All Years Seminars
[INMA] 2017-04-21 (11:00) : It's not MPC ! Explicit Reference Governors for the supervision of constrained nonlinear systems
At Euler building (room A.002)
Speaker :
Emanuele Garone (ULB)
Abstract :
This talk introduces a control framework which dynamically modifies the reference of a pre-compensated nonlinear system so as to ensure the satisfaction of constraints, without resorting to online optimization. The basic ERG scheme is built translating state space constraints into a constraint on the Lyapunov function and limiting its value by modulating the velocity of the applied reference. The theory is introduced for general nonlinear systems subject to constraints and will be specialized to the large and highly relevant class of nonlinear systems admitting a Lyapunov function that is lower-bounded by a quadratic form. A complete generalization of the presented scheme will be also presented. Design and implementation aspects will be discussed as well.
[INMA] 2017-04-20 (14:00) : Invariant processes on infinite trees
At Euler building (room A.002)
Speaker :
Viktor Harangi (Rényi Institute of Mathematics Budapest, Hungary)
Abstract :
In this talk we will demonstrate how studying certain invariant processes on infinite trees can help to answer questions about (large) finite graphs/networks (such as questions about the maximal size of an independent set or about the eigenvectors of the adjacency matrix). Our main focus will be the class of factor of IID processes (which are essentially factors of Bernoulli shifts from an ergodic theoretic point of view). We will also mention some entropy inequalities that played a central role in a couple of remarkable results recently.
[INMA] 2017-03-21 (14:00) : Variational Methods for Manifold Valued Image Processing
At Euler building (room A.002)
Speaker :
Ronny Bergmann (University of Kaiserslautern)
Abstract :
In many real life scenarios measured data appears as values from a Riemannian
manifold. For example in interferometric Synthetic Aperture Radar (InSAR) data
is given as a phase, in electron backscattered diffraction (EBSD) as data items
being from a quotient of the orientation group SO(3), and in diffusion tensor
magnetic resonance imaging (DT-MRI) the measured data are symmetric positive
definite matrices. These data items are often measured on a pixel grid like
usual images and they also suffer from the same measurement errors like noisy
or incompleteness.Hence there is a need to perform image processing tasks like
denoising, inpainting or segmentation on these manifold-valued images. Recently
the ROF-Model for TV regularization has been transferred to the setting of
manifold-valued images to perform such image processing tasks.
In this talk we present methods and algorithms to compute the TV regularization
for manifold-valued images efficiently using variational methods. We present
generalizations to second order methods, and to the case, where the data is not
given on a pixel grid, for example when dealing with nonlocal methods.
[INMA] 2017-03-14 (14:00) : The structure of complex networks
At Euler building (room A.002)
Speaker :
Remco van der Hofstad (TU Eindhoven)
Abstract :
Many phenomena in the real world can be phrased in terms of networks. Examples include the World-Wide Web, social interactions, traffic and Internet, but also the interaction patterns between proteins, food webs and citation networks.
The large-scale networks have, despite their diversity in backgrounds, surprisingly much in common. Many of these networks are small worlds, in the sense that one requires few links to hop between pairs of vertices. Also the variability of the number of connections between elements tends to be enormous, which is related to the scale-free phenomenon.
In this lecture for a broad audience, we describe a few real-world networks and some of their empirical properties. We also describe the effectiveness of abstract network modeling in terms of graphs and how real-world networks can be modeled, as well as how these models help us to give sense to the empirical findings. We continue by discussing some random graph models for real-world networks and their properties, as well as their merits and flaws as network models. We conclude by discussing the implications of some of the empirical findings on competition on such networks.
[INMA] 2017-03-07 (14:00) : Optimization of electrical distribution systems
At Euler building (room A.002)
Speaker :
Bertrand Cornélusse (ULg)
Abstract :
Electrical distribution systems are quickly evolving nowadays because of changes in the way electricity is produced and consumed, and because increasing communication and computation capacities offer new optimization possibilities. In this presentation, I will explain how electrical distribution systems are operated, what is their role in the broader power system, and how they are evolving. I will then review several research topics I have been interested in over the last 4 years, such as active network management, the estimation of the network hosting capacity, and the study of interactions between stakeholders when someone wants to play with flexibility within a distribution system.
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