1,721,834 research outputs found
Direct numerical simulation of weakly spanwise-rotating turbulent plane Couette flow
No full textIn this report, we conduct direct numerical simulations (DNS) of weakly spanwise-rotating plane Couette flows at Reynolds number (here, is the half the wall velocity difference, and is half-channel height). A series of simulations with different rotation numbers ( is constant angular velocity component in the spanwise direction) is carried out to investigate the effect of on the flow statistics. Our results show that the flow statistics are affected by the , and a "critical" rotation number (between and ) is observed, where the kinetic energy of secondary flow contributes about a half of the turbulent kinetic energy, and the mean shear rate at the center line reaches a minimum value. We conjecture that different mechanisms should exist around , and will be investigated further
Review of Application of FFTBM Method for Code Accuracy Quantification
No full textThe fast Fourier transform based method (FFTBM) was proposed in the 1990s and is used for accuracy quantification of computer codes. FFTBM provides frequency-based measures for each single TH variables as well as the whole transient calculations. The measurement-prediction discrepancies in the frequency domain are assessed by the average amplitude (AA). An AA close to 0 indicates good agreement between measured and predicted results. AA is dependent to the proper selection of time windows, weighting factors, number of discrete data used. This paper summarized the application of FFTBM from publications in the last 30 years, including the relevant experimental tests, codes, number of selected parameters and AAtot, etc. It attempts to provide some insights and guidelines for FFTBM application
Prioritizing pressure drop research in nuclear thermal hydraulics
No full textPrediction of pressure drop by wall friction and at geometric discontinuities is important in nuclear thermal
hydraulics simulation. Pressure-drop models were established and upgraded for decades; however, errors in
predictions of experimental data are up to 40%, namely in low flow and two-phase conditions and particularly at
geometric discontinuities. In order to clarify the impact in situations of interest for nuclear reactors, noticeably
accident scenarios investigated in scaled experimental facilities, we propose a virtual benchmark on Reverse
Natural Circulation (RNC) in the PKL test facility
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
FFTBM assessment of reverse natural circulation transient in PKL test facility
No full textThe fast Fourier transform based method (FFTBM) was proposed in the 1990s and is used for accuracy quantification of computer codes. FFTBM provides frequency-based measures for each single TH variables as well as the whole transient calculations. The measurement-prediction discrepancies in the frequency domain are assessed by the average amplitude (AA), which is dependent to the proper selection of time windows, weighting factors, number of discrete data used. This paper summaries the application of FFTBM from publications in the last 30 years based on the previous review papers. It attempts to provide some insights and guidelines for FFTBM application. The second part deals with the applications of FFTBM for code accuracy quantification, to perform a sensitivity analysis on loss coefficients at geometric discontinuities in the framework of a virtual benchmark activity. RELAP5/MOD3.3 code was used for calculation, with qualified nodalizations for PKL test facility. The objective of the virtual benchmark and the sensitivity calculation is to investigate the impact of pressure drop modeling inadequacies in the selected transients
- …
