Identification aveugle de structure propre sous excitation non-stationnaire

L'identification aveugle de la structure propre d'un système linéaire multivariable est effectuée par une méthode sous-espace appliquée aux matrices de covariances des seuls signaux de sortie, les entrées étant inconnues et non-stationnaires. L'analyse des vibrations est un exemple important de problèmes réels pouvant être posés et résolus de cette manière. Le traitement conjoint de signaux enregistrés à des moments différents, et sous excitations différentes, est un problème crucial dans ce domaine. La méthode sous-espace proposée pour résoudre ce problème de fusion est, comme la méthode classique, basée essentiellement sur une propriété de factorisation de la matrice de Hankel (et des covariances des sorties) du système. Des résultats expérimentaux illustrent les performances de la méthode. L'utilisation pour l'exploitation des données de vols d'essai d'avions est discutée

In-flight structural identification:input/output versus output-only data processing

The problem of in-flight data analysis, for the purpose of structural model identification under both measured and uncontrolled non-stationary excitation, is addressed. Input/output and output-only eigenstructure identification methods are described and compared, within two classes of methods: subspace-based and prediction error. In particular, different types of relevant projections for handling the known (measured) and unknown (uncontrolled) inputs are discussed. The relevance of the methods is emphasized through numerical results obtained on flight test data sets

Constructing Memory through Television in Argentina

La televisión representa el pasado reciente de la Argentina a través de vínculos específicos con la memoria social: como un “emprendedor de la memoria” definiendo las agendas públicas, como un vehículo de transmisión intergeneracional sobre el pasado y como un creador de significados por medio de imágenes, sonidos y palabras, esto es, un “escenario para la memoria”. Un análisis de los vínculos entre televisión y memorias, construido alrededor de la desaparición forzada de personas durante la dictadura militar de 1976 a 1983, revela la manera compleja en la cual los obstáculos para relatar ese periodo trágico se combinan con el intento de vender un producto y entretener al espectador.Television represents Argentina’s recent past through three specific links with social memory: as an “entrepreneur of memory,” shaping public agendas, as a vehicle of intergenerational transmission of past events, and as a creator of meaning through images, sounds, and words, a “stage for memory”. An analysis in terms of the links between television and the memories constructed around the forced disappearance of persons during the 1976–1983 military dictatorship reveals the complex way in which the obstacles when narrating an extreme experience are combined with the attempt to sell a product and entertain the spectator.Fil: Feld, Claudia Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones Sociales. Instituto de Desarrollo Económico y Social. Centro de Investigaciones Sociales; Argentin

Duhemian Themes in Expected Utility Theory

This monographic chapter explains how expected utility (EU) theory arose in von Neumann and Morgenstern, how it was called into question by Allais and others, and how it gave way to non-EU theories, at least among the specialized quarters of decion theory. I organize the narrative around the idea that the successive theoretical moves amounted to resolving Duhem-Quine underdetermination problems, so they can be assessed in terms of the philosophical recommendations made to overcome these problems. I actually follow Duhem's recommendation, which was essentially to rely on the passing of time to make many experiments and arguments available, and evebntually strike a balance between competing theories on the basis of this improved knowledge. Although Duhem's solution seems disappointingly vague, relying as it does on "bon sens" to bring an end to the temporal process, I do not think there is any better one in the philosophical literature, and I apply it here for what it is worth. In this perspective, EU theorists were justified in resisting the first attempts at refuting their theory, including Allais's in the 50s, but they would have lacked "bon sens" in not acknowledging their defeat in the 80s, after the long process of pros and cons had sufficiently matured. This primary Duhemian theme is actually combined with a secondary theme - normativity. I suggest that EU theory was normative at its very beginning and has remained so all along, and I express dissatisfaction with the orthodox view that it could be treated as a straightforward descriptive theory for purposes of prediction and scientific test. This view is usually accompanied with a faulty historical reconstruction, according to which EU theorists initially formulated the VNM axioms descriptively and retreated to a normative construal once they fell threatened by empirical refutation. From my historical study, things did not evolve in this way, and the theory was both proposed and rebutted on the basis of normative arguments already in the 1950s. The ensuing, major problem was to make choice experiments compatible with this inherently normative feature of theory. Compability was obtained in some experiments, but implicitly and somewhat confusingly, for instance by excluding overtly incoherent subjects or by creating strong incentives for the subjects to reflect on the questions and provide answers they would be able to defend. I also claim that Allais had an intuition of how to combine testability and normativity, unlike most later experimenters, and that it would have been more fruitful to work from his intuition than to make choice experiments of the naively empirical style that flourished after him. In sum, it can be said that the underdetermination process accompanying EUT was resolved in a Duhemian way, but this was not without major inefficiencies. To embody explicit rationality considerations into experimental schemes right from the beginning would have limited the scope of empirical research, avoided wasting resources to get only minor findings, and speeded up the Duhemian process of groping towards a choice among competing theories