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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.
331

Silné tvary raně středoanglických adjektiv z hlediska syntaktického a aktuálního členění větného / Strong adjectival forms in Early Middle English: a syntactic and FSP perspective

Kupková, Tereza January 2014 (has links)
The Master's thesis proceeds from a corpus-based analysis and focuses on strong forms of Early Middle English adjectives. A formal distinction between weak and strong adjectival forms had disappeared during the period of Middle English, the work, therefore, aims at the transitional period between Old and Middle English, when the strong forms could still be identified, either due to the relics of inflectional endings, syntactic position, or context. A representative sample of the most frequent adjectives was chosen from the corpus comprising the extant Middle English texts with help of specific searching code. Consequently, the strong forms were manually chosen from these according to their formal characteristics and position in the sentence. This sample was then analyzed from the syntactic point of view, as well as from the point of view of functional sentence perspective. The results of the analysis show that the indication of indefiniteness was mostly expressed by the mix of syntactic and contextual means in EME. It has also been found out that the adjectives, being used both attributively and predicatively, were by rule part of the rheme.
332

Localisation de la lumière et effets coopératifs dans des nuages d'atomes froids / Light localization and cooperative effects in cold atom clouds

Bellando de Castro, Louis 12 November 2013 (has links)
Ce travail de thèse présente une étude numérique et théorique de l’influence des effets coopératifs sur la localisation de la lumière dans des vapeurs atomiques, suivie d’une étude expérimentale de ces effets coopératifs dans le régime de diffusion multiple dans des nuages d’atomes froids dilués. Le premier chapitre décrit le modèle que nous utilisons, basé sur l’Hamiltonien effectif d’interaction matière rayonnement, afin d’étudier numériquement la localisation de la lumière et les effets coopératifs. Nous discutons également des différences fondamentales existant entre la situation réelle où la lumière est assimilée à une onde vectorielle et l’approximation scalaire plus facile à traiter analytiquement. Le deuxième chapitre se concentre sur la présentation des résultats numériques complétée d’une comparaison systématique entre les cas scalaire et vectoriel. Nous remarquons dans cette partie que l’approximation scalaire, valable dans la limite des milieux spatialement dilués, présente des différences drastiques avec le cas vectoriel lorsque nous considérons des milieux spatialement denses. Nous n’observons pas également d’indications suffisantes nous permettant de discriminer le fait que les effets coopératifs ne soient pas à la base des mécanismes de localisation de la lumière. Dans la dernière partie nous nous intéressons expérimentalement aux signatures des effets coopératifs dans le régime de diffusion multiple en confrontant à nos résultats expérimentaux plusieurs approches théoriques tenant compte ou pas des effets d’interférences. / In this thesis we present a numerical and theoretical study of the interplay between cooperative effects and light localization in atomic vapour, completed by an experimental study of these cooperative effects for dilute cold atom clouds in the multiple scattering regime. The first chapter describes the model we use, based on the light matter effective Hamiltonian, in order to investigate numerically light localization and cooperative effects. We also discuss the fundamental differences existing between the real situation where light is considered as a vector wave and its scalar approximation easier to treat analytically. The second chapter focuses on the numerical results where we compare systematically the scalar and the vector cases. We show that the scalar approximation, valid for spatially dilute systems, leads to drastic differences compared to the vector case when we consider spatially dense clouds. We also do not observe sufficient proofs to establish that cooperative effects are not at the origin of light localization mechanisms. In the last chapter we investigate experimentally the signatures of cooperative effects in the multiple scattering regime, comparing our results to several theoretical approaches taking or not into account interference effects related to the wave nature of light.
333

Controlling the dynamics of electrons and nuclei in ultrafast strong laser fields

Kling, Nora G. January 1900 (has links)
Doctor of Philosophy / Department of Physics / Itzik Ben-Itzhak / One ultimate goal of ultrafast, strong- field laser science is to coherently control chemical reactions. Present laser technology allows for the production of intense (>10[superscript]13 W/cm[superscript]2), ultrashort ( 5 fs), carrier-envelope phase-stabilized pulses. By knowing the electric field waveform, sub-cycle resolution on the order of 100's of attoseconds (1 as=10[superscript]-18 s) can be reached -- the timescale for electron motion. Meanwhile, the laser field strengths are comparable to that which binds electrons to atoms or molecules. In this intense-field ultrashort-pulse regime one can both measure and manipulate dynamics of strong-field, quantum-mechanical processes in atoms and molecules. Despite much progress in the technology, typical durations for which lasers can be reliably locked to a specific carrier-envelope phase ranges from a few minutes to a few hours. Experiments investigating carrier-envelope phase effects that have necessarily long data acquisition times, such as those requiring coincidence between fragments originating from the same atom or molecule, are thus challenging and uncommon. Therefore, we combined the new technology for measuring the carrier-envelope phase of each and every laser shot with other single-shot coincidence three-dimensional momentum imaging techniques to alleviate the need for carrier-envelope phase stabilized laser pulses. Using phase-tagged coincidence techniques, several targets and laser-induced processes were studied. One particular highlight uses this method to study the recollision process of non-sequential double ionization of argon. By measuring the momentum of the two electrons emitted in the process, we could study their energy sharing. Furthermore, by selecting certain carrier-envelope phase values, and therefore laser pulses with a particular waveform, events with single recollision could be isolated and further analyzed. Another highlight is our studies of carrier-envelope phase effects in the dissociation of the benchmark H[subscript]2[superscript[+] ion beam. Aided by near-exact quantum mechanical calculations, we could identify interfering pathways which lead to the observed spatial asymmetry. These and other similar experiments are described in this thesis as significant steps toward their ultimate control.
334

Ultrafast imaging: laser induced electron diffraction

Xu, Junliang January 1900 (has links)
Doctor of Philosophy / Department of Physics / Chii-Dong Lin / Imaging of molecules has always occupied an essential role in physical, chemical and biological sciences. X-ray and electron diffraction methods routinely achieve sub-angstrom spatial resolutions but are limited to probing dynamical timescales longer than a picosecond. With the advent of femtosecond intense lasers, a new imaging paradigm emerges in last decade based on laser-induced electron diffraction (LIED). It has been placed on a firm foundation by the quantitative rescattering theory, which established that large-angle e-ion elastic differential cross sections (DCS) can be retrieved from the LIED spectrum. We further demonstrate that atomic potentials can be accurately retrieved from those extracted DCSs at energies from a few to several tens of electron volts. Extending to molecules, we show mid-infrared (mid-IR) lasers are crucial to generate high-energy electron wavepackets (> 100 eV) to resolve the atomic positions in a molecule. These laser-driven 100 eV electrons can incur core-penetrating collisions where the momentum transfer is comparable to those attained in conventional keV electron diffraction. Thus a simple independent atom model (IAM), which has been widely used in conventional electron diffractions, may apply for LIED. We theoretically examine and validate the applicability of IAM for electron energies above 100 eV using e-molecule large-angle collision data obtained in conventional experiments, demonstrating its resolving powers for bond lengths about 0.05 angstrom. The Validity of IAM is also checked by an experimental LIED investigation of rare gas atoms in the mid-IR regime. We show that the electron’s high energy promotes core-penetrating collisions at large scattering angles, where the e-atom interaction is dominated by the strong short range atomic-like potential. Finally, we analyze the measured LIED spectrum of N[subscript]2 and O[subscript]2 at three mid-IR wavelengths (1.7, 2.0, and 2.3 μm). As expected, the retrieved bond lengths of N[subscript]2 at three wavelengths are about same as the equilibrium N[subscript]2 bond length. For O[subscript]2, the data is also consistent with a bond length contraction of 0.1 angstrom within 4-6 fs after tunnel ionization. This investigation establishes a foundation for this novel imaging method for spatiotemporal imaging of gas-phase molecules at the atomic scale.
335

An analysis of results of a high-resolution world ocean circulation model

Barton, Wesley A. 03 1900 (has links)
Approved for public release; distribution is unlimited / Results of a highly vectorized and multitasked model of the world ocean circulation were analyzed. This model which uses realistic physics, geometry, and forcing on a high-resolution grid, was run on the NCAR Cray X-MP/48 using a robust-diagnostic strategy. Twenty years of model integration using one-half degree horizontal resolution and 20 levels of vertical resolution were accomplished after 200 wall-clock hours at a maximum FORTRAN performance speed of 450 megaflops. Seven key regions of the world ocean were analyzed using an ocean model processor. A representation of the global ocean circulation emerged that compared well with observations and that included strong advective features, fronts, and subtropical meanders. A diagnostic analysis program was developed to analyze meridional heat and volume transports. The results in all basins appear to be reasonable when compared to the results of other studies. For example, an anomalous northward heat transport of 3.8 x 10 to the 14th power W at 30 deg in the South Atlantic compares favorably with the estimate of 4.2 x 10 to the 14th power W at 32 deg S by Bennett (1978) using hydrographic data. The results of simulations conducted in this study can be compared and contrasted against the results of future eddy-resolving simulations. Keywords: Digital simulation, Advection, Heat transport, Meridional volume transport, Oceanographic fronts, Meanders, Thermoclines, Finite difference analysis. Theses. (EDC) / http://archive.org/details/analysisofresult00bart / Lieutenant Commander, United States Naval Reserve
336

Capacitance spectroscopy in hydrogenated amorphous silicon Schottky diodes and high efficiency silicon heterojunction solar cells / Spectroscopie de capacité de diodes Schottky en silicium amorphe hydrogéné et de cellules photovoltaïques à haut rendement à hétérojonctions de silicium

Maslova, Olga 14 June 2013 (has links)
Les travaux développés dans cette thèse sont dédiés à l’étude des propriétés électroniques de diodes Schottky de silicium amorphe hydrogéné (a-Si:H) et d'hétérojonctions entre silicium amorphe hydrogéné et silicium cristallin, a-Si:H/c-Si au moyen de spectroscopies de capacité de jonctions.Lors de la fabrication des cellules solaires à haut rendement plusieurs paramètres d’une hétérojonction a-Si:H/c-Si doivent être considérés. Premièrement, la densité d’états dans le gap du a-Si:H est d’une grande importance car il s’agit de défauts qui favorisent le piégeage et la recombinaison de porteurs. Deuxièmement, la détermination des désaccords des bandes entre la couche amorphe et la couche cristalline est indispensable puisque ceux-ci contrôlent le transport à travers la jonction et déterminent la courbure des bandes dans c-Si, ce qui va notamment influencer la recombinaison des porteurs sous lumière, donc la tension de circuit ouvert des cellules. Cette thèse a pour but d’étudier la spectroscopie de capacité comme technique d'analyse de paramètres clés pour les dispositifs à hétérojonctions de silicium : la densité d’états dans le a-Si:H et les désaccords des bandes entre a-Si:H et c-Si.La première partie est dédiée à l’étude de la capacité de diodes Schottky. Nous nous concentrons sur un traitement simplifié de la capacité en fonction de la température et de la fréquence reposant sur une expression analytique obtenue par une résolution approchée de l'équation de Poisson. Ce traitement permet en principe d’extraire la densité d’états au niveau de Fermi dans le a-Si:H et la fréquence de saut des électrons depuis un état localisé au niveau de Fermi vers la bande de conduction. En appliquant ce traitement simplifié à la capacité calculée sans approximation à l'aide de deux logiciels de simulation numérique, nous montrons que sa fiabilité et sa validité dépendent fortement de la distribution des états localisés dans la bande interdite du a-Si:H et de la position du niveau de Fermi. Puis nous abordons l’étude de la capacité des hétérojonctions entre a-Si:H de type p et c-Si de type n, et nous mettons particulièrement en avant l’existence d'une couche d’inversion forte à l’interface dans le c-Si, formant un gaz bidimensionnel de trous. Dans une première partie, nous présentons une étude par simulation numérique de la dépendance de la capacité en fonction de la température, pour laquelle un ou deux échelons peuvent être mis en évidence à basse température. Leur analyse montre qu’un des ces échelons est attribué à l’activation de la réponse de la charge dans le a-Si:H, alors que l’autre, présentant une énergie d'activation plus grande, est lié à la modulation de la concentration des trous dans la couche d’inversion forte, lorsque celle-ci existe. On présente ensuite une discussion de résultats expérimentaux. Le régime quasi-statique de la capacité fait ainsi l’objet d’une discussion. Nous mettons en relief le fait que l’approximation de la zone de déplétion ne permet pas de reproduire cette augmentation de la capacité en fonction de la température. Du fait de l’existence de la couche d’inversion forte, la chute de potentiel dans la zone de déplétion du c-Si est plus faible que la valeur déterminée par le calcul attribuant toute la chute de potentiel à la zone de déplétion. Par conséquent, cette approximation conduit à sous-estimer la capacité ainsi que son augmentation avec la température. Nous présentons alors un calcul analytique complet qui tient compte à la fois de la distribution particulière du potentiel dans le a-Si:H, et des trous dans le c-Si dont la contribution à la concentration totale de charges n'est pas négligeable dans la couche d’inversion forte. Le calcul analytique complet permet de bien reproduire les résultats expérimentaux de capacité en fonction de la température; ceci confirme la présence de la couche d’inversion forte dans les échantillons étudiés. / In this thesis, research on a-Si:H Schottky diodes and a-Si:H/c-Si heterojunctions is presented with the focus on the capacitance spectroscopy and information on electronic properties that can be derived from this technique. Last years a-Si:H/c-Si heterojunctions (HJ) have received growing attention as an approach which combines wafer and thin film technologies due to their low material consumption and low temperature processing. HJ solar cells benefit from lower fabrication temperatures thus reduced costs, possibilities of large-scale deposition, better temperature coefficient and lower silicon consumption. The most recent record efficiency belongs to Panasonic with 24.7% for a cell of 100 cm² was obtained. The aim of this thesis is to provide a critical study of the capacitance spectroscopy as a technique that can provide information on both subjects: DOS in a-Si:H and band offset values in a-Si:H/c-Si heterojunctions.The first part of the manuscript is devoted to capacitance spectroscopy in a-Si:H Schottky diodes. The interest is concentrated on the simplified treatment of the temperature and frequency dependence of the capacitance that allows one to extract the density of states at the Fermi level in a-Si:H. We focus on the study of the reliability and validity of this approach applied to a-Si:H Schottky barriers with various magnitudes and shapes of the DOS. Several structures representing n-type and undoped hydrogenated amorphous silicon Schottky diodes are modeled with the help of numerical simulation softwares. We show that the reliability of the studied treatment drastically depends on the approximations used to obtain the explicit analytical expression of the capacitance in such an amorphous semiconductor.In the second part of the chapter, we study the possibility of fitting experimental capacitance data by numerical calculations with the input a-Si:H parameters obtained from other experimental techniques. We conclude that the simplified treatment of the experimentally obtained capacitance data together with numerical modeling can be a valuable tool to assess some important parameters of the material if one considers the results of numerical modeling and performs some adjustments. The second part is dedicated to capacitance spectroscopy of a-Si:H/c-Si heterojunctions with special emphasis on the influence of a strong inversion layer in c-Si at the interface. Firstly, we focus on the study of the frequency dependent low temperature range of capacitance-temperature dependencies of a-Si:H/c-Si heterojunctions. The theoretical analysis of the capacitance steps in calculated capacitance-temperature dependencies is presented by means of numerical modeling. It is shown that two steps can occur in the low temperature range, one being attributed to the activation of the response of the gap states in a-Si:H to the small signal modulation, the other one being related to the response of holes in the strong inversion layer in c-Si at the interface. The experimental behavior of C-T curves is discussed. The quasi-static regime of the capacitance is studied as well. We show that the depletion approximation fails to reproduce the experimental data obtained for (p) a-Si:H/(n) c-Si heterojunctions. Due to the existence of the strong inversion layer, the depletion approximation overestimates the potential drop in the depleted region in crystalline silicon and thus underestimates the capacitance and its increase with temperature. A complete analytical calculation of the heterojunction capacitance taking into account the hole inversion layer is developed. It is shown that within the complete analytical approach the inversion layer brings significant changes to the capacitance for large values of the valence band offset. The experimentally obtained C-T curves show a good agreement with the complete analytical calculation and the presence of the inversion layer in the studied samples is thus confirmed.
337

Structure and magnetic properties in half-doped manganites Ln0.5Ca0.5MnO3 (Ln=La, Pr, Nd, …, Lu) : A systematic study by neutron scattering and ab-initio calculations / Propriétés structurelles et magnétiques dans les composants de manganèse Ln0.5Ca0.5MnO3 (Ln=La, Pr, Nd, …, Lu) : Une étude systématique par diffusion des neutrons et calculs ab initio.

Pusceddu, Emanuela 16 May 2011 (has links)
Le but de ce travail était de réaliser une étude systématique de la structure électronique et magnétique de la famille des manganites semi-dopés du Ca: Ln0.50Ca0.50MnO3 (Ln=REE). Nous avons focalisé notre attention sur l'ordre de charge (CO) et l'ordre orbital (OO) présents dans les manganites. Nous avons dérivé un modèle microscopique de structure nucléaire et magnétique à partir de la diffraction neutronique sur les poudres (NPD) et de calculs ab-initio afin de comparer les résultats expérimentaux et les modèles numériques et comprendre ainsi le rôle de l'inhomogénéité chimique et magnétique dans ces systèmes. La modification de l'état de spin électronique et du métal de transition par le dopage correspond à une modification structurale de la géométrie du polyèdre de coordination des atomes autour du métal de transition, induisant des changements structurels de coopération. En contraste avec l'ordre par le dopage chimique, un désordre chimique intrinsèque est associé à l'élément de dopage sur le site A du perovskite (formule générale ABO3) où sont placés les ions trivalents (RE3+) et bivalents (Ca2+). Ceci est dû à la différence de rayon ionique et d'affinité chimique entre ces ions. Afin d'étudier systématiquement l'effet de la substitution au niveau du site A et la relation entre les propriétés structurales et magnétiques, plusieurs échantillons ont été caractérisés. Les résultats de NPD sont une étape fondamentale vers la compréhension de la relation entre les propriétés structurales et magnétique et sont une source de motivation pour l'étude de la structure magnétique et des phénomènes de CO/OO par des simulations ab-initio. L'effet Jahn-Teller, les interactions de double- et super-échange, et le modèle de Zener seront introduits. Les propriétés magnétiques macroscopiques ont été mesurées en fonction de la température á l'aide d'un SQUID. La technique microscopique principale utilisée pour cette étude a été la NPD. Les instruments utilisés à l'institut Laue Langevin à Grenoble, D20 et D1A, et la méthode de Rietveld utilisée pour affiner les données expérimentales et en extraire les informations structurales seront décrits. Les résultats expérimentaux correspondant à l'étude systématique sur les échantillons de manganites de Ln0.50Ca0.50MnO3 (Ln = Pr, Nd, Tb, Dy, Ho, Tm, Yb and Lu) et une description de leur préparation seront présentés. La susceptibilité magnétique mesurée jusqu'à 530 K présente un pic large à températures élevées correspondant à la température de CO (TCO). Nous définissons la nature des corrélations magnétiques au-dessus et en-dessous de TCO dans le cadre du modèle des polarons de Zener. Nous présentons la structure nucléaire et magnétique pour tous les échantillons en fonction de la température et les déformations dues au dopage et à l'effet du rayon ionique. Tous nos systèmes ont une configuration magnétique de type pseudo-CE à la plus basse température correspondant à un état de type CE avec un effet de canting. Nous décrirons les calculs ab-initio pour modéliser notre série : le programme VASP, utilisé pour les calculs, la théorie DFT, les approximations faite, comme le fonctionnelle d'échange-corrélation (GGA-PBE), la correction d'Hubbard (GGA+U) seront présentée. Les calculs ont été effectués pour confirmer les résultats expérimentaux et pour accéder à d'autres quantités significatives comme la densité d'états électroniques. Les simulations ont été effectuées avec la DFT spin-polarisée, le GGA-PBE, et la GGA+U, pour considérer la corrélation électronique forte. Nous avons choisi deux systèmes purs: CaMnO3 et NdMnO3. Deux systèmes semi-dopés (Ln=Nd et Lu), ont été considérés, parce que les composés avec le La et le Pr ont été déjà étudié (Picozzi, Anisimov), et nous suivons la série avec Ln=Nd, et l’outre parce que le Lu, à l'instar de La, est saturé au niveau de ses orbitales 4f et qu'il présente de surcroit le plus petit rayon ionique dans la série de lanthanides. / The aim of this work was to realize a systematic study of the electronic and magnetic structure of Ca half-doped manganite family: Ln0.50Ca0.50MnO3 (Ln=REE). In particular, we focused our attention on charge ordering (CO) and orbital ordering (OO) phenomena present in manganites. We derived a microscopic model of nuclear and magnetic structure using both neutron powder diffraction (NPD) techniques and ab-initio calculations in order to compare experimental results and numerical models and to understand the role of chemical and magnetic in-homogeneity in our systems. The change of the electronic and spin state of the transition metal by doping, corresponds to a structural modification of the coordination polyhedron geometry of the atoms around the transition metal, inducing cooperative structural changes. In contrast with this order induced by doping, an intrinsic chemical disorder is associated with the doping element on the A site of the perovskite (general formula ABO3) on which the trivalent (RE3+) and divalent ions (Ca2+) reside. This disorder is due to the difference of the ionic radius and chemical affinity between the ions. In order to study systematically the effect of the A site substitution and the relation between the structural properties and the macroscopic magnetic properties, several samples have been synthesized and characterized by macroscopic magnetic measurements. Neutron diffraction is a fundamental step towards understanding the relation between the structural and macroscopic properties. The resulting structures represent a good starting point for ab-initio calculations in the study of magnetic structure and CO/OO phenomena. Important concepts and models are described: Jahn-Teller effect, double and super-exchange interaction and the Zener polarons model. The macroscopic magnetic properties have been measured versus temperature by using a SQUID magnetometer. The principal microscopic technique used for this thesis was NPD. The technique and the layout of the instruments - D20 and D1A at the Institute Laue Langevin, Grenoble - are described together with details of the Rietveld method used to refine the diffraction data. Experimental results from the systematic study of the Ln0.50Ca0.50MnO3 (Ln = Pr, Nd, Tb, Dy, Ho, Tm, Yb and Lu) manganites, are presented, with a description of sample preparation. The magnetic susceptibility, measured up to 530 K for our samples, presents a broad peak at high temperatures corresponding to the onset of the CO (TCO). From these results we define the nature of the magnetic correlations above and below TCO in the framework of the Zener polarons model. We also present the details of the nuclear and magnetic structure for all samples versus temperature, analyzing the distortions due to the doping and the effect of the ionic radius of the cations. All our samples have a pseudo-CE magnetic configuration at the lowest temperatures, corresponding to a CE-type ground state with canting. We describe the ab-initio method using the density functional theory (DFT), that have been used to model the Ln0.50Ca0.50MnO3 series. We present DFT and we discuss the most important features (spin polarization), approximations (pseudo-potentials and exchange-correlation functional) and (Hubbard) corrections used in this work, including a presentation of the VASP code used for the DFT calculations, with the corresponding input files. These calculations have been performed to confirm our experimental results and to access other significant quantities such as the electronic density of states. The computational approach has been tested on two pure systems: CaMnO3 and NdMnO3. Two half-doped systems have been chosen with Ln=Nd and Lu. The first because the La and Pr compounds were already studied (Picozzi, Anisimov) so we continued the series with the Nd system, and the Lu has the smallest ionic radius in the lanthanides series, its 4f shell is full and Lu is therefore comparable with La.
338

Perturbation theory for string sigma models

Bianchi, Lorenzo 22 February 2016 (has links)
In dieser Arbeit untersuchen wir Quanten-Aspekte des Green-Schwarz Superstrings in verschiedenen AdS-Hintergründen, die für die AdS/CFT Korrespondenz von Bedeutung sind, und geben einige Beispiele für perturbative Rechnungen in den entsprechenden integrablen Sigma-Modellen. Wir beginnen mit einer detaillierten Darstellung der Konstruktion der Wirkung des Typ-IIB-Superstrings auf dem AdS5 x S5-Hintergrund, die durch eine Supercoset-Sigma-Modell definiert wird, und zeigen die Grenzen dieser Herangehensweise für Hintergründe auf, die in niedrig-dimensionalen Beispielen der Eich/Gravitations-Dualität von Interesse sind. Daraufhin betrachten wir die Entwicklung um das BMN-Vakuum und die S-Matrix für die Streuung von Weltflächen-Anregungen. Um ihre Elemente effizient auszuwerten, entwickeln wir eine auf Unitarität basierende Methode für allgemeine massive, zweidimensionale Feldtheorien. Weiterhin betrachten wir den AdS-Lichtkegel eichfixierten String in AdS4 x CP3 in einer Entwicklung um das "null-cusp"-Vakuum. Die freie Energie dieses Modells hängt zusammen mit der anomalen Cusp-Dimension der Eichtheorie. Wir berechnen Korrekturen zur Zustandssumme des Superstring-Modells und leiten somit die anomale Cusp-Dimension der ABJM-Theorie bei starker Kopplung bis zur Zweischleifen-Ordnung her. Schlie\sslich berechnen wir auf Einschleifen-Ebene die Dispersionsrelation von Anregungen um das GKP-Vakuum. Unsere erfolgreiche Anwendung von auf Unitarität basierenden Cut-Techniken auf verschiedene Beispiele stützt die Vermutung, dass die S-Matrizen zweidimensionaler, integrabler Feldtheorien cut-konstruierbar sind. Weiterhin liefern unsere Ergebnisse wertvolle Daten, die die Konsistenz der String-Wirkung auf Quanten-Niveau belegen und stellen nicht-triviale stringente Tests der Quanten-Integrabilität der untersuchten Modelle dar. / In this thesis we investigate quantum aspects of the Green-Schwarz superstring in various AdS backgrounds relevant for the AdS/CFT correspondence, providing several examples of perturbative computations in the corresponding integrable sigma-models. We start by reviewing in details the construction of the type IIB superstring action in AdS5 x S5 background defined as a supercoset sigma model, pointing out the limits of this procedure for backgrounds interesting in lower-dimensional examples of the gauge/gravity duality. We then consider the expansion about the BMN vacuum and the S-matrix for the scattering of worldsheet excitations. To evaluate its elements efficiently we develop a unitarity-based method for general massive two-dimensional field theories. We also analyze the AdS light-cone gauge fixed string in AdS4 x CP3 expanded around a “null cusp” vacuum. The free energy of this model is related to the cusp anomalous dimension of the gauge theory and, indirectly, to a non-trivial effective coupling entering all integrability-based calculations in AdS4/CFT3. We calculate corrections to the superstring partition function of the model, thus deriving the cusp anomalous dimension of ABJM theory at strong coupling up to two-loop order and giving support to a recent conjecture. Finally, we calculate at one-loop the dispersion relation of excitations about the GKP vacuum. Our successful application of unitarity-cut techniques on several examples supports the conjecture that S-matrices of two-dimensional integrable field theories are cut-constructible. Furthermore, our results provide valuable data in support of the quantum consistency of the string actions and furnish non-trivial stringent tests for the quantum integrability of the analyzed models.
339

Mat- och tekniknytt : Kommunikation och informationsspridning för ökad innovation inom gotländska livsmedelsförädlingsindustrin

Axner, Tom, Zetterlund, Philip January 2019 (has links)
Hållbarhet är ett ämne som konstant är på dagens agenda. Många länder gör idag omställningar föratt nå de uppsatta klimatmålen inom FN, EU och på en nationell nivå. Gotland Grönt Centrum är enaktör på Gotland som genom sitt projekt “Ökad livsmedelsförädling” drar sitt strå till stacken för att ökaden hållbara utvecklingen på ön. Gotland Grönt Centrum vill öka kunskapsspridningen ochinnovationsgraden inom den gotländska livsmedelsförädlingsindustrin genom att upprätta enFacebooksida där aktörer kan mötas. Forskningsfrågan för uppsatsen är därför fokuserad på hurkommunikationen bör se ut för att nå de uppsatta målen i GGC:s projekt. Genom en kvalitativ studieämnar denna uppsats besvara forskningsfrågan genom teorier om social network theory,sensemaking, strukturella hål med flera för att sedan mynna ut i en slutsats. Genom en kodning avempirin kunde analysen visa flera aspekter som är vitala för att GGC ska kunna föra en framgångsrikkommunikation för att nå sina mål. Svaret blev att genom att arbeta med sensemaking för att formasitt budskap efter målgruppen kan engagemanget gentemot projektet öka. Detta kan leda till eninstitutionalisering och gemensam förståelse, vilket kan leda till framtida samarbeten mellan aktörer.Innovationsgraden kan dessutom öka ifall GGC antar en roll som länk och gränsöverskridare inomnätverket för att överbrygga strukturella hål och således få in ny information i flödet. / Sustainability is a topic that is constantly on the agenda of today. Many countries today are makingadjustments to achieve the set climate goals within the UN, the EU and at a national level. GotlandGrönt Centrum is an regional actor on Gotland, which through its project "Increased food processing"aim to increase the sustainable development on the island. Gotland Grönt Centrum wants to increasethe dissemination of knowledge and the degree of innovation within Gotland’s food processingindustry by establishing a platform where players can meet. The research question for the essay istherefore focused on how the communication should be formulated to achieve the set goals in theGGC project. Through a qualitative study, this paper aims to answer the research question throughtheories of social network theory, sensemaking, structural holes, and more, in order to draw aconclusion. Through the coding of the empirical data, the analysis could show several aspects thatare vital for GGC to be able to conduct successful communication in order to achieve its goals. Theanswer was that by working with sensemaking to shape their message according to the target group,the commitment to the project can increase. This can lead to institutionalization and mutualunderstanding, which can lead to future collaboration between actors. The degree of innovation canalso increase if GGC assumes a role as a link and boundary spanner within the network to bridgestructural holes and thus bring in new information in the flow.
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HoloGo: um modelo de mobilidade de código orientado ao holoparadigma / Hologo: a strong code mobility model focused on the holoparadigm

Lermen, Gustavo 15 March 2007 (has links)
Made available in DSpace on 2015-03-05T13:58:26Z (GMT). No. of bitstreams: 0 Previous issue date: 15 / Nenhuma / A rápida popularização de dispositivos computacionais cada vez mais poderosos está trazendo a computação móvel para um grande número de pessoas. Na medida em que os dispositivos ganham mais poder computacional, diferentes aplicações podem ser desenvolvidas de modo a atender as necessidades de um número cada vez maior de usuários. Esta evolução, entretanto, não é livre de desafios. Com o aumento do número de usuários, a demanda por customização torna-se uma questão chave. Entre as soluções que oferecem a customização encontra-se a mobilidade de código. Neste sentido esta dissertação apresenta um modelo de mobilidade forte de código orientado ao Holoparadigma. Até então somente a mobilidade lógica era suportada, estando à mobilidade de código apenas na especificação. Este modelo é chamado HoloGo e foi desenvolvido tendo como base a HoloVM, uma máquina virtual com suporte a blackboards e programação concorrente. A validação deste modelo ocorreu através da implementação de um protótipo que foi utilizado no desen / The rapid popularization of increasingly powerful computational devices is setting the mobile computing into daily life of a great number of people. As devices evolve along with its computational power, many applications can be developed in order to accomplish the different needs of a growing number of users. This evolution, however, it is not free of challenges. As the number of users increase, the need of customization becomes a major concern. Among the solutions that offer customization to software applications is code mobility. In this way, this dissertation presents a strong code mobility model focused in the Holoparadigm. Until now only logical mobility was provided, being the code mobility only in the specification. This model is called HoloGo and was developed on top of HoloVM, a virtual machine with blackboards and concurrent programming support. HoloGo was validated through the implementation of a prototype used in the development of applications that use code mobility. In this context, the main con

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