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The Global ETD Search service is a free service for researchers
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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.
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Showing 141 to 149 of 149 (0.017 seconds)| 141 |
Contribution au diagnostic expert et à l’analyse de risques dans les ouvrages souterrains en maçonnerie par la modélisation numérique / Contribution into expert diagnosis and risk analysis in the underground masonry using numerical modelingDaca, Taous 06 December 2013 (has links)
L’état de contrainte des galeries et tunnels souterrains évolue dans le temps, tout d’abord en raison de l’avancement du front de taille lors de la construction, mais aussi en raison des changements graduels des propriétés du terrain ou des caractéristiques mécaniques des matériaux constitutifs de l’ouvrage (réduction de la cohésion, vieillissement). Ces changements sont causés par des actions combinées comme: les processus d’altération dus aux infiltrations des eaux météoriques et de réseaux concessionnaires, mais aussi par l’apparition des fissures qui induisent par ailleurs des redistributions de contraintes et de déformations, ainsi que par le fluage des matériaux. Dans cette étude, un travail préliminaire, nous permet de quantifier l’état de contrainte initial lors de la construction des ouvrages. Notre approche basée sur la modélisation éléments finis 2D permet de simuler l’état d’équilibre interne des excavations, nos résultats sont en adéquation avec ceux issus des méthodes analytiques de la littérature. Cet état initial est ensuite calibré via une modélisation 3D. Puis, une macro-modélisation à base d’éléments finis nous permet d’envisager différents scénarios de détérioration des soutènements, notamment à l’extrados des galeries de couloirs d’accès et tunnels de ligne de métro Parisien. Un des scénarios étudié prend en considération la réduction de la résistance mécanique du piédroit et de la zone interface entre le sol et la paroi, ainsi que le fluage de l’encaissant et du revêtement. En utilisant une loi qui permet de simuler la perte de cohésion, paramètre qui évolue en fonction de la déformation inélastique et en fonction du temps, le comportement mécanique des zones dégradées est ainsi reproduit par un modèle viscoplastique de type adoucissant ou à écrouissage négatif. Nous mettons bien en exergue les processus de dégradation observés sur ces galeries durant leur exploitation. Les différentes modélisations permettent de mieux évaluer l’état des différents composants de l’ouvrage selon le type de dégradation et selon le temps traduisant ainsi son vieillissement. Elles permettent également de jauger la sensibilité et la pertinence de différents paramètres. In fine, nous évaluons les pathologies de ces structures, ce qui permet de fournir des indicateurs quant à la gestion de ce patrimoine. / The stress state of underground tunnels and galleries evolves over time , firstly because of the advancement of the working face during construction , then due to gradual changes in soil properties and mechanical properties of materials component of the infrastructures (reduction of cohesion, aging). These changes are caused by combined actions such as: weathering processes due to infiltration of meteoric waters and concessionaires networks, but also by the cracks appearance that induce further redistribution of stress and strain, and the creep. A particular attention is paid to the determination of the initial state of stresses applied on the structure right after the construction. In order to approach this initial stress state which corresponds to the construction phase of underground structures, we propose a methodology based on comparing the numerical model with analytical methods taken from literature. Then we compare 2D and 3D numerical models. Thereafter, a macro- modeling based on the finite elements method allows considering different scenarios of the tunnel-linings deterioration, specifically at the extrados of the galleries and Paris metro line tunnels. One of the studied cases takes into account the mechanical strength loss of the abutment and the interface between the ground and the wall area including their creeps. Therefore, Elasto-viscoplastic with strain softening constitutive model is used in this study to reproduce the degraded zone behavior. The numerical models show that we can reproduce the underground structure behavior during degradation and assess the state of different structure components. The approach used here for the Parisian metro tunnels may be used by the other underground structures managers.
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User Attribute Inference via Mining User-Generated DataDing, Shichang 01 December 2020 (has links)
No description available.
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Fluid ExperienceJane, Sarah January 2012 (has links)
No description available.
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A Place to Be: The Relationship Between Setting and Character in Short StoriesDannemiller, Alexander S. 12 June 2013 (has links)
No description available.
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Dynamisk analys och utmattningskontroll med hjälp av fältmätningar och FEM : Fallstudie över SL:s Bro norr om Söderströmsbron / Dynamic analysis and fatigue assessment using field measurements and FEM : A case study of the SL bridge north of the Söderström bridgeJanhunen, Tony, Mikus, Martin January 2010 (has links)
Följande examensarbete omfattar en fallstudie av Bro norr om Söderströmsbron, en tunnelbanebro i stål med fyra spår. Den byggdes 1956 som en del av förbindelsen mellan station Gamla stan och station Slussen i Stockholm. I fallstudien, som är ett samarbete mellan KTH och SL, ingår att bedöma brons dynamiska egenskaper, tillstånd avseende utmattning samt att skapa en finita elementmodell av bron. Vidare begränsas fallstudien till brokonstruktionen för det spår som går närmast slussen mellan Mälaren och Saltsjön, och som i dagsläget utgör gröna tunnelbanelinjen mot Farsta strand, Hagsätra och Skarpnäck. Under 2005 trafikerades det aktuella spåret under högtrafik av 30 tåg i timmen och under lågtrafik av 15 tåg i timmen. När tåg passerar visar bron stora förskjutningar och glapp mellan sliprar och underliggande stålkonstruktion. Dessa förskjutningar skapar spänningar i stålet och avgörande för brons tillstånd avseende utmattning är antalet skadliga spänningsvidder vid kritiska snitt som inträffat sedan brons färdigställande. Dagens spänningsvidder mäts med hjälp av töjningsgivare placerade i fältmitt. Mätningen har utförts av KTH, avdelningen för Brobyggnad i samband med examensarbetet. Av intresse är utmattningsrisk för svetsad anslutning mellan lång- och tvärbalkar. Utmattningsrisken beräknas dels med typiserade spänningskollektiv enligt BSK 07, dels med verkliga spänningskollektiv enligt Palmgren-Miners delskadehypotes. Enligt båda metoderna konstateras utmattningshållfastheten vara uttömd, med reservation för förbandsklasser och partialkoefficienter. Kollektivparametern κ enligt BSK 07, vilken vid dimensionering beaktar spänningskollektivets form, uppskattas vara närmare 2/3 än SL:s nuvarande värde 5/6. Ur responsen från givarna konstateras att den dynamiska förstoringsfaktorn vid 60 km/h varierar mellan 0.63 och 1.43, vilket visar att brons respons har ett stort dynamiskt innehåll. En finita elementmodell skapas i Abaqus med hjälp av Matlab, med syftet att komplettera resultat från mätningar. I modellen studeras töjning, vertikal förskjutning och acceleration, dynamisk förstoringsfaktor och egenmoder. Den statiska responsen för modell och bro konstateras vara snarlik. / This thesis includes a case study of the Bro norr om Söderströmsbron, a steel subway bridge with four rail tracks. The bridge was built in 1956 as a part of the connection between the two subway stations Gamla stan and Slussen in Stockholm. The case study, which is a collaboration between KTH and SL, includes an evaluation of the dynamic properties of the bridge, in which condition it is regarding fatigue and the creation of a finite element model of the bridge. The case study is limited to the construction carrying the rail track closest to the lock between Mälaren and Saltsjön, and now represents the green subway line towards Farsta strand, Hagsätra and Skarpnäck. In 2005, the train frequency during rush hour was 30 trains per hour and during low traffic 15 trains per hour. When a train crosses, the bridge shows large displacements and gaps between the sleepers and the underlying steel structure. The displacements cause stresses in the steel and crucial to the bridge fatigue state is the number of damaging stress ranges that have occurred since the opening of the bridge. The current stress variations are measured using strain gauges positioned in the mid-span. Measurements were carried out by KTH, division of Structural Design & Bridges, during this thesis. Of key interest is a welded edge between the main- and crossbeams. The risk of fatigue is calculated using standardised stress ranges according to BSK 07 and Palmgren-Miners cumulative damage theory. According to both methods, the fatigue life of the bridge is exceeded, with reservations to the detail category and partial coefficients. The stress collective parameter κ according to BSK 07, which in design accounts for the distribution of the stress collective, is estimated closer to 2/3 than SL’s present value of 5/6. According to the strain gauges, the dynamic amplification factor at 60 km/h varies between 0.63 and 1.43, indicating that the bridge’s response has a large dynamic content. A finite element model is created in Abaqus using Matlab, with the purpose of complementing results from the measurements. In the model, the strain, vertical displacements and acceleration, dynamic amplification and natural modes are studied. The static response of the model and bridge were found to be similar. / QC 20100707
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Att dela ett bostadshus eller kommunikationen till staden / To share a residential building or the communication to the cityWallerius, Gustav January 2013 (has links)
Detta projekt handlar om hur vi kan bo nära varandra i en stad och samtidigt ha tydliga gränser kring de ytor vi delar. Var möts vi i staden? Var är vi tillsammans i bostaden? När övergår den privata sfären till gemensam? Kommunikationen i dagens bostadshus har reducerats till minsta möjliga vilket helt tar över dess utformning. Att istället se denna som en social yta har potential att skapa ett levande atmosfär där mer privata funktioner delas med kommunikationen. Delandet handlar också om de saker vi har i hemmet, är delning av kökmaskiner och städredskap ett möjligt sätt att spara energi? Hur kan vi bygga för att främja detta? I processen har jag försökt definiera vad som skapar ett attraktivt boende i stadskontext och se hur detta går att applicera i morgondagens Stockholm. Jag har gjort detta genom att skissa i modell och analysera dessa i jämförelse med exempel på lyckade bostadshus. Utformning av kommunikation och vad vi kan dela i ett bostadshus är de två frågor jag har fokuserat på i detta projekt. Hur kan bostadshuset vara en förlängning av staden och samtidigt signalera en privathet? / This project is about how we can live near each other in the city, while having clear boundaries around the areas we share. Where do we meet in the city? Where does the private sphere become commune? Communication, such as stairs and corridors, in residential houses has been reduced to a minimum. The result of this is that the balance between architecture and function is very unstable. To instead see this as a social area has the potential to create a vibrant atmosphere where more private functions are shared with the communication. How can we share space? What can the house share with the city? What can the user share with each other? Sharing is a potential way to save energy. How can we build to promote this? In the process, I have tried to define what creates an attractive residential building in a city context. I have done this by model sketching and analyze these in relation to examples of successful residential buildings. The formation of the communication and what we can share in a residential building are the two main questions in this project. How can the dwelling house be an extension to the city while signal a private sphere?
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Automated Performance Test Generation and Comparison for Complex Data Structures - Exemplified on High-Dimensional Spatio-Temporal IndicesMenninghaus, Mathias 23 August 2018 (has links)
There exist numerous approaches to index either spatio-temporal or high-dimensional data. None of them is able to efficiently index hybrid data types, thus spatio-temporal and high-dimensional data. As the best high-dimensional indexing techniques are only able to index point-data and not now-relative data and the best spatio-temporal indexing techniques suffer from the curse of dimensionality, this thesis introduces the Spatio-Temporal Pyramid Adapter (STPA). The STPA maps spatio-temporal data on points, now-values on the median of the data set and indexes them with the pyramid technique. For high-dimensional and spatio-temporal index structures no generally accepted benchmark exists. Most index structures are only evaluated by custom benchmarks and compared to a tiny set of competitors. Benchmarks may be biased as a structure may be created to perform well in a certain benchmark or a benchmark does not cover a certain speciality of the investigated structures. In this thesis, the Interface Based Performance Comparison (IBPC) technique is introduced. It automatically generates test sets with a high code coverage on the system under test (SUT) on the basis of all functions defined by a certain interface which all competitors support. Every test set is performed on every SUT and the performance results are weighted by the achieved coverage and summed up. These weighted performance results are then used to compare the structures. An implementation of the IBPC, the Performance Test Automation Framework (PTAF) is compared to a classic custom benchmark, a workload generator whose parameters are optimized by a genetic algorithm and a specific PTAF alternative which incorporates the specific behavior of the systems under test. This is done for a set of two high-dimensional spatio-temporal indices and twelve variants of the R-tree. The evaluation indicates that PTAF performs at least as good as the other approaches in terms of minimal test cases with a maximized coverage. Several case studies on PTAF demonstrate its widespread abilities.
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A Pedagogy of Holistic Media Literacy: Reflections on Culture Jamming as Transformative Learning and HealingStasko, Carly 14 December 2009 (has links)
This qualitative study uses narrative inquiry (Connelly & Clandinin, 1988, 1990, 2001) and self-study to investigate ways to further understand and facilitate the integration of holistic philosophies of education with media literacy pedagogies. As founder and director of the Youth Media Literacy Project and a self-titled Imagitator (one who agitates imagination), I have spent over 10 years teaching media literacy in various high schools, universities, and community centres across North America. This study will focus on my own personal practical knowledge (Connelly & Clandinin, 1982) as a culture jammer, educator and cancer survivor to illustrate my original vision of a ‘holistic media literacy pedagogy’. This research reflects on the emergence and impact of holistic media literacy in my personal and professional life and also draws from relevant interdisciplinary literature to challenge and synthesize current insights and theories of media literacy, holistic education and culture jamming.
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A Pedagogy of Holistic Media Literacy: Reflections on Culture Jamming as Transformative Learning and HealingStasko, Carly 14 December 2009 (has links)
This qualitative study uses narrative inquiry (Connelly & Clandinin, 1988, 1990, 2001) and self-study to investigate ways to further understand and facilitate the integration of holistic philosophies of education with media literacy pedagogies. As founder and director of the Youth Media Literacy Project and a self-titled Imagitator (one who agitates imagination), I have spent over 10 years teaching media literacy in various high schools, universities, and community centres across North America. This study will focus on my own personal practical knowledge (Connelly & Clandinin, 1982) as a culture jammer, educator and cancer survivor to illustrate my original vision of a ‘holistic media literacy pedagogy’. This research reflects on the emergence and impact of holistic media literacy in my personal and professional life and also draws from relevant interdisciplinary literature to challenge and synthesize current insights and theories of media literacy, holistic education and culture jamming.
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