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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Bringing methodological light to ecological processes : are ecological scales and constrained null models relevant solutions? / Apporter une lumière méthodologique aux processus écologiques : les échelles écologiques et les modèles nuls contraints sont-ils des solutions pertinentes?

Clappe, Sylvie 14 December 2018 (has links)
Les distributions d'espèces observées dans un environnement hétérogène résultent de plusieurs processus déterministes et stochastiques agissant comme des filtres pour contraindre la coexistence des espèces. L’action successive de ces processus a pour conséquence directe de structurer spatialement la composition des communautés et la variation de ces compositions (i.e., diversité bêta). Un des objectifs majeurs de l'écologie des communautés et métacommunautés consiste à identifier et quantifier les effets respectifs de ces différents processus sur la diversité bêta des communautés afin de mieux comprendre et prédire la distribution de la biodiversité. L'expérimentation étant difficilement possible, les processus responsables de la variation spatiale de la composition des communautés sont généralement inférés à partir des structures spatiales des distributions d’espèces observées dans la nature. La thèse s’inscrit dans ce contexte et vise à améliorer les outils de statistique multivariée permettant d’identifier et quantifier l'effet des processus écologiques structurant les communautés et métacommunautés. En particulier, il est proposé d’intégrer les échelles écologiques et les modèles nuls contraints pour étudier l’effet de l’environnement. La décomposition des relations trait-environnement dans les échelles spatiales et phylogénétiques permet une étude plus approfondie du filtrage environnemental en associant son échelle spatiale d’action au signal phylogénétique des traits sélectionnés pour capturer l’histoire évolutive associée au filtrage environnemental. L’interprétation en terme de processus évolutifs est néanmoins limitée et mériterait l’intégration de modèles nuls phylogénétiquement contraints pour une analyse plus fine. Dans la continuité, des modèles nuls spatialement contrains ont été développés et intégrés à deux analyses multivariées très largement utilisées en écologie des communautés (i.e., partitionnement de variation et test de Mantel) pour estimer et tester l’effet de l’environnement sur les assemblages d’espèces. Ces deux analyses présentaient une surestimation de leur statistique mesurée ainsi qu’un taux anormal de faux positifs lorsque les distributions d’espèces (via processus de dispersion limitée) et l’environnement étaient indépendamment spatialement structurés. L’intégration de modèles nuls spatialement contraints a permis d’ajuster à la fois les estimations et les tests de ces deux analyses illustrant ainsi le besoin d’utiliser des modèles nuls écologiquement contraints pour une identification et quantification correctes des processus écologiques / Species distributions observed in an heterogeneous environment result from multiple deterministic and stochastic processes acting as filters to constrain species co-existence. As a direct consequence, the successive actions of these processes spatially structure communities composition and the variation of these compositions (i.e., beta-diversity). One of the major objective in community and metacommunity ecology is to identify and quantify the respective effects of these different processes on communities beta-diversity to better understand and predict the distribution of biodiversity. Experiments being hardly possible, processes responsible for the spatial variation of communities composition are generally inferred from spatial patterns of species distributions observed in nature. In this context, the thesis aims at improving multivariate statistical tools conducted to identify and quantify the effects of ecological processes shaping communities and metacommunities. In particular, this thesis proposes to integrate ecological scales and constrained null models to study the effect of environment.Decomposing trait-environment relationships through spatial and phylogenetic scales allows to further study environmental filtering. The association of spatial scales involved in environmental filtering with the phylogenetic signals of traits allowed to capture the evolutive history related to environmental filtering. The interpretation in terms of evolutive processes is however limited and phylogenetically-constrained null models should be considered to improve the analysis. Following on from this work, spatially-constrained null models were developed and integrated into two multivariate analyses widely used in community ecology (i.e., variation partitioning and Mantel tests) to estimate and test the effect of environmental filtering on species assemblages. Both approaches presented overestimation of their computed statistic as well as high rates of false positive when species distributions (via limited dispersal) and environmental conditions were independently spatially structured. Integrating spatially-constrained null models allowed to adjust both their tests and the values of their statistic, as such demonstrating the need of using ecologically-constrained null models to correctly identify and quantify ecological processes.For future works, the thesis suggests that adopting a scaling approach to study ecological processes in addition to mechanistic null models could offer the possibility to distinguish processes from one another
182

Realization and comparison of various mesh refinement strategies near edges

Apel, T., Milde, F. 30 October 1998 (has links)
This paper is concerned with mesh refinement techniques for treating elliptic boundary value problems in domains with re- entrant edges and corners, and focuses on numerical experiments. After a section about the model problem and discretization strategies, their realization in the experimental code FEMPS3D is described. For two representative examples the numerically determined error norms are recorded, and various mesh refinement strategies are compared.
183

A posteriori error estimation for non-linear eigenvalue problems for differential operators of second order with focus on 3D vertex singularities

Pester, Cornelia 21 April 2006 (has links)
This thesis is concerned with the finite element analysis and the a posteriori error estimation for eigenvalue problems for general operator pencils on two-dimensional manifolds. A specific application of the presented theory is the computation of corner singularities. Engineers use the knowledge of the so-called singularity exponents to predict the onset and the propagation of cracks. All results of this thesis are explained for two model problems, the Laplace and the linear elasticity problem, and verified by numerous numerical results.
184

Entwicklung transparent geklebter Glas-Rahmenecken und Untersuchung des Tragverhaltens

Prautzsch, Volker 15 September 2015 (has links)
Im Konstruktiven Glasbau ist es keine Besonderheit mehr, Glasträger für Dachkonstruktionen und Glasschwerter in Fassaden einzusetzen, um leichte, transparente und in den Hintergrund tretende Tragkonstruktionen umzusetzen. Für die Fügung dieser tragenden Bauteile werden bisher Verbindungsmittel aus Edelstahl eingesetzt, die optisch beeinträchtigen, Bohrungen im Glas erfordern und ungünstige Spannungsspitzen im Glas hervorrufen. Demgegenüber ist das Kleben für den spröden Werkstoff Glas ein materialgerechteres Fügeverfahren. Die Untersuchung einer flächigen Klebverbindung zum Lastabtrag zwischen tragenden Glas-Bauteilen im Primärtragwerk ist Gegenstand der vorliegenden Arbeit. Bei einer relativ großen Schichtdicke bildet die transparente Ausführung eine ganz wesentliche Prämisse. Ein weiterer Anspruch liegt in der Alterungsbeständigkeit und der Tragfähigkeit. An einer Auswahl von 14 potentiell geeigneten, transparenten Acrylat-, Epoxidharz- und Polyurethanklebstoffen werden mit Hilfe thermomechanischer und mechanischer Prüfverfahren temperaturabhängige Materialeigenschaften ermittelt. Ergänzend wird die Langzeitbeständigkeit der Klebstoffe durch eine künstliche Alterung im Verbund überprüft. Im Anschluss erfolgt die Ermittlung der lichttechnischen Eigenschaften sowie die visuelle Beurteilung der Sichtproben. Im Resultat wird ein UV- und lichthärtender Acrylatklebstoff als besonders geeignet identifiziert. Für diesen Klebstoff werden Haftfestigkeitsuntersuchungen im Druckscherversuch unter Temperatur- und Alterungseinflüssen sowie Zeitstandversuche an Substanzproben und kleinen Prüfkörpern durchgeführt. Für den Einsatz in einer flächigen Klebung wird ein geeignetes Dosier- und Aushärteverfahren entwickelt. Der Tragfähigkeitsnachweis der geklebten Verbindung erfolgt an großformatigen Bauteilmustern. Bei diesen Versuchen wird jeweils die Belastbarkeitsgrenze des Glases erreicht, während die Klebung intakt bleibt. Ein Zeitstandversuch dient zur Aufzeichnung des Kriechverhaltens an Bauteilmustern bei erhöhter Temperatur. Begleitend zum Entstehen der vorliegenden Arbeit werden mehrere Bauvorhaben mit Ganzglaskonstruktionen umgesetzt. Der Verzicht auf jegliche metallische Verbindungsmittel stellt bei diesen Objekten in Deutschland ein bauaufsichtliches und bautechnisches Novum dar. Die Fügung von Glasstütze und Glasträger innerhalb des gläsernen Primärtragwerks erfolgt ausschließlich und erstmals über eine transparente Acrylatklebung, deren Ausführung auf Erkenntnissen der vorliegenden Arbeit basiert. Die umschließende Verglasung wird mit einem zugelassenen Silikonklebstoff an der Tragkonstruktion befestigt. Zwei der beschriebenen Bauvorhaben werden seit der Erstellung in einem umfangreichen Monitoring beobachtet, um weitergehende Aussagen zum Langzeitverhalten der Klebungen zu erhalten. Die weitgehenden Untersuchungen der vorliegenden Arbeit wie auch des laufenden Monitorings sollen Bedeutung und Zuverlässigkeit der transparenten, lastabtragenden Klebungen im Konstruktiven Glasbau belegen helfen. / The use of glass beams in transparent roofs and glass fins as part of the facade is already state-of-the-art construction to achieve a transparent and lightweight appearance. Until now, mechanical fasteners made from stainless steel are used to join these structural components. Those fasteners visually interfere, require holes in the glass and cause unfavorable stress peaks in the glass. In contrast, adhesive bonding is much more appropriate to join the brittle material glass. The subject of this dissertation is the study of a planar adhesive joint which transfers the load between the load-bearing glass components into the primary structure. With a relatively large layer thickness, the manufacturing of the transparent joint represents a major challenge. Furthermore, the aging resistance and the load-bearing capacity must be proven. A selection of 14 potentially suitable, transparent adhesives of acrylate, epoxy resin and polyurethane are tested for temperature-depending material properties. These tests are based on thermo-mechanical and mechanical test methods. In addition, the long-term durability of the adhesives is verified by artificial aging test on bonded specimens. Subsequently, the photometric characteristics and the visual quality of the samples are assessed. As the result an UV- and light-curing acrylate adhesive is identified as particularly suitable. Compression shear tests under temperature and aging influences as well as creep tests are performed on substance samples and small-scale specimens to determine the adhesive strength of this adhesive. A suitable application and curing process is developed for use in planar bonded joints. Tests on specimen components were carried out to determine the load-bearing capacity of the bonded glass frame corners. In these experiments, the glass fails while the adhesive joint remains intact. Creep test are used to record the creep deformation of component specimen at increased temperature. Accompanying the study, several building projects are realized to use adhesive bonding technology in all-glass constructions. Without any visible forms of connection, the glass construction represents a significant innovation in Germany in terms of both building legislation and building technology. It´s the first time, glass fins and glass beams are joint to a glass primary structural system via transparent acrylate adhesive. The connection method is based on the findings of the present study. The glass panels of the envelope are joined to the primary glass structure with an approved silicone adhesive. Two of the described construction projects are monitored to obtain further knowledge about the long-term behaviour of the bonded joints. The comprehensive studies of this thesis as well as the ongoing monitoring have proven the significance and the reliability of transparent, load-bearing bonded joints in the field of glass construction.
185

Sälgen 4 : Adaptable housing in Stockholm / Sälgen 4 : Flexibla bostäder i Stockholm

Berg, Martin January 2014 (has links)
I have designed a housing project that is an infill to an existing housing block in the city center of Stockholm. When I started this project the themes everydayness and building typology was central for me. That is why I also chose to work with the site Sälgen 4; a corner site and one of few remaining gaps in the block structure of the city center. Today there is a gas station on the site, which I for this project presume could be removed. When working with this project I found interest in what simplified could be called soft flexibility, where measurement, shape and connection to other spaces are dealt with in order to enable for different kinds of usage. This type of flexibility I encountered when studying late 19th century dwellings in Stockholm city center. I have developed similar apartments, often with a size of about 140 m2 with 4,5 rooms and an additional kitchen. Even all the room units are similar with over 4 m width and close to square shapes. This enabled the creation of very generic spaces but also introduced me to an interesting paradox; the on the architectural drawing less dynamic floor plan create on the other hand the most dynamic ways to inhabit the spaces. Also the loggia has been an important feature in my design. / Jag har ritat ett bostadshus som är ett infill till ett befintligt kvarter i Stockholms innerstad. När jag började projektet så var temana vardaglighet och byggnadstypologi viktiga för mig. Därför valde jag att arbeta med tomten Sälgen 4; en hörntomt och en av få luckor i kvartersstaden. Idag finns där en bensinmack men jag har sett det som en förutsättning för projektet att den kan tas bort.   Under projektets gång har jag intresserat mig för vad som förenklat kan kallas för mjuk flexibilitet, där rummens mått, form och angöring möjliggör för många olika typer av användning. Den typen av flexibilitet upptäckte jag då jag studerade gamla sekelskifteshus i Stockholm   Jag har arbetat fram likartade lägenheter på oftast runt 140 m2 med 4,5 rum och kök. Även rumsenheterna är nästan identiska med drygt 4 m i bredd och nära kvadratisk form. På så vis har jag skapat en hög grad av generallitet men också konfronterats med en spännande paradox; de å ena sidan som ritning minst dynamiska planerna, kommer å andra sidan att generera den mest dynamiska och tillåtande användningen av dem. Även loggian har varit ett viktigt inslag i min design.
186

Correlation of Watershed NDVI Values to Benthic Macroinvertebrate Biodiversity in Eight North American Wadeable Streams

Gallagher, Denice Lynne 05 1900 (has links)
Water quality of a stream or river is influenced by the surrounding landscape and vegetation. The Normalized Difference Vegetation Index (NDVI) is commonly used to characterize landcover and vegetation density. Benthic macroinvertebrates are ubiquitous in freshwater streams and are excellent indicators of the quality of freshwater habitats. Data from one NDVI remote sensing flight and one macroinvertebrate sampling event for eight wadeable stream study sites in the National Ecological Observatory Network (NEON) were acquired. Proportions of high, moderate, and sparse vegetation were calculated for each stream watershed using ArcGIS. Functional feeding groups and tolerance values were assigned to macroinvertebrate taxa. The Fourth-corner and RLQ methods of analysis, available in the ade4 package for R software, were used to evaluate the relationships of macroinvertebrate traits with environmental variables. Hypothesis testing using Model 6 in the ade4 package resulted in p-values of 0.066 and 0.057 for global (overall) significance. Mean NDVI values of moderately vegetated areas and proportion of sparse vegetation were found to be significant to percent shredders at alpha ≤ 0.05. Results of these methods of analysis, when combined with traditional macroinvertebrate sampling metrics, show that NDVI can be a useful, additional tool to characterize a watershed and its effects on macroinvertebrate community composition and structure.
187

Analys av hörnsekvenser i svensk elitfotboll : Gruppering av hörnsekvenser och utvärdering av sannolikhet för skott med logistisk hierarkisk modellstruktur / Analysis of corner sequences in the top Swedish football leagues : Clustering of corner sequences and evaluation of the probability of shot with logistical hierarchical model structure

Rydström, Sidney, Lindén, Jakob January 2020 (has links)
Sportanalys definieras av Alamar (2013) som användning av historisk data för att applicera modeller som kan ge information till beslutstagare inom en viss organisation. Det ger dem möjlighet att assistera sin organisation för att få en sportslig fördel. I den här studien utförs sportanalys, mer specifikt analyseras hörnsekvenser inom svensk elitfotboll. En hörnsekvens är den sekvens av händelser som sker från att bollen sätts i spel från hörnans startposition tills det att något av följande villkor uppfylls: 8 händelser sker givet att hörnan slås kort 6 händelser sker givet att hörnan slås långt 15 sekunder passerar Försvarande lag tar över bollen Något lag utför ett regelbrott Skott utförs av attackerande lag Datamaterialet som används är framtaget av företaget Wyscout och tillhandahållet av Football Analytics Sweden AB. De ligor och säsonger som betraktas är de svenska herrligorna Allsvenskan och Superettan för säsongerna 2017, 2018 och 2019. I datamaterialet erhålls information om varje händelse som sker under matchen. Utifrån information om händelsen samt koordinater om var händelsen sker framställs variabler som ska kunna beskriva vad som sker inom en hörnsekvens. Syftet med studien är att först identifiera hörnsekvenser med liknande egenskaper och gruppera dem. Utifrån gruppindelningen undersöks sedan sannolikheten för att en hörnsekvens leder till skott samt vad som påverkar sannolikheten. Algoritmen Partitioning Around Medoids (PAM) används med avståndsmåttet Gower och utvärderingsmåttet silhouette för att identifiera följande fem hörnsekvenstyper: Utåtskruvade hörnor från vänsterhörn med tendens mot främre stolpen och relativt nära mållinjen. Inåtskruvade hörnor från vänsterhörn med tendens mot främre stolpen och längre förflyttning ut från mållinjen. Utåtskruvade hörnor från högerhörn med tendens mot främre stolpen och relativt nära mållinjen. Korta varianter som har längre varaktighet, innefattar fler händelser och involverar fler spelare. Inåtskruvade hörnor från högerhörn med tendens mot främre stolpen och längre förflyttning ut från mållinjen. Betraktas förekomsten av skott i datamaterialet givet klusterstrukturen konstateras att hörnsekvenstyp 4 i störst utsträckning lett till skott med förekomsten 19 procent inom klustret. Hörnsekvenstyperna 2 och 5 är något sämre med respektive 18 procent av hörnsekvenserna som lett till skott. Med dessa hörnsekvenstyper i fokus anpassas flera Bayesianska hierarkiska logitmodeller för att undersöka sannolikheten för att en hörnsekvens leder till skott givet de framtagna variablerna. Vid skapandet av modellerna undersöktes om en hierarkisk modellstruktur var behövlig för att undersöka sannolikheten för skott. Slutsatsen blev att det är väsentligt att tillämpa en hierarkisk modellstruktur. Av vald modell så dras slutsatsen att det som påverkar sannolikheten att komma till skott allra mest, med avseende de variabler som undersökts, är antalet händelser som sker i hörnsekvensen. Den hörnsekvenstyp som påverkas mest av antalet händelser är den korta varianten. Det diskuteras om hur det kan vara problematiskt att undersöka den linjära påverkan på log-oddset. Detta eftersom påverkan på sannolikheten för skott inte är densamma för en ökning mellan en och två händelser som mellan tre och fyra händelser. Det är även näst intill omöjligt att komma till skott på första händelsen i hörnsekvensen då händelsen utgörs av att hörnan slås. / Sports analysis is defined by Alamar (2013) as the management of structured historical data, the application of analytical models that utilize that data, and the use of information systems to inform decision makers and enable them to help their organization in gaining a competitive advantage on the field of play. This study focuses on sports analysis, more specifically corner sequences in Swedish elite football. A corner sequence is defined as the sequence of events that occur after the ball have been put into play from the corners start position up until that one of the following conditions are met: 8 events occur given a short corner is played 6 events occur given a long corner is played 15 seconds passes The defending team overtake the ball Some team performs a foul The attacking team performs a shot The data set used comes from Wyscout and is provided by Football Analytics Sweden AB. The data consist of games from the top Swedish football leagues for men: Allsvenskan and Superettan, and consists of games played in the seasons 2017, 2018 and 2019. In the data, information about every event that occur during the game is provided, where all events are classified to provide information about what happens at the specific event. The information about each event and its coordinates is then used produce variables to describe what occurs during a corner sequence. The purpose is to identify corner sequences with similar characteristics and group them together. Then use these groups to examine the probability that a corner sequence leads to a shot, and what influences this probability. The clustering algorithm Partitioning Around Medoids (PAM) is used with Gower as the dissimilarity measure and silhouette to evaluate the clusters, then the five following clusters are identified: Corners curled away from goal from the left corner with a tendency towards the front post and relatively close to the goal line. Corners curled towards goal from the left corner with a tendency towards the front post further away from the goal line. Corner curled away from goal from the right corner with a tendency towards the goal line. Short corner variant with longer duration, more events occurring and more players involved. Corners curled towards goal from the right corner with a tendency towards the front post and further away from the goal line. Given the clustering structure it is noted that the corner sequence of type 4 has led to the greatest extent of shots with the proportion of 19 percent within the cluster. The corner sequences of type 2 and 5 have a slightly lower shot occurrence with 18 percent per corner seqence type. With these corner sequence types in focus, several Hierarchical Bayesian Logistic Regression models are fitted to analyze the probability that a corner sequence leads to a shot given the produced explanatory variables. When fitting the models it is examined if it is necessary to apply a hierarchichal strutcture to the model. The conclusion is drawn that the hierarchical model structure is crucial to the model's performance. The conclusion is drawn from the final model that the explanatory variable which explains the probability to shoot best is the number of events that occur during the corner sequence. The corner sequence type that is most influenced by the number of events that occur during the corner sequence is the short corner variant. In the study it is discussed if there is an issue to suppose that this variable has a linear effect on the log-odds, since the impact on the probability to shoot is not the same for an increase between one and two as three and four events. Furthermore it is near impossible to shoot in the first event that occurs in the corner sequence.
188

Detekce výrobků na pásovém dopravníku / Detection of Objects on Belt Conveyer

Láník, Aleš January 2008 (has links)
In this master thesis, object's detection in image and tracking these objects in temporal area will be presented. First, theoretical background of the image's preprocessing, image filtration, the foreground extraction, and many others various image's features will be described. Next, design and implementation of detector will be processed. This part of my master thesis containes mainly information about detection of objects on belt conveyer Finally,results, conclusion and many supplementary data such as a photography camera's location will be shown.
189

Three-dimensional Effects on Unsteady Dynamics and Turbulent Transport Mechanisms of an Impinging Shock Wave/Boundary-layer Interaction

Vyas, Manan A. January 2021 (has links)
No description available.
190

Intrication dans les systèmes de Hall quantiques : négativité logarithmique et autres mesures

Geoffrion, Juliette 08 1900 (has links)
Nous explorons l’intrication d’états mixtes, particulièrement d’états de Hall quantiques, par le biais de l’information mutuelle (MI) et de la négativité logarithmique (LN) fermionique. Cette dernière est une bonne mesure d’intrication pour des états mixtes quantiques car elle ne capture pas de corrélations classiques comme la MI. Nous étudions des géométries tripartites qui contiennent des coins où, en plus de la loi du périmètre standard, l’intrication reçoit une contribution angulaire : le terme de coin. Avec l’entropie d’intrication, ce terme a été étudié pour divers états purs, y compris les états de Hall quantiques entier (IQH), et il a été constaté que la fonction angulaire est presque universelle ; elle ne dépend pas des détails microscopiques de l’état en considération. Nous faisons des prédictions sur la forme du terme de coin de la LN et de la MI en utilisant des propriétés générales. Nous testons numériquement nos prédictions sur des états IQH à différents remplissages et sur différentes géométries en utilisant deux méthodes, une dans l’espace des impulsions et une dans l’espace réel. Dans les états fondamentaux, nous trouvons que les termes de coin de la MI et de la LN suivent également le comportement quasi-universel. À température finie et des coins d’angle π/2, le coefficient de la loi du périmètre et les termes de coin atteignent d’abord un plateau puis décroissent rapidement avec la température. Les effets de température finie sont étudiés davantage en travaillant dans les limites de faibles et fortes températures. / We explore the entanglement of quantum mixed states, with an emphasis on quantum Hall states, via the mutual information (MI) and the fermionic logarithmic negativity (LN). The latter is a good measure of entanglement for quantum mixed states as it does not capture classical correlations, unlike the MI. We study tripartite geometries with corners where in addition to the standard boundary law, the entanglement receives an angle-dependent contribution : the corner term. Using the entanglement entropy, this corner term has been studied for various pure states, including integer quantum Hall (IQH) states, and it was found that the angle-dependent function is almost super-universal; it does not depend on the microscopic details of the state under consideration. First, we make predictions on the form of the corner term for the LN and MI using general properties. Then, we test our predictions numerically on IQH states at different fillings and on different geometries, using two approaches, one in momentum space and one in real space. In groundstates, we find that the corner terms of the MI and LN also follow the quasi-universal behaviour. At finite temperatures and angle π/2, we find that the boundary law coefficient and corner terms first plateau then decay rapidly with temperature. The finite-temperature effects are studied in more details by working in low and high temperature limits.

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