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Maaß, Stefanie [Verfasser]. "Niche and neutral processes in a dry grassland: the example of oribatid mites / Stefanie Maaß." Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1077212038/34.
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Schröder, Arne. "Alternative Stable States in Size-Structured Communities : Patterns, Processes, and Mechanisms." Doctoral thesis, Umeå University, Ecology and Environmental Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1628.
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<p>Alternative stable states have been, based on theoretical findings, predicted to be common in ecological systems. Empirical data from a number of laboratory and natural studies strongly suggest that alternative stable states also occur in real populations, communities and ecosystems. Potential mechanisms involve population size-structure and food-dependent individual development. These features can lead to ontogenetic niche shifts, juvenile recruitment bottlenecks and emergent Allee effects; phenomena that establish destabilising positive feedbacks in a system and hence create alternative stable states.</p><p>I studied the consequences of population size-structure for community dynamics at different scales of system complexity. I performed laboratory and ecosystem experiments. Small poecilliid fishes and planktonic invertebrates with short generation times and life spans were used as model organisms. This allowed me to assess the long-term dynamics of the populations and communities investigated.</p><p>The main experimental results are: (a) An ontogenetic niche shift in individuals of the phantom midge <i>Chaoborus</i> made the population vulnerable to an indirect competitive recruitment bottleneck imposed by cladoceran mesozooplankton via rotifers. Consequentially the natural zooplankton food web exhibited two alternative attractors. (b) Body size determined the success of <i>Poecilia reticulata</i> invading resident population of <i>Heterandria formosa</i> and thus the type of alternative stable state that established. Small invaders were outcompeted by the residents, whereas large invaders excluded their competitor by predating on its recruits. (c) External juvenile and adult mortality altered the internal feedback structure that regulates a laboratory population of <i>H. formosa</i> in such a way that juvenile biomass increased with mortality. This biomass overcompensation in a prey population can establish alternative stable states with top-predators being either absent or present.</p><p>The major conclusion is that size-structure and individual growth can indeed lead to alternative stable states. The considerations of these ubiquitous features of populations offer hence new insights and deeper understanding of community dynamics. Alternative stable states can have tremendous consequences for human societies that utilise the ecological services provided by an ecological system. Understanding the effects of size-structure on alternative stability is thus crucial for sustainable exploitation or production of food resources.</p>
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Delgado, de la flor Yvan A. "Spider and Beetle Communities across Urban Greenspaces in Cleveland, Ohio: Distributions, Patterns, and Processes." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587656050129337.
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Meager, Justin J. "The microhabitat distribution of juvenile banana prawns, Penaeus merguiensis de Man in subtropical Eastern Australia and processes affecting their distribution and abundance." Thesis, Queensland University of Technology, 2003.
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Valverde-Barrantes, Oscar Jesus. "A phylogenetic perspective on fine root ecology: assessing the role of root evolution on fine root functional traits and ecological interactions in woody angiosperms." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1384641579.
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Berggren, Christina. "PRODUCT MANAGEMENT SYSTEM : A BRIDGE BETWEEN THE CUSTOMER ANDCOMPANY’S BUSINESS MODEL AND STRATEGY FORNICHE COMPANIES IN OLIGOPOLY MARKETS." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-300383.
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For smaller niche companies in an oligopoly market to survive and grow, they need to focus on either having unique products and/or unique, more efficient internal processes compared to their larger competitors. One possible success factor for these smaller companies is to exploit the business potential found in an increasingly digitalized world. To fully utilize this potential, it is necessary for companies to ensure that their business models and strategies include performing a digital transformation as one of their key focus areas. This study focuses on the benefits that a company can derive from creating a digitalized back-end product management system that is integrated with a front-end, online user interface. The two research questions answered in this study are related to the interrelationship between business model and strategy and the creation of a digitalized product management system. In order to answer these questions, two case studies of three smaller, niche companies operating on the Swedish oligopoly markets of telecommunication and power distribution were performed. Interviews were held with representatives from these companies and the results of the interviews were coded by utilizing a Research Framework created for this study. The Research Framework was created based on the performed literature review including the dynamic capabilities concept that encompasses a company’s ability to sense, seize and transform itself to create a successful business model. The results of the case studies showed the benefits of digitalization in designing and utilizing a product management system that is integrated with a front-end user interface. Such an integrated platform should support in achieving increased customer satisfaction, as customers increasingly expect their suppliers to have a platform that enables them to online make their product choices, administrate their own accounts and retrieve historical data. This is part of a societal trend that smaller niche companies can utilize in their business model and strategy to in an agile manner meet the competition from their larger competitors. Besides increasing customer satisfaction, a well designed, digitalized product management system integrated with an online user interface makes it possible to decrease the need for manual administrative processes. This results in an increase in efficiency and reduced costs within a company or gives the employees the opportunity to focus on more value added activities. In this manner, the product management system has shown to be an important bridge between customers, product offerings, internal business management processes and a company’s business model and strategy.<br>För att mindre nischföretag på en oligopolmarknad ska kunna överleva och växa måste de fokusera på att ha unika produkter och/eller unika, effektivare interna processer jämfört med sina större konkurrenter. En möjlig framgångsfaktor för dessa mindre företag är att dra fördel av den affärspotential som finns i en alltmer digitaliserad värld. För att fullt ut kunna utnyttja denna potential är det nödvändigt för företag att se till att deras affärsmodell och strategi inkluderar att genomföra en digital omvandling som ett av dess viktigaste fokusområden. Denna studie fokuserar på de fördelar som ett företag kan få av att skapa ett digitaliserat produkthanteringssystem som är integrerat med ett online kundanvändargränssnitt. De två forskningsfrågorna som besvaras i denna studie är relaterade till sambandet mellan affärsmodell och strategi och skapandet av ett digitaliserat produkthanteringssystem. För att svara på dessa frågor utfördes två fallstudier av tre mindre nischföretag som verkar på de svenska oligopolmarknaderna för telekommunikation och kraftdistribution. Intervjuer hölls med representanter från dessa företag och resultaten av intervjuerna kodades genom att använda ett ramverk som skapats för denna studie. Ramverket skapades baserat på den utförda litteraturstudien, inklusive konceptet om dynamisk kapabilitet som omfattar ett företags förmåga att känna, agera och förändra för att skapa en framgångsrik affärsmodell. Resultaten från fallstudierna visade värdet av en digitalisering i utformningen och användningen av ett produkthanteringssystem som är integrerat med ett online kundanvändargränssnitt. Dessa fördelar inkluderar ökad kundnöjdhet, eftersom kunder i allt högre grad förväntar sig att deras leverantörer har produkthanteringssystem som gör det möjligt för dem att online göra sina produktval och administrera sina egna konton. Detta är en del av en samhällelig trend som mindre nischföretag kan använda i sin affärsmodell och strategi för att på ett agilt sätt möta konkurrensen från sina större konkurrenter. Förutom ökad kundnöjdhet gör ett väl utformat och digitaliserat produkthanteringssystem integrerat med ett online kundanvändargränssnitt det möjligt att minska behovet av manuella administrativa processer. Detta resulterar i en effektivitetsökning och minskade kostnader i ett företag och ger medarbetarna möjlighet att fokusera på arbetsuppgifter som ger mervärde. På detta sätt har produkthanteringssystemet visat sig vara en viktig bro mellan kunder, produktutbud, interna affärshanteringsprocesser och företagets affärsmodell och strategi.
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Hornoy, Benjamin. "Processus évolutifs contribuant au succès envahissant de l'ajonc d'Europe, Ulex europaeus." Phd thesis, Université Rennes 1, 2012. http://tel.archives-ouvertes.fr/tel-00740154.
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Etudier les invasions biologiques est essentiel dans le cadre de la conservation de la biodiversité. De plus, elles représentent de véritables expérimentations grandeur nature pour appréhender les processus écologiques et évolutifs. La problématique de cette thèse est d‟étudier la contribution de processus évolutifs dans le succès envahissant de l‟ajonc d‟Europe, Ulex europaeus, à travers le monde, notamment en relation avec la perte de ses ennemis naturels (Enemy Release). La première partie s‟intéresse à l‟évolution de l‟ajonc dans sa zone d‟origine et au moment de l‟introduction dans de nouvelles régions, (i) en synthétisant les résultats concernant le polymorphisme de traits et la plasticité phénotypique, (ii) en couplant des données historiques et moléculaires pour inférer le mode d‟introduction de l‟ajonc dans le monde et ses conséquences sur la diversité génétique introduite. La deuxième partie s‟intéresse à l‟évolution post-introduction des populations d‟ajonc. Elle s‟appuie principalement sur des comparaisons en jardin expérimental d‟ajoncs issus de populations de régions d‟origine et envahies. L‟évolution des traits d‟histoire de vie et des stratégies de défense contre les ennemis a été étudiée en lien avec la perte d‟ennemis spécialistes en zone introduite. Nos résultats suggèrent que l‟histoire évolutive dans la zone d‟origine et le mode d‟introduction volontaire par l‟Homme ont conféré un fort potentiel évolutif aux populations d‟ajonc introduites. De plus, un relâchement des corrélations génétiques dans les régions d‟introduction a pu entraîner une évolution plus libre des traits d‟histoire de vie, facilitant l‟adaptation locale à une large gamme d‟environnements. Ces résultats suggèrent que l‟étude conjointe des niches écologiques et des matrices G pourrait permettre une meilleure compréhension des processus impliqués dans les invasions biologiques.
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Kelner, Maëlle. "Analyse des processus de glissements gravitaires sous-marins par une approche géophysique, géotechnique et expérimentale : cas de la pente continentale de Nice." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4113/document.
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Les glissements de terrains sous-marins, même de petite taille, représentent un risque majeur d’érosion littorale et de submersion marine lorsqu’ils sont déclenchés à proximité des côtes. Ce fut le cas à Nice (France) avec l’effondrement en mer d’une partie de la plateforme aéroportuaire, suivit d’un tsunami du fait d’un glissement sous-marin en octobre 1979. Du fait que la pente continentale niçoise soit abrupte, à proximité des côtes et soumise à une activité sismique modérée, elle constitue un véritable laboratoire naturel pour l’étude des glissements sous-marins de petite échelle. Ce travail repose sur une approche multidisciplinaire permettant une étude globale des processus de glissement dans la zone proximale. Il intègre des données issues de la géophysique marine, de la sédimentologie de la géotechnique et une phase préliminaire de modélisation numérique. Pour la première fois, la morphologie ainsi que l’architecture des dépôts du delta du Var ont été investigués à partir de données de très haute résolution. Elles ont permis d’identifier la signature de nombreux processus gravitaires de petite taille en surface (morphologie / taille / répartition spatiale) ainsi que leur imbrication en profondeur. Dans le cas du glissement de 1979, des éléments encore inconnus ont été identifiés tels que : 1) ses cicatrices Est et Ouest ; 2) des blocs et paquets glissés non évacués ; 3) la surface de glissement en profondeur ; 4) l’estimation d’un volume total déplacé différent du volume de sédiments évacués. Les carottes sédimentaires ont ensuite permis de discuter de la répartition en zone proximale des dépôts/érosion et de l’enregistrement de paléoglissement à partir de l’état de surconsolidation des dépôts. L’activité des glissements a été estimée dans le temps. Les plus grands glissements (V > 106 m3) ont des fréquences estimées ~50 ans, les glissements de taille moyenne (105 < V < 106 m3) autour de 3 à 25 ans, et les nombreux petits glissements (V < 105 m3) tous les 1-2 mois à 5 ans au cours des périodes actives des 50 dernières années. Ces glissements sont enregistrés dès la zone proximale à des fréquences de 3-7 ans au cours des périodes de plus forte activité depuis 400 ans. L’évolution de la morphologie suit des cycles successifs de déclenchement/quiescence/rechargement. À l’échelle de temps humaine deux cycles s’étendent de 1967-1999 et de 1999-2011 ; les ruptures se regroupent en cluster de 5-10 ans. À l’échelle pluriséculaire, les clusters de turbidites durent 20-40 ans et les périodes de quiescence ~100 ans. Enfin, cette étude apporte de nouvelles contraintes à propos des facteurs déclenchants ou préconditionnants agissant sur le delta du Var. L’état de stabilité de la zone semble être fortement préconditionné par la complexité de la topographie, l’état de consolidation des sédiments et l’importance des apports sédimentaires du Var. L’architecture des dépôts semble principalement contraindre la profondeur des instabilités. Parmi les forçages externes connus sur la zone, nous avons cartographié l’extension de la zone riche en gaz ainsi que des panaches de fluides dans la colonne d’eau. Notre analyse montre que l’amplitude des précipitations, des crues et du niveau de la nappe alluviale seraient trop faibles au cours des 50 dernières années pour agir en tant que facteur déclenchant de manière isolée. Afin de déstabiliser les pentes, ces forçages semblent devoir être couplés entre eux ou associés à l’action de séismes. Les analyses des bases de données en lien avec l’activité des glissements ainsi que les tests numériques permettent de suggérer que la sismicité régionale et que les séismes historiques sont soit 1) de magnitude trop faible, soit 2) à de trop grandes distances des zones de déclenchement, pour générer des PGA assez fort (0,2 g) et avoir individuellement un impact sur les pentes du Delta<br>Small submarine landslides, when triggered near the coast represent a major coastal hazard due to erosion of the coastline and marine submersion. In October 1979, a submarine landslide generated a part of the airport platform of Nice (France) to collapse at sea and provoked a tsunami. Because the continental slope off this region is abrupt, close to the coast and subject to moderate seismic activity it is a natural laboratory to study small-scale submarine mass movements processes. This work is based on a multidisciplinary approach allowing a global study of landslide processes in the source area. It integrates data from marine geophysics, sedimentology, geotechnics and numerical modelling. For the first time morphology and architecture of the Var delta deposits are investigated using very high resolution data. It allows identification of numerous small-size gravitational processes signatures as well as their embedding at depth. In the case of the 1979 landslide previously unknown features are identified: 1) eastern and western scars, 2) in-situ blocks and lateral spreading’s traces, 3) in-depth sliding surface, 4) estimation of a total displaced volume, which is different from the evacuated sediment volume. The sedimentary cores are then used to discuss the proximal distribution of deposits, erosion and paleo-landslides records from the deposits overconsolidation. The landslide activity has been estimated over time in terms of return frequencies. The largest landslides (>106 m3) have return frequencies nearing 50 years; the medium-size landslides (105 > V > 106 m3) between 3 and 25 years; and the numerous small landslides (<105 m3) every 1-2 months to 5 years during the most active periods in the last 50 years. Landslides deposits recorded in the source area show return frequencies of 3-7 years during periods of greater activity over the last 400 years. The morphology’s evolution follows successive cycles of sliding/quiescence/reloading. In recent times, two main cycles can be observed (from 1967 to 1999 and from 1999 to 2011) during which triggering are clustered in 5-10 years. On a longer time scale, the turbidites clusters span 20-40 years and quiescence periods ~100 years. Finally, this study brings new constraints on preconditioning and triggering factors acting on the Var delta. The stability of the area seems to be strongly conditioned by the complexity of the topography, the sediments consolidation and the quantity of sediments brought by the Var river. The deposits architecture mainly constrains the depth of the instabilities. Among the external drivers known in the area the extension of the gas-rich zone as well as fluids plumes in the water column have been considered and mapped. Looking at other external drivers, the analysis shows that the magnitude of rainfall and floods, and the alluvial water level would be too low over the past 50 years to act as an isolated triggering factor. In order to destabilize slopes, these external drivers need to be tackled together or associated to earthquakes. Relationships between databases analyses, landslides activity and numerical tests suggest that regional seismicity and historical earthquakes are either too small or too distant from the source areas to generate sufficient peak ground acceleration (0.2 g) and to have an individual impact on the delta slopes
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Barros, Tadeu de Siqueira. "Integrando processos ambientais e espaciais na ecologia de comunidades aquáticas em escala regional." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/1674.
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Previous issue date: 2010-06-25<br>Universidade Federal de Sao Carlos<br>For decades the search for determinants of biodiversity and structuring processes of natural communities has been concentrated on the role of environmental factors and differences in species niche. The neutral theory of biodiversity challenged this view by assuming functional equivalence between species and a major role of stochastic spatial processes. In this thesis, I aimed at analyzing how local and regional ecological processes interact to influence the structure of aquatic metacommunities. The thesis has three chapters. In the first one, I investigated one of the most widespread patterns in ecology, the relationship between species local abundance and regional distribution. I used niche characteristics, estimated independently from local and landscape metrics, to explain the relationship. In the second chapter, I tested whether common and rare species are influenced by environmental and spatial processes in a different manner. In the last chapter, I tried to identify taxon association within the Chironomidae that occur in São Paulo State. Besides, I built ecological models considering information from environmental and spatial processes at different scales aiming at predicting theses associations. In general, I conclude that to understand the dynamics of aquatic metacommunities one must include local, landscape and spatial variables in the analyses. Furthermore, it seems that some species do not differ in their realized niches. In other words, they occupy parts of the environmental gradient in a similar way, thus they respond in a similar way to the same type of ecological processes. This opens an avenue for monitoring and conservation programs. For example, we can use a reduced number of species to monitor entire communities. In my opinion, now we need to advance the way we measure and include spatial processes like dispersal in our models.<br>Durante décadas a procura pelos processos que estruturam as comunidades e os determinantes da biodiversidade esteve voltada para o papel de fatores ambientais locais e diferenças no nicho das espécies. A teoria neutra de biodiversidade desafiou esta visão assumindo equivalência funcional entre espécies e maior importância de processos espaciais estocásticos. Nesta tese, eu procurei analisar como processos ecológicos locais relacionados aos nichos das espécies e regionais relacionados a dispersão de espécimes interagem para influenciar a estrutura de metacomunidades. A tese está dividida em três capítulos. No primeiro, eu investiguei um dos padrões mais recorrentes em ecologia, a relação entre abundância local e distribuição regional de espécies. Eu usei características do nicho dos táxons (Chironomidae: Diptera), utilizando métricas locais e de paisagem independentemente, para explicar a relação. No capítulo dois, eu testei se espécies comuns e raras são influenciadas por processos ambientais e espaciais de diferentes maneiras. No último capítulo, eu busquei identificar associações de táxons concordantes entre os Chironomidae que ocorrem no Estado de São Paulo. Além disso, construí modelos contendo informação sobre processos ambientais e espaciais em diferentes escalas para predizer essas associações. Considerando os três estudos, é possível concluir que o entendimento da dinâmica de metacomunidades passa pela inclusão de variáveis locais, de paisagem e espaciais nas análises e que muitas espécies podem não diferir marcadamente em seus nichos realizados. Ou seja, elas ocupam partes do gradiente ambiental de maneira similar, e portanto respondem de maneira similar aos mesmos tipos de processos ecológicos. Isso abre um caminho promissor para programas de monitoramento e conservação da biodiversidade. Podemos, por exemplo, usar um número reduzido de espécies táxons associados para monitorar grande parte das comunidades. Em minha opinião, agora devemos nos aprofundar em conseguir medir melhor processos espaciais como dispersão e colonização.
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Melo, Lilian Sayuri Ouchi de [UNESP]. "A similaridade no uso do microhabitat por girinos (Amphibia, Anura) reflete processos ecológicos ou filogenéticos?" Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110980.
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000799449.pdf: 2022440 bytes, checksum: 61bf7f3ec81de445521cb6b8518efe4a (MD5)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Inúmeros processos tem sido sugeridos para explicar a estruturação de comunidades, como por exemplo competição, predação, dispersão, deriva continental, filtragem ambiental, especiação. A compreensão da influência desses processos em escala local é capaz de possibilitar uma melhor compreensão dos determinantes da composição e riqueza de espécies em comunidades, especialmente as bem delimitadas fisicamente, como é o caso das comunidades de girinos. Nosso objetivo neste estudo foi investigar a influência de características ambientais na estruturação de comunidades de girinos em corpos d'água lênticos e lóticos. Realizamos as amostragens em uma área de Mata Atlântica no sudeste do Brasil. Este trabalho está dividido em dois capítulos. No primeiro capítulo verificamos quais características ambientais dos microhabitats de corpos d'água lênticos e lóticos influenciam positivamente a riqueza de espécies. Além da riqueza, avaliamos ainda a composição de espécies nos microhabitats, testando se ela é determinada pelas características ambientais ou um reflexo da estrutura espacial dos corpos d'água. No segundo capítulo, investigamos a relação entre os gradientes ambientais contínuos e descontínuos - considerando as características ambientais de corpos d'água lênticos e lóticos - com a diversidade taxonômica, filogenética e funcional de girinos em escala local. Os resultados do primeiro capítulo demonstram que a riqueza de espécies nos microhabitats dos corpos d’água lênticos e lóticos foi influenciada, respectivamente, pela quantidade de vegetação e de areia. A vegetação aquática influenciou positivamente a riqueza, provavelmente por proporcionar maior quantidade de alimento e de refúgios contra predadores. Nos ambientes lóticos, a relação positiva da riqueza de espécies com o substrato arenoso provavelmente decorre da seleção de microhabitats com menor correnteza, onde a areia fica ...<br>Inumerous processes have been suggested to explain the community structure, such as competition, predation, dispersal, continental drift, environmental filtering, speciation. To comprehend the influence of these processes on a local scale provide a better understanding of the composition and species richness determinants in communities, especially physically well defined communities, as is the case of the communities of tadpoles. Our goal in this study was to investigate the influence of environmental characteristics in communities structures of tadpoles in lotic and lentic water bodies. We conducted sampling in an area of Atlantic Rain Forest in southeastern Brazil. This work is divided into two section. In the first chapter we verified which environmental microhabitat characteristics of lotic and lentic water bodies positively influence species richness. Besides species richness, we evaluated species composition in microhabitats, testing if it is determined by the environmental characteristics of microhabitats or a consequence of water bodies spatial structure. In the second chapter, we seek to investigate the relationship between continuous and discontinuous environmental gradients - considering the environmental characteristics of lotic and lentic water bodies - with the taxonomic, phylogenetic and functional diversity of tadpoles on a local scale. The results of the first chapter show that species richness in microhabitats in lentic and lotic water bodies was influenced, respectively, by the amount of vegetation and sand. The aquatic vegetation had a positively relationship with tadpoles richness, probably due to the greater amount of food and refuge from predators provided. In lotic environments, the positive relationship of species richness with sand probably due to the selection of microhabitats with lower currents, where the sand is accumulated. In contrast, species composition in lentic and lotic microhabitats was mainly ...<br>FAPESP: 12/09243-0
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Melo, Lilian Sayuri Ouchi de. "A similaridade no uso do microhabitat por girinos (Amphibia, Anura) reflete processos ecológicos ou filogenéticos? /." São José do Rio Preto, 2014. http://hdl.handle.net/11449/110980.
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Orientador: Denise de Cerqueira Rossa-Feres<br>Banca: Ricardo Janinni Sawaya<br>Banca: Fabrício Barreto Teresa<br>Resumo: Inúmeros processos tem sido sugeridos para explicar a estruturação de comunidades, como por exemplo competição, predação, dispersão, deriva continental, filtragem ambiental, especiação. A compreensão da influência desses processos em escala local é capaz de possibilitar uma melhor compreensão dos determinantes da composição e riqueza de espécies em comunidades, especialmente as bem delimitadas fisicamente, como é o caso das comunidades de girinos. Nosso objetivo neste estudo foi investigar a influência de características ambientais na estruturação de comunidades de girinos em corpos d'água lênticos e lóticos. Realizamos as amostragens em uma área de Mata Atlântica no sudeste do Brasil. Este trabalho está dividido em dois capítulos. No primeiro capítulo verificamos quais características ambientais dos microhabitats de corpos d'água lênticos e lóticos influenciam positivamente a riqueza de espécies. Além da riqueza, avaliamos ainda a composição de espécies nos microhabitats, testando se ela é determinada pelas características ambientais ou um reflexo da estrutura espacial dos corpos d'água. No segundo capítulo, investigamos a relação entre os gradientes ambientais contínuos e descontínuos - considerando as características ambientais de corpos d'água lênticos e lóticos - com a diversidade taxonômica, filogenética e funcional de girinos em escala local. Os resultados do primeiro capítulo demonstram que a riqueza de espécies nos microhabitats dos corpos d'água lênticos e lóticos foi influenciada, respectivamente, pela quantidade de vegetação e de areia. A vegetação aquática influenciou positivamente a riqueza, provavelmente por proporcionar maior quantidade de alimento e de refúgios contra predadores. Nos ambientes lóticos, a relação positiva da riqueza de espécies com o substrato arenoso provavelmente decorre da seleção de microhabitats com menor correnteza, onde a areia fica ...<br>Abstract: Inumerous processes have been suggested to explain the community structure, such as competition, predation, dispersal, continental drift, environmental filtering, speciation. To comprehend the influence of these processes on a local scale provide a better understanding of the composition and species richness determinants in communities, especially physically well defined communities, as is the case of the communities of tadpoles. Our goal in this study was to investigate the influence of environmental characteristics in communities structures of tadpoles in lotic and lentic water bodies. We conducted sampling in an area of Atlantic Rain Forest in southeastern Brazil. This work is divided into two section. In the first chapter we verified which environmental microhabitat characteristics of lotic and lentic water bodies positively influence species richness. Besides species richness, we evaluated species composition in microhabitats, testing if it is determined by the environmental characteristics of microhabitats or a consequence of water bodies spatial structure. In the second chapter, we seek to investigate the relationship between continuous and discontinuous environmental gradients - considering the environmental characteristics of lotic and lentic water bodies - with the taxonomic, phylogenetic and functional diversity of tadpoles on a local scale. The results of the first chapter show that species richness in microhabitats in lentic and lotic water bodies was influenced, respectively, by the amount of vegetation and sand. The aquatic vegetation had a positively relationship with tadpoles richness, probably due to the greater amount of food and refuge from predators provided. In lotic environments, the positive relationship of species richness with sand probably due to the selection of microhabitats with lower currents, where the sand is accumulated. In contrast, species composition in lentic and lotic microhabitats was mainly ...<br>Mestre
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Carlucci, Marcos Bergmann. "Padrões e processos de organização de comunidades de plantas lenhosas : nicho, evolução e biogeografia histórica." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/131937.
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Abordagens funcionais e filogenéticas têm sido amplamente utilizadas no estudo de ecologia de comunidades e têm propiciado um melhor entendimento de como atributos funcionais e sua evolução influenciam padrões ecológicos observados atualmente na natureza. A incorporação da variabilidade intraespecífica em estudos recentes de ecologia de comunidades vegetais tem demonstrado que, apesar de a variabilidade intraespecífica de um atributo ser normalmente menor do que sua variabilidade interespecífica, estudos que consideram a variabilidade intraespecífica inferem mecanismos de organização de comunidades com mais acurácia. Além disso, abordagens analíticas que incluem a variabilidade intraespecífica em estudos de comunidades possibilitam integrar as escalas de populações e comunidades em ecologia. Abordagens filogenéticas recentes permitem a avaliação da interação entre composição filogenética de bancos regionais de espécies e a estrutura filogenética local de comunidades, o que permite a inferência de processos históricos e ecológicos que estruturam comunidades atuais. O objetivo geral desta tese foi avaliar padrões e inferir processos de organização de comunidades de plantas lenhosas da escala local à regional. Para isso, utilizei abordagens baseadas em atributos funcionais para avaliar o nicho de indivíduos (capítulo 2) e das espécies (capítulo 2 e 3) e abordagens filogenéticas para avaliar como a evolução influencia a similaridade funcional entre as espécies (capítulo 3), a formação de bancos de espécies locais (capítulo 3) e regionais (capítulo 4) e a estruturação de comunidades locais (capítulo 4). No capítulo 2, avaliei qual a importância relativa da substituição (turnover) de espécies e da variabilidade intraespecífica nas respostas médias e de dispersão de área foliar específica no nível de comunidade a um gradiente de abertura de dossel em uma metacomunidade de árvores juvenis. Nesse capítulo, concluí que a variabilidade intraespecífica é fundamental para a organização de comunidades lenhosas em florestas e arbustais, pois a área foliar específica dentro da mesma espécie varia conforme o ambiente e o contexto local de espécies interatoras. Essa plasticidade permite o estabelecimento de espécies em uma porção maior do gradiente de abertura do dossel. No capítulo 3, avaliei se espécies ocorrentes tanto na floresta quanto no campo diferem de espécies restritas à floresta ou ao campo quanto a resposta de seus atributos a espécies coocorrentes e ao gradiente ambiental. Concluí que uma ação combinada entre área foliar específica, espessura foliar e densidade de folhagem ajuda a explicar a organização de comunidades de plantas lenhosas em ecótonos floresta-campo. A plasticidade nesses atributos permite a colonização do campo por espécies que também ocorrem na floresta. No capítulo 4, avaliei se há associação entre a estrutura filogenética local (agrupamento ou repulsão) de comunidades de árvores e a distribuição geográfica de grandes linhagens de angiospermas no Neotrópico e Afrotrópico. A conclusão foi que diferenças regionais de composição filogenética entre o Neotrópico e o Afrotrópico são provavelmente um resultado de taxas diferenciais de especiação e extinção que seguiram a separação de Gondwana e atualmente influenciam a estrutura filogenética local de comunidades de árvores de florestas pluviais nos dois reinos.<br>Functional and phylogenetic approaches have been widely used in community ecology studies and have provided a better understanding of how functional traits and their evolution influence ecological patterns that are currently observed in nature. The incorporation of intraspecific variability in recent plant community ecology studies have demonstrated that, despite intraspecific variability of a given trait extent be usually lower than its interspecific variability, studies that account for intraspecific variability more accurately infer mechanisms of community assembly. Moreover, analytical approaches that incorporate intraspecific variability in community ecology studies enable integrating population and community scales in ecology. Recent phylogenetic approaches permit evaluating the interaction between the phylogenetic composition of regional species pools and local phylogenetic structure of communities, which enables the inference of historical and ecological processes structuring current communities. The general aim of this dissertation was to evaluate and infer assembly processes of woody plant communities from local to regional scales. For this, I used trait-based approaches to assess the niche of individuals (chapter 2) and species (chapter 2 and 3) and community phylogenetics approaches to evaluate how evolution influences the trait similarity between species (chapter 3), the formation of local and regional species pools (chapter 3 and 4, respectively) and the structuring of local communities (chapter 4). In chapter 2, I evaluated what is the relative importance of species turnover and intraspecific variability to the variation in trait mean and spread responses of specific leaf area at the community level across a canopy openness gradient in a tree juvenile metacommunity. In this chapter, I conclude that intraspecific variability is essential to woody community assembly in forests and shrublands, since specific leaf area within the same species varies according to the environment and local context of interacting species. This plasticity permits species establishment in a wider portion of the canopy openness gradient. In chapter 3, I evaluated whether species both in forest and grassland differ from species restricted to either forest or grassland regarding their trait-based responses to co-occurring species and environmental gradient. I concluded that an interplay between specific leaf area, leaf thickness and foliage density help explaining the assembly of woody plant communities in forest-grassland ecotones. The plasticity in these traits enables the colonization of the grassland by species that also occur in the forest. In chapter 4, I evaluated whether there is association between local phylogenetic structure (clustering or overdispersion) of tree communities and geographical distribution of major angiosperm lineages in the Neotropics and Afrotropics. In this chapter, I concluded that regional differences in phylogenetic composition between the Neotropics and Afrotropics are likely an outcome of differential rates of speciation and extinction following the breakup of Gondwana and currently influence local phylogenetic structure of rainforest tree communities in both realms.
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Andlauer, Christiane. "Le processus de décision dans un synode diocésain." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0113/document.
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Cette étude est entreprise dans la perspective de présenter l’évolution d’un projet de pastorale d’ensemble sous l’impulsion conciliaire mise en place de 1963 à 2000 dans le diocèse de Nice par trois évêques Mgr Mouisset, Mgr Saint-Macary et Mgr Bonfils. Elle s’articule autour de trois concepts : conversion, structures, évangélisation qui répondent aux trois critères définis par Mgr Saint-Macary pour l’opération « Diocèse 2000 » : proximité, coresponsabilité et évangélisation. L’étude de la démarche synodale de Nice nous renvoie à la vie en communion de l’Eglise locale. Parmi toutes les formes d’expression de la communion, nous retenons celle de la synodalité. Le processus de décision est fondamental dans un synode diocésain. Nous en rechercherons les mécanismes dans cette thèse. Nous verrons comment il s’articule à la « pastorale d’ensemble » ou pastorale de communion qui est la convergence profonde de toutes les formes d’action et de présence dans le monde, l’union et l’interpellation réciproque de toutes les forces apostoliques, prêtres, laïcs et religieux. Si donc, la « coresponsabilité de tous » rend compte de la mission du baptisé dans l’Église en tant qu’individu, la décision synodale traduit l’expression de la communauté des baptisés. Nous verrons si le processus de décision en émane ou non. Cette thèse veut répondre à la question de savoir si le processus de décision dans un synode diocésain, en tant que facteur de synodalité, tend à réguler la forme communionnelle de l’Eglise et reflète au moins partiellement la personnalité de l’évêque. Il s’agit d’une étude pluri disciplinaire. L’examen du processus synodal, dans son contexte théorique et pratique, repose sur les domaines de la sociologie religieuse, de l’ecclésiologie et du droit canonique<br>This study is undertaken with a view to present the evolution of an overall pastoral project under the conciliar impetus implementation of 1963 to 2000 in the diocese of Nice by three bishops : Mgr. Mouisset, Mgr. Saint-Macary and Mgr. Bonfils. It revolves around three concepts: conversion, structures, evangelization that meet the three criteria defined by Bishop Saint-Macary for "Diocese 2000" operation: proximity, shared responsibility and evangelization. The study of the Nice synodal process sends us back to life in communion with the local Church. Of all the forms of expression of communion, we retain that of synodality. The decision process is fundamental in a diocesan synod. We will look for its mechanisms in this thesis. We will see how it binds to the "overall pastoral" or pastoral communion that is the deep convergence of all forms of action and presence in the world, unity and mutual interpellation of all forces apostolic : priests, religious and laity. If so, the "co-responsibility of all" reflects the mission of the baptized in the Church as an individual, the synodal decision represents the expression of the community of the baptized. We'll see if the process of decision comes in or not. This thesis wants to answer the question of whether the decision process in a diocesan synod as synodality factor tends to regulate the communal aspect of the Church and at least partly reveal the personality of the bishop. This is a multi disciplinary study. The review of the synod process, in its theoretical and practical context, is based on the areas of the sociology of religion, ecclesiology and canon law
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Saito, Victor Satoru. "Padrões de montagem de comunidades : investigando a estrutura funcional e filogenética para inferir processos em comunidades naturais." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8572.
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Previous issue date: 2016-11-18<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Community ecology aims to disentangle the relative influence of the drivers of
community assembly. My thesis is composed of four chapters with different focus on
the drivers of assembly in natural and simulated communities. In the first chapter we
studied stream aquatic insects over 600 km extension. We found that the phylogenetic
structure of communities had a spatial signature, suggesting dispersal limitation. We
found that large insects, with high flight capacity and with univoltine life cycles were
the most affected by spatial distance. We suggest that the number of generation per year
and hence the number of dispersal events is a strong factor for the distribution of aquatic
insects. In the second chapter we studied the assembly of stream insects over a smaller
scale in the Itanhaém river basin. We were interested on the influence of competition
and environmental filtering on the functional and phylogenetic structure of insects. If
environmental filtering was strong, traits of respiration type and pollution sensitivity
should be more similar than expected by chance, while if competition was strong we
should find less similarity in feeding strategies among co-occurring taxa. We found
evidence of environmental filtering but not of strong competition. Additionally, we
found common co-occurrence of ancient clades of aquatic insect orders, likely due to
the stability of stream habitats along evolutionary scale. In the third chapter we also
investigated competition and environmental filtering, but we used odonates, a group
with aggressive behavior against visually similar species. This happen because it cannot
properly identify if a similar individual is a mate competitor or not. Even in this case,
we found more evidence of environmental filtering, likely because related odonates
have similar reproductive strategies linked to specific riverine characteristics, forcing
these related species to co-occur. In the fourth chapter we were interested again on the
signatures of competition, however we used computational simulations to generate
communities assembled by competition. We aimed to identify if the observational
approach could indeed identify competitive exclusion. Simulated communities were
generally composed of similar species, because species with small competitive
difference do not exclude each other. Strikingly, we commonly found random patterns
owing to the relaxed competition diluted among multiple species. In conclusion, we
found that the assembling of natural and simulated communities is influenced by
dispersal and history on the regional scale, and by environmental filtering on the local
scale. The influence of competition is still open to questioning given the lack of
reliability of the traditional observational approach.<br>A ecologia de comunidade visa separar a influência relativa de diferentes processos na
montagem de comunidades naturais. Minha tese é composta por quatro capítulos com
diferentes focos sobre os processos de montagem de comunidades naturais e simuladas.
No primeiro capítulo, estudamos insetos aquáticos de riachos ao longo de 600 km.
Descobrimos que a estrutura filogenética de comunidades tinha uma assinatura espacial,
sugerindo limitação de dispersão. Descobrimos que grandes insetos, com capacidade de
voo alta e com apenas um ciclo de vida ao ano foram os mais estruturados
espacialmente. Sugerimos que o número de gerações por ano e, consequentemente, o
número de eventos de dispersão é um forte fator para a distribuição de insetos aquáticos.
No segundo capítulo, estudamos a montagem de insetos em uma escala menor, na bacia
do rio Itanhaém-SP. Nosso interesse foi na competição e filtragem ambiental sobre a
estrutura funcional e filogenética de insetos aquáticos. Se a filtragem ambiental fosse
forte, atributos de respiração e sensibilidade à poluição deveriam ser mais semelhantes
do que o esperado ao acaso, enquanto que, se a competição fosse forte deveríamos
encontrar uma menor semelhança em estratégias de alimentação entre taxa
coocorrentes. Encontramos evidências de filtragem ambiental, mas não de forte
competição. Além disso, encontramos coocorrência de insetos aquáticos de clados
antigos, provavelmente devido à estabilidade dos habitats de riachos ao longo da escala
evolutiva. No terceiro capítulo, também investigamos a competição e a filtragem
ambiental, mas usamos libélulas, um grupo com o comportamento agressivo contra
espécies visualmente semelhantes. Isto acontece porque elas não identificam
corretamente se um indivíduo é um competidor por parceiros da mesma espécie, ou não.
No mesmo estudo, encontramos mais evidências de filtragem ambiental, provavelmente
porque libélulas aparentadas têm estratégias reprodutivas semelhantes ligadas a
características específicas dos rios, forçando estas espécies aparentadas a coocorrer. No
quarto capítulo estávamos interessados novamente na competição, no entanto, usamos
simulações computacionais para gerar comunidades influenciadas pela competição.
Objetivamos identificar se a abordagem observacional poderia realmente identificar
exclusão competitiva. Comunidades simuladas foram compostas por espécies
semelhantes, porque as espécies com poucas diferenças competitivas não se excluem
mutuamente. Surpreendentemente, nós comumente encontramos padrões aleatórios,
devido à competição relaxada diluída entre múltiplas espécies. Concluindo, nós
identificamos que a montagem de comunidades naturais e simuladas é influenciada pela
dispersão e história na escala regional, e pela filtragem ambiental na escala local. A
influência de competição ainda está aberta a perguntas, dada à falta de confiabilidade
que encontramos na abordagem observacional tradicional.
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Plos, Ornella, Ameziane Aoussat, and Stéphanie Buisine. "Innover pour et par le handicap. Méthodologie de conception de produits adaptée aux marchés de niche: application au marché du handicap moteur." Phd thesis, Ecole nationale supérieure d'arts et métiers - ENSAM, 2011. http://pastel.archives-ouvertes.fr/pastel-00578706.
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La loi du 11 février 2005 a permis de changer le regard que nous portons sur le handicap. Parallèlement à l'évolution des modèles et définitions, les associations de personnes en situation de handicap (PSH) continuent à se battre pour une société plus accessible. C'est dans ce contexte que nos travaux de recherche revendiquent l'intérêt d'une conception de l'innovation qui prend en compte les besoins de ces utilisateurs considérés comme une population de niche de la part des industriels. En effet, si l'on considère que les PSH représentent environ 50 millions d'européens, ce marché est-il encore considéré comme un marché de niche ? L'analyse du marché des technologies pour l'autonomie montre qu'il existe un réel champ d'action pour une démarche d'innovation centrée sur les besoins des PSH afin de pallier les manques existants. Pouvoir définir les caractéristiques et besoins de ces utilisateurs cibles, nécessite alors de comprendre et de caractériser ce qui crée une situation de handicap. Enfin, certains besoins spécifiques des PSH ont déjà donné lieu à des inventions et des progrès technologiques dont la majorité de la population dispose aujourd'hui (e.g. la télécommande, les robinets mitigeurs, la reconnaissance vocale, etc.). Nous essaierons donc de démontrer au travers d'expérimentations menées en partenariat avec l'Association Française contre les Myopathies que la connaissance des besoins de ces utilisateurs cibles peut donc être considérée comme une source potentielle d'innovation pour tous.
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Ostermann, Kai, and Gerhard Rödel. "Die Zellatmung: ein effizienter biologischer Prozess nicht ohne Risiken." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1173085508539-87774.
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The energy supplies of modern society seem to be necessarily associated with risks. In this paper, we address the question as to whether the efficient utilisation of energy in biological systems is also coupled to hazards. Most organisms oxidise highly reduced substrates with molecular oxygen in order to gain energy. In eukaryotes, this process takes place at the inner membrane of specialised organelles, the mitochondria. Interestingly, about 1% of the consumed oxygen molecules are reduced not to water, but to ROS (reactive oxygen species), which are deleterious to many macromolecules, including mitochondrial DNA. As a result, mitochondrial DNA mutations accumulate, in turn affecting the energy supply and inducing degeneration and ageing<br>Nach dem heutigen Stand der Technik scheint eine ausreichende Energieversorgung der Gesellschaft stets mit Risiken verbunden zu sein. Wir gehen in dem Artikel der Frage nach, ob auch biologische Systeme bei der Nutzung von Energie Risiken in Kauf nehmen. Zur effizienten Energiegewinnung nutzen Organismen meist Sauerstoff zur Oxidation energiereicher Substrate. In Eukaryonten erfolgt die Energiegewinnung vor allem an der inneren Membran von Mitochondrien. Etwa 1 % des verbrauchten Sauerstoffs wird dabei nicht zu Wasser, sondern zu ROS (reactive oxygen species, reaktive Sauerstoffspezies) reduziert, die unter anderem die mitochondriale DNA schädigen und Mutationen hervorrufen. Diese akkumulieren auf Dauer und führen zu einer Störung der Energiegewinnung, in deren Folge Degenerations- und Alterungsphänomene auftreten
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Leplat, Johann. "Développement saprotrophe de fusarium graminearum : rôle respectif de différents habitats naturels du champignon dans le processus d'infection du blé en Bourgogne ; recherche d'indicateurs prédictifs du risque de fusariose." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00843896.
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La fusariose est une des maladies les plus importantes altérant le blé en Bourgogne. L'espèce fongique Fusarium graminearum est l'un des agents principaux de la maladie. L'interaction hôte-pathogène peut entrainer la production de mycotoxines toxiques pour l'homme et l'animal.La seule alternative pour prévenir le développement de la maladie est de contrôler l'inoculum primaire dans son habitat naturel : les adventices, le sol et les résidus de culture. En raison de la tendance à la réduction du travail du sol, une attention particulière doit être portée au rôle des résidus de culture dans la survie et le développement de F. graminearum. Dans ce travail de thèse, deux approches ont été choisies pour mieux comprendre le développement saprotrophe du champignon et ses conséquences. La première, à travers un essai en champ dans le contexte pédoclimatique Bourguignon, avait pour but de définir la part relative des différentes sources d'inoculum dans le développement de la fusariose et l'accumulation des mycotoxines dans les grains. Cet essai devait en outre permettre de déterminer si des indicateurs précoces du développement de la maladie sur épi et de l'accumulation de mycotoxines pouvaient être identifiés. La seconde, à travers un essai en microcosmes, avait pour but de suivre le développement de F. graminearum dans le sol et les résidus.Ce travail a permis de souligner l'importance de la gestion des résidus de culture dans le développement de la fusariose du blé. Favoriser une décomposition biologique rapide des résidus de culture et/ou introduire des cultures intermédiaires assainissantes constituent des perspectives de recherche sur lesquelles doivent porter nos efforts
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Nicvert, Lisa. "Méthodes statistiques et outils logiciels pour l'analyse et l'inférence de réseaux écologiques et le traitement de données multi-espèces." Electronic Thesis or Diss., Lyon 1, 2024. http://www.theses.fr/2024LYO10130.
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Les interactions entre espèces dans les communautés écologiques sont complexes : de nombreuses espèces peuvent interagir les unes avec les autres de façons variées et à différentes échelles spatiales et temporelles. De plus, ces réseaux d'interactions sont la résultante de multiples causes, engendrent de multiples processus et ont des conséquences parfois indirectes transmises au travers de la structure du réseau. Cette complexité nécessite une diversité d'approches pour comprendre les déterminants des interactions et prédire leurs effets dans les systèmes écologiques. Cette thèse étudie plusieurs aspects des réseaux d'interactions écologiques par une approche méthodologique qui se concentre sur la description, l'évaluation et le développement de méthodes statistiques et d'outils logiciels. Dans une première partie, j'étudie les causes de la structure des réseaux d'interactions en me concentrant sur les niches d'interactions et en utilisant la notion de concordance des traits entre espèces. Pour cela, j'utilise des méthodes de la famille de l'analyse des correspondances et j'applique et j'étends des méthodes de mise à l'échelle réciproque à l'analyse de réseaux bipartites. J'applique ces méthodes à l'analyse d'un réseau d'interactions plantes-frugivores d'une forêt de montagne péruvienne et je montre que les traits des espèces peuvent être reliés à leur largeur de niche. Dans une deuxième partie, j'étudie les conséquences des interactions au travers de leur influence sur la répartition spatio-temporelle des espèces. Pour cela, j'utilise des processus de Hawkes multivariés pour analyser des données de pièges photographiques. J'illustre ces modèles sur cinq mammifères de la savane sud-africaine et je montre des attractions et évitements entre plusieurs de ces espèces à courte échelle spatio-temporelle. Dans une troisième partie, je me penche sur l'analyse de données collectées par pièges photographiques. Je développe un package R pour nettoyer et standardiser ces données à l'usage du programme Snapshot Safari, ainsi qu'une application Shiny destinée à un usage plus général pour visualiser de données de façon interactive et reproductible. Cette thèse présente des méthodes statistiques et outils logiciels pour analyser des données écologiques complexes et améliorer la compréhension des réseaux d'interactions. Ces résultats ouvrent des perspectives nouvelles concernant l'analyse de données écologiques ainsi que les développement méthodologique en écologie<br>Interactions between species in ecological communities are complex: many species can interact with each other in a variety of ways and at different spatial and temporal scales. Moreover, these interaction networks are the result of multiple causes, generate multiple processes and can have indirect effects transmitted through the structure of the network. This complexity calls for a variety of approaches to understand the determinants of interactions and predict their effects in ecological systems. This thesis studies several aspects of ecological interaction networks using a methodological approach that focuses on the description, evaluation and development of statistical methods and software tools. In a first part, I study causes of the structure of interaction networks, focusing on interaction niches and using the notion of trait matching between species. To this end, I use methods from the correspondence analysis family and apply and extend reciprocal scaling methods to the analysis of bipartite networks. I apply these methods to the analysis of a plant-frugivore interaction network in a Peruvian montane forest, and show that species traits can be related to their niche width. In a second part, I study the consequences of interactions through their influence on the spatio-temporal distribution of species. To this end, I use multivariate Hawkes processes to analyze camera trap data. I illustrate these models on five mammals from the South African savanna, showing attraction and avoidance between several of these species at a short spatio-temporal scale. In a third part, I consider camera trap data analysis. I develop a R package to clean and standardize camera trap data intended for the Snapshot Safari program, as well as a Shiny application intended for a more general use to visualize data in an interactive and reproducible way. This thesis presents statistical methods and software tools to analyze complex ecological data and improve our understanding of interaction networks. These results open new perspectives on ecological data analysis and methodological development in ecology
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Gabriela, Dan. "Processus Gravitaires et Évaluation de la Stabilité des Pentes : Approches Géologique et Géotechnique. Application à la marge algérienne et à l'effondrement de l'aéroport de Nice en 1979." Phd thesis, Université de Bretagne occidentale - Brest, 2007. http://tel.archives-ouvertes.fr/tel-00274695.
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Le travail présenté dans le cadre de ce mémoire concerne l'étude de deux zones : la marge algérienne et la zone du glissement de Nice en 1979.<br />La marge au large d'Alger n'avait fait l'objet d'aucune campagne scientifique majeure jusqu'à la réalisation de la campagne Maradja en 2003. Du coup, le travail de thèse sur la zone d'Alger a d'abord concerné la caractérisation morpho-sédimentaire de la zone et la cartographie des instabilités et des dépôts gravitaires. Dans un deuxième temps, il s'est concentré sur la caractérisation des propriétés physiques et mécaniques des sédiments, l'identification des mécanismes responsables de l'initiation des instabilités observées dans la zone d'étude et l'évaluation de la stabilité actuelle de la zone d'étude. Plusieurs résultats importants ont été obtenus : <br />• les processus sédimentaires sont très clairement influencés par la morphologie de la marge, elle-même contrôlée par l'activité tectonique. La sédimentation sur la marge algérienne est donc très hétérogène, contrastée et contrôlée par deux processus : (a) les processus gravitaires incluant les courants turbiditiques et les glissements sous-marins et (b) la sédimentation hémipélagique ; <br />• de nombreux glissements ont été observés et décrits sur la zone d'étude. La majorité des glissements est caractérisée par une surface inférieure à 0.2 km2 et un volume moyen de 0.003 km3. Seul, un glissement au large de la ville de Dellys est hors norme, caractérisé par un volume très supérieur à la moyenne et égal à 0.18 km3 ;<br />• la présence de couches de silt et sable susceptibles de se liquéfier est un facteur prépondérant d'initiation des glissements. L'évaluation du potentiel de liquéfaction pour les couches de sable, montre une possibilité de liquéfaction pour des séismes soumettant la colonne sédimentaire à un PGA de 0.2 g, une valeur qui a pu être atteinte par les séismes historiques connus ;<br />• l'évaluation de la stabilité de la même zone montre l'instabilité et la rupture de la pente pour un PGA de seulement 0.1 g, valeur encore plus facilement atteinte par les séismes historiques connus ; <br /><br />Au contraire de la marge algérienne, la zone de Nice avait déjà fait l'objet de nombreuses études décrivant le contexte géologique lié à l'accident de 1979 et cherchant à comprendre son fonctionnement. Le travail présenté ici a d'abord concerné une synthèse de l'ensemble des données disponibles et en particulier des mesures géotechniques nouvelles réalisées dans la zone, ainsi que de nouveaux prélèvements de terrain. Ceci a permis de mieux modéliser la stabilité de la pente niçoise près de l'aéroport et de simuler la stabilité du prodelta du Var avant et après la construction de l'aéroport. Une nouvelle explication du déclenchement du glissement est proposée : ce serait le fluage d'une couche d'argile sensible sous l'effet de la charge de l'aéroport qui aurait initié la rupture. Cette hypothèse semble très solide au regard des nouvelles données obtenues. Le poids des différents facteurs déclenchant de l'accident de 1979 est aussi discuté et sert de cadre pour une estimation des risques actuels.
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Mohamed, N. M. Z. Nik. "The Development of a Hybrid Knowledge-Based System for Designing a Low Volume Automotive Manufacturing Environment. The Development of A Hybrid Knowledge-Based (KB)/Gauging Absences of Pre-Requisites (GAP)/Analytic Hierarchy Process (AHP) System for the Design and Implementation of a Low Volume Automotive Manufacturing (LVAM) Environment." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5515.
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The product development process for the automotive industry is normally complicated, lengthy, expensive, and risky. Hence, a study on a new concept for Low Volume Automotive Manufacturing (LVAM), used for niche car models manufacturing, is proposed to overcome this issue. The development of a hybrid Knowledge Based (KB) System, which is a blend of KB System, Gauging Absences of Pre-requisites (GAP), and Analytic Hierarchy Process (AHP) is proposed for LVAM research. The hybrid KB/GAP/AHP System identifies all potential elements of LVAM issues throughout the development of this system. The KB System used in the LVAM analyses the gap between the existing and the benchmark organisations for an effective implementation. The novelty and differences in the current research approach emphasises the use of Knowledge Based (KB) System in the planning and designing stages by suggesting recommendations of LVAM implementation, through: a) developing the conceptual LVAM model; b) designing the KBLVAM System structure based on the conceptual LVAM model; and c) embedding Gauging Absences of Pre-requisites (GAP) analysis and Analytic Hierarchy Process (AHP) approach in the hybrid KBLVAM System. The KBLVAM Model explores five major perspectives in two stages. Planning Stage (Stage 1) consists of Manufacturer Environment Perspective (Level 0), LVAM Manufacturer Business Perspective (Level 1), and LVAM Manufacturer Resource Perspective (Level 2). Design Stage (Stage 2) consists of LVAM Manufacturer Capability - Car Body Part Manufacturing Perspective (Level 3), LVAM Manufacturer Capability - Competitive Priorities Perspective (Level 4), and LVAM Manufacturer Capability - Lean Process Optimisation Perspective (Level 5). Each of these perspectives consists of modules and sub-modules that represent specific subjects in the LVAM development. Based on the conceptual LVAM model, all perspectives were transformed into the KBLVAM System structure, which is embedded with the GAP and AHP techniques, hence, key areas of potential improvement are recommended for each activity for LVAM implementation. In order to be able to address the real situation of LVAM environment, the research verification was conducted for two automotive manufacturers in Malaysia. Some published case studies were also used to check several modules for their validity and reliability. This research concludes that the developed KBLVAM System provides valuable decision making information and knowledge to assist LVAM practitioners to plan, design and implement LVAM in terms of business organisation, manufacturing aspects and practices.
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Röttger, Simone. "Systematische Prozessunterstützung für die Entwicklung laufzeitkritischer Softwaresysteme." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25206.
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In vielen Bereichen des täglichen Lebens, angefangen vom Online-Banking bis hin zur Steuerung im Flugzeug, kommt Software mit laufzeitkritischen nicht-funktionalen Eigenschaften (NFE) zum Einsatz. Die Erfüllung der NFE spielt in diesen Anwendungen eine zentrale Rolle. Um dies zu erreichen, ist eine systematische und zielorientierte Behandlung dieser Anforderungen während der Entwicklung zwingend erforderlich.
NFE zeichnen sich im Gegensatz zu funktionalen Eigenschaften durch besondere Merkmale aus, die ein adaptives Vorgehen zur Definition des Entwicklungsprozesses erzwingen. In der Arbeit wird eine Methodik zur kontextbasierten Anpassung von Vorgehensmodellen an laufzeitkritische NFE auf der Basis von Prozessmustern sowie das PROKRIS-Framework als unterstützende Umgebung vorgestellt.
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Derambure, Angélique. "L'image et son empreinte dans les mises en scène de Daniel Benoin : Itinéraire et processus de création de la Comédie de Saint-Étienne au Théâtre National de Nice (1975-2010)." Thesis, Nice, 2014. http://www.theses.fr/2014NICE2018.
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Metteur en scène contemporain dont l’itinéraire personnel est une conséquence de la décentralisation théâtrale, Daniel Benoin tire sa force de création du passage de l’image mentale à sa concrétisation dans le spectacle vivant par l’hybridation de savoirs multiples et de techniques artistiques. Cette étude d’un destin particulier dans un rapport holiste avec l’art dramatique permet une théorisation du processus de création dans lequel un regard croisé entre phénoménologie et pragmatique confirme l’hypothèse d’une empreinte matérielle et stylistique. L’approche comparative d’un grand nombre de représentations et de l’ensemble des répétitions préalables à cinq spectacles (Wozzeck, La Cantatrice chauve, Faces, la reprise de La Cantatrice chauve, Le roman d’un trader) définira cette empreinte comme idiosyncrasique, formelle et originale, le tout commun à l’ensemble de l’œuvre observée. Ainsi, grâce aux concours de pré-images modulables et fécondes, les images mentales primordiales s’installent au cœur de la création et la vision onirique se révèle être l’essence même de la particularité artistique de ce metteur en scène. La recherche entreprise ouvre alors des perspectives renouvelées quant à l’esthétique et à la présence/absence de l’artiste dans des domaines élargis (cinéma, danse, peinture, photographie, musique, écriture)<br>Daniel Benoin, a contemporary stage director whose personal career was a consequence of theatrical decentralization, draws his creative strength from his ability to make mental images become concrete in live shows by using numerous knowledge and artistic techniques in a hybrid way. This project on a distinctive destiny in a holist connexion with Drama enables to theorize about the creation process in which a crossed look at phenomenology and pragmatism confirms the hypothesis of a material and stylistic imprint. The comparative approach of many performances and of all the preliminary rehearsals to five theatrical shows (Wozzeck, La Cantatrice chauve, Faces, the remake of La Cantatrice chauve, Le roman d'un trader) will eventually define this mark as an idiosyncratic, formal and original one, to be found in the whole work which was studied. Thus, thanks to the help of fertile and adjustable pre-images, essential mental images settle in the heart of creation and the oneiric vision turns out to be the very essence of the artistic particularity of this stage director. Therefore the research opens up renewed angles about the aesthetics and the presence/absence of the artist in enlarged fields (such as cinema, dancing, painting, photography, music, writing)
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Prager, Tobias. "Synchronization in periodically driven and coupled stochastic systems a discrete state approach /." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980110262.
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Maître, Élisa. "Le tramway dans l'espace public : entre complication des espaces et complexité des processus de conception." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0065.
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Le redéploiement des réseaux de tramways en France a modifié considérablement les espaces publics et la façon dont ils sont pratiqués. Au-delà de l’image de développement urbain durable portée par le tramway, la question des difficultés d’usage de ces espaces est peu investiguée. Ce travail s’appuie principalement sur la mise en lien des analyses des pratiques des espaces publics réaménagés pour le tramway (observations in situ, interviews d’usager, analyses des accidents), avec celles des processus de conception de ces espaces (entretiens réalisés avec les différents acteurs des projets de tramway étudiés, révélant les enjeux, les choix, les conflits, les contraintes et les compromis ayant pesé dans l’aménagement de ces espaces). Les villes de Montpellier, Marseille et Nice sont les trois terrains d’étude sur lesquels ont porté ces investigations. Les résultats de cette thèse montrent d’une part que l’insertion de tramways modernes dans les villes françaises pose certains problèmes de complication des espaces publics. Ces complications, liées à la restructuration des espaces publics pour le tramway, engendrent des difficultés d’usage et des problèmes de sécurité. Ils montrent d’autre part que les processus de conception jouent un rôle dans la genèse de ces problèmes. Cette thèse établit ainsi des liens particuliers entre complexité des processus de conception (au sens de la pensée complexe) et complication des espaces publics<br>The reintroduction of tram networks in France has considerably changed public spaces and the way citizens use them. Above and beyond the image of sustainable urban development conveyed by trams, the question of the difficulties encountered by the users of these spaces has not been studied much. This work is mainly based on the coordination of the analysis of the uses of these re-designed public spaces (through observations, interviews of users and accident studies) and the analysis of the conditions and processes involved in the design of these spaces (mainly based on interviews with the actors of these tram projects, to identify the choices made, compromises accepted, and conflicts and constraints at work that determine the layout of these spaces). The cities of Montpellier, Marseille and Nice are the three fields of study on which the demonstration of this thesis is based. On the one hand, the results of this research show that the insertion of tram tends to complicate the public spaces. These complications related to the restructuring of public spaces for the tram create difficulties of use and safety concerns. On the other hand, this research shows to what extent the complexity of the design processes plays a role in the genesis of these problems. This thesis thus establishes particular links between complex design processes (in the sense of “complex thought”) and complicated public spaces
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Kristiansen, Pernilla, and Anna Allebert. "Barns övergång från förskola till förskoleklass : En undersökning av bilderböcker." Thesis, Karlstads universitet, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-85018.
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The aim of the study is to investigate a selection of picture books about the start of school to see how children's transitions from preschool to preschool class are depicted. This is to further investigate whether picture books can be used as a complement to transition activities. Through this study, we aim to gain more knowledge about whether the books in the study could serve as a complement to transition activities. In total, six picture books have been processed using close-up reading as a method and the developmental ecological niche theory. Previous research shows that the transition between preschool and preschool class is a problem area where there are major shortcomings in the interaction between these different activities. Therefore, the study aims to investigate a transitional activity without collaboration requirements for the activities. The results show that the characters in the picture books place the greatest emphasis on the community rather than the teaching and education in school. The social interaction and emotions are close in the plot and are difficult to distinguish as they often reflect each other.<br>Syftet med studien är att undersöka ett urval av bilderböcker om skolstarten för att se hur barns övergångar från förskola till förskoleklass skildras. Detta för att vidare undersöka om bilderböcker kan användas som komplement till övergångsaktiviteter. Genom denna undersökning strävar vi efter att få mer kunskap kring huruvida böckerna i studien skulle kunna fungera som ett komplement till övergångsaktiviteter. Totalt har sex bilderböcker bearbetats med hjälp av närläsning som metod och den utvecklingsekologiska nischteorin. Den tidigare forskningen visar att övergången mellan förskola och förskoleklass är ett problemområde där stora brister finns i samverkan mellan dessa olika verksamheter. Därav eftersträvar studien att undersöka en övergångsaktivitet utan samverkanskrav för verksamheterna. Resultatet visar att karaktärerna i bilderböckerna lägger störst vikt vid gemenskapen snarare än undervisningen och utbildningen i skolan. Det sociala samspelet och känslor ligger nära i handlingen och är svåra att särskilja då de ofta återspeglar varandra.
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Gard, Benjamin. "Processus écologiques et évolutifs influençant la colonisation de l'ambroisie à feuilles d'armoise (Ambrosia artemisiifolia L.) en France." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00985748.
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La compréhension des mécanismes déterminant le succès des espèces invasives est une étape essentielle dans la gestion des invasions biologiques actuelles et la prédiction des futurs risques d'invasion. En adoptant un cadre d'étude conceptuel intégrant les processus écologiques et évolutifs, l'objectif de ce travail était d'analyser les déterminants de la colonisation de l'ambroisie à feuilles d'armoise en France. Tout d'abord, l'étude des interactions biotiques et abiotiques a permis de montrer la capacité de tolérance de l'ambroisie à l'herbivorie et au stress hydrique. L'ambroisie est capable de tolérer la défoliation grâce à une croissance compensatoire efficace, sans que sa reproduction en soit affectée. Cette forte tolérance à l'herbivorie est maintenue chez les populations introduites, malgré la faible pression des ennemis naturels dans la zone d'introduction. En condition de stress hydrique, l'ambroisie produit une biomasse racinaire supérieure aux espèces présentes dans les communautés qu'elle envahit. De plus, les différences dans les valeurs moyennes pour les traits mesurés suggèrent une occupation différente par l'ambroisie des niches écologiques disponibles. La comparaison en jardins communs de populations de l'aire d'origine avec des populations de l'aire d'introduction isolées et issues du foyer central d'invasion a montré que l'adaptation de l'ambroisie à son environnement reposait principalement sur la plasticité phénotypique plutôt que sur la différenciation des traits. Les études de génétiques quantitatives ont mis en évidence un potentiel évolutif élevé pour les traits liés à la germination. Les traits liés à la morphologie, à la phénologie et à la physiologie de la plante montrent une variance additive et une héritabilité plus faibles et donc un potentiel évolutif moindre. En revanche, la variation dans les normes de réaction indique un potentiel évolutif important de la plasticité phénotypique. La tolérance au stress hydrique et à l'herbivorie sont des facteurs qui potentiellement augmentent la capacité de l'ambroisie à coloniser une large gamme d'habitat. De plus, la plasticité phénotypique et le potentiel évolutif important peuvent favoriser une augmentation ou un déplacement de la niche écologique de l'espèce et ainsi favoriser l'expansion de son aire de répartition
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TAHAEI, Ali. "Investigation on welding and corrosion properties of the UNS S32304 & UNS S32570 duplex stainless steels and development of Nickel-Tungsten Carbide hardfacing by Plasma Transferred Arc (PTA) process." Doctoral thesis, Università degli studi di Ferrara, 2016. http://hdl.handle.net/11392/2403215.
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Gli acciai inossidabili duplex presentano proprietà meccaniche, resistenza alla corrosione e tenacità superiori rispetto agli acciai inossidabili ferritici, austenitici e martensitici. L’ottimo bilanciamento delle loro proprietà è dovuto alla particolare microstruttura che è costituita da percentuali pressoché uguali di ferrite (δ) e di austenite (γ). L’austenite è responsabile della resistenza a corrosione e della tenacità, la ferrite fornisce l’elevata resistenza meccanica; grazie a questa combinazione di proprietà l’acciaio inossidabile duplex offre molti vantaggi rispetto agli acciai inossidabili monofasici. Gli acciai duplex possono sopportare condizioni di esercizio più gravose e possono essere utilizzati in svariati settori industriali come l’alimentare, il petrolchimico, l’oil & gas, la trasmissione di potenza ed in ambiente marino. La saldatura è il principale metodo per la fabbricazione delle strutture in acciaio inossidabile e molteplici sono i processi che possono essere utilizzati a tale scopo. Tuttavia, la saldatura determina inevitabilmente un cambiamento delle proprietà del materiale base nella zona interessata dell’alterazione microstrutturale. Nella zona di saldatura si può assistere alla perdita del giusto bilanciamento delle due principali fasi, nonché si può verificare la precipitazione di fasi intermetalliche complesse. I processi di saldatura applicabili agli acciai inossidabili duplex possono essere molteplici; in questo lavoro sono stati studiati gli effetti prodotti da alcune varianti del tradizionale processo TIG sulla saldatura dell’acciaio duplex UNS S32304 e dell’acciaio superduplex UNS S32570. In particolare, sono stati considerati gli effetti dell’aggiunta di polveri di nichel, dell’utilizzo di azoto come gas di processo e dell’esecuzione di uno specifico trattamento termico a valle della realizzazione dei giunti saldati. È stata successivamente effettuata una caratterizzazione microstrutturale al microscopio ottico metallografico (MO) e sono state utilizzate tecniche di analisi di immagine al fine di studiare l’evoluzione delle percentuali di fase nelle diverse zone dei giunti. Prove di trazione e prove di microdurezza hanno consentito di valutare i miglioramenti ottenuti sulle proprietà meccaniche. Inoltre, su campioni ricavati dai giunti stessi sono state eseguite prove elettrochimiche per studiare la resistenza a corrosione al variare delle condizioni di processo e del trattamento termico. I risultati ottenuti mostrano che, sia l’aggiunta delle polveri di nichel, sia l’utilizzo dell’azoto come gas di processo determinano un incremento delle proprietà meccaniche e microstrutturali dei giunti. Risulta tuttavia che il processo che consente il miglior incremento prestazionale è l’esecuzione del trattamento termico post saldatura, in quanto tende a ripristinare le percentuali delle fasi ferritica e austenitica a livelli confrontabili con quelli del metallo base. Nella seconda parte della tesi sono state studiate le proprietà di un riporto a base di polveri di nichel e particelle di carburo di tungsteno applicato mediante processo PTA (Plasma Transferred Arc) sulla superficie dell’acciaio da utensili D2, adatto per lavorazioni a freddo. Con un riporto superficiale di tale tipologia è possibile incrementare sia la qualità dell’acciaio sia aumentare la sua vita in esercizio in molte applicazioni industriali. Per ottenere una appropriata combinazione dei parametri di processo e per eseguire il numero minimo di prove, è stato utilizzato la metodologia DoE (Design of Experiment). Come parametri variabili sono stati considerati la corrente, la velocità di avanzamento e il preriscaldamento. Questi parametri sono importanti per ottenere un riporto finale con una appropriata geometria del cordone di saldatura e con buone proprietà metallurgiche. Tutti i campioni sono stati preparati per le necessarie caratterizzazioni metallografiche ed è stato considerato l’effetto dei parametri di processo sulla geometria del cordone di saldatura. Nel corso di ciascun esperimento sono stati misurati i parametri della geometria del cordone tra cui la diluizione, la penetrazione e il rinforzo. Le microstrutture e la distribuzione delle particelle di carburo di tungsteno sono stati analizzati sia al microscopio ottico metallografico (OM) sia al microscopio elettronico a scansione (SEM) dotato di microsonda EDS. Inoltre, sono state eseguite prove di microdurezza per valutare le proprietà meccaniche dei riporti realizzati. Infine, fra tutti gli esperimenti, è stato selezionato il campione con l’appropriata geometria del cordone e l’adeguata microstruttura. Nell’ultima parte della tesi si è cercato di valutare l’effetto dell’aggiunta di nanoparticelle di carburo di tungsteno sul comportamento meccanico e metallurgico dell’esistente polvere di nichel.
Per questi campioni, in aggiunta a quelli sopra menzionati, sono stati eseguiti test di usura ed analisi mediante profilometro sulla superficie, al fine di confrontare e selezionare l’ottima percentuale di aggiunta di nanoparticelle. I dettagli degli esperimenti e dei metodi sono descritti negli abstracts relativi a ciascun capitolo.<br>Duplex stainless steels show high mechanical strength, corrosion resistance and toughness with respect to ferritic, austenitic and martensitic stainless steels. These favourable properties are largely conferred by the peculiar microstructure of the material, which contains roughly equal percentage of ferrite (δ) and austenite (γ). Austenite is responsible for toughness and corrosion resistance and ferrite provides high strength; thanks to this combination, duplex stainless steel has many advantages over monophase stainless steels. This makes them better able to withstand harsher conditions, and therefore they are more applicable in different sectors such as the food, petrochemical, oil and gas, marine and power industries. As it is clear, welding is the main method for fabrication of steel structures, which cause to change the base metal properties on that zone. In fusion zone, due to melting, the balance between ferrite and austenite is destroyed and the risk of precipitation of intermetallic phases increase. Different welding methods can be applied to duplex stainless steels for the production of several equipments and structures. Nevertheless, fusion welding processes, due to intrinsic properties, cause to destroy the equal percentage of ferrite and austenite phases in the fusion zone, which is responsible for their good engineering properties. In this study I tried to use different methods to to solve these problems especially for the duplex UNS S32304 and superduplex UNS S32570. Due to that, effect of addition of nickel powder, nitrogen gas, post weld heat treatment (PWHT) and combination of these methods were applied. After that, the joints were characterized by optical microscopy (OM) and the evolution of the phase percentages in the different zones was studied by means of the image analysis technique. Tensile and microhardness tests were carried out on the joints in order to evaluate the improvement of the mechanical properties. In addition electrochemical tests were applied on the samples to observe the corrosion resistance of the joints after modifications. The results showed that both the addition of nickel powder and nitrogen gas during the welding process cause to improve the welding characteristics but the effect of applying PWHT is better than addition of alloying elements especially in restoring the phase percentages close to the base metal. In another part of the thesis, a nickel-base powder mixed with tungsten carbide particles was applied by Plasma Transferred Arc welding (PTA) on the surface of the D2 cold work tool steel in order to improve the surface quality and to extend its life time during industrial applications. To obtain appropriate combination of hardfacing parameters and to run minimum number of tests, the Design of Experiment (DoE) method was applied. Current, travel speed and preheat were considered as variable parameters. These parameters are important to reach a final layer with an appropriate bead geometry, accompanied with good metallurgical properties. All samples were prepared for metallurgical investigations and effects of process parameters on the weld bead geometry were considered. For each run of experiment, weld bead geometry parameters including dilution, penetration and reinforcement were measured. Microstructures and the distribution of tungsten carbide particles after welding were analysed by Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) equipped with EDS microprobe. In addition, microhardness tests were performed to evaluate the mechanical properties of the weld bead layers. Finally, among all the experiments, the best sample with appropriate bead geometry and microstructure was selected. In the last part, I tried to study the effect of addition of tungsten carbide nanoparticles on the mechanical and metallurgical behavior of the existing nickel powder. For these samples, in addition to the above tests mentioned, wear test and surface profilometry analysis was performed for comparison and selecting optimum percentage of the addition of nanoparticles. Details of each experiments and methods are explained in the abstract of each chapter separately.
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Lenz, Michael. "Neuartige Ultraschallmeßverfahren unter Nutzung von Schallfeldinformationen." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-135656.
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Die vorliegende Arbeit untersucht, wie die genaue Kenntnis der Sende- und Empfangsschallfelder eines Ultraschallwandlers zur Entwicklung neuer Meßverfahren genutzt werden kann. Insbesondere werden dargestellt: - ein neuartiges, nichtscannendes Verfahren zur Bestimmung der Krümmung eines Reflektors, basierend auf der Analyse der Wellenfrontkrümmung reflektierter Schallfelder - ein neuartiges, nichtinvasives Verfahren zur Bestimmung der Schallgeschwindigkeit in einer Flüssigkeit durch Auswertung der Echosignale von im Ausbreitungsmedium vorhandenen Streupartikeln und - ein Verfahren zur Wandlercharakterisierung durch Messungen in Fluiden mit Streupartikeln, sowie verschiedene Zuordnungen von Schallfeldmerkmalen zu spezifischen Eigenschaften eines Ultraschallwandlers. Im Zusammenspiel von Simulation und Experiment konnten die Funktionstüchtigkeit aller Meßverfahren nachgewiesen und vielversprechende innovative Ansätze für zukünftige Entwicklungen angeregt werden: 1. Das nichtscannende Verfahren zur Krümmungsmessung erlaubt bei guter Justage eine Krümmungsbestimmung von Reflektoren mit Radien zwischen 6 und 11 mm mit einer Unsicherheit von ungefähr 0,5 mm. In Kombination mit herkömmlichen scannenden Verfahren bietet es Ansätze zur präzisen Größenbestimmung von Fehlern in der zerstörungsfreien Prüfung. 2. Das Verfahren zur nichtinvasiven Schallgeschwindigkeitsmessung erlaubt eine Bestimmung von Schallgeschwindigkeiten mit einer statistischen Meßunsicherheit von 0,1 %. Mögliche Weiterentwicklungen zur Messung der Schallgeschwindigkeit mit örtlicher Auflösung und zur Gewinnung neuer Diagnosemöglichkeiten in Metallurgie (nichtinvasive Charakterisierung von Mischungsvorgängen) und Biomedizintechnik (nichtinvasive Temperaturmessung in Körpergewebe zur Überwachung der Hyperthermiebehandlung, Gewebecharakterisierung) werden erläutert. Aus verschiedenen bekannten sowie einem neuartigen, leicht anwendbaren Meßverfahren werden neue Schlüsse gezogen a) zur Bestimmung der akustisch effektiven Elementgröße von Wandlerelementen mittels Schallfeldmessungen, b) zur Qualitätssicherung im Hinblick auf Schallkopfasymmetrien und c) zur Verbesserung von Schallfeldsimulationen<br>The current thesis explores how the precise knowledge of the sending and receiving sound fields of an ultrasonic transducer can contribute to the development of novel measuring techniques. Emphasis is placed on: - a novel, non-scanning method for the determination of the curvature radius of a spherical reflector, based on the analysis of the wave front curvature of the reflected sound field, - a novel non-invasive method for sound velocity measurements in fluids using the echo signals from scattering particles, and - novel conclusions on how to use well-known sound field measurement methods for transducer characterisation, as well as an introduction to a novel easy-to-use method for transducer characterisation exploiting the echo signals from scattering particles. Proof of concept is shown for all methods by simulation and measurement, and different promising improvements for further techniques are suggested: - The non-scanning method for curvature measurements makes it possible to determine reflector radii between 6 and 11 mm with an uncertainty of about 0.5 mm, provided that there is a good reflector alignment. In combination with conventional methods, a novel approach for the determination of the size of discontinuities in non-destructive testing is outlined. - The method for non-invasive sound velocity measurements allows the determination of sound velocity in homogeneous fluids with a statistical uncertainty of 0.1 %. Future improvements are suggested to allow sound velocity measurements with local resolution, which enables novel approaches for metallurgy (non-invasive characterisation of mixing processes) and biomedical engineering (non-invasive temperature control for hyperthermia treatment, tissue characterisation). - New conclusions are drawn based on well-established and a novel easy-to-implement measurement method regarding a) the determination of the acoustically effective element size of transducer elements, b) transducer asymmetries, thereby improving quality control, and c) the improvement of sound field simulations
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Bezerra, Amarilys Dantas. "Influ?ncias do espa?o, do ambiente e do hist?rico de uso em uma floresta mista subtropical." Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br/handle/123456789/20498.
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Previous issue date: 2014-12-18<br>Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)<br>Um dos principais objetivos da ecologia ? entender os fatores que influenciam a forma??o e a estrutura das comunidades. V?rios trabalhos t?m apontado que os fatores ambientais e estoc?sticos s?o igualmente relevantes, embora suas import?ncias variem entre comunidades. Diferentes mecanismos parecem atuar em grupos de esp?cies distintos e em escalas distintas: a import?ncia do determinismo ecol?gico parece aumentar com o tamanho do organismo, com a progress?o da sucess?o ecol?gica e com o aumento da escala espacial e decrescer com o tamanho do prop?gulo e o tamanho do conjunto regional de esp?cies. Haveria tamb?m din?micas diferentes entre esp?cies raras e abundantes, sendo as esp?cies raras mais influenciadas pela estocasticidade que as abundantes. Neste trabalho investigamos a contribui??o dos efeitos ambientais, espaciais e relacionados aos eventos hist?ricos na estrutura de uma floresta mista subtropical e testamos as seguintes hip?teses: (1) Os fatores estoc?sticos, representados pela fra??o puramente espaciais, t?m maior influ?ncia nas comunidades rec?m impactadas (in?cio da sucess?o), enquanto que os fatores ambientais t?m maior influ?ncia nas n?o impactadas ou h? mais tempo em regenera??o; (2) A import?ncia relativa dos fatores espaciais ? maior na estrutura das esp?cies de grupos ecol?gicos com melhor capacidade dispersiva; (3) Os fatores hist?ricos e espaciais s?o mais impactantes para as esp?cies raras que para as esp?cies abundantes. Chegamos ? conclus?o que os fatores ambientais foram t?o importantes quanto os demais processos analisados para a defini??o da estrutura da comunidade. Tamb?m que os fatores ambientais, espacias e hist?ricos tiveram influ?ncias diferentes em grupos de esp?cies com estrat?gias ecol?gicas distintas e em ?reas com hist?ricos de pertuba??o diferentes. A inclus?o dos fatores hist?ricos demonstrou ser bastante relevante para o entendimento da estrutura da comunidade. Consideramos que a inclus?o dos principais fatores de pertuba??o nas an?lises pode aprofundar nosso entendimento dos processos ligados ? forma??o das comunidades ecol?gicas.<br>One of the main goals of the science of ecology is to uncover the factors that influence community assembly and structure. Recent research has pointed that both environmental and stochastic factors play an important role, although their relative importance change from one community to another. Distinct mechanisms seem to act on ecological species groups and on different spatial scales. In the present work we investigate the contribution of environmental, spatial and historical factors on the structure of a subtropical mixed forest. We tested the following hypotheses: (1) Stochasatic factors, represented by the purely spatial fraction of compositional variation, are more influential in recently impacted communities, while environmental factors are more influential in mature communities. (2) Stochastic factors are more strongly related to better dispersed ecological groups. (3) Historic and spatial factors prevail among rare species but not among abundant species. We found that environmental factors were as important as stochastic spatial factors in shaping community structure. Environmental, historical, and spatial factors had different relative importances in each of 5 ecological species groups. The inclusion of historical disturbance factors in community composition analysis can deepen our understanding of community assembly and structure.
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Fischer, Michael. "Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-148848.
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The non-adiabatic quantum molecular dynamics (NA-QMD) method couples self-consistently classical nuclear motion with time-dependent density functional theory (TDDFT) in basis expansion for the electron dynamics. It has become a versatile approach to study the dynamics of atoms, molecules and clusters in a wide range of scenarios. This work presents applications of the NA-QMD method to important benchmark systems and its systematic extension to include quantum effects in the nuclear motion.
Regarding the first objective, a complete study of the strong-field ionization and dissociation dynamics of nature’s simplest molecule H2+ is performed. By including all electronic and nuclear degrees of freedom and all reaction channels, molecular rotation is shown to play an important role in the ionization process. In addition, strong orientation effects in the energy deposition process of the Buckminster fullerene C60 in short intense laser pulses are surprisingly found in full dimensional calculations. Their consequences on the subsequent nuclear relaxation dynamics shed new light on available experimental data and future experiments are proposed to confirm the detailed predictions.
Regarding the second objective, the NA-QMD formalism is basically extended to take electron-nuclear correlations into account. This extension is achieved by means of a trajectory surface hopping scheme in the adiabatic Kohn-Sham framework. First studied examples from collision physics and photochemistry illustrate the relevance and importance of quantum effects in the nuclear dynamics.
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Nava-Sedeño, Josue Manik, Haralampos Hatzikirou, Rainer Klages, and Andreas Deutsch. "Cellular automaton models for time-correlated random walks: derivation and analysis." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-231568.
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Many diffusion processes in nature and society were found to be anomalous, in the sense of being fundamentally different from conventional Brownian motion. An important example is the migration of biological cells, which exhibits non-trivial temporal decay of velocity autocorrelation functions. This means that the corresponding dynamics is characterized by memory effects that slowly decay in time. Motivated by this we construct non-Markovian lattice-gas cellular automata models for moving agents with memory. For this purpose the reorientation probabilities are derived from velocity autocorrelation functions that are given a priori; in that respect our approach is “data-driven”. Particular examples we consider are velocity correlations that decay exponentially or as power laws, where the latter functions generate anomalous diffusion. The computational efficiency of cellular automata combined with our analytical results paves the way to explore the relevance of memory and anomalous diffusion for the dynamics of interacting cell populations, like confluent cell monolayers and cell clustering.
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Bank, Peter. "Singular control of optional random measures." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2000. http://dx.doi.org/10.18452/14556.
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In dieser Arbeit untersuchen wir das Problem der Maximierung bestimmter konkaver Funktionale auf dem Raum der optionalen, zufälligen Maße. Deartige Funktionale treten in der mikroökonomischen Literatur auf, wo ihre Maximierung auf die Bestimmung des optimalen Konsumplans eines ökomischen Agenten hinausläuft. Als Alternative zu den wohlbekannten Methoden der dynamischen Programmierung wird ein neuer Zugang vorgestellt, der es erlaubt, die Struktur der maximierenden Maße in einem über den üblicherweise angenommenen Markovschen Rahmen hinausgehenden, allgemeinen Semimartingalrahmen zu klären. Unser Zugang basiert auf einer unendlichdimensionalen Version des Kuhn-Tucker-Theorems. Die implizierten Bedingungen erster Ordnung erlauben es uns, das Maximierungsproblem auf ein neuartiges Darstellungsproblem für optionale Prozesse zu reduzieren, das damit als ein nicht-Markovsches Substitut für die Hamilton-Jacobi-Bellman Gleichung der dynamischen Programmierung dient. Um dieses Darstellungsproblem im deterministischen Fall zu lösen, führen wir eine zeitinhomogene Verallgemeinerung des Konvexitätsbegriffs ein. Die Lösung im allgemeinen stochastischen Fall ergibt sich über eine enge Beziehung zur Theorie des Gittins-Index der optimalen dynamischen Planung. Unter geeigneten Annahmen gelingt ihre Darstellung in geschlossener Form. Es zeigt sich dabei, daß die maximierenden Maße absolutstetig, diskret und auch singulär sein können, je nach Struktur der dem Problem zugrundeliegenden Stochastik. Im mikroökonomischen Kontext ist es natürlich, daß Problem in einen Gleichgewichtsrahmen einzubetten. Der letzte Teil der Arbeit liefert hierzu ein allgemeines Existenzresultat für ein solches Gleichgewicht.<br>In this thesis, we study the problem of maximizing certain concave functionals on the space of optional random measures. Such functionals arise in microeconomic theory where their maximization corresponds to finding the optimal consumption plan of some economic agent. As an alternative to the well-known methods of Dynamic Programming, we develop a new approach which allows us to clarify the structure of maximizing measures in a general stochastic setting extending beyond the usually required Markovian framework. Our approach is based on an infinite-dimensional version of the Kuhn-Tucker Theorem. The implied first-order conditions allow us to reduce the maximization problem to a new type of representation problem for optional processes which serves as a non-Markovian substitute for the Hamilton-Jacobi-Bellman equation of Dynamic Programming. In order to solve this representation problem in the deterministic case, we introduce a time-inhomogeneous generalization of convexity. The stochastic case is solved by using an intimate relation to the theory of Gittins-indices in optimal dynamic scheduling. Closed-form solutions are derived under appropriate conditions. Depending on the underlying stochastics, maximizing random measures can be absolutely continuous, discrete, and also singular. In the microeconomic context, it is natural to embed the above maximization problem in an equilibrium framework. In the last part of this thesis, we give a general existence result for such an equilibrium.
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Nava-Sedeño, Josue Manik, Haralampos Hatzikirou, Rainer Klages, and Andreas Deutsch. "Cellular automaton models for time-correlated random walks: derivation and analysis." Nature Publishing Group, 2017. https://tud.qucosa.de/id/qucosa%3A30690.
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Many diffusion processes in nature and society were found to be anomalous, in the sense of being fundamentally different from conventional Brownian motion. An important example is the migration of biological cells, which exhibits non-trivial temporal decay of velocity autocorrelation functions. This means that the corresponding dynamics is characterized by memory effects that slowly decay in time. Motivated by this we construct non-Markovian lattice-gas cellular automata models for moving agents with memory. For this purpose the reorientation probabilities are derived from velocity autocorrelation functions that are given a priori; in that respect our approach is “data-driven”. Particular examples we consider are velocity correlations that decay exponentially or as power laws, where the latter functions generate anomalous diffusion. The computational efficiency of cellular automata combined with our analytical results paves the way to explore the relevance of memory and anomalous diffusion for the dynamics of interacting cell populations, like confluent cell monolayers and cell clustering.
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Radtke, Paul Kaspar. "Mesoscopic Models of Stochastic Transport." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19152.
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Transportphänomene treten in biologischen und künstlichen Systemen auf allen Längenskalen auf. In dieser Arbeit untersuchen wir sie für verschiedene Systeme aus einer mesoskopischen Perspektive, in der Fluktuationen physikalischer Größen um ihre Mittelwerte eine wichtige Rolle spielen.
Im ersten Teil untersuchen wir die persistente Bewegung aktiver Brownscher Teilchen mit zusätzlichem Drehmoment, wie sie z.B. für Spermien oder Janus Teilchen auftritt. Wird ihre Bewegung auf einen Tunnel variierender Breite beschränkt, so setzt im thermischen Nichtgleichgewicht Transport ein; ungerichtete Fluktuationen des rauschhaften Antriebs werden gleichgerichtet. Hierdurch wird ein neuer Ratschentyp realisiert.
Im zweiten Teil untersuchen wir den intrazellulären Cargotransport in den Axonen von Nervenzellen mithilfe molekularer Motoren. Sie werden als asymmetrischer Ausschlussprozess simuliert. Zusätzlich können die Cargos zwischen benachbarten Motoren ausgetauscht werden. Dadurch lassen sich charakteristische Eigenschaften des langsamen axonalen Transports mit einer einzigen Motorspezies reproduzieren. Bewerkstelligt wird dies durch die transiente Anbindung der Cargos an rückwärtslaufende Motorstaus.
Im dritten Teil diskutieren wir resistive switching, die nicht volatile Widerstandsänderung eines Dielektrikums durch elektrische Impulse. Es wird für Anwendungen im Computerspeicher ausgenutzt, dem resistive RAM. Wir schlagen ein auf Sauerstoffvakanzen basierendes stochastisches Gitterhüpfmodell vor. Wir definieren binäre logische Zustände mit Hilfe der zugrunde liegenden Vakanzenverteilung und definieren Schreibe- und Leseoperationen durch Spannungsimpulse für ein solches Speicherelement. Überlegungen über die Unterscheidbarkeit dieser Operationen unter Fluktuationen zusammen mit der Deutlichkeit der unterschiedlichen Widerstandszustände selbst ermöglichen es uns, eine optimale Vakanzenzahl vorherzusagen.<br>Transport phenomena occur in biological and artificial systems at all length scales. In this thesis, we investigate them for various systems from a mesoscopic perspective, in which fluctuations around their average properties play an important role.
In the first part, we investigate the persistent diffusive motion of active Brownian particles with an additional torque. It can appear in many real life systems, for example in sperm cells or Janus particles. If their motion is confined to a tunnel of varying width, transport arises out of thermal equilibrium; unbiased fluctuations of the noisy drive are rectified. This way, we have realized a novel kind of ratchet.
In the second part, we study intracellular cargo transport in the axons of nerve cells by molecular motors. They are modeled by an asymmetric exclusion process. In a new approach, we add a cargo exchange interaction between the motors. This way, the characteristics of slow axonal transport can be accounted for with a single motor species. It is explained by the transient attachment of cargos to reverse walking motors jams.
In the third part, we discuss resistive switching, the non-volatile change of resistance in a dielectric due to electric pulses. It is exploited for applications in computer memory, the resistive random access memory (ReRAM). We propose a stochastic lattice hopping model based on the on oxygen vacancies. We define binary logical states by means of the underlying vacancy distributions, and establish a framework of writing and reading such a memory element with voltage pulses. Considerations about the discriminability of these operations under fluctuations together with the markedness of the resistive switching effect itself enable us to predict an optimal vacancy number.
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Droste, Felix. "Signal transmission in stochastic neuron models with non-white or non-Gaussian noise." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17294.
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Die vorliegende Arbeit befasst sich mit dem Einfluss von nicht-weißem oder nicht-Gauß’schem synaptischen Rauschen auf die Informationsübertragung in stochastischen Neuronenmodellen. Ziel ist es, zu verstehen, wie eine Nervenzelle ein Signal in ihrer Pulsaktivität kodiert. Synaptisches Rauschen beschreibt hier den Einfluss anderer Nervenzellen, die nicht das interessierende Signal tragen, aber seine Übertragung durch ihre synaptische Wirkung auf die betrachtete Zelle beeinflussen. In stochastischen Neuronenmodellen wird diese Hintergrundaktivität durch einen stochastischen Prozess mit geeigneter Statistik beschrieben. Ist die Rate, mit der präsynaptische Pulse auftreten, hoch und zeitlich konstant, die Wirkung einzelner Pulse aber verschwindend gering, so wird das synaptische Rauschen durch einen Gauß’schen Prozess beschrieben. Oft wird zudem angenommen, dass das Rauschen unkorreliert (weiß) ist. In dieser Arbeit wird neuronale Signalübertragung in dem Fall untersucht, dass eine solche Näherung nicht mehr gerechtfertigt ist, d.h. wenn der synaptische Hintergrund durch einen stochastischen Prozess beschrieben werden muss, der nicht weiß, nicht Gauß’sch, oder weder weiß noch Gauß’sch ist. Mittels Simulationen und analytischer Rechnungen werden drei Szenarien behandelt: Zunächst betrachten wir eine Zelle, die nicht ein, sondern zwei Signale empfängt, welche zusätzlich durch synaptische Kurzzeitplastizität gefiltert werden. In diesem Fall muss der Hintergrund durch ein farbiges Rauschen beschrieben werden. Im zweiten Szenario betrachten wir den Fall, dass der Effekt einzelner Pulse nicht mehr als schwach angenommen werden kann. Das Rauschen ist dann nicht mehr Gauß’sch, sondern ein Schrotrauschen. Schließlich untersuchen wir den Einfluss einer präsynaptischen Population, deren Feuerrate nicht zeitlich konstant ist, sondern zwischen Phasen hoher und niedriger Aktivität, sogenannten up und down states, springt. In diesem Fall ist das Rauschen weder weiß noch Gauß’sch.<br>This thesis is concerned with the effect of non-white or non-Gaussian synaptic noise on the information transmission properties of single neurons. Synaptic noise subsumes the massive input that a cell receives from thousands of other neurons. In the framework of stochastic neuron models, this input is described by a stochastic process with suitably chosen statistics. If the overall arrival rate of presynaptic action potentials is high and constant in time and if each individual incoming spike has only a small effect on the dynamics of the cell, the massive synaptic input can be modeled as a Gaussian process. For mathematical tractability, one often assumes that furthermore, the input is devoid of temporal structure, i.e. that it is well described by a Gaussian white noise. This is the so-called diffusion approximation (DA). The present thesis explores neuronal signal transmission when the conditions that underlie the DA are no longer met, i.e. when one must describe the synaptic background activity by a stochastic process that is not white, not Gaussian, or neither. We explore three distinct scenarios by means of simulations and analytical calculations: First, we study a cell that receives not one but two signals, additionally filtered by synaptic short-term plasticity (STP), so that the background has to be described by a colored noise. The second scenario deals with synaptic weights that cannot be considered small; here, the effective noise is no longer Gaussian and the shot-noise nature of the input has to be taken into account. Finally, we study the effect of a presynaptic population that does not fire at a rate which is constant in time but instead undergoes transitions between states of high and low activity, so-called up and down states.
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Hauser, Gerd. "Analyse von Schweißnahtunregelmäßigkeiten beim WIG-Orbitalschweißen von vollaustenitischen Stahlrohren." Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-83466.
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Die Bildung von Anlauffarben durch molekularen Sauerstoff im Wurzelschutzgas ist bereits gut erforscht. Weitere Sauerstoffquellen für die Bildung von Anlauffarben sind Feuchte und CO2. Besonders Feuchte ist in diesem Zusammenhang kritisch, da sie sich wesentlich langsamer mit den etablierten Mitteln entfernen lässt. Im Rahmen dieser Arbeit konnte für durch Feuchte verursachte Anlauffarben im Wurzelschutzgas ein Grenzwert von 300 ppm bei 23 °C ermittelt werden. Die Farbausprägung der durch Feuchte verursachten Anlauffarben tendiert besonders bei schwachen bis mittleren Ausprägungen (450-800 ppm) stärker ins Bräunliche als die durch molekularen Sauerstoff verursachten Anlauffarben. Mit Hilfe des an der TU Dresden entwickelten Algorithmus für die Auswahl von Gaskomponenten für Prozessgase, wurde für das gepulste WIG-Orbitalschweißverfahren von austenitischen CrNi-Stahlrohren das Gasgemisch Ar/He/H2 20/70/10 ausgewählt. Gegenüber dem ursprünglich als Prozessgas verwendeten Argon und einem Ar/He 70/30 Gemisch, zeigte sich eine mögliche Steigerung der Vorschubgeschwindigkeit um den Faktor 3,5. Bei Fragen und Anmerkungen zur Arbeit sowie beim Verfassen einer weiterführenden Arbeit bitte Kontakt mit dem Autor aufnehmen (gerd.hauser@gmx.de). Dieser ist an einer Weiterführung des Themas sowie einer unabhängigen Überprüfung der Messwerte sehr interessiert<br>The formation of annealing colors by molecular oxygen in the backing gas is already well understood. Other sources of oxygen for the formation of annealing colors are humidity and CO2. Moisture is especially critical in this context, since they can be removed much more slowly with the established agents. As part of this work can be set a limit for annealing colors (caused by moisture in the root protection gas) of 300 ppm moisture with a environment temparatur of 23 ° C. The annealing colors caused by humidity tends especially in low to moderate conzentrtions (450-800 ppm) mor to a brownish than the annealing colors caused by molecular oxygen. Using the algorithm developed at the TU Dresden for the selection of gas components for process gases,the gas mixture Ar/He/H2 20/70/10 was chosen for the pulsed TIG orbital welding of austenitic stainless steel tubes. Compared to the originally used process gas argon and Ar/He-mixture 70/30, showed the Ar/He/H2 mixtur a possible increase in feed rate by a factor of 3.5
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Eurich, Jacob G. "Processes underlying the fine-scale partitioning and niche diversification in a guild of coral reef damselfishes." Thesis, 2018. https://researchonline.jcu.edu.au/55992/1/JCU_55992_eurich_2018_thesis.pdf.
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A major goal of ecology is to explain the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment. The distributions and coexistence of ecologically similar animals may depend on the degree of niche diversification and competitive interactions within and among species. The extent of ecological partitioning in guilds of coral reef fishes was hotly debated in the 1980s, and despite 4 decades of research, the issue remains unresolved. In particular, the link between niche partitioning and agonistic interactions together have received little attention. In the thesis I investigated finescale species distributions, resource use (e.g., habitat and food), and competition in a guild of 7 territorial damselfish species in Kimbe Bay, Papua New Guinea. Common generalisations about the ecological function of territorial damselfish and associated interactions with important roving herbivorous fishes were also investigated. Using ecological surveys, laboratory-based analytical methods, observational studies, and manipulative field experiments, this thesis addresses novel questions about the ecology and functional role of territorial damselfish and the resulting community effects.
Competition over resources is recognised to play a primary role in the structure of coral reef fish communities. The distribution of ecologically similar species may depend on the degree to which traditional niche mechanisms operate alongside competitive dynamics. In Chapter 2 these effects were examined by investigating fine-scale species distributions, microhabitat use, and aggression among territorial damselfishes. I documented patterns of habitat partitioning across the 3 reef zones – reef flat, reef crest, and reef slope – with distinct patterns of distribution within these zones at extremely fine scales (1 − 2 m). Distinct differences between neighbouring species in the microhabitat use selected were also observed. Furthermore, aggression elicited by neighbouring species was significantly higher for all species, compared with non-adjacent species. This chapter revealed a fine level of spatial partitioning among reef zones and microhabitats in this guild of damselfish, which was likely maintained by agonistic interactions among neighbouring species.
While Chapter 2 found that neighbouring damselfish constrain their microhabitat use to facilitate the co-habitation of reef zones, microhabitat selectivity alone was insufficient to explain the distinct zonation and limited distributional overlap. I hypothesised that in this highly partitioned ecological community, where there are intense agonistic interactions for resources, ecologically neighbouring territorial damselfish may also partition food resources. Other studies had previously quantified diet contributions for the study species, but no isotopic analysis had been conducted for territorial damselfish to date to specifically target pelagic-based food sources. In Chapter 3 I quantified the trophic niches of the territorial damselfish guild through the use of stable isotopes (δ¹³C and δ¹⁵N). Adjacent species on the reef flat, reef crest, and reef slope exhibited high to intermediate trophic niche partitioning when examining pelagic versus reef-based dietary sources, with two species previously described as benthic herbivores actually exhibiting pelagic feeding. Findings of Chapter 3 indicate that diet choice reinforces the patterns of spatial partitioning and coexistence among ecologically similar species. In addition, evidence of planktivorous pelagic feeding adds to the growing view that interspecific differences among similar species are lost when categorizing species into broad functional classifications.
In Chapter 4 the direct and indirect effects of interference competition on resource partitioning were measured. The previous chapters found that microhabitat selectivity and dietary diversification facilitated the co-habitation of reef zones among the territorial damselfish guild. Additionally, evidence suggested that interspecific aggression helped maintain the distributional boundaries between neighbouring species. However, an experimental removal of a dominant competitor was necessary to understand if interference competition is present and if subordinate distributional shifts would occur. I employed an observational experiment and a large-scale removal experiment (220 m²) to examine the intensity of agonistic interactions among species and the extent to which the most abundant species influenced the distribution and abundance of neighbouring and non-neighbouring species in the guild. The findings indicated that the distinct distribution patterns among the reef crest species were linked to levels of interspecific agonistic behaviour. The competitive release following the removal of a superior competitor resulted in comprehensive direct and indirect effects, with the subordinate neighbour shifting into the newly available space, followed by successive shifts in species responding to the change in the distributions of their immediate neighbours. Through a novel multi-species large-scale experiment, Chapter 4 provides the conclusive evidence that distributions and the coexistence of the territorial damselfish guild are a result of niche diversification and competitive interactions within and among species.
Chapter 5 broadens the thesis by investigating the common perception that all territorial damselfish negatively influence overall reef function and roving herbivorous fishes. Similar to Chapter 2 where generalisations about the guild's diet were questioned, here I challenged the paradigm that intermediate-sized territorial damselfishes have a negative influence on surgeonfish, parrotfish, and rabbitfish abundance and foraging behaviour. To test this, I conducted experimental removals (220 m²) of the most abundant territorial damselfish to examine its impact on roving herbivores and the benthic community structure. The overall relative abundance (MaxN) of roving herbivores was not influenced by the removal. No changes in foraging patterns were observed for parrotfish, the family that received the highest rate of agonistic interactions, and rabbitfish. Instead, the removal resulted in a significant decrease in surgeonfish feeding, suggesting the territorial damselfish species altered foraging patterns indirectly through territorial maintenance and not aggression. The results indicate that all territorial damselfishes do not have a negative impact on all roving herbivores and instead may enhance surgeonfish foraging indirectly through the removal of sediment. The generalisation that territorial damselfish reduce foraging rates of roving herbivores may not be applicable in all systems or for all species.
In summary, this thesis investigated the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment as a precursor to the long-term ecological changes on coral reefs. It first established fine-scale partitioning in a guild of competing fishes on a high-diversity coral reef. Second, the research showed that microhabitat selectivity and dietary diversification facilitates the co-habitation of reef zones, and that interspecific aggression maintains the distributional boundaries between neighbouring species. In order to demonstrate how competitive interactions and resource partitioning influence species coexistence in a complex ecosystem a large-scale field experiment was conducted. The results demonstrate that when exploring coexistence in reef fish communities, the more traditional niche mechanisms operate alongside direct and indirect competitive dynamics, and within highly diverse systems these ecological processes are magnified. Moreover, the thesis highlights the importance of challenging common generalisations and paradigms. By examining the functional role of territorial damselfishes this research provides evidence of novel dietary diversification and demonstrates the complexity of territorial damselfish and roving herbivore interactions.
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Ronconi, Robert Alfredo. "Patterns and processes of marine habitat selection: foraging ecology, competition and coexistence among coastal seabirds." Thesis, 2008. http://hdl.handle.net/1828/941.
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Changes in the marine ecosystem can affect the distribution, survival, and reproductive success of seabirds. Therefore, a better understanding of factors influencing the marine distribution and abundance of seabirds can provide insight into ecological hypotheses and have important conservation implications. Yet at-sea habitat selection by seabirds has received far less attention than have investigations of their breeding biology. I studied the patterns and processes of marine habitat selection by seabirds in nearshore waters of Pacific Rim National Park Reserve, Vancouver Island, British Columbia. The study focused on comparative analyses among five sympatric species: marbled murrelet (Brachyramphus marmoratus), common murre (Uria aalge), rhinoceros auklet (Cerorhinca monocerata), pigeon guillemot (Cepphus columba) and pelagic cormorant (Phalacrocorax pelagicus). I used a multi-scaled and multi-disciplined approach combining shore-based telescope observations, vessel-based surveys, and developed new techniques for mapping nearshore seabird distributions.
Patterns of habitat selection were examined through vessel-based surveys and species-habitat modeling. Vessel-based transects are fundamental to studies of seabird ecology, yet standardized protocols often fail to account for detectability biases. Distance-sampling methods were used to quantify seabird detectability along transects and showed extensive variability (20-80% of birds detected) depending on species, year, and observer. Corrected estimates of bird densities were used in habitat selection modeling, which demonstrated inter-specific and inter-annual differences in species-habitat associations. Most species showed distinct partitioning in habitats, particularly with respect to substrate and along gradients of depth and sea-surface temperature/salinity. Thus, environmental variability is a key factor structuring habitat use and coexistence in this community of piscivorous seabirds.
Processes of habitat selection were studied through observations of foraging behaviour, estimates of prey availability, and spatial-statistical analysis of seabird distributions. Marbled murrelets increased foraging effort in years and seasons with scarce prey and poor oceanographic conditions and decreased foraging effort at sites with high prey availability. Despite their flexible activity budgets, increased foraging effort was inadequate to buffer reproductive success in a poor prey year, suggesting that prey availability is a limiting factor in habitat use and population growth for murrelets. Theodolite-based mapping studies examined the fine-scale distribution patterns of murrelets and murres. Nearest neighbour spatial statistics tested for competition over foraging space and showed avoidance of murres by murrelets.
The results of these studies have implications for the management and conservation of the imperiled marbled murrelet in British Columbia and elsewhere in their range. I demonstrate a clear link between prey availability and consequences for reproductive success. Habitat selection models provide a step towards identifying critical marine habitats which must be protected under the Species at Risk Act. Murrelets show high forage site fidelity and associations with spatially fixed habitat components (beaches), suggesting that marine protected areas may have an important role to play in the conservation, management and recovery of murrelet populations.
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Saxena, Abigail Green. "Sulfur-Cycling in Methane-Rich Ecosystems: Uncovering Microbial Processes and Novel Niches." Thesis, 2013. https://thesis.library.caltech.edu/7755/12/SaxenaAbigail2013_intro.pdf.
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<p>Microbial sulfur cycling communities were investigated in two methane-rich ecosystems, terrestrial mud volcanoes (TMVs) and marine methane seeps, in order to investigate niches and processes that would likely be central to the functioning of these crucial ecosystems. Terrestrial mud volcanoes represent geochemically diverse habitats with varying sulfur sources and yet sulfur-cycling in these environments remains largely unexplored. Here we characterized the sulfur-metabolizing microorganisms and activity in 4 TMVs in Azerbaijan, supporting the presence of active sulfur-oxidizing and sulfate-reducing guilds in all 4 TMVs across a range of physiochemical conditions, with diversity of these guilds being unique to each TMV. We also found evidence for the anaerobic oxidation of methane coupled to sulfate reduction, a process which we explored further in the more tractable marine methane seeps. Diverse associations between methanotrophic archaea (ANME) and sulfate-reducing bacterial groups (SRB) often co-occur in marine methane seeps, however the ecophysiology of these different symbiotic associations has not been examined. Using a combination of molecular, geochemical and fluorescence <i>in situ</i> hybridization coupled to nano-scale secondary ion mass spectrometry (FISH-NanoSIMS) analyses of in situ seep sediments and methane-amended sediment incubations from diverse locations, we show that the unexplained diversity in SRB associated with ANME cells can be at least partially explained by preferential nitrate utilization by one particular partner, the seepDBB. This discovery reveals that nitrate is likely an important factor in community structuring and diversity in marine methane seep ecosystems. The thesis concludes with a study of the dynamics between ANME and their associated SRB partners. We inhibited sulfate reduction and followed the metabolic processes of the community as well as the effect of ANME/SRB aggregate composition and growth on a cellular level by tracking <sup>15</sup>N substrate incorporation into biomass using FISH-NanoSIMS. We revealed that while sulfate-reducing bacteria gradually disappeared over time in incubations with an SRB inhibitor, the ANME archaea persisted in the form of ANME-only aggregates, which are capable of little to no growth when sulfate reduction is inhibited. These data suggest ANME are not able to synthesize new proteins when sulfate reduction is inhibited.</p>
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Silva, Júlia Marina. "A influência de dinâmicas do abuso sexual e da idade da criança nos processos mnésicos : contributos para a adaptação do protocolo do NICHD ao contexto português." Master's thesis, 2014. http://hdl.handle.net/10400.14/26361.
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O presente estudo teve como objetivo compreender a influência de dinâmicas do abuso sexual e idade da criança nos processos mnésicos, contribuindo para a adaptação e aplicação do protocolo NICHD ao contexto português. Os objetivos específicos do mesmo consistiram em compreender de que forma a frequência do abuso, a idade da criança e a influência do intervalo de tempo, entre o primeiro evento abusivo e a entrevista forense, condicionam a capacidade da criança fornecer informação.
Para tal, recorreu-se a uma amostra de 21 crianças alegadamente abusadas sexualmente e entrevistadas com o Protocolo de Entrevista Forense do NICHD (National Institute of Child Health and Human Development). Estas entrevistas foram sujeitas a uma análise de conteúdo, através da contabilização do número de palavras total do discurso da criança, relativa a parte substantiva da entrevista, permitindo assim quantificar o mesmo. Posteriormente foi elaborada uma análise quantitativa, ao nível das variáveis em estudo.
Os resultados deste estudo demonstraram que não existem diferenças significativas ao nível da frequência do abuso, da idade da criança e da influência do intervalo de tempo, entre o primeiro evento abusivo e a entrevista forense, relativamente à capacidade da criança fornecer informação.
Alguns dos resultados permitem-nos tirar conclusões que vão de encontro ao que a literatura científica aponta, nomeadamente, o facto de crianças mais novas também serem capazes de fornecer informação, a qualidade da entrevista potenciar a capacidade da criança para descrever eventos, a ausência de diferenças na capacidade de fornecer informação entre crianças com diferentes idades e perante experiências repetidas de abuso, e o facto de as crianças serem capazes fornecer informação por longos períodos de tempo.
Estas conclusões foram explicadas à luz da literatura e de estudos científicos já realizados, bem como em função do que consideramos ser as limitações do estudo.<br>The present study aimed to understand the influence of the sexual abuse and age of the child dynamics in mnemonic processes, contributing to the adaptation and application of the NICHD protocol to the Portuguese context. The specific objectives consisted in understanding how the abuse frequency, child’s age and the time interval influence, between the first abusive event and the forensic interview, determine the child’s ability to provide information.
To this end, we resorted to a 21 children sample allegedly sexually abused and interviewed with the Forensic Interview Protocol NICHD (National Institute of Child Health and Human Development). These interviews were subjected to a content analysis, by counting the total number of words of the child’s speech, on the substantive part of the interview, thus quantify the same. Posteriorly, was elaborated a quantitative analysis of the variables under study.
The results of this study demonstrated that there are no significant differences in the frequency of the abuse, child’s age and the time interval influence, between the first abusive event and the forensic interview relative to the child’s ability to provide information.
Some of the results allow us to draw conclusions that are in accordance to what the scientific literature indicates, in particular, the fact that younger children are also able to provide information, the quality of the interview potentiate the child’s ability to describe events, the absence of differences in the ability to provide information among children of different ages and before repeated abuse experiments, and the fact that children are able to provide information for long periods of time.
These conclusions were explained in the light of literature and conducted scientific studies, as well as in terms of what we consider to be the study limitations.
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Alonzo-Proulx, Agnès. "Entrevues auprès d’enfants qui dévoilent une agression sexuelle : examen du processus d’enquête et du parcours judiciaire des dossiers." Thèse, 2015. http://hdl.handle.net/1866/13734.
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Cette étude a été rendue possible grâce aux bourses doctorales accordées à la première auteure par les organismes suivants : le Conseil de recherche en sciences humaines (CRSH), la Chaire interuniversitaire Marie-Vincent sur les agressions sexuelles envers les enfants (CIMV), l’Équipe violence sexuelle et santé (ÉVISSA) et le Centre de recherche interdisciplinaire sur les problèmes conjugaux et les agressions sexuelles (CRIPCAS). Cette étude a également été soutenue par une subvention de recherche accordée par le Bureau d’aide aux victimes d’actes criminelle (BAVAC) du ministère de la justice du Québec accordée à Mireille Cyr.<br>Cette thèse visait à explorer l’apport de variables contextuelles sur le récit des enfants qui dévoilent une agression sexuelle de même que sur les suites judiciaires de leur dossier.
Plus spécifiquement, le premier article examinait la valeur prédictive des caractéristiques de l’agression sexuelle (lien avec le suspect, présence de coercition, sévérité et fréquence de l’agression) et de son dévoilement (dévoilement volontaire ou accidentel, croyance et protection maternelle) sur la proportion de détails centraux dévoilés durant l’entrevue d’enquête. Les effets de l’âge et de l’adhésion au protocole d’entrevue du National Institute of Child Health and Human Development (NICHD) ont également été contrôlés étant donné leurs impacts significatifs sur le contenu de l’entrevue. L’ensemble de ces variables ont été extraites de 116 entrevues et dossiers d’agression sexuelle considérés comme fondés par les policiers. Les résultats de la régression hiérarchique montrent que conformément à la littérature, l’adhésion au Protocole NICHD ainsi que l’âge de l’enfant étaient les deux plus importants prédicteurs de la proportion de détails centraux dévoilés. La coercition sous forme d’une combinaison de coercition verbale et physique, de même que la présence d’une mère qui protège son enfant suite au dévoilement étaient également des prédicteurs significatifs qui augmentaient la proportion de détails centraux. Ces résultats sont discutés, de même que les limites de l’étude et les pistes de recherche futures.
Le deuxième article, quant à lui, explorait la valeur prédictive des caractéristiques de l’enfant, de l’agression sexuelle, de la garde partagée, du contexte de dévoilement, des preuves disponibles et de l’entrevue d’enquête sur les chances que le dossier soit considéré comme fondé par les enquêteurs et autorisé à procéder en cour criminelle par les procureurs de la couronne. Ces caractéristiques ont été cotées à partir d’un échantillon de 169 entrevues et dossiers d’agression sexuelle. Les résultats montrent que 117 des 169 dossiers (69%) de l’échantillon ont été considérés comme fondés par les enquêteurs. La régression logistique révèle que, en ordre d’importance, l’âge de l’enfant, le fait que le dévoilement soit accidentel, le choix du premier confident, la fréquence des agressions et la corroboration des faits par le suspect étaient des prédicteurs significatifs à la décision policière. De ces 117 dossiers fondés et soumis aux procureurs, 96 dossiers (82%) ont été autorisés par ces derniers à procéder en cour. Les résultats de la régression logistique révèlent en outre que, en ordre d’importance, le nombre de faits corroborés par le suspect, la protection maternelle, l’adhésion au protocole NICHD de même que le nombre de faits corroborés par le témoin augmentaient significativement la prédiction que les dossiers soient autorisés alors que le jeune âge de l’enfant diminuait cette prédiction. Ces résultats sont discutés ainsi que les limites de l’étude et les pistes de recherches futures.<br>This thesis aimed to explore the contribution of contextual variables to the formal disclosure of alleged child sexual abuse victims as well as to the legal proceedings of their case.
More specifically, the first article examined the predictive value of child sexual abuse’s characteristics (relationship between the child and the suspect, reported coercion, type and frequency of abuse) as well as the disclosure context (purposeful or accidental disclosure, maternal belief and protective actions) on the proportion of central forensically relevant (CFR) details elicited during the investigative interview. The study also controlled for the well documented effects of the child’s age and use of the National Institute of Child Health and Human Development (NICHD) Investigative Protocol. All these variables were collected from 116 interview transcripts and child sexual abuse files. As expected, results from hierarchical regression showed that adhesion to the NICHD Protocol and the child’s age were the two strongest predictors of the proportion of CFR details obtained. Coercion (physical and verbal) as well as the presence of a protective mother also increased the proportion of CFR details obtained. Explanations for these results are discussed, as well as the study’s limitations and implications for further research.
The second article explored the predictive value of the characteristics of the child, sexual abuse, shared custody, disclosure context, available evidence and investigative interviews on the investigators’ decision to substantiate the complaint and on the district attorney’s decision to authorize its proceeding in court. These characteristics were collected from 169 child sexual abuse police files and interview transcripts. Results show that 117 files out of 169 (69%) were classified as substantiated by the investigators. Logistic regression reveal that the child’s age, an accidental disclosure, the choice of the first person who received the disclosure, the frequency of the abuse, and the suspect’s corroboration were significant predictors in finding the case substantiated. Of these 117 substantiated files submitted to the district attorneys, 96 of them (82%) were authorized to proceed in criminal court. Significant predictors on the district attorneys’ level were the corroboration of the suspect, the protection offered by the mother following her child’s disclosure, the adhesion to the NICHD investigative Protocol and the corroboration of the witness which increased the chances of authorizing the case whereas the child’s age diminished it. The results are discussed, as well as well as the study’s limitations and implications for further research.
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Isselin-Nondedeu, Francis. "Déterminismes géomorphologique et fonctionnels de la distribution des plantes dans les milieux d'altitude : essai d'éco-géomorphologie.Implications et applications pour la restauration de la biodiversité des pistes de ski." Phd thesis, 2005. http://tel.archives-ouvertes.fr/tel-00012198.
Full textAbstract:
La restauration des milieux d'altitude dégradés se déroule dans des conditions où à la fois la végétation, le sol et le relief ont été profondément perturbés. En conséquence, la restauration échoue souvent à rétablir une structure et un fonctionnement proche de celui des écosystèmes naturels. Même si en montagne, il est reconnu que la végétation s'organise en fonction des variations du relief, les mécanismes en jeu restent méconnus. <br />C'est pourquoi afin de gérer au mieux l'installation et le maintien de la végétation, nous proposons un modèle explicatif qui relie les contraintes imposées par le relief à des caractéristiques adaptatives du fonctionnement des plantes. La mesure de traits fonctionnels des plantes, aux différents stades de leur vie, nous permet de déterminer ces caractéristiques. D'autre part, nous supposons que le relief induit une variation des contraintes climatiques, édaphiques, des interactions biotiques (compétition, prédation) mais aussi des contraintes liées aux processus gravitaires (érosion-sédimentation). Les études sont conduites dans le subalpin (la Plagne, Alpes du Nord) et le montagnard (le Saignon, Hautes Alpes).<br />La première partie met en évidence une variation des traits biologiques des plantes impliqués dans la gestion des ressources, la réponse au pâturage et la régénération, en fonction d'un gradient méso-topographique. Celui ci détermine effectivement le régime des températures, les durées d'enneigement, les niveaux de ressources du sol et la fréquentation par les herbivores.<br />La deuxième partie analyse les traits des plantes en relation avec les processus gravitaires. La pente détermine ainsi des mécanismes de dispersion des graines à la surface du sol. L'ampleur de ces déplacements va dépendre de la forme des graines, relative aux espèces, et de l'existence de pièges sur le sol. Ces pièges sont soit des accumulations de sédiments générés par la présence d'obstacles végétaux, soit des empreintes de sabots laissées par les grands herbivores.<br />Les études réalisées dans la troisième partie, indiquent que ces mêmes pièges favorisent le recrutement des plantes. Cependant l'identification des plantules révèle que les graines ont été piégées différemment selon leur forme. Par ailleurs, une expérimentation met en évidence que la germination et la croissance des plantules constitue un trait de réponse déterminant pour la ségrégation des espèces dans les communautés en fonction de la nature des substrats géologiques.<br />Enfin, la quatrième partie, analyse les traits des espèces en relation avec leur capacité compétitive, et montre par la modélisation et l'expérimentation que la distribution des plantes dans les communautés est liée à la disponibilité en ressource du sol et aux traits d'utilisation et de gestion de celle ci (surface spécifique foliaire, taille). <br />En synthèse, l'étude se conclu par un essai d'éco-géomorphologie appliquée aux milieux d'altitude. Ce modèle enrichit la relation traits/environnements et espèces/habitats en reliant les traits de réponse et les traits d'effets des plantes aux processus géomorphologiques, et éclaire sur la création de nouvelles niches dans les milieux restaurés. Ce modèle offre une nouvelle grille d'analyse des milieux naturels et un outil de prédiction pour la restauration des milieux d'altitude.
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Collins, Joshua. "Niches of Activity and Reprieve: An Architectural Induction in Service of Environmental Presence." Thesis, 2011. http://hdl.handle.net/10222/14380.
Full textAbstract:
Design is the meeting of the processes that one employs and the intentions that one brings.
Exploring an inductive methodology situates the design environmentally. The inherent dynamic and constructive processes, which arise from the qualities of methodological inquiries, are the basis for the inhabitation within place.
An inductive process began by exploring the role of aural perception prior to contextual and design intentions. This resulted in a strong emphasis on experience and presence. Research into analogous disciplines resulted in an exploration of methods that facilitate the inductive operations of media, particularly noise.
The provision of a contextual framework for observations provided order to method. A strategy was posited, where the development of constructs that addressed the entire range of environmental dimensions, from site to structure, could supply integrity to the situation of contextual forces; their tension and release.
Hence, a general theory for the constructive inhabitation of place.
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Malinowski, Alexander. "Financial Models of Interaction Based on Marked Point Processes and Gaussian Fields." Doctoral thesis, 2012. http://hdl.handle.net/11858/00-1735-0000-000D-F0EF-6.
Full text
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Lenz, Michael. "Neuartige Ultraschallmeßverfahren unter Nutzung von Schallfeldinformationen." Doctoral thesis, 2013. https://tud.qucosa.de/id/qucosa%3A27667.
Full textAbstract:
Die vorliegende Arbeit untersucht, wie die genaue Kenntnis der Sende- und Empfangsschallfelder eines Ultraschallwandlers zur Entwicklung neuer Meßverfahren genutzt werden kann. Insbesondere werden dargestellt:
- ein neuartiges, nichtscannendes Verfahren zur Bestimmung der Krümmung eines Reflektors, basierend auf der Analyse der Wellenfrontkrümmung reflektierter Schallfelder
- ein neuartiges, nichtinvasives Verfahren zur Bestimmung der Schallgeschwindigkeit in einer Flüssigkeit durch Auswertung der Echosignale von im Ausbreitungsmedium vorhandenen Streupartikeln und
- ein Verfahren zur Wandlercharakterisierung durch Messungen in Fluiden mit Streupartikeln, sowie verschiedene Zuordnungen von Schallfeldmerkmalen zu spezifischen Eigenschaften eines Ultraschallwandlers.
Im Zusammenspiel von Simulation und Experiment konnten die Funktionstüchtigkeit aller Meßverfahren nachgewiesen und vielversprechende innovative Ansätze für zukünftige Entwicklungen angeregt werden:
1. Das nichtscannende Verfahren zur Krümmungsmessung erlaubt bei guter Justage eine Krümmungsbestimmung von Reflektoren mit Radien zwischen 6 und 11 mm mit einer Unsicherheit von ungefähr 0,5 mm. In Kombination mit herkömmlichen scannenden Verfahren bietet es Ansätze zur präzisen Größenbestimmung von Fehlern in der zerstörungsfreien Prüfung.
2. Das Verfahren zur nichtinvasiven Schallgeschwindigkeitsmessung erlaubt eine Bestimmung von Schallgeschwindigkeiten mit einer statistischen Meßunsicherheit von 0,1 %. Mögliche Weiterentwicklungen zur Messung der Schallgeschwindigkeit mit örtlicher Auflösung und zur Gewinnung neuer Diagnosemöglichkeiten in Metallurgie (nichtinvasive Charakterisierung von Mischungsvorgängen) und Biomedizintechnik (nichtinvasive Temperaturmessung in Körpergewebe zur Überwachung der Hyperthermiebehandlung, Gewebecharakterisierung) werden erläutert.
Aus verschiedenen bekannten sowie einem neuartigen, leicht anwendbaren Meßverfahren werden neue Schlüsse gezogen a) zur Bestimmung der akustisch effektiven Elementgröße von Wandlerelementen mittels Schallfeldmessungen, b) zur Qualitätssicherung im Hinblick auf Schallkopfasymmetrien und c) zur Verbesserung von Schallfeldsimulationen.<br>The current thesis explores how the precise knowledge of the sending and receiving sound fields of an ultrasonic transducer can contribute to the development of novel measuring techniques. Emphasis is placed on:
- a novel, non-scanning method for the determination of the curvature radius of a spherical reflector, based on the analysis of the wave front curvature of the reflected sound field,
- a novel non-invasive method for sound velocity measurements in fluids using the echo signals from scattering particles, and
- novel conclusions on how to use well-known sound field measurement methods for transducer characterisation, as well as an introduction to a novel easy-to-use method for transducer characterisation exploiting the echo signals from scattering particles.
Proof of concept is shown for all methods by simulation and measurement, and different promising improvements for further techniques are suggested:
- The non-scanning method for curvature measurements makes it possible to determine reflector radii between 6 and 11 mm with an uncertainty of about 0.5 mm, provided that there is a good reflector alignment. In combination with conventional methods, a novel approach for the determination of the size of discontinuities in non-destructive testing is outlined.
- The method for non-invasive sound velocity measurements allows the determination of sound velocity in homogeneous fluids with a statistical uncertainty of 0.1 %. Future improvements are suggested to allow sound velocity measurements with local resolution, which enables novel approaches for metallurgy (non-invasive characterisation of mixing processes) and biomedical engineering (non-invasive temperature control for hyperthermia treatment, tissue characterisation).
- New conclusions are drawn based on well-established and a novel easy-to-implement measurement method regarding a) the determination of the acoustically effective element size of transducer elements, b) transducer asymmetries, thereby improving quality control, and c) the improvement of sound field simulations.
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Fischer, Michael. "Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations: Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations." Doctoral thesis, 2013. https://tud.qucosa.de/id/qucosa%3A28198.
Full textAbstract:
The non-adiabatic quantum molecular dynamics (NA-QMD) method couples self-consistently classical nuclear motion with time-dependent density functional theory (TDDFT) in basis expansion for the electron dynamics. It has become a versatile approach to study the dynamics of atoms, molecules and clusters in a wide range of scenarios. This work presents applications of the NA-QMD method to important benchmark systems and its systematic extension to include quantum effects in the nuclear motion.
Regarding the first objective, a complete study of the strong-field ionization and dissociation dynamics of nature’s simplest molecule H2+ is performed. By including all electronic and nuclear degrees of freedom and all reaction channels, molecular rotation is shown to play an important role in the ionization process. In addition, strong orientation effects in the energy deposition process of the Buckminster fullerene C60 in short intense laser pulses are surprisingly found in full dimensional calculations. Their consequences on the subsequent nuclear relaxation dynamics shed new light on available experimental data and future experiments are proposed to confirm the detailed predictions.
Regarding the second objective, the NA-QMD formalism is basically extended to take electron-nuclear correlations into account. This extension is achieved by means of a trajectory surface hopping scheme in the adiabatic Kohn-Sham framework. First studied examples from collision physics and photochemistry illustrate the relevance and importance of quantum effects in the nuclear dynamics.
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Hauser, Gerd. "Analyse von Schweißnahtunregelmäßigkeiten beim WIG-Orbitalschweißen von vollaustenitischen Stahlrohren." Master's thesis, 2011. https://tud.qucosa.de/id/qucosa%3A25895.
Full textAbstract:
Die Bildung von Anlauffarben durch molekularen Sauerstoff im Wurzelschutzgas ist bereits gut erforscht. Weitere Sauerstoffquellen für die Bildung von Anlauffarben sind Feuchte und CO2. Besonders Feuchte ist in diesem Zusammenhang kritisch, da sie sich wesentlich langsamer mit den etablierten Mitteln entfernen lässt.
Im Rahmen dieser Arbeit konnte für durch Feuchte verursachte Anlauffarben im Wurzelschutzgas ein Grenzwert von 300 ppm bei 23 °C ermittelt werden. Die Farbausprägung der durch Feuchte verursachten Anlauffarben tendiert besonders bei schwachen bis mittleren Ausprägungen (450-800 ppm) stärker ins Bräunliche als die durch molekularen Sauerstoff verursachten Anlauffarben.
Mit Hilfe des an der TU Dresden entwickelten Algorithmus für die Auswahl von Gaskomponenten für Prozessgase, wurde für das gepulste WIG-Orbitalschweißverfahren von austenitischen CrNi-Stahlrohren das Gasgemisch Ar/He/H2 20/70/10 ausgewählt. Gegenüber dem ursprünglich als Prozessgas verwendeten Argon und einem Ar/He 70/30 Gemisch, zeigte sich eine mögliche Steigerung der Vorschubgeschwindigkeit um den Faktor 3,5.
Bei Fragen und Anmerkungen zur Arbeit sowie beim Verfassen einer weiterführenden Arbeit bitte Kontakt mit dem Autor aufnehmen (gerd.hauser@gmx.de). Dieser ist an einer Weiterführung des Themas sowie einer unabhängigen Überprüfung der Messwerte sehr interessiert.:1 Einleitung 1
2 Stand der Technik 2
2.1 WIG-Schweißen 2
2.1.1 Gepulstes WIG-Schweißen 2
2.1.2 WIG-Orbitalschweißen 5
2.2 Schweißen von austenitischem CrNi-Stahl 7
2.2.1 Schweißtechnische Verarbeitung von austenitischem CrNi-Stahl 7
2.2.2 Schweißnahtunregelmäßigkeit: Anlauffarben 12
2.3 Prozess- und Wurzelschutzgase 17
2.3.1 Prozessgase 18
2.3.2 Wurzelschutzgase 21
2.4 Messung von Sauerstoff und Feuchte bei schweißtechnischen Anwendungen 23
3 Präzisierung der Aufgabenstellung 28
4 Analyse von Baustellenbedingungen und Maßnahmen auf Winterbaustellen 29
4.1 Beschreibung der Bedingungen 29
4.2 Beschreibung der Unregelmäßigkeiten 31
4.3 Bewertung der etablierten Maßnahmen 33
5 Versuchsplanung und Durchführung 35
5.1 Experimentelle Randbedingungen 35
5.1.1 Geräte, Messmittel und Software 35
5.1.2 Versuchswerkstoffe und Materialien 42
5.1.3 Schweißparameter 43
5.1.4 Auswertungsmethoden 44
5.2 Einfluss der Feuchte in Wurzelschutzgasen 47
5.2.1 Schweißversuche bei konstanten und wechselnden Temperaturen 47
5.2.2 Versuche zur Feuchteansammlung im Rohr 49
5.2.3 Versuch zur Bildung von Anlauffarben bei unterschiedlichen Feuchtekonzentrationen im Wurzelschutzgas 51
5.3 Einfluss der Prozessgaszusammensetzung für die Gasgemische Ar, Ar/He, Ar/He/H2 53
6 Auswertung der Versuchsergebnisse und Schlussfolgerungen 56
6.1 Anlauffarben auf Winterbaustellen 56
6.1.1 Einfluss der Außentemperatur auf den Schweißprozess 56
6.1.2 Einfluss von Feuchteansammlungen in Rohren 61
6.1.3 Einfluss von unterschiedlichen Feuchtekonzentrationen im Wurzelschutzgas 63
6.1.4 Schlussfolgerungen für die Anwendung in der Praxis 68
6.2 Einfluss der Prozessgaszusammensetzung beim WIG-Orbitalschweißen 74
6.2.1 Versuchsauswertung 74
6.2.2 Anwendung des Mischgases Ar/He/H2 in der Praxis 80
7 Zusammenfassung und Ausblick 81
8 Quellenverzeichnis 82
9 Verzeichnis der Abbildungen und Tabellen 87
10 Anlagenverzeichnis 92<br>The formation of annealing colors by molecular oxygen in the backing gas is already well understood. Other sources of oxygen for the formation of annealing colors are humidity and CO2. Moisture is especially critical in this context, since they can be removed much more slowly with the established agents.
As part of this work can be set a limit for annealing colors (caused by moisture in the root protection gas) of 300 ppm moisture with a environment temparatur of 23 ° C.
The annealing colors caused by humidity tends especially in low to moderate conzentrtions (450-800 ppm) mor to a brownish than the annealing colors caused by molecular oxygen.
Using the algorithm developed at the TU Dresden for the selection of gas components for process gases,the gas mixture Ar/He/H2 20/70/10 was chosen for the pulsed TIG orbital welding of austenitic stainless steel tubes. Compared to the originally used process gas argon and Ar/He-mixture 70/30, showed the Ar/He/H2 mixtur a possible increase in feed rate by a factor of 3.5.:1 Einleitung 1
2 Stand der Technik 2
2.1 WIG-Schweißen 2
2.1.1 Gepulstes WIG-Schweißen 2
2.1.2 WIG-Orbitalschweißen 5
2.2 Schweißen von austenitischem CrNi-Stahl 7
2.2.1 Schweißtechnische Verarbeitung von austenitischem CrNi-Stahl 7
2.2.2 Schweißnahtunregelmäßigkeit: Anlauffarben 12
2.3 Prozess- und Wurzelschutzgase 17
2.3.1 Prozessgase 18
2.3.2 Wurzelschutzgase 21
2.4 Messung von Sauerstoff und Feuchte bei schweißtechnischen Anwendungen 23
3 Präzisierung der Aufgabenstellung 28
4 Analyse von Baustellenbedingungen und Maßnahmen auf Winterbaustellen 29
4.1 Beschreibung der Bedingungen 29
4.2 Beschreibung der Unregelmäßigkeiten 31
4.3 Bewertung der etablierten Maßnahmen 33
5 Versuchsplanung und Durchführung 35
5.1 Experimentelle Randbedingungen 35
5.1.1 Geräte, Messmittel und Software 35
5.1.2 Versuchswerkstoffe und Materialien 42
5.1.3 Schweißparameter 43
5.1.4 Auswertungsmethoden 44
5.2 Einfluss der Feuchte in Wurzelschutzgasen 47
5.2.1 Schweißversuche bei konstanten und wechselnden Temperaturen 47
5.2.2 Versuche zur Feuchteansammlung im Rohr 49
5.2.3 Versuch zur Bildung von Anlauffarben bei unterschiedlichen Feuchtekonzentrationen im Wurzelschutzgas 51
5.3 Einfluss der Prozessgaszusammensetzung für die Gasgemische Ar, Ar/He, Ar/He/H2 53
6 Auswertung der Versuchsergebnisse und Schlussfolgerungen 56
6.1 Anlauffarben auf Winterbaustellen 56
6.1.1 Einfluss der Außentemperatur auf den Schweißprozess 56
6.1.2 Einfluss von Feuchteansammlungen in Rohren 61
6.1.3 Einfluss von unterschiedlichen Feuchtekonzentrationen im Wurzelschutzgas 63
6.1.4 Schlussfolgerungen für die Anwendung in der Praxis 68
6.2 Einfluss der Prozessgaszusammensetzung beim WIG-Orbitalschweißen 74
6.2.1 Versuchsauswertung 74
6.2.2 Anwendung des Mischgases Ar/He/H2 in der Praxis 80
7 Zusammenfassung und Ausblick 81
8 Quellenverzeichnis 82
9 Verzeichnis der Abbildungen und Tabellen 87
10 Anlagenverzeichnis 92