1,720,966 research outputs found
Calibrazione dei parametri di contatto e discretizzazione di particelle non sferiche per analisi con il metodo agli elementi discreti
Full text linkIl Metodo degli Elementi Discreti (DEM) consente di rappresentare i materiali granulari a partire dalla descrizione delle particelle che lo compongono, dalla loro forma, dai modelli e parametri al contatto. Al fine di rappresentare elementi granulari appartenenti a ghiaie, ed in particolar modo volendo replicare con buona approssimazione la loro forma, è possibile adottare una discretizzazione dei corpi tramite aggregati rigidi di sfere (clumps). Eseguendo analisi sui materiali naturali in maniera da ricavarne le curve granulometriche, gli angoli di resistenza al taglio e i coefficienti di restituzione elastica, attraverso questo lavoro ci si propone di investigare la calibrazione numerica delle dimensioni e delle forme degli elementi, e dei parametri al contatto dei materiali
Monitoring and Modeling Tidally Induced Pore-Pressure Oscillations in the Soil of St. Mark's Square in Venice, Italy
Full text linkSea level rise and high tide events are threatening many coastal cities, which require adequate and sustainable protection measures. The historic city centre of Venice (Italy) is often flooded during very high tide events, especially the area of St. Mark's Island, which is at the lowest elevation among all the islands forming the city. To design cost-effective protection interventions to safeguard the historical heritage, a deep understanding of flooding mechanisms and the relationship between groundwater pressure and tidal oscillations is necessary. Geotechnical survey and analyses play an important role in this process. This paper presents the results of a recent monitoring campaign carried out in St. Mark's Island. A simplified one-dimensional analytical model was derived for saturated conditions to understand the key parameters that govern tidal induced pressure oscillations in soil (material properties, geometrical features, and wave properties). Additional features, such as partially saturated soil conditions and two-dimensional effects, were investigated numerically. Results showed that significant pressure oscillations occur in the subsoil, which should not be neglected when considering the stability of horizontal architectural structures, such as the historical mosaics and paving. However, seepage flow rate is small, and thus its impact on the drainage system is limited in terms of water discharge
Monitoring of Dry Granular Flows in Unsteady State Down an Inclined Chute
No full textDebris flows are common hazardous events in mountainous areas generally triggered by heavy rainfalls, snow melting or earthquakes. The energy carried by the granular materials that descend steep slopes can put in jeopardy both people and constructions, thus entailing the need to monitor such hazards and to mitigate the risk of these events. Given the natural long runout of these unsteady flow phenomena, it could be interesting to monitor and study their behaviour along transversal cross-sections. To reduce the complexity related to the morphology of the basal surface, the grain size and shape of the flowing material and its water content, this research phase has been carried out with an inclined chute of constant width and with granular materials characterised by high uniformity. A numerical approach based on the Discrete Element Method (DEM) has been considered to have an insight into the experimental observations of the flow characteristics. Clusters of spheres have been used to account for the grains’ shape in the numerical model and the contact parameters have been calibrated against experimental data. Velocity and granular temperature profiles have been considered in order to better understand the behaviour of the flow both along time and space in the monitoring section
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
Analisi numeriche DEM di interazione terreno-geogriglia
Full text linkL’analisi dell’interazione geogriglie-terreno risulta particolarmente importante per ottimizzare i materiali e le geometrie al fine di ottimizzare il rinforzo ed è condotta tipicamente con prove di laboratorio. Dal punto di vista numerico, il metodo degli elementi discreti (DEM) si è dimostrato un valido strumento per analizzare nel dettaglio le specificità dell’interazione geogriglia-terreno sia a livello locale che macroscopico. Nel presente studio è stato utilizzato un modello 3D-DEM per simulare prove di estrazione di geogriglie eseguite in laboratorio (test di pull-out). Le caratteristiche e le proprietà micro-meccaniche degli elementi costituenti la geogriglia sono state calibrate e confrontate con prove eseguite in laboratorio su una geogriglia tessuta in PET. I terreni granulari sono stati simulati nel modello numerico utilizzando sia particelle sferiche di differenti dimensioni, sia gruppi di più sfere sovrapposte (clumps), in grado di simulare più realisticamente la forma irregolare della ghiaia
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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