1,720,970 research outputs found
Heliostat aiming point optimization for external tower receiver
Full text linkReduction of peak fluxes on solar receiver is an important research topic because peak minimization can lead to lower receiver temperatures with advantages in terms of thermal efficiency and mechanical stresses. This work proposes different approaches for the minimization of the heat flux on external tower receiver with surround field. The mathematical formulation is implemented in Matlab, while Delsol is used for the heliostat field modeling. Since the number of variables is very high, branching the original optimization problem in a set of sub-problems is a beneficial technique. Four approaches, based on this concept, are here proposed: they differ for the number of field sectors considered in the optimization process and on the heliostat projection modeling. The best approach, which considers the overlapping effect between adjacent sectors, can reduce the peak flux down to 770 kW/m2in 120 s of computational time. This value is about 15% lower than reference aiming strategies available in literature. The optimized flux is almost flat in the central part of the receiver while it has significant gradient at the lower and upper border. Finally, a sensitivity analysis shows that the proposed approaches work well at any given solar position and with different heliostat assumptions (i.e. curvature and errors)
A synergic integration of desalination and solar energy systems in stand-alone microgrids
Full text linkIn this study, we investigated the possible synergies between desalination technologies and solar energy in a remote energy system modelled as a small-size island with the goal to increase system sustainability. The solar systems implemented are photovoltaic panels (PV) and a Concentrating Solar Power system coupled with an Organic Rankine Cycle (CSP-ORC). For the desalination both Reverse Osmosis (RO) and Multi-Effect Distillation (MED) are considered. We found that the simple installation of PV is a valuable option to decrease electricity costs in remote context presently based on Diesel fuel generators but it struggles with achieving high penetration of Renewable Energy Sources (RES) (> 40%) due to the intermittent nature of solar energy and the consequent need for large batteries. The installation of a CSP-ORC allows further reducing the fossil fuel consumption thanks to the use of thermal energy storage and the effective integration with a MED facility. The results show that both solar energy technologies allow a considerable cost saving compared with the traditional solutions based on diesel generation. The most promising solution is a hybrid integration of all four above mentioned technologies, enabling RES penetration over 75% with > 10% of cost savings
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
Danno complesso alla spalla determinato da infortuni ed errore professionale
No full textLa valutazione delle varie condotte teraputiche che si sono succedute nel caso in esame mettono in risalto i risultati positivi e non nel trattamento
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