1,721,132 research outputs found
Strutture da retroscorrimento sul rilievo di M. Serrone (fianco esterno dell'anticlinale di M. Nerone, Appennino Umbro-Marchigiano).
No full textThe Marne a Fucoidi Formation: a relatively minor disharmony/detachment level in the Umbro-Marchean Apennines (Italy).
No full textHydrogen production from ethanol steam reforming: energy efficiency analysis of traditional and membrane processes
No full textThe ethanol steam reforming reaction has been considered for producing pure hydrogen to be used for feeding a PEM fuel cell of power 4 kW. As an innovative technology, Pd-Ag thin wall membranes are proposed for building membrane reactors: accordingly, the energy efficiency analysis of the processes producing hydrogen from the ethanol steam reforming has been carried out and, particularly, the comparison among a traditional process and different membrane processes is reported.
The traditional process studied consists of an ethanol reformer followed by two water gas shift reactors operating at high and low temperature, respectively: the final hydrogen purification is carried out by a preferential oxidizer in order to reduce the CO concentration below 10 ppm before feeding the PEM fuel cell.
Then two membrane processes using Pd-Ag tubes and operating with a feed H2O/ethanol have been considered. The first one uses a traditional ethanol reformer and a Pd-Ag membrane reactor where the water gas shift reaction and the hydrogen separation take simultaneously place: the pure hydrogen recovered in the permeate side of the membrane reactor is sent to the PEM anode. In the second membrane process, one Pd-Ag membrane reactor performs both the ethanol steam reforming and the hydrogen separation: also in this case, the pure hydrogen recovered in the permeate side of the membrane reactor is directly sent to the PEM anode.
The analysis showed that the highest values of the energy efficiency have been attained by the process using one membrane reformer: this process has a net electric efficiency higher than the traditional one by 10 %.
Finally, an efficiency field-to-wheel analysis has been also carried out: a conventional application of the pure bio-ethanol in a reciprocating engine has been compared to a membrane system processing humid bio-ethanol and fuelling a PEM driven electrical engine. As a result, the membrane process presents a higher energy efficiency up to 50% and mainly as a consequence of the direct use of water-ethanol mixtures: in fact, in this case the distillation and dehydration of the bio-ethanol is avoided thus increasing the energy efficiency
Produzione di metano da carbone con l'uso di fonti energetiche rinnovabili
No full textPer coniugare un più ampio sfruttamento del carbone e delle fonti energetiche rinnovabili, è stato studiato un processo che prevede
la produzione di idrogeno da eolico o solare e, quindi, la conversione di carbone in metano attraverso reazioni di idro-gassificazione.
Un’analisi economica preliminare mostra che questo processo potrebbe essere vantaggiosamente applicato all’area del Sulcis
in Sardegna.A process aimed at the exploitation of both coal reserves and renewable energies has been studied. It produces hydrogen from wind or solar and, then,
methane via coal hydro-gasification. A preliminary economic analysis demonstrated the applicability of such a process to the Sulcis coalfield in Sardinia
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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