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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.
51

Massive MIMO channel characterization and propagation-based antenna selection strategies : application to 5G and industry 4.0 / Caractérisation des canaux massive MIMO et stratégies de sélection d'antenne : application pour la 5G et l'industrie 4.0

Challita, Frédéric 26 September 2019 (has links)
Dans le domaine des télécommunications sans fil, les domaines applicatifs sont de plus en plus larges, s’étendant par exemple du grand public, à la voiture connectée, à l’internet des objets (IoT Internet of Things) et à l’industrie 4.0. Dans ce dernier cas, l’objectif est d’aboutir à une flexibilité et à une versatilité accrues des chaînes de production et à une maintenance prédictive des machines, pour ne citer que quelques exemples. Cependant, les réseaux sans fil actuels ne sont pas encore en mesure de répondre aux nombreuses lacunes de la quatrième génération des réseaux mobiles (4G) et aux exigences de la 5G quant à une connectivité massive, une ultra fiabilité et des temps de latence extrêmement faibles. L’optimisation des ressources spectrales est également un point très important. La 5G était initialement considérée comme une évolution, rendue possible grâce aux améliorations apportées à la LTE (Long Term Evolution), mais elle ne tardera pas à devenir une révolution et une avancée majeure par rapport aux générations précédentes.Dans ce cadre, la technologie des réseaux massifs ou Massive MIMO (Multiple-Input Multiple-Output) s’est imposée comme l’une des technologies de couche physique les plus prometteuses. L'idée principale est d'équiper les stations de base de grands réseaux d’antennes (100 ou plus) pour communiquer simultanément avec de nombreux terminaux ou équipements d’utilisateurs. Grâce à un prétraitement intelligent au niveau des signaux d’émission, les systèmes Massive MIMO promettent d’apporter une grande amélioration des performances, tout en assurant une excellente efficacité spectrale et énergétique. Cependant certains défis doivent encore être relevés avant le déploiement complet des communications basées sur le massive MIMO. Par exemple, l’élaboration de modèles de canaux représentatifs de l’environnement réel, l'impact de la diversité de polarisation, les stratégies de sélection optimale d’antennes et l'acquisition d'informations d'état du canal, sont des sujets importants à explorer. En outre, une bonne compréhension des canaux de propagation en milieu industriel est nécessaire pour optimiser les liens de communication de l'industrie intelligente du futur.Dans cette thèse, nous essayons de répondre à certaines de ces questions en nous concentrant sur trois axes principaux :1) La caractérisation polarimétrique des canaux massive MIMO en environnement industriel. Pour cela, on étudie des scénarios correspondant à des canaux ayant ou non une visibilité directe entre émetteur et récepteur (Line of Sight – LOS) ou Non LOS, et en présence de divers types d’obstacles. Les métriques associées sont soit celles utilisées en propagation telles que le facteur de Rice et la corrélation spatiale, soit orientées système comme la capacité totale du canal incluant des stratégies de précodage linéaire. De plus, les schémas de diversité de polarisation proposés montrent des résultats très prometteurs.2) En massive MIMO, un objectif important est de réduire le nombre de chaînes de fréquences radio et donc la complexité du système, en sélectionnant un ensemble d'antennes distribuées. Cette stratégie de sélection utilisant la corrélation spatiale du récepteur et une métrique de propagation comme facteur de mérite, permet d'obtenir une capacité totale quasi-optimale.3) Une technique efficace de réduction des ressources lors de l’acquisition d’informations du canal de propagation dans les systèmes FDD (frequency-division-duplex) est enfin proposée. Elle repose sur la corrélation spatiale au niveau de l'émetteur et consiste à résoudre un ensemble d'équations auto-régressives simples. Les résultats montrent que cette technique permet d’atteindre des performances qui ne sont pas trop éloignées de celles des systèmes TDD (time-division-duplex) initialement proposés pour le massive MIMO. / Continuous efforts have been made to boost wireless systems performance, however, current wireless networks are not yet able to fulfill the many gaps from 4G and requirements for 5G. Thus, significant technological breakthroughs are still required to strengthen wireless networks. For instance, in order to provide higher data rates and accommodate many types of equipment, more spectrum resources are needed and the currently used spectrum requires to be efficiently utilized. 5G, or the fifth generation of mobile networks, is initially being labeled as an evolution, made available through improvements in LTE, but it will not be long before it becomes a revolution and a major step-up from previous generations. Massive MIMO has emerged as one of the most promising physical-layer technologies for future 5G wireless systems. The main idea is to equip base stations with large arrays (100 antennas or more) to simultaneously communicate with many terminals or user equipments. Using smart pre-processing at the array, massive MIMO promises to deliver superior system improvement with improved spectral efficiency, achieved by spatial multiplexing and better energy efficiency, exploiting array gain and reducing the radiated power. Massive MIMO can fill the gap for many requirements in 5G use-cases notably industrial IOT (internet of things) in terms of data rates, spectral and energy efficiency, reliable communication, optimal beamforming, linear processing schemes and so on. However, the hardware and software complexity arising from the sheer number of radio frequency chains is a bottleneck and some challenges are still to be tackled before the full operational deployment of massive MIMO. For instance, reliable channel models, impact of polarization diversity, optimal antenna selection strategies, mutual coupling and channel state information acquisition amongst other aspects, are all important questions worth exploring. Also, a good understanding of industrial channels is needed to bring the smart industry of the future ever closer.In this thesis, we try to address some of these questions based on radio channel data from a measurement campaign in an industrial scenario using a massive MIMO setup. The thesis' main objectives are threefold: 1) Characterization of massive MIMO channels in Industry 4.0 (industrial IoT) with a focus on spatial correlation, classification and impact of cross-polarization at transmission side. The setup consists in multiple distributed user-equipments in many propagation conditions. This study is based on propagation-based metrics such as Ricean factor, correlation, etc. and system-oriented metrics such as sum-rate capacity with linear precoding and power allocation strategies. Moreover, polarization diversity schemes are proposed and were shown to achieve very promising results with simple allocation strategies. This work provides comprehensive insights on radio channels in Industry 4.0 capable of filling the gap in channel models and efficient strategies to optimize massive MIMO setups. 2) Proposition of antenna selection strategies using the receiver spatial correlation, a propagation metric, as a figure of merit. The goal is to reduce the number of radio frequency chain and thus the system complexity by selecting a set of distributed antennas. The proposed strategy achieves near-optimal sum-rate capacity with less radio frequency chains. This is critical for massive MIMO systems if complexity and cost are to be reduced. 3) Proposition of an efficient strategy for overhead reduction in channel state information acquisition of FDD (frequency-division-duplex) systems. The strategy relies on spatial correlation at the transmitter and consists in solving a set of simple autoregressive equations (Yule-Walker equations). The results show that the proposed strategy achieves a large fraction of the performance of TDD (time-division-duplex) systems initially proposed for massive MIMO.
52

The Use of Body-Mapping in Interpretative Phenomenological Analyses: A Methodological Discussion

Klein, Maike, Milner, Rebecca J. 20 March 2019 (has links)
The increasing popularity of Interpretative Phenomenological Analysis (IPA) in social research brings an increasing criticism about its validity, robustness and, more recently, its lack of expressive features. Recently, the novel arts-based research approach called body-mapping was recognized as enhancing social science research in creative and nuanced ways. Body-mapping allows for unique insights into participants’ lived experiences, the meaning thereof, and into how meaning is impacted by their socio-cultural contexts. This article provides new understandings about the potential use of body-mapping as part of an IPA framework by drawing upon existing literature to critically discuss their philosophical and methodological congruence. The following discussion demonstrates how particular strengths of body-mapping align with weaknesses of IPA and that, when merged, they may be especially useful for research with vulnerable and hard-to-reach populations. Limitations of this discussion and implications for future research are provided.
53

The Geometry of Taking Flight: Limb Morphometrics in Mesozoic theropods

Hedrick, Brandon P., Manning, Phillip L., Lynch, Eric R., Cordero, Samantha A., Dodson, Peter 01 January 2015 (has links)
Theropoda was one of the most successful dinosaurian clades during the Mesozoic and has remained a dominant component of faunas throughout the Cenozoic, with nearly 10,000 extant representatives. The discovery of Archaeopteryx provides evidence that avian theropods evolved at least 155 million years ago and that more than half of the tenure of avian theropods on Earth was during the Mesozoic. Considering the major changes in niche occupation for theropods resulting from the evolution of arboreal and flight capabilities, we have analyzed forelimb and hindlimb proportions among nonmaniraptoriform theropods, nonavian maniraptoriforms, and basal avialans using reduced major axis regressions, principal components analysis, canonical variates analysis, and discriminant function analysis. Our study is the first analysis on theropod limb proportions to apply phylogenetic independent contrasts and size corrections to the data to ensure that all the data are statistically independent and amenable to statistical analyses. The three ordination analyses we performed did not show any significant groupings or deviations between nonavian theropods and Mesozoic avian forms when including all limb elements. However, the bivariate regression analyses did show some significant trends between individual elements that suggested evolutionary trends of increased forelimb length relative to hindlimb length from nonmaniraptoriform theropods to nonavian maniraptoriforms to basal avialans. The increase in disparity and divergence away from the nonavian theropod body plan is well documented within Cenozoic forms. The lack of significant groupings among Mesozoic forms when examining the entire theropod body plan concurrently suggests that nonavian theropods and avian theropods did not substantially diverge in limb proportions until the Cenozoic. J. Morphol. 276:152-166, 2015.
54

Palynology and Palynofacies Analyses of the Gray Fossil Site, Eastern Tennessee: Their Role in Understanding the Basin-Fill History

Zobaa, Mohamed K., Zavada, Michael S., Whitelaw, Michael J., Shunk, Aaron J., Oboh-Ikuenobe, Francisca E. 01 August 2011 (has links)
The Gray Fossil Site (GFS) includes multiple karst sub-basins that are filled with lacustrine sediments. Early paleontologic work on one of the sub-basins (GFS-2) indicates a late Miocene/early Pliocene age based on an assemblage of well-preserved vertebrate fossils. However, detailed palynological analysis of the 38.7. m deep GFS-1 core recovered from another sub-basin indicates an older age. The presence of Caryapollenites imparalis, C. inelegans and C. prodromus association suggests a Paleocene to Eocene age for the GFS-1 core section. This age is also supported by the absence of pollen of the Poaceae, the grass family that is not commonly present until the Neogene. Age constraints from palynologic data suggest that the GFS has a more complex basin-fill history than previously suspected, and that multiple depo-centers within the basin may have been periodically active through the Cenozoic. Palynofacies analysis of the GFS-1 core indicates that phytoclasts and opaques are the most abundant organic constituents and have diluted both the palynomorph population and amorphous organic matter. Two possible scenarios can account for this observation: 1) an oxidizing depositional paleoenvironment; and 2) a localized high flux of charcoal following wildfires and subsequent increased runoff.
55

A Genome-Wide Quantitative Trait Loci Scan of Neurocognitive Performances in Families With Schizophrenia

Lien, Y. J., Liu, C. M., Faraone, S. V., Tsuang, M. T., Hwu, H. G., Hsiao, P. C., Chen, W. J. 01 October 2010 (has links)
Patients with schizophrenia frequently display neurocognitive dysfunction, and genetic studies suggest it to be an endophenotype for schizophrenia. Genetic studies of such traits may thus help elucidate the biological pathways underlying genetic susceptibility to schizophrenia. This study aimed to identify loci influencing neurocognitive performance in schizophrenia. The sample comprised of 1207 affected individuals and 1035 unaffected individuals of Han Chinese ethnicity from 557 sib-pair families co-affected with DSM-IV (Diagnostic and Statistical Manual, Fourth Edition) schizophrenia. Subjects completed a face-to-face semi-structured interview, the continuous performance test (CPT) and the Wisconsin card sorting test (WCST), and were genotyped with 386 microsatellite markers across the genome. A series of autosomal genome-wide multipoint nonparametric quantitative trait loci (QTL) linkage analysis were performed in affected individuals only. Determination of genome-wide empirical significance was performed using 1000 simulated genome scans. One linkage peak attaining genome-wide significance was identified: 12q24.32 for undegraded CPT hit rate [nonparametric linkage z (NPL-Z) scores = 3.32, genome-wide empirical P = 0.03]. This result was higher than the peak linkage signal obtained in the previous genome-wide scan using a dichotomous diagnosis of schizophrenia. The identification of 12q24.32 as a QTL has not been consistently implicated in previous linkage studies on schizophrenia, which suggests that the analysis of endophenotypes provides additional information from what is seen in analyses that rely on diagnoses. This region with linkage to a particular neurocognitive feature may inform functional hypotheses for further genetic studies for schizophrenia.
56

Expressive Writing and Breast Cancer: Outcomes and Linguistic Analyses

Hughes, Kelly N. 01 May 2006 (has links)
This project examined the imp act of an expressive writing intervention as compared to a general health in formation control on breast cancer patients' postradiation treatment. It further examined the content of the expressive writing narratives. The sample included women who were completing radiation treatment for breast cancer at the Huntsman Cancer Institute and City of Hope hospital. The measures utilized in this study were self-report instruments targeting psychological distress (PANAS, JES) and general functioning (SIP), as well as demographic questionnaires. Results revealed the expressive writing intervention significantly impacted positive affect over time. Furthermore, participants from both the treatment and control groups evidenced improvements in psychological distress and general functioning over time. Linguistic analyses revealed participants' use of positive affect words increased across writing sessions, whereas the use of negative affect words and cognitive words did not change. Additionally, the use of past tense words decreased across writing sessions, whereas the use of present tense words increased and the use of future tense remained constant. The findings revealed from this study indicate that an expressive writing intervention can positively impact breast cancer patients up to 1 year postradiation treatment. Furthermore, the analysis of writing trends suggests that the use of positive affect words, the decrease in use of past tense words, along with the increase of present tense words across writing sessions, may be important linguistic components in positive outcomes.
57

En undersökning av Storsjön och Lillsjön, särskilt när det gäller metaller / An Investigation of the Lakes Storsjön and Lillsjön, Especially in Terms of Metals

Hamid, Ghadir January 2018 (has links)
Storsjön och Lillsjön är två små sjöar vid Roslagsbanan nära Lindholmen.Sjöarna tillsammans med omkringliggande våtmarksområde utgör ett fint naturområde. Målet är att undersöka hur metaller påverkar sjöarnas miljö. pH är lågt (=6,7) och vattnetinnehåller mycket organiskt material. Området påverkas starkt av omkringliggande vägar. Klorid från vägsaltningen och metaller från bilarna transporteras genom området och lagrasdelvis i sjöarnas sediment. Sedimenteringsdammar bör anläggas i tillrinnande vatten. / Storsjön and Lillsjön are two small lakes near Roslagsbanan and close to Lindholmen. The lakes together with the surrounding wetland makes a very nice natural park. The aim of this work is to investigate the impact of metals on the enviroment of the lakes. pH is very low(=6,7) and the water contains a lot of organic material. The area is seriously impacted by the nearby roads. Sodium cloride from road salt spread during the winter and metal ions fromthe cars are transported through this area and are partly stored in the sediments of the lakes. Dams should be constructed in the incoming creeks for sedimentation of metal ions.
58

Loop, cutset, hybrid and state analyses of linear multiple-loop feedback systems

Elsherif, Hassan Mohamed January 1980 (has links)
No description available.
59

An index of wind band literature analyses from periodicals and university research

Allen, Milton 14 July 2006 (has links)
No description available.
60

Phylogenetic Analyses of subtribe Goodyerinae and Revision of <i>Goodyera</i> section <i>Goodyera</i> (Orchidaceae) from Indonesia, and Fungal Association of <i>Goodyera</i> section <i>Goodyera</i>

Juswara, Lina S. 03 September 2010 (has links)
No description available.

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