1,721,060 research outputs found
Nanofilamentos de carbono obtenidos mediante descomposición catalítica de corrientes ricas en metano como precursores de materiales grafénicos
No full textLa descomposición catalítica de corrientes ricas en metano como el gas natural o el biogás
para la producción de hidrógeno o gas de síntesis, representa una alternativa viable a los
procesos convencionales de reformado de metano con vapor de agua y reformado seco de
metano. La formación de materiales de carbono nanométricos, como las nanofibras o los
nanotubos de carbono, juega un papel importante en la viabilidad económica de estos
procesos, donde la selección de un catalizador idóneo no solo acelera la velocidad de la
reacción o modera la temperatura de operación, sino que también determina las características
y propiedades de los nanofilamentos de carbono generados. El trabajo presentado en esta Tesis Doctoral aborda la obtención de nanofilamentos de
carbono con unas características y propiedades controladas a partir de la descomposición
catalítica de corrientes ricas en metano, y su aplicación posterior como precursores para la
obtención de materiales de grafeno mediante rutas de oxidación/exfoliación. De este modo, se
pretenden valorizar los productos carbonosos de la descomposición catalítica de metano y
biogás, controlando previamente su morfología y características mediante el diseño de
catalizadores, y profundizar en el conocimiento de la oxidación y exfoliación de nanotubos y nanofibras de carbono para la preparación de diferentes materiales de grafeno. La obtención de nanofilamentos de carbono conlleva tanto el desarrollo de catalizadores y
la determinación de las condiciones óptimas de reacción, como la búsqueda de instalaciones
experimentales adecuadas que permitan un mayor rendimiento a dichos materiales. En este
contexto, se han utilizado catalizadores metálicos masivos basados en Ni y Fe, cuya
composición, contenido en dopante (Cu y Mo) y tipo de soporte (Al2O3 y MgO) han sido
modificados, evaluándose su influencia en la obtención de nanofibras y nanotubos de
carbono, respectivamente. Asimismo, se ha abordado el escalado y optimización del proceso
utilizando catalizadores masivos de Fe y Fe-Mo en instalaciones semipiloto basadas en
reactores de lecho rotatorio y fluidizado, en las cuales se generan por batch decenas de gramos
de nanofilamentos de carbono con características similares a los obtenidos a menor escala.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Carbon nanofilaments from catalytic decompositon of methane-rich streams as precursors of graphenic materials: reseña tesis doctoral
No full text3 Figuras.-- Resumen de la Tesis llevada a cabo por Daniel Torres Gamarra para conseguir el grado de doctor en la Universidad de Zaragoza en 2016.The catalytic decomposition of methane-rich streams such as natural gas or biogas is a viable alternative to conventional H2 or syngas production processes such as steam or dry methane reforming. The formation of nanosized carbon materials as carbon nanofibers (CNF) or nanotubes (CNT) plays an important role in the economic feasibility of these processes. This Thesis work addresses the control of the morphology of the carbonaceous products obtained from catalytic decomposition of methane (CDM) and biogas (CDB) by catalysts design, and their transformation into graphene oxide-based materials through oxidation/exfoliation routes. Thus, Ni and Fe based catalysts were developed and used for fishbone-like CNF and multi-wall carbon nanotubes (MWCNT) obtention, respectively. The subsequent transformation of these nanofilaments to graphene oxide-based materials was based on its chemical oxidation using the modified Hummers method and subsequent exfoliation by sonication. Resulting graphene materials with different chemical and morphological characteristics included: few-layer graphene oxide (FLGO) from both carbon nanofilaments types, and graphene oxide nanofibers (GONF) and graphene oxide quantum dots (GOQD) exclusively from CNF. The oxygen content of these materials was partially removed by hydrothermal reduction methods, resulting in the restoration of the graphene network. Furthermore, a novel and green reduction method based on the supercritical water gasification of glycerol was developed, enhancing the reduction performance thanks to H2 and autogenous pressure generated. On the other hand, an effective separation process based on degressive differential centrifugation was implemented for the separation by size and oxidation degree of the different fractions obtained by exfoliation of CNF: GONF, FLGO sheets and GOQD. This method produces GOQD in high weight yields with controllable photoluminescent properties by hydrothermal reduction treatments.Peer reviewe
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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
Topology Based Fuzzy Clustering for Robust ANFIS Creation
Get PDFThis paper describes how the clustering topology of an input space data distribution is utilized to properly initialize an Adaptive Neuro-Fuzzy Inference System (ANFIS). We used a new unsupervised clustering algorithm called Topology based Fuzzy Clustering (TFC) that performs better than Growing Neural Gas (GNG) in extracting the input-space topology. The topology information in the form of number of nodes, node positions and node connectivity is used for the initialization of the ANFIS. Using two robotic modeling tasks as benchmarks, we demonstrate the improved performance of TFC-derived ANFIS when compared to the subclustering method found in the Fuzzy Logic Toolbox of Matlab
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