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See detailEigenproblem formulation for electromechanical microsystem pull-in voltage optimization
Lemaire, Etienne ULg; Van Miegroet, Laurent ULg; Tromme, Emmanuel ULg et al

Conference (2013)

Electrostatic actuators are often used in MEMS since they are relatively easy to manufacture and provide a short response time. Previous studies have already considered topology optimization of such micro ... [more ▼]

Electrostatic actuators are often used in MEMS since they are relatively easy to manufacture and provide a short response time. Previous studies have already considered topology optimization of such micro-actuators like the work by Raulli and Maute [1] and by Yoon and Sigmund [2]. Raulli considers maximization of the actuator output displacement for given electric potential input locations. The paper by Yoon et al. goes further by replacing the staggered modeling used by Raulli by a monolithic approach where both physical fields (electric and mechanical) are solved at once. However, electrostatic micro-actuators possess a limit input voltage called the pull-in voltage, beyond which they become unstable. If a voltage greater than the pull-in voltage is applied to the device, elastic forces of the suspension system are not able to balance electrostatic forces and electrodes stick together. In some cases, the pull-in effect can damage the device. Previous researches by the authors [3] have considered the possibility to control pull-in voltage using topology optimization. In this first approach, pull-in voltage itself was included in the optimization problem and treated as objective function. Nevertheless, in some applications, the developed pull-in voltage optimization procedure suffers from design oscillations that prevent from reaching solution. As illustrated in this paper, the issue is similar to the mode switching problem that arises in eigenvalue optimization problems. The classical solution to this issue consists in including several eigenvalues in a ‘max-min’ formulation. However as the classical pull-in voltage optimization problem is not formulated as an eigenproblem, direct application is not possible. Indeed, pull-in being a nonlinear instability phenomenon, strictly speaking, it is only possible to compute one instability mode and upcoming instability modes cannot be captured. Therefore, this paper is dedicated to the development of a linear eigenproblem approximation for the nonlinear stability problem after the work on nonlinear buckling by Lindgaard and Lund [4]. The proposed stability eigenproblem leads to an alternative optimization procedure aiming at maximizing pull-in voltage. The first eigenmode corresponds to the actual pull-in mode while higher order modes allow estimating upcoming instability modes. Using a multiobjective formulation to maximize the smallest eigenvalue of the stability problem, it is possible to circumvent oscillation issues met with pull-in voltage optimization. Moreover, numerical results show that even if the eigenproblem formulation is an approximation of the actual pull-in voltage optimization problem, eigenproblem formulation leads to significant improvement of pull-in voltage. References [1] M. Raulli and K. Maute, Topology optimization of electrostatically actuated Microsystems, Struct. & Mult. Opt., 30(5):342-359, November 2005. [2] G.H. Yoon and O. Sigmund, A monolithic approach for topology optimization of electrostatically actuated devices, Comput. Methods Appl. Mech. Engrg., 194:4062-4075, 2008. [3] E. Lemaire, V. Rochus, J.-C. Golinval, and P. Duysinx, Microbeam pull-in voltage topology optimization including material deposition constraint, Comput. Methods Appl. Mech. Engrg., 194:4040-4050, 2008. [4] E. Lindgaard and E. Lund, Nonlinear bucking optimization of composite structures, Comput. Methods Appl. Mech. Engrg., 199:37-40, 2010. [less ▲]

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See detailEigenschappen van glucosamine
Reginster, Jean-Yves ULg; Halkin, V

in Medi-Sfeer (2000), 116

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See detailEigenvector-based approach to neutrino mixing
Aristizabal Sierra, Diego ULg; Houet, Eric; Ivo, Medeiros Varzielas

in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2013), 87

We propose a model-independent analysis of the neutrino mass matrix through an expansion in terms of the eigenvectors defining the lepton mixing matrix, which we show can be parametrized as small ... [more ▼]

We propose a model-independent analysis of the neutrino mass matrix through an expansion in terms of the eigenvectors defining the lepton mixing matrix, which we show can be parametrized as small perturbations of the tribimaximal mixing eigenvectors. This approach proves to be powerful and convenient for some aspects of lepton mixing, in particular when studying the sensitivity of the mass matrix elements to departures from their tribimaximal form. In terms of the eigenvector decomposition, the neutrino mass matrix can be understood as originating from a tribimaximal dominant structure with small departures determined by data. By implementing this approach to cases when the neutrino masses originate from different mechanisms, we show that the experimentally observed structure arises very naturally. We thus claim that the observed deviations from the tribimaximal mixing pattern might be interpreted as a possible hint of a ``hybrid'' nature of the neutrino mass matrix. [less ▲]

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See detailEight years of denosumab treatment in postmenopausal women with osteoporosis: results from the first five years of the freedom extension
Papapoulos, S; Lippuner, K; Roux, C et al

in Osteoporosis International (2014), 25(2), 46-47

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See detailEight years of National Health Insurance in Ghana: Evaluation of the Health financign Sub-Functions
Jousten, Alain ULg; Nsiah-Boateng, Eric

in Roscoe, Coleen (Ed.) Ghana: Social Economic and Political Issues (2014)

In 2003, Ghana introduced National Health Insurance Scheme (NHIS) to provide financial access to healthcare for all residents. It was implemented in 2004 in 145 districts nationwide. This study aimed to ... [more ▼]

In 2003, Ghana introduced National Health Insurance Scheme (NHIS) to provide financial access to healthcare for all residents. It was implemented in 2004 in 145 districts nationwide. This study aimed to evaluate the NHIS in terms of health financing sub-functions of revenue collection, risks pooling, and purchasing of health care using the Ashiedu Keteke District NHIS Office as a case study. The review and participant observation methods were employed to analyze secondary data of the NHIS. Reviews were conducted on NHIS operational documents, annual reports, and published literature. A data compilation sheet was used to collect membership, revenue and expenditure data from the AshieduKeteke District NHIS Office. Out of 158,466 members who registered over the period under study (2005-2012), about 30% were active card-bearing members. The population coverage increased consistently from 6.4% to 29.9% over the study period. Children below eighteen years of age were the most registered members (42.2%). Membership is legally mandatory and household-based. The NHIS is largely tax-funded: prepaid contributions declined from 20% to 15.4% over the study period. There was multiple fund system between 2005 and 2009; however, in 2011, a single risk pool (single fund system) was implemented to maximize risk pooling and administrative efficiency. There is comprehensive one-for-all benefit package for ensuring equity and adequate financial protection. The provider payment mechanism changed from fee-for-service in 2005 to Diagnostic Related Groupings (DRG) in 2008; although, fee-for-service is still used to pay for medications. In 2011, capitation payment was implemented for out-patient services at primary health centers. The administrative expenditure is relatively high; however, it declined from 42.1% to 13.3% over the period, 2006- 2012. The population coverage of the Ashiedu Keteke District NHIS Office is increasing with a decreasing trend in administrative expenditure. Given that more than fifty percent of the membership groups are exempted from paying contributions and the extent of prepayment is declining, large scope of government subsidies would be needed to ensure long-term financial sustainability. [less ▲]

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See detailEin Devon/Karbon-Grenzprofil im Untergrund Der Niederrheinischen Bucht Bei Krefeld.
Bless, M.J.M.; Brauckmann, C.; Conil, R. et al

in Fortschr. Geol. Rheinld. U. Westf (1998), 37

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See detailEin erhabener Affekt. Passions, émotions et raison chez Kant
Bolmain, Thomas ULg

Scientific conference (2009, April 03)

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See detailDas Eine und die Vielen in Neuägyptischen
Winand, Jean ULg

Scientific conference (1990, January 30)

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See detailDer Einfluss der Historischen Rechtsschule auf Belgien
Gerkens, Jean-François ULg

Conference (2014, September 12)

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See detailEinfluss der Medienwelt auf vier moderne Kurzprosatexte. Versuch einer Deutung
Simons, Germain ULg

Master's dissertation (1988)

Ce mémoire analyse l'influence du monde des médias sur quatre "Kurzgeschichten" :"Paula" (1980) de E. Jelinek ; "Ein Pferd wird erschossen" (1982) de H. C. Buch ; "Wie ich lebe" (1979) de F. Hohler ; "Die ... [more ▼]

Ce mémoire analyse l'influence du monde des médias sur quatre "Kurzgeschichten" :"Paula" (1980) de E. Jelinek ; "Ein Pferd wird erschossen" (1982) de H. C. Buch ; "Wie ich lebe" (1979) de F. Hohler ; "Die Namen" (1979) de G. Neumann. [less ▲]

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See detailDer Einfluss von Imperfektionen in dünnwandigen geschweiBten Rechteckquerschnitten unter Druckbeanspruchung
Degée, Hervé ULg; Kuhlmann, U.; Detzel, A. et al

in Stahlbau (2008), 77(4), 257-265

This contribution presents the results of a research projects analysing some aspects of stability failure of thin-walled RHS compression members that are likely to exhibit combined global and local ... [more ▼]

This contribution presents the results of a research projects analysing some aspects of stability failure of thin-walled RHS compression members that are likely to exhibit combined global and local buckling. In particular the influence of various imperfections, namely residual stresses due to welding and local as well as global geometrical defects, on the load-carrying capacity is subjected to detailed experimental and numerical investigations. The insight into the structural behaviour leads to recommendations for standardized imperfections that should be used in the context of the numerical modelling of class-4 square and rectangular hollow section members subjected to compression. [less ▲]

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See detailEinführung
Küpper, Achim ULg

Scientific conference (2011, April 02)

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See detailEinführung
Küpper, Achim ULg

Scientific conference (2010, February 24)

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