Vertrauensbasierte Empfehlungen in mehrschichtigen Netzwerken

The huge interest in social networking applications - Friendster.com, for example, has more than 40 million users - led to a considerable research interest in using this data for generating recommendations. Especially recommendation techniques that analyze trust networks were found to provide very accurate and highly personalized results. The main contribution of this thesis is to extend the approach to trust-based recommendations, which up to now have been made for unlinked items such as products or movies, to linked resources, in particular documents. Therefore, a second type of network, namely a document reference network, is considered apart from the trust network. This is, for example, the citation network of scientific publications or the hyperlink graph of webpages. Recommendations for documents are typically made by reference-based visibility measures which consider a document to be the more important, the more often it is referenced by important documents. Document and trust networks, as well as further networks such as organization networks are integrated in a multi-layer network. This architecture makes it possible to combine classical measures for the visibility of a document with trust-based recommendations, giving trust-enhanced visibility measures. Moreover, an approximation approach is introduced which considers the uncertainty induced by duplicate documents. These measures are evaluated in simulation studies. The trust-based recommender system for scientific publications SPRec implements a two-layer architecture and provides personalized recommendations via a Web interface.Soziale Netzwerke mit ihren Millionen von Nutzern haben zu einem großen Interesse an der Fragestellung geführt, wie die Informationen aus solchen sozialen Netzwerken in Empfehlungssystemen genutzt werden können. Aktuelle Forschungsarbeiten haben gezeigt, dass vor allem Techniken, die soziale Vertrauensnetzwerke zur Grundlage nehmen, sehr gute Ergebnisse liefern. Die vorliegende Dissertation erweitert Ansätze zu vertrauensbasierten Empfehlungen, die bisher nur isolierte Objekte wie beispielsweise Produkte oder Filme berücksichtigt haben, zu Ansätzen für vernetzte Ressourcen, insbesondere Dokumente. Daher wird neben dem Vertrauensnetzwerk eine zweite Art von Netzwerk betrachtet, ein Dokumentennetzwerk. Beispiele für Dokumentennetzwerke sind Zitationsnetzwerke wissenschaftlicher Publikationen oder der Hyperlink-Graph zwischen Webseiten. Dokumentenempfehlungen werden typischerweise mit referenzbasierten Sichtbarkeitsmaßen berechnet, die ein Dokument als wichtig erachten, wenn es von vielen wichtigen Dokumenten referenziert wird. Vertrauensnetzwerke und Dokumentennetzwerke werden in einer zweischichtigen Architektur integriert. Weitere Netzwerke, wie zum Beispiel Organisationsnetzwerke bauen sie zu einer mehrschichtigen Architektur aus. In dieser Architektur können klassische Maße für Dokumentensichtbarkeit mit vertrauensbasierten Empfehlungen kombiniert werden, nämlich in den sogenannten vertrauensbasierten Sichtbarkeitsmaßen. Darüberhinaus führt die Dissertation einen Ansatz ein, um die vertrauensbasierte Sichtbarkeit dann approximieren zu können, wenn das Dokumentennetzwerk Duplikate von Dokumenten enthält. Die entwickelten Sichtbarkeitsmaße werden in einer Simulationsstudie analysiert. Das webbasierte Empfehlungssystem für wissenschaftliche Veröffentlichungen SPRec implementiert die vertrauensbasierten Sichtbarkeitsmaße und generiert personalisierte Empfehlungen

Epistemology and methodology of urban cultural tourism: the case of the artistic sociology of mobile cultures and tourism communication in urban social networks

The epistemological, theoretical and methodological debates that aim at scientific credibility, cannot ignore the corresponding application to the social fabric. Conversely, action should always inform reflection. This article rationally demonstrates and sensorialy exhibits the following: one of the sociological genres, Artistic Sociology, transports sociology and its scientific language, from the academia to creative extension activities such as the exhibition of sociological knowledge within urban public space, for example in the case of the art gallery. In the same way, artistic knowledge and language should contaminate sociological discussion through an innovative sensibility. This is possible through the insertion, within a sociological text, not only of images from an art exhibition, presented as ‘Figures’ (1,2 ... n). In addition, the art exhibition itself can be understood as a social and sociological configuration that is an organic part of the very body of the traditional sociological text. Thus, a profound hybridization of knowledge is sought, which can enrich, but also subvert, both sociological debates and art exhibitions. This purpose is accomplished here by several interconnected means: an epistemological approach between Artistic Sociology and Hybridogy; the theoretical problematization of mobile cultures; the empirical field work in the context of urban communication at City 3.0 and tourism communication in the context of Tourism 3.0; and the exhibition ‘New Art Fest’17, as the field for the application of innovative sociological and artistic methodological approaches. A first step was Sociological Exibition on Tourism 3.0 / Cidade 3.0, that demonstrated and showed the urban and travel knowledge, within the space of the art gallery. In a second phase, this knowledge tested through the exhibition audience, is reintroduced in a scientific journal article. Such a double research movement hybridizes and confronts, in both originary and original forms, scientific and artistic knowledge and practice

Epistemology and methodology of urban cultural tourism: the case of the artistic sociology of mobile cultures and tourism communication in urban social networks

Os debates epistemológicos, teóricos e metodológicos que visam credibilidade científica não podem prescindir da correspondente aplicação ao tecido social. Inversamente, a ação deverá sempre informar a reflexão. Pretende-se neste artigo demonstrar racionalmente e mostrar sensorialmente que um dos géneros sociológicos, a Sociologia Artística, faz transbordar a Sociologia e a sua linguagem científica da academia para atividades de extensão criativas, como a exposição do saber sociológico no espaço público urbano, por exemplo no caso da galeria de arte. Do mesmo modo, o conhecimento e linguagem artísticos deverão contaminar a discussão sociológica através de uma sensibilidade inovadora. Isso é possível por intermédio da inserção, num texto sociológico, não apenas das imagens oriundas de uma exposição de arte, apresentadas enquanto Figuras (1,2…n). Para além disso, a própria exposição de arte poderá ser entendida como uma configuração social e sociológica que faz parte orgânica do próprio corpo do texto sociológico tradicional. Busca-se assim uma hibridação de saberes profunda, que poderá enriquecer, mas também subverter, tanto os debates sociológicos quanto as exposições de arte.Este propósito realiza-se aqui por diversos meios interligados: uma aproximação epistemológica entre a Sociologia Artística e a Hibridologia; a problematização teórica das culturas móveis; o trabalho de campo empírico no quadro da comunicação urbana na Cidade 3.0 e a comunicação turística no contexto do Turismo 3.0; e a exposição ‘New Art Fest’17, como palco da aplicação de abordagens metodológicas sociológicas e artísticas inovadoras. Numa primeira etapa, a Exposição Sociológica sobre Turismo 3.0/Cidade 3.0 demonstrou e mostrou os saberes urbanos e da viagem, no seio do espaço da galeria de arte. Numa segunda fase, este saber testado no público da exposição é reintroduzido num artigo de revista científica. Um tal duplo movimento de pesquisa hibridiza e confronta, em moldes ao mesmo tempo originários e originais, o conhecimento e a prática científicos e artísticos.The epistemological, theoretical and methodological debates that aim at scientific credibility, cannot ignore the corresponding application to the social fabric. Conversely, action should always inform reflection. This article rationally demonstrates and sensorialy exhibits the following: one of the sociological genres, Artistic Sociology, transports sociology and its scientific language, from the academia to creative extension activities such as the exhibition of sociological knowledge within urban public space, for example in the case of the art gallery. In the same way, artistic knowledge and language should contaminate sociological discussion through an innovative sensibility. This is possible through the insertion, within a sociological text, not only of images from an art exhibition, presented as ‘Figures’ (1,2 ... n). In addition, the art exhibition itself can be understood as a social and sociological configuration that is an organic part of the very body of the traditional sociological text. Thus, a profound hybridization of knowledge is sought, which can enrich, but also subvert, both sociological debates and art exhibitions. This purpose is accomplished here by several interconnected means: an epistemological approach between Artistic Sociology and Hybridogy; the theoretical problematization of mobile cultures; the empirical field work in the context of urban communication at City 3.0 and tourism communication in the context of Tourism 3.0; and the exhibition ‘New Art Fest’17, as the field for the application of innovative sociological and artistic methodological approaches. A first step was Sociological Exibition on Tourism 3.0 / Cidade 3.0, that demonstrated and showed the urban and travel knowledge, within the space of the art gallery. In a second phase, this knowledge tested through the exhibition audience, is reintroduced in a scientific journal article. Such a double research movement hybridizes and confronts, in both originary and original forms, scientific and artistic knowledge and practice.info:eu-repo/semantics/publishedVersio

Are Search Engines Biased? Detecting and Reducing Bias using Meta Search Engines

International audienceThe search neutrality debate stems from content or service providers complaining about being discriminated and therefore losing market shares due to an unfairly low ranking given by search engines. Those questions stress the need for methodologies and tools to verify bias in search engine rankings and analyze their potential impact. We develop in this paper a simple yet effective framework comparing the results of existing search engines. We present statistical tests based on outlier detection pointing out potential biases, and introduce two meta engines aiming at reducing bias. All this is implemented in a publicly-available tool from which extensive comparisons and bias investigations are carried out

Semantic segmentation of astronomical radio images: a computer vision approach

The new generation of radio telescopes, such as the MeerKAT, ASKAP (Australian Square Kilometre Array Pathfinder) and the future Square Kilometre Array (SKA), are expected to produce vast amounts of data and images in the petabyte region. Therefore, the amount of incoming data at a specific point in time will overwhelm any current traditional data analysis method being deployed. Deep learning architectures have been applied in many fields, such as, in computer vision, machine vision, natural language processing, social network filtering, speech recognition, machine translation, bioinformatics, medical image analysis, and board game programs. They have produced results which are comparable to human expert performance. Hence, it is appealing to apply it to radio astronomy data. Image segmentation is one such area where deep learning techniques are prominent. The images from the new generation of telescopes have a high density of radio sources, making it difficult to classify the sources in the image. Identifying and segmenting sources from radio images is a pre-processing step that occurs before sources are put into different classes. There is thus a need for automatic segmentation of the sources from the images before they can be classified. This work uses the Unet architecture (originally developed for biomedical image segmentation) to segment radio sources from radio astronomical images with 99.8% accuracy. After segmenting the sources we use OpenCV tools to detect the sources on the mask images, then the detection is translated to the original image where borders are drawn around each detected source. This process automates and simplifies the pre-processing of images for classification tools and any other post-processing tool that requires a specific source as an input.Thesis (MSc) -- Faculty of Science, Physics and Electronics, 202

Machine learning-based anomaly detection for radio telescopes

Radio telescopes are getting bigger and are generating increasing amounts of data to improve their sensitivity and resolution. The growing system size and resulting complexity increases the likelihood of unexpected events occurring thereby producing datasets containing anomalies. These events include failures in instrument electronics, miscalibrated observations, environmental and astronomical effects such as lightning and solar storms as well as problems in data processing systems among many more. Currently, efforts to diagnose and mitigate these events are performed by human operators, who manually inspect intermediate data products to determine the success or failure of a given observation. The accelerating data-rates coupled with the lack of automation results in operator-based data quality inspection becoming increasingly infeasible.This thesis focuses on applying machine learning-based anomaly detection to spectrograms obtained from the LOFAR telescope for the purpose of System Health Management (SHM). It does this across several chapters, with each chapter focusing on a different aspect of SHM in radio telescopes. We provide an overview of the data processing systems in LOFAR so to create a workflow for SHM that could effectively be integrated into the scientific data processing pipeline