1,721,031 research outputs found
Tidal range energy resource assessment of the Gulf of California, Mexico
Full text linkThere is growing interest in harnessing renewable energy resources in Latin America. Converting the energy of the tides into electricity has the distinct advantage of being predictable, yet the tidal range resource of Latin America is largely unquantified. The northern part of the Gulf of California (GC) in Mexico has a relatively large mean tidal range (4m–5m), and so could be a potential site for tidal range energy exploitation. A detailed quantification of the theoretical tidal range energy resource was performed using tidal level predictions from a depth-averaged barotropic hydrodynamic model. In addition, a 0-D operation modelling approach was applied to determine the power that can be technically extracted at four key sites. The results show that the annual energy yield ranges from 20 to 50 kWh/m2, while the maximum values are between 45 and 50 kWh/m2 in the vicinity of the Gulf of Santa Clara. Within the region, the Gulf of Santa Clara is one of the most promising, delivering a technical annual energy output of 125 GWh (ebb-only generation), 159 GWh (two-way) and 174 GWh (two-way with pumping) within an impoundment area of 10 km2. This equates to 50%, 40% and 33% of the absolute energy conversion relative to a much-studied reference site (Swansea Bay, UK) that has been under consideration as the world’s first tidal lagoon power plant. This study provides the basis for more detailed analysis of the GC to guide selection of suitable sites for tidal range energy exploitation in the region
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
Sensitivity assessment of bathymetry and choice of tidal constituents on tidal-stream energy resource characterisation in the Gulf of California, Mexico
Full text linkThere has been a significant increase in the number of published tidal-stream energy resource assessments in recent years due to the growing availability of open-source hydrodynamic models, and freely available data for model bathymetry (e.g. GEBCO_2014 and ETOPO) and boundary conditions (e.g. TPXO, FES, EOT). This study examines how the choice of bathymetry and tidal constituents affects the quantification of a tidal-stream energy resource, by conducting sensitivity tests for the Gulf of California. We find that the mean KPD (Kinetic Power Density) and annual mean power are significantly underestimated when using just GEBCO_2014 or ETOPO bathymetry data sources on their own. For the Midriff region, between San Lorenzo and San Esteban Islands (herein the San Lorenzo Passage), the annual mean power potential was estimated to be around 50 MW when using freely available bathymetry data, while the annual mean power increased to ~200 MW when using a bespoke dataset that was a combination of GEBCO and higher-resolution bathymetry provided by CICESE (The Centre for Scientific Research and Higher Education at Ensenada). Current speeds reduce from 2.4 m/s when using high-resolution to around 1.2 m/s and 0.8 m/s when using open source bathymetry products. Finally, we compared the estimated energy using tidal levels predicted from 29 tidal constituents compared with simulations that included just the principal semi-diurnal lunar (M2) and solar (S2) constituents. The annual mean KPD reduced by almost 1/3rd in the San Lorenzo Passage, when just considering M2 and S2 constituents, suggesting that diurnal and higher order harmonic constituents are important for accurate resource assessments in this region
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
Tidal-stream energy resource characterization for the Gulf of California, México
No full textThere has been a growing interest in tidal-stream energy, with most past studies focusing on assessing the potential resource of sites with fast tidal currents in relatively shallow water. Regions with less energetic tidal currents, but in deeper waters, have been overlooked. One potential tidal-stream energy region, which fits this categorization, is the Gulf of California. In this paper we quantify the theoretical tidal-stream energy resource in this region. The resource is estimated with an unstructured depth-averaged hydrodynamic model. We find that the highest flow speeds of 2.4 m/s occur in the channel between San Lorenzo and San Esteban Island, and three lower-velocity potential sites are identified in the channels between: (1) Baja California Peninsula and San Lorenzo Island; (2) San Esteban and Tiburon Islands and (3) Baja California Peninsula and Angel de la Guarda Island. Although peak kinetic power density in these regions is found to be relatively low (∼ 3 to 6 kW/m2), the large water depth (100 to 500 m), results in an undisturbed theoretical annual mean power of between 100 to 200 MW. We therefore find the tidal energy resource to be large, but new turbine technologies would be required to exploit these ‘next generation’ resource regions
Sensitivity of bathymetry and choice of tidal constituents on tidal-stream energy resource characterization in the Gulf of California, Mexico
No full textResource assessments are essential, yet many are based on hydrodynamic models forced with coarse global data products for bathymetry and open-boundary forcing. The aim of this paper is to examine how selection of: (1) two open source bathymetry products (GEBCO and ETOPO) and the inclusion of a higher-resolution bathymetry survey; and (2) considering different numbers of tidal constituents; affects the quantification of the tidal-stream energy resource for the Gulf of California. For the location with fastest current speeds, a 18 km wide passage between the San Lorenzo and San Esteban Islands, (herein San Lorenzo Passage), the annual mean power was estimated at around 120 MW and 20 MW when using freely available bathymetry data (GEBCO and ETOPO respectively), but increased to ~200 MW when using a bespoke dataset that was a combination of GEBCO and higher resolution bathymetry. Integrating higher resolution of bathymetry data within the model simulations increase the accuracy to resolve flows within the midriff region. We also compared the estimated energy computed using 29 tidal constituents compared with simulations that included just the M2 and S2 tidal constituents. The annual mean kinetic power density decreased by almost 1/3rd in the channel between San Lorenzo and San Esteban Islands, when considering just the M2 and S2 constituents, suggesting that diurnal and higher order harmonic constituents are important for accurate resource assessments in this region
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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