1,720,976 research outputs found
The effectiveness of channel control works: how multi-temporal sediment dynamics analysis could support watershed management
Full text linkSustainable and effective planning of the channel control works has become an essential tool to manage the hydro-geomorphic risk in mountain basins. However, quite often, there is a lack of information on the efficiency and effectiveness of existing structures and a priori in-depth studies analysing the interaction between sediment morphology dynamics and the possible new channel control works. Nowadays, thanks to multi-temporal (4D) High-Resolution Topography (HRT) surveys, it is possible to derive accurate 4D Digital Terrain Models (DTMs), and reliable DTMs of Difference (DoDs) that greatly simplify the analysis of geomorphological changes and enables the development of innovative approaches to monitor sediment morphology dynamics and the interaction with channel control works.
This research aims at introducing and applying a methodological approach. It is based on integrating sediment morphology dynamics data over large time spans in various mountain catchments with an updated, quick, and user-friendly efficiency index for the existing channel control works.
The results show how the information provided by sediment morphology dynamics coupled with an updated state of efficiency of existing interventions, could help to support the development of watershed management strategies, assess afterwards the effectiveness of existing structures, and foster a more complete decision-making chain. In the basins analysed, several real examples of the proposed methodology emphasized the usefulness of providing more complete information on the ongoing phenomena, than in the past, by exploiting field surveys and remote sensing data. The realized database could provide numerical data for prediction models of the life-cycle of channel control works or be a starting point for further analysis. Furthermore, the proposed workflow could provide increasingly up-to-date information. This would allow the constant identification of the areas most prone to hazards, support effective risk management decisions, direct maintenance works and find more appropriate solutions
Recent glaciers variations in Alta Valtellina (Ortles-Cevedale Group, Italian Alps): quantitative analysis of a strong glacial decline during the last 60 years
No full textAlpine glaciers are very sensitive to climate variations that modify their shape and size in response to changes in their mass balance. In the framework of detailed investigations concerning global change-induced glacier variations and loss of water resources stored in the Italian glaciers, this work presents an analysis of recent changes (1954-2012) in the Alta Valtellina’s glaciers (Ortles-Cevedale Group). The analysis was based on a multi-temporal dataset of aerial photographs and historical maps, which have been organized and processed in a multi-temporal glaciological database using Geographic Information Systems (GIS).
This work provides quantitative evidence of accelerated glacial decline, in particular since the end of the 20th century. Our results highlight an areal reduction of about 45% in the last 60 years, with a strong increase in the areal reduction rate from -0,51% y-1 during 1954-1982 to -1,26% y-1 during 1982-2012. Applying empirical formulas of volume-area scaling, we estimate a volume loss of about 45%, corresponding to about 700 million m3, for the period 1954-2012. More than 400 million m3 have been lost in the period from 1982 to 2006. Geodetic mass balance calculations for the 1982-2006 time interval indicate a strongly negative annual balance of about 0,55 m w.e. yr-1, and also suggest that volume loss estimates require a correction factor of 1.3.
Results underline the strong imbalance of glaciers in the study area, and highlight the rapid increase in their reduction rate during the last decades, which is leading to impressive change in glacier shape and dimensions
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
Automatic measurement of bankfull widths from high resolution LiDAR DTMs: a new tool to analyze the link between hydraulic and morphological variables
No full textThe study of the morphological characteristics of rivers and of their degree morphological alterations is a basis
for a proper management of mountain watershed, and the availability of detailed topographic data is a key tool.
Channel geometry and stream flow are interrelated and mutually interact with each other to create the morphology
of a river system, and the dimensions of the bankfull channel. However, determining bankfull is not often a simple
exercise particularly where the channel or watershed have been modified or the channel is unstable. The evaluation
of channel geometry variability determined by hydrodynamic and geomorphological processes is usually reached
through field surveys, or through visual interpretations of digital orthophotos. However these two approaches are
challenged respectively by the inaccessibility of the areas under analysis, and by time and financial constraints, and
by an unsufficient accuracy. It is therefore strategic to adopt new and more accurate methods to estimate channel
geometries, based on the availability of high-resolution Digital Terrain Models (DTMs), such as the one derived
from airborne laser scanner (LiDAR). In mountain areas many studies have explored the potential of LiDAR DTMs
for the proper characterization of the network and the objective of this study is to highlight their potential in the
automatic determination of values representative of bankfull widths.
The analysis is based on a topographic index (Elevation Percentile - EP) used to measure the variability of the
elevation: channelized areas have EP values greater than convex areas. Values of EP are read along cross sections
perpendicular to the thalweg, and by applying a statistical threshold to the EP it is possible to obtain the potential
channel width at each point of the network. The geometries derived from this map are approximated due to the
resolution of the DTM, but they show a good agreement with those detected in the field, with low values of RMSE,
and the range of the estimated values is compatible with the surveyed ones. Relationships between bankfull channel
dimensions (field-measured and automatically extracted) and their associated drainage areas are established and
compared for some colluvial and alluvial channels, underlining how the high number of data obtained automatically
from the DTM allows to have a support tool to analyze in detail the geometry of the channels, without the usual
cost and time constraints associated with traditional field measurement
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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