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This thesis introduces and analyses the emerging Website genre of Resource Centre Sites. RCSs are sites which combine news, rumours and background information as well as community discussion and commentary on their chosen topic, and frequently serve as a first point of entry for readers interested in learning more about the field. They also offer spaces for virtual communities of specialists or enthusiasts to emerge, who in the process and as a product of their interaction on these sites collate detailed resource collections and hyperlink directories for their fields of interest. Therefore, Resource Centre Sites significantly involve their users as content contributors and producers, turning them into what is here termed ‘produsers’ of the site. Aiming to evaluate all the content relevant to their field that is becoming available online, and to coopt or at least link to this information from the news and resources collection that is a central part of the RCS, Resource Centre Site produsers engage in an adaptation of both traditional journalistic gatekeeping methodologies and librarianly resource collection approaches to the Web environment: in the absence of gates to keep online, they have become ‘gatewatchers’, observing the publication of news and information in other sources and publicising its existence through their own sites. Their operation is studied here through a number of case studies of major existing Resource Centre Sites from various fields of interest. These sites are analysed both based on their available Web content, and using background information obtained in a series of email interviews with RCS creators. In combination, this offers insights into the operating philosophies of sites and site editors, and provides an opportunity to assess to what extent these ideas have been translated into everyday practice. Chapter 1 provides an overview of past and current theoretical views of the Web in an effort to evaluate their suitability for the current study. Older approaches positing an abstract ‘ideal’ form of hypertext are rejected in favour of a direct engagement with the World Wide Web as the now dominant mode of hypertextuality. Chapter 2 outlines the principles of gatewatching in contrast to traditional methods of evaluating news and information as they exist in journalistic media and archival institutions, and investigates the effects such gatewatching practices may have on editors and users. Chapter 3 describes the overall characteristics of Resource Centre Sites as a genre of Web publications. It notes the special role site users play in the operation of such sites (in their new role as ‘produsers’), and distinguishes the RCS genre from similar Website models such as portals and cybermediaries. Chapter 4 observes the everyday operation of such Websites in practice, using case studies of major existing Resource Centre Sites including Slashdot, MediaChannel and CountingDown, and interviews with their creators. (These interviews are included in full in the Appendix.) This analysis works with both a synchronic view to the variety of topics existing Resource Centre Sites are able to address, and a diachronic view to the evolution of proto-RCSs (such as enthusiast community or online advocacy sites) into fully-featured Resource Centre Sites. Finally, based on this analysis, Chapter 5 is then able to point out some of the implications and effects that increasing use of this media form may have on its users and the network of news and information publications on- and offline, and to indicate the potential for further developments of the site genre.

This thesis introduces and analyses the emerging Website genre of Resource Centre Sites. RCSs are sites which combine news, rumours and background information as well as community discussion and commentary on their chosen topic, and frequently serve as a first point of entry for readers interested in learning more about the field. They also offer spaces for virtual communities of specialists or enthusiasts to emerge, who in the process and as a product of their interaction on these sites collate detailed resource collections and hyperlink directories for their fields of interest. Therefore, Resource Centre Sites significantly involve their users as content contributors and producers, turning them into what is here termed ‘produsers’ of the site. Aiming to evaluate all the content relevant to their field that is becoming available online, and to coopt or at least link to this information from the news and resources collection that is a central part of the RCS, Resource Centre Site produsers engage in an adaptation of both traditional journalistic gatekeeping methodologies and librarianly resource collection approaches to the Web environment: in the absence of gates to keep online, they have become ‘gatewatchers’, observing the publication of news and information in other sources and publicising its existence through their own sites. Their operation is studied here through a number of case studies of major existing Resource Centre Sites from various fields of interest. These sites are analysed both based on their available Web content, and using background information obtained in a series of email interviews with RCS creators. In combination, this offers insights into the operating philosophies of sites and site editors, and provides an opportunity to assess to what extent these ideas have been translated into everyday practice. Chapter 1 provides an overview of past and current theoretical views of the Web in an effort to evaluate their suitability for the current study. Older approaches positing an abstract ‘ideal’ form of hypertext are rejected in favour of a direct engagement with the World Wide Web as the now dominant mode of hypertextuality. Chapter 2 outlines the principles of gatewatching in contrast to traditional methods of evaluating news and information as they exist in journalistic media and archival institutions, and investigates the effects such gatewatching practices may have on editors and users. Chapter 3 describes the overall characteristics of Resource Centre Sites as a genre of Web publications. It notes the special role site users play in the operation of such sites (in their new role as ‘produsers’), and distinguishes the RCS genre from similar Website models such as portals and cybermediaries. Chapter 4 observes the everyday operation of such Websites in practice, using case studies of major existing Resource Centre Sites including Slashdot, MediaChannel and CountingDown, and interviews with their creators. (These interviews are included in full in the Appendix.) This analysis works with both a synchronic view to the variety of topics existing Resource Centre Sites are able to address, and a diachronic view to the evolution of proto-RCSs (such as enthusiast community or online advocacy sites) into fully-featured Resource Centre Sites. Finally, based on this analysis, Chapter 5 is then able to point out some of the implications and effects that increasing use of this media form may have on its users and the network of news and information publications on- and offline, and to indicate the potential for further developments of the site genre.

This thesis introduces and analyses the emerging Website genre of Resource Centre Sites. RCSs are sites which combine news, rumours and background information as well as community discussion and commentary on their chosen topic, and frequently serve as a first point of entry for readers interested in learning more about the field. They also offer spaces for virtual communities of specialists or enthusiasts to emerge, who in the process and as a product of their interaction on these sites collate detailed resource collections and hyperlink directories for their fields of interest. Therefore, Resource Centre Sites significantly involve their users as content contributors and producers, turning them into what is here termed ‘produsers’ of the site. Aiming to evaluate all the content relevant to their field that is becoming available online, and to coopt or at least link to this information from the news and resources collection that is a central part of the RCS, Resource Centre Site produsers engage in an adaptation of both traditional journalistic gatekeeping methodologies and librarianly resource collection approaches to the Web environment: in the absence of gates to keep online, they have become ‘gatewatchers’, observing the publication of news and information in other sources and publicising its existence through their own sites. Their operation is studied here through a number of case studies of major existing Resource Centre Sites from various fields of interest. These sites are analysed both based on their available Web content, and using background information obtained in a series of email interviews with RCS creators. In combination, this offers insights into the operating philosophies of sites and site editors, and provides an opportunity to assess to what extent these ideas have been translated into everyday practice. Chapter 1 provides an overview of past and current theoretical views of the Web in an effort to evaluate their suitability for the current study. Older approaches positing an abstract ‘ideal’ form of hypertext are rejected in favour of a direct engagement with the World Wide Web as the now dominant mode of hypertextuality. Chapter 2 outlines the principles of gatewatching in contrast to traditional methods of evaluating news and information as they exist in journalistic media and archival institutions, and investigates the effects such gatewatching practices may have on editors and users. Chapter 3 describes the overall characteristics of Resource Centre Sites as a genre of Web publications. It notes the special role site users play in the operation of such sites (in their new role as ‘produsers’), and distinguishes the RCS genre from similar Website models such as portals and cybermediaries. Chapter 4 observes the everyday operation of such Websites in practice, using case studies of major existing Resource Centre Sites including Slashdot, MediaChannel and CountingDown, and interviews with their creators. (These interviews are included in full in the Appendix.) This analysis works with both a synchronic view to the variety of topics existing Resource Centre Sites are able to address, and a diachronic view to the evolution of proto-RCSs (such as enthusiast community or online advocacy sites) into fully-featured Resource Centre Sites. Finally, based on this analysis, Chapter 5 is then able to point out some of the implications and effects that increasing use of this media form may have on its users and the network of news and information publications on- and offline, and to indicate the potential for further developments of the site genre.

Avec l'ouverture de la bande 57-66 GHz en Europe, de nouvelles technologies de communication sans fil à haut débit sont en cours de développement. De nombreux avantages liés à cette bande de fréquence ont notamment conduit à envisager la transposition du principe de l'identification par radiofréquence (RFID) en bande millimétrique : la MMID. Les réglementations internationales font notamment apparaître une bande passante commune de 5 GHz qui permettrait la mise en place de solutions universelles. De plus la sécurisation des communications point-à-point et la directivité des réseaux d'antennes offrent des perspectives intéressantes.Les travaux présentés dans cette thèse visent à contribuer au développement de la MMID. Ils soulignent les principaux verrous de cette technologie et présentent les différentes solutions proposées qui couvrent de multiples aspects : conception d'antennes et de réseaux d'antennes, conception de prototypes de tags MMID passifs, caractérisation et méthodologie de mesure dont la conception intégrale d'un banc de mesure en bande V, amélioration des performances des tags, et étude de fonctionnalités de capteur intégrées aux tags. Les différents prototypes de tags MMID fabriqués ont permis de réaliser des communications passives de type rétro-modulation jusqu'à 20 cm. De plus, des fonctions de capteur d'humidité et capteur de pression intégrées aux tags MMID ont été montrées expérimentalement. L'ensemble de ces résultats ouvre la voie à de nouvelles perspectives pour les domaines des télécommunications et des réseaux de capteurs en bande millimétrique. / With the opening of the 57-66 GHz band in Europe, new high data-rate wireless communication technologies are currently under development. Numerous advantages linked to the frequency band conducted to consider the transposition of the radiofrequency identificaion (RFID) principle to the millimeter frequency band: the MMID. The international regulations provide a common bandwidth of 5 GHz allowing universal solutions. Moreover, the communication security of point-to-point networks and the directivities of the antennas present interesting perspectives.The presented work in this thesis looks for contributing to the development of MMID. The work underlines the principal locks of this technology and it presents the different proposed solutions covering multiple aspects: conception of antennas and antennas arrays, conception of MMID tags prototypes, characterization and measurement methodology including the complete conception of a measurement bench in V-band, improvement of the tags performances and study of sensing functionalities integrated in the tags. Different prototypes of MMID tags are fabricated and passive communications based on the backscattering of the tags were demonstrated up to 20 cm. In addition, humidity and pressure sensing functionalities were proved by experimentations. The overall of these results pave the way for new perspectives for the wireless communication domain and sensors networks in the millimeter-wave band.

Le travail réalisé dans le cadre de cette thèse a pour but de caractériser des signaux aléatoires, rencontrés dans le domaine aérien et sous-marin, en s’appuyant sur une approche statistique. En traitement du signal, l'analyse statistique a longtemps été fondée sous l'hypothèse de Gaussianité des données. Cependant, ce modèle n'est plus valide dès lors que la densité de probabilité des données se caractérise par des phénomènes de queues lourdes et d'asymétrie. Une famille de lois est particulièrement adaptée pour représenter de tels phénomènes : les distributions α-stables. Dans un premier temps, les distributions α-stables ont été présentées et utilisées pour estimer des données synthétiques et réelles, issues d'un sondeur monofaisceau, dans une stratégie de classification de fonds marins. La classification est réalisée à partir de la théorie des fonctions de croyance, permettant ainsi de prendre en compte l'imprécision et l'incertitude liées aux données et à l'estimation de celles-ci. Les résultats obtenus ont été comparés à un classifieur Bayésien. Dans un second temps, dans le contexte de la surveillance maritime, une approche statistique à partir des distributions α-stables a été réalisée afin de caractériser les échos indésirables réfléchis par la surface maritime, appelés aussi fouillis de mer, où la surface est observée en configuration bistatique. La surface maritime a d'abord été générée à partir du spectre d'Elfouhaily puis la Surface Équivalente Radar (SER) de celle-ci a été déterminée à partir de l'Optique Physique (OP). Les distributions de Weibull et ont été utilisées et comparées au modèle α-stable. La validité de chaque modèle a été étudiée à partir d'un test de Kolmogorov-Smirnov. / The purpose of this thesis is to characterize random signals, observed in air and underwater context, by using a statistical approach. In signal processing, the hypothesis of Gaussian model is often used for a statistical study. However, the Gaussian model is not valid when the probability density function of data are characterized by heavy-tailed and skewness phenomena. A family of laws can fit these phenomena: the α-stable distributions. Firstly, the α-stable distribution have been used to estimate generated and real data, extracted from a mono-beam echo-sounder, for seabed sediments classification. The classification is made by using the theory of belief functions, which can take into account the imprecision and uncertainty of data and theirs estimations. The results have been compared to a Bayesian approach. Secondly, in a context a marine surveillance, a statistical study from the α-stable distribution has been made to characterize undesirable echo reflected by a sea surface, called sea clutter, where the sea surface is considered in a bistatic configuration. The sea surface has been firstly generated by the Elfouhaily sea spectrum and the Radar Cross Section (RCS) of the sea surface has been computed by the Physical Optics (PO). The Weibull and distributions have been used and the results compared to the α-stable model. The validity of each model has been evaluated by a Kolmogorov-Smirnov test.

Le travail réalisé dans le cadre de cette thèse s’intègre bien dans le domaine de la télédétection de l’environnement maritime. Il porte notamment, d’une part sur l’étude de l’interaction d’une onde électromagnétique avec une surface maritime en présence d’une cible complexe et observée en configuration bi-statique. D’autre part l’étude est complétée par l’étude et l’analyse de l’influence des différents paramètres à la fois liés à la cible et aussi à l’environnement. Dans ce contexte d’étude, le présent travail s’articule autour de deux volets importants. Le premier vise l’étude et la simulation de la Surface Equivalente Radar(SER) d’une cible complexe placée dans son environnement maritime. Et un deuxième volet applicatif traite l’imagerie radar ISAR d’une scène observée, avec prise en compte des cibles présentes sur la surface. Afin de traiter le premier point, le modèle électromagnétique retenu est basé sur une combinaison de méthodes asymptotiques (Optique Physique (OP), Optique Géométrique (OG), Méthode des courants équivalents (MCE)). Pour l’étude de l’influence de la surface de mer sur la réponse électromagnétique de la cible, nous avons opté pour une représentation de la scène (cible+surface de mer) par un ensemble de facettes triangulaires. Dans ce cadre, la cible discrétisée par un maillage triangulaire est générée à l’aide d’un outil de CAO (CATIA V5), quant à la surface de la mer, elle est générée en utilisant le spectre de mer d’Elfouhaily (et le modèle de Debye pour la prise en compte des paramètres diélectriques de l’eau de mer). Enfin, pour l’application de l’imagerie radar ISAR, le calcul de la SER de la cible navale a été effectué en considérant une nouvelle représentation de la cible en parallélépipèdes. La méthodologie proposée a été évalué via des simulations ainsi que des expérimentations sur un modèle générique d’un navire. / The work presented here interset with remote sensing of the maritime environment.It espacially carried with the study of electromagnetic scattering by sea surface with the presence of the target. This study is done in bistatic configuration. So, it is completed by the analysis of the influence of various parameters related to the target and also to the environment. In this context, this work focuses on two important parts. The first is the study and simulation of Radar Cross Section (RCS) of a complex target placed in the maritime environment.And the second part deals with the application of ISAR radar imagery of an observed scene, with consideration of target on the sea surface. We have opted for a combination between Physical Optics (PO), Geometrical Optics (GO) and Equivalent Edge Currents (ECM) (POGO/ EMC) to estimate the RCS. In order to take into account the infuence of sea surface, we have genereted a 2D sea surface from the Elfouhaily spectrum. In order to integrate the target into the scenario (the target in its environment, radar imagery), we propose a parallelepiped representation of the naval taget and RCS calculation. The proposed methodology was evaluated through simulations and measurements on a generic model of a ship.

The emergence of Ultra-wideband (UWB) technology application has yielded tremendous and vital impacts in the field of microwave wireless communications. These applications include military radar imaging, security screening, and tumour detection, especially for early detection of breast cancer. These indicators have stimulated and inspired many researchers to make the best use of this promising technology. UWB technology challenges such as antenna design, the problem of imaging reconstruction techniques, challenges of severe signal attenuation and dispersion in high loss material. Others are lengthy computational time demand and large computer memory requirements are prevalent constraints that need to be tackled especially in a large scale and complex computational electromagnetic analysis. In this regard, it is necessary to find out recently developed optimisation techniques that can provide solutions to these problems. In this thesis, designing, optimisation, development, measurement, and analysis of UWB antennas for near-field microwave imaging applications are considered. This technology emulates the same concept of surface penetrating radar operating in various forms of the UWB spectrum. The initial design of UWB monopole antennas, including T-slots, rectangular slots, and hexagonal slots on a circular radiating patch, was explicitly implemented for medical imaging applications to cover the UWB frequency ranging from 3.1 GHz to 10.6 GHz. Based on this concept, a new bow-tie and Vivaldi UWB antennas were designed for a through-the-wall imaging application. The new antennas were designed to cover a spectrum on a lower frequency ranging from 1 GHz - 4 GHz to ease the high wall losses that will be encountered when using a higher frequency range and to guarantee deeper penetration of the electromagnetic wave. Finally, both simulated and calculated results of the designed, optimised antennas indicate excellent agreement with improved performance in terms of return loss, gain, radiation pattern, and fidelity over the entire UWB frequency. These breakthroughs provided reduced computational time and computer memory requirement for useful, efficient, reliable, and compact sensors for imaging applications, including security and breast cancer detection, thereby saving more lives. / Tertiary Education Trust Fund (TET Fund) Supported by the Nigerian Defence Academy (NDA)