http://hdl.handle.net/2268/80 Search this channel search http://orbi.ulg.ac.be/simple-search http://hdl.handle.net/2268/148782 Title: Computational Homogenization for Laminated Ferromagnetic Cores in Magnetodynamics <br/> <br/>Author, co-author: Niyonzima, Innocent; V Sabariego, Ruth; Dular, Patrick; Henrotte, François; Geuzaine, Christophe <br/> <br/>Abstract: In this paper, we investigate the modeling of ferromagnetic multiscale materials. We propose a computational homogenization technique based on the heterogeneous multiscale method (HMM) that includes both eddy-current and hysteretic losses at the mesoscale. The HMM comprises: 1) a macroscale problem that captures the slow variations of the overall solution; 2) many mesoscale problems that allow to determine the constitutive law at the macroscale. As application example, a laminated iron core is considered. Mon, 20 May 2013 15:48:56 GMT http://hdl.handle.net/2268/148766 Title: Lyapunov-based sufficient conditions for exponential stability in hybrid systems <br/> <br/>Author, co-author: Teel, Andrew; Forni, Fulvio; Zaccarian, Luca <br/> <br/>Abstract: Lyapunov-based sufficient conditions for exponential stability in hybrid systems are presented. The focus is on converting non-strict Lyapunov conditions, having certain observability properties, into strict Lyapunov conditions for exponential stability. Both local and global results are considered. The utility of the results is illustrated through an example. Mon, 20 May 2013 09:35:04 GMT http://hdl.handle.net/2268/148763 Title: Follow the bouncing ball: global results on tracking and state estimation with impacts <br/> <br/>Author, co-author: Forni, Fulvio; Teel, Andrew; Zaccarian, Luca <br/> <br/>Abstract: In this paper we formulate tracking and state- estimation problems of a translating mass in a polyhedral billiard as a stabilization problem for a suitable set. Due to the discontinuous trajectories arising from the impacts, we use hybrid systems stability analysis tools to establish the results. Using a novel concept of mirrored images of the target mass we prove that 1) a tracking control algorithm, and 2) an observer algorithm guarantee global exponential stability results for specific classes of polyhedral billiards, including rectangles. Moreover, we combine these two algorithms within dynamic controllers that guarantee global output feedback tracking. The results are illustrated via simulations. Mon, 20 May 2013 09:27:47 GMT http://hdl.handle.net/2268/148711 Title: Transboundary hydraulic modelling of extreme floods in the Meuse River <br/> <br/>Author, co-author: Dewals, Benjamin; Erpicum, Sébastien; Pirotton, Michel; Archambeau, Pierre <br/> <br/>Abstract: Detailed inundation modelling was conducted along a 100 km long transnational section of the Meuse River (in Belgium and The Netherlands), using very similar models for the whole computation (2D unsteady models). As a result, damping of the flood waves could be quantified and the possible relevance of using a steady-state approach could be assessed. The new detailed 2D hydraulic simulations have demonstrated that only a very limited damping of the flood waves occurs along the simulated reaches. From the perspective of the variation in peak discharge, the study concludes that running the hydraulic model in steady mode makes perfectly sense. Nonetheless, the steady computations lead to extensive overestimations of the inundated extent and of the stored volume in the floodplains. The 2D unsteady model constitutes also a tool of primary interest, which is readily available to design and evaluate protection measures for flood-prone areas such as in the city of Liege. Fri, 17 May 2013 16:13:57 GMT http://hdl.handle.net/2268/148642 Title: What is the right pathway to be sustainable? Case of biofuels and bioproducts in Europe <br/> <br/>Author, co-author: Belboom, Sandra; Léonard, Angélique Fri, 17 May 2013 09:16:37 GMT http://hdl.handle.net/2268/148631 Title: SAXS analysis in terms of density fluctuations within random observation window <br/> <br/>Author, co-author: Gommes, Cédric Fri, 17 May 2013 08:26:57 GMT 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 Thu, 16 May 2013 21:49:35 GMT 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. Thu, 16 May 2013 20:22:12 GMT http://hdl.handle.net/2268/148612 Title: Modélisation régionale et locale sur base des données de la carte géologique <br/> <br/>Author, co-author: Orban, Philippe Thu, 16 May 2013 19:28:25 GMT http://hdl.handle.net/2268/148611 Title: Photobioreactors for efficient production of molecules with high added value, based upon an innovative technology for the production of porous materials <br/> <br/>Author, co-author: Tocquin, Pierre Thu, 16 May 2013 19:13:52 GMT http://hdl.handle.net/2268/148543 Title: Matériaux et systèmes constructifs: critères de sélection <br/> <br/>Author, co-author: Courard, Luc <br/> <br/>Abstract: Donner quelques idées sur les raisons qui amènent l'ingénieur à baser son choix des matériaux sur des critères autres que techniques Thu, 16 May 2013 06:49:32 GMT http://hdl.handle.net/2268/148542 Title: Frequency-domain subspace identification of nonlinear mechanical systems <br/> <br/>Author, co-author: Noël, Jean-Philippe; Kerschen, Gaëtan <br/> <br/>Abstract: The objective of the present paper is to address the identification of a real-life strongly nonlinear space structure, the EADS-Astrium SmallSat spacecraft. To this end, a new nonlinear subspace identification method formulated in the frequency domain is exploited, referred to as the FNSI method. The frequency response functions of the underlying linear spacecraft and the amplitudes of the nonlinear internal forces are estimated based on a periodic-random data set corrupted by noise. This application is challenging for several reasons, including high modal density, highly non-proportional damping and the non-smooth nature of the nonlinearities. Thu, 16 May 2013 06:37:47 GMT http://hdl.handle.net/2268/148526 Title: Eléments de mécanique des fluides <br/> <br/>Author, co-author: Archambeau, Pierre; Pirotton, Michel Wed, 15 May 2013 14:14:07 GMT http://hdl.handle.net/2268/148514 Title: THREE-DIMENSIONAL RECONSTRUCTION OF LIQUID PHASES CONFINED IN DISORDERED POROUS MEDIA: AN IN SITU SYNCHROTRON SAS ANALYSIS <br/> <br/>Author, co-author: Gommes, Cédric; Hermida Merino, Daniel <br/> <br/>Abstract: We use Synchrotron Small-Angle X-ray Scattering to investigate temperature-induced morphological changes in binary hexane/nitrobenzene solutions confined in the pores of disordered mesoporous solids. The scattering data is analyzed with a plurigaussian model, which enables us to reconstruct the 3D morphology of the phases with a nanometer resolution. The reconstructions bring to light wetting transitions whereby the morphology of the nitrobenzene passes from a nanometer-thin layer that uniformly covers the solid surface to plugs that locally occlude the pore space. Our analysis enables us to quantitatively analyze the SAS data in terms of changing interface areas and wetting angles. The present contribution offers unprecedented insight into nanometer-scale wetting transitions. It also presents a novel SAS data analysis methodology that is applicable to a host of experimental situations involving disordered mesoporous materials. Wed, 15 May 2013 11:16:36 GMT http://hdl.handle.net/2268/148480 Title: Development of riveting technology through an analysis of Belgian patents (1830-1940) <br/> <br/>Author, co-author: Collette, Quentin; Wouters, Ine; de Favereau, Corentin; Peters, Arnaud <br/> <br/>Abstract: The development of riveting technology in iron and steel structures in the 19th and 20th centuries were highly promoted by patents. Although riveting was widely used in buildings and civil engineering structures, little information about the development of this technology – how rivets were manufactured, various installation techniques – is available in literature. This paper discusses a database of patents related to riveting technology that was created to better understand the innovations in riveted connections and their technological evolution. The database includes patents relating to rivets registered in Belgium between 1830 and 1940. Belgian patents are a good proxy for inventiveness in riveting technology in this period, in industrialized countries generally, not only Belgium. As one of the most industrialized countries, Belgium attracted inventors from many countries seeking to register their inventions: foreign inventions represented approximately 75% of all patents. Breakthroughs by important Belgian, French, British, and American inventors/companies are represented in this source. A methodology based on both quantitative and qualitative analyses was implemented. The quantitative analysis dealt with the entire database and explored several key parameters, for example, the subject of the patent and the patenting organization/person. The database also permitted qualitative analyses; specifically, it helped enlarge our understanding of pioneering inventors and their inventions, in the important categories of rivet manufacturing (1855-1870) and installation techniques (1895-1910). As background for the conservation and renovation of historic iron and steel structures, it is vital to have an understanding of the know-how that was available over time. This kind of information is revealed in the patent record Tue, 14 May 2013 15:15:04 GMT http://hdl.handle.net/2268/148479 Title: Quasi-One-Dimensional Numerical Simulations of Post-Stall Compression Systems <br/> <br/>Author, co-author: Du, Wenhai Tue, 14 May 2013 15:11:25 GMT http://hdl.handle.net/2268/148467 Title: Hydraulic modelling in civil and environmental engineering <br/> <br/>Author, co-author: Dewals, Benjamin; Erpicum, Sébastien; Archambeau, Pierre; Pirotton, Michel Tue, 14 May 2013 13:04:21 GMT http://hdl.handle.net/2268/148453 Title: Meta-learning of Exploration/Exploitation Strategies: The Multi-Armed Bandit Case <br/> <br/>Author, co-author: Maes, Francis; Wehenkel, Louis; Ernst, Damien <br/> <br/>Abstract: The exploration/exploitation (E/E) dilemma arises naturally in many subfields of Science. Multi-armed bandit problems formalize this dilemma in its canonical form. Most current research in this field focuses on generic solutions that can be applied to a wide range of problems. However, in practice, it is often the case that a form of prior information is available about the specific class of target problems. Prior knowledge is rarely used in current solutions due to the lack of a systematic approach to incorporate it into the E/E strategy. To address a specific class of E/E problems, we propose to proceed in three steps: (i) model prior knowledge in the form of a probability distribution over the target class of E/E problems; (ii) choose a large hypothesis space of candidate E/E strategies; and (iii), solve an optimization problem to find a candidate E/E strategy of maximal average performance over a sample of problems drawn from the prior distribution. We illustrate this meta-learning approach with two different hypothesis spaces: one where E/E strategies are numerically parameterized and another where E/E strategies are represented as small symbolic formulas. We propose appropriate optimization algorithms for both cases. Our experiments, with two-armed “Bernoulli” bandit problems and various playing budgets, show that the metalearnt E/E strategies outperform generic strategies of the literature (UCB1, UCB1-T UNED, UCB-V, KL-UCB and epsilon-GREEDY); they also evaluate the robustness of the learnt E/E strategies, by tests carried out on arms whose rewards follow a truncated Gaussian distribution. Tue, 14 May 2013 11:09:10 GMT http://hdl.handle.net/2268/148450 Title: Conception et calcul des éléments de machine <br/> <br/>Author, co-author: Debongnie, Jean-François <br/> <br/>Abstract: Texte du cours de conception mécanique donné par l'auteur aux étudiants ingénieur mécanicien de l'Université de Liège. Tue, 14 May 2013 10:07:20 GMT 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 Mon, 13 May 2013 16:39:45 GMT