References of "Marchot, Pierre"
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See detailComparison of hydrodynamic parameters obtained by 2D measurements in a flat rectangular column with X-ray radiography and data from literature on 3D columns
Calvo, Sébastien ULg; Beugre, Djomice Antoine ULg; Crine, Michel ULg et al

Poster (2010)

Hydrodynamic tests are performed in a flat rectangular column packed with two sheets of Mellapak 250 Y (Sulzer structured packing). Measurements are realized with a single phase liquid flow as well as ... [more ▼]

Hydrodynamic tests are performed in a flat rectangular column packed with two sheets of Mellapak 250 Y (Sulzer structured packing). Measurements are realized with a single phase liquid flow as well as with a gas-liquid counter-current flow. Hydrodynamic parameters are compared to experimental results obtained in 3D columns found in the literature, as well as to literature model predictions and to values computed using an in-house Lattice Boltzmann CFD simulation code. [less ▲]

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See detailX-ray CT study of the influence of liquid viscosity on fluid phase distribution in modular catalytic packings
Aferka, Saïd ULg; Viva, Aurora; Toye, Dominique ULg et al

in AIDIC Conference series (2010), 10

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an ... [more ▼]

In the frame of the present study, the influence of liquid viscosity on liquid holdup distribution in a packed column equipped with the modular catalytic packing Katapak-SP 11 is measured. Water and an aqueous solution of glycerine, the viscosity of which equals 10 cP, are used as feed liquids. The estimation of liquid holdup is of great interest due to its strong influence on pressure drop, on solid wetting and on heat and mass transfer coefficients. The experimental technique used is high energy X-ray tomography, which is a unique technique to visualize the local liquid distribution inside the complex structure of packings and to quantify the liquid holdup at different scales. [less ▲]

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See detailMeasurement of liquid hold-up in catalytic structured packings: comparison of different experimental techniques
Viva, Aurora ULg; Aferka, Saïd ULg; Toye, Dominique ULg et al

in de Haan, A. B.; Kooijman, H.; Gorak, A. (Eds.) Proceedings of 9th Distillation and Absorption Conference (DA2010), Eindhoven, Pays-Bas, 12-15 septembre 2010 (2010)

This paper presents the results of an experimental study carried out to examine liquid hold-up in 100 mm diameter catalytic structured packing Katapak-SP. Two versions of the packing have been ... [more ▼]

This paper presents the results of an experimental study carried out to examine liquid hold-up in 100 mm diameter catalytic structured packing Katapak-SP. Two versions of the packing have been investigated. Both global and local measurements were carried out on the very same packings, using water at ambient conditions as working liquid. To this scope, traditional methods like draining techniques were used to obtain global hold-up values. A non-intrusive high energy X-ray tomography was used for gathering information on local scale and study axial distribution of the liquid hold-up over the packed column, inside and outside the catalyst containing baskets. The total liquid hold-up of the catalytic packed bed was evaluated by averaging hold-up values obtained at different cross sections over the corresponding volume. Very good agreement was found between global values estimated with the different techniques. The experimental results are useful for supporting theoretical developments in hydrodynamic and mass transfer modeling. [less ▲]

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See detailLiquid hold-up measurement in Mellapak Plus 752Y packed bed using X-ray tomography
Aferka, Saïd ULg; Viva, Aurora ULg; Brunazzi, Elisabetta et al

in VCIPT (Ed.) Proceedings of 6th World Congress On Industrial Process Tomography (WCIPT6), Beijing, China, 6-9 Septembre 2010 (2010)

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See detailInfluence of the viscosity on liquid hold-up in modular catalytic packings
Aferka, Saïd ULg; Viva, Aurora ULg; Brunazzi, Elisabetta et al

Conference (2010)

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See detailInterfacial area measurement in a catalytic distillation packing using high energy x-ray CT
Aferka, Saïd ULg; Marchot, Pierre ULg; Crine, Michel ULg et al

in Chemical Engineering Science (2010), 65(1), 511-516

In this paper, we report on the use of X-ray tomography to visualize and quantify the gas–liquid interfacial area in modular catalytic distillation packing elements. The calculation method is based on ... [more ▼]

In this paper, we report on the use of X-ray tomography to visualize and quantify the gas–liquid interfacial area in modular catalytic distillation packing elements. The calculation method is based on processing of tomographic images. It is validated by comparing specific surface area determined on dry packings (Mellapak™ 752Y and Katapak™ SP12) tomographic binary images (gas and solid) to values announced by manufacturers, based on geometrical considerations. These data agree fairly well. However, tomographic images show that the specific area is not distributed uniformly over the height of a packing element due to the presence of perforations in corrugated sheets and of wall wipers between the packing and the column wall. X-ray tomography is a unique technique to access to the spatial distribution of these geometrical details in a non-intrusive way. The method used to determine the specific surface area of dry packing is then applied to irrigated packing in order to determine the gas–liquid interfacial area. The axial distribution of the interfacial area is non-uniform and is correlated to the packing specific area. The maxima of the specific surface area correspond to the presence of wall wipers. The gas–liquid interfacial area averaged over the column length is determined. It increases logically with the liquid superficial velocity and slightly with the gas velocity. The effect of the gas velocity is however more pronounced when reaching loading point. [less ▲]

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See detailLiquid load point measurement in a reactive distillation packing by x-ray tomography
Aferka, Saïd ULg; Viva, Aurora ULg; Brunazzi, Elisabetta et al

Poster (2009, August)

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See detail3D characterisation of the structure of activated carbon packed beds using X-ray microtomography
Almazan, Maria del Carmen; Léonard, Angélique ULg; López-Garzón, J. et al

in 3rd International Workshop on Process Tomography (CD Rom) (2009, April)

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See detailDistributed Dynamic Load Balancing for Iterative-Stencil Applications
Dethier, Gérard ULg; Marchot, Pierre ULg; de Marneffe, Pierre-Arnoul ULg

in Cracow Grid Workshop '08 Proceedings (2009, March)

In the context of jobs executed on heterogeneous clusters or Grids, load balancing is essential. Indeed, a slow machine must receive less work than a faster one otherwise the overall job termination will ... [more ▼]

In the context of jobs executed on heterogeneous clusters or Grids, load balancing is essential. Indeed, a slow machine must receive less work than a faster one otherwise the overall job termination will be delayed. This is particularly true for Iterative-Stencil Applications where tasks are run simultaneously and are interdependent. The problem of assigning coexisting tasks to machines is called mapping. With dynamic clusters (where the number of machines and their available power can change over time), dynamic mapping must be used. A new mapping must be calculated each time the cluster changes. The mapping calculation must therefore be fast. Also, a new mapping should be as close as possible to the previous mapping in order to minimize task migrations. Dynamic mapping methods exist but are based on iterative optimization algorithms. Many iterations are required to reach convergence. In the context of a distributed implementation, many communications are needed. We developed a new distributed dynamic mapping method which is not based on iterative optimization algorithms. Current results are encouraging. Load balancing execution time remains bounded for tested cluster sizes. Also, a decrease of ~20% of the global available computational power of a cluster leads to ~30% of migrated tasks during load rebalancing. A new mapping is therefore close to the previous one. [less ▲]

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See detailLattice Boltzmann 3D flow simulations on a metallic foam
Beugre, Djomice Antoine ULg; Calvo, Sébastien ULg; Dethier, Gérard ULg et al

in Journal of Computational & Applied Mathematics (2009)

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See detailSimulation de l’écoulement dans des filtres à charbons actifs par la méthodologie des réseaux de Boltzmann
Verdin, Emeline ULg; Beugre, Djomice Antoine ULg; Ania, Conchi et al

in SFGP (Ed.) Récents Progrès en Génie des Procédés - N°98 - A la croisée des sciences et des cultures pour relever les défis industriels du XXIème siècle - Actes du 12ème Congrès de la Société Française de Génie des Procédés, Marseille, France, 14-16 octobre 2009 (2009)

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See detailPositively Cooperative Binding of Zinc Ions to Bacillus cereus 569/H/9 beta-Lactamase II Suggests that the Binuclear Enzyme Is the Only Relevant Form for Catalysis
Jacquin, Olivier ULg; Balbeur, Dorothée ULg; Damblon, Christian ULg et al

in Journal of Molecular Biology (2009), 392(5), 1278-1291

Metallo-beta-lactamases catalyze the hydrolysis of most beta-lactam antibiotics and hence represent a major clinical concern. While enzymes belonging to subclass B1 have been shown to display maximum ... [more ▼]

Metallo-beta-lactamases catalyze the hydrolysis of most beta-lactam antibiotics and hence represent a major clinical concern. While enzymes belonging to subclass B1 have been shown to display maximum activity as dizinc species, the actual metal-to-protein stoichiometry and the affinity for zinc are not clear. We have further investigated the process of metal binding to the beta-lactamase H from Bacillus cereus 569/H/9 (known as BcII). Zinc binding was monitored using complementary biophysical techniques, including circular dichroism in the far-UV, enzymatic activity measurements, competition with a chromophoric chelator, mass spectrometry, and nuclear magnetic resonance. Most noticeably, mass spectrometry and nuclear magnetic resonance experiments, together with catalytic activity measurements, demonstrate that two zinc ions bind cooperatively to the enzyme active site (with K-1/K-2 >= 5) and, hence, that catalysis is associated with the dizinc enzyme species only. Furthermore, competitive experiments with the chromophoric chelator Mag-Fura-2 indicates K-2 < 80 nM. This contrasts with cadmium binding, which is clearly a noncooperative process with the mono form being the only species significantly populated in the presence of 1 molar equivalent of Cd(II). Interestingly, optical measurements reveal that although the apo and dizinc species exhibit undistinguishable tertiary structural organizations, the metal-depleted enzyme shows a significant decrease in its alpha-helical content, presumably associated with enhanced flexibility. (C) 2009 Elsevier Ltd. All rights reserved. [less ▲]

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See detailPhase distribution measurements in metallic foam packing using X-ray radiography and micro-tomography
Calvo, Sébastien ULg; Beugre, Djomice Antoine ULg; Crine, Michel ULg et al

in Chemical Engineering & Processing (2009), 48(5), 1030-1039

Some structural and hydrodynamic properties of RCM-NCX-1116, a Ni-Cr metallic foam packing manufactured by Recemat International B.V (The Netherlands) are investigated using X-ray radiography and X-ray ... [more ▼]

Some structural and hydrodynamic properties of RCM-NCX-1116, a Ni-Cr metallic foam packing manufactured by Recemat International B.V (The Netherlands) are investigated using X-ray radiography and X-ray micro-tomography. Local values of porosity and pore diameters are measured on a foam sample 3D image obtained with a Skyscan-1172 high-resolution desk-top micro-CT system operated at 100 kV. Structural parameters computed on tomography images agree well with manufacturer data. Hydrodynamic tests are performed in a flat rectangular column packed with a sheet of metallic foam packing. Measurements are realized with a single-phase flow of liquid as well as with a counter-current flow of gas and liquid. Dynamic and static liquid holdup distributions and liquid radial spreading coefficient are measured on 2D radiographic images of the bed obtained with the high energy large scale ULG 420 kV scanner operated in the radiographic mode at 420 kV. Pressure drop measurements are successfully compared to experimental results reported in literature, as well as to the literature model predictions and to values computed using an in-house Lattice Boltzmann CFD simulation code. (C) 2009 Elsevier B.V. All rights reserved. [less ▲]

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See detailSimulations of Structures in Packed Columns and Validation by X-ray Tomography
Caulkin, R.; Jia, X.; Xu, C. et al

in Industrial & Engineering Chemistry Research (2009), 48(1), 202-213

Packing simulations of generic, nonspherical pellets were performed and compared with experimental data sets obtained using X-ray Computerized tomography (CT). Two modified versions of what was previously ... [more ▼]

Packing simulations of generic, nonspherical pellets were performed and compared with experimental data sets obtained using X-ray Computerized tomography (CT). Two modified versions of what was previously a purely geometrical, digitally based packing algorithm were implemented. Both are aimed at incorporating the effects of particle interaction forces, one utilizing the distinct element method (DigiDEM) and the other an intermediate solution (collision-guided packing or DigiCGP). This article summarizes the models and the simulations performed using these two modified versions of DigiPac and, for model validation purposes, compares the predicted results with the corresponding X-ray tomographic scans of packed columns, in terms of bulk density, local packing density profiles, and pellet orientation distributions. For packed beds of relatively large and identical pellets, the simulation results indicate that particle-particle and particle-wall interactions cannot be ignored if realistic packing structures are to be obtained by simulation and even a simplistic treatment of these interactions can produce significantly more realistic packing structure than none at all. [less ▲]

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See detailLBG-SQUARE - Fault Tolerant, Locality-Aware Co-allocation in P2P Grids
Dethier, Gérard ULg; Briquet, Cyril ULg; Marchot, Pierre ULg et al

in Huang, Zhiyi; Xu, Zhiwei; Rountree, Nathan (Eds.) et al Ninth International Conference On Parallel And Distributed Computing, Applications And Technologies : PDCAT 2008 (2008, December)

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily ... [more ▼]

In this paper, the deployment and execution of Iterative Stencil applications on a P2P Grid middleware are investigated. So-called Iterative Stencil applications are composed of sets of heavily-communicating, long-running Tasks. They thus require co-allocation of multiple reliable resources for extended periods of time. P2P Grids are totally decentralized and provide on-demand, transparent access to edge resources, e.g. Internet-connected, non-dedicated desktop computers. A P2P Grid has the potential to provide access to a large number of resources at the fraction of the cost of a dedicated cluster. However, edge resources are heterogeneous in performance and intrinsically unreliable: Task execution failures are common due to resource preemption or resource failure. Furthermore, P2P Grid schedulers usually target sets of independent computational Tasks, i.e. so-called Bags of Tasks applications. It is therefore not trivial to deploy and run an Iterative Stencil application on a P2P Grid. Checkpointing is a common fault-tolerance mechanism in High Performance Distributed Computing, often based on a centralized architecture. Locality-aware co-allocation in P2P Grids has been recently investigated. Checkpointing and locality-aware co-allocation yet have to be integrated in P2P Grids. We propose to provide co-allocation through an existing middleware-level Bag of Tasks scheduling mechanism. We also introduce a layer of fault-tolerance for the Iterative Stencils that relies on a scalable, application-level, P2P checkpointing mechanism. Finally, LBG-SQUARE is described. This software results from the combination of a specific Iterative Stencil application (a Computational Fluid Dynamics simulation software called LaBoGrid) with a P2P Grid middleware (Lightweight Bartering Grid). [less ▲]

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See detailArchitecture of a Grid-Enabled Lattice-Boltzmann Middleware
Dethier, Gérard ULg; Marchot, Pierre ULg; de Marneffe, Pierre-Arnoul ULg

Poster (2008, May)

Lattice-Boltzmann (LB) simulation methods constitute a family of computational fluid dynamics methods that can deal with complex multiphysics models and are easily parallelizable. They are based on ... [more ▼]

Lattice-Boltzmann (LB) simulation methods constitute a family of computational fluid dynamics methods that can deal with complex multiphysics models and are easily parallelizable. They are based on modified lattice-gas automata. The algorithm of LB simulations is quite simple. Space is discretized into a lattice. Each node of this lattice has a state. This state indicates the proportion of particules moving along fixed directions (these proportions are generally called “fields”). At each time step, the state of all lattice nodes is updated. Each node first receives fields coming from its neighbors and then “collides” them by applying a collision operator which generates the new state. Grid computing can be defined as “coordinated resource sharing and problem solving in dynamic, multi-institutional collaborations”. In practice, a Grid user (which can be a software component) submits a job composed of tasks to the Grid. The tasks are automatically run on available computational resources across organizational boundaries (i.e. clusters of multiple departments). LaBoGrid is an application combining the concepts of LB modelling and Grid computing. It is able to run LB simulations on an arbitrary number of computational resources from a Grid. It deals with operating system and hardware performance heterogeneity. The former because LaBoGrid is written in Java. The latter thanks to load-balancing. This is essential because all LaBoGrid tasks are inter- connected and depend on information from one another. A slow LaBoGrid task will slow down the overall process. LaBoGrid is based on asynchronous agents exchanging messages. The two main agents are the Controller agent (CA) and the distributed agent (DA). In a deployed LaBoGrid system, the CA exists in only one instance. It keeps track of the DAs and their topology. A task agent running some arbitrary code can be attached to the CA (CAT) and the DAs (DAT). In LaBoGrid, LB-specialized task agents are used (this system could be adapted to other problems). A configuration file parsed by the LB CAT gives the parameters of an LB simulation. The LB CAT configures automatically the LB DATs which handle the simulation code. Currently, LB simulations are done on 3D fluids with 19 fields per state. However, the code can be adapted very easily to other fluid dimensions and different state definitions, storage and computation precisions and collision types. [less ▲]

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See detailInfluence of Back Mixing on the Convective Drying of Residual Sludges in a Fixed Bed
Léonard, Angélique ULg; Meneses, Eustedio; Le Trong, Emmanuel et al

in Water Research (2008), 42(10-11), 2671-2677

The influence of a backmixing operation on the convective belt drying of two wastewater sludges was studied. The expansion of the sludge extrudates bed due to increasing additions of dry product was ... [more ▼]

The influence of a backmixing operation on the convective belt drying of two wastewater sludges was studied. The expansion of the sludge extrudates bed due to increasing additions of dry product was quantified by using X-ray tomography. This non-invasive technique was used to determine the bed porosity and the total exchange area available for heat and mass transfers, for increasing levels of backmixing. For a same drying flux, the expansion of the drying bed leads to higher drying rates, allowing a reduction of the total drying time. In this context, rheological properties of the sludges are key properties. [less ▲]

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See detailIn situ observation of wall effects in activated carbon filters by X-ray microtomography
Léonard, Angélique ULg; Wullens, Hilda; Blacher, Silvia ULg et al

in Separation & Purification Technology (2008), 64(1), 127-130

X-ray microtomography is a powerful non-invasive visualisation technique which can be advantageously used to get a better understanding or dynamic adsorption processes. In the present work, this technique ... [more ▼]

X-ray microtomography is a powerful non-invasive visualisation technique which can be advantageously used to get a better understanding or dynamic adsorption processes. In the present work, this technique is shown to be able to detect wall effects during the dynamic adsorption of methyl iodide on activated carbon filters. The analysis of transversal cross-sections along the filter height clearly shows the existence of radial concentration profiles. These radial adsorption profiles are directly linked to velocity profiles due to a higher permeability at the wall. Obtaining Such in situ information constitutes a real progress in order to validate simulation models allowing predicting reliable breakthrough times. (C) 2008 Elsevier B.V. All rights reserved. [less ▲]

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See detailApplications de la microtomographie à rayons X en génie des procédés
Léonard, Angélique ULg; Toye, Dominique ULg; Marchot, Pierre ULg et al

Scientific conference (2007, November)

Detailed reference viewed: 32 (8 ULg)