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See detailGeneralized shape optimization using XFEM and Level Set method
Duysinx, Pierre ULg; Van Miegroet, Laurent ULg; Jacobs, Thierry

Conference (2006, November)

This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended ... [more ▼]

This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended Finite Element Method (XFEM). The method takes benefit of the fixed mesh work using XFEM and of the smooth curves description of the Level Set method. Design variables are shape parameters of basic geometric features like circles, triangles etc. The number of design variables of this formulation is small whereas various global and local constraints can be considered. The Level Set description allows to modify the connectivity of the structure as geometric features can merge or separate from each other. However no new entity can be introduced by the programme. A central problem that is investigated here is the sensitivity analysis and the way it can be carried out efficiently. Numerical applications revisit some classical (academic) benchmarks from shape and topology optimization. [less ▲]

Detailed reference viewed: 102 (7 ULg)
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See detailGeneralized shape optimization using XFEM and Level Set methods
Duysinx, Pierre ULg; Van Miegroet, Laurent ULg; jacobs, Thibaut et al

in Bendsoe, M.-P.; Olhoff, N.; Sigmund, O. (Eds.) Proceedings of Topopt SYMP2005, IUTAM Symposium. Topological Design Optimization of Structures, Machines and Materials. Status and Perspectives (2005, October)

This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended ... [more ▼]

This paper presents an intermediate approach between parametric shape optimization and topology optimization. It is based on using the recent Level Set description of the geometry and the novel eXtended Finite Element Method (XFEM). The method takes benefit of the fixed mesh work using X-FEM and of the curves smoothness of the Level Set description. Design variables are shape parameters of basic geometric features. The number of design variables of this formulation is small whereas various global and local constraints can be considered. The Level Set description allows to modify the connectivity of the structure as geometric features can merge or separate from each other. However no new entity can be introduced. A central problem that is investigated here is the sensitivity analysis and the way it can be carried out efficiently. Numerical applications revisit the classical elliptical hole benchmark from shape optimization. [less ▲]

Detailed reference viewed: 80 (3 ULg)
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See detailA Generalized Simulation Model of Chillers and Heat Pumps to be Calibrated on Published Manufacturer's Data
Lemort, Vincent ULg; Bertagnolio, Stéphane ULg

(2010, August 07)

This paper shows how semi-empirical models of chillers and heat pumps can be calibrated on the basis of manufacturer’s published data, which is most of the time the only available source of information. A ... [more ▼]

This paper shows how semi-empirical models of chillers and heat pumps can be calibrated on the basis of manufacturer’s published data, which is most of the time the only available source of information. A calibration methodology is proposed and illustrated for different technologies of vapor-compression machines, pointing out tips and tricks. Whatever the size and technology (e.g. scroll, screw or reciprocating compressors), the semi-empirical model is found to predict both full load and part load performance with a very good accuracy. This is partially due to the tailor-made formalism of the model, which allows describing the main features of the machine. [less ▲]

Detailed reference viewed: 107 (37 ULg)
See detailGeneralized Treynor Ratio
Hübner, Georges ULg

in Gregoriou, Greg (Ed.) Encyclopedia of Alternative Investments (2008)

Detailed reference viewed: 14 (8 ULg)
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See detailThe Generalized Treynor Ratio
Hübner, Georges ULg

in Review of Finance (2005), 9(3), 415-435

This paper extends the Treynor performance ratio for a single index to the case of multiple indexes. The new measure, called the Generalized Treynor Ratio, preserves the same key geometric and analytical ... [more ▼]

This paper extends the Treynor performance ratio for a single index to the case of multiple indexes. The new measure, called the Generalized Treynor Ratio, preserves the same key geometric and analytical properties of the original Treynor Ratio. The Generalized Treynor Ratio is defined as the abnormal return of a portfolio per unit of premium-weighted average systematic risk, normalized by the premium-weighted average systematic risk of the benchmark. Numerical simulations reveal that the portfolio rankings produced with this measure are more precise and more stable than the ones provided by Jensen's alpha and the Information Ratio. [less ▲]

Detailed reference viewed: 30 (6 ULg)
See detailThe Generalized Variational Metric
Alexandre, Patrick; Tossings, Patricia ULg

E-print/Working paper (1996)

The variational convergence theory has known these last years a lot of developments. This theory is fundamental to give a global approach of problems which consist in searching a zero of a maximal ... [more ▼]

The variational convergence theory has known these last years a lot of developments. This theory is fundamental to give a global approach of problems which consist in searching a zero of a maximal monotone operator on a real Hilbert space. The notion of perturbation is often used in the resolution of such problems. More and more authors work also with a special or a variable metric on the space to solve this kind of problems. In the present paper, we give a unified context to couple these two approaches: a variational metric between operators, taking into account different metrics on the space. [less ▲]

Detailed reference viewed: 21 (1 ULg)
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See detailThe generalized-alpha method in mechatronic applications
Bruls, Olivier ULg; Golinval, Jean-Claude ULg

in ZAMM-Zeitschrift fur Angewandte Mathematik und Mechanik (2006), 86(10 Sp. Iss. SI), 748-758

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second ... [more ▼]

This paper presents an extension of the generalized-a time-integrator to mechatronic systems represented by coupled first and second-order DAEs. A simple reformulation of those equations as full second-order DAEs allows the implementation of a monolithic integration scheme, so that the numerical dissipation properties are preserved, and second-order accuracy is obtained at least in the unconstrained case. The algorithmic parameters can be optimized either for the mechanical or the control subsystem. Two illustrative applications are treated in the fields of vehicle dynamics and robotics. [less ▲]

Detailed reference viewed: 136 (21 ULg)
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See detailThe generalized-alpha scheme as a linear multistep integrator: Toward a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Journal Of Computational And Nonlinear Dynamics (2008), 3(4), 041007

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics; and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulas, which leads to elegant results related to consistency, order conditions for constant and variable step-size methods, as well as global convergence. Those results are illustrated for a controlled spring-mass system, and the method is also applied for the simulation of a vehicle semi-active suspension. [less ▲]

Detailed reference viewed: 105 (2 ULg)
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See detailThe generalized-alpha scheme as a linear multistep integrator: Towards a general mechatronic simulator
Bruls, Olivier ULg; Arnold, Martin

in Proceedings of the ASME 2007 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (2007)

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller ... [more ▼]

This paper presents a consistent formulation of the generalized-alpha time integration scheme for mechanical and mechatronic systems. The algorithm can deal with a nonconstant mass matrix, controller dynamics, and kinematic constraints. The theoretical background relies on the analogy with linear multistep formulae, which leads to elegant results related with consistency, order conditions for constant and variable stepsize methods, as well as global convergence. The algorithm is applied for the simulation of a vehicle semi-active suspension. [less ▲]

Detailed reference viewed: 47 (0 ULg)
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See detailThe generalized-alpha time-integration scheme for mechatronic systems with elastic components
Bruls, Olivier ULg

Conference (2006, May)

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a ... [more ▼]

This talk concerns the numerical simulation of mechatronic systems, such as robots, machine-tools or modern vehicles. In general, a mechatronic system is composed of various technological components: a mechanism, actuators, sensors, and control units. For critical applications, it is also necessary to account for elastic deformations in the mechanism. The generalized-alpha method has been initially developed for the dynamic simulation of flexible mechanical structures, which are represented by lightly damped second-order ODEs. Usually, those equations are obtained after a finite element spatial discretization, with the consequence that they are affected by a large number of high-frequency modes with a purely numerical origin. The generalized-alpha method has very interesting properties in this context, such as an adjustable amount of high-frequency numerical dissipation, A-stability, second-order accuracy, and a high level of computational efficiency. A mechanism with elastic components can be described using the nonlinear finite element formalism. Due to the presence of kinematic constraints, the equations of motion are second-order DAEs, and we shall consider the generalized-alpha method for the direct simulation of the index-3 problem. In particular, some results about the convergence and the stability of the algorithm will be discussed. Finally, a mechatronic system involves mechanical and non-mechanical components, and it is thus modelled as a mixed set of second- and first-order DAEs. We will show that those coupled equations of motion can also be solved in the time domain according to the generalized-alpha scheme. An important problem is then associated with the selection of the parameters of the method. The presentation will be illustrated by academic and non-academic applications, for example in vehicle dynamics and in robotics. [less ▲]

Detailed reference viewed: 122 (3 ULg)
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See detailGeneralizing Grasps Across Partly Similar Objects
Detry, Renaud ULg; Ek, Carl Henrik; Madry, Marianna et al

in IEEE International Conference on Robotics and Automation (2012)

Detailed reference viewed: 13 (1 ULg)
Peer Reviewed
See detailGeneralizing Task Parameters Through Modularization
Detry, Renaud ULg; Hjelm, Martin; Ek, Carl Henrik et al

Conference (2013)

Detailed reference viewed: 9 (2 ULg)
See detailGenerating Dicke states with photodetector arrays in trapped ions
Thiel, C.; von Zanthier, J.; Bastin, Thierry ULg et al

Poster (2006)

Detailed reference viewed: 1 (0 ULg)
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See detailGenerating informative trajectories by using bounds on the return of control policies
Fonteneau, Raphaël ULg; Murphy, Susan; Wehenkel, Louis ULg et al

in Proceedings of the Workshop on Active Learning and Experimental Design 2010 (in conjunction with AISTATS 2010) (2010, May)

We propose new methods for guiding the generation of informative trajectories when solving discrete-time optimal control problems. These methods exploit recently published results that provide ways for ... [more ▼]

We propose new methods for guiding the generation of informative trajectories when solving discrete-time optimal control problems. These methods exploit recently published results that provide ways for computing bounds on the return of control policies from a set of trajectories. [less ▲]

Detailed reference viewed: 33 (12 ULg)
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See detailGenerating random percolation clusters.
Bogaert, Jan ULg; Impens, I

in Applied Mathematics and Computation (1998), 91(2-3), 197-208

Detailed reference viewed: 7 (2 ULg)
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See detailGenerating smooth surface meshes from labelled medical datasets
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in Nithiarasu, Perumal; Löhner, Rainald; van Loon, Raoul (Eds.) et al CMBE11: 2nd International Conference on Computational & Mathematical Biomedical Engineering, 30 March - 1 April, 2011, Washington D.C. U.S.A. (2011, March 30)

In this article, an innovative procedure to create high quality triangular meshes from medical scans is proposed. The approach is based on an enhanced Marching Tetrahedra algorithm that extracts a ... [more ▼]

In this article, an innovative procedure to create high quality triangular meshes from medical scans is proposed. The approach is based on an enhanced Marching Tetrahedra algorithm that extracts a consistent multiple region surface mesh from a labelled volume data set; coupled with a surface reconstruction method to avoid typical staircase artifacts. Mesh smoothing and decimation algorithms are also revised to conform to the multiple material nature of the system as well as to adhere to the underlying volume data. The proposed method is well suited for subsequent volume mesh generation and finite element simulations. [less ▲]

Detailed reference viewed: 37 (14 ULg)
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See detailGenerating smooth surface meshes from multi-region medical images
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

in International Journal for Numerical Methods in Biomedical Engineering (2012), 28(6-7), 642-660

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It ... [more ▼]

Thanks to advances in medical imaging technologies and numerical methods, Patient-Specific Modelling is more and more used to improve diagnosis and to estimate the outcome of surgical interventions. It requires the extraction of the domain of interest from the medical scans of the patient, as well as the discretisation of this geometry. However, extracting smooth multi-material meshes that conform to the tissue boundaries described in the segmented image is still an active field of research. We propose to solve this issue by combining an implicit surface reconstruction method with a multi-region mesh extraction scheme. The surface reconstruction algorithm is based on multi-level partition of unity implicit surfaces which we extended to the multi-material case. The mesh generation algorithm consists in a novel multidomain version of the marching tetrahedra. It generates multi-region meshes as a set of triangular surface patches consistently joining each other at material junctions. This paper presents this original meshing strategy, starting from boundary points extraction from the segmented data, to heterogeneous implicit surface definition, multi-region surface triangulation and mesh adaptation. Results indicate that the proposed approach produces smooth and high-quality triangular meshes with a reasonable geometric accuracy. Hence, the proposed method is well suited for subsequent volume mesh generation and Finite Element simulations. [less ▲]

Detailed reference viewed: 69 (36 ULg)
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See detailGénération automatique d'un modèle de bâtiment à partir d'un croquis
Demaret, Jean-Noël ULg; Leclercq, Pierre ULg

in Complexité(s) des modèles de l'architecture numérique : Actes du 5ème séminaire de Conception Architecturale Numérique (SCAN'12) (2012)

Detailed reference viewed: 50 (11 ULg)