Optimization of the electrochemical impedance spectroscopy measurement parameters for PEM fuel cell spectrum determination

Currently, electrochemical Impedance Spectroscopy (EIS) is a widely used tool for the study of electrochemical systems, in general; and fuel cells, in particular. A great effort is typically invested in the analysis of the obtained spectra; whereas, little time is usually spent optimizing the measurement parameters used to obtain these spectra. In general, the default settings provided by the control software used to perform the measurements, or the parameters used in similar systems available in literature, are selected to carry out the measurements. The goal of this work is to determine the optimal measurement parameters for obtaining impedance spectra of a commercial PEM fuel cell. In order to achieve this, a 2^5 factorial design was considered. Five factors were considered, the five impedance spectroscopy measurement parameters: maximum integration time; minimum number of integration cycles; number of stabilization cycles; maximum stabilization time; and minimum cycle fraction. For each factor combination envisaged in the experimental design, the cell spectrum was obtained in given operation conditions, for which the reference spectrum of the system was known, since it had been determined in previous works. The experimentally obtained spectra were fitted to the reference electric equivalent circuit. The mean square error between the experimental data fitting and the reference spectrum fitting was determined in each case, and was used as the dependant variable for the experimental design analysis. An analysis of the variance was performed in order to determine which measurement parameters have a significant effect on the dependant variable; and a model relating the dependant variable and the measurement parameters was built. This model was used in order to obtain the optimal value of each one of the measurement parameters that minimized the mean square error of the fit obtained from the experimental data with respect to the reference fit.The authors are very grateful to the Generalitat Valenciana for its economic support in form of Vali+d grant (Ref: ACIF-2013-268).Giner Sanz, JJ.; Ortega Navarro, EM.; Pérez-Herranz, V. (2015). Optimization of the electrochemical impedance spectroscopy measurement parameters for PEM fuel cell spectrum determination. Electrochimica Acta. 174:1290-1298. https://doi.org/10.1016/j.electacta.2015.06.106S1290129817

Convergence of time - stepping schemes for passıie and extended linear complementarity systems

Generalizing recent results in [M. K. Camlibel, Complementarity Methods in the Analysis of Piecewise Linear Dynamical Systems, Ph.D. thesis, Center for Economic Research, Tilburg University, Tilburg, The Netherlands, 2001], [M. K. Camlibel, W. P. M. H. Heemels, and J. M. Schumacher, IEEE Trans. Circuits Systems I: Fund. Theory Appl., 49 (2002), pp. 349-357], and [J.-S. Pang and D. Stewart, Math. Program. Ser. A, 113 (2008), pp. 345-424], this paper provides an in-depth analysis of time-stepping methods for solving initial-value and boundary-value, non-Lipschitz linear complementarity systems (LCSs) under passivity and broader assumptions. The novelty of the methods and their analysis lies in the use of "least-norm solutions" in the discrete-time linear complementarity subproblems arising from the numerical scheme; these subproblems are not necessarily monotone and are not guaranteed to have convex solution sets. Among the principal results, it is shown that, using such least-norm solutions of the discrete-time subproblems, an implicit Euler scheme is convergent for passive initial-value LCSs; generalizations under a strict copositivity assumption and for boundary-value LCSs are also established

Convergence of Time-Stepping Schemes for Passive and Extended Linear Complementarity Systems

Generalizing recent results in [M. K. Camlibel, Complementarity Methods in the Analysis of Piecewise Linear Dynamical Systems, Ph.D. thesis, Center for Economic Research, Tilburg University, Tilburg, The Netherlands, 2001], [M. K. Camlibel, W. P. M. H. Heemels, and J. M. Schumacher, IEEE Trans. Circuits Systems I: Fund. Theory Appl., 49 (2002), pp. 349-357], and [J.-S. Pang and D. Stewart, Math. Program. Ser. A, 113 (2008), pp. 345-424], this paper provides an in-depth analysis of time-stepping methods for solving initial-value and boundary-value, non-Lipschitz linear complementarity systems (LCSs) under passivity and broader assumptions. The novelty of the methods and their analysis lies in the use of "least-norm solutions" in the discrete-time linear complementarity subproblems arising from the numerical scheme; these subproblems are not necessarily monotone and are not guaranteed to have convex solution sets. Among the principal results, it is shown that, using such least-norm solutions of the discrete-time subproblems, an implicit Euler scheme is convergent for passive initial-value LCSs; generalizations under a strict copositivity assumption and for boundary-value LCSs are also established.</p

Optimisation de la configuration magnétique d'un propulseur à effet Hall par résolution du problème magnétostatique inverse

Les travaux effectués lors de cette thèse portent sur l'optimisation de la configuration magnétique des propulseurs à effet Hall. Ceci regroupe deux objectifs: d'une part la réalisation d'un propulseur à effet Hall dont la topologie magnétique est entièrement paramétrable, ce qui constituera un outil précieux pour l'étude de l'impact du champ magnétique sur le fonctionnement du propulseur et d'autre part, l'étude de moyen de conception rationalisée de circuits magnétiques pour ces mêmes propulseurs. Le premier sujet a conduit à la réalisation du PPS-Flex, un propulseur proposant une structure de circuit magnétique innovante offrant un grand nombre de degrés de liberté en termes de réglage du champ magnétique produit. La deuxième thématique a quant à elle été abordée en s'appuyant sur des méthodes d'optimisation (paramétrique et topologique) permettant d'aboutir à un circuit magnétique optimal pour un ou plusieurs critères de conception (fidélité du champ magnétique généré, minimisation de la masse, du volume total, etc.) ABSTRACT : The works made during this thesis concern the optimization of the magnetic configuration of propellers with effect Hall. This groups two objectives: on one hand the realization of a propeller with effect Hall the magnetic topology of which is completely customizable, which will establish a precious tool for the study of the impact of the magnetic field on the functioning of the propeller and on the other hand, the study of way of design rationalized of magnetic circuits for these same propellers. The first subject led to the realization of the PPS-Flex, a propeller proposing an innovative magnetic structure of circuit offering a large number of degrees of freedom in terms of regulation of the magnetic field produces. The second theme approached as for her resting on method

Optimisation de la configuration magnétique d'un propulseur à effet Hall par résolution du problème magnétostatique inverse

Les travaux effectués lors de cette thèse portent sur l'optimisation de la configuration magnétique des propulseurs à effet Hall. Ceci regroupe deux objectifs: d'une part la réalisation d'un propulseur à effet Hall dont la topologie magnétique est entièrement paramétrable, ce qui constituera un outil précieux pour l'étude de l'impact du champ magnétique sur le fonctionnement du propulseur et d'autre part, l'étude de moyen de conception rationalisée de circuits magnétiques pour ces mêmes propulseurs. Le premier sujet a conduit à la réalisation du PPS-Flex, un propulseur proposant une structure de circuit magnétique innovante offrant un grand nombre de degrés de liberté en termes de réglage du champ magnétique produit. La deuxième thématique a quant à elle été abordée en s'appuyant sur des méthodes d'optimisation (paramétrique et topologique) permettant d'aboutir à un circuit magnétique optimal pour un ou plusieurs critères de conception (fidélité du champ magnétique généré, minimisation de la masse, du volume total, etc.