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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.
31

Examining Argumentative Coherence in Essays by Undergraduate Students of English as a Foreign Language in Mainland China and Their English Speaking Peers in the United States

Gao, Lianhong 16 February 2012 (has links)
I conducted this study to provide insights toward deepening understanding of association between culture and writing by building, assessing, and refining a conceptual model of second language writing. To do this, I examined culture and coherence as well as the relationship between them through a mixed methods research design. Coherence has been an important and complex concept in ESL/EFL writing. I intended to study the concept of coherence in the research context of contrastive rhetoric, comparing the coherence quality in argumentative essays written by undergraduates in Mainland China and their U.S. peers. In order to analyze the complex concept of coherence, I synthesized five linguistic theories of coherence: Halliday and Hasan’s cohesion theory, Carroll’s theory of coherence, Enkvist’s theory of coherence, Topical Structure Analysis, and Toulmin’s Model. Based upon the synthesis, 16 variables were generated. Across these 16 variables, Hotelling t-test statistical analysis was conducted to predict differences in argumentative coherence between essays written by two groups of participants. In order to complement the statistical analysis, I conducted 30 interviews of the writers in the studies. Participants’ responses were analyzed with open and axial coding. By analyzing the empirical data, I refined the conceptual model by adding more categories and establishing associations among them. The study found that U.S. students made use of more pronominal reference. Chinese students adopted more lexical devices of reiteration and extended paralleling progression. The interview data implied that the difference may be associated with the difference in linguistic features and rhetorical conventions in Chinese and English. As far as Toulmin’s Model is concerned, Chinese students scored higher on data than their U.S. peers. According to the interview data, this may be due to the fact that Toulmin’s Model, modified as three elements of arguments, have been widely and long taught in Chinese writing instruction while U.S. interview participants said that they were not taught to write essays according to Toulmin’s Model. Implications were generated from the process of textual data analysis and the formulation of structural model defining coherence. These implications were aimed at informing writing instruction, assessment, peer-review, and self-revision.
32

Perceptual processing in autism : an investigation of face processing

Rouse, Helen January 2003 (has links)
No description available.
33

The Role of Early Visual Cortex in Global Motion Processing

Green, Marshall L 14 December 2018 (has links)
Both visual area V1 and the medial temporal (MT) region of the human brain play a role in motion perception. V1 is thought to process "local motion," such as the movement of a single bird flying across a relatively small part of space, while MT is thought to process "global motion," such as the movement of an entire flock of birds flying across the sky. However, recent studies using fMRI to measure human brain activity have identified signals in V1 that appear to be global motion signals, although it is unclear whether these are related to global motion processing or stem from some other process. In two experiments, a series of stimulus manipulations were conducted to determine the extent to which these signals in V1 really reflect global motion. Although initial results have so far proven inconclusive, they highlight discrepancies between previous results, suggesting that these motion signals in V1 may be more interesting than researchers have assumed.
34

Development of optical sources for optical coherence tomography

Beitel, David January 2007 (has links)
No description available.
35

A Quest for Coherence: A Study of Internal Quotations in the Book of Job

Ho, Edward January 2012 (has links)
The book of Job is well-known for its internal tensions. The major challenge of interpreting this work is to provide a coherent reading of the whole narrative while giving the conflicting elements their due. The purpose of this dissertation is thus twofold. First, this study seeks to defend the intrinsic cohesiveness of the book of Job. Second, it attempts to demonstrate that a reading guided by these internal verbal and thematic connections is able to produce a coherent meaning of this literary masterpiece. This dissertation offers a section-by-section reading of the book of Job. In each section, I conduct a two-phase analysis. In the first phase, I identify the literary connections between the passage under study and those which come before it, and reflect on the way the antecedent texts are being reused. In the second phase, I discern the impact that the insights from the first phase of analysis make upon the reading process of the passage under study and examine how the resulting interpretation contributes to the development of the story up to that point. In order to facilitate the discussion, I borrow some insights from literary critic James Phelan, who views narrative as rhetoric. Phelan argues that the author of a narrative cultivates the interests of the reader by means of two types of unstable relations. The first, called instabilities, are those occurring within the story, conflicts between characters, created by situations, and complicated and resolved through actions. The second, called tensions, are conflicts ofvalue, belief, opinion, knowledge, expectation between the author and the reader. The development oftensions and instabilities in tum guide the reader to establish a coherent configuration ofthe narrative. This dissertation demonstrates that a satisfactory reading experience of the book of Job can be attained at both the narrative and the rhetorical levels. The analysis reveals that the central problem ofthe book is appropriate religious expressions in the context of suffering. / Thesis / Doctor of Philosophy (PhD)
36

Coherent spaces, Boolean rings and quantum gates

Vourdas, Apostolos 26 July 2016 (has links)
Yes / Coherent spaces spanned by a nite number of coherent states, are introduced. Their coherence properties are studied, using the Dirac contour representation. It is shown that the corresponding projectors resolve the identity, and that they transform into projectors of the same type, under displacement transformations, and also under time evolution. The set of these spaces, with the logical OR and AND operations is a distributive lattice, and with the logical XOR and AND operations is a Boolean ring (Stone's formalism). Applications of this Boolean ring into classical CNOT gates with n-ary variables, and also quantum CNOT gates with coherent states, are discussed.
37

Partial Coherence and Optical Vortices

Maleev, Ivan 13 July 2004 (has links)
"Optical vortices are singularities in phase fronts of optical beams. They are characterized by a dark core in the center and by a helical wave front. Owing to azimuthal components of wave vectors, an optical vortex carries orbital angular momentum. Previously, optical vortices were studied only in coherent beams with a well-defined phase. The object of this dissertation is to explore vortices in partially coherent systems where statistics are required to quantify the phase. We consider parametric scattering of a vortex beam and a vortex placed on partially coherent beam. Optical coherence theory provides the mathematical apparatus in the form of the mutual coherence function describing the correlation properties of two points in a beam. Experimentally, the wave-front folding interferometer allows analysis of the cross-correlation function, which may be used to study partial coherence effects even when traditional interferometric techniques fail. We developed the theory of composite optical vortices, which can occur when two coherent beams are superimposed. We then reported the first experimental observation of vortices in a cross-correlation function (which we call spatial correlation vortices). We found numerically and experimentally how the varying transverse coherence length and position of a vortex in a beam may affect the position and existence of spatial correlation vortices. The results presented in this thesis offer a better understanding of the concept of phase in partially coherent light. The spatial correlation vortex presents a new tool to manipulate coherence properties of an optical beam."
38

Coherent transfer of electron spins in tunnel-coupled quantum dots / Transport cohérent des spins d’électrons dans des boîtes quantiques couplées

Flentje, Hanno 26 September 2016 (has links)
De récentes avancées technologiques laissent entrevoir le potentiel des spins électroniques uniques comme supports pour le stockage et la manipulation de l'information. En raison de leur nature quantique, les spins électroniques contrôlé à l’échelle de l’électron unique peuvent non seulement être utilisés pour stocker l'information classique, mais pourraient également être mis en œuvre pour réaliser des qubits dans un ordinateur quantique. Dans un tel dispositif, les superpositions de différents états de spin peuvent être utilisées pour calculer plus efficacement que les ordinateurs classiques.Une mise en œuvre prometteuse d'un tel système est un électron piégé dans une boite quantique latérale. Ce dispositif nanométrique défini dans des structures semiconductrices permet d'isoler et de manipuler le spin d’un électron de façon cohérente avec des potentiels électrostatiques. Dans cette thèse, nous manipulons les électrons dans des boites quantiques dans un régime dit « isolé». La manipulation de charges électroniques individuelles en plusieurs boites quantiques connectées entre elles apparaît alors être simplifiée. Cette manipulation de spin se fait grâce à l’échange cohérent d’un quantum de spin entre deux électrons piégés. Le contrôle du couplage tunnel entre ces deux boites quantiques rend cet échange contrôlé. De cette façon, la manipulation de spin peut se faire à un "sweet spot", un point insensible au bruit de charge, permettant ainsi d'obtenir des oscillations de spin de haute qualité.Le contrôle précis de la charge dans le régime isolé est ensuite utilisé pour contrôler le déplacement d’un électron dans un système circulaire de trois boites quantiques qui sont fortement couplées par effet tunnel. Ainsi la cohérence d'une superposition de deux spins électroniques déplacée le long d’une boucle fermée a été étudiée. Nos mesures montrent le transport cohérent de spins électroniques uniques sur des distances allant jusqu'à 5 μm. Pendant le transfert, le temps de cohérence se révèle être considérablement augmenté. Nous avons identifié le mécanisme sous-jacent à cette amélioration comme provenant d’un rétrécissement, lors du mouvement, des gradients de champ nucléaires générées par l'environnement cristallin. Les sources de décohérence sont discutées et permettent d’obtenir de nouvelles connaissances sur la dynamique interne du processus de transfert entre des boites quantiques couplées. Nos résultats sur le transport cohérent d'électrons peuvent être utilisés pour évaluer les possibilités d’intégration à grande échelle de qubits de spin dans des réseaux de boites quantiques à deux dimensions. / Recent technological advances hint at the future possibility to use single electron spins as carriers and storage of information. Due to their quantum nature, individually controlled electron spins can not only be used to store classical information, but could also find implementation as quantum bits in a quantum computer. In this envisioned device, the superposition of different spin states could be used to perform novel calculation procedures more efficiently than their classical counterparts.A promising implementation of a controllable single electron spin system is an electron trapped in a lateral quantum dot. This nanoscale solid state device allows to isolate and coherently manipulate the spin of individual electrons with electrostatic potentials. In this thesis we study electrons in quantum dot structures using a manipulation technique which we call the "isolated regime". In this regime the manipulation of individual electron charges in several connected quantum dots is shown to be simplified. This allows to implement a novel spin manipulation scheme to induce coherent exchange of a quantum of spin between two electrons via a variation of the tunnel-coupling between adjacent quantum dots. This manipulation scheme is observed to lead to a reduced sensibility to charge noise at a "sweet spot" and thereby allows to obtain high quality spin oscillations.The improved charge control in the isolated regime is then used to achieve circular coupling in a triple quantum dot device with high tunnel-rates. This allows to directly probe the coherence of a superposition of two electron spins which are displaced on a closed loop in the three quantum dots. Our measurements demonstrate coherent electron transport over distances of up to 5 μm. During the transfer the coherence time is found to be significantly increased. We identify the underlying mechanism for the enhancement with a motional narrowing of the nuclear field gradients originating from the crystal environment. The limiting decoherence source is found to be single electron spin-flips induced by a real space motion of the electrons. Our results on the coherent transport of electrons can be used to asses the scaling possibilities of spin qubit implementations on two-dimensional lattices.
39

Temporal relations in English and German narrative discourse

Schilder, Frank January 1997 (has links)
Understanding the temporal relations which hold between situations described in a narrative is a highly complex process. The main aim of this thesis is to investigate the factors we have to take into account in order to determine the temporal coherence of a narrative discourse. In particular, aspectual information, tense, and world and context knowledge have to be considered and the interplay of all these factors must be specified. German is aspectually speaking an interesting language, because it does not possess a grammaticalised distinction between a perfective and imperfective aspect. In this thesis I examine the German aspectual system and the interaction of the factors which have an influence on the derived temporal relation for short discourse sequences. The analysis is carried out in two steps: First, the aspectual and temporal properties of German are investigated, following the cross-linguistic framework developed by Carlota S. Smith. An account for German is given which emphasises the properties which are peculiar to this language and explains why it has to be treated differently to, for example, English. The main result for the tense used in a narrative text—the Preterite—is that information regarding the end point of a described situation is based on our world knowledge and may be overridden provided context knowledge forces us to do this. Next, the more complex level of discourse is taken into account in order to derive the temporal relations which hold between the described situations. This investigation provides us with insights into the interaction of different knowledge sources like aspectual information as well as world and context knowledge. This investigation of German discourse sequences gives rise to the need for a time logic which is capable of expressing fine as well as coarse (or underspecified) temporal relations between situations. An account is presented to describe exhaustively all conceivable temporal relations within a computationally tractable reasoning system, based on the interval calculus by James Allen. However, in order to establish a coherent discourse for larger sequences, the hierarchical structure of a narrative has to be considered as well. I propose a Tree Description Grammar — a further development of Tree Adjoining Grammars — for parsing the given discourse structure, and stipulate discourse principles which give an explanation for the way a discourse should be processed. I furthermore discuss how a discourse grammar needs to distinguish between discourse structure and discourse processing. The latter term can be understood as navigating through a discourse tree, and reflects the process of how a discourse is comprehended. Finally, a small fragment of German is given which shows how the discourse grammar can be applied to short discourse sequences of four to seven sentences. The conclusion discusses the outcome of the analysis conducted in this thesis and proposes likely areas of future research.
40

The Effects Of The Allocation Of Attention Congruent With Lateralized Cognitive Tasks On EEG Coherence Measurements

Hill, Cynthia DeLeon 05 1900 (has links)
The single task condition of the Urbanczyk and Kennelly (1991) study was conducted while recording a continuous electroencephalographic (EEG) record. Attention was allocated by instructed lateral head orienting and eye gaze either congruently or incongruently with lateralized cognitive tasks. Thirty university subjects retained a digit span or a spatial location span for a 20 second retention interval. EEG data were extracted from the 20 second retention intervals and interhemispheric coherence was calculated for homologous sites in the temporal, parietal and occipital regions of the brain. There was a main effect for group, with congruent orienting producing greater coherence values than incongruent orienting. This effect of attention on alpha coherence values was found in the low alpha (8-10 Hz) frequency band. This provides evidence that the lower alpha frequency band is reflective of manipulations of attention. The higher coherence measures for the congruent orienting group indicates that homologous regions of the two hemispheres are more coupled into a single system when lateralized attention activates the same hemisphere performing the cognitive task. In the higher alpha frequency band (11-13 Hz) group, sex, site and task interacted. This provides evidence that the higher alpha band is more affected by cognitive processing of the specific task undertaken. An interhemispheric brain system, affected by the lateral orientation of attention, may underlie psychometric intelligence's general “g” ability (Spearman, 1927.)

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