua oferta de serviços para gerar novas fontes de receita. Por possuírem ampla infra-estrutura instalada, as operadoras de telecomunicações passaram a oferecer, também, serviço de TV aos usuários, através de suas redes (convergentes) de telefonia e dados já existentes, o chamado IPTV. O objetivo deste trabalho foi possibilitar, neste cenário, que estas empresas consigam oferecer, além dos serviços convencionais de TV (e.g., transmissões lineares dos conteúdos nos canais de TV), serviços diferenciados empregando-se a mesma infra-estrutura. O foco deste trabalho é a oferta do serviço de apresentação deslocada no tempo dos conteúdos transmitidos linearmente nos canais de TV, sem a necessidade de configuração prévia por parte do usuário. Desta maneira, dá-se maior flexibilidade ao usuário, possibilitando-o assistir aos conteúdos que lhe interessam, no horário mais conveniente, sem ter que se preocupar com isso antecipadamente (i.e., sem a necessidade de configurar algum equipamento para gravar o conteúdo ou saber antecipadamente quais programas lhe interessam). Para isso foram pesquisadas e analisadas tanto tecnologias de transmissão e distribuição de conteúdos, como também o paradigma peer-to-peer, muito utilizado atualmente no compartilhamento de arquivos na Internet. A partir daí, foi concebida uma arquitetura capaz de oferecer tanto o serviço tradicional de transmissão linear de TV, quanto de apresentar vídeos deslocados no tempo (i.e., vídeos cuja transmissão linear já foi iniciada ou até concluída, a partir de qualquer posição já transmitida), combinando-se técnicas de multidifusão de dados, armazenamento distribuído e protocolos peer-to-peer. Desta maneira, obteve-se uma solução eficiente, utilizando-se os recursos disponíveis em todo o sistema, incluindo recursos ociosos dos usuários finais, para auxiliar no armazenamento e distribuição dos conteúdos deslocados no tempo. Finalmente, um protótipo foi desenvolvido como prova de conceito da arquitetura proposta neste trabalho, e, juntamente com os testes realizados, comprovam a viabilidade de se utilizar redes P2P para a distribuição dos conteúdos para a apresentação deslocada no tempo.Telecommunication companies are suffering from the increasing offer of cheap and reliable voice over IP services, being forced to diversify their services looking for new revenue possibilities. Since these companies have a vast infrastructure, they are now providing TV services through the same telephony and data infrastructure, using their IP networks to offer IPTV. The goal of the present work is to allow, in this scenario, that such companies offer, additionally to the traditional TV services (e.g., the linear transmissions of the TV channels), differentiated services through the same infrastructure. The focus of the present work is, therefore, the offering of the time-shift service, allowing users to watch linear transmitted contents, time-shifted, without the need for any in-advance configuration. This approach gives more flexibility to the users, allowing them to choose the most appropriate time to watch some content without having to specify their interests in advance (i.e., without configuring some equipment to record the content or knowing in advance which programs will interest themselves). To achieve this goal, technologies for content transmission and distribution, as well as the peer-to-peer paradigm for file sharing were studied, resulting in the development of an architecture capable of offering the traditional linear transmissions service as well as the possibility of time-shift, combining multicast, distributed caching and peer-to-peer technologies. Accordingly, an efficient solution was envisioned, making use of all available resources in the system, including idle resources in the user equipments, to help in the caching and distribution of the time-shifted contents. Finally, a prototype was developed as a proof-of-concept for the designed architecture, which together with the performed tests, shows the viability of utilizing P2P networks in the distribution of time-shifted contents.
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Sirois-Delisle, Catherine. "Modeling Future Climate Change Impacts on North American Bumblebee Distributions." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/37028.
Full textAbstract:
Climate change is an important contributor to the modification of many bumblebee species’ range boundaries. It was linked to widespread decline at the southern edge of their distribution and to their inability to colonize new areas at the northern edge. Additionally, bumblebee decline is aggravated by other anthropogenic threats like land use change, agricultural practices and pathogen spillover. Predicted consequences are numerous, and could lead to severe economic and ecological impacts on human populations. A species-specific assessment of potential climate change impacts on North American bumblebees, based on the most recent global change scenarios as used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), was done for the first time. Using a massive dataset of georeferenced bumblebee observations and general circulation models, a series of species distribution models explore the impact of different climate change scenarios on climatically suitable areas of 30 bumblebee species. Northward range shifts occur in most bumblebee species’ projected climatic niches, revealing potential hotspots – places projected to be climatically suitable to multiple species – under future climate scenarios. Areas where species are likely to be lost in the absence of intervention are substantial, particularly in eastern parts of the continent. Models showed significant contractions of current ranges even under the very optimistic scenario in which all species disperse at 10 km/year. Results indicate that managed relocation as well as habitat management should be considered as a conservation strategy for some species. This research serves as a foundation for broader discussion and research in a nascent research area. It may assist in establishing localities where first conservation efforts could be directed for vulnerable bumblebee species.
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Cox, Dennis R. "A business approach for detecting shifts in defect counts modeled by the Poisson distribution /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136092151&sid=8&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Rapacciuolo, Giovanni. "Predicting species' range shifts under global change : when can species distribution models be useful?" Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18025.
Full textAbstract:
Predicting how species’ distributions will change in response to environmental changes is fundamental for many aspects of agriculture, ecosystem service provision, human and animal health, and wildlife conservation. Correlative species distribution models (SDMs) are the primary tool for making such predictions; however, assessing their predictive accuracy is notoriously difficult, since predicted events are yet to occur. In this thesis, I tested the temporal transferability of widely-used SDMs based on coarse climate and land cover variables by validating these against records of recently-observed distribution changes in British vascular plants, birds, and butterflies. When transferred to a new time period, SDMs were generally accurate at discriminating between presence and absence across large portions of species’ ranges that had remained unchanged through time; however, their discrimination ability over portions of species ranges which had been observed to change occupancy status in time was no better than random. When considering the probabilistic nature of predictions, this lack of discrimination ability over dynamic portions of species’ ranges translated into significant deviations between values of predicted and observed probabilities of species’ gain and loss at given sites. Nonetheless, species’ gains and losses were more likely to be observed at sites with higher predicted probabilities of gain and loss, respectively. In addition, there was considerable variation in the temporal transferability of models with some models being more transferable than others. Differences amongst species were a major determinant of this variation. In particular, models of species found across a distinct and narrow range of environments, which also occurred across most geographical sites satisfying these requirements, were more transferable over time than others. Other factors leading to significant variation in temporal transferability were the choice of modelling framework and the geographical area over which a model was projected. My findings suggest that SDMs are unlikely to generate projections of single species’ range shifts that are accurate enough to provide a solid basis for local-scale conservation and management. However, they may be useful in pinpointing species and areas that are particularly vulnerable to environmental change and should thus be monitored closely. Clearly, more processes will need to be explicitly accounted for in our predictive models if we want to significantly increase their biological realism in the face of environmental change.
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Venne, Simon. "Can Species Distribution Models Predict Colonizations and Extinctions?" Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38465.
Full textAbstract:
Aim
MaxEnt, a very popular species distribution modelling technique, has been used extensively to relate species’ geographic distributions to environmental variables and to predict changes in species’ distributions in response to environmental change. Here, we test its predictive ability through time (rather than through space, as is commonly done) by modeling colonizations and extinctions.
Location
Continental U.S. and southern Canada.
Time period
1979-2009
Major taxa studied
Twenty-one species of passerine birds.
Methods
We used MaxEnt to relate species’ geographic distributions to the variation in environmental conditions across North America. We then modelled site-specific colonizations and extinctions between 1979 and 2009 as functions of MaxEnt-estimated previous habitat suitability and inter- annual change in habitat suitability and neighborhood occupancy. We evaluated whether the effects were in the expected direction, we partitioned model’s explained deviance, and we compared colonization and extinction model’s accuracy to MaxEnt’s AUC.
Results
IV
Colonization and extinction probabilities both varied as functions of previous habitat suitability, change in habitat suitability, and neighborhood occupancy, in the expected direction. Change in habitat suitability explained very little deviance compared to other predictors. Neighborhood occupancy accounted for more explained deviance in colonization models than in extinction models. MaxEnt AUC correlates with extinction models’ predictive ability, but not with that of colonization models.
Main conclusions
MaxEnt appears to sometime capture a real effect of the environment on species’ distributions since a statistical effect of habitat suitability is detected through both time and space. However, change in habitat suitability (which is much smaller through time than through space) is a poor predictor of change in occupancy. Over short time scales, proximity of sites occupied by conspecifics predicts changes in occupancy just as well as MaxEnt. The ability of MaxEnt models to predict spatial variation in occupancy (as measured by AUC) gives little indication of transferability through time. Thus, the predictive value of species distribution models may be overestimated when evaluated through space only. Future prediction of species’ responses to climate change should make a distinction between colonization and extinction, recognizing that the two processes are not equally well predicted by SDMs.
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Bickel, Steffen. "Learning under differing training and test distributions." Phd thesis, Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/3333/.
Full textAbstract:
One of the main problems in machine learning is to train a predictive model from training data and to make predictions on test data. Most predictive models are constructed under the assumption that the training data is governed by the exact same distribution which the model will later be exposed to. In practice, control over the data collection process is often imperfect. A typical scenario is when labels are collected by questionnaires and one does not have access to the test population. For example, parts of the test population are underrepresented in the survey, out of reach, or do not return the questionnaire. In many applications training data from the test distribution are scarce because they are difficult to obtain or very expensive. Data from auxiliary sources drawn from similar distributions are often cheaply available.
This thesis centers around learning under differing training and test distributions and covers several problem settings with different assumptions on the relationship between training and test distributions-including multi-task learning and learning under covariate shift and sample selection bias. Several new models are derived that directly characterize the divergence between training and test distributions, without the intermediate step of estimating training and test distributions separately. The integral part of these models are rescaling weights that match the rescaled or resampled training distribution to the test distribution. Integrated models are studied where only one optimization problem needs to be solved for learning under differing distributions. With a two-step approximation to the integrated models almost any supervised learning algorithm can be adopted to biased training data.
In case studies on spam filtering, HIV therapy screening, targeted advertising, and other applications the performance of the new models is compared to state-of-the-art reference methods.Eines der wichtigsten Probleme im Maschinellen Lernen ist das Trainieren von Vorhersagemodellen aus Trainingsdaten und das Ableiten von Vorhersagen für Testdaten. Vorhersagemodelle basieren üblicherweise auf der Annahme, dass Trainingsdaten aus der gleichen Verteilung gezogen werden wie Testdaten. In der Praxis ist diese Annahme oft nicht erfüllt, zum Beispiel, wenn Trainingsdaten durch Fragebögen gesammelt werden. Hier steht meist nur eine verzerrte Zielpopulation zur Verfügung, denn Teile der Population können unterrepräsentiert sein, nicht erreichbar sein, oder ignorieren die Aufforderung zum Ausfüllen des Fragebogens. In vielen Anwendungen stehen nur sehr wenige Trainingsdaten aus der Testverteilung zur Verfügung, weil solche Daten teuer oder aufwändig zu sammeln sind. Daten aus alternativen Quellen, die aus ähnlichen Verteilungen gezogen werden, sind oft viel einfacher und günstiger zu beschaffen. Die vorliegende Arbeit beschäftigt sich mit dem Lernen von Vorhersagemodellen aus Trainingsdaten, deren Verteilung sich von der Testverteilung unterscheidet. Es werden verschiedene Problemstellungen behandelt, die von unterschiedlichen Annahmen über die Beziehung zwischen Trainings- und Testverteilung ausgehen. Darunter fallen auch Multi-Task-Lernen und Lernen unter Covariate Shift und Sample Selection Bias. Es werden mehrere neue Modelle hergeleitet, die direkt den Unterschied zwischen Trainings- und Testverteilung charakterisieren, ohne dass eine einzelne Schätzung der Verteilungen nötig ist. Zentrale Bestandteile der Modelle sind Gewichtungsfaktoren, mit denen die Trainingsverteilung durch Umgewichtung auf die Testverteilung abgebildet wird. Es werden kombinierte Modelle zum Lernen mit verschiedenen Trainings- und Testverteilungen untersucht, für deren Schätzung nur ein einziges Optimierungsproblem gelöst werden muss. Die kombinierten Modelle können mit zwei Optimierungsschritten approximiert werden und dadurch kann fast jedes gängige Vorhersagemodell so erweitert werden, dass verzerrte Trainingsverteilungen korrigiert werden. In Fallstudien zu Email-Spam-Filterung, HIV-Therapieempfehlung, Zielgruppenmarketing und anderen Anwendungen werden die neuen Modelle mit Referenzmethoden verglichen.
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Honkomp, Nora. "Exploring shifts in migration phenology and breeding distribution of declining North American avian aerial insectivores." Kent State University Honors College / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1620686253404077.
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Annand, Colin T. "Scaling Relations as Cognitive Dipsticks: Distribution Analysis of Contextually Driven Performance Shifts in Three Linguistic Tasks." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504796379537155.
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Lättman, Håkan. "Description of spatial and temporal distributions of epiphytic lichens." Licentiate thesis, Linköping University, Linköping University, Department of Physics, Chemistry and Biology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11561.
Full textAbstract:
Lichens are, in most cases, sensitive to anthropogenic factors such as air pollution, global warming, forestry and fragmentation. Two studies are included in this thesis. The first is an evaluation of the importance of old oak for the rare epiphytic lichen Cliostomum corrugatum (Ach.) Fr. This study analysed whether C. corrugatum was limited by dispersal or restricted to tree stands with an unbroken continuity or the substrate old oaks. The results provide evidence that the investigated five populations in Östergötland, Sweden, of C. corrugatum exhibit substantial gene flow, an effective dispersal and a small genetic variation between the sites. Most of the genetic variation was within the populations. Thus, C. corrugatum is more dependent of the substrate old oaks, rather than limited by dispersal. The second study investigated possible range shift of some common macrolichens, due to global warming, from 64 sites in southern Sweden comparing the two years 1986 and 2003. The centroid of three lichen species had moved a significant distance, all in a north east direction: Hypogymnia physodes (L.) Nyl. and Vulpicida pinastri (Scop.) J.-E. Mattsson and M. J. Lai on the tree species Juniperus communis L. (50 and 151 km, respectively) and H. physodes on Pinus sylvestris L. (41 km). Considering also the non-significant cases, there is strong evidence for a prevailing NE direction of centroid movement.
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Sng, Sin Hie. "Radio channel modeling for mobile ad hoc wireless networks." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FSng.pdf.
Full textAbstract:
Thesis (M.S. in Engineering Science (Electrical Engineering))--Naval Postgraduate School, June 2004.Thesis advisor(s): Murali Tummala, Roberto Cristi. Includes bibliographical references (p. 71). Also available online.
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AL, SALEH-MAHROUSSEH SALOUA. "Calcul relativiste, en electrodynamique quantique, de la diffusion compton sur un electron lie." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21098.
Full textAbstract:
Pour expliquer le deplacement et l'elargissement du pic compton,lorsque l'energie du photon est voisine de l'energie de liaison de l'electron, il est necessaire d'introduire non seulement la liaison et le mouvement de l'electron, mais aussi le recul du mnoyau. On donne un calcul relativiste de la valeur quadratique moyenne de l'impulsion de l'electron et une expression generale des fonctions d'onde radiales. Pour le calcul analytique covariant de l'element de matrice ou utilise un propagateur pour un electron lie dans le schema de furry et determine la secton efficace, sans aucune integration
34
Pit, Vincent. "Codage du flot géodésique sur les surfaces hyperboliques de volume fini." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00553138.
Full textAbstract:
Cette thèse traite de l'étude des objets reliés au codage de Bowen-Series du flot géodésique pour des surfaces hyperboliques de volume fini. On démontre d'abord que le billard géodésique associé à domaine fondamental "even corners" d'un groupe fuchsien cofini est conjugué à une bijection du tore, appelée codage étendu, dont l'un des facteurs est la transformation de Bowen-Series. L'intérêt principal de cette conjugaison est qu'elle ne fait toujours intervenir qu'un nombre fini d'objets. On retrouve ensuite des résultats classiques sur le codage de Bowen-Series : il est orbite-équivalent au groupe, ses points périodiques sont denses, et ses orbites périodiques sont en bijection avec les classes d'équivalence d'hyperboliques primitifs du groupe ; ce qui permet finalement de relier sa fonction zeta de Ruelle à la fonction zeta de Selberg. Les preuves de ces résultats s'appuient sur un lemme combinatoire qui abstrait la propriété d'orbite-équivalence à des familles de relations qui peuvent être définies sur tout ensemble sur lequel agit le groupe. Il est aussi possible de conjuguer le codage étendu à un sous-shift de type fini, sauf pour un ensemble dénombrable de points. Enfin, on prouve que les distributions propres pour la valeur propre 1 de l'opérateur de transfert sont les distributions de Helgason de fonctions propres du laplacien sur la surface, puis que l'on peut associer à toute telle distribution propre une fonction propre non triviale de l'opérateur de transfert et que ce procédé admet un inverse dans certains cas
35
Lowry, Sonia L. "Analysis of statnamic load test data using a load shed distribution model." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001238.
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Jönsson, Emil. "Pressure distributions on a valve disk at different opening angles and their impacts on the shaft." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-44367.
Full textAbstract:
Valves are used in the most pipe systems today. There are a lot of different valves used depending on the system. They all do have in common to withstand all possible kind of failure that might occur. Common issues are cavitation, water hammer and friction torque. Friction torque is dependent on the deflection of the valve due to the high load on the valve body, for a butterfly valve this will be the disk. The pressure distributed on the disk differ depending on the opening angle of the butterfly valve. Opening angles of 3, 15 and 30 degrees are investigated. The further the valve is opened the lower the pressure will be on the downstream side and also the total pressure on the disk is decreased. This investigation shows that the impact in terms of deflection angle is constant for the lower opening degrees but for 30 degrees of opening there is a drop in deflection angle on the shaft. This means that the shaft will absorb less force due to loading on the disk and lead to reduced friction torque. With use of the same inlet pressure the angle causing the deflection increased linearly.
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Barrachina, Civera Xavier. "Distributional chaos of C0-semigroups of operators." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/28241.
Full textAbstract:
El caos distribucional fue introducido por Schweizer y Smítal en [SS94] a partir de
la noción de caos de Li-Yorke con el fín de implicar la entropía topológica positiva
para aplicaciones del intervalo compacto en sí mismo. El caos distribucional para
operadores fue estudiado por primera vez en [Opr06] y fue analizado en el contexto
lineal de dimensión infinita en [MGOP09].
El concepto de caos distribucional para un operador (semigrupo) consiste en la
existencia de un conjunto no numerable y un numero real positivo ¿ tal que para dos
elementos distintos cualesquiera del conjunto no numerable, tanto la densidad superior
del conjunto de iteraciones (tiempos) en las cuales la diferencia entre las órbitas de
dichos elementos es mayor que ¿, como la densidad superior del conjunto de iteraciones
(tiempos) en las cuales dicha diferencia es tan pequeña como se quiera, es igual a uno.
Esta tesis est'a dividida en seis capítulos. En el primero, hacemos un resumen del
estado actual de la teoría de la din'amica caótica para C0-semigrupos de operadores
lineales.
En el segundo capítulo, mostramos la equivalencia entre el caos distribucional de
un C0-semigrupo y el caos distribucional de cada uno de sus operadores no triviales.
Tambi'en caracterizamos el caos distribucional de un C0-semigrupo en t'erminos de la
existencia de un vector distribucionalmente irregular.
La noción de hiperciclicidad de un operador (semigrupo) consiste en la existencia de
un elemento cuya órbita por el operador (semigrupo) sea densa. Si adem'as el conjunto
de puntos periódicos es denso, diremos que el operador (semigrupo) es caótico en el
sentido de Devaney. Una de las herramientas mas útiles para comprobar si un operador
es hipercíclico es el Criterio de Hiperciclicidad, enunciado inicialmente por Kitai en
1982. En [BBMGP11], Bermúdez, Bonilla, Martínez-Gim'enez y Peris presentan elCriterio para Caos Distribucional (CDC en ingl'es) para operadores. Enunciamos y
probamos una versión del CDC para C0-semigrupos.
En el contexto de C0-semigrupos, Desch, Schappacher y Webb tambi'en estudiaron
en [DSW97] la hiperciclicidad y el caos de Devaney para C0-semigrupos, dando un
criterio para caos de Devaney basado en el espectro del generador in¿nitesimal del C0-
semigrupo. En el tercer capítulo, establecemos un criterio de existencia de una variedad
distribucionalmente irregular densa (DDIM en sus siglas en ingl'es) en t'erminos del
espectro del generador in¿nitesimal del C0-semigrupo.
En el Capítulo 4, se dan algunas condiciones su¿cientes para que el C0-semigrupo de
traslación en espacios L
p ponderados sea distribucionalmente caótico en función de la
función peso admisible. Ademas, establecemos una analogía completa entre el estudio
del caos distribucional para el C0-semigrupo de traslación y para los operadores de
desplazamiento hacia atras o ¿backward shifts¿ en espacios ponderados de sucesiones.
El capítulo quinto está dedicado al estudio de la existencia de C0-semigrupos para
los cuales todo vector no nulo es un vector distribucionalmente irregular. Tambi'en
damos un ejemplo de uno de dichos C0-semigrupos que además no es hipercíclico.
En el Capítulo 6, el criterio DDIM se aplica a varios ejemplos de C0-semigrupos.
Algunos de ellos siendo los semigrupos de solución de ecuaciones en derivadas parciales, como la ecuación hiperbólica de transferencia de calor o la ecuación de von
Foerster-Lasota y otros son la solución de un sistema in¿nito de ecuaciones diferenciales ordinarias usado para modelizar la dinámica de una población de c'elulas bajo
proliferación y maduración simultáneas.Barrachina Civera, X. (2013). Distributional chaos of C0-semigroups of operators [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/28241
TESIS
Premiado
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Silva, Libania Araújo. "Estrutura produtiva, desigualdade regional e distribuição de renda : dois ensaios para o estado da Bahia." Pós-Graduação em Economia, 2018. http://ri.ufs.br/jspui/handle/riufs/8694.
Full textAbstract:
The present study consists of two independent essays that approach two types of inequality on the state of Bahia which, although being related, have distinct features. The first essay sought to understand the dynamics of production and income disparities between the micro regions of the state of Bahia and to decompose the regional employment growth between 2004-2014, using the Williamson’s coefficient and the shift-share analysis. The results showed that there was a reduction of the interregional inequality of income in the Brazilian territory of Bahia, as well as the reallocation of the formal employment by the productive activities in the micro regions. On the other hand, the second essay brings a discussion about the productive structure influence on the changes in the interpersonal income distribution in the Brazilian State of Bahia. In this case, the base of the analysis is the application of Leontief-Miyazawa’s (1976) model and the impact measurement of exogenous changes on the income. For this purpose, we used data from an input-output matrix of the Bahia state for the year 2009 (PEROBELLI et al., 2015), as well as information about families consumption and income from Household Budge Survey – POF 2002/2003 – and the National Household Sampling Survey – PNAD 2009. Following, we run two simulations aiming to analyze the income’s transfer impact, respectively, on poor and extremely poor families, and the measurement of the Gini's coefficients. The results suggest that the productive sectors present different capacities among themselves to cause changes upon the income distribution, and that governmental transfer cause the reduction of income inequality in the Brazilian State of Bahia.A presente dissertação é composta por dois ensaios independentes que abordam dois tipos de desigualdade no estado da Bahia que, embora estejam inter-relacionados, possuem caráter distinto. Assim, o primeiro ensaio buscou compreender a dinâmica das disparidades produtiva e de renda entre as microrregiões do estado da Bahia e decompor o crescimento regional do emprego entre os anos 2004 e 2014, utilizando, respectivamente, o coeficiente de Williamson e a análise diferencial-estrutural. Os resultados obtidos revelaram que houve redução da desigualdade inter-regional de renda no território baiano, bem como a realocação do emprego formal gerado pelas atividades produtivas em suas microrregiões. Por sua vez, o segundo ensaio apresenta a discussão acerca da influência da estrutura produtiva sobre as alterações na distribuição interpessoal de renda no estado da Bahia. Nesse caso, a análise está centrada na aplicação do modelo de insumo-produto de Leontief-Miyazawa (1976), a partir do qual foram estimados os impactos de mudanças exógenas sobre a renda. Para tanto, foram utilizados os dados da matriz insumo-produto da Bahia para o ano-base de 2009 (PEROBELLI et al., 2015), bem como as informações de consumo e rendimento das famílias obtidas, respectivamente, por meio da Pesquisa de Orçamento Familiares (POF 2002/2003) e da Pesquisa Nacional por Amostra de Domicílios (PNAD 2009). Na sequência, foram realizadas duas simulações visando analisar o impacto da redução nas transferências de renda (benefícios previdenciários e programas de transferências direta), respectivamente, às famílias pobres e extremamente pobres, e calculados os indicadores de desigualdade de Gini. Os resultados obtidos sugerem que os setores produtivos possuem capacidades distintas entre si de provocar mudanças sobre a distribuição de renda, e que as transferências governamentais atuam como redutores das desigualdades de rendimentos no estado.
São Cristóvão, SE
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Shiell, Glenn Raymond. "The spatial distribution and temporal shifts in the biology of Holothuria whitmaei Bell [Echinodermata: Holothuroidea], Ningaloo Reef, Western Australia." University of Western Australia. School of Animal Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0081.
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[Truncated abstract] Aspects of the biology of the commercial sea cucumber Holothuria whitmaei were investigated at Coral Bay, Ningaloo Reef, Western Australia. The study was partitioned into several components: i) spatial distribution, ii) temporal changes in behaviour and iii) reproduction biology. The spatial distribution of H. whitmaei at Coral Bay was typical of that reported in the literature. H. whitmaei had distinct preferences for outer reef habitats, including the outer reef flat and reef slope. However, the distribution of H. whitmaei within these habitats was heterogeneous, or, aggregated within certain micro-habitat zones - predominantly at the leading edge of the reef flat, perpendicular to the prevailing current. Two potential biological advantages of this distribution were hypothesised: i), that species aggregation enhances prospects for gamete fertilisation, a process which may be impeded under typical densities, and ii), large deposits of detrital matter, an important food source for holothurians, may accumulate within these zones. ... A striking feature of the reproduction biology of this species was the potential for specimens to mature asynchronously. It was hypothesised that this phenomenon may be a reflection of isolated individuals located too far from conspecifics to receive pheromone signals; cues which are known to entrain synchronous gonad development in some holothurians. Hence, it was proposed that aggregations of H. whitmaei may be important to the maintenance of population recruitment, given that animals at the periphery of species concentrations may have relatively little chance of achieving fertilisation. ... Given that H. whitmaei were observed to maintain highly specific patterns of distribution, this may have significant ramifications for trophic level cascades in the outer reef zone, particularly where this species is present in higher densities (i.e. >100 ind. ha-1). The findings of this study, apart from highlighting the spatial and temporal biological attributes which may facilitate feeding and reproductive success, also emphasised the importance of biological knowledge to the management of sea cucumber fisheries. The study highlighted the need for further research to ascertain both the importance of species aggregations to population recruitment, and of the actual densities required to achieve high rates of gamete fertilisation. Such knowledge may help ultimately to identify suitable habitats for inclusion in marine protected areas.
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Shiell, Glenn Raymond. "The spatial distribution and temporal shifts in the biology of Holothuria whitmaei Bell [Echinodermata: Holothuroidea], Ningaloo Reef, Western Australia /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0081.
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Marshall, A. M. "Understanding shifts in body size distributions : a comparative study of the impacts of fishing and climate on North Sea demersal fishes." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18955/.
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The North Sea is a huge economic resource for millions of people and is undergoing dramatic changes due to overfishing and climate change. The extent to which fishing and climate are causing changes in the North Sea demersal fish community status and ecosystem health is difficult to quantify. This thesis implements newly combined empirical methods and adaptive modelling techniques in an attempt address this area of uncertainty. The first study develops a statistical framework for understanding variations in size-based indicators (SBIs), metrics for describing ecosystem health, across space and time simultaneously, as well as finding the most likely driver of observed changes. SBIs declined in the central North Sea due to fishing, but increased in the Norwegian trench region due to changing sea bottom temperature. This highlights the need to consider environmental and fishing impacts on the change in body size distribution of fish communities. The remainder of the thesis improves an existing multispecies, size-structured model by incorporating empirical relationships between growth and temperature and oxygen. Including temperature or temperature and oxygen leads to a smaller body size distribution under warmer, deoxygenated waters. When oxygen alone is included no significant effects on either the individual size or the community size structure are found. The temperature-oxygen size-structured model is subsequently used alongside extracted environmental data from two global climate models (GCMs) to project a number of size-based indicators for 2100. The most striking result is the huge difference in size-based indicators depending on which GCM is used. Corrections to the GCMs must therefore be made before the use in ecological projections. The common result, however, is that temperature and oxygen will cause changes in the body size distribution. Although these effects are much smaller than fishing effects, they demonstrate that ignoring impacts of climate change could cause considerable overestimates in the biomass of North Sea demersal fish.
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Excoffier, Mathilde. "Chance-Constrained Programming Approaches for Staffing and Shift-Scheduling Problems with Uncertain Forecasts : application to Call Centers." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112244/document.
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Le problème de dimensionnement et planification d'agents en centre d'appels consiste à déterminer sur une période le nombre d'interlocuteurs requis afin d'atteindre la qualité de service exigée et minimiser les coûts induits. Ce sujet fait l'objet d'un intérêt croissant pour son intérêt théorique mais aussi pour l'impact applicatif qu'il peut avoir. Le but de cette thèse est d'établir des approches en contraintes en probabilités en considérant l'incertitude de la demande.Tout d'abord, la thèse présente un modèle en problème d'optimisation stochastique avec contrainte en probabilité jointe traitant la problématique complète en une étape afin d'obtenir un programme facile à résoudre. Une approche basée sur l'idée de continuité est proposée grâce à des lois de probabilité continues, une nouvelle relation entre les taux d'arrivées et les besoins théoriques et la linéarisation de contraintes. La répartition du risque global est faite pendant le processus d'optimisation, permettant une solution au coût réduit. Ces solutions résultantes respectent le niveau de risque tout en diminuant le coût par rapport à d'autres approches.De plus, le modèle en une étape est étendu pour améliorer sa représentation de la réalité. D'une part, le modèle de file d'attente est amélioré et inclus la patience limitée des clients. D'autre part, une nouvelle expression de l'incertitude est proposée pour prendre la dépendance des périodes en compte.Enfin, une nouvelle représentation de l'incertitude est considérée. L'approche distributionally robust permet de modéliser le problème sous l'hypothèse que la loi de probabilité adéquate est inconnue et fait partie d'un ensemble de lois, défini par une moyenne et une variance données. Le problème est modélisé par une contrainte en probabilité jointe. Le risque à chaque période est définie par une variable à optimiser.Un problème déterministe équivalent est proposé et des approximations linéaires permettent d'obtenir une formulation d'optimisation linéaireThe staffing and shift-scheduling problems in call centers consist in deciding how many agents handling the calls should be assigned to work during a given period in order to reach the required Quality of Service and minimize the costs. These problems are subject to a growing interest, both for their interesting theoritical formulation and their possible applicative effects. This thesis aims at proposing chance-constrained approaches considering uncertainty on demand forecasts.First, this thesis proposes a model solving the problems in one step through a joint chance-constrained stochastic program, providing a cost-reducing solution. A continuous-based approach leading to an easily-tractable optimization program is formulated with random variables following continuous distributions, a new continuous relation between arrival rates and theoritical real agent numbers and constraint linearizations. The global risk level is dynamically shared among the periods during the optimization process, providing reduced-cost solution. The resulting solutions respect the targeted risk level while reducing the cost compared to other approaches.Moreover, this model is extended so that it provides a better representation of real situations. First, the queuing system model is improved and consider the limited patience of customers. Second, another formulation of uncertainty is proposed so that the period correlation is considered.Finally, another uncertainty representation is proposed. The distributionally robust approach provides a formulation while assuming that the correct probability distribution is unknown and belongs to a set of possible distributions defined by given mean and variance. The problem is formulated with a joint chance constraint. The risk at each period is a decision variable to be optimized. A deterministic equivalent problem is proposed. An easily-tractable mixed-integer linear formulation is obtained through piecewise linearizations
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Noorani, Mohd Salmi Md. "Spectral and distributional problems for homogeneous extensions of dynamical systems and the rate of mixing of two-dimensional Markov shifts." Thesis, University of Warwick, 1993. http://wrap.warwick.ac.uk/110749/.
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This thesis consists of four chapters. Chapters 1 and 2 are somewhat related in the sense that they deal with similar dynamical systems. Each chapter comes complete with its own references and notations. For the convenience of the reader, we provide an introduction and indeed an elongated summary to the whole thesis in Chapter 0. In Chapter 1, we study how closed orbits of a subshift of finite type hits to a finite homogeneous extension. In particular, we obtain an asymptotic formula for the number of closed orbits according to how they lift to the extension space. We apply our findings to the case of finite extensions and also to automorphism extensions of hyperbolic toral automorphisms. Chapter 2 deals with lifting ergodic properties of an arbitrary measure preserving transformation T to homogeneous extensions of T. Our results extends well known theorems already obtained for the case of compact group extensions of measure-preserving transformations. We also give simplified results to the special case when the base transformation is a Markov shift and the skewing-function depends on a finite number of coordinates. In Chapter 3, we look at the rate of mixing of rectangle sets of two dimensional Markov shifts with respect to the natural shift actions. We show that if one of the matrix defining the Markov measure is aperiodic then this rate is exponentially fast. We provide an example to illustrate what could happen in general.
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Bodin, Jeanne. "Observed changes in mountain vegetation of the Alps during the XXth century - Role of climate and land-use changes." Phd thesis, Université Henri Poincaré - Nancy I, 2010. http://tel.archives-ouvertes.fr/tel-00592144.
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La végétation herbacée est un bon indicateur des conditions environnementales. Pour cette raison, elle a souvent été utilisée pour mettre en évidence les changements environnementaux causés par les actions humaines, tels qu'eutrophisation, dépôts atmosphériques acides, changements de l'usage des sols ou de la pression d'herbivorie. Depuis peu, on s'intéresse aux effets des changements climatiques sur les écosystèmes en général, et sur la végétation en particulier. Le choix des zones d'étude s'est naturellement porté sur la montagne, car le gradient thermique induit par le relief (-0,56°C pour 100 mètres d'altitude) y est mille fois plus élevé qu'en plaine le long du gradient latitudinal. D'autre part, les zones de montagne sont soumises à une urbanisation et une pression agricole moindre qu'en plaine, limitant ainsi les obstacles à la migration des espèces. Ces deux arguments font des régions de montagne une zone privilégiée pour l'étude de la réponse migratoire précoce de la végétation aux changements climatiques. Jusqu'ici, les études effectuées se sont focalisées pour la plupart sur la limite supérieure des espèces, ou sur de petites zones géographiques, ou bien encore sur des zones où il est difficile de dissocier les effets du réchauffement de ceux des changements d'usage des sols, qui se produisent eux aussi à grande échelle. Une partie de cette thèse est consacrée aux milieux forestiers montagnards, dans lesquels l'effet du pastoralisme est réduit. D'autre part, une méthode basée sur la modélisation des changements de la réponse de la végétation au gradient d'altitude est développée, permettant le rééchantillonnage sur placettes non-permanentes, et ainsi d'étendre l'utilisation de données anciennes à des séries de relevés non géolocalisés. En s'appuyant sur cette méthode, deux caractéristiques de la végétation ont été analysées : la position de l'optimum d'espèces prises individuellement d'une part (données de l'Inventaire Forestier National dans les montagnes méditerranéennes du sud-est de la France), et les changements de la valeur indicatrice des communautés végétales d'autre part (vallée de la Maurienne, France). Par ailleurs, on a étudié les déplacements à long terme de la limite inférieure des espèces dans la vallée de la Bernina (Suisse), pour tester si la réponse des espèces en limite inférieure, peu étudiée jusque là, est identique à celle en limite supérieure de leur distribution. Enfin, on a étudié l'évolution de la flore d'une zone très localisée, mais par ailleurs protégée des migrations d'espèces par une large barrière physique constituée par deux glaciers (Nunatak Isla Persa, Bernina, Suisse) permettant de s'affranchir totalement des effets potentiels d'autres perturbations anthropiques concomitantes. Dans ces différentes études, les intervalles de temps entre chaque inventaire ou échantillonnage varient de 14 ans à un siècle. Chacun des cas étudiés montre une remontée des espèces en altitude : remontée moyenne de +12,6 m/décennie des optimums de 175 espèces forestières dans les montagnes méditerranéennes, communautés des forêts de Maurienne évoluant vers une végétation plus thermophile à une altitude donnée équivalent à une remontée moyenne de +29.6m/décennie, retrait de la limite inférieure des espèces en Bernina de +5,6 m/décennie, arrivée d'espèce d'étages inférieurs sur le nunatak Isla Persa. Mais d'autres phénomènes expliquant la réponse observée de la végétation sont clairement mis en cause dans cette étude : fermeture et maturation du couvert forestier relativement plus importante à basse altitude dans les montagnes méditerranéennes, eutrophisation importante de la végétation en vallée de la Maurienne probablement due à l'augmentation du trafic routier, probable fragmentation de l'habitat ou dispersion par les randonneurs en Bernina. Ces perturbations anthropiques directes jouent à des échelles de temps et d'espace comparables à l'effet anthropique indirect du changement climatique. Il est donc primordial de les prendre en compte dans les changements de végétation observés, avant de conclure à un effet du réchauffement climatique seul.
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Hussain, Zahir M. "Adaptive instantaneous frequency estimation: Techniques and algorithms." Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/36137/7/36137_Digitised%20Thesis.pdf.
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This thesis deals with the problem of the instantaneous frequency (IF) estimation of sinusoidal signals. This topic plays significant role in signal processing and communications.
Depending on the type of the signal, two major approaches are considered. For IF estimation of single-tone or digitally-modulated sinusoidal signals (like frequency shift keying signals) the approach of digital phase-locked loops (DPLLs) is considered, and this is Part-I of this thesis. For FM signals the approach of time-frequency analysis is considered, and this is Part-II of the thesis.
In part-I we have utilized sinusoidal DPLLs with non-uniform sampling scheme as this type is widely used in communication systems. The digital tanlock loop (DTL) has introduced significant advantages over other existing DPLLs. In the last 10 years many efforts have been made to improve DTL performance. However, this loop and all of its modifications utilizes Hilbert transformer (HT) to produce a signal-independent 90-degree phase-shifted version of the input signal. Hilbert transformer can be realized approximately using a finite impulse response (FIR) digital filter. This realization introduces further complexity in the loop in addition to approximations and frequency limitations on the input signal. We have tried to avoid practical difficulties associated with the conventional tanlock scheme while keeping its advantages. A time-delay is utilized in the tanlock scheme of DTL to produce a signal-dependent phase shift. This gave rise to the time-delay digital tanlock loop (TDTL). Fixed point theorems are used to analyze the behavior of the new loop. As such TDTL combines the two major approaches in DPLLs: the non-linear approach of sinusoidal DPLL based on fixed point analysis, and the linear tanlock approach based on the arctan phase detection. TDTL preserves the main advantages of the DTL despite its reduced structure. An application of TDTL in FSK demodulation is also considered. This idea of replacing HT by a time-delay may be of interest in other signal processing systems. Hence we have analyzed and compared the behaviors of the HT and the time-delay in the presence of additive Gaussian noise.
Based on the above analysis, the behavior of the first and second-order TDTLs has been analyzed in additive Gaussian noise.
Since DPLLs need time for locking, they are normally not efficient in tracking the continuously changing frequencies of non-stationary signals, i.e. signals with time-varying spectra. Nonstationary signals are of importance in synthetic and real life applications. An example is the frequency-modulated (FM) signals widely used in communication systems. Part-II of this thesis is dedicated for the IF estimation of non-stationary signals. For such signals the classical spectral techniques break down, due to the time-varying nature of their spectra, and more advanced techniques should be utilized.
For the purpose of instantaneous frequency estimation of non-stationary signals there are two major approaches: parametric and non-parametric. We chose the non-parametric approach which is based on time-frequency analysis. This approach is computationally less expensive and more effective in dealing with multicomponent signals, which are the main aim of this part of the thesis.
A time-frequency distribution (TFD) of a signal is a two-dimensional transformation of the signal to the time-frequency domain. Multicomponent signals can be identified by multiple energy peaks in the time-frequency domain. Many real life and synthetic signals are of multicomponent nature and there is little in the literature concerning IF estimation of such signals. This is why we have concentrated on multicomponent signals in Part-H.
An adaptive algorithm for IF estimation using the quadratic time-frequency distributions has been analyzed. A class of time-frequency distributions that are more suitable for this purpose has been proposed. The kernels of this class are time-only or one-dimensional, rather than the time-lag (two-dimensional) kernels. Hence this class has been named as the T -class. If the parameters of these TFDs are properly chosen, they are more efficient than the existing fixed-kernel TFDs in terms of resolution (energy concentration around the IF) and artifacts reduction. The T-distributions has been used in the IF adaptive algorithm and proved to be efficient in tracking rapidly changing frequencies. They also enables direct amplitude estimation for the components of a multicomponent
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Fomicheva, Marina. "The Role of human reference translation in machine translation evaluation." Doctoral thesis, Universitat Pompeu Fabra, 2017. http://hdl.handle.net/10803/404987.
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Both manual and automatic methods for Machine Translation (MT) evaluation heavily rely on professional human translation. In manual evaluation, human translation is often used instead of the source text in order to avoid the need for bilingual speakers, whereas the majority of automatic evaluation techniques measure string similarity between MT output and a human translation (commonly referred to as candidate and reference translations), assuming that the closer they are, the higher the MT quality. In spite of the crucial role of human reference translation in the assessment of MT quality, its fundamental characteristics have been largely disregarded. An inherent property of professional translation is the adaptation of the original text to the expectations of the target audience. As a consequence, human translation can be rather different from the original text, which, as will be shown throughout this work, has a strong impact on the results of MT evaluation. The first goal of our research was to assess the effects of using human translation as a benchmark for MT evaluation. To achieve this goal, we started with a theoretical discussion of the relation between original and translated texts. We identified the presence of optional translation shifts as one of the fundamental characteristics of human translation. We analyzed the impact of translation shifts on automatic and manual MT evaluation showing that in both cases quality assessment is strongly biased by the reference provided. The second goal of our work was to improve the accuracy of automatic evaluation in terms of the correlation with human judgments. Given the limitations of reference-based evaluation discussed in the first part of the work, instead of considering different aspects of similarity we focused on the differences between MT output and reference translation searching for criteria that would allow distinguishing between acceptable linguistic variation and deviations induced by MT errors. In the first place, we explored the use of local syntactic context for validating the matches between candidate and reference words. In the second place, to compensate for the lack of information regarding the MT segments for which no counterpart in the reference translation was found, we enhanced reference-based evaluation with fluency-oriented features. We implemented our approach as a family of automatic evaluation metrics that showed highly competitive performance in a series of well-known MT evaluation campaigns.Tanto los métodos manuales como los automáticos para la evaluación de la Traducción Automática (TA) dependen en gran medida de la traducción humana profesional. En la evaluación manual, la traducción humana se utiliza a menudo en lugar del texto original para evitar la necesidad de hablantes bilingües, mientras que la mayoría de las técnicas de evaluación automática miden la similitud entre la TA y una traducción humana (comúnmente llamadas traducción candidato y traducción de referencia), asumiendo que cuanto más cerca están, mayor es la calidad de la TA. A pesar del papel fundamental que juega la traducción de referencia en la evaluación de la calidad de la TA, sus características han sido en gran parte ignoradas. Una propiedad inherente de la traducción profesional es la adaptación del texto original a las expectativas del lector. Como consecuencia, la traducción humana puede ser bastante diferente del texto original, lo cual, como se demostrará a lo largo de este trabajo, tiene un fuerte impacto en los resultados de la evaluación de la TA. El primer objetivo de nuestra investigación fue evaluar los efectos del uso de la traducción humana como punto de referencia para la evaluación de la TA. Para lograr este objetivo, comenzamos con una discusión teórica sobre la relación entre textos originales y traducidos. Se identificó la presencia de cambios de traducción opcionales como una de las características fundamentales de la traducción humana. Se analizó el impacto de estos cambios en la evaluación automática y manual de la TA demostrándose en ambos casos que la evaluación está fuertemente sesgada por la referencia proporcionada. El segundo objetivo de nuestro trabajo fue mejorar la precisión de la evaluación automática medida en términos de correlación con los juicios humanos. Dadas las limitaciones de la evaluación basada en la referencia discutidas en la primera parte del trabajo, en lugar de enfocarnos en la similitud, nos concentramos en el impacto de las diferencias entre la TA y la traducción de referencia buscando criterios que permitiesen distinguir entre variación lingüística aceptable y desviaciones inducidas por los errores de TA. En primer lugar, exploramos el uso del contexto sintáctico local para validar las coincidencias entre palabras candidato y de referencia. En segundo lugar, para compensar la falta de información sobre los segmentos de la TA para los cuales no se encontró ninguna relación con la traducción de referencia, introdujimos características orientadas a la fluidez de la TA en la evaluación basada en la referencia. Implementamos nuestro enfoque como una familia de métricas de evaluación automática que mostraron un rendimiento altamente competitivo en una serie de conocidas campañas de evaluación de la TA.
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Jakel, Roland. "Das neue Kontaktmodell in Mechanica WF 4.0 mit Reibung : Theoretische Grundlagen und Anwendungsbeispiele." Universitätsbibliothek Chemnitz, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200900787.
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Der Vortrag stellt das neue, unendlich reibungsbehaftete Kontaktmodell der FEM-Berechnungssoftware Pro/ENGINEER Mechanica in der Version Wildfire 4.0 von PTC vor. Dabei werden sowohl die Grundlagen des reibungsfreien Kontaktes als auch die Theorie des unendlich reibungsbehafteten Kontaktmodells behandelt sowie die Grundlagen der zur numerischen Lösung in der Software verwendeten Penalty- und Newton-Raphson-Methode erläutert.
Als Anwendungsbeispiel für das reibungsfreie Kontaktmodell wird ein Zylinderrollenlager vollständig mit sämtlichen Wälzkontakten für verschiedene Lager- und Einbauspiele berechnet, die Ergebnisse umfassend dargestellt sowie eine analytische Gegenrechnung nach der Hertzschen Theorie ausgeführt, die sehr gute Übereinstimmung mit der numerischen Simulation zeigt. Für das reibungsbehaftete Kontaktmodell wird exemplarisch eine geschrumpfte Welle-Nabe-Verbindung unter Torsion berechnet. Diese wird einer analytischen Lösung sowie verschiedenen 2D-Idealisierungen (ebener Spannungszustand, ebener Dehnungszustand, 2D-Axialsymmetrie) gegenübergestellt.
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Bodnarova, Adriana. "Texture analysis for automatic visual inspection and flaw detection in textiles." Thesis, Queensland University of Technology, 2000.
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Fang, Chih-Shan, and 方之珊. "Security of Differential Phase Shift Quantum Key Distribution." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8hkctt.
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碩士國立臺灣大學
物理學研究所
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In this thesis I discuss one of the quantum key distribution (QKD) protocols, the differential phase shift (DPS) protocol, which is designed mainly for the weak coherent state source, and is considered secure under photon number splitting attack. Starting from a brief introduction to the elements needed in the field of QKD, we reviewed the proof of single photon DPS based on Shor-Preskill approach and coherent state DPS based on complementarity approach. Then key rates for DPS QKD with various sources including single photon, parametric down-conversion and coherent state are calculated. Finally, a short conclusion is given and further development is proposed.
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Chang, Chin-Hsuan, and 張進宣. "Toward Demonstration of Differential Phase Shift Quantum Key Distribution." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/4mw2ct.
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