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See detailThree-stage autoignition of gasoline in an HCCI engine: An experimental and chemical kinetic modeling investigation
Machrafi, Hatim ULg; Cavadias, Simeon

in Combustion & Flame (2008), 155(4), 557-570

The alternative HCCI combustion mode presents a possible means for decreasing the Pollution with respect to conventional gasoline or diesel engines, while maintaining the efficiency of a diesel engine or ... [more ▼]

The alternative HCCI combustion mode presents a possible means for decreasing the Pollution with respect to conventional gasoline or diesel engines, while maintaining the efficiency of a diesel engine or even increasing it. This paper investigates the possibility Of using gasoline in an HCCI engine and analyzes the autoignition of gasoline in such an engine. The compression ratio that has been used is 13.5, keeping the inlet temperature at 70 degrees C, varying the equivalence ratio from 0.3 to 0.54, and the EGR (represented by N-2) ratio from 0 to 37 vol%. For comparison, a PRF95 and a Surrogate containing 11 vol% n-heptane, 59 vol% iso-octane, and 30 vol% toluene are used. A previously validated kinetic surrogate mechanism is Used to analyze the experiments and to yield possible explanations to kinetic phenomena. From this work, it seems quite possible to use the high octane-rated gasoline for autoignition purposes, even Under lean inlet conditions. Furthermore, it appeared that gasoline and its Surrogate, unlike PRF95, show a three-stage autoignition. Since the PRF95 does not contain toluene, it is Suggested by the Kinetic mechanism that the benzyl radical, issued from toluene, causes this so-defined "obstructed preignition" and delaying thereby the final ignition for gasoline and its surrogate. The results of the kinetic mechanism supporting this explanation are shown in this paper. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved. [less ▲]

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See detailAn experimental and numerical investigation on the influence of external gas recirculation on the HCCI autoignition process in an engine: Thermal, diluting, and chemical effects
Machrafi, Hatim ULg; Cavadias, Simeon; Guibert, Philippe

in Combustion & Flame (2008), 155(3), 476-489

In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of ... [more ▼]

In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of particular interest. Experiments performed with EGR present some difficulties in interpreting results using only the diluting and thermal aspect of EGR. Lately, the chemical aspect of EGR is taken more into consideration, because this aspect causes a complex interaction with the dilution and thermal aspects of EGR. This paper studies the influence of EGR on the autoignition process and particularly the chemical aspect of EGR. The diluents present in EGR are stimulated by N-2 and CO2, with dilution factors going from 0 to 46 vol%. For the chemically active species that could be present in EGR, the species 0 and 170 ppm, while that of CH2O alters between 0 and 1400 ppm. For the investigation of the effect of the chemical species on the autoignition, a fixed dilution factor of 23 vol% and a fixed EGR temperature of 70 degrees C are maintained. The inlet temperature is held at 70 degrees C, the equivalence ratios between 0.29 and 0.41, and the compression ratio at 10.2. The fuels used for the autoignition are n-heptane and PRF40. It appeared that CO, in the investigated domain, did not influence the ignition delays, while NO had two different effects. At concentrations up until 45 ppm, NO advanced that ignition delays for the PRF40 and at higher concentrations, the ignition delayed. The influence of NO on the autoignition of n-heptane seemed to be insignificant, probably due to the higher burn rate of n-heptane. CH2O seemed to delay the ignition. The results suggested that especially the formation of OH radicals or their consumption by the chemical additives determines how the reactivity of the autoignition changed. (C) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved. [less ▲]

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See detailAn experimental and numerical analysis of the influence of the inlet temperature, equivalence ratio and compression ratio on the HCCI auto-ignition process of Primary Reference Fuels in an engine
Machrafi, Hatim ULg; Cavadias

in Fuel Processing Technology (2008), 89(11), 1218-1226

In order to understand better the auto-ignition process in an HCCI engine, the influence of some important parameters on the auto-ignition is investigated. The inlet temperature, the equivalence ratio and ... [more ▼]

In order to understand better the auto-ignition process in an HCCI engine, the influence of some important parameters on the auto-ignition is investigated. The inlet temperature, the equivalence ratio and the compression ratio were varied and their influence on the pressure, the heat release and the ignition delays were measured, The inlet temperature was changed from 25 to 70 degrees C and the equivalence ratio from 0.18 to 0.41, while the compression ratio varied from 6 to 13.5. The fuels that were investigated were PRF40 and n-heptane. These three parameters appeared to decrease the ignition delays, with the inlet temperature having the least influence and the compression ratio the most. A previously experimentally validated reduced surrogate mechanism, for mixtures of n-heptane, iso-octane and toluene, has been used to explain observations of the auto-ignition process. The same kinetic mechanism is used to better understand the underlying chemical and physical phenomena that make the influence of a certain parameter change according to the operating conditions. This can be useful for the control of the auto-ignition process in an HCCI engine. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailAn experimental and numerical analysis of the HCCI auto-ignition process of primary reference fuels, toluene reference fuels and diesel fuel in an engine, varying the engine parameters
Machrafi, Hatim ULg; Cavadias, Simeon; Gilbert, Philippe

in Fuel Processing Technology (2008), 89(11), 1007-1016

For a future HCCI engine to operate under conditions that adhere to environmental restrictions, reducing fuel consumption and maintaining or increasing at the same time the engine efficiency, the choice ... [more ▼]

For a future HCCI engine to operate under conditions that adhere to environmental restrictions, reducing fuel consumption and maintaining or increasing at the same time the engine efficiency, the choice of the fuel is crucial. For this purpose, this paper presents an auto-ignition investigation concerning the primary reference fuels, toluene reference fuels and diesel fuel, in order to study the effect of linear alkanes, branched alkanes and aromatics on the auto-ignition. The auto-ignition of these fuels has been studied at inlet temperatures from 25 to 120 degrees C, at equivalence ratios from 0.18 to 0.53 and at compression ratios from 6 to 13.5, in order to extend the range of investigation and to assess the usability of these parameters to control the auto-ignition. It appeared that both iso-octane and toluene delayed the ignition with respect to n-heptane, while toluene has the Strongest effect. This means that aromatics have higher inhibiting effects than branched alkanes. In an increasing order, the inlet temperature, equivalence ratio and compression ratio had a promoting effect on the ignition delays. A previously experimentally validated reduced surrogate mechanism, for mixtures of n-heptane, iso-octane and toluene, has been used to explain observations of the auto-ignition process. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailPlace et rôle de l´éducateur physique dans la société contemporaine
Cloes, Marc ULg

in Antala, Branislav (Ed.) Školská telesná výchova z pohľadu výsledkov vedeckého výskumu (2008)

Le terme "éducateur physique" est une expression tirée du vocabulaire québecois. Il provient des institutions universitaires ayant proposé cette dénomination afin d'identifier leurs programmes de ... [more ▼]

Le terme "éducateur physique" est une expression tirée du vocabulaire québecois. Il provient des institutions universitaires ayant proposé cette dénomination afin d'identifier leurs programmes de formation dans le domaine de la motricité humaine. En partant principalament du contexte spécifique de la Communauté française de Belgique, nous nous attachons à identifier les missions des éducateurs sportifs et à déterminer l'impact de leur action. Nous cloturerons cette analyse en proposant quelques pistes d'action susceptibles d'améliorer la qualité de leur travail. ... [less ▲]

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See detailIs there a difference in hypertension screening and care in urban population vs rural company in the Democratic Republic of Congo (DRC)?
Sumali, E. K.; Nseka, N. M.; Zinga, C. V. et al

in Hypertension (2008), 26

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See detailSupports visuels réalisés dans le cadre des travaux pratiques de Chimie Analytique (Partie II)
Ziemons, Eric ULg; Lejeune, Robert ULg; Hubert, Philippe ULg

Learning material (2008)

Plusieurs vidéos (étalonnage des pipettes, argentimétrie: méthode de Fajans et argentimétrie: méthode de Mohr) illustrent les manipulations des travaux pratiques de 2ème Baccalauréat en Sciences ... [more ▼]

Plusieurs vidéos (étalonnage des pipettes, argentimétrie: méthode de Fajans et argentimétrie: méthode de Mohr) illustrent les manipulations des travaux pratiques de 2ème Baccalauréat en Sciences pharmaceutiques. [less ▲]

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See detailCaprice-Revue. Avant la norme.
Paques, Frédéric ULg

in Art&Fact (2008), 28

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See detailCytochemical and immunocytological study of the reptilian nucleolus
Lamaye, Françoise; Thiry, Marc ULg

Poster (2008)

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See detailInverse analysis in geotechnics: soil parameter identification by genetic algorithm
Levasseur, Séverine ULg; Malécot, Yann; Boulon, Marc et al

in 8th. World Congress on Computational Mechanics (WCCM8) & 5th. European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) (2008)

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See detailLe lexique des lieux de culte dans la Périégèse de Pausanias
Pirenne-Delforge, Vinciane ULg

in Archiv für Religionsgeschichte (2008), 10

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See detailP. H. Liotta, the Graveyard of Fallen Monuments
Delville, Michel ULg

in Sentence: A Journal of Prose Poetics (2008), 7

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See detailMorton Marcus, Pursuing the Dream Bone
Delville, Michel ULg

in Sentence: A Journal of Prose Poetics (2008), 7

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See detailPrise de décision en handball : point de vue interne des joueuses et externe du coach
Lenzen, Benoît; Theunissen, Catherine ULg; Cloes, Marc ULg

in Wallian, N.; Poggi, M. P.; Musard, E. (Eds.) Co-construire des savoirs: les métiers de l’intervention dans les APSA. Actes du colloque (2008)

Dans les sports collectifs, l’idée que le coach est le plus à même d’analyser le jeu depuis le bord du terrain et de décider des choix tactiques de ses joueurs est largement répandue. Vraie ou fausse ... [more ▼]

Dans les sports collectifs, l’idée que le coach est le plus à même d’analyser le jeu depuis le bord du terrain et de décider des choix tactiques de ses joueurs est largement répandue. Vraie ou fausse, elle pose la question de la dualité des points de vue interne des joueurs et externe du coach. Pour établir cette comparaison, nous avons soumis six joueuses de handball de haut niveau à des entretiens d’autoconfrontation portant sur des séquences vidéo enregistrées lors de deux matches de championnat. Parallèlement, nous avons utilisé la technique de « film occlusion » (Debanne, 2003) consistant à projeter ces séquences au coach en les interrompant juste avant l’action. Les tentatives du coach de prédire les choix tactiques opérés par ses joueuses se sont soldées par 15 propositions correctes contre 6 erronées. La comparaison des points de vue interne des joueuses et externe du coach est illustrée par quatre situations distinctes : prédictions (a) correcte d’une action négative ; (b) correcte d’une action positive ; (c) incorrecte d’une action négative ; et (d) incorrecte d’une action positive. La discussion souligne les convergences et les divergences entre ces deux points de vue, en insistant plus particulièrement sur les conséquences des divergences. [less ▲]

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See detailLa notion de « populaire » est-elle applicable au polythéisme grec ?
Pirenne-Delforge, Vinciane ULg

in Bobas, C.; Evangelidis, E.; Milioni, T. (Eds.) et al Croyances populaires. Rites et représentations en Méditerranée orientale. Actes du Colloque de Lille (2-4 décembre 2004) (2008)

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See detailOntogenetic shape changes in Pomacentridae (Teleostei, Perciformes) and their relationships with feeding strategies: a geometric morphometric approach
Frederich, Bruno ULg; Adriaens, Dominique; Vandewalle, Pierre ULg

in Biological Journal of the Linnean Society (2008), 95

The present study explores the shape changes of cranial structures directly involved in food capturing during growth after reef settlement in two species of Pomacentridae (Dascyllus aruanus and ... [more ▼]

The present study explores the shape changes of cranial structures directly involved in food capturing during growth after reef settlement in two species of Pomacentridae (Dascyllus aruanus and Pomacentrus pavo). Landmark-based geometric morphometrics were used to study allometric patterns and related shape changes in four skeletal units: neurocranium, suspensorium and opercle, mandible and premaxilla. At settlement, the larvae of both species have a relatively similar morphology, especially with respect to the mandible. Their shapes suggest a feeding mode defined as ram/suction-feeding. Ontogenetic shape changes show a shift to a suction feeding mode of prey capture. The main transformations involved are an increase in height of the suspensorium and the opercle, an elevation of the supraoccipital crest, a relative shortening of the mandible, and a lengthening of the ascending process of the premaxilla. Shape changes of the mandible in the two studied species also reflect an increase of biting capacities. The high disparity between adult shape results from differences in the rate and in the length of ontogenetic trajectories, from divergence of the ontogenetic trajectories (neurocranium, mandible, and premaxilla) and parallel shifts of the trajectories in the size-shape space (suspensorium and opercle). In an evolutionary context, allometric heterochronies during ontogeny of different skeletal unit of the head may be considered as a basis for the explanation of the diversity of damselfishes. [less ▲]

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See detailThe tropical sea anemone Aiptasia pallida as a lab model for the study of coral bleaching
Ladrière, Ophélie ULg; Roberty, Stéphane ULg; Baudesson, Charlotte et al

Poster (2008)

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone ... [more ▼]

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone Aiptasia pallida as experimental model for coral bleaching. Aiptasia appears as a good candidate as it is easy to maintain in aquarium and subjected to bleaching like corals. Both morphological and physiological approaches were performed to investigate the ultrastructure of the anemone tissues (TEM) and the zooxanthellae photophysiology (chlorophyll a fluorescence, respiration and pigmentation). Experiments under light and dark stress reveal that anemone tissues ultrastructure can be differently affected. In darkness, the ectoderm activity is reoriented to capture prey by increasing cnidocyte density. In contrast, intense light affects especially the gastroderm : intercellular spaces increase, the expulsion of intact algae in the gastric cavity and the degradation of zooxanthellae inside vacuoles seem to reduce the zooxanthellae density, chloroplast thylakoids lose their parallel arrangement. The analysis of the fluorescence induction curve appears as a powerful tool to analyse the physiological events series previous to bleaching. Although no significant zooxanthellae density reduction was observed, the decrease of pigments concentrations indicates that light or dark stresses induce anemone bleaching. Under strong light intensity, A. pallida zooxanthellae show an increased proportion of PSII QB non reducing, leading to partial photoinhibition. This phenomenon favours the ROS production that damages cellular structures of host and zooxanthellae. In darkness, there is no photosynthesis; anemones have therefore to find other feeding sources, as suggested by the ultrastructural approach. As the present results confirm some of those obtained on scleractinians, A. pallida can be regarded as a good model for coral bleaching studies and has numerous advantages for experimentation. [less ▲]

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