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International audience; IntroductionLes objectifs du contrôle glycémique en réanimation se sont complexifiés depuis la première étude de Louvain [1] mettant en évidence une réduction de mortalité associée au seul respect d’une cible glycémique stricte (4,4–6,1 mmol/L). Au-delà de la controverse concernant la cible glycémique qui s’en est suivie, hypoglycémie et variabilité glycémique élevée seraient associées à un pronostic défavorable [2]. Le but de l’étude est de vérifier si ces associations existent dans le collectif de patients inclus dans l’étude multicentrique CGAO-REA visant à comparer l’impact sur la mortalité à J90 d’un contrôle glycémique informatisé strict (4,4–6,1 mmol/L) à un contrôle glycémique conventionnel (< 10 mmol/L) [3].Matériel et méthodesPour chacun des 2556 patients (parmi les 2648 randomisés analysables de l’étude CGAO-REA) pour lesquels les données de monitorage glycémique étaient disponibles, nous avons déterminé, pour l’ensemble du séjour en réanimation, la glycémie minimale Gmin, la glycémie maximale Gmax, la différence Gmax–Gmin, et la glycémie moyenne. La division en quintiles de la distribution de ces paramètres descriptifs du contrôle glycémique a permis de construire 5 groupes de patients pour chaque paramètre. La mortalité à J90 a été déterminée dans chacun des groupes et comparée à l’aide d’un test Chi2 à la mortalité attendue.RésultatsParmi les 2556 patients, 835 sont décédés à J90 (mortalité attendue 32,7 %). Les 4 graphiques suivants indiquent la mortalité dans chacun des quintiles pour chaque paramètre (Fig. 1)DiscussionL’analyse des patients inclus dans l’étude CGAO-REA semble confirmer l’association entre hypoglycémie et variabilité glycémique et pronostic défavorable.

The present study examined whether the ventilatory thresholds during an incremental exhaustive running test could be determined using heart rate variability (HRV) analysis. Beat-to-beat RR interval, V(.-)O (2), V(.-)CO (2) and V(.-) (E) of twelve professional soccer players were collected during an incremental test performed on a track until exhaustion. The "smoothed pseudo Wigner-Ville distribution" (SPWVD) time-frequency analysis method was applied to the RR time series to compute the usual HRV components vs. running speed stages. The ventilatory equivalent method was used to assess the ventilatory thresholds (VT1 and VT2) from respiratory components. In addition, ventilatory thresholds were assessed from the instantaneous components of respiratory sinus arrhythmia (RSA) by two different methods: 1) from the high frequency peak of HRV ( FHF), and 2) from the product of the spectral power contained within the high frequency band (0.15 Hz to fmax) by FHF (HF x FHF) giving two thresholds: HFT1 and HFT2. Since the relationship between FHF and running speed was linear for all subjects, the VTs could not be determined from FHF. No significant differences were found between respective running speeds at VT1 vs. HFT1 (9.83 +/- 1.12 vs. 10.08 +/- 1.29 km x h (-1), n.s.) nor between the respective running speeds at VT2 vs. HFT2 (12.55 +/- 1.31 vs. 12.58 +/- 1.33 km x h (-1), n.s.). Linear regression analysis showed a strong correlation between VT1 vs. HFT1 (R (2) = 0.94, p < 0.001) and VT2 vs. HFT2 (R (2) = 0.96, p < 0.001). The Bland-Altman plot analysis reveals that the assessment from RSA gives an accurate estimation of the VTs, with HF x FHF providing a reliable index for the ventilatory thresholds detection. This study has shown that VTs could be assessed during an incremental running test performed on a track using a simple beat-to-beat heart rate monitor, which is less expensive and complex than the classical respiratory measurement devices.

International audience; Based on the techniques of high gain observer and adaptive estimation, an adaptive observer is proposed in this paper for sensor fault estimation in a class of uniformly observable non-linear systems. It is first assumed that a high gain observer exists for the fault-free system. With a parametric model of sensor fault, a high gain adaptive observer is then designed for sensor fault estimation. In order to establish the global convergence of the adaptive observer, in addition to the usual conditions for high gain observer convergence, a persistent excitation condition is also required, like in most recursive parameter estimation problems.

International audience; Patient-specific cardiac modelling can help in understanding pathophysiology and predict therapy effects. This requires the personalization of the geometry, kinematics, electrophysiology and mechanics. We use the Bestel-Clément-Sorine (BCS) electromechanical model of the heart, which provides reasonable accuracy with a reduced parameter number compared to the available clinical data at the organ level. We propose a preliminary specificity study to determine the relevant global parameters able to differentiate the pathological cases from the healthy controls. To this end, a calibration algorithm on global measurements is developed. This calibration method was tested successfully on 6 volunteers and 2 heart failure cases and enabled to tune up to 7 out of the 14 necessary parameters of the BCS model, from the volume and pressure curves. This specificity study confirmed domain-knowledge that the relaxation rate is impaired in post-myocardial infarction heart failure and the myocardial stiffness is increased in dilated cardiomyopathy heart failures.

International audience; We consider the chemostat model with the substrate concentration as the single measurement. We propose a control strategy that drives the system at a steady state maximizing the gas production without the knowledge of the specific growth rate. Our approach separates the extremum seeking problem from the feedback control problem such that each of the two subproblems can be solved with relatively simple algorithms. We are then free to choose any numerical optimization algorithm. We give a demonstration for two choices: one is based on slow-fast dynamics and numerical continuation, the other is a combination of golden-section and Newton iteration. The method copes with non-monotonic growth functions.

International audience; In this paper fault diagnosis is studied for linear time varying descriptor systems, which are the discrete time counterpart of the continuous time dynamic systems described by differential-algebraic equations. This class of systems includes and is broader than the well-known state space systems. The framework of descriptor systems is particularly useful for studying dynamic systems exhibiting time varying singularities. Actuator faults and sensor faults are respectively modeled as parametric changes in the state equation and in the output equation. The main result of this paper consists in extending an adaptive observer, initially designed for state space systems, to descriptor systems. Based on this result, fault diagnosis is performed by estimating the parameters characterizing actuator and sensor faults.

International audience; This study introduces a new signal analysis method, based on a semiclassical approach. The main idea in this method is to interpret a pulse-shaped signal as a potential of a Schrödinger operator and then to use the discrete spectrum of this operator for the analysis of the signal. We present some numerical examples and the first results obtained with this method on the analysis of arterial blood pressure waveforms.

International audience; The study in this paper is motivated by the modeling of control valves with significant stiction. By assuming linear dynamics of the controlled process, the joint characterization of the control valve and of the controlled process is formulated as the identification of an extended Hammerstein system. A point-slope-based hysteresis model is used to describe the input hysteresis nonlinearity of the control valve. An iterative algorithm is proposed to solve the identification problem. The basic idea is to separate the ascent and descent paths of the input hysteresis nonlinearity subject to oscillatory excitations. Some identifiability analysis is performed: the proposed extended Hammerstein model structure is identifiable, and given the true input nonlinearity, the oscillatory signals in feedback control loops are shown to be informative by exploiting the cyclo-stationarity of these oscillatory signals. Industrial examples are provided to verify the effectiveness of the proposed identification algorithm in characterizing complicated characteristics of control valve stiction in practice.

International audience; This paper describes a statistical approach to fault detection and isolation for linear time-varying (LTV) systems subject to parametric additive faults. The proposed approach combines a GLR test with a recursive filter that cancels out the dynamics of the monitored faults effects. To our knowledge, the proposed recursive filter is new for the considered faults with time-varying profiles. The resulting algorithm handles fault diagnosis with weaker assumptions than usual, in particular on the number of sensors and on the stability of the monitored system.

International audience; In this paper we propose a muscle tissue model -- valid for striated muscles in general, and for the myocardium in particular -- based on a multi-scale physiological description. This model extends and refines an earlier-proposed formulation by allowing to account for all major energy exchanges and balances, from the chemical activity coupled with oxygen supply to the production of actual mechanical work, namely, the biological function of the tissue. We thus perform a thorough analysis of the energy mechanisms prevailing at the various scales, and we proceed to propose a complete discretization strategy -- in time and space -- respecting the same balance laws. This will be crucial in future works to adequately model the many important physiological -- normal and pathological -- phenomena associated with these energy considerations.

International audience; Having in mind applications to the fault-detection/diagnosis of lossless electrical networks, here we consider some inverse scattering problems for Schrödinger operators over star-shaped graphs. We restrict ourselves to the case of minimal experimental setup consisting in measuring, at most, two reflection coefficients when an infinite homogeneous (potential-less) branch is added to the central node. First, by studying the asymptotic behavior of only one reflection coefficient in the high-frequency limit, we prove the identiability of the geometry of this star-shaped graph: the number of edges and their lengths. Next, we study the potential identification problem by inverse scattering, noting that the potentials represent the inhomogeneities due to the soft faults in the network wirings (potentials with bounded H1-norms). The main result states that, under some assumptions on the geometry of the graph, the measurement of two reflection coefficients, associated to two different sets of boundary conditions at the external vertices of the tree, determines uniquely the potentials; it can be seen as a generalization of the theorem of the two boundary spectra on an interval.

International audience; Diesel Particulate Filters (DPF) has now been proven as an efficient solution in order to reduce Diesel PM emissions. Concerned by environment, Renault will equip all serial production Diesel vehicles with this technology. Main issue of such devices is the mandatory periodical regeneration in order to eliminate their soot content. The particulate filter (DPF) is used to store the soot emitted by the combustion engine. When the mass of particles in the filter reaches a certain limit mass, it is regenerated thanks to a temperature rise (Over 600◦C). In this paper, we develop a model that describes the impact of the amount of soot in the filter on the Diesel engine performance. This model is used to determine the optimal amount of soot on which the regeneration of the particulate filter shall start. Then we propose a physical model that describes the pressure drop of particulate filter according to the mass of accumulated soot and inlet DFP temperature and flow conditions. Thus, we improve a literature model so that it takes on account the passive regeneration of the filter. Finally, we design an extended kalman filter using the combination of the simplified model and a pressure drop measurement. All the experimental validations are made thanks to different configurations: engine dynamometer, chassis dynamometer and vehicles.

In this paper, we study a scalar conservation law that models a highly re-entrant manufacturing system as encountered in semi-conductor production. As a generalization of \cite{CKWang}, the velocity function possesses both the local and nonlocal character. We prove the existence and uniqueness of the weak solution to the Cauchy problem with initial and boundary data in $L^{\infty}$. We also obtain the stability (continuous dependence) of both the solution and the out-flux with respect to the initial and boundary data. Finally, we prove the existence of an optimal control that minimizes, in the $L^p$-sense with $p\in [1,\infty)$, the difference between the actual out-flux and a forecast demand over a fixed time period., Comment: 32 pages, 12 figures

International audience; This study proposes a Semi-Classical Signal Analysis (SCSA) method for stroke volume (SV) variations assessment from arterial blood pressure measurements. One of the SCSA parameters, the first systolic invariant (INVS1), has been shown to be linearly related to SV. To technically validate this approach, the comparison between INVS1 and SV measured with the currently used PiCCO technique was performed during a 15-min recording in 20 mechanically ventilated patients in intensive care. A strong correlation was estimated by linear regression and cross-correlation analysis (mean coefficient = 0.90 ± 0.01 SEM at the two tests).

International audience; The Two-Stage Algorithm (TSA) has been extensively used and adapted for the identification of Hammerstein systems. It is essentially based on a particular formulation of Hammerstein systems in the form of bilinearly parameterized linear regressions. This paper has been motivated by a somewhat contradictory fact: though the optimality of the TSA has been established by Bai in 1998 only in the case of some special weighting matrices, the unweighted TSA is usually used in practice. It is shown in this paper that the unweighted TSA indeed gives the optimal solution of the weighted nonlinear least squares problem formulated with a particular weighting matrix. This provides a theoretical justification of the unweighted TSA, and also leads to a generalization of the obtained result to the case of colored noise with noise whitening. Numerical examples of identification of Hammerstein systems are presented to validate the theoretical analysis.

The fertility of ram semen after cervical insemination is substantially reduced by 24 h of storage in liquid form. The effects of liquid storage on the transit of ram spermatozoa in the ewe genital tract was investigated using a new procedure allowing direct observation of the spermatozoa in the genital tract. Ejaculated ram spermatozoa were double labeled with R18 and MitoTracker Green FM, and used to inseminate ewes in estrus either cervically through the vagina or laparoscopically into the base of the uterine horns. Four hours after insemination, the spermatozoa were directly observedin situusing fibered confocal fluorescence microscopy in the base, middle and tip of the uterine horns, the utero-tubal junction (UTJ) and the oviduct. The high resolution video images obtained with this technique allowed determination of the distribution of spermatozoa and individual motility in the lumen of the ewe's genital tract. The results showed a gradient of increasing concentration of spermatozoa from the base of the uterus to the UTJ 4 h after intra-uterine insemination into the base of the horns. The UTJ was shown to be a storage region for spermatozoa before their transfer to the oviduct. Thein vitrostorage of spermatozoa in liquid form decreased their migration through the cervix and reduced the proportion of motile spermatozoa and their straight line velocity at the UTJ and their transit into the oviduct.

Cette revue présente l’état des connaissances sur la folliculogenèse et l’ovulation chez les mammifères. La folliculogenèse basale est une phase de croissance folliculaire lente, au cours de laquelle l’ovocyte acquiert la compétence méiotique. La folliculogenèse terminale est une phase de développement rapide, au cours de laquelle le follicule ovulatoire est sélectionné et termine sa maturation, tandis que l’ovocyte acquiert la compétence au développement. La revue décrit les différents changements fonctionnels qui s’opèrent dans le follicule et l’ovocyte au cours de ces deux phases, ainsi que les mécanismes qui les régulent et qui déterminent le quota ovulatoire caractéristique de chaque espèce ou race. Les facteurs-clés identifiés de la folliculogenèse sont les BMP, le KITLG et l’AMH pour le démarrage de croissance folliculaire, l’IGF et l’insuline pour la transition entre folliculogenèse basale et terminale, la FSH pour le début de la folliculogenèse terminale et la sélection des follicules ovulatoires, et la LH pour le développement folliculaire final, la maturation ovocytaire et l’ovulation. L’ovulation est déclenchée par une décharge préovulatoire de LH qui induit la maturation du complexe cumulus-ovocyte dans le follicule ovulatoire, suivie de la rupture de la paroi folliculaire et de la formation du corps jaune. La folliculogenèse ovarienne est contrôlée par des facteurs externes, tels que la photopériode et la nutrition, et c’est essentiellement le système hypothalamo-hypophysaire qui intègre les signaux endocriniens et environnementaux. Des modifications de l’apport alimentaire, relayées par des variations de signaux hormonaux et métaboliques, modulent l’activité de l’axe hypothalamo-hypophyso-ovarien à ses différents étages., This review is a state of the art on follicullogenesis and ovulation in mammals. Basal folliculogenesis is a phase of slow follicular growth, during which the oocyte acquires meiotic competence. Terminal folliculogenesis is a phase of rapid development, during which the ovulatory follicle is selected and completes its maturation while the oocyte acquires developmental competence. This review describes the different functional changes occurring within follicles and oocytes throughout these two phases, the underlying regulatory mechanisms and the mechanisms that determine natural ovulation rate in different species and breeds. Known key factors for folliculogenesis are BNTP, KITLG and AMH for the initiation of follicular growth, IGF and insulin for transition between basal and terminal folliculogenesis, FSH for the outset of terminal folliculogenesis and the selection of ovulatory follicles, and LH for final follicular development, oocyte maturation and ovulation. Ovulation is triggered by a preovulatory LH surge that induces maturation of the cumulus oocyte complex within the ovulatory follicle, rupture of the follicular wall and corpus luteum formation. Ovarian folliculogenesis is controlled by external factors such as photoperiod and nutrition, and the hypothalamo-pituitary system integrates endocrine and environmental signals. Nutritional supply, relayed by hormonal and metabolic signals, can modulate both the hypothalamo-pituitary and ovarian activity.

International audience; The local statistical approach for fault detection and isolation is applied to fuzzy models validation. The method detects the inconsistencies between a fuzzy rule base and the modelled system. It can also identify which are the faulty parameters of the fuzzy model. The Fisher information matrix explains the detectability of changes in the parameters of the fuzzy model. Simulation tests illustrate the method's credibility.

International audience; In vertebrates, the gonadotrope axis is made up of the hypothalamus, belonging to the central nervous system, the pituitary gland and the gonads. These organs communicate with one another within entangled endocrine loops. From a dynamical viewpoint, the gonadotrope axis exhibits remarkable features, such as the pulsatile mode of secretion of the master reproductive hormone GnRH (gonadotropin releasing hormone) and the permanent renewal of the gonadic tissues related to the maturation of the germ cell lines. We will present a multilevel and multiscale modelling approach of the gonadotrope axis focusing on the ovulation process. On the gonadic level, we address the question of the selection of ovarian follicles within the framework of controlled conservation laws. We have to deal with a 2D EDP with integro-differential expressions in the velocity and source terms. On the hypothalamic level, we design a model of GnRH secretion within the framework of weakly coupled nonlinear oscillators. The model outputs reproduce the transition from the pulsatile to the surge pattern and the changes in pulse frequency. To explain the behaviour of the model and meet qualitative and quantitative endocrinological specifications, we explore the whole sequence of bifurcations occurring within the model.; Chez les vertébrés, l'axe gonadotrope est constitué par l'hypothalamus (structure du système nerveux central), l'hypophyse et les gonades, dont les activités sont coordonnées par des boucles de rétrocontrôle endocrines. Le fonctionnement de ce système exhibe des propriétés remarquables sur le plan dynamique, telles que le caractère pulsatile de la sécrétion de la GnRH (gonadotropin releasing hormone) par les neurones hypothalamiques, et le remaniement permanent (au cours de la vie reproductive) des tissus gonadiques, en liaison avec la maturation des cellules germinales. Il s'agit ici de présenter une approche de modélisation et de contrôle multi-échelles et multi-niveaux de l'axe gonadotrope. Au niveau gonadique, nous décrirons un modèle multi-échelles du processus de sélection des follicules ovulatoires, au sein de la population de follicules ovariens en croissance, rentrant dans le cadre des lois de conservation contrôlées. Au niveau hypothalamique, nous présenterons un modèle de sécrétion de la GnRH, dans le cadre du couplage d'oscillateurs non linéaires. Les sorties du modèle reproduisent non seulement la transition entre régime pulsatile et décharge ovulatoire, mais aussi l'accéleration en fréquence avant la décharge, et l'existence d'une pause après la décharge. Nous étudions la séquence complète de bifurcations sous-jacentes au modèle, afin de respecter fidèlement les spécifications qualitatives et quantitatives du cahier des charges endocrine, qui portent sur les rapports en durée, amplitude et fréquence, entre les différents événements sécrétoires

International audience; The Two-Stage Algorithm (TSA) has been extensively used and adapted for the identification of Hammerstein systems. It is essentially based on a particular formulation of Hammerstein systems in the form of bilinearly parameterized linear regressions. This paper has been motivated by a somewhat contradictory fact: though the optimality of the TSA has been established by Bai in 1998 only in the case of some special weighting matrices, the unweighted TSA is usually used in practice. It is shown in this paper that the unweighted TSA indeed gives the optimal solution of the weighted nonlinear least-squares problem formulated with a particular weighting matrix. This provides a theoretical justification of the unweighted TSA, and leads to a generalization of the obtained result to the case of colored noise with noise whitening. Numerical examples of identification of Hammerstein systems are presented to validate the theoretical analysis.

International audience; A parsimonious representation of signals is a mathematic model parametrized with a small number of parameters. Such models are useful for analysis, interpolation, filtering, feature extraction, and data compression. A new parsimonious model is presented in this paper based on scattering transforms. It is closely related to the eigenvalues and eigenfunctions of the linear Schrödinger equation. The efficiency of this method is illustrated in this paper with examples of both synthetic and real signals.

This thesis work focuses on the detection of insulation faults in very long transmission lines. This is detecting soft defects related to the insulation between the conductors of a long cable which are represented by the leakage conductance parameter. Detect these faults, signs of a possible future short-circuit, is an important issue but requires a noninvasive method. For example, in the case of railway signaling cables, it is to develop a method of diagnosis of very low leakage conductances in signaling cables along railways compatible with the movement of trains. Be aware estimate from measurements in one point of the cable, strong resistance distributed over several hundred meters without disturbing the continuous frequency range to 40 kHz, reserved for service signals. Indeed, the signal cables from the train that interest us have an average length 1500 m and are used in the frequency band 0-40 kHz.We propose so a frequency method for estimating low defects to medium frequency in uniform transmission lines with losses. It is based on two main ideas : a detailed analysis of joint effects of dissipation and dispersion and a method of comparing two lines having the same characteristics and differing only leak conductance parameter. This method of comparison was widespread in the case of multiconductor lines by adopting a statistical approach.This thesis has brought new results : losses estimation formulas resulting from the detailed analysis of a share of joint effects of dissipation and dispersion and also the method of comparing two lines. Numerical simulations were made in both cases to validate the proposed frequency method. Experiments were performed to validate the statistical analysis in the case of multiconductor lines., Ces travaux de thèse portent sur la détection de défauts d'isolement dans des lignes de transmission de grandes longueurs. Il s'agit de détecter des défauts non francs liés à l'isolant entre les conducteurs d'un câble de grande longueur qui sont représentés par le paramètre de conductance de fuite. Détecter ces défauts, signes d'un possible futur court-circuit, est un enjeu important mais nécessite une méthode non invasive. Par exemple, dans le cas des câbles de signalisation SNCF, il s'agit de développer une méthode de diagnostic de très faibles conductances de fuite dans les câbles de signalisation le long des voies ferrées compatible avec la circulation des trains. Il faut savoir estimer, à partir de mesures en un seul point du câble, de fortes résistances distribuées sur plusieurs centaines de mètres sans perturber la bande de fréquences du continu à 40 kHz, réservée aux signaux de service. En effet, les câbles de signalisation de la SNCF qui nous intéressent ont une longueur moyenne de 1500 m et sont utilisés dans la bande de fréquence 0-40 kHz. Nous proposons donc une méthode fréquentielle permettant d'estimer de faibles défauts à moyenne fréquence dans des lignes de transmission uniformes avec pertes. Elle repose sur deux idées principales : une analyse fine des effets conjoints de la dissipation et de la dispersion et une méthode de comparaison de deux lignes ayant les mêmes caractéristiques et ne différant que du paramètre de conductance de fuite. Cette méthode de comparaison a été généralisée dans le cas de lignes multiconducteurs en adoptant une démarche statistique.\\Cette thèse a apporté de nouveaux résultats : des formules d'estimation de pertes découlant de l'analyse fine d'une part des effets conjoints de la dissipation et de la dispersion et d'autre part de la méthode de comparaison de deux lignes. Des simulations numériques ont été faites dans les deux cas afin de valider la méthode fréquentielle proposée. Des expériences ont été réalisées afin de valider l'analyse statistique développée dans le cas de lignes multiconducteurs.

Actuator fault diagnosis is often studied under strong assumptions on available sensors: typically it is assumed that either the sensors are fault-free or there is a sufficient redundancy among the sensors. The purpose of this paper is to propose a new method for actuator fault diagnosis which is robust to sensor distortion. It does not require sensor redundancy to compensate sensor distortion. The essential assumption is that sensor distortions are strictly monotonous. Despite the nonlinear and unknown nature of distortions, such sensors still provide useful information for fault diagnosis. A numerical example is provided to illustrate the efficiency of the proposed method. Copyright © 2006 IFAC

International audience; A Wiener system is composed of a linear dynamic subsystem followed by a static nonlinearity. It is well known in the literature that the identification of the linear subsystem of a Wiener system can be separated from that of the output nonlinearity, if the input signal is a Gaussian noise. In order to deal with the non Gaussian input case, two new algorithms are proposed in this paper for direct identification of the linear subsystem, regardless of any parametrization of the output nonlinearity. The essential assumption required in this paper is the strict monotonousness of the output nonlinearity.

National audience; Xcos est un module interne à Scilab dédié à la modélisation et la simulation de systèmes dynamiques hybrides. Il comprend un éditeur graphique permettant de réaliser simplement des modèles en agençant des blocs et des connecteurs. Une bibliothèque de palettes spécialisées dans différents domaines est proposée nativement, que l'utilisateur peut compléter par des modules externes disponibles sur ATOMS ou par ses propres palettes et blocs.Ce manuel, entièrement consacré à Xcos, vous explique comment en tirer pleinement parti, de la réalisation de schémas simples à la configuration de vos propres palettes.Les deux premières parties vous enseignent un premier niveau d'utilisation, prise en main de l'interface et compréhension de la signification des composants graphiques.Les parties suivantes vous permettront d'aller plus loin, de comprendre la modélisation au niveau système, d'analyser plus finement vos modèles, de les caler par optimisation paramétriques, mais aussi de générer les codes C. Enfin, vous apprendrez à créer vos propres composants graphiques.

LGEP 2014 ID = 1716; La présente invention concerne les procédés de diagnostic par réflectométrie, les faisceaux de lignes électriques et les kits correspondants. Plus particulièrement, l’invention concerne un procédé de diagnostic par réflectométrie d’un faisceau de lignes électriques comportant au moins un point d’entrée et une pluralité de branches, un tel faisceau de lignes électriques en arbre et un kit de diagnostic par réflectométrie d’un tel faisceau.

This thesis focuses on fault diagnosis of wired electric networks using reflectometry. To develop diagnostic algorithms, we studied the direct problem (numerical simulations of electrical networks) and the inverse problem (determination of certain properties of a network from reflectometry measurements). For the direct problem, we developed a method for the computation of reflection coefficients. This method is based on the successive solving for a Riccati differential equation. We also generalized the BLT equation for the nonuniform electric networks and automated the resolution of this method. The thesis has made two new results concerning the inverse problem. The first result concerns the estimation of lengths and loss coefficients of the branches of a star network via an iterative method. The second focuses on the identification, at least partially, of the branches admittance matrices of a electric network modeled by the equation of BLT. The methodologies and formalisms proposed in this thesis are validated either by numerical simulations or by real measurements.; Cette thèse s’intéresse au diagnostic de défauts de réseaux électriques filaires à l'aide de la réflectométrie. Pour concevoir des algorithmes de diagnostic, nous avons étudié le problème direct (simulations numériques des réseaux électriques) et le problème inverse (détermination de certaines propriétés d’un réseau à partir des mesures de réflectométrie). Concernant le problème direct, nous avons développé une méthode de calcul du coefficient de réflexion d’un réseau sous forme d’arbre qui est basée sur la résolution successive d’équations différentielles de Riccati. Nous avons également généralisé l’équation de BLT pour des réseaux électriques composés de branches non uniformes et automatisé la méthode de sa résolution. La thèse a apporté deux nouveaux résultats concernant le problème inverse. Le premier résultat porte sur l’estimation des longueurs et des coefficients de pertes des branches d'un réseau électrique sous forme d’étoiles via une méthode itérative. Le deuxième porte sur l’identification, au moins partiellement, des matrices d’admittance des branches d’un réseau électrique modélisé par l’équation de BLT. Les méthodologies et les formalismes proposés dans la thèse sont validés soit par des simulations numériques, soit par des mesures réelles.

International audience; Purpose: Both the blood glucose target range in critically ill adult patients and the optimal method to reach this target range remain a matter of debate. To test whether a Computer Decision Support System (CDSS) might improve the outcome of critically ill adult patients through facilitation of a tighter blood glucose control. Methods: We conducted a multicenter randomized trial in 34 French closed-format intensive care units in 19 university hospitals and 15 nonuniversity hospitals from October 2009 to June 2011. Adult patients who were expected to require treatment in the ICU at least 3 days were randomly assigned without blinding to undergo tight computerized glucose control with CDSS or conventional glucose control, with the respective blood glucose targets of 80 to 110 and < 180 mg per deciliter. The primary outcome was all-cause death within 90 days after ICU admission. Results: Of the 2,684 patients who underwent randomization, 1,351 were assigned to tight computerized glucose control and 1,333 to conventional glucose control. Data with regard to the primary outcome were available for 1,335 and 1,311 patients, respectively. A total of 431 (32.3%) patients in the tight computerized glucose control group and 447 (34.1%) in the conventional glucose control group died at day 90 (odds ratio for death in the tight computerized glucose control, 0.92; 95% CI, 0.78-1.78; p = 0.32). Severe hypoglycemia (< 40 mg/dL) was reported in 174 of 1,317 patients (13.2%) in the tight computerized glucose control group and 79 of 1,284 patients (6.2%) in the conventional glucose control group (p < 0.001). Conclusions: In critically ill patients, tight computerized glucose control with CDSS did not significantly change 90-day mortality and is associated with more frequent severe hypoglycemia in comparison with conventional glucose control performed without CDSS.

International audience; This article concerns the phenomenon of Mixed-Mode Bursting Oscillations (MMBOs). These are solutions of fast-slow systems of ordinary differential equations that exhibit both small-amplitude oscillations (SAOs) and bursts consisting of one or multiple large-amplitude oscillations (LAOs). The name MMBO is given in analogy to Mixed-Mode Oscillations, which consist of alternating SAOs and LAOs, without the LAOs being organized into burst events. In this article, we show how MMBOs are created naturally in systems that have a spike-adding bifurcation or spike-adding mechanism, and in which the dynamics of one (or more) of the slow variables causes the system to pass slowly through that bifurcation. Canards are central to the dynamics of MMBOs, and their role in shaping the MMBOs is two-fold: saddle-type canards are involved in the spike-adding mechanism of the underlying burster and permit one to understand the number of LAOs in each burst event, and folded-node canards arise due to the slow passage effect and control the number of SAOs. The analysis is carried out for a prototypical fourth-order system of this type, which consists of the third-order Hindmarsh-Rose system, known to have the spike-adding mechanism, and in which one of the key bifurcation parameters also varies slowly. We also include a discussion of the MMBO phenomenon for the Morris-Lecar-Terman system. Finally, we discuss the role of the MMBOs to a biological modeling of secreting neurons.

L'invention concerne un système de traitement des gaz d'échappement 2, comprenant un dispositif de réduction catalytique sélective 13 des oxydes d'azote et un moyen d'estimation 18 apte à estimer la quantité d'agent réducteur stockée dans le dispositif 13, le débit d'oxydes d'azote alimentant le dispositif 13 et les débits d'oxydes d'azote et d'agent réducteur sortant du dispositif 13. Le système comprend un unique capteur 15 apte à mesurer le débit global d'oxydes d'azote et d'agent réducteur, ledit capteur 15 étant monté en aval du dispositif 13. Le moyen d'estimation 18 est également apte à corriger lesdites estimations en fonction de l'écart entre le débit global mesuré par ledit capteur 15 et les débits estimés d'oxydes d'azote et d'agent réducteur sortant du dispositif 13. L'invention concerne également le procédé correspondant.

In this work we consider a periodically forced generic integrate-and-fire model with a unique attracting equilibrium in the subthreshold dynamics and study the dependence of the firing rate on the frequency of the drive. The biological motivation underlying this work is the differential control exerted by the hypothalamic gonadotropin releasing hormone (GnRH), which is secreted in a pulsatile manner, on the secretion of the pituitary hormones FSH (follicle stimulating hormone) and LH (lutenizing hormone) according to GnRH pulse frequency. Our forcing satisfies the constraint of dose conservation, which can be interpreted as fixing the average GnRH concentration, while the frequency, amplitude and duty cycle are allowed to vary. The bifurcation structure in the parameter space formed by these last ones has been rigorously studied in \cite{GraKruCle13} where the firing rate was related with the rotation number of the existing periodic orbits. In this work we rigorously study how these bifurcation structures behave upon frequency variation. This allows us to show that the dependence of the firing rate on frequency of the drive follows a devil's staircase with non-monotonic steps and that there is an optimal response in the whole frequency domain. We also characterize certain bounded frequency windows in which the firing rate exhibits a bell-shaped envelope with a global maximum.

International audience; Stabilizing a quantum system in a desired state has important implications in quantum information science. In control engineering, stabilization is usually achieved by the use of feedback. The closed-loop control paradigm consists of measuring the system in a non-destructive manner, analyzing in real-time the measurement output to estimate the dynamical state and finally, calculating a feedback law to stabilize the desired state. However, the rather short dynamical time-scales of most quantum systems impose important limitations on the complexity of real-time output signal analysis and retroaction. An alternative control approach for quantum state stabilization, bypassing a real-time analysis of output signal, is called reservoir engineering. In this paper, we start with a general description of quantum reservoir engineering. We then apply this method to stabilize the ground state (lowest energy state) of a single two-level quantum system. Applying the averaging theorem and some simple Lyapunov techniques, we prove the convergence of our proposed scheme. This scheme has recently been successfully implemented on a superconducting qubit and has led to a fast and reliable reset protocol for these qubits

We propose a dissipation engineering scheme that prepares and protects a maximally entangled state of a pair of superconducting qubits. This is done by off-resonantly coupling the two qubits to a low-Q cavity mode playing the role of a dissipative reservoir. We engineer this coupling by applying six continuous-wave microwave drives with appropriate frequencies. The two qubits need not be identical. We show that our approach does not require any fine-tuning of the parameters and requires only that certain ratios between them be large. With currently achievable coherence times, simulations indicate that a Bell state can be maintained over arbitrary long times with fidelities above 94%. Such performance leads to a significant violation of Bell's inequality (CHSH correlation larger than 2.6) for arbitrary long times., Comment: 5 pages, 4 figures

International audience; In this paper we study the dynamics of a quadratic integrate-and-fire neuron, spiking in the gamma (30-100 Hz) range, coupled to a delta/theta frequency (1-8 Hz) neural oscillator. Using analytical and semi-analytical methods we were able to derive characteristic spiking times for the system in two distinct regimes (depending on parameter values): one regime where the gamma neuron is intrinsically oscillating in the absence of theta input, and a second one in which gamma spiking is directly gated by theta input, i.e. windows of gamma activity alternate with silence periods depending on the underlying theta phase. In the former case we transform the equations such that the system becomes analogous to the Mathieu differential equation. By solving this equation we can compute numerically the time to the first gamma spike and then use singular perturbation theory to find successive spike times. On the other hand in the excitable condition we make direct use of singular perturbation theory to obtain an approximation of the time to first gamma spike, and then extend the result to calculate ensuing gamma spikes in a recursive fashion. We thereby give explicit formulas for the onset and offset of gamma spike burst during a theta cycle, and provide an estimation of the total number of spikes per theta cycle both for excitable and oscillator regimes.

International audience; This paper is motivated by modeling the control valve stiction phenomena in feedback control loops. An extended Hammerstein system with discretized Preisach model as the input nonlinearity is proposed to capture hysteretic dynamic behaviors of cascading systems consisting of control valves followed by linear dynamic subsystems. An iterative method is p- resented to identify the extended Hammerstein systems. An informative input needs to have multiple local extreme values in order to ensure the discretized Preisach model identifiable. However, if only a single hysteresis loop of the discretized Preisach model is in active, then an oscillatory input with only two extreme values is shown to be persistently excited for identification. Hence, the proposed identification method for extended Hammerstein systems is applicable to general types of input- s as well as oscillatory ones. Two industrial examples are provided to demonstrate the effectiveness of the proposed identification method for extended Hammerstein systems.

International audience; The purpose of this paper is to study the stability properties of the Kalman filter applied to process noise free systems. Due to the absence of the process noise (also known as state noise), such a system cannot be controllable regarding the process noise. The stability of the Kalman filter is typically based on the boundedness of the error covariance matrix governed by a dynamic Riccati equation (DRE), which is usually ensured by the controllability regarding the process noise and by the observability. This classical result cannot be applied to the considered case because of the lack of controllability. It is shown in this paper that, under the observability condition, the solution of the DRE is bounded and converges to a solution of the algebraic Riccati equation (ARE), regardless of the stability of the considered system. In the case of asymptotically unstable systems, the solution of the ARE is not unique. In this case the relationship between the DRE and the ARE is clarified. It is also shown that the DRE based Kalman filter is always valid, whereas the ARE based Kalman filter cannot be applied when the process noise free system has marginally stable modes. A numerical example is presented to verify the correctness of the theoretical analysis.

International audience; Wiener system identification with a finite impulse response (FIR) model is investigated in this paper, focusing on the challenging case of non Gaussian input distribution and non monotonic nonlinearity. The proposed method assumes that the static nonlinear function of the Wiener system has a single minimum (or maximum), but does not assume any parametrization of the nonlinear function. Based on a modified principal component analysis (PCA), referred to as weighted PCA, the FIR coefficients of the Wiener system are estimated without estimating the nonlinear function of the Wiener system. The numerical computation cost is essentially equivalent to those of two standard PCA. Numerical examples in harsh practical conditions, with data generated by Wiener systems involving a discontinuous nonlinear function or an infinite impulse response, are presented to illustrate the robustness and effectiveness of the proposed method.

The main problem evaluated in this manuscript is the stabilization of periodic orbits of non-linear dynamical systems by use of feedback control. The goal of the control methods proposed in this work is to achieve a stable periodic oscillation. These control methods are applied to systems that present unstable periodic orbits in the state space, and the latter are the orbits to be stabilized.The methods proposed here are such that the resulting stable oscillation is obtained with low control effort, and the control signal is designed to converge to zero when the trajectory tends to the stabilized orbit. Local stability of the periodic orbits is analyzed by studying the stability of some linear time-periodic systems, using the Floquet stability theory. These linear systems are obtained by linearizing the trajectories in the vicinity of the periodic orbits.The control methods used for stabilization of periodic orbits here are the proportional feedback control, the delayed feedback control and the prediction-based feedback control. These methods are applied to discrete and continuous-time systems with the necessary modifications. The main contributions of the thesis are related to these methods, proposing an alternative control gain design, a new control law and related results.; Le problème principalement étudié dans ce manuscrit est la stabilisation d’orbites périodiques de systèmes dynamiques non linéaires à l’aide d’une commande de rétroaction (feedback). Le but des méthodes de contrôle proposées ici est d’obtenir une oscillation périodique stable. Ces méthodes de contrôle sont appliquées à des systèmes présentant des orbites périodiques instables dans l’espace d’état, et ces dernières sont les orbites destinées à être stabilisées.Les méthodes proposées ici sont telles que l’oscillation stable qui en résulte est obtenue avec un effort de contrôle faible, et que la valeur de la commande tend vers zéro lorsque la trajectoire tend vers l’orbite stabilisée. La stabilité locale des orbites périodiques est analysée par l’étude de la stabilité des systèmes linéaires périodiques à l’aide de la théorie de Floquet. Ces systèmes linéaires sont obtenus par linéarisation des trajectoires au voisinage de l’orbite périodique.Les méthodes de contrôle utilisées ici pour la stabilisation des orbites périodiques sont une loi de commande proportionnelle, une loi de commande de rétroaction retardée et une loi de commande de rétroaction basée sur une prédiction. Ces méthodes sont appliquées aux systèmes en temps discret et aux systèmes en temps continu avec les modifications nécessaires. Les contributions principales de cette thèse sont associées à ces méthodes, proposant une méthode alternative de design de gain, une nouvelle loi de commande et des résultats associés.; O principal problema avaliado neste manuscrito é a estabilização de órbitas periódicas em sistemas dinâmicos não-lineares utilizando controle por realimentação. O objetivo dos métodos de controle propostos neste trabalho é obter uma oscilação periódica estável. Estes métodos de controle são aplicados a sistemas que apresentam órbitas periódicas instáveis no espaço de estados, estas são as órbitas a serem estabilizadas.Os métodos propostos aqui são tais que a oscilação periódica estável resultante é obtida utilizando um baixo esforço de controle, e o sinal de controle é projetado de forma a convergir para zero quanto a trajetória tende à órbita estabilizada. A estabilidade local de órbitas periódicas é analisada através do estudo da estabilidade de alguns sistemas lineares periódicos no tempo, utilizando a teoria de estabilidade de Floquet. Estes sistemas lineares são obtidos por linearização das trajetórias na vizinhança da órbita periódica.Os métodos de controle utilizados aqui para estabilização de órbitas periódicas são o proportional feedback control, o delayed feedback control e o prediction-based feedback control (controle por realimentação baseado em predição). Estes métodos são aplicados a sistemas de tempo discreto e de tempo contínuo, com as modificações necessárias. As principais contribuições da tese são relacionadas a esses métodos, propondo um projeto de ganho de controle alternativo, uma nova lei de controle e resultados relacionados.

International audience

International audience

The purpose of this study is to develop mathematical reduced order models for components of low consumption motor vehicles : the lean NOx trap and the SCR catalysts, used in the exhaust of Diesel engines and involved in the reduction of pollutants in exhaust emissions. These systems have in common that they aim at controling the boundaries on pollutant emissions in order to achieve the forthcoming Euro standards and they allow the optimization of the aftertreatment systems to reduce greenhouse gases.The lean NOx trap catalyst aims at collecting the NOx in order to avoid the pollution of the environment and the SCR catalyst uses the selective reduction of the NOx by the ammonia (NH3), initially produced by an embedded urea system.The similarity between the two technologies allow the implementation of common methodologies for reduced order modeling of catalytic reactors based on thermochemical and kinetic studies. After application, respectively to the NOx trap and the SCR, we obtain reduced order models which were identified, validated and implemented for the control and diagnosis of the amount of stock of the pollutants (respectively NOx and NH3).; Dans cette étude, on s'est intéressé à la modélisation réduite et au contrôle d’organes intervenant dans la réduction des émissions de polluants des véhicules automobiles à basse consommation. Il s’agit des réacteurs catalysés de type « piège à NOx » et SCR, utilisés dans les architectures de post-traitement des gaz d’échappement des véhicules Diesel. Ces systèmes ont en commun la nécessité de contrôler les niveaux des émissions de polluants stockés sur les sites catalytiques et l’optimisation du fonctionnement du GMP en vue d’approcher les futures normes Euro et les nouvelles incitations sur les émissions de gaz à effet de serre.Le piège à NOx est un système catalytique dont la fonction première est de collecter les oxydes d’azote (NOx) des gaz d’échappement afin qu’ils ne soient pas rejetés dans l’environnement. Le réacteur SCR est un système catalytique qui utilise le principe de réduction sélective des NOx par l’ammoniac (NH3), initialment produit et délivré à partir d’un stock d’urée embarqué.La similitude des technologies a permis la mise en œuvre de méthodologies communes de modélisation cinétique et de réduction de modèles, basées sur l’étude thermochimique et cinétique des réseaux réactionnels. Après application aux systèmes respectifs de piège à NOx et SCR, nous avons obtenus des modèles réduits qui ont pu être identifiés, validés et appliqués à l’observation et au contrôle des niveaux de stock des polluants (respectivement NOx et NH3).

The purpose of this study is to develop mathematical reduced order models for components of low consumption motor vehicles : the lean NOx trap and the SCR catalysts, used in the exhaust of Diesel engines and involved in the reduction of pollutants in exhaust emissions. These systems have in common that they aim at controling the boundaries on pollutant emissions in order to achieve the forthcoming Euro standards and they allow the optimization of the aftertreatment systems to reduce greenhouse gases.The lean NOx trap catalyst aims at collecting the NOx in order to avoid the pollution of the environment and the SCR catalyst uses the selective reduction of the NOx by the ammonia (NH3), initially produced by an embedded urea system.The similarity between the two technologies allow the implementation of common methodologies for reduced order modeling of catalytic reactors based on thermochemical and kinetic studies. After application, respectively to the NOx trap and the SCR, we obtain reduced order models which were identified, validated and implemented for the control and diagnosis of the amount of stock of the pollutants (respectively NOx and NH3).; Dans cette étude, on s'est intéressé à la modélisation réduite et au contrôle d’organes intervenant dans la réduction des émissions de polluants des véhicules automobiles à basse consommation. Il s’agit des réacteurs catalysés de type « piège à NOx » et SCR, utilisés dans les architectures de post-traitement des gaz d’échappement des véhicules Diesel. Ces systèmes ont en commun la nécessité de contrôler les niveaux des émissions de polluants stockés sur les sites catalytiques et l’optimisation du fonctionnement du GMP en vue d’approcher les futures normes Euro et les nouvelles incitations sur les émissions de gaz à effet de serre.Le piège à NOx est un système catalytique dont la fonction première est de collecter les oxydes d’azote (NOx) des gaz d’échappement afin qu’ils ne soient pas rejetés dans l’environnement. Le réacteur SCR est un système catalytique qui utilise le principe de réduction sélective des NOx par l’ammoniac (NH3), initialment produit et délivré à partir d’un stock d’urée embarqué.La similitude des technologies a permis la mise en œuvre de méthodologies communes de modélisation cinétique et de réduction de modèles, basées sur l’étude thermochimique et cinétique des réseaux réactionnels. Après application aux systèmes respectifs de piège à NOx et SCR, nous avons obtenus des modèles réduits qui ont pu être identifiés, validés et appliqués à l’observation et au contrôle des niveaux de stock des polluants (respectivement NOx et NH3).

We study Mixed Mode Oscillations (MMOs) in systems of two weakly coupled slow/fast oscillators. We focus on the existence and properties of a folded singularity called FSN II that allows the emergence of MMOs in the presence of a suitable global return mechanism. As FSN II corresponds to a transcritical bifurcation for a desingularized reduced system, we prove that, under certain non-degeneracy conditions, such a transcritical bifurcation exists. We then apply this result to the case of two coupled systems of FitzHugh- Nagumo type. This leads to a non trivial condition on the coupling that enables the existence of MMOs.

International audience; Some engineering systems are naturally described by differential-algebraic equations (DAE), whereas it may be difficult or impossible to model them with ordinary differential equations (ODE). This paper proposes an approach to fault diagnosis for systems described by DAEs. Through a particular discretization method and under realistic assumptions, the considered continuous time DAE model is transformed to an explicit state space model in discrete time. An adaptive observer is then applied to the discretized system for monitoring faults possibly affecting the system and represented by changes in model parameters.

We consider a controlled quantum system whose finite dimensional state is governed by a discrete-time nonlinear Markov process. In open-loop, the measurements are assumed to be quantum non-demolition (QND). The eigenstates of the measured observable are thus the open-loop stationary states: they are used to construct a closed-loop supermartingale playing the role of a strict control Lyapunov function. The parameters of this supermartingale are calculated by inverting a Metzler matrix that characterizes the impact of the control input on the Kraus operators defining the Markov process. The resulting state feedback scheme, taking into account a known constant delay, provides the almost sure convergence of the controlled system to the target state. This convergence is ensured even in the case where the filter equation results from imperfect measurements corrupted by random errors with conditional probabilities given as a left stochastic matrix. Closed-loop simulations corroborated by experimental data illustrate the interest of such nonlinear feedback scheme for the photon box, a cavity quantum electrodynamics system., Comment: submitted (16 pages, 4 figures)

We study methods to compute invariant manifolds in slow-fast systems where the time scale separation is not explicit. We relate such manifolds to the existence of canard solutions in dimension 2 and 3.

Tracking Quantum Evolution The actual process of measuring a quantum system has an effect on the result making the outcome unpredictable. Using a superconducting qubit placed in a microwave cavity, Hatridge et al. (p. 178 ) found that a series of partial measurements on a quantum system left the system in a pure state. Looking at the record of the actual measurements allowed the final state of a superconducting-based quantum system to be determined accurately. Such control is crucial for achieving full feedback control of a general quantum system.

International audience; We introduce a new gate that transfers an arbitrary state of a qubit into a superposition of two quasi-orthogonal coherent states of a cavity mode, with opposite phases. This qcMAP gate is based on conditional qubit and cavity operations exploiting the energy level dispersive shifts, in the regime where they are much stronger than the cavity and qubit linewidths. The generation of multi-component superpositions of quasi-orthogonal coherent states, non-local entangled states of two resonators and multi-qubit GHZ states can be efficiently achieved by this gate.

We show that a planar slow–fast piecewise-linear (PWL) system with three zones admits limit cycles that share a lot of similarity with van der Pol canards, in particular an explosive growth. Using phase-space compactification, we show that these quasi-canard cycles are strongly related to a bifurcation at infinity. Furthermore, we investigate a limiting case in which we show the existence of a continuum of canard homoclinic connections that coexist for a single-parameter value and with amplitude ranging from an order of ε to an order of 1, a phenomenon truly associated with the non-smooth character of this system and which we call super-explosion .

International audience; We propose to encode a quantum bit of information in a superposition of coherent states of an oscillator, with four different phases. Our encoding in a single cavity mode, together with a protection protocol, significantly reduces the error rate due to photon loss. This protection is ensured by an efficient quantum error correction scheme employing the nonlinearity provided by a single physical qubit coupled to the cavity. We describe in detail how to implement these operations in a circuit quantum electrodynamics system. This proposal directly addresses the task of building a hardware-efficient quantum memory and can lead to important shortcuts in quantum computing architectures.