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See detailHybrid modelling of dike-break induced flows
Roger, Sebastian; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Dittrich, Andreas; Koll, Katinka; Aberle, Jochen (Eds.) et al River Flow 2010 (2010)

In a hybrid approach experimental model data are combined with results from 3D and 2D numerical modelling. The latter was conducted by two different models solving the depth-averaged shallow water ... [more ▼]

In a hybrid approach experimental model data are combined with results from 3D and 2D numerical modelling. The latter was conducted by two different models solving the depth-averaged shallow water equations. 3D computations are based on the REYNOLDS-averaged NAVIER-STOKES equations (RANS) using a volume of fluid approach to capture the free water surface. Measurements were performed on a scale model which was especially designed to reproduce the specific conditions of dike breaks. In various simulations it turned out that 2D shallow water models are able to reproduce steadystate flow patterns of dike-break induced flows and that there is a low sensitivity of the solution concerning turbulence modelling, bed and wall roughness. Nevertheless, final flow splits and breach discharges are systematically underestimated. This discrepancy seems to result from inherent modelling assumptions such as zero-vertical velocity and hydrostatic pressure distribution. Therefore, the complementary use of 3D RANS and 2D depth-averaged modelling frameworks for detailed predictions of dike-break induced flows is discussed in the present paper, based on BOUSSINESQ and pressure coefficients, which represent effects of non-uniform velocity profiles and non-hydrostatic pressure distribution over water depth, respectively. Values of these coefficients are inferred from 3D numerical results for the final steady state. [less ▲]

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See detailA hybrid optimization technique coupling an evolutionary and a local search algorithm
Kelner, Vincent ULg; Capitanescu, Florin ULg; Léonard, Olivier ULg et al

in Journal of Computational & Applied Mathematics (2006), 215(2), 281-287

Evolutionary algorithms are robust and powerful global optimization techniques for solving large-scale problems that have many local optima. However, they require high CPU times, and they are very poor in ... [more ▼]

Evolutionary algorithms are robust and powerful global optimization techniques for solving large-scale problems that have many local optima. However, they require high CPU times, and they are very poor in terms of convergence performance. On the other hand, local search algorithms can converge in a few iterations but lack a global perspective. The combination of global and local search procedures should offer the advantages of both optimization methods while offsetting their disadvantages. This paper proposes a new hybrid optimization technique that merges a genetic algorithm with a local search strategy based on the interior point method. The efficiency of this hybrid approach is demonstrated by solving a constrained multi-objective mathematical test-case. [less ▲]

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See detailA hybrid optimization technique coupling evolutionary and local search algorithms
Kelner, Vincent ULg; Capitanescu, Florin ULg; Léonard, Olivier ULg et al

in Journal of Computational & Applied Mathematics (2008), 215(2), 448-456

Evolutionary Algorithms are robust and powerful global optimization techniques for solving large scale problems that have many local optima. However, they require high CPU times, and they are very poor in ... [more ▼]

Evolutionary Algorithms are robust and powerful global optimization techniques for solving large scale problems that have many local optima. However, they require high CPU times, and they are very poor in terms of convergence performance. On the other hand, local search algorithms can converge in a few iterations but lack a global perspective. The combination of global and local search procedures should offer the advantages of both optimization methods while offsetting their disadvantages. This paper proposes a new hybrid optimization technique that merges a Genetic Algorithm with a local search strategy based on the Interior Point method. The efficiency of this hybrid approach is demonstrated by solving a constrained multi-objective mathematical test-case. [less ▲]

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See detailHybrid photosynthetic materials derived from microalgae Cyanidium caldarium encapsulated within silica gel
Rooke, J. C.; Léonard, Alexandre ULg; Meunier, C. F. et al

in Journal of Colloid & Interface Science (2010), 344(2), 348-352

Cyanidium caldarium (Tilden) Geitler SAG 16.91 has been encapsulated within a porous silica host structure to target novel photosynthetic hybrid materials suitable for use in solar cells or CO2 fixation ... [more ▼]

Cyanidium caldarium (Tilden) Geitler SAG 16.91 has been encapsulated within a porous silica host structure to target novel photosynthetic hybrid materials suitable for use in solar cells or CO2 fixation. C. caldarium cells are both thermophilic and acidophilic; on account of these tolerances the hybrid materials could be employed in more extreme heat conditions. TEM highlights that the external cell membrane can remain intact after encapsulation. The images reveal an alignment of silica gel around the external membrane of the cell, providing evidence that the cell wall acts as both a nucleation and polymerisation site for silica species and that the silica scaffold formed by the aggregation of colloidal particles, generates a porosity that can facilitate the transport of nutrients towards the cell. Epifluorescence microscopy and UV-visible spectroscopy have revealed the preservation of photosynthetic apparatus post-immobilisation. Productivity studies showed how the presence of silica nanoparticles within the matrix can adversely interact with the exterior cellular structures preventing the production of oxygen through photosynthesis. © 2009 Elsevier Inc. All rights reserved. [less ▲]

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See detailHybrid robust observers for locally Lipschitz systems
Bobtsov, Alexey; Efimov, Denis ULg

in Proc. European Control Conference, Budapest (2009)

State observer design procedure is proposed for nonlinear locally Lipschitz systems. Possible presence of disturbances is taken into account. The solution is based on logic-based control approach ... [more ▼]

State observer design procedure is proposed for nonlinear locally Lipschitz systems. Possible presence of disturbances is taken into account. The solution is based on logic-based control approach applicable to nonlinear systems with bounded solutions. [less ▲]

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See detailHybrid Sampling/Spectral Method for Solving Stochastic Coupled Problems
Arnst, Maarten ULg; Soize, Christian; Ghanem, Roger

in SIAM/ASA Journal on Uncertainty Quantification (2013), 1(1), 218-243

In this paper, we present a hybrid method that combines Monte Carlo sampling and spectral methods for solving stochastic coupled problems. After partitioning the stochastic coupled problem into subsidiary ... [more ▼]

In this paper, we present a hybrid method that combines Monte Carlo sampling and spectral methods for solving stochastic coupled problems. After partitioning the stochastic coupled problem into subsidiary subproblems, the proposed hybrid method entails iterating between these subproblems in a way that enables the use of the Monte Carlo sampling method for subproblems that depend on a very large number of uncertain parameters and the use of spectral methods for subproblems that depend on only a small or moderate number of uncertain parameters. To facilitate communication between the subproblems, the proposed hybrid method shares between the subproblems a reference representation of all the solution random variables in the form of an ensemble of samples; for each subproblem solved by a spectral method, it uses a dimension-reduction technique to transform this reference representation into a subproblem-specific reduced-dimensional representation to facilitate a computationally efficient solution in a reduced-dimensional space. After laying out the theoretical framework, we provide an example relevant to microelectomechanical systems. [less ▲]

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See detailThe Hybrid Scalar and Vector Potential Formulation for Magnetic Field Computations by means of the FE Method
Gyselinck, J.; Vandevelde, L.; Geuzaine, Christophe ULg et al

in Proceedings of the 14th Conference on the Computation of Electromagnetic Fields, COMPUMAG 2003 (2003)

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See detailA Hybrid Systems Approach to Trajectory Tracking Control for Juggling Systems
Sanfelice, Ricardo G.; Teel, Andrew R.; Sepulchre, Rodolphe ULg

in Proceedings of the 46th IEEE Conference on Decision and Control (2007, December)

From a hybrid systems point of view, we provide a modeling framework and a trajectory tracking control design methodology for juggling systems. We present the main ideas and concepts in a one degree-of ... [more ▼]

From a hybrid systems point of view, we provide a modeling framework and a trajectory tracking control design methodology for juggling systems. We present the main ideas and concepts in a one degree-of-freedom juggler, which consists of a ball bouncing on an actuated robot. We design a hybrid control strategy that, with only information of the ball’s state at impacts, controls the ball to track a reference rhythmic pattern with arbitrary precision. We extend this hybrid control strategy to the case of juggling multiple balls with different rhythmic patterns. Simulation results for juggling of one and three balls with a single actuated robot are presented. [less ▲]

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See detailA hybrid tabu search heuristic for a bilevel competitive facility location model
Kucukaydin, Hande ULg; Aras, Necati; Altinel, I. Kuban

in Blesa, Maria J.; Blum, Christian; Raidl, Günther (Eds.) et al Hybrid metaheuristics: 7th International Workshop, HM 2010, Vienna, Austria, October 2010, Proceedings (2010)

We consider a problem in which a firm or franchise enters a market by locating new facilities where there are existing facilities belonging to a competitor. The firm aims at finding the location and ... [more ▼]

We consider a problem in which a firm or franchise enters a market by locating new facilities where there are existing facilities belonging to a competitor. The firm aims at finding the location and attractiveness of each facility to be opened so as to maximize its profit. The competitor, on the other hand, can react by adjusting the attractiveness of its existing facilities, opening new facilities and/or closing existing ones with the objective of maximizing its own profit. The demand is assumed to be aggregated at certain points in the plane and the facilities of the firm can be located at prespecified candidate sites. We employ Huff's gravity-based rule in modeling the behavior of the customers where the fraction of customers at a demand point that visit a certain facility is proportional to the facility attractiveness and inversely proportional to the distance between the facility site and demand point. We formulate a bilevel mixed-integer nonlinear programming model where the firm entering the market is the leader and the competitor is the follower. In order to find a feasible solution of this model, we develop a hybrid tabu search heuristic which makes use of two exact methods as subroutines: a gradient ascent method and a branch-and-bound algorithm with nonlinear programming relaxation. [less ▲]

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See detailHybrid Tabu Search Heuristics for a Bilevel Competitive Facility Location Model
Kucukaydin, Hande ULg; Aras, Necati; Altinel, I. Kuban

Conference (2012, February 02)

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See detailHybrid wetting state on micro-waffle textures
Caps, Hervé ULg; Vandormael, Denis; Loicq, Jerôme ULg et al

in Europhysics Letters (2009), 88

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See detailHybrid wheat - a different wheat crop?
Bodson, Bernard ULg; Franc, Jean; Destain, Jean-Pierre ULg et al

in Aspects of Applied Biology (1997, December 15), (50), 23-30

From 1994 to 1996, trials have been carried out in Gembloux (Belgium) to evaluate the agronomical value of hybrid wheat varieties and to determine the best adapted growing conditions for these new wheats ... [more ▼]

From 1994 to 1996, trials have been carried out in Gembloux (Belgium) to evaluate the agronomical value of hybrid wheat varieties and to determine the best adapted growing conditions for these new wheats. These experiments show that the best hybrids have a yield potential hyghly superior to classical varieties. In order to improve the cost-effectiveness of hybrid wheat crops, a reduction in seed rate may be possible together with changes in nitrogen fertilisation, if the results of preliminary studies are confirmed. [less ▲]

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See detailHybrid γ Doradus/δ Scuti Stars: Comparison Between Observations and Theory
Bouabid, M-P; Montalban Iglesias, Josefa ULg; Miglio, Andrea ULg et al

in AIP Conference Proceedings (2009), 1170

γ Doradus (γ Dor) are F-type stars pulsating with high order g-modes. Their instability strip (IS) overlaps the red edge of the δ Scuti δ Sct) one. This observation has led to search for objects in this ... [more ▼]

γ Doradus (γ Dor) are F-type stars pulsating with high order g-modes. Their instability strip (IS) overlaps the red edge of the δ Scuti δ Sct) one. This observation has led to search for objects in this region of the HR diagram showing p and g-modes simultaneously. The existence of such hybrid pulsators has recently been confirmed [10] and the number of candidates is increasing (e.g. [17]). From a theoretical point of view, non-adiabatic computations including a time-dependent treatment of convection (TDC) predict the existence of γ Dor/δ Sct hybrid pulsators ([5], [8]). Our aim is to confront the properties of the observed hybrid candidates with the theoretical predictions from non-adiabatic computations of non-radial pulsations including the convection-pulsation interaction. [less ▲]

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See detailHybridations dans le film d’animation
Tomasovic, Dick ULg

Conference (1999, January 11)

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See detailHybride Modellierung deichbruchinduzierter Strömungen
Roger, Sebastian; Dewals, Benjamin ULg; Schüttrumpf, Holger

in Heimerl, S.; Meyer, H. (Eds.) Vorsorgender und nachsorgender Hochwasserschutz (2014)

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See detailHybride Modellierung deichbruchinduzierter Strömungen
Roger, Sebastian; Dewals, Benjamin ULg; Schüttrumpf, Holger

in Wasserwirtschaft (2012), (12), 31-37

Experimentelle Modellversuche und numerische Simulationen ergänzen sich gegenseitig in einem hybriden Untersuchungskonzept für deichbruchinduzierte Strömungen. Unter Berücksichtigung der ... [more ▼]

Experimentelle Modellversuche und numerische Simulationen ergänzen sich gegenseitig in einem hybriden Untersuchungskonzept für deichbruchinduzierte Strömungen. Unter Berücksichtigung der deichbruchspezifischen Randbedingungen werden in Laborversuchen charakteristische Strömungsfeldgrößen mit hochgenauer Messtechnik detailliert aufgezeichnet. Die korrespondierenden numerischen Modellierungen werden auf Basis der zweidimensional tiefengemittelten Flachwassergleichungen sowie der Reynolds-gemittelten Navier-Stokes-Gleichungen durchgeführt. [less ▲]

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See detailHybridisation efficiency in generating Hybridisation efficiency in generating invasive progeny in the alien Fallopia (Polygonaceae) complex
Saad, Layla ULg; Tiébré, Marie-Solange; Hardy, Olivier et al

Poster (2007, November 16)

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See detailHybridization And Morphogenetic Variation In The Invasive Alien Fallopia (Polygonaceae) Complex In Belgium
Tiebre, Ms.; Bizoux, Jean-Philippe ULg; Hardy, Oj. et al

in American Journal of Botany (2007), 94(11), 1900-1910

The invasive alien knotweeds, Fallopia spp. (Polygonaceae), are some of the most troublesome invasive species in Europe and North America. Invasive success in Fallopia may be enhanced by multiple ... [more ▼]

The invasive alien knotweeds, Fallopia spp. (Polygonaceae), are some of the most troublesome invasive species in Europe and North America. Invasive success in Fallopia may be enhanced by multiple hybridization events. We examined the pattern of hybridization and its evolutionary consequences in Belgium with a concerted analysis of ploidy levels (chromosome counts and flow cytometry), morphological variation, and genetic variation (RAPDs). At least four taxa with different ploidy levels were part of the pattern of invasion in Belgium. Hybrid F.3bohemica with various chromosome numbers restored the genotypic diversity that was lacking in the parental species. Hybrid genotypes were mainly assigned to a specific genetic pool and not to a mixture between the genetic pools of the putative parental species as would be expected for hybrids. Parental species and hexaploid hybrids differed significantly for a set of well-defined morphological characters, enabling future researchers to distinguish these taxa. On the basis of our results, the importance of hybridization has probably been underestimated in large parts of the adventive range of alien Fallopia species, pointing to the need for concerted molecular and morphological analyses in the study of the evolutionary consequences of hybridization. [less ▲]

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