1,720,954 research outputs found
Analisi tecnico-economica del processo di upgrading del biogas mediante Pressure Swing Adsorption
Full text linkLa Pressure Swing Adsorption (PSA) è una tecnologia diffusamente applicata l'upgrading del biogas a biometano, soprattutto per impianti di relativamente piccola potenzialità. In questo studio viene presentato un modello di simulazione dinamica che descrive il funzionamento di unità multibed di PSA, a partire dalla conoscenza dell'equilibrio e della cinetica di adsorbimento dei due componenti da separare (anidride carbonica e metano) sul materiale adsorbente utilizzzato, e consente di valutarne parametri sintetici di performance quali la purezza del biometano prodotto, il recupero di metano, la produttività, i consumi energetici. Il modello è stato utilizzato per analizzare diversi cicli e condizioni operative: in particolare, a partire da un ciclo base, con le classiche fasi di pressurizzazione, alimentazione/adsorbimento ad alta pressione (3-5 atm), blow-down e spurgo sotto vuoto (0.1 atm), sono stati studiati cicli
che includono step di equalizzazione della pressione, in modo da ridurre i consumi energetici e migliorare il recupero del metano; per ogni sequenza sono riportati i risultati di diversi test run, modificando le variabili di progetto in modo da ottenere una specifica di purezza >97% (come richiesto attualmente per il gas naturale immesso nella rete gas italiana) con un recupero elevato (>85%) e consumi energetici bassi.
Lo studio effettuato indica che, a partire da biogas al 50% di metano, è possibile ottenere la specifica di purezza richiesta con recuperi intorno al 90% e consumi di energia del 2.5-3% del contenuto energetico del biometano ottenuto; il recupero aumenta e il consumo energetico all'1.5-2% se il biogas ha un contenuto di metano del 65%. Sulla base dei dimensionamenti effettuati si è stimato un costo per un impianto di upgrading di circa 530 Nm3/h di biogas (potenzialità corrispondente all'ottenimento di 1 MWel ) intorno ai 1200-1600 k e, tenendo conto dell'ammortamento del capitale, degli oneri finanziari e dei costi di esercizio, un costo del biometano ottenuto di 0.25 /Nm3, per un biogas al 50% di metano, o inferiore a 0.2 /Nm3 se si alimenta l'impianto con un biogas al 65% di CH4. Questo costo deve essere aggiunto al costo di produzione del biogas, al costo del pretrattamento del biogas per la rimozione di umidità e inquinanti (in particolare H2S) e tutti i costi relativi all'immissione in rete. E' inoltre necessario considerare il problema della destinazione dell'olio-gas, che ha un contenuto di metano dall'8 al 18% e dal quale dovrebbe essere recuperata energia termica. Un confronto con la tecnologia a membrana, sviluppato facendo in particolare riferimento ai risultati ottenuti da ENEA Trisaia, indica che la PSA consente di ottenere recuperi maggiori
con consumi energetici più bassi; nel caso della separazione con membrana i consumi energetici vanno dal 4.4 % (recupero del 75%) al 5.8% se si vuole ottenere un recupero del 94.5% (in questo caso, però il biometano è reso alla pressione di 31 atm)
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
Biogas upgrading through CO2 removal by chemical absorption in an amine organic solution. Physical and technical assessment, simulation and experimental validation
No full textAn experimental and modelling study of CO2 removal from a simulated biogas feed by chemical absorption in an organic solution of 2-amine-2-methyl-1-propanol in an ethylene glycol and n-propanol solvent is presented. Absorption was carried out under different temperature, feed flow rate, and feed recirculation conditions. Regeneration was carried at different temperatures. Cyclability tests showed that the absorption capacity remained stable starting from the fourth cycle. In the conditions analyzed, higher temperatures and liquid recirculation favor absorption. With all other conditions constant, the CO2 absorption efficiency increased from 72% to 87% when the temperature increased from 23 to 45°C. At 33°C, liquid recirculation enhanced the absorption efficiency from to 93%–97%. A model was developed and validated against experimental results. Absorption and desorption rates are proportional to the carbon dioxide and AMP concentrations and to the alkyl carbonate concentration, respectively. The two rate constants were fitted from the experimental data: their values at 30°C are 0.033 s−1 (kmol/m3)−1 and 1.5 × 10−6 s−1, respectively. The model indicates that the beneficial effect of temperature and liquid recirculation is due to the increased mass transfer coefficient of CO2 from the gas to the liquid solution, which increased from 4 × 10−3 s−1 at 20°C to 1.3 × 10−2 s−1 at 70°C and by a factor of 8.8 as a consequence of feed recirculation. An increase in the biogas flow rate reduced the absorption efficiency by decreasing the contact time. Higher temperatures also increased the rate of CO2 desorption
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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