1,720,974 research outputs found
Caratterizzazione statistica completa di segnale e rumore in collegamenti amplificati otticamente
No full textComplete Statistical Characterization of Signal and Noise in Optically Amplified Fiber Channels
No full textA very simple model is found for phase insensitive laser amplification, Signal and noise along the active fiber are modeled as marked Poisson processes (corresponding to flows of photon bunches of random size) and are dealt with as independent processes, A probabilistic approach, founded on the theory of birth-and-death processes, enables us to give a simple characterization of the amplifier in terms of the statistics of the random gain, of the time intensity of the ASE (amplified spontaneous emission) noise bunches, and finally of the statistics of their sizes. The theory is limited to the linear amplification range, while is valid also for nonhomogeneous inversion along the active fiber. The model can be easily applied for the evaluation of the statistics of the global gain and of the accumulated ASE noise in optically amplified links
A Probabilistic Model of Traveling Wave Optical Amplification
No full textA probabilistic model for traveling wave optical amplifiers is presented. Optical signal and noise are assumed to be bunches of photons traveling along the active region with size varying accordingly to simple random rules. The theory leads to the complete statistical characterization of signal and noise as marked Poisson processes. In spite of the fact that its validity is confined to small-signal regimes, the result may be very useful for a more accurate performance evaluation and design criteria of optical transmission systems using recently developed erbium-doped fiber amplifiers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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