1,720,968 research outputs found
Indagine morfologica su un tratto del fiume Zambesi, nella Repubblica del Mozambico. Misure batimetriche ed analisi dei dati
Full text linkLo Zambesi è il quarto fiume del continente africano per estensione del bacino idrografico ed è il più importante tra quelli che sfociano nell’Oceano Indiano. Nello Zambesi Inferiore, ovvero nel tratto terminale del fiume che scorre nel territorio della Repubblica del Mozambico, il deflusso è regolato dalla presenza, a monte, delle dighe di Kariba e di Cahora Bassa, costruite nella seconda metà dello scorso secolo. La presenza degli invasi artificiali provoca profondi cambiamenti sul regime idrologico e sulla dinamica dei sedimenti, con prevedibili conseguenze sulla morfologia fluviale e, in generale, sul territorio e sull’ecosistema. Tuttavia, in letteratura non sono disponibili i risultati di rilievi batimetrici o altre misure in sito negli invasi o lungo il corso del fiume per la valutazione del trasporto solido e lo studio della morfodinamica fluviale. Nel marzo 2013, l’ENEA ha condotto un’estesa campagna di ricerca multidisciplinare
lungo un tratto dello Zambesi Inferiore, in collaborazione con la società mozambicana Minas Rio Bravo. Tra le varie attività svolte in campo, sono state eseguite misure batimetriche del fondo fluviale mediante l’utilizzo di ecoscandaglio, GPS e sistema di navigazione/acquisizione integrata. Nel presente rapporto, in particolare, sono descritte le risorse e le metodologie utilizzate per l’esecuzione delle misure batimetriche e l’elaborazione dei dati; sono, inoltre, presentati e discussi i risultati ottenuti, mediante mappe batimetriche e sezioni trasversali. I risultati qui riportati sono uno dei
pochissimi esempi di misure in campo nell’area dello Zambesi Inferiore e potranno essere utilizzati come base di confronto per ulteriori campagne a scopo di monitoraggio, o, eventualmente, come dato di input per la calibrazione e validazione sia di modelli matematici, sia di misure ottenute mediante telerilevamento.The Zambezi River is the fourth largest river in Africa as regards catchment area, and the most important flowing into Indian Ocean. In the Lower Zambezi, i.e. the final reach flowing across the Republic of Mozambique, river flow is regulated by the Kariba and Cahora Bassa dams, built in the second half of the last century. The presence of
impoundments causes important changes on hydrologic regime and dynamics of sediments downstream, with expected consequences on river morphology and, more in general, on territory and ecosystem. However, no results of bathymetric surveys or other in situ measures in the reservoirs and along the river aimed at quantifying sediment
transport and studying river morphodynamic are available in literature. In march 2013 ENEA, in cooperation with Minas Rio Bravo Company (Mozambique), performed an extensive multidisciplinary research along a reach of the Lower Zambezi. Among different field activities, bathymetric measures of riverbed were performed using echo sounder, GPS and integrated navigation/acquisition system. In the present report materials and methods used for bathymetric measures and data processing are described; results are presented and discussed, by means of bathymetric maps and
cross-section graphs. Results hereby reported are one of the fewest examples of direct field measures in the Lower Zambezi area and they can be used either for comparison with further monitoring survey, or, possibly, as input data for validation and calibration of both mathematical models and remote sensing data
Modeling the suspended sediment yield in Lesotho rivers
No full textThe present work was carried out in the framework of the Lesotho-Italy cooperation project “Renewable Energy Maps for Lesotho,” launched in 2016, with the main purpose to produce a series of maps aimed to support the Government of Lesotho in planning and expanding the exploitation of renewable energy sources (wind, solar and hydro). A multiple regression model specifically developed for sediment yield assessment in Lesotho catchments is here presented with a view to contributing to the follow-up of development projects in the field of hydroelectric energy. The “Lesotho model,” based on observations at 16 gauging stations, takes into account the proportions of agricultural and sedimentary bedrock areas as explanatory variables. Statistical reliability tests proved the model robustness after previous models, developed at continental or sub-continental scale, revealed to be ineffective or hardly applicable. A map of simulated sediment yields at sub-catchment level is provided, as an example of model application
Analisi idro-geomorfometrica di alcuni bacini idrogeografici italiani
Full text linkNel presente lavoro sono riportati i risultati dell’analisi idro-geomorfometrica di 30 bacini fluviali italiani. Nel complesso, a partire dalle basi cartografiche e dai dati storici disponibili, è stato realizzato un ampio insieme di parametri descrittivi delle caratteristiche idrologiche, morfometriche e di erodibilità che, in diversa misura, possono contribuire alla dinamica del trasporto dei sedimenti. L’analisi è stata condotta utilizzando il toolset originale QMorphoStream, sviluppato in ambiente QGIS. I risultati presentati rappresentano il primo obiettivo di un programma di ricerca più ampio, finalizzato allo sviluppo di metodi e modelli di previsione del trasporto solido in sospensione dei corsi d'acqua italiani, per la stima del potenziale apporto sedimentario dai bacini idrografici ai litorali, nell'ambito degli scenari di
cambiamento climatico e di rischio di erosione/sommersione di alcuni tratti delle coste italiane.In the present paper, the results of the hydro-geomorphometric analysis of 30 Italian river basins are reported. Basing on digital cartographic sources and available data records, a broad set of variables was built up describing hydrologic, morphometric and erodibility features that may have a role in river sediment transport and delivery. The analysis was performed using the original toolset QMorpho-Stream, developed in QGIS environment. The results hereby presented are the first step of a wider research program aimed at developing methods and models for the estimate of the potential sediment supply from river basins to the coasts, in the framework of current climate change scenarios and the
risk of erosion/submersion of some Italian coastal areas
Assessment of a Simplified Connectivity Index and Specific Sediment Potential in River Basins by Means of Geomorphometric Tools
No full textSediment connectivity is a major topic in recent research because of its relevance in the characterization of the morphology of river systems and assessing of sediment transport and deposition. Currently, the connectivity indices found in the literature are generally dimensionless and need to be coupled with quantitative soil-loss data for land management and design purposes. In the present work, a simple methodology is proposed to assess two different indices, namely, the simplified connectivity index (SCI) and the specific sediment potential (SSP), based on geomorphometric tools that are commonly available in commercial and open-source geographic information system (GIS) platforms. The proposed metrics allows us to easily assess both the SCI and the SSP as functions of the estimated soil erosion per unit area of the catchment and of the inverse distance of each unit area from the river outlet, this distance being measured along the network path. The proposed indices have been devised to express, respectively, the potential sediment transfer ability and the sediment mass potentially available at a given section of the drainage network. In addition to other parameters used to describe the catchment characteristics potentially affecting the river sediment delivery capacity, the SCI and SSP indices can help to refine theoretical models in order to assess the sediment yield (SY) in ungauged river basins
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
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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