Subproblem finite element solutions for efficient repetitive analyses of low frequency electromagnetic systems

(2009, March)

Repetitive finite element (FE) computations are needed when studying variations of geometrical and physical characteristics, which is the case for, e.g., parameterized analyses, optimisation, movement ... [more ▼]

Repetitive finite element (FE) computations are needed when studying variations of geometrical and physical characteristics, which is the case for, e.g., parameterized analyses, optimisation, movement modelling, multi-physical coupling and model refinement. It is worth then benefiting from previous computations instead of starting a new complete solution for any new variation. A subproblem approach with perturbations of solutions is developed to efficiently tackle such repetitive computations. It consists in iteratively solving successive subproblems, the addition of their solutions giving the solution of a complete problem. At the discrete level, each subproblem is defined in its own domain and mesh, which decreases the problem complexity and allows distinct mesh refinements. A special attention is given to the proper discretization of the source constraints of each subproblem. This approach allows a natural progression from simple to elaborate models: from 1D to 3D geometries, from statics to dynamics, from low to high frequencies, from perfect to real materials, from linear to nonlinear materials, from initially simple models with magnetic or electric equivalent circuits to detailed geometrical models with the FE method, etc. Each model refinement can be quantified to justify its utility. A general frame is developed for electrostatic, electrokinetic, magnetostatic and magnetodynamic FE formulations, with their possible couplings. The perturbation method offers a way to follow the solution and its complexity through graphical representations and animations, which facilitates the understanding of the developed numerical tools as well as various physical behaviors. Numerous applications benefit from this sub-problem approach and will be presented. They concern magnetic circuits, skin and proximity effects, moving systems, eddy current non-destructive testing, magnetic screening, grounding systems, etc. [less ▲]

Subproblem h-Conform Magnetodynamic Finite Element Formulation for Accurate Model of Multiply Connected Thin Regions

in Proceedings of the 7th European Conference on Numerical Methods in Electromagnetism (NUMELEC 2012) (2012, July 03)

A subproblem $\vh$-conform eddy current finite element method is proposed for correcting the inaccuracies inherent to thin shell models. Such models replace volume thin regions by surfaces but neglect ... [more ▼]

A subproblem $\vh$-conform eddy current finite element method is proposed for correcting the inaccuracies inherent to thin shell models. Such models replace volume thin regions by surfaces but neglect border effects in the vicinity of their edges and corners. The developed surface-to-volume correction problem is defined as a step of the multiple subproblems applied to a complete problem, consisting of inductors and magnetic or conducting regions, some of these being thin regions. The general case of multiply connected thin regions is considered. [less ▲]

Subset-Specific Analysis of Calcium Fluxes in Murine Aids

in International Immunology (1996), 8(11), 1715-27

Infection of susceptible strains of mice with the Duplan strain of murine leukemia viruses induces a syndrome called MAIDS (murine acquired immunodeficiency syndrome) characterized by immunodeficiency and ... [more ▼]

Infection of susceptible strains of mice with the Duplan strain of murine leukemia viruses induces a syndrome called MAIDS (murine acquired immunodeficiency syndrome) characterized by immunodeficiency and lymphoproliferation. In addition to a complete refractoriness of most subsets of lymphocytes to mitogen stimulation, the development of phenotypic abnormalities occurs such as the appearance of an abnormal CD4+ T cell subset lacking membranes Thy-1. This study was performed to compare the calcium responses during the early stages of MAIDS (week 9 or earlier) between T cells and B cells and between CD4+Thy-1- and CD4+Thy-1+ T cells. B cells were strikingly less affected than T cells: their baseline [Ca2+]i did not significantly increase, and their calcium response to anti-IgM antibody and concanavalin A (Con A) was partially maintained. In contrast, the response to Con A was completely abolished in T cells. Interestingly, calcium mobilization in response to membrane receptor-independent stimuli such as ionophores and thapsigargin was strongly inhibited in T cells, while no such inhibition was found in B cells. In comparison with their CD4+Thy-1+ counterparts, CD4+Thy-1- T cells had blunted calcium responses in controls, as well as in infected mice. However, CD4+Thy-1+ T cells were also strikingly altered, suggesting that the loss of membrane Thy-1 could be associated with, but not directly responsible for abnormalities of calcium responses in CD4+ T cells from RadLV-Rs-infected mice. [less ▲]

Subsonic and Transonic Blade Design

in Proceedings od the 2nd Belgian National Congress on Theoretical and Applied Mechanics (1990)

Subsonic and Transonic Cascade Design

in Van den Braembussche, René (Ed.) Inverse Methods for Airfoil Design for Aeronautical and Turbomachinery Applications (1990)

Subspace-based Methods for Machinery Analysis and Monitoring

Conference (2010)

The objective of this presentation is to address the problem of structural damage detection or fault diagnosis in mechanical systems using subspace-based methods. Different methods are reviewed starting ... [more ▼]

The objective of this presentation is to address the problem of structural damage detection or fault diagnosis in mechanical systems using subspace-based methods. Different methods are reviewed starting from Principal Component Analysis (PCA) also known as Proper Orthogonal Decomposition (POD) of time responses. PCA is known as an efficient method for extracting modal features of linear structures from output-only measurements. Those features define a subspace which characterizes the dynamical behavior of the structure. It becomes than possible to detect structural damage by comparing a reference subspace (obtained from the healthy structure) with current subspaces on the basis of the concept of angles between subspaces. Other damage indexes based on statistics may also be used. One of the drawbacks of PCA is the need of several sensors. If the number of sensors is too small, modal identification and/or damage detection may not be performed in good conditions using PCA. An alternative PCA-based method named Null Subspace Analysis (NSA) may then be used. The NSA method generates data by means of block Hankel matrices and is proven to be efficient when the number of available sensors is small or even reduced to one sensor only. However, when damage activates nonlinearity, the detection problem may necessitate methods which are more sensitive to nonlinear behaviors. To this purpose, Kernel Principal Component Analysis (KPCA) is a nonlinear extension of PCA built to authorize features with nonlinear dependence between variables. The method is “flexible” in the sense that different kernel functions may be used to better fit the testing data. Industrial applications are presented to illustrate the proposed methods. [less ▲]

Substance P protects spiral ganglion neurons from apoptosis via PKC-Ca2+-MAPK/ERK pathways

in Journal of Neurochemistry (2003), 87(2), 508-521

In the current study, we have investigated the ability of substance P (SP) to protect 3-day-old (P3) rat spiral ganglion neurons (SGNs) from trophic factor deprivation (TFD)-induced cell death. The ... [more ▼]

In the current study, we have investigated the ability of substance P (SP) to protect 3-day-old (P3) rat spiral ganglion neurons (SGNs) from trophic factor deprivation (TFD)-induced cell death. The presence of SP high affinity neurokinin-1 receptor (NK1) transcripts was detected in the spiral ganglion and the NK1 protein localized to SGNs both ex vivo and in vitro. Treatment with SP increased cytoplasmic Ca2+ in SGNs, further arguing for the presence of functional NK1 on these neurons. Both SP and the agonist [Sar(9), Met(O-2)(11)]-SP significantly decreased SGN cell death induced by TFD, with no effect on neurite outgrowth. The survival promoting effect of SP was blocked by the NK1 antagonist, WIN51708. Both pan-caspase inhibitor BOC-D-FMK and SP treatments markedly reduced activation of caspases and DNA fragmentation in trophic factor deprived-neurons. The neuroprotective action of SP was antagonised by specific inhibitors of second messengers, including 1.2-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) to chelate cytosolic Ca2+, the protein kinase C (PKC) inhibitors bisindolylmaleimide I, Go6976 and LY333531 and the MAPK/ERK inhibitor U0126. In contrast, nifedipine, a specific inhibitor of L-type Ca2+ channel, and LY294002, a phosphatidylinositol-3-OH kinase (PI3K) inhibitor, had no effect on SP trophic support of SGNs. Moreover, activation of endogenous PKC by 4beta-phorbol 12-myristate 13-acetate (PMA) also reduced the loss of trophic factor-deprived SGNs. Thus, NK1 expressed by SGNs transmit a survival-promoting regulatory signal during TFD-induced SGN cell death via pathways involving PKC activation, Ca2+ signalling and MAPK/ERK activation, which can be accounted for by an inhibition of caspase activation. [less ▲]

Substance P-induced histamine release from human basophils, skin and lung fragments: effect of nedocromil sodium and theophylline.

in International Archives of Allergy and Applied Immunology (1990), 92(4), 329-33

We compared histamine release induced by substance P with those obtained with classical secretagogues on human basophils, lung and skin fragments. We also tested the capacity of nedocromil sodium and ... [more ▼]

We compared histamine release induced by substance P with those obtained with classical secretagogues on human basophils, lung and skin fragments. We also tested the capacity of nedocromil sodium and theophylline to inhibit histamine release in these 3 experimental models. Substance P (10(-4) M) caused a noncytotoxic histamine release (about 10% of total) from basophils, lung and skin fragments. Substance P-induced histamine release was always smaller than that obtained with optimal doses of anti-IgE, formyl-methionine phenylalanine or compound 48/80. Nedocromil sodium did not prevent secretagogue-induced histamine release from basophils or sliced skin. In contrast, it significantly inhibited anti-IgE- or substance P-induced histamine release from human lung. Theophylline caused a dose-related inhibition on these 3 models. We conclude that substance P is a modest secretagogue for human basophils and mast cells, and that skin and lung mast cells are heterogeneous with respect to their response to nedocromil sodium. [less ▲]

Substances de croissance de nature hormonale pour l'engraissement: actualisation et perspectives d'avenir.

in Annales de Gembloux (1987), 93(1),

Les substances toxicomanogènes en 2004

Conference given outside the academic context (2004)