Dissertations / Theses: 'Passive traces'

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Devillers, Delphine. "Fiabilisation de la quantification des éléments traces cationiques et anioniques par la technique d'échantillonnage DGT en milieu aquatique naturel." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0058/document.

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La technique d’échantillonnage passif DGT (« Diffusive Gradients in Thin Films ») possède de nombreux avantages (intégration des variations temporelles, abaissement des limites de quantification) qui font d’elle une méthode prometteuse pour une utilisation en réseaux de mesure pour quantifier les éléments traces dans les eaux naturelles. Cependant, il existe encore des zones d’ombre qui constituent des freins à son utilisation dans un contexte réglementaire. Ce travail a donc pour objectif d’identifier des biais potentiels et ainsi contribuer à fiabiliser la méthode. Cette étude montre que l’obtention d’un résultat avec une incertitude minimisée doit passer par la détermination expérimentale des facteurs d’élution ; cependant, l’utilisation d’une valeur standard de 0,8 pour le Cr(III) et de 0,85 pour Al(III), Cd(II), Co(II), Cu(II), Ni(II), Pb(II) et Zn(II) est proposée afin d’alléger les manipulations tout en conservant une incertitude raisonnable (<10%). L’étude de l’influence de l’encrassement des dispositifs DGT a montré que la sorption des cations Cd(II), Cu(II) et Pb(II) sur les filtres encrassés affectent respectivement peu, modérément et fortement leur accumulation dans les échantillonneurs et donc leur quantification. Des durées d’exposition de moins d’une semaine sont alors préconisées pour ces éléments. En revanche, l’encrassement a eu un impact négligeable sur le Ni(II) et sur les oxyanions As(V), Cr(VI), Sb(V) et Se(VI). Enfin, une méthode de quantification simultanée du Cr(III), essentiel à la vie, et du Cr(VI), toxique, a été développée en vue d’améliorer l’évaluation de la toxicité d’une eau. Un unique échantillonneur DGT fixe les deux formes tandis qu’elles sont ensuite sélectivement séparées par une étape d’élution. Cette méthode est robuste sur une large gamme de forces ioniques et de concentrations en sulfate mais sur une gamme de pH plus restreinte ne couvrant pas toutes les eaux naturelles (4 à 6)
The passive sampling DGT technique (Diffusive Gradients in Thin Films) has a lot of benefits (time-weighted average concentrations, low limits of quantification) and would therefore be a useful tool for monitoring studies to quantify trace elements in natural water. However, there are still some limitations and grey areas that put the brakes on the development of the method for regulatory applications. The aim of this work is to identify potential biases and contribute to increase the method reliability. This study shows that a minimized uncertainty on results can be obtained only if elution factors are experimentally determined; however, standard values of 0.8 for Cr(III) and 0.85 for Al(III), Cd(II), Co(II), Cu(II), Ni(II), Pb(II) and Zn(II) are suggested to reduce manipulations while keeping reasonable uncertainty (<10%). Studying the influence of fouling developed on DGT devices showed that the sorption of cations Cd(II), Cu(II) and Pb(II) had, respectively, a slight, moderate and strong impact on their accumulation in DGT samplers and therefore on their quantification. Samplers should then be deployed for less than one week. In contrast, fouling had a negligible impact on oxyanions As(V), Cr(VI), Sb(V) and Se(VI). Finally, a method was developed to simultaneously quantify both Cr oxidation states naturally occurring in natural waters, which are Cr(III), essential to life, and Cr(VI), toxic. Both forms are accumulated in a single DGT sampler before being selectively separated during an elution step. This method is robust for wide ranges of ionic strengths and sulfate concentrations but for a narrower range of pH (4 to 6)

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Vystavna, Yuliya. "Environmental and socio-economic determinants, their impacts on trace metals and pharmaceuticals in watercourses : a comparison on two watersheds of France and Ukraine." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14486/document.

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Les objectifs de cette étude comparative de deux bassins versants en France et en Ukraine» sont de trois ordres : i) déterminer l’occurrence des micropolluants émergents (métaux traces et molécules pharmaceutiques) dans les eaux de surface, ii) permettre leur évaluation qualitative et quantitative et enfin iii) estimer leur distribution en fonction du contexte socio-économique. Cette recherche porte sur l'analyse de l'origine, sur les propriétés physico-chimiques et sur le comportement des micropolluants (métaux traces et molécules pharmaceutiques) dans les eaux de surface des rivières Jalle (Bordeaux, France) et Udy & Lopan (Kharkiv, Ukraine). Un suivi des métaux traces et des produits pharmaceutiques dans les eaux naturelles de surface dans différents contextes et conditions climatiques a été réalisé. La description et l'analyse des facteurs environnementaux et socio-économiques influençant l’hydrochimie locale en vue de conclure sur l’opportunité et l'intérêt des micropolluants émergents comme indicateurs anthropiques du contexte socio-économique et environnemental d‘un bassin versant ont été mis en œuvre. L’étude a combiné des techniques de prélèvements d’échantillons d’eau classiques et par capteurs passifs in situ. L’analyse semi quantitative des micropolluants émergents a porté sur les métaux traces (sonde DGT) et les produits pharmaceutiques (POCIS). L’usage de ces capteurs a permis d’évaluer les différentes formes d'éléments, les sources, les variations saisonnières et spatiales, l'accumulation et les risques environnementaux. A partir des données environnementales collectées, acquises, actualisées et validées il a été possible de modéliser la consommation régionale de médicaments dans le cas de (1) la région de Kharkiv, en Ukraine, sur les rivières Lopan et Udy du bassin Seversky Donets et (2) la région de Bordeaux, en France, sur la rivière Jalle, du bassin de la Garonne. Les sites ont été sélectionnés pour représenter une diversité tant du point de vue de l'état de pollution des eaux (nature et flux) que de celui du paysage socio-économique (contexte urbain, social et indicateurs économiques). Les résultats majeurs de cette étude sont : (i) méthodologique pour le développement et la validation de protocoles d’échantillonnage classique et passif (intérêt, limites, recommandations), ii) analytique quant à la mesure des éléments traces des eaux de surface naturelles dans des conditions extrêmes, iii) scientifique par l’obtention d’un jeu de données sur l’hydrochimie des éléments traces ( présence, accumulation, origine et variabilité spatiale et temporelle et iv) prospectif quant à l’usage des métaux traces et de produits pharmaceutiques comme traceurs anthropiques de l’état des eaux naturelles de surfaces et reflet du contexte socio-économique. La modélisation socio-économique (statistique) et environnementale (balance de masse) aide à comprendre l’évolution de la qualité des eaux de surface dans leur contexte régional et permet d’identifier certains contaminants comme des indicateurs des activités anthropiques d’un bassin versant et permet de définir une typologie. L’ensemble des résultats de la thèse sont présentés sous la forme d'articles publiés ou soumis dans des revues scientifiques internationales
The PhD study focuses on the understanding of processes of the impact of environmental and socio-economic determinants on the occurrence, accumulation and distribution of trace metals and pharmaceuticals in urban watercourses. The research has been based on the analysis of the origin; physico-chemical properties and behavior of trace pollutants. The study was performed in two general steps: (i) monitoring of trace metals and pharmaceuticals in natural waters; (ii) description and analysis of environmental and socio-economic determinants that influence the water chemistry and (iii) evaluation of trace pollutants as environmental and socio-economic indicators. The monitoring of trace metals in natural water was proceed using the combination of passive and grab water sampling techniques, in order to evaluate various forms of elements, sources, seasonal and spatial variations, accumulation and environmental risks associated with the presence of contaminants in the study areas. The monitoring of pharmaceuticals was done using passive sensors to determine their capacity to register chemicals variation in time and adequation to use environmental data for the regional medicament consumption modeling. Monitoring data were also investigated in term of potential applications of trace metals and pharmaceuticals as environmental and socio-economic indicators. Two study sites were chosen: (1) the Kharkiv region in Ukraine where research was focused on the Lopan and Udy rivers of the Seversky Donets water basin and (2) the Bordeaux region in France where water monitoring was done in the Jalle River, Garonne water basin. Sites were mainly selected to represent the water pollution status in different socio-economic regions. General PhD results can be described as follows:1. The methodology for pilot and continuous monitoring of trace elements in the water with combination of traditional (grab) and innovative (passive) sampling procedures help to get data on trace elements presence, accumulation and sources, considering time variations.2. The analysis of trace metals and pharmaceuticals in two river basins of France and Ukraine and determination of environmental factors that impact on the occurrence, accumulation and distribution of these chemicals.3. The establishment of links between regional socio-economic issues and water quality data. The socio-economic and environmental modeling helps us to understand the water pollution process in regional context and give the opportunity to propose contaminants as tracers of anthropogenic activities and water quality assessment.Results of the PhD study are presented in the form of published or submitted peer-reviewed articles
Диссертация «Экологические и социально-экономические факторы распространения металлов и фармацевтических веществ в природных водах: на примере рек Харькова, Украина и Бордо, Франция» на соискание степени Доктора Философии (Environmental Science) подготовлена в рамках договора о научном сотрудничестве и совместном руководстве между Университетом Бордо, Франция и Харьковской национальной академией городского хозяйства, Украина.Актуальность работы связана с сушествующими проблемами мониторинга природных вод, недостатком исследований микро-загрязнителей водотоков как во Франции, так и в Украине, существующим экологическим риском, который возникает при поступлении и накоплении металов и фармацевтических веществ в урбанизированных водотоках, а также возможностью использования химических веществ в качестве экологических и социально – экономических индикаторов. Целью диссертационной работы стало усовершенствование методов мониторинга микро-загрязнителей в природных водах и оценка возможности использования отдельных микро-загрязнителей в качестве экологических и социально-экономических показателей. Предметом исследования являются экологические и социально-экономические факторы, влияющие на распространение металлов и фармацевтических веществ в природных водах. Объектом исследования стали реки Уды и Лопань, Харьковская область, Украина и река Жаль, регион Бордо, Франция.Основные задачи: (1) провести мониторинг рек на различные формы металлов и фармацевтические вещества с применением стандартных и инновационных (пассивных) методов отбора проб; (2) опеределить экологические и социально- экономические факторы, которые влияют на распространение микрозагрязнителей в природных водах; (3) изучить возможность использования металлов и фармацевтических веществ в качестве индикаторов антропогенного загрязнения природных вод.В результате проведенных исследований был: Впервые: (а) осуществлен мониторинг лабильных форм металлов в реках бассейна Северского Донца, в результате которого определены концентрации токсичных металлов в водотоках, источники и количество их поступления; (б) проведен мониторинг фармацевтических веществ в природных водах Украины, (в) определены концентрации и основные источники поступления фармацевтических препаратов и удельные показатели потребления различных медикаментов в Харьковском регионе; Усовершенствованы: (а) методика проведения мониторинга воды за счет применения стандартных и инновационных пассивных методов отбора проб воды в контрастных климатических и гидрологических условиях с целью исследования различных форм загрязнителей и их временных вариаций; (б) балансово-статистическая модель, которая позволяет использовать данные мониторинга природных вод для социально-экономической характеристики регионов – водопользователей; Предложены:(а) система определения геохимического фона рек на основании торий – нормализованных концентраций металлов в донных отложениях; (б) метод использование металлов и фармацевтических веществ в качестве индикаторов поступления сточных вод для идентификации несанкционированных сбросов.Основу диссертационного исследования составили натурные данные полевых исследований рек Харькова и Бордо, которые были организованы и проведены с непосредственным участием автора в 2008 – 2011 гг. Большинство лабораторных анализов было лично проведено автором в сертифицированных лабораториях Университета Бордо и Университета Орлеан, Франция.Диссертация имеет теоретическое и практическое значение для дальнейшего развития мониторинга природных вод, а также повышения уровня экологической и социальной безопасности в регионах. По теме опубликовано 4 статьи в международных журналах с высоким ИМПАКТ фактором, а также 5 статей в изданиях, реглиментированных ВАК Украины и России

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Mouttappa, Pramila. "A symbolic-based passive testing approach to detect vulnerabilities in networking systems." Phd thesis, Institut National des Télécommunications, 2013. http://tel.archives-ouvertes.fr/tel-01017860.

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Due to the increasing complexity of reactive systems, testing has become an important part in the process of the development of such systems. Conformance testing with formal methods refers to checking functional correctness, by means of testing, of a black-box system under test with respect to a formal system specification, i.e., a specification given in a language with a formal semantics. In this aspect, passive testing techniques are used when the implementation under test cannot be disturbed or the system interface is not provided. Passive testing techniques are based on the observation and verification of properties on the behavior of a system without interfering with its normal operation, it also helps to observe abnormal behavior in the implementation under test on the basis of observing any deviation from the predefined behavior. The main objective of this thesis is to present a new approach to perform passive testing based on the analysis of the control and data part of the system under test. During the last decades, many theories and tools have been developed to perform conformance testing. However, in these theories, the specifications or properties of reactive systems are often modeled by different variants of Labeled Transition Systems (LTS). However, these methodologies do not explicitly take into account the system's data, since the underlying model of LTS are not able to do that. Hence, it is mandatory to enumerate the values of the data before modeling the system. This often results in the state-space explosion problem. To overcome this limitation, we have studied a model called Input-Output Symbolic Transition Systems (IOSTS) which explicitly includes all the data of a reactive system. Many passive testing techniques consider only the control part of the system and neglect data, or are confronted with an overwhelming amount of data values to process. In our approach, we consider control and data parts by integrating the concepts of symbolic execution and we improve trace analysis by introducing trace slicing techniques. Properties are described using Input Output Symbolic Transition Systems (IOSTSs) and we illustrate in our approach how they can be tested on real execution traces optimizing the trace analysis. These properties can be designed to test the functional conformance of a protocol as well as security properties. In addition to the theoretical approach, we have developed a software tool that implements the algorithms presented in this paper. Finally, as a proof of concept of our approach and tool we have applied the techniques to two real-life case studies: the SIP and Bluetooth protocol

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Toumi, Khalifa. "A trust framework for multi-organization environments." Phd thesis, Institut National des Télécommunications, 2014. http://tel.archives-ouvertes.fr/tel-00997693.

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The widespread of inexpensive communication technologies, distributed data storage and web services mechanisms currently urge the collaboration among organizations. Partners are participating in this environment motivated by several advantages such as: (1) the ability to use external and professional resources, services and knowledge, (2) the reduction of time-consuming requirements and (3) the benefaction of experts experience. However, this collaboration is not perfect since several problems can arise such as the misuse of resources, disclosure of data or inadequate services. Therefore, security is an important concern of the participants. In particular trust management and access control are one of the major security issues for an organization. This thesis addresses these two areas in particular. It proposes a novel and comprehensive trust framework for Multi-Organization Environments. Our approach is organized in four parts. First, we propose a vector based model approach for defining trust vectors. These vectors evaluate a set of requirements, under conditions, and provide a degree of confidence. In our approach, we consider two different types of vectors. On the one hand, a vector that links a user to an organization and, on the other hand, a vector that links two organizations. We also show how these vectors are evaluated and shared among the different organizations, and how we combine the provided trust information in order to enhance the security. Second, the TRUST-OrBAC model was designed to add the previous trust approach to the ORBAC model. Moreover, this solution was applied with a real collaboration network between companies. Third, we present a trust ontology methodology based on access control concepts. This ontology will be used to share the trust beliefs between participants and to make equivalence between their trust objectives. How to define this trust relationship, how to understand the trust objective of a requester, and how to evaluate the recommendation value is addressed in this thesis. Fourth, we improve our work by designing a passive testing approach in order to evaluate the behavior of a user. This contribution is based on the monitoring tool MMT. Finally the entire architecture of our system is proposed

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Lelarge, Maria Lidia Meideros Vignol. "Thermochronologie par la méthode des traces de fission d'une marge passive (dôme de Ponta Grossa, se Brésil) et au sein d'une chaîne de collision (zone externe de l'arc alpin, France)." Université Joseph Fourier (Grenoble), 1993. https://tel.archives-ouvertes.fr/tel-00603209.

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La méthode de datation par les traces de fission sur apatite a été appliquée dans deux contextes différents: une marge passive (dôme de Ponta Grossa dans l'état du Paraná au sud-est du Brésil) et une chaine de collision (massifs de Belledonne et du grand Châtelard, ainsi que la zone dauphinoise interne, dans les Alpes occidentales françaises). L'objectif de ce mémoire était de retracer l'histoire du refroidissement des roches de ces deux régions et dans une certaine mesure d'établir une chronologie des processus géodynamiques qui s'y sont produits. Les apatites du dôme de Ponta Grossa ont enregistré le refroidissement provoqué par la surrection-érosion de la serra do mar, chaïne montagneuse qui longe la côte sud-est brésilienne. La serra do mar correspond probablement a une réponse tardive à l'ouverture de l'Atlantique sud, qui s'est effectuée vers 120 MA aux environs de la latitude 26s. Les âges tracés de fission (tf) apparents des 21 échantillons analyses s'échelonnent entre 100 MA et 80 MA. L'analyse des résultats tf sur apatite, obtenus sur les 33 échantillons alpins, indique que l'histoire du refroidissement de cette région est extrêmement complexe. Les âges apparents tf sont compris entre 7,5 MA et 1,7 MA. Les taux de dénudation sont variables selon le secteur étudié et expriment ainsi un comportement différent vis-à-vis des processus tectoniques. Depuis le miocène supérieur jusqu'a 1 MA, les taux de dénudation apparents sont estimes a 0,4 mm/an pour le massif de Belledonne et à 0,7 mm/an pour le grand Châtelard et la zone du flysch. A partir d'un million d'années jusqu'à l'actuel le taux de dénudation apparent augmente et devient de l'ordre de 2 mm/an, pour l'ensemble de la région

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VASSIO, LUCA. "Data Analysis and Modelling of Users’ Behaviour on the Web." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2703665.

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As novas tecnologias e as suas aplicações modificaram as nossas interações com o mundo que nos circunda. O advento da Internet, com a sua capilaridade e seu uso generalizo, foi a transformação mais importante e repentina dos últimos 30 anos. Minha pesquisa nasce da necessidade de entender como as pessoas interagem com a web, de compreender como a web está evoluindo, e de modelar os hábitos e comportamentos dos usuários da Internet. Logs que registram o comportamentos dos usuários interagindo com a web, coletados através de medições passivas, oferecem uma oportunidade inigualável para estudar esses fenômenos. Baseado nesse tipo de logs, o meu trabalho foca em dois aspectos complementares: (i) na análise da navegação dos usuários e (ii) na modelagem do comportamento dos usuários. Muitos desafios devem de ser enfrentados para viabilizar essa análise: medições passivas são em geral volumosas, ou seja \textit{big data}, e por isso requerem metodologias e infra-estrutura escaláveis para seu processamento. A análise dos dados necessita de métricas significativas e a introdução de metodologias inovadoras para a obtenção de informações confiáveis, filtradas, limpas e, sobretudo, úteis. A análise requer métodos estatísticos, de aprendizagem de máquina e de mineração de dados robustos. Além disso, a análise deve servir de base para a criação de modelos analíticos que sejam aderentes à realidade. Em soma, entender a aplicabilidade dos modelos é um passo fundamental para analisar possíveis cenários de uso e otimizar a performance dos serviços web. Durante o doutorado eu analisei três anos de dados de cerca de 30\,000 consumidores de Internet de alta velocidade, reconstruindo a atividade dos usuários na web. Reconstruí as suas atividades de navegação, destacando a evolução no uso de diferentes dispositivos, a estrutura da navegação e a interação dos usuários com as redes sociais e os motores de busca. Introduzi uma nova metodologia de aprendizado de máquina para identificar páginas web e sites intencionalmente solicitados pelos usuários nos logs de medidas passivas. A partir dessas informações, demonstrei ser possível criar uma assinatura baseado nos sites visitados por cada usuário, que pode ser utilizadas para re-identificar usuários, com claras implicações para a privacidade on-line. Modelei a sequência de serviços visitados pelos usuários na web, representando-os de forma sucinta e interpretável. Mostrei como extrair automaticamente grupos de sites similares ou conectados, agrupando os interesses de usuários e de comunidades. Também modelei a interação dos usuários com sistemas de recomendação on-line, apresentando um modelo de comportamento que captura o impacto da dinâmica temporal dos anúncios exibidos nas páginas. Finalmente, mostrei como melhorar os ganhos de uma plataforma de propaganda digital, otimizando os horários nos quais os anúncios deveriam ser exibidos aos usuários. Os resultados dessa tese têm várias implicações para diferentes personagens na Internet e para a comunidade acadêmica. Na atual transformação digital, todas as pessoas e todos os objetos estão produzindo dados que podem ser explorados para criar novas aplicações revolucionarias. A análise dos dados de navegação nos permite realizar transformações incríveis não só na web, mas também em nossas cidades, na industria e na produção de energia. Aproveitar o conhecimento do comportamento do usuário obtido a partir de medições na rede e depois modelar e otimizar os sistemas, como feito neste trabalho, será um fator chave para a concepção de futuras cidades inteligentes.
Le nuove tecnologie e le loro applicazioni modificano il nostro approccio con ciò che ci circonda. L'avvento di Internet, con la sua capillarità e pervasività, è stata la trasformazione più importante e repentina degli ultimi 30 anni. La mia ricerca è stata guidata dalla necessità di capire come le persone interagiscano con il web, di catturare come il web stesso cambi, e di modellare le abitudini e i comportamenti degli utenti. Tracce e registri dell'attività online, altrimenti dette misure passive, offrono informazioni inestimabili per raggiungere questi obiettivi. Grazie a queste tracce, il mio lavoro si concentra nello studiare il comportamento delle persone quando navigano su Internet, da due punti di vista complementari: (i) l'analisi dei dati di navigazione e (ii) i modelli analitici di comportamento. Tuttavia, vi sono molteplici sfide da affrontare: questo tipo di dati, detti \textit{big data}, necessitano di hardware e software scalabili, e dell'introduzione di metodologie e metriche innovative per ottenere informazioni che siano pulite, affidabili e soprattutto utili. L'analisi dati viene eseguita grazie a metodi statistici, di machine learning e di data mining. Inoltre, l'analisi è un prerequisito per costruire dei modelli analitici dei fenomeni studiati, che siano il più possibile aderenti alla realtà. Infine, capire l'applicabilità dei modelli costruiti è un passaggio fondamentale per ottimizzare le prestazioni e capire i possibili scenari. Più in dettaglio, durante il mio dottorato, ho analizzato 3 anni di dati di circa 30\,000 abitazioni, e ne ho ricostruito le attività online. Grazie a ciò, ho potuto mostrare l'evoluzione nell'utilizzo di diversi dispositivi, la struttura intrinseca delle navigazioni e l'interazione con le reti sociali e i motori di ricerca. Ho introdotto dei sistemi automatici per identificare le pagine e i servizi web intenzionalmente richiesti. Ho anche analizzato la costruzione di profili degli utenti, tracciando i loro domini visitati, per poi mostrare come poterli re-identificare nel futuro. Ho modellato le sequenze di siti visti, rappresentandole succintamente in una maniera facilmente interpretabile. Ho mostrato come estrarre automaticamente gruppi di siti web simili in contenuto o strettamente relazionati, e come riunire interessi e trend di utenti singoli o intere comunità. Ho anche modellato l'interazione con i sistemi di raccomandazione, introducendo un modello di comportamento umano che cattura l'impatto della dinamica temporale delle pubblicità mostrate. Infine, ho migliorato sperimentalmente i ricavi di una piattaforma di pubblicità, ottimizzandone i tempi di visualizzazione delle inserzioni. I miei risultati hanno diverse implicazioni per i molteplici attori nel panorama web e per il mondo della ricerca. Seguendo un corretto approccio scientifico, I dataset usati in questa tesi sono resi disponibili in modo anonimizzato per la comunità, in modo da garantire la riproducibilità dei miei risultati. Inoltre, il tema della privacy online in un mondo in forte cambiamento è stato affrontato e analizzato, con l'obiettivo di trovare un compromesso tra il bisogno di ottenere la conoscenza per lo sviluppo delle tecnologie e la necessità di non violare la riservatezza degli individui. Infine, l'attuale trasformazione digitale comporta che tutte le persone e oggetti producono dati che possano essere sfruttati per creare sconvolgenti possibilità. L'analisi dati ci permette di realizzare incredibili trasformazioni non solo di Internet, ma anche nelle nostre città, nella produzione di energia o nell'industria. Sfruttare i comportamenti delle persone che si ottengono attraverso questi dati, modellare e ottimizzare le prestazioni dei sistemi così come ho fatto in questo lavoro, sarà un fattore chiave per progettare le città intelligenti di un futuro molto vicino.
New technologies and services strongly transform our approach with the world. The Internet and its pervasive use was certainly the most dramatic leap in the last 30 years. My research was driven by the need to understand how people interact with the web, capturing its characteristics and changes, and modelling people's inner habits and interactions. Traces and logs of users' behaviours collected in the Internet (i.e., passive measurements) offer invaluable information to obtain this goal. Thanks to these passive traces, my work focuses on studying the behaviour of the users on the Internet, with focus on two complementary aspects: (i) data analytics, and (ii) user modelling. There are many key challenges to face: (big) data requires the use of scalable software and hardware. It demands also the introduction of innovative methodologies and meaningful metric to obtain trustable, filtered, clean and useful information. Data analytics is performed by means of a variety of statistical, machine learning and data mining approaches. Moreover, it is also a pre-requisite for creating analytical models of the studied phenomena, that should be as much as possible adherent to the reality. Lastly, understanding the applicability of derived models is a fundamental step for optimizing performances and understanding possible scenarios. More in details, during my PhD I analyzed 3 years of data of about 30\,000 households. I reconstruct users' online activity. Thanks to this, I was able to highlight device usage evolution, the intrinsic structure of the navigation and the interactions with social networks and search engines. I introduced a new machine learning approach to identify the intentionally visited web-pages and web-sites. Then, I built specific users' profiles, fingerprinting their visited domains, and then I showed how to re-identify users in a future time. I modelled the sequence of the visited web services, representing them in a succinct and interpretable manner. I showed that I can automatically extract groups of similar or likely connected web-sites, and monitor the interests and browsing patterns of single users or communities. I also modelled the user interaction with online recommendation systems, introducing a user behavioural model that captures the impact of the temporal dynamics of shown advertisement. Lastly, I demonstrate how to improve the revenue of an advertisement platform, optimizing the timings when ads are shown to users. My findings have several direct implications to the different Internet actors and to the research community. Following the scientific approach, I made available the anonymized datasets for the community, in order to guarantee the reproducibility of my results. Moreover, I addressed the problem of privacy online in today changing world, with the objective of finding a trade-off between the desire to obtain knowledge for shaping new technologies and the need to not violate the privacy of individuals. Finally, the current digital transformation implicates that everyone and everything produce data that can be exploited to create new disruptive capabilities. Data analytics allows us to realize incredible transformations not only in the web, but also in our cities, in the energy production, and in manufacturing. Exploiting the knowledge of the users' behaviour from these data, modelling and optimizing system performances as I did in my work, will be a key factor for designing near future smart-cities.

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Villanueva, Jessica Denila. "Suivi par capteurs passifs des polluants émergents dans les eaux de surface en contexte urbain." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14186/document.

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L’étude a pour objectif de déterminer la qualité des eaux de surface sous différentes conditions climatiques et pratiques de gestion des eaux de surface. Trois sites ont étés choisis pour: (1) la rivière Jalle de Blanquefort, (2) le lac de Bordeaux, France et (3) la rivière Pasig aux Philippines. Les sites français présentent des collecteurs d'eau qui se déversent directement dans les eaux de surface. La rivière Pasig sert de collecteur d'eaux usées en l’absence de stations de traitement des eaux usées et collectées. Au cours des campagnes de mesure, il a été possible de suivre l’impact de la variabilité climatique (pluviométrie) et d’événements aléatoires sur la qualité chimiques (éléments traces métalliques et polluants organiques) des eaux ; en combinant échantillonnage classique et par capteurs passifs. Les propriétés physico-chimiques de l'eau ainsi que les caractéristiques des particules et l'utilisation d'analyses statistiques permettent de préciser le comportement des molécules détectées et de décrire l’evolution hydrochimique des eaux de surface urbaines et estuariennes vis-à-vis d’aléas climatiques contrastés
The study aimed to assess the water quality of the surface water in differingclimate conditions and management practices. Three interesting sites were chosen, (1)Jalle River and (2) Bordeaux Lac both in France and the (3) Pasig River in thePhilippines. The French sites have rainfall and run-off collectors that directly dischargewater to the water bodies. Pasig River, on the other hand, becomes a waste collector aswaste management and treatment plant are lacking. Trace metals and organics(pesticides, herbicides, pharmaceuticals and drugs) were measured. Conventional andpassive sampling approches were employed. The mass fluxes were obtained in order tocalculate the pollution transport. Physico-chemical properties and the particlecharacteristics, integrating statistical analyses, facilitated in explaining the behavior of themeasured molecules and describing the hydrological system in relation to climatevariability

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Veyret, Nathalie. "Traces d'un passage : l'oeuvre de Barbara Pym." Bordeaux 3, 1996. http://www.theses.fr/1996BOR30036.

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Cette etude de l'oeuvre de barbara pym inclut pour la premiere fois en france l'examen des papiers personnels de l'auteur, deposes a la bodleian library, oxford : manuscrits des romans, journal, correspondance, carnets litteraires, textes de conferences. La richesse de ces materiaux permet d'envisager l'etude des romans sous un nouveau jour. L'oeuvre se fait trace du passage de l'auteur dans l'angleterre de l'apres-guerre. Veritable historiographie, elle montre des personnages plutot ternes qui vivent une vie rangee, loin du bruit et de la fureur. Elle pourrait s'articuler sur l'aphorisme de cioran : "rater sa vie, c'est acceder a la poesie". Le monde de pym est le monde de l'insucces, dans lequel les hommes et les femmes se livrent a des jeux de roles sans jamais reussir a communiquer. Les liaisons sont dangereuses, aussi sont-elles evitees. On leur prefere une solitude confortable, agrementee de petits plaisirs egoistes, dont la bonne chere n'est pas des moindres. Le quotidien est detourne et les personnages s'inventent les cles d'une vie marquee au sceau de l'insignifiance. Le texte pymien aussi joue de la banalite pour mieux mettre en lumiere la tragedie de la vie humaine. La tension du recit tient ainsi au poids qui se cache derriere l'insignifiance. Pym reussit a ecrire le livre sur rien appele par flaubert
This study of the works of barbara pym includes for the first time in france the analysis of the author's personal papers deposited at the bodleian library : manuscripts of the novels, her diary, letters, notebooks and conference scripts. The wealth of this material is the starting point for a new study of the novels. The works are the traces of the author's passage in post-var england. Pym's characters are rather dull and lead a quiet unobtrusive life. Pym's world is the world of failure, in which men and women play games but never achieve communication. Love affairs are so dangerous that they are avoided. Solitude sometimes is best company, especially when relieved by the prosaic, mundane pleasures of food for instance. The characters invent a life of their own, in which humdrum tasks play a prominent role. Pym's writing also uses banality to emphasise the tragedy of human life. Simple words bide a profound meaning. Pym achieves this book about nothing flaubert wished for

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Fabbroni, Nicoletta <1979&gt. "Numerical simulations of passive tracers dispersion in the sea." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1733/1/Fabbroni_Nicoletta_Tesi.pdf.

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Fabbroni, Nicoletta <1979&gt. "Numerical simulations of passive tracers dispersion in the sea." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1733/.

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Siberlin, Charlotte. "Time-scales of passive tracers in the ocean with paleoapplications." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59790.

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Thesis (S.M. in Climate Physics and Chemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 131-134).
Quantifying time-responses of the ocean to passive and active tracers is critical when interpreting paleodata from sediment cores. Surface-injected tracers are not spreading instantaneously or uniformly throughout the ocean. To obtain insights into these time-scales, a transition matrix is used to compute successive states of a passive tracer concentration in the global ocean. Times to equilibrium are longer than 1500 years for any one region in the global ocean and, near the equilibrium, concentration gradients give time-lags from hundreds to thousands of years between the Atlantic and Pacific bottom, depending on the injection region and the nature of the boundary condition. Ice volume (glacio-eustatic) corrections to deep-sea and surface values cannot be assumed instantaneous, challenging previous paleodata interpretations from sediment cores. Preliminary results on time-responses of the ocean to active tracers, using a global circulation model limited to the North Atlantic box, show no major differences between a freshwater and a dye input, at least during the first 50 years of the experiment and for a small amount of freshwater.
by Charlotte Siberlin.
S.M.in Climate Physics and Chemistry

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Ferrari, Raffaele. "Dispersion of passive and active tracers in the upper ocean /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035412.

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Matheu, Nathalie. "Passage à l’écriture, écriture du passage : sur les traces d’adultes migrants en ateliers d’écriture." Thesis, Montpellier 3, 2018. http://www.theses.fr/2018MON30089.

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Depuis une vingtaine d’années, la didactique de l’écrit enrichit ses réflexions et ses pratiques par les recherches menées notamment en sciences du langage et en génétique textuelle (Fabre, 1990 ; Doquet, 2011 ; Chiss, 2012). Ces travaux, qui envisagent l’écriture dans sa dynamique scripturale, s’interrogent sur la façon dont se construit l’écriture en acte (Fénoglio & Chanquoy, 2007). En effet, après les travaux de J. Derrida (1967) et de J. Goody (1977/1979), qui ont destitué l’hégémonie de la pensée logocentriste, nous ne pouvons plus réduire l’écriture à un code second, comme double représentation de la pensée et du langage qui l’oralise. L’écriture, par ses fonctions spécifiques, tisse des liens étroits avec la mémoire, à la fois par l’activation anamnésique et par l’usage averti des artefacts hypomnésiques (instrument graphique et support). Ce double jeu de la mémoire (anamnèse et hypomnèse), qui répond à celui de l’écriture, permet le passage au scriptural en orchestrant une chaîne qui, de façon symbolique, réunit voix et écriture et ouvre ainsi des espaces d’inscription du sujet écrivant. Cette réflexion épistémologique a nourri l’élaboration de séquences didactiques expérimentales favorisant le passage à l’écriture d’adultes migrants, sous la forme d’ateliers d’écriture, qui s’inscrivent dans l’introduction didactique des Arts du Langage (Meschonnic, 1982 ; Auger & Pierra, 2006 ; Aden, 2008) dans des contextes d’enseignement-apprentissage de français langue seconde (FLS). Ce dispositif a permis de construire un corpus de 74 textes manuscrits, recueillis en observation participante, en contexte associatif. L’analyse qualitative des données, en mobilisant les outils théoriques et méthodologiques de l’analyse du discours et de la génétique textuelle, s’est organisée autour d’une triple mise en perspective des notions de passage et d’écriture. L’examen des traces graphiques permet en effet de mettre au jour (1) les stratégies d’entrée des scripteurs dans l’écriture en FLS, (2) les retours sur le déjà écrit, notamment par le biais des ratures, qui donnent à voir une dialogisation interne (Bres, 1988) inhérente à la mise en écriture et (3) l’émergence des souvenirs reconstruisant le parcours migratoire, créant ainsi une écriture du passage
For the last twenty years, writing pedagogy has been enriched in reflection and practice by research, most notably, from linguistics and genetic criticism (Fabre, 1990; Doquet, 2011; Chiss, 2012). These studies, which consider writing within its scriptural dynamic, have examined the construction of the act of writing (Fénoglio & Chanquoy, 2007). In light of the contributions of J. Derrida (1967) and J. Goody (1977/1979), who dismissed the hegemony of logocentric thought, writing can effectively no longer be reduced to a secondary code, a dual representation of thought and the language that gives voice to it. With its specific functions, writing is intertwined with memory, both through anamnesic activation and the informed use of hypomnesic artifacts (writing instruments and media). The double memory game (anamnesis and hypomnesis), which contributes to the process of writing, enables the transition to the written mode by orchestrating a chain that, in a symbolic way, links voice and writing and thus opens inscriptional spaces for the writing subject. This epistemological refection supported the development of experimental instructional sessions, which took the form of writing workshops, designed to support migrant adults’ transition to writing. The workshops were implemented as part of a broader introduction to the language arts (Meschonnic, 1982; Auger & Pierra, 2006; Aden, 2008) in contexts of teaching and learning French as a second language (FSL). This arrangement allowed for the construction of a corpus of 74 textual manuscripts, collected by means of participant observation in the context of volunteer work. The qualitative analysis of data, examined through the application of theory and methods from discourse analysis and textual genetics, was organized around a three-pronged approach to the notions of transition and writing. The examination of graphic marks makes it possible to uncover (1) the initial strategies of FLS writers, (2) their reconsideration of previously written text, notably by means of deletions, which reveal inner dialogism (Bres, 1988) inherent to the production of writing, and (3) the emergence of memories that reconstruct the migrant experience, and which constitute writing in transition

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Sundermeyer, Miles Aaron. "Mixing in the North Atlantic tracer release experiment : observations and numerical simulations of Lagrangian particles and passive tracer." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/57846.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.
Includes bibliographical references (leaves 89-90).
by Miles Aaron Sundermeyer.
M.S.

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Zygalakis, Konstantinos C. "Effective diffusive behaviour for passive tracers and inertial particles : homogenization and numerical algorithms." Thesis, University of Reading, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494970.

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The long-time / large-scales behaviour of solutions to stochastic differentials equations (SDEs) describing the motion of a single particle in a velocity field subject to molecular diffusion is the central topic of this thesis. The particle can be considered mass-less (passive tracers) or not (inertia! particles). Under appropriate assumptions on the different velocity fields studied, we show, using homogenization theory, that the effective behaviour of passive tracers and inertial particles is described by a pure diffusion characterized by the effective diffusivity matrix K.

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Poulier, Gaelle. "Etude de l’échantillonnage intégratif passif pour l’évaluation réglementaire de la qualité des milieux aquatiques : application à la contamination en pesticides et en éléments trace métalliques des bassins versants du Trec et de l’Auvézère." Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0032/document.

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Parce qu’ils sont peu coûteux, faciles d’utilisation, et surtout très efficaces, les pesticides sont devenus une composante majeure de l’agriculture moderne et se sont imposés dans de nombreuses activités urbaines et domestiques. Ces molécules se retrouvent aujourd’hui dans tous les compartiments de l’environnement notamment dans les milieux aquatiques. Le suivi resserré des substances actives et de leurs résidus, présents dans l’environnement à des concentrations potentiellement dommageables pour les écosystèmes, apparaît aujourd’hui comme une nécessité. L’application de la Directive cadre sur l’eau, l’une des principales réglementations européenne ciblant les eaux, requiert des techniques d’échantillonnage et d’analyse performantes, alliant haute sensibilité, facilité de mise œuvre, coûts abordables, et surtout précision et fiabilité. Actuellement, la méthodologie employée consiste en des prélèvements ponctuels d’eau à pas de temps lâche (une fois par mois en général) suivi de l’analyse en laboratoire. Cette approche souffre d’un manque de représentativité temporelle, couplée à une sensibilité analytique souvent peu satisfaisante. Les techniques d’échantillonnage passif développées au cours des 20 dernières années pourraient être intégrées dans les réseaux de surveillance réglementaires afin de pallier ces manques, mais des questions subsistent encore quant à leur opérationnalité. Ces travaux de thèse visent à développer puis tester les échantillonneurs passifs sur le terrain afin de déterminer leur adéquation avec les exigences de la Directive cadre sur l’Eau, et le cas échéant, mettre en évidence les principaux verrous scientifiques résiduels. L’originalité de ce travail réside dans:- la variété des outils évalués : trois échantillonneurs différents ont été étudiés (Le Polar Organic Chemical Integrative Sampler (POCIS), le Chemcatcher et le Diffusive Gradient in Thin film (DGT). Les méthodes classiques de prélèvement ponctuels ont également été mise en œuvre.- la variété des environnements étudiés : deux bassins versant très différents ont été considérés, l’un présentant une contamination en pesticides forte, l’autre une contamination modérée.- La mise en en œuvre des échantillonneurs passifs dans un réel contexte réglementaire, les cours d’eau choisis faisant l’objet d’un contrôle opérationnel. Les données acquises avec les échantillonneurs passifs ont ainsi pu être comparées avec les suivis de l’Agence de l’Eau
The intensive use of pesticides in agriculture and urban activities since the 1950s has led to diffuse contamination of environmental compartments (air, soil, water). The presence of these molecules can lead to toxic effects for biota. The implementation of the Water Framework Directive (WFD) requires the use of an efficient monitoring network, based on reliable sampling and analytical techniques. Nowadays, grab sampling followed by extraction of analytes and chromatographic analysis is the most widespread strategy because of its simplicity of implementation but it also has numerous drawbacks. The crux of the issue lies in the lack of temporal representativeness and the low analytical sensibility. An alternative strategy to overcome some of these problems could be the use of passive samplers. This contribution aims at discuss about the possible application of passive samplers in regulatory monitoring programs. The originality of this work lies in :The variety of tested devices: three different samplers was studied (The Polar Organic Chemical Integrative Sampler (POCIS), the Chemcatcher and the Diffusive Gradient in Thin Film (DGT). Conventional grab sampling strategies were also evaluated.The variety of studied environments: two very different watersheds were selected. The first one presented a high level of contamination; the second had a low contamination in pesticides.The implementation of passive samplers in a real regulatory context, as the selected streams were monitored by the Water Agency for operational control. Data from the Water Agency could therefore be compared with passive sampler data

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Pöschke, Patrick. "Influence of Molecular Diffusion on the Transport of Passive Tracers in 2D Laminar Flows." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19526.

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In dieser Arbeit betrachten wir das Strömungs-Diffusions-(Reaktions)-Problem für passive Markerteilchen, die in zweidimensionalen laminaren Strömungsmustern mit geringem thermischem Rauschen gelöst sind. Der deterministische Fluss umfasst Zellen in Form von Quadraten oder Katzenaugen. In ihnen tritt Rotationsbewegung auf. Einige der Strömungen bestehen aus wellenförmigen Bereichen mit gerader Vorwärtsbewegung. Alle Systeme sind entweder periodisch oder durch Wände begrenzt. Eine untersuchte Familie von Strömungen interpoliert kontinuierlich zwischen Reihen von Wirbeln und Scherflüssen. Wir analysieren zahlreiche numerische Simulationen, die bisherige theoretische Vorhersagen bestätigen und neue Phänomene offenbaren. Ohne Rauschen sind die Teilchen in einzelnen Bestandteilen des Flusses für immer gefangen. Durch Hinzufügen von schwachem thermischen Rauschen wird die normale Diffusion für lange Zeiten stark verstärkt und führt zu verschiedenen Diffusionsarten für mittlere Zeiten. Mit Continuous-Time-Random-Walk-Modellen leiten wir analytische Ausdrücke in Übereinstimmung mit den numerischen Ergebnissen her, die je nach Parametern, Anfangsbedingungen und Alterungszeiten von subdiffusiver bis superballistischer anomaler Diffusion für mittlere Zeiten reichen. Wir sehen deutlich, dass einige der früheren Vorhersagen nur für Teilchen gelten, die an der Separatrix des Flusses starten - der einzige Fall, der in der Vergangenheit ausführlich betrachtet wurde - und dass das System zu vollkommen anderem Verhalten in anderen Situationen führen kann, einschließlich einem Schwingenden beim Start im Zentrum einesWirbels nach einer gewissen Alterungszeit. Darüber hinaus enthüllen die Simulationen, dass Teilchenreaktionen dort häufiger auftreten, wo sich die Geschwindigkeit der Strömung stark ändert, was dazu führt, dass langsame Teilchen von schnelleren getroffen werden, die ihnen folgen. Die umfangreichen numerischen Simulationen, die für diese Arbeit durchgeführt wurden, mussten jetzt durchgeführt werden, da wir die Rechenleistung dafür besitzen.
In this thesis, we consider the advection-diffusion-(reaction) problem for passive tracer particles suspended in two-dimensional laminar flow patterns with small thermal noise. The deterministic flow comprises cells in the shape of either squares or cat’s eyes. Rotational motion occurs inside them. Some of the flows consist of sinusoidal regions of straight forward motion. All systems are either periodic or are bounded by walls. One examined family of flows continuously interpolates between arrays of eddies and shear flows. We analyse extensive numerical simulations, which confirm previous theoretical predictions as well as reveal new phenomena. Without noise, particles are trapped forever in single building blocks of the flow. Adding small thermal noise, leads to largely enhanced normal diffusion for long times and several kinds of diffusion for intermediate times. Using continuous time random walk models, we derive analytical expressions in accordance with numerical results, ranging from subdiffusive to superballistic anomalous diffusion for intermediate times depending on parameters, initial conditions and aging time. We clearly see, that some of the previous predictions are only true for particles starting at the separatrix of the flow - the only case considered in depth in the past - and that the system might show a vastly different behavior in other situations, including an oscillatory one, when starting in the center of an eddy after a certain aging time. Furthermore, simulations reveal that particle reactions occur more frequently at positions where the velocity of the flow changes the most, resulting in slow particles being hit by faster ones following them. The extensive numerical simulations performed for this thesis had to be done now that we have the computational means to do so. Machines are powerful tools in order to gain a deeper and more detailed insight into the dynamics of many complicated dynamical and stochastic systems.

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18

Gough, William A. (William Arthur). "Lateral and isopycnal mixing of passive and active tracers in an ocean general circulation model." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70297.

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The parameterization of isopycnal mixing is examined in an ocean general circulation model. The results are compared to those obtained with lateral mixing.
In the equilibrium experiments, the isopycnal case has more gyre kinetic energy, a less intense thermohaline circulation, and less interior downwelling than the lateral case. Convection is replaced by enhanced vertical diffusion in the isopycnal case.
In the time dependent passive tracer experiments, the isopycnal case has smaller depth penetration of a surface released tracer. This is likely due to induced recirculation rather than numerical limitations.
The active tracer experiments examine the long term asymmetric behaviour of warm and cold surface anomalies introduced in an abrupt and gradual fashion for the lateral and isopycnal models. The thermal anomalies produce asymmetric transient responses. The abrupt and gradual changes produce the same equilibrium but different transient responses. The isopycnal case responds more rapidly and energetically than the lateral case.

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19

Watkins, Eric Andrew. "Development of Potential Remote Coal Mine Fire Response Measures: Use of Multiple Passive Source Tracers and Simulation of High Expansion Foam Flow in Simulated Gob Material." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83788.

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This thesis examines potential improvements to current coal mine fire response measures. In the event of a fire scenario, indirect testing and analysis of the exhausting air is needed to characterize changes in the fire. The application of multiple passive source tracers provides improved detail of complex ventilation interactions over an extended period of time. The first work in this thesis details the testing of the passive release rates for three Perfluorocarbon tracer compounds over a 180-day period. The results of this study demonstrate the ability for the permeation plug release vessel design to release Perfluorocarbon tracers at a steady rate. Current response methods for a fire in a coal mine gob consist of injection of inert gas and sealing of the mine openings. Injection of high expansion foam into the gob from the surface has potential to improve extinguishment of the fire and reduce the time needed to bring the mine back to an operational state. The applicability of this method requires computational modeling and field testing. The second part of this thesis determines the Darcy and Forchheimer values for high expansion foam flow in simulated gob material with a lab experiment. The experiment was replicated in the CFD software, OpenFOAM, to validate the methods for calculation of the Darcy and Forchheimer values. The results of this study provide a tested methodology for a future full scale modeling of high expansion foam injection in a coal mine gob.
Master of Science

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20

Hankin, Barry Gwyn. "Modelling the dispersion of a passive tracer in complex open channel flows using random walk, particle tracking techniques." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296886.

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21

Seo, Daniele. "Avaliação dos teores de Br, Cl, K, Mg, Mn e V em mexilhões Perna perna (Linnaeus, 1758: Mollusca, Bivalvia) coletados no litoral do estado de São Paulo, Brasil." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-08032013-161647/.

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O ambiente costeiro tem sido fortemente alterado em função de múltiplos impactos ambientais decorrentes das atividades antrópicas, como por exemplo, o escoamento de esgoto proveniente de áreas urbanas, a liberação de inúmeros produtos químicos das indústrias, a agricultura e o fluxo de embarcações, que podem acarretar vazamentos acidentais de petróleo e derivados, combustíveis e outros produtos transportados por via marítima. Neste contexto, um dos meios para avaliação da contaminação ambiental causada por essas substâncias potencialmente tóxicas em água do mar é a monitoração por meio de diferentes espécies de bivalves, que tem sido utilizada por diversos pesquisadores, do Brasil e do exterior. No que se refere aos moluscos bivalves, particularmente os mexilhões, o seu uso no biomonitoramento da contaminação marinha deve-se principalmente à sua ampla distribuição geográfica, hábito séssil e habilidade de concentrar metais tóxicos em até 102 - 105 vezes em relação às concentrações detectadas na água. No presente trabalho, foi empregado o biomonitoramento passivo com o uso do molusco bivalve Perna perna com relação aos elementos Br, Cl, K, Mg, Mn e V. Foram escolhidos estes elementos uma vez que eles podem ser determinados pelo método de INAA (Análise por Ativação com Nêutrons Instrumental), por meio da irradiação curta o que proporciona análises mais rápidas e também por serem importantes do ponto de vista nutricional ou ambiental. O objetivo do presente trabalho foi avaliar os teores de Br, Cl, K, Mg, Mn e V em amostras de mexilhões Perna perna (Linnaeus, 1758: Mollusca, Bivalvia) coletados em regiões costeiras de São Paulo sujeitas à contaminação antrópica (Ponta de Itaipu e Ilha das Palmas, em Santos), comparando os valores obtidos nos sítios possivelmente impactados com os valores do sítio controle situado na Praia da Cocanha, em Caraguatatuba. Os pontos de coleta no litoral de São Paulo estão localizados nas regiões geográficas 23º 37 S 45º 24 W (Caraguatatuba) e 23º 57\' S - 46º 20\' W (Santos). A coleta dos organismos foi realizada em todas as estações do ano, com início na primavera de 2008 e término no inverno de 2009. As amostras coletadas foram limpas, trituradas, homogeneizadas e secas por meio da liofilização para posterior INAA. O procedimento de INAA consistiu em irradiar alíquotas das amostras obtidas na forma de pó em invólucros de polietileno no reator nuclear IEA R1 do IPEN/CNEN - SP juntamente com padrões sintéticos de elementos. O tempo de irradiação no reator foi de 8 a 10 s e sob o fluxo de nêutrons térmicos de 6,6 x 1012 n cm-2 s-1. As concentrações dos elementos foram calculadas pelo método comparativo. O procedimento de INAA foi validado com relação à exatidão e precisão, por meio das análises dos materiais de referência certificados NIST SRM 1566b Oyster Tissue e NIST SRM 2876 Mussel Tissue. Os resultados destes materiais de referência certificados indicaram uma boa qualidade dos resultados com relação à precisão e exatidão. As faixas das concentrações (em base seca) dos elementos obtidos nos mexilhões coletados em Santos e na Praia da Cocanha para as quatro estações do ano foram de: 173,80 a 358,99 mg kg-1 para Br; 45658 ± 1811 a 109166 ± 824 mg kg-1 para Cl; 7043 ± 856 a 12506 ± 675 mg kg-1 para K; 2774 ± 211 a 5691 ± 717 mg kg-1 para Mg; 7,01 ± 0,30 a 29,74 ± 3,32 mg kg-1 para Mn e 0,77 ± 0,02 a 3,43 ± 0,28 mg kg-1 para V. Foi estudada a variação sazonal e espacial das concentrações desses elementos e também foram comparados esses resultados com valores da literatura. A partir dos resultados obtidos pode - se concluir que os mexilhões da espécie Perna perna, podem ser utilizados como biomonitores da contaminação marinha.
The coastal environment has been heavily altered by multiple environmental impacts of human activities, such as disposal of sewage from urban areas, the release of numerous chemical industries, agriculture and the flow of vessels, which can lead to accidental spills of oil and oil products, fuels and other products transported by sea. In this context, a means of determining concentrations of these potentially toxic substances in the sea water is the biomonitoring by means of different types of bivalves, which have been used by various researchers, in Brazil and other countries. With regard to bivalve mollusks, particularly mussels, their use in monitoring the marine contamination is mainly due to their wide geographic distribution, sessile habit and ability to concentrate toxic metals to 102-105 times in relation to the concentrations detected in water. In the present study, we employed the passive biomonitoring using the Perna perna bivalve mollusk with respect to the elements Br, Cl, K, Mg, Mn and V. These elements were chosen since they can be determined by INAA method (Instrumental Neutron Activation Analysis), by means of short irradiation which provides faster analyzes and also due to their importance from the standpoint of environmental or nutritional studies. The aim of this study was to evaluate the content of Br, Cl, K, Mg, Mn and V in samples of Perna perna mussels (Linnaeus, 1758: Mollusca, Bivalvia) collected in coastal regions of São Paulo subject to anthropogenic contamination (Ponta de Itaipu and Palmas Island, in Santos), comparing the values obtained in sites potentially impacted with the values of the control site in Praia da Cocanha, in Caraguatatuba. The collection points located in São Paulo coast are located in the geographical areas 23º 37\'S - 45° 24\' W (Caraguatatuba) and 23º 57\'S - 46º 20\' W (Santos). The collection of organisms was performed in all seasons of the year, beginning in spring 2008 and ending in winter 2009. The samples were cleaned, crushed, homogenized and dried by lyophilization for further analysis by INAA. The INAA procedure consisted of irradiating aliquots of the samples obtained in powder form in polyethylene envelopes in the nuclear research reactor IEA - R1 of IPEN / CNEN - SP together with synthetic standards of elements. The irradiation time in the reactor was 8 to 10 s under the thermal neutron flux of 6.6 x 1012 n cm-2 s-1. The concentrations of the elements were calculated using the comparative method. The INAA procedure was validated with respect to accuracy and precision, through the analysis of certified reference materials NIST SRM 1566b Oyster Tissue and NIST SRM 2876 Mussel Tissue. The results of these certified reference materials indicated good quality of results with respect to precision and accuracy. The ranges of concentrations (dry basis weight) of the elements obtained in mussels collected in Santos and Praia da Cocanha for the four seasons of the year were: 173.80 to 358.99 mg kg-1 for Br; 45658 ± 1811 to 109166 ± 824 mg kg-1 for Cl; 7043 ± 856 to 12506 ± 675 mg kg-1 for K; 2774 ± 211 to 5691 ± 717 mg kg-1 for Mg; 7.01 ± 0.30 to 29.74 ± 3.32 mg kg-1 for Mn and 0.77 ± 0.02 to 3.43 ± 0.28 mg kg-1 for V. The seasonal and spatial variations of the concentrations of these elements were studied and the values compared to the literature. From the results obtained it can be concluded that the species of Perna perna mussels, can be used as biomonitors of marine contamination.

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Bohlin, Pernilla. "Passive sampling of PAHs and some trace organic compounds in occupational and residential air : needs, evaluation and limits /." Göteborg : Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, 2010. http://hdl.handle.net/2077/2.

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23

BERSANO, ANDREA. "Analysis of natural circulation and passive systems phenomenology in nuclear plants." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2829632.

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24

Jong, Edmund Chime. "Development and Evaluation of a Permeation Plug Release Vessel (PPRV) for the Release of Perfluoromethylcyclohexane (PMCH) in Underground Mine Tracer Gas Studies." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/24912.

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The use of sulfur hexafluoride (SF6) as a tracer gas for analyzing underground mine ventilation systems has been practiced for over 30 years. As a result, the methods used to release, sample, and analyze SF6 are well accepted. Although improvements are still being made to enhance the analysis of this tracer, the overall technique remains largely the same. However, as the complexity and size of underground mine ventilation networks increase, coupled with steadily rising SF6 background levels, the ability of a single gas to function as a convenient, rapid means of analysis diminishes. The utilization of multiple tracer gases can mitigate these problems by allowing for a more comprehensive evaluation using multi-zone techniques. A well-documented alternative in HVAC studies to SF6 as a tracer are perfluorocarbon tracers (PFT). Many PFTs exist as volatile liquids at room temperature and pressure. This characteristic prevents a PFT from being released using the same technique as SF6. This paper introduces a passive release method for PMCH. Details about the development of the permeation plug release vessel (PPRV) from creating a GC calibration curve for vapor PMCH to the final field evaluation are presented. The following study successfully developed a mine-scale PPRV. The PPRV is designed to passively deploy PMCH vapor at linear. An equation was derived in this study that allows the prediction of the release rate as a function of temperature and plug thickness. Details regarding the development of the PPRV from preliminary laboratory studies to final field evaluations are provided.
Ph. D.

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25

JULLIEN, MARIE-CAROLINE. "Dispersion de traceurs passifs dans des experiences de turbulence bidimensionnelle." Paris 6, 2000. http://www.theses.fr/2000PA066236.

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Nous presentons des resultats experimentaux concernant la dispersion de traceurs passifs dans des experiences de turbulence bidimensionnelle entretenue. Les experiences sont realisees pour des ecoulements forces electromagnetiquement dans de minces couches de fluides stratifiees de facon stable. Les champs de vitesse sont analyses a l'aide d'une technique de velocimetrie. Dans une premiere approche, nous faisons une analyse statistique de la dispersion d'une tache de fluoresceine, successivement dans la cascade directe d'enstrophie et dans la cascade inverse d'energie, conformement aux conjectures formulees par kraichnan en 1967 a propos du mecanisme de double cascade en turbulence bidimensionnelle. Dans la cascade d'enstrophie, nous montrons que le spectre des fluctuations de concentration suit la loi de batchelor en k - 1, et que les solutions analytiques formulees par chertkov et al. Sont en tres bon accord avec nos experiences : ailes exponentielles pour les distributions de fluctuations ainsi que de ses increments, loi logarithmique pour la fonction de structure d'ordre 2. Dans la cascade inverse, nous montrons que la statistique d'ordre 2 est bien decrite par le formalisme de corrsin-obukhov. L'analyse des moments d'ordres plus eleves revele en revanche une saturation des exposants de fonction de structure vers une valeur constante. Une seconde approche est une approche lagrangienne. Elle consiste a suivre des paires de particules le long de leur trajectoires, determinees en integrant numeriquement les champs de vitesse experimentaux. Cette etude a ete realisee dans la cascade inverse d'energie. La loi hyperdiffusive de richardson r 2 t 3 est observee et un comportement fortement non-gaussien est obtenu pour les distributions des separations des paires. Le processus est temporellement auto-similaire et de fortes correlations temporelles sont presentes.

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Quirino, Valquiria Ferraz. "Evaluating the Potential for Estimating Age of Even-aged Loblolly Pine Stands Using Active and Passive Remote Sensing Data." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/71309.

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Data from an airborne laser scanner, a dual-band interferometric synthetic aperture radar (DBInSAR), and Landsat were evaluated for estimating ages of even-aged loblolly pine stands in Appomattox-Buckingham State Forest, Virginia, U.S.A. The DBInSAR data were acquired using the GeoSAR sensor in summer, 2008 in both the P- and X-bands. The LiDAR data were acquired in the same summer using a small-footprint laser scanner. Loblolly pine stand ages were assigned using the establishment year of loblolly pine stands provided by the Virginia Department of Forestry. Random circular plots were established in stands which varied in age from 5 to 71 years and in site index from 21 to 29 meters (base age 25 years). LiDAR- and GeoSAR-derived independent variables were calculated. The final selected LiDAR model used common logarithm of age as the dependent variable and the 99.5th percentile of height above ground as the independent variable (R2adj = 90.2%, RMSE = 4.4 years, n=45). The final selected GeoSAR models used the reciprocal of age as the dependent variable and had three independent variables: the sum of the X-band magnitude, the 25th percentile of X/P-band magnitudes, and the 90th percentile of the X-band height above ground (R2adj = 84.1%, RMSE = 7.9 years, n=46). The Vegetation Change Tracker (VCT) algorithm was run using a digital elevation layer, a land cover map, and a series of Landsat (5 and 7) images. A comparison was made between the loblolly pine stand ages obtained using the three methods and the reference data. The results show that: (1) although most of the time VCT and reference data ages were different, the differences were normally small, (2) all three remote sensing methods produced reliable age estimates, and (3) the Landsat-VCT algorithm produced the best estimates for younger stands (5 to 22 years old, RMSEVCT=2.2 years, RMSEGeoSAR=2.6 years, RMSELiDAR=2.6 years, n=35) and the model that used LiDAR-derived variables was better for older stands. Remote sensing can be used to estimate loblolly pine stand age, though prior knowledge of site index is required for active sensors that rely primarily on the relationship between age and height.
Ph. D.

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27

Kumar, Ratnesh. "Segmentation vidéo et suivi d'objets multiples." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4135/document.

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Dans cette thèse nous proposons de nouveaux algorithmes d'analyse vidéo. La première contribution de cette thèse concerne le domaine de la segmentation de vidéos avec pour objectif d'obtenir une segmentation dense et spatio-temporellement cohérente. Nous proposons de combiner les aspects spatiaux et temporels d'une vidéo en une seule notion, celle de Fibre. Une fibre est un ensemble de trajectoires qui sont spatialement connectées par un maillage. Les fibres sont construites en évaluant simultanément les aspects spatiaux et temporels. Par rapport a l’état de l'art une segmentation de vidéo a base de fibres présente comme avantages d’accéder naturellement au voisinage grâce au maillage et aux correspondances temporelles pour la plupart des pixels de la vidéo. De plus, cette segmentation à base de fibres a une complexité quasi linéaire par rapport au nombre de pixels. La deuxième contribution de cette thèse concerne le suivi d'objets multiples. Nous proposons une approche de suivi qui utilise des caractéristiques des points suivis, la cinématique des objets suivis et l'apparence globale des détections. L'unification de toutes ces caractéristiques est effectuée avec un champ conditionnel aléatoire. Ensuite ce modèle est optimisé en combinant les techniques de passage de message et une variante de processus ICM (Iterated Conditional Modes) pour inférer les trajectoires d'objet. Une troisième contribution mineure consiste dans le développement d'un descripteur pour la mise en correspondance d'apparences de personne. Toutes les approches proposées obtiennent des résultats compétitifs ou meilleurs (qualitativement et quantitativement) que l’état de l'art sur des base de données
In this thesis we propose novel algorithms for video analysis. The first contribution of this thesis is in the domain of video segmentation wherein the objective is to obtain a dense and coherent spatio-temporal segmentation. We propose joining both spatial and temporal aspects of a video into a single notion Fiber. A fiber is a set of trajectories which are spatially connected by a mesh. Fibers are built by jointly assessing spatial and temporal aspects of the video. Compared to the state-of-the-art, a fiber based video segmentation presents advantages such as a natural spatio-temporal neighborhood accessor by a mesh, and temporal correspondences for most pixels in the video. Furthermore, this fiber-based segmentation is of quasi-linear complexity w.r.t. the number of pixels. The second contribution is in the realm of multiple object tracking. We proposed a tracking approach which utilizes cues from point tracks, kinematics of moving objects and global appearance of detections. Unification of all these cues is performed on a Conditional Random Field. Subsequently this model is optimized by a combination of message passing and an Iterated Conditional Modes (ICM) variant to infer object-trajectories. A third, minor, contribution relates to the development of suitable feature descriptor for appearance matching of persons. All of our proposed approaches achieve competitive and better results (both qualitatively and quantitatively) than state-of-the-art on open source datasets

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Howell, Jamie Robert. "Learning through stories : An investigation into how Tracks Rites of Passage Programme impacts on the development of young men and their family systems." Thesis, University of Canterbury. Educational Studies and Leadership, 2012. http://hdl.handle.net/10092/7611.

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The Tracks rites of passage are processes that mark the adolescent transition, for the participant, the family and the community, between the two life stages of childhood and adulthood. Adolescent initiation rites offer a community led journey of separation, transition and integration as a way to work meaningfully with adolescents as they move between the life stages of childhood into adulthood. In Aotearoa/New Zealand the Tracks programme provides a five day contemporary rite of passage for adolescents and, where possible, their fathers. The rite of passage is based on the assumption that adolescents need opportunities to find their voices and make meaning if they are to become more aware of who they are and where they belong. The methodology recognises that I, as researcher and insider in the Tracks organisation, needed to develop a holistic approach to insider research so that I could call on my understandings of the organisation and also guard against bias. The holistic approach involves the four interpenetrating strategies of appreciative inquiry, narrative inquiry, a blend of approaches to self-study that include meditation and critical reflection, and most importantly organic inquiry. The four strategies are based on coherence theories that describe learning as being organic, interconnected and emergent. Data were gathered from interviews and cycles of critical self-reflection in the form of a learning journal. Data comes from interviews with the mother or fathers and young men of six families who have participated in the Tracks rite of passage programme. I have also discussed this work with a number of professionals in the field of youth work. The project found that Tracks had created conditions that empowered these young men with an increased capacity to make sense of their lives. Fathers expressed how challenging and rewarding they had found it to speak in honest terms with their sons, and that they were supported to do the inner work necessary to be able to speak in such ways. All of the family members expressed a need to have more support after the event. The findings suggest a need to explore further the nature of the work happening at Tracks. It validates Lashlie’s (2005) theory that adolescents need their fathers and other men to be involved in their lives at the time of transition. Tracks also helps fathers to get to grips with the inner work of developing emotional maturity. The work happening at Tracks invites further research into and debate on the value of emotional intelligence. The Tracks rite of passage offers an alternative perspective to understand the unacceptably high rates of adolescent morbidity and mortality happening in New Zealand.

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Flynn, Ross Christopher. "Persistence of diatoms as trace evidence in clothing fabrics: The effects of active removal (machine washing) and passive removal (time and environment)." Thesis, Flynn, Ross Christopher (2021) Persistence of diatoms as trace evidence in clothing fabrics: The effects of active removal (machine washing) and passive removal (time and environment). Masters by Research thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/63158/.

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Literature available in the field of forensics covering terrestrial-based evidence is comprehensive; however, many aspects of aquatic environmental evidence have yet to be well researched. One such developing area of aquatic evidence is that of diatoms, a major group of unicellular algae that exist in natural bodies of both fresh and marine waters. Due to their unique qualities and characteristics, diatoms have the potential to be used as evidence of contact with specific water sources. While initially used in forensics to aid drowning diagnoses, more recent case studies and research have investigated diatoms in the context of their use as a form of trace evidence, as well as factors affecting initial transfer and subsequent extraction. This research was the first to investigate factors affecting the persistence of diatoms in fabrics in both passive and active removal pressure contexts. The pressure environments selected represent realistic case circumstances, in which someone may discard (passively affect), or machine wash (actively affect) their clothing after its exposure to diatoms. Additionally, this study investigated whether cross contamination of diatoms could occur between diatom enriched fabrics and blank fabrics within a washing machine environment. Both experiments' test fabrics were immersed in diatom enriched waters containing equal parts C. Muelleri and Navicula sp. species at 2,000,000 dv/mL. The passive removal experiment tested the influence of exposure (indoor and outdoor environments) and time (week 1/2/3/4/8/12) on the concentration of diatoms across three various fabrics (cotton knit/denim weave/polyester knit). The active removal experiment tested the machine type (front loader/top loader), wash temperature (warm ~40°C/cold) and the number of washes (1/2/3) on concentrations within DEFs, in addition to testing for cross contamination using blank fabrics within the washing load. Diatoms were extracted from fabrics using the established H2O2 method and quantified under a compound light microscope (CLM) at 400x magnification. The passive experiment (PE) showed that exposure environment and time both played an important role in diatom persistence, with concentration reductions occurring much quicker initially outdoors compared to indoors, but still featuring notable loss for the indoor group during experiment. Rainfall was noted as heavier on average when the outdoor group lost the majority of its diatom concentrations. The active experiment (AE) showed that the number of washes most greatly impacted the concentration, followed by machine type, followed by wash temperature and these trends were consistent across all tested fabrics. By the first wash all groups still contained diatoms, however at a much lower concentration, and by the second, mostly the top loader washes still contained quantifiable diatoms and by the third wash none of the groups contained quantifiable diatoms. Front loader washes removed diatoms from clothing more effectively than top loaders, and within these machine groups, warm washes were more effective at removal than cold washes. Trends observed in the PE and AE were mostly consistent across all varieties of fabrics tested. Additionally, the AE showed that cross contamination between DEFs and blank fabrics was possible, however at relatively low levels. Across both the passive and active experiments, it is consistently shown that time is of the utmost importance when it comes to retrieving DEF evidence as diatoms appear to be lost passively over time even when left alone in different environments in addition to being vulnerable to machine washing removal.

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Pöschke, Patrick [Verfasser], Igor [Gutachter] Sokolov, Benjamin [Gutachter] Lindner, and Marcin [Gutachter] Magdziarz. "Influence of Molecular Diffusion on the Transport of Passive Tracers in 2D Laminar Flows / Patrick Pöschke ; Gutachter: Igor Sokolov, Benjamin Lindner, Marcin Magdziarz." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1185175024/34.

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31

Braun, Joanne. "Box Turtles, Terrapene carolina, as Potential Seed Dispersers: Effects of Passage Through Digestive Tracts on Seed Germination." W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539625298.

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32

Ericsson, Anton, and Anton Erickson. "Does the Active Country Momentum Portfolio Beat the Passive Market Portfolio? : an empirical study on exchange-traded funds." Thesis, Örebro universitet, Handelshögskolan vid Örebro Universitet, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-89230.

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The thesis examines the strategy of country momentum and is evaluated with 30 different country exchange-traded funds (ETFs) for the period 1996-2018. The empirical evaluation is designed to apply different formation- and holding periods with overlapping portfolios. The results show positive momentum returns in various periods and a few portfolios present a higher average return than the market. However, none of the portfolios is presenting any significant positive returns or alphas, meaning that the three hypotheses cannot be rejected. On the other hand, some portfolios have higher Sharpe ratios and Morningstar value than the market. Thus, meaning that the individual investor could prefer the momentum portfolio over the market despite the insignificant returns.

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33

Lesouëf, Dorothée. "Étude numérique des circulations locales à la Réunion : application à la dispersion de polluants." Phd thesis, Université de la Réunion, 2010. http://tel.archives-ouvertes.fr/tel-00633096.

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Les régimes dynamiques dans les basses couches de l'atmosphère à l'île de la Réunion sont conditionnés par l'action du relief et du rayonnement sur l'écoulement synoptique. L'île est située en permanence dans le flux des alizés de sud-est et son relief élevé, culminant à 3000 m dans le centre de l'île et 2600 m au sud, constitue un obstacle important pour l'écoulement moyen. Le relief, le chauffage différentiel des pentes et le contraste thermique avec l'océan influent sur les échanges locaux entre la couche limite marine et la troposphère libre.L'analyse des phénomènes complexes de l'écoulement atmosphérique au niveau de l'île a pour but initial de caractériser les transferts de polluants émis localement. Cette étude a deux applications : * La première rentre dans le cadre préparatoire à la mise en place, à 2200 m d'altitude sur le Piton Maïdo, de l'observatoire atmosphérique de l'OPAR, à l'horizon 2011. L'objectif est de comprendre les circulations locales induites par le relief et les transports associés afin de discriminer d'éventuelles pollutions par les sources locales sur le signal qui sera mesuré in situ au sommet du Maïdo.* La seconde vise à étudier la diffusion des panaches volcaniques du Piton de la Fournaise. L'éruption majeure d'avril 2007 du volcan réunionnais a montré que des panaches pouvaient générer d'importantes pollutions dans diverses parties de l'île allant jusqu'à poser de réels problèmes environnementaux et de santé publique.Ces applications s'appuient sur une étude par modélisation numérique à haute résolution des écoulements atmosphériques dans les basses couches au niveau de l'île, au moyen du modèle météorologique de recherche MésoNH, permettant de conduire un ensemble de simulations sur cas idéalisés puis sur cas réels avec diffusion de traceurs passifs.

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34

Lapointe, Frédérique, and Frédérique Lapointe. "Tracer son chemin : la transition à la vie adulte des femmes ayant expérimenté l'itinérance." Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37561.

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Certains groupes de la population sans domicile fixe sont identifiés comme particulièrement vulnérables. Les femmes et les jeunes adultes en font partie. En plus d’être spécifiquement touchées par certaines formes d’adversité au courant de leur vécu de rue, ces franges minorisées des populations en situation d’itinérance sont rarement représentées dans les politiques sociales et les dénombrements entourant ce phénomène. Le but de cette recherche est de faire entendre les voix de femmes ayant expérimenté l’itinérance sur la façon dont elles vivent ou ont vécu leur transition à la vie adulte. Prenant appui sur la perspective intersectionnelle socioconstructionniste, cette étude a cherché à éclairer leur expérience et leur compréhension de leur situation, tout en mettant en lumière les mécanismes d’oppression et les stratégies de résistance présents dans leur parcours. Misant sur une approche narrative, cette recherche qualitative a été réalisée par le biais d’entretiens individuels auprès de cinq jeunes femmes afin de recueillir le récit personnel de leur passage à la vie adulte. Ainsi, le parcours singulier de chacune de ces femmes de même que les similitudes et les différences entre leurs situations respectives ont été analysées pour mieux comprendre leurs expériences semblables et variables de l’itinérance au cours du passage à la vie adulte. Les résultats décrivent des parcours faits de départs, de nouvelles rencontres et de prises de décisions menant vers diverses situations de revenus et d’hébergement. Au-delà des interprétations qu’elles font de leur vécu respectif, les participantes éclairent les mécanismes d’oppression auxquels elles sont confrontées, incluant diverses formes de mise à l’écart et de violence, ainsi que les stratégies qu’elles emploient pour améliorer leur sort.
Certains groupes de la population sans domicile fixe sont identifiés comme particulièrement vulnérables. Les femmes et les jeunes adultes en font partie. En plus d’être spécifiquement touchées par certaines formes d’adversité au courant de leur vécu de rue, ces franges minorisées des populations en situation d’itinérance sont rarement représentées dans les politiques sociales et les dénombrements entourant ce phénomène. Le but de cette recherche est de faire entendre les voix de femmes ayant expérimenté l’itinérance sur la façon dont elles vivent ou ont vécu leur transition à la vie adulte. Prenant appui sur la perspective intersectionnelle socioconstructionniste, cette étude a cherché à éclairer leur expérience et leur compréhension de leur situation, tout en mettant en lumière les mécanismes d’oppression et les stratégies de résistance présents dans leur parcours. Misant sur une approche narrative, cette recherche qualitative a été réalisée par le biais d’entretiens individuels auprès de cinq jeunes femmes afin de recueillir le récit personnel de leur passage à la vie adulte. Ainsi, le parcours singulier de chacune de ces femmes de même que les similitudes et les différences entre leurs situations respectives ont été analysées pour mieux comprendre leurs expériences semblables et variables de l’itinérance au cours du passage à la vie adulte. Les résultats décrivent des parcours faits de départs, de nouvelles rencontres et de prises de décisions menant vers diverses situations de revenus et d’hébergement. Au-delà des interprétations qu’elles font de leur vécu respectif, les participantes éclairent les mécanismes d’oppression auxquels elles sont confrontées, incluant diverses formes de mise à l’écart et de violence, ainsi que les stratégies qu’elles emploient pour améliorer leur sort.
Some groups of the homeless population are identified as particularly vulnerable. Women and young adults are part of them. In addition to being specifically affected by certain forms of adversity when they are on the streets, these minority fringes of homelessness are rarely represented in social policies and are not included in the numbers regarding this phenomenon. The purpose of this research is to put forward the experience of transition to adulthood of women who experience, or have experienced, homelessness. Drawing on the intersectional socioconstructionist perspective, this study sought to shed light on their path and understanding of their situation, while highlighting the mechanisms of oppression and the strategies of resistance. Using a narrative approach, this qualitative research was conducted through individual interviews with five young women. Thus, each of these women's unique pathways as well as the similarities and differences between their respective situations were analyzed to better understand their similar and variable experiences of homelessness during the pathway of adult life. The results describe journeys made of departures, new encounters and decision-making leading to various income and housing situations. Beyond the interpretations they make of their experiences, the participants shed light on the oppression mechanisms they face, including various forms of exclusion and violence, as well as the strategies they employ to improve their lives.
Some groups of the homeless population are identified as particularly vulnerable. Women and young adults are part of them. In addition to being specifically affected by certain forms of adversity when they are on the streets, these minority fringes of homelessness are rarely represented in social policies and are not included in the numbers regarding this phenomenon. The purpose of this research is to put forward the experience of transition to adulthood of women who experience, or have experienced, homelessness. Drawing on the intersectional socioconstructionist perspective, this study sought to shed light on their path and understanding of their situation, while highlighting the mechanisms of oppression and the strategies of resistance. Using a narrative approach, this qualitative research was conducted through individual interviews with five young women. Thus, each of these women's unique pathways as well as the similarities and differences between their respective situations were analyzed to better understand their similar and variable experiences of homelessness during the pathway of adult life. The results describe journeys made of departures, new encounters and decision-making leading to various income and housing situations. Beyond the interpretations they make of their experiences, the participants shed light on the oppression mechanisms they face, including various forms of exclusion and violence, as well as the strategies they employ to improve their lives.

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35

Musa, Arshad. "Passive versus active applications of industry exchange traded funds (ETFs) : an empirical investigation on the S&P Global 1200 Index." University of the Western Cape, 2015. http://hdl.handle.net/11394/4912.

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Magister Commercii - MCom
The notion of market efficiency posits that stock prices fully reflect all available information in a timely manner. The efficient market hypothesis (EMH) proposed by Fama (1970) systematically rules out the profitability of information driven investing, and implicitly promulgates a passive market capitalisation weighted investment strategy such as indexing. The appeal of passive strategies has largely been driven by the growth of passive tracking instruments, which allow investors to earn underlying index performance by purchasing a single security such as an exchange traded fund (ETF). On the contrary, proponents of behavioural finance suggest that investors are irrational and subject to psychological biases. Furthermore, the noisy market hypothesis of Siegel (2006) asserts that the deviations from the economic ideal of rationality proposed by the EMH, introduces noise in the market which could lead prices to deviate from their intrinsic values. The resultant drag in performance of market capitalisation weighted indices suggests that the optimal cap-weighted market portfolio promulgated by the modern portfolio theory (MPT) of Markowitz (1952), ceases to be the most mean-variance approach to asset allocation. With the goal of testing the applications of ETF’s, this study first evaluates the performance of passive sector ETF’s in the global equity market. In addition, motivated by the potential inefficiencies of capweighted portfolios, the study tests optimisation based asset allocation techniques, and technical analysis based market timing strategies. The study employs the S&P Global 1200 sector indices and their respective sector ETF’s to test their performances and applications in passive and active investment strategies, over the period from July 5th, 2002 to February 6th, 2015. The ETF’s are evaluated based on their tracking ability and price efficiency. All 10 sector ETF’s possess insignificant tracking errors and successfully replicate the performance of their underlying indices. In addition, the globalsector ETF’s are not price efficient over the study period, as they possess persistent price deviations from their net asset values (NAV’s). Furthermore, the ETF trading strategy based on the relationship between ETF returns and price deviations, proves to be effective in outperforming the passive buy and hold strategy in the majority of the sectors. The sector decomposition of the cap-weighted S&P Global 1200 index which is employed as the market proxy, reveals that its sector allocation remains fairly stable throughout the study period. In contrast, the optimal historical sector composition incurs large changes in sector exposure from year to year and provides substantially superior performance relative to the cap-weighted market portfolio. The cap-weighted portfolio tends to overweight cyclical sectors and underweight resilient sectors during major economic downturns. The long-only, long-short and market neutral strategies developed from the S&P Global 1200 index and its constituent sector indices provide exceptional risk-adjusted performance, and more meanvariance efficient portfolios than the cap-weighted market proxy. The relaxation of the longonly constraint also improves the optimised portfolios risk-adjusted performance, mainly through risk reduction benefits. The performance of the optimised global sector based portfolios also resembles the performances of the global style based optimised portfolios developed by Hsieh (2010), thereby suggesting that the two approaches are analogous. The 3 technical market timing strategies tested in this research provide varying results. The sector momentum portfolios experience significant positive returns during bull markets, however the portfolios incur significant drawdowns during periods of economic turmoil such as the 2008 global financial crisis. As a result, all sector momentum portfolios provide inferior risk-adjusted returns relative to the passive cap-weighted buy and hold strategy. The exponential moving average (EMA) trend timing strategy promulgated by Hsieh (2010) provides impressive risk-management attributes and superior risk-adjusted performance relative to passive buy and hold benchmarks. Similarly, the alternative technical charting heuristics trend timing strategy helps reduce drawdowns during market crashes, however the charting strategy provides inferior cost and risk-adjusted performance relative to the capweighted buy and hold approach due to larger timing errors and longer hedging periods in comparison to the EMA strategy. In addition, the global tactical sector allocation (GTSA) model tests the EMA and technical charting trend timing tools in the context of a global sector portfolio, and the model provides outstanding cost and risk-adjusted performances relative to the passive investing alternatives. The portfolio based GTSA model highlights the benefits of portfolio diversification and successfully hedges market exposure during economic downturns.

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36

Liaghati, Tania. "Trace metal geochemistry and weathering mineralogy in a quaternary coastal plain, Bells Creek catchment, Pumicestone Passage, Southeast Queensland, Australia." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15998/1/Tania_Liaghati_Thesis.pdf.

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The Bells Creek catchment covers an area of 100 km2 in the northern part of the Pumicestone Passage region of southeast Queensland. This catchment is an example of a low-lying sub-tropical coastal plain including both freshwater and estuarine settings. The main creeks drain into Pumicestone Passage, a large shallow estuary, which is a declared marine habitat and a Ramsar listed wading bird location. The Bells Creek catchment has undergone land-use change from bushland to grazing to pine plantations and is now coming under pressure for urban development. Quaternary age unconsolidated sediments are the dominant surface material in this area and formed during the last marine transgression. Of significance for such a setting is that estuarine sediments can retain metals mobilised as a result of natural processes (e.g. weathering) and anthropogenic activities (e.g. land-use disturbance). As trace metals can also occur naturally in rocks and their weathered products, it is of value to clearly distinguish natural and anthropogenic controls over metal source, distribution and mobility. To achieve this aim two approaches were taken: 1) to determine the factors controlling the geochemistry of weathered profiles, unconsolidated sediments, soils and natural waters, and 2) to identify the most effective analytical and numerical methods for evaluating metal concentration in different solid materials. This investigation is structured around four linked papers. The influence of mineralogy, geological setting, location of water table and depth of burial on the geochemistry of weathered profile are assessed in Paper 1. The second paper is an investigation of different analytical approaches for studying weathered sedimentary rocks, as well as the testing of several numerical methods for evaluating geochemical data from weathered profiles. In paper 3, a large heterogeneous geochemical data set including trace metals, total organic carbon and sulfur content, in addition to mineralogy and land use practices are integrated to enable evaluation of geochemical and anthropogenic processes controlling metal distribution. The fourth paper considers the distribution of iron and its transport as well as variations in size and morphology of different forms of framboidal pyrite within a smaller sub-catchment in the southern part of the study area. The labile and heterogeneous nature of the bedrock of the region, the Landsborough Sandstone, along with the sub-tropical climate of the area have resulted in weathering profiles up to 26 m deep. Due to the absence of industrial activity in the Bells Creek catchment, such weathering of the bedrock constitutes the major process governing metal distribution throughout the area. Analysis by X-ray diffraction (XRD) shows that the primary minerals occurring in the weathered profiles are quartz, plagioclase and K-feldspars while kaolinite is the most dominant secondary mineral present. Overall, parent rock silicates have been extensively replaced by clay minerals and Fe oxides. The relative influence of mineralogy, geological setting and groundwater over chemical weathering and geochemical cycling of metals can be summarised as follows: Mineralogy>geological setting>watertable position>depth of profile burial As the relationship between the total metal composition and the extractable and mobile component has environmental significance, a comparison was made between these forms of metals in weathered material. This comparison shows that metals such as V, Cr and Fe are part of the aluminosilicate matrix and remain largely in primary mineral structures. The retention of these metals may lead to their future release to the environment during on-going weathering. Other elements such as Cu, Zn, Pb, however, are found to be primarily adsorbed to sediment particles and therefore, easily releasable to the environment. As limited information on weathering of sedimentary rocks is reported in the literature, a variety of chemical analysis and numerical assessment methods were used to understand the geochemical processes involved in trace metal mobility in the weathered profiles. Two analytical methods of digestion, hydrofluoric acid and x-ray fluorescence were tested and found to be highly comparable except for refractory elements such as V and Cr. Among the numerical methods applied to the dataset were "chemical and mineralogical indices", "weight loss factor" and "immobile element approach". The "immobile element approach" was found to be the most appropriate method to characterise the weathering profiles typical of the catchment. This method considers a weathering system to be open and transforms the absolute values of trace metals enabling a quantitative evaluation of metal mobility. The following sequence of mobility was determined after applying this method to the data generated in this study: Zn>Pb>Cu>Cr>V The above sequence of mobility is supported by the comparison between extractable and total metal concentrations where Cr and V were identified as being part of aluminosilicate matrix and less mobile. On the other hand, Zn, Pb and Cu were found to exist in adsorbed form and to be readily released to the environment. Trace elements released through weathering and erosion of the bedrock can accumulate in estuarine and coastal sediments. Therefore, both the lateral and vertical distribution of trace metals within sediments and soils of Bells Creek catchment were investigated. Natural and anthropogenic factors controlling metal distribution were compared and it was concluded that the natural sediment character such as its mineral content is more significant than anthropogenic influences in controlling lateral and vertical metal distribution. Further, due to varying degrees of weathering and the heterogeneous nature of soils and sediments, the data were normalised. After testing several methods, it was concluded that calculation of an enrichment factor was the most appropriate. The enrichment factor revealed that elevated trace metal concentrations at some sites are due to bedrock weathering. Due to the environmental persistence of iron, excess of this common metal has always been of environmental concern in many coastal settings. In the small Halls Creek sub-catchment, for example, iron anomalies were detected in bottom sediments (Fe up to 14%). This finding has significance in the area, as iron has been identified as one of the major contributors in the growth of the toxic cyanobacteria "Lyngbya majuscula" which can negatively impact on aquatic fauna. Iron concentrations were also shown to be high in natural stream waters of this coastal zone (up to 16 mg/L); in the bottom sediments of the creek, iron occurs as hematite (freshwater section) or pyrite (estuarine section). A variety of pyrite morphologies were identified in both bottom sediments and particulate matter samples including spherical closely packed framboids, and the rare form of euhedra which indicates slow crystallisation. The different components of this investigation have: 1) established the order and extent to which natural factors control weathering, 2) tested a number of analytical and numerical methods in evaluating weathering profiles, 3) assessed natural and anthropogenic factors and established the mobility sequence for trace metals in weathered profiles and, 4) determined the iron mineral speciation and established morphological variations of pyrite. As the area of Bells Creek catchment will be under development pressure in the future, findings of this study represent a baseline of comparison for environmental assessment and are of importance for environmental management.

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37

Liaghati, Tania. "Trace metal geochemistry and weathering mineralogy in a quaternary coastal plain, Bells Creek catchment, Pumicestone Passage, Southeast Queensland, Australia." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15998/.

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Abstract:

The Bells Creek catchment covers an area of 100 km2 in the northern part of the Pumicestone Passage region of southeast Queensland. This catchment is an example of a low-lying sub-tropical coastal plain including both freshwater and estuarine settings. The main creeks drain into Pumicestone Passage, a large shallow estuary, which is a declared marine habitat and a Ramsar listed wading bird location. The Bells Creek catchment has undergone land-use change from bushland to grazing to pine plantations and is now coming under pressure for urban development. Quaternary age unconsolidated sediments are the dominant surface material in this area and formed during the last marine transgression. Of significance for such a setting is that estuarine sediments can retain metals mobilised as a result of natural processes (e.g. weathering) and anthropogenic activities (e.g. land-use disturbance). As trace metals can also occur naturally in rocks and their weathered products, it is of value to clearly distinguish natural and anthropogenic controls over metal source, distribution and mobility. To achieve this aim two approaches were taken: 1) to determine the factors controlling the geochemistry of weathered profiles, unconsolidated sediments, soils and natural waters, and 2) to identify the most effective analytical and numerical methods for evaluating metal concentration in different solid materials. This investigation is structured around four linked papers. The influence of mineralogy, geological setting, location of water table and depth of burial on the geochemistry of weathered profile are assessed in Paper 1. The second paper is an investigation of different analytical approaches for studying weathered sedimentary rocks, as well as the testing of several numerical methods for evaluating geochemical data from weathered profiles. In paper 3, a large heterogeneous geochemical data set including trace metals, total organic carbon and sulfur content, in addition to mineralogy and land use practices are integrated to enable evaluation of geochemical and anthropogenic processes controlling metal distribution. The fourth paper considers the distribution of iron and its transport as well as variations in size and morphology of different forms of framboidal pyrite within a smaller sub-catchment in the southern part of the study area. The labile and heterogeneous nature of the bedrock of the region, the Landsborough Sandstone, along with the sub-tropical climate of the area have resulted in weathering profiles up to 26 m deep. Due to the absence of industrial activity in the Bells Creek catchment, such weathering of the bedrock constitutes the major process governing metal distribution throughout the area. Analysis by X-ray diffraction (XRD) shows that the primary minerals occurring in the weathered profiles are quartz, plagioclase and K-feldspars while kaolinite is the most dominant secondary mineral present. Overall, parent rock silicates have been extensively replaced by clay minerals and Fe oxides. The relative influence of mineralogy, geological setting and groundwater over chemical weathering and geochemical cycling of metals can be summarised as follows: Mineralogy>geological setting>watertable position>depth of profile burial As the relationship between the total metal composition and the extractable and mobile component has environmental significance, a comparison was made between these forms of metals in weathered material. This comparison shows that metals such as V, Cr and Fe are part of the aluminosilicate matrix and remain largely in primary mineral structures. The retention of these metals may lead to their future release to the environment during on-going weathering. Other elements such as Cu, Zn, Pb, however, are found to be primarily adsorbed to sediment particles and therefore, easily releasable to the environment. As limited information on weathering of sedimentary rocks is reported in the literature, a variety of chemical analysis and numerical assessment methods were used to understand the geochemical processes involved in trace metal mobility in the weathered profiles. Two analytical methods of digestion, hydrofluoric acid and x-ray fluorescence were tested and found to be highly comparable except for refractory elements such as V and Cr. Among the numerical methods applied to the dataset were "chemical and mineralogical indices", "weight loss factor" and "immobile element approach". The "immobile element approach" was found to be the most appropriate method to characterise the weathering profiles typical of the catchment. This method considers a weathering system to be open and transforms the absolute values of trace metals enabling a quantitative evaluation of metal mobility. The following sequence of mobility was determined after applying this method to the data generated in this study: Zn>Pb>Cu>Cr>V The above sequence of mobility is supported by the comparison between extractable and total metal concentrations where Cr and V were identified as being part of aluminosilicate matrix and less mobile. On the other hand, Zn, Pb and Cu were found to exist in adsorbed form and to be readily released to the environment. Trace elements released through weathering and erosion of the bedrock can accumulate in estuarine and coastal sediments. Therefore, both the lateral and vertical distribution of trace metals within sediments and soils of Bells Creek catchment were investigated. Natural and anthropogenic factors controlling metal distribution were compared and it was concluded that the natural sediment character such as its mineral content is more significant than anthropogenic influences in controlling lateral and vertical metal distribution. Further, due to varying degrees of weathering and the heterogeneous nature of soils and sediments, the data were normalised. After testing several methods, it was concluded that calculation of an enrichment factor was the most appropriate. The enrichment factor revealed that elevated trace metal concentrations at some sites are due to bedrock weathering. Due to the environmental persistence of iron, excess of this common metal has always been of environmental concern in many coastal settings. In the small Halls Creek sub-catchment, for example, iron anomalies were detected in bottom sediments (Fe up to 14%). This finding has significance in the area, as iron has been identified as one of the major contributors in the growth of the toxic cyanobacteria "Lyngbya majuscula" which can negatively impact on aquatic fauna. Iron concentrations were also shown to be high in natural stream waters of this coastal zone (up to 16 mg/L); in the bottom sediments of the creek, iron occurs as hematite (freshwater section) or pyrite (estuarine section). A variety of pyrite morphologies were identified in both bottom sediments and particulate matter samples including spherical closely packed framboids, and the rare form of euhedra which indicates slow crystallisation. The different components of this investigation have: 1) established the order and extent to which natural factors control weathering, 2) tested a number of analytical and numerical methods in evaluating weathering profiles, 3) assessed natural and anthropogenic factors and established the mobility sequence for trace metals in weathered profiles and, 4) determined the iron mineral speciation and established morphological variations of pyrite. As the area of Bells Creek catchment will be under development pressure in the future, findings of this study represent a baseline of comparison for environmental assessment and are of importance for environmental management.

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38

Mattos, Igino Zucchi de. "Competição inter familiar: exchange traded funds e fundos de investimentos passivos." reponame:Repositório Institucional do FGV, 2011. http://hdl.handle.net/10438/8532.

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With the ETF going to be used for more sophisticated investors and with the possibility to go on to win representation, either for a passive strategy or strategy combined with more specialized and higher risk assets, this paper seeks to explain and justify the coexistence of these vehicles, which has similar goals, but with different structures. With this objective, the study seeks to analyze the behavior and the effectiveness of passive investment products-funds classified as ETF´s (acronym for Exchange-Traded Fund) and Passive mutual funds in the Brazilian market. Study seeks to benchmark, demonstrating differentiations of products from a technical point of view, validating the behavior of managers and product for final investors. Despite recent academic literature, the study seeks to elucidate potential opportunities and relevant aspects to investors. The objective doesn't include make comparison between active funds and ETF´s in Brazil, only display the figures - returns obtained - in recent periods. Concluding with numeric examples, ETF becomes an attractive to investors as harnessing their potential, the fact this with relevant developments in the markets of Europe and United States, mainly.
Com o ETF passando a ser utilizado por investidores mais sofisticados e com a possibilidade de passar a ganhar representatividade, seja para uma estratégia passiva ou para uma estratégia combinada com ativos de maior risco e mais especializados, este paper busca explicar e justificar a coexistência destes veículos, que tem objetivos semelhantes, mas com estruturas diferentes. Com este objetivo, o estudo busca analisar o comportamento e a eficácia dos produtos passivos de investimentos - fundos classificados como ETF´s (sigla para Exchange-Traded Fund) e Fundos Mútuos Passivos no mercado brasileiro. Buscamos avaliar comparativamente, demonstrando diferenciações dos produtos do ponto de vista técnico, validando o comportamento dos gestores em relação a gestão passiva e de produto para os investidores finais. Apesar de literatura acadêmica recente sobre a comparatividade, o estudo busca elucidar possíveis oportunidades e aspectos relevantes para os investidores. Não é objetivo deste trabalho fazer relação comparativa entre produtos ativos de ações e os ETF´s no Brasil, apenas detalharemos o retorno obtido nos últimos períodos. O trabalho demonstra, com exemplos númericos, que o ETF torna-se um instrumento atrativo aos investidores na medida do aproveitamento de suas potencialidades, fato este com evolução relevante nos mercados da Europa e Estados Unidos, principalmente.

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39

Krepysheva, Natalia. "Transport anormal de traceurs passifs en milieux poreux hétérogènes : équations fractionnaires, simulation numérique et conditions aux limites." Avignon, 2005. http://www.theses.fr/2005AVIG0502.

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Dans de nombreux milieux poreux désordonnés, la dispersion de soluté n'évolue pas en accord avec la loi de Fick. Cette dernière prévoit l'évolution d'un panache de traceur à partir de données initiales modélisant, en particulier, une injection localisée. Alors, la concentration est une Gaussienne dont l'écart type est proportionnel à la racine carrée du temps. Des données expérimentales obtenues dans des aquifères ont mis en évidence des comportements qualitativement différents, remplaçant les Gaussiennes par des lois stables de Lévy. Celles-ci sont aussi des fonctions décroissantes, mais leur comportement asymptotique est celui d'une puissance, et en général leur second moment ne converge pas. Or les densités des lois stables de Lévy sont les solutions fondamentales d'une vaste classe d'équations aux dérivées partielles. Il s'agit des équations fractionnaires en espace, obtenues à partir de l'équation de la chaleur en remplaçant le Laplacien par une dérivée d'ordre non entier. D'autre part, ces équations régissent l'évolution de la concentration d'une population de marcheurs aléatoires effectuant des vols de Lévy : ces derniers généralisent le mouvement Brownien, avec, pour la densité des longueurs des sauts, une loi stable de Lévy. Ces point sont détaillés dans la thèse. Les principaux résultats concernent la dispersion dans un milieu semi-infini au sein duquel, tant que les particules de traceur n'approchent pas la frontière, la dispersion est décrite par des vols de Lévy, à petite échelle. On montre qu'avec une paroi reflexive, il est nécessaire de modifier le noyau de la dérivée fractionnaire présente dans l'équation régissant l'évolution de la concentration des marcheurs. Ce résultat théorique est illustré par une simulation de type Monte Carlo de cette évolution. On compare avec la simulation numérique de l'équation fractionnaire en milieu semi-infini
In a number of disordered porous, solute spreading does not obey Fick's law. The latter describes the evolution of a plume of tracer. When initial data represent a local impulse, the concentration is a Gaussian variance is proportional to time. Experimental data obtained in aquifers have put into evidence qualitatively different behaviors, replacing Gaussians by stable Lévy densities, which also are non increasing functions. But in the large values asymptotics, they behave algebraically, and in general the second moment does not converge. Moreover, stable Lévy densities are the fundamental solutions of a wide class of partial differetial equations, which are space-fractional equations. They resemble heat equation, with the Laplacean being replaced by a derivative of non-integer order. They also rule the evolution of the concentration of a cloud of random walkers performing Lévy flights, wich are more general than Brownian motion, with the jump length density being a stable Lévy law. All these point are detailed in the thesis. The main results concern the spreading of matter in a semi-infinite medium where the motion of tracer particles is described by Lévy flights (on the small scale) except when they meet the boundary. With a reflexive wall, it is necessary to modify the kernel of the fractional derivative on the right hand-side of the equation ruling the evolution of the concentration of walkers. The theoretical result is illustrated by a Monte Carlo simulation, and compared with the numerical discretization of the fractional equation in a semi-infinite medium

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Rigaud, Solange. "" La parure : traceur de la géographie culturelle et des dynamiques de peuplement au passage Mésolithique-Néolithique en Europe "." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00668694.

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De nombreux scenarii, incluant une variété de processus culturels et populationnels, ont été proposés pour décrire le phénomène de néolithisation en Europe. Le travail mené consiste à discuter ces processus, à travers une analyse diachronique des objets de parure utilisés par les communautés de chasseurs-cueilleurs et d'agriculteurs européens impliqués dans ces changements. La première partie du travail a consisté en l'analyse de 4 177 objets de parure, combinant des analyses morphométriques, technologiques et tracéologiques. Le matériel provient des séries archéologiques attribuées au Mésolithique final de Braña-Arintero (Espagne), de Hohlenstein-Stadel, Groβe Ofnet (Allemange) et des premières phases du Néolithique ancien de Essenbach-Ammerbreite (Allemagne). Les axes de travail développés à l'échelle régionale au cours de l'analyse du matériel ont ensuite été testés à l'échelle continentale à travers la constitution et l'analyse spatiale et statistique (analyses de voisinage, d'ordination, calculs de densité de Kernel et interpolations Spline) d'une base de données des éléments de parure recensés sur 1 022 unités stratigraphiques appartenant à 408 gisements attribués au Mésolithique et au Néolithique ancien en Europe. Les résultats obtenus ont été croisés et discutés dans une synthèse développée à l'échelle du continent européen. Il apparait que certains types d'ornements ont une fonction forte de marqueur identitaire territorial, alors que d'autres signent des échanges inter-régionaux et une diffusion des pratiques à une large échelle géographique. Il ressort également que les pratiques ornementales néolithiques semblent se construire sur un substrat mésolithique, à l'exclusion du Bassin égéen, où une discontinuité dans les pratiques ornementales mésolithiques et néolithiques semble exister. Cette participation active du substrat mésolithique dans l'évolution des pratiques ornementales a favorisé une régionalisation de celles-ci entre le Mésolithique et le Néolithique ancien. Parallèlement à cette variabilité régionale, un phénomène de " globalisation " des pratiques néolithiques s'observe à travers l'ensemble du territoire européen, par la présence de certains types d'ornements sur l'ensemble du continent, tout le long du Néolithique ancien. Cette globalisation des pratiques ornementales participe à une recomposition partielle de la géographie culturelle proposée pour le Mésolithique dans notre analyse. La variabilité ornementale régionale accrue à la fin du Néolithique ancien témoignerait d'une stabilisation territoriale de groupes, s'affranchissant partiellement des normes stylistiques des premières phases du Néolithique, tout en maintenant une partie de leur identité héritée des chasseurs-cueilleurs, enrichie par l'émergence de nouvelles pratiques. Nos résultats proposent ainsi qu'une mosaïque de processus culturels et populationnels aient été mis en œuvre au cours de la néolithisation européenne.

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Trommetter, Guillaume. "Développements analytiques et d’échantillonneurs passifs appliqués aux terres rares et platinoïdes : application aux systèmes aquatiques anthropisés." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R051.

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Les écosystèmes aquatiques sont des systèmes fragiles, vitaux pour la biosphère et cependant soumis à de nombreuses pressions anthropiques, parfois importantes. Actuellement, des méthodes fiables permettent la quantification et l’étude du devenir des éléments traces métalliques (Pb, Zn, Cd, etc.) et bon nombre de micropolluants organiques dans les eaux et les sédiments. Pour d’autres éléments comme les terres rares ou les platinoïdes, de plus en plus utilisés par l’industrie, leur quantification demeure en revanche plus complexe, voire encore incertaine du fait de leurs très faibles concentrations. Leur quantification est pratiquement impossible sans l’utilisation de techniques de préconcentration ou le développement de méthodes analytiques spécifiques pour réduire les interférences spectrales liés à des interférents présents en forte concentration dans l’environnement. Ce travail de recherche a permis (i) de quantifier précisément ces éléments par spectrométrie de masse à plasma par couplage inductif combiné à l’utilisation d’une cellule de collision/réaction en choisissant judicieusement le gaz et son flux appliqué dans la cellule ; (ii) de préconcentrer in situ puis de déterminer des concentrations variant du pg L-1 au ng L-1 pour les éléments du groupe du platine, dans des zones impactées par les activités humaines (lessivages des routes, rejets de médicaments à base de Pt), en développant des techniques d’échantillonnage passif dites « Diffusive Gradients in thin films (DGTs) » basées sur l’utilisation de deux résines différentes, et (iii) de mieux comprendre comment certains de ces éléments peuvent servir de traceurs de rejets urbains notamment liés aux stations de traitement des eaux usées contenant des rejets domestiques et hospitaliers, en complément des traceurs habituellement utilisés. Pour ce faire, la Marque Rivière a servi de site pilote pour cette étude prospective au cours d’une période d’étiage. Ces études ont permis de déterminer les concentrations actuelles des terres rares et platinoïdes dans des milieux fortement impactés par les activités humaines rendant possible le suivi de leur évolution et l’évaluation de leur potentiel impact dans le futur
Aquatic ecosystems are fragile systems, vital for the biosphere and yet subject to numerous, sometimes significant, anthropogenic pressures. Currently, reliable methods allow the quantification and study of the fate of metallic trace elements (Pb, Zn, Cd, etc.) and many organic micropollutants in water and sediments. For other elements such as rare earths or platinum group elements, which are increasingly used by industry, their quantification remains more complex and even uncertain due to their very low concentrations. Their quantification is practically impossible without the use of preconcentration techniques or the development of specific analytical methods to reduce the spectral interferences linked to interferents present in high concentrations in the environment. This research work has allowed (i) to quantify precisely these elements by inductively coupled plasma mass spectrometry combined with the use of a collision/reaction cell by judiciously choosing the gas and its flow applied in the cell ; (ii) to preconcentrate in situ and then determine concentrations ranging from pg L-1 to ng L-1 for platinum group elements, in areas impacted by human activities (road leaching, Pt-based drug releases), by developing passive sampling techniques called "Diffusive Gradients in thin films (DGTs)" based on the use of two different resins, and (iii) to better understand how some of these elements can be used as tracers of urban discharges, particularly in connection with wastewater treatment plants containing domestic and hospital discharges, in addition to the tracers usually used. To this end, the Marque River served as a pilot site for this prospective study during a period of low water levels. These studies made it possible to determine the current concentrations of rare earths and platinum in environments heavily impacted by human activities, making it possible to monitor their evolution and evaluate their potential impact in the future

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Leisher, Thomas Kai. "Exchange-Traded Funds: The Unknown Investment Opportunity." Wittenberg University Honors Theses / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wuhonors1617280855446967.

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Vystavna, Yuliya. "Déterminants environnementaux et socio-économiques, leur influence sur les métaux traces et les produits pharmaceutiques dans les cours d'eau : étude comparée sur deux rivières de France et d'Ukraine." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00716793.

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Les objectifs de cette étude comparative de deux bassins versants en France et en Ukraine sont de trois ordres. i) déterminer l'occurrence des micropolluants émergents (métaux traces et molécules pharmaceutiques) dans les eaux de surface, ii) permettre leur évaluation qualitative et quantitative et enfin iii) estimer leur distribution en fonction du contexte socio-économique. Cette recherche porte sur l'analyse de l'origine, sur les propriétés physico-chimiques et sur le comportement des micropolluants (métaux traces et molécules pharmaceutiques) dans les eaux des rivières Jalle (Bordeaux, France) et Udy & Lopan (Kharkiv, Ukraine). Un suivi des métaux traces et des produits pharmaceutiques dans les eaux naturelles de surface dans différents contextes et conditions climatiques a été réalisé. La description et l'analyse des facteurs environnementaux et socio-économiques influençant l'hydrochimie locale en vue de conclure sur l'opportunité et l'intérêt des micropolluants émergents comme indicateurs anthropogéniques du contexte socio-économique et environnemental d'un bassin versant ont été mis en oeuvre. L'étude a combiné des techniques de prélèvements d'échantillons d'eau classiques et par capteurs passifs in situ. L'analyse semi quantitative des micropolluants émergents a porté sur les métaux traces (sondes DGT) et les produits pharmaceutiques (POCIS). L'usage de ces capteurs a permis d'évaluer les différentes formes d'éléments, les sources, les variations saisonnières et spatiales, l'accumulation et les risques environnementaux. A partir des données environnementales collectées, acquises, actualisées et validées il a été possible de modéliser la consommation régionale de médicaments dans le cas de (1) la région de Kharkiv, en Ukraine, sur les rivières Lopan et Udy du bassin Seversky Donets et (2) la région de Bordeaux, en France, sur la rivière Jalle, du bassin de la Garonne. Les sites ont été sélectionnés pour représenter une diversité tant du point de vue de l'état de pollution des eaux (nature et flux) que de celui du paysage socio-économique (contexte urbain, social et indicateurs économiques). Les résultats majeurs de cette étude sont : (i) méthodologique pour le développement et la validation de protocoles d'échantillonnage classique et passif (intérêt, limites, recommandations), ii) analytique quant à la mesure des éléments traces des eaux de surface naturelles dans des conditions extrêmes, iii) scientifique par l'obtention d'un jeu de données sur l'hydrochimie des éléments traces ( présence, accumulation, origine et variabilité spatiale et temporelle et iv) prospectif quant à l'usage des métaux traces et de produits pharmaceutiques comme traceurs anthropiques de l'état des eaux naturelles de surfaces et reflet du contexte socio économique. La modélisation socio-économique (statistique) et environnementale (balance de masse) aide à comprendre l'évolution de la qualité des eaux de surface dans leur contexte régional et permet d'identifier certains contaminants comme des indicateurs des activités anthropiques d'un bassin versant et permet de définir une typologie. L'ensemble des résultats de la thèse ont présentés sous la forme d'articles publiés ou soumis dans des revues scientifiques internationales.

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Kummer, Larissa. "REMEDIAÇÃO DE SOLOS CONTAMINADOS POR METAIS PESADOS USANDO BIOSSURFACTANTE PRODUZIDO A PARTIR DE RESÍDUO AGROINDUSTRIAL." Universidade Estadual do Oeste do Parana, 2014. http://tede.unioeste.br:8080/tede/handle/tede/190.

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Made available in DSpace on 2017-05-12T14:47:01Z (GMT). No. of bitstreams: 1 Larissa_ Kummer.pdf: 3836984 bytes, checksum: 1746a7b3c060c75c722565a4bf452739 (MD5) Previous issue date: 2014-02-21
High concentrations of heavy metals in the soil can affect the sustainability of ecosystems and the health of humans and animals. The metal availability in the environment is related to the characteristics of each element, historical and source of contamination, as well as the properties of each soil. The presence of more than one element is common in contaminated areas and their interaction can affect their behavior in the environment. Researches have been developed to study the behavior of metals in different types of soils and thus help in cases of remediation. In recent years, the soil washing with biosurfactant has been presented as a promising method of remediation with little or no effect on the physico-chemical and microbiological characteristics of the soil, but the costs of obtaining this biosurfactant are still high, because most manufacturers use artificial means for production. Thus, this study had the objective of evaluating the remediation potential of the biosurfactant obtained from the fermentation of cassava water through the action of the bacteria Bacillus subtilis. This biosurfactant was characterized as surfactin, an anionic lipopeptide. Soils of different origins were used, one of them typical of the southwestern state of Paraná and the other from the northwest. The soils were first evaluated according to their potential for adsorption of the elements copper, zinc and lead in monometallic and multimetalic conditions, representing non-competitive and competitive conditions respectively. This evaluation was carried out by tests of adsorption and application of the matematical models of Langmuir and Freündlich. Soils were characterized chemically, physically and mineralogically. After that, it was performed the process of artificial contamination of these soils for application in the experiments of soil washing with biosurfactant in different conditions, having pH and concentration of biosurfactant solution as the main variables. Furthermore, it was also assessed the adsorption s capacity for metals by biosurfactant in liquid medium. The results showed that metals have different behaviors related to the adsorption and desorption to soil and to the biosurfactant. The soil type is also very important for the efficiency of metal removal. The clay soil showed higher adsorption capacity and therefore lower capacity of metal removal when compared to the sandy soil. In general, the soils showed the following sequence of adsorption capacity: Pb > Cu > Zn. The Pb was the element that less desorved by the washing process. It can also be concluded that, when soils are contaminated by more than one element at the same time, its ability to leach is greater than when the element is alone in the medium. This situation occurs because of differences between the competitive processes that take place in the active sites. The washing experiments showed that the biosurfactant was not able to improve the efficiency of removal of metals. The results obtained by the control treatments (only pure water) had very similar values to those that contained biosurfactant. When the wash solution containing the biosurfactant was in high concentrations, decrease in removel efficiency was found in some of the samples. Analysis of high performance liquid chromatography showed that the biosurfactant was adsorbed to soil samples, which is the consequence of not observing the effectiveness of the extractor in the removal of metals. It is notable, however, that the surfactin obtained has the potential to bind to metals, since the tests of adsorption to metals was confirmed by experiments. According to the results obtained, it can be inferred that the surfactin has greater potential for metal removal in liquid media than in solid medium, because of the lower possibility of adsorption. In soil, the results indicated potential use of this biosurfactant as stabilizing of metals in methods of remediation "in situ".
Concentrações elevadas de metais pesados no solo podem afetar a sustentabilidade dos ecossistemas e também a saúde dos seres humanos e animais. A disponibilidade do metal no ambiente está relacionada às características de cada elemento, histórico e fonte de contaminação, bem como às propriedades de cada solo. A presença de mais de um elemento em áreas contaminadas é comum e a interação entre eles pode afetar o seu comportamento no ambiente. Diante do problema, pesquisas vêm sendo realizadas a fim de estudar o comportamento dos metais em diferentes tipos de solos e assim auxiliar nos procesos de remediação. Nos últimos anos, a lavagem do solo com biossurfactante tem sido apresentada como um método promissor de remediação com pequeno ou nenhum efeito sobre as características físico-químicas e microbiológicas do solo, porém os custos de obtenção deste biossurfactante ainda são altos, pois a maioria dos fabricantes utiliza meios artificiais para sua produção. Neste sentido, este trabalho teve como objetivo geral avaliar o potencial de remediação do biossurfactante obtido a partir do bioprocessamento da manipueira pela ação de bactérias Bacillus subtilis. Este biossurfactante foi caracterizado como surfactina, um lipopeptídeo aniônico. Foram utilizados solos de origens distintas, sendo um deles típico da região sudoeste do estado do Paraná e outro da região noroeste. Os solos utilizados foram primeiramente avaliados de acordo com o seu potencial de adsorção dos elementos cobre, zinco e chumbo em condições monometálicas e multimetálicas, representando condições não-competitivas e competitivas, respectivamente. Esta avaliação foi feita por meio de testes de adsorção e aplicação de modelos matemáticos de Langmuir e Freündlich. Os solos foram caracterizados química, física e mineralogicamente. A partir de então realizou-se o processo de contaminação artificial destes solos para posterior aplicação dos experimentos de lavagem com o biossurfactante em diferentes condições, sendo as variáveis pH e concentração da solução de biossurfactante como as principais. Além disso, também foi avaliada a capacidade de adsorção dos metais pelo próprio biossurfactante, em meio líquido. Os resultados mostraram que os metais apresentam comportamentos distintos quanto a adsorção e dessorção ao solo e ao biossurfactante. O tipo de solo também é muito importante para a avaliação da eficiência de remoção de metais. O solo argiloso apresentou maior capacidade de adsorção e consequentemente menor capacidade de remoção dos metais quando comparado ao solo arenoso. De modo geral, os solos apresentaram a seguinte sequência de capacidade de adsorção: Pb > Cu > Zn. O Pb foi o elemento que menos dessorveu pelos processos de lavagem. Foi possível também concluir que quando os solos estão contaminados por mais de um elemento ao mesmo tempo, a capacidade de lixiviar-se é maior do que quando o elemento está sozinho no meio. Esta situação ocorre em virtude dos processos competitivos existentes entre os sítios ativos. Os experimentos de lavagem mostraram que o biossurfactante não foi capaz de melhorar a eficiência de remoção dos metais. Os resultados obtidos pelos tratamentos controle (somente água pura) tiveram valores muito semelhantes aos que continham biossurfactante. Quando a solução de lavagem continha o biossurfactante em altas concentrações, foi encontrada, em algumas amostras, queda na eficiência de remoção. Análises de cromatografia líquida permitiram concluir que o biossurfactante foi adsorvido às amostras de solo, sendo esta a consequência da não observação da eficácia do extrator na remoção dos metais. Cabe ressaltar, entretanto, que a surfactina obtida apresenta potencial de ligar-se aos metais, uma vez que os testes de adsorção desta aos metais foi confirmado pelos experimentos realizados. De acordo com os resultados encontrados, pode-se inferir que a surfactina tem maior potencial de remoção de metais em meio líquido do que em meio sólido, devido a menor possibilidade de adsorção na matriz sólida. Em solo, os resultados indicaram potencial de utilização deste biossurfactante como agente de estabilização dos metais em métodos de remediação in situ .

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Rodts, Stéphane. "Etude du passage micro-macro pour le transport par diffusion en milieu poreux. Application aux expériences de RMN-GCP." Phd thesis, Ecole des Ponts ParisTech, 2001. http://tel.archives-ouvertes.fr/tel-00005684.

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Ce travail a un double but :
1) Observer et identifier les mécanismes physiques via lesquels, dans les matériaux poreux homogènes, les lois microscopiques du transport par diffusion induisent généralement des lois de transport effectives macroscopiques très simples, quelque soit la complexité du réseaux poreux sous jacent.
2) Contribuer à développer le cadre d'interprétation des expériences RMN de Gradient de Champ Pulsé (GCP) pour la mesure de l'autodiffusion dans les fluides confinés dans les systèmes poreux.
Nous étudions le cas académique de la diffusion Fickienne sans adsorption. Nous observons le transport à échelle de longueur fixée, en suivant la cinétique avec laquelle "s'affaisse" par diffusion l'amplitude G(q,t) de "profils de concentration sinusoïdaux" de vecteur d'onde q variable. Vis à vis de la RMN cette approche revient à étudier le propagateur de diffusion G(q,t) - grandeur mesurée par l'expérience - de manière non traditionnelle, c'est à dire, à q fixé en fonction du temps t. A q donné, 3 régimes de temps sont mis en évidence : un régime de temps court de diffusion non confinée, un régime de temps intermédiaire renseignant sur la diffusion à l'échelle de longueur 2pi/q, et un régime de temps long sensible à la "dimensionnalité" de l'espace poral.
Nous caractérisons la cinétique d'affaissement aux temps intermédiaires par un coefficient e diffusion D(q). Son étude théorique et expérimentale en fonction de q dans des systèmes périodiques et/ou désordonnés simples fait apparaître clairement trois phénomènes lors du passage micro-macro : une première interaction avec l'interface, une différentiation brutale du rôle des différents pores, puis une diffusion anormale due à cette différentialité, susceptible de perdurer aux échelles macroscopiques, et suivie par un retour au régime "Fickien".
Une expérience macroscopique de traceur est enfin proposée et développée pour observer ces phénomènes de diffusion anormale dans quelques systèmes modèles.

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Dubos, Thomas. "Cascade bidimensionnelle d'un traceur : diagnostic dans l'espace physique et modélisation." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2001. http://tel.archives-ouvertes.fr/tel-00007421.

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Nous présentons des résultats numériques et théoriques concernant les cascades en turbulence bidimensionnelle, et plus spécialement la cascade d'un traceur, en développant une approche dans l'espace physique. Une telle approche permet de mettre en évidence l'absence d'intermittence dans la cascade inverse d'énergie, y compris dans des situations dominées par les structures cohérentes. Le coeur de la thèse est consacré à l'analyse et à la modélisation de la cascade d'un traceur. Nous proposons une méthode de diagnostic de la cascade d'un traceur : considérant l'évolution d'un incrément de traceur, nous définissons dans l'espace physique le flux entre échelles de la variance de traceur. Nous nous intéressons ensuite au problème de la paramétrisation du mélange turbulent. Nous justifions l'emploi une paramétrisation anisotrope, que nous baptisons diffusivité de déformation (strain diffusivity, SD)[Dubos01]. Nous relions ses propriétés diffusives aux propriétés géométriques de l'écoulement. La vorticité est en deux dimensions un traceur actif, et la paramétrisation sous-maille pour la vorticité agit sur la vitesse. La cascade inverse d'énergie impose aux paramétrisations admissibles de conserver l'énergie. Nous montrons que la SD conserve l'énergie, et qu'elle est la seule d'une classe de modèles simples. Nous étudions numériquement les propriétés des outils introduits. Nous montrons que, contrairement à une diffusivité/hyperdiffusivité isotrope, la SD induit une diffusion bien corrélée au flux local de variance de traceur. Le filtre effectif qu'elle impose correspond au filtre gaussien à partir duquel elle est calculée. Cependant la réduction de l'erreur commise en cas d'utilisation d'une méthode spectrale et d'un filtre raide n'est pas évidente. Appliquée à la vorticité dans une situation où le forçage est à très petite échelle, la SD démontre en revanche une bien meilleure représentation des grandes échelles qu'une hyperdiffusivité. Enfin, nous analysons comparativement les propriétés de cascade de la vorticité et d'un traceur passif. Les critères de comparaison reposent sur des moyennes conditionnelles des dérivées lagrangiennes du carré du gradient du traceur. Nous mettons en évidence pour un champ aléatoire une différence cinématique entre traceur passif et vorticité, dont il subsiste une trace dans des champs turbulents.

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Hafsaoui, Aymen. "Peformances de Niveau Applicatif en Environnement Filaire et sans Fil." Phd thesis, Télécom ParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00669973.

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L'intérêt pour l'analyse passive de traces a considérablement augmenté, nous offrant de nouvelles approches pour analyser et améliorer les performances réseaux. L'hétérogénéité d'Internet est en constante évolution : nouvelles technologies d'accès, des clients avec mobiles et toujours de plus en plus de services et d'applications. D'autre part, l'intérêt pour la mesure de performance des réseaux d'entreprises ne cesse de se développer. Ces sujets sont d'une importance cruciale pour les fournisseurs de services Internet, gestionnaires de réseaux et des entreprises, puisqu'ils ont déjà reçu une attention considérable de la part de la communauté de recherche. Malgré ces efforts, un certain nombre de questions reste ouvert. Dans cette thèse on traite le trafic TCP, qui représente la majorité des flux Internet. Lors de cette analyse, nous nous concentrons sur les connexions complètes, du point de vue TCP. Le présent travail se compose de trois parties traitant différent aspects sur les approches actuelles d'analyse de performances de TCP, l'étude des performances et la détection d'anomalies de niveau applicatif. Dans la première partie, nous présentons les travaux les plus importants, les traces réseaux sur lesquelles nous nous sommes basé ainsi que les problèmes rencontrés lors de l'étude des performances de TCP au niveau applicatif. Nous présentons un premier aperçu de l'impact de l'application sur les transferts TCP. Nous démontrons que si les pertes peuvent avoir un impact négatif sur les petits transferts TCP, l'application affecte de manière significative le temps de transfert de la majorité des flux. Dans cette partie, nous démontrons que certaines mesures peuvent être biaisées par des technologies spécifiques mises en oeuvre dans les réseaux Cellulaires. Dans la seconde partie, nous comparons sur des traces passives, les performances de clients Internet, d'un même operateur sur les trafics : Cellulaires, FTTH et ADSL. Nous montrons que l'étude des paramètres classiques d'analyse de performance ne permet pas d'expliquer totalement les performances perçues par les clients. Ensuite, nous validons une approche plus fine, permettant de décomposer chaque connexion TCP, bien formée, en intervalles de temps. Notre approche de décomposition de connexion TCP permet d'extraire automatiquement l'impact du comportement de l'application, l'accès, le serveur et le client. Nous regroupons, avec des algorithmes adéquats, les transferts avec des performances similaires sur les différents types d'accès. Puis, nous proposons une caractérisation de certains aspects de l'analyse de trafic dans un reseau d'entreprise. Dans la dernière partie, nous nous concentrons sur la problématique de profilage d'anomalies sur les connexions TCP, définis comme correct mais avec des performances anormales. Notre méthode permet d'identifier la cause des problèmes de performance, qui peuvent être soit des pertes ou bien des temps perdus lors de la préparation des données ou du transfert. Nous appliquons cette approche pour le cas de plusieurs traces de trafic Internet et entreprise. Nous démontrons l'existence d'une adaptation spécifique pour la récupération sur les pertes sur le réseau Cellulaire qui semble plus efficace que sur les réseaux filaires.

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48

Hennequin-Marot, Elisabeth. "Utilisation des réactions nucléaires (neutron, α) et (neutron, proton) pour la détection d'isotopes stables en biologie." Rouen, 1986. http://www.theses.fr/1986ROUES023.

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Exemple de l'application en biologie des détecteurs solides de traces: localisation quantitative de la réaction nucléaire 6 lithium (neutron, alpha) 3 hydrogène dans l'étude du transfert placentaire du lithium, au cours du développement embryonnaire de la souris. Recherche des conditions d'obtention de détecteurs à bas mouvement propre dans le but d'appliquer la technique à la détection d'autres éléments tels que l'azote et l'oxygène

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49

Roche, Agnès. "Mise au point et étude d'échantillonneurs diffusifs pour le suivi de l'exposition personnelle aux concentrations atmosphériques de benzène, toluène, éthylbenzène et xylènes BTEX et d'aldéhydes." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10018.

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Le principe des echantillonneurs diffusifs repose sur la diffusion des composes organiques volatils, regie par la premiere loi de fick, jusqu'a un adsorbant sur lequel ils sont pieges. Ces appareils sont de plus en plus utilises pour controler les atmospheres de travail, mais on connait tres peu leurs capacites en milieu peu pollue. Il s'agit donc d'une etude menee sur des echantillonneurs de type tube pour les btex en les testant et en les etalonnant a tres basses concentrations (ppbv) dans des chambres de simulation, dans differentes conditions (humidite, agitation atmospherique), et si besoin en les modifiant (changement de la phase d'adsorption). Les durees d'exposition ont varie de une heure a cinq jours. Les etalonnages ont ete effectues a partir de la determination des concentrations par un echantillonnage dynamique des atmospheres. Nous avons d'abord tester le tenax ta comme adsorbant, et avons montre que les vitesses d'enrichissement des composes les plus volatils tels que l'hexane et le benzene n'etaient pas lineaires. Nous avons pu expliquer ces phenomenes par la difference de volatilite et par l'equilibre entre les composes et l'adsorbant. Pour etudier ces phenomenes, nous avons teste un deuxieme adsorbant, le carbopack b. Celui ci possede une plus grande affinite pour les composes etudies. En effet, nous obtenons a doses d'exposition egales un enrichissement legerement plus important sur le carbopack b, mais nous avons conserve cette non-linearite. Cette derniere n'empeche pas l'utilisation de ces echantillonneurs : on peut tracer une courbe de tendance d'enrichissement, et s'y referer pour calculer la concentration moyenne a laquelle l'echantillonneur a ete expose. L'utilisation de ces echantillonneurs a ete validee par des campagnes de prelevements en milieu urbain avec des comparaisons entre prelevements dynamiques et diffusifs. Pour les composes aldehydiques un echantillonneur de type badge a ete cree. Dans ce dernier cas, le milieu adsorbant est un filtre impregne de 2,4 dinitrophenylhydrazine. Cet echantillonneur a ete calibre en suivant le meme protocole que celui etabli auparavant. Afin d'etudier les parametres qui influent sur ces prelevements diffusifs, nous avons fait varier le nombre de filtres dans un echantillonneur, ainsi que la porosite des filtres. Nous avons ainsi pu ameliorer la limite de detection et la quantitativite par rapport aux echantillonneurs commercialises. L'utilisation de ces echantillonneurs a ete validee par des mesures en atmosphere faiblement concentree.

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Bhurtun, Pratima. "Dynamique de la qualité des masses d’eau dans le bassin Artois-Picardie : compréhension des mécanismes actuels et prévision des évolutions dans un contexte de changement climatique." Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1R055.

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La Selle Rivière, cours d’eau non canalisé du bassin Artois-Picardie est considérée par l’Agence de l’Eau comme une masse d’eau prioritaire dont la qualité est à améliorer. L’objet de ce travail a été d’étudier le comportement spatio-temporel de plusieurs substances déclassantes ou non, avec des échelles de temps allant du prélèvement ponctuel à la mesure haute fréquence, en passant par des échantillonneurs passifs intégrateurs. Nous nous sommes intéressés à plusieurs traceurs de la contamination urbaine, agricole et industrielle, au travers des nitrates, des phosphates, des éléments traces métalliques, de certains produits phytosanitaires et pharmaceutiques, et de la matière organique dissoute. Dans un premier temps, nous avons confirmé que la Selle est principalement alimentée par les eaux souterraines riches en nitrates, avec des teneurs résiduelles en atrazine qui se retrouvent dans le cours d’eau à des concentrations similaires. Par ailleurs, le bassin versant étant très agricole dans sa partie amont et avec des ilots urbains plutôt localisé en aval, quelques pesticides et médicaments sont retrouvés à l’état d’ultra-traces par temps sec, et des teneurs en phosphates souvent supérieures à 0,2 mg L-1. Les métaux sont peu présents dans le cours d’eau malgré des teneurs pouvant être élevées en sortie de stations d’épuration (notamment Gd et Zn) car les débits des stations représentent des apports mineurs. La mesure haute fréquence a permis de préciser des problèmes de qualité d’eau par temps de pluie avec des lessivages de sols, et des pics importants mais limités dans le temps en phosphore et carbone organique alors que l’on observe une dilution des nitrates. La composition de la matière organique étudiée par spectroscopie de fluorescence a permis de caractériser la signature spectrale de différents types d’eau (souterraine, de surface et effluent de station d’épuration) et de différencier les apports allochtones des apports autochtones. Enfin, ces résultats permettent de discuter qualitativement les futurs effets du changement climatique à l’échelle régionale sur l’évolution de la qualité de la Selle Rivière
The River Selle is a non-channelised stream in the Artois-Picardy basin and is considered as a priority waterbody by the Artois-Picardy Water Agency. The aim of this work was to study the spatio-temporal behaviour of several substances at different time scales, ranging from low-frequency (grab sampling, passive samplers) to high-frequency monitoring. More specifically, tracers of pollution reflecting urban, agricultural and industrial contamination (nitrates, phosphates, trace metal elements, pesticides, pharmaceutical residues, dissolved organic matter) were investigated. We confirmed that the River Selle is mainly fed by a nitrate-rich groundwater. Besides, the nitrates and atrazine concentrations in the river water were similar to those found in the groundwater. At the upstream of the river, the land-use is mainly dominated by agriculture whereas most of the urban islets are located at the downstream of the river. Consequently, during dry weather, ultra-trace concentrations of some pesticides and pharmaceutical residues were recorded and phosphate levels often exceeded 0.2 mg L-1. Due to the minor flow input of the wastewater treatment plants into the river, metallic contamination in the River Selle (particularly Gd and Zn) is quite low despite the high concentrations measured in wastewater effluents. Water quality issues during storm events were identified by high-frequency monitoring. Significant but time-limited peaks in phosphorus and organic carbon were observed, while nitrates were diluted. The composition of dissolved organic matter was studied by fluorescence spectroscopy. The spectral signature of different types of water (groundwater, surface water and wastewater effluents) was characterised as well as the origins of this organic matter (autochtonous vs allochthonous). Finally, these results enable to discuss qualitatively the future effects of climate change at a regional scale on the evolution of the water quality of the River Selle

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Dissertations / Theses on the topic 'Passive traces'

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