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Planning under Uncertainties with Closed-Loop Sensitivity: Recent Results and Perspectives
No full textInternational audienceBackground and aims - Urinary zinc has been associated with cardiometabolic endpoints, including diabetes and cardiovascular disease, but evidence for peripheral artery disease (PAD) is limited. We evaluated prospective associations between urinary zinc and incident PAD and amputation events in the Strong Heart Study (SHS), a large epidemiological cohort of American Indian adults in the United States. Methods - A total of 2,045 PAD-free and 2,180 amputation-free participants were included at baseline (1989-91), (mean age 56 years, 61% female). PAD (defined as ankle brachial index < 0.9 or > 1.4) and diabetes-related amputation events were collected through two SHS visits over 10 years. Odds ratios (OR) of PAD and amputation by baseline urinary zinc levels adjusted by creatinine (µg/g) were evaluated with progressively adjusted logistic regression models. Results - 344 participants developed PAD and 23 underwent diabetes-related amputations. The ORs (95% CI) per one interquartile range increment in baseline urinary zinc levels were 1.29 (1.10, 1.51) and 2.36 (1.43, 3.90) for incident PAD and amputation, respectively, when adjusting for sociodemographic and clinical risk factors. Estimates were attenuated by further adjusting for diabetes status (OR: 1.16 (0.98, 1.38) for incident PAD), and fasting plasma glucose (OR: 1.09 (0.91, 1.31) and OR: 1.39 (0.76, 2.54) for incident PAD and amputation, respectively). Associations between urinary zinc levels and incident PAD were stronger among participants with diabetes at baseline (OR: 1.43 (1.11, 1.86)). Conclusions - We identify prospective associations between higher urinary zinc levels and increased risk of PAD and amputation in the SHS, with stronger effects among participants with diabetes. Supplementary information - The online version contains supplementary material available at 10.1007/s44417-025-00005-0
Performance bounds for priority-based stochastic coflow scheduling
No full textWe consider the coflow scheduling problem in the non-clairvoyant setting, assuming that flow sizes are realized on-line according to given probability distributions. The goal is to minimize the weighted average completion time of coflows in expectation. We first obtain inequalities for this problem that are valid for all non-anticipative order-based rate-allocation policies and define a polyhedral relaxation of the performance space of such scheduling policies. This relaxation is used to analyze the performance of a simple priority policy in which the priority order is computed by Sincronia from expected flow sizes instead of their unknown actual values. We establish a bound on the approximation ratio of this priority policy with respect to the optimal priority policy for arbitrary probability distributions of flow sizes (with finite first and second moments). Tighter upper bounds are obtained for some specific distributions. Extensive numerical results suggest that performance of the proposed policy is much better than the upper bound.</div
Grayscale evaporation of organic thin-film microstructures
No full textInternational audienceWe demonstrate that the deposition of organic thin films whose thickness is spatially shaped with sub-100-µm lateral resolution can be achieved by evaporation through a reusable flux-controlling micrometric-hole sieve that is separated from the to-be-coated substrate. This approach offers a practical way to grayscale-pattern organic materials without exposing them to detrimental ambient air or chemical solutions. As such, it facilitates the fabrication of long-lasting organic microstructured devices such as the reported spatially-varying absorptive color filters based here on the organic semiconductor (4,4'-Bis[4-(di-p-tolylamino)-styryl]biphenyl (DPAVBi)). Additionally, the ability to readily make multiple thickness-coated samples offers a material-sparing yet convenient way to measure the properties of the evaporated material, a feature exploited hereafter to extract the optical dielectric constants of DPAVBi over the visible and near-infrared range. This work and its extensions to inorganic compounds and freeform shaping pave the way for a new generation of devices that should find applications in light-matter coupling studies, hyperspectral imaging, structural coloring, or optical systems exploiting freeform optics
Resource Allocation for a Constellation of Low Earth Orbit Telecommunication Satellites: Optimization of the User-Satellite Link Network
No full textInternational audienceThe deployment of Low Earth Orbit (LEO) constellations for telecommunications is a growing market for satellite manufacturers. Such constellations offer a global coverage, low latency, resilience and redundancy, but their design requires numerous steps for which decision tools are more than necessary. In this paper, we propose to develop optimization algorithms to handle the resource allocation problem on the forward link between the LEO satellites and the end-users. In this problem, given a LEO constellation and an on-ground traffic model, the goal is to allocate the available resources of the satellites (bandwidth and power) in order to provided the maximum quantity of service to the end-users. A key point is that due to the high velocity of the satellites on their low orbits, each end-user can only stay connected to a satellite for a few minutes. To maintain a continuous service, it is crucial to extend the connection times with each satellite to avoid handovers. Failure to do so may negatively impact the quality of service due to frequent and abrupt disconnections. To tackle this problem, we propose two heuristic methods exploiting the computation of maximum flows with minimum cost in graphs. These heuristic methods are compared with mixed integer linear programming approaches.La mise en place de constellations en orbite terrestre basse (LEO) pour les télécommunications est un marché en croissance pour les fabricants de satellites. De telles constellations offrent une couverture mondiale, une faible latence, une résilience et une redondance, mais leur conception nécessite de nombreuses étapes pour lesquelles des outils de décision sont plus que nécessaires. Dans cet article, nous proposons de développer des algorithmes d'optimisation pour gérer le problème d'allocation des ressources sur le lien aller entre les satellites LEO et les utilisateurs finaux. Dans ce problème, étant donné une constellation LEO et un modèle de trafic au sol, l'objectif est d'allouer les ressources disponibles des satellites (bande passante et puissance) afin de fournir la quantité maximale de service aux utilisateurs finaux.Un point clé est que, en raison de la haute vitesse des satellites sur leurs orbites basses, chaque utilisateur final ne peut rester connecté à un satellite que pendant quelques minutes. Pour maintenir un service continu, il est crucial d'étendre les temps de connexion avec chaque satellite pour éviter les transferts. Ne pas le faire peut négativement impacter la qualité de service en raison de déconnexions fréquentes et abruptes. Pour résoudre ce problème, nous proposons deux méthodes heuristiques exploitant le calcul des flux maximaux à coûts minimaux dans les graphes. Ces méthodes heuristiques sont comparées avec des approches de programmation linéaire en nombres entiers
A formal statechart model of immediate neonatal adaptation guidelines
No full textInternational audienceResearch highlights the importance of applying physiological criteria for optimal umbilical cord clamping, underlining its lasting advantages. In response, the Division of Pediatrics, Perinatology, and Neonatology at the National University of Colombia has pioneered the Immediate Neonatal Adaptation Guideline, focusing on Physiologically-based Cord Clamping. This study has two main objectives: The first is to represent the medical guideline through a statechart model to enhance clarity and detail. Secondly, to evaluate the effectiveness of statechart models in depicting medical guidelines for educational and training purposes within a human-centric framework. In this study, a group of medical professionals and engineers designed the statechart model for the Immediate Neonatal Adaptation guideline through a progressive refinement method. The model comprises 20 states, 38 events, and 4 superstates, offering clear visual language for its evaluation by an interdisciplinary panel of engineers and health professionals. This visual representation facilitates a more explicit identification of patient states, criteria, and clinical indicators involved in the procedure. Feedback indicates general satisfaction with the Versatility, Usability, Scalability and Moderate visual complexity of the model
Exponential stabilization of linear systems using nearest-action control with countable input set
No full textInternational audienceThis paper studies stabilization of linear time-invariant (LTI) systems when control actions can only be realized in {\em finitely} many directions where it is possible to actuate uniformly or logarithmically extended positive scaling factors in each direction. Furthermore, a nearest-action selection approach is used to map the continuous measurements to a realizable action where we show that the approach satisfies a {\em weak} sector condition for multiple-input multiple-output (MIMO) systems. Using the notion of input-to-state stability, under some assumptions imposed on the transfer function of the system, we show that the closed-loop system converges to the target ball exponentially fast. Moreover, when logarithmic extension for the scaling factors is realizable, the closed-loop system is able to achieve asymptotic stability instead of only practical stability. Finally, we present an example of the application that confirms our analysis
Turning judges ranking into biomechanical parameters for cheerleading
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Measurement of skidding to determine the optimum ergonomic configuration of the racing wheelchair
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Optimizing shifted stabilizers with asymmetric input saturation
No full textInternational audienceA stabilizing controller design for linear systems subject to asymmetric actuator saturation is proposed. Stabilization is achieved by focusing on shifted equilibria selected via the solution of an optimization problem ensuring convergence to the origin of the shifted equilibrium. To enable the computational time required by the optimizer, we impose sampled-data updates of the shifted equilibria and cast our description within a hybrid dynamical systems formulation. Two feedback solutions are given, using exact and inaccurate optimization algorithms, thus establishing interesting trade-offs between continuous-time dynamics and computationally expensive iterative discrete-time parametric optimization schemes. Through numerical examples, estimates of the region of attraction obtained through the method outlined in this paper are compared to other methods in the literature. Additionally, the real-time applicability of the control law is illustrated on numerical examples
State prediction using a high-gain distributed scheme
No full textInternational audienceTime delays pose unique challenges in control engineering, as the inherent delays can introduce instabilities and compromise system performance. To overcome these complexities, the concept of predictors or compensators has been instrumental in stabilising closed-loop systems. Still, it requires an accurate delayed state estimation through the design and implementation of predictors. In this paper, we delve into the design of novel prediction architectures tailored to nonlinear systems with input and output delays that not only ensure stability but also bolster robustness, emphasising their ability to preserve stability despite measurement noises or external perturbations