1,721,275 research outputs found
A hybrid observer for linear systems under delayed sporadic measurements
No full textThis paper proposes a hybrid observer for state estimation over a network. The network provides delayed measurements of the output of the plant at time instants that are not necessarily periodic and are accompanied by timestamps provided by a clock that synchronizes with the clock of the observer in finite time. The proposed observer, along with the plant and communication network, are modeled by a hybrid dynamical system that has two timers, a logic variable, and two memory states to capture the mechanisms involved in the events associated with sampling and arrival of information, as well as the logic in the estimation algorithm. The hybrid model also includes a generic clock synchronization scheme to cope with a mismatch between the clocks at the plant and the observer. Convergence properties of the estimation error of the system are shown analytically and supported by numerical examples
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
Modified Halloysite as Catalyst for the Conversion of Hydroxymethylfurfural to Furandicarboxylic Acid: A DFT Investigation
Full text linkThe reaction steps involved in the 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid conversion by means of H2O2 were investigated employing a dedicated computational protocol based on density functional theory. The catalytic environment of choice was a molecular model representing a portion of the halloysite nanotube outer surface, functionalized by an organosilane, the 3-aminopropyltriethoxysilane, whose amino group bonds one gold atom. At this stage of the investigation, the process was fully detailed in terms of the interactions between the reaction intermediates and the catalyst, and the reaction standard free energies. In addition, the energy barriers of the elementary steps involving the hydrogen migration from the adsorbed organic species to the gold atom were analyzed. On the basis of the interaction geometries, a certain distinction among the preferred reaction path can be inferred as a function of the net negative charge characterizing the catalyst outer surface. Since the inner surface of halloysite can represent the acid environment needed to obtain 5-hydroxymethylfurfural through dehydration of fructose, the present study is framed in a wider research field where the possibility to consider functionalized halloysite as one-pot reactor for the valorization of biomass is explored.A novel catalyst architecture is proposed with potential one-pot activity for the valorization of biomass. It exploits the gold coordination on the organosilane functionalization in the outer surface of the halloysite spiral nanotube, to be coupled with the acid catalytic activity of its inner surface. The work is a preliminar computational exploration of the structural and energetic characteristics of the species involved. imag
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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