Key Research and Innovation Challenges in Cyber-physical...

37
Key Research and Innovation Challenges in Cyber-physical Systems of Systems Sebastian Engell TU Dortmund Germany

Transcript of Key Research and Innovation Challenges in Cyber-physical...

Page 1: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Key Research and Innovation Challenges in Cyber-physical

Systems of Systems

Sebastian Engell TU Dortmund

Germany

Page 2: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

2 S. Engell: Key Research and Innovation Challenges in CPSoS

Page 3: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Cyber-physical Systems of Systems

• Key elements of the socio-technical infrastructure • Providing essential services to the citizens • Backbone of the industrial infrastructure • Vulnerable • Difficult to engineer and to operate • Good engineering and efficient management is crucial for

– Energy and resource efficiency – Economic competitiveness of the industries – Quality of life

• The main potential is on the system level, not on subsystem control and optimization

S. Engell: Key Research and Innovation Challenges in CPSoS 3

Page 4: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Enabling Technologies

• Communication technologies, standardized protocols, Internet of Things

• Computing technologies, high-performance and distributed computing, multicore and mixed-criticality computing, low power processing / energy harvesting for ubiquitous installation

• Sensors, including energy harvesting • Management and analysis of huge amounts of data (“big data”). • Human-machine interfaces, e.g. head up displays, display

glasses, polymer electronics and organic LEDs • Security of distributed/ cloud computing and of communication

systems • Systems and control theory and technology • …

S. Engell: Key Research and Innovation Challenges in CPSoS 4

Page 5: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

• Cyber-physical systems of systems require a multi-disciplinary approach! • The behaviour of the physical part of the system must be modelled,

simulated and analysed using methods from continuous systems theory, e.g. large-scale simulation, stability analysis, design of stabilizing controls

• Methods and tools from computer science for the modelling of distributed discrete systems, for verification and testing, assume-guarantee methods, contract-based assertions etc. are indispensable to capture both the behaviour on the low level (discrete control logic, communication, effects of distributed computing) and global effects, in the latter case based on abstract models of complete subsystems.

• Logistic models as well as models and tools for performance analysis of discrete systems are needed for system-wide performance analysis.

• Theories from physics, e.g. structure formation in large systems, and from economics and social science (market mechanisms, evolution of beliefs and activity in large groups) may also prove to be useful.

S. Engell: Key Research and Innovation Challenges in CPSoS

Transdisciplinary Approach Needed

5

Page 6: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Support Action Oct. 2013 – March 2016

Main goal: Define a European research and innovation agenda on Cyber-physical Systems of Systems

• Not campaigning for a single community but bridging between communities

• Bottom-up and top-down approach – Analyse the needs in application domains – Analyse the state of the art in methods and tools – Integrate the two views to define the most important gaps

and actions needed

The Support Action CPSoS

S. Engell: Key Research and Innovation Challenges in CPSoS 6

Page 7: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Consortium

• TU Dortmund – Sebastian Engell – Radoslav Paulen – Christian Sonntag

• Haydn Consulting – Haydn Thompson

• TU Eindhoven – Michel Reniers

• Inno TSD – Svetlana Klessova – Bertrand Copigneaux

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 8: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Working Groups

WG1: Systems of Systems in Transportation and Logistics Chair: Haydn Thompson, Haydn Consulting

S. Engell: Key Research and Innovation Challenges in CPSoS

Members: John AMOORE Railway Infrastructure Technology Ltd Carlos CANUDAS DE WIT CNRS GIPSA-Lab Uwe CLAUSEN Fraunhofer IML & ITL, TU Dortmund University Judith DAHMANN MITRE Charles DIBSDALE OSyS (Rolls Royce) Philippe LIATARD CEA – Leti Antonio PASCOAL IST, Istituto Superior Tecnico María Victoria CENGARLE fortiss GmbH – Delegate FP7 project CyPhERS Christina DIAKAKI Technical University of Crete – Delegate FP7 project Local4Global Hermann KOPETZ Vienna University of Technology – Delegate FP7 project AMADEOS

8

Page 9: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Members: Göran ANDERSSON ETH Zürich Vladimir HAVLENA Honeywell Prague Laboratory Alf ISAKSSON ABB AB Västerås Patrick PANCIATICI RTE – Réseau de Transport d’Electricité Francesco BRANCATI ResilTech SRL – Delegate FP7 Project AMADEOS John FITZGERALD Newcastle University – Delegate FP7 project COMPASS Elias KOSMATOPOULOS Technical University of Crete – Delegate FP7 project Local4Global Stefan KRÄMER INEOS Köln – Delegate FP7 Project DYMASOS John LYGEROS ETH Zürich – Delegate FP7 project DYMASOS and Local4Global Radoslav PAULEN TU Dortmund (Consortium member)

Working Groups

WG1: Systems of Systems in Transportation and Logistics Chair: Haydn Thompson, Haydn Consulting WG2: Physically Connected Systems of Systems Chair: Sebastian Engell, TU Dortmund

S. Engell: Key Research and Innovation Challenges in CPSoS 9

Page 10: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Members: Alberto BEMPORAD IMT Lucca Alessandro CIMATTI Bruno Kessler Foundation Marika DI BENEDETTO University of L’Aquila Peter FRITZSON Linköping University Robert Howe Verum Software Tools BV Stefan KOWALEWSKI RWTH Aachen Erwin SCHOITSCH AIT – Austrian Institute of Technology Wil VAN DER AALST Technische Universiteit Eindhoven Peter Gorm LARSEN Aarhus University – Delegate FP7 Project COMPASS Martin TÖRNGREN KTH Stockholm – Delegate FP7 project CyPhERS Christian SONNTAG euTeXoo / TU Dortmund Bertrand COPIGNEAUX inno TSD (Consortium member)

Working Groups

WG1: Systems of Systems in Transportation and Logistics Chair: Haydn Thompson, Haydn Consulting

WG3: Tools for Systems of Systems Engineering and Management Chair: Michel Reniers, TU Eindhoven

S. Engell: Key Research and Innovation Challenges in CPSoS 10

Page 11: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Analysis of the State of the Art

• Report "State of the art and future challenges in cyber-physical SoS”

• Available on the web-site www.cpsos.eu – Consultation page open for comments!

• Based on input from the working group members and additionally more than 45 in-depth interviews with representatives of industry plus some with academics

• Identifies industrial and societal needs and analyses the state of the art in tools, theories and engineering methodologies for cyber-physical systems engineering and management

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 12: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Example: Inputs to Domain 2

S. Engell: Key Research and Innovation Challenges in CPSoS 12

Page 13: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

13

• Distributed management of cyber-physical systems of systems

• Engineering support for the design-operation continuum of cyber-physical systems of systems

• Cognitive CPSoS – Which make full use of the large amounts of data that are

collected in CPSoS

3 Key Research and Innovation Challenges

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 14: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

14

Distributed management of cyber-physical systems of systems

Challenge 1

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 15: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Page 15 October 2014 Corporate Technology unrestricted © Siemens AG 2014. All rights reserved

Self-Organizing Energy Automation Systems coordinating smart components within the grid

*) Personal Energy Agent

Balance Master

Electricity Police

Network Transport

Agent

Area Administrator

Design Principles: • Smart components.

• Use plug and play for engineering.

• Coordination of local algorithms whenever necessary

*)

*) *)

*)

*)

*)

*)

*) Personal Energy Agent

MULTI-AGENT ARCHITECTURE FOR POWER GRIDS (SCHEMATIC)

Böse, C.; Hoffmann, C; Kern, C.; Metzger M.: New Principles of Operating Electrical Distribution Networks with a high Degree of Decentralized Generation, 20th International Conference on Electricity Distribution, Prague (2009).

Courtesy of SIEMENS Used on permission by the authors

Page 16: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

16

• Decision structures and system architectures • Real-time monitoring, exception handling, fault detection and

mitigation of faults and degradation • Adaptation and integration of new components • Trust in large distributed systems • Self-organization, structure formation, and emergent behaviour in

technical systems of systems • Humans in the loop and collaborative decision making

Distributed Management of Cyber-physical Systems of Systems

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 17: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

17

• Investigation of strategies for coordination and distributed control and optimization of systems of systems, as e.g. – Population control – Market-based coordination methods – Coalitional games

• Understanding how the management structure (centralized, hierarchical, distributed, clustered) influences system performance and robustness

• Stochastic optimization and risk management for CPSoS

Decision Structures and System Architectures

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 18: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

18

• Due to the large scale and the complexity of systems of systems, the occurrence of failures is the norm in CPSoS.

• Performance is crucially influenced by the reactions to unforeseen events.

• Faults propagate over the different layers of the management and automation hierarchy.

• Mechanisms for the detection of abnormal states and fail-soft mechanisms and fault tolerance by suitable exchange of information and mechanisms at the systems level

• Unforeseen events must therefore be handled across the layers. • Advanced monitoring of the state of the system and triggering of

preventive maintenance to improve performance

Monitoring and Exception Handling

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 19: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

19

• Cyber-security is a very important element in cyber-physical systems of systems.

• A specific CPSoS challenge is the recognition of obstructive injections of signals or takeovers of components in order to cause malfunctions, suboptimal performance, shutdowns or accidents, e.g. power outages.

• The detection of such attacks requires to take into account both the behaviour of the physical elements and of the computerized monitoring, control and management systems.

• Suitable isolation procedures and soft (partial) shut-down strategies must be designed.

Trust in Large Distributed Systems

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 20: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

20

• Due to local autonomy and dynamic interactions, cyber-physical systems of systems can realize self-organization and exhibit structure formation and system-wide oscillations or instability.

• The prediction of such system-wide phenomena is an open challenge at the moment.

• Distributed management and control methods must be designed such that CPSoS do not show undesired emerging behaviour.

• Inputs from the field of dynamic structure formation or pattern formation in large systems with uncertain elements could be combined with classical stability analysis and assume-guarantee reasoning.

Structure Formation, Emergent Behaviours

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 21: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

21

• Filtering and appropriate presentation of information to human users and operators are crucial for the acceptance of advanced computer-based solutions.

• The human capacity of attention and how to provide motivation for sufficient attention and consistent decision making must be investigated.

• Monitoring of the actions of the users and anticipating their behaviours and modelling their situation awareness

• Social phenomena (e.g. the dynamics of user groups) should also be taken into account.

• Capabilities of humans and machines in real-time monitoring and decision making must be combined optimally.

Interaction with Human Users / Operators

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 22: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

22

Engineering support for the design-operation continuum of

cyber-physical systems of systems

Challenge 2

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 23: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

23

… to support the design-operation continuum of cyber- physical systems of systems • Integrated engineering of CPSoS over their full life-cycle • Establishing system-wide and key properties of CPSoS • Modelling, simulation, and optimization of CPSoS

Engineering Methods and Tools

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 24: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Development Cycles for CPSoS

Traditional Iterative (re-)design (DANSE)

CPSoS are never finished!

Page 25: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Modelling, simulation, and optimization of CPSoS

• High cost for building and maintaining models • Modelling of human users and operators • Simulation and analysis of stochastic behaviour • Models for validation and verification purposes • Software tools for model management and for the integration of models from

different domains. Meta-modelling. • Efficient simulation algorithms for system-wide simulation of large

heterogeneous CPSoS, including dynamic on-the-fly reconfiguration • Global high-level modelling and simulation for performance and risk analysis

(including stochastic phenomena and the occurrence of abnormal states) • Collaborative environments for model exchange between competing companies • Integration of legacy system simulations as well as open approaches for tight

and efficient integration and consolidation of data, models, and engineering tools

S. Engell: Key Research and Innovation Challenges in CPSoS 25

Page 26: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

• Separation between the design/engineering phases and operational stage is disappearing

• Asynchronous lifecycles of the constituent parts • Components are developed independently • Incomplete information on legacy systems

• New engineering frameworks that support the specification, adaptation,

evolution, and maintenance of requirements, structural and behavioural models, and realizations not only during design, but over their complete life cycle

• Engineering frameworks supporting integrated cross-layer design for fault-resilient management and control architectures spanning all automation hierarchies, and model-based analysis facilities to detect design errors and to perform risk management

• Collaborative engineering and runtime environments for joint work on some aspects of the CPSoS while competing on others

• Open, easy-to-test interfaces and platforms for integration, semantic integration to simplify the interactions of existing systems as well as the deployment of new systems

• Demonstrate industrial business cases and application of tools

Integrated engineering of CPSoS over their full life-cycle

S. Engell: Key Research and Innovation Challenges in CPSoS 26

Page 27: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Establishing system-wide properties of CPSoS

• New algorithms and tools to enable the analysis of complete, large-scale, dynamically varying and evolving CPSoS

• Formal languages and verification techniques for heterogeneous distributed hybrid systems including communication systems

• Theory for successive refinement and abstraction of continuous and discrete systems, joint use of assume-guarantee reasoning and simulation-based (Monte Carlo) and exhaustive (model checking) verification techniques

S. Engell: Key Research and Innovation Challenges in CPSoS 27

• New approaches for dynamic requirements management during the continuous evolution of a cyber-physical system, ensuring correctness by design during its evolution

Page 28: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

28

Cognitive cyber-physical systems of systems

Challenge 3

S. Engell: Key Research and Innovation Challenges in CPSoS

Page 29: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Cognitive Cyber-physical Systems of Systems

• Need for improved situational awareness, however, gaining an overview of the entire SoS is inherently complicated by the presence of decentralized management and control

• The introduction of cognitive features to aid both operators and users of complex Cyber-physical Systems of Systems is seen as a key contribution to reduce the complexity management burden from increased inter-connectivity and the data deluge due to acquisition of more and more data

• Requires research in a number of supporting areas to allow vertical integration from the sensor level to supporting algorithms for information extraction, decision support, automated and self-learning control, dynamic reconfiguration features and consideration of the interactions with operators and users

S. Engell: Key Research and Innovation Challenges in CPSoS 29

Page 30: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Key Research Challenges

• Situational awareness in large distributed systems with decentralized management and control

• Handling large amounts of data in real time to monitor the system performance and to detect faults and degradation

• Automatic reconfiguration and adaptation, learning good operation patterns from past examples

• Analysis of user behaviour and detection of needs and anomalies

S. Engell: Key Research and Innovation Challenges in CPSoS 30

Page 31: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Situation awareness in large distributed systems

• Detect changes in demands and subsystem behaviour and deal with anomalies and failures within the system. Provide the operators with information on the situation of the system.

• Switching between strategies according to the situation • Take into account the effects of the behaviour of not exactly

known distributed optimization and control systems and of human operators or users?

Enablers: • Novel, easy to install, low cost, sensor technologies as well as

robust communication protocols that can deal with efficient transmission of individual data values from a multitude of sensors to streaming of data at high data rates, e.g. for vibration and video monitoring

• Model-based and model-free data analysis, recognition of patterns and trends

S. Engell: Key Research and Innovation Challenges in CPSoS 31

Page 32: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Handling large amounts of data in real time to monitor the system performance

• Analysis of large amounts of data in real time to monitor system performance and to detect faults or degradation

• Visualization tools to manage the complexity of the data produced allowing managers to understand the “real world in real time”, to manage risk and to make informed decisions on how to control and optimize the system

S. Engell: Key Research and Innovation Challenges in CPSoS 32

Page 33: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Learning good operational patterns from past examples

• Huge amounts of data are recorded but not used in operations. Operators use heuristic knowledge.

• Auto-reconfiguration and adaptation

features • Aid system operators by incorporating

learning capabilities within decision support tools to identify good operational patterns from past examples

S. Engell: Key Research and Innovation Challenges in CPSoS 33

Page 34: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Analysis of user behaviour and detection of needs and anomalies • CPSoS are socio-technical systems and

as such humans are an integral element of the systems

• Systems of systems need to be resilient to the effects of the unpredictable behaviour of humans

• There is thus a need to continuously analyse user behaviour and its impact upon the system to ensure that this does not result in system disruption.

S. Engell: Key Research and Innovation Challenges in CPSoS 34

Page 35: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Future Cognitive CPSoS

• The end result of combining real-time information for decision support with autonomous control and learning features will be Cognitive Cyber-physical Systems of Systems

• These will support both users and operators by providing – Situational awareness and situation dependent operator support – Fault recognition and self-adaptation – Monitoring of users and operators

S. Engell: Key Research and Innovation Challenges in CPSoS 35

Page 36: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Next steps

• Public consultation open until end of June www.cpsos.eu • Evaluation of the inputs, refinement • Simplified “glossy” version of the document • Discussion of medium-term priority topics with the WGs • Networking event at ICT 2015 in Lisbon (if approved) • Finalization of the Research and Innovation Agenda November 2015 • Discussion with the EC December 2015 • Final event (Symposium), possibly linked to the Cyber-physical

Systems Week in Vienna (April 2016)

S. Engell: Key Research and Innovation Challenges in CPSoS 36

Page 37: Key Research and Innovation Challenges in Cyber-physical …cpsos.eu/wp-content/uploads/2015/06/ARTEMIS-Summer-Camp... · 2019. 9. 10. · simulated and analysed using methods from

Thank you very much for your attention!