1,721,093 research outputs found
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
A hierarchical approach for bounding the completion time distribution of stochastic task graphs
No full textThe analytical evaluation of the completion time distribution of a general directed acyclic graph (DAG) is known to bean NP-complete problem. In this paper we present a new algorithm, named Tree Bound , for the evaluation of bounds onthe completion time of stochastic graphs assuming ideal conditions for shared resources and independent random variablesas task execution times. The Tree Bound method uses a hierarchical approach that first gives a tree-like representation ofthe graph, and then evaluates lower and upper bounds through a single visit of the tree. As lower bound the method takesthe distribution of an embedded series–parallel graph which is evaluated by means of a simple recursion. The upper boundis based on a hierarchical application of other bounding techniques. In this paper, we use the Shogan algorithm because itsdeterminism allows us to demonstrate some interesting properties of the Tree Bound method.Indeed, through stochastic ordering and stochastic comparison techniques, we demonstrate analytically that our approachprovides tighter bounds than Shogan’s and Yazici-Pekergin’s bounds. On the other hand, we cannot compare formally theTree Bound accuracy to that of other important methods, such as Kleinöder and Dodin, because of their non-determinism.Various empiric comparisons show that the Tree Bound algorithm provides analogous or superior results than heuristicsderived from main non-deterministic methods. Moreover, the Tree Bound algorithm keeps linear complexity and avoidsnon-determinism. Finally, it represents a useful basis for the combination of different bounding techniques which seems theonly way to achieve even tighter bounds on the completion time distribution of stochastic graphs
THE EVOLUTION OF DENSITY CURRENTS AND NEPHELOID BOTTOM LAYERS IN THE ROSS SEA (ANTARCTICA)
No full textIn this study we have analyzed the thermohaline, light transmission and particulate matter data, obtained in the western sector of the Ross Sea during the X Italian Expedition, for the purpose of investigating the evolution of the High Salinity Shelf Water in this area. In particular CTD data were used to estimate the baroclinic velocity field. Light transmission and total particulate matter data (from Niskin bottles mounted on a Carousel water sampler) were used to analyze the nepheloid layers and the evolution of the suspended sediments. This basin is characterized by a northward flow of very dense High Salinity Shelf Water (θ ∼ −1.95°C, S ∼ 34.90), much colder than the incoming Circumpolar Deep Water (θ ∼ 1.20°C, S ∼ 34.70). We obtained a scenario in which the High Salinity Shelf Water interacts with the Circumpolar Deep Water along the Antarctic Slope Front, and deviates from its geostrophic equilibrium. Interestingly, this cold dense water mixes with Circumpolar Deep Water at the shelf break and flows downward until it seems to disappear. Below this cold flow, a thin turbulent current has been observed, again moving northward with a high velocity ∼ 0.2-1.0 m s−1. This thin flow also contains high concentration of suspended matter produced by the interaction of the dense water and the bottom sediments. The various elementary mechanisms ruling the dynamics of such down-flows, namely the effects of topographic irregularities, bottom friction, Ekman benthic boundary layers or the effect of the variability of the Antarctic Circumpolar Current, which can push offshore the dense water, are discussed in this paper
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
CARATTERISTICHE E DISTRIBUZIONE DEL MATERIALE PARTICOLATO SOSPESO NEL TIRRENO SUD ORIENTALE (1994 E 1995)
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