http://hdl.handle.net/2268/91 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/148617 Title: Réseau Qualité des Laboratoires de l'ULg - Rapport d'activité Février 2013 <br/> <br/>Author, co-author: Dumont, Fabien; Hubert, Philippe; Beauvois, Véronique; Widart, Joëlle http://hdl.handle.net/2268/148616 Title: Reference mirroring for control with impacts <br/> <br/>Author, co-author: Forni, Fulvio; Teel, Andrew; Zaccarian, Luca <br/> <br/>Abstract: We illustrate a peculiar concept of mirrored reference to address reference tracking control systems for plants subject to impacts. The idea is based on the constructions of artificial references corresponding to suitable reflections of the actual reference performed with respect to the impacting surfaces. We illustrate the application of this idea to reference tracking and state observation for a number of examples of control systems subject to impacts: a one-dimensional hammer hitting a surface, a two-dimensional Newton’s cradle, a two-dimensional mass moving in a planar equilateral triangle and a mass moving in an n-dimensional polyhedral region. For each one of these examples, we provide controllers inducing global exponential stability of the error dynamics. Despite the apparently different nature among the examples, we show that the controller/observer design follows the same paradigm based on mirrored references and we highlight the similarities of the different proofs by showing that they are all based on a specific result about Lyapunov conditions for global exponential stability of hybrid dynamical systems. http://hdl.handle.net/2268/148417 Title: Clean Coal Technologies and Carbon Capture and Storage in Kazakhstan – Reflections and ACCESS project results <br/> <br/>Author, co-author: Nesladek,, Milos; Helsen, S; Piessens, Kris; van Passel, S; Gaydardzhiev, Stoyan; Kryukova, V; Myngheer, S; Janssens, R; Welkenhuysen, K; Compernolle, T; Mathieu, Philippe; Dusar, Michel http://hdl.handle.net/2268/148412 Title: Overview of technologies for mineral/metal recuperation – challenges and technological gaps <br/> <br/>Author, co-author: Gaydardzhiev, Stoyan http://hdl.handle.net/2268/148057 Title: Inverse dynamics of serial and parallel underactuated multibody systems using a DAE optimal control approach <br/> <br/>Author, co-author: Guimaraes Bastos Junior, Guaraci; Seifried, Robert; Bruls, Olivier <br/> <br/>Abstract: The inverse dynamics analysis of underactuated multibody systems aims at determining the control inputs in order to track a prescribed trajectory. This paper studies the inverse dynamics of non-minimum phase underactuated multibody systems with serial and parallel planar topology, e.g. for end-effector control of flexible manipulators or manipulators with passive joints. Unlike for minimum phase systems, the inverse dynamics of non-minimum phase systems cannot be solved by adding trajectory constraints (servoconstraints) to the equations of motion and applying a forward time integration. Indeed, the inverse dynamics of a non-minimum phase system is known to be non-causal, which means that the control forces and torques should start before the beginning of the trajectory (preactuation phase) and continue after the end-point is reached (post-actuation phase). The existing stable inversion method roposed for general nonlinear non-minimum phase systems requires to derive explicitly the equations of the internal dynamics and to solve a boundary value problem. This paper proposes an alternative solution strategy which is based on an optimal control approach using a direct transcription method. The method is illustrated for the inverse dynamics of an underactuated serial manipulator with rigid links and four degrees-of-freedom and an underactuated parallel machine. An important advantage of the proposed approach is that it can be applied directly to the standard equations of motion of multibody systems either in ODE or in DAE form. Therefore, it is easier to implement this method in a general purpose simulation software. http://hdl.handle.net/2268/148044 Title: Anisotropy preserving interpolation of diffusion tensors <br/> <br/>Author, co-author: Collard, Anne; Bonnabel, Silvère; Phillips, Christophe; Sepulchre, Rodolphe http://hdl.handle.net/2268/147814 Title: Evaluation of a Model-Based Hemodynamic Monitoring Method in a Porcine Study of Septic Shock <br/> <br/>Author, co-author: Revie, James; Stevenson, David; Chase, J. Geoffrey; Pretty, Christopher; LAMBERMONT, Bernard; GHUYSEN, Alexandre; Kolh, Philippe; Shaw, Geoffrey; Desaive, Thomas http://hdl.handle.net/2268/147683 Title: Model-based glycemic control in critical care <br/> <br/>Author, co-author: Pretty, Christopher; Penning, Sophie; Le Compte, Aaron J.; Fisk, Liam; Benyo, Balazs; Chase, J. Geoffrey; Desaive, Thomas http://hdl.handle.net/2268/147682 Title: Model-based glycemic control in critical care <br/> <br/>Author, co-author: Pretty, Christopher; Penning, Sophie; Le Compte, Aaron J.; Fisk, Liam; Benyó, Balazs; Chase; Desaive, Thomas http://hdl.handle.net/2268/147300 Title: Design and validation of a real-time spiking-neural-network decoder for brain–machine interfaces <br/> <br/>Author, co-author: Dethier, Julie; Nuyujukian, Paul; Ryu, Stephen I; Shenoy, Krishna V.; Boahen, Kwabena <br/> <br/>Abstract: Objective. Cortically-controlled motor prostheses aim to restore functions lost to neurological disease and injury. Several proof of concept demonstrations have shown encouraging results, but barriers to clinical translation still remain. In particular, intracortical prostheses must satisfy stringent power dissipation constraints so as not to damage cortex. Approach. One possible solution is to use ultra-low power neuromorphic chips to decode neural signals for these intracortical implants. The first step is to explore in simulation the feasibility of translating decoding algorithms for brain–machine interface (BMI) applications into spiking neural networks (SNNs). Main results. Here we demonstrate the validity of the approach by implementing an existing Kalman-filter-based decoder in a simulated SNN using the Neural Engineering Framework (NEF), a general method for mapping control algorithms onto SNNs. To measure this system's robustness and generalization, we tested it online in closed-loop BMI experiments with two rhesus monkeys. Across both monkeys, a Kalman filter implemented using a 2000-neuron SNN has comparable performance to that of a Kalman filter implemented using standard floating point techniques. Significance. These results demonstrate the tractability of SNN implementations of statistical signal processing algorithms on different monkeys and for several tasks, suggesting that a SNN decoder, implemented on a neuromorphic chip, may be a feasible computational platform for low-power fully-implanted prostheses. The validation of this closed-loop decoder system and the demonstration of its robustness and generalization hold promise for SNN implementations on an ultra-low power neuromorphic chip using the NEF. http://hdl.handle.net/2268/147213 Title: MOSAIC: a multiscale model of osteogenesis and sprouting angiogenesis with lateral inhibition of endothelial cells. <br/> <br/>Author, co-author: Carlier, Aurélie; Geris, Liesbet; Bentley, Katie; Carmeliet, Geert; Carmeliet, Peter; Van Oosterwyck, Hans <br/> <br/>Abstract: The healing of a fracture depends largely on the development of a new blood vessel network (angiogenesis) in the callus. During angiogenesis tip cells lead the developing sprout in response to extracellular signals, amongst which vascular endothelial growth factor (VEGF) is critical. In order to ensure a correct development of the vasculature, the balance between stalk and tip cell phenotypes must be tightly controlled, which is primarily achieved by the Dll4-Notch1 signaling pathway. This study presents a novel multiscale model of osteogenesis and sprouting angiogenesis, incorporating lateral inhibition of endothelial cells (further denoted MOSAIC model) through Dll4-Notch1 signaling, and applies it to fracture healing. The MOSAIC model correctly predicted the bone regeneration process and recapitulated many experimentally observed aspects of tip cell selection: the salt and pepper pattern seen for cell fates, an increased tip cell density due to the loss of Dll4 and an excessive number of tip cells in high VEGF environments. When VEGF concentration was even further increased, the MOSAIC model predicted the absence of a vascular network and fracture healing, thereby leading to a non-union, which is a direct consequence of the mutual inhibition of neighboring cells through Dll4-Notch1 signaling. This result was not retrieved for a more phenomenological model that only considers extracellular signals for tip cell migration, which illustrates the importance of implementing the actual signaling pathway rather than phenomenological rules. Finally, the MOSAIC model demonstrated the importance of a proper criterion for tip cell selection and the need for experimental data to further explore this. In conclusion, this study demonstrates that the MOSAIC model creates enhanced capabilities for investigating the influence of molecular mechanisms on angiogenesis and its relation to bone formation in a more mechanistic way and across different time and spatial scales. http://hdl.handle.net/2268/147037 Title: Investigation on gas pressure measurement inside small caliber weapons with piezoelectric transducers <br/> <br/>Author, co-author: Elkarous, Lamine; Pirlot, Marc; Golinval, Jean-Claude; Maldague, Marc http://hdl.handle.net/2268/146909 Title: Modeling and Prediction of Time-Varying Environmental Data Using Advanced Bayesian Methods <br/> <br/>Author, co-author: Mansouri, Majdi; Dumont, Benjamin; Destain, Marie-France <br/> <br/>Abstract: The problem of state/parameter estimation represents a key issue in crop models which are nonlinear, non-Gaussian and include a large number of parameters. The prediction errors are often important due to uncertainties in the equations, the input variables, and the parameters. The measurements needed to run the model (input data), to perform calibration and validation are sometimes not numerous or known with some uncertainty. In these cases, estimating the state variables and/or parameters from easily obtained measurements can be extremely useful. In this work, we address the problem of modeling and prediction of leaf area index and soil moisture (LSM) using state estimation. The performances of various conventional and state-of-the-art state estimation techniques are compared when they are utilized to achieve this objective. These techniques include the extended Kalman filter (EKF), unscented Kalman filter (UKF), particle filter (PF), and the more recently developed technique variational Bayesian filter (VF). The objective of this work is to extend the state and parameter estimation techniques (i.e., EKF, UKF, PF and VF) to better handle nonlinear and non-Gaussian processes without a priori state information, by utilizing a time-varying assumption of statistical parameters. In this case, the state vector to be estimated at any instant is assumed to follow a Gaussian model, where the expectation and the covariance matrix are both random. The randomness of the expectation and the covariance of the state/parameter vector are assumed here to further capture the uncertainty of the state distribution. One practical choice of these distributions can be a Gaussian distribution for the expectation and a multi-dimensional Wishart distribution for the covariance matrix. The assumption of random mean and random covariance of the state leads to a probability distribution covering a wide range of tail behaviors, which allows discrete jumps in the state variables. http://hdl.handle.net/2268/146759 Title: High-speed imaging use to predict spray retention on barley leaves <br/> <br/>Author, co-author: Boukhalfa, Hassina dite Hafida; Massinon, Mathieu; Lebeau, Frédéric <br/> <br/>Abstract: Laboratory studies were conducted to validate the effectiveness of the use of high-speed imaging method to replace chemical nalysis by fluoremetrie. Measurements were performed with a high-speed camera coupled with a retro-LED lighting. Size and velocity of the drop were extracted by image analysis. Drop impact types were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Two surfactants (Break-Thru® S240 and Li700 ®) were sprayed on BBCH 12 barley leaves to highlight the effect of the reduction of surface tension. Relative volume proportions were computed within of an energy scale divided into 11 classes based on the Weber number. results are compared to the results of the chemical analysis by spectrofluerometry. http://hdl.handle.net/2268/146671 Title: Résonance stochastique dans les modèles neuronaux de type Hodgkin-Huxley : Etude et Application <br/> <br/>Author, co-author: Collard, Anne <br/> <br/>Abstract: En 1981, Benzi et al ont introduit le phénomène de résonance stochastique pour expliquer leurs observations sur les changements climatiques de notre planète. Depuis, ce phénomène a été largement étudié dans toutes sortes de domaines, dont la neurophysiologie. La résonance stochastique est un phénomène qui peut se manifester dans des systèmes non-linéaires, lorsqu'une entrée peut être amplifiée (optimisée) grâce à la présence de bruit dans le système. La présence d'une barrière énergétique, d'un seuil à franchir,… dans le système empêche généralement les signaux de faible amplitude d'être transmis. La présence de bruit permettra d'amplifier l'entrée faible et provoquera des transitions du système. Le signal faible sera alors transmis grâce au bruit. Les neurones étant habituellement représentés par des systèmes à seuils, la théorie de la résonance stochastique a été largement utilisée dans ce contexte. Ce travail pose les bases de la théorie de la résonance stochastique et introduit les principales mesures qui y sont liées, telles que le rapport signal-à-bruit et l'histogramme des intervalles de temps entre transitions. Ces mesures sont illustrées sur différentes sortes de modèles neuronaux, notamment le modèle de FitzHugh-Nagumo. Plusieurs variantes de ce dernier modèle sont introduites, et les différents résultats sont comparés. Dans un deuxième temps, nous étudions l'effet du bruit sur un modèle de Hodgkin et Huxley. Ce modèle a été modifié de façon à prendre en compte l'effet de la concentration intracellulaire en calcium. Il est étudié dans deux cas de figures, notamment grâce à une réduction à deux dimensions permettant l'analyse du plan de phase du modèle réduit. Cette recherche théorique combinée à des simulations numériques permettra d'aboutir à deux hypothèses biologiques, à savoir que les courants potassiques calcium-dépendants présents sur les neurones pourraient jouer le rôle de protecteurs de la dynamique du potentiel de membrane face au bruit et que les variations stochastiques de la concentration en calcium intracellulaire doivent être empêchées par un mécanisme biologique afin d'éviter des irrégularités du rythme d'émission de potentiels d'action. http://hdl.handle.net/2268/146670 Title: Means and medians in nonlinear spaces <br/> <br/>Author, co-author: Collard, Anne; Sepulchre, Rodolphe http://hdl.handle.net/2268/146669 Title: Selecting an appropriate metric for the processing of Diffusion Tensor Images <br/> <br/>Author, co-author: Collard, Anne; Sepulchre, Rodolphe http://hdl.handle.net/2268/146450 Title: Functional Analysis and the Finite Element Method <br/> <br/>Author, co-author: Stainier, Laurent; Tossings, Patricia http://hdl.handle.net/2268/146442 Title: A feedback control perspective on models of apoptosis signal transduction <br/> <br/>Author, co-author: Readman, Mark C.; Schliemann, Monica; Kalamatianos, Dimitrios; Bullinger, Eric <br/> <br/>Abstract: Apoptosis is a key regulator for replacing unused, old and damaged cells. Here we analyse three models of apoptosis. We deconstruct these models by linearising the models about the life steady state and applying methods from linear control theory. This control viewpoint uncovers a decentralised control scheme with a clear separation of plant and controller and reveals that the caspase inhibitors act as decentralised phase lead controllers. © 2013 Elsevier Ltd. All rights reserved. http://hdl.handle.net/2268/146345 Title: Étalonnage dynamique des capteurs piézoélectriques pour la mesure de haute pression balistique <br/> <br/>Author, co-author: Elkarous, Lamine; Pirlot, Marc; Golinval, Jean-Claude