• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 572
  • 129
  • 96
  • 92
  • 87
  • 37
  • 25
  • 21
  • 20
  • 19
  • 19
  • 18
  • 6
  • 6
  • 5
  • Tagged with
  • 1274
  • 335
  • 194
  • 191
  • 190
  • 174
  • 149
  • 115
  • 105
  • 93
  • 84
  • 83
  • 79
  • 75
  • 66
  • 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.
761

Modulateur sigma-delta complexe passe-bande à temps continu pour la réception multistandard

Jouida, Nejmeddine 18 February 2010 (has links)
Le travail de recherche que nous présentons dans cette thèse s’inscrit dans le domaine de la conception des circuits et systèmes pour la numérisation des signaux radio large bande multistandard. La finalité de ces travaux est l’établissement de nouvelles méthodologies de conception des circuits analogiques et mixtes VLSI, et à faible consommation pour le convertisseur analogique numérique (CAN). Nous proposons l’utilisation d’un CAN de type S? complexe passe-bande à temps-continu pour l’architecture Low-IF. Ce qui permet de simplifier l’étage analogique en bande de base en esquivant le besoin de circuits tels que le contrôleur de gain automatique, le filtre anti-repliement et les filtres de rejection d’images. Le récepteur est plus linéaire et présente un degré d’intégrabilité adéquat pour les applications multistandard de type Radio logicielle Restreinte (SDR). La première contribution consiste à proposer une méthodologie originale et complètement automatisée de dimensionnement du modulateur ?? pour la réception SDR. Une nouvelle stratégie de stabilisation, basée sur le placement des zéros et des pôles du filtre de boucle, est élaborée permettant ainsi de simplifier le passage du temps-discret vers le temps-continu par une simple correspondance entre les domaines pour les intégrateurs et les résonateurs du filtre de boucle. La deuxième contribution concerne la construction d’une architecture générique du modulateur ?? complexe à temps-continu en suivant une méthodologie originale. Les éléments de base de cette architecture sont les deux modulateurs ?? passe-bas pour les voies I et Q à temps-continu. Les deux filtres de boucles sont en couplage croisé en structure polyphase, ce qui permet le décalage vers la fréquence intermédiaire du récepteur. Nous avons conçu un outil de dimensionnement sous MATLAB pour les modulateurs S? multistandard stables d’ordre élevés à temps-continu, passe bas, passe-bande réel et complexe. La troisième contribution de ces travaux concerne la proposition d’une méthodologie de conception avancée de circuits mixtes VLSI pour les CANs de type ??. Cette méthodologie de conception permet une combinaison des approches descendante ‘Top-down’ et montante ‘Bottom-up’, ce qui rend possible l’analyse des compromis de conception par l’utilisation concurrente des circuits au niveau transistor et des modèles comportementaux. Cette approche permet de faire allier à la fois la précision et la vitesse de processus de simulation lors de la conception des CANs de type ??. La modélisation comportementale du modulateur S?, en utilisant le langage VHDL-AMS, nous a permis de développé une bibliothèque de modèles permettant la prise en compte des imperfections tels que le bruit, le jitter, le retard de boucle au niveau comportemental. Afin d’illustrer la méthodologie de conception proposée, un exemple de la vérification par la simulation mixte est fourni à travers la conception d’un quantificateur en technologie CMOS. L’extraction des paramètres des imperfections du schéma au niveau transistor a permit d’enrichir le modèle comportemental et de prévenir les anomalies causant la dégradation des performances du modulateur S?. / Abstract
762

Soft Revolvers et les interfaces créées sur mesure : la performance de musique numérique dans une perspective d’œuvre totale

Bleau, Myriam 01 1900 (has links)
Cette version du mémoire a été tronquée des éléments de composition originale. Une version plus complète est disponible en ligne pour les membres de la communauté de l’Université de Montréal et peut aussi être consultée dans une des bibliothèques UdeM. / Ce texte présente le processus de composition ayant mené à la création de la performance Soft Revolvers. Cette œuvre repose sur la conception d’interfaces sur mesure, soit quatre toupies lumineuses évoquant les tables tournantes. Je situe la création d’un tel dispositif, connoté et totalement intégré au propos artistique, dans la continuité historique du Gesamtkunstwerk (œuvre totale). Cette perspective englobante permet de questionner tous les aspects qui affectent la réception d’une œuvre. J’exposerai donc comment la lutherie utilisée, la gestuelle développée, la forme musicale et la scénographie ont été articulées autour d’un concept central dans la performance Soft Revolvers. Je présenterai finalement deux autres œuvres connexes, la performance Tempo Deluxe, qui utilise les mêmes interfaces de toupies, et la pièce Lumens&Profits, qui revisite les mêmes thématiques et techniques de composition dans une version fixée. Cette mise en parallèle permettra de mieux cerner les limitations impliquées par la spécificité des interfaces, tout en faisant ressortir l’efficacité du dispositif créé sur mesure dans le contexte numérique. / This text examines the composition process leading to the creation of the performance Soft Revolvers. The work is based on performance specific interfaces: four luminous spinning tops that evoke turntables. These connoted devices, fully integrated in the artistic discourse, are located within the historic continuum of the Gesamtkunstwerk (total work of art). This holistic perspective allows the renegociation of all the aspects that might influence the reception of a performance. Each of these aspects - the digital instrumentation, the gestural language, the musical form and the scenography - is discussed and articulated around the central concept in Soft Revolvers. Finally, two related works are presented, the performance Tempo Deluxe, which uses the same spinning top interfaces, and the piece Lumens&Profits, which explores the same thematic material as Soft Revolvers in a fixed version. Comparing these works allows a better delineation of the limitations implied by the interfaces' specificity, while confirming the effectiveness of the performance specific device in the digital realm.
763

Factors affecting the outcome of IVF/ICSI

Veleva, Z. (Zdravka) 16 September 2008 (has links)
Abstract Fertility declines with advancing age and the number of couples seeking infertility treatment at an older age is constantly increasing. A top quality embryo is believed to have the highest potential for implantation and development into a child. A better understanding of the relative importance of patient and treatment characteristics and of embryo quality could help to optimise the existing therapeutic schemes and the safety of in vitro fertilisation/intracytoplasmic sperm injection (IVF/ICSI). In this work, databases of five Finnish infertility clinics were studied retrospectively. Data on treatments performed in the years 1994–2005 were collected. A total of 19,000 treatment cycles were analysed. Special attention was paid to the relative significance of the transfer of top quality embryos with regards to pregnancy, miscarriage, live birth and cost of treatment in the general IVF/ICSI patient population and in groups with expected poor outcome. The results showed that the transfer of a top quality embryo is associated with a better chance of pregnancy and live birth. However, it does not diminish the probability of miscarriage. Both low and high BMI increase the miscarriage rate. Advancing age and a positive history of previous miscarriages are also associated with a higher probability of miscarriage. In addition, the need for hormonal substitution in cases of frozen-embryo transfer is a risk factor of miscarriage, probably because of suboptimal endometrial function. Since the transfer of several embryos leads to multiple pregnancies, which are associated with a high risk of maternal and fetal complications, elective single embryo transfer (eSET) of a top quality embryo allows all additional good quality embryos to be frozen and transferred later in frozen-thawed embryo transfer cycles. The present work demonstrates that eSET is a safe treatment strategy at least until the age of 40. However, it might not be performed in women with fewer than four collected oocytes, since the prognosis might remain poor even if the response is improved in a following cycle. When eSET is applied routinely and on a large scale, it diminishes treatment costs while increasing the number of deliveries occurring at term, making IVF/ICSI at the same time safer and more affordable even to patients without access to reimbursed IVF treatment.
764

Rotation-vibration spectroscopic studies of formaldehyde and formic acid

Lohilahti, J. (Jarmo) 10 May 2006 (has links)
Abstract The thesis consists of seven studies dealing with high resolution vibration-rotation spectra of planar asymmetric tops. Six studies deal with D212CO and D213CO species of the formaldehyde molecule and one study is from DCOOH specie of the formic acid molecule. The measurements were carried out at high accuracy and the rotational analyses of the recorded spectra were performed. The observed anharmonic and Coriolis resonances were taking into account in the analyses. The rotational constants of the present and literature studies were used in evaluation of the planarity defects of formaldehyde and formic acid molecules in the summary part of the thesis. Finally, a semi-experimental structure for formaldehyde was obtained by employing experimental and theoretical data.
765

Politické strany a výzkumy veřejného mínění / Political parties and public opinion polls

Romoliniová, Michaela January 2017 (has links)
This diploma thesis Political parties and public opinion polls deals with the use of research in political party. From a theoretical point of view, the thesis focuses on defining the concept of public opinion, its influence on political tradition, and the importance of public opinion polls and their criticism. The main part of the thesis focuses on political communication introducing the use of methods and tools of political marketing, namely utilizing public opinion polls. It describes a change in political communication that has led to professionalization and the need to hire professionals from outside sources, and the role of media, which is often the only source of information for citizens. It explains the difference between particular mediated public opinion polls and focuses on their medial impact on voters. The research section have a form of a case study which focuses on how the public opinion polling is used to develop the electoral strategy in the political party TOP 09 before the elections to the regional councils in 2016. The result of the analysis shows that this political party is highly professionalized, continues to develop its electoral strategy based on research results, and follows recommendations of research agencies, using modern political marketing methods.
766

Field observations of wave induced coastal cliff erosion, Cornwall, UK

Earlie, Claire Siobhan January 2015 (has links)
Coastal cliff erosion is a widespread problem that threatens property and infrastructure along many of the world’s coastlines. The management of this risk calls for robust quantification of cliff erosion rates, which are often difficult to obtain along rocky coasts. Quantification of sea-cliff rates of retreat on annual to decadal time scales has typically been limited to rapidly eroding soft rock coastlines. Rates of erosion used for shoreline management in the UK are generally based on analysis of historic maps and aerial photographs which, in rocky coast environments, does not wholly capture the detail and timing at which the processes operate and the failures occur across the cliff face. The first stage of this study uses airborne LiDAR (Light Detection and Ranging) data at nine sites around a rocky coastline (Cornwall, UK) to gain a quantitative understanding of cliff erosion where average recession rates are relatively low (c. 0.1 m yr-1). It was found that three-dimensional volumetric changes on the cliff face and linear rates of retreat can be reliably calculated from consecutive digital elevation models (DEMs) several years apart. Rates of erosion ranged between 0.03–0.3 m yr-1. The spatial variability in recession rates was considered in terms of the relationship with the varying boundary conditions (rock mass characteristics, cliff geometries, beach morphology) and forcing parameters (wave climate and wave exposure). Recession rates were statistically correlated with significant wave height (Hs), rock mass characteristics (GSI) and the ratio between the two (GSI/Hs). Although the rates derived using airborne LiDAR are comparable to the longer term rates of retreat, the detail of erosion to the cliff-face provides additional insight into the processes occurring in slowly eroding environments, which are vital for understanding the failure of harder rock coastlines. In addition to this, the importance of the wave climate and rainfall needs further attention on a more localised scale. Monthly cliff face volume changes, at two particularly vulnerable sites (Porthleven and Godrevy, Cornwall, UK), were detected using a Terrestrial Laser Scanner (TLS). Using these volumes alongside information on beach profile, beach- cliff junction elevation changes and nearshore hydrodynamics have allowed an insight into how the cliffs respond to seasonal fluctuations in wave climate and beach morphology. Monthly variability in beach morphology between the two sites over a one-year survey period i  indicated the influence that beach slope and the elevation of the beach-cliff junction have on the frequency of inundation and the power of wave-cliff impacts. Failure mechanisms between the two sites ranged from rotational sliding of superficial material to quarrying and block removal over the entire cliff elevation, according to the extent of wave-cliff interaction. This particular survey period highlighted the sensitivity of cliff erosion to the variability in wave climate and beach morphology at two different locations in the south-west of the UK, where the vast majority (over 85% of the annual value) of cliff face erosion occurs during the winter when extreme storm waves prevail. Coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs, limiting our understanding of cliff processes. Over January-March 2014, during the largest Atlantic storms in at least 60 years with deep water significant wave heights of 6 – 8 m, cliff-top ground motions of a rocky cliff in the south-west of the UK (Porthleven, Cornwall) showed vertical ground displacements in excess of 50–100 μm; an order of magnitude larger than observations made previously. Repeat terrestrial laser scanner surveys, over a 2-week period encompassing the extreme storms, gave a cliff face volume loss 2 orders of magnitude larger than the long-term erosion rate. Cliff-top ground motions and erosion volumes were compared at two different locations, one a reflective beach with steeply shelving bathymetry (Porthleven, Cornwall) and the other an intermediate, low tide bar-rip beach with a wide coastal slope (Godrevy, Cornwall). Under similar wave conditions (6–8 m Hs and 15–20 s. Tp) the vertical ground motions were an order of magnitude greater at the cliffs fronted by steeply shelving bathymetry, where the breaking waves plunge right at the shoreline, with little prior dissipation, leading to large energetic runup impacting the cliff. These storm results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long-term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts as well as the wave dissipation that occurs as a function of the nearshore bathymetry. Having recorded microseismic cliff-top motion on this scale for the first time and determined an effective method of monitoring the energetic wave impacts, this study emphasises how investigations of cliff behaviour during storms is not only obtainable, but paramount to understanding coastal evolution under extreme conditions.
767

Mesure de la masse du quark top dans le canal électron-muon à l'aide de la méthode des éléments de matrice avec les données à 8 TeV de l'expérience ATLAS du LHC / Measurement of the top quark mass in the decay channel electron-muon with the matrix element method on the 8 TeV data recorded by the ATLAS detector at LHC

Pires, Sylvestre 03 July 2015 (has links)
Les travaux présentés au sein de cette thèse s'inscrivent dans le cadre de la mesure de la masse du quark top dans le canal de désintégration électron-muon. Cette mesure expérimentale est réalisée à l'aide de la méthode des éléments de matrice et à partir des événements produits par le LHC à une énergie dans le centre de masse de 8 TeV et enregistrés par le détecteur ATLAS en 2012. Après une introduction du contexte phénoménologique associé au modèle standard et à la physique du quark top, une description du détecteur ATLAS, de la simulation et de la reconstruction des événements de collisions est donnée. La première analyse présentée a été réalisée en début de thèse et estime l'impact qu'a l'installation d'une nouvelle couche de pixels dans le détecteur ATLAS, au plus proche du point de collision, sur les performances d'étiquetages des jets de b lors de prises de données à une énergie dans le centre de masse de 13 TeV enregistrées à partir de 2015. La seconde partie est consacrée à la mesure de la masse du quark top. Après avoir décrit la sélection à laquelle cette analyse est liée, l'étalonnage de la méthode des éléments de matrice est présenté. La masse du quark top mesurée est :m_top = 172,40 ± 0,35 (stat.) ± 1,12 (syst.) GeV.Cette mesure est obtenue avec une précision de 0,64% et est compatible à la fois avec la combinaison mondiale de la masse du quark top et avec les mesures récentes publiées par la collaboration ATLAS. / The work presented in this thesis lies within the scope of the measurement of the top quark mass in the decay channel electron-muon. This experimental measurement is achieved by the use of the matrix element method with events produced at LHC at a centre of mass energy of 8 TeV and collected by the ATLAS detector in 2012. After introducing the theoretical context of the Standard Model and the physics of the top quark, a detailed description of the ATLAS detector design and of both the event simulation and reconstruction is given. The first analysis presented was done during the beginning of the thesis and focuses on the impact of the insertion of an innermost new pixel layer in the ATLAS detector on the b-tagging performance during the data taking starting in 2015 with an centre of mass energy of 13 TeV. The second part of the thesis is dedicated the top quark mass measurement. After reviewing the selection procedure to which the analysis is linked, the calibration of the matrix element method is presented. The top quark mass is measured as :m_top = 172,40 ± 0,35 (stat.) ± 1,12 (syst.) GeV.This measurement is obtained with a precision of 0.64% and is compatible with both the World combination of the top quark mass and with recent measurements published by the ATLAS collaboration.
768

Dynamique de la végétation et transformations des systèmes d'élevage sur les marges arides du Tell oriental de Soughas à Souar : (dorsale tunisienne) / Vegetation dynamics and changes in farming systems on the eastern margins arid Tell, Tunisian dorsal

Abdallah, Hédi 04 September 2015 (has links)
Le rôle croissant de la pression pastorale sur la végétation en Tunisie, et en particulier dans la Dorsale tunisienne, a été étudié par plusieurs chercheurs (Long, 1959 ; Gounot et Schoenenberger, 1967 ; Le Houérou, 1959 et 1969). Cependant, ces études sous.estiment le rôle de l'homme et particulièrement l'activité d'élevage dans la variation spatiale de la végétation en Tunisie. L'un des premiers objectifs de cette thèse est donc, la production d'une carte de végétation à grande échelle qui prend en compte l'influence de l'homme sur le paysage. Les mutations récentes des modes de vie des paysans conduisent à placer l'élevage au centre des relations de l'homme à son milieu. Le rôle de la pression pastorale est considéré comme l'un des éléments explicatifs de la dynamique de la végétation forestière. Cette thèse adopte une démarche socio-économique et historique pour tester l'hypothèse suivante : bien que l'élevage soit reconnu comme un facteur d'influence dans la dynamique de végétation dans les marges arides du Tell oriental, son rôle n'a jamais été dominant. Il a été toujours associé à d'autres activités paysannes jugées nuisibles à la végétation comme le charbonnage, les incendies, les défrichements... L'abandon et/ou le ralentissement de ces activités dans le cadre des nouvelles mutations socio-économiques, ont fait de l'élevage un facteur déterminant dans la dynamique de la végétation. La thèse comprend trois parties : La première partie aborde la reconstitution de l'évolution qui a conduit au peuplement actuel. Cette évolution est dominée par la sédentarisation des pasteurs et a conduit à la genèse des douars actuels peuplés de petits agriculteurs-éleveurs. Dans ce système de production, la place de l'élevage pastoral est prépondérante et persistante. La deuxième partie de la thèse montre les analyses qui ont permis de réaliser une cartographie détaillée du couvert végétal. La cartographie de la végétation est utilisée pour faire le point sur l'état de conservation du couvert végétal et procéder à une estimation qualitative et quantitative des ressources fourragères disponibles au sein de chaque unité spatiale homogène. Dans la troisième partie La troisième partie analyse principalement les enquêtes, les observations de terrain, les données sur les effectifs des troupeaux, les sources d'alimentation du bétail et l'évolution de son état corporel. L'analyse de ces données permet de définir les systèmes d'élevage développés dans la région étudiée, de cartographier la répartition de leur pression pastorale sur la végétation forestière et steppique, à partir de chaque foyer de peuplement assurant la gestion du troupeau et de l'espace. / The growing role of grazing pressure on vegetation in Tunisia, and in particular in the Tunisian Dorsal has been studied by several researchers (Long, 1959; Gounot et Schoenenberger, 1967; Le Houérou, 1959 and 1969). However, these studies neglect the role of man and especially the breeding activity in the spatial variation of vegetation in Tunisia. One of the primary objectives of this thesis is the production of a large.scale vegetation map that takes into account the influence of man on the landscape. Recent changes in farmer's lifestyles lead to put livestock in human relations center in the middle. The role of grazing pressure has become one of the factors explaining the dynamics of forest vegetation. This thesis adopts a socio-economic and historical approach to test the assumption that farming is recognized as an influential factor in the dynamic vegetation in arid margins Tell East; its role has never been dominant. It was always associated with other activities deemed harmful to vegetation peasant like coal, fire, land clearing ... The abandonment and / or deceleration of these activities in the framework of the new socio-economic changes have made Livestock a major factor in the dynamics of vegetation. The thesis has three parts: The first part deals with the reconstruction of the evolution that led to the current settlement. This evolution is dominated by the settlement of pastoralists and has led to the genesis of the current douars inhabited by small farmers and breeders. In this production system, instead of pastoralism is predominant and persistent. The second part of the thesis shows the analysis that enabled a detailed land cover mapping. The vegetation mapping is used to take stock of the vegetation cover conservation status and conduct a qualitative and quantitative estimation of forage resources available within each homogeneous spatial unit. In the third part, based primarily on surveys, field observations, data on the number of livestock, livestock feeding sources and changes in body condition. Analysis of these data to define farming systems developed in the study area; map the distribution of their grazing pressure on forest and steppe vegetation, from each stand home use management herd management and space.
769

A comparison of the rate and accuracy of symbol location on visual displays using colour-coded alphabetic and categorisation strategies in Grade 1 to 3 children

Herold, M.P. (Marina Patricia) 14 October 2012 (has links)
The ability to locate symbols on a visual display forms an integral part of the effective use of AAC systems. Characteristics of display design and perceptual features of symbols have been shown to influence rate and accuracy of symbol location (Thistle&Wilkinson, 2009; Wilkinson, Carlin,&Jagaroo, 2006). The current study endeavoured to compare the use of two colour-coded organisational strategies (alphabetical order and categorisation) for their effectiveness in symbol location and to investigate if some bottom-up features influenced the performance of the participants in these tasks. 114 learners in Grade 1 to 3 in a mainstream school were randomly divided into two groups. Both of the groups were exposed to two visual search tests in alternating order. The tests involved searching for 36 visual targets amongst 81 coloured Picture Communication Symbols on a computer screen in one of two colour-coded organizational methods, namely alphabetical order or categorisation. The data from the research task was collected through computer logging of all mouse selections. Findings showed that locating symbols on a computer screen with a categorisation strategy was significantly faster and more accurate than with an alphabetical strategy for the Grade 1 to 3 participants. The rate and accuracy of target symbol location in both the strategies decreased significantly as grade increased, as did the differences between rate and accuracy of target location when using the two strategies. It was also found that although the tests in this study placed heavy top-down processing demands on the participants, there was still evidence of bottom-up factors influencing their performance. Implications for display design in AAC clinical practice were discussed. / Thesis (PhD)--University of Pretoria, 2012. / Centre for Augmentative and Alternative Communication / unrestricted
770

Emergency Preparedness and Response Planning: A Value-Based Approach to Preparing Coastal Communities for Sea Level Rise

Chung, Alexander Quoc Huy January 2014 (has links)
Extreme weather events have become a common occurrence and coastal communities are adversely affected by it. Studies have shown that the changing climate has increased the frequency and severity of storms, surging sea levels, and floods, as was seen with Hurricane Sandy (2012) and Typhoon Haiyan (2013). The need to be proactive in preparing for these events, as a means of climate change adaptation and disaster risk reduction, is evident. This study focuses on the formal definition, measurement and simulation of coastal community preparedness and response to severe storm events. Preparedness and response requires resources, emergency plans, informed decision making and the ability to cope with unexpected events. A suite of preparedness indicators is developed using a three level hierarchical framework in the construction of a coastal community preparedness index to evaluate resources and plans. Informed decision making for emergency management personnel in the Emergency Operations Centre (EOC) is evaluated through a table-top exercise using a five-phase approach. Lastly, decision making with risk is introduced with a storm decision making simulation model. This study is applied to the case of the breakwater failure in the coastal community of Little Anse, Cape Breton, Nova Scotia.

Page generated in 0.0321 seconds