1,720,956 research outputs found
A system of cross-beams as energy dissipater in expanding channels
No full textSeveral studies have demonstrated that in abruptly expanding channels flow asymmetry phenomena can arise for certain tailwater depths. These undesired conditions are characterized by high velocity concentrations and backward flows in the tailwater channel. Based on the description of the main features of hydraulic jumps in expanding channels, this paper presents the results of an experimental investigation carried out to study the effects of a system of cross-beams in improving flow patterns in the tailwater channel. Four different beam spacings, two beam orientations and slopes, two locations and two beam heights were tested in order to define the most adequate geometry of the dissipater. Downstream flow characteristics, velocity distribution and stability under variable tailwater conditions were considered for analyzing the performances of the system. It was found that, for almost all tested configurations, the presence of the cross-beams induced a significant improvement in the flow field in the tailwater channel
Effects of wildfires on peak discharges in watersheds
Full text linkIt is acknowledged that wildfires can alter hydrologic processes in watersheds, increasing runoff peak discharge, which is one of the most important hydrological variables used in water resources applications. Then it is evident that usual rainfall-runoff methods should be modified in some of their components in order to model the different watershed response in burned condition. This paper contains some considerations on the estimation of the SCS runoff Curve Number, needed for the calculation of peak discharge in the small urban basin of San Giuliano in L’Aquila (Italy), which has been recently affected by a wildfire, causing a significant reduction in the forest cover
Turbulence characteristics of the flow resulting from the hydrodynamic interaction of multiple counter flow jets in expanding channels
No full textVarious methods exist to stabilize asymmetric hydraulic jumps occurring in suddenly expanding channels. In this study, the effects of the interaction of multiple submerged counter flow jets are investigated experimentally in terms of the hydrodynamic characteristics of the flow resulting in the tailwater channel. To this aim, three-dimensional flow velocities downstream of the jet system were measured for different configurations of the device. The stability in the performance of the dissipation system under variable tailwater conditions was analyzed in terms of flow velocity distribution, turbulent kinetic energy, turbulence intensity and Reynolds shear stresses. The results reveal the good performance of the investigated system in preventing the phenomena of flow instability associated with suddenly expanding channels
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
Impact of Climate Change on Crop Yields: Insights from the Abruzzo Region, Central Italy
No full textClimate change poses a major sustainability challenge, with potential far-reaching economic and social impacts, including fluctuations in agricultural yields and subsequent volatility in the availability and prices of essential food resources. In this study, we analyze the changes in climatic variables and agricultural yields for main crops cultivated in the Abruzzo Region (Central Italy), as well as their reciprocal correlation pattern in the time range, 1952–2014. Central Italy exhibits a well-developed agricultural sector and is characterized by a Mediterranean climate; given its proximity to the semi-arid and arid North African climate zone, such a region may be particularly vulnerable to climate change impacts. The analysis reveals an increase in drought intensity and persistence, starting from the 1980s, with a shift towards more temperate conditions in winter months and a transition to a warmer and more arid climate during the summer season. Moreover, the study identifies an overall increase in the correlation magnitude between crop yield fluctuations and climatic variables in the period 1983–2014 compared to that during the previous thirty-year time range. This finding can be interpreted as a change in the resilience (or increased vulnerability) of the agricultural production system to climate change. This work can be thus considered as an interesting case study in the Mediterranean region, offering valuable insights for constructing probabilistic models of fluctuations in agricultural production possibly induced by climate change
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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