1,721,997 research outputs found
The spectrum of the force-based quasicontinuum operator for a homogeneous periodic chain
Full text linkWe show under general conditions that the linearized force-based quasicontinuum (QCF) operator has a real, positive spectrum. The spectrum is identical to that of the quasinonlocal quasicontinuum (QNL) operator in the case of second-neighbor interactions. We construct an eigenbasis for the linearized QCF operator whose condition number is uniform in the number of atoms and the size of the atomistic region. These results establish the validity of and improve upon recent numerical observations [M. Dobson, M. Luskin, and C. Ortner, Comput. Methods Appl. Mech. Engrg., 200 (2011), pp. 2697--2709, Multiscale Model. Simul., 8 (2010), pp. 782--802]. As immediate consequences of our results we obtain rigorous estimates for convergence rates of (preconditioned) GMRES algorithms as well as a new stability estimate for the QCF method
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
Photosynthetic characteristics, stomatal responses and water relations of Fagus sylvatica: impact of air quality at a site in southern Britain
No full textTransplants of beech (Fagus sylvatcia L.) were grown in open-top chambers ventilated with either charcoal-filtered or unfiltered air. From May until September measurements of stomatal conductance to water vapour (gs) were made on trees in the chambers. On six out of seven occasions, leaves which had expanded during the first flush (initial shoot extension, during May) in unfiltered air, had lower stomatal conductances, compared with those grown in filtered air; this was significant on three occasions (P < 0.05). Leaves which expanded later in the season (second Hush or lammas growth) responded differently to the air quality treatments, with greater stomatal conductances recorded for trees exposed to unfiltered air. Measurements of leaf (psychrometry) and shoot (pressure bomb) water relations indicated that air quality had little effect on turgor pressure (P). Values of solute (?s) and water (?w) potential were higher for trees grown in unfiltered air.Trees were transported to the laboralory for measurement of photosynthesis (A), transpiration (E) and stomatal conductance (gs). Measurements of CO, uptake were also made whilst the CO, concentration within the leaf (Cf) was experimentally controlled (A/Ci analysis). This revealed that higher rates of photosynthesis for lammas leaves grown in unfiltered air were due to enhanced regeneration of RuBP (increased Jmax, P < 0.08). Carboxylation efficiency (d.A/dCf) and percentage stomatal limitation were not significantly altered by air quality. Jmax and dA/dCi were similarly reduced following exposure to drought regardless of the air quality treatment
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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