1,720,963 research outputs found
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
Design, modelling and simulation of compact ammonia chiller and heat pump units
No full textLarge-scale ammonia refrigeration and heating systems have been widely used in industry due to their high efficiency, broad temperature ranges of operation and innocuous environmental effects. However, implementing this technology in small to medium systems has not been very successful. Toxicity of the refrigerant and ammonia equipment prices are obstacles this technology must overcome before entering a market dominated by systems running on HFC refrigerants. A comparison of ammonia properties with other refrigerants and a concise review of the research and development of ammonia systems is presented. After that, a preliminary design and modelling approach of a medium capacity low charge ammonia chiller and heat pump is presented. The correlations for heat transfer coefficient, pressure drop and void fraction that can be used for modelling the performance of plate heat exchangers are presented. A 29 kW ammonia chiller with a highpressure receiver and direct expansion evaporator was used to collect data of different operating conditions. After that, the most representative data from the system were used to validate the numerical models of the plate heat exchangers. The model simulated the performance using several combinations of heat transfer coefficient correlations. The results showed that a suitable combination of correlations yielded maximum deviations of 4.8 % for heat transfer and 9.1 % for pressure drop in the condenser. Maximum deviations of 12.2 % for heat transfer and 57.3 % for pressure drop were calculated for the evaporator. Furthermore, an estimation of refrigerant charge distribution showed that the evaporator would tend to accumulate the largest share of refrigerant with a maximum of 1 kg when the chiller was working at 725 RPM.A 31 kW ammonia chiller with a split condensation process and direct expansion evaporator was used to collect data of the system when used with different amounts of refrigerant charge. The results showed that a suitable combination of correlations yielded maximum deviations of 1.9 % for heat transfer and 8.8 % for pressure drop in the condenser. Maximum deviations of 12.7 % for heat transfer and 8.3 % for pressure drop were calculated for the evaporator. A design of two medium capacity low charge ammonia chiller and heat pump units was proposed based on two different design conditions. The units have a low pressure receiver, a direct expansion evaporator, and a subcooling control approach. The plate heat exchanger models for condenser and evaporator with the identified correlations for heat transfer coefficient, pressure drop and void fraction were used to design the optimum geometry of plate heat exchangers that could guarantee low refrigerant charge. A dynamic model of the chiller and heat pump units was implemented on Dymola using the identified correlations for heat transfer coefficient, pressure drop and void fraction. The models helped to study the control structure of the units when shifting between the different modes of operation. As a result, the dynamic simulations showed that the subcooling control approach would only work when control values below 10 K are used when shifting between the different operating modes. Otherwise, the system controller would saturate due to the lower values of effective flow area needed by the electronic expansion valve when selecting higher values of subcooling. <br/
Diseño de aspas para un generador eólico horizontal que duncionará en condiciones de vientos moderados inferiores a 6 m/s en el sector de Carcelén
No full textAs a result of this research work, a wind turbine model was designed for horizontal wind generators that optimizes starting at wind speeds of 2m / s. First we looked for an aerodynamic profile suitable for low Reynolds numbers. Then a polymeric matrix was proposed as suitable material for its construction. Wind loads were calculated on the blade with the BEM method and finally simulations of stresses and fluids were carried out to corroborate its operationComo resultado de este trabajo de investigación se diseñó un modelo de aspa para generadores eólicos horizontales que optimice el arranque a velocidades de viento de 2m/s. Primero se buscó un perfil aerodinámico apropiado para bajos números de Reynolds. Luego se propuso una matriz polimérica como material adecuado para su construcción. Se calculó las cargas del viento sobre el aspa con el método BEM y finalmente se realizaron simulaciones de esfuerzos y fluidos para corroborar su funcionamient
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
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