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See detailMultiphase flow from a civil engineering perspective
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2012, June)

For over 15 years, our research group at the University of Liege has been conducting basic and applied research on flow and transport phenomena involved in environmental and civil engineering applications ... [more ▼]

For over 15 years, our research group at the University of Liege has been conducting basic and applied research on flow and transport phenomena involved in environmental and civil engineering applications. The research topics cover a wide range of multiphase flow, including aerated flow and sediment-laden flow. The research group has developed the modelling system WOLF, which performs 1D, 2D-horizontal, 2D-vertical and 3D simulations of free surface and pressurized flow, coupled with air- or sediment-transport as well as morphodynamic simulations [9]. An original depth-averaged k- model is used to evaluate the eddy viscosity and diffusivity [5]. In a composite modelling approach [e.g., 2, 8], the numerical simulations have systematically been carried out in parallel with experimental research in flumes and scale models of hydraulic structures [3, 4, 7]. A particularly challenging issue in multiphase flow modelling is the need to handle accurately and efficiently a wide range of time scales involved in the relevant phenomena (e.g., sediment transport). Therefore, the modelling system provides a series of complementary numerical schemes designed to be combined for covering the whole range of relevant time scales. This presentation will provide examples of analysis of aerated flow, such as on stepped spillways and in penstocks [6], and of reservoir sedimentation. In particular, recent experimental findings have revealed that the flow pattern in rectangular shallow reservoirs is considerably modified at a macro-scale when suspended load is added to the flow [1]. This sudden change in flow pattern has been observed to take place quickly after the beginning of the experiment, so that it is very unlikely to result from morphodynamic changes of the reservoir bottom. Therefore, the numerical model WOLF has been used to investigate the effect of two other possible feedback mechanisms of sediment deposits and suspended load on the overall flow pattern, namely (i) increased bottom roughness and (ii) turbulence damping. From the simulations results, it can be argued that turbulence intensity is probably the main cause for the flow pattern to change at a macro-scale, as suspended load exerts a turbulence damping effect at a micro-scale in the two-phase flow (water-sediment mixture). Finally, the analysis of flow and sediment transport in shallow rectangular reservoirs also highlights the need, when structures are designed based on numerical simulations, to carefully check the stability of the computed flow fields needs by conducting sensitivity analyses, not only with respect to the modelling parameters but also with respect to the initial conditions. [less ▲]

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See detailA Multiphase Model for the Transport of Dispersed Phases in Environmental Flows: Theoretical Contribution
Kerger, François ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in European Journal of Mechanical and Environmental Engineering (2010), 3

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See detailMultiphase Saturation Curves of the Oxoglutarate Carrier : A mathematical Model
Holzhütter, H.-G.; Sluse-Goffart, C.; Sluse, Francis ULg

in Mathematical & Computer Modelling (1994), 19(6-8), 263-272

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See detailMultiphase time dependent compression behaviour of two chalks
De Gennaro, Vincenzo; Delage, Pierre; Priol, Grégoire et al

Conference (2005)

In this paper, the multiphase time dependent compression behaviour of two chalks are considered within a fully coupled general hydro-mechanical framework derived from the mechanics of unsaturated soil. In ... [more ▼]

In this paper, the multiphase time dependent compression behaviour of two chalks are considered within a fully coupled general hydro-mechanical framework derived from the mechanics of unsaturated soil. In the former case, reservoir chalks contain oil and water and subsidence appeared once enhanced oil recovery by waterflooding started. In the latter case, water saturated chalk is periodically desaturated by water evaporation, resulting in air penetration. In this paper, the fluid retention curves of both samples are determined and the data obtained are used in the interpretation of suction controlled compression tests where time effects appear to be significant. The experimental data obtained show the relevance of the approach adopted. [less ▲]

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See detailMultiphase Transient Flow and Pressures in Rock Joints due to High Velocity Jet Impact: an Experimental and Numerical Approach
Bollaert, Erik; Pirotton, Michel ULg; Schleiss, Anton

in International Symposium on Environmental Hydraulics (2001)

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See detailA Multiphycics approach to calculate shear stresses during neotissue growth in perfusion bioreactor
Guyot, Yann ULg; Papantoniou, Ioannis; Schrooten, Jan et al

Conference (2014, July)

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See detailMultiphysic topology optimization of electromechanical micro-actuators considering pull-in effect
Lemaire, Etienne ULg; Van Miegroet, Laurent ULg; Schoonjans, Thibaut et al

in Proceedings of the IVth European Conference on Computational Mechanics (ECCM 2010) (2010)

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See detailMultiphysic topology optimization of electromechanical microdevices considering pull-in voltage using an electrostatic force filter
Lemaire, Etienne ULg; Duysinx, Pierre ULg; Rochus, Véronique ULg

in Proceeding of the 8th World Congress on Structural and Multidisciplinary Optimization (2009)

Electrostatic actuation is often used in microsystems as it is relatively easy to implement and provides a short response time. However, because of the non-linearity of electrostatic forces, these devices ... [more ▼]

Electrostatic actuation is often used in microsystems as it is relatively easy to implement and provides a short response time. However, because of the non-linearity of electrostatic forces, these devices may suffer from an unstable behavior called pull-in effect. Previous work of the authors intended to delay pull-in effect by maximizing pull-in voltage studying a simplified problem where the optimization domain was purely mechanical. The present paper generalizes the approach by considering a multiphysic optimization domain. However, the generalization of the optimization problem is not straightforward as local pull-in modes appear after a few optimization iterations. Therefore, the paper investigates several solutions to prevent the appearance of local pull-in modes. [less ▲]

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See detailA Multiphysics model of neotissue growth in a perfu sion bioreactor
Guyot, Yann ULg; Papantoniou, Ioannis; Schrooten, Jan et al

Conference (2014, September)

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See detailMultiphysics modeling and optimization of mechatronic multibody systems
Samin, Jean-Claude; Bruls, Olivier ULg; Collard, Jean-François et al

in Multibody System Dynamics (2007), 18(3), 345-373

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are ... [more ▼]

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are currently proposed to deal with multiphysics modeling, e.g., graph theories, equational approaches, co-simulation techniques. Recent works have pointed out their relative advantages and drawbacks, depending on the application to deal with: model size, model complexity, degree of coupling, frequency range, etc. This paper is the result of a close collaboration between three laboratories, and aims at showing that for "non-academic" mechatronic applications (i.e., issuing from real industrial issues), multibody dynamics formulations can be generalized to mechatronic systems, for the model generation as well as for the numerical analysis phases. Model portability being also an important aspect of the work, they must be easily interfaced with control design and optimization programs. A global "demonstrator", based on an industrial case, is discussed: multiphysics modeling and mathematical optimization are carried out to illustrate the consistency and the efficiency of the proposed approaches. [less ▲]

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See detailMULTIPHYSICS MODELING OF CELL/MATRIX GROWTH ON 3D STRUCTURES.
Guyot, Yann ULg; Papantoniou, Ioannis; Chai, Yoke Chin et al

Conference (2013, August 26)

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See detailMultiphysics modeling of mechatronic multibody systems
Fisette, Paul; Bruls, Olivier ULg; Swevers, Jan

in Proceedings of ISMA 2006 (2006, September)

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are ... [more ▼]

Modeling mechatronic multibody systems requires the same type of methodology as for designing and prototyping mechatronic devices: a unified and integrated engineering approach. Various formulations are currently proposed to deal with multiphysics modeling, e.g. graph theories, equational approaches, co-simulation techniques. Recent works have pointed out their relative advantages and drawbacks, depending on the application to deal with: model size, model complexity, degree of coupling, frequency range, etc. This paper is the result of a close collaboration between three Belgian laboratories, and aims at showing that for "non-academic" mechatronic applications (i.e. issuing from real industrial issues), multibody dynamics formulations can be generalized to mechatronic applications, for the model generation as well as for the numerical analysis phases. Model portability being also an important aspect of the work, they must be easily interfaced with control design and optimization programs. A global "demonstrator", based on an industrial case, is discussed: multiphysics modeling, control design and mathematical optimization are carried out to illustrate the consistency and the efficiency of the proposed approaches. [less ▲]

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See detailMultiplane two-dimensional versus real time three-dimensional transesophageal echocardiography in ischemic mitral regurgitation.
Fattouch, K.; Castrovinci, S.; Murana, G. et al

in Echocardiography (2011)

OBJECTIVES: Intraoperative three-dimensional (3D) transesophageal echocardiography (TEE) has been suggested to be a valuable technique for the evaluation of the mechanisms of ischemic mitral regurgitation ... [more ▼]

OBJECTIVES: Intraoperative three-dimensional (3D) transesophageal echocardiography (TEE) has been suggested to be a valuable technique for the evaluation of the mechanisms of ischemic mitral regurgitation (IMR). Studies comparing multiplane two-dimensional (2D) with 3D TEE reconstruction of the mitral valve using the new mitral valve quantification (MVQ) software are lacking. We undertook a prospective comparison between multiplane 2D and 3D TEE for the assessment of IMR. METHODS: We evaluated echocardiographically 45 patients with IMR who underwent mitral valve surgery in our institution. 2D and 3D TEE examinations followed by a 3D offline assessment of the mitral valve apparatus were performed in all patients. Offline analysis of mitral valve apparatus was conducted with QLAB-MVQ. RESULTS: 3D TEE image acquisitions were performed in a short period of time and were feasible in all patients. Real time 3D TEE imaging was superior to 2D in identifying specific mitral scallops (A1, A3, P1, P3) and commissures. When compared with 2D TEE, 3D offline reconstruction of the mitral valve allows an accurate quantification of the shape and diameters of the mitral annulus. Both approaches provide almost similar values for the tenting area and the coaptation depth. The 3D approach gave the advantage of direct calculation of the leaflets angles, tenting volume, and surface of the leaflets. The interpapillary muscles distance at the level of the papillary muscle head was greater in 2D than in 3D. CONCLUSIONS: 3D TEE imaging provides valuable and complementary information to multiplane 2D TEE for the assessment of patients with IMR. [less ▲]

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See detailMultiple allosteric effectors control the affinity of DasR for its target sites
Tenconi, Elodie; Urem, Mia; Świątek-Połatyńska, Magdalena et al

in Biochemical and Biophysical Research Communications (2015)

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See detailMultiple analyses of microbial communities applied to the gut of the wood-feeding termite Reticulitermes flavipes fed on artificial diets
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

in Symbiosis (2015)

The purpose of this work was the observation of the differences between the microbial communities living in the gut of the termite Reticulitermes flavipes fed on different diets. The termites were fed on ... [more ▼]

The purpose of this work was the observation of the differences between the microbial communities living in the gut of the termite Reticulitermes flavipes fed on different diets. The termites were fed on poplar wood (original diet) and artificial diets consisting of crystalline cellulose (with and without lignin), α-cellulose (with and without lignin) and xylan. The termites were then dissected and the protist communities were analyzed through microscopy, leading to the conclusion that protist species are strongly influenced by diets. BIOLOG ECO Microplates® were used to assess the metabolic properties of the different types of consortia, highlighting strong differences on the basis of principal component analysis and calculation of similarity rates. The microorganisms were cultivated in liquid media corresponding to the artificial diets before being characterized through a metagenetic analysis of gut microbiota (16S ribosomal DNA). This analysis identified several phyla: Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Fibrobacteres, Firmicutes, Nitrospirae, OP9, Planctomycetes, Proteobacteria, Spirochaetes, TM6, Tenericutes, Verrucomicrobia and WS3. The OTUs were also determined and confirmed the abundance of Proteobacteria, Bacteroidetes, Firmicutes and Verrucomicrobia. It was possible to isolate several strains from the liquid media, and one bacterium and several fungi were found to produce interesting enzymatic activities. The bacterium Chryseobacterium sp. XAvLW produced α-amylase, β-glucosidase, endo-1,4-β-D-glucanase, endo-1,4-β-D-xylanase and filter paper-cellulase, while the fungi Sarocladium kiliense CTGxxyl and Trichoderma virens CTGxAviL generated the same activities added with endo-1,3-β-D-glucanase. [less ▲]

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See detailA multiple case study of verbal short-term memory in velo-cardio-facial syndrome
Majerus, Steve ULg; Glaser, B.; Van der Linden, Martial ULg et al

in Journal of Intellectual Disability Research (2006), 50(Pt 6), 457-469

Background: Velo-cardio-facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short-term memory (STM), a ... [more ▼]

Background: Velo-cardio-facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short-term memory (STM), a cognitive function critically involved in language development, in eight children with VCFS. Methods: Using a multiple case study design, we presented a series of STM tasks exploring immediate serial recall for word and non-word lists to eight children with VCFS (aged 8 - 12 years) and to chronological-age-matched control groups. A first task assessed the integrity of phonological coding in verbal STM by comparing recall for phonologically similar and dissimilar words. Subsequently, the interaction between verbal knowledge and STM capacity was investigated by comparing recall for high- and low-imageability words, for high- and low-frequency words, and for words and non-words. A final task assessed short-term serial order recognition for digit sequences. Results: When computing the number of items recalled in the word recall tasks, independently of their serial position, only one child presented consistent difficulties. Short-term recall of non-words was normal in each child. Phonological similarity and verbal knowledge influenced STM performance to a similar extent in children with VCFS and controls. On the other hand, when applying a strict serial recall criterion, difficulties with the word and non-word recall tasks were observed in most children. Half of the patients were also impaired in the serial order recognition task. Conclusions: Despite mild intellectual disability, it is possible for short-term retention capacities for verbal item information to be at an age-appropriate level in VCFS. However, STM for serial order information could be impaired more specifically. [less ▲]

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See detailMultiple changes in peptide and lipid expression associated with regeneration in the nervous system of the medicinal leech
Mériaux, Céline; Arafah, Karim; Tasiemski, Aurélie et al

in PLoS ONE (2011), 6(4), 18359

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See detailMultiple Citizenship at Stake: a Critical Assessment of the Croatian Citizenship Policy Towards National Minorities
Mazur Kumric, Nives ULg

in Mediterranean Journal of Social Sciences (2014), 5

The question of (multiple) citizenship of national minorities has been omnipresent in the intellectual and public discourse of the Republic of Croatia since the very beginnings of its independence in the ... [more ▼]

The question of (multiple) citizenship of national minorities has been omnipresent in the intellectual and public discourse of the Republic of Croatia since the very beginnings of its independence in the course of early 90s of the 20th century. The transition period of the post-socialism era marked the effort of political elites to establish a balance among the democratic and nationalist concepts of the Croatian statehood, whereat the repercussions of this clash reflected on both the definition of citizenship and the fate of national minorities. With its ethnocentric approach, the Croatian citizenship regime comes out of standard frameworks which define citizenship as a legal bond between the state and an individual, also adding a cultural and political dimension to the nexus in which citizenship frequently becomes an instrument of self-identification with ethnic Croats. The paper aims to shed light on the positioning of national minorities in such social constellations, accentuating the issue of their access to (multiple) citizenship and challenges they face thereof, as well as the inconsistent and selective nature of the Croatian citizenship policy towards different parts of its multi-ethnic corpus. This is primarily done through a concise analysis and interpretation of the Law on Croatian Citizenship – its evolution, core provisions and socio-political circumstances surrounding it. In that vein, the fundamental method used for scientific inquiry is legal dogmatic. The focus of the interest refers to the question to what extent the norms on multiple citizenship accommodate the needs of national minorities, help them preserve their peculiar identities and encourage their wider integration into the Croatian post-transitional society. [less ▲]

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