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Modeling and Analysis of Covid’19 Patients Hospitalization Dynamic Reliability by a Semi-Markovian Model
No full textInternational audienceWe have data on the follow-up of 260 Covid’19 patients at major hospital in Madagascar. According to specialists, the patient’s daily oxygen saturation and requirement allow us to characterize the form of the patient’s case in free different states: mild form, moderate form, severe form. We propose a semi-Markovian model with five states (Mild form, Moderate form, Sever form, Cured and Deceased) to analyze the time scales of recovery and death as well as the probability of recovery and death as a function of patient status. The model was also used to measure the dynamic reliability of care up to hospital discharge, i.e. the probability of not being severely ill as a function of hospitalization time
Planification intégrée des sillons et des matériels roulants dans une échelle microscopique
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Experimental observation and encircling of an exceptional point in coupled pendulums
No full textVibro-acoustique : session générale; GVB - Vibro acoustique et Contrôle du BruitNational audienceExceptional points (EPs) are special degeneracies corresponding to specific values of the system parameters for which both eigenfrequencies and eigenvectors coalesce simultaneously, leading to a defective eigenvalue problem. In recent years, these singularities, typical of non-Hermitian dynamics, have gained interest in physics because of the counter-intuitive concepts associated with them. In the fields of acoustics and vibration, understanding EPs may lead to a better comprehension of modal energy exchanges and decay. This work aims at exploring the key concepts related to EPs by revisiting the well-known coupled pendulums problem in the presence of damping. First, the free response of the experimental system is investigated after tuning it on an EP. Then an encircling is performed by varying the parameters through time. Our experimental results illustrate in a pedagogical manner nearly-optimal dissipation, energy exchange and chirality effects which have been recently evidenced in physics. Finally, the influence of the encircling time on the chirality is explored experimentally, numerically and theoretically using the multiple-scale approach for periodic modulation
Analyse Théorique et Expérimentale du Couplage Vibro- acoustique à Forts Niveaux : Application à la Conception des Absorbants Passifs
No full textVibro-acoustique : session générale; GVB - Vibro acoustique et Contrôle du BruitNational audienceLa réduction du bruit, notamment l’atténuation sur de larges gammes fréquentielles et plus particulièrement en basses fréquences, constitue un enjeu sociétal majeur. Cette étude propose l’utilisation d’absorbeurs présentant une raideur régie par une loi non linéaire, offrant un avantage par rapport aux absorbeurs à masses accordées classiques. Ces oscillateurs non linéaires, sont appelés puits d’énergie non linéaire (ou NES (pour Nonlinear Energy Sinks)). Un tel système, couplé à un oscillateur primaire (acoustique ou vibratoire), permet un transfert irréversible d’énergie à partir d’un niveau d’excitation suffisant. L’énergie est alors majoritairement transférée du système primaire vers l’absorbeur non linéaire, où elle est dissipée. Dans ce contexte, l’application d’un NES pour l’atténuation du premier mode acoustique d’un conduit est étudiée. L’analyse se concentre sur l’étude d’un NES constitué d’une fine membrane viscoélastique en caoutchouc qui, sous de forts niveaux acoustiques, vibre avec des déplacements importants, induisant des non-linéarités géométriques. Un modèle original réduit à un oscillateur est proposé pour prendre en compte l’hyperélasticité du matériau. En effet, les observations expérimentales montrent qu’un oscillateur à raideur cubique, associée dans la littérature aux non-linéarités géométriques, ne suffit pas pour expliquer les tendances. Enfin, une limitation majeure de ces systèmes réside dans la nécessité de niveaux d’excitation élevés pour déclencher le transfert d’énergie. Ces travaux proposent d’abord une comparaison de résultats issus de ce modèle aux observations expérimentales, en vue de réaliser une analyse paramétrique approfondie (dimensions, amortissement, etc.) et d’optimiser le NES en termes de seuil d’activation, de bande de fréquence et de part d’énergie dissipée
Ultrasound, pulsed electric fields, and high-voltage electrical discharges assisted extraction of cellulose and lignin from walnut shells
No full textInternational audienceExtracting The extraction of cellulose and lignin from biomass is essential for the development of sustainable bio-based materials. This study examines the effects of physical pretreatment techniques—ultrasound (US), pulsed electric fields (PEF), and high-voltage electrical discharges (HVED)—on the efficiency of alkali treatment for cellulose and lignin extraction from walnut shells. The primary objective was to enhance extraction yields and improve extract quality while evaluating the effectiveness of these methods. The results revealed that the combined treatments achieved lignin and cellulose yields of up to 17.03 % and 33.40 %, respectively, with US and HVED showing significantly higher extraction efficiencies compared to other techniques. Characterization of the extracted materials using FTIR, XRD, 2D HSQC NMR, TGA/DTG, and DSC confirmed the presence of key functional groups, crystalline structures, and detailed molecular features, while also providing insights into thermal stability. These findings underscore the potential of walnut shells as a sustainable source for bio-based materials and demonstrate the influence of physical pretreatments on the structural and thermal properties of extracted cellulose and lignin. This study paves the way for further research into industrial applications, such as wood adhesives. Future work should focus on optimizing extraction processes, scaling up operations, and investigating the effects of biomass variability on extraction outcomes
Phytochemical composition, phytotoxicity, and ADME modeling of Artemisia absinthium L.: implications for food safety and pharmaceutical applications
No full textInternational audienceArtemisia absinthium, an aromatic herb distinguished by its characteristic bitter flavour, has been used in a variety of culinary applications. This study investigates its metabolites through phytochemical methods. The primary minerals in Artemisia absinthium stems are potassium (41%) and calcium (38.3%), forming most of its mineral content. The ethanolic extract exhibited the highest phenolic compound content, with 37.6 ± 0.09 mg GAE/g DE. The primary volatile compound identified was β-thujone, comprising over 26.6% of the volatile content. Palmitic acid is the predominant fatty acid in the hexanic extract (18.7%), while linoleic acid is the main fatty acid in the ethyl acetate extract (42.4%). Twenty phenolic compounds were identified, with 8-methoxyflavone, (+)-catechin hydrate, and chlorogenic acid as major compounds in dichloromethane, ethyl acetate, and ethanol extracts, respectively. ADME modeling indicating that 8-methoxyflavone, a major component in the dichloromethane extract, is a promising candidate for drug development targeting the central nervous system
Joint Scheduling of Production and Condition‐Based Maintenance Activities for Make‐To‐Order Deteriorating Manufacturing Systems Under Repairmen Constraint
No full textInternational audienceABSTRACT For a make‐to‐order manufacturing system, randomly fluctuating customer orders determine its production planning, and further influence the deterioration of machines in the manufacturing system. Maintenance activities are then conducted to recover machines to a better status by a limited number of repairmen with different skill levels. Production and maintenance are two conflicting activities for manufacturing systems, and they need to be jointly optimized to attain the global optimum. However, the joint optimization of production and maintenance for manufacturing systems considering randomly fluctuating customer orders with repairman constraints has not been studied yet. In this work, first, the reliability of production machines and a group maintenance model of the manufacturing system considering limited repairmen with different skill levels are constructed. Second, the production plan is first made according to the predicted customer orders and then updated by considering the influence of maintenance with limited repairmen. Third, the production plan and maintenance schedule are jointly optimized to minimize the entire operation and maintenance costs. Finally, the proposed method is applied to a real‐world make‐to‐order manufacturing system of the shell of an air‐conditioning compressor to prove its feasibility
Assessment of the influence of model powder characteristics on their flowability using correlation matrices
No full textInternational audienceThis study focuses on the use of correlation matrices as a tool to investigate the relationship between the physical characteristics of powders and their flowability. The correlation coefficients are calculated for a dataset containing various types of powders, allowing the study of the influence of particle size, morphology and density on flow properties. Flowability is estimated through various tests such as the shear test, density ratio, powder rheometer and rotating drum. The analysis revealed that correlations between flowability indices are not strictly associated with specific flow regimes (quasi-static and dense regimes). Instead, the physical mechanisms of interparticle cohesion and friction appear to play a determinant role in these correlations. Further analysis involving the division of the dataset into fine and coarse powders provided additional insights, underscoring the different mechanisms governing the flow behavior of cohesive and non-cohesive powders. In a second step, this research work also incorporated data from existing literature, confirming the general trends observed with the initial dataset. Future research should focus on developing more sophisticated models that can account for multiple input parameters simultaneously and consider non-linear relationships, for example, through semi-empirical models or machine learning techniques
A nonparametric distribution-free test of independence among continuous random vectors based on L1-norm
No full textInternational audienceWe propose a novel statistical test to assess the mutual independence of multidimensional random vectors. Our approach is based on the L1-distance between the joint density function and the product of the marginal densities associated with the presumed independent vectors. Under the null hypothesis, we employ Poissonization techniques to establish the asymptotic normal approximation of the corresponding test statistic, without imposing any regularity assumptions on the underlying Lebesgue density function, denoted as f(⋅). Remarkably, we observe that the limiting distribution of the L1-based statistics remains unaffected by the specific form of f(⋅). This unexpected result contributes to the robustness and versatility of our method. Moreover, our tests exhibit nontrivial local power against a subset of local alternatives, which converge to the null hypothesis at a rate of n−1∕2h−d∕4n, d≥2, where n represents the sample size and hn denotes the bandwidth. Finally, the theory is supported by a comprehensive simulation study to investigate the finite-sample performance of our proposed test. The results demonstrate that our testing procedure generally outperforms existing approaches across various examined scenarios