1,721,178 research outputs found
Evaluating SOA nonlinearity effects by high-order susceptibility on constant envelope signals in WDM systems
Full text linkNonlinearity effects, arising within a semiconductor
optical amplifier, have been deeply investigated with particular
interest for exploiting them in wavelength conversion. This application
shrinks the research area to a precise scenario: a strong
pump signal travels through the active medium simultaneously
with a modulated signal to be converted. In this case it is possible
to neglect the spectral distribution of the optical power and phase
relationship between propagating signals. SOAs have been also
studied as line amplifiers for WDM phase modulated signals.
Aim of this paper is to extend the propagation model in a SOA,
in order to simulate nonlinearities occurring in the amplification
of a WDM comb signal evaluating FWM on constant envelope
modulation schemes (DPSK). This can be carried out thanks
to an enanched analytical model based on the optical field and
medium interaction, overcoming the wide-used Rate Equation
approach, which is based on the overall photons density
Optical intersatellite system based on DPSK modulation
No full textThe use of optical carrier for intersatellite link (ISLs) can lead the whole system at higher data rates performing low probability of jamming, lower interference, lower power requirements and smaller antenna size. The choice of 1550 nm wavelength technology gives rise to some problems, such as higher antenna size, but offers important benefits: less Doppler shift, less complexity in tracking and acquisition procedure. The main constraint affecting the system performance concerns on the Doppler effect suffered by the signal due to the relative movement between satellites. An analysis of the optical transmitter/receiver performance, operating at 1550 nm will be developed. The communication system is based on a DPSK modulator with Direct Detection receiver, in order to improve system sensitivity with respect to conventional Intensity Modulation-Direct Detection (IM-DD) systems. © 2005 IEEE
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
Over-stratospheric-altitude optical free space links: System performance evaluation
No full textThe wide bandwidth offered by optical communications systems, is attracting more and more interest in space applications. Investigation has been carried out either on suitable modulations or resilient architectures for communications and Earth Observation (E0) missions. New elements have been introduced: High-Altitude-Platforms (HAP's), whose characteristics allow us to carry out an optical link between unmoving terminals, if GEO satellites are involved. This paper is describing an architecture for EO, based on two HAP's linked via a GEO satellite, whose optical payload offers an inline-like amplification for an overall link that can extend over 80,000 km. The aim of our work is to present a low power consumption system that guarantees the required Bit Error Rate (BER). Both Direct Detection (DD) and coherent (homodyne and heterodyne) systems will be considered
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
HAP-GEO optical links: Performance analysis under weak turbulence conditions
No full textHigh altitude Platforms represent a very attractive solution to enhance space communications in terms of available capacity and system topology. They can be geared with multi-functional payload, both for communications and Earth Observation missions. Thanks to their opportune position, they are the key for optics and RF technology integration in space communications. In this paper we evaluate the feasibility of an optical HAP-GEO-HAP link over more than 80,000 km above the stratosphere. In particular, we consider a system based on 1550 nm technology, that exploits the potentialities of DPSK modulation format with Direct-Detection balanced interferometer receiver, and optical amplifier
The translational revolution in atopic dermatitis. the paradigm shift from pathogenesis to treatment
No full textAtopic dermatitis (AD) is the most common inflammatory skin disease, and it is considered a complex and heterogeneous condition. Different phenotypes of AD, defined according to the patient age at onset, race, and ethnic background; disease duration; and other disease characteristics, have been recently described, underlying the need for a personalized treatment approach. Recent advancements in understanding AD pathogenesis resulted in a real translational revolution and led to the exponential expansion of the therapeutic pipeline. The study of biomarkers in clinical studies of emerging treatments is helping clarify the role of each cytokine and immune pathway in AD and will allow addressing the unique immune fingerprints of each AD subset. Personalized medicine will be the ultimate goal of this targeted translational research. In this review, we discuss the changes in the concepts of both the pathogenesis of and treatment approach to AD, highlight the scientific rationale behind each targeted treatment and report the most recent clinical efficacy data
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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