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Patients virtuels pour l'apprentissage du raisonnement clinique : atouts et limites, état des lieux et création d'une plateforme de cas cliniques vétérinaires en ligne
Get PDFAvec l’évolution de la place de l’animal dans la société, la formation vétérinaire fait face à de nouvelles exigences éthiques. Le nombre grandissant d’étudiants à former doit respecter le paradigme « jamais la première fois sur le patient ». Dans ce cadre, les outils numériques constituent une voie utile et occupent une place croissante dans la formation. Parmi ces outils, le recours à des patients virtuels permet d’améliorer l’apprentissage du raisonnement clinique. Les établissements de formation vétérinaires cherchent à les intégrer activement dans le cursus. Dans cette optique, cette thèse présente un état des lieux des plateformes permettant la création de patients virtuels dans le domaine de la médecine humaine et vétérinaire. Elle révèle que de tels outils sont rares, coûteux ou difficiles à mettre en place. Une plateforme permettant l’édition de cas cliniques rapide et utilisable sans compétences informatiques particulières a été élaborée au cours de ce travail et constitue une contribution à la mise en place de telle solution
A neuroergonomic approach to performance estimation in a psychomotor vigilance task
Get PDFIntroduction: Passive brain-computer interfaces (pBCI; tools that enable an implicit mental state
estimation) have gained attention in a wide range of applications, including performance and vigilance
monitoring in high-risk work settings (Lotte & Roy, 2019). Vigilance can be defined as the ability to
maintain sustained attention to a stimulus for an extended period of time (Al-Shargie et al., 2019), and is
influenced by the time of day and fatigue (Lim and Dinges, 2008). A vigilance decrement impacts
performance over time (called time-on-task -TOT) during tedious monitoring tasks, resulting in slower
reaction times or increased errors (Pattyn et al., 2008). This effect is experienced in all kinds of activities
such as in aeronautics where pilots can experience a performance drop during the flight (Wiggins, 2011).
Hence, vigilance and performance estimation is a crucial step towards the implementation of safer work
settings. Machine learning applied to physiological measures, such as cerebral activity (via
electroencephalogram -EEG- recordings), is a promising way to estimate performance. EEG’s spectral
activity is impacted by fluctuations in vigilance (Matousek & Petersén, 1983) and the power in both theta
and alpha bands can be considered as robust biomarkers of mental fatigue (Tran et al., 2020). Numerous
studies have attempted to estimate performance during a vigilance task based on EEG measures (Tian et
al. 2018), or electrocardiographic (ECG) measures (e.g., heart rate -HR-, and its variability -HRV; Chua et
al., 2012). To our knowledge, performance estimation during monotonous tasks has not reached a high
accuracy, and pBCI pipelines could be improved. Hence, the objective of this study is to employ a
comprehensive neuroergonomic approach to vigilance and performance characterization for a typical
vigilance task: the Psychomotor Vigilance Task (PVT; Dinges & Powell, 1985) encompassing statistical
analyses, as well as EEG-based performance classification using pre-stimulus signal.
Methods: Ten volunteers (3 females; Mage=25, sd=3; ethical number from Univ. Toulouse: 2021-342)
performed a 10-minute PVT (i.e., 90 stimuli) from a task battery. They had to complete a fatigue
questionnaire (Karolinska Sleepiness Scale; Åkerstedt & Gillberg, 1990) and their response time (RT) was
measured. In addition, EEG and ECG activities were recorded using an ActiCHamp system (63+1
electrodes). Data were processed in two ways: i) TOT analysis: data were split into ten 1-minute
windows; and ii) Performance analysis: response-based epoching (-2:0s for EEG; -10:0s for ECG), only the
30 best and 30 worst trials were kept (labeled according to RT), and also used for performance
classification. Considering statistical analyses, one-way repeated measures ANOVAs and paired samples
t-tests (Student and Wilcoxon), were performed separately on each dataset. To perform TOT analysis on
RT, the signal was cut into 10 periods of 9 simultaneous stimuli and the reciprocal RT (mean 1/RT) was
calculated on each period. EEG data were filtered (1-40 Hz) and ocular artifacts were automatically
removed (SOBI method). The theta, alpha, and beta power were extracted for three electrode clusters
(frontal, central, posterior). The Task Load Index (TLI: thetaFz/alphaPz) and the engagement ratio
(beta/[theta+alpha]; average on all electrodes) were also calculated. ECG data were filtered (1-40 Hz)
and normalized using a 1-minute eyes-open resting state period. HR and HRV (as SDNN) were then
extracted. For EEG-based estimation, a dimensionality reduction method based on Laplacian was applied
(Xu et al., 2021), and a minimum distance to mean with geodesic filtering classifier (FgMDM) was trained
and tested using a 10-fold cross-validation procedure.
Results: There was no significant difference in subjective fatigue (regardless of PVT order in battery).
There was a significant linear downward trend on reciprocal RT (p<.05; other contrasts n.s.; Fig.1.A).
There was a significant effect of TOT on alpha power at frontal (p<.05, ηp²=.26) and posterior (p<.05,
ηp²=.27) sites, as well as on the engagement ratio (p<.05, ηp²=.31; Fig.1.B). TOT also significantly impacted
HR (p<.001, ηp²=.31; Fig.1.C) and HRV (p<.05, ηp²=.27). Regarding performance (best/worst trials), alpha
power was significantly lower for the best than worst trials at frontal (p<.01, rB=-.93), and posterior
(p<.01, rB=-.89) sites, while the TLI was higher for the best trials (p<.05, d=.87). In terms of performance
classification, the FgMDM classifier achieved a mean accuracy of 58.2% without dimensionality
reduction. By selecting the number of dimensions that gives the best accuracy for each subject, the
mean accuracy with dimensionality reduction was 70.5% (mean number of dimensions = 27.3, Fig.2.A).
By comparison, the principal component analysis (PCA) achieved a mean accuracy of 71.1% (mean
number of dimensions = 23).
Discussion: The results showed that the neuroergonomic approach employed in this study enabled us to
assess physiological modulations due to vigilance fluctuations, such as alpha power and engagement
ratio decreased over time. However, the HR drop observed in the first minutes may be due to the initial
presentation novelty (Kelsey et al., 1999). Also, analyses of the best and worst trials showed that
vigilance decreased during the bad trials. However, some results were not as strong as those obtained in
the literature. This may be due to either the short task duration (10 minutes) compared to the several
sessions performed over several hours or days in the literature, or because our participants were not
sleep deprived. Besides, these analyses were performed on a small number of participants (n=10).
Regarding performance estimation, the classification accuracy was low for several reasons. Firstly, there
is little difference in terms of vigilance during the 10-minute PVT task, even though we have chosen the
30 best and worst trials. Secondly, the number of training samples is quite limited (i.e., 60 per subject). In
this case, dimensionality reduction becomes essential as shown by the results. Both dimensionality
reduction methods (non-supervised) significantly improve accuracy while reducing the computation
time. Moreover, on average the Laplacian-based method performs better in lower dimensions than PCA
(Fig.2.B). In summary, this study shows that even with a short task and a normal level of fatigue, it is
possible to observe an impact of a monotonous task on behavioral and physiological measures at the
group level. Yet, it remains difficult to implement an accurate performance estimation pipeline using a
single short session at the individual level
Étude générale du lapin domestique (Oryctolagus cuniculus) : domestication, répartition actuelle et perspective d’avenir
Get PDFLa domestication du lapin a conduit à l’élevage de cet animal pour sa chair mais aussi pour sa fourrure et sa peau. Actuellement, la production de fourrure tend à devenir marginale. De la même façon, la production de viande de lapin reste modeste comparée à d’autres. Le lapin domestique s’est également révélé être un animal de laboratoire indispensable en toxicologie, maladie infectieuse ou en biologie médicale. Plus récemment, il est un animal de compagnie de plus en plus apprécié. Le futur du lapin de compagnie dans notre société repose principalement sur les attentes économiques, écologiques et culturelles des jeunes générations. Enfin l’élevage et la recherche devront répondre aux attentes sur le bien-être animal pour voir leur secteur subsister
Carbonation and Captation of CO2: optimisation of a feasibilitry demonstration
No full textIn this work, we are interested in the sources of raw materials for mineral carbonation as well as the valorization of the products resulting from this carbonation. To achieve carbonation of waste and to obtain a valuable product we need carbonatable materials such as Fe, Mg, Mn, Ca: it is necessary to seek these compounds in the waste considered. We will focus on particular sources of waste, the residues of cement industries, bottom ash (steel mills, incineration of household waste) or building deconstruction residues. The objective of this paper is to describe the functional specifications of a carbonation unit that is both flexible enough to treat a wide variety of these materials, and compact enough to allow it to be moved from one source to another. These specifications will concern two different uses of this mobile unit: that of initial feasibility demonstration, and those corresponding to its current operation
Large scale simulations of swirling and particle-laden flows using the Lattice-Boltzmann Method
Get PDFSince the development of high performance computers, numerical simulations have evolved into an important scientific tool by means of mathematical modeling to address physical problems that are complex to handle experimentally. Predicting the behavior of physical systems which are not directly observable helps to design and optimize new technology. Computational fluid dynamics in specific aims to understand natural flow phenomena as well as to design and operate engineering processes in industry. With the continuous increase in computational power every year, the question of how to efficiently use computational resources becomes increasingly more important. Improving existing practices involves a better understanding of the underlying physical mechanisms as well as optimizing the algorithms that are used to solve them with robust and rapid numerical methods. The Lattice-Boltzmann method (LBM) is a mesoscopic approach to approximate the macroscopic equations of mass and momentum balance equations for a fluid flow. The objective of this study is to apply this concept to large scale problems and present its capabilities in terms of physical modelling and computing efficiency. As a validation step, computational models are tested against referenced theoretical, numerical and experimental evidences over a wide range of hydrodynamic conditions from creeping to turbulent flows and granular media. Turbulent flows are multi-scale flows that required fine meshes and long simulation times to converge statistics.Special care is taken to verify the fluid-solid interface for dispersed two-phase flows.Two main setups are examined – the non-reacting, swirling flow inside an injector and a particle-laden flow around a cylinder. Swirling flows are typical of aeronautical combustion chambers. The selected configuration is used to benchmark three different large eddy simulation solvers regarding their accuracy and computational efficiency. The obtained numerical results are compared to experimental results in terms of mean and fluctuating velocity profiles and pressure drop. The scaling, that is the code performance on a large range of processors, is characterized. Differences between several algorithmic approaches and different solvers are evaluated and commented. Next, we focused on particle laden flows around a cylinder as generic configuration for the interaction of a dispersed phase and flow hydrodynamic instabilities. It has been shown that the viscosity of a suspension increases relative to the particle volume fraction and for a certain range of particle material and concentration, this a fairly good model of interphase coupling. This phenomenon only occurs in numerical simulations that are able to describe finite size effects for rigid bodies. Comparing global flow parameters of suspensions at different particle volume fractions and sizes have shown that these flow features can be obtained for an equivalent single phase fluid with effective viscosity. Starting from neutrally buoyant particles the transition to granular flow is investigated. By increasing the relative density of particles, the influence of particle inertia on the equivalent fluid prediction is investigated and the contribution of particle collisions on the drag coefficient for varying relative densities is discussed. Conclusions are drawn regarding the code performance and physical representativeness of results
Tailoring glass fiber surface for the polymerization and crystallization of anionic polyamide 6
Get PDFMonomer polymerization after the impregnation of reinforcements is a relevant option for the manufacturing of thermoplastic composites by liquid processes (infusion or RTM). In the case of polyamide 6 synthesized by this process, the system composed of monomers, catalyst and activator reacts within the fibrous environment. Therefore, fiber surface chemistry is a crucial parameter because it does not only influence the polymerization and crystallization processes, but it also controls the fiber-matrix adhesion
Additive manufacturing of silicon carbide-based ceramics by powder bed selective laser processing : from the functionalized powder to the final part
Get PDFSilicon carbide (SiC) is a widely used industrial ceramic because of its excellent properties which makes it useful for a wide range of applications. For some specific applications, the component design could be improved by additive manufacturing. As one of additive manufacturing methods, Powder Bed Selective Laser Processing, also called Selective Laser Sintering/Melting (SLS/SLM), has been expected to fabricate complicated shape components in recent years. In general, Powder Bed Selective Laser Processing (PBSLP) of ceramics is classified in direct and indirect. Direct PBSLP is the method by which the ceramic powder is heated by a laser beam to bond particles as a result of solid-state sintering or melting and, in contrast indirect PBSLP is the method by which the laser irradiation melts sacrificial organic polymer binder added to the ceramic powder, resulting in the bonding of the ceramic particles. The main difference between both techniques is the debinding process which is only present in the indirect method. In consequence, indirect PBSLP involves melting of a sacrificial (generally) organic binder phase to produce green parts. However, direct PBSLP is considered unfit for making silicon carbide component because the high density of the ceramic components and the high preheating temperature when forming leads to stress during the manufacturing process and can result in cracking. Moreover, this process is specifically complicate since SiC does not have a melt phase under normal atmospheric circumstances but instead decomposes at temperatures in excess of 2545 °C into liquid Si and solid C. The original scientific approach of this PhD thesis resides in the production of innovative SiC powders that enable direct PBSLP by grain surface functionalization. This surface modification, where a SiC preceramic precursor is grafted onto the grain surface of SiC powder, is a potential method to improve the sintering behaviour of this ceramic material. The purpose is to directly grow polymer thin films from or onto the surface of the particles resulting in a core-shell type material architecture that does not affect the flowability of the powder which would imply the impossibility of using this feedstock in PBSLP processes. Moreover, the sintering behaviour of both SiC powder and surface modified SiC was studied in spark plasma sintering prior the use of the modified surface in PBSLP. On the other hand, regarding the PBSLP process, firstly, a study was carried out to investigate the manufacturing possibility of SiC by direct PBSLP experimentally and numerically. The results showed that the direct PBSLP of SiC is possible with the optimization of the process parameters. Secondly, the scanning strategies effect on direct PBSLP of SiC was also studied. We conclude that hexagonal stagey can be considered the best strategy to be used with SiC as it succeeds to eliminate all the problems happened with other scanning strategies. Finally, following the results obtained previously, silicon carbide parts were manufactured by means of direct PBSLP in absence of post-treatments and any addition of additives in the initial powder mixture. The individual optimization of each parameter was performed. The final SiC parts exhibit 81% of relative density and 5%, /1% of residual Silicon and Carbon, respectively, which corresponds to some decomposition during process due to high peaks inherently generated by the scanning strategy. Moreover, the process viability can be confirmed with the manufacturing of SiC complex shapes, specific, SiC lattice structures which cannot be obtained with traditional manufacturing techniques
Robust control of rotation-floating space robots with flexible appendages for on-orbit servicing
Get PDFOn-orbit operations are facing a growing need for autonomous robotic systems to achieve
risky and repetitive tasks. Debris removal, on-orbit servicing and in-space
deployment/assembly are examples of applications considering the use of robot
manipulators. The presence of large and light appendages in future spacecrafts, such as
solar arrays, antennas and sun shields yields to flexible disturbances inside the structure
making the control of the manipulator challenging. This paper addresses design and contro
Système et procédé de fabrication d'un produit composite à base de particules cellulosiques à défibrer et d'un liant thermoplastique
Get PDFL’invention propose un procédé de fabrication d'un produit composite à base de particules cellulosiques à défibrer (21) et d’un liant thermoplastique (22), au moyen d'une machine d'extrusion (10) comprenant deux vis (11) parallèles engrenant l'une dans l'autre et entraînées en rotation à l'intérieur d'un fourreau allongé (12), chaque vis étant constituée d’un arbre central et d’une pluralité d’éléments de vis (15) présentant chacun un type, une longueur et un pas de vis déterminés. Selon l’invention les particules cellulosiques à défibrer et le liant thermoplastique sont à l’état solide à l’entrée, de sorte qu’on réalise, à l'intérieur du fourreau (12) en un seul passage, un défibrage des particules cellulosiques à défibrer (21), une fonte du liant thermoplastique (22) et un mélange intime des particules cellulosiques défibrées obtenues avec le liant thermoplastique fondu et un agent de plastification (40) pour obtenir un produit composite extrudable (60)
Recommendations on using VPN over SATCOM
Get PDFVPN are a secured tunnel that help service providers to exchange data over non-secured networks. There is a large variety of VPN solutions that have variable deployment impacts on the target architecture as well as performance limitations or opportunities. This technical report compares Wireguard and OpenVPN for various SATCOM deployment scenarios and topologies