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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.
171

Anomalie des antineutrinos de réacteurs : recherche d’un état stérile avec l’expérience STEREO / Reactor Antineutrino Anomaly : search for a sterile state with the STEREO experiment

Bonhomme, Aurélie 26 September 2018 (has links)
L’anomalie des antineutrinos de réacteurs (RAA) a été révélée en 2011 suite à une réévaluation de la prédiction des spectres associés. Elle indique un déficit de 6% dans les taux mesurés auprès de réacteurs. Une explication consiste en l’introduction d’un neutrino stérile à l’eV, ne se manifestant que par le mécanisme d’oscillations. L’expérience STEREO a été conçue pour explorer l’espace des paramètres d’oscillations indiqués par la RAA, en plaçant une cible segmentée à 10 m du cœur quasiment pur en uranium 235 de l’ILL, à Grenoble. Les antineutrinos sont détectés par désintégration bêta inverse (IBD) dans du liquide scintillant dopé au gadolinium. Si elle existe, une oscillation se développerait alors le long des six cellules identiques de la cible. La comparaison relative de leurs spectres d’antineutrinos en énergie permet de tester l’hypothèse d’une oscillation en s’affranchissant des prédictions et avec des incertitudes systématiques réduites. Les forts rendements lumineux des liquides permettent d’atteindre de bonnes résolutions en énergie, nécessaires pour la sensibilité de la mesure. Les cellules sont séparées optiquement par des plaques hautement réfléchissantes; cette technologie a été validée sur cellule prototype dans un premier temps lors de cette thèse. Un modèle effectif pour ces parois optiques a été inclus à la simulation, et les détails de la géométrie ont été implémentés. La deuxième partie de ce travail est orientée vers l’analyse des données. La signature de l’IBD est un signal en deux temps, requérant un algorithme de recherche de paires pour extraire les candidats antineutrino. Le programme dédié est optimisé pour l’application de sélections d’isolations temporelles, permettant de se débarrasser de la majeure partie du bruit de fond d’origine cosmique. Le bruit de fond corrélé résiduel dans la région d’intérêt provient de désintégrations de muons et de réactions induites par des neutrons. Une modélisation des figures de discrimination en forme des signaux (PSD) de ce bruit de fond est employée pour extraire le signal antineutrino. Basée sur les spectres qui en résultent, les premières analyses d’oscillations de STEREO rejettent le meilleur ajustement de la RAA à 98% de niveau de confiance. / The Reactor Antineutrino Anomaly (RAA) was highlighted in 2011, when a reevaluated prediction of reactor antineutrinos spectra showed a 6% deficit in the rates observed by previous reactor experiments. A possible explanation for this anomaly consists in introducing a sterile neutrino state at the eV mass scale, participating to the neutrino oscillations mecanism only. The STEREO experiment has been designed to probe the phase-space region indicated by the RAA, by placing a segmented antineutrino target at 10m from the virtually pure uranium 235 compact core of the ILL research reactor facility, in Grenoble. Antineutrinos are detected via inverse beta decay (IBD) in gadolinium-doped liquid scintillator. An oscillation pattern - if any - would develop along the six identical target cells. The relative comparison of their energy distributions allows to test the sterile neutrino hypothesis with reduced systematic uncertainties and without referring to an external prediction. High light yields of the liquids enable to reach good energy resolutions, needed for the sensibility of the measurement. Cells are optically separated thanks to highly reflective plates; this technology has been validated on a prototype cell in the first stage of this thesis. An effective model of these walls has been included in the simulation, and details of the geometry have been carefully implemented. The second part of this work focuses on data analysis. The IBD signature is a two-fold signal, requiring a proper pair search algorithm for extracting the antineutrinos candidates. The dedicated software is optimized to apply specific temporal isolation selections, which allow to get rid of the majority of the background produced by cosmic events. The residual correlated background in the region of interest comes from muon decays and neutron induced reactions. A modelisation of the Pulse Shape Discrimination (PSD) distributions of this background is used to extract the antineutrino signal. Based on the resulting spectra, the first STEREO oscillation analysis rejects the RAA best fit point at 98% of confidence level.
172

VR systems for memory assessment and depth perception

Cárdenas Delgado, Sonia Elizabeth 15 January 2018 (has links)
La evolución de la tecnología de Realidad Virtual (RV) ha contribuido en todos los campos, incluyendo la psicología. Esta evolución implica mejoras tanto en hardware como en software, que permiten experiencias más inmersivas. En un entorno de RV los usuarios pueden percibir la sensación de "presencia" y sentirse "inmersos". Estas sensaciones son posibles utilizando HMDs. Hoy en día, el desarrollo de los HMDs se ha centrado en mejorar sus características técnicas para ofrecer inmersión total. En psicología, los entornos de RV son una herramienta de investigación. Hay algunas aplicaciones para evaluar la memoria espacial que utilizan métodos básicos de interacción. Sin embargo, sistemas de RV que incorporen estereoscopía y movimiento físico todavía no se han explotado en psicología. En esta tesis, se ha desarrollado un nuevo sistema de RV que combina características inmersivas, interactivas y de movimiento. El sistema de RV (tarea en un laberinto virtual) se ha utilizado para evaluar la memoria espacial y la percepción de profundidad. Se han integrado dos tipos diferentes de interacción: una basada en locomoción que consistió en pedalear en una bicicleta fija (condición1) y otra estacionaria usando un gamepad (condición2). El sistema integró dos tipos de visualización: 1) Oculus Rift (OR); 2) Una gran pantalla estéreo. Se diseñaron dos estudios. El primer estudio (N=89) evaluó la memoria espacial a corto plazo usando el OR y los dos tipos de interacción. Los resultados indican que existían diferencias significativas entre ambas condiciones. Los participantes que utilizaron la condición2 obtuvieron mejor rendimiento que los que utilizaron la tarea en la condición1. Sin embargo, no se encontraron diferencias significativas en las puntuaciones de satisfacción e interacción entre ambas condiciones. El desempeño en la tarea correlacionó con el desempeño en las pruebas neuropsicológicas clásicas, revelando la verosimilitud entre ellas. El segundo estudio (N=59) incluyó participantes con y sin estereopsis. Este estudio evaluó la percepción de profundidad comparando los dos sistemas de visualización. Los participantes realizaron la tarea usando la condición2. Los resultados mostraron que las diferentes características del sistema de visualización no influyeron en el rendimiento en la tarea entre los participantes con y sin estereopsis. Se encontraron diferencias significativas a favor del HMD entre las dos condiciones y entre los dos grupos de participantes respecto a la percepción de profundidad. Los participantes que no tenían estereopsis y no podían percibir la profundidad cuando utilizaban otros sistemas de visualización, tuvieron la ilusión de percepción de profundidad cuando utilizaron el OR. El estudio sugiere que para las personas que no tienen estereopsis, el seguimiento de la cabeza influye en gran medida en la experiencia 3D. Los resultados estadísticos de ambos estudios han demostrado que el sistema de RV desarrollado es una herramienta apropiada para evaluar la memoria espacial a corto plazo y la percepción de profundidad. Por lo tanto, los sistemas de RV que combinan inmersión total, interacción y movimiento pueden ser una herramienta útil para la evaluación de procesos cognitivos humanos como la memoria. De estos estudios se han extraído las siguientes conclusiones generales: 1) La tecnología de RV y la inmersión proporcionada por los actuales HMDs son herramientas adecuadas para aplicaciones psicológicas, en particular, la evaluación de la memoria espacial a corto plazo; 2) Un sistema de RV como el presentado podría ser utilizado como herramienta para evaluar o entrenar adultos en habilidades relacionadas con la memoria espacial a corto plazo; 3) Los dos tipos de interacción utilizados para la navegación en el laberinto virtual podrían ser útiles para su uso con diferentes colectivos; 4) El OR permite que los usuarios sin estereopsis puedan percibir l / The evolution of Virtual Reality (VR) technology has contributed in all fields, including psychology. This evolution involves improvements in hardware and software allowing more immersive experiences. In a VR environment users can perceive the sensation of "presence" and feel "immersed". These sensations are possible using VR devices as HMDs. Nowadays, the development of the HMDs has focused on improving their technical features to offer full immersion. In psychology, VR environments are research tools because they allow the use of new paradigms that are not possible to employ in a real environment. There are some applications for assessing spatial memory that use basic methods of HCI. However, VR systems that incorporate stereoscopy and physical movement have not yet been exploited in psychology. In this thesis, a novel VR system combining immersive, interactive and motion features was developed. This system was used for the assessment of the spatial memory and the evaluation of depth perception. For this system, a virtual maze task was designed and implemented. In this system, two different types of interaction were integrated: a locomotion-based interaction pedaling a fixed bicycle (condition1), and a stationary interaction using a gamepad (condition2). This system integrated two types of display systems: 1) The Oculus Rift; 2) A large stereo screen. Two studies were designed to determine the efficacy of the VR system using physical movement and immersion. The first study (N=89) assessed the spatial short term memory using the Oculus Rift and the two types of interaction The results showed that there were statistically significant differences between both conditions. The participants who performed the condition2 got better performance than participants who performed the condition1. However, there were no statistically significant differences in satisfaction and interaction scores between both conditions. The performance on the task correlated with the performance on other classical neuropsychological tests, revealing a verisimilitude between them. The second study (N=59) involved participants who had and who had not stereopsis. This study assessed the depth perception by comparing the two display systems. The participants performed the task using the condition2. The results showed that the different features of the display system did not influence the performance on the task between the participants with and without stereopsis. Statistically significant differences were found in favor of the HMD between the two conditions and between the two groups of participants regard to depth perception. The participants who did not have stereopsis and could not perceive the depth when they used other display systems (e.g. CAVE); however, they had the illusion of depth perception when they used the Oculus Rift. The study suggests that for the people who did not have stereopsis, the head tracking largely influences the 3D experience. The statistical results of both studies have proven that the VR system developed for this research is an appropriate tool to assess the spatial short-term memory and the depth perception. Therefore, the VR systems that combine full immersion, interaction and movement can be a helpful tool for the assessment of human cognitive processes as the memory. General conclusions from these studies are: 1) The VR technology and immersion provided by current HMDs are appropriate tools for psychological applications, in particular, the assessment of spatial short-term memory; 2) A VR system like the one presented in this thesis could be used as a tool to assess or train adults in skills related to spatial short-term memory; 3) The two types of interaction (condition1 and condition2) used for navigation within the virtual maze could be helpful to use with different collectives; 4) The Oculus Rift allows that the users without stereopsis can perceive the depth perception of 3D objects and have rich 3D experiences. / L'evolució de la tecnologia de Realitat Virtual (RV) ha contribuït en tots els camps, incloent la psicologia. Aquesta evolució implica millores en el maquinari i el programari que permeten experiències més immersives. En un entorn de RV, els usuaris poden percebre la sensació de "presència" i sentir-se "immersos". Aquestes sensacions són possibles utilitzant HMDs. Avui dia, el desenvolupament dels HMDs s'ha centrat a millorar les seves característiques tècniques per oferir immersió plena. En la psicologia, els entorns de RV són eines de recerca. Hi ha algunes aplicacions per avaluar la memòria espacial que utilitzen mètodes bàsics d'interacció. Tanmateix, sistemes de RV que incorporen estereoscòpia i moviment físic no s'han explotat en psicologia. En aquesta tesi, s'ha desenvolupat un sistema de RV novell que combina immersió, interacció i moviment. El sistema (tasca en un laberint virtual) s'ha utilitzat per a l'avaluació de la memòria espacial i la percepció de profunditat. S'han integrat dos tipus d'interacció: una interacció basada en locomoció pedalejant una bicicleta fixa (condició1), i l'altra una interacció estacionària usant un gamepad (condició2). S'han integrat dos tipus de sistemes de pantalla: 1) L'Oculus Rift; 2) Una gran pantalla estereoscòpica. Dos estudis van ser dissenyats. El primer estudi (N=89) va avaluar la memòria a curt termini i espacial utilitzant l'Oculus Rift i els dos tipus d'interacció. Els resultats indiquen que hi havia diferències significatives entre les dues condicions. Els participants que van utilitzar la condició2 van obtenir millor rendiment que els participants que van utilitzar la condició1. Tanmateix, no hi havia diferències significatives dins satisfacció i puntuacions d'interacció entre les dues condicions. El rendiment de la tasca va correlacionar amb el rendiment en les proves neuropsicològiques clàssiques, revelant versemblança entre elles. El segon estudi (N=59) va implicar participants que van tenir i que van haver-hi no estereopsis. Aquest estudi va avaluar la percepció de profunditat comparant els dos sistemes de pantalla. Els participants realitzen la tasca utilitzant la condició2. Els resultats van mostrar que les diferents característiques del sistema de pantalla no va influir en el rendiment en la tasca entre els participants qui tenien i els qui no tenien estereopsis. Diferències significatives van ser trobades a favor del HMD entre les dues condicions i entre els dos grups de participants. Els participants que no van tenir estereopsis i no podien percebre la profunditat quan van utilitzar altres sistemes de pantalla (per exemple, CAVE), van tenir la il.lusió de percepció de profunditat quan van utilitzar l'Oculus Rift. L'estudi suggereix que per les persones que no van tenir estereopsis, el seguiment del cap influeix en gran mesura en l'experiència 3D. Els resultats estadístics dels dos estudis han provat que el sistema de RV desenvolupat per aquesta recerca és una eina apropiada per avaluar la memòria espacial a curt termini i la percepció de profunditat. Per això, els sistemes de RV que combinen immersió plena, interacció i moviment poden ser una eina útil per la avaluació de processos cognitius humans com la memòria Les conclusions generals que s'han extret d'aquests estudis, són les següents: 1) La tecnologia de RV i la immersió proporcionada pels HMDs són eines apropiades per aplicacions psicològiques, en particular, la avaluació de memòria espacial a curt termini; 2) Un sistema de RV com el presentat podria ser utilitzat com a eina per avaluar o entrenar adults en habilitats relacionades amb la memòria espacial a curt termini; 3) Els dos tipus d'interacció utilitzats per navegació dins del laberint virtual podrien ser útils per al seu ús amb diferent col.lectius; 3) L'Oculus Rift permet que els usuaris que no tenen estereopsis puguen percebre la percepció de profunditat dels objectes 3D i tenir / Cárdenas Delgado, SE. (2017). VR systems for memory assessment and depth perception [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94629 / TESIS
173

Realizace kamerového modulu pro mobilní robot jako nezávislého uzlu systému ROS - Robot Operating System / Realization of camera module for mobile robot as independent ROS node

Albrecht, Ladislav January 2020 (has links)
Stereo vision is one of the most popular elements in the field of mobile robots and significantly contributes to their autonomous behaviour. The aim of the diploma thesis was to design and implement a camera module as a hardware sensor input, which is independent, with the possibility of supplementing the system with other cameras, and to create a depth map from a pair of cameras. The diploma thesis consists of theoretical and practical part, including the conclusion of results. The theoretical part introduces the ROS framework, discusses methods of creating depth maps, and provides an overview of the most popular stereo cameras in robotics. The practical part describes in detail the preparation of the experiment and its implementation. It also describes the camera calibration and the depth map creating. The last chapter contains an evaluation of the experiment.
174

Systém pro autonomní mapování závodní dráhy / System for autonomous racetrack mapping

Soboňa, Tomáš January 2021 (has links)
The focus of this thesis is to theoretically design, describe, implement and verify thefunctionality of the selected concept for race track mapping. The theoretical part ofthe thesis describes the ORB-SLAM2 algorithm for vehicle localization. It then furtherdescribes the format of the map - occupancy grid and the method of its creation. Suchmap should be in a suitable format for use by other trajectory planning systems. Severalcameras, as well as computer units, are described in this part, and based on parametersand tests, the most suitable ones are selected. The thesis also proposes the architectureof the mapping system, it describes the individual units that make up the system, aswell as what is exchanged between the units, and in what format the system output issent. The individual parts of the system are first tested separately and subsequently thesystem is tested as a whole. Finally, the achieved results are evaluated as well as thepossibilities for further expansion.
175

Měření vzdálenosti stereoskopickým senzorem / Stereoscopic sensor for distance measurement

Vavroš, Ondřej January 2014 (has links)
This master's thesis will take us through theoretical procedure that allows us to determine the distance of an object by stereoscopic sensor. Part of this work presents the description of the steps to achieve image of objects, calibraton and rectification. At the next part our study provides an overview of algortihms for creating disparity maps and determining the distance of the object from sensor. In the following part of thesis deals with the implementation of these processes into aplication which aim is to measure the distance.
176

Měření vzdálenosti stereoskopickým senzorem / Stereoscopic sensor for distance measurement

Vavroš, Ondřej January 2015 (has links)
This master's thesis will take us through theoretical procedure that allows us to determine the distance of an object by stereoscopic sensor. Part of this work presents the description of the steps to achieve image of objects, calibraton and rectification. At the next part our study provides an overview of algortihms for creating disparity maps and determining the distance of the object from sensor. In the following part of thesis deals with the implementation of these processes into aplication which aim is to measure the distance.
177

Stereovizní systém pro počítání cestujících v hromadných dopravních prostředcích / Passenger Counting System Based on Stereovision

Vrzal, Radek January 2016 (has links)
This thesis deals with a concept of system for automatic passenger counting in different  modes of transport. Counting units are placed in top of the door area in the vehicle. Passengers are detected at the disparity map counted from the stereo-camera images. Object tracking is achieved with Global nearest neighbor and Multiple hypothesis tracking algorithm. This system is used for public transportation surveys.
178

Localization and panning of musical sources within the context of a musical mix

Backlund, Alice January 2022 (has links)
In recent years, the research on the localization of audio objects within a stereo context has started to include musical audio objects. This study seeks to explore a research gap: localization ability whilst hearing multiple sounds. This study aims to investigate listeners’ ability to localize panned musical audio objects within a musical context. Subjects listened to two different versions of the same mix and were asked to simultaneously pan musical audio objects with different characteristics. When comparing the results from the different mixes, both mixes gave similar results. Therefore, the differences between the mixes had no impact on localization accuracy. Additionally, this study was able to reconstruct previous findings indicating that localization blur affects localization accuracy of wide-panned audio objects.
179

Fusion of Stationary Monocular and Stereo Camera Technologies for Traffic Parameters Estimation

Ali, Syed Musharaf 07 March 2017 (has links)
Modern day intelligent transportation system (ITS) relies on reliable and accurate estimated traffic parameters. Travel speed, traffic flow, and traffic state classification are the main traffic parameters of interest. These parameters can be estimated through efficient vision-based algorithms and appropriate camera sensor technology. With the advances in camera technologies and increasing computing power, use of monocular vision, stereo vision, and camera sensor fusion technologies have been an active research area in the field of ITS. In this thesis, we investigated stationary monocular and stereo camera technology for traffic parameters estimation. Stationary camera sensors provide large spatial-temporal information of the road section with relatively low installation costs. Two novel scientific contributions for vehicle detection and recognition are proposed. The first one is the use stationary stereo camera technology, and the second contribution is the fusion of monocular and stereo camera technologies. A vision-based ITS consists of several hardware and software components. The overall performance of such a system does not only depend on these single modules but also on their interaction. Therefore, a systematic approach considering all essential modules was chosen instead of focusing on one element of the complete system chain. This leads to detailed investigations of several core algorithms, e.g. background subtraction, histogram based fingerprints, and data fusion methods. From experimental results on standard datasets, we concluded that proposed fusion-based approach, consisting of monocular and stereo camera technologies performs better than each particular technology for vehicle detection and vehicle recognition. Moreover, this research work has a potential to provide a low-cost vision-based solution for online traffic monitoring systems in urban and rural environments.
180

Vyhledávání korespondence ve stereosnímcích tváří / Stereoscopic Face Images Matching

Klaudíny, Martin Unknown Date (has links)
This thesis is dedicated to the problem of 3D face capture. A majority of current face capture systems exploits a pattern projection. The goal of thesis was to develop the 3D face capture system based on the passive stereo photogrammetry. The high-resolution images of a face are captured by one pair of the calibrated digital still cameras. The image pre-processing consists of the removal of lens distortion, rectification of image pair and face extraction. The stereo image matching is accentuated. Three different approaches to the stereo correspondence search are presented - the local technique, the global technique using a graph cut and the hybrid technique merging previous two. At last, the 3D model is reconstructed according to the found correspondence. The results show that the high-quality 3D face models can be obtained despite traditional difficulties with matching pattern-free face images. Also it is possible to keep the computational demands on the acceptable level, although the high-resolution images are processed.

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