1,720,969 research outputs found
Channel adjustments, bedload transport and sediment sources in a gravel-bed river, Brenta River, Italy
No full textThis paper deals with the Brenta River (the Alps, Italy), a gravel-bed river strongly affected
by human impact. The aims of this work are (a) to reconstruct the channel adjustments that
have occurred during the last decades and (b) to analyse the present condition of the river in
terms of bedload transport and sediment sources. The study reach, which is 23 km long, was
investigated using historical maps, aerial photographs, 12 monumented cross-sections, laser
altimetry data and field survey. Bedload transport rates were estimated by a morphological
approach, which allows the construction of a sediment budget.
Dramatic channel adjustments have occurred in response to an alteration of sediment
fluxes caused by different human interventions (gravel mining, dams, torrent-control works).
Major channel adjustments, specifically incision (up to 8–9 m) and narrowing, took place
between the 1950s and the 1980s. On the other hand, widening has become the most important
process, and incision has continued only in the upper part of the study reach in more
recent times (about the last 20–25 years).
The estimate of bedload transport rates for the period 1984–1997 was carried out starting
from the erosion and deposition volumes of the single sub-reaches. Such an estimate has
shown that (a) a high spatial variability of gravel transport rates exists (from 0 up to 73 200–
85 400 m3/year) and (b) most of the bedload is supplied by local sources. Bank erosion is the
main source of sediments for bedload transport and its contribution can be estimated as
from 9 up to 20 times higher than the upstream contribution. Finally, from a practical point
of view, results from this study should be taken into account in addressing maintenance,
sediment management and restoration along a dynamic and unstable river such as the Brenta
Variazioni morfologiche degli alvei dei principali corsi d'acqua veneto-friulani negli ultimi 200 anni
No full textThe streams of the Veneto and Friuli Venezia Giulia Regions, as many other Italian streams, have undergone remarkable channel adjustments
in the last decades, which have been induced by a range of human interventions. The paper, which reports the state of the art
about five streams (Brenta River, Piave River, Cellina Torrent, Tagliamento River and Torre Torrent), aims to compare the evolutionary
trends of such streams and the factors that have driven to channel changes in the medium and short periods (last 200 years). The
selected streams are relatively large (their drainage basins range between 446 km2 and 3899 km2) and have very wide gravel channels,
often with a braided morphology, in the study reaches. Planform changes, in particular channel width variations, have been analysed
using maps and aerial photographs (9 to 12 different maps/photos were available for each stream). Bed-level changes have been investigated
through cross-section comparisons and field surveys.
The river channels have shown very similar evolutionary trends and magnitude of adjustments. Channel changes were not notable over
the 19th century, whereas the channels have been in an unstable condition in the following period. Narrowing and incision have been
the dominant processes during the 20th century, up to the 1980s-1990s. Channel width reduction has been of 50-70 %, referring to the
width in the first half of the 19th century, and bed-level lowering of 2-3 m on average, but locally up to 8-9 m. A different evolutionary
trend, except for the Torre Torrent, has occurred in the last 15-20 years, since channel widening and aggradation have been the most
common processes. The magnitude of changes during the last phase has been generally much smaller in comparison with those of the
previous phases of adjustment.
The gravel mining and channelization works have been the main causes of channel changes, in particular as for the main phase of adjustment
that took place from the 1950s to the 1980s/1990s. The dams (except for the Cellina Torrent), torrent control works, and reforestation
have probably had a smaller effect on channel dynamics than mining and channelization. As pointed out in previous studies, it is
confirmed that human interventions have dramatically altered the sediment regime, whereas a significant change of channel-forming
discharges has been documented in just one case (Cellina)
The Late Quaternary evolution of the Friuli upper plain (NE Italy)
No full textThe central Friuli upper plain and the Tagliamento Moraine Amphitheatre (NE Italy) provide good evidence of how the joint analysis of field survey data and surface digital representations (DEM derived maps) can enable more careful geological mapping and a more accurate analysis of landforms and the related forming processes. During the Late Pleistocene and the Holocene, climate fluctuations, active tectonics, and erosional and depositional processes repeatedly affected the study area, leading to a complex evolution in the landscape. The step-by-step reconstruction introduced here is based on recent field data supported by microrelief, shaded relief and 3D map analyses (DEMs). In addition, the advantages of surface digital representations in understanding the evolutions of the study area are considered and discussed in terms of methodology
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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