1,720,969 research outputs found
On Capillary barrier effects in unsaturated layered soils, with special reference to pyroclastic covers of Pizzo d’Alvano in Campania, Italy
No full textThe present work proposes a study on the presence of capillary barrier effects in a particular soil stratigraphy, characterized by an alternation of layers with contrasting differences in permeability. This is a common situation on the slopes of Pizzo D’Alvano (Campania, Southern Italy), where severe landslides were triggered on may 1998, and in many other geological environments, where geological, sedimentological, geomorphologic and pedological processes might have produced a sequence of soils with different hydraulic conductivity. During prolonged rainfall events, particularly at low rainfall rates, such phenomena can condition infiltration processes and lead to a significant increase in saturation within the least permeable soil layers, due to particular water infiltration patterns. Results of laboratory column infiltration tests and evidence of capillary barrier effects are presented and used in calibration of numerical unsaturated flow models
Analysis of capillary barrier effects in the activation of debris avalanches in pyroclastic cover, Campania (Southern Italy)
No full textOn May 1998 many landslides involving pyroclastic covers lying on the slope of Pizzo
D’Alvano relief hit the towns of Bracigliano, Quindici, San Felice a Cancello, Sarno (Campania, Italy).
They were triggered by a prolonged and continuous rainfall event but certainly not extraordinary in
terms of return time. The aim of the investigations carried out within this work, by means of in situ and
lab testing, and by means of numerical simulations, is to point out some aspects related to triggering
mechanisms of debris flows that appear relevant to the authors. In particular, attention is paid to
retention phenomena of filtering waters due to the build up of capillary barriers in the interface between
fine and coarser pyroclastic layers, causing suction head to drop to a level that triggers a landslide
On capillary barrier effects and debris slide triggering in unsaturated layered covers
No full textThe present work is focused on investigating the potential role of capillary barriers on the stability of layered soil deposits laying upon high permeability steep slopes. In presence of capillary barrier effects, often possible on a soil stratigraphy characterized by contrasting hydraulic properties (pyroclastics deposit over pumices, silt upon fractured bedrock, silt over sand) failure might originate in less permeable layers, where unsaturated conditions might provide a crucial contribution to stability. Basic ideas and considerations have been drawn from a peculiar case study, the catastrophic landslide occurred in Campania, Southern Italy, on May 1998, which is discussed in this paper from a different perspective.
The areal extent of failures’ distribution, their dense concentration at the steeper and higher slopes, the extremely high number of initial failures occurred within a relatively short time span suggest that the intimate cause of the event is related at some extent to the soil state rather than positive pore pressure pulses from water circulation in coarser layers or groundwater rising from bedrock. A widespread loss of soil strength related to saturation can likely explain such phenomena.
Capillary barrier effects favour accumulation and lateral distribution of percolating unsaturated flow and possibly divert flowlines downslope, thus leading to localized increases in water content. Diversion of percolating waters facilitate lateral redistribution of soil moisture along the slope with possible further localized saturation, because more permeable layers may act temporarily as barriers and not as drains, as one could expect. Numerical 2-D infiltration models with parameters calibrated versus laboratory data show a relevant influence of capillary barrier effects on infiltration in layered slopes with vertically stratified variations of hydraulic properties and point out significant localized moisture accumulation with possible consequences on slope stability. Landslide initiation phenomena in layered covers might thus be due to the increase in saturation within the least permeable soil layers due to capillary barrier phenomena
Analisi dell’evoluzione della distribuzione delle precipitazioni nell’area di Taranto
No full textNell’ambito degli studi relativi alle variazioni climatiche recenti nell’area di Taranto sono state analizzate le serie storiche delle precipitazioni giornaliere misurate in due stazioni pluviometriche per le quali era disponibile una lunga serie storica di valori di precipitazione: Castellaneta e Grottaglie. Entrambe le stazioni mostrano un trend generale di decrescita delle precipitazioni, che un’analisi di dettaglio ha consentito di evidenziare è concentrata nei mesi invernali e soprattutto in quelli autunnali quando avviene la ricarica delle falde ed ha riguardato essenzialmente le precipitazioni di media entità con valori di pioggia giornaliera compresi fra 20 e 35 mm/d.
L’analisi dei massimi valori annui delle piogge di durata pari a 1h, 3h, 6h, 12 h, 24 h ha evidenziato che sono diventate più intense le piogge di durata fino a 8 ore, e meno intense quelle di durata maggiore, con un incremento della vulnerabilità idraulica del territorio
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
Data assimilation of forecasted errors in hydrodynamic models using inter-model correlations
No full text10.1002/fld.1533International Journal for Numerical Methods in Fluids566587-605IJNF
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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