1,721,110 research outputs found
State-to-state rotational transition rates of the HCO+ ion by collisions with helium
No full textThe rates of rotational transitions for HCO+, the most abundant ion in interstellar space, induced by collision with helium are obtained for temperatures ranging from 10 to 80 K.
The calculations are based on a new potential energy surface for the He–HCO+ interaction and on a scattering matrix whose accuracy was checked by pressure broadening and shift measurements. The rates qjj decrease for increasing values of j and j, with a temperature trend depending on the energy involved in the transitions: if it is small, the rates are almost constant, while an increase with T is found for other cases. Comparison with previous and less accurate results shows an agreement within 50 per cent. Comparison between state-to-state and pressure broadening cross-sections allows us to discuss importance and influence of elastic and inelastic collisions
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
N2-, O2- and He- collision-induced broadening of sulphur dioxide ro-vibrational lines in the 9.2 micron atmospheric window
No full textSulfur dioxide (SO2) is a molecule of considerable interest for both atmospheric chemistry and astrophysics. In the Earth’s atmosphere, it enters in the sulfur cycle and it is ubiquitous present in polluted atmospheres, where it is responsible for acid rains. It is also of astrophysical and planetological importance, being present on Venus and in interstellar clouds. In this work the collisional broadening of a number of ν1 ro-vibrational lines of SO2 perturbed by N2, O2 and He are investigated at room temperature in the 9 μm atmospheric region by means of high resolution tunable diode laser (TDL) infrared spectroscopy. From N2- and O2-broadening coefficients, the broadening parameters of sulfur dioxide in air, useful for atmospheric applications, are derived as well. From the present measurements some conclusions on the quantum number dependence of the N2-, O2- and He-broadening coefficients are drawn. While the J dependence is weak for all the perturbers investigated, different trends with Ka are reported. N2-broadening coefficients show a slight decrease with increasing values of Ka, whereas O2 and He broadening cross sections first increase up to and then they keep a nearly constant value. A comparison and a brief discussion on the efficiency of self-, N2-, O2- and He-collisional dynamics are given. The data obtained represent a significant analysis on foreign broadening of SO2 useful for atmospheric remote sensing and astrophysical applications
Studio dell’evoluzione microstrutturale indotta da friction stir welding in giunti skin-stringer (2024/T4-7075/T6)
Full text linkAppropriate 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
Forgeability characterization of multi-material based functionally graded materials manufactured through friction stir consolidation
Full text linkSolid state recycling allows direct recycling of metal chips into semi-finished products.
This process category proved to lower the environmental impact of metals recycling. Friction
stir consolidation (FSC) is a new solid-state technique taking advantage of friction heat
generation and severe plastic deformation to consolidate chips into billets. The new frontier of
FSC process could be its evolution from recycling techniques towards the concept of upcycling
technique: reuse (discarded objects or material) in such a way as to create a product of higher
quality or value than the original. The authors have recently successfully applied FSC for
producing multi-material based functionally graded materials (FGM). In this paper, the
forgeability of the billet consolidated out of two dissimilar aluminium alloys AA 7075 and AA
2011-T3 chips, was analyzed. A proper forging test was designed, and mechanical and
metallurgical properties of the forged parts were assessed through Vickers hardness
measurements
Precise THz measurements of HCO+, N2H+ and CF+ for astrophysical observations
No full textThe ground-state rotational spectra of HCO+, N2H+ and CF+ (both (12)C- and (13)C-containing isotopologues) have been recorded in the 1.0 - 1.6 THz frequency range. The present measurements allowed us to improve the spectroscopic parameters, which in turn enable the prediction of rotational transitions up to 2.0-2.5 THz with a good accuracy. We therefore consider the present results of great value in view of the extended spectral coverage opened up by the Herschel Space Observatory, Stratospheric Observatory for Infrared Astronomy, and Atacama Large Millimeter Array. Furthermore, we re-investigated the ground-state rotational spectrum of N2H+ in the 93 - 750 GHz frequency range, thus addressing the open issue of the frequency of the J =
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