1,720,995 research outputs found
Analysis of pool-riffle dynamics through numerical morphological modelling
No full textAn issue that has puzzled geomorphologists for a long time is the ubiquity and persistence of pool-riffle sequences in rivers over a wide range of slope and substrate conditions. In particular, the mechanisms responsible for the self-maintenance of pools and riffles have been the subject of intense research and controversy. Most of the investigation has focused on inferring the observed morphological dynamics based on some characteristics of both the spatial and temporal variability of the flow, often overlooking intermediate sediment transport processes that are responsible for the link between flow and morphology. The main reason of this omission is the inherent difficulty in measuring and predicting transport variables (e.g. fractional transport, bed grain size distribution) over a range of time and spatial scales, even under controlled laboratory conditions. This paper analyses some important aspects of pool-riffle dynamics through continuous simulations of a coupled unsteady 1D flow-morphology- bed sorting model. The model is used to simulate the evolution of a reach with pools and riffles on the Bear Creek, Arkansas, for a one-year period. Based on the detailed model prediction regarding the time and spatial distribution of fractional sediment transport (bedload by size class), bed composition and topography, some important mechanisms controlling pool-riffle maintenance that so far have been omitted in the literature are unveiled and used to propose a more complete explanation for this phenomenon
The effect of unsteady hydrographs and non-uniform sediment transport on morphology of pool-riffle sequences
No full textRising tides, rising gates: The complex ecogeomorphic response of coastal wetlands to sea-level rise and human interventions
Full text linkDepartment of Hydraulics and Research Council of National University of Rosario (CIUNR), Rosario 2000, ArgentinaFil: Sandi, Steven. School of Engineering, The University of Newcastle; AustraliaFil: Rodriguez, Jose F. Centre for Water Security and Environmental Sustainability, The University of Newcastle; AustraliaFil: Saintilan, Neil. Department of Environmental Sciences, Macquarie University; AustraliaFil: Riccardi, Gerardo A. Department of Hydraulics and Research Council of National University of Rosario (CIUNR); ArgentinaFil: Saco, Patricia M. Department of Hydraulics and Research Council of National University of Rosario (CIUNR); Argentin
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
A pull-back algorithm to determine the unloaded vascular geometry in anisotropic hyperelastic AAA passive mechanics
No full textBiomechanical studies on abdominal aortic aneurysms (AAA) seek to provide for better decision criteria to undergo surgical intervention for AAA repair. More accurate results can be obtained by using appropriate material models for the tissues along with accurate geometric models and more realistic boundary conditions for the lesion. However, patient-specific AAA models are generated from gated medical images in which the artery is under pressure. Therefore, identification of the AAA zero pressure geometry would allow for a more realistic estimate of the aneurysmal wall mechanics. This study proposes a novel iterative algorithm to find the zero pressure geometry of patient-specific AAA models. The methodology allows considering the anisotropic hyperelastic behavior of the aortic wall, its thickness and accounts for the presence of the intraluminal thrombus. Results on 12 patient-specific AAA geometric models indicate that the procedure is computational tractable and efficient, and preserves the global volume of the model. In addition, a comparison of the peak wall stress computed with the zero pressure and CT-based geometries during systole indicates that computations using CT-based geometric models underestimate the peak wall stress by 59 +/- A 64 and 47 +/- A 64 kPa for the isotropic and anisotropic material models of the arterial wall, respectively.</p
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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