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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.
231

Systemization of RFID Tag Antenna Design Based on Optimization Techniques and Impedance Matching Charts

Butt, Munam 16 July 2012 (has links)
The performance of commercial Radio Frequency Identification (RFID) tags is primarily limited by present techniques used for tag antenna design. Currently, industry techniques rely on identifying the RFID tag application (books, clothing, etc.) and then building antenna prototypes of different configurations in order to satisfy minimum read range requirements. However, these techniques inherently lack an electromagnetic basis and are unable to provide a low cost solution to the tag antenna design process. RFID tag performance characteristics (read-range, chip-antenna impedance matching, surrounding environment) can be very complex, and a thorough understanding of the RFID tag antenna design may be gained through an electromagnetic approach in order to reduce the tag antenna size and the overall cost of the RFID system. The research presented in this thesis addresses RFID tag antenna design process for passive RFID tags. With the growing number of applications (inventory, supply-chain, pharmaceuticals, etc), the proposed RFID antenna design process demonstrates procedures to design tag antennas for such applications. Electrical/geometrical properties of the antennas designed were investigated with the help of computer electromagnetic simulations in order to achieve optimal tag performance criteria such as read range, chip-impedance matching, antenna efficiency, etc. Experimental results were performed on the proposed antenna designs to compliment computer simulations and analytical modelling.
232

Realisierung einer prototypischen Hardwarelösung für ein inverses Pendel / FPGA-only Based Closed-loop Control for a Very Compact Inverted Pendulum with Kalman Filter

Berger, Benjamin 17 February 2011 (has links) (PDF)
Ziel der Arbeit ist die anschauliche Demonstration der Leistungsfähigkeit von Hardware- Systemen zur Regelung instabiler Systeme am Beispiel des Inversen Pendels. Dabei handelt es sich um das Balancieren eines Stabes, einem Standard-Problem der Regelungstechnik. Es wird die Konzeption und Implementierung einer Hardware-Regelung in einem FPGA-Prototypenboard zur Realisierung dieser Aufgabe beschrieben. Die Regelung basiert mit LQR-Entwurf und Kalman-Filter auf klassischen Methoden der Regelungstechnik. Zur Demonstration der Regelung wurde ein mechanischer Aufbau vorgenommen, an dem die Funktionsfähigkeit des Inversen Pendels praktisch gezeigt wurde.
233

Investigating and Enhancing Performance of Multiple Antenna Systems in Compact MIMO/Diversity Terminals

Zhang, Shuai January 2013 (has links)
Today, owners of small communicating device are interested in transmitting or receiving various multimedia data. By increasing the number of antennas at the transmitter and/or the receiver side of the wireless link, the diversity/Multiple-Input Multiple-Output (MIMO) techniques can increase wireless channel capacity without the need for additional power or spectrum in rich scattering environments. However, due to the limited space of small mobile devices, the correlation coefficients between MIMO antenna elements are very high and the total efficiencies of MIMO elements degrade severely. Furthermore, the human body causes high losses on electromagnetic wave. During the applications, the presence of users may result in the significant reduction of the antenna total efficiencies and highly affects the correlations of MIMO antenna systems. The aims of this thesis are to investigate and enhance the MIMO/diversity performance of multiple antenna systems in the free space and the presence of users. The background and theory of multiple antenna systems are introduced briefly first. Several figures of merits are provided and discussed to evaluate the multiple antenna systems. The decoupling techniques are investigated in the multiple antenna systems operating at the higher frequencies (above 1.7 GHz) and with high radiation efficiency. The single, dual and wide band isolation enhancements are realized through the half-wavelength decoupling slot, quarter-wavelength decoupling slot with T-shaped impedance transformer, tree-like parasitic element with multiple resonances, as well as the different polarizations and radiation patterns of multiple antennas. In the lower bands (lower than 960 MHz), due to the low radiation efficiency and strong chassis mode, the work mainly focused on how to directly reduce the correlations and enlarge the total efficiency. A new mode of mutual scattering mode is introduced. By increasing the Q factors, the radiation patterns of multiple antennas are separated automatically to reduce the correlations. With the inter-element distance larger than a certain distance, a higher Q factor also improved the total efficiency apart from the low correlation. A wideband LTE MIMO antenna with multiple resonances is proposed in mobile terminals. The high Q factors required for the low correlation and high efficiencies in mutual scattering mode is reduced with another mode of diagonal antenna-chassis mode. Hence, the bandwidth of wideband LTE MIMO antenna with multiple resonances mentioned above can be further enlarged while maintaining the good MIMO/diversity performance. The user effects are studied in different MIMO antenna types, chassis lengths, frequencies, port phases and operating modes. Utilizing these usefully information, an adaptive quad-element MAS has been proposed to reduce the user effects and the some geranial rules not limited to the designed MAS have also been given. / <p>QC 20130121</p> / EU Erasmus Mundus External Cooperation Window TANDEM
234

Approches algorithmiques pour l’inférence d’histoires de duplication en tandem avec inversions et délétions pour des familles multigéniques

Lajoie, Mathieu 08 1900 (has links)
[Français] Une fraction importante des génomes eucaryotes est constituée de Gènes Répétés en Tandem (GRT). Un mécanisme fondamental dans l’évolution des GRT est la recombinaison inégale durant la méiose, entrainant la duplication locale (en tandem) de segments chromosomiques contenant un ou plusieurs gènes adjacents. Différents algorithmes ont été proposés pour inférer une histoire de duplication en tandem pour un cluster de GRT. Cependant, leur utilisation est limitée dans la pratique, car ils ne tiennent pas compte d’autres événements évolutifs pourtant fréquents, comme les inversions, les duplications inversées et les délétions. Cette thèse propose différentes approches algorithmiques permettant d’intégrer ces événements dans le modèle de duplication en tandem classique. Nos contributions sont les suivantes: • Intégrer les inversions dans un modèle de duplication en tandem simple (duplication d’un gène à la fois) et proposer un algorithme exact permettant de calculer le nombre minimal d’inversions s’étant produites dans l’évolution d’un cluster de GRT. • Généraliser ce modèle pour l’étude d’un ensemble de clusters orthologues dans plusieurs espèces. • Proposer un algorithme permettant d’inférer l’histoire évolutive d’un cluster de GRT en tenant compte des duplications en tandem, duplications inversées, inversions et délétions de segments chromosomiques contenant un ou plusieurs gènes adjacents. / [English] Tandemly arrayed genes (TAGs) represent an important fraction of most genomes. A fundamental mechanism at the origin of TAG clusters is unequal crossing-over during meiosis, leading to the duplication of chromosomal segments containing one or many adjacent genes. Such duplications are called tandem duplications, as the duplicated segment is placed next to the original one on the chromosome. Different algorithms have been proposed to infer the tandem duplication history of a TAG cluster. However, their applicability is limited in practice since they do not take into account other frequent evolutionary events such as inversion, inverted duplication and deletion. In this thesis, we propose different algorithmic approaches allowing to integrate these evolutionary events in the original tandem duplication model of evolution. Our contributions are summarized as follows: • We integrate inversion events in a tandem duplication model restricted to single gene duplications, and we propose an exact algorithm allowing to compute the minimum number of inversions explaining the evolution of a TAG cluster. • We generalize this model to the study of orthologous TAG clusters in different species. • We propose an algorithm allowing to infer the evolutionary history of a TAG cluster through tandem duplication, inverted duplication, inversion and deletion of chromosomal segments containing one or many adjacent genes.
235

Σχεδιασμός και υλοποίηση δημοσιογραφικού RDF portal με μηχανή αναζήτησης άρθρων

Χάιδος, Γεώργιος 11 June 2013 (has links)
Το Resource Description Framework (RDF) αποτελεί ένα πλαίσιο περιγραφής πόρων ως μεταδεδομένα για το σημασιολογικό ιστό. Ο σκοπός του σημασιολογικού ιστού είναι η εξέλιξη και επέκταση του υπάρχοντος παγκόσμιου ιστού, έτσι ώστε οι χρήστες του να μπορούν ευκολότερα να αντλούν συνδυασμένη την παρεχόμενη πληροφορία. Ο σημερινός ιστός είναι προσανατολισμένος στον άνθρωπο. Για τη διευκόλυνση σύνθετων αναζητήσεων και σύνθεσης επιμέρους πληροφοριών, ο ιστός αλλάζει προσανατολισμό, έτσι ώστε να μπορεί να ερμηνεύεται από μηχανές και να απαλλάσσει το χρήστη από τον επιπλέον φόρτο. Η πιο φιλόδοξη μορφή ενσωμάτωσης κατάλληλων μεταδεδομένων στον παγκόσμιο ιστό είναι με την περιγραφή των δεδομένων με RDF triples αποθηκευμένων ως XML. Το πλαίσιο RDF περιγράφει πόρους, ορισμένους με Uniform Resource Identifiers (URI’s) ή literals με τη μορφή υποκείμενου-κατηγορήματος-αντικειμένου. Για την ορθή περιγραφή των πόρων ενθαρρύνεται από το W3C η χρήση υπαρχόντων λεξιλογίων και σχημάτων , που περιγράφουν κλάσεις και ιδιότητες. Στην παρούσα εργασία γίνεται υλοποίηση ενός δημοσιογραφικού RDF portal. Για τη δημιουργία RDF/XML, έχουν χρησιμοποιηθεί τα λεξιλόγια και σχήματα που συνιστούνται από το W3C καθώς και των DCMI και PRISM. Επίσης χρησιμοποιείται για την περιγραφή typed literals to XML σχήμα του W3C και ένα σχήμα του portal. Η δημιουργία των μεταδεδομένων γίνεται αυτόματα από το portal με τη χρήση των στοιχείων που συμπληρώνονται στις φόρμες δημοσίευσης άρθρων και δημιουργίας λογαριασμών. Για τον περιορισμό του χώρου αποθήκευσης τα μεταδεδομένα δεν αποθηκεύονται αλλά δημιουργούνται όταν ζητηθούν. Στην υλοποίηση έχει δοθεί έμφαση στην ασφάλεια κατά τη δημιουργία λογαριασμών χρήστη με captcha και κωδικό ενεργοποίησης με hashing. Για τη διευκόλυνση του έργου του αρθρογράφου, έχει εισαχθεί και επεκταθεί ο TinyMCE Rich Text Editor, o οποίος επιτρέπει τη μορφοποίηση του κειμένου αλλά και την εισαγωγή εικόνων και media. Ο editor παράγει αυτόματα HTML κώδικα από το εμπλουτισμένο κείμενο. Οι δυνατότητες του editor επεκτάθηκαν κυρίως με τη δυνατότητα για upload εικόνων και media και με την αλλαγή κωδικοποίησης για συμβατότητα με τα πρότυπα της HTML5. Για επιπλέον συμβατότητα με την HTML5 εισάγονται από το portal στα άρθρα ετικέτες σημασιολογικής δομής. Εκτός από τα άρθρα που δημιουργούνται με τη χρήση του Editor, δημοσιοποιούνται και άρθρα από εξωτερικές πηγές. Στη διαδικασία που είναι αυτόματη και επαναλαμβανόμενη, γίνεται επεξεργασία και αποθήκευση μέρους των δεδομένων των εξωτερικών άρθρων. Στον αναγνώστη του portal παρουσιάζεται ένα πρωτοσέλιδο και σελίδες ανά κατηγορία με τα πρόσφατα άρθρα. Στο portal υπάρχει ενσωματωμένη μηχανή αναζήτησης των άρθρων, με πεδία για φιλτράρισμα χρονικά, κατηγορίας, αρθρογράφου-πηγής αλλά και λέξεων κλειδιών. Οι λέξεις κλειδιά προκύπτουν από την περιγραφή του άρθρου στη φόρμα δημιουργίας ή αυτόματα. Όταν τα άρθρα προέρχονται από εξωτερικές πηγές, η διαδικασία είναι υποχρεωτικά αυτόματη. Για την αυτόματη ανεύρεση των λέξεων κλειδιών από ένα άρθρο χρησιμοποιείται η συχνότητα της λέξης στο άρθρο, με τη βαρύτητα που δίνεται από την HTML για τη λέξη (τίτλος, έντονη γραφή), κανονικοποιημένη για το μέγεθος του άρθρου και η συχνότητα του λήμματος της λέξης σε ένα σύνολο άρθρων που ανανεώνεται. Για την ανάκτηση των άρθρων χρησιμοποιείται η τεχνική των inverted files για όλες τις λέξεις κλειδιά. Για τη μείωση του όγκου των δεδομένων και την επιτάχυνση απάντησης ερωτημάτων, αφαιρούνται από την περιγραφή λέξεις που παρουσιάζουν μεγάλη συχνότητα και μικρή αξία ανάκτησης πληροφορίας “stop words”. Η επιλογή μιας αντιπροσωπευτικής λίστας με stop words πραγματοποιήθηκε με τη χρήση ενός σώματος κειμένων από άρθρα εφημερίδων, τη μέτρηση της συχνότητας των λέξεων και τη σύγκριση τους με τη λίστα stop words της Google. Επίσης για τον περιορισμό του όγκου των δεδομένων αλλά και την ορθότερη απάντηση των ερωτημάτων, το portal κάνει stemming στις λέξεις κλειδιά, παράγοντας όρους που μοιάζουν με τα λήμματα των λέξεων. Για to stemming έγινε χρήση της διατριβής του Γεώργιου Νταή του Πανεπιστημίου της Στοκχόλμης που βασίζεται στη Γραμματική της Νεοελληνικής Γραμματικής του Μανώλη Τριανταφυλλίδη. Η επιστροφή των άρθρων στα ερωτήματα που περιλαμβάνουν λέξεις κλειδιά γίνεται με κατάταξη εγγύτητας των λέξεων κλειδιών του άρθρου με εκείνο του ερωτήματος. Γίνεται χρήση της συχνότητας των λέξεων κλειδιών και της συχνότητας που έχουν οι ίδιες λέξεις σε ένα σύνολο άρθρων που ανανεώνεται. Για την αναζήτηση γίνεται χρήση θησαυρού συνώνυμων λέξεων. / The Resource Description Framework (RDF) is an appropriate framework for describing resources as metadata in the Semantic Web. The aim of semantic web is the development and expansion of the existing web, so users can acquire more integrated the supplied information. Today's Web is human oriented. In order to facilitate complex queries and the combination of the acquired data, web is changing orientation. To relieve the user from the extra burden the semantic web shall be interpreted by machines. The most ambitious form incorporating appropriate metadata on the web is by the description of data with RDF triples stored as XML. The RDF framework describes resources, with the use of Uniform Resource Identifiers (URI's) or literals as subject-predicate-object. The use of existing RDF vocabularies to describe classes and properties is encouraged by the W3C. In this work an information-news RDF portal has been developed. The RDF / XML, is created using vocabularies and schemas recommended by W3C and the well known DCMI and PRISM. The metadata is created automatically with the use of data supplied when a new articles is published. To facilitate the journalist job, a Rich Text Editor, which enables formatting text and inserting images and media has been used and expanded. The editor automatically generates HTML code from text in a graphic environment. The capabilities of the editor were extended in order to support images and media uploading and media encoding changes for better compatibility with the standards of HTML5. Apart from uploading articles with the use of the editor the portal integrates articles published by external sources. The process is totally automatic and repetitive. The user of the portal is presented a front page and articles categorized by theme. The portal includes a search engine, with fields for filtering time, category, journalist-source and keywords. The keywords can be supplied by the publisher or selected automatically. When the articles are integrated from external sources, the process is necessarily automatic. For the automatic selection of the keywords the frequency of each word in the article is used. Extra weight is given by the HTML for the words stressed (e.g. title, bold, underlined), normalized for the size of the article and stem frequency of the word in a set of articles that were already uploaded. For the retrieval of articles by the search engine the portal is using an index as inverted files for all keywords. To reduce the data volume and accelerate the query processing words that have high frequency and low value information retrieval "stop words" are removed. The choice of a representative list of stop words is performed by using a corpus of newspaper articles, measuring the frequency of words and comparing them with the list of stop words of Google. To further reduce the volume of data and increase the recall to questions, the portal stems the keywords. For the stemming the rule based algorithm presented in the thesis of George Ntais in the University of Stockholm -based Grammar was used. The returned articles to the keywords queried by the search engine are ranked by the proximity of the keywords the article is indexed. To enhance the search engine synonymous words are also included by the portal.
236

Recuperação de imagens digitais com base na distribuição de características de baixo nível em partições do domínio utilizando índice invertido

Proença, Patrícia Aparecida 29 March 2010 (has links)
Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The main goal of a images retrieval system is to obtain images from a collection that assist a need of the user. To achieve this objective, in generally, the systems of retrieval of images calculate the similarity between the user's need represented by a query and representations of the images of the collection. Such an objective is dicult of being obtain due to the subjectivity of the similarity concept among images, because a same image can be interpreted in dierent ways by dierent people. In the attempt of solving this problem the content based image retrieval systems explore the characteristics of low level color, forms and texture in the calculation of the similarity among the images. A problem of this approach is that in most of the systems the calculation of the similarity is accomplished being compared the query image with all of the images of the collection, turning the dicult and slow processing. Considering the indexation of characteristics of low level of partitions of digital images mapped to an inverted index, this work looks for improvements in the acting of the processing of querys and improve in the precision considering the group of images retrieval in great bases of data. We used an approach based in inverted index that is here adapted for partitions images. In this approach the concept of term of the retrieval textual, main element of the indexation, it is used in the work as characteristic of partitions of images for the indexation. Experiments show improvement in the quality of the precision using two collections of digital images. / O principal objetivo de um sistema de recuperação de imagens é obter imagens de uma coleção que atendam a uma necessidade do usuário. Para atingir esse objetivo, em geral, os sistemas de recuperação de imagens calculam a similaridade entre a necessidade do usuário, representada por uma consulta, e representações das imagens da coleção. Tal objetivo é difícil de ser alcançado devido à subjetividade do conceito de similaridade entre imagens, visto que uma mesma imagem pode ser interpretada de formas diferentes por pessoas distintas. Na tentativa de resolver este problema os sistemas de recuperação de imagens por conteúdo exploram as características de baixo nível cor, forma e textura no cálculo da similaridade entre as imagens. Um problema desta abordagem é que na maioria dos sistemas o cálculo da similaridade é realizado comparando-se a imagem de consulta com todas as imagens da coleção, tornando o processamento difícil e lento. Considerando a indexação de características de baixo nível de partições de imagens digitais mapeadas para um índice invertido, este trabalho busca melhorias no desempenho do processamento de consultas e ganho na precisão considerando o conjunto de imagens recuperadas em grandes bases de dados. Utilizamos uma abordagem baseada em índice invertido, que é aqui adaptada para imagens particionadas. Nesta abordagem o conceito de termo da recuperação textual, principal elemento da indexação, é utilizado no trabalho como característica de partições de imagens para a indexação. Experimentos mostram ganho na qualidade da precisão usando duas coleções de imagens digitais. / Mestre em Ciência da Computação
237

Konstruktion och reglering av inverterad pendel

Hellmers, Robin, Boström, Viktor January 2018 (has links)
Syftet med projektet är att konstruera en inverterad pendel som sedan med hjälp av reglertekniska metoder ska stabiliseras. De linjära regulatorer som prövats är Proportionell, Integrerande och Deriverande (PID) -regulatorn och Linnear Quadratic Gaussian (LQG) -regulatorn som båda är populära och beprövade i industrin. PID-regulatorn är den absolut mest använda regulatorn medan LQG-regulatorn är mer raffinerad och i vissa avseenden en optimal regulator. Regulatorerna programmerades in i mikrokontrollern Arduino Nano som skickar signaler till en motordrivare som styr den stegmotor som ska balansera pendeln. Mycket av arbetet har handlat om att skapa en uppställning som tillåter goda förutsättningar för att pröva regulatorerna. I uppställningen finns delar som utformats i Computor-Aided design (CAD) -verktyget OpenSCAD och skrivits ut på en 3D-skrivare. Den givare vi använt för att mäta pendelns vinkel är en potentiometer infäst i dessa 3D-utskrivna delar. Motorn kunde styras till sin maximala kapacitet och en uppställning har skapats. Dock skulle en starkare motor och en mer robust uppställning möjliggöra en avsevärt bättre reglering. Regulatorerna klarade inte av att stabilisera systemet mer än ett fåtal sekunder, detta bland annat pågrund av tidsbrist till att justera regleringsvariablerna.
238

Recherche multi-descripteurs dans les fonds photographiques numérisés / Multi-descriptor retrieval in digitalized photographs collections

Bhowmik, Neelanjan 07 November 2017 (has links)
La recherche d’images par contenu (CBIR) est une discipline de l’informatique qui vise à structurer automatiquement les collections d’images selon des critères visuels. Les fonctionnalités proposées couvrent notamment l’accès efficace aux images dans une grande base de données d’images ou l’identification de leur contenu par des outils de détection et de reconnaissance d’objets. Ils ont un impact sur une large gamme de domaines qui manipulent ce genre de données, telles que le multimedia, la culture, la sécurité, la santé, la recherche scientifique, etc.Indexer une image à partir de son contenu visuel nécessite d’abord de produire un résumé visuel de ce contenu pour un usage donné, qui sera l’index de cette image dans la collection. En matière de descripteurs d’images, la littérature est désormais trés riche: plusieurs familles de descripteurs existent, et dans chaque famille de nombreuses approches cohabitent. Bon nombre de descripteurs ne décrivant pas la même information et n’ayant pas les mêmes propriétés d’invariance, il peut être pertinent de les combiner de manière à mieux décrire le contenu de l’image. Cette combinaison peut être mise en oeuvre de différentes manières, selon les descripteurs considérés et le but recherché. Dans cette thése, nous nous concentrons sur la famille des descripteurs locaux, avec pour application la recherche d’images ou d’objets par l’exemple dans une collection d’images. Leurs bonnes propriétés les rendent très populaires pour la recherche, la reconnaissance et la catégorisation d'objets et de scènes. Deux directions de recherche sont étudiées:Combinaison de caractéristiques pour la recherche d’images par l’exemple: Le coeur de la thèse repose sur la proposition d’un modèle pour combiner des descripteurs de bas niveau et génériques afin d’obtenir un descripteur plus riche et adapté à un cas d’utilisation donné tout en conservant la généricité afin d’indexer différents types de contenus visuels. L’application considérée étant la recherche par l’exemple, une autre difficulté majeure est la complexité de la proposition, qui doit correspondre à des temps de récupération réduits, même avec de grands ensembles de données. Pour atteindre ces objectifs, nous proposons une approche basée sur la fusion d'index inversés, ce qui permet de mieux représenter le contenu tout en étant associé à une méthode d’accès efficace.Complémentarité des descripteurs: Nous nous concentrons sur l’évaluation de la complémentarité des descripteurs locaux existant en proposant des critères statistiques d’analyse de leur répartition spatiale dans l'image. Ce travail permet de mettre en évidence une synergie entre certaines de ces techniques lorsqu’elles sont jugées suffisamment complémentaires. Les critères spatiaux sont exploités dans un modèle de prédiction à base de régression linéaire, qui a l'avantage de permettre la sélection de combinaisons de descripteurs optimale pour la base considérée mais surtout pour chaque image de cette base. L'approche est évaluée avec le moteur de recherche multi-index, où il montre sa pertinence et met aussi en lumière le fait que la combinaison optimale de descripteurs peut varier d'une image à l'autre.En outre, nous exploitons les deux propositions précédentes pour traiter le problème de la recherche d'images inter-domaines, correspondant notamment à des vues multi-source et multi-date. Deux applications sont explorées dans cette thèse. La recherche d’images inter-domaines est appliquée aux collections photographiques culturelles numérisées d’un musée, où elle démontre son efficacité pour l’exploration et la valorisation de ces contenus à différents niveaux, depuis leur archivage jusqu’à leur exposition ou ex situ. Ensuite, nous explorons l’application de la localisation basée image entre domaines, où la pose d’une image est estimée à partir d’images géoréférencées, en retrouvant des images géolocalisées visuellement similaires à la requête / Content-Based Image Retrieval (CBIR) is a discipline of Computer Science which aims at automatically structuring image collections according to some visual criteria. The offered functionalities include the efficient access to images in a large database of images, or the identification of their content through object detection and recognition tools. They impact a large range of fields which manipulate this kind of data, such as multimedia, culture, security, health, scientific research, etc.To index an image from its visual content first requires producing a visual summary of this content for a given use, which will be the index of this image in the database. From now on, the literature on image descriptors is very rich; several families of descriptors exist and in each family, a lot of approaches live together. Many descriptors do not describe the same information and do not have the same properties. Therefore it is relevant to combine some of them to better describe the image content. The combination can be implemented differently according to the involved descriptors and to the application. In this thesis, we focus on the family of local descriptors, with application to image and object retrieval by example in a collection of images. Their nice properties make them very popular for retrieval, recognition and categorization of objects and scenes. Two directions of research are investigated:Feature combination applied to query-by-example image retrieval: the core of the thesis rests on the proposal of a model for combining low-level and generic descriptors in order to obtain a descriptor richer and adapted to a given use case while maintaining genericity in order to be able to index different types of visual contents. The considered application being query-by-example, another major difficulty is the complexity of the proposal, which has to meet with reduced retrieval times, even with large datasets. To meet these goals, we propose an approach based on the fusion of inverted indices, which allows to represent the content better while being associated with an efficient access method.Complementarity of the descriptors: We focus on the evaluation of the complementarity of existing local descriptors by proposing statistical criteria of analysis of their spatial distribution. This work allows highlighting a synergy between some of these techniques when judged sufficiently complementary. The spatial criteria are employed within a regression-based prediction model which has the advantage of selecting the suitable feature combinations globally for a dataset but most importantly for each image. The approach is evaluated within the fusion of inverted indices search engine, where it shows its relevance and also highlights that the optimal combination of features may vary from an image to another.Additionally, we exploit the previous two proposals to address the problem of cross-domain image retrieval, where the images are matched across different domains, including multi-source and multi-date contents. Two applications of cross-domain matching are explored. First, cross-domain image retrieval is applied to the digitized cultural photographic collections of a museum, where it demonstrates its effectiveness for the exploration and promotion of these contents at different levels from their archiving up to their exhibition in or ex-situ. Second, we explore the application of cross-domain image localization, where the pose of a landmark is estimated by retrieving visually similar geo-referenced images to the query images
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Anotação e classificação automática de entidades nomeadas em notícias esportivas em Português Brasileiro / Automatic named entity recognition and classification for brazilian portuguese sport news

Rodrigo Constantin Ctenas Zaccara 11 July 2012 (has links)
O objetivo deste trabalho é desenvolver uma plataforma para anotação e classificação automática de entidades nomeadas para notícias escritas em português do Brasil. Para restringir um pouco o escopo do treinamento e análise foram utilizadas notícias esportivas do Campeonato Paulista de 2011 do portal UOL (Universo Online). O primeiro artefato desenvolvido desta plataforma foi a ferramenta WebCorpus. Esta tem como principal intuito facilitar o processo de adição de metainformações a palavras através do uso de uma interface rica web, elaborada para deixar o trabalho ágil e simples. Desta forma as entidades nomeadas das notícias são anotadas e classificadas manualmente. A base de dados foi alimentada pela ferramenta de aquisição e extração de conteúdo desenvolvida também para esta plataforma. O segundo artefato desenvolvido foi o córpus UOLCP2011 (UOL Campeonato Paulista 2011). Este córpus foi anotado e classificado manualmente através do uso da ferramenta WebCorpus utilizando sete tipos de entidades: pessoa, lugar, organização, time, campeonato, estádio e torcida. Para o desenvolvimento do motor de anotação e classificação automática de entidades nomeadas foram utilizadas três diferentes técnicas: maximização de entropia, índices invertidos e métodos de mesclagem das duas técnicas anteriores. Para cada uma destas foram executados três passos: desenvolvimento do algoritmo, treinamento utilizando técnicas de aprendizado de máquina e análise dos melhores resultados. / The main target of this research is to develop an automatic named entity classification tool to sport news written in Brazilian Portuguese. To reduce this scope, during training and analysis only sport news about São Paulo Championship of 2011 written by UOL2 (Universo Online) was used. The first artefact developed was the WebCorpus tool, which aims to make easier the process of add meta informations to words, through a rich web interface. Using this, all the corpora news are tagged manually. The database used by this tool was fed by the crawler tool, also developed during this research. The second artefact developed was the corpora UOLCP2011 (UOL Campeonato Paulista 2011). This corpora was manually tagged using the WebCorpus tool. During this process, seven classification concepts were used: person, place, organization, team, championship, stadium and fans. To develop the automatic named entity classification tool, three different approaches were analysed: maximum entropy, inverted index and merge tecniques using both. Each approach had three steps: algorithm development, training using machine learning tecniques and best score analysis.
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Investigação da distribuição de tamanho de bolhas em um separador gás-líquido do tipo shroud invertido / Investigation of bubble-diameter distribution in a gas-liquid inverted-shroud separator

Marcel Cavallini Barbosa 13 November 2015 (has links)
Operações de produção de petróleo, que utilizam sistemas de bombeamento centrífugo submerso, constantemente encontram a presença de gás livre nos poços, o que pode gerar ou agravar problemas como cavitação e falhas dinâmicas, quando o gás é succionado pela bomba. O separador gravitacional do tipo shroud invertido é uma solução possível para este problema nos casos de operação em poços direcionais de petróleo. O trabalho tem como objetivo apresentar um estudo do diâmetro das bolhas que ocorrem no interior de um separador gravitacional gás-líquido do tipo shroud invertido. A finalidade é o aprimoramento de um modelo fenomenológico do funcionamento deste tipo de separador, aplicado à indústria petrolífera, sendo que o modelo fenomenológico garante total separação de gás, fornecidas determinadas condições. O modelo prevê, através do cálculo da energia cinética turbulenta, o tamanho médio das bolhas carregadas para o seio do líquido por aeração no duto anular. Partindo de estudos anteriores, uma verificação do modelo fenomenológico foi feita utilizando um aparato experimental com misturas bifásicas ar-água e ar-óleo em três diferentes inclinações. O aparato possui dimensões radiais reais de um poço de petróleo offshore. Foi utilizado um sensor 3D ORM para a medição do tamanho médio (sauter) das bolhas arrastadas pelo líquido até a entrada do tubo de produção, em diversas combinações de vazões da mistura água-ar. Esta medição permite o ajuste das correlações que regem o modelo fenomenológico, no que diz respeito às equações dependentes do diâmetro teórico de bolhas arrastadas pela fase líquida. As descobertas provenientes deste estudo foram implementadas em um código computacional que será utilizado pela PETROBRAS, financiadora do projeto, para suas operações de bombeamento. / Oil mining operations powered by centrifugal submersible pumping systems suffer constant setbacks due to the presence of free gas in wells. Decompression in the reservoir liberates this gas in the form of bubbles that, upon reaching the suction end of the pump, cause cavitation and dynamic failures resulting in production and equipment losses. The Inverted-shroud gravitational separator is a possible solution to this problem. This work presents a study on diameters of bubbles that occur inside this separator. The goal is the improvement of the understanding of this kind of separator as well as the enhancement of a previously reported phenomenological model, which ensures total gas separation when the separator is installed in directional wells and under specific operational conditions. Empirically adjusted correlations are used to ensure that all entrained bubbles do not reach the pump. The model was tested for two-phase flows of water-air and oil-air mixtures using three different inclinations. Tests were performed with an experimental apparatus that simulates a pilot-scale well casing with an inverted-shroud separator installed. A 3D ORM particle-size sensor was employed in order to measure the average (sauter) diameter of entrained bubbles that are dragged by the liquid flow towards the end of the production tube. This investigation will be used to improve the reliability of the phenomenological model and reduce its dependency on a theoretical prediction of the bubble size. The findings were incorporated to the final version of an in-house gas separator design software developed at the request of PETROBRAS, the project funder and Inverted-shroud patent holder, for usage on its oil mining operations.

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