1,721,300 research outputs found
Replication Data for: Hidden Performance: Salary History Bans and Gender Pay Gap
No full textThis file provides replication codes for "Hidden Performance: Salary History Bans and Gender Pay Gap
A second-order-accurate immersed boundary ghost-cell method with hybrid reconstruction for compressible flow simulations
No full textThis study presents an improved ghost-cell immersed boundary method for geometrically complex boundaries in compressible flow simulations. A bilinearly complete extrapolation scheme is developed for the reconstruction of the ghost cell. The second-order accuracy of the improved ghost-cell method (GCM) is shown in unit test cases and is also theoretically proven. A hybrid GCM based on both baseline GCM and improved GCM is proposed and constructed. The hybrid GCM applied in compressible flow is validated against five test cases: (a) Stationary rotating vortex, (b) Prandtl-Meyer expansion flow, (c) Double Mach reflection, \textcolor[rgb]{0,0,1}{(d) Moving-shock/obstacle interaction}, (e) Blunt body shock-induced combustion. This paper provides a comprehensive comparison of their performance in terms of various accuracy and computation time measurements. The simulation results demonstrate that the hybrid GCM has higher accuracy and convergence than the remaining two GCMs in all cases. By directly comparing the primitive variables along the boundary, it can be concluded that the hybrid GCM has significant advantages in compressible flow simulations. The results of CPU time show that the hybrid GCM can provide more accurate results while ensuring the efficiency of the calculation.<br/
Effect of transverse jet position on flame propagation regime
No full textWe studied the mechanisms of flame acceleration (FA) and deflagration to detonation transition (DDT) triggered by a combination of solid and jet obstacles. The Navier-Stokes equations with a detailed hydrogen-air kinetics model were utilized. Vast Kelvin-Helmholtz instabilities generate intensive turbulence-flame interactions, leading to an increase in surface area and high propagation velocity. The jet position has a significant effect on the FA and DDT. A choking flame and detonation flame are obtained by the transverse jet with different positions and mixing times even though in a lower blockage ratio.</p
Detonation simulations in supersonic flow under circumstances of injection and mixing
No full textThe unsteady, reactive Navier-Stokes equations with a detailed chemical mechanism of 11 species and 27 steps were employed to simulate the mixing, flame acceleration and deflagration to detonation transition (DDT) triggered by transverse jet obstacles. Results show that multiple transverse jet obstacles ejecting into the chamber can be used to activate DDT. But the occurrence of DDT is tremendously difficult in a supersonic non-uniform mixture so that it required several groups of transverse jets with increasing stagnation pressure. The jets introduce flow turbulence and produce oblique and bow shock waves even in an inhomogeneous supersonic mixture. The DDT is enhanced by multiple explosion points that are generated by the intense shock wave focusing of the leading flame front. It is found that the partial detonation front decouples into shock and flame, which is mainly caused by the fuel deficiency, nevertheless the decoupled shock wave is strong enough to reignite the mixture to detonation conditions. The resulting transverse wave leads to further mixing and burning of the downstream non-equilibrium chemical reaction, resulting in a high combustion temperature and intense flow instabilities. Additionally, the axial and transverse gradients of the supersonic non-uniform mixture induce a highly dynamic behavior with sudden propagation speed increase and detonation front instabilities
Flame-turbulence interactions during flame acceleration using solid and fluid obstacles
No full textA combination of solid and transverse jet obstacles is proposed to trigger flame acceleration and deflagration-to-detonation transition (DDT). A numerical study of this approach is performed by solving the reactive Navier-Stokes equations deploying an adaptive mesh refinement technique. A detailed hydrogen-air reaction mechanism with 12 species and 42 steps is employed. The efficiency and mechanisms of the combined obstacles on the flame acceleration are investigated comprehensively. The effects of multiple jets, jet start time, and jet stagnation pressure on the DDT process are studied. Results show that there is a 22.26% improvement in the DDT run-up time and a 33.36% reduction in the DDT run-up distance for the combined obstacles compared to that having only solid obstacles. The jet acts as an obstruction by producing a suitable blockage ratio and introducing an intense turbulent region due to the Kelvin-Helmholtz instability. This leads to dramatic flame-turbulence interactions, increasing the flame surface area dramatically. The dual jet produces mushroom-like vortices, leading to a significantly stretched flame front and intensive Kelvin-Helmholtz instabilities, and therefore, these features produce a high flame acceleration. As the jet operation time decreases, the jet obstacle almost changes its role from both physical blockage ratio and turbulence and vorticity generator to a physical blockage ratio. There is a moderate jet stagnation pressure that reduces the run-up time to detonation and run-up distance to detonation in the obstacle-laden chamber. While further increasing the jet stagnation pressure, it does not have a positive effect on shortening the detonation transition.</p
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
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