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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.
21

Science of synthetic turf surfaces : player-surface interactions

Severn, Kathryn A. January 2010 (has links)
This research project has investigated the mechanical properties and behaviour of third generation synthetic turf surfaces used for football and rugby, with a focus on the traction behaviour produced at the shoe-surface interface. The physical characteristics and mechanical properties of the component materials used in the construction of third generation surfaces were examined. The bulk density of the rubber infill material was found to be a key variable. This was shown to be influenced by compaction and the resulting compression of the rubber infill material under an applied load. Increasing the compactive effort and/or compression under loading increased the bulk density. Shear strength of the rubber infill material was shown to be influenced by bulk density, increasing with a higher bulk density. The composite surface system behaviour of third generation synthetic turf surfaces was investigated. Several surface variables were measured including; shockpad thickness, synthetic turf carpet construction, infill thickness, infill bulk density and infill material type. Shockpad thickness, rubber infill thickness and bulk density were found to influence the impact behaviour, with a thicker rubber layer (shockpad and/or rubber infill layer) reducing the hardness of a surface system. Increasing the bulk density of the rubber infill with compactive effort increased the surface system hardness. Traction behaviour of composite surface systems was explored using three traction test methods to measure both rotational and translational traction. Rubber infill bulk density was shown to be a primary influencing variable from the playing surface variables investigated. Several further traction variables were explored to provide a fuller understanding of the mechanisms involved in the production of traction at the shoe-surface interface including; vertical stress, stud configuration, stud dimension, stud penetration, water and temperature. Vertical stress and stud configuration were found to be primary variables influencing traction development. A traction framework has been developed identifying the factors affecting the production of traction at the shoe-surface interface. It is intended that the traction framework can be used by the sports surface industry, sports governing bodies and academia to aid in the decisions and judgements made during the design, construction and maintenance of these surfaces to obtain desired characteristics and optimise performance and safety.
22

The turn to a 'neo-revivalist' religious identity as a form of 'self-othering'

Naqvi-Sherazee, Aaliyeh January 2008 (has links)
This thesis investigates the turn to a neo-revivalist Muslim identity in the West as a form of self-othering. The binary dichotomy of self and other is used as a framework for the apparent divide between Muslims and the West. Second and third-generation disapora neo-revivalists personalise religion and through their hermeneutics seek an expression of religion that transcends cultural practice. They self-other in a way reactionary to society, and also react to the religion of their parents’ generation, which for them is not spiritual enough and instead is too steeped in cultural practices. Secularism and the post-secular turn is considered in Western society to provide context to the West that these neo-revivalists are located within. The diversity of Muslims is investigated to contextualise the neo-revivalist shift, which rather than being tolerant of diversity amongst Muslims seeks a separation of culture from religion. As second- and third-generation diaspora Muslims are the children of Muslim migrants to the West, the inter-generational divide is investigated. First-generation migrants have a continuity to their religious expression based on their experiences within the country of origin, whereas second- and third-generation migrants engage in a re-negotiation process to enable their religiosity to be relevant to Western societies. Qualitative case studies relating to the performance of religious identity, that is necessarily public, are utilised from Britain and the United States to further contextualise neo-revivalism. Literary mediation and mediatisation are examined in the context and globalisation. Contemporary literature is utilised to consider the self-critique of issues relating to integration and assimilation of Muslims in Western society by Muslims in Western societies. These cosmopolitan voices provide an internal understanding of the issues involved. Media-technologies have enabled a wide range of discourses to circulate about the current geopolitic following ‘9/11’ and Muslims themselves have utilised these mediated-technologies, and as such, neo-revivalism is necessarily a product of time, place and circumstance. Finally, a conclusion is reached and in seeking to understand the neo-revivalist turn and the place of Muslims in the West, a cosmopolitan ethic of integration is proposed that seeks to turn away from essentialisations and binary oppositions, but instead, through an engagement in respectful and reflexive critical dialogue, it is hoped that our shared universal humanity may be realised.
23

Towards silicon quantum dot solar cells : comparing morphological properties and conduction phenomena in Si quantum dot single layers and multilayers / Towards Silicon Quantum Dot Solar Cells : comparing Morphological Properties and Conduction Phenomena in Si Quantum Dot Single Layers and Multilayers

Surana, Kavita 21 September 2011 (has links)
Le confinement quantique dans le silicium, sous forme de boîtes quantiques de silicium de diamètre 5 nm, permet de contrôler le bandgap et donc l'émission de lumière. Cette ingénierie du bandgap des nanocristaux de silicium est utile pour les applications photovoltaïques avancées et présente l'avantage de conserver la compatibilité avec les technologies silicium existantes. Ces boîtes quantiques peuvent aider à réduire les pertes par thermalisation dans une cellule solaire homo-jonction. Ce travail se concentre sur la fabrication à grande échelle des nanocristaux de silicium dans SiO2 en utilisant le Dépôt Chimique en Phase Vapeur assisté par Plasma (PECVD), suivi d'un recuit à haute température. Des monocouches sont comparées avec des multicouches pour les propriétés morphologiques, électriques et optiques et des dispositifs avec ces différents couches sont comparés. Dans le cas d'une structure monocouche, l'épaisseur de la couche contrôle l'organisation des nanocristaux et permet de mettre en évidence l'amélioration de la conductivité électrique, avec cependant une réponse optique faible. Les multicouches montrent un bandgap du Si augmentée et controlee, avec une meilleure absorption dans la gamme bleu-vert visible, accompagnée d'une conductivité électrique faible. L'amélioration de ces propriétés optiques est un signe prometteur pour une potentielle intégration photovoltaïque. / Quantum confined silicon, in the form of silicon quantum dots of diameters 5 nm or less, has the property of bandgap control and light emission. This bandgap engineering gives silicon quantum dots applications in novel photovoltaic devices, while maintaining compatibility with existing silicon technologies. These dots can help reduce lattice thermalisation losses in a single-junction solar cell. This work focusses on the large scale fabrication of silicon quantum dots in SiO2 using Plasma Enhanced Chemical Vapour Deposition (PECVD), followed by high-temperature annealing. Thick single layers are compared with multilayers for morphological, electrical and optical properties. Devices with these layers are compared with different electrode materials. Film thickness dependent organization of dots is observed in thick single layer structures which demonstrate improved electrical conductivity, but poor optical response. Multilayer films demonstrate augmented and controlled Si bandgaps and improved absorption in the blue-green visible range, accompanied by poor electrical conductivity. The improved optical properties are a promising sign for any potential photovoltaic integration.
24

Biosynthesis and accumulation of terpenoids in plants : production of energy-rich triterpenoids in Euphorbia lathyris, a potential crop for third generation biofuels / Biosynthèse et accumulation des terpénoïdes dans les plantes : production de triterpénoïdes énergétiques dans Euphorbia lathyris, une culture potentielle pour la génération de biocarburant de troisième génération

Forestier, Edith 28 November 2013 (has links)
L’objectif de ce projet de thèse était de caractériser le métabolisme de terpénoïdes (ou isoprénoïdes) chez les plantes supérieures. L’essentiel du travail a consisté à caractériser des triterpènes synthases (TTPS) d’Arabidopsis thaliana, un modèle végétal, ainsi que celles de l’épurge (Euphorbia lathyris), une euphorbe pour laquelle des applications agronomiques sont envisagées. Au cours de ma thèse, j’ai aussi contribué à l’étude du métabolisme et des fonctions des précurseurs de triterpènes et de stérols, ainsi qu’à leurs fonctions biologiques.Les triterpènes synthases, ou 2,3-oxydosqualène cyclases (OSCs), convertissent le substrat 2,3-oxydosqualene (SqO) en une multitude d'alcools triterpéniques, et ainsi amorcent la biosynthèse de dérivés triterpénoïdes (triterpènes oxydés, conjugués, etc ..). Arabidopsis thaliana contient 13 OSCs produisant divers squelettes triterpéniques, de type stéroïdien ou non-stéroïdien. Les produits de cyclisation du SqO ont été élucidés structuralement (GC-MS, RMN) après expression hétérologue des enzymes en levure erg7. Cette levure est déficiente en lanostérol synthase (ERG7), ce qui permet d'accumuler le SqO, substrat des cyclases. Lorsque le mutant est transformé avec un ADNc codant une triterpène synthase, il est capable de convertir le SqO en un ou plusieurs triterpènes. Cependant, la caractérisation des 13 OSCs d'Arabidopsis réalisée de façon hétérologue en levure n’a pas été établie inplanta. De façon surprenante, certains des composés produits dans les levures erg7 transformées n'ont jamais été détectés chez Arabidopsis. C'est pourquoi il a été nécessaire de reconsidérer les fonctions biochimiques exactes de ces enzymes dans un contexte végétal. / The subject of this PhD thesis is part of a research project entitled "Production of energy-rich triterpenoids in Euphorbia lathyris, a potential crop for third generation biofuels," whose acronym is EULAFUEL. This project is funded by a multipartner program ANR-KBBE and has been extended until December 2013. The aim of this PhD project is to get new insights into the aspects related with the biosynthesis and accumulation of latex triterpenoids. In addition, for comparison, a major objective of the thesis is to characterize functionally the enzymes involved in the synthesis of triterpenes in the model plant Arabidopsis thaliana. Triterpene synthases, also named oxidosqualene cyclases (OSCs), convert 2,3-oxidosqualene (OS) into a multitude of triterpene alcohols and there by initiate triterpene biosynthesis. Arabidopsis thaliana for instance has 13 OSCs producing diverse skeletons of steroidal or non-steroidal triterpenes. Cyclization products of a given enzyme have been characterized biochemically using a yeast heterologous expression system. However, for the majority of Arabidopsis triterpene synthases, inplanta studies are lacking. In fact, most of the compounds produced in yeast expressing such enzymes have never been detected in wild-type Arabidopsis. This is a reason why we should reconsider the exact biochemical function of triterpene synthases in the plant context. Then, in a comparative approach in E. lathyris, we project to study the specific triterpene accumulation in the laticifers, a specialized cell type where high amounts of lanosterol, an unusual OS cyclization product for plants, accumulate.
25

Adaptive performance management for universal mobile telecommunications system networks

Lindemann, Christoph, Lohmann, Marco, Thümmler, Axel 17 December 2018 (has links)
In this paper, we introduce a framework for the adaptive control of universal mobile telecommunications system (UMTS) networks in order to improve bandwidth utilization of the radio channels. The key contribution of the paper constitutes the introduction of a performance management information base for dynamically adjusting the packet scheduler and admission controller. Thus, the adaptive control framework closes the loop between network operation and network control. Furthermore, the adaptive control framework can effectively deal with the different time scales of packet scheduling and admission control. Moreover, we present a traffic model for non-real-time UMTS traffic based on measured trace data. The analysis and scaling process of the measured trace data with respect to different UMTS bandwidth classes constitutes the basic concept of this traffic characterization. Using this traffic model and simulation on the IP level, the gain of employing the adaptive control framework is illustrated by performance curves for various quality of service measures.
26

Chilean diaspora in Sweden & the effects of social media platforms on their desire to travel back

Ramirez, Patricia January 2022 (has links)
This study examines what role, impact and relationship social media platforms have on second and third generation Chilean diaspora that are living in Sweden when traveling back to Chile. The study uses thematic analysis and 25 qualitative semi-structured interviews with second and third generation Chilean diaspora members, whose age is between 25 and 50 and who has traveled to Chile or are planning to travel there. Through the 25 interviews and the thematic analysis, three themes were identified which were push and pull factors, feelings when traveling back, and travel influenced by social media.  The findings from the study, showed that both second and third generation Chilean diaspora have been motivated by and through social media platforms to visit Chile. It has been found that the priorities of second- and third- generation Chilean diaspora while traveling back to the homeland are different. As social media allows individuals to stay in touch with relatives and friends, it can affect their decision to travel to Chile again. By watching their relatives via video calls, their willingness to go to the country can be greater, which means that the term Visiting friends and relatives (VFR) has a strong connection with diaspora tourism, and this has had a huge impact on the second-generation diaspora. For the third-generation diaspora, their priority to travel to Chile has been a mix of both VFR and exploring the country more. The findings from the study even indicate that UGCs (User Generated Contents) such as pictures or videos that are shared on Instagram, Facebook or YouTube introduces new destinations in Chile, which persuaded both generations of the Chilean diaspora to visit Chile. But this will persuade most of those third-generation participants that have for example did not visit their homeland but want to do it to get more knowledge about their roots, or those who always traveled to the same city but want to explore more.
27

SELECTIVE OXIDATION AND REACTIVE WETTING OF FE-0.1C-6MN-2SI-xSN ADVANCED HIGH STRENGTH STEELS DURING CONTINUOUS HOT-DIP GALVANIZING

Pourmajidian, Maedeh January 2018 (has links)
Third generation advanced high-strength steels (3G-AHSS) have received significant interest from leading auto steel industries and OEMs as candidate materials for reduced mass Body In White (BIW) components due to their unique combination of high specific strength and ductility. However, the continuous hot-dip galvanizing of these steels is challenging due to selective oxidation of the main alloying elements such as Mn, Si, Al and Cr at the steel surface during the annealing step prior to immersion in the galvanizing Zn(Al, Fe) bath, as extensive coverage of the substrate surface by these oxides is detrimental to reactive wetting, good coating adhesion and integrity. Simulated galvanizing treatments were conducted on two prototype Fe-0.1C-6Mn-2Si (wt pct) 3G steels; one as the reference steel and the other with 0.05 wt pct Sn added to the composition. The combined effects of annealing temperature, time, process atmosphere oxygen partial pressure and 0.05 wt pct Sn addition on the selective oxidation of the steel substrates were determined. Subsequently, the reactive wetting of the steels with respect to the pre-immersion surface structures of the samples annealed for 120 s was examined. Annealing heat treatments were carried out at 800˚C and 690˚C in a N2-5 vol pct H2 process atmosphere under three dew points of –50˚C, –30˚C and +5˚C, covering process atmosphere oxygen partial pressures within the range of 1.20  10-27 atm to 1.29  10-20 atm. MnO was present at the outmost layer of the external oxides on all samples after annealing. However, the morphology, distribution, thickness and surface coverage were significantly affected by the experimental variables. Annealing the reference steel under the low dew point process atmospheres, i.e. –50˚C and –30˚C, resulted in the highest Mn surface concentration as well as maximum surface oxide coverage and thickness. The oxides formed under these process atmospheres generally comprised coarse, compact and continuous film forming nodules, whereas the surface morphologies and distributions obtained under the +5˚C dew point process atmosphere, which was consistent with the internal oxidation mode, exhibited wider spacing between finer and thinner MnO nodules. The grain boundary internal oxide networks had a multi layer structure with SiO2 and MnSiO3 at the oxide cores and shells, respectively. Significant morphological changes were obtained as a result of Sn addition. The continuous film-like external MnO nodules were modified to a fine and discrete globular morphology, with less surface coverage by the oxides and reduced external oxide thickness. Both the external and internal oxidations followed parabolic growth kinetics, where the depth of the internal oxidation zone decreased with Sn addition and decreasing oxygen partial pressure. Poor reactive wetting was observed for the reference steel substrates that were annealed for 120 s under the –50˚C and –30˚C dew point process atmospheres at 800˚C and under the –50˚C dew point atmosphere at 690˚C, such that no integral metallic coating was formed after the 4 s immersion in the Zn(Al, Fe) bath. By contrast, excellent coating quality was obtained for the Sn-added steels when the –30˚C and +5˚C dew point process atmospheres were employed when annealing at 690˚C. The remainder of the experimental conditions demonstrated good reactive wetting with intermediate coating quality. For the two reference steels annealed at 800˚C under the –50˚C and –30˚C dew point process atmospheres, poor reactive wetting was due to full coverage of the surface by 116 nm and 121 nm thick and continuous MnO films. In the case of the 690˚C  –50˚C reference steel with the external layer thickness of only 35 nm, however, poor wetting was attributed to substantial coverage of the surface by continuous, film-like oxides. In both cases, exposure of the underlying substrate to the bath alloy and an intimate contact between the substrate Fe and the bath dissolved Al could not take place and the formation of the Fe2Al5Znx interfacial layer was hidered. For the processing conditions that satisfactory reactive wetting was obtained despite the pre-immersion selective oxidation of the surfaces, several reactive wetting mechanisms were determined. For the samples with a sufficiently thin external MnO layer, good reactive wetting was attributed to partial reduction of MnO by the bath dissolved Al, as well as bridging of the Mn sub-oxides by the Zn coating or Fe2Al5Znx interfacial intermetallics. Partial or full formation of the Fe2Al5Znx interfacial layer was observed in the successfully galvanized substrates with Fe-Al crystals formed between, underneath and also on top of the reduced oxides. Furthermore, for cases with widely-spaced, fine oxide nodules, it was found that the liquid bath alloy was able to infiltrate the external oxide/substrate interface, resulting in surface oxide lift-off and enhanced coating adhesion. It was globally concluded that the thin, discrete and fine globular morphology of external MnO, resultant of annealing the steel substrates with 0.05 wt pct Sn addition under the process atmosphere oxygen partial pressures consistent with internal oxidation, allowed for an enhanced reactive wetting by the Zn(Al, Fe) galvanizing bath which was manifested by increased amount of Al uptake and population of the Fe2Al5Znx intermetallics at the coating/steel interface. / Thesis / Doctor of Science (PhD)
28

Traffic Dimensioning for Multimedia Wireless Networks

Ribeiro, Leila Zurba 28 April 2003 (has links)
Wireless operators adopting third-generation (3G) technologies and those migrating from second-generation (2G) to 3G face a number of challenges related to traffic modeling, demand characterization, and performance analysis, which are key elements in the processes of designing, dimensioning and optimizing their network infrastructure. Traditional traffic modeling assumptions used for circuit-switched voice traffic no longer hold true with the convergence of voice and data over packet-switched infrastructures. Self-similar models need to be explored to appropriately account for the burstiness that packet traffic is expected to exhibit in all time scales. The task of demand characterization must include an accurate description of the multiple user profiles and service classes the network is expected to support, with their distinct geographical distributions, as well as forecasts of how the market should evolve over near and medium terms. The appropriate assessment of the quality of service becomes a more complex issue as new metrics and more intricate dependencies have to be considered when providing a varying range of services and applications that include voice, real-time, and non-real time data. All those points have to be considered by the operator to obtain a proper dimensioning, resource allocation, and rollout plan for system deployment. Additionally, any practical optimization strategy has to rely on accurate estimates of expected demand and growth in demand. In this research, we propose a practical framework to characterize the traffic offered to multimedia wireless systems that allows proper dimensioning and optimization of the system for a particular demand scenario. The framework proposed includes a methodology to quantitatively and qualitatively describe the traffic offered to multimedia wireless systems, solutions to model that traffic as practical inputs for simulation analysis, and investigation of demand-sensitive techniques for system dimensioning and performance optimization. We consider both theoretical and practical aspects related to the dimensioning of hybrid traffic (voice and data) for mobile wireless networks. We start by discussing wireless systems and traffic theory, with characterization of the main metrics and models that describe the users’ voice and data demand, presenting a review of the most recent developments in the area. The concept of service class is used to specify parameters that depend on the application type, performance requirements and traffic characteristics for a given service. Then we present the concept of “user profile,“ which ties together a given combination of service class, propagation environment and terminal type. Next, we propose a practical approach to explore the dynamics of user geographical distribution in creating multi-service, multi-class traffic layers that serve as input for network traffic simulation algorithms. The concept of quality-of-service (QoS) is also discussed, focusing on the physical layer for 3G systems. We explore system simulation as a way to dimension a system given its traffic demand characterization. In that context, we propose techniques to translate geographical distributions of user profiles into the actual number of active users of each layer, which is the key parameter to be used as input in simulations. System level simulations are executed for UMTS systems, with the purpose of validating the methodology proposed here. We complete the proposed framework by applying all elements together in the process of dimensioning and optimization of 3G wireless networks using the demand characterization for the system as input. We investigate the effects of modifying some elements in the system configuration such as network topology, radio-frequency (RF) configuration, and radio resource management (RRM) parameters, using strategies that are sensitive to traffic geographical distribution. Case study simulations are performed for Universal Mobile Telecommunications System (UMTS) networks, and multiple system variables (such as antenna tilts, pilot powers, and RRM parameters) are optimized using traffic sensitive strategies, which result in significant improvements in the overall system capacity and performance. Results obtained in the case studies, allied to a generic discussion of the trade-offs involved in the proposed framework, demonstrate the close dependence between the processes of system dimensioning and optimization with the accurate modeling of traffic demand offered to the system. / Ph. D.
29

Simulation of Third Generation CDMA Systems

Alam, Fakhrul 31 December 1999 (has links)
The goal for the next generation of mobile communications system is to seamlessly integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. The technology needed to tackle the challenges to make these services available is popularly known as the Third Generation (3G) Cellular Systems. One of the most promising approaches to 3G is to combine a Wideband Code Division Multiple Access (WCDMA) air interface with the fixed network of Global System for Mobile communications (GSM). In this thesis a signal simulator was implemented according to the physical layer specification of the IMT-2000 WCDMA system. The data is transmitted in a frame by frame basis through a time varying channel. The transmitted signal is corrupted by multiple access interference which is generated in a structured way rather than treating it as Additive White Gaussian Noise (AWGN). The signal is further corrupted by AWGN at the front end of the receiver. Simple rake diversity combining is employed at the receiver. We investigate the bit error rate at both uplink and downlink for different channel conditions. Performance improvement due to error correction coding scheme is shown. The simulator developed can be an invaluable tool for investigating the design and implementation of WCDMA systems. / Master of Science
30

Análise cromatografica de biocidas anti-incrustantes em amostras de água de mar e tecido de moluscos / Chromatographic analysis of booster antifouling biocides in seawater samples and molluscs tissue

Diniz, Lia Gracy Rocha 02 September 2016 (has links)
A indústria naval é uma das mais importantes para economia e desenvolvimento de um país, no entanto, as diversas atividades desenvolvidas em zonas portuárias contribuem para o impacto ambiental a ambientes costeiros, dentre os vários grupos de micropoluentes orgânicos potencialmente danosos a esses ecossistemas, emergiram nos últimos anos os biocidas anti-incrustantes. Pinturas anti-incrustantes são tratamentos utilizados para minimizar processos corrosivos, diminuindo custos com manutenção, economizando combustíveis e reduzindo a veiculação de espécies não nativas entre ecossistemas costeiros. Neste estudo foi desenvolvido, validado e aplicado um método analítico para determinação dos biocidas anti-incrustantes, clorotalonil, diuron, irgarol e tiram em amostras de água, e tecido biológico em diferentes regiões portuárias da costa brasileira e da Ilha de Gran Canaria -Espanha. / The maritime industry is an important aspect of a countries economy, however, the cumulative activities of port areas has an impact on coastal environments, this can include the addition of harmful micro-organic material. Among the potentially harmful micro-organic material being added to ecosystems, are recently emerged anti-fouling biocidal paints. Anti-fouling paints are used as a treatment to minimize corrosive processes, reduce maintenance costs, save fuel and reduce the transmission of non-native species to coastal ecosystems. This study developed, validated and applied an analytical method for the determination of the anti-fouling biocidal paints, chlorothalonil, diuron, irgarol and tiram in water samples and biological tissue in different port areas of the Brazilian coast and the Gran Canaria Island in Spain.

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