Structural validation of a realistic wing structure: the RIBES test article

Several experimental test cases are available in literature to study and validate fluid structure interaction methods. They, however, focus the attention mainly on replicating typical cruising aerodynamic conditions forcing the adoption of fully steel made models able to operate with the high loads generated in high speed facilities. This translates in a complete loss of similitude with typical realistic aeronautical wing structures configurations. To reverse this trend, and to better study the aerolastic mechanism from a structural point of view, an aeroelastic measurement campaign was carried within the EU RIBES project. A half wing model for wind tunnel tests was designed and manufactured replicating a typical metallic wing box structure, producing a database of loads, pressure, stress and deformation measurements. In this paper the design, manufacturing and validation activities performed within the RIBES project are described, with a focus on the structural behavior of the test article. All experimental data and numerical models are made freely available to the scientific community

Rolling horizon procedures in Semi-Markov Games: The Discounted Case

We study the properties of the rolling horizon and the approximate rolling horizon procedures for the case of two-person zero-sum discounted semi-Markov games with infi nite horizon, under several assumptions on the reward function, when the state space is a borelian set and the action spaces are considered compact. Under suitable conditions, we prove that the equilibrium is the unique solution of its dynamic programming equation, and we prove bounds which imply the convergence of the procedures when the horizon length tends to in finity. The approach is based on the formalism for Semi-Markov games developed by Luque-Vásquez, together with extensions of the results of Hernández-Lerma and Lasserre for Markov Decision Processes and Chang and Marcus for Markov Games, both in discrete time. In this way we generalize the results on the rolling horizon and approximate rolling horizon procedures previously obtained for discrete-time problems.Nous étudions les propriétés de la procédure de décision à horizon roulant et une approximation de cette procédure, pour le cas de jeux semi-Markoviens à somme nulle avec horizon in fini et actualisation, sous diff érentes hypothèses concernant la fonction de récompense, quand l'espace d'états est un ensemble borélien et les espaces d'actions sont compacts. Sous des hypothèses appropriées, nous montrons que l'équilibre est l'unique solution de l'équation de programmation dynamique associée au jeu, puis nous prouvons des bornes d'erreur impliquant la convergence des procédures quand l'horizon de programmation tend vers l'infi ni. Notre approche est basée sur le formalisme pour les jeux semi-Markoviens développé par Luque-Vásquez, joint à des extensions des résultats de Hernández-Lerma et Lasserre pour les processus de décision Markoviens et Chang et Marcus pour les jeux Markoviens, ces deux derniers travaux étant en temps discret. De cette façon, nous généralisons les résultats sur la procédure à horizon roulant obtenus pour les problèmes en temps discret

Illustrated review of convergence conditions of the value iteration algorithm and the rolling horizon procedure for average-cost MDPs

International audienceThis paper is concerned with the links between the Value Iteration algorithm and the Rolling Horizon procedure, for solving problems of stochastic optimal control under the long-run average criterion, in Markov Decision Processes with finite state and action spaces. We review conditions of the literature which imply the geometric convergence of Value It- eration to the optimal value. Aperiodicity is an essential prerequisite for convergence. We prove that the convergence of Value Iteration generally implies that of Rolling Horizon. We also present a modified Rolling Horizon procedure that can be applied to models without analyzing periodicity, and discuss the impact of this transformation on convergence. We il- lustrate with numerous examples the different results. Finally, we discuss rules for stopping Value Iteration or finding the length of a Rolling Horizon. We provide an example which demonstrates the difficulty of the question, disproving in particular a conjectured rule pro- posed by Puterman

Approximations on Risk-Averse Markov Decision Processes

We consider the problem of approximating the values and the optimal policies in risk-averse discounted Markov Decision Processes with in nite horizon. We study the properties of the rolling horizon and the approximate rolling horizon procedures, proving bounds which imply the convergence of the procedures when the horizon length tends to in nity. We also analyze the e ects of uncertainties on the transition probabilities, the cost functions and the discount factors.Nous considérons le problème de l'approximation de la fonction de valeur et des politiques optimales dans un processus de décision Markovien avec actualisation et aversion au risque. Nous étudions les propriétés de la procédure de l'horizon roulant et son approximation, et montrons des bornes qui impliquent la convergence de ces procédures quand l'horizon de temps tend vers l'in ni. Nous analysons aussi les e ets d'incertitudes sur les probabilités de transition, les fonctions de coût et les facteurs d'actualisation

Structural approximations in discounted semi-Markov games

We consider the problem of approximating the values and the equilibria in two-person zero-sum discounted semi-Markov games with infinite horizon and compact action spaces, when several uncertainties are present about the parameters of the model. Specifically: on the one hand, we study approximations made on the transition probabilities, the discount factor and the reward functions when the state space is a borelian set. On the other hand, we study approximations on the state space for denumerable ones. Our results are based on those of Tidball and Altman (SIAM J. Control and Optimization, 1996) on generic zero-sum games. We provide conditions under which these results can be applied. We also discuss the application of such approximations for finite-horizon games, in relation with the Approximate Rolling Horizon procedure proposed in Della Vecchia et al. (INRIA RR 8019, 2012).Nous considérons le problème de l'approximation des valeurs et des équilibres d'un jeu semi-Markovien actualisé, en horizon infi ni avec des ensembles d'actions compacts, en présence d'incertitude sur plusieurs paramètres du modèle. Spécifi quement: d'une part nous étudions les approximations sur les probabilités de transition, sur le facteur d'actualisation et sur les coûts, quand l'espace d'états est un ensemble Borélien. D'autre part, nous étudions les approximations de l'ensemble d'états quand celui-ci est dénombrable. Nos résultats sont basés sur ceux de (SIAM J. Control and Optimization, 1996). Nous donnons des conditions sous lesquelles ces résultats peuvent être appliqués. Nous discutons aussi de l'application de telles approximations à des jeux en horizon fini, en relation avec la procédure de l'horizon roulant approchée, proposée dans Della Vecchia et al. (INRIA RR 8019, 2012)

3D-electrical resistivity tomography monitoring of salt transport in homogeneous and layered soil samples

Monitoring transport of dissolved substances in soil deposits is particularly relevant where safety is concerned, as in the case of geo-environmental barriers. Geophysical methods are very appealing, since they cover a wide domain, localising possible preferential flow paths and providing reliable links between geophysical quantities and hydrological variables. This paper describes a 3D laboratory application of Electrical Resistivity Tomography (ERT) used to monitor solute transport processes. Dissolution and transport tests on both homogeneous and heterogeneous samples were conducted in an instrumented oedometer cell. ERT was used to create maps of electrical conductivity of the monitored domain at different time intervals and to estimate concentration variations within the interstitial fluid. Comparisons with finite element simulations of the transport processes were performed to check the consistency of the results. Tests confirmed that the technique can monitor salt transport, infer the hydro-chemical behaviour of heterogeneous geomaterials and evaluate the performances of clay barrier

Estimation of the hydraulic parameters of unsaturated samples by electrical resistivity tomography

In situ and laboratory experiments have shown that electrical resistivity tomography (ERT) is an effective tool to image transient phenomena in soils. However, its application in quantifying soil hydraulic parameters has been limited. In this study, experiments of water inflow in unsaturated soil samples were conducted in an oedometer equipped to perform three-dimensional electrical measurements. Reconstructions of the electrical conductivity at different times confirmed the usefulness of ERT for monitoring the evolution of water content. The tomographic reconstructions were subsequently used in conjunction with a finite-element simulation to infer the water retention curve and the unsaturated hydraulic conductivity. The parameters estimated with ERT agree satisfactorily with those determined using established techniques, hence the proposed approach shows good potential for relatively fast characterisations. Similar experiments could be carried out on site to study the hydraulic behaviour of the entire soil deposi

Factors associated with SARS-CoV-2 infection risk among healthcare workers of an italian university hospital

We report the results of a study on the cumulative incidence of SARS-CoV-2 infections in about 6000 workers of the University Hospital of Modena, Northern Italy, in the period March 2020–January 2021, and the relations with some individual and occupational factors. Overall, in healthcare workers (HCW) the cumulative incidence of COVID-19 during the period was 13.8%. Results confirm the role of overweight and obesity as significant risk factors for SARS-CoV-2 infection. Chronic respiratory diseases, including asthma, also proved to be significantly associated with the infection rate. Considering occupational factors, the COVID-19 risk was about threefold (OR: 2.7; 95% CI 1.7–4.5) greater in nurses and nurse aides than in non-HCW, and about double (OR: 1.9; 95% CI 1.2–3.2) in physicians. Interestingly, an association was also observed between infection risk and nightshifts at work (OR: 1.8; 95% CI 1.4–2.3), significantly related to the total number of shifts in the whole eleven-month period. Even if the vaccination campaign has now greatly modified the scenario of SARS-CoV-2 infections among HCW, the results of this study can be useful for further development of health and policy strategies to mitigate the occupational risk related to the new variants of coronavirus, and therefore the evolution of the pandemic

Prevalence and severity of airway obstruction in an Italian adult population

Background. This study sets out to estimate the prevalence and the degree of severity of bronchial obstruction in an adult population with three different diagnostic criteria: the European Respiratory Society (ERS), the American Thoracic Society (ATS), and the World Health Organization (WHO) defined as Global Obstructive Lung Disease (GOLD). Methods. 1514 subjects underwent complete medical evaluation and spirometry. Results. The prevalence of bronchial obstruction was respectively 27.5% (ERS), 33% (GOLD), and 47.3% (ATS). The prevalence of bronchial obstruction in the smoker group was 33.4% (ERS), 38.1% (GOLD), and 52.3% (ATS). The prevalence of obstruction in the ex-smoker group was 33% (ERS), 41.4% (GOLD), and 57.1% (ATS). The prevalence of obstruction in the non-smoker group was 21.1% (ERS), 24.9% (GOLD), and 38.6% (ATS). Conclusions. The results show that the prevalence of airway obstruction increases proportionally with age; the cigarette smoking represents an important conditioning factor. These observations warrant the necessity of a more complete and multi-parametric analysis in the evaluation of patients with airway obstruction using methodologies that explore the functional state and the risk factors that cause the airway obstruction