1,720,970 research outputs found
Modeling and optimization for arrays of water turbine OWC devices
Full text linkThe large-scale implementation of wave energy conversion requires the installation of parks of devices. We study the problem of optimizing park layout and control for wave energy converters of the oscillating water column type. As a test case, we consider a device with a Wells turbine working in water. First, a novel model based on a nonlinear ordinary differential equation is derived to describe the behavior of the water column and used to estimate the power matrix. Then, its linearization is derived in order to enable the fast simulation of large parks of devices. The choice of the hydrodynamic model allows obtaining the gradient of the power with respect to the positions through an adjoint approach, making it especially convenient for optimization. We consider in particular the case of interaction with the piles of a floating wind energy plant. The results from the developed computational framework allow us to draw interesting conclusions about park layout design. In particular, we observe that mutual interaction effects can be significant even in parks made up of devices of small size, and that wave reflection from the piles of an offshore structure can improve energy production
Innovative numerical modeling to investigate local scouring problems induced by fluvial structures
No full textThe local scouring problems induced by fluvial structures have been traditionally investigated by means of scaled physical models that allow to compare on a quality level different design solutions and to search for the better configuration from the scouring point of view. In the frame of the Italian Electric System Research Projects a work devoted to develop innovative numerical models, based both on a classic CFD and on a new SPH approaches, has been carried out with the goal of improving the accuracy of the results and to support very detailed analyses. The CFD model is based on fully 3D finite volume hydrodynamic module, accounting for the turbulence effects, coupled with a solid transport module using a moving bed technique, while the innovative SPH model is based on a meshless smoothed particle hydrodynamics for describing the coupled dynamics of two different materials (the water and the sediment) and their interactions with the solid structures. The paper shows the application of the two models to simulate the local scouring effects induced by a barrage, comparing the accuracy of the results with experimental measurements and discussing advantages and limits of each model. Therefore, the innovative numerical models can be applied successfully to investigate local scouring problems when fixed structures, as barrages, bridge piles, spur dykes etc., are involved and they can be used in conjunction with the physical models to investigate safety aspect and to support optimization design of fluvial structures
A closed-form solution for the deposition of atmospheric particulate matter on electrical insulators
No full textThe present study provides a simplified closed-form solution for the deposition flux of atmospheric Particulate Matter on electrical insulators. Due to the lack of experimental data on deposition over this type of solid bodies, the mathematical model is closed by means of a 4D regression procedure on obstacle-scale numerical data. This dataset is obtained with the Lagrangian Stochastic Model SPRAY-WEB (Università del Piemonte Orientale et al., 2021). The code was already validated on Particulate Matter dispersion and deposition on solid obstacles (Amicarelli et al. in Environ Fluid Mech 21(2): 433–463, 2021) and is here applied to a XP-70 porcelain-disk electrical insulator. A published tutorial is associated with this numerical dataset (SPRAY-WEB, 2021). The verification metrics on the performance of the closed-form solution show that the errors lie below the guideline thresholds for air-quality numerical simulations (Chang and Hanna in Meteorol Atmos Phys 87:167–196, 2004) and are limited by a Maximum Gross Error of ca.24% for an external verification. Although they cannot be used to close any mathematical model or to represent any specific event, the long-term averaged deposition fluxes of Zhang et al. (IEEE Trans Dielectr Electr Insulat 21(4):1901–1909, 2014. 10.1109/TDEI.2014.004343) are associated with the same insulator used for this study. With respect to the full-scale experiment mentioned above, the present solution provides an overestimation of 13%. The closed-form solution can be used for instantaneous preliminary estimates or be integrated within air-quality numerical codes for fast assessments of contamination maps for electrical insulators. Such applications aim to quantify the insulator functional damage (i.e., flashovers, short-circuits). The closed-form solution can be also generalized any time new data are available
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
Experimental and numerical investigation on the impulsive dynamics of underwater non-cohesive sediment
No full textThis paper shows the recent results obtained in the field of the numerical and
experimental investigation on the dynamics of an underwater non-cohesive sediment
deposit subjected to an impulsive forcing. The aim of this work is to provide the
basis for the development of an innovative technique that could be applied to
increase the effectiveness of sediment removal at the bottom of an artificial reservoir
through the combined use of submerged explosions and flushing maneuvers.
The first part of the paper deals with the early Smoothed Particle Hydrodynamics
(SPH) 2D simulations of a gas explosion and interaction with heterogeneous media.
Subsequently are illustrated the experimental tests concerning the injection of a cold
CO2 jet from the bottom of a 2D laboratory tank containing water and a sand bed at
initial rest condition: these experiments were carried out to provide a first insight in
the physics of the water-sediment impulsive dynamics including some similarities
with the underwater explosion inside a non-cohesive sediment layer at rest.
Finally the experimental tests were simulated with the SPH method by introducing
some severe approximations in order to handle heterogeneous materials. Both
initial rest condition and flushing maneuver were investigated.
Even if some improvements of the model are required, the results show good
qualitative agreement with the experimental frames; the SPH model can therefore
lead to a first evaluation of the scouring effect when the gas injection and flushing
maneuvers are combined
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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