All Years Seminars
[INMA] 2020-03-03 (15:00) : Special event: visit of intoPIX
At Euler building (room A.002)
Speaker :
No author specified
Abstract :
The students from the Seminar in Applied Mathematics (LINMA2120) organize a visit intoPIX, an LLN-based world-class company specialized in image processing, video compression and security technologies.
Registration is free but mandatory (number of places limited; the registraiton form has been sent by email)
The schedule is as follows:
15:00 : meeting at the entrance of the Euler building for group departure (carpool)
15:30 : start of the visit
16:30 (approx.): end of the visit and drink
[INMA] 2020-03-03 (14:00) : Koopman operator-based identification of nonlinear ODEs and PDEs
At Euler building (room A.002)
Speaker :
Mauroy, Alexandre
Abstract :
The Koopman operator provides a linear description of nonlinear systems. In this talk, we will exploit this description in the context of nonlinear identification and parameter estimation. Since the generator of the semigroup of Koopman operators is directly connected to the underlying dynamics, we will exploit the key idea that identifying the linear generator is equivalent to identifying the nonlinear dynamics. Using this systematic approach, we will report on two dual linear techniques. These techniques will be illustrated with several examples and complemented with convergence properties derived from the theory of strongly continuous linear semigroups. Finally, the proposed identification framework will be extended to nonlinear PDEs by considering Koopman operator semigroups acting on a space of nonlinear functionals.
[INMA] 2020-02-25 (14:00) : Binarizing Johnson-Lindenstrauss transforms
At Euler building (room A.002)
Speaker :
Stollenwerk, Alexander
Abstract :
In many problems from data science, the encountered data is massive and encoded by high-dimensional vectors. For applications it is therefore appealing to first reduce its dimensionality before performing computations. If enough geometric information between data vectors is preserved, then the problem can be solved approximately using the embedded data. In this talk, we will focus on the problem of encoding a set of high-dimensional vectors into a small number of bits, while approximately preserving their pairwise Euclidean distances. By binarizing fast Johnson-Lindenstrauss transforms, we will see that this can be achieved efficiently, even for infinite data sets of low-complexity. The talk is based on joint work with Sjoerd Dirksen.
[INMA] 2020-02-19 (14:00) : Model-Free Practical Cooperative Control Using Passivity and Network Optimization
At Euler building (room A.207)
Speaker :
Miel Sharf (Technion, Israel)
Abstract :
Please note the unusual location and day of this talk.
In recent times, networked control systems have become an important field of research, as multi-agent and large-scale networks have become common, and the system-of-systems design philosophy has become the state-of-the-art. The ever-growing complexity of systems makes the process of obtaining a reliable mathematical model arduous and time-consuming, especially for networked systems which include many different agents corresponding to many different models. Coincidentally, technological advancements introduced more efficient ways to gather, store, and analyze data. This motivates the idea of data-driven controller design, in which data is used to solve control problems, either by building an approximate model for the system, or by learning a control policy directly.
In this talk, we'll consider a problem in which the relative output between the (nonlinear) agents must converge -close to prescribed values (e.g., consensus or formation control). Our approach relies on a connection between passivity theory and network optimization, as well as high-gain control. We use network optimization to show not only that there exists a gain attaining the desired control goal, but also prescribe a data-driven method of estimating it. We further present another data-driven solution using iterative sampling schemes. We will also discuss how to verify the required passivity assumptions and illustrate the developed methods in a case study.
The talk is based on joint work with Anne Romer, Daniel Zelazo and Frank Allgöwer.
[INMA] 2020-02-18 (14:00) : Computer-aided worst-case analyses and design of first-order optimization methods
At Euler building (room A.002)
Speaker :
Taylor, Adrien
Abstract : The goal of this presentation, is to provide a high-level overview of recent computer-assisted approaches for analyzing and designing first-order optimization methods (mostly for convex optimization).
In other words, we want to illustrate how to use computer algebra software (symbolic computations) and/or numerical tools (semidefinite programming solvers) for analyzing optimization schemes.
The presentation will be example-based, as the main ingredients necessary for understanding the methodologies are already present in basic examples such as the vanilla gradient method.
For convincing the audience, we will provide other examples that include novel analyses of the Douglas-Rachford splitting, and a variant of the celebrated conjugate gradient method.
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