Scientific Publications of the University of Toulouse II Le Mirail
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On L¹ and time-optimal state transitions in piecewise linear models of gene-regulatory networks
No full textInternational audienceIn this paper, we investigate optimal state transfers for a generic class of piecewise-linear models widely used to qualitatively describe gene-regulatory networks. Motivated by the main practical drawbacks of artificially regulating gene expression through chemical inducers, the optimality of the transitions is defined as the convex combination of the total time and the L¹ cost of the control. Solutions are studied through a Hybrid Pontryagin's Maximum Principle approach, which allows to characterize the optimal trajectories and control for the general formulation of the problem. Then, we focus on two practical examples of two-dimensional regulatory networks: the bistable switch, for which the objective is to induce optimal transitions between its two stable steady states, and the damped genetic oscillator, where the goal is to induce sustained oscillatory behaviors. The resulting optimal control strategies can be expressed in state feedback form, involving both bang arcs and inactive control periods, and are shown to slide over certain separatrices of the uncontrolled system that characterize the boundaries of the admissibility set
Existence of monostable fronts for a KPP infinite-difference numerical scheme
No full textInternational audienceWe study the existence of traveling wave solutions for a numerical counterpart of the KPP equation. We obtain the existence of monostable fronts for all super-critical speeds in the regime where the spatial step size is small. The key strategy is to transfer the invertibility of certain linear operators related to the front solutions from the continuous setting to the discrete case we are interested in. We rely on resolvent bounds which are uniform with respect to the step size, a procedure which is also known as spectral convergence. The approach is also able to handle infinite range discretizations with geometrically decaying coefficients that are allowed to have both signs, which prevents the use of the comparison principle
Predictive validity of cognitive abilities for air traffic controllers selection among proficient scientific candidates
No full textInternational audienceMost air traffic controllers (ATCO) are selected after high school graduation, partly based on cognitive abilities. On the contrary, French ATCO are selected after an intensive scientific post-secondary program without undergoing cognitive assessment. This study examines the potential incremental validity of cognitive predictors in ATCO training for such proficient applicants. Initial and unit training results were available for 414 and 277 ATCO students, respectively. All students took cognitive ability tests, encompassing visuospatial processing, quantitative knowledge, and work samples. We compared a baseline regression model with academic performance as sole predictor to an extended model with the addition of the cognitive abilities composite score. The R2 of the extended model increased significantly, by 0.04 (p < .001) and 0.06 (p < .001), respectively, for predicting practical initial and unit training outcome. In conclusion, even for scientific proficient candidates, cognitive assessment can enhance the success rate of ATCO training
Insight into cooling requirements for thermophotovoltaic devices
No full textInternational audiencePerformance of thermophotovoltaic conversion devices depends on the operating temperature of the cell, and thus on how heat generated in the cell is dissipated. The present research examines the cooling requirements that allow the cell to operate at a specified temperature, based on the parameters influencing electrical power generation. A detailed balance approach and a simple thermal model involving an effective heat transfer coefficient are used. Key parameters, such as emitter temperature, view factor, in-band transmission and out-of-band transmission functions, and external radiative efficiency, are systematically varied to evaluate their influence on pairwise efficiency and power density, and on the required effective heat transfer coefficient to ensure that the cell operates at selected temperatures. Although thermophotovoltaic cells are typically presumed to function at close to ambient, our findings indicate that maintaining this operating temperature necessitates a cooling system with a substantially high effective heat transfer coefficient (∼ 10^3 -10^4 Wm -2 K -1 ). The cooling challenge grows when the cell bandgap diminishes, due to the interplay of rising power density and decreasing pairwise efficiency. The cooling requirements increase with the temperature of the emitter and the view factor. Nevertheless, they can be mitigated by reducing both in-band and out-of-band transmission functions. They are underestimated, and the bandgap optimizing pairwise efficiency or power density is inadequately predicted when the cell is assumed to operate in the radiative limit. These insights into cooling requirements imply that they should be considered from the initial stages of thermophotovoltaic device design
Model-based dependability and performance analysis for satellite systems with collaborative maintenance maneuvers via stochastic games
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Naissance des cités à travers l’appropriation des territoires multiples
No full textNational audienceLe présent bilan partiel des activités de notre opération se concentre sur le volet initial des cités, c’est-à-dire sur les périodes les plus anciennes et sur l’appropriation des espaces ruraux et urbains
Repenser l’empowerment en santé à l’aune des dispositifs numériques de surveillance de la santé : une approche par le sense-making
No full textInternational audienceThis contribution examines the forms of empowerment mobilized by users of non professional self-tracking (Quantified Self) devices through an analysis of their infor mational and communicational practices. Based on a qualitative study conducted on the MyFitnessPal and Fitbit forums, it explores how individuals interpret the health data produced by these devices and integrate them into their daily routines. The theoretical framework draws on sense-making theory and the sociology of uses to investigate processes of appropriation, contestation, and negotiation of digital norms. Three forms of empowerment are identified: cognitive (the ability to interpret and adapt data), critical (distancing oneself from algorithmic authority), and collective (peer support and learning). Far from a purely individualistic model, these forms of empowerment are situated, relational, and sometimes conflictual. The study thus highlights the complexity of health-related connected device uses, emphasizing their role as sociotechnical mediation devices where relationships to the body, information, and autonomy are continuously reconfigured.Cette contribution examine les formes d’ empowerment mobilisées par les usagers de dispositifs non professionnels de quantification de soi (quantified self) à travers l’analyse de leurs pratiques informationnelles et communicationnelles. En s’appuyant sur une enquête qualitative menée sur les forums MyFitnesspal et Fitbit , il explore la manière dont les individus interprètent les données de santé produites par ces dispositifs et les intègrent à leurs routines. L’approche théorique mobilise les apports du sense-making et de la sociologie des usages pour interroger les processus d’appropriation, de contestation et de négociation des normes numériques. Trois formes d’empowerment sont mises en évidence : cognitif (capacité à interpréter et à adapter les données), critique (mise à distance de l’autorité algorithmique) et collectif (soutien et apprentissage par les pairs). Loin d’un modèle purement individualiste, ces formes d’empowerment sont situées, relationnelles et parfois conflictuelles. L’étude met ainsi en lumière la complexité des usages des objets connectés de santé, en soulignant leur rôle de dispositifs de médiation sociotechnique où se rejouent les rapports au corps, à l’information et à l’autonomie
Qui prend les cars régionaux et pourquoi ? Résultats d’une enquête dans le Midi toulousain
No full textInternational audienceThis article presents the results of a survey of regional coach users conducted as part of a Master’s workshop on behalf of the Occitanie region. Sixteen routes were studied, on which commercial passengers form the majority. They are mainly located in the departments of Haute-Garonne and Tarn. The responses obtained highlight a high level of user satisfaction with this mode of transport, including in terms of comfort. Whilst ‘captive’ users do indeed constitute a significant proportion of the passenger base (52%), many users have a choice of transport mode and opt for the coach, which offers an alternative to the car that is primarily economical and, less frequently, environmentally friendly. Quite logically, the higher the level of service on a route, the greater its ability to attract this second type of user appears to be.Cet article présente les résultats d’une enquête réalisée auprès des usagers des cars régionaux dans le cadre d’un atelier de master pour le compte de la région Occitanie. Seize lignes ont été étudiées, pour lesquelles les passagers commerciaux sont majoritaires. Elles sont principalement situées dans les départements de la Haute-Garonne et du Tarn. Les réponses obtenues permettent de mettre en avant une adhésion importante des usagers vis-à-vis de ce mode de transport, y compris sur la question du confort. Si les usagers « captifs » constituent bien un public important (52 %), beaucoup d’usagers sont en situation de choix modal et adoptent le car, qui constitue une alternative à la voiture avant tout économique et, plus rarement, écologique. Assez logiquement, plus le niveau de service sur une ligne est élevé, plus sa capacité à attirer ce deuxième type d’usager apparaît importante
