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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.
531

Tectonic evolution of the southern Appalachian Inner Piedmont: Identification and interpretation of crustal features from aeromagnetic data and detailed geologic mapping in central Georgia

Davis, Brittany Allison 01 May 2010 (has links)
The Inner Piedmont (IP) is the Neoacadian migmatitic orogenic core of the southern Appalachians, exhibiting the widest area of high-grade metamorphism; regional upper amphibolite facies with isolated pods of granulite grade metamorphism. Peak P-T conditions in central GA reached 4.0-7.6 kbars and 630-715 ̊ C. The Brindle Creek fault (BCf) separates high-grade metasedimentary rocks of the eastern Tugaloo terrane (Tt) and Cat Square terrane (CSt). The Tt consists of the Neoproterozoic to early Paleozoic(?) Tallulah Falls Formation, Chauga River Formation, and the Mid-Ordovician Poor Mountain Formation, intruded by Early to Middle Ordovician granitoids. The CSt consists of Siluro-Devonian metasedimentary rocks, such as sillimanite-schist, biotite gneiss, amphibolite, and minor calc-silicate, intruded by Acadian-Neoacadian plutons. Original termination of the CSt was mapped by the USGS just south of Athens, GA, against the central Piedmont suture; however, new evidence from aeromagnetic anomalies and detailed geologic mapping revealed that the CSt and BCf extend into central GA. The BCf truncates a suite of curved magnetic anomalies on the aeromagnetic map. The curved anomalies that truncate against the linear feature may represent the Neoacadian deflection of the IP southwestward along the crustally weak Brevard fault zone. Another prominent lineament was identified southeast of the BCf; detailed geologic mapping revealed an additional thrust sheet in the CSt. Mesozoic brittle reactivation of the late Paleozoic dextral Towaliga fault was also identified striking NE-SW through the field area. Multiple episodes of movement were observed in outcrop and at the micro-scale, defined by crosscutting fracture sets. Low temperature quartz mylonite (350-450 ̊ C) may signify continued shearing of the IP into the late Alleghanian orogeny. A felsic plutonic suite extends the length of the field area, consisting of three distinct granitoids: (1) an older biotite-rich megacrystic granite with megacrysts of K-feldspar; (2) a weakly foliated medium to coarse grained inequigranular granodiorite; and (3) a younger non-foliated fine-grained granodiorite. Analysis revealed that granitoids from central GA are similar texturally and petrographically with granitoids from NC’s CSt. Further whole-rock geochemical analysis revealed that these rocks share similar REE, trace element, and tectonic discriminate patterns. The most important point garnered from the trace element and REE patterns in spider diagrams, such as similarities in peaks and troughs, is that they must share either a common parent, process, or contaminant.
532

Influence, information and item response theory in discrete data analysis

Magis, David 04 May 2007 (has links)
The main purpose of this thesis is to consider usual statistical tests for discrete data and to present some recent developments around them. Contents can be divided into three parts. In the first part we consider the general issue of misclassification and its impact on usual test results. A suggested diagnostic examination of the misclassification process leads to simple and direct investigation tools to determine whether conclusions are very sensitive to classification errors. An additional probabilistic approach is presented, in order to refine the discussion in terms of the risk of getting contradictory conclusions whenever misclassified data occur. In the second part we propose a general approach to deal with the issue of multiple sub-testing procedures. In particular, when the null hypothesis is rejected, we show that usual re-applications of the test to selected parts of the data can provide non-consistency problems. The method we discuss is based on the concept of decisive subsets, set as the smallest number of categories being sufficient to reject the null hypothesis, whatever the counts of the remaining categories. In this framework, we present an iterative step-by-step detection process based on successive interval building and category count comparison. Several examples highlight the gain our method can bring with respect to classical approaches. The third and last part is consecrated to the framework of item response theory, a field of psychometrics. After a short introduction to that topic, we propose first two enhanced iterative estimators of proficiency. Several theoretical properties and simulation results indicate that these methods ameliorate the usual Bayesian estimators in terms of bias, among others. Furthermore, we propose to study the link between response pattern misfit and subject's variability (the latter as individual latent trait). More precisely, we present "maximum likelihood"-based joint estimators of subject's parameters (ability and variability); several simulations suggest that enhanced estimators also have major gain (with respect to classical ones), mainly in terms of estimator's bias.
533

C-optimal Designs for Parameter Testing with Survival Data under Bivariate Copula Models

Yeh, Chia-Min 31 July 2007 (has links)
Current status data are usually obtained with a failure time variable T which is diffcult observed but can be determined to lie below or above a random monitoring time or inspection time t. In this work we consider bivariate current status data ${t,delta_1,delta_2}$ and assume we have some prior information of the bivariate failure time variables T1 and T2. Our main goal is to find an optimal inspection time for testing the relationship between T1 and T2.
534

Prédire l'âge de personnes à partir de photos du visage : une étude fondée sur la caractérisation et l'analyse de signes du vieillissement

Nkengne, Alex A. 13 June 2008 (has links) (PDF)
L'âge a de tout temps constitué un attribut identitaire important. Nous avons développé au fil de l'évolution une aptitude innée à classer les individus en fonction de leur âge. Cette classification s'appuie en grande partie sur le visage et sur les transformations anatomiques qu'il subit au cours du temps. De plus en plus de traitements cosmétiques, dermatologiques et d'interventions chirurgicales s'attaquant à un signe ou un groupe de signes spécifiques du vieillissement sont mis en oeuvre pour annuler, ou tout au moins masquer partiellement l'effet du temps sur le visage. On peut dès lors s'interroger sur l'influence de chacun des signes sur notre capacité à prédire l'âge d'un individu en observant son visage. Afin de construire un algorithme capable de déterminer l'âge d'individus à partir de leurs photos, nous nous sommes intéressés aux signes du vieillissement et à leur impact sur l'âge apparent. Dans un premier temps, nous avons déterminé et analysé les transformations anatomiques qui altèrent le visage à partir de l'âge adulte (au-delà de 20 ans). Puis nous avons étudié les signes sur lequel on se base pour prédire l'âge d'une personne. Enfin, nous avons construit et validé un modèle prédictif de l'âge en s'appuyant sur les observations précédentes. Transformations anatomiques du visage avec l'âge : La prévalence d'un certain nombre de signes de vieillissement (rides, tâches brunes, forme du visage...) a été mesurée sur un panel représentatif de femmes volontaires âgées de 20 à 74 ans. Ces données ont permis d'établir la cinétique d'apparition de ces signes. Appréciation subjective de l'âge: Il s'agissait de déterminer les signes sur lesquels un observateur s'appuie lorsqu'il évalue l'âge d'un sujet. Pour ce faire, nous avons demandé à un panel constitué de 48 observateurs d'attribuer un âge aux volontaires sur lesquelles nous avions précédemment mesuré les signes du vieillissement. Nous avons confirmé avec ce groupe d'observateurs que la perception de l'âge est liée au sexe et à l'âge de l'observateur. De plus, à l'aide d'une régression PLS (Partial Least Square régression), nous avons établi des relations entre les signes du vieillissement et l'âge observé et démontré que selon que l'on soit jeune ou âgé, un homme ou une femme, on n'exploite pas les mêmes signes de vieillissement pour prédire l'âge.Modèle de prédiction : Enfin, nous avons proposé un modèle s'appuyant sur la régression PLS pour prédire automatiquement l'âge à partir des photos du visage. Ce modèle présente la particularité d'associer, dans une approche unifiée, les signes relatifs à la couleur, à la forme et à la texture du visage, à l'âge des sujets. A l'instar des Modèles Actifs D'apparence (AAM), le modèle construit vise à réduire fortement l'information portée par l'ensemble des pixels du visage. Toutefois, ce dernier est supervisé : Il est donc très approprié dans notre contexte puisque que l'on peut mettre en oeuvre une procédure d'apprentissage pilotée par le but. Les performances sont de fait comparables à celles des humains.
535

Cellular Reactions and Behavioral Changes in Focal and Diffuse Traumatic Brain Injury : A Study in the Rat and Mouse

Ekmark Lewén, Sara January 2013 (has links)
Traumatic brain injury (TBI) is a severe condition and a major cause of death and disability. There is no pharmacological treatment available in clinical practice today and knowledge of brain injury mechanisms is of importance for development of neuroprotective drugs. The aims of the thesis were to get a better understanding of astrocyte reactions and immune responses, as well as behavioral changes after focal unilateral cortical contusion injury and diffuse bilateral central fluid percussion injury in rats and mice. In the focal injury models, the astrocyte reactions were generally restricted to the ipsilateral hemisphere. After diffuse TBI, vimentin and glial fibrillary acidic protein (GFAP) positive reactive astrocytes were bilaterally expressed in brain regions even distant from the injury site, including regions where axonal injury was seen. Early after diffuse TBI, there was a robust immune response, including activation of macrophages/microglia (Mac-2+) and infiltration of neutrophils (GR-1+) and T-cells (CD3+). In order to measure functional outcome, the recently established Multivariate Concentric Square Field™ (MCSF) test for complex behaviors, including risk taking and explorative strategies was used. The Morris water maze (MWM) was applied for testing learning and memory. The MCSF test revealed alterations in risk taking, risk assessment and exploratory behavior, in the mice subjected to focal injury whereas mice subjected to the diffuse injury showed a deviant stereotyped behavior. After focal injury mice showed a decreased ability to adapt to the arena in the second trial, when tested repeatedly in the MCSF test. Mice subjected to diffuse injury had an impaired memory but not learning, in the MWM test. Post-injury treatment with the anti-inflammatory anti-interleukin-1β (IgG2 a/k) antibody showed a positive effect on functional outcome in the diffuse injury model. Altogether, the results demonstrate that focal and diffuse TBI models produce differences in cellular reactions and behavioral outcome and that the immune response plays a key role in the pathology after brain injury.
536

The Application of Finite Element Methods to Aeroelastic Lifting Surface Flutter

Guertin, Matthew 06 September 2012 (has links)
Aeroelastic behavior prediction is often confined to analytical or highly computational methods, so I developed a low degree of freedom computational method using structural finite elements and unsteady loading to cover a gap in the literature. Finite elements are readily suitable for determination of the free vibration characteristics of eccentric, elastic structures, and the free vibration characteristics fundamentally determine the aeroelastic behavior. I used Theodorsen’s unsteady strip loading formulation to model the aerodynamic loading on linear elastic structures assuming harmonic motion. I applied Hassig’s ‘p-k’ method to predict the flutter boundary of nonsymmetric, aeroelastic systems. I investigated the application of a quintic interpolation assumed displacement shape to accurately predict higher order characteristic effects compared to linear analytical results. I show that quintic interpolation is especially accurate over cubic interpolation when multi-modal interactions are considered in low degree of freedom flutter behavior for high aspect ratio HALE aircraft wings.
537

House of Reconciliation

Noufaily, Farid J. 14 September 2007 (has links)
The signing of the Ta'if Agreement on October 22, 1989 marked the beginning of the end of the divisive and destructive Lebanese Civil War that had raged since 1975. The war was finally ended in March 1991, when the new Lebanese Parliament enacted the General Amnesty Law, which stated that there were to be no victors and no victims in the war ( la ghalib le maghlub). Unfortunately, this law allowed the Lebanese people to turn a blind eye to the ugly truths of the war, and it ushered in an era of uneasy silence in Lebanon. Today, as Lebanon's political battle for independence and a unified national identity continues, there is still no government supported public attempt to break this silence. I believe that this legislated lack of collective/public self-expression has rendered both the local and the Diaspora populations incapable of reconciliation with their recent traumatic past, let alone allowing them to forge a brighter future. This thesis investigates the unrelenting silence permeating every layer of Lebanese society today and proposes architectural solutions that may help to break the silence and thus reconcile Lebanese to their past. The core of this study consists of three architectural interventions aimed at breaching this silence. These are put into context through historical analysis, family interviews, and personal narratives from field research to Beirut conducted by the author in the fall of 2005, as well as photographs, maps, illustrations, and other documents drawn from first person experience. As such, this thesis probes not just the public, but also a personal experience in overcoming Lebanon's silence. Certainly, there can be no reconciliation based on silence.
538

A Comparative Study of the SIMPLE and Fractional Step Time Integration Methods for Transient Incompressible Flows

Hines, Jonathan January 2008 (has links)
Time integration methods are necessary for the solution of transient flow problems. In recent years, interest in transient flow problems has increased, leading to a need for better understanding of the costs and benefits of various time integration schemes. The present work investigates two common time integration schemes, namely the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) and the Fractional Step (FS) method. Three two-dimensional, transient, incompressible flow problems are solved using a cell centered, finite volume code. The three test cases are laminar flow in a lid-driven skewed cavity, laminar flow over a square cylinder, and turbulent flow over a square cylinder. Turbulence is modeled using wall functions and the k - ε turbulence model with the modifications suggested by Kato and Launder. Solution efficiency as measured by the effort carried out by the flow equation solver and CPU time is examined. Accuracy of the results, generated using the SIMPLE and FS time integration schemes, is analyzed through a comparison of the results with existing experimental and/or numerical solutions. Both the SIMPLE and FS algorithms are shown to be capable of solving benchmark flow problems with reasonable accuracy. The two schemes differ slightly in their prediction of flow evolution over time, especially when simulating very slowly changing flows. As the time step size decreases, the SIMPLE algorithm computational cost (CPU time) per time step remains approximately constant, while the FS method experiences a reduction in cost per time step. Also, the SIMPLE algorithm is numerically stable for time steps approaching infinity, while the FS scheme suffers from numerical instability if the time step size is too large. As a result, the SIMPLE algorithm is recommended to be used for transient simulations with large time steps or steady state problems while the FS scheme is better suited for small time step solutions, although both time-stepping schemes are found to be most efficient when their time steps are at their maximum stable value.
539

House of Reconciliation

Noufaily, Farid J. 14 September 2007 (has links)
The signing of the Ta'if Agreement on October 22, 1989 marked the beginning of the end of the divisive and destructive Lebanese Civil War that had raged since 1975. The war was finally ended in March 1991, when the new Lebanese Parliament enacted the General Amnesty Law, which stated that there were to be no victors and no victims in the war ( la ghalib le maghlub). Unfortunately, this law allowed the Lebanese people to turn a blind eye to the ugly truths of the war, and it ushered in an era of uneasy silence in Lebanon. Today, as Lebanon's political battle for independence and a unified national identity continues, there is still no government supported public attempt to break this silence. I believe that this legislated lack of collective/public self-expression has rendered both the local and the Diaspora populations incapable of reconciliation with their recent traumatic past, let alone allowing them to forge a brighter future. This thesis investigates the unrelenting silence permeating every layer of Lebanese society today and proposes architectural solutions that may help to break the silence and thus reconcile Lebanese to their past. The core of this study consists of three architectural interventions aimed at breaching this silence. These are put into context through historical analysis, family interviews, and personal narratives from field research to Beirut conducted by the author in the fall of 2005, as well as photographs, maps, illustrations, and other documents drawn from first person experience. As such, this thesis probes not just the public, but also a personal experience in overcoming Lebanon's silence. Certainly, there can be no reconciliation based on silence.
540

A Comparative Study of the SIMPLE and Fractional Step Time Integration Methods for Transient Incompressible Flows

Hines, Jonathan January 2008 (has links)
Time integration methods are necessary for the solution of transient flow problems. In recent years, interest in transient flow problems has increased, leading to a need for better understanding of the costs and benefits of various time integration schemes. The present work investigates two common time integration schemes, namely the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) and the Fractional Step (FS) method. Three two-dimensional, transient, incompressible flow problems are solved using a cell centered, finite volume code. The three test cases are laminar flow in a lid-driven skewed cavity, laminar flow over a square cylinder, and turbulent flow over a square cylinder. Turbulence is modeled using wall functions and the k - ε turbulence model with the modifications suggested by Kato and Launder. Solution efficiency as measured by the effort carried out by the flow equation solver and CPU time is examined. Accuracy of the results, generated using the SIMPLE and FS time integration schemes, is analyzed through a comparison of the results with existing experimental and/or numerical solutions. Both the SIMPLE and FS algorithms are shown to be capable of solving benchmark flow problems with reasonable accuracy. The two schemes differ slightly in their prediction of flow evolution over time, especially when simulating very slowly changing flows. As the time step size decreases, the SIMPLE algorithm computational cost (CPU time) per time step remains approximately constant, while the FS method experiences a reduction in cost per time step. Also, the SIMPLE algorithm is numerically stable for time steps approaching infinity, while the FS scheme suffers from numerical instability if the time step size is too large. As a result, the SIMPLE algorithm is recommended to be used for transient simulations with large time steps or steady state problems while the FS scheme is better suited for small time step solutions, although both time-stepping schemes are found to be most efficient when their time steps are at their maximum stable value.

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