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Tesi amb menció de Doctorat Industrial (Generalitat de Catalunya), (English) Media producers publish large amounts of multimedia content online - both text, audio, image and video. As the online media market grows, the management and delivery of contents becomes a challenge. Semantic and linking technologies can be used to organize and exploit these contents through the use of knowledge graphs. This industrial doctorate dissertation addresses the problem of constructing knowledge resources and integrating them into a system used by media producers to manage and explore their contents. For that purpose, knowledge graphs and their maintenance through Information Extraction (IE) from news streams is studied. This thesis presents solutions for multimedia understanding and knowledge extraction from online news, and their exploitation in real product applications, and it is structured in three parts. The first part consists on the construction of IE tools that will be used for knowledge graph population. For that, we built an holistic Entity Linking (EL) system capable of combining multimodal data inputs to extract a set of semantic entities that describe news content. The EL system is followed by a Relation Extraction (RE) model that predicts relations between pairs of entities with a novel method based on entity-type knowledge. The final system is capable of extracting triples describing the contents of a news article. The second part focuses on the automatic construction of a news event knowledge graph. We present an online multilingual system for event detection and comprehension from media feeds, called VLX-Stories. The system retrieves information from news sites, aggregates them into events (event detection), and summarizes them by extracting semantic labels of its most relevant entities (event representation) in order to answer four Ws from journalism: who, what, when and where. This part of the thesis deals with the problems of Topic Detection and Tracking (TDT), topic modeling and event representation. The third part of the the, (Català) Els productors de contingut multimèdia publiquen grans quantitats de contingut en línia, tant en forma de text, àudio, imatge com de vídeo. A mesura que el mercat dels mitjans de comunicació en línia creix, la gestió i distribució de continguts es converteixen en un repte. Les tecnologies semàntiques i d'enllaç es poden utilitzar per organitzar i explotar aquests continguts mitjançant l'ús de grafs de coneixement. Aquesta tesi de doctorat industrial aborda el problema de construir recursos de coneixement i integrar-los en un sistema utilitzat pels productors multimedia per gestionar i explorar els seus continguts. Amb aquest propòsit, s'estudien els grafs de coneixement i el seu manteniment mitjançant l'extracció d'informació a partir de fonts de notícies. Aquesta tesi presenta solucions per a la comprensió multimèdia i l'extracció de coneixement de les notícies en línia, així com la seva explotació en aplicacions de productes reals. Està estructurada en tres parts. La primera part consisteix en la construcció d'eines d'extracció d'informació que s'utilitzaran per a la població del graf de coneixement. Per això, hem desenvolupat un sistema holístic d'enllaç d'entitats (EL), capaç de combinar dades multimodals per extreure un conjunt d'entitats semàntiques que descriuen el contingut de les notícies. El sistema de EL es complementa amb un model d'extracció de relacions (RE) que prediu les relacions entre parells d'entitats mitjançant un mètode innovador basat en el coneixement del tipus d'entitat. El sistema final és capaç d'extreure tripletes de coneixement que descriuen el contingut d'un article de notícies. La segona part es centra en la construcció automàtica d'un graf de coneixement d'esdeveniments de notícies. Presentem un sistema en línia multilingüe per a la detecció i comprensió d'esdeveniments a partir de "feeds" de mitjans de comunicació, anomenat VLX-Stories. El sistema recupera informació de llocs web de notícies, les agrega en esdeveniments (det, (Español) Los productores audiovisuales publican grandes cantidades de contenido multimedia en línea, en forma de texto, audio, imagen o video. A medida que crece el mercado de medios en línea, la gestión y entrega de contenidos se convierte en un desafío. Las tecnologías semánticas y de enlace se pueden utilizar para organizar y explotar estos contenidos mediante el uso de grafos de conocimiento. Esta tesis de doctorado industrial aborda el problema de construir recursos de conocimiento e integrarlos en un sistema utilizado por los productores de medios para gestionar y explorar sus contenidos. Con ese propósito, se estudian los grafos de conocimiento y su mantenimiento a través de la extracción de información de flujos de noticias. Esta tesis presenta soluciones para la comprensión multimedia y la extracción de conocimiento de noticias en línea, y su explotación en aplicaciones de productos reales, y está estructurada en tres partes. La primera parte consiste en la construcción de herramientas de extracción de la información que se utilizarán para la población del grafo de conocimiento. Para eso, construimos un sistema holístico de enlace de entidades (EL) capaz de combinar datos multimodales para extraer un conjunto de entidades semánticas que describen el contenido de las noticias. El sistema de EL se complementa con un modelo de extracción de relaciones (RE) que predice las relaciones entre pares de entidades con un método novedoso basado en el conocimiento del tipo de entidad. El sistema final es capaz de extraer tripletas que describen el contenido de un artículo de noticias. La segunda parte se centra en la construcción automática de un grafo de conocimiento de eventos de noticias. Presentamos un sistema en línea multilingüe para la detección y comprensión de eventos a partir de "feeds" de medios de comunicación, llamado VLX-Stories. El sistema recopila información de sitios de noticias, las agrega en eventos (detección de eventos) y las resume extrayendo et, Postprint (published version)

Knowledge Graphs (KG) are becoming essential to organize, represent and store the world’s knowledge, but they still rely heavily on humanly-curated structured data. Information Extraction (IE) tasks, like disambiguating entities and relations from unstructured text, are key to automate KG population. However, Natural Language Processing (NLP) methods alone can not guarantee the validity of the facts extracted and may introduce erroneous information into the KG. This work presents an end-to-end system that combines Semantic Knowledge and Validation techniques with NLP methods, to provide KG population of novel facts from clustered news events. The contributions of this paper are two-fold: First, we present a novel method for including entity-type knowledge into a Relation Extraction model, improving F1-Score over the baseline with TACRED and TypeRE datasets. Second, we increase the precision by adding data validation on top of the Relation Extraction method. These two contributions are combined in an industrial pipeline for automatic KG population over aggregated news, demonstrating increased data validity when performing online learning from unstructured web data. Finally, the TypeRE and AggregatedNewsRE datasets build to benchmark these results are also published to foster future research in this field., This work was partially supported by the Government of Catalonia under the industrial doctorate 2017 DI 011., Peer Reviewed, Postprint (author's final draft)

© <2020>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0, Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future Earth Observation (EO) missions. While the adoption of these satellite architectures is gaining momentum for the attaining of ever more stringent application requirements and stakeholder needs, the efforts to analyze their benefits and suitability, and to assess their impact for future programmes remains as an open challenge to the EO community. In this context, this paper presents the mission and system architecture conceived during the Horizon 2020 ONION project, a European Union research activity that proposes a systematic approach to the optimization of EO space infrastructures. In particular, ONION addressed the design of complementary assets that progressively supplement current programs and took part in the exploration of needs and implementation of architectures for the Copernicus Space Component for EO. Among several use cases considered, the ONION project focused on proposing system architectures to provide improved revisit time, data latency and image resolution for a demanding application scenario of interest: Marine Weather Forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been performed to the selected architecture for the MWF use ca, This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 687490., Peer Reviewed, Postprint (author's final draft)

Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future Earth Observation (EO) missions. While the adoption of these satellite architectures is gaining momentum for the attaining of ever more stringent application requirements and stakeholder needs, the efforts to analyze their benefits and suitability, and to assess their impact for future programmes remains as an open challenge to the EO community. In this context, this paper presents the mission and system architecture conceived during the Horizon 2020 ONION project, a European Union research activity that proposes a systematic approach to the optimization of EO space infrastructures. In particular, ONION addressed the design of complementary assets that progressively supplement current programs and took part in the exploration of needs and implementation of architectures for the Copernicus Space Component for EO. Among several use cases considered, the ONION project focused on proposing system architectures to provide improved revisit time, data latency and image resolution for a demanding application scenario of interest: Marine Weather Forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been performed to the selected architecture for the MWF use ca

Knowledge Graph representations for entity disambiguation

Growing demand for structured knowledge has led to great interest in relation extraction, which is the task of extracting semantic relationships from the text. It has been proven that neural methods can solve this problem with high accuracy when a small number of classes (relations) are considered. In order to provide relation extraction on the wild or for industrial applications (where the number of relationships and their variability is more critical), these methods require large datasets, which are expensive to generate.

We present an online multilingual system for event detection and comprehension from media feeds. The system retrieves information from news sites, aggregates them into events (event detection), and summarizes them by extracting semantic labels of its most relevant entities (event representation) in order to answer the journalism Ws: who, what, when and where. The generated events populate VLX-Stories -an event ontology- transforming unstructured text data to a structured knowledge base representation. Our system exploits an external entity Knowledge Graph (VKG) to help populate VLX-Stories. At the same time, this external knowledge graph can also be extended with a Dynamic Entity Linking (DEL) module, which detects emerging entities (EE) on unstructured data. The system is currently deployed in production and used by media producers in the editorial process, providing real-time access to breaking news. Each month, VLX-Stories detects over 9000 events from over 4000 news feeds from seven different countries and in three different languages. At the same time, it detects over 1300 EE per month, which populate VKG., Peer Reviewed, Postprint (published version)

Over the next few years, Europe will take important steps towards implementing the architecture of the Copernicus Space Component for Earth Observation (EO), fulfilling the needs of stakeholders concerned with land monitoring, marine monitoring, atmosphere monitoring, emergency management, security, and climate change. Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future EO Missions. It is of paramount importance for Europe to properly analyse these trends and assess whether or not they could provide a competitive advantage for EO systems. The paper presents the mission and system architecture design of the H2020 ONION project, a European Union research activity that proposes a system concept to supplement in a progressive way the current European EO infrastructures and to serve emerging needs in an optimal fashion. Among several use cases considered, the ONION project focussed on proposing system architectures to provide competitive revisit time, data latency and image resolution for a demanding application scenario of interest: marine weather forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been applied to the selected architecture for the MWF use case, including refined data flow analysis to opt, Postprint (author's final draft)

In the recent years, video sharing in social media from different video recording devices has resulted in a exponential growth of videos on the Internet. Such video data is continuously increasing with daily recordings related to a wide number of topics. In this context, video understanding has become a critical problem to address. Video search and indexation benefits from the use of keyword tags related to the video content, but most of the shared video content does not contain these tags. Although the use of deep learning has become essential for image analysis in several areas, video domain is still a relatively unexplored field for these type of methods. On the other hand knowledge graphs as Freebase or WordNet store high quantities of information about the word and relations that can be used to disambiguate concepts and relate them through contextual information In this research project we search to explore and improve the understanding of video content through the use of automatic tagging models based on Machine Learning and Deep Learning techniques, improved by the use of knowledge bases., Peer Reviewed, Postprint (published version)

A la pàgina 265 diu: "In an effort to facilitate the reproduction of results, both the source code of the simulation environment and the configuration files that were prepared for the design characterisation are available in an open repository: https://github.com/carlesaraguz/aeoss, Satellite imagery has become an essential resource for environmental, humanitarian, and industrial endeavours. As a means to satisfy the requirements of new applications and user needs, novel Earth Observation (EO) systems are exploring the suitability of Distributed Satellite Systems (DSS) in which multiple observation assets concurrently sense the Earth. Given the temporal and spatial resolution requirements of EO products, DSS are often envisioned as large-scale systems with multiple sensing capabilities operating in a networked manner. Enabled by the consolidation of small satellite platforms and fostered by the emerging capabilities of distributed systems, these new architectures pose multiple design and operational challenges. Two of them are the main pillars of this research, namely, the conception of decision-support tools to assist the architecting process of a DSS, and the design of autonomous operational frameworks based on decentralised, on-board decision-making. The first part of this dissertation addresses the architecting of heterogeneous, networked DSS architectures that hybridise small satellite platforms with traditional EO assets. We present a generic design-oriented optimisation framework based on tradespace exploration methodologies. The goals of this framework are twofold: to select the most optimal constellation design; and to facilitate the identification of design trends, unfeasible regions, and tensions among architectural attributes. Oftentimes in EO DSS, system requirements and stakeholder preferences are not only articulated through functional attributes (i.e. resolution, revisit time, etc.) or monetary constraints, but also through qualitative traits such as flexibility, evolvability, robustness, or resiliency, amongst others. In line with that, the architecting framework defines a single figure of merit that aggregates quantitative attributes and qualitative ones-the so-called ilities of a system. With that, designers can steer the des, La imatgeria per satèl·lit ha esdevingut un recurs essencial per assolir tasques ambientals, humanitàries o industrials. Per tal de satisfer els requeriments de les noves aplicacions i usuaris, els sistemes d’observació de la Terra (OT) estan explorant la idoneïtat dels Sistemes de Satèl·lit Distribuïts (SSD), on múltiples observatoris espacials mesuren el planeta simultàniament. Degut al les resolucions temporals i espacials requerides, els SSD sovint es conceben com sistemes de gran escala que operen en xarxa. Aquestes noves arquitectures promouen les capacitats emergents dels sistemes distribuïts i, tot i que són possibles gràcies a l’acceptació de les plataformes de satèl·lits petits, encara presenten molts reptes en quant al disseny i operacions. Dos d’ells són els pilars principals d’aquesta tesi, en concret, la concepció d’eines de suport a la presa de decisions pel disseny de SSD, i la definició d’operacions autònomes basades en gestió descentralitzada a bord dels satèl·lits. La primera part d’aquesta dissertació es centra en el disseny arquitectural de SSD heterogenis i en xarxa, imbricant tecnologies de petits satèl·lits amb actius tradicionals. Es presenta un entorn d’optimització orientat al disseny basat en metodologies d’exploració i comparació de solucions. Els objectius d’aquest entorn són: la selecció el disseny de constel·lació més òptim; i facilitar la identificació de tendències de disseny, regions d’incompatibilitat, i tensions entre atributs arquitecturals. Sovint en els SSD d’OT, els requeriments del sistema i l’expressió de prioritats no només s’articulen en quant als atributs funcionals o les restriccions monetàries, sinó també a través de les característiques qualitatives com la flexibilitat, l’evolucionabilitat, la robustesa, o la resiliència, entre d’altres. En línia amb això, l’entorn d’optimització defineix una única figura de mèrit que agrega rendiment, cost i atributs qualitatius. Així l’equip de disseny pot influir en les solucions d, Postprint (published version)

Autonomous operational strategies for Earth Observation systems are called to address the challenging task of coordinating multiple sensing assets to deliver very short revisit times and near-real-time access to data. Contributing to the on-going exploration of autonomous operations, this paper presents one particular solution based upon knowledge exchange (through Inter-Satellite Links) and spacecraft-level mission planning and resource allocation. The goals of such autonomous DSS is the constant monitoring of the Earth (i.e. global coverage) that collectively minimizes revisit times. The objectives of this work are twofold: to explore the suitability of decentralized, on-board decision-making for generic EO systems, and to propose a characterization framework to evaluate the goodness of autonomous operations. The application of a simulation-based design exploration is detailed in this paper to show the impact that some design parameters (structural and functional) present upon system behavior. The results show performance trends under different operational constraints, including energy or limited ISL capacity. Finally, this work also applies the autonomous framework to the PlanetScope constellation, highlighting its suitability for a large-scale DSS encompassing 117 nano-satellite units., Postprint (published version)

The design of autonomous operational schemes for distributed, decentralized systems is expected to bring multiple qualities to systems of this kind. One of their instances are Earth-observing swarms of nano-satellites, in which their collective function targets global performance figures. The design of autonomous operations can be modelled as a collective scheduling problem subject to resource constraints. There are many system-wide qualities of interest, such as resiliency, adaptability, responsiveness, among others, that need specific frameworks to characterize the proposed solutions. This paper presents one such design-oriented tool that can evaluate these autonomous organization schemes-potentially for large-scale and highly heterogeneous scenarios with dynamic contexts and multiple time-scales-and illustrates its usage in the evaluation of an autonomous nano-satellite swarm that collectively optimizes revisit times., Peer Reviewed, Postprint (published version)

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, subkilometric spatial resolutions, and near-real-time data access times. These stringent requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous, and heavily networked satellite systems that can potentially replace or complement traditional space assets. In this context, this paper presents partial results from ONION, a research project devoted to studying distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for the given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 potential architectures, the framework has been able to preselect 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space are presented in this paper along with the selected solution and the results of a detailed performance analysis., Postprint (author's final draft)

Today's media and news organizations are constantly generating large amounts of multimedia content, majorly delivered online. As the online media market grows, the management and delivery of contents is becoming a challenge. Computational approaches can help to overcome this challenge by governing different applications such as content creation, production, search, and its promotion and distribution to different audiences. In this abstract we present a success story of the adoption of semantic technologies on the aforementioned applications, which are built on top of a semantic tagging framework, based on a Knowledge Graph (KG). The presented pipeline combines multimodal inputs into a contextual entity linking module, which indexes documents and links them to trends and stories developing on the news. We will describe how documents are linked and provided to media producers through Vilynx's platform, which is currently indexing over 20k media documents a day., Peer Reviewed, Postprint (published version)

In this thesis we present the design, implementation and deployment of a building recognition system. First, we have developed a pipeline to find and retrieve relevant images containing landmarks and buildings from the Internet. Moreover, we propose an unsupervised approach to clean the noise present in the classes associated with each landmark/building. This method for mining and denoising images has been presented in the WebVision Workshop at CVPR'18. Then, we introduce the full system for the building recognition module, which has been developed using different computer vision and deep learning techniques. Finally, we propose a set of experiments that show the difficulties of working with a noisy dataset, we analyze the performance of the networks based blocks and finally we show the global results of the building recognition system.

While monolithic satellite missions still pose significant advantages in terms of accuracy and operations, novel distributed architectures are promising improved flexibility, responsiveness, and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance satellites are becoming feasible and advantageous alternatives requiring the adoption of new operation paradigms that enhance their autonomy. While autonomy is a notion that is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy is also presented as a necessary feature to bring new distributed Earth observation functions (which require coordination and collaboration mechanisms) and to allow for novel structural functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission Planning and Scheduling (MPS) frameworks are then presented as a key component to implement autonomous operations in satellite missions. An exhaustive knowledge classification explores the design aspects of MPS for DSS, and conceptually groups them into: components and organizational paradigms; problem modeling and representation; optimization techniques and metaheuristics; execution and runtime characteristics and the notions of tasks, resources, and constraints. This paper concludes by proposing future strands of work devoted to study the trade-offs of autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that consider some of the limitations of small spacecraft technologies., Postprint (author's final draft)

Satellite architectures where networked, heterogeneous observation nodes capture data in a distributed manner are seen as feasible solutions to address the needs of next-generation Earth observation services (i.e. higher spatial, spectral and temporal resolutions at viable costs). Nevertheless, the problems that designers face when approaching these systems-of-systems are still eclipsed by the heterogeneity, dimensionality and multi-level complexity of those. In spite of the many underlying technological challenges, how to optimally architect distributed satellite systems, remains an open source of debate. In this context, this paper presents a design-oriented methodology that is aimed at providing high-level design solutions for this type of architectures in generic EO use-cases. In order to find optimal solutions, the methodology detailed in this paper is grounded on an aggregated architectural figure-of-merit that compresses: (a) system-level performance metrics; (b) use-case requirements; (c) development and launch costs; and (d) a set of architectural quality attributes. The latter contributing term models, assesses and weights several of the so-called 'ilities' of an architecture and allows to select designs that exhibit some desired qualities. With a dimensionality of more than five thousand architectural alternatives, the study has been illustrated with a marine weather forecast use-case. Both the exploration of design alternatives and the analysis of the results have shown the benefits of medium and small satellite platforms and have stressed their potential in the design of distributed satellite systems. Finally, this paper concludes by suggesting that this very optimization framework and methodology could also be used for a quantitative gap analysis aiming at deriving the technological road map for future engineering teams., Peer Reviewed, Postprint (published version)

News broadcasters and on-line publishers daily generate a large amount of articles and videos describing events currently happening in the world. In this work, we present a system that automatically indexes videos from a library and links them to stories developing in the news. The user interface displays in an intuitive manner the links between videos and stories and allows navigation through related content by using associated tags. This interface is a powerful industrial tool for publishers to index, retrieve and visualize their video content. It helps them identify which topics require more attention or retrieve related content that has already been published about the stories., Peer Reviewed, Postprint (published version)

Despite their limited lifespan and reduced cost, nanosatellite missions have proved to be suitable platforms for Earth observation, scientific experiments, and technology demonstration. During the last years, the number of nanosatellite missions has noticeably increased, posing the need to improve several system characteristics to ultimately endorse the full potential of this class of spacecraft. In this context, this paper presents three design guidelines that can be applied in nanosatellite software to improve the system robustness, modularity, and autonomy. The design guidelines presented in this paper, namely, hierarchy-enabled robustness, payload-oriented modularity, and onboard planning capabilities, are complemented with a structured review of software techniques and architectural concepts that have been found in the literature. The paper justifies that these systemwide qualities are some of the most critical when designing flight software for CubeSat-like spacecraft and explores how they can improve mission performances and operability, enhance the system’s tolerance to failures, and ease the development cycles. Finally, this paper illustrates the application of the design guidelines by detailing the onboard software architecture for the Cat3-1, a CubeSat program carried out at the Nano-Satellite and Payload Laboratory of the Technical University of Catalonia—UPC BarcelonaTech., Postprint (author's final draft)

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., IEEE Access Best Multimedia Award 2018, pel video de 4'50'' que acompanya l'article: sobre el sistema ONION (a Distributed Satellite Systems (DSS) concept formed by a Walker-Delta constellation formed by 8 heavy nodes including a SAR-X and an optical imager, and 8 small nodes including a GNSS-R payload. ONION provides innovative solutions to complement the current and planned Copernicus offer, targeting relevant and large user communities), The space industry is currently witnessing two concurrent trends: the increased modularity and miniaturization of technologies and the deployment of constellations of distributed satellite systems. As a consequence of the first trend, the relevance of small satellites in line with the “cheaper and faster” philosophy is increasing. The second one opens up completely new horizons by enabling the design of architectures aimed at improving the performance, reliability, and efficiency of current and future space missions. The EU H2020 ONION project (“Operational Network of Individual Observation Nodes”) has leveraged on the concept of Fractionated and Federated Satellite Systems (FFSS) to develop and design innovative mission architectures resulting in a competitive advantage for European Earth Observation (EO) systems. Starting from the analysis of emerging needs in the European EO market, the solutions to meet these needs are identified and characterized by exploring FFSS. In analogy with terrestrial networks, these systems envision the distribution of satellite functionalities amongst multiple cooperating spacecrafts (nodes of a network), possibly independent, and flying on different orbits. FFSS are considered by many as the future of spacebased infrastructures, as they offer a pragmatic, progressive, and scalable approach to improve existing and future space missions. This work summarizes the main results of the ONION project and the high-level design of the Marine Weather Forecast mission for polar regions., Peer Reviewed, Award-winning, Postprint (author's final draft)

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, sub-kilometric spatial resolutions and near-real-time data access times. These stringent requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous and heavily networked satellite systems that can potentially replace or complement traditional space assets. In this context, this paper presents partial results from ONION, a research project devoted to study distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for a given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 unique architectures, the framework has been able to pre-select 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space, are presented in this paper along with the selected solution and the results of a detailed performance analysis., Postprint (published version)

The popularization of multimedia content on the Web has arised the need to automatically understand, index and retrieve it. In this paper we present ViTS, an automatic Video Tagging System which learns from videos, their web context and comments shared on social networks. ViTS analyses massive multimedia collections by Internet crawling, and maintains a knowledge base that updates in real time with no need of human supervision. As a result, each video is indexed with a rich set of labels and linked with other related contents. ViTS is an industrial product under exploitation with a vocabulary of over 2.5M concepts, capable of indexing more than 150k videos per month. We compare the quality and completeness of our tags with respect to the ones in the YouTube-8M dataset, and we show how ViTS enhances the semantic annotation of the videos with a larger number of labels (10.04 tags/video), with an accuracy of 80,87%., Postprint (published version)

This article introduces 3 Cat-1, the first project of the Technical University of Catalonia to build and launch a nano-satellite. Its main scope is to develop, construct, assemble, test and launch into a low Earth orbit a CubeSat with seven different payloads (mono-atomic oxygen detector, graphene field-effect transistor, self-powered beacon, Geiger radiation counter, wireless power transfer (WPT), new topology solar cells and WPT experiment), all fitted in a single-unit CubeSat. On one hand, this is mainly an educational project in which the development of some of the subsystems is carried out by undergraduate and postgraduate students. The satellite demonstrates its capabilities as a cost-effective platform to perform small scientific experiments and to demonstrate some of the new technologies that it incorporates., Postprint (published version)

Resonant Inductive Coupling Wireless Power Transfer (RIC-WPT) has been proven to provide very high power transfer efficiencies (above 80%) for moderate distances, and is hence foreseen as a key technology to enable wireless power transfer to a myriad of different devices and related applications. Due to the multidisciplinary nature of the WPT underlying principles, several approaches have been provided to analyze RIC-WPT systems from different perspectives (encompassing Electromagnetic fields, Circuit models and Optics), but they have failed to provide a unified model to understand and ultimately to design the behaviour of such systems. This thesis is therefore aimed to, first, provide a multi-modal RIC-WPT complete model oriented to the design and in turn optimisation of RIC-WPT systems and, secondly, to explore and characterize the fundamental challenges precluding the widespread deployment of RIC-WPT and thereby accordingly to yield a set of design guidelines to overcome them. Finally, and due to the fact that multi-node RIC-WPT systems are key to the adoption of this technology, this thesis models, characterizes and analyzes Multiple-Input Multiple-Output RIC WPT Systems, making special emphasis on their scalability., La transferencia inalámbrica de potencia basada en acoplamiento resonante inductivo (RIC-WPT) ha demostrado ser capaz de proporcionar eficiencias muy altas en la transferencia de potencia (hasta 80%) a distancias moderadas, de modo que ésta se anticipa por tanto como una tecnología clave para posibilitar la transferencia inalámbrica de energía a una miríada de diferentes dispositivos y sus aplicaciones asociadas. Debido a la naturaleza multisciplinar de los principios que rigen los sistemas RIC­WPT, se han propuesto varias aproximaciones para analizar los sistemas RIC-WPT desde diferentes perspectivas (bien sean campos electromagnéticos, modelos circuitales, u óptica), pero no se ha conseguido proporcionar un modelo unificado que permita la comprensión y, en última instancia, el diseño del comportamiento y las prestaciones de estos sistemas. Esta tesis tiene por tanto como objeto, primero, proporcionar un modelo completo multi-modo de la tecnología RIC-WPT, orientado al diseño y a su vez la optimización de estos sistemas, y, como segundo foco, el explorar y caracterizar los retos fundamentales que todavía evitan un amplio despliegue de los sistemas RIC-WPT, ofreciendo en consonancia un conjunto de pautas de diseño para sobreponerlos. Finalmente, y debido al hecho de que los sistemas RIC-WPT con múltiples nodos son cruciales para la adopción de esta tecnología, en esta tesis doctoral se modelan, caracterizan y analizan los sistemas RIC-WPT de entrada y salida múltiple, con un especial énfasis en sus tendencias de escalabilidad., Postprint (published version)

The need for autonomy in several fields of aerospace engineering has become apparent and widely accepted during the last decade. Autonomy promises to improve the systems' performances, their robustness and tolerance to failures, reduce operational costs and, ultimately increase the intelligence of the system. Many are the researchers that have tackled the design and implementation of autonomy technologies for system-specific purposes: from the control of a UAV fleet or the coordination of a team of robots, to the implementation of spacecraft FDIR techniques. In the area of satellite missions, autonomous systems may drastically reduce their response times when in the presence of internal perturbations (e.g. subsystem failures), or external changes (i.e. changes in the environment) and may allow new monitoring approaches such as the on-board identification of interesting targets (e.g. autonomous detection of natural disasters, crop and forest change detection, etc.) Autonomy has been deemed essential in the design and deployment of several distributed satellite architectures, especially for Earth Observation applications. The latter systems, grounded on small spacecraft technologies, potentially present node heterogeneity at the functional level as well as in terms of computational and communication capabilities. This, combined with some of their network characteristics (which are dynamic and are affected by the node's orbital properties) and architectural aspects (potentially hierarchically structured and composed of a massive number of spacecraft), enforces the need of autonomous operations. Finally, the absence of autonomy in Distributed Satellite Systems (DSS) architectures, not only could compromise their controllability but could complicate the operational requirements unnecessarily. This presentation is aimed at gathering the design, functional and execution aspects of autonomous mission planning software for DSS architectures and to identifying open issues tha, Postprint (author's final draft)

This paper introduces the concept of switch-mode tunable emulated reactive networks. The idea of implementing reactive networks based on the theory of gyrators is proposed and characterized in an application-driven design-oriented context. By means of using switch-mode power processing converters to synthesize gyrators, small capacitors or inductors are effectively multiplied to emulate larger ideally lossless reactive elements. The proposed idea enables to electronically tune the values of reactive elements by means of timing control variables. The proposed tunable reactive networks target many potential applications such as tunable-front-ends for energy harvesting, electronic compensating active power filters, and tunable-front-ends for wireless power transfer links., Peer Reviewed, Postprint (published version)

L'objectiu d'aquest treball és dissenyar i implementar part de l'arquitectura de software per a una plataforma de desenvolupament de nano-satèl·lits oberta basada en Android. Per un costat, afegir temps real al kernel. Per un altre costat, implementar un repartidor de missatges modular i flexible., The aim of this thesis is to design and implement part of the software architecture for an open nano-satellite development platform based on an Android smartphone. On one side, extend the kernel with real-time capabilities. On the other side, implement a flexible and modular message distributor.

The thesis deals with model-based scalability-oriented design of resource-constrained fractionated satellite networks., [ANGLÈS] Fractionated Satellite Networks are a novel concept in space systems where several satellites cooperate and collaborate by exchanging resources wirelessly in order to obtain an aggregated network capability higher than the sum of the individual capabilities of the different satellites that compose it. In addition, Fractionated Satellite Networks can be easily expanded to extend the objectives of the mission or provide support to a larger number of satellites. Because of this expandable nature of Fractionated Satellite Networks, the concept of scalability is critical on these architectures, as systems that do not scale well present a very poor performance when adding new agents, increasing costs and harming quality of service and stakeholder satisfaction. This thesis presents a model and a framework to analyze scalability on Fractionated Satellite Networks. Our model includes descriptions of the system at the resource, satellite, network and mission level. Connections and resource transfer among nodes are modeled using graphs whereas the study is approached from a resource allocation problem perspective. Two case studies are analyzed in order to show the usefulness of the model. The first one studies the scalability of Federated Satellite Systems (dynamic system) whereas the second one analyzes the scalability of a cluster of nanosatellites that depend on a central node (a static system). Finally, based on the conclusions of the analysis conducted and the nanosatellite-technologies state of the art, some guidelines to design nanosatellites that can be easily integrated in fractionated networks are provided., [CASTELLÀ] Las redes de satélites fraccionados son un innovador concepto en la industria espacial donde varios satélites cooperan y colaboran intercambiando recursos inalámbricamente con el fin de obtener una capacidad agregada en la red superior a la suma de capacidades individuales de cada uno de los satélites que la componen. Además, estas redes pueden ser fácilmente expandidas para ampliar los objetivos de la misión o dar soporte a un mayor número de satélites. Debido a esta naturaleza expandible, el concepto de escalabilidad es crítico en estas arquitecturas, ya que los sistemas que no escalan debidamente presentan un comportamiento muy deficiente al añadir nuevos agentes, aumentando costes y dañando la calidad de servicio y la satisfacción de los stakeholders. Esta tesis presenta un modelo y un marco para analizar la escalabilidad en las redes de satélites fraccionados. Nuestro modelo incluye una descripción del sistema a los niveles de recurso, satélite, red y misión. Las conexiones y la transferencia de recursos entre nodos son modelados empleando grafos, mientras que el estudio se afronta desde la perspectiva de la resolución de un problema de asignación de recursos. Con el fin de mostrar la utilidad del modelo y el framework, dos análisis son presentados. El primero de ellos estudia la escalabilidad de un Federated Satellite System (sistema dinámico) mientras que el segundo de ellos analiza un clúster de nanosatélites que dependen de un nodo central (sistema estático). Finalmente, empleando las conclusiones de los análisis conducidos y el estado del arte de las tecnologías para nanosatélites, ciertas guías de diseño para que los nanosatélites puedan ser integrados en redes fraccionadas fácilmente son proporcionadas., [CATALÀ] Les xarxes de satèl·lits fraccionats són un innovador concepte en la indústria espacial on diversos satèl·lits cooperen i col·laboren intercanviant recursos sense fil amb la finalitat d'obtenir una capacitat agregada a la xarxa superior a la suma de capacitats individuals de cada un dels satèl·lits que la componen. A més, aquestes xarxes poden ser fàcilment expandides per ampliar els objectius de la missió o donar suport a un major nombre de satèl·lits. A causa d'aquesta naturalesa expandible, el concepte d'escalabilitat és crític en aquestes arquitectures, ja que els sistemes que no escalen degudament presenten un comportament molt deficient en afegir nous agents, augmentant costos i danyant la qualitat de servei i la satisfacció dels stakeholders. Aquesta tesi presenta un model i un marc per analitzar la escalabilitat en les xarxes de satèl·lits fraccionats. El nostre model inclou una descripció del sistema als nivells de recurs, satèl·lit, xarxa i missió. Les connexions i la transferència de recursos entre nodes són modelats emprant grafs, mentre que l'estudi s'afronta des de la perspectiva de la resolució d'un problema d'assignació de recursos. Per tal de mostrar la utilitat del model i el framework, dues anàlisis es presenten. El primer d'ells estudia l'escalabilitat d'un Federated Satellite System (sistema dinàmic) mentre que el segon d'ells analitza un clúster de nanosatèl·lits que depenen d'un node central (sistema estàtic). Finalment, emprant les conclusions de les anàlisis conduïts i l'estat de l'art de les tecnologies per nanosatèl·lits, certes guies de disseny perquè els nanosatèl·lits puguin ser integrats en xarxes fraccionades fàcilment són proporcionades.

Coupled magnetic resonance is considered to be a key enabling technology for mid-range wireless power transfer. Models and systems have hitherto considered linear resonators as underlying dynamics, thereby limiting practical deployability due to the extreme sensitivity in front of parameter mismatch and resonance detuning. In this work, structural nonlinear modeling of constituent elements of the resonant link-resonant coils- is considered to unveil the existence of nonlinear dynamic regimes. The methodology considered to explore the nonlinear behavior is based on a behavioral model consisting of state equations, Floquet theory and Filippov method to study the stability of the periodic regime through the associated monodromy matrix. The ultimate aim of the investigation is a design-oriented parameter space exploration which characterizes the border of occurrence of the different dynamic modes in wireless power transfer links. © 2014 IEEE., Peer Reviewed, Postprint (published version)

Recent research in wireless power transfer (WPT) using resonant inductive coupling has demonstrated very high efficiencies at large distances compared to the transmitting element dimensions, thereby increasing the number of potential applications of WPT. Since resonant inductive coupling is a very multidisciplinary field of research, different approaches have been proposed to predict the behaviour of these systems from the physical theory of resonators (coupled-mode theory) and circuit theory. Although the equivalence of these models for a point-to-point link has already been studied together with the performance metrics Power Transferred to the Load (PTL) and Power Transfer Efficiency (PTE), the new challenges and applications of this technology emphasize the necessity of analytical models to predict and assess the behavior of Multiple Input - Multiple Output (MIMO) links. In this article we revisit the current analytical models from the MIMO perspective, derive the analytical equations for the equivalent performance metrics PTE and PTL and demonstrate how to maximize them in a non-radiative resonant wireless power transfer link from a circuit-centric point of view, providing design guidelines in terms of optimal source and load impedances. This work concludes with a prospective discussion on open challenges of WPT. © 2014 IEEE., Peer Reviewed, Postprint (published version)

[ANGLÈS] This thesis covers the design, implementation and application of a capstone project surrounding Air-Sensing Engines in Smart Cities. The task is to achieve autonomous control of an Unmanned Air Vehicle (a quadcopter; small four rotor helicopter) using an onboard smartphone and an Arduino board with air quality sensors., [CASTELLÀ] Esta tesis cubre el diseño, implementación y aplicación de un capstone project que rodea soluciones de medición de calidad del aire en Smart Cities. El objetivo es conseguir control autónomo de un Vehículo Aéreo no Tripulado (un quadcopter, helicóptero de cuatro rotores) utilizando un teléfono inteligente i una placa Arduino con sensores de calidad del aire., [CATALÀ] Aquesta tesi cobreix el disseny, implementació i aplicació d’un capstone project que envolta solucions de mesura de qualitat de l’aire en Smart Cities. L’objectiu és aconseguir control autònom d’un Vehicle Aeri no Tripulat (un quadcopter, helicòpter de quatre rotors) utilitzant un telèfon intel·ligent i una placa Arduino amb sensors de qualitat de l’aire.

The Resonant Inductive Near-Field Generation System uses a single set of hardware to perform both electromagnetic formation flight and wireless power transfer operations in a six-degree-of-freedom microgravity environment. The system serves primarily as a test bed for control algorithms, and operation onboard the International Space Station allows for more complicated and realistic algorithms to be tested. This offers an advantage compared with the restrictive, dynamic environment of flat floor facilities on the ground or the limited duration of reduced-gravity flights. The hardware attaches to the formation flight-test facility inside the International Space Station referred to as the Synchronized Position Hold, Engage, Reorient, Experimental Satellites. Design and development of the support hardware and electronics, as well as some test results from ground testing, a parabolic flight campaign, and preliminary test sessions on the International Space Station are presented. Ground tests and the parabolic flight campaign results include preliminary inertia and thruster characterization of the combined Resonant Inductive Near-field Generation System/Synchronized Position Hold, Engage, Reorient, Experimental Satellites assembly. Preliminary on-orbit test results include data demonstrating wireless power transfer of approximately 30% and qualitative observations of electromagnetic formation flight with one Resonant Inductive Near-Field Generation System unit restrained and the other unit free floating., Peer Reviewed, Postprint (published version)

Maximum power transfer and maximum efficiency are two important design constraints in wireless power transfer applications. Several works have investigated the proper load and impedance match conditions to optimize either efficiency or power transfer. In this paper we show that the optimal load for maximum power transfer and maximum efficiency is the same (a conjugate matched load) when the source resistance is zero. This is important, as many WPT systems have a relatively low, unknown source impedance. Since the optimal load for both efficiency and power is the same as the source impedance approaches zero, the designer can use a bi-conjugate load for a near optimal design for both maximum power and efficiency. As the source impedance becomes significant, the bi-conjugate matched system provides higher power, but at the expense of lower efficiency. Maximum efficiency is achieved with a non-bi-conjugate load, when the source impedance is non-negligible., Peer Reviewed, Postprint (published version)