1,720,988 research outputs found
Greenhouse gas reductions and primary energy savings linked to the upgrade of conventional plants by means of hybrid plants
No full textWith the Kyoto agreement, there has been a greater emphasis on lowering energy waste and supporting low-emissions systems such as fuel cells, photovoltaic (PV) systems or solar thermal systems (SEGS). These technologies produce environmental benefits since non-renewable energy can be preserved and environmental pollution can be drastically reduced. In addition to this, the decentralization of the electricity production plants mitigates the grid distribution losses. This paper developes a theoretical analysis focused on the environmental benefits achievable through a shift from the conventional systems, normally operating in hospitals, to different hybrid plants eventually enhanced by absoorption chillers. The model site is a hospital located near Ferrara (Italy). At first, a numerical procedure has been adopted in order to calculate the electrical and thermal requirements associated to the existing plant. Then several hybrid schemes have been investigated and compared: PAFCs (phosporic acid fuel cells), SEGS, PV systems. An energy analysis is developed for each option assuming the conventional systems, operating in the medical center, as the reference. At the same time, an economic study is developed for all the retrofit scenarios in terms of the payback period and the IRR. The results are presented with reference to the primary energy requirements and the pollutant emissions; it is demonstrated that in case the existing conventional systems would be upgraded with these hybrid plants, overall greenhouse emissions could be abated with a significant reduction in fossil primary energy consumptions
Sull’analisi statistica del fattore di attrito
No full textIl fattore di attrito f per il moto nei condotti è valutato statisticamente in funzione delle variabili aleatorie: diametro del condotto, portata defluente, salto di pressione su una lunghezza assegnata. Il suo valore effettivo (medio) è paragonato al valore apparente calcolato a partire dalle quantità medie misurate. Viene fornito un esempio numerico che mostra come la differenza tra le due quantità sia trascurabile nella maggior parte dei casi
Monitoraggio con controllo a microprocessore dell'equipotenzialità delle sale operatorie
No full textViscous spreading of non-Newtonian gravity currents in radial geometry
No full textA gravity current originated by a power-law viscous fluid propagating in axisymmetric geometry on a horizontal rigid plane below a fluid of lesser density is examined. The intruding fluid is considered to have a pure power-law constitutive equation. The set of equations governing the flow is presented, under the assumption of buoyancy-viscous balance and negligible inertial forces. The conditions under which the above assumptions are valid are examined and a self-similar solution in terms of a nonlinear ordinary differential equation is derived for the release of a fixed volume of fluid. The space-time development of the gravity current is discussed for different flow behavior indexes
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
Bingham fluid flow in spatially variable fractures
No full textNon-Newtonian fluid flow in fractured media is of interest to hydrologists, geophysicists, and mining engineers. Since laboratory and field investigations evidence a strong degree of variability in fracture aperture, a large body of literature is specifically concerned with evaluation of an equivalent aperture (or permeability), adopting different constitutive equations and aperture variability models. The equivalent aperture for non-Newtonian fluid flow is defined as the parallel plate aperture which would permit a given volumetric flux under an assigned pressure gradient, thereby generalizing the concept of hydraulic aperture used for Newtonian flow. In this paper, the Bingham model with yield stress t0 has been adopted to describe the fluid rheology; the aperture is taken to vary as a spatially homogeneous and correlated random field with a lognormal aperture density distribution of assigned mean and variance s2. The equivalent fracture aperture is derived for a specific geometry where the flow is perpendicular to the aperture variation. Under ergodicity, results are obtained by discretizing the fracture into elements of equal aperture and assuming that the resistances due to each aperture element are in parallel. The equivalent fracture aperture is greater than the mean, and their ratio is found to depend on aperture variability, represented by log-aperture variance s2, and on a dimensionless parameter w, equal to the wall shear stress in a fracture with aperture equal to divided by the Bingham yield stress. The ratio is weakly dependent on w, and tends to increase as s2 increases. When w tends to infinity, all our expressions reduce to those derived in the past for Newtonian flow and lognormal aperture distribution
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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