1,721,064 research outputs found
Multi-Band and Multi-Service Open Optical Networks: Applications and Perspectives
No full textWorldwide, most of the countries are fast moving towards the deployment of pervasive optical network infrastructures based on fiber optics transmission. First, to support core data-networks, then progressively towards metro and access networks to support 5G, as well as cloud services, data-center interconnects and content delivery networks. Network operators are progressively requiring the implementation of the openness paradigm to better exploit the infrastructures down to the optical transport, and to develop and control the deployed services. We address the physics of propagation of optical signals over a transparent optical infrastructure and show how the optical transmission can be abstracted. We comment on the control and management of multiband optical network arguing on the capability for operators to implement network slicing for different services. We address the use of optical infrastructures for non-data services - e.g., Time and frequency distribution or sensing signals - either on dedicated fibers, or on dedicated bands or spectral portions, in general
Improved set-up for the ytterbium optical clock at INRIM
No full textWe present an upgraded setup for cooling and trapping of ytterbium atoms in a optical clock experiment. The experiment aims to cool and trap ytterbium atoms in a two stage magneto-optical trap (MOT) (at 399nm and 556nm for the first and second stage, respectively) and to probe the narrow-line clock transition at 578 nm in an optical lattice at the magic wavelength (759 nm). We describe here the generation of all the laser sources and the design of a new physic package, including the vacuum chamber and the atomic source
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
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
Gravitational redshift at INRIM
No full textAbstract
The gravitational redshift is one of the main biases in the comparison of
primary frequency standards; even if it is not a limit for the present accuracy
of the microwave frequency standards such as Cs beam or fountain clocks, it
could be a challenge for the forthcoming generation of atomic optical clocks.
In this article we report the evaluation of the gravitational redshift with
respect to the Geoid reference at Istituto Nazionale di Ricerca Metrologica
(INRIM) laboratories, with an accuracy of 1 × 10−17 in terms of relative
frequency. The evaluation is based on GPS/levelling measurements and on
the use of both a local and a global model for the Earth Geoid; the main
limitation to the accuracy is given by the Geoid reference potential itself
Robust optical frequency dissemination with a dual-polarization coherent receiver
Full text linkFrequency dissemination over optical fiber links relies on measuring the phase of fiber-delivered lasers. Phase is extracted from optical beatnotes and the detection fails in case of beatnotes fading due to polarization changes, which strongly limit the reliability and robustness of the dissemination chain. We propose a new method that overcomes this issue, based on a dual-polarization coherent receiver and a dedicated signal processing that we developed on a field programmable gated array. Our method allowed analysis of polarization-induced phase noise from a theoretical and experimental point of view and endless tracking of the optical phase. This removes a major obstacle in the use of optical links for those physics experiments where long measurement times and high reliability are required
Extensive cosmic showers detection: the importance of timing and the role of GPS in the EEE experiment
Full text linkExtreme Energy Events (EEE) is an extended Cosmic Rays (CRs) Observatory, composed of about 60 tracking telescopes spread over more than 10 degrees in Latitude and Longitude. We present the metrological characterization of a representative set of actually installed EEE GPS receivers, their calibration and their comparison with respect to dual-frequency receivers for timing applications, as well as plans for a transportable measurement system to calibrate the currently deployed GPS receivers. Finally, the realization of an INRIM Laboratory dedicated to EEE, aimed at hosting reference telescopes and allowing timing studies for Particle Physics/Astrophysics experiments, is presented, as well as the possibility of synchronizing already deployed telescopes utilizing White Rabbit Technique, over optical fiber links, directly with the Universal Time Coordinated time scale, as realized by INRIM (UTC(IT))
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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