1,721,338 research outputs found
Lecture Recital with Alfred Brendel
No full textRedik, W. (Violin), Girardi, M. (Violin), Lermer, F. (Viola), Rummel, M. (Cello
Multi-object spectroscopy of CL1821+643: a dynamically relaxed cluster with a giant radio halo?
Full text linkWe present the study of the dynamical status of the galaxy cluster CL1821+643, a rare and intriguing cool-core cluster hosting a giant radio halo. We base our analysis on new spectroscopic data for 129 galaxies acquired at the Italian Telescopio Nazionale Galileo. We also use spectroscopic data available from the literature and photometric data from the Sloan Digital Sky Survey. We select 120 cluster member galaxies and compute the cluster redshift ̃ 0.296 and the global line-of-sight velocity dispersion σV ̃ 1100 km s-1. The results of our analysis are consistent with CL1821+643 being a massive (M > 1015 M⊙) dynamically relaxed cluster dominated by a big and luminous elliptical at the centre of the cluster potential well. None of the tests employed to study the cluster galaxies kinematics in the 1D (velocity information), 2D (spatial information), and 3D (combined velocity and spatial information) domains is able to detect significant substructures. While this picture is in agreement with previous results based on X-ray data and on the existence of the central cool core, we do not find any evidence of a merging process responsible for the radio halo discovered in this cluster. Thus, this radio halo remains an open problem that raises doubts about our understanding of diffuse radio sources in clusters
La bergamasca Isotta Brembati sulle tracce di Vittoria Colonna
No full textIn order to investigate the possible 'Colonna function', the essay focuses on a minor voice, but of non-negligible quality, in sixteenth-century poetry: that of Isotta Brembati from Bergamo
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
A spectroscopic survey of Abell 1703: is it a rare relaxed cluster hosting a radio halo or a usual merging system?
Full text linkWe present the study of the internal dynamics of the intriguing galaxy cluster Abell 1703, a system hosting a probable giant radio halo whose dynamical status is still controversial. Our analysis is based on unpublished spectroscopic data acquired at the Italian Telescopio Nazionale Galileo and data publicly available in the literature. We also use photometric data from the Sloan Digital Sky Survey. We select 147 cluster members and compute the cluster redshift ̃ 0.277 and the global line-of-sight velocity dispersion σv ̃ 1300 km s-1. We infer that Abell 1703 is a massive cluster: M200 ̃ 1-2 × 1015 M☉. The results of our study disagree with the picture of an unimodal, relaxed cluster as suggested by previous studies based on the gravitational lensing analysis and support the view of a perturbed dynamics proposed by recent works based on Chandra X-ray data. The first strong evidence of a dynamically disturbed cluster comes from the peculiarity of the BCG velocity with respect to the first moment of the velocity distribution of member galaxies. Moreover, several statistical tests employed to study the cluster galaxies kinematics find significant evidence of substructure, being Abell 1703 composed by at least two or three subclumps probably caught after the core-core passage. In this observational scenario, the suspected existence of a radio halo in the centre of this cluster is not surprising and well agrees with the theoretical models describing diffuse radio sources in clusters
BREAKING 70% NET ELECTRIC COMBINED CYCLE EFFICIENCY WITH CMC GAS TURBINE BLADES
No full textThis work focuses on the optimal cycle design criteria for heavy duty gas turbines employing CMC blades. A combined cycle model with detailed description of the cooled gas turbine is used to determine the optimal Turbine Inlet Temperature and pressure ratio for two values of maximum allowed CMC wall temperatures (1300, 1500 degrees C). Results indicate that the maximum efficiency of the combined cycle is achieved with pressure ratio above 60, posing the need of adopting two shafts for the gas turbine and high temperature materials for the high-pressure compressor. Net electric efficiency above 70% (LHV basis) can be approached with CMC blade wall temperatures of 1300 degrees C (TIT = 2000 degrees C) and efficiency values approaching 72% with CMC blade wall temperatures of 1500 degrees C and TIT of 2200 degrees C. Compared to current H-class gas turbines, the simple cycle efficiency increases by about 10 percentage points (> 53% vs. 43% LHV basis) and the net specific work/net power output by 66%-110% depending on the pressure ratio and TIT. The most critical challenge to achieve such performance appears to be the temperature gradient across the blade wall and the temperature capability (maximum surface temperature and temperature gradient) of the blade coatings
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