1,721,024 research outputs found
3D Mapping of liquefaction phenomena induced by May 2012 Emilia earthquakes (Po Plain, Northern Italy)
No full textCoseismic effects may have a very short life; most of the sand boils and cracks triggered by the main shocks of
the May 20
th
and 29
th
Emilia earthquakes have disappeared just a few days after, both because of the
atmospheric agents, and due to human intervention. In order to create an accurate database of these small
micro-morphologies, several photogrammetric surveys were carried out using digital reflex cameras. Fixing in
three dimensions the impact that shocks have made on the landscape allows to extract many morphometric
parameters with high precision and, in a relatively simple way. Structure From Motion (SFM) algorithms are well
known computer vision technique for the ability of reconstruct sparse point cloud from overlapping photographs;
when they are combined with fixed calibrated optical and complemented with robust stereo-matching algorithms,
detailed three dimensional models can be built with great resolution and accuracy. In order to obtain high
resolution DEMs several convergent images were taken trying to cover all the angles and the whole area of the
object. The first step called alignment, the reconstruction of the photograph shooting position is done by SFM
that detect some images key points and subsequently correlates the movement of these along the image
sequence. Once the basically geometry of the scene is known, dense stereo matching algorithm processes the
scene trying to correlate every pixel for each photo in order to reconstruct a dense point cloud. Finally the
obtained point cloud is triangulated and a detailed mesh is constructed. In order to build a local reference system
suitable for use in GIS different targets of known size were distributed around every scene and ground control
points were collected. More zenithal pictures were used to orthophotos production. Using this methodology we
were able to develop DEMs with resolutions ranging from one millimeter for the small forms to some centimeter
for the big ones
A geospatial approach for mapping the earthquake-induced liquefaction risk at the european scale
Full text linkThis paper presents a geospatial methodology for zoning the earthquake-induced soil liquefaction risk at a continental scale and set-up in a Geographic Information System (GIS) environment by coupling data-driven and knowledge-driven approaches. It is worth mentioning that liquefaction is a phenomenon of soil instability occurring at a very local spatial scale; thus, the mega-zonation of liquefaction risk at a continental scale is a hard facing challenge. Since the risk from natural disasters is the convolution of hazard, vulnerability, and exposure, the liquefaction risk mapping is based on the combination of geospatial explanatory variables, available at the continental scale, of the previously listed three assumed independent random variables. First, by applying a prediction model calibrated for Europe, the probability of liquefaction is mapped for the whole continent. Then, the Analytical Hierarchy Process (AHP) is adopted to identify areas that have a high risk of liquefaction, taking into account proxy data for exposure. The maps are computed for different levels of severity of ground shaking specified by three return periods (i.e., 475, 975, and 2475 years). A broad variety of stakeholders would benefit from the outcomes of this study, such as civil protection organizations, insurance and re-insurance companies, and infrastructure operators
Monitoring of a slope susceptibility to shallow landslides: preliminary results
No full textLe frane superficiali indotte da piogge intense e concentrate sono annoverabili tra i fenomeni franosi che causano il maggior numero di danni. Al fine di identificare, a scala di versante, i processi idrologici e geotecnici che controllano il loro innesco è stata installata una stazione sperimentale in un’area campione dell’Oltrepo Pavese per il monitoraggio del contenuto in acqua del terreno, della pressione interstiziale negativa, delle precipitazioni, della direzione ed intensità del vento e della radiazione netta. Il lavoro presenta i risultati preliminari ottenuti nel corso dei primi mesi di monitoraggio
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
Differences between mechanical and electrical cone penetration test in the liquefaction hazard assessment and soil profile reconstruction
Full text linkLiquefaction - hazard assessment is often accomplished by means of simplified procedures, which are based on CPT. The CPT liquefaction procedures, generally, require cone penetration test with electrical tip or the measure of u (CPTu); however, in most countries, as Italy, penetrometric tests are carried out with mechanical tip (CPTm). Generally, CPTm leads to an estimate of the Liquefaction Potential lower than that inferred from CPTu. Moreover, CPTm has a reduced resolution in soil profiling. While the cone – shape effects on qc are not very relevant, those on fs can strongly influence the FSL calculation, especially in the case of silty sands. Within this framework, the main aim of this work is to identify the differences in liquefaction - hazard evaluation and soil profile interpretation in pairs of CPTm/CPTu. After that, two methodologies were used to correct CPTm results. At first, it was developed an empirical correlation between the sleeve friction measured with CPTm and that measured with electrical CPT/CPTu. After that, a method developed in literature was applied to the same CPTm/CPTu pairs. The two corrections were compared in order to see which one led to the best results in terms of enhancement of the liquefaction hazard assessment and soil profile reconstruction. Tests have been carried out in the area interested by the 2012 Emilia earthquake (Italy)
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
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