Research

Future IT systems will be to a far greater extent than today consist of many different components. Such systems are often too large and dynamic, to be managed centrally. Therefore, we focus on algorithmic problems dealing with decentralized methods for the control and optimization of such systems.

Modern distributed IT-systems, such as the Internet, peer-topeersystems, and wireless communication systems, as wellas swarms of sensors or mobile robots, pose new challengesfor algorithm design. As their components (peers, robots, etc.)only have a limited local view of a system‘s current state, newlocal-algorithmic methods for utilizing and controlling thesesystems have to be developed. Our research addresses suchproblems from various perspectives.

Resource Management and Scheduling

In modern heterogeneous data centres, resource management gains more and more importance. Computing power, energy or data rate are only some examples for limited resources. In our workgroup, we develop approaches to make scheduling algorithms more efficient and to cope with the increasing size of computing centres. A special focus of our workgroup lies in scheduling with shared resources and the placement of resources in networks.

Dynamic in Networks

Dynamic networks, that is, networks whose topology changes over time, play an important role in many areas. For example, they surface as so-called overlay networks for the support of peer-to-peer systems, whose topology is permanently modified by coming and going peers. Due to the size and dynamics of such networks, it is often impossible to operate and optimise them through central control. In this research area, we address, among others, the development of local strategies that permanently adapt the network to changing needs of applications.

Local Strategies for Self-Organising Robot Swarms

In robot swarms of arbitrary size and unavailable infrastructure like, for example, on a foreign planet, the robots must calculate their action only based on local information. Hence, we develop formation strategies that do not need any global information, i. e. visibility only up to a constant distance, only local communication and no compass. Currently, we are investigating the robot gathering on an a priori undefined point. Here, the focus of our research is the optimality of the running time and the collision avoidance. We formally prove the correctness and complexity of our strategies in discrete as well as continuous synchronous time models on the grid and the Euclidean plane, respectively.

Swarm Intelligence and Evolutionary Robotics

Engineered systems are getting more and more complex. We develop bio-inspired approaches that start by principle from simple algorithms but still achieve complex tasks by cooperation of many simple entities. Our approaches are supported by mathematical modelling and we test them in applications of distributed robotics. Within the field called Evolutionary Robotics, we develop methods to automatically generate controllers for robots. In a project started this year, we apply our methods in distributed robot systems that interact with natural plants.

Algorithmic Game Theory

In many relevant problem areas, for example, in large decentralized networks, the question of resolution through a central authority is no longer the focal point. The solution is instead resolved through a multitude of actors. Here, actors chose their strategies according to their egoistic interests, which may lead to resolutions that are worse than those from a central authority are. On the one hand, we investigate how much the actor‘s strategic actions influence the resolution quality. On the other hand, we are interested in forecasting the resolutions, to which strategic actions may lead.



Our Activities 2016

Publications

[Translate to English:] Abshoff, Sebastian; Cord-Landwehr, Andreas; Fischer, Matthias; Jung, Daniel; Meyer auf der Heide, Friedhelm: Gathering a Closed Chain of Robots on a Grid. In: Proceedings of the 30th International Parallel and Distributed Processing Symposium (IPDPS), S. 689 – 699, Mai 2016, IEEE


Abshoff, Sebastian; Kling, Peter; Markarian, Christine; Meyer auf der Heide, Friedhelm; Pietrzyk, Peter: Towards the price of leasing online. Journal of Combinatorial Optimization, 32: S. 1197 – 1216 2016


Abu-Khzam, Faisal N. ; Li, Shouwei; Markarian, Christine; Meyer auf der Heide, Friedhelm; Podlipyan, Pavel: On the Parameterized Parallel Complexity and the Vertex Cover Problem. In: Proceedings of the 10th Annual International Conference on Combinatorial Optimization and Applications (COCOA) (accepted), LNCS, Band 10043 , 16. – 18. Dez. 2016, Springer, Heidelberg


Abu-Khzam, Faisal N. ; Li, Shouwei; Markarian, Christine; Meyer auf der Heide, Friedhelm; Podlipyan, Pavel: The Monotone Circuit Value Problem with Bounded Genus Is in NC. In: Dinh, Thang N. ; Thai, My T. (Hrsg.) Computing and Combinatorics, The 22nd International Computing and Combinatorics Conference, Band 9797, S. 92 – 102, Aug. 2016, Springer Verlag LNCS


Cord-Landwehr, Andreas; Fischer, Matthias; Jung, Daniel; Meyer auf der Heide, Friedhelm: Asymptotically Optimal Gathering on a Grid. In: Proceedings of the 28th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA), S. 301 – 312, Jul. 2016, ACM


Divband Soorati, Mohammad; Hamann, Heiko: Robot Self-Assembly as Adaptive Growth Process: Collective Selection of Seed Position and Self-Organizing Tree-Structures. In: IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2016) (accepted), 2016


Drees, Maximilian; Feldkord, Björn; Skopalik, Alexander: Strategic Online Facility Location. In: Proceedings of the 10th Annual International Conference on Combinatorial Optimization and Applications (COCOA) (accepted), LNCS, Band 10043 , 16. – 18. Dez. 2016, Springer, Heidelberg


Drees, Maximilian; Gmyr, Robert; Scheideler, Christian: Churn- and DoS-resistant Overlay Networks Based on Network Reconfi guration. In: Proceedings of the 28th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA), S. 417 – 427, Jul. 2016, ACM


Feldotto, Matthias; Graffi , Kalman: Systematic evaluation of peer-to-peer systems using PeerfactSim. KOM. Concurrency and Computation: Practice and Experience, 28: S. 1655 – 1677, Apr. 2016


Feldotto, Matthias; Leder, Lennart; Skopalik, Alexander: Congestion Games with Mixed Objectives. In: Proceedings of the 10th Annual International Conference on Combinatorial Optimization and Applications (COCOA) (accepted), LNCS, Band 10043 , 16. – 18. Dez. 2016, Springer, Heidelberg


Fischer, Matthias; Jähn, Claudius; Meyer auf der Heide, Friedhelm; Petring, Ralf: Algorithm Engineering Aspects of Real-Time Rendering Algorithms. In: Algorithm Engineering (accepted), LNCS, Band 9220, Dez. 2016, Springer, Heidelberg


Hamann, Heiko; Khaluf, Yara; Botev, Jean; Divband Soorati, Mohammad; Ferrante, Eliseo; Kosak, Oliver; Montanier, Jean-Marc; Mostaghim, Sanaz; Redpath, Richard; Timmis, Jon; Veenstra, Frank; Wahby, Mostafa; Zamuda, Ales: Hybrid Societies: Challenges and Perspectives in the Design of Collective Behavior in Self-organizing Systems. Frontiers in Robotics and AI, 3. Apr. 2016


Hamann, Heiko; Valentini, Gabriele; Dorigo, Marco: Population Coding: A New Design Paradigm for Embodied Distributed Systems. In: 10th Int. Conf. on Swarm Intelligence, ANTS 2016, LNCS, S. 173 – 184, 2016, Springer


Harks, Tobias; Hoefer, Martin; Schewior, Kevin; Skopalik, Alexander: Routing Games With Progressive Filling. IEEE/ACM Transactions on Networking, 24: S. 2553 – 2562, Sep. 2016

Heider, Michael; Von Mammen, Sebastian; Hamann, Heiko: Robot Gardens: An Augmented Reality Prototype for Plant-Robot Biohybrid Systems. In: ACM Symposium on Virtual Reality Software and Technology (VRST), S. 139 – 142, 2016, ACM


Heinrich, Mary Katherine; Wahby, Mostafa; Divband Soorati, Mohammad; Hofstadler, Daniel; Zahadat, Payam; Ayres, Phil; Stoy, Kasper; Hamann, Heiko: Self-Organized Construction with Continuous Building Material: Higher Flexibility based on Braided Structures. In: Proc. of the 1st International Workshop on Self-Organising Construction (SOCO) (accepted), 2016


Khaluf, Yara; Hamann, Heiko: On the Definition of Self-organizing Systems: Relevance of Positive/Negative Feedback and Fluctuations. In: ANTS 2016, LNCS, Band 9882 , S. 298, 2016, Springer


König, Jürgen; Mäcker, Alexander; Meyer auf der Heide, Friedhelm; Riechers, Sören: Scheduling with Interjob Communication on Parallel Processors. In: Proceedings of the 10th Annual International Conference on Combinatorial Optimization and Applications (COCOA) (accepted), LNCS, Band 10043 , 16. – 18. Dez. 2016, Springer, Heidelberg


Kühne, Thomas; Hamann, Heiko; Arifulina, Svetlana; Engels, Gregor: Patterns for Constructing Mutation Operators: Limiting the Search Space in a Software Engineering Application. In: Proceedings of the 19th European Conference on Genetic Programming (EuroGP 2016), LNCS, volume 9594 , S. 278 – 293, Mar 30 – Apr 1, 2016, Springer,


Li, Shouwei; Meyer auf der Heide, Friedhelm; Podlipyan, Pavel: The impact of the Gabriel subgraph of the visibility graph on the gathering of mobile autonomous robots. In: Algorithms for Sensor Systems, Proceedings of the 12th International Symposium on Algorithms and Experiments for Wireless Sensor Networks (ALGOSENSORS 2016) (accepted), LNCS, 25. – 26. Aug. 2016, Springer-Verlag


Mäcker, Alexander; Malatyali, Manuel; Meyer auf der Heide, Friedhelm; Riechers, Sören: Cost-efficient Scheduling on Machines from the Cloud. In: Proceedings of the 10th Annual International Conference on Combinatorial Optimization and Applications (COCOA) (accepted), LNCS, Band 10043, 16. – 18. Dez. 2016, Springer, Heidelberg


Mäcker, Alexander; Malatyali, Manuel; Meyer auf der Heide, Friedhelm: On Competitive Algorithms for Approximations of Top-k-Position Monitoring of Distributed Streams. In: Proceedings of the 30th International Parallel and Distributed Processing Symposium (IPDPS), S. 700 – 709, Mai 2016, IEEE


Meyer auf der Heide, Friedhelm; Sanders, Peter; Sitchinava, Nodari: Introduction to the Special Issue on SPAA 2014. ACM Transactions on Parallel Computing, 3: S. 1 – 2, Aug. 2016


Rybar, Milan; Hamann, Heiko: Inspiration-Triggered Search: Towards Higher Complexities by Mimicking Creative Processes. In: Proceedings of the Genetic and Evolutionary Computation Conference (GECCO 2016), S. 165 – 172, 2016


Valentini, Gabriele; Brambilla, Davide; Hamann, Heiko; Dorigo, Marco: Collective Perception of Environmental Features in a Robot Swarm. In: 10th Int. Conf. on Swarm Intelligence, ANTS 2016, LNCS, Band 9882 , S. 65 – 76, 2016, Springer


Valentini, Gabriele; Ferrante, Eliseo; Hamann, Heiko; Dorigo, Marco: Collective Decision with 100 Kilobots: Speed vs Accuracy in Binary Discrimination Problems. Journal of Autonomous Agents and Multi-Agent Systems, 30: S. 553 – 580, 2016


Wahby, Mostafa; Hofstadler, Daniel; Heinrich, Mary Katherine; Zahadat, Payam; Hamann, Heiko: An Evolutionary Robotics Approach to the Control of Plant Growth and Motion: Modeling Plants and Crossing the Reality Gap. In: Proc. of the 10th International Conference on Self-Adaptive and Self-Organizing Systems (accepted), 2016, IEEE


PhD Theses

Sebastian Abshoff
On the Complexity of Fundamental Problems in Dynamic Ad-hoc Networks
This thesis studies the complexity of fundamental problems in dynamic, i.e., time-variant, adhoc networks. Based on the model by Kuhn et al. (Symposium on Theory of Computing 2010), the network is controlled by an adaptive adversary that tries to prevent the effi cient execution of algorithms and only guarantees connectivity in each round. In this thesis, three main aspects are considered, which can be found in three different parts of the thesis. In the fi rst part, the adversary is restricted geometrically and an information dissemination problem is analyzed. The second part focusses on the counting problem (How many nodes are there in the network?) and establishes a relation to information dissemination problems. Finally, the third part studies the continuous, i. e., the repeated, computation of aggregation functions (e. g., the maximum of all inputs given to all nodes) in more stable variants of dynamic networks.

Claudius Jähn
Evaluation of Rendering Algorithms for Complex 3D Scenes
The efficiency of rendering algorithms for complex virtual 3D scenes does not only dependent on the scene's overall properties, but also on the observer's position inside the scene. To experimentally evaluate an algorithm, measurements are typically performed along a characteristic camera path. This allows only for a weak assessment of the algorithm's general performance even for a fi xed scene. I present an approach to represent aspects of an algorithm's behavior, like its running time or the number of performed operations, as position dependent scene properties. The properties' distribution can be approximated for all positions in the scene using an adaptive sampling technique. A distribution's statistical evaluation allows for a direct and objective comparison of different algorithms and parameter values. Its visualization yields intuitive insight into the algorithms behavior. Additionally, I present the point-based Progressive Blue Surfels rendering algorithm for visualizing highly complex virtual scenes. The algorithm places a sorted sequence of points on the visible surface of the scene's geometry, so that every prefi x of the points represents a complete
approximation of the geometry. By choosing the rendered sequence's length, image quality and running time can be adjusted at runtime. The presented techniques are implemented in PADrend, a rendering system specially designed for supporting the process of developing rendering algorithms.

Christine Markarian
Online Resource Leasing
Many markets have seen a shift from the idea of buying and moved to leasing instead. Arguably, the latter has been a major catalyst for their success. In the wake of this shift, we study in this thesis leasing concepts from an algorithmic perspective. In particular, we design theoretic models, study their inherent difficulty, and devise provably good (often optimal), efficient algorithms, with the goal to cope with real-world resource leasing scenarios. A major difficulty faced by most of these markets is the uncertainty of future demands. Consider a subcontractor who leases expensive resources from other companies to rent them out to clients. The subcontractor may buy long/expensive leases for some resource, just to realize later on that no more requests are issued for this resource in subsequent time steps. Or, the subcontractor may buy short leases, just to notice later on that having bought a longer lease would have cost less. In attempt to capture this difficulty, our algorithms tend to be online, thus providing solutions in the present without knowing the future.


Additional Functions

Prof. Meyer auf der Heide

  • Member of the “Hochschulrat” of the Paderborn University
  • Director of the Collaborative Research Center (SFB 901) “On-The-Fly Computing”
  • Member of the German Academy of Sciences “Leopoldina”
  • Member of the NRW Academy of Sciences, Humanities and the Arts
  • DFG Special Advisor (Vertrauensdozent) of the Paderborn University
  • Assistant Chairman of the Paderborn Institute for Scientific Computation (PaSCo)
  • Managing Editor of “Journal of Interconnection Networks (JOIN)”, World Scientific Publishing
  • Chairman of the Scientifi c Advisory Board of the Leibniz-Zentrum für Informatik, Schloss Dagstuhl
  • Member of the Evaluation Committee of the Bundeswettbewerb “Jugend Forscht”, Coordinator of the section on Computer Science and Mathematics
  • Member of the Milner Award Committee, The Royal Society
  • Member of the program committee of the 23rd International Colloquium on Structural Information and Communication Complexity (SIROCCO 2016)
  • Member of the program committee of the workshop Parallele Algorithmen, Rechnerstrukturen und Systemsoftware (PARS 2016)
  • Vice Chairman of the organisation committee of the 17th International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc 2016)
  • Chairman of the organisation committee of the 10th International Heinz Nixdorf Symposium “On-the-Fly Computing”, 2016

Jun.-Prof. Hamann

  • Young fellow of the North Rhine-Westphalian Academy of Sciences, Humanities and the Arts
  • Associate editor of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2016
  • Co-organizer of the 2nd International Workshop “Methods for Self-Organizing Distributed Systems” (MeSoDiSy) 2016
  • Editorial board member of “Swarm Intelligence” (Springer), "Natural Computing" (Springer), “Frontiers in Robotics and AI” (Frontiers Media)
  • Member of the program committee of the International Conference on Artifi cial Life (Alife) 2016
  • Member of the program committee of the IEEE Congress on Evolutionary Computation (CEC) 2016
  • Member of the program committee of the Evolutionary Computation in Robotics (EvoROBOT, EvoStar) 2016
  • Member of the program committee of the Genetic and Evolutionary Computation Conference (GECCO) 2016
  • Member of the program committee of the Towards Autonomous Robotics Systems (TAROS) 2016
  • Member of the program committee of the International Conference on Bio-inspired Information and Communications Technologies (BICT) 2016
  • Member of the program committee of the Guided Self-Organization Workshop (GSO 2016)
  • Member of the program committee of the Int. Workshop on Machine Learning, Optimization and Big Data (MOD) 2016
  • Member of the program committee of the International Symposium on Distributed Autonomous Robotics Systems (DARS) 2016

Jun.-Prof. Skopalik

  • Member of the program committee of the 9th International Symposium, on Algorithmic Game Theory (SAGT)
  • Member of the program committee of the 25th International Joint Conference on Artificial Intelligence (IJCAI)

School programmes

  • DFG Research Training Centre „Research Training Group Automatisms – Emerging structures in information technology, media, and culture“

Current research projects

DFG Collaborative Research Center 901
The objective of CRC 901 – On-The-Fly Computing (OTF Computing) – is to develop techniques and processes for automatic on-the-fly configuration and provision of individual IT services out of base services that are available on world-wide markets. In addition to the configuration by special OTF service providers and the provision by what are called OTF Compute Centers, this involves developing methods for quality assurance and the protection of participating clients and providers, methods for the target-oriented further development of markets, and methods to support the interaction of the participants in dynamically changing markets. Friedhelm Meyer auf der Heide is coordinator of this collaborative research centre scince 2011.

Term: 2011 – 2019

DFG Collaborative Research Centre 901 “On-The-Fly Computing”, subproject A1 “Capabilities and limitations of local strategies in dynamic networks ”
This subproject started in 2011 with the objective to explore the capabilities and limits of local methods for control and optimization of big dynamic networks. Our focus lies on overlay networks, which allow the interaction between actors of the OTF market (the clients) and service providers to support services and provide infrastructure. “Local” in this context means that the control and optimization is not performed by a central instance but distributed by the actors, based on their local information. In the first funding period, we focused our research on developing and analyzing algorithms, which e. g. allow the effi cient search for services, the distributed organization of actors in groups, or to adapt the positioning of resources in an overlay to better serve the requirements of the clients. This subproject is coordinated by Friedhelm Meyer auf der Heide and Christian Scheideler.

Term: 2015 – 2019


DFG Collaborative Research Centre 901 “On-The-Fly Computing”, subproject A3 “The market for services: Incentives, algorithms,
implementation”

In subproject A3 we model and analyze the market for composed IT-services. The main challenges in the economic considerations are the composition aspect, automatization of transactions, and the dynamics of composed services. For the analysis we use and develop methods from the fields of non-cooperative, cooperative, and algorithmic game theory. Furthermore, the study of bounded rational behavior rests on methods from evolutionary game theory, behavioral economics and the theory of learning. This subproject is coordinated by Claus-Jochen Haake, Burkhard Hehenkamp, and Alexander Skopalik.

Term: 2015 – 2019


DFG Collaborative Research Centre 901 “On-The-Fly Computing”, subproject B1 “Parameterized Service Specifications”
In subproject B1 we deal with requirements specifications of software services. They are important for a successful search, composition, and analysis of services. In particular, we investigate means of (semi-)automatically synthesizing requirements specifications based
on examples, which were prepared by a domain expert. This subproject is coordinated by Gregor Engels, Michaela Geierhos, and Heiko Hamann.

Term: 2015 – 2019


DFG Collaborative Research Centre 901 “On-The-Fly Computing”, subproject C4 “On-The-Fly Compute Centers II: Execution of Composed Services in Configurable Compute Centers”
In this subproject we are concerned with efficiently utilizing resources within a highly configurable compute center. First, we build on the scheduling results that were achieved in the first phase of subproject C2. Secondly, we incorporate the results of the complete subproject A2, especially the work on software-defined networking (SDN). This subproject emphasizes the collaboration between theoretical and practical computer science on closely related issues. We will examine these issues by using different methods (theoretical analysis, simulation, emulation and prototyping) on different levels of abstraction. OTF Compute Centers are particularly characterized by their ability to profi tably exploit the properties of OTF services. They are therefore heterogeneous, in that they have various types of calculation units and persistent storage units. They also have one or more networks that connect these resources with each other. OTF services can be provided by a single or several interacting geographically or organizationally distributed
OTF Compute Centers and, if necessary, they are supplemented by temporarily rented resources from the cloud. We will therefore develop and analyze scheduling processes, that consider the characteristics of OTF services on the one hand, and OTF Compute Centers on the other. This subproject is coordinated by Holger Karl and Friedhelm Meyer auf der Heide.

Term: 2015 – 2019


EU project (IP) Foundational Research on MULTIlevel comPLEX networks and systems (MULTIPLEX)
MULTIPLEX is a large-scale integrating project (IP) with 17 participating research institutes from all over Europe, funded by the European Commission. It addresses the objective “Dynamics of Multi-Level Complex Systems” of the FP7-ICT work program. The project started in November 2012 and will last for 48 month. The goal of the project is to understand how multilevel complex systems evolve, and how they can be controlled and optimized. Indeed, multilevel dependencies may amplify cascading failures that might result in a sudden collapse of the entire system. Recent large-scale blackouts resulting from cascades in the power-grid coupled to the control communication system witness this point very clearly. A better understanding of multi-level systems is essential for future ICTs and for improving life quality and security in an increasingly interconnected and interdependent world. In this respect, complex networks science is particularly suitable for the many challenges that we face today, from critical infrastructures and communication systems to techno-social and socio-economic networks. In Paderborn, Friedhelm Meyer auf der Heide, Christian Scheideler and Alexander Skopalik contribute to this project.

Term: 2012 – 2016


DFG project: Distributed Data Streams in Dynamic Environments (DISDAS) in the DFG-Priority Programme 1736 Algorithms for Big Data
In this project we lay the foundations for the design and analysis of distributed algorithm that continuously compute aggregated information of streams of data which are observed by a multitude of devices. These devices may be mobile, i. e. capable of moving in the plane or in space, and contain both (wireless) communication devices and sensors for observing their environment. The major challenge is to cope with the huge amount of data generated by the devices. Typically, the data streams are too big and arrive too fast to be completely stored, or sent to a central server through a network, or processed in real time. Thus we have to find ways to extract useful information from the streams using restricted resources like memory, communication volume and computation time. In this project, we are developing continuous algorithms in distributed environments, taking both the dynamics of the devices and of the observed events into account. This reflects the scenario of moving people with smartphones who observe their environment. Friedhelm Meyer auf der Heide coordinates this project.

Term: 2014 – 2017


EU H2020 FET project “flora robotica: Societies of Symbiotic Robot-Plant Bio-Hybrids as Social Architectural Artifacts”
The objective is to develop tightly coupled, symbiotic relationships between robots and natural plants, in particular we investigate the potential in plant-robot societies to create architectural artifacts and living spaces. Heiko Hamann is coordinator of this European project.

Term: 2015 – 2019

 

BMBF-Project: Resilience by Spontaneous Volunteers Networks for Coping with Emergencies and Disaster (RESIBES)
In RESIBES, we set up network of spontaneous volunteers, which can be quickly activated and deployed in a coordinated manner in a crisis. Individuals can register as so-called active or passive spontaneous volunteers in the network. Active spontaneous volunteers offer their workforce, while passive spontaneous volunteers provide material resources. In our project part, we are building a robust communication network, which in the case of application supports the coordination of the deployed spontaneous volunteers and the comprehensive assessment. Communication is also possible if the communication infrastructure is damaged or overloaded. To this end, we develop an ad-hoc network using the smartphones of the spontaneous volunteers. In Paderborn, Friedhelm Meyer auf der Heide, Matthias Fischer and Bernd Kleinjohann coordinate this project.

Term: 2016 – 2019


Scientific cooperations

  • University of Liverpool, Martin Gairing, Ph.D., United Kingdom
  • University of Maastricht, Tobias Harks, Ph.D., The Netherlands
  • Universität Wien, Prof. Dr. Monika Henzinger, Austria
  • Sapienza University of Rome, Prof. Stefano Leonardi, Ph.D., Italy
  • IMT Alti Studi Lucca, Prof. Guido Caldarelli Ph.D., Italy
  • University of Patras, CTI, Greece, and University of Liverpool, United Kingdom, Prof. Paul Spirakis
  • Universite Libre de Bruxelles, Prof. Marco Dorigo, Ph.D., Belgium
  • Otto von Guericke Universität Magdeburg, Prof. Dr. Sanaz Mostaghim, Germany