Eldorado - Repository of the TU Dortmund
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Probabilistic graphical models in the manufacturing of electric vehicles
(2024) Kertel, Maximilian; Pauly, Markus; Klein, Nadja
Introduction: Battery electric vehicles (BEVs) are crucial to the reduction of green house gas emissions in the transportation sector. The primary component of BEVs is the energy storage system, consisting of battery cells. However, its manufacturing process is intricate, characterized by numerous causal interdependencies across production steps. The limited understanding of these interdependencies contributes to high scrap rates, resulting in increased environmental, ethical, and economic costs associated with BEVs.
Methods: In order to address this challenge, this dissertation leverages the data and measurements collected by modern manufacturing facilities and production machines. Specitically, Probabilistic Graphical Models (PGMs), which can be grouped into directed and undirected models, are applied to this data to enhance the understanding of the production process, addressing the lack of knowledge. By utilizing PGMs, this research aims to uncover hidden relationships and dependencies within the manufacturing data, enabling more informed decision-making in battery cell manufacturing. In order to tackle the inherent complexity of the data, we focus on non-linear methods.
Specifically:
1. Missing Data: We address the challenge of estimating the joint distribution when parts of the data are missing, which is a common occurrence in manufacturing data that comprises sensor measurements. The proposed estimation procedure can be viewed as a learning algorithm for undirected PGMs.
2. Real-Data Application: Additionally, we apply a state-of-the-art learning procedure for directed PGMs to actual manufacturing data.
3. Boosting: Finally, we utilize the concept of boosting to learn directed PGMs from the data and investigate the theoretical and practical benefits.
We account for the circumstances in manufacturing scenarios. This includes leveraging prior knowledge in various aspects.
We account for the circumstances in manufacturi11g scenarios. This includes leveraging prior knowledge in various aspects.
Results:
1. Missing Data: The proposed method effectively learns joint distributions semi parametrically. A simulation study shows that the estimates improve with the sample size of the data, and the inclusion of expert knowledge in the estimation process leads to a holistic improvement in the accuracy of the estimates.
2. Real-Data Application: In contrast to other applications of PGMs, we observe large local variations in the number of relationships, challenging the assumption of sparsity. The integration of expert knowledge provides more reliable estimates in real-world manufacturing data applications.
3. Boosting: We demonstrate the consistency of a boosting-based learning algorithm for directed PGMs, which is a rare statistical guarantee for such algorithms. The practical adaptation of this algorithm proves to be competitive and, in some relevant cases, even outperforms state-of-the-art methods.
The results collectively demonstrate the significance and practical applicability of PGMs in the context of manufacturing applications.
Discussion & Outlook: We critically assess the derivation of causal relationships from data collected at the steady state of the production workflow. We propose a novel point of view on causal discovery as a recommendation system for potential causal relationships in manufacturing. Additionally, we sketch the idea of an iterative procedure involving PGM learning algorithms and experiments to derive causal relationships.
Institutions, roles, and agency
(2024) Gab, Max Magnus; Crone, Katja; Schmidt, Eva
This thesis provides an analysis of institutional group agency, i.e. the capacity of institutional groups to perform actions. I explore different accounts of institutional group agency and consequently argue that it is best explained by so called role-based accounts. According to such role-based accounts of institutional agency, the actions of institutional groups consist of the contributory actions of the groups’ members, who act according to the tasks and functions of their institutional roles. I will, however, argue that such role-based theories of institutional action face certain problems. Most importantly, they under-theorize the relation between institutional roles and the individuals who occupy them. In order to illuminate this relation, I develop my own, novel account of Role Agency. Role Agency describes a form of agency that individuals engage in when they act within their institutional roles. It is best thought of as a form of perspective taking, which includes both the internalization and idealization of institutional roles.
Towards squaramide-based coordination cages with catalytic activity
(2025) Yalçin, Ertuğrul; Clever, Guido H.; Schäfer, Lars
This thesis explores two main topics: the computational study of strain in heteroleptic coordination cages and the incorporation of squaramide functionalities into coordination cages to investigate their host-guest properties.
The computational study aimed at expanding the understanding of the thermodynamic driving forces behind the non-statistical self-assembly of cis-[Pd2L2L´2] and trans-[Pd2L2L´2] nanocages. Previous studies on Pd(II)-based homo- and heteroleptic cages composed of a carbazole ligand with either an elongated or non-elongated phenanthrene ligand were analyzed using NMR spectroscopy, ESI-MS and single-crystal X-ray analysis. The findings of these studies raised the question of whether differences in ring strain could be reproduced through gas-phase electronic energy comparisons via DFT geometry optimization. To address this, cage-to-cage transformations were examined, and ligands excised from heteroleptic cages were compared with their fully relaxed counterparts to assess strain in self-assembled coordination cages. This work extends these studies to acridone- and inverted carbazole-based ligands paired with the respective phenanthrene ligands. The calculations revealed that acridone- and inverted carbazole-based ligands preferentially form heteroleptic coordination cages with elongated phenanthrene ligands rather than with the shorter phenanthrene ligands. Additionally, the incorporation of diketopyrrolopyrrole-based ligands in trans-[Pd2L2L´2] cages featuring self-penetrated motifs was examined. Computational studies demonstrated that the release of strain upon transformation of a self-penetrated homoleptic diketopyrrolopyrrole cage to a heteroleptic cage plays a significant role in driving the preferential formation of the heteroleptic structures. Hydrogen bonding is a key noncovalent interaction that influences molecular recognition and catalytic processes. Squaramides are well-known hydrogen bond receptors and catalysts, possessing both hydrogen bond donor and acceptor groups. The second focus of this thesis is the heteroleptic cage formation of squaramidebased ligands with square-planar Pd(II) cations. Poorly soluble squaramide-based ligands assembled into a distinct assembly in DMSO-d6. To enhance the likelihood of observing the effects of hydrogen bonding on host-guest interactions, derivatives of squaramide-based ligands were synthesized and formed analogous heteroleptic cis-[Pd2L2L´2] cages in CD2Cl2. The resulting assemblies were analyzed using NMR spectroscopy, ESI-MS and single-crystal X-ray crystallography. When two squaramide ligands were combined, the formation of a heteroleptic cage was observed. X-ray analysis revealed that the hydrogen bond donor functionalities of one squaramide is oriented outward, with intramolecular hydrogen bonding occurring within the cage. This raised the question of whether such intramolecular hydrogen bonding contributes to a cooperative effect in guest binding. To investigate this, a reference cage was designed by pairing a squaramide-based ligand with a benzothiadiazole-based ligand, forming a distinct heteroleptic cage with the same topology. Computational studies suggested that the cooperative effect of intramolecular hydrogen bonding is more pronounced when two squaramide units are involved in intramolecular hydrogen bonding. To validate this, binding constants for neutral guest molecules were determined via 1H NMR titration experiments and compared across the two different cage systems. The results confirmed a cooperative effect in guest binding, particularly for caffeine and β-nitrostyrene. Additionally, the host-guest properties of the assembled coordination cages were examined with chloride, disulfonate and phosphate anions. However, attempts to determine binding constants for anions to the solely squaramide-based heteroleptic cage in CD2Cl2 revealed broadening in the 1H NMR spectra, suggesting aggregation, likely due to ion pairing effects. Nevertheless, binding constants for two disulfonates with the benzothiadiazole-based cage were successfully obtained, demonstrating a binding constant that is an order of magnitude stronger than for other palladium-based cages. In addition, the incorporation of 1,3-squaramides with a piperazine linker into coordination cages with Pd(II) was investigated. The self-assembled structures and their host-guest complexes were analyzed using NMR spectroscopy, ESI-MS and single-crystal X-ray crystallography. A ringlike topology with the molecular formula [Pd3L6]6+ was characterized. Binding constants for Allura Red and ferrocene-1,1’-disulfonate were determined via 1H NMR titration experiments. Cyclic voltammetry experiments showed that the redox event of Pd3L6 is electrochemically reversible, whereas the free ligand exhibits no reversibility.
Spectroscopic studies of biological tribofilms at hip implant taper junctions and transfer material at MoS2-steel wear couples
(2024) Wittrock, Adrian; Debus, Jörg; Westphal, Carsten
In this thesis, the structural and chemical characteristics of the tribomaterial using spectroscopic techniques are investigated. Specifically, MoS2-steel wear couples, commonly employed in industrial applications, and biomedical artificial hip joints are analyzed.
Modular hip implants are widely used to treat arthritis, but complications due to friction and wear at the head-taper interface may cause the necessity for revision surgery. The mechanical-chemical reaction products and structural features at the head-taper interface of Ti6Al4V and low-carbon cobalt alloy or high-nitrogen steel surfaces, which were subjected to in vitro fretting corrosion tests using bovine calf serum, are investigated using Raman spectroscopy. From these spectra, protein folding/unfolding, the formation of proteinaceous clusters, and the adsorption behavior of short and long aliphatic chains can be deducted. All these structural changes depend on the hydrophilicity of the metallic surfaces and the duration of the fretting process. The analysis also identifies significant differences in the composition of agglomerated wear particles, including chromates, iron oxides, and adsorbed proteins. On both materials, long fretting duration leads to protein cleavage and the formation of sp2-hybridized amorphous carbon. Additionally, the formation of a thin (15 nm), areal, nanocrystalline-amorphous CoSx tribofilm is revealed on the Co-alloy surface. This tribofilm forms from sulfur ions released by cysteine decomposition and cobalt ions from tribocorrosion and may act as an extreme-pressure anti-wear layer. Thus, it may improve the taper junction longevity and mitigate corrosive attacks. The CoSx compound's structure is similar to that of the solid lubricant MoS2.
The tribological contact between MoS2 and steel leads to structural-chemical changes, which are another focus of this thesis. Raman spectroscopy shows compressive and tensile strain within the MoS2 transfer material. In addition, if MoS2 is no longer present in the contact area, Mo, S, and Fe oxidation is detected, for instance, Mo4O11 in the Magnéli-phase. Thereby, the formation of tribo-chemical oxides depends on the modifying element. The study also reveals the formation of disordered graphene in a few layers on the counter body surface. The results characterize the structural and chemical features of the MoS2 transfer material and thus enable the prediction of material failure at microscopic level.
In addition to these mechanism-driven investigations, a novel method, ablation-Raman coating thickness analysis (ARCTA), is developed for coating thickness measurement, especially for curved coatings. This method uses a high-energy pulsed laser to ablate a part of the MoS2 coating in the µm range, followed by Raman spectroscopy to detect the transition from coating to substrate. The method is calibrated on planar surfaces and applied to curved surfaces, demonstrating that the number of laser pulses required for ablation increases approximately linear to the layer thickness. ARCTA shows significant potential for various applications with advantages over other thickness measurement methods.
In total, this thesis reveals structural-chemical characteristics of biological tribofilms at hip implant taper junctions and transfer material at MoS2-steel wear couples by spectroscopic studies and develops a novel method for thickness measurement.
Rechtliche Instrumente zur Unterstützung der Umsetzung des Masterplans in der Autonomen Region Kurdistan
(2025) AL-Doski, Diman; Gruehn, Dietwald; Baumgart, Sabine
Das Fehlen bzw. mangelhafte Umsetzung von Masterplänen führt zu unkontrollierter Stadtentwicklung und ist durch negative Merkmale wie Fehlen von Infrastruktur, informelle Siedlungen und Wohnungsnot gekennzeichnet. Besonders betroffen sind Städte in den Entwicklungsländern. Dazu gehören auch Städte in der autonomen Region Kurdistan in Irak. Seit Jahren kämpfen sie mit den Folgen einer unkontrollierten Stadtentwicklung. Vor diesem Hintergrund widmet sich diese Untersuchung der Problematik der Masterplanumsetzung in der autonomen Region Kurdistan und untersucht, wie diese künftig durch rechtliche Instrumente sowie eine aktive Beteiligung der Öffentlichkeit in der Planungsphase unterstützt werden kann. Die Ergebnisse sollen dabei helfen, erstellte Pläne besser umzusetzen und damit steuernd auf die räumliche Entwicklung Einfluss zu nehmen. Als Ergebnis kann festgehalten werden, dass eine besondere Schwachstelle im Bereich Planung und Planumsetzung in Kurdistan das Fehlen von gesetzlichen Grundlagen ist. Insbesondere fehlt bisher ein gebündeltes Baugesetzbuch. Die rechtlichen Strukturen, unter denen der Masterplan umgesetzt wird, sind zu schwach, um die unzähligen Probleme der räumlichen Entwicklung anzugehen. Die in der Region Kurdistan vorhandenen rechtlichen Instrumente sind noch zu sehr auf die Ausübung hoheitlicher Gewalt ausgerichtet. Konsensuale Instrumentarien haben bisher wenig Bedeutung gehabt. Zudem ist die derzeit praktizierte Öffentlichkeitsbeteiligung als sehr schwach zu bewerten. Die Öffentlichkeit wird unzureichend informiert und hat kaum Möglichkeiten, die Planentscheidungen zu beeinflussen. Um die Umsetzung planerischer Ziele zu fördern und damit steuernd auf die Stadtentwicklung einzuwirken, sind rechtliche Instrumente, die der Erweiterung der Handlungsmöglichkeiten der Gemeinden dienen, erforderlich. Zudem ist eine aktive Beteiligung der Öffentlichkeit in der Planung unabdingbar, um eine breite Akzeptanz zu schaffen und eine möglichst konfliktfreie Umsetzung zu gewährleisten. Hierfür ist eine rechtliche Verankerung notwendig.