1,721,121 research outputs found
Asymptotic quantum behavior of classically anomalous maps
No full textIn the framework of quantum chaos, the theory of dynamical localization plays an outstanding role, both for its conceptual relevance and physical import. Theoretical arguments, confirmed by a large amount of numerical simulations, have shown in the case of complete classical chaos, that the localization length is related to the classical diffusion constant and the effective Planck's constant h. We investigate the quantum behavior when classical dynamics exhibits anomalous diffusion (so that the diffusion constant is not defined): we show that dynamical localization still takes place, and that the scaling with the quantum parameter is the same as the, classically diffusive case
Active Feedback Control on Post-Mission Disposal Compliance to Limit the Space Debris Proliferation
Full text linkModeling and Simulation of Milani CubeSat Contact Motion on the Surface of the Secondary Asteroid of Didymos Binary System
No full textApplication of Active Feedback Control for Investigation of Debris Mitigation Strategies on a Density-Based Model of the Population Evolution
Full text linkThe population of objects in space faced an unforeseeable growth in the last decades. There-fore, it is now imperative to reiterate the debris mitigation guidelines and reconsider the approach to the debris proliferation problem. Different counteractions are available to deal with the sit-uation. However, how to efficiently combine and apply these methods for sustainable use of the space environment is still an open question. To respond to this need, the GREEN SPECIES project, funded by a consolidator grant of the European Research Council, will develop a con-trolled model of the space debris population to define optimal mitigation policies. In its current version, the system exploits a statistical model in which debris and intact objects move in a one-dimensional domain in orbital radius and binned in spherical shells. The evolution of the environment is modelled in terms of the objects' density dynamics. The system includes the effect of atmospheric drag, sources as launches and in-orbit fragmentations, and artificial sink mechanisms such as post mission disposals and active debris removals. The resulting set of ordi-nary differential equations is integrated with a state-dependent linear feedback controller to tune different inputs and reach a predefined target. The novel appraoch exploits the benefits of control techniques to investigate the effectiveness of diversified rules in space and time to mitigate the debris proliferation and its risk to missions in low Earth orbit
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
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