1,065 research outputs found

    Using alcohol fuels in dual fuel operation of compression ignition engines: a review

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    Because of global warming and increasing air pollution, alternative fuels are increasingly being considered for use in internal combustion engines (ICEs). Among the alternatives, alcohol fuels seem very interesting. They can be produced in a renewable way and possess certain advantageous properties that give them the potential to lower pollutants and CO2 emissions from ICEs. Methanol and ethanol are the most researched alcohols today. In fact, in some areas of the world, gasoline is blended with methanol or ethanol for use in spark ignition (SI) engines. These alcohols are ideally suited for SI engines because of their high octane number (low tendency to knock). That makes them, however, not very well suited for compression ignition (CI) engines which require high cetane number fuels. There exist, however, CI engine technologies that burn alcohol fuels. One of these technologies is Dual Fuel (DF) operation. In DF operation, the engine runs effectively on two fuels. There exist several concepts to achieve this. One of these is to inject a mixture of diesel and alcohol fuel directly into the cylinder. Another is to separately inject diesel and alcohol fuel directly into the cylinder. A third concept (so-called fumigation) is to inject the alcohol fuel into the intake and the diesel directly into the cylinder (the homogeneous alcohol-air mixture is then ignited by a pilot injection of diesel). The paper will provide an overview of the literature regarding this fumigation concept. This work has been carried out as a part of the LeanShips project. LeanShips stands for 'Low Energy And Near-to-Zero emission Ships'. It is a Horizon 2020 (H2020) project funded by the European Commission aimed at developing green shipping technologies and bringing these to the market. One of the Work Packages of the LeanShips project, 'Demonstrating the Potential of Methanol as an Alternative Fuel' aims to demonstrate a high-speed heavy-duty marine diesel engine converted to Dual Fuel (DF) operation on methanol (and diesel) while achieving significant reductions of emitted pollutants

    Omtrent de Oostende-Doverlijn

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    Hydrotreating model catalysts : from characterization to kinetics

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    166 hlm.: ilus. ; tab. ; 24 cm

    The role of avoidance and learning behaviours on the formation and movement of biological aggregations

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    Communication forms the basis of any animal aggregation. However, not all organisms communicate the same way. Moreover, different psychological and physiological characteristics of individuals can lead to avoidance behaviours between different individuals. This can have implications on the formation and structure of large biological aggregations. In this article, we use a mathematical model to investigate the effects of avoidance behaviour by a subpopulation, on the spatial dynamics of the whole population. We show that avoidance (exhibited even by a small fraction of the population) can alter the spatio-temporal patterns of the whole groups, leading to new patterns difficult to predict from the case without avoidance. Generally, these patterns show the segregation of the populations into different aggregations (spatially separated) or inside the same aggregation. Moreover, we investigate numerically the situation where individuals can learn to tolerate their neighbours. In this case, we observe an unexpected spatial segregation inside moving aggregations of individuals that tolerate their neighbours and those that avoid their neighbours

    Enhanced catch-up growth after a challenge in animals on organic feed

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    A feeding experiment was performed in two generations of three groups of chickens with different immune responsiveness. All groups were fed identically composed feeds from either organic or conventional production. In the young animals of the second generation an immune challenge was imposed. The chickens fed conventional feed showed overall a higher weight gain, whereas feed intake of the groups was similar. The animals on organic feed showed an enhanced immune reactivity, a stronger reaction to the immune challenge, as well as an enhanced ’catch-up-growth’ after the challenge

    L'influence du gouvernement d'entreprise et du co-commissariat aux comptes sur la détermination des honoraires d'audit des sociétés cotées françaises

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    Notre recherche a pour but, en utilisant des information disponibles grâce à la publication des honoraires d'audit par une partie des entreprises cotées françaises, de tester un modèle de déterminants des honoraires d'audit intégrant l'influence des caractéristiques spécifiques du co-commissariat aux comptes à la française. En accord avec les recherches antérieures, nous contrôlons que les honoraires d'audit sont positivement liés avec la taille, la complexité de l'entreprise, et la cotation sur un marché anglo-saxon (Londres ou New York). Notre recherche montre que les mécanismes de gouvernement d'entreprise contribuent à renforcer le contrôle exercé par les auditeurs et que le pourcentage d'administrateurs indépendants se traduit par une augmentation des honoraires d'audit. Enfin, concernant le co-commissariat aux comptes, nos résultats mettent en évidence une double prime aux BIG 4 dans le contexte français et confirment que la fourniture de services autres que l'audit entraîne une augmentation des honoraires d'audit légaux.Honoraires d'audit ; commissariat aux comptes; gouvernement d'entreprise

    Les déterminants de la publication volontaire des honoraires d'audit par les sociétés cotées françaises en 2002 et 2003

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    En France, à partir de 2002 et avant l'élargissement de l'obligation de publication des honoraires d'audit pour l'ensemble des sociétés faisant appel public à l'épargne en 2005, seules certaines sociétés avaient l'obligation de publier cette information. Dans ce contexte, certaines sociétés cotées ont choisi de publier les honoraires d'audit de façon volontaire. Comme l'objectif de cette réglementation est de révéler la nature du lien (économique) existant entre l'entreprise auditée et ses commissaires aux comptes, nous nous sommes interrogés sur les déterminants de cette publication volontaire. En utilisant la théorie de l'agence et la théorie du signal, ce papier teste l'hypothèse d'une publication volontaire de honoraires d'audit destinée à signaler la qualité des états financiers et à réduire les coûts d'agence et l'asymétrie d'information. Les résultats montrent que la publication volontaire des honoraires d'audit est une réponse à des coûts d'agence élevés et est renforcée par la présence d'auditeurs BIG4.Publication volontaire; honoraires d'audit

    Amélioration de sols polderiens à mauvaise structure par labour profond

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    In the Belgian marsh-area many soils have a bad surface-structure. Their top soil is non-calcareous, while the subsoil presents a considerable amount of lime. In many cases an impermeable claylayer is found at a depth of 30-40 cm. After heavy rainfalls these soils show a strong degradation of the structure. The topsoil is muddy, with a typical shiny appearance and the seeds do not run out or only partially. These soils can be improved by deep- ploughing to 50-100 cm, given that the calcareous subsoil is brought to the surface. After this process had been successfully applied in 1952 as a field experiment, there was no decrease of yield. In 1955 the yield had increased with 8 %. The soil had become more productive and the new topsoil needed no more liming
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