1,720,954 research outputs found
A method to calculate the probability of dike failure due to wave overtopping, including the infragravity waves and morphological changes
No full textIn this thesis, a method was developed, with which the infragravity waves and morphological changes of a sandy foreshore are included in the calculation of the probability of dike failure due to wave overtopping. Constructing a natural foreshore in front of the dike can be an attractive and innovative method to decrease the failure probability. However, the uncertainty in the morphological development of these foreshores leads to uncertainty with respect to their contribution in protection against flooding. The morphological stability of a foreshore during extreme conditions is not well known. The current Dutch safety assessment tools do not yet include the infragravity waves and morphological changes of a foreshore during a storm. Hence, it is not yet possible to guarantee the robustness and safety of dike-foreshore system. This thesis considered hybrid defences (dike-foreshore systems), where the dike is still of importance in the protection of the hinterland. The considered hybrid defence was a schematized version of the Westkapelle sea defence, located at the coast of Walcheren in the Netherlands. The morphological changes of the foreshore calculated in this thesis, were the changes during (severe) storms. Because a single model that includes all the different relevant processes does not exist, a model framework or ‘model train’ was developed, in which different models were combined. The modelling framework best fit to solve the research questions was determined as a combination of XBeach hydrostatic, the EurOtop formulae and the probabilistic method Adaptive Directional Importance Sampling (ADIS). Including infragravity waves (and wave set-up) lead to much larger failure probabilities for the hybrid defence considered in this thesis. This difference is mainly caused by the difference in wave period at the toe of the dike. Including the morphological changes lead to a somewhat larger failure probability. The fact that this difference was not that large, was mainly caused by less wave dissipation due to erosion of the foreshore, but at the same time less transfer of energy to the low frequencies, thus a smaller wave period. The combination of a (very) shallow foreshore and dike slope of 1:8 make that the case considered here is (largely) outside the previously studied wave overtopping area. It is possible, that when the wave period becomes very large, the wave overtopping is not dependent anymore on the dike slope, but on the wave parameters only. It is therefore questionable if the EurOtop formulae calculate the right amount of wave overtopping for these types of situations, because in the formulae, the wave overtopping is dependent on the dike slope. Furthermore, the EurOtop formulae use the Tm-1,0 wave period. This wave period is very sensitive to the low frequencies. Clear guidelines should be determined on which frequency resolution and, if necessary, cut-off frequencies should be used when determining wave spectra. This thesis presented a method with which infragravity waves and morphological changes of a sandy foreshore can be included in the calculation of the probability of dike failure due to wave overtopping. Before this thesis, this was not yet possible. As shown in this thesis, it is important that the infragravity waves are included in the calculation of the dike failure probability due to wave overtopping at this dike-foreshore system, because they had a large influence on the probability of failure. The method developed in this thesis can be used at other locations without many problems, however the influence of the infragravity waves and morphological change as determined in this thesis, could be different at another location.Hydraulic Structures & Flood RiskHydraulic EngineeringCivil Engineering and Geoscience
Nearshore waves and related wave overtopping in complex estuaries
No full textThis dissertation focuses on the Eems-Dollard estuary in the north of the Netherlands and contributes to the MVED (’Meerjarige Veldmetingen Eems-Dollard’) field measurement project in the area. The Eems-Dollard estuary is part of the Wadden Sea, a shallow shelf sea with barrier islands, deep tidal channels, shallow tidal flats and wetlands. The Eems-Dollard estuary is even more complex than theWadden Sea, because of the deep channels, which run close to the dikes, and the very shallow flats, as well as the funnel shape, which can lead to very high water levels during storms. A particular aspect for this area is that the dike design conditions consist of an offshore-directed wind and very obliquely incident waves, up to 80° relative to the dike normal. Almost no studies have been performed on the estuary and almost no measurements were available inside the estuary.This dissertation considers two main knowledge gaps, related to the modelling of wave propagation effects and measuring of (very) oblique wave run-up and overtopping, in a complex estuary. First, the performance of the SWAN wave model in predicting the wave conditions in a highly complex area, such as the Eems-Dollard estuary, has not been assessed before. Second, knowledge on and (field) measurements of the extra parameters (such as front velocities) necessary for the cumulative overload method are still scarce. This method considers the overtopping and erosion of the dike cover explicitly. Added to this, the few available (lab) investigations on wave run-up and overtopping during (very) oblique wave attack have not yet led to clear conclusions or guidelines. Therefore, the aim of this dissertation is to gain more insight into the uncertainties related to wave propagation processes and (very) oblique wave run-up and overtopping, which are important for the extreme wave loads on the dikes around the Eems-Dollard estuary.Hydraulic Structures and Flood Ris
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
Influence of very oblique waves on wave overtopping
No full textThe main goal of this study is to determe the relation between very oblique wave attack and overtopping, and to accordingly adjust the formulae for oblique wave attack. The required knowledge to be able to read and understand this report is of a Bachelor in civil engineering level. All around the world different types of structures are built to protect adjacent areas from river or coastal flooding during high water levels. Only limited research is available on the influence of oblique wave attack (for angles over 45 degrees) on wave overtopping. Hydralab is an EU-project, which gives researchers in the European Union the possibility to carry out research in large hydraulic facilities. Cornerdike is a part of the Hydralab IV program. The Cornerdike research project was performed at the shallow-water basin at DHI in Hørsholm, Denmark. To achieve the goal of this research, tests, data processing and analysis were done.Hydraulic EngineeringCivil Engineering and Geoscience
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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