1,720,960 research outputs found
Experimental Analysis of Solid Oxide Fuel Cells under Dry Reforming of Methane
No full textDuring the last decades, the increase in world population, living standard, along with the industrial and transportation sectors led to a pronounced increase in the energy consumption. A consistent improvement of energy production systems is needed to satisfy the world energy demands in terms of fuel and energy. The increasing attention to reduce emissions of pollutants and the concerns about global warming motivate the development of environmental friendly technologies and the enhancement of energy conversion systems efficiency. Although renewable energies are becoming more and more relevant, fossil fuels are still the predominant resources used for stationary and mobile devices. In the last years, many efforts have been devoted to the pollution control and improvements in energy efficiency, with the achievement of remarkable progresses in the electric power sector. Nevertheless, a further improvement can be reached with the development of relatively new technologies, which show great potential in terms of electrical efficiency and low level of pollutant [1-3]. In this context, fuel cells are interesting energy conversion systems, which operate without combusting fuel and directly converting chemical energy to electrical energy. They show electrical efficiency higher than the traditional power generating systems and do not produce significant quantities of pollutants as power plants or internal combustion engines. Hence, fuel cells are very appealing from both energy and environmental point of view. Furthermore, the fuel flexibility of some kind of fuel cells is a very interesting feature for the prospective possibility to use hydrocarbon or alcohol fuels. In particular, the direct feeding of fuel cells with biogas represents a very attractive option for coupling a renewable source with a high efficiency energy conversion system [4-5]. In this PhD thesis, a detailed experimental analysis of Solid Oxide Fuel Cells (SOFC) fed by a mixture of methane and carbon dioxide (which are the main components of biogas) is presented. A brief summary of the contributions of this thesis is reported below: • In Chapter 1, a brief introduction on the state-of-the-art of SOFCs is provided. An overview on the state-of-the-art materials and the potential alternative materials to be used as anodes is given. Some typical issues related to the direct internal reforming of hydrocarbon and alcohol fuels on the anode surface (in particular, carbon deposition build-up on the anode surface of the cell) are reported, along with some common techniques and processes performed in order to prevent these deleterious phenomena. • In Chapter 2, the performances of a Ni/YSZ anode supported tubular SOFC running on direct internal dry forming of methane were studied through polarization curves and performance maps under different carbon dioxide-methane volumetric ratios in a carbon safe region; • In Chapter 3, planar anode-supported SOFCs under direct dry reforming of methane were studied. Aging tests, EIS measurements and post-mortem SEM and FE-SEM analysis of the cells were performed for different carbon dioxide-methane volumetric ratios. A detailed analysis of carbon formation mechanism over the anode surface is reported; • In Chapter 4, the catalytic properties of commercial Ni/YSZ anode supports under different mixture of methane and carbon dioxide were investigated. A particular attention was devoted to the investigation and the explanation of the conversion mechanism: the kinetics and stability of the reactions over the catalyst were investigated by means of Temperature-programmed Techniques. The relevance and the contribution of the chemical reactions (i.e. without the contribution of the electrochemical reactions occurring under current load) involved in these processes on the anode surface were analyzed. This part of the thesis is the most original and was carried out to provide a deeper insight on the conversion mechanism and the catalytic properties for this combination of gases and anode material. As a matter of fact, this topic was only partially explored in literature from an experimental standpoint. The "optimal" operating conditions were indentified for these conditions; • In Chapter 5, the main results are summarized. Some practical conclusions on the optimization of the operation of Solid Oxide Fuel Cells under direct internal dry reforming of methane are give
Experimental study of dry reforming of biogas in a tubular anode-supported solid oxide fuel cell
No full text
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
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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