1,720,963 research outputs found
Probability distributions of daily rainfall extremes in Lazio and Sicily, Italy, and design rainfall inferences
Get PDFStudy region: We investigate samples from two Italian regions, i.e. Lazio and Sicily, located in central and south Italy, respectively, and characterized by two diverse climates. Study focus: In engineering practice, the study of maxima daily rainfall values is commonly dealt with light-tailed probability distribution functions, such as the Gumbel. The choice of a distribution rather than another may cause estimation errors of rainfall values associated to specific return periods. Recently, several studies demonstrate that heavy-tailed distributions are preferable for extreme events modelling. Here, we opt for six theoretical probability distribution functions and evaluate their performance in fitting extreme precipitation samples. We select the samples with two common methods, i.e. the Peak-Over-Threshold and the Annual Maxima. We assess the best fitting distribution to the empirical samples of extreme values through the Ratio Mean Square Error Method and the Kolmogorov-Smirnov test. New hydrological insights for the region: The assessment of the best fitting distribution to daily rainfall of the two different areas investigated here leads to interesting remarks. Despite the diversity of their climate, results suggest that heavy-tailed distributions describe more accurately empirical data rather than light-tailed ones. Therefore, extreme events may have been largely underestimated in the past in both areas. The proposed investigation can prompt the choice of the best fitting probability distribution to evaluate the design hydrological quantities supporting common engineering practice
Il rischio idraulico nei torrenti etnei: Il torrente Lavinaio- Platani
No full textIl bacino imbrifero del torrente Lavinaio-Platani, interessa il versante SE dell’Etna con un’estensione di circa 65 Km2 e con quote oltre i 2000 m.s.m. Si tratta di un’ampia area molto ripida che include l’antica caldera del centro vulcanico primordiale di Monte Po, quasi del tutto smantellato a sud dall’attività erosiva delle acque meteoriche che confluiscono prevalentemente al torrente stesso. Questo torrente, oggi, costituisce il principale solco torrentizio del versante SE dell’Etna, è lungo circa 18 km ed attraversa i Comuni di Acireale, Aci Catena, Aci S.Antonio, Viagrande, Trecastagni, Pedara, Nicolosi e Zafferana Etnea. Il vasto bacino imbrifero del torrente Lavinaio-Platani non è proporzionale alla sezione idraulica dell’alveo torrentizio
nei pressi di Aci Platani a monte della via S. Piero Patti, nell’ultimo tratto a valle di via Anzalone e soprattutto poco prima della foce. Le ragioni di questa discrasia sono da ricercare nelle eruzioni etnee preistoriche e storiche che hanno deviato in più riprese il corso delle acque. Esso risulta tombato nel tratto in cui attraversa il centro abitato e in passato, a causa di eventi meteorici eccezionali, è esondato provocando numerosi danni, oltre a perdita di vite umane; tragiche alluvioni si sono verificate sia in tempi passati, rimasta alla storia è l’alluvione del 1761, ma soprattutto in tempi recenti e recentissimi: settembre 2013, settembre 2005, ottobre 2006, marzo 1995
Kinetic energy and rainfall intensity relationships: A review
No full textAlthough it is widely recognized how the knowledge of the kinetic energy (KE) of precipitation plays a fundamental role in soil erosion studies, its direct evaluation is not widespread. As a matter of facts, direct measurements of the kinetic energy of precipitation require the use of sophisticated and expensive tools. Commonly, the following approach is used to deal with this issue, that is the indirect estimation of the kinetic energy from other most widespread measured hydrological variables (i.e rainfall intensity, I). Precipitation intensity measurements are widely available for many countries throughout world, on the other hand the challenge is therefore represented by establishing the best expression to relate the kinetic energy to the rainfall intensity. The aim of the study is to define among the KE-I expressions proposed in literature which best fits KE values calculated from potential erosive events collected by a disdrometer installed in Rome (Italy)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Relevance of the net natural inflow for investigating long-term hydrological changes in a managed lake catchment
No full textThe net natural inflow to a lake is an important quantity for developing lake management strategies and assessing hydrological change. The net natural inflow embeds the relevant hydrological processes governing the lake levels and it determines the lake levels and the emissary discharge under natural conditions, i.e. without withdrawals. The net natural inflow can be calculated by using an inverse procedure that reduces some of the sources of uncertainty that characterize the hydrological balance. In this paper we use the inverse procedure to analyze the net natural inflow of an Italian lake (Lake Bracciano) for which over a century of data are available. The behavior of the net natural inflow to the lake is analyzed, highlighting the high inter-annual variability and the consequent exposure of the lake to extreme events, in particular droughts. Evidence of hydrological change is discussed, as well as the importance of the availability of long time series for meaningful lake analysis and management. The analysis demonstrates the advantages of using the net natural inflow for lake hydrological analysis
Assessment of the watershed DEM mesh size influence on a large dam design hydrograph
No full textThe present study aims to assess the digital elevation model (DEM) resolution influence on the peak flow estimation for the design hydrograph of a large dam. This was executed by comparing the design hydrograph peak flows, with respect to a 2000years return period, which wereestimated for the Pietrarossa dam, in the South-East of Sicily, for different DEM spatial resolutions. The methodology consisted of the watershed extraction from the catchment basin in which the directly wired area belongs. Furthermore, the intensity duration frequency (IDF) curves were estimated starting from the observational time seriescollected by two rain gauges located near the dam. Finally, through a rainfall-runoff transformation, the design hydrographs were obtained by using both the watershed and the IDF curves. Considering different spatial resolutions, it was found that both the peak flow and the total volume decreases as the DEM spatial resolution decreases
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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