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Dissertation
Development of Selectively Actuatable Micromirror Arrays and Scalable Lithography Processes for Large-Area Applications as Smart Window
(2023)
This thesis provides an extensive overview on the state-of-the-art daylighting systems for applications in buildings and subsequently addresses the implementation of subfield addressing in micromirror arrays and investigation of a potential scalable lithography process for the large-area fabrication, both have been identified as the research gap in achieving the envisioned application as smart window. The work is conducted in continuation of the optimized fabrication process and the successful fabrication of a lab ...
Dissertation
Practical application of active premagnetization in transformerless DC/DC converters
(2023-05-17)
Magnetic devices are used in almost every power electronic system. Therefore, their purpose and with that their requirements can vary in a wide range. The consequence is a large number of options regarding the priority of optimisation. In this work, the focus is on reducing the volume or weight of inductors in transformerless DC-DC converters. Active prmeagnetization is choosed as an optimisation approach. The technique enables an operation of the DC-DC-converter in the Triangular Current Mode (TCM), whereby ...
Dissertation
Explaining and Visualizing Structural Knowledge in Bipartite Graphs
(2023)
Bipartite graphs are an important model for the representation and analysis of relationships between two different types of entities. Datasets in this form are commonly found in many fields, such as social networks, biology, and economics. Formal concept analysis is a research approach that allows for the analysis of such bipartite graphs by clustering the data into so-called concepts and ordering those in a lattice structure.
In this thesis we propose multiple approaches for the extraction and visualization of ...
Dissertation
Learning planning communication in cooperative multi-agent settings
(2023)
This work is a holistic investigation of the question of how and why reinforcement learning (RL) agents fail to develop planning communication in a cooperative setting. It is also a guide to anyone trying to build a system that learns to use planning communication patterns. We examine the state of the art in multi-agent systems and emergent communication for the existence of communication patterns that share information about future actions and plans. To do this, we strategically formulate hypotheses that question ...
Dissertation
Attribute Exploration with Multiple Experts
(2023)
Attribute exploration is a knowledge acquisition method from the realm of formal concept analysis that allows a domain expert to efficiently uncover the dependencies in a domain. It is based on a question-answering scheme where the exploration algorithm generates questions about dependencies in the domain that are then answered by a domain expert. Even though many variants and extension to this were developed, only few attempts to incorporate multiple experts were made. The overarching goal of this thesis is to extend ...
Dissertation
Situative Teams in Cooperative Autonomous Systems
(2023)
Distributed systems have been established in many areas of IT and will play an even more significant role in the future. Such systems are no longer limited to specific fields of application but interconnect many different domains. They encompass, e. g. Cloud Computing, Internet of Things, service robotics, and autonomous vehicles. The integrated sub-systems communicate in order to exchange information and, if necessary, perform tasks together. Moreover, the number of interconnected sub-systems is constantly growing. ...
Dissertation
Numerical simulation of a sub-wavelength plasmonic THz antenna for bio-sensing applications
(2023)
In the past decades, bio-sensing has become a steadily growing field in the life-sciences. Popular subjects of investigation are proteins, which for instance mediate intra-cellular transfer of substances and thus are attractive drug targets. They are also responsible for the occurence of degenerative diseases such as Alzheimer’s disease and the Creutzfeld-Jakob disease. Examining proteins to uncover their fundamental properties and behavior is important in order to advance modern health care and medicine. One way to ...
Dissertation
Investigation and Elimination of Substructures in Formal Concept Analysis focusing on Boolean Suborders and Subcontexts
(2023)
In the field of Formal Concept Analysis, data is mainly presented in so-called formal contexts, which assign to a set of objects their respective attributes. From those concept lattices can be generated, where the objects are grouped with respect to their common attributes to represent the relationships in the data in a way that enhances the understandability for humans. However, since a concept lattice can be of exponential size compared to its associated formal context, the presented relationships often become hard ...
Dissertation
Trajectory Mapping in Physical and Topical Spaces
(2023)
In this dissertation, two different types of trajectories are investigated. In the engfirst part of this work, we investigate methods for the analysis of physical trajectories. We focus on scenarios, in which signal strengths ofWiFi access points are recorded. In detail, they are recorded through smartphone devices by people moving through a building. By means of theWiFi signal strengths, (physical) trajectories of humans are reconstructed, which reflect the locations visited over time. Accurate localization based ...
Dissertation
Microfluidics Based 3D Printed Reconfigurable Antenna for K-Band Applications
(2023)
In dieser Arbeit werden neuartige mikrofluid-basierte, rekonfigurierbare Antennen für Mikrowellen-Anwendungen vorgestellt. Ebenfalls vorgestellt wird eine kosteneffektive Methode zur ultra-breitbandigen Erhöhung (definiert als Bandbreite von 20% oder höher als die zentrale Frequenz) des Antennengewinns basierend auf dielektrischen Linsen. Zunächst wird dabei ein fest-verdrahtetes Design entwickelt. Diese Antenne verwendet kapazitive Lasten, um die -10 dB Bandbreite um den Faktor 2.5 (+150%) zu erhöhen. Die vorgeschlagene ...