Eldorado - Repository of the TU Dortmund
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High-dimensional solid-state NMR facilitated by transverse-mixing optimal control
(2025-11-20) Linser, Rasmus; Klein, Alexander; Blahut, Jan; Tošner, Zdeněk; Blokhin, Dmitrii; Vasa, Suresh
Owing to fast magic-angle spinning, solid-state nuclear magnetic resonance has evolved as a versatile method to decipher protein structure, dynamics, and chemical properties. While higher-dimensional approaches such as 4D and 5D correlation spectra are generally capable of exceeding the established molecular-weight limitations by ameliorating signal overlap, their intrinsic implications for sensitivity and measurement times required have severely limited these important prospects in practice. Here we show that the extensive use of dedicated transverse-mixing optimal control pulses (TROPs) in high-dimensional experiments to enable concomitant transfer of complex signals along complex magnetization transfer pathways can reduce the necessary measurement time by an order of magnitude. Owing to the multiplicative benefits of the enhancement for successive indirect chemical-shift dimensions, combined with non-linear benefits upon spectral reconstruction, the combination of non-uniformly sampled, higher-dimensional approaches with an extensive use of TROPs hence presents itself as transformative for the conventional limitations of solid-state NMR.
Einfluss einer zusätzlichen Torsion auf das Tragverhalten von Spannbetonträgern
(2026) Lavrentyev, Vladimir; Maurer, Reinhard; Hegger, Josef; Ricker, Marcus
Die vorliegende Dissertation beschäftigt sich mit der Erweiterung eines ingenieurmäßigen Bemessungsmodells zur genaueren Ermittlung der Querkrafttragfähigkeit von Spannbetonträgern mit Plattenbalkenquerschnitten, insbesondere bei gleichzeitiger Beanspruchung durch Biegung (M), Querkraft (V) und Torsion (T). Im Fokus steht die Verifikation des erweiterten Druckbogenmodells (EDBM) unter der kombinierten Beanspruchung mit zusätzlicher Torsion, das gegenüber konventionellen Modellen Tragreserven berücksichtigt, die in der bisherigen Normung unzureichend erfasst worden sind.
Im Rahmen eines umfangreichen experimentellen Versuchsprogramms, durchgeführt an der TU Dortmund im Auftrag der Bundesanstalt für Straßenwesen (BASt), wurden in Kooperation mit der RWTH Aachen und TU München Großversuche an vorgespannten Plattenbalkenträgern als Einfeldträger mit Kragarm durchgeführt, die typische Schubschlankheiten und Belastungszustände von Bestandsbrücken repräsentieren. Mit den Abmessungen von 8,25 m im Feld und 2 m am Kragarm weisen die Versuchsträger ein Alleinstellungsmerkmal für Versuchsträger unter der kombinierten Beanspruchung auf. Der besondere Fokus lag dabei auf der Untersuchung der Interaktion der Schnittgrößen M+V+T in der Biegedruckzone. Es zeigte sich, dass insbesondere die Mitwirkung der Gurtplatte, die normalerweise in der Torsionsbemessung vernachlässigt wird, signifikant zur Tragfähigkeit beitragen kann.
Zur Verifikation der Versuchsergebnisse wurden nichtlineare numerische Analysen mittels der Finite-Elemente-Methode (FEM) durchgeführt. Diese erlaubten nicht nur eine wirklichkeitsnahe Abbildung der Versuchsergebnisse, sondern auch die Durchführung parametergestützter Studien zur Bestimmung einzelner Einflussgrößen, wie etwa Vorspannungsgrad, Gurtbreite und Torsionsbewehrung.
Die Dissertation formuliert drei zentrale Forschungsfragen, die sich mit der Aktivierung zusätzlicher Tragreserven, der Eignung der normativen Interaktionsbedingung und der Anwendbarkeit des EDBM unter M+V+T-Beanspruchung befassen. Auf alle Fragen konnten gesicherte Antworten gegeben werden. Damit leistet die Arbeit einen bedeutenden Beitrag zur Nachrechnung und Ertüchtigung bestehender Spannbetonbrücken und bietet eine fundierte Grundlage für zukünftige Anpassungen der Nachrechnungsrichtlinie.
Designing trust-enabling blockchain systems for the inter-organizational exchange of capacity
(2024-01-23) Große, Nick; Möller, Frederik; Schoormann, Thorsten; Henke, Michael
In times of rapid and unpredictable developments, companies experience significant volatility in capacity utilization. Virtual capacity exchange platforms help to mitigate this challenge by exchanging capacities with anonymous participants in market-like peer-to-peer networks. However, its efficiency is hindered by behavioral uncertainties, including a lack of inter-organizational trust in other participants. To leverage the potential of such exchange platforms, this paper reports on a Design Science Research project aiming to derive and validate design principles for establishing trust in inter-organizational capacity exchange in two design iterations. Using blockchain technology, we instantiate six design principles into an artifact and perform experimental evaluations to investigate their effect on perceived trust. Our paper contributes to research and practice by identifying and applying prescriptive design knowledge and advancing our understanding of how to design trust-enabling inter-organizational systems. The originality lies within the empirical investigation of how and why different design principle combinations can be established through blockchain technology as one of the promising approaches for establishing trust. In doing this, we also disclose future pathways for IS and blockchain researchers and practitioners.
Determination of energies in high-speed blanking
(2024-07-17) Schmitz, Fabian; Clausmeyer, Till; Hahn, Marlon; Tekkaya, A. Erman
High speed blanking is a process in which the speed of the punch exceeds a specific material threshold to produce localization phenomena in the blanking clearance, leading to thermal softening and eventually to a shear band formation. The analysis of the formation of these shear bands requires the analysis of the energies for the initiation of shear bands for the mechanical and thermal boundary conditions, and the knowledge of the amount of energy for maintaining the localized deformation until material separation. This paper presents an approach to determine the available process energy for a high-speed blanking process, and the energy dissipated for high carbon steel C75 and a AA5083 aluminum alloy. With these energies the material-independent efficiency of the tool (28 %) and the material-dependent efficiency of the blanking process (2.6–71.8 %) are calculated, leading to a total efficiency between 0.73 % to 20.1 %. This approach provides a basis to compare various investigations on high speed blanking. Using process forces and strain formulation, an instability criterion identifies instability points, approximating energy dissipation pre- and post-instability for blanking. It was found, that the energy required for deformation from the instant of instability until material separation increases as the tool speed increases. When ASB are formed, the evaluation of these energies shows increased energy dissipation per volume by a factor of 20 or more. For all blanking experiments a peak acceleration larger than 26,120 g was measured, revealing the dynamic nature of this impact process.
Destigmatizing urban villages by examining their attractiveness: quantification evidence from Shenzhen
(2024-06-12) Rui, Jin; Xu, Yuhan; Li, Xiang
While existing social and political research has qualitatively discussed the stigmatization of urban villages (UVs), there's a lack of quantitative support. This study innovatively attempts to provide quantitative evidence, employing a spatial perspective for the destigmatization of UVs. We integrated population trajectory, GDP data, employment and residential points of interest, and developed a spatial gravity model to derive the spatial attractiveness index. Concurrently, we selected environmental, spatial structure, and housing economic indicators to construct a regression analysis. Our findings revealed that urban villagers exhibit a preference for shorter daily commutes, underscoring the positive role of UVs in promoting job-housing balance and providing diverse services. The high-frequency mobility of villagers accelerates the categorization of UVs and enhances intra-area circulation. We further discussed the interaction between UV renewal and its destigmatization. To counter spatial stigmatization, enhancing the spatial quality and infrastructure of UVs, as well as promoting diversified land use can reduce the public's stereotypical impressions. Moreover, prioritizing affordable housing and equitable distribution of facilities, along with fostering synergies between urban capital and UVs, can facilitate the destigmatization process. Stigmatization in informal settlements is a widespread issue. Our quantitative approaches, as well as targeted renovation and policy recommendations, can serve as a blueprint for addressing similar challenges in informal settlements globally.