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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

UNDERSTANDING THE QUALITY OF LIFE AMONG INDIVIDUALS WITH SCHIZOPHRENIA: AN EXPLORATION OF RISK AND RESILIENCE FACTORS

Khalesi, Zahra January 2023 (has links)
The objective of this dissertation was to examine the relation between shyness and quality of life (QoL) among adults with schizophrenia in a series of three studies. I first began by understanding whether commonly used measures of shyness and sociability were reliable in this population (Study 1). Next, I examined two moderating variables related to stress-responses subserved by the central (Study 2) and peripheral (Study 3) nervous systems. Study 1, used self-report questionnaires of shyness and sociability to determine whether individuals with schizophrenia responded to these questionnaires in the same way as healthy controls. Studies 2 and 3 used linear regression analyses to determine whether passive neural responses (ERP’s) to social stimuli (emotional faces) and hormonal levels (baseline salivary cortisol and testosterone), respectively, moderated the relation between shyness and QoL. I found that individuals with schizophrenia responded to self-reported shyness and sociability items in a similar way as their nonclinical peers, suggesting that self-reported shyness and sociability are equivalent across populations (Study 1). Study 2, found that individuals who were shy and displayed a hyposensitivity to the processing of fearful faces displayed the lowest QoL. Those who were shy and took longer to process happy faces also demonstrated hindered QoL. Finally, individuals who were shy and had relatively lower baseline salivary cortisol levels also had the lowest QoL. In all circumstances, individuals who were relatively less shy were not susceptible to factors relating to the central and peripheral nervous system. The results of these three studies show that interpretations of findings using self-reported measures of shyness and sociability can be made with confidence in this population. The results also provide support that factors related to processing stressful stimuli can influence the relation between shyness and QoL, thereby further increasing our understanding of this nuanced relation. Theoretical and practical implications of these findings are discussed. / Dissertation / Candidate in Philosophy / Individuals with schizophrenia have been shown to experience reduced quality of life (QoL). Many studies have tried to understand what factors lead to reduced QoL, with one of them being individual differences in personality. This dissertation focused on the personality trait of shyness and addressed two main questions: 1. Are we correctly measuring shyness in people with schizophrenia? 2. What other factors influence the relation between shyness and QoL among individuals with schizophrenia? I first examined whether the meaning of shyness was equivalent between adults with schizophrenia and nonclinical controls. I then examined two different biological factors (i.e., neural and hormonal) related to stress responses to see if they influenced the relation between shyness and QoL in adults with schizophrenia. The answers to these questions have theoretical and practical implications for helping us understand who is at increased and decreased risk for experiencing hindered QoL, and possible targets for intervention.
32

A translation invariant pure DEA model

Vincent, Charles, Färe, R., Grosskopf, S. 15 December 2019 (has links)
Yes / This communication complements the DEA model proposed by Lovell and Pastor (1999), by incorporating both positive and negative criteria in the model. As such, we propose a DEA model, known as pure DEA, using a directional distance function approach.
33

Test of Gauge Invariance: Charged Harmonic Oscillator in an Electromagnetic Field

Wen, Chang-tai 08 1900 (has links)
The gauge-invariant formulation of quantum mechanics is compared to the conventional approach for the case of a one-dimensional charged harmonic oscillator in an electromagnetic field in the electric dipole approximation. The probability of finding the oscillator in the ground state or excited states as a function of time is calculated, and the two approaches give different results. On the basis of gauge invariance, the gauge-invariant formulation of quantum mechanics gives the correct probability, while the conventional approach is incorrect for this problem. Therefore, expansion coefficients or a wave function cannot always be interpreted as probability amplitudes. For a physical interpretation as probability amplitudes the expansion coefficients must be gauge invariant.
34

Nonlinear control and visual servoing of autonomous robots / Commande non linéaire et asservissement visuel de robots autonomes

Dib, Alaa 21 October 2011 (has links)
Dans ce travail de thèse, on s’intéresse au problème de déplacement et de la localisation d'un robot mobile autonome dans son environnement local. La première partie du manuscrit les deux tâches de mouvement de base : c'est-à-dire, la stabilisation et le suivi de trajectoire. Deux stratégies de commande ont été traitées: le mode de glissement intégral, et la méthode dite «Immersion et Invariance». La deuxième partie porte sur l'asservissement visuel, les deux techniques 2D et 3D d'asservissement visuel ont été appliquées. Les moments d'image ont été choisis comme indices visuels car ils sont moins sensibles au bruit d'image et autres erreurs de mesure. Une nouvelle approche de l'asservissement visuel qui repose sur l'image est ici proposée. Elle est basée sur la génération de trajectoires sur le plan de l'image directement (calcul des valeurs des primitives d’image correspondantes à une trajectoire cartésienne donnée). Cette approche garantit que la robustesse et la stabilité bien connues de l'asservissement 2D ont été étendues en raison du fait que les emplacements initial et désiré de la caméra sont proches. Les trajectoires obtenues garantissent aussi que la cible reste dans le champ de vue de la caméra et que le mouvement du robot correspondant est physiquement réalisable. Des tests expérimentaux ont été effectués et des résultats satisfaisants ont été obtenus à partir des implémentations des stratégies de commande et d'asservissement visuel. Bien qu'ils soient développés et expérimentés dans le cadre spécifique d'un robot de type unicycle, ces travaux sont assez génériques pour être appliqués sur autres types de véhicules. / This thesis focuses on the problem of moving and localizing an autonomous mobile robot in its local environments. The first part of the manuscript concerns two basic motion tasks, namely the stabilization and trajectory tracking. Two control strategies were discussed: the integral sliding mode, and the method known as “Immersion and Invariance” for nonlinear control. The second part focuses on both 2D and 3D visual servoing techniques. Image moments were chosen as visual features as they provide a more geometric and intuitive meaning than other features, and they are less sensitive to image noise and other measurement errors. A new approach to visual servoing based on image is herein proposed. It is based on the generation of trajectories directly on the image plane (Calculation of the image features corresponding to a given Cartesian path). This approach ensures that the robustness and stability are extended due to the fact that the initial and desired locations of the camera are close. The trajectories obtained guarantee that the target remains in the field of view of the camera and the corresponding movement of the robot is physically feasible. Experimental tests have been conducted, and satisfactory results have been obtained from both implementations regarding motion control and visual servoing strategies. Although developed and tested in the specific context of a unicycle type robot, this work is generic enough to be applied to other types of vehicles.
35

Approche par invariance positive et les techniques de l'intelligence artificielle pour la régulation des carrefours signalisés / Positive invariance approach and techniques of artificial intelligence for control of signalized intersections

Motawej, Fadi 30 May 2012 (has links)
La régulation du trafic dans un carrefour à feux concerne en général deux objectifs distincts: la fluidification ou la résorption de congestion. Dans le premier cas, on évite de se retrouver dans une situation de trafic très dense en essayant d'ajuster les durées de commutations des feux en fonction de la demande d'affluence au carrefour: c'est une action a priori. Dans le second cas, on est confronté à un trafic saturé (état de congestion). Dans ce cas, il faudra agir a posteriori.Dans ce travail, nous nous intéressons essentiellement à un travail en amont (action a priori) permettant d'éviter la congestion en forçant les files d'attente à ne pas dépasser le niveau du trafic correspondant à l'optimum opérationnel des lignes. Plus précisément, après avoir modélisé le système, nous proposons une commande par retour d'état basée sur le concept d'invariance positive des ensembles et permettant d'atteindre l’objectif. Deux approches sont utilisées: La première fait appel aux inégalités matricielles Linéaires (LMI). La deuxième approche utilise le concept de la (A-B)-invariance issu de la généralisation du théorème de Farkas. Ensuite, nous enrichissons ces deux approches par la technique des réseaux de neurones pour estimer les flux d'entrée au carrefour afin de garantir la faisabilité en temps réel de la commande proposée. Enfin, les résultats de ces travaux sont appliqués sur un carrefour réel du boulevard Anatole France afin de montrer leur intérêt. / Traffic control in a signalized intersection relates generally two distinct objectives: the thinning or reduction of congestion. In the first case, we avoid ending up in a situation of heavy traffic trying to adjust the durations of switching lights depending on the demand for attendance at the crossroads: it is an action a priori. In the second case, one is faced with a saturated traffic (congestion state). In this case, it will act retrospectively. In this work, we focus mainly on upstream work (action a priori) to avoid congestion by forcing queues to not exceed the level of traffic corresponding to the optimum operational lines. Specifically, modeled after the system, we propose a state feedback control based on the concept of positive invariance of sets and to achieve the objective. Two approaches are used: The first uses the Linear matrix inequalities (LMI). The second approach uses the concept of (AB)-invariance from the generalization of the theorem of Farkas. Then, we enrich both approaches by the technique of neural networks to estimate the inflow at the crossroads to ensure real-time feasibility of the proposed control. Finally, the results of this work are applied to a real intersection of the boulevard Anatole France to show their interest.
36

Longitudinal Factor Structure of the Wechsler Intelligence Scale for Children-Fourth Edition in a Referred Sample

January 2012 (has links)
abstract: Standardized intelligence tests are some of the most widely used tests by psychologists. Of these, clinicians most frequently use the Wechsler scales of intelligence. The most recent version of this test for children is the Wechsler Intelligence Scale for Children - Fourth Edition (WISC-IV); given the multiple test revisions that have occurred with the WISC, it is essential to address evidence regarding the structural validity of the test; specifically, that the internal structure of the test corresponds with the structure of the theoretical construct being measured. The current study is the first to investigate the factor structure of the WISC-IV across time for the same individuals. Factorial invariance of the WISC-IV was investigated using a group of 352 students eligible for psychoeducational evaluations tested, on average, 2.8 years apart. One research question was addressed: Does the structure of the WISC-IV remain invariant for the same individuals across time? Using structural equation modeling methods for a four-factor oblique model of the WISC-IV, this study found invariance at the configural and weak levels and partial invariance at the strong and strict levels. This indicated that the overall factor structure remained the same at test and retest with equal precision of the factor loadings at both time points. Three subtest intercepts (BD, CD, and SI) were not equivalent across test and retest; additionally, four subtest error variances (BD, CD, SI, and SS) were not equivalent across test and retest. These results indicate that the WISC-IV measures the same constructs equally well across time, and differences in an individual's cognitive profile can be safely interpreted as reflecting change in the underlying construct across time rather than variations in the test itself. This allows clinicians to be more confident in interpretation of changes in the overall cognitive profile of individual's across time. However, this study's results did not indicate that an individual's test scores should be compared across time. Overall, it was concluded that there is partial measurement invariance of the WISC-IV across time, with invariance of all factor loadings, invariance of all but three intercepts, and invariance of all but four item error variances. / Dissertation/Thesis / Ph.D. Educational Psychology 2012
37

Structure spatio-temporelle des fortes précipitations : application à la région Cévennes Vivarais / Space-time structure of heavy rainfall events : application to the Cevennes-Vivarais region

Ceresetti, Davide 21 January 2011 (has links)
Ce travail de thèse concerne la caractérisation de la structure spatio-temporelle des fortes précipitations dans la région Cévennes-Vivarais. La région est soumise à des événements de pluie catastrophiques dont la magnitude gouverne les conséquences à différentes échelles de temps et d'espace. La détermination de la probabilité d'occurrence des orages est problématique à cause du caractère extrême des ces événements, de leur dimension spatio-temporelle et du manque de données pluviométriques aux échelles d'intérêt. Nous proposons d'adopter des approches d'invariance d'échelles afin d'estimer la fréquence d'occurrence de ces événements. Ces approches permettent d'extrapoler la distribution de la pluie à haute résolution à partir de données d'intensité pluvieuse à plus faible résolution. La paramétrisation de ces modèles étant fortement dépendante de l'incertitude de la mesure, nous avons d'abord caractérisé l'erreur commise dans la mesure de la pluie par un réseau de pluviomètres à augets. Nous avons ensuite exploré le comportement des pluies extrêmes dans la région d'étude, identifiant les gammes d'invariance d'échelles des extrêmes. Dans cette gamme d'échelles, nous présentons un modèle régional Intensité-Durée-Fréquence qui prend en considération l'hétérogénéité spatiale des extrêmes dans la région. Étant donné que le réseau pluviométrique ne permet pas de détecter les propriétés d'invariance d'échelle spatiale des champs de pluie, nous avons adopté une méthode semi-empirique pour modéliser des intensités de pluie intégrés sur des surfaces données (pluie surfacique) sur la base du concept de la mise en échelle dynamique (« dynamic scaling »). Cette modélisation permet la construction d'un modèle régional Intensité-Durée-Fréquence-Surface. Enfin, nous avons appliqué ce modèle à la construction des diagrammes de sévérité pour trois événements marquants en région Cévennes-Vivarais, afin d'identifier les échelles spatio-temporelles critiques pour chaque événement. Grâce aux diagrammes de sévérité, nous avons pu évaluer, pour ces mêmes événements, la performance d'un modèle météorologique de méso-échelle. / The thesis is devoted to the characterization of the space-time structure of heavy rainfall events in the Cévennes-Vivarais area (France). The region is prone to catastrophic storms whose magnitude governs social and economic consequences at different space and time scales. The magnitude of an event cannot be univocally related to a probability of occurrence. The determination of the occurrence probability of storms is problematic because of their extreme character, of their complex space-time development and of the lack of rainfall data at the spatial and temporal scales of interest. We propose to adopt scale-invariant approaches in order to estimate the heavy rainfall frequency assessment. These approaches allow to extrapolate the high resolution rainfall distribution based on low resolution rainfall intensity data. The model estimation being heavily dependent of the data accuracy, the first step consists in the characterization of the error committed in the point and spatial rainfall estimated by tipping-bucket raingage networks. We then explore the extreme rainfall behavior in the region, detecting the range where extremes are scale-invariant. In this range, we present a regional Intensity-Duration-Frequency model for point rainfall maxima taking into account the heterogeneity of extremes in the region. We demonstrate that the rainfall network does not allow to detect scale-invariant properties of extreme rainfall fields, and then we adopt a semi-empirical method based on the concept of « dynamic scaling » to build regional Intensity-Duration-Area-Frequency curves. Finally, we apply this model for the determination of the severity diagrams for three significant storms in the Cévennes-Vivarais region, with the aim to identify the critical space-time scales of each event. Based on severity diagrams, we then evaluate, for the same events, the performances of a mesoscale meteorological model.
38

Modélisation dynamique des réseaux d'énergie électrique tenant compte des propriétés d'invariance d'échelle / Modelling of power systems dynamic, taking into account the properties of scale invariance

Le, Thi-Tinh-Minh 07 May 2014 (has links)
L'arrivée massive de la production décentralisée, l'intégration de technologies d'information et de communication et de convertisseurs d'électronique de puissance permettent aux réseaux électriques de devenir plus flexibles, plus accessibles, plus efficaces. Mais ils deviennent aussi plus complexes et plus difficiles à modéliser, à analyser et à dimensionner. Dans cette thèse, nous allons nous focaliser sur le problème de la modélisation dynamique du réseau électrique. En effet, la complexité du fonctionnement du réseau électrique moderne rend encore plus indispensable de comprendre comment il se comporte suite à des perturbations ou tout simplement à des changements de son état de fonctionnement. C'est cette compréhension qui doit permettre d'éviter que le réseau perde sa stabilité. Grâce aux modèles développés dans la thèse, on veut notamment retrouver des liens de connaissance forts entre le comportement dynamique et les propriétés topologiques du réseau. On espère ainsi pouvoir fournir à termes des préconisations pour l'évolution des topologies de réseaux ou de leurs modes d'exploitation. Pour mener à bien ce travail, l'invariance d'échelle d'un réseau électrique est tout d'abord explorée. Pour cela, des méthodes issues de la géométrie fractale sont exposées et appliquées à des réseaux réalistes. Partant du constat que les réseaux électriques étudiés présentent une invariance d'échelle sur une plage d'observation importante, une nouvelle modélisation dynamique est proposée. Cette modélisation a l'intérêt d'une représentation plus parcimonieuse que les représentations classiques par des approches boite noire et permet de conserver des liens de connaissance avec entre la topologie et les propriétés dynamiques. / The influx of distributed generation, the integration of information as well as communication technologies and the integration of electronic power converters allows electrical grids to become more flexible, more accessible and more effective. However they become at the same time more complex thus making the modeling, analyzing and sizing more difficult. This thesis will focus on the problem of dynamic modeling of electrical networks. Indeed, the operation's complexity of the modern power grid makes it even more essential to understand how it behaves after disturbances or just simply after changes in operation condition. It is this understanding that should allow one to prevent the case that the system loses its stability. With models developed in this thesis, we particularly want to find strong links between the dynamic behavior and the topological properties of the network. It is hoped to provide eventually propositions for evolution of topology or operation modes of networks. To carry through this study, the scale invariance of an electrical network is first explored. For this purpose, methods issued from fractal geometry are presented and applied to realistic networks. Noting that the considered electrical networks exhibit scale invariance over a large observation range, a new dynamic modeling is proposed.
39

Caractérisation de l'effet response shift par l'approche des forêts aléatoires : application à la sclérose en plaques et à la schizophrénie / Caracterisation of response shift effect using the Random Forest method

Boucekine, Mohamed 16 December 2015 (has links)
Evaluer la qualité de vie (QV) a pris une importance croissante dans le domaine de la santé, tout particulièrement pour les maladies graves tels que les cancers. Cependant l’analyse des données de QV demeure complexe et reste peu utilisée pour changer les standards de prise en charge des patients. Une des raisons est que les patients pourraient exprimer un effet « response shift » (changement de réponse) au cours de la maladie et par conséquent biaiser les résultats en sur- ou sous estimant l’effet traitement mesurer par le différentiel de QV. En effet lorsque l’évolution de la QV est étudiée, on fait souvent l’hypothèse que la perception qu’ont les patients du concept étudié ne va pas se modifier au cours du temps. Or les patients font face à une maladie et à des traitements. L’impact que peuvent avoir la maladie et les traitements sur la vie du patient va généralement l’amener à s’adapter et modifier sa perception du concept étudié. Ainsi l’occurrence potentielle d’un effet « Response Shift » est une des problématiques à appréhender pour distinguer ce qui relève d’un « vrai » changement de QV et de ce qui est de l’adaptation. / To asses Quality Of Life, patients are often asked to evaluate their well-being using a self-report instrument to document patient-reported outcome (PROs) measures. The data are often collected on multiple domains, such as physical function, social health and emotional health. However, longitudinal PROs, which are collected at multiple occasions from the same individual, may be affected by adaptation or "response shift" effects and may lead to under- or overestimation of the treatment effects. Response shift is the phenomenon by which an individual's self-evaluation of a construct changes due to change in internal standards of measurement (recalibration), a change in value or priorities (reprioritization), or a personal redefinition of the target construct (reconceptualisation). If the response shift is present in the data, the interpretation of change is altered and conventional difference between post-test and pre-test may not be able to detect true change in PROs measures. The aim of the work is to propose an innovative method, based on random forest method, to highlight response shift effect.
40

Signatures of Unparticle Self-Interactions at the Large Hadron Collider

Bergström, Johannes January 2009 (has links)
Unparticle physics is the physics of a hidden sector which is conformal in the infrared and coupled to the Standard Model. The concept of unparticle physics was introduced by Howard Georgi in 2007 and has since then received a lot of attention, including many studies of its phenomenology in different situations. After a review of the necessary background material, the implications of the self-interactions of the unparticle sector for LHC physics is studied. More specifically, analyses of four-body final states consisting of photons and leptons are performed. The results are upper bounds on the total cross sections as well as distributions of transverse momentum.

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