1,721,144 research outputs found
Principles of Hydraulics of Open Channels
No full textThe present chapter reports the basic principles governing open channel flows. The aim is to furnish a synthetic but comprehensive analysis of the main phenomena occurring in open channels. Nevertheless, the most important governing equations are analytically derived in order to give readers a complete and, at the same time, rigorous explanation of the flow characteristics in open channels.
The chapter is sub-divided into several sections. Namely, basic definitions relative to different flow regimes are discussed and illustrated, involving practical applications. The flow characteristics, including pressure distribution and velocity distribution are also illustrated and discussed. Then the analysis focuses on the uniform flow condition, for which all the main empirical relationships are provided. The analysis of the flow energy is conducted in a rigorous but simple way, providing all the essential analytical steps to generalize the proposed derivations and to highlight the main theoretical concepts. In particular, critical flow conditions are deeply analyzed and related to both specific energy and total hydrodynamic force. An ample part of the chapter is then dedicated to the description of the water surface profile characteristics. Also in this case, the analysis is conducted starting from a rigorous analytical approach and then it is specialized to the various cases, i.e. mild bed slope and steep bed slope. Finally, hydraulic jump characteristics are illustrated and discussed, along with all the analytical steps to derive both the conjugate depth ratio and the energy dissipation
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
Probabilistic Models for Erosion Parameters and Reliability Analysis of Earth Dams and Levees
No full textProbabilistic models for two soil erosion parameters needed to model the erodibility of water-retaining structures are developed. The models predict the values of the critical shear stress and the coefficient of erosion starting from other measurable soil properties.
The models include both noncohesive and cohesive contributions to the erosion behavior. An importance sampling simulation method is parallelized to be implemented in parallel computing resources to calibrate the models and estimate the unknown parameters using laboratory data. The probabilistic models are then used to develop fragility curves that capture the vulnerability of a typical earth dam to internal
erosion
Influences of Sex on Muscle Architecture and Performance in Elite Field Hockey Players
Full text linkThe aim of this study was to compare muscle architecture and performance between male and female elite Field Hockey players and to investigate the relationships between echo intensity and performance. Twenty-one male (24.3 ± 3.6 y; 75.1 ± 8.5 kg; 176.8 ± 6.4 cm) and nineteen female players (27.4 ± 3.9 y; 61.2 ± 7.4 kg; 164.4 ± 4.9 cm) were tested for muscle thickness (MT) and echo intensity (EI) of trapezius (Trap) and vastus lateralis (VL) muscles. Participants were also assessed for bench press power, and 30 m sprint. Results showed a higher VLMT and TrapMT in male players compared to female players (+22.1%; p = 0.004 and +25.8%; p = 0.001 for VLMT and TrapMT, respectively). A lower VLEI was detected in male players compared to female players (−20.7%; p = 0.001), while no significant differences were detected for TrapEI. Male players were faster than female players in a 30 m sprint and more powerful at the bench press (p < 0.001). Significant correlations were detected between VLEI and 30 m sprint (r = 0.74) in female players only. Results indicate that differences exist between male and female elite Field Hockey players in the EI of lower body muscles, while these differences are not present in the upper body muscles. EI, together with other sprint and power assessments, may represent an important parameter for elite Field Hockey players
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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