1,720,956 research outputs found
Parametric reduced order model built from RBF-FD meshless simulations of flow and temperature fields in a 3D pipe with wavy surfaces
No full textThe building of a Proper Orthogonal Decomposition based Reduced Order Model (ROM) representation from Radial Basis Function-generated Finite Differences (RBF-FD) meshless simulations is proposed, thus introducing a novel and original approach to the analysis of parametric problems. The RBF-FD meshless method is most suitable when solving thermofluid dynamic problems on parametric domains, because it can handle complex geometries and large deformations without the need for mesh, grid, or tessellation generation and refinement. A simple distribution of nodes over the domain is only needed, and the convergence rate of RBF-FD methods can be easily increased. Nevertheless, a reliable exploration of the parameter space still requires many simulations to capture the behaviour of the analysed system. So, reduced order modelling methods can be used to significantly speed up the analysis, aiming to accurately describe the physical process with a relatively small number of degrees of freedom. In particular, we want to compare the capability of a low-fidelity approximation of the problem and a ROM built from a few high-fidelity simulations to represent the parametric solution. The intent is to understand how to exploit the two models to achieve the best multi-fidelity ROM representation of the parametric problem. The approach is applied to the parametric analysis of flow and temperature fields in a 3D pipe with wavy surfaces, considering geometric and physical parameters
Integration of multi-fidelity methods in parametrized non-intrusive reduced order models for industrial applications
Full text linkExploring the behavior of complex industrial problems might become burdensome, especially in high-dimensional design spaces. Reduced Order Models (ROMs) aim to minimize the computational effort needed to study different design choices by exploiting already available data. In this work, we propose a methodology where the full-order solution is replaced with a Proper Orthogonal Decomposition based ROM, enhanced by a multi-fidelity surrogate model. Multi-fidelity approaches allow to exploit heterogeneous information sources, and consequently reduce the cost of creating the training data needed to build the ROM. To explore the multi-fidelity ROM capabilities, we present and discuss results and challenges for an automotive aerodynamic application, based on a geometric morphing of the DrivAer test case with multi-fidelity fluid-dynamics simulations
A multi-fidelity reduced-order model to quantify aerodynamic forces on a vertical-axis wind turbine with uncertain rotational speed
No full textWind turbines experience various uncertainties that can impact both design and control. In particular, rotational velocity is a crucial parameter, often controlled to ensure a stable and optimal power output or to avoid turbine overspeeding. This work investigates uncertainty quantification (UQ) for a vertical-axis wind turbine (VAWT), with a focus on the Darrieus VAWT type, using a multi-fidelity (MF) non-intrusive reduced order model (ROM), parameterized on the tip-speed ratio (TSR). A 2D computational fluid dynamic (CFD) model gives the high-fidelity (HF) representation of a three-bladed Darrieus VAWT with NACA0015 airfoils. A similar model with a coarser computational mesh represents the low-fidelity (LF) one. Both allow us to study the aerodynamic forces acting on the blades at different azimuthal angles for a wide range of TSRs. However, multiple evaluations of the HF model can become excessively expensive due to high computational costs, making demanding operations such as UQ not always a feasible choice. ROMs, on the other hand, can compute HF approximations in almost real-time. However, ROMs can be burdensome due to their high off-line computational costs relative to the training phase. Multi-fidelity methods extended to ROMs aim to reduce the amount of HF data required, leveraging inexpensive LF information. The present study compares the effectiveness of a MF ROM to more classical UQ approaches, such as Polynomial Chaos Expansion (PCE) on the HF solutions, and whether it is advantageous to equivalent single-fidelity ROMs. In particular, the focus is on the effect of rotational speed uncertainty on the aerodynamic forces acting on the blades, which are pivotal for turbine performances. Moreover, evaluating a ROM multiple times enables slow-convergence methods, such as Monte Carlo, with minimal effort. The MF ROM showed good UQ performance when compared to an equivalent single-fidelity ROM, especially for the mean estimates, closing the gap with a 4th degree PCE in the proposed use-case
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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