Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: ray chaos, eikonal equations, turbulence. Includes bibliographical references. (p.98-102).

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 1, 2007) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 64-65).

by Alan J. Laub. / Bibliography: p. 44-46. / Research supported by Contract ERDA-E(49-18)-2087.

Made available in DSpace on 2014-06-11T19:23:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-27Bitstream added on 2014-06-13T18:50:45Z : No. of bitstreams: 1 coutinho_rm_me_ift.pdf: 521382 bytes, checksum: ce085be624237f602ec76319b0b41813 (MD5) / Neste trabalho estudamos uma equação diferencial com retardo, a equação de Hutchinson, que é um modelo simples para a dinâmica de uma população que exibe dependência em tempos passados por meio de uma variável defasada. Essa equação pode ser vista como uma equação mínima que é capaz de dar origem a soluções oscilatórias em modelos de uma única espécie. Para analisar a solução próxima do ponto de bifurcação em que surgem as oscilações, empregamos o método de múltiplas escalas. Os resultados obtidos mostram as próprias limitações do método, concordando apenas parcialmente com os resultados numéricos. Também analisamos uma variante da equação de Hutchinson com capacidade de suporte dependente do tempo e periódica, e vimos que, mesmo com amplitudes de perturbação muito pequenas, o acoplamento entre as frequências da capacidade de suporte e da oscilação natural pode ter um efeito pronunciado sobre a dinâmica da população. Apresentamos uma análise de ressonâncias para este caso e mostramos a existência de frequências da capacidade de suporte perto das quais a solução da equação exibe um comportamento inesperado / In the present work, we study a delay diUerential equation, namely the Hutchinson equation, which is a simple model for the dynamics of a population that shows dependence on past times through a lagged variable. This equation can be seen as a minimal equation that is able to produce oscillatory solutions in single species models. In order to analyze the solution near the bifurcation point at which oscillations set in, we employ the multiple scales method. The results obtained expose the limitations of the method, agreeing only partially with numerical results. We also analyze a variation of the Hutchinson equation with a periodic timevarying carrying capacity, and Vnd that, even at very small amplitude perturbations, the coupling of frequencies between the carrying capacity oscillation and the natural oscillation can have a major eUect on the population dynamics. We present a resonance analysis for this case and show the existence of carrying capacity frequencies near which the equation’s solution exhibit an unexpected behavior

Les sciences expérimentales font régulièrement usage de séries chronologiques, pour représenter certains des résultats expérimentaux, qui consistent en listes chronologiques de valeurs (indexées par le temps), généralement fournies par des capteurs reliés à un système (objet de l’expérience). Ces séries sont analysées dans le but d’obtenir un modèle mathématique permettant de décrire les données et ainsi comprendre et expliquer le comportement du système étudié. De nos jours, les technologies de stockage et analyse de séries chronologiques sont nombreuses et matures, en revanche, quant au stockage et à la gestion de modèles mathématiques et leur mise en lien avec des données numériques expérimentales, les solutions existantes sont à la fois récentes, moins nombreuses et moins abouties. Or,les modèles mathématiques jouent un rôle essentiel dans l’interprétation et la validation des résultats expérimentaux. Un système de stockage adéquat permettrait de faciliter leur gestion et d’améliorer leur ré-utilisabilité. L’objectif de ce travail est donc de développer une base de modèles permettant la gestion de modèle mathématiques et de fournir un système de « requête par les données », afin d’aider à retrouver/reconnaître un modèle à partir d’un profil numérique expérimental. Dans cette thèse, je présente donc la conception (de la modélisation des données, jusqu’à l’architecture logicielle) de la base de modèles et les extensions qui permettent de réaliser le système de « requête par les données ». Puis, je présente le prototype de la base de modèle que j’ai implémenté, ainsi que les résultats obtenus à l’issu des tests de ce-dernier. / It is common practice in experimental science to use time series to represent experimental results, that usually come as a list of values in chronological order (indexed by time) and generally obtained via sensors connected to the studied physical system. Those series are analyzed to obtain a mathematical model that allow to describe the data and thus to understand and explain the behavio rof the studied system. Nowadays, storage and analyses technologies for time series are numerous and mature, but the storage and management technologies for mathematical models and their linking to experimental numerical data are both scarce and recent. Still, mathematical models have an essential role to play in the interpretation and validation of experimental results. Consequently, an adapted storage system would ease the management and re-usability of mathematical models. This work aims at developing a models database to manage mathematical models and provide a “query by data” system, to help retrieve/identify a model from an experimental time series. In this work, I will describe the conception (from the modeling of the system, to its software architecture) of the models database and its extensions to allow the “query by data”. Then, I will describe the prototype of models database,that I implemented and the results obtained by tests performed on the latter.

Recent epidemiological data from the National Comorbidity Survey (NCS) estimate significant lifetime prevalence rates for anxiety and mood disorders, suggesting nearly one in three people would meet diagnostic criteria for an anxiety and/or mood disorder at some point during their lifetime (NCS, 2007). Comorbidity research has also revealed that people often suffer from these disorders concurrently (Rodriguez et al., 2004). Many have argued that anxiety and mood disorders frequently co-occur because they share similar etiological factors (Barlow, 1991; Clark & Watson, 1991; Watson, 2005). Additional empirical research has suggested that depressive and anxiety disorders share similar genetic diatheses and merely present differently because of variation in environmental stressors (Hettema, Neale, & Kendler, 2001; Rutter Moffit, & Caspi, 2006). As a result, an investigation of shared emotion regulation and affective processes across anxiety and mood disorders may reveal parallel etiological factors and areas for intervention. Research examining emotion and affective dysregulation indicates that mood and anxiety pathology may be characterized by similar emotional control and understanding deficits (Amstadter, 2008; Bradley, 2000; Sandin et al., 1996). Models of emotion dysregulation suggest that individuals suffering from anxiety pathology report decreased understanding of emotions, higher reactivity and sensitivity to emotions, and poor emotional management and mood repair skills (Mennin et al., 2005). Similarly, studies have observed parallel difficulties in those with depression (Liverant, Brown, Barlow, & Roemer, 2008; Rude and McCarthy, 2003). Additionally, research has indicated that efforts to reappraise or suppress emotions may affect the intensity and valence of emotional experiences (Gross & John, 2004). The current study builds off this research by incorporating elements of previous models of emotion dysregulation and anxiety and mood pathology in an effort to develop a comprehensive model of affective process that may underlie both anxious and depressive symptomatology. A total of 526 undergraduate students participated in the present investigation by completing a series of self-report instruments measuring affect and psychopathology. Response patterns were analyzed using AMOS 4.0 in order to examine the structural relationships between negative affectivity, positive affectivity, emotion reappraisal, emotion suppression, negative emotional reactivity, and poor understanding of emotions. Initial tests of a single model of emotion dysregulation suggested that the development of two separate models best represented subject responses. As a result, distinct models for suppression and reappraisal were tested concurrently. Tests of model invariance revealed similar structural qualities across gender, ethnicity, and levels of general distress for both models. Following modification, final fit indices suggested good fit for the reappraisal model (CFI = .99, TLI = .99, RMSEA = .057); however, the suppression model did not appear similarly representative of subject response behavior (CFI = .89, TLI = .85, RMSEA = .073). Findings of the current study suggest that the use of emotional reappraisal may be associated with increased positive affective and decreased negative affective states. Further, attempts to reappraise emotional experiences may influence the relationships poor understanding of emotions and fear of strong affect demonstrated with negative and positive affect. Data support previously articulated psychotherapy treatment strategies (Beck, 1979; Barlow & Cerny, 1988; Linehan, 1993; Hayes, 2004), but also indicate that current cognitive behavioral therapies may benefit from heightened attention to emotions and the incorporation of affective regulation skill building strategies. Future research directions, study strengths and limitations, and additional implications of present results are included.

abstract: III-nitride InGaN light-emitting diodes (LEDs) enable wide range of applications in solid-state lighting, full-color displays, and high-speed visible-light communication. Conventional InGaN quantum well LEDs grown on polar c-plane substrate suffer from quantum confined Stark effect due to the large internal polarization-related fields, leading to a reduced radiative recombination rate and device efficiency, which limits the performance of InGaN LEDs in high-speed communication applications. To circumvent these negative effects, non-trivial-cavity designs such as flip-chip LEDs, metallic grating coated LEDs are proposed. This oral defense will show the works on the high-modulation-speed LEDs from basic ideas to applications. Fundamental principles such as rate equations for LEDs/laser diodes (LDs), plasmonic effects, Purcell effects will be briefly introduced. For applications, the modal properties of flip-chip LEDs are solved by implementing finite difference method in order to study the modulation response. The emission properties of highly polarized InGaN LEDs coated by metallic gratings are also investigated by finite difference time domain method. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

Made available in DSpace on 2014-10-09T12:30:27Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:09Z (GMT). No. of bitstreams: 1 01262.pdf: 10916566 bytes, checksum: 2385abcdb07cf5e475019706bd6fea6f (MD5) / Tese (Doutoramento) / IPEN/T / Universite Scientifique et Medicale de Grenoble, France

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