1,720,958 research outputs found
Generation of attenuation time series for simulation purposes starting from Italsat
No full textA model is presented that extends the applicability of the propagation data collected during a long measurements campaign in a particular site and for a particular radiolink, to a generic link in a generic site. In fact, the objective of the model is to create a set of attenuation time series to be used in the design of advanced TLC systems. The model assumes that the marked differences of the rain statistics observed in various locations are, in first approximation, mainly due to the different frequency of occurrence of the various rainy events rather than to their shape. Starting from this assumption the model selects, from a large database of rain attenuation events collected in a particular site, a subset that, after an appropriate frequency and elevation scaling, can be used to represent time series of attenuation recorded in other experimental conditions (as for both site and link). The model has been applied to the attenuation data collected at Spino d’Adda (Milan, Italy) during the ITALSAT propagation campaign in order to simulate attenuation time series in several different links and sites. The model demonstrated good performance both in link conditions and climates, similar and different from the Spino d’Adda ones
Multi-channel propagation simulator: a new tool for the design of complex satellite-based adaptive radio networks
No full textEffetti propagativi sul segnale radio ricevuto in ambito urbano: confronto fra tecniche di tracciamento dei raggi e metodi statistici
No full textEffetti propagativi sul segnale radio ricevuto in ambito urbano: confronto tra tecniche di tracciamento dei raggi e metodi statistici
No full textEight Years of ITALSAT Copolar Attenuation Statistics at Spino d'Adda
No full textThe ITALSAT propagation experiment started in early 1991 and ended in January 2001. A receiving station for
the radio-wave propagation experiment at 18.7, 39.6 and 49.5 GHz was installed in 1992 at Spino d’Adda (45.4 N, 9.5 E),
near Milano, Northern Italy. In addition to the beacon receiver, which records every second the attenuation measured at the 3
frequencies along a slant path of 37.8◦ elevation angle, the earth station was equipped with a tipping bucket rain-gauge and
meteorological instruments recording temperature, humidity and pressure.
This paper presents 8 years (1993–2000) of copolar attenuation statistics. The cumulative distribution functions (c.d.f.) of
attenuation due to rain for 1993 and total attenuation (gas, clouds, turbulence and rain effects) for the period 1994–2000 are
presented along with the rain intensity c.d.f. for the period 1992–2000.
The total attenuation c.d.f., averaged over 7 years, is compared with predictions obtained using ITU-R Rec. P.618-7 as for gas,
clouds and scintillation contributions and ITU-R Rec. P.618-7 and EXCELL model for rain contribution. The measured long-term
cumulative distribution of rain intensity, averaged over the period 1992–2000, is used as input for rain attenuation models.
The ratio between standard deviation and mean value of total attenuation calculated at various time percentages for the 7 years
is used to characterize the year-to-year variability. C.d.f. of total attenuation conditioned to the season and the hour of the day are
also calculated
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
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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