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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.
1

Synthetic Data Generation for 6D Object Pose and Grasping Estimation

Martínez González, Pablo 16 March 2023 (has links)
Teaching a robot how to behave so it becomes completely autonomous is not a simple task. When robotic systems become truly intelligent, interactions with them will feel natural and easy, but nothing could be further from truth. Make a robot understand its surroundings is a huge task that the computer vision field tries to address, and deep learning techniques are bringing us closer. But at the cost of the data. Synthetic data generation is the process of generating artificial data that is used to train machine learning models. This data is generated using computer algorithms and simulations, and is designed to resemble real-world data as closely as possible. The use of synthetic data has become increasingly popular in recent years, particularly in the field of deep learning, due to the shortage of high-quality annotated real-world data and the high cost of collecting it. For that reason, in this thesis we are addressing the task of facilitating the generation of synthetic data with the creation of a framework which leverages advances in modern rendering engines. In this context, the generated synthetic data can be used to train models for tasks such as 6D object pose estimation or grasp estimation. 6D object pose estimation refers to the problem of determining the position and orientation of an object in 3D space, while grasp estimation involves predicting the position and orientation of a robotic hand or gripper that can be used to pick up and manipulate the object. These are important tasks in robotics and computer vision, as they enable robots to perform complex manipulation and grasping tasks. In this work we propose a way of extracting grasping information from hand-object interactions in virtual reality, so that synthetic data can also boost research in that area. Finally, we use this synthetically generated data to test the proposal of applying 6D object pose estimation architectures to grasping region estimation. This idea is based on both problems sharing several underlying concepts such as object detection and orientation. / Enseñar a un robot a ser completamente autónomo no es tarea fácil. Cuando los sistemas robóticos sean realmente inteligentes, las interacciones con ellos parecerán naturales y fáciles, pero nada más lejos de la realidad. Hacer que un robot comprenda y asimile su entorno es una difícil cruzada que el campo de la visión por ordenador intenta abordar, y las técnicas de aprendizaje profundo nos están acercando al objetivo. Pero el precio son los datos. La generación de datos sintéticos es el proceso de generar datos artificiales que se utilizan para entrenar modelos de aprendizaje automático. Estos datos se generan mediante algoritmos informáticos y simulaciones, y están diseñados para parecerse lo más posible a los datos del mundo real. El uso de datos sintéticos se ha vuelto cada vez más popular en los últimos años, especialmente en el campo del aprendizaje profundo, debido a la escasez de datos reales anotados de alta calidad y al alto coste de su recopilación. Por ello, en esta tesis abordamos la tarea de facilitar la generación de datos sintéticos con la creación de una herramienta que aprovecha los avances de los motores modernos de renderizado. En este contexto, los datos sintéticos generados pueden utilizarse para entrenar modelos para tareas como la estimación de la pose 6D de objetos o la estimación de agarres. La estimación de la pose 6D de objetos se refiere al problema de determinar la posición y orientación de un objeto en el espacio 3D, mientras que la estimación del agarre implica predecir la posición y orientación de una mano robótica o pinza que pueda utilizarse para coger y manipular el objeto. Se trata de tareas importantes en robótica y visión por computador, ya que permiten a los robots realizar tareas complejas de manipulación y agarre. En este trabajo proponemos una forma de extraer información de agarres a partir de interacciones mano-objeto en realidad virtual, de modo que los datos sintéticos también puedan impulsar la investigación en esa área. Por último, utilizamos estos datos generados sintéticamente para poner a prueba la propuesta de aplicar arquitecturas de estimación de pose 6D de objetos a la estimación de regiones de agarre. Esta propuesta se basa en que ambos problemas comparten varios conceptos subyacentes, como la detección y orientación de objetos. / This thesis has been funded by the Spanish Ministry of Education [FPU17/00166]
2

Nya spelregler för skogsindustrin : En studie om möjligheter att gamifiera ett skogsbolags transportstyrningssystem

Edmon, Jannika January 2018 (has links)
Today, companies need to constantly improve in order to be competitive and achieve good results. Gamification is a concept that is being implemented by more and more companies to increase motivation for employees as well as to engage them to work in a way that can help fulfil the goals of the company, which in the long run can lead to improved results. This study is based on a case with an international IT consulting company and their customer who works in the forest industry. The consulting company has developed an IT system for the customer, where timber car drivers are the system users among others. The purpose of the study has been to explore the possibilities to gamify the existing IT system in order to increase the system usage and encourage certain behaviors of the drivers that are aligned with the customer’s goals. Furthermore, the goal of the study has been to follow a gamification framework to develop suggestions on features in the system that can support these behaviors of the drivers. The framework has been used in combination with different methods for data collection such as interviews and open questionnaires. The use of the framework has resulted in four features that can be implemented in the system to support certain behaviors of the drivers. All features provide feedback to the user in different ways, following an action taken, to motivate continued use. Prior to implementation however, it is recommended that measures be taken to ensure that the gamification project is able to succeed. / Idag behöver företag ständigt förbättra sig för att vara konkurrenskraftiga och uppnå goda resultat. Gamification är ett koncept som implementeras av allt fler företag för att öka motivationen hos anställda samt för att engagera dem så att de arbetar efter verksamhetens mål, något som långsiktigt kan leda till ett förbättrat resultat. Denna studie är baserad på ett fall hos ett internationellt IT-konsultbolag och deras kund som verkar inom skogsindustribranschen. Konsultbolaget har utvecklat ett IT-system för kunden där några av systemanvändarna är timmerbilschaufförer. Syftet med studien har varit att undersöka möjligheter till att gamifiera det befintliga IT-systemet för att öka systemanvändningen och uppmuntra till beteenden hos chaufförerna som går i linje med kundföretagets mål. Vidare har målet med studien varit att följa ett gamification-ramverk för att ta fram förslag på funktioner i systemet som kan stödja dessa beteenden. Ramverket har använts i kombination med olika metoder för datainsamling som exempelvis intervjuer och öppna enkätfrågor. Användningen av ramverket har resulterat i fyra funktioner som kan implementeras i systemet för att stödja vissa beteenden hos chaufförerna. Samtliga funktioner ger på olika sätt återkoppling till användaren efter en utförd handling, för att motivera till fortsatt användning. Innan implementering rekommenderas dock vidtagande av åtgärder för att gamification-projektet ska ha möjlighet att lyckas.
3

Les utilités EQ-5D et SF-6D dans la polyarthrite débutante / Indirect utility measures, EQ-5D and SF-6D, in early arthritis

Gaujoux-Viala, Cécile 07 November 2012 (has links)
La notion d’instauration rapide d’un traitement efficace et agressif dans la polyarthrite débutante a renforcé la nécessité de disposer de mesures d’utilité validées afin d’optimiser l’évaluation médico-économique de ces traitements. Actuellement, il n’y a pas de consensus sur le choix du questionnaire multi-attributs à utiliser pour le calcul des utilités. L’objectif de cette thèse est donc d’étudier les niveaux, les performances et les déterminants des 2 outils indirects de mesure d’utilité (EQ-5D et SF-6D) dans la polyarthrite débutante, au travers des données de la cohorte ESPOIR, cohorte multicentrique française de polyarthrites débutantes. En conclusion, l’EQ-5D et le SF-6D ne sont pas interchangeables dans la polyarthrite débutante : ils ont des échelles, des distributions, une reproductibilité et une sensibilité au changement différentes. Ils ne donnent pas les mêmes résultats surtout quand les patients ont un mauvais état de santé et plus particulièrement une incapacité fonctionnelle importante. La distribution bimodale de l’EQ-5D, sa moins bonne reproductibilité, le fait qu’il soit moins sensible à l’amélioration, sa plus grande variabilité dans l’estimation du gain d’utilité et donc des QALYs, les problèmes soulevés par la signification d’un état « pire que la mort » (qui n’est pas celle du patient), favoriseraient plutôt l’utilisation du SF-6D dans les essais sur les nouvelles biothérapies dans la polyarthrite débutante / The explosion of drug development for rheumatoid arthritis and the revolution of early aggressive therapy for the disease have fuelled the search for better approaches to establish cost-effectiveness in early arthritis (EA), but consensus is lacking on the choice of utility instrument. We aimed to compare the EQ-5D and SF-6D, 2 indirect utility measures widely used to calculate quality-adjusted life-years (QALYs), in terms of their utility values, their performance and their determinants in a large prospective cohort of patients with EA. In conclusion, the EQ-5D and SF-6D are not interchangeable: their scales, distributions, reliability and responsiveness are different. There is systematic disagreement between the EQ-5D and SF-6D in EA especially in patients with worse clinical outcomes and more specifically with high functional disability. Several elements suggest that the SF-6D may be more appropriate for clinical trials of biologics in patients with EA: the bimodal distribution of the EQ-5D, its lower reliability and responsiveness for EA improvement than the SF-6D, its high variability in the estimation of the utility gains and thus QALYs gains and the problems raised by the meaning of a state labeled " worse than the death " (which is not the one from the patient)
4

Mesure et interprétation du changement d'utilité dérivée d'instruments de qualité de vie psychométriques / Measurement and interpretation of change utility derived from psychometric instruments

Hosseini, Kossar 13 December 2013 (has links)
Dans le domaine de la santé, la mesure d'utilité permet d'exprimer la valeur que peut donner un individu à un état de santé, comprise généralement entre 0 (la mort) et 1 (meilleur état de santé envisageable). L'utilité permet de valoriser simultanément le résultat clinique et son impact sur l'état de santé du patient, et d'exprimer ainsi la qualité de vie liée à la santé. Nous nous sommes intéressés dans ce travail à l'approche indirecte d'estimation d'utilité, consistant à dériver une utilité à partir des échelles psychométriques de mesure de l'état de santé (questionnaires génériques). Cette approche permet de répéter la mesure de l'utilité dans le temps et ouvre des perspectives pour l'analyse du changement d'utilité. Les objectifs étaient de définir un seuil de changement pour l'utilité dérivée des instruments de mesure psychométrique de la qualité de vie, et de prendre en compte dans l'interprétation du seuil la présence des comorbidités ou d'un phénomène de response-shift. Afin de répondre à nos objectifs, nous avons étudié, d'une part, le changement d'utilité mesurée par le SF-6D dans une cohorte de patients atteints d'arthrose des membres inférieurs (cohorte KHOALA) et l'effet des comorbidités sur l'utilité et son changement. D'autre part, nous avons estimé l'utilité de donneur vivant de rein à partir des questionnaires EQ-5D et SF-6D avant et 3 mois après le prélèvement du rein. Un seuil de changement a été estimé et un phénomène de response-shift a été recherché. Les résultats ont montré l'effet délétère des comorbidités sur la mesure de l'utilité chez les patients atteints d'arthrose, et mis en évidence l'importance de la sévérité fonctionnelle de l'arthrose dans l'expression de l'utilité et son changement. Chez les donneurs vivants de rein nous avons mis en évidence une diminution significative de l'utilité à 3 mois, avec une proportion de plus de 30% de donneurs ayant atteint le seuil de détérioration significative. L'estimation du seuil de changement diffère selon la population étudiée, l'instrument de mesure de l'utilité, et la méthodologie appliquée pour définir ce seuil. En conclusion, l'évaluation du changement d'utilité doit tenir compte de l'existence des comorbidités ainsi que de l'adaptation du jugement de valeur que l'individu porte sur son état de santé lorsque celui-ci évolue. La complexité des méthodes psychométriques pour la mesure de l'utilité doit amener à être prudent sur leur prise en compte dans les modèles d'évaluation économique. L'identification d'un seuil pour l'interprétation du changement peut être un élément complémentaire utile dans la démarche d'analyse décisionnelle / In health economic, the concept of utility was used to describe a state of health in patients. The unit value of health state utility ranges between 0, representing "death" state, and 1 representing a "perfect" health state. It is possible to recover through the measurement of utility both the clinical outcome and their impact on the health of the patient, and thus express the quality of life related to health. In this work, we used the indirect approach for estimating utility that is derived from a generic utility scales (quality of life questionnaires). The objectives of this thesis were to define a threshold of change for the utility derived from psychometric instruments measuring quality of life, and to take into account for the change interpretation, the presence of comorbidities or a response-shift phenomenon. We used data from a cohort of patients with osteoarthritis of lower limbs (KHOALA cohort) for estimate the impact of comorbidities in utility measured by the SF-6D its change over 3 years. We are also interested in the particular case of living kidney donors. The utility was estimated by the EQ-5D and SF-6D before and 3 months after kidney donation. A threshold of significant deterioration has been estimated and the presence of a response-shift phenomenon was controlled. The results showed the deleterious effect of comorbidities on utility measurement for patients with lower limbs osteoarthritis, and highlighted the importance of the functional severity of osteoarthritis in the expression of utility and its change over time. Living kidney donors experienced a significant decrease in their utility score in the short term, and more than third of donors have reached the threshold of significant deterioration. The threshold of utility change varies depending on the population studied, the measurement instrument, and the methodology used to define the threshold. In conclusion, the assessment of utility change must take into account the existence of other diseases and the adaptation of the individual on his health state variation. The complexity of measuring individual preferences by psychometric instruments should lead to be careful about introducing them in the economic evaluation. The use of a threshold for the interpretation of utility change can be an additional element in the decision-making process
5

Más allá de la tecnología: BIM como una nueva filosofía

Fernández Ramos, Leandro, Ríos Rugel, Renzo, Marreros Aguilar, John 10 April 2018 (has links)
BIM (Building Information Modeling, por sus siglas en inglés) es una metodología de trabajo multidisciplinario basado en modelos interoperables que mejora la comunicación y el flujo de la información de los stakeholders durante todo el ciclo de vida del proyecto. Esta metodología busca reemplazar a las herramientas tradicionales en el proceso de desarrollo de un proyecto y fomentar la industrialización dentro del sector de la construcción en cada una de sus fases. En este artículo, se brindará un resumen de los beneficios de emplear BIM en cada una de sus dimensiones (BIM-3D, BIM-4D, BIM-5D, BIM-6D y BIM-7D).
6

Generating Synthetic Data for Evaluation and Improvement of Deep 6D Pose Estimation

Löfgren, Tobias, Jonsson, Daniel January 2020 (has links)
The task of 6D pose estimation with deep learning is to train networks to, from an im-age of an object, determine the rotation and translation of the object. Impressive resultshave recently been shown in deep learning based 6D pose estimation. However, many cur-rent solutions rely on real-world data when training, which as opposed to synthetic data,requires time consuming annotation. In this thesis, we introduce a pipeline for generatingsynthetic ground truth data for deep 6D pose estimation, where annotation is done auto-matically. With a 3D CAD-model, we use Blender to render 2D images of the model fromdifferent view points. We also create all other relevant data needed for pose estimation, e.g.,the poses of an object, mask images and 3D keypoints on the object. Using this pipeline, itis possible to adjust different settings to reduce the domain gap between synthetic data andreal-world data and get better pose estimation results. Such settings could be changing themethod of extracting 3D keypoints and varying the scale of the object or the light settingsin the scene.The network used to test the performance of training on our synthetic data is PVNet,which achieves state-of-the-art results for 6D pose estimation. This architecture learns tofind 2D keypoints of the object in the image, as well as 2D–3D keypoint correspondences.With these correspondences, the Perspective-n-Point (PnP) algorithm is used to extract apose. We evaluate the pose estimation of the different settings on the synthetic data andcompare these results to other state-of-the-art work. We find that using only real-worlddata for training is worse than using a combination of synthetic and real-world data. Sev-eral other findings are that varying scale and lightning, in addition to adding random back-ground images to the rendered images improves results. Four different novel keypoint se-lection methods are introduced in this work, and tried against methods used in previouswork. We observe that our methods achieve similar or better results. Finally, we use thebest possible settings from the synthetic data pipeline, but with memory limitations on theamount of training data. We are close to state-of-the-art results, and could get closer withmore data.
7

Integrability of super spin chains in 6D N=(1,0) SCFTs

He, Zuxian January 2023 (has links)
Superconformal field theories (SCFTs) are an important class of quantum field theories. These SCFTs have been a significant component in exploring and comprehending the fundamental framework of quantum field theories. In the vast realm of quantum field theories, integrability plays a crucial role, providing powerful analytic tools that allow us to solve certain physical quantities exactly. In this thesis, we focus on the representation theory of the algebraic structure in six-dimensional (6D) SCFTs and investigate the intricate interplay between 6D SCFTs and integrability. To begin, we delve into the fundamental concepts of representation theory, establishing a solid foundation for our subsequent analysis. The discussion then will move on to all possible generators in the SCFTs, explaining how they are realized in terms of bosonic and fermionic oscillators. Finally, we investigate spin chains and their application in 6D SCFTs. We demonstrate that symmetry arguments derived from representation theory are not sufficient to establish the integrability of the spin chains in 6D SCFTs. This conclusion does not imply the absence of integrable systems within 6D SCFTs; rather, it suggest there are other potential methods available e.g., correlation functions, to explore the appearance of integrable systems in 6D SCFTs. / Superkonforma fältteorier (SCFTs) är en viktig klass av kvantfältteorier. Dessa SCFTs utgör en viktig komponent för att utforska och förstå det fundamentala ramverket för kvantfältteorin. Inom det stora riket av kvantfältteori spelar integrabilitet en avgörande roll, vilket tillhandahåller kraftfulla analytiska verktyg som gör att vi kan lösa vissa fysiska storheter exakt. I denna avhandling fokuserar vi på representationsteorin av den algebraiska strukturen i sexdimensionella (6D) SCFTs och undersöker det intrikat samspelet mellan 6D SCFTs och integrabilitet. Till att börja med kommer vi att fördjupa oss i de grundläggande begreppen inom representationsteori och skapa en gedigen grund för vår efterföljande analys.  Diskussionen kommer sedan att gå vidare till alla möjliga generatorer i SCFTs, och förklarar hur de realiseras i termer av bosoniska och fermioniska oscillatorer. Slutligen kommer spinnkedjor och dess tillämpningar i 6D SCFTs att undersökas. Vi kommer visa att symmetriargument som härleds från representationsteori inte är  tillräckliga för att fastställa integrerbarhet av spinnkedjor i 6D SCFTs. Denna slutsats innebär inte att integrerbara system inte existerar inom 6D SCFTs, utan föreslår att det finns andra potentiella metoder, till exempel korrelationsfunktioner, för att utforska existensen av integrerbara system i 6D SCFTs.
8

Cross-Cultural Comparative Study of Entrepreneurial Leadership Traits Among Brazil and China in Small Businesses

Mueller Meirinho, Ana Clara, Mengting, Li January 2019 (has links)
Title: Cross-Cultural Comparative Study of Entrepreneurial Leadership Traits Among Brazil and China in Small Businesses Authors: Ana Clara Mueller Meirinho and Li Mengting Level: Master Thesis, 30 hp Keywords: Entrepreneurial leadership, Leader traits, Hofstede’s 6D Model, Small Business, Cross-Cultural leadership, Brazil, China. Background: Entrepreneurship is important among all the countries for the growth and prosperity of nations due to movement of economic activities that they generate. To sustain a business, the character behind it, known as a leader, plays an important role since for guiding a business the entrepreneurs needs to provide a clear vision for the company. Entrepreneurial leaders can have different postures when leading business inside a country. Yet, when comparing between countries, their behaviors can be influenced by many aspects, mainly because of the culture of the nation. However, a study showed that appear to be a convergence of entrepreneurial leadership among the BRICS countries. Also, there have been a lack of studies of entrepreneurial leadership in emergent economies like the BRICS countries, and for that reason, Brazil and China were selected to be the main focus of this study. Furthermore, studies also lack measurements of entrepreneurial leadership traits and behaviors. Research Question: What are the predominant traits of entrepreneurial leaders of small business and which cultural aspect impact on the behaviour of leaders among Brazil and China? Sub research question: What are the similarities and differences on the way that leadership is conducted by entrepreneurs of small businesses among Brazil and China? Purpose: The purpose of this study is, therefore, to describe, explore and instigate predominant traits of leaders as entrepreneurs in small businesses that can lead to distinct behaviour, through investigations in Brazil and China. In addition, this study also verifies similarities and differences of leaders behaviour that can differ from one culture to another, due to cultural impact. This way, the authors developed a framework, to better visualize entrepreneurial leadership traits comparison between Brazil and China, giving the readers a better understanding of preferred traits in both countries, directing them to take right actions considering the cultural values. Method: A mixed method approach was used in this research. Qualitative semi-structured exploratory interviews with abductive approach were conducted with leaders who are entrepreneurs of small businesses in South Brazil and Urban China, which focuses on entrepreneurial leadership traits. Also, quantitative surveys were collected, aiming to measure cultural value and predominant traits of leaders, complementing the qualitative interview. Theoretical Framework: Articles used for this study were meticulously selected, focusing on reliable sources and quality content; also, it was given preferences to new data from well- known journals. This section covers subjects that are interesting and fit to the thematic, such as regarding of Entrepreneurial Leadership and Traits, Hofstede 6D Model, Importance of Micro and Small Businesses to Society, and economic and political facts about Brazil and China, alike as definitions and data of micro and small business characteristics in each nation, and the nations own beliefs. Particular information from the countries was brought from organizations and governmental related websites. Discussion and Conclusion: Based on the results of respondent’s surveys and the interpretation of interviews with entrepreneurs among south Brazil and China. The results are structured and analyzed in the same sequence as the surveys and interviews are designed using Hofstede 6D model, discussing first south Brazil and urban China and then a general overview about similarities and differences of both countries for each section. The study revealed that the preferred entrepreneurial leadership traits are divergence between two countries, while there appear to be a convergence of entrepreneurial leadership style that encompass more democratic, flexible, opportunity oriented yet still remaining the traits of paternalistic and authoritative leadership including directing, participative, consideration of subordinates in small businesses among both countries. Furthermore, the author presented an overview of similarities and different entrepreneurial leadership traits among two countries by categorized based on distal attributes, including personality, cognitive ability and motives values, as well as proximal attributes, including social appraisal skills, problem solving skills and expertise/tacit knowledge are shown in the end.
9

Higher-dimensional field theories from type II supergravity: Théories des champs à haute dimension résultant de la supergravité de type II

Fazzi, Marco 04 July 2016 (has links) (PDF)
Dans cette thèse, nous présentons des constructions explicites de la correspondance AdS/CFT dans le contexte de la théorie des cordes de type II. Ces constructions sont visées à mieux comprendre aspects de la physique nonperturbative de théories des champs superconformes à d = 6,5,4 dimensions. Dans la première partie de la thèse nous introduisons les systèmes de NS5-Dp-D(p+2)-branes de Hanany-Witten, au moyen desquels on peut construire théories des champs avec 8 supercharges. Quand p = 6, le système de NS5-D6-D8-branes permet de construire théories des champs superconformes à 6 dimensions, caractérisées par des multiplets tenseur, vecteur et hypermultiplets de la superalgèbre chirale N = (1,0). Ces théories sont décrites par des «quivers» linéaires; nous analysons en détails leurs propriétés. Dans le cadre de la correspondance AdS/CFT, une théorie superconforme à (d - 1) dimensions décrit la même physique qu’un vide de la théorie des cordes de type II compactifiée sur un espace-temps Anti-de Sitter à d dimensions (AdSd). Par le biais de la géométrie complexe généralisée nous reformulons les équations qui doivent être résolues pour trouver ces vides AdS. La seconde partie contient les contributions originales. Nous présentons une classification exhaustive des vides de la théorie des cordes de type II compactifiée sur AdS7. En type IIB, il n’y a aucun vide; en type IIA massif, nous construisons une nouvelle classe infinie (et analytique) de vides. L’espace interne est topologiquement une 3-sphere, déformée par la présence de D6 et D8-branes. Les isométries de cet espace réalisent la symétrie R des théories superconformes N = (1,0) à 6 dimensions. Nos vides AdS7 sont les duaux holographiques de ces dernières, et peuvent être obtenus par une limite près de l’horizon des systèmes de NS5-D6-D8-branes. Le second résultat est la construction d’une classe infinie de vides analytiques AdS5 en type IIA massif. L’espace interne est le produit d’une 3-sphere par une surface de Riemann. Les isométries de cet espace réalisent la symétrie R des théories superconformes N = 1 à 4 dimensions, dont nos vides AdS5 sont les duaux holographiques. Nous décrivons une bijection entre ces derniers et les vides AdS7 susmentionnés. L’interprétation holographique indique que les théories N = 1 à 4 dimensions sont obtenues en compactifiant celles N = (1,0) à 6 dimensions sur la même surface de Riemann. Troisièmement, nous réduisons à deux equations différentielles le problème de classification des vides AdS6 en type IIB duaux à théories superconformes N = 1 à 5 dimensions. L’espace interne de ces vides contient une 2-sphere, réalisant la symétrie R des ces dernières. / In this thesis we present explicit constructions of the AdS/CFT correspondence obtained from type II string theory. These constructions are aimed at studying aspects of the nonperturbative physics of 6d, 5d, 4d SCFTs. In the first part we introduce NS5-Dp-D(p+2) Hanany--Witten brane systems, capable of engineering field theories with 8 Q supercharges. In particular, when p=6, the NS5-D6-D8 brane systems are known to engineer 6d SCFT featuring tensor, vector and hypermultiplets of the chiral N=(1,0) superalgebra. These theories can be described by linear quivers. We analyze in detail their properties. In AdS/CFT, the same physics can be equivalently described by a (d-1)-dimensional SCFT and by type II string theory compactified on a d-dimensional AdS space (AdSd), giving rise to a so-called AdSd vacuum. By using techniques derived from generalized complex geometry we reformulate the equations that need to be satisfied in order to find these AdS vacua. The second part of the thesis contains the original contributions. We present a full classification of vacua of type II string theory compactified on AdS7. In type IIB there are no such vacua; in massive type IIA, we construct a new infinite class of (analytic) vacua. The internal space is topologically a three-sphere, deformed by the presence of D6 and D8-branes. The isometries of this space realize the R-symmetry of the 6d (1,0) SCFTs. Our AdS7 vacua are the holographic duals of the latter, and can be obtained via a near-horizon limit of the NS5-D6-D8 brane systems. The second result is the construction of an infinite class of analytic AdS5 vacua of massive IIA. The internal space is a fibration of a (distorted) three-sphere over a Riemann surface. Its isometries realize the R-symmetry of putative 4d N=1 SCFTs, holographically dual to our AdS5 vacua. We describe a universal one-to-one map between the latter and the aforementioned AdS7 vacua. The natural interpretation of this is that the 4d N=1 SCFTs can be obtained by compactifying (in a twisted way) the 6d (1,0) ones on the same Riemann surface. In the third and last part, we reduce to two PDEs the classification problem of AdS6 vacua of type IIB supergravity, which should be the holographic duals to 5d N=1 SCFTs. The latter can be engineered by webs of (p,q)-fivebranes in type IIB string theory. The internal space of the AdS6 vacua is given by a fibration of a round two-sphere over a two-dimensional surface; the isometries of the fibers should realize the R-symmetry of the dual field theories. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
10

CAD-Based Pose Estimation - Algorithm Investigation

Lef, Annette January 2019 (has links)
One fundamental task in robotics is random bin-picking, where it is important to be able to detect an object in a bin and estimate its pose to plan the motion of a robotic arm. For this purpose, this thesis work aimed to investigate and evaluate algorithms for 6D pose estimation when the object was given by a CAD model. The scene was given by a point cloud illustrating a partial 3D view of the bin with multiple instances of the object. Two algorithms were thus implemented and evaluated. The first algorithm was an approach based on Point Pair Features, and the second was Fast Global Registration. For evaluation, four different CAD models were used to create synthetic data with ground truth annotations. It was concluded that the Point Pair Feature approach provided a robust localization of objects and can be used for bin-picking. The algorithm appears to be able to handle different types of objects, however, with small limitations when the object has flat surfaces and weak texture or many similar details. The disadvantage with the algorithm was the execution time. Fast Global Registration, on the other hand, did not provide a robust localization of objects and is thus not a good solution for bin-picking.

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