1,720,968 research outputs found
Hydrodynamics and sediment transport on a macro-tidal, mixed (sand and shingle) beach
No full textA field investigation of a macro-tidal, ridge and runnel beach at Morfa Dyffryn, North Wales, is described, which examines the distinctive characteristics of a mixed (sand and shingle) beach.The moments of the velocity field and wave reflection at Morfa Dyffryn are compared with those from a similarly macro-tidal, sandy beach at Neiuwpoort-aan-Zee, Belgium. Strong, wind-enhanced, mean longshore currents persist into shallow water. Results of the velocity moment analysis indicate that the mean flows dominate the sediment transport patterns, particularly in shallow water, early in the flood and late in the ebb phases of the tide. The mean longshore current can be responsible for mobilising (in addition to transporting) sediment, when in excess of 0.3 m s-1. Mean fluxes dominate the measured suspended sediment transport patterns, in common with other macro-tidal beaches. Suspended sediment fluxes are generally at their highest in shallow water, although extremely high fluxes were observed just after High Water. These patterns are attributed to increased re-suspension due to wind/resolved mean current interaction. Therefore, high transport rates can occur, even in the absence of storm conditions. The relict sand/shingle ridge has little influence on reflection of wind wave energy. However, reflection of swell waves is enhanced, once the swash zone inundates the sand/shingle berm, due to its steeper gradient.Fluctuations in the beach water table due to tidal inundation are compared to groundwater behaviour on a sandy beach at Canford Cliffs, Dorset. The GRIST I model (which was derived for sandy beaches) predicts well both the location and translation of a seepage face across the sand/shingle profile. The sand fraction of the sediment determines the response of the water table. Laboratory hydraulic conductivity tests undertaken on sand/shingle mixtures indicate that the shingle content of a beach should be in excess of 80% to 90%, before increased dissipation of energy through percolation can occur.The main significance of the sand/shingle mixture, in relation to the morphodynamic response of the ridge is through its ability to maintain a steeper slope than would be supported by a sandy beach. The change in gradient across the mixed beach profile has more influence on the hydrodynamics, than does the sediment composition.</p
Spatial Characteristics and Duration of Extreme Wave Events around the English Coastline
No full textThis paper presents an analysis of the spatial characteristics and duration of extreme wave events around the English coast. There are five geographic regions which are affected as coherent units under extreme wave conditions, incorporating a sixth micro-wave climate region (western Lyme Bay). Characteristic storm tracks are associated with each region. Storms affecting the East region (North Sea coast) seldom impact other areas of England, whilst in contrast, storms affecting the Southwest or Northwest also have some impact on the Southeast. Average storm duration varies from 5 h in the Northwest to 14 h on the East coast north of the Humber. Storm duration exceeding 12.5 h in the Southwest and East (northern half) near guarantees that storm waves will span High Water, when it is of most significance for beach management operations. Storms along the East coast can be associated with anticyclonic conditions, as well as low pressure system
An Energetics Approach for Suspended Sand Transport on Macrotidal Ridge and Runnel Beaches
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Coastal flood analysis and visualisation for a small town
No full textExtreme sea levels and floods are a widespread threat to coastal communities, and sea-level rise is increasing the probability of such events. This paper describes how inundation modelling was used to engage local stakeholders about climate change and adaptation, for a town (Yarmouth) on the UK south coast. This included a participatory visualisation exercise using three extreme sea level scenarios, informed by a recent flood event. Further analysis, informed by the repeated floods during the 2013/14 storm surge season, placed these scenarios in a broader perspective across a range of events. Results indicate that coastal flooding may become a significant issue during this century due to sea-level rise, unless there is adaptation. These methods engaged the interest of the community, and this paper presents practical considerations for future studies. A similar approach could be applied widely at the community level and form an important component of coastal flood management, including planning responses to sea-level rise
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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