TU Dortmund University
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Mathematische Konsistenz – individuelle mathematische Lehrtätigkeit zwischen Intuition, Algorithmus und Formalem
No full textDer Beitrag untersucht mathematische Konsistenz als zentrales Merkmal sinnstiftender Lehrtätigkeit. Basierend auf Fischbeins (1994) Komponenten mathematischer Tätigkeit werden mit der Kontextanalyse nach Mayring (2022) multimodale Äußerungen von Lehrpersonen im Mathematikunterricht zur Bruchaddition analysiert. Ergebnisse zeigen, dass Lehrende sowohl intra- als auch interkomponentielle Konsistenz nutzen, jedoch auch mathematische Inkonsistenzen auftreten. Die Arbeit unterstreicht das Potenzial multimodaler Ansätze und eröffnet Perspektiven für die Lehrkräftebildung und zukünftige Forschung
Towards squaramide-based coordination cages with catalytic activity
No full textThis 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
Entwicklung eines Herstellungsverfahrens für 3D-gedruckte patientenindividuelle Hilfsmittelkomponenten aus Flüssigsilikonen und thermoplastischen Kunststoffen
No full textThe orthopaedics sector is undergoing major transition, not least because of the increasing shortage of skilled workers as well as mounting cost pressure. Therefore, frequently still very manual manufacturing processes are to be automated and digitised. Apart from that, there is a need for optimization concerning patient specific shaping of assistive aid components. This is because conventional manufacturing techniques are limited, especially regarding the combination of a high performance load bearing material and a cushioning component. These hybrid products cannot reasonably be produced by either conventional methods or state of the art additive processes, currently.
For this reason, in the context of this work a holistic production process for additive manufacturing of patient specific assistive aid components from silicones and thermoplastics is being devised, to contribute to the solution of the aforementioned challenges in the orthopaedics sector.
To implement the overall process, amongst a fulfillment system for data transmission, a software solution for the automated creation of the connections of sub objects made from different materials is being developed. Additionally, a software solution for generating the machine code for the additive manufacturing of the product model is being worked out.
Based on this, two different 3D printing systems are being constructed that can produce the previously prepared product models as hybrid products from liquid silicone rubber and thermoplastics or in combination with high performance thermoplastics. To ensure the necessary quality of the additively manufactured assistive aid components for the care of the patient, a quality management system based on DIN EN ISO 13485 is being conceptualized.
Ultimately, the proposed holistic manufacturing process was successfully validated by the production of a soft socket from a liquid rubber silicone and a high performance thermoplastic. Therefore, the groundwork for the successful deployment of the process in the medical and orthopaedics sector has been laid.Die Orthopädiebranche befindet sich derzeit in einem starken Wandel, was nicht zuletzt auf den zunehmenden Fachkräftemangel sowie einen steigenden Kostendruck zurückgeführt werden kann. Demzufolge sollen die vielfach noch händisch geprägten Fertigungsprozesse sukzessive automatisiert und digitalisiert werden. Dessen ungeachtet besteht Optimierungsbedarf in Bezug auf eine patientenangepasste Gestaltung der individuellen Komponenten von Hilfsmitteln, da die konventionelle Fertigung insbesondere in Hinblick auf die Herstellung der Materialkombination eines belastungsfähigen Hochleistungsmaterials mit einer polsternden Komponente nach wie vor mit Einschränkungen verbunden ist. Diese Hybridprodukte können derzeit weder mithilfe von konventionellen Verfahren noch unter der Anwendung von bestehenden additiven Verfahren mit einem vertretbaren Aufwand hergestellt werden.
Aus diesem Grund wird im Rahmen dieser Arbeit ein ganzheitliches Herstellungsverfahren zur additiven Fertigung von patientenindividuellen Hilfsmittelkomponenten aus Silikonen und Thermoplasten entwickelt, um einen Beitrag zur Lösung der Herausforderungen in der Orthopädiebranche zu leisten.
Zur Umsetzung des Gesamtprozesses wird neben einem Auftragsabwicklungssystem für die Datenübermittlung auch eine Software zur automatisierten Generierung einer Verbindung der Teilobjekte unterschiedlichen Materials entwickelt. Zusätzlich wird eine Softwarelösung zur Erzeugung eines maschinenfähigen Codes für die additive Fertigung des Produktmodells erarbeitet. Auf dieser Basis werden zwei unterschiedliche 3D Drucksysteme entwickelt, mit denen die generierten Produktmodelle als Hybridprodukte aus Flüssigsilikonen und Thermoplasten oder kombiniert mit Hochleistungsthermoplasten hergestellt werden können. Nicht zuletzt wird ein Qualitätsmanagementsystem in Anlehnung an die DIN EN ISO 13485 ausgearbeitet, das die zur Patientenversorgung erforderliche Qualität der additiv gefertigten Hilfsmittelkomponenten sicherstellt.
Schlussendlich kann das entwickelte ganzheitliche Herstellungsverfahren am Beispiel der additiven Fertigung eines Weichwandinnentrichters aus einem Flüssigsilikon und einem Hochleistungsthermoplast validiert und damit die Grundlage für einen erfolgreichen Einsatz des Gesamtprozesses im Sanitäts und Orthopädiebereich geschaffen werden
Land expropriation policy and its impacts on agricultural land consumption
No full textExpropriating agricultural land for urbanization is widespread in developing countries, justified legally to serve the public interest, with affected people receiving fair compensation. However, implementing this policy carries severe consequences, primarily consuming vast fertile agricultural land. In Iraq, particularly in the Kurdistan Region, historical, political, and economic circumstances have been crucial in developing this policy and its applications. Population growth, economic considerations, and institutional factors have accelerated land expropriation to meet the
rising demand.
Over the past three decades, the cities of the Kurdistan Region have developed rapidly, depleting their fertile lands through expropriation. This development has resulted in numerous social, economic, and environmental consequences and institutional conflicts. This study examines approaches to facilitate sustainable land expropriation, focusing on the Kurdistan Region and a more in-depth analysis of the Semel and Zakho territories. In the view of the principles of good governance approach, the research finds an interaction between these principles and the expropriation policy through a detailed review of this policy and a study of its consequences, including intensive land consumption. Furthermore, the study delves into the driving forces behind expropriation and evaluates its intensifying influence on accelerating expropriation.
The ethodology is designed to follow an appropriate research strategy and establish adequate data collection and analysis methods. Based on various criteria, the study has selected Semel and Zakho areas, achieving a comprehensive analysis of the impacts of agricultural land expropriation, the factors influencing it, and the regulatory framework in the given context. The study utilizes quantitative and qualitative research techniques, including document and archive analysis, observation, and in-depth interviews. The findings of this research are shown in the form of a conceptual proposal outlining transparency, participation, accountability, the rule of law and justice, equity, and the interviewee's perception as criteria for sustainable land expropriation in the selected areas and the Kurdistan Region. Moreover, this research recommends general strategies as the essential base for shifting toward an efficient expropriation policy. The recommendations are closely related to the expropriation legal and institutional framework and its consequences
Modeling, control and opportunities of mechanical interfaces across the scales
No full textThis treatise analyzes various roles of mechanical interfaces in natural and artificial environments. From the classic perspective of spatial scales, the chapters evolve from modeling at the atomistic scale, to single continuum interfaces to larger systems of interfaces. They will cover molecular descriptions, sharp and diffuse interface models as well as effective ensemble properties. From the perspective of control, they evolve from naturally arising to artificially created objects. Freely evolving cracks, phase changes and interface design for controlled fluid-structure interaction will be shown for illustration. From the perspective on new opportunities, finally, they evolve from risk-bearing imperfections to technical and scientific opportunities. While damage is investigated as a typical risk scenario, novel potentials will be explored for non-destructive characterization, low-frequency attenuation and information enhancement for artificial neural networks.Diese Arbeit analysiert die verschiedenen Rollen mechanischer Grenzflächen in natürlichen und künstlichen Umgebungen. Ausgehend von der klassischen Perspektive der Längenskalen erstrecken sich die Kapitel von der atomaren Skala über einzelne kontinuierliche Grenzflächen bis hin zu größeren Grenzflächensystemen. Dies schließt molekulare Beschreibungen ebenso ein wie zweidimensionale Untermannigfaltigkeiten, diffuse Grenzflächenübergänge und effektive Ensembleeigenschaften. Die Perspektive von Kontrollmöglichkeit spannt den Bogen von natürlichen zu künstlich erzeugten Objekten. Zur Veranschaulichung gehören dabei freier Rissfortschritt, Phasenwechsel und Grenzflächendesign für kontrollierte Fluid-Struktur-Interaktion. Die Perspektive neuer Anwendungsmöglichkeiten entwickelt sich schließlich von risikobehafteten Unzulänglichkeiten zu technischen und wissenschaftlichen Chancen. Während Schäden als typisches Risikoszenario untersucht werden, werden Potenziale für die zerstörungsfreie Charakterisierung, die niederfrequente Dämpfung und den Informationstransfer in künstlichen neuronalen Netze erkundet
Fostering the Acceptance of Congestion Charges: Experimental Evidence for Europe
No full textAlthough there is ample empirical evidence that congestion charges can effectively reduce traffic congestion and its detrimental effects, this instrument has only been implemented in a handful European cities. On the basis of a randomized information experiment that was embedded in a survey across seven European countries, this paper empirically investigates whether information on their (i) effectiveness and (ii) a-posteriori acceptance may increase the public support for congestion charges. Relative to the control group, the results indicate that, on average, this information can raise acceptance by 9.3% and 7.1%, respectively. Moreover, while there is substantial heterogeneity in the acceptance across countries, attributing a concrete price level to the charge uniformly raises acceptance at low charge levels, but lowers it at high levels. Based on these results, we conclude that information campaigns on congestion charges and their benefits for commuters and city-dwellers are essential for fostering public support for this rarely employed transport policy instrument