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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.
161

AdS/CFT Correspondence and Hydrodynamics of Relativistic Heavy Ion Collisions

Alsup, James Ethan 01 August 2010 (has links)
The experiments performed at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab have discovered a state of matter called the strongly coupled quark-gluon plasma (sQGP). The strong coupling has limited the ability of the standard theory to describe such matter, namely Quantum Chromodynamics (QCD). However, string theory's anti-de Sitter/conformal field theory (AdS/CFT) correspondence has provided a new way to study the situation and in an analytical manner. So far, hydrodynamic properties of RHIC's plasma, such as elliptic flow and longitudinal expansion, have been seen to follow from classical supergravity calculations. In this dissertation I discuss some of the field's development as well as the research done by the author and collaborators.
162

Amélioration du modèle de cascade intranucléaire de Liège en vue de l'étude de cibles de spallation pour les systèmes hybrides

Aoust, Thierry 22 June 2007 (has links)
Lintérêt pour les réactions de spallation comme source intense de neutrons sest renouvelé ces dix dernières années avec les études de transmutation des actinides mineurs dans les systèmes hybrides (ADS). Parmi les modèles de réaction de spallation, le modèle de cascade intranucléaire de Liège (INCL), couplé au modèle dévaporation ABLA, sest révélé être lun des plus prédictifs pour des nucléons incidents de 200 MeV à quelques GeV. Cependant le modèle INCL présente encore quelques lacunes et fait donc encore lobjet de développements. Dans cette thèse nous avons tenté de remédier aux points suivants: - évaluation du pic quasi-élastique en introduisant la dépendance en isospin et en énergie du champ nucléaire moyen des baryons, - les voies faisant intervenir les pions en étendant les sections efficaces pion-nucléon de part et dautre de la résonnance D et en introduisant un potentiel moyen pour les pions déterminé par ajustement sur de nombreuses données expérimentales de production de pions et induites par des pions. En vue de lextension du modèle INCL aux basses énergies nous avons également comparé ce modèle à des modèles de prééquilibre, en théorie mieux adaptés pour des énergies incidentes comprises entre 10 et 200 MeV. Finalement nous avons étudié limpact de nos investigations pour létude de cibles de spallation épaisses et dADS. Le résultat le plus important de nos recherches tant pour des cibles minces que pour la conception de cibles épaisses, est une nette amélioration (réduction) de lestimation des isotopes hautement radiotoxiques du Po à partir de cibles en Bi.
163

Mobiltelefonin, det sjunde massmediet : Mobiltelefonens lämplighet som relationsmarknadsföringskanal.

Eriksson, Daniel, Andersson, Fredrik January 2009 (has links)
Den här uppsatsen behandlar mobilmarknadsföring och ämnar svara på frågan om hur lämplig mobiltelefonen egentligen är som relationsmarknadsföringskanal. Vi har funnit de metoder som är vanligast förekommande för att sprida reklambudskap och jämför hur bra de uppfyller kraven för att vara relationsskapande. För att utröna detta har vi intervjuat branschkunniga personer från två av landets största mobiloperatörer samt personer som arbetar på nordiska mobilmarknadsföringsbyråer. För att mäta styrkan hos mobilmarknadsföring som relationsfrämjande marknadskanal har vi genom modeller från relationsmarknadsföringen skapat ett eget ramverk vilket vi applicerat på olika marknadsföringsmetoder via mobiltelefonen. Resultatet av vår studie visar på att mobilmarknadsföring kan användas för att bygga långsiktiga, ömsesidiga och vinstgivande relationer, vid rätt användning. Den metod som uppfyllde kriterierna bäst var applikationer. Övriga metoder som vi undersökte kan till viss del användas som komplement inom ramen för relationsmarknadsföring. Vi belyser även att mobilmarknadsföring verkar på en omogen marknad där tekniska aspekter, kunskapsöverföring och standardiseringar måste byggas ut för att genomslagskraften av mobiltelefonen som hjälpmedel inom relationsmarknadsföring ska bli så stor som möjligt. / This thesis is dealing with mobile marketing and the aim is to answer the question: how suitable is the mobile phone as a relationship marketing channel. We have located the methods that are most common to deliver the marketing message and we are comparing them with the criteria’s that we found necessary for creating relationships. In order to determine these methods and criteria’s we’ve been conducting interviews with people working in this business, both Swedish mobile network operators and employees from Nordic mobile marketing firms. We have been using existing models from relationship marketing to create our own framework in order to determine the strength of mobile marketing as a relationship creating market channel. Our study shows that mobile marketing if used in the right way can be used in order to establish long-lasting, mutual and profitable relations. The method that fulfilled most of the criteria’s was application. The other methods that we investigated are more suitable to be used as complement to other tools. Our investigation also shows that the mobile marketing market is immature and technical issues, knowledge transfer and standards have to be established in order to create a breakthrough for the mobile phone as a tool for relationship marketing.
164

Etude de systèmes et scénarios électronucléaires double strate de transmutation des actinides mineurs en ADS

Clavel, Jean-Baptiste 30 November 2012 (has links) (PDF)
La loi française du 28 juin 2006, sur la gestion des déchets radioactifs, demande une évaluation pour définir la future stratégie industrielle. L'étude présentée ici, concerne plus spécifiquement l'axe de recherche sur la transmutation des actinides mineurs. Dans ce but, un concept d'ADS (Accelerator DrivenSystem) de haute puissance a été développé à SUBATECH. Dans ce réacteur sous-critique, un faisceau de protons de 1 GeV alimente trois cibles de spallation de plomb-bismuth. L'ADS MUST (MUltipleSpallation Target) peut ainsi atteindre une puissance thermique de plus de 1 GW avec une densité de puissance élevée. Une méthode de dimensionnement de ces réacteurs a été développée et appliquée pour différents scénarios double strate. Dans ces scénarios, des réacteurs électrogènes de type SFR (Sodium Fast Reactors) ou REP (Réacteurs à Eau Pressurisée) produisent des actinides mineurs destinés à être transmutés en ADS. Dans chaque cœur, un multi-recyclage du plutonium est réalisé et dans les réacteurs sous-critiques les éléments à transmuter le sont également. Pour limiter la réactivité du cœur et améliorer la conductivité thermique, le combustible contenant les actinides mineurs est mélangé à une matrice inerte de MgO. Des filières, avec des ADS à caloporteurs plomb et sodium, ont été étudiées pour différentes durées d'irradiation, et deux stratégies de transmutation : soit l'ensemble des actinides mineurs, soit seulement l'américium est incinéré. Le dimensionnement des ADS MUST de chaque filière et de leur combustible à l'équilibre est présenté dans cette thèse. Puis l'évolution du combustible et du coefficient de multiplication, sur un cycle, est réalisée et analysée. La radiotoxicité et la puissance thermique des déchets produits sont ensuite comparées. Enfin, l'étude de scénarios double strate est effectué afin d'analyser les inventaires d'actinides mineurs et de plutonium en cycle, ainsi que les déchets produits en fonction de la stratégie de transmutation adoptées et de l'évolution de la première strate.
165

Design and Simulation of Microstrip Phase Array Antenna using ADS

Khattak, Muhammad Kamran, Siddique, Osama, Ahmed, Waqar January 2011 (has links)
The aim of this project is to design a microstrip phase array antenna in ADS (Advance Design System) Momentum. The resonant frequency of which is 10 GHz. Two circular patches with a radius of 5.83 mm each are used in designing the array antenna. RT-DURROID 5880 is used as a substrate for this microstrip patch array design. These circular patches are excited using coaxial probe feed and transmission lines of particular lengths and widths. These transmission lines perfectly match the impedance of the circular patches. Various parameters, for example the S-parameters, two dimensional and three dimensional radiation patterns, excitation models, gain, directivity and efficiency of the designed antenna are obtained from ADS Momentum.
166

Design and simulation of beam steering for 1D and 2D phased antenna arrays using ADS.

Afridi, Muhammad Zeeshan, Umer, Muhammad, Razi, Daniyal January 2012 (has links)
Phased arrays eliminate the problems of mechanical steering by using fast and reliable electronic components for steering the main beam. Modeling and simulation of beam steering for 1D and 2D arrays is the aspect that is considered in this thesis. A 1D array with 4 elements and a 2D array with 16 elements are studied in the X-band (8-12 GHz). The RF front-end of a phased array radar is modeled by means of ADS Momentum (Advanced design system).
167

Characterisation of a data transmission link / Characterisation of a data transmission link

Johansson, Christian, Karlsson, Marcus January 2004 (has links)
This report is the result of a Master Thesis work that has been performed between October 2003 and March 2004. The purpose of the work was to evaluate a part of the signal chain in a product of Micronic Laser Systems AB. The evaluation was performed to obtain the characterisation for the signal chain, such as impedances and crosstalk. The work started with a literature study in order to refresh and increase the knowledge that was needed before the practical work. Then measurements, computer aided simulations and comparisons between these were performed. Measurements were performed using TDR (Time Domain Reflectometry). The results showed the impedance levels along the signal chain. This was interesting since it showed how well the different parts in the system are matched. Unmatched parts result in reflections that disturb the transmitted signal and contribute to crosstalk, which also was measured. Simulations were done using ADS (Advance Design System), a tool from Agilent Technologies Inc. A substantial part of the simulation work was to build models of the real system. These models have been used for simulation. The simulation results were then compared to the measurement results. The results show that the system can be better matched concerning the channel impedance. There are large variations in impedance levels along the signal chain, resulting in signal reflections. Another effect studied is crosstalk between channels. Measurements and simulations showed the presence of crosstalk but it seems to be a minor problem in the current machine.
168

Taub-NUT Spacetime in the (A)dS/CFT and M-Theory

Clarkson, Richard January 2005 (has links)
In the following thesis, I will conduct a thermodynamic analysis of the Taub-NUT spacetime in various dimensions, as well as show uses for Taub-NUT and other Hyper-Kahler spacetimes. <br /><br /> Thermodynamic analysis (by which I mean the calculation of the entropy and other thermodynamic quantities, and the analysis of these quantities) has in the past been done by use of background subtraction. The recent derivation of the (A)dS/CFT correspondences from String theory has allowed for easier and quicker analysis. I will use Taub-NUT space as a template to test these correspondences against the standard thermodynamic calculations (via the N&ouml;ether method), with (in the Taub-NUT-dS case especially) some very interesting results. <br /><br /> There is also interest in obtaining metrics in eleven dimensions that can be reduced down to ten dimensional string theory metrics. Taub-NUT and other Hyper-Kahler metrics already possess the form to easily facilitate the Kaluza-Klein reduction, and embedding such metrics into eleven dimensional metrics containing M2 or M5 branes produces metrics with interesting Dp-brane results.
169

Consumer response to ads in social network sites : an exploration into the role of ad location and path

Bang, Hye Jin 13 September 2013 (has links)
Past research repeatedly suggests consumer’s defensive response to persuasive attempts is a key challenge for advertisers. Given the explosive growth of social media, this study aims to understand if consumer response to ads placed in a social network site could be influenced by ad location and the path through which the ad is delivered. Findings from an experiment suggest that consumers’ attention to ads in SNSs is remarkably low. Furthermore, the interaction between ad location and the path significantly influences consumers’ attitudes toward the ad, attitudes toward the brand, and purchase intention. Specifically, it appears that an ad placed inside users’ timeline and sent through via known others, the indirect path, yielded favorable consumer response. On the other hand, consumers responded more favorably to an ad sent by the advertiser, the direct path, than that sent by known others if the ad is placed outside users’ timeline. Implications and suggestions for future research are provided. / text
170

Effect of Curvature Squared Corrections to Gravitational Action on Viscosity-to-Entropy Ratio of the Dual Gauge Theory

Petrov, Pavel January 2012 (has links)
In this thesis we study the properties of strongly-coupled large-N conformal field theories (CFT’s) using AdS/CFT correspondence. Chapter 1 serves as an introduction. In Chapter 2 we study the shear viscosity of strongly-coupled large-N conformal field theories. We find that it is affected by \(R^2\) corrections to the AdS action and present an example of 4D theory in which the the conjectured universal lower bound on viscosity-to-entropy ratio \(\eta/s > 1/4 \pi\) is violated by 1/N corrections. This fact proves that there is no universal lower bound of \(1/4 \pi\) on viscosity-to-entropy ratio and may be relevant for the studies of QCD quark-gluon plasma for which this ratio is experimentally found to be close to \(1/4 \pi\). In Chapter 3 we study the formation of the electron star in 4D AdS space. We show that in a gravity theory with charged fermions a layer of charged fermion fluid may form at a finite distance from the charged black hole. We show that these “electron stars” are candidate gravity duals for strongly interacting fermion systems at finite density and finite temperature. Entropy density for such systems scales as \(s \sim T^{2/z}\) at low temperatures as expected from IR criticality of electron stars solutions. / Physics

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