1,720,974 research outputs found
Italian seas wave extremes: a preliminary assessment
No full textOccasional damages occurring to offshore structures and routing ships have brought attention on whether conventional analyses of stormy seas are adequate to represent wave extremes. Indeed, field and laboratory data showed that in short-crested seas (typical of stormy conditions) the maximum wave elevation is rarely retrieved by a single-point observation (a buoy, for example), which tends to underestimate the actual extreme that occurs over an area surrounding the point. Recently, stochastic models for the prediction of maxima of multidimensional Gaussian random fields (e.g. the Piterbarg’s theorem and the Adler and Taylor’s Euler Characteristics approach) have been successfully applied to ocean wave statistics, thus permitting to extend the extreme value analysis from the time to the space–time domain. Results from space–time models are here firstly compared to observations gathered by an optical stereo system, and then used to preliminarily assess wave extremes over the Italian Seas, by using a numerical model analysis covering the period 2007–2013. In particular, space–time maxima are estimated as affecting a fishing boat and a cruise ship, showing that, locally, space–time extremes may exceed time-based values up to about 50 %
Towards an Operational Stereo System for Directional Wave Measurements From Moving PlatformsVolume 8B: Ocean Engineering
No full textStereo video imaging of water surface has become an effective instrumentation to gather wind waves 3-D data from small to medium range spatial scales. Indeed, recent applications of stereo techniques provided new insights of space-time distributions of sea wave elevations, small scale wave statistics, and directional wave spectra. Like most photogrammetric applications, an accurate calibration of the optical acquisition machinery is required to provide a low-noise, precise and reliable surface reconstruction adequate to extract meaningful wavy surfaces. However, for practical open field applications, there is a strong interest to provide a calibration procedure apt to be performed in an uncomfortable environment in which it may be unfeasible to take apart or even physically access the device. Here, we propose a stereo pipeline suitable for 3-D wave measurements from fixed and moving platforms. In particular, within the Wave Acquisition Stereo System (WASS) framework, we contemplated a self-calibration technique for a robust estimation of the stereo extrinsic parameters, a fast dense stereo correspondence algorithm, and a two-step correction of the cameras motion. As for other applications, wave information collected by WASS includes synthetic wave parameters (e.g., significant wave height, wave periods, and directions), wavenumber and frequency-direction spectra, spatial distribution of wave elevations, heights, and lengths. The new pipeline features has been firstly assessed by installing WASS on top of the "Acqua Alta" oceanographic tower in the northern Adriatic Sea (Italy) and comparing WASS measurements against those acquired at the tower with reference instrumentation. Afterwards, the stereo system has been mounted on board the R/V "Urania" during a cruise on April 2013 in the southern Adriatic Sea. During the cruise, to correct for ship's motion, WASS has been synchronized to the motion unit used for the vessel's navigation. For validation, sea wave state gathered by WASS has been compared to theoretical models and results from the numerical wave model SWAN. Results presented show that the accuracy of 3-D waves provided by the new algorithms is comparable to that of other WASS applications, although significantly reducing the installation effort and the computational time by more than one order of magnitude. Additionally, encompassing for ship's motion makes stereo system a perspective instrumentation for operational wave measuring from research and opportunity vessels. The manuscript is completed by a discussion on the limitations and troubleshooting related to the proposed pipeline
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
