1,721,020 research outputs found
Adaptive covolume technique for 2-D incompressible Navier-Stokes Solutions on unstructured grids
No full textThree-Dimensional analysis of flow forces on directional control valves
No full textThis paper deals with a sufficiently complete analysis of flow forces acting on spools of hydraulic directional control valves. The analysis performed, using the very reliable and commercially widespread "Fluent" code, aims to describe global parameters in order to evaluate such forces with a reasonable accuracy and without performing expensive three-dimensional calculations. To this aim, different fluid dynamics analyses have been carried out inside the valve, starting from simple axis-symmefric models, up to full three-dimensional simulations. A comparison of the 2D and 3D results is then presented
A review analysis of unsteady forces in hydraulic valves
No full textIn the fluid power applications where the typical operating conditions are dynamic the knowledge of the unsteady flow forces that act on the spools of the hydraulic valves represents an important issue to be addressed in order to make a correct design of the valve geometry and its driving system. This paper deals with a rigorous unsteady numerical study of the fluid dynamic behavior of a hydraulic directional control valve. A theoretical approach based upon the application of the momentum equation in the transient fluid dynamic conditions is presented, while a successive numerical analysis is performed by using the commercial FluentTM code that provided, in the past, a correct evaluation of the stationary flow forces.7 Unsteady simulations have been carried out considering three different conditions: constant pressure boundary conditions during the spool movement, inlet pressure ripple at a constant spool position, damped pressure oscillations during the spool opening phase. The main objective is to estimate the critical magnitude orders of the pressure ripple frequency and of the axial spool velocity above which the pseudo-steadiness assumption fails; in order to reach this aim, in some cases, the effects of the fluid dynamic phenomena connected with the unsteady flow conditions have been amplified
La sindrome compartimentale addominale. Complicanza della chirurgia dei vasi addominali e non solo
No full textExperimental and numerical analysis of heat transfer in the cavities of hollow blocks
No full textGiven the importance of the assessment of the insulation performance of the building envelope in the context of energy certification of buildings, a detailed analysis of the reliability of the methods of evaluation of heat transfer in the air cavities of hollow blocks has been carried out.
An experimental study was conducted in the laboratory. Heat transfer measurements on specimens with parallelepiped cavities were done, through a guarded hot plate device according to UNI EN 12664. A numerical analysis of the heat transfer in the specimens through the software ANSYS FLUENT was carried out.
The analysis of the numerical and experimental results when compared with the predictions obtained from simplified models of technical standards, have called attention to the order of magnitude of the calculation accuracy obtainable with such procedures. For some geometric configurations and boundary conditions, the application of the standards can lead to large errors of evaluation of the thermal resistance of the cavity
Esiste ancora un ruolo per la simpaticectomia lombare tra le opzioni terapeutiche nelle arteriopatie ostruttive?
No full text
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
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