# Fakultätskolloquium der Technischen Fakultät im WS 2017/18

• ### Die Kolloquien an den Instituten für Elektrotechnik und Informationstechnik sowie Materialwissenschaften:

Jeweils montags eine halbe Stunde vor Beginn der Vorträge, also um 16.45 Uhr, werden die Gastredner den Besuchern des Kolloquiums in einer zwanglosen Runde bei einer Tasse Kaffee in der "Eisdiele" (Eingangshalle Geb. D, neben dem "Aquarium") vorgestellt.

Ansprechpartner:  Daniel Johannsen (Tel. 0431-880-6068) dekanat@tf.uni-kiel.de

• ### Die Kolloquien am Institut für Informatik:

Alle Vorträge finden - soweit nicht anders angegeben - im Raum Ü2/K des Instituts für Informatik (Ludewig-Meyn-Str. 2, Vorbau des Mathematischen Seminars) freitags um 14 Uhr c.t. statt. 45 Minuten vor Vortragsbeginn stehen Tee und Kaffee bereit.

Ansprechpartner/innen: Geschäftszimmer des Instituts für Informatik (Tel. 0431 880-7270)aktuell@informatik.uni-kiel.de

• ### Wenn Sie die Einladungen per E-Mail erhalten möchten tragen Sie sich bitte in die Mailingliste ein.

Bitte achten Sie bei Sonderkolloquien auf die Zeit- und Raumangaben!

Nachfolgend alle Vortragstermine in chronologischer Abfolge

# Kolloquiumsvortrag, nn / am 02.10.2017

02.10.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Kolloquiumsvortrag, nn / am 06.10.2017

06.10.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 09.10.2017

09.10.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Kolloquiumsvortrag, nn / am 13.10.2017

13.10.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 16.10.2017

16.10.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Sonderkolloquium (INF), Vijay Ganesh, University of Waterloo, Kanada / am 17.10.2017

17.10.2017 von 14:00 bis 15:00

Institut für Informatik, Christian-Albrechts-Platz 4, 24118 Kiel

Titel: On The Unreasonable Effectiveness of Boolean SAT Solvers

Abstract: Modern conflict-driven clause-learning (CDCL) Boolean SAT solvers routinely solve very large industrial SAT instances in relatively short periods of time. This phenomenon has stumped both theoreticians and practitioners since Boolean satisfiability is an NP-complete problem widely believed to be intractable. It is clear that these solvers somehow exploit the structure of real-world instances. However, to-date there have been few results that precisely characterize this structure or shed any light on why these SAT solvers are so efficient.

In this talk, I will present results that provide a deeper empirical understanding of why CDCL SAT solvers are so efficient, which may eventually lead to a complexity-theoretic result. Our results can be divided into two parts. First, I will talk about structural parameters that can characterize industrial instances and shed light on why they are easier to solve even though they may contain millions of variables compared to small crafted instances with hundreds of variables. Second, I will talk about internals of CDCL SAT solvers, and describe why they are particularly suited to solve industrial instances.

Brief Bio: Dr. Vijay Ganesh is an assistant professor at the University of Waterloo since 2012. Prior to that he was a research scientist at MIT, and completed his PhD in computer science from Stanford University in 2007. Vijay's primary area of research is the theory and practice of automated reasoning aimed at software engineering, formal methods, security, and mathematics. In this context he has led the development of many SAT/SMT solvers, most notably, STP, The Z3 string solver, MapleSAT, and MathCheck. He has also proved several decidability and complexity results relating to the SATisfiability problem for various mathematical theories. For his research, he has won over 20 awards including an ACM Test of Time Award at CCS 2016, two Google Faculty Research Awards in 2011 and 2013, and a Ten-Year Most Influential Paper Award at DATE 2008.

# Kolloquiumsvortrag, nn / am 20.10.2017

20.10.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 23.10.2017

23.10.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Kolloquiumsvortrag, nn / am 27.10.2017

27.10.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 30.10.2017

30.10.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Kolloquiumsvortrag, nn / am 03.11.2017

03.11.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 06.11.2017

06.11.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

# Kolloquiumsvortrag, nn / am 10.11.2017

10.11.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), Prof. Elisabetta Chicca, Uni Bielefeld / am 13.11.2017

13.11.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Learning in silico beyond STDP

Abstract: Synaptic plasticity empowers biological nervous systems with the ability to learn from experience and adjust to environmental changes. Such abilities are a must for artificial autonomous systems and therefore researchers have been devoting significant efforts to the understanding and modelling of plasticity mechanisms. In particular, the field of neuromorphic engineering focuses on the development of full-custom hybrid analog/digital electronic systems for the implementation of models of biological computation and learning in hardware. I will give a short historical overview of the most important plasticity circuits developed following the approach originally proposed by Carver Mead in the late eighties. Afterwards, I will present recent advancements in this field.

# Kolloquiumsvortrag, nn / am 17.11.2017

17.11.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), M.Sc. Jonas Sauter, Nuance Communications / am 20.11.2017

20.11.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Artificial Bandwidth Extension for Speech Signals Using Deep Neural Networks

Abstract: In mobile communication, the bandwidth of transferred speech signals is either narrow-band (300Hz – 3.4kHz) or wide-band (50Hz – 7kHz or higher). As the limitation to 3.4kHz degrades the speech quality and intelligibility, it is of great interest to artificially extend narrow-band speech signals to wide-band speech.

This talk presents a deep neural network (DNN) approach to artificial bandwidth extension with a focus on robustness in practical applications.

It is based on the source-filter model which decomposes the signal into two parts: an excitation signal and a spectral envelope. The excitation (source part) describes the fine spectral structure which consists of white noise for unvoiced speech and an impulse train for voiced speech. The spectral envelope (filter part) describes the coarse spectral structure, i.e. the formants or resonance frequencies that make up different phonemes.

While the extension of the excitation signal can be done with simple mathematical methods that do not introduce strong artifacts, the envelope is much more relevant for the quality of the reconstructed wide-band signal. That is why the wide-band envelope is estimated with DNNs in this approach, which are trained on a large speech corpus.

Short biography

Jonas Sautter studied Electrical Engineering, Information Technology and Computer Engineering at RWTH Aachen University, Germany. He received his Master of Science degree in 2016. The Master’s thesis with the title “Digital Robust Control for Active Noise Cancellation in Headphones and Hearing Aids” was composed at the Institute of Communication Systems at RWTH Aachen. Since November 2016, he is a PhD student at Nuance Communications in Ulm, supervised by Professor Gerhard Schmidt, Head of the Digital Signal Processing and System Theory group at Christian-Albrechts-Universität, Kiel.

# Kolloquiumsvortrag, nn / am 24.11.2017

24.11.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), Dr.-Ing. Vasudev Kanade Rajan / am 27.11.2017

27.11.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Digital Road Noise Cancellation System Through Active Noise Control

Abstract: The application of active noise cancellation in real-world has not been fully realized yet. From reducing environment noise through the usage of headphones, to engine noise on commercial jets there are a number of use cases. Each of these use case brings its own set of challenges which can be understood only through multi-disciplinary work. One such use case the the reduction of road noise in vehicles. Structure-borne road noise dominates the cabin of modern vehicles. Several road noise cancellation (RNC) prototype systems have been implemented and demonstrated. These systems are based mainly on analog sensors. The placement of these sensors has been so far been based on random optimization methods. In this talk I will talk about the challenges in developing a generic digital RNC system which includes problem analysis, sensor placement, and performance. An adaptive algorithm process the acceleration signals with high convergence and reaction time for various speed and surface ranges, in order to maintain high audible effects for the passengers. Several modern vehicle platforms are integrated with the digital RNC system with ANC microphone at the headliners and the standard audio loudspeaker setup in order to integrate the technology with the existing audio layout of the vehicle.

#### Short biography

Vasudev Kandade Rajan received Bachelors degree in Electronics and Communication from Visvesvaraya Technological University, Bangalore, India. He joined as Project Research Assistant in July 2008 in the Electrical Communication Engineering Dept, Indian Institute of Science, Bangalore. There he worked on performance management of IEEE 802.11 WLANs until Sept 2009. He then went to obtain his Masters degree (MSc.) in Digital Communications, 2011 and PhD degree in Signal Processing, 2017 from Universtiy of Kiel, Germany. Currently he is working in the R&D department of Harman Becker Automotive Systems GmbH, Straubing, Germany.

# Kolloquiumsvortrag, nn / am 01.12.2017

01.12.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), Dr. Andreas Bisplinghoff, Cisco / am 04.12.2017

04.12.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: From Long-Haul to Data-Center-Interconnect - Effiziente Signalverarbeitungsalgorithmen für Flexible Optische Netze

Abstract: First coherent optical communication systems, operating at 40Gbps, have been deployed in 2005. Since then, coherent optical technology has undergone remarkable development in the most recent years. Nowadays, state of the art products support line rates up to 400Gbps per wavelength. Next generation systems will primarily target for higher integration density but will presumably also reach line rates of 600Gbps and beyond.

With progress both in CMOS technology and of optical components, coherent optical transmission continuously pushes forward to highest reach for ultra-long haul applications as well as to highest capacity for shorter reach data-center interconnects. Both directions involve very specific requirements both on the capabilities of applied DSP algorithms and integration density of electrical and optical components.

Each new CMOS technology node facilitates the implementation of more sophisticated DSP algorithms. Many DSP components have undergone tremendous development during the most recent years, enabling coherent systems operating at highest transmission rates. Very efficient equalizer algorithms compensate for linear (CD, PMD) and non-linear (SPM, XPM) signal distortions, enhanced soft-decoded forward error correction schemes improve the noise tolerance, and with probabilistic constellation shaping performance will ultimately approach the Shannon limit.

This talk gives a high-level overview about state of the art DSP algorithms and most recent developments in coherent optical communication. It then discusses the balancing act to address the specific requirements of highest reach as well as highest capacity transmission within a single ASIC. Finally, some selected tradeoffs in algorithm and architecture optimization are shown by means of soft-decoded forward error correction as an example.

Bio: Andreas Bisplinghoff was born in Forchheim in 1984. He received the Dipl.-Ing. and Dr.-Ing. degrees both in electrical and electronic engineering from the Friedrich-Alexander University of Erlangen in 2009 and 2015, respectively.

From 2010 to 2013, he was a Research Assistant with the Institute of Microwaves and Photonics at the University of Erlangen. Since 2013 he has been a Hardware Engineer in Advanced Development with the Cisco Optical GmbH. His research interests include the development of slip-reduced carrier phase recovery techniques and of power-efficient forward error correction schemes for coherent optical communication. Andreas Bisplinghoff has broad experience in complexity-aware algorithm design, FPGA-based prototyping, and power-optimized ASIC implementation.

# Kolloquiumsvortrag, nn / am 08.12.2017

08.12.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (MaWi), Prof. Friedrich Frischknecht, Universität Heidelberg / am 11.12.2017

11.12.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Malaria transmission: new insights from in vivo imaging and materials science

Abstract: Malaria parasites are transmitted by mosquitoes and multiply to large numbers in red blood cells to cause disease. When taken up by mosquitoes the parasite develop in large cysts in their guts from where they emerge to colonize the salivary glands of the insect. From there the parasites are injected into the skin where they have to migrate to find a blood vessel. After entering the blood vessel the parasites first enter liver cells where they multiply without causing disease symptoms. In this seminar I will illuminate some of this curious biology using a set of different microscopy techniques, molecular genetics and biophysical approaches. We will see how parasites form within the cysts, how they leave the cysts, move within salivary glands and in the skin. Using laser tweezers we have measured the force they can produce and using micro-pillar arrays we have asked whether they adapted their shape in order to find the small blood capillaries into which they enter. For more info see: www.sporozoite.org

# Kolloquiumsvortrag, Dr. Patrick Totzke / Laboratory for Foundations of Computer Science at Edinburgh/ am 15.12.2017

15.12.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

Titel: Combined Objectives in Simple Stochastic Games

Abstract: SSG are turn-based, perfect information games where states are controlled by Adam, Eve or a randomized environment. The two opposing players compete to maximize/minimize the probability of a given winning condition (the objective of the game). I will outline a line of research that considers combinations of objectives classically studied for the verification of reactive systems, such as Parity, Mean-Payoff or limit-reward criteria. The aim is to determine under which conditions, to what extend, and with how much extra effort a player can achieve multiple objectives simultaneously. Time permitting, I will outline a recent result that exposes a subtle bug in the literature and shows how to fix it.

# Kolloquiumsvortrag (MaWi), PD Dr. Pavel Levkin, Karlsruhe Institute of Technology / am 18.12.2017

18.12.2017 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Abstract: Patterns of different surface properties are ubiquitous in nature and serve various important purposes. Desert beetles exploit superhydrophilic spots on their superhydrophobic back to collect water from the morning mist in the desert. Hydrophilic spots on a superhydrophobic surface of lichen plants allow them to uptake water, but also prevent the formation of water layers on the surface that could interfere with the discharge of lichen spores into the air. Superhydrophobic and omniphobic surfaces possess various unique properties including self-cleaning, liquid repellent and cell repellent properties. We are interested in creating precise two-dimensional micropatterns of apparently incompatible and opposite properties such as superhydrophobicity and superhydrophilicity or slippery and adhesive properties. To create such patterns we develop surface coatings with special wettabilities and photochemical surface functionalization strategies. Combining seemingly opposite properties in micropatterns leads to functionalities non-existent on the original homogeneous interfaces. For example, we showed that superhydrophobic-superhydrophilic patterned surfaces could be used to create patterns of cells, arrays of microdroplets suitable for high-throughput cell screenings, formation of arrays of hydrogel micropads or free-standing hydrogel particles with defined shapes for 3D cell culture. Patterned liquid-infused interfaces could be also used to form cell microarrays or arrays of isolated biofilm colonies for biofilm screenings.

# Kolloquiumsvortrag, nn / am 22.12.2017

22.12.2017 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag, nn / am 05.01.2018

05.01.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT) - muss leider entfallen - Prof. Frank Vollmer, University of Exeter / am 08.01.2018

08.01.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Sensing the Nanoscale with Optoplasmonics

Abstract: Nanophotonic device building blocks, such as optical nano/microcavities and plasmonic nanostructures, lie at the forefront of sensing and spectrometry of trace biological and chemical substances. My laboratory is developing a new class of nanophotonic architectures by combining optically resonant dielectric nano/microcavities with plasmonically resonant metal nanostructures to enable detection at the nanoscale with extraordinary sensitivity. Initial demonstrations include single-molecule detection and even single-ion sensing. The coupled photonic-plasmonic resonator system promises a leap forward in the nanoscale analysis of physical, chemical, and biological entities. I will review our work in this burgeoning field of optoplasmonic biosensors. I will also talk about our most recent advances in localising light at the nanoscale in disordered 2D photonic crystals.

1Department of Physics and Astronomy, Living Systems Institute, University of Exeter, EX44QD, Exeter, UK

E-mail: f.vollmer@exeter.ac.uk

CV: Frank Vollmer is a Professor of Biophysics at the Living Systems Institute at the University of Exeter. Prof Vollmer pioneers optical technology to study processes at the nanoscale. He held several appointments at leading US institutions including Instructor in Medicine at Harvard Medical School. Before moving to the LSI in 2016, he held the position of Research Group Leader at the Max Planck Institute for the Science of Light (DE). In 2017 Prof Vollmer was awarded the Royal Society Wolfson Research Merit Award.

References

# Kolloquiumsvortrag, nn / am 12.01.2018

12.01.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (MaWi), Prof. Weller, Uni Hamburg / am 15.01.2018

15.01.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Nanocrystals in Materials and Life Science Applications

Abstract:

Horst Weller,
Institut für Physikalische Chemie, Universität Hamburg, Fraunhofer-Zentrum für Angewandte Nanotechnologie (CAN), The Hamburg Centre for Ultrafast Imaging (CUI)

Nanocrystals are already used for many applications in technical products for every day life. The talk will describe actual developments such as quantum dots in display and lighting technology and ultra-hard nanocomposite materials. Modern aspects of particle synthesis will be discussed.
The key idea for using nanocrystals for biomedical diagnostics is to benefit from their outstanding physical properties in the visualization of biological events or malignant cells or tissues. This requires a special design of the ligand shell, which preserves the fluorescent, magnetic and plasmonic properties of the particles in the biological environment on one side and allows a specific targeting on the other. The lecture reports on different chemical approaches and describes factors determining the biological response on fully synthetic nanocrystals. We will highlight concepts based on PEGylation and show how small deviations in the ligand shell alter the behavior in biological environment substantially. Moreover, we will present combinatorial approaches for the functionalization of the nanocrystals with biological affinity molecules to improve targeting specificity and concepts to optimize the physical properties of the inorganic core to increase the sensitivity for the respective imaging techniques.

# Kolloquiumsvortrag, nn / am 19.01.2018

19.01.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), Prof. Martjin van den Heuvel, Brain Center Rudolf Magnu Utrecht / am 22.01.2018

22.01.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Exploring the human connectome

Abstract: Using network science as a general framework to study the network architecture of nervous system connectivity, more and more studies have highlighted the human and animal brain to display features of an efficient communication network. In my talk I will discuss potential general principles of wiring of connectome organization, principles conserved across species, and which may play an important role in general nervous system functioning. I will highlight findings that show connectomes to display cost-effective wiring, pronounced community structure, short communication relays, and the existence of richly connected 'hub regions'. I will discuss theories on how these themes of wiring may play a role in brain disorders, as well as establish a putative link between the micro- and macroscale organization of the human brain in health and disease.

# Kolloquiumsvortrag, nn / am 26.01.2018

26.01.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (MaWi), Prof. Kläui, Uni Mainz / am 29.01.2018

29.01.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Topological Spin Dynamics for GreenIT

Abstract: In our information-everywhere society IT is a major player for energy consumption. Novel spintronic
devices can play a role in the quest for GreenIT if they are stable and can transport and manipulate
spin with low power. Devices have been proposed, where switching by energy-efficient approaches,
such as spin-polarized currents is used [1], for which we develop new highly spin-polarized materials
and characterize the spin transport using THz spectroscopy [2]. Firstly to obtain ultimate stability, topological spin structures that emerge due to the
Dzyaloshinskii-Moriya interaction (DMI) at structurally asymmetric interfaces, such as chiral domain
walls and skyrmions with enhanced topological protection can be used [3-5]. We have investigated in
detail their dynamics and find that it is governed by the topology of their spin structures [3]. By
designing the materials, we can even obtain a skyrmion lattice phase as the ground state of the thin
films [4]. Secondly, for ultimately efficient spin manipulation, we use spin-orbit torques, that can transfer
more than 1ħ per electron by transferring not only spin but also orbital angular momentum. We
combine ultimately stable skyrmions with spin orbit torques into a skyrmion racetrack device [4],
where the real time imaging of the trajectories allows us to quantify the novel skyrmion Hall effect
[5]. Finally to obtain efficient spin transport, we study graphene and low damping ferro- and
antiferromagnetic insulators as spin conduits for long distance spin transport [6] and explore the
superfluid spin current regime in antiferromagnets [7]. We find that we can control magnonic spin
currents by a newly developed magnon spin valve device [8].

[1] Reviews: O. Boulle et al., Mater. Sci. Eng. R 72, 159
(2011); G. Finocchio et al., J. Phys. D: Appl. Phys. 49,
423001 (2016); A. Bisig et al., PRL 117, 277203 (2016)
[2] M. Jourdan et al., Nature Commun. 5, 3974 (2014);
Z. Jin et al., Nature Phys. 11, 761 (2015).
[3] F. Büttner et al., Nature Phys. 11, 225 (2015).
[4] S. Woo et al, Nature Mater. 15, 501 (2016).
[5] K. Litzius et al., Nature Phys. 13, 170 (2017).
[6] A. Kehlberger et al., Phys. Rev. Lett. 115, 096602 (2015);
S. Geprägs et al., Nature Commun. 7, 10452 (2016).
[7] Y. Tserkovnyak and M. Kläui, arxiv:1707.01082
[8] J. Cramer et al., arxiv:1706.07592

# Kolloquiumsvortrag (INF) Arindam Khan, TU München / am 02.02.2018

02.02.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

Titel: Approximating Geometric Knapsack via L-packings

Abstract: We study the two-dimensional geometric knapsack problem (2DK), a
geometric variant of the classical knapsack problem. In this problem, we
are given a set of axis-aligned rectangular items, each one with an
associated profit, and an axis-aligned square knapsack. The goal is to
find a (non-overlapping) packing of a maximum profit subset of items
inside the knapsack without rotating items. This is a very well-studied
optimization problem and finds applications in scheduling, memory
approximation factor for this problem (even just in the cardinality
case) is $2+\epsilon$ [Jansen and Zhang, SODA 2004].

After more than a decade, in this paper we break the 2-approximation
barrier, achieving a polynomial-time $17/9+\epsilon<1.89$ approximation,
which improves to $558/325+\epsilon<1.72$ in the cardinality case. We
also consider the variant of the problem with rotations (2DKR), where
the items can be rotated by $90$ degrees. Also, in this case, the
best-known polynomial-time approximation factor (even for the
cardinality case) is $2+\epsilon$ [Jansen and Zhang, SODA 2004].
Exploiting part of the machinery developed for 2DK plus a few additional
ideas, we obtain a polynomial-time $3/2+\epsilon$-approximation for
2DKR, which improves to $4/3+\epsilon$ in the cardinality case (joint
work with Waldo Galvez, Fabrizio Grandoni, Sandy Heydrich, Salvatore
Ingala and Andreas Wiese.).

Bio: Arindam Khan is a postdoc in Lehrstuhl für Theoretische Informatik
at Technische Universität München. His research areas include
approximation algorithms, online algorithms and computational geometry.
He has obtained his PhD in Algorithms, Combinatorics and Optimization
(ACO) from Georgia Institute of Technology, Atlanta, USA under Prof.
Prasad Tetali. Previously he has been a research intern in Theory group,
Microsoft Research Redmond and Microsoft Research Silicon Valley USA, a
visiting researcher at Simons Institute, Berkeley, USA; a blue scholar
in IBM Research India and a researcher at IDSIA, Lugano, Switzerland.

# Kolloquiumsvortrag (MaWi), Frau Dr. Berit Zeller-Plumdorf, Helmholtz Zentrum Geesthacht / am 05.02.2018

05.02.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Imaging and image-based modelling of biological and material systems

Abstract: Synchrotron radiation-based computed tomography (SRμCT) is a powerful tool for high-resolution imaging of materials. Whilst it traditionally depends on the X-ray attenuation by material components with high Z-numbers, it can be enhanced to enable imaging of biological soft tissues and other low-attenuation materials through propagation-based phase contrast. Due to the available high photon flux it is also possible to perform in situ testing, e.g. of material corrosion or mechanical loading experiments. In combination with image-based mathematical modelling, SRμCT enables the correlation between morphological and/or structural material measures and their function. In this presentation, showcases will be presented where SRμCT and image-based modelling have successfully been used to this end. These showcases include the assessment of osseointegration and in vitro degradation of biodegradable implants, the computational analysis of oxygenation in mouse muscle and the corrosion of steel embedded in concrete in aqueous solutions.

# Kolloquiumsvortrag, nn / am 09.02.2018

09.02.2018 von 14:15 bis 15:45

Institut für Informatik, Ludewig-Meyn-Straße 2, 24118 Kiel, Raum: Übungsraum 2/K

# Kolloquiumsvortrag (ET&IT), Dr. Timm Faulwasser, Karlsruhe Institute of Technology / am 12.02.2018

12.02.2018 von 17:15 bis 18:00

Institute Ostufer, Geb. D, "Aquarium", Kaiserstr. 2, 24143 Kiel

Titel: Recent Progress on Distributed and Stochastic Optimization for Power Systems

Abstract: The increasing need for the de-carbonization of energy supply calls for new operational methods for power systems. In this context, tailored system and control approaches are pivotal- The specific challenges include the consideration of volatile renewable generation, uncertain forecasts thereof, and highly nonlinear system behavior.

In this talk, we focus on the so-called Optimal Power Flow (OPF) problem, which refers to a class of large-scale non-convex steady-state optimization problems frequently arising in power systems. For example, OPF problems provide optimal set points for power dispatch that satisfy the power flow equations and technical limitations such as generation and/or transmission limits. However, OPF problems are highly non-convex and subject to considerable uncertainties, which includes forecasts of renewable generation and household consumption, line parameters and grid topology.

After a concise problem statement, we provide an overview of the state of the art techniques to considering uncertainties in OPF problems and their bottlenecks. Moreover, we will discuss the concept of Polynomial Chaos Expansions (PCE) which allows to consider non-Gaussian uncertainties in OPF problems. PCE builds upon a series expansion of random-variables. We will present recent results on PCE for convex DC-OPF problems and non-convex AC-OPF problems [1, 2]. Moreover, we will comment on the quantification of PCE truncation errors [3].

Due to their large-scale nature, the distributed solution of OPF problems is subject to considerable research efforts. Thus, we will also comment on our recent results on the distributed solution of OPF problems [4].

References

[1] Mühlpfordt, T.; Faulwasser, T.; Roald, L. & Hagenmeyer, V. Solving optimal power flow with non-Gaussian uncertainties via polynomial chaos expansion. 56th IEEE Conference on Decision and Control, 2017. To appear.

[2] Mühlpfordt, T.; Faulwasser, T. & Hagenmeyer, V. Solving stochastic AC power flow via polynomial chaos expansion. IEEE International Conference on Control Applications, 2016, 70-76.

[3] Mühlpfordt, T.; Findeisen, R.; Hagenmeyer, V. & Faulwasser, T. Comments on Quantifying Truncation Errors for Polynomial Chaos Expansions. arXiv:1708.07655.

[4] Engelmann, A.; Mühlpfordt, T.; Jiang, Y.; Houska, B. & Faulwasser, T. Distributed AC optimal power flow using ALADIN. 20th IFAC World Congress, 2017.

Bio Sketch

Timm Faulwasser has studied Engineering Cybernetics at the University Stuttgart, with majors in systems and control and philosophy, where he graduated 2006. In 2007 he joined the group of Rolf Findeisen at the Institute of Automation Engineering at the Otto-von-Guericke University Magdeburg, Germany. From 2008-2012 he was a member of the International Max Planck Research School for Analysis, Design and Optimization in Chemical and Biochemical Process Engineering Magdeburg. In 2012 he obtained his PhD (with distinction) from Faculty of Electrical Engineering and Information Engineering, Otto-von-Guericke University Magdeburg, Germany. 2013-2016 he was with the Laboratoire d’Automatique, Ecole Polytechnique Fédérale de Lausanne, Switzerland. Since April 2015, he is with the Institute for Applied Informatics at the Karlsruhe Institute for Technology, where he leads the Optimization and Control Group.

His main research interests are optimization-based and predictive control of nonlinear systems with applications in energy systems, mechatronics/robotics, physics, process systems engineering and climate economics.