1,721,253 research outputs found
Phase-averaged characterization of turbulent isothermal free swirling jet after vortex breakdown
Full text linkThis work mainly focused on the near-exit region of a round isothermal free swirling jet to characterize the effect of
swirl on the flow field and to identify large coherent structures. 3C-2D PIV was employed to capture the
instantaneous flow field close to the nozzle exit for non-swirling (S=0) and a high swirling jets (S=1.26) both with a
Reynolds number of 21800. At swirl level of 1.26 the pressure fluctuations measured by a capacitive microphone
indicate the existence of periodic instability, the so called precessing vortex core (PVC). A three-component proper
orthogonal decomposition (POD) applied to the instantaneous velocity fields allow to identify the dominant flow
structure associated to the PVC. The time coefficients of the two first most energetic POD modes were used to
reconstruct the phase of the oscillatory motion in the swirling flow. The phase information was then used to
conditionally average the instantaneous velocity field s, this allowed the 3D structure of the PVC to be reconstructed.
The instantaneous minima of negative swirling strength values calculated from the instantaneous velocity field
revealed the presence of two helical structures located in the inner and outer shear layers. By phase averaging the
instantaneous swirling strength maps, the 3D helical vortex structure was reconstructed . The two co-winding
counter-rotating helical structure fade out at an axial location of approximately z/ D = 1.5. The findings evidence
that the combined application of PIV, POD and frequency analysis using capacitive microphone can provide
detailed observations of coherent fluctuations ind uced by vortex precession
AN EXPERIMENTAL INVESTIGATION ON ISOTHERMAL FREE SWIRLING JET
Full text linkThis paper reports an experimental investigation on the dynamics of turbulent unconfined swirling flows. Isothermal free swirling jets with five different swirl
numbers (S) and fixed Reynolds number (Re = 21800) are investigated to analyze the effect of swirl intensity on the recirculation, vortex breakdown and the occurrence of the precession vortex core (PVC) by means of 3C-2D Stereoscopic Particle image velocimetry (PIV). The contours and radial profiles of mean axial velocity confirmed the central recirculation zone (CRZ) for high swirl number. The importance of central recirculation zone is to ensure a good mixing of air/ fuel and combustion products and to generate a low velocity region for flame stabilization. Results shows that swirl intensity increases the backflow rate in the recirculation zone and jet spreads almost linearly with a higher spread rate as compared to non swirling flow. The frequency characteristics have been measured with a capacitive microphone. The frequency spectrum indicates the presence of periodic oscillation related to the
existence of PVC. The Strouhal number associated with the frequency of the PVC vary almost linearly with swirl intensity
Comparative Analysis of Prior Knowledge-Based Machine Learning Metamodels for Modeling Hybrid Copper–Graphene On-Chip Interconnects
Full text linkIn this article, machine learning (ML) metamodels have been developed in order to predict the per-unit-length parameters of hybrid copper–graphene on-chip interconnects based on their structural geometry and layout. ML metamodels within the context of this article include artificial neural networks, support vector machines (SVMs), and least-square SVMs. The salient feature of all these ML metamodels is that they exploit the prior knowledge of the p.u.l. parameters of the interconnects obtained from cheap empirical models to reduce the number of expensive full-wave electromagnetic (EM) simulations required to extract the training data. Thus, the proposed ML metamodels are referred to as prior knowledge-based machine learning (PKBML) metamodels. The PKBML metamodels offer the same accuracy as conventional ML metamodels trained exclusively by full-wave EM solver data, but at the expense of far smaller training time costs. In this article, detailed comparative analysis of the proposed PKBML metamodels have been performed using multiple numerical examples
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
sj-docx-1-pie-10.1177_09544089231172015 - Supplemental material for Performance of single slope solar still with various operation parameters—An experimental, statistical, and CFD simulation approach toward optimality
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089231172015 for Performance of single slope solar still with various operation parameters—An experimental, statistical, and CFD simulation approach toward optimality by Rakesh Prasad, Yashvir Singh, Anuj Kumar Sharma, Rohit Sahu, Vijay Kumar Dwivedi and Sanjeev Kumar in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
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