1,721,034 research outputs found
Experimental study of thermodynamic properties of liquid mixtures with interest as biofuels: binary systems: 2-Propanol, DIPE and 1 Hexene
Full text linkAbout 25% of CO2 emissions in the EU are originated by the transport
sector. In this segment, road transport is the largest emitter, accounting for
over 70% of all greenhouse gas (GHG) emissions. One of the main strategies for
reducing emissions is the promotion of low emission alternative energy for
transport, such as biofuels.
Some alcohols and ethers, such as oxygenate additives, are added to
gasoline to reduce the emission of gases that produce environmental impact.
These components can be obtained from renewable or agricultural raw
materials, reducing dependence on fossil sources. The thermodynamic
properties of liquid blends with interest as biofuels are of great importance to
the petrochemical industry, not only because of their application in new
gasoline formulations but also for refining design, purification and deposition
processes.
This work reports experimental densities, speeds of sound, refractive
indices of binary systems 2-propanol + di-isopropyl-ether (DIPE), 2-propanol +
1-hexene and di-isopropyl-ether (DIPE) + 1-hexene at the temperature of 298.15
K. Besides, the viscosity of the same binary systems at the temperatures of
293.15 K, 298.15K and 313.15K are also reported. Excess molar volumes,
deviations in isentropic compressibility and deviations in speeds of sound were
correlated by the Redlich-Kister polynomial. In total, 756 experimental
measurements were collected and analyzed to scientifically contribute for the
validation of new models and equations which could satisfactorily predict the
liquid blend behavior of these compounds as biofuels.Cerca de 25% das emissões de CO2 na UE provêm do setor de transportes.
Nesse segmento, o transporte rodoviário é o maior emissor, respondendo por
mais de 70% de todas as emissões de gases de efeito estufa. Uma das principais
estratégias de redução de emissões é a promoção de energia alternativa de
baixa emissão para o transporte, como os biocombustíveis.
Alguns álcoois e éteres, como aditivos de oxigénio, são adicionados à
gasolina para reduzir a emissão de gases que produzem impacto ambiental.
Esses componentes podem ser obtidos a partir de matérias-primas renováveis
ou agrícolas, reduzindo a dependência de fontes fósseis. As propriedades
termodinâmicas das misturas líquidas com interesse como biocombustíveis são
de grande importância para a indústria petroquímica, não apenas por sua
aplicação em nova formulaçao da gasolina, mas também para o projeto dos
processos de refino, purificação e deposição.
Este trabalho reporta densidades experimentais, velocidades de som,
índices de refração de sistemas binários 2-propanol + éter diisopropílico (DIPE),
2-propanol + 1-hexeno e éter diisopropílico (DIPE) + 1-hexeno na temperatura
de 298,15 K. Além disso, é apresentada a viscosidade dos mesmos sistemas
binários nas temperaturas de 293,15 K, 298,15 K e 313,15 K. Volumes molares
excessivos, desvios na compressibilidade isentrópica e desvios nas velocidades
do som foram correlacionados pelo polinómio de Redlich-Kister. No total, 756
medições experimentais foram coletadas e analisadas para contribuir
cientificamente na validação de novos modelos e equações que possibilitem a
previsão satisfatória do comportamento da mistura líquida desses compostos
como biocombustíveis
Experimental study of thermodynamic properties of liquid mixtures with interest as biofuels: binary systems: 2-Propanol, DIPE and 1 Hexene
No full textAbout 25% of CO2 emissions in the EU are originated by the transport
sector. In this segment, road transport is the largest emitter, accounting for
over 70% of all greenhouse gas (GHG) emissions. One of the main strategies for
reducing emissions is the promotion of low emission alternative energy for
transport, such as biofuels.
Some alcohols and ethers, such as oxygenate additives, are added to
gasoline to reduce the emission of gases that produce environmental impact.
These components can be obtained from renewable or agricultural raw
materials, reducing dependence on fossil sources. The thermodynamic
properties of liquid blends with interest as biofuels are of great importance to
the petrochemical industry, not only because of their application in new
gasoline formulations but also for refining design, purification and deposition
processes.
This work reports experimental densities, speeds of sound, refractive
indices of binary systems 2-propanol + di-isopropyl-ether (DIPE), 2-propanol +
1-hexene and di-isopropyl-ether (DIPE) + 1-hexene at the temperature of 298.15
K. Besides, the viscosity of the same binary systems at the temperatures of
293.15 K, 298.15K and 313.15K are also reported. Excess molar volumes,
deviations in isentropic compressibility and deviations in speeds of sound were
correlated by the Redlich-Kister polynomial. In total, 756 experimental
measurements were collected and analyzed to scientifically contribute for the
validation of new models and equations which could satisfactorily predict the
liquid blend behavior of these compounds as biofuels.Cerca de 25% das emissões de CO2 na UE provêm do setor de transportes.
Nesse segmento, o transporte rodoviário é o maior emissor, respondendo por
mais de 70% de todas as emissões de gases de efeito estufa. Uma das principais
estratégias de redução de emissões é a promoção de energia alternativa de
baixa emissão para o transporte, como os biocombustíveis.
Alguns álcoois e éteres, como aditivos de oxigénio, são adicionados à
gasolina para reduzir a emissão de gases que produzem impacto ambiental.
Esses componentes podem ser obtidos a partir de matérias-primas renováveis
ou agrícolas, reduzindo a dependência de fontes fósseis. As propriedades
termodinâmicas das misturas líquidas com interesse como biocombustíveis são
de grande importância para a indústria petroquímica, não apenas por sua
aplicação em nova formulaçao da gasolina, mas também para o projeto dos
processos de refino, purificação e deposição.
Este trabalho reporta densidades experimentais, velocidades de som,
índices de refração de sistemas binários 2-propanol + éter diisopropílico (DIPE),
2-propanol + 1-hexeno e éter diisopropílico (DIPE) + 1-hexeno na temperatura
de 298,15 K. Além disso, é apresentada a viscosidade dos mesmos sistemas
binários nas temperaturas de 293,15 K, 298,15 K e 313,15 K. Volumes molares
excessivos, desvios na compressibilidade isentrópica e desvios nas velocidades
do som foram correlacionados pelo polinómio de Redlich-Kister. No total, 756
medições experimentais foram coletadas e analisadas para contribuir
cientificamente na validação de novos modelos e equações que possibilitem a
previsão satisfatória do comportamento da mistura líquida desses compostos
como biocombustíveis
Investigación sobre propiedades de nuevos fluidos industriales de bajo impacto ambiental como sustitutivos de gases fluorados para reducción del cambio climático
Full text linkA lo largo de los últimos 40 años, y a expensas de los Protocolos de Montreal (1987), Kyoto (1997), y más recientemente el Acuerdo de París (2015), se han ido desarrollando nuevas alternativas de fluidos medioambientalmente más limpios con respecto a los ampliamente utilizados fluorocarbonos (CFCs, HCFCs, HFCs, PFEs, etc), para su empleo en multitud de aplicaciones como son la refrigeración, limpieza de precisión, fluidos de transferencia de calor, entre otros. Los hidrofluoroéteres (HFEs) se presentan como una buena opción dadas sus propiedades termofísicas, y su bajo impacto sobre el medio ambiente. Esta Tesis ha basado su objetivo en la caracterización experimental de varias propiedades termofísicas (equilibrios líquido-vapor, densidad a alta presión, viscosidad a alta presión, velocidad del sonido a alta presión, y capacidades caloríficas), de cuatro hidrofluoroéteres de alto peso molecular, y de sus mezclas binarias con alcoholes o éteres. Para las propiedades obtenidas se han aplicado correlaciones a distintas ecuaciones, así como modelos matemáticos.Along the last 40 years, and at the expense of the Montreal Protocol (1987), the Kyoto Protocol (1997), and more recently, the Paris Agreement (2015), environmentally friendly alternatives to commonly used fluorocarbons (CFCs, HCFCs, HFCs, PFEs, etc), have been developed to be used in multiple applications such as cooling, high precision cleaning, as heat transfer fluids, among others. Hydrofluoroether fluids (HFEs), are a good choice due to their desirable thermophysical properties, and their low environmental impact. This Thesis has based its main objective in the experimental characterization of some thermophysical properties (liquid-vapor equilibria, high pressure density, high pressure viscosity, high pressure speed of sound and heat capacities), of four high molar weight hydrofluoroethers and their binary mixtures with alcohols and ethers. For the obtained properties, equation correlations have been implemented, as well as mathematical models
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
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
Investigación sobre el equilibrio de fases de nuevos materiales y fluidos renovables para usos energéticos mediante técnicas experimentales
Full text linkLa creación de sistemas de gestión y generación energética más sostenibles sigue siendo
una prioridad tanto a nivel europeo como internacional, tal y como muestran proyectos
como el Horizonte Europa, los Objetivos de Desarrollo Sostenible (ODS) o las iniciativas
de la Agencia Internacional de Energía (IEA). Si bien las energías renovables obstentan
un papel central en esta transición energética, otras técnicas complementarias están
siendo también desarrolladas para compensar algunas de sus desventajas, como el
suministro intermitente o el desacoplo entre generación y consumo de energía. Así, el
almacenamiento de energía adquiere un matiz indispensable, incluyendo el
almacenamiento de energía térmica (TES). En concreto, el almacenamiento de energía
térmica mediante materiales de cambio de fase (PCM) concentra parte de la atención de
la comunidad científica por su gran potencial y versatilidad. En la presente Tesis se
cubren las principales metodologías experimentales empleadas en el estudio y la
creación de los PCM, incluyendo resultados experimentales para respaldar su validez.The creation of more sustainable energy generation and management systems remains
a priority at both European and international levels, as shown by projects such as
Horizon Europe, the Sustainable Development Goals (SDGs) or the initiatives of the
International Energy Agency (IEA). While renewable energies hold a key role in this
energy transition, other complementary techniques are also being developed to
compensate for some of their disadvantages, such as intermitent supply or the
decoupling of energy generation and consumption. Thus, energy storage becomes
indispensable, including Thermal Energy Storage (TES). Thermal energy storage by
means of Phase Change Materials (PCM) is particularly receiving a great deal of atention
from the scientific community due to its great potential and versatility. The present
Thesis covers the main experimental methodologies employed in the study and creation
of PCMs, including experimental results to support their validity.El desarrollo de esta Tesis se enmarca en las actividades realizadas por la Red Española
de Almacenamiento de Energía Térmica (RedTES), que ha sido financiada de nuevo
recientemente para los próximos años (ayuda RED2022-134219-T) por la Agencia Estatal
de Investigación mediante las ayudas 2022 a “Redes de Investigación” en el marco del
Programa Estatal para Impulsar la Investigación Cientifico-Técnica y su Transferencia, del
Plan Estatal de Investigación Cientifica, Técnica y de Innovación 2021-2023. Quiero
agradecer profundamente a la RedTES toda la ayuda que me han brindado sus miembros,
tanto material como humana, sin la cual el desarrollo de esta Tesis no habría sido posible.
También quiero agradecer al Ministerio de Ciencia, Innovación y Universidades la
financiación obtenida estos años mediante una beca de Formación del Profesorado
Universitario (FPU), convocatoria 2018, que me ha permitido llevar a cabo todo el
trabajo realizado estos años
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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