1,720,961 research outputs found
Particles and fibers in fluid flows for environmental applications
No full textThe thesis is divided in two parts showing applications of active and passive models, in which the Lagrangian tracking of rigid fibers and slender swimmers can be employed to access to flow properties, and to study a turbulent puff in order to access information on spreading of virus-containing droplets.
The first part of the thesis addresses the measure of flow properties by means of slender objects, i.e. rigid fibers. Two different strategies have been employed to model the fiber: first an active model, a fully-coupled fiber described in terms of an immersed-boundary method, and, second, a passive model, a one-way coupling where the fiber is described by the slender body theory. After the characterization of the fiber inertia in terms of rotational Stokes Number, the motion of the fiber is investigated for different classes
of closed streamline flows, steady or time dependent, two-dimensional or three dimensional. For sufficiently small Stokes, the fiber turns out to be a proxy of the underlying flow by considering the velocity difference between the fiber end points and the same difference relative to the underlying fluid velocity, both projected along the direction normal to the fiber.
Moreover, by composing an assembly of rigid fiber, the whole flow gradient tensor can be accurately reconstructed by simply tracking the fiber assembly and measuring suitable fiber velocity differences evaluated at the fiber ends.
Furthermore, it has been investigated the possibility to measure two points flow properties by
means of slender swimmers. A swimmer model, describing both pusher and puller swimmers,
has been proposed and validated in the Stokes limit finding excellent agreement. The slender
swimmer model has been exploited in a chaotic flow field up to a flow Reynolds number of
10, a swimming number ranging between zero and one and different swimmer inertia measured
in terms of a suitable definition of the swimmer Stokes number. The following results have
been obtained: (i) pusher and puller reach different swimming velocities for the same, given,
propulsive force, due to a different distribution of the vorticity within the wake. (ii) for a wide
range of flow/swimmer Reynolds numbers, both pusher and puller swimmers are able to sense
hydrodynamic signals with good accuracy.
The second part of the thesis is devoted to understand the role of the turbulence on the fate
of virus-containing droplets expelled during a human cough, modeled as a turbulent puff, under
realistic conditions. To this aim, high resolution DNS have been performed for the fluid flow
and humidity field, complemented by a passive Lagrangian solver for the droplet dynamics
including a dynamical equation for the evolution of the droplet radii modeling the evaporation-condensation process. After having validated the turbulent puff against theoretical predictions,
the results show how a full account of turbulence is crucial to determine the fate of virus-containing droplets. Then, the dependence of the results on the droplets initial size distribution
and different ambient humidity is investigated. As a further step, it is analyzed the dependence
of results on the airborne virus spreading on gender. Finally, the effectiveness of the
barriers as protection devices within indoor environment is investigated.
This study is clearly motivated by the recent pandemic situation due to COVID-19 infection,
although it is valid for all the infections where the main route of transmission is via airborne
virus-containing droplets, by contributing to select optimal strategies of protection and mitigation of the airborne infection transmission, within indoor and outdoor environments
A novel AI-assisted forecasting strategy reveals the energy imbalance sign for the day-ahead electricity market
No full textAn advanced artificial intelligence (AI)-assisted methodology for predicting the sign of energy imbalances within the day-ahead energy market is introduced in this study, with a focus on the integration of renewable energy sources. By leveraging deep learning techniques and Numerical Weather Prediction (NWP) models, a nuanced understanding of energy market dynamics over a comprehensive five-year period is provided by the research. The findings reveal the substantial predictive advantage of the AI model over traditional forecasting methods, with fold-averaged Area Under the Curve (AUC) values of about 0.7 achieved for the two distinct macro-zones N and S. Economically, the model indicates potential for significant market participant gains, with mean efficiencies reaching 16% and 11% for macro-zones N and S, respectively. The implications extend beyond the Italian market, suggesting transformative potentials for European energy markets at large. This work not only fills a critical gap in the literature but also sets a new benchmark for predictive accuracy and economic viability in energy market forecasting
Novel strategies of Ensemble Model Output Statistics (EMOS) for calibrating wind speed/power forecasts
No full textThe issue of the accuracy of wind speed/power forecasts is becoming more and
more important as wind power production continues to increase year after year.
Having accurate forecasts for the energy market clashes with intrinsic
difficulties of wind forecasts due to, e.g., the coarse resolution of Numerical
Weather Prediction models. Here, we propose a novel Ensemble Model Output
Statistics (EMOS) which accounts for nonlinear relationships between
predictands and both predictors and other weather observables used as
conditioning variables. The strategy is computationally cheap and
easy-to-implement with respect to other more complex strategies dealing with
nonlinear regressions. Our novel strategy is assessed in a systematic way to
quantify its added value with respect to ordinary, linear, EMOS strategies.
Wind speed/power forecasts over Italy from the Ensemble Prediction System (EPS)
in use at the European Centre for Medium-Range Weather Forecasts (ECMWF) are
considered for this purpose. The calibrations are based on the use of past wind
speed measurements collected by 69 SYNOP stations over Italy in the years 2018
and 2019. Our results show the key role played by conditioning variables to
disentangle the model error thus allowing a net improvement of the calibration
with respect to ordinary EMOS strategies. Finally, we have quantified the
impact of calibrated wind forecasts on the wind power forecasts finding results
of interest for the renewable energy market
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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