992 resultados para Modulação digital


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Optical networks are under constant evolution. The growing demand for dynamism require devices that can accommodate different types of traffic. Thus the study of transparent optical networks arises. This approach makes optical networks more "elegant" , due to a more efficient use of network resources. In this thesis, the author proposes devices that intend to form alternative approaches both in the state of art of these same technologies both in the fitting of this technologies in transparent optical networks. Given that full transparency is difficult to achieve with current technology (perhaps with more developed optical computing this is possible), the author proposes techniques with different levels of transparency. On the topic of performance of optical networks, the author proposes two techniques for monitoring chromatic dispersion with different levels of transparency. In Chapter 3 the proposed technique seems to make more sense for long-haul optical transmission links and high transmission rates, not only due to its moderate complexity but also to its potential moderate/high cost. However it is proposed to several modulation formats, particularly those that have a protruding clock component. In Chapter 4 the transparency level was not tested for various modulation formats, however some transparency is achieved by not adding any electrical device after the receiver (other than an analog-digital converter). This allows that this technique can operate at high transmission rates in excess of 100 Gbit / s, if electro-optical asynchronous sampling is used before the optical receiver. Thus a low cost and low bandwidth photo-detector can be used. In chapter 5 is demonstrated a technique for simultaneously monitoring multiple impairments of the optical network by generating novel performance analysis diagrams and by use of artificial neural networks. In chapter 6 the author demonstrates an all-optical technique for controlling the optical state of polarization and an example of how all-optical signal processing can fully cooperate with optical performance monitoring.

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This co-edited book focuses on core theories and research on technologies, from the first audio guides to contemporary and future mobile digital devices, which inform practical design considerations. It is framed in case studies and focuses generally on informal learning by museum and gallery visitors. The book fills a significant gap in the literature on museum practice with regard to uses of digital technologies, which are not generally grounded in rigorous research, and is intended to retain its relevance as technologies evolve and emerge. The book includes chapters by invited authors from the USA, UK and Europe who contribute expertise in a number of areas of museum research and practice. The research resulted in invited keynote speeches in France (‘Technologie de l’apprentissage humain dans les musées’ seminar at Laboratoire d’Informatique de Grenoble on 5 March 2009), Iceland (keynote at ‘NODEM Network of Design and Digital Heritage’ conference on 3 December 2008) and London (Keynote at ‘Mobile Learning Conference’ on 26 January 2009). The book was given the highest recommendation ('Essential') by the American Library Association, and was reviewed in MedieKultur (2011, 50, 185–92). Walker’s chapter includes some of the initial findings from his PhD research on visitor-constructed trails in museums, which shifts focus from the design of technologies to the design of activities intended to structure the use of technologies, and constitutes some of the first published research on visitor-generated trails using mobile technologies. Structures such as trails are shown to act as effective mental models for museum visitors, especially structures with a narrow subject focus and manageable amount of data capture; those created as a narrative or a conversation; and those that emphasise construction, rather than data capture. Walker also selected most of the other chapter authors, suggested their topics and led the editing of the publication.