• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 146
  • 67
  • 52
  • 17
  • 16
  • 11
  • 9
  • 3
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 381
  • 37
  • 37
  • 34
  • 31
  • 30
  • 28
  • 24
  • 21
  • 20
  • 19
  • 18
  • 16
  • 16
  • 16
  • 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.
71

Cristallisation et convection sous hyper-gravité / Crystallization and convection under hyper-gravity

Huguet, Ludovic 15 October 2014 (has links)
L’interface noyau-graine (ICB) est instable et une zone dendritique se forme sous des conditions très particulières, c’est à dire que la cristallisation est très lente par rapport à la convection très vigoureuse du noyau liquide. Afin de reproduire expérimentalement des conditions semblables, nous avons étudié une zone dendritique sous hyper gravite, dans une centrifugeuse. La hauteur de cette zone diminue quand la gravite augmente alors que la fraction solide augmente fortement : similairement, les études sismologiques suggèrent que la fraction solide dans la graine est proche de l’unité a l’ICB. De plus, la sismologie montre une graine très hétérogène en termes d’anisotropie élastique, d’atténuation ou de vitesse des ondes et met en lumière une forte dichotomie Est-Ouest. Celle-ci pourrait être engendrée par une translation de la graine qui provoquerait de la cristallisation sur une face et de la fusion sur l’autre. Cette hypothèse est testée en conduisant des expériences de cristallisation et de fusion d’une zone dendritique. Nous avons utilisé des ultrasons comme analogues aux ondes sismiques pour quantifier les changements de structure dans la zone dendritique à partir des mesures de l’atténuation et la diffraction. Extrapoles a la graine, nos résultats montrent que l’ICB pourrait fondre sur l’hémisphère Ouest et cristalliser sur l’hémisphère Est. D’autre part, avec du gaz xénon en hyper-gravite, nous avons observé un gradient adiabatique, pour la première fois dans un dispositif expérimental. Cette thèse montre la faisabilité de ces expériences et la possibilité de vérifier expérimentalement les approximations utilisées pour la convection compressible. / The inner core boundary (ICB) is unstable, and a mushy layer forms under very particular conditions in which the crystallization is very slow compared to the very vigorous convection of the liquid core. To mimic these conditions, we have investigated a mushy layer under hyper-gravity in a centrifuge. The thickness of a mushy layer decreases with gravity and the solid fraction increases. This is coherent with seismological studies suggesting that the solid fraction at the ICB is close to unity. Moreover, seismology shows that the inner core is very heterogeneous in terms of elastic anisotropy, attenuation or wave velocity and that there exists a strong East-West dichotomy on the ICB. One hypothesis is that the latter is due to a translation of the inner core that would cause crystallization on one hemisphere and melting on the other one. We have tested that hypothesis with experiments of solidification and melting of a mush. We have used ultrasounds as an analogue to the seismic waves to quantify structural changes in the mush from measurements of attenuation and scattering. From our observations, it is plausible that the ICB on the Western hemisphere s melting while it is solidifying on the Eastern hemisphere. In other experiments, using xenon gas under hyper-gravity, we have observed an adiabatic gradient for the first time. This thesis shows the feasibility of these experiments and the possibility to check experimentally the approximations used for compressible convection.
72

Diffusion de second harmonique en milieux liquides : approche comparée des réponses de volume et de surface / Second harmonic scattering in liquids media : comparison between volume and surface

Maurice, Anthony 15 December 2016 (has links)
Ce manuscrit décrit le processus optique non linéaire de Génération de Second Harmonique (acronyme anglais SHG pour Second Harmonic Generation) réalisé en phase liquide. En particulier, la propriété de cohérence de ce processus est étudiée en détail. En effet, en raison de la parité du processus SHG, cette cohérence est perdue dans les liquides. Ces études portent ainsi sur plusieurs géométries afin d’accéder aux réponses de volume et de surface. Les avantages d’une méthode combinée sont aussi discutés. Dans une première partie, la configuration classique de la Diffusion Hyper Rayleigh (acronyme anglais HRS pour Hyper Rayleigh Scattering ou SHS Second harmonic scattering) est utilisée pour l’étude de systèmes simples comme les solvants purs. Cette étude porte en particulier sur les méthodes de normalisation des hyperpolarisabilités moléculaires. Une voie alternative est proposée basée sur l’introduction d’une section efficace HRS ou SHS. Par la suite, les effets liés aux ordres non linéaires supérieurs sont démontrés et interprétés, ceux-ci pouvant altérer les valeurs absolues qui peuvent être mesurées.La seconde partie porte sur l’introduction de plusieurs améliorations dans les mesures HRS ou SHS. En particulier, l’évolution vers des géométries non conventionnelles s’éloignant de la géométrie standard ainsi que sur des évolutions permettant d’accéder aux aspects dynamiques sont proposées. Des expériences sont réalisées sur des systèmes simples comme les solvants purs, des composés moléculaires et des nanoparticules, tous présentant des spécificités propres. Cette partie finit sur l’exploration des systèmes aléatoires diffusants et les problèmes associés. Enfin, dans une dernière partie, la réponse HRS ou SHS de solutions aqueuses de sels est discutée. Les mesures portent plus particulièrement sur une étude comparée des aspects cohérents et incohérents et les propriétés qu’il est possible de mesurer dans ces systèmes / This manuscript describes the nonlinear optical process of Second Harmonic Generation (SHG acronym for Second Harmonic Generation) carried out in liquid phase. In particular, this process coherence property is studied in detail. Indeed, due to the parity of the SHG process, this coherence is lost in liquids. These studies covers several geometries to access the volume and surface responses. The benefits of a combined method are also discussed. In the first part, the typical configuration of the Hyper Rayleigh Scattering(HRS or SHS for Second harmonic scattering) is used for the study of simple systems like pure solvents. This particular study focuses on methods of standardization of molecular hyperpolarizabilities. An alternative route is proposed based on the introduction of a HRS or SHS cross. Subsequently, the effects of the higher nonlinear orders are demonstrated and interpreted, they can alter the absolute values that can be measured.The second part deals with the introduction of several improvements in the HRS or SHS measurement. In particular, the trend towards unconventional geometries away from the standard geometry as well as developments for accessing dynamic aspects are proposed. Experiments are performed on simple systems such as pure solvents, molecular compounds and the nanoparticles, all presenting specificities. This part ends on exploring the random scattering systems and associated problems. Finally, in the last part, the HRS or SHS response of aqueous salt solutions is discussed. The measures focus specifically on a comparative study of coherent and incoherent aspects and properties that can be measured in these systems
73

Hyper-optimalizace neuronových sítí založená na Gaussovských procesech / Gaussian Processes Based Hyper-Optimization of Neural Networks

Coufal, Martin January 2020 (has links)
Cílem této diplomové práce je vytvoření nástroje pro optimalizaci hyper-parametrů umělých neuronových sítí. Tento nástroj musí být schopen optimalizovat více hyper-parametrů, které mohou být navíc i korelovány. Tento problém jsem vyřešil implmentací optimalizátoru, který využívá Gaussovské procesy k predikci vlivu jednotlivých hyperparametrů na výslednou přesnost neuronové sítě. Z provedených experimentů na několika benchmark funkcích jsem zjistil, že implementovaný nástroj je schopen dosáhnout lepších výsledků než optimalizátory založené na náhodném prohledávání a snížit tak v průměru počet potřebných kroků optimalizace. Optimalizace založená na náhodném prohledávání dosáhla lepších výsledků pouze v prvních krocích optimalizace, než si optimalizátor založený na Gaussovských procesech vytvoří dostatečně přesný model problému. Nicméně téměř všechny experimenty provedené na datasetu MNIST prokázaly lepší výsledky optimalizátoru založeného na náhodném prohledávání. Tyto rozdíly v provedených experimentech jsou pravděpodobně dány složitostí zvolených benchmark funkcí nebo zvolenými parametry implementovaného optimalizátoru.
74

Výroba odlitků z austeniticko-feritických hyperduplexních korozivzdorných ocelích / Production of castings from austenitic-ferritic hyperduplex stainless steels

Kaněra, Miloš January 2021 (has links)
The thesis deals with hyper duplex stainless austenitic-ferritic steels and their mechanical and castability properties. The evaluation of resistance to pitting corrosion is divided by PRE values. Steels with a PRE value higher than 48 belong to the group of hyper duplex steels. The theoretical part contains an introduction to the chemical composition, structure and properties of these steels. The practical part is focused on the conditions of tendency to crack castings during solidification and cooling. Furthermore, there is evaluated influence of intermetallic phases on mechanical properties.
75

Contributions à la fusion des informations : application à la reconnaissance des obstacles dans les images visible et infrarouge / Contributions to the Information Fusion : application to Obstacle Recognition in Visible and Infrared Images

Apatean, Anca Ioana 15 October 2010 (has links)
Afin de poursuivre et d'améliorer la tâche de détection qui est en cours à l'INSA, nous nous sommes concentrés sur la fusion des informations visibles et infrarouges du point de vue de reconnaissance des obstacles, ainsi distinguer entre les véhicules, les piétons, les cyclistes et les obstacles de fond. Les systèmes bimodaux ont été proposées pour fusionner l'information à différents niveaux: des caractéristiques, des noyaux SVM, ou de scores SVM. Ils ont été pondérés selon l'importance relative des capteurs modalité pour assurer l'adaptation (fixe ou dynamique) du système aux conditions environnementales. Pour évaluer la pertinence des caractéristiques, différentes méthodes de sélection ont été testés par un PPV, qui fut plus tard remplacée par un SVM. Une opération de recherche de modèle, réalisée par 10 fois validation croisée, fournit le noyau optimisé pour SVM. Les résultats ont prouvé que tous les systèmes bimodaux VIS-IR sont meilleurs que leurs correspondants monomodaux. / To continue and improve the detection task which is in progress at INSA laboratory, we focused on the fusion of the information provided by visible and infrared cameras from the view point of an Obstacle Recognition module, this discriminating between vehicles, pedestrians, cyclists and background obstacles. Bimodal systems have been proposed to fuse the information at different levels:of features, SVM's kernels, or SVM’s matching-scores. These were weighted according to the relative importance of the modality sensors to ensure the adaptation (fixed or dynamic) of the system to the environmental conditions. To evaluate the pertinence of the features, different features selection methods were tested by a KNN classifier, which was later replaced by a SVM. An operation of modelsearch, performed by 10 folds cross-validation, provides the optimized kernel for the SVM. The results have proven that all bimodal VIS-IR systems are better than their corresponding monomodal ones.
76

Evoluční algoritmy pro vícekriteriální optimalizaci / Evolutionary Algorithms for Multiobjective Optimization

Pilát, Martin January 2013 (has links)
Multi-objective evolutionary algorithms have gained a lot of atten- tion in the recent years. They have proven to be among the best multi-objective optimizers and have been used in many industrial ap- plications. However, their usability is hindered by the large number of evaluations of the objective functions they require. These can be expensive when solving practical tasks. In order to reduce the num- ber of objective function evaluations, surrogate models can be used. These are a simple and fast approximations of the real objectives. In this work we present the results of research made between the years 2009 and 2013. We present a multi-objective evolutionary algo- rithm with aggregate surrogate model, its newer version, which also uses a surrogate model for the pre-selection of individuals. In the next part we discuss the problem of selection of a particular type of model. We show which characteristics of the various models are im- portant and desirable and provide a framework which combines sur- rogate modeling with meta-learning. Finally, in the last part, we ap- ply multi-objective optimization to the problem of hyper-parameters tuning. We show that additional objectives can make finding of good parameters for classifiers faster. 1
77

Élaboration de matériaux silicone au comportement mécanique adapté pour la réalisation de fantômes aortiques patients-spécifiques / Elaboration of silicone materials with a mechanical behavior tailored for manufacturing patient-specific aortic phantom

Courtial, Edwin-Joffrey 26 February 2015 (has links)
Le travail présenté dans ce manuscrit concerne la fabrication de fantômes d'aorte patient spécifiques utilisant une technique de fabrication additive par impression 3D. Ces répliques sont fabriquées en matériaux synthétiques dont les caractéristiques morphologiques et les propriétés mécaniques doivent être proches de celles déterminées sur un patient. Elles permettent d'optimiser ou de développer les techniques d'imagerie médicale, de comprendre les relations entre le comportement mécanique de la paroi aortique et les caractéristiques hémodynamiques du flux sanguin mais aussi de réaliser des entrainements préopératoires aux interventions chirurgicales, telles que le traitement endovasculaire. Dans cette étude, le comportement mécanique hyper-viscoélastique de la paroi aortique est modélisé par un modèle de Maxwell solide généralisé, dont les paramètres ont permis la sélection et le développement de matériaux élastomères de type silicone aux comportements mécaniques contrôlés. Ces matériaux ont été élaborés à partir de mélanges de formulations existantes et des lois de mélange ont été comparées pour guider la définition de la composition idéale permettant d'imiter le comportement mécanique désiré. Nous avons mis au point une méthode basée sur l'imagerie médicale par ultrason, capable d'identifier les paramètres hyper-viscoélastiques d'une paroi vasculaire. Cette méthode a été validée sur des tubes réalisés avec ces formulations de silicone, dont les propriétés mécaniques ont été mesurées avec des méthodes de référence. Puis, ces silicones ont été utilisés dans un processus de fabrication additive utilisant l'impression 3D par voie indirecte. Un travail de conception assistée par ordinateur a été réalisé pour produire un fantôme d'aorte patient-spécifique présentant un anévrisme fusiforme et non-thrombosé dans la région thoracique / The present work deals with the producing of patient-specific aortic phantoms using an additive manufacturing technique by 3D printing. Phantoms are manufactured from synthetic materials with morphological and mechanical characteristics which should be close to these identified on a patient. They can be used to develop techniques of medical imaging, to understand the relationship between aortic mechanical behavior and hemodynamic properties of blood flow, as well as to perform a preoperative training of interventions, such as endovascular treatment. In this study, the hyper-viscoelastic aortic mechanical behavior was described using a generalized solid Maxwell model. Silicone materials were developed based on the model’s mechanical parameters to mimic various aortic mechanical behaviors. These materials were formulated from commercials silicones, and then mixing rules were compared to define the ideal mixture which can mimic the specific mechanical behavior. A nondestructive method based on medical imaging by ultrasound was developed to identify the parameters of a blood vessel hyper-viscoelastic model. Silicone tubes made of our formulations with known reference mechanical parameters, were used to validate this method. Then, these silicone materials were used in an additive manufacturing process using indirect 3D printing. A work of computer aided design was done to produce a patient-specific aortic phantom with a thoracic fusiform aneurysm without thrombosis
78

A Thematic Analysis of Gender Stereotypes in Children's Top Mobile Applications of 2018

Keene, Kyra Margaret 24 June 2020 (has links)
People around the globe rely on their mobile devices for instant access to entertainment and social media. Children comprise a large majority of individuals who use smartphone applications, particularly for gaming and learning opportunities. Understandably, these apps become part of the identity development process, including the formation of one's gender identity. App developers include gendered content to capture and maintain children's attention, but much of the existing research examines children in late childhood and early adolescence, leaving the ages of six to eight relatively undiscussed. The researcher utilized a thematic analysis to review 20 children's mobile applications for instances of gender stereotypes. Social cognitive theory offers a guiding principle for understanding the process of developing one's gender identity, as well as the role that external stimuli, such as digital media examples and parent models, play. This study aimed to determine whether mobile applications targeting the identified age group use gender stereotypes, as well as how they employ these stereotypes within the application. The researcher randomly selected 20 top children's applications on the Apple App Store and examined them for gendered instances, such as occupations and interests as well as character depictions. The results reflect that instances of gender stereotypes do occur in the children's mobile applications. Many of the applications portrayed feminine stereotypes surrounding nurturing and caregiving tasks ("Mommy in Training"), making it one of the most frequently exploited feminine stereotypes in the sample. The "Boys will be Boys" stereotype comprised the most frequently displayed masculine stereotypes across the studied applications. These findings represent the idea that society places higher value on these stereotypes than others, such as social relationships ("The Power of Motivational Friendship") or recklessness ("The Risk Taker"). Implications include modeling of traditionally masculine and feminine stereotypes for young users by utilizing popular characters recognizable by most children in the target age range. / Master of Arts / Handheld electronic devices, such as smartphones and tablets, encompass some of the most widely used electronic devices in today's society. Most families in America have at least one mobile device with internet capability. Apple, the manufacturer of perhaps the most popular brand of electronic devices, pre-install their App Store on all devices they sell, giving users instant access to hundreds of thousands of different mobile applications that offer functions to make every aspect of life simpler. Young children spend a significant amount of their time playing games on these devices, although the American Academy of Pediatrics (2017) recommends that parents limit their children's daily screen time to no more than 2 hours, depending on the age of the child. The games that children download and play impose a number of different messages and stereotypes on their users, including gender stereotypes. Due to the substantial time children dedicate to these apps, the messages communicated regarding gender play crucial roles in the development of their gender identity. Social cognitive theory offers valuable insight and guidance into the gender identity development process. Therefore, the present study examines the gender stereotypes conveyed within 20 of the top children's mobile applications available on the Apple App Store in April 2018. The researcher randomly selected 20 children's applications, 10 each from the Top Free and Top Paid categories and examined them for gendered instances, such as occupations and interests as well as character depictions. The results reflect that instances of gender stereotypes do occur in the children's mobile applications. These represent the idea that society places higher value on certain stereotypes, like being caring and nurturing ("Mommy in Training") or engaging in messy, adventurous play ("Boys will be Boys"), than others, such as social relationships ("The Power of Motivational Friendship") or recklessness ("The Risk Taker"). Implications include modeling of traditionally masculine and feminine stereotypes for young users by utilizing popular characters recognizable by most children in the target age range.
79

The black eyes of Bruce Lee : From Normative to Descriptive & Prescriptive Multiculturalism

Khosravi Noori, Behzad January 2012 (has links)
Multiculturalism or cultural pluralism is a policy, ideal, or reality that emphasizes the unique characteristics of different cultures in the world, especially as they relate to one another in immigrant receiving nations. The word was first used in 1957 to describe Switzerland but first came into common currency in Canada in the late 1960s2. It quickly spread to other English- speaking and western developed countries.Although There is no clear link between the multiculturalism and the term that so called Balkanization, But this research tries to present the similar possibility of Multiculturalism discourse and Balkanization as a geopolitical term. In fact this research believes that   balkanization is The same idea of multiculturalism in practice, when it comes to the idea of state. On the other hand Vijay Parshad in his book Everybody was Kung Fu fighting  says that "I am interested in “how an investigation of kung fu can help us move from a limited multicultural framework into an antiracist, polycultural one.” This is the research and video that has been made about Bruce lee statue in Mostar, the divided city in Bosnia and Herzegovina", as a method of working in hyper- politicized society.
80

HYPER-X (X-43A) FLIGHT TEST RANGE OPERATIONS OVERVIEW

Lux-Baumann, Jessica, Burkes, Darryl A. 10 1900 (has links)
ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / The Hyper-X program flew X-43A research vehicles to hypersonic speeds over the Pacific Ocean in March and November 2004 from the Western Aeronautical Test Range, NASA Dryden Flight Research Center, Edwards, California. The program required multiple telemetry ground stations to provide continuous coverage of the captive carry, launch, boost, experiment, and descent phases of these missions. An overview is provided of vehicle telemetry and distributed assets that supported telemetry acquisition, best-source selection, radar tracking, video tracking, flight termination systems, and voice communications. Real-time data display and processing are discussed, and postflight analysis and comparison of data acquired are presented.

Page generated in 0.0451 seconds