1,721,007 research outputs found
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
An experimental description of the double positive effect of CO2 injection in methane hydrate deposits in terms of climate change mitigation
No full textn this paper, the possibility of injecting CO2 into a hydrate reservoir, with the only aim of preventing
methane release was investigated. Pure methane hydrates were formed and then partially dissociated,
due to a provoked temperature increase of 2 C. The same procedure was applied to a system composed
by a core of CH4 hydrates and an external shell made with CO2 hydrates. In tests with only methane
hydrate, that temperature increase caused partial hydrate dissociation, with a consequent increase in
pressure about 7.81–8.42 bar. In presence of CO2 hydrate, the same temperature increase did not cause
any dissociation, even if the new established condition were not suitable for CH4 hydrates stability.
Results proved that CO2 is capable to form a strong hydrate shell around the methane core, which hinders
its dissociation. Two positive contributions were reached: CO2 permanent storage and the prevention of
CH4 release in the atmosphere
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
nalyses on CH4 and CO2 hydrate formation to define the optimal pressure for CO2 injection to maximize the replacement efficiency into natural gas hydrate in presence of a silica-based natural porous medium, via depressurization techniques
No full textTo make natural gas hydrate an energy source available for large-scale applications, some issues must be solved;
amongst them, the low kinetic characterizing the process and re-formation of methane hydrate are the most
significant. In this paper methane and carbon dioxide hydrate formation was tested in presence of a natural
silica-based porous sand, with the aim of define the most useful pressure value for carbon dioxide injection into
reservoirs in order to apply replacement strategies via depressurization. A direct comparison between CO2 hydrate formation tests starting respectively from 30 bar and 40 bar, revealed that this latter solution represents the
most effective solution. While moles of CO2 involved into hydrate and, more in general, moles of CO2 permanently stored, are similar in both typologies of tests, the time necessary to complete the formation process was
drastically lower in tests started from 40 bar. Moreover, a lower pressure drop would be required. The more
effective kinetic of the process and the negligible risk of methane hydrate re-formation verified during experiments, allowed to consider the CO2 injection into the reservoir at 40 bar the best solution to optimize methane
recovery, carbon dioxide storage and seafloor deformations due to the reservoir exploitation
Variations in terms of CO2 capture and CH4 recovery during replacement processes in gas hydrate reservoirs, associated to the “memory effect”
No full textThe replacement of methane molecules, contained within natural hydrates reservoirs, with a theoretical equal
number of carbon dioxide molecules, represents a promising opportunity for the near future. However, the
maximum theoretical efficiency was proved to be approximately equal to 75% and, in the real applications, it is
drastically lower. This article focused the attention on the possible reasons of such difference and found in the
memory effect one of them. Firstly, the formation process of pure CH4 and CO2 hydrates was performed and
thermodynamically characterized; then, the replacement process was realized on a system excluding memory
and on a system including it. In the first situation, the theoretical efficiency was reached, while, in presence of
memory effect, the results were drastically less effective, both in terms of methane recovery and in terms of
carbon dioxide storage. When the system did not retain memory of previous formation processes, the quantity of
CO2 captured ranged from 73.97 to 75.05 vol% and the quantity of methane released was approximately equal to
the one of CO2 captured. Conversely, in presence of memory effect, the percentage of CO2 captured dropped to
26 vol% and the quantity of methane release was still lower (24.97–26.03 vol%)
- …
