1,720,986 research outputs found
Thermal–hydraulic separators unveiled
Full text linkA key issue in the design of heating/cooling networks consists in attaining the hydraulic independence of the connected circuits while simultaneously providing the required flow rate of thermal fluid at the design temperature under different operation loads. In this respect, thermal- hydraulic separators offer a valid alternative over other devices used for the same service (as, e.g., heat exchangers, accumulation tanks or double-tee junctions), providing the opportunity to integrate the functions of de-gassing and of removal of solid debris in a single piece of equipment.The present numerical investigation improves the characterization and modelling of these devices. The major outcome of the proposed research is the improvement of the base model widely-used in the design of thermal-hydraulic networks encompassing thermal-hydraulic sep-arators. The proposed model accounts for the turbulent mixing within the device. Furthermore, we propose an original network representation of thermal-hydraulic separators, which supports the physical intuition about their internal flow patterns and can be integrated in thermal network solvers used for plant design and optimization. To the authors' best knowledge, this is the first numerical investigation accounting for the impact of the internal mesh strainer on the behaviour of the device
Assessment of infection probability indices for airborne diseases in confined spaces: combination of CFD and analytical modelling
Full text linkThe paper presents a framework for probabilistic assessment of likelihood of infection from airborne diseases in confined spaces which are continuously occupied for relatively long periods (e.g., school classrooms). The proposed approach is based on a combination of computational fluid dynamics (CFD) pre-calculations and analytical post-processing, to define relevant indices of infection probability. The practical applicability of the method is demonstrated through a case study, where different ventilation scenarios are considered for a school classroom. Corresponding infection probability indices are determined globally for the group of occupants. Furthermore, since the method does not rely on the well-mixing assumption, local probability indices are determined for each occupied location. The obtained results confirm the intuition that an increase of ventilation and/or air filtration reduces the overall likelihood of infection, though the observed positive effect is not uniform within the space. The presented methodology can also be considered as complementary to simpler approaches
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
An enquiry into the causes of an explosion accident occurred in a biogas plant
Full text linkBiogas is a versatile carrier of renewable energy produced by means of the digestion of crops, residues, or other wastes, and storage of the gas in dedicated plants. Safety regulations impose operational and technical restrictions to areas interested by the presence of the biogas in order to limit the explosion risk. Conversely, other areas of the plant are not subject to strict safety requirements. Nevertheless, explosions can be triggered in these areas as well, as the present investigation confirms. In the specific case, the production of biogas by anaerobic digestion in a storm‐water tank and its infiltration and accumulation into a technical building through a pipe connection caused the explosion of the building itself. The authors describe the procedures adopted for the enquiry and suggest possible improvements to the safety regulations for biogas plants
Design and Assessment of an Innovative Thawing Equipment for the Professional Food Service
No full textThe need for faster, safer, and environmentally compatible thawing methods is perceived in different branches of food industry, as, e.g., in the fast-food sector. We investigate a prototype of jet-impingement, batch-process thawing machine, exploiting high-speed impact of heated atmospheric air onto food items. The results of combined experimental and numerical study show the promising potential of this technology beyond the expected increased thawing rate, especially when the proposed two-side arrangement of the jets is adopted. A series of thawing indicators are calculated and used to account for the thawing uniformity and the risk of bacterial proliferation. A computationally efficient two-stage model of the considered thawing process is conceived, which can be used for design and optimization
Finite Volume Compact Schemes on Staggered Grids
No full textCompact finite-difference schemes have been recently used in several Direct Numerical Simulations of turbulent
flows, since they can achieve high-order accuracy and high resolution without exceedingly increasing the size of the
computational stencil. The development of compact finite-volume schemes is more involved, due to the appearance of
surface and volume integrals. While Pereira et al. [J. Comput. Phys. 167 (2001)] and Smirnov et al. [AIAA Paper, 2546,
2001] focused on collocated grids, in this paper we use the staggered grid arrangement. Compact schemes can be tuned
to achieve very high resolution for a given formal order of accuracy. We develop and test high-resolution schemes by
following a procedure proposed by Lele [J. Comput. Phys. 103 (1992)] which, to the best of our knowledge, has not yet
been applied to compact finite-volume methods on staggered grids. Results from several one- and two-dimensional
simulations for the scalar transport and Navier–Stokes equations are presented, showing that the proposed method is
capable to accurately reproduce complex steady and unsteady flows
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
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