1,720,986 research outputs found
Wave field mapping with Particle Image Velocimetry
No full textA number of different methods for the 3D measurement of the water surface in previous termwave fieldsnext term have been proposed in the literature, based mostly on refraction, photogrammetry and/or reflected light intensity. Although these methods can map the distorted water surface, they appear to be difficult in practical applications in hydraulic engineering laboratories. A novel previous termwave mappingnext term technique using previous termparticle image velocimetrynext term to measure surface flow velocities, and linear previous termwavenext term theory to determine previous termwavenext term heights from the measured velocities, has been developed and validated for regular previous termwaves.next term The method allows for the previous termmappingnext term even of complex previous termwave fieldsnext term with simple means and appears robust enough for application in the laboratory
Resonating wave energy converter for delivery of water for desalination and energy generation
No full textThe supply of clean drinking water is of great concern in many remote coastal areas. One method of providing this clean water is the process of desalination of seawater. This process generally requires either high temperatures(evaporation processes) or very high pressures (6 MPa for reverse osmosis processes). Current research at the University of Southampton focuses on the development of a wave powered standalone system for desalination and/or electricity production. A high pressure pump has been developed for pressurization of seawater for direct use in a reverse osmosis desalination process. The high pressure pump is driven by a supply of water, of 2 meter head, delivered by a simple wave energy converter. The proposed system has the benefit of simple technology and possesses significant potential for use in developing countries. This paper focuses on the device which will deliver water to the high pressure pump. The delivery device constitutes a wave energy converter and uses the principles common to most Oscillating Water Column (OWC) systems to pump water
Surface tension effects on energy dissipation by small scale, experimental breaking waves
No full textMuch of the existing knowledge about breaking waves comes from physical model experiments scaled using Froude's law. A widely held assumption is that surface tension effects are not significant at typical laboratory scales and specifically for waves longer than 2 m. Since, however, smaller wavelengths are not untypical in small to medium scale laboratory facilities, a consideration of surface tension effects is indeed important. Although some emphasis has been given in the past, little is known regarding the importance of surface tension following impingement of the breaking-wave crest and especially on the overall energy dissipation by laboratory breaking waves.To answer this question a laboratory study was conducted comparing the energy dissipation rate by waves breaking in fresh-water and in a 10% isopropyl-alcohol and distilled water solution of lower surface tension. It was found that when waves shorter than 4 mand smaller than 0.11 mbreak under the weakened influence of surface tension they dissipate up to 65% more wave energy. Visual observations link the increased wave energy dissipation with greater breaking intensity, increased air entrainment and longer bubble lifetime. Overall, the results presented here indicate that the inability to maintain Weber similarity (ratio of fluid inertia to its surface tension) has a more significant effect on the intensity of wave energy dissipation than previously assumed
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
Measuring wave impact induced pressures with a pressure mapping system
Get PDFThe use of a pressure mapping system for measuring wave impact induced pressures is evaluated in this paper. A set-up and a calibration methodology are suggested and employed for this work. The system is validated against pressure transducer and load cell measurements and for a range of waves breaking on a vertical seawall. For a large number (120 measurements for each case considered) of breaking and broken waves interacting with the wall, the peak pressure (Ppeak) profiles and the pressure distribution maps reported by the system agree well with results acquired using pressure transducers. Although the pressure mapping system tends to underestimate Ppeak, differences on the mean of the 3, 5 and 10 highest Ppeak rangewithin±10%, while for the majority of the measurements the error on the integral of the acting pressures (the acting force compared with the force measured by the load cell) ranges within ±20%. It is concluded, that through careful calibration and set-up the pressure mapping system has the capacity to provide pressure distribution maps with a good accuracy. It is not, however, considered to constitute the absolute alternative to pressure transducers and thus a combined use is suggested for applications where a very high level of accuracy is required
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
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