All Years Seminars
[INMA] 2020-02-11 (14:00) : Minkowski, Lyapunov, and Bellman: Inequalities and Equations for Stability and Optimal Control
At Euler building (room A.002)
Speaker :
Sasa V. Rakovic
Abstract : The algebraic Lyapunov and Bellman equations, and inequalities, are cornerstone objects in linear systems theory. These equations, and inequalities, are concerned with convex quadratic functions verifying stability in case of Lyapunov equation and providing optimality in case of Bellman equation. Rather peculiarly, very little had been known about Lyapunov and Bellman equations, and inequalities, within space of Minkowski functions of nonempty convex compact subsets containing the origin in their interior prior to my work in the area. Key results of my related research on these fundamental problems have provided characterization of solutions to both Lyapunov and Bellman equations within space of Minkowski functions, referred to as the Minkowski Lyapunov and Minkowski Bellman equations. The talk outlines key results underpinning these two fundamental equations and related inequalities, and draws parallel to classical results on algebraic Lyapunov and Bellman equations and inequalities.
[INMA] 2020-02-04 (14:00) : Three 15-minute talks
At Euler building (room A.002)
Section 1: Local dynamics identification via a graph-theoretical approach
Speaker :
Legat, Antoine
Abstract : In this talk we propose a novel approach to network identification: the recovery of the local dynamics from the global input-output behavior and the network structure. First, we express identifiability conditions on the rank of transfer matrices, which can be computed by routing vertex disjoint paths in the network. We then address the unstudied case of partial measurement and excitation, and derive a linearization which yields promising conditions for the identifiability of the whole network, backed up by our implementation.
Section 2: Mathematical modeling of malaria transmission taking into account the influence of current prevention and treatment
Speaker :
Ousmane Diao
Abstract : Malaria is a parasitic infection transmitted by a mosquito (female Anophele) which is very deadly for humans. Many strategies are provided from the Senegal s National Malaria Control Program of to reduce morbidity and mortality. We have insecticide-treated bed-nets (ITNs), Vaccines, L'Artemisinin-based combination therapy (ACT) and indoor residual spraying (IRS) etc For it, mathematical modelling may play an important role in operational and optimizing this strategies on control. So we want to develop compartments mathematical model of malaria transmission to show the effects of prevention and treatment.
Section 3: Lower bounds for the nonnegative rank
Speaker :
Dewez, Julien
Abstract : Nonnegative matrix factorization (NMF) consists in finding two nonnegative matrices whose product is equal to/approximates a nonnegative data matrix. It has many interesting applications in data analysis when the observed data is nonnegative by nature, e.g., in text mining, in hyperspectral unmixing, and many more. Computing the minimum dimension of such a factorization, called the nonnegative rank, is NP-hard in general. However, it also has interesting applications, e.g., in combinatorial optimization, in statistics, etc.
In this talk, we introduce new lower bounds on the nonnegative rank based on properties of some geometric representations of the matrix.
[INMA] 2019-12-17 (14:00) : Nonlinear matrix recovery
At Euler building (room A.002)
Speaker :
Florentin Goyens (Alan Turing Institute and University of Oxford, UK)
Abstract :
In this talk we investigate the recovery of a partially observed high-rank matrix whose columns obey a nonlinear structure. The structures we cover include points grouped as clusters or belonging to an algebraic variety, such as a union of subspaces. Using a mapping to a space of features, we reduce the problem to a constrained non-convex optimization formulation, which we solve using Riemannian optimization methods. We also show how the same tools allow to align point clouds that belong to the same algebraic variety (point set registration).
[INMA] 2019-12-10 (14:00) : How scale-free texture segmentation turns out to be a strongly convex optimization problem?
At Euler building (room A.002)
Speaker :
Pascal Barbara (ENS Lyon, France)
Abstract : Texture segmentation still constitutes an ongoing challenge, especially when processing large-size images. The aim of this work is twofold. First, we provide a variational model for simultaneously extracting and regularizing local texture features, such as local regularity and local variance. For this purpose, a scale-free wavelet-based model, penalised by a Total Variation regularizer, is embedded into a convex optimisation framework. Second, we investigate convergence acceleration strategies, relying on strong-convexity of the objective function, in order to deal with computational cost induced by the minimization. Finally, we illustrate the developed procedures on real-world images of multiphasic flows.
[INMA] 2019-12-03 (14:00) : Optimization for ultrabroadband internet access
At Euler building (room A.002)
Speaker :
Tsiaflakis, Paschalis
Abstract :
Broadband internet access is an essential part in modern life society. Offering universal, cheap and ultrabroadband internet connectivity is a top priority within the European Digital Agenda. The Nokia Bell Labs Fixed Networks Team located in Antwerp is recognized for pioneering and contributing to breakthroughs in wireline broadband internet access technologies. These technologies enable data communication at gigabit speeds between residential customers and the fiber backbone, and are characterized by optimization-intensive physical-layer designs. This seminar will explain a number of optimization problems that are considered in practice to innovate communication technologies. The main aim of this seminar is to show that the application of optimization theory is very relevant for industry.
Seminars
Subscribe (ICS)
INMA Contact Info
Mathematical Engineering (INMA)
L4.05.01
Avenue Georges Lemaître, 4
+32 10 47 80 36
secretaire-inma@uclouvain.be
Mon – Fri 9:00A.M. – 5:00P.M.
JOIN US