1,721,115 research outputs found
Evolution récente des vents de surcote sur les cotes de la Méditerranée Centrale et de l'Adriatique.
No full textModeling of core-annular and plug flows of Newtonian/non-Newtonian shear-thinning fluids in pipes and capillary tubes
No full textSolutions for concentric core-annular laminar flows of Newtonian/non-Newtonian shear-thinning fluids in horizontal and inclined pipes are presented. The solution is computed for the general case of a Carreau non-Newtonian fluid proposing an iterative method based on Chebyshev collocation points. The effect of the rheology of the shear-thinning liquid on two-phase flow characteristics is investigated both for gas/liquid and liquid/liquid systems. Concurrent and counter-current flows in horizontal and inclined pipes were studied, while referring to practical two-phase flow aspects, such as the in-situ hold-up, lubrication effects and Ledinegg instability. The main characteristic of such systems is that even though the liquid has a complex rheology (Carreau fluid), the two-phase annular flow can exhibit a Newtonian/Newtonian behavior for a wide range of operational conditions. The identification of those conditions is a key aspect in the modeling activity, as to avoid unphysical predictions by the widely used power-law model. Particular attention is given to the core-annular flow characteristics in capillaries, where we propose also a model for the plug flow regime. Predictions of film thickness and plug propagation velocity are tested by comparison with experimental data, showing promising results and offering new insights on plug flow characteristics in capillaries, in particular for liquid-liquid plug flow. (C) 2018 Elsevier Ltd. All rights reserved
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
Sea Surges in Camargue: Trends over the 20th century.
No full textContinental Shelf Research 27 (2007) 922–934
Sea surges in Camargue: Trends over the 20th century
A. Ullmanna,b,, P.A. Pirazzolic, A. Tomasind,e
aUFR des Sciences Ge´ographiques et de l’Ame´nagement, Universite´ d’Aix-Marseille I, Aix en -Provence, France
bCEREGE—UMR 6635, Aix en Provence, France
cCNRS-Laboratoire de Ge´ogrphie Physique, 1 place Aristide Briand, 92 195-Meudon, France
dCNR-ISMAR, Venezia, Italy
eUniversita` di Venezia, Venezia, Italy
Received 8 November 2005; received in revised form 24 November 2006; accepted 4 December 2006
Available online 25 January 2007
Abstract
The vulnerability to short-term and long-term sea-level rises is particularly high in subsiding deltaic areas, especially in
microtidal seas, when surges (the differences between the observed sea heights and the simultaneous astronomical tide) are
frequent. At the Grau-de-la-Dent tide-gauge in the Camargue (Rhone delta, France), daily sea-level records are available
since 1905. Hourly tide data spanning the period 1979–1995 were obtained through the digitisation of the original paper
records: the local harmonic constants and the surges for the whole 20th century have been computed from these hourly
observations. It appears that the annual maximum observed sea-level height increases by 4 mm/yr at a rate that is two
times faster than the average observed relative sea level. The increasing trend of the annual maximum positive sea surges
(+1.9 mm/yr), which is equal to the average relative sea-level rise, is thus responsible for this difference. The most
important meteorological factor associated with local sea-surge occurrences is wind blowing from 1001 to 1201 sectors,
which tends to push the water toward the coasts. Since 1961, the frequency and the speed of wind from this sector
increased, although with some variability, thus contributing in part to the increase in the frequency and intensity of the
surges. Due to the changing hydrodynamics phenomenon in the Camargue, a positive feedback mechanism between
extreme marine events and shoreline regression is another factor to explain the sea-surge rise over the long term. The
increase in sea-surge frequency and height during the last century is especially of concern in the deltaic area if the nearfuture
global sea-level rise predicted by climate models is also taken into account.
r 2007 Elsevier Ltd. All rights reserved.
Keywords: Sea level; Surge; Tide; Wind; Flooding risk; Camargue; Rhone delta
1. Introduction
Any rise in sea level will have adverse impacts
such as coastal erosion and flooding, depending on
the time scale and the magnitude of the rise and the
human response to it (Paskoff, 1993). A rise in sea
level may be due to several factors acting on various
time scales, i.e., atmospheric storms (Bouligand and
Pirazzoli, 1999; Pirazzoli, 2000; Trigo and Davies,
2002; Pirazzoli and Tomasin, 2002), river flooding
in estuaries (Svensson and Jones, 2002), but also
land sinking or similar non climate-related changes,
linked to sediment compaction, isostasy, coastal
geomorphologic evolutions or urban development.
ARTICLE IN PRESS
www.elsevier.com/locate/csr
0278-4343/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.csr.2006.12.001
Corresponding author. CEREGE, Europoˆ le Me´diterrane´en
de l’Arbois, B.P 80, 13545 Aix-en-Provence, France.
E-mail address: [email protected] (A. Ullmann)
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
Motion of a confined bubble in a shear-thinning liquid
Full text linkThe motion of a gaseous Taylor bubble in a capillary tube is typical of many biological and engineering systems, such as small-scale reactors and microfluidic devices. Although the dynamics of a bubble in a Newtonian liquid has been the subject of several studies since the seminal works of Taylor (J. Fluid Mech., vol. 10, issue 2, 1961, pp. 161-165) and Bretherton (J. Fluid Mech., vol. 10, issue 2, 1961, pp. 166-188), the case where the fluid exhibits a shear-thinning behaviour is much less understood. To fill this gap, we study the dynamics of a bubble that moves in a shear-thinning fluid whose viscosity is described by the Ellis viscosity model. With this aim, we derive a lubrication model in the film region to identify the scaling laws for the bubble speed, the film thickness and the pressure drop as a function of the Ellis number and the degree of shear thinning. Our model generalizes Bretherton's results to shear-thinning fluids by identification of a universal scaling law for the effective viscosity that accounts for the interplay of the zero-shear-rate and shear-thinning effects. The film thickness follows a scaling law with respect to the capillary number based on the proposed effective viscosity. The ratio between the bubble speed and the average velocity of the fluid ahead of the bubble is a function of the effective capillary number only. We show that some portions of the bubble are dominated by the zero-shear-rate effect discussing the extent to which the use of the power-law viscosity model can be legitimized. Finally, we study the location of the recirculating vortices ahead of the bubble
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