1,720,955 research outputs found
Evaluación de motores open rotor contra rotativos con caja de reducción para vuelos de corta distancia
Get PDFAs a consequence of increased stringent environmental regulations in a highly competitive market, airlines require radically more efficient and environmentally friendly aircraft.Engine manufacturers propose four different alternatives for the replacement of the A320: the geared turbofan, the advanced turbofan, the counter-rotating geared open rotor and the counterrotating direct drive open rotor. The open rotor technology offers the more potential fuel saves than the other options but there are major challenges associated with the development of this technology such as: the design of reliable counter-rotating components, the design of silent propellers, the design of a pitch changing mechanism capable of safely operating in hot sections of the engine and the stable operation in reverse thrust setting.
In order to design the most efficient engine that meets the certification requirements, a multidisciplinary simulation tool is required to quantify the implication of different design and operation choices. This article focuses on the performance module of this simulation tool and on the performance assessment of the geared open rotor architecture. The simulation results suggest that the geared open rotor has the potential to reduce the fuel consumption by approximately 21% compared to a current turbofan. This is directly translated into a 21% reduction of gaseous emissions and approximately a 7.7% reduction of the average European airline total operating cost.Como resultado de la presente situación económica, la continua subida en el precio del combustible y las normativas ambientales cada día más exigentes, las aerolíneas requieren aviones radicalmente más eficientes y amigables con el medio ambiente. Los fabricantes de motores proponen actualmente cuatro alternativas para la reposición del A320: el turbofan con caja de reducción, turbofan avanzado, el open rotor contra rotativo con caja de reducción y el open rotor contra rotativo a transmisión directa. El open rotor contra rotativo es la tecnología que ofrece un mayor potencial de ahorro de combustible pero presenta mayores desafíos técnicos como son: el diseño de componentes contra rotativos fiables, el diseño de hélices silenciosas, el diseño de un mecanismo de cambio de ángulo de hélices capaz de funcionar en la parte caliente del motor, la operación estable en modalidad de frenado, etc. Para diseñar un motor lo más eficiente posible y que a su vez cumpla con los requisitos de certificación para la aviación civil es necesaria una plataforma de simulación multidisciplinar que ayude a cuantificar el impacto de las decisiones de diseño y operación. Este artículo describe el módulo de performance del motor de esta herramienta y propone como caso deestudio la evaluación del open rotor con caja de reducción. Los resultados de este estudio muestran que el open rotor con caja de reducción podría reducir cerca de un 21% el consumo de combustible frente a un turbofan actual. Esto significa aproximadamente una ventaja del 21% de emisiones gaseosas y un 7.7% del costo operativo de una aerolínea europea promedio
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
Evaluación de motores open rotor contra rotativos con caja de reducción para vuelos de corta distancia
No full textAs a consequence of increased stringent environmental regulations in a highly competitive market, airlines require radically more efficient and environmentally friendly aircraft.Engine manufacturers propose four different alternatives for the replacement of the A320: the geared turbofan, the advanced turbofan, the counter-rotating geared open rotor and the counterrotating direct drive open rotor. The open rotor technology offers the more potential fuel saves than the other options but there are major challenges associated with the development of this technology such as: the design of reliable counter-rotating components, the design of silent propellers, the design of a pitch changing mechanism capable of safely operating in hot sections of the engine and the stable operation in reverse thrust setting.
In order to design the most efficient engine that meets the certification requirements, a multidisciplinary simulation tool is required to quantify the implication of different design and operation choices. This article focuses on the performance module of this simulation tool and on the performance assessment of the geared open rotor architecture. The simulation results suggest that the geared open rotor has the potential to reduce the fuel consumption by approximately 21% compared to a current turbofan. This is directly translated into a 21% reduction of gaseous emissions and approximately a 7.7% reduction of the average European airline total operating cost.Como resultado de la presente situación económica, la continua subida en el precio del combustible y las normativas ambientales cada día más exigentes, las aerolíneas requieren aviones radicalmente más eficientes y amigables con el medio ambiente. Los fabricantes de motores proponen actualmente cuatro alternativas para la reposición del A320: el turbofan con caja de reducción, turbofan avanzado, el open rotor contra rotativo con caja de reducción y el open rotor contra rotativo a transmisión directa. El open rotor contra rotativo es la tecnología que ofrece un mayor potencial de ahorro de combustible pero presenta mayores desafíos técnicos como son: el diseño de componentes contra rotativos fiables, el diseño de hélices silenciosas, el diseño de un mecanismo de cambio de ángulo de hélices capaz de funcionar en la parte caliente del motor, la operación estable en modalidad de frenado, etc. Para diseñar un motor lo más eficiente posible y que a su vez cumpla con los requisitos de certificación para la aviación civil es necesaria una plataforma de simulación multidisciplinar que ayude a cuantificar el impacto de las decisiones de diseño y operación. Este artículo describe el módulo de performance del motor de esta herramienta y propone como caso deestudio la evaluación del open rotor con caja de reducción. Los resultados de este estudio muestran que el open rotor con caja de reducción podría reducir cerca de un 21% el consumo de combustible frente a un turbofan actual. Esto significa aproximadamente una ventaja del 21% de emisiones gaseosas y un 7.7% del costo operativo de una aerolínea europea promedio
Evaluación de motores open rotor contra rotativos con caja de reducción para vuelos de corta distancia
Get PDFAs a consequence of increased stringent environmental regulations in a highly competitive market, airlines require radically more efficient and environmentally friendly aircraft.Engine manufacturers propose four different alternatives for the replacement of the A320: the geared turbofan, the advanced turbofan, the counter-rotating geared open rotor and the counterrotating direct drive open rotor. The open rotor technology offers the more potential fuel saves than the other options but there are major challenges associated with the development of this technology such as: the design of reliable counter-rotating components, the design of silent propellers, the design of a pitch changing mechanism capable of safely operating in hot sections of the engine and the stable operation in reverse thrust setting.
In order to design the most efficient engine that meets the certification requirements, a multidisciplinary simulation tool is required to quantify the implication of different design and operation choices. This article focuses on the performance module of this simulation tool and on the performance assessment of the geared open rotor architecture. The simulation results suggest that the geared open rotor has the potential to reduce the fuel consumption by approximately 21% compared to a current turbofan. This is directly translated into a 21% reduction of gaseous emissions and approximately a 7.7% reduction of the average European airline total operating cost.Como resultado de la presente situación económica, la continua subida en el precio del combustible y las normativas ambientales cada día más exigentes, las aerolíneas requieren aviones radicalmente más eficientes y amigables con el medio ambiente. Los fabricantes de motores proponen actualmente cuatro alternativas para la reposición del A320: el turbofan con caja de reducción, turbofan avanzado, el open rotor contra rotativo con caja de reducción y el open rotor contra rotativo a transmisión directa. El open rotor contra rotativo es la tecnología que ofrece un mayor potencial de ahorro de combustible pero presenta mayores desafíos técnicos como son: el diseño de componentes contra rotativos fiables, el diseño de hélices silenciosas, el diseño de un mecanismo de cambio de ángulo de hélices capaz de funcionar en la parte caliente del motor, la operación estable en modalidad de frenado, etc. Para diseñar un motor lo más eficiente posible y que a su vez cumpla con los requisitos de certificación para la aviación civil es necesaria una plataforma de simulación multidisciplinar que ayude a cuantificar el impacto de las decisiones de diseño y operación. Este artículo describe el módulo de performance del motor de esta herramienta y propone como caso deestudio la evaluación del open rotor con caja de reducción. Los resultados de este estudio muestran que el open rotor con caja de reducción podría reducir cerca de un 21% el consumo de combustible frente a un turbofan actual. Esto significa aproximadamente una ventaja del 21% de emisiones gaseosas y un 7.7% del costo operativo de una aerolínea europea promedio
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
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