1,721,016 research outputs found
Governance condivisa e consonanza: due dimensioni del problema organizzativo nelle reti di franchising
No full textCatalytic secondary methods for the removal of tar derived from biomass gasification: use of low-cost materials and study of the effect of sulfur species on the steam reforming activity of the catalysts
No full textBiomass gasification could potentially mitigate the actual dependency on fossil fuels. The practical application of this technology still faces many challenges to be considered a sustainable and profitable energy production source. One of the drawbacks of this technology is the production of undesirable by-products such as high molecular weight hydrocarbons collectively known as “tar” and sulfur compounds. These unwanted compounds must be removed before syngas end-use applications as they can foul pipes and reduced the performance of equipment downstream the gasifier as well as poison the catalyst used for upgrading the syngas. Catalytic steam reforming stands as an appealing tar removal technology in the small and medium sized gasification plants where heat management is crucial and recovery of the energy content within the tar compounds is desirable avoiding wastewater effluents and disposal of adsorbents. Nickel based catalysts have been the preferred choice in industrial applications for the reforming reactor. However, deactivation by carbon deposition is at present an unresolved problem which must be addressed before commercial application of biomass gasification technology. Moreover, the presence of sulfur compounds even at the low concentration found in most biomass feedstocks is deleterious for the steam reforming activity of the catalyst. This thesis comprises four experimental studies, each of them deal with a specific arguments of the hot gas cleanup technology of biomass syngas. The main focus was on the steam reforming activity of nickel-based catalyst and the effect of sulfur and the potassium-sulfur interactions on the steam reforming performance of the catalyst.
The main contributions from these studies are; 1) the development of a less time and energy consuming synthesis procedure for the production of a mayenite-supported nickel catalyst using low-cost precursors. This new method involves the addition of the nickel precursor during the mayenite synthesis procedure. Compared to the “wet impregnation” technique the developed method showed slightly lower toluene steam reforming activity but greater stability, which was ascribed to a higher carbon deposition tolerance. 2) Better understanding on the sulfur poisoning of catalysts under steam reforming conditions at laboratory scale. The results evidenced that for a deeper knowledge of the sulfur poisoning, the calculation of the sulfur coverage should be more accurate and new methods for its measurement are required. 3) Comprehension of the mechanism of interaction between potassium and sulfur on a sulfur passivated commercial nickel catalyst under reforming conditions using real biomass syngas. The preferential adsorption site for sulfur and potassium was determined for the applied experimental conditions and catalyst and a mechanism involving the interaction of potassium with the sulfur chemisorbed on the active sites was propose
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
Waste cement interaction in the frame of the use of lead-zinc slags as inert materials in a Portland cement mortar
No full textDalla valutazione della rilevanza intersistemica alla progettazione della consonanza e della risonanza
No full textLo studioso d'imrpea che nell'ottica sistemico-vitale vuole procedere ad una lettura dei rapporti che il sistema impresa intrattiene con le differenti entità sistemiche (sovrasistemi rilevanti) presenti nel contesto deve necessariamente porsi dal punto di vista dell'organo di governo (odg) che decide il grado e la capacità di apertura dell'impresa stess con entità terze al fine di scambiare flussi di materia, energia e informazioni. Emerge da ciò la crticità dell'attività dell'odg nel monitorare il contesto, progettando prima ed implementando dopo la propria stuttura ampliata. L'obiettivo del presente lavoro è quello di verificare le modalità e le condizioni che consentono all'impresa di perseguire efficacemente le condizioni di consonanza e risonanza con i sovrasistemi rilevanti al fine di realizzare migliori condizioni di sopravvivenza dell'impresa
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