1,720,974 research outputs found
An adaptive high-order hybrid scheme for compressive, viscous flows with detailed chemistry
No full textA hybrid weighted essentially non-oscillatory (WENO)/centered-difference numerical method, with low numerical dissipation, high-order shock-capturing, and structured adaptive mesh refinement (SAMR), has been developed for the direct numerical simulation of the multicomponent, compressible, reactive Navier–Stokes equations. The method enables accurate resolution of diffusive processes within reaction zones. The approach combines time-split reactive source terms with a high-order, shock-capturing scheme specifically designed for diffusive flows. A description of the order-optimized, symmetric, finite difference, flux-based, hybrid WENO/centered-difference scheme is given, along with its implementation in a high-order SAMR framework. The implementation of new techniques for discontinuity flagging, scheme-switching, and high-order prolongation and restriction is described. In particular, the refined methodology does not require upwinded WENO at grid refinement interfaces for stability, allowing high-order prolongation and thereby eliminating a significant source of numerical diffusion within the overall code performance. A series of one-and two-dimensional test problems is used to verify the implementation, specifically the high-order accuracy of the diffusion terms. One-dimensional benchmarks include a viscous shock wave and a laminar flame. In two-space dimensions, a Lamb–Oseen vortex and an unstable diffusive detonation are considered, for which quantitative convergence is demonstrated. Further, a two-dimensional high-resolution simulation of a reactive Mach reflection phenomenon with diffusive multi-species mixing is presented
Shepherd, J.E.
No full textCarte de Visite of Adjutant J.E. Shepherd, 9th Maine Infantry; From the Maine State Archives Collectionhttps://digitalmaine.com/arc_civilwarportraits/1307/thumbnail.jp
Shepherd, J.E.
No full textCarte de Visite of Adjutant J.E. Shepherd, 9th Maine Infantry; From the Maine State Archives Collectionhttps://digitalmaine.com/arc_civilwarportraits/1307/thumbnail.jp
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
Detonation front structure and the competition for radicals
No full textWe examine the role of competition for radical species in determining detonation front structure for hydrogen and selected hydrocarbon fuels in air and oxygen. Numerical simulations and detailed reaction mechanisms are used to characterize the reaction zone length, shape, and sensitivity to temperature variation. We find that the effect of the competition for radicals on the energy release rate characteristics varies significantly for the chosen mixtures. Hydrogen exhibits a strong effect while in methane and ethane mixtures the effect is absent. Other hydrocarbons including acetylene, ethylene, and propane fall between these extreme cases. This competition is manifested by a peak in effective activation energy associated with a shift in the dominant reaction pathway in the initial portion of the reaction zone. The peak of the effective activation energy is centered on the extended second explosion limit. A five-step, four species reaction model of this competition process has been developed and calibrated against numerical simulations with detailed chemistry for hydrogen. The model includes a notional radical species and reactive intermediate in addition to reactants and products. The radical species undergoes chain-branching and there is a competing pathway through the reactive intermediate that is mediated by a three-body reaction followed by decomposition of the intermediate back to the radical species. We have used this model in two-dimensional unsteady simulations of detonation propagation to examine the qualitative differences in the cellular instability of detonation fronts corresponding to various degrees of competition between the chain-branching and reactive intermediate production. As the post-shock state approaches the region of competition between the radical and reactive intermediate, the detonation front becomes irregular and pockets of the reactive intermediate appear behind the front, but the detonation continues to propagate
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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