# Talks

Talks 1 to 10 of 543 | show all

Date Time Venue Talk
07/11/22 03:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 TBA
Albrecht Seelmann, TU Dortmund, Fakultät für Mathematik
07/07/22 02:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 tba
Giovanni Samaey, KU Leuven

tba
06/20/22 03:00 pm Zoom tba
Julio Urizarna Carasa

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06/13/22 03:00 pm Zoom tba
Riccardo Morandin, TU Berlin

tba
05/30/22 03:00 pm Am Schwarzenberg-Campus 3 (E), Room 3.074 Spectral deferred correction methods for second-order problems
Ikrom Akramov

Spectral deferred corrections (SDC) is an iterative method for the numerical solution of ordinary differential equations. It can be interpreted as a Picard iteration for the collocation problem, preconditioned with a low order method. SDC has been studied for first order problems, using explicit, implicit or implicit-explicit Euler as preconditioner. It has been shown that SDC can achieve arbitrary high order of accuracy and possesses good stability properties.

In this talk, we will present an analysis of the convergence and stability properties of the SDC method when applied to second-order ODEs and using velocity-Verlet as preconditioner. While a variant of this method called Boris-SDC for the Lorentz equation has been investigated, no general analysis of its properties for general second order problems exists.

We will show that the order of convergence depends on whether the force on the right hand side of the system depends on velocity (like in the Lorentz equation) or not (like in the undamped harmonic oscillator). Moreover, we also show that the SDC iteration is stable under certain conditions. We compare its stability domain with that of the Picard iteration and validate our theoretical analysis in numerical examples.
05/23/22 03:00 pm Zoom On observability estimates for semigroups in Banach spaces
Dennis Gallaun

In this talk, I would like to present the main results of my PhD thesis.
We study a general method to obtain observability estimates for control systems in infinite dimensional spaces by combining an uncertainty principle and a dissipation estimate. Contrary to previous results obtained in the context of Hilbert spaces, we obtain conditions for observability in Banach spaces, allow for more general asymptotic behavior in the assumptions, and retain explicit estimates on the observability constant.
Our approach has applications, e.g., to control systems on non-reflexive spaces and anomalous diffusion operators.
Further, we derive duality results that connect observability estimates to controllability and stabilizability properties. As an application, we study controllability properties of systems given by fractional powers of elliptic differential operators with constant coefficients in $L_p(\mathbb{R}^d)$ for $p\in [1,\infty)$ and thick control sets.

https://tuhh.zoom.us/j/84729171896?pwd=ODArbForaUxMM3Q3VTJsNG1kaVNYQT09
05/09/22 03:00 pm Zoom Resilience in Spectral Deferred Corrections
Thomas Baumann, FZ Jülich

Advancement in computational speed is nowadays gained by using more processing units rather than faster ones.
Faults in the processing units caused by numerous sources including radiation and aging have been neglected in the past.
However, the increasing size of HPC machines makes them more susceptible and it is important to develop a resilience strategy to avoid losing millions of CPU hours.
Parallel-in-time methods target the very largest of computers and are hence required to come with algorithm-based fault tolerance.
We look here at spectral deferred corrections (SDC), which is a time marching scheme that is at the heart of parallel-in-time methods such as PFASST.
Due to its iterative nature, there is ample opportunity to plug in computationally inexpensive fault tolerance schemes, many of which are also easy to implement.
We experimentally examine the capability of various strategies to recover from single bit flips in time serial SDC, which will later be applied to parallel-in-time methods.

https://tuhh.zoom.us/j/84729171896?pwd=ODArbForaUxMM3Q3VTJsNG1kaVNYQT09
05/02/22 03:00 pm Zoom Robot manipulation in real-time, in the real-world, and under uncertainty.*
Wisdom Agboh, University of Leeds

Robots have the potential to disrupt many aspects of our lives, from healthcare to manufacturing. To realize this potential, a key challenge is real-time robot manipulation. Given a task, how can a robot quickly generate a motion plan to successfully complete it? How can the robot react in real-time to potential uncertainties in the real-world as it executes its plan? In this talk, we will overview recent developments at the University of Leeds, to realize real-time robot manipulation. These will include parallel-in-time integration methods that leverage parallel computing to significantly speed-up physics predictions for various robot manipulation tasks. It will also include learning-based and optimal control-based methods for robots to handle real-world uncertainties in object pose estimation and model parameters. We hope these recent advances will help accelerate the next generation of intelligent robots.