Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailThe Perturbation Finite Element Method for Magnetic Modeling of a Loudspeaker
Ferreira da Luz, Mauricio V.; Dular, Patrick ULg; V Sabariego, Ruth ULg et al

in Proceedings of 6ème Conférence Européenne sur les Méthodes Numériques en Electromagnétisme (NUMELEC2008) (2008)

This paper shows that the application of a perturbation finite element method can provide a useful alternative to correct the equivalent magnetic circuits used to model loudspeakers. A ring magnet design ... [more ▼]

This paper shows that the application of a perturbation finite element method can provide a useful alternative to correct the equivalent magnetic circuits used to model loudspeakers. A ring magnet design of a loudspeaker is modeled by means of an axisymmetric magnetic vector potential formulation. The effects of geometry variations on its performances are analyzed. The perturbation solution allows further adapting and refining the equivalent magnetic circuit model of the loudspeaker to each possible variation. Results will be compared with the classical finite element solution. [less ▲]

Detailed reference viewed: 104 (0 ULg)
Full Text
Peer Reviewed
See detailPerturbation Finite Element Method for Magnetostatic and Magnetodynamic Problems
Dular, Patrick ULg; V Sabariego, Ruth ULg; Krähenbühl, Laurent

in Proceedings of MOMAG2008 (2008, September)

Magnetic flux distributions are calculated in magnetostatic and magnetodynamic problems via a subproblem finite element method based on a perturbation technique. An approximate finite element problem ... [more ▼]

Magnetic flux distributions are calculated in magnetostatic and magnetodynamic problems via a subproblem finite element method based on a perturbation technique. An approximate finite element problem considering ideal flux tubes or ideal materials is first solved. It gives the source for finite element perturbation problems considering the flux tubes with their exterior regions, accounting thus for leakage fluxes, as well as for changes of material properties and shapes. The proposed technique aims to accurately quantify the gain given by each model refinement on both local fields and global quantities and to justify the usefulness of this refinement. It is also well adapted to parameterized analyses on geometrical and material data. [less ▲]

Detailed reference viewed: 25 (2 ULg)
Full Text
Peer Reviewed
See detailA Perturbation Finite Element Method for Modeling Electrostatic MEMS without Remeshing
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in Proceedings of the 9th International Conference on Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems (EuroSimE2008) (2008)

This paper deals with the coupled electrostatic- mechanical analysis of electrostatically actuated MEMS. An iterative perturbation procedure in conjunction with the finite element method is used to solve ... [more ▼]

This paper deals with the coupled electrostatic- mechanical analysis of electrostatically actuated MEMS. An iterative perturbation procedure in conjunction with the finite element method is used to solve the coupled problem without the need of remeshing the whole electric domain. The method offers the advantage of overcoming degenerated finite elements in the mesh of some electric regions where the deflection of the MEMS moving parts is critical. The actuation of such systems is achieved by applying either an electric voltage or a global charge. [less ▲]

Detailed reference viewed: 49 (25 ULg)
Full Text
Peer Reviewed
See detailA perturbation finite element method for modeling moving conductive and magnetic regions without remeshing
Dular, Patrick ULg; V Sabariego, Ruth ULg

in COMPEL (2007), 26(3), 700-711

Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology ... [more ▼]

Purpose - To develop a sub-domain perturbation technique for efficiently modeling moving systems in magnetodynamics with a magnetic field h-conform finite element (FE) formulation. Design/methodology/approach - A reference problem is first solved in a global mesh excluding some moving regions and thus avoiding the inclusion of their meshes. Its solution gives the sources for a sequence of perturbation problems with the supplementary moving magnetic and conductive regions. Each of these sub-problems requires an appropriate proper volume mesh of the associated moving region and its surrounding region, with no need of interconnection. The solutions are transferred from one problem to the other through projections of source fields between meshes. Findings - The consideration of sub-problems and associated sources, in a sequence of perturbation problems, leads to a significant speed-up of the repetitive solutions in analyses of moving systems. A free movement in any direction can be considered with no need of remeshing. Originality/value - When working with the perturbation fields, the volume sources can be limited to the moving regions, what allows for homogeneous perturbation boundary conditions and reduces the computational efforts for projecting and evaluating the sources. The curl-conformity of the unknown magnetic field is preserved during the whole process thanks to the use of edge FEs for both the magnetic field and the intermediate source quantities. The sub-problem approach also gives an easy way to directly express the time derivatives in moving frames. [less ▲]

Detailed reference viewed: 29 (3 ULg)
Full Text
Peer Reviewed
See detailPerturbation Finite Element Method for Refining Magnetic Circuit Models
Dular, Patrick ULg; V Sabariego, Ruth ULg; Ferreira da Luz, Mauricio Valencia et al

in Proceedings of the XX Symposium Electromagnetic Phenomena in Nonlinear Circuits (EPNC2008) (2008)

Model refinements of magnetic circuits are performed via a subproblem finite element method based on a perturbation technique. An approximate problem considering ideal flux tubes is first solved. It gives ... [more ▼]

Model refinements of magnetic circuits are performed via a subproblem finite element method based on a perturbation technique. An approximate problem considering ideal flux tubes is first solved. It gives the sources for finite element perturbation problems considering all the details of the exterior regions, thus accounting for leakage fluxes. The procedure simplifies both meshing and solving processes. It quantifies the gain given by each model refinement on both local and global quantities. [less ▲]

Detailed reference viewed: 20 (1 ULg)
Full Text
Peer Reviewed
See detailPerturbation finite element method for the analysis of earthing systems with vertical and horizontal rods
V Sabariego, Ruth ULg; Ferreira da Luz, Mauricio V.; Nzuru Nsekere, Jean-Pierre et al

in Proceedings of the 6ème Conférence Européenne sur les Méthodes Numériques en Electromagnétisme (NUMELEC2008) (2008, December)

This paper deals with the electrokinetic modeling of earthing systems by means of a sub-domain perturbation finite element technique. An axisymmetric problem is solved for each single grounding rod or ... [more ▼]

This paper deals with the electrokinetic modeling of earthing systems by means of a sub-domain perturbation finite element technique. An axisymmetric problem is solved for each single grounding rod or cable. Its solution must then be corrected by taking into account the influence of the other rods and cables. The electric scalar potential is transferred from one problem to the other through projections between meshes. An inherently 3D problem can thus be solved as a succession of 2D sub-problems, which significantly speeds up the solution and enables to tackle complicated grounding systems. [less ▲]

Detailed reference viewed: 68 (9 ULg)
Full Text
Peer Reviewed
See detailPerturbation finite element method for the analysis of earthing systems with vertical rods
V Sabariego, Ruth ULg; Ferreira da Luz, Mauricio V.; Nsekere, Jean-Pierre et al

in Proceedings of MOMAG2008 (2008, September)

This paper deals with the electrokinetic modeling of earthing systems by means of a sub-domain perturbation finite element technique. An axisymmetric problem is solved for each single grounding rod. Its ... [more ▼]

This paper deals with the electrokinetic modeling of earthing systems by means of a sub-domain perturbation finite element technique. An axisymmetric problem is solved for each single grounding rod. Its solution must then be corrected by taking into account the influence of the other rods. The electric scalar potential is transferred from one problem to the other through projections between meshes. An inherently 3D problem can thus be solved as a succession of 2D sub-problems, what significantly speeds up the solution and enables to tackle complicated grounding systems. The method is validated by means of both analytical formulas and 3D computations. [less ▲]

Detailed reference viewed: 101 (22 ULg)
Full Text
Peer Reviewed
See detailPerturbation finite-element method for magnetic circuits
Dular, Patrick ULg; V Sabariego, Ruth ULg; Ferreira da Luz, Mauricio et al

in IET Science, Measurement & Technology (2008), 2(6), 440-446

Accurate magnetic flux distributions are calculated in magnetic circuits via a subproblem finite-element (FE) method based on a perturbation technique. An approximate FE problem considering ideal flux ... [more ▼]

Accurate magnetic flux distributions are calculated in magnetic circuits via a subproblem finite-element (FE) method based on a perturbation technique. An approximate FE problem considering ideal flux tubes is first solved. It gives the source for FE perturbation problems considering the flux tubes with their exterior regions, accounting thus for leakage fluxes, as well as for changes of material properties and shapes. The proposed technique aims to accurately quantify the gain given by each model refinement on both local fields and global quantities and to justify the usefulness of this refinement. It is also well adapted to parameterised analyses on geometrical and material data. [less ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
See detailA perturbation method for computing field distortions due to conductive regions with h-conform magnetodynamic finite element formulations
Dular, Patrick ULg; V Sabariego, Ruth ULg

in IEEE Transactions on Magnetics (2007), 43(4), 1293-1296

A method for solving eddy current problems in two separate steps is developed for global-local analyses with h-conform finite element formulations. An unperturbed problem is first solved in a global mesh ... [more ▼]

A method for solving eddy current problems in two separate steps is developed for global-local analyses with h-conform finite element formulations. An unperturbed problem is first solved in a global mesh excluding additional conductive regions. Its solution gives the sources for a sequence of other problems, perturbed by adding conductive regions. Each problem only requires a new adapted mesh of a local region. The way the local problems and their sources are defined leads to a significant speedup of parameterized analyses, e.g., in optimization and sensitivity analyses. [less ▲]

Detailed reference viewed: 18 (0 ULg)
Full Text
Peer Reviewed
See detailA perturbation method for the 3D finite element modeling of electrostatically driven MEMS
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in Sensors (2008), 8(2), 994-1003

In this paper, a finite element (FE) procedure for modeling electrostatically actuated MEMS is presented. It concerns a perturbation method for computing electrostatic field distortions due to moving ... [more ▼]

In this paper, a finite element (FE) procedure for modeling electrostatically actuated MEMS is presented. It concerns a perturbation method for computing electrostatic field distortions due to moving conductors. The computation is split in two steps. First, an unperturbed problem (in the absence of certain conductors) is solved with the conventional FE method in the complete domain. Second, a perturbation problem is solved in a reduced region with an additional conductor using the solution of the unperturbed problem as a source. When the perturbing region is close to the original source field, an iterative computation may be required. The developed procedure offers the advantage of solving sub-problems in reduced domains and consequently of benefiting from different problem-adapted meshes. This approach allows for computational efficiency by decreasing the size of the problem. [less ▲]

Detailed reference viewed: 82 (29 ULg)
Full Text
Peer Reviewed
See detailA Perturbation Method for the 3D Finite Element Modeling of Electrostaticaly Driven MEMS
Boutaayamou, Mohamed ULg; V Sabariego, Ruth ULg; Dular, Patrick ULg

in Proceedings of the 8th International Conference on Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems (2007, April)

In this paper, a finite element (FE) procedure for modeling electrostatically actuated MEMS is presented. It concerns a perturbation method for computing electrostatic field distortions due to moving ... [more ▼]

In this paper, a finite element (FE) procedure for modeling electrostatically actuated MEMS is presented. It concerns a perturbation method for computing electrostatic field distortions due to moving conductors. The computation is split in two steps. First, an unperturbed problem (in the absence of certain conductors) is solved with the conventional FE method in the complete domain. Second, a perturbation problem is solved in a reduced region with an additional conductor using the solution of the unperturbed problem as a source. When the perturbing regions are close to the original source field, an iterative computation may be required. The developed procedure offers the advantage of solving sub-problems in reduced domains and consequently of benefiting from different problem-adapted meshes. This approach allows for computational efficiency by decreasing the size of the problem. [less ▲]

Detailed reference viewed: 33 (9 ULg)
Full Text
Peer Reviewed
See detailA perturbation method for the T-Ω geometric eddy-current formulation
Codecasa, Lorenzo; Dular, Patrick ULg; Specogna, Ruben et al

in IEEE Transactions on Magnetics (2010), 46(8), 3045-3048

A perturbation method for the T-Ω geometric formulation to solve eddy-current problems is introduced. The proposed formulation is applied to the feasibility design of a nondestructive evaluation device ... [more ▼]

A perturbation method for the T-Ω geometric formulation to solve eddy-current problems is introduced. The proposed formulation is applied to the feasibility design of a nondestructive evaluation device suitable to detect “long” longitudinal flaws in hot steel bars. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailPerturbation methods for the determination of the statistical response of nonlinear Volterra systems
Denoël, Vincent ULg; Carassale, Luigi

in Proceedings of the Eurodyn 2014 Conference (2014)

The point-like quasi-steady aerodynamic loading in a turbulent flow is formally expressed as a function of the squared relative velocity between the fluid and the investigated structure. The three major ... [more ▼]

The point-like quasi-steady aerodynamic loading in a turbulent flow is formally expressed as a function of the squared relative velocity between the fluid and the investigated structure. The three major terms governing the low-order statistics of the response are known to be related to the average loading, the linear turbulent loading and the aerodynamic damping. The three other terms in the loading, namely the quadratic turbulence term, the parametric velocity feedback term and the squared velocity term, may significantly affect the higher order statistical cumulants of the response. These latter two sources of fluid-structure interaction are usually disregarded, by lack of efficient simulation tools, except a Monte Carlo simulation of the nonlinear equation. In this paper, we provide a formal analysis of the complete nonlinear model, including thus all six terms, but mainly focusing on the importance of the two nonlinear coupling terms of the loading. Closed form solutions of the response are derived for a second-order Volterra model of this problem, under the assumption of different timescales in the loading and in the structural behavior. Two major outcomes of the analysis are, on the one hand, that the squared structural velocity term has no influence on the cumulants of the response up to order 4 and, on the other hand, that the parametric velocity feedback acts as a reduction of the non Gaussianity of the response. [less ▲]

Detailed reference viewed: 17 (0 ULg)
Full Text
Peer Reviewed
See detailPerturbation of actin dynamics induces NF-kappa B activation in myelomonocytic cells through an NADPH oxidase-dependent pathway
Kustermans, Gaëlle ULg; El Benna, Jamel; Piette, Jacques ULg et al

in Biochemical Journal (2005), 387(Pt 2), 531-540

Although several reports showed the effect of compounds disrupting microtubules on NF-kappa B (nuclear factor kappa B) activation, nothing is known about agents perturbing actin dynamics. In the present ... [more ▼]

Although several reports showed the effect of compounds disrupting microtubules on NF-kappa B (nuclear factor kappa B) activation, nothing is known about agents perturbing actin dynamics. In the present study, we have shown that actin cytoskeleton disruption induced by actin-depolymerizing agents such as cytochalasin D and latrunculin B and actin-polymerizing compounds such as jasplakinolide induced NF-kappa B activation in myelomonocytic cells. The transduction pathway involved the I kappa B (inhibitory kappa B) kinase complex and a degradation of I kappa B alpha. We have shown that NF-kappa B activation in response to the perturbation of actin dynamics required reactive oxygen species. as demonstrated by the effect of antioxidants. Actin cytoskeleton disruption by cytochalasin D induced O-2(-) release from human monocytes, through the activation of the NADPH oxidase, as confirmed by the phosphorylation and by the membrane translocation of p47(phox). NF-kappa B activation after actin cytoskeleton disruption could be physiologically relevant during monocyte activation and/or recruitment into injured tissues, where cellular attachment, migration and phagocytosis result in cyclic shifts in cytoskeletal organization and disorganization. [less ▲]

Detailed reference viewed: 34 (13 ULg)
Peer Reviewed
See detailA perturbation technique for Finite Element Modelling of Piezoelectric Vibrations in Travelling Wave Ultrasonic Motors
Ledinh, T.; Dular, Patrick ULg; Gyselinck, J. et al

in Proceedings of the second international conference on advanced computational methods in engineering, ACOMEN 2002 (2002)

Detailed reference viewed: 6 (0 ULg)
Full Text
Peer Reviewed
See detailPerturbation technique for the finite element modelling of differential probes in non-destructive eddy-current testing
V Sabariego, Ruth ULg; Dular, Patrick ULg

in IET Science, Measurement & Technology (2007), 1(1), 25-29

The paper deals with a new finite element scheme for non-destructive eddy-current testing (ECT) problems involving multiply connected test pieces and differential probes. It concerns a perturbation ... [more ▼]

The paper deals with a new finite element scheme for non-destructive eddy-current testing (ECT) problems involving multiply connected test pieces and differential probes. It concerns a perturbation technique applied to the magnetodynamic h - phi formulation. The unperturbed field (in the absence of the flaw) is conventionally computed in the complete domain. The source of the perturbation problem is then determined by the projection of the unperturbed field in a relatively small region around the defect, the optimum size of which depends on the working frequency. The discretisation of this reduced domain is well adapted to the size of the defect and chosen independently of the dimensions of the excitation probe and the specimen under study. At a discrete level, the voltage change is efficiently computed by integration only over the defect and a layer of elements in the reduced domain that touches the defect's boundary. The accuracy of the proposed perturbation model is illustrated by comparison of the results obtained for different dimensions of the reduced domain with those achieved in the conventional way. The considered test case involves a differential probe scanning the outer surface of a metal tube for the detection of through-wall cracks. [less ▲]

Detailed reference viewed: 19 (2 ULg)
Full Text
See detailA perturbation technique for the finite element modelling of non-destructive eddy current testing
V Sabariego, Ruth ULg; Dular, Patrick ULg

in Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering (2006)

This paper deals with a new 3D finite element scheme for nondestructive eddy-current testing (ECT) problems. It concerns a perturbation technique applied to the magnetodynamic h- φ formulation. The ... [more ▼]

This paper deals with a new 3D finite element scheme for nondestructive eddy-current testing (ECT) problems. It concerns a perturbation technique applied to the magnetodynamic h- φ formulation. The unperturbed field (in the absence of the flaw) is computed conventionally in the complete domain. The source of the perturbation problem is determined by the projection of the unperturbed field in a relatively small region around the defect that depends on the work frequency. The discretisation of this reduced domain is adapted to the size of the defect and independent of the discretisation of the complete domain. The impedance change is computed by integrating only over the defect and a layer of elements in the reduced domain that touch its boundary. As test case, we consider the second eddy current benchmark problem proposed by the WFNDEC. It involves a pancake coil scanning the inner surface of a metal tube for the detection of flaws on the outer surface. [less ▲]

Detailed reference viewed: 13 (1 ULg)