Robust Hypothesis Testing with a Relative Entropy Tolerance

This paper considers the design of a minimax test for two hypotheses where the actual probability densities of the observations are located in neighborhoods obtained by placing a bound on the relative entropy between actual and nominal densities. The minimax problem admits a saddle point which is characterized. The robust test applies a nonlinear transformation which flattens the nominal likelihood ratio in the vicinity of one. Results are illustrated by considering the transmission of binary data in the presence of additive noise.Comment: 14 pages, 5 figures, submitted to the IEEE Transactions on Information Theory, July 2007, revised April 200

A Contraction Analysis of the Convergence of Risk-Sensitive Filters

A contraction analysis of risk-sensitive Riccati equations is proposed. When the state-space model is reachable and observable, a block-update implementation of the risk-sensitive filter is used to show that the N-fold composition of the Riccati map is strictly contractive with respect to the Riemannian metric of positive definite matrices, when N is larger than the number of states. The range of values of the risk-sensitivity parameter for which the map remains contractive can be estimated a priori. It is also found that a second condition must be imposed on the risk-sensitivity parameter and on the initial error variance to ensure that the solution of the risk-sensitive Riccati equation remains positive definite at all times. The two conditions obtained can be viewed as extending to the multivariable case an earlier analysis of Whittle for the scalar case.Comment: 22 pages, 6 figure

Robust Kalman Filtering: Asymptotic Analysis of the Least Favorable Model

We consider a robust filtering problem where the robust filter is designed according to the least favorable model belonging to a ball about the nominal model. In this approach, the ball radius specifies the modeling error tolerance and the least favorable model is computed by performing a Riccati-like backward recursion. We show that this recursion converges provided that the tolerance is sufficiently small

Robust State Space Filtering under Incremental Model Perturbations Subject to a Relative Entropy Tolerance

This paper considers robust filtering for a nominal Gaussian state-space model, when a relative entropy tolerance is applied to each time increment of a dynamical model. The problem is formulated as a dynamic minimax game where the maximizer adopts a myopic strategy. This game is shown to admit a saddle point whose structure is characterized by applying and extending results presented earlier in [1] for static least-squares estimation. The resulting minimax filter takes the form of a risk-sensitive filter with a time varying risk sensitivity parameter, which depends on the tolerance bound applied to the model dynamics and observations at the corresponding time index. The least-favorable model is constructed and used to evaluate the performance of alternative filters. Simulations comparing the proposed risk-sensitive filter to a standard Kalman filter show a significant performance advantage when applied to the least-favorable model, and only a small performance loss for the nominal model

Assistante sociale et militante, une évidence ?: l'engagement militant comme compétence de la pratique professionnelle des assistantes sociales

Pour la plus grande majorité, travail social et militantisme sont associés. Mais alors, pourquoi l’engagement militant est-il si peu visible dans la formation d’assistante sociale comme dans la profession ? Est-ce une notion qui, au fil des années, s’est gentiment éteinte dans le milieu du travail social ou est-ce les professionnelles qui ne ressentent plus la nécessité d’être militantes ? Aujourd’hui, de nombreuses professionnelles de service social se plaignent des conditions de travail ou des conditions sociales et financières des bénéficiaires. Les services sont surchargés et les assistantes sociales en souffrance. A partir de ces constatations, ne faudrait-il pas envisager de repenser la formation ainsi que le métier d’assistante sociale

Prediction of the Spectrum of a Digital Delta–Sigma Modulator Followed by a Polynomial Nonlinearity

This paper presents a mathematical analysis of the power spectral density of the output of a nonlinear block driven by a digital delta-sigma modulator. The nonlinearity is a memoryless third-order polynomial with real coefficients. The analysis yields expressions that predict the noise floor caused by the nonlinearity when the input is constant

Le travail prescrit à l'épreuve du réel: analyse de la mise en pratique d'un concept éducatif

S’appuyant sur les apports de l’analyse de l’activité, ce travail de mémoire a pour objectif de mettre en évidence l’écart qui existe entre le travail prescrit par le concept éducatif du Foyer St-Martin « Grandir ensemble » et le travail réel effectué par les éducateurs au quotidien. Afin d’avoir accès au réel de l’activité, la chercheuse a suivi la méthodologie de l’autoconfrontation croisée. Cette méthode utilise l’image vidéo comme support d’analyse, permettant aux professionnels de prendre du recul, de mener une réflexion au sujet de leur travail et ainsi, d’augmenter leur pouvoir d’agir. Quatre séquences de films ont été retenues pour ce travail, co-analysées par les éducateurs et la chercheuse. Au fil des échanges, trois thèmes, à savoir l’autonomie, le lien et les règles, étaient récurrents. Ils forment le coeur de l’analyse dans ce travail. En définitive, cette recherche montre que les professionnels du Foyer St-Martin construisent leurs pratiques en se basant fortement sur leur concept éducatif mais également sur leurs expériences personnelles et professionnelles, leurs ressentis, leurs valeurs. Le concept « Grandir ensemble » n’est pas directement prescriptif, il donne des repères pour la pratique

Hypertension and microvascular remodelling

In the present review, microvascular remodelling refers to alterations in the structure of resistance vessels contributing to elevated systemic vascular resistance in hypertension. We start with some historical aspects, underscoring the importance of Folkow's contribution made half a century ago. We then move to some basic concepts on the biomechanics of blood vessels, and explicit the definitions proposed by Mulvany for specific forms of remodelling, especially inward eutrophic and inward hypertrophic. The available evidence for the existence of remodelled resistance vessels in hypertension comes next, with relatively more weight given to human, in comparison with animal data. Mechanisms are discussed. The impact of antihypertensive drug treatment on remodelling is described, again with emphasis on human data. Some details are given on the three studies to date which point to remodelling of subcutaneous resistance arteries as an independent predictor of cardiovascular risk in hypertensive patients. We terminate by considering the potential role of remodelling in the pathogenesis of end-organ damage and in the perpetuation of hypertensio

Knowledge as an Intellectual Property: The Effect of Knowledge Sharing and Encouragement by Others on Information Systems Use in the Workplace

Organizations invest in Information Systems (IS) to help achieve strategic goals and to disseminate knowledge in order to enhance employee productivity. Most individuals consider knowledge as their intellectual property. However, sharing the knowledge about using IS and encouraging others to use IS has received limited attention in research. This study examined employees’ knowledge sharing (collegial and technical knowledge), encouragement by others to share knowledge, and their role in predicting computer self-efficacy (CSE) and IS usage. This study included 256 participants from five different organizations. Web-based instrument was used based on prior measures from literature, and an expert panel review was done. We conducted a confirmatory data analysis using Structural Equation Modeling (SEM) with AMOS®. Our results indicate that encouragement by others does significantly impact knowledge sharing. We also found that while technical knowledge sharing had a significantly positive influence on CSE, collegial knowledge sharing had a negative influence on CSE

L'éco-entrepreneuriat, un objet de gestion non identifié ?: Proposition d'un nouveau cadre conceptuel et enquête exploratoire en milieu agricole breton en vue d'appréhender sa diversité

20 pages. A paraitre dans Thierry Levy-Tadjine et Zhan SU-2013-Eds= "Entrepreneuriat, PME durables et réseaux sociaux, Mélanges en l'honneur du Professeur Robert Paturel", L'Harmattan. . Ce chapitre s'inscrit dans le cadre du programme de recherches GEODD (Gestion des Entreprises et Organisations orientées vers le Développement Durable) financé par l'ANR (Agence Nationale de la Recherche). Ce projet dirigé par Florence Palpacuer (Université de Montpellier et ERFI) associe plusieurs groupes de recherche dont l'Equipe Entrepreneuriat du Laboratoire ICI (Université de Bretagne Occidentale) sous la responsabilité de Robert Paturel.National audienceLe chapitre discute de la représentation du phénomène éco-entrepreneurial en proposant de mobiliser la théorie des conventions pour rendre compte de la diversité de ses manifestations. Le modèle conceptuel proposé est ensuite confronté aux représentations et aux discours d'experts du monde agricole breton