1,721,014 research outputs found
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
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
Error response surfaces in large eddy simulation of a spatially evolving mixing layer
No full textInternational audienceno abstrac
Simulations of the flow around a circular cylinder by a continuous universal hybrid model
No full textA new hybrid RANS/LES approach is presented.
The key feature of this approach is a blending between
two eddy-viscosities, one given by the k-\epsilon RANS
model and the other by the Smagorinsky VMS-LES
(variational multiscale LES) closure. The blending
is set by a parameter theta: VMS-LES mode is active when theta=0,
RANS mode if theta=1, a hybrid mode for 0<theta<1.
The hybrid model is applied to the simulation of the flow
around a circular cylinder at Re=140000, testing the sensitivity of the model to blending parameter variations, to grid refinements and to preconditioning changes.
The results are also compared with those obtained using the detached eddy simulation (DES) approach and with experimental data avaible in the literature
Augmented Prediction of Turbulent Flows via Sequential Estimators Sensitivity of State Estimation to Density of Time Sampling for Available Observation
Get PDFInternational audienceA sensitivity analysis of new methodological approaches for state estimation (Meldi and Poux J. Comput. Phys. 347, 207-234, 2017) is proposed in this manuscript. The performance of the estimator is tested via the analysis of a number of aspects that play a major role in the augmented prediction process, such as the density in time sampling of available observation, the placement of sensors and the interaction with boundary conditions. The work is developed for the turbulent spatially evolving mixing layer test case, using high precision DNS samples as observation and Smagorinsky LES as underlying model. A number of estimators combining LES with DNS data integrated via sensors are performed, varying the frequency of time sampling of observation f T = 1// T , where T is the period between successive assimilation phases. It is concluded that if T ≤≈ 0.5t A , where t A is the characteristic average advection time, the prediction via estimator shows minimal differences i.e. the process of state estimation has reached convergence. This relation can be interpreted as a threshold for converged state estimation. However, the results show as well that a linear converge towards pure model performance is not obtained for every physical quantity with progressive decrease of f T , while eventually pure model results are obtained for f T → 0. In addition, the effect of upstream boundary conditions over the state estimation are investigated and strategies for optimized positions of sensors are derived
Quantification of epistemic uncertainties and parameter calibration in RANS turbulence models
No full textThanks to its limited computational requirements, the RANS approach has extensively been used and is still used to predict the low-order statistics of high Reynolds number turbulent flows. The main drawback is that an universal setup of the closure turbulence models has proved to be elusive. The free parameters present in turbulence models are usually derived from estimated deterministic values of some properties of benchmark turbulent flows, as e.g. the energy power law exponent for decaying homogeneous isotropic turbulence or the value of the Von Karman constant. The free parameters present in different well-known turbulence models are obtained herein by considering the underlying properties as random variables over a bounded range. This range has been recovered from the results reported in literature for the relevant properties, so that the considered epistemic uncertainty is realistic. The sensitivity to this uncertainty of the results of turbulent channel flow RANS simulations is then investigated for different Reynolds numbers and for two popular RANS models, viz. the K-epsilon Launder-Sharma and the Menter K-omega SST. The RANS solution is reconstructed over the continuous multi-dimensional uncertainty space of the considered random variables through the application of a surrogate model (response surface) obtained by means of generalized Polynomial Chaos. The model coefficients of the two considered RANS models are then calibrated and compared to literature standard values
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
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