Recent Submissions
Beyond uncertain material properties : possibility-based uncertainty propagation in computational modal analysis
(2025) Könecke, Tom; Kaupp, Lars; Cillo, Pierfrancesco; Ziegler, Pascal; Hanss, Michael; Eberhard, Peter
Modal analysis relies on computational models that approximate experimental systems through the identification of material and geometry parameters. However, beyond these properties, the model creation process itself involves other critical choices, such as solver schemes, reduction order, element type, mesh density, and boundary conditions, that are typically treated as fixed choices rather than uncertain parameters. This study presents a widened perspective that treats these modeling choices as additional uncertain parameters alongside traditional material and geometry properties. Using possibility theory for forward uncertainty propagation, we quantify uncertainty without requiring probabilistic distributions over modeling choices. That is, instead of treating all choices as equally likely, possibility theory captures the range of feasible modeling options while incorporating quantitative information where available, particularly for material properties.
We apply this framework to evaluate eigenfrequency predictions under imprecise input parameters, yielding uncertain output ranges rather than point estimates. A critical innovation is the accurate matching of results from varying parameters to corresponding eigenfrequencies using modal assurance criterion (MAC) clustering. The methodology is demonstrated through a case study of a guitar soundboard model, showing how possibility theory provides a robust framework for uncertainty quantification in structural dynamics without requiring probabilistic assumptions about modeling choices.
Sri Lanka - ein Architekturführer : entstanden im Rahmen eines Seminars mit anschließender Studienreise im Sommer 2025
(Stuttgart : Institut für Öffentliche Bauten, Universität Stuttgart, 2025) Krupičkova, Kateřina; Masla, Elena; Riedle, Dorothee; Magnago, Fabio; Kuch, Marie; Paczkowski, Lilian; Philipp, Laetitia; Knüppel, Felicitas; Nogger, Kathrin; Dannenfelser, Ellen; Reißner, Vivien; Schöpflin, Daniel; Thiemann, Felix; Müller, Kai; Segelbacher, Pauline; Reeg, Tom; Sundheimer, Damian; Plankar, Katharina; Santos Mendonça, Barbara dos; Kuschwald, Jonas; Plötner, Amelie; Broghammer, Christin; Kojic, Elisabeth; Ladenburger, Felix; Tietz, Emilia; Kuhn, Chiara; Simen, Paula; Schwarz, Alexander
Architekturführer Sri Lanka, entstanden im Rahmen eines Seminars mit anschließender Studienreise im Sommer 2025
Adaptive epitaxy of C‐Si‐Ge‐Sn : customizable bulk and quantum structures
(2025) Concepción, Omar; Devaiya, Ambrishkumar J.; Zoellner, Marvin H.; Schubert, Markus A.; Bärwolf, Florian; Seidel, Lukas; Reboud, Vincent; Tiedemann, Andreas T.; Bae, Jin‐Hee; Tchelnokov, Alexei; Zhao, Qing‐Tai; Broderick, Christopher A.; Oehme, Michael; Capellini, Giovanni; Grützmacher, Detlev; Buca, Dan
The successful demonstration of (Si)Ge1‐xSnx alloys as direct‐gap materials for infrared lasers has driven intense research on group IV‐based devices for nanoelectronics, energy harvesting, and quantum computing applications. The material palette of direct‐gap group‐IV alloys can be further extended by introducing carbon to fine‐tune their structural and electronic properties, significantly expanding their functionality. This work presents heteroepitaxial growth of C(Si)GeSn alloys using an industry‐standard reduced‐pressure chemical vapor deposition reactor. The introduction of CBr4 as a precursor enables controlled incorporation of C atoms (<1 at.%) into the epilayer lattice, while simultaneously increasing the Sn content in the CGeSn alloy up to ≈18 at.%. Carbon plays a key role in modulating strain, stabilizing the crystal structure, and influencing material properties. By leveraging alloying and strain engineering, quaternary CSiGeSn bulk layers and CGeSn/GeSn heterostructures are epitaxially grown. The impact of C incorporation on optical emission is investigated in LEDs based on CGeSn/GeSn multiple quantum wells, demonstrating enhanced near‐infrared emission at 2.54 µm, which is sustained up to room temperature.
The stretch-shortening cycle effect is not associated with cortical or spinal excitability modulations
(2025) Rissmann, Lea‐Fedia; Raiteri, Brent James; Seiberl, Wolfgang; Siebert, Tobias; Hahn, Daniel
It is unclear whether cortical and spinal excitability modulations contribute to enhanced stretch-shortening cycle (SSC) performance. Therefore, this study investigated cortical and spinal excitability modulations during and following shortening of SSC contractions compared with pure shortening (SHO) contractions. Participants ( n = 18) performed submaximal voluntary plantar flexion contractions while prone on the dynamometer bench. The right foot was strapped onto the dynamometer's footplate attachment, and the resultant ankle joint torque and crank arm angle were recorded. Cortical and spinal excitability modulations of the soleus muscle were analysed by eliciting compound muscle actional potentials via electrical nerve stimulation, cervicomedullary motor‐evoked potentials (CMEPs) via electrical stimulation of the spinal cord, and motor‐evoked potentials (MEPs) via magnetic stimulation of the motor cortex. Mean torque following stretch was significantly increased by 7 ± 3% ( P = 0.029) compared with the fixed‐end reference (REF) contraction, and mean torque during shortening of SSC compared with SHO was significantly increased by 12 ± 24% ( P = 0.046). Mean steady‐state torque was significantly lower by 13 ± 3% ( P = 0.006) and 9 ± 12% ( P = 0.011) following SSC compared with REF and SHO, respectively. Mean steady‐state torque was not significantly different following SHO compared with REF (7 ± 8%, P = 0.456). CMEPs and MEPs were also not significantly different during shortening of SSC compared with SHO ( P ≥ 0.885) or during the steady state of SSC, SHO and REF ( P ≥ 0.727). Therefore, our results indicate that SSC performance was not associated with cortical or spinal excitability modulations during or after shortening, but rather driven by mechanical mechanisms triggered during active stretch.
A magnetically transformable twisting millirobot for cargo delivery at low Reynolds number
(2025) Jeong, Moonkwang; Tian, Jiyuan; Zhang, Meng; Qiu, Tian
Inspired by bacteria flagella, miniature robots often use a helical shape to propel themselves in fluids at low Reynolds numbers. The helical microstructures in the robots are often rigid and are made by advanced 3D micro‐/nanofabrication techniques. However, it remains challenging to fabricate these 3D helical structures without complicated machinery. Herein, for the first time, a magnetically transformable millirobot-TwistBot-with a flexible body that can transform from a simple flat ribbon to a helical shape under an applied magnetic field is reported, enabling its propulsion in viscous fluids. The robot's twisting is modeled using numerical simulation and its geometry is optimized to maximize the twist angle. The unique shape transformation not only allows the propulsion through narrow lumens but also facilitates TwistBot in carrying and delivering solid cargo successfully to the target. The concept of the TwistBot opens new opportunities in designing soft transformable minirobots for targeted cargo delivery.
Synthetic and structural peculiarities in molybdenum(VI) nitrido N‐heterocyclic carbene complexes
(2025) Kundu, Koushani; Frey, Wolfgang; Buchmeiser, Michael Rudolf
The synthesis of molybdenum(VI) nitrido N‐heterocyclic carbene (NHC) complexes bearing alkoxide and siloxide ligands, respectively, is reported. The molybdenum nitrido trisalkoxide precursor Mo(≡N)(OC(CF3)2(CH3))3 is reacted with the NHCs 1,3‐diisopropylimidazol‐2‐ylidene (IiPr), 1,3‐dimethylimidazol‐2‐ylidene (IMe), and 1,3‐dicyclohexylimidazol‐2‐ylidene (ICy), respectively, to yield the corresponding molybdenum nitrido trisalkoxide NHC complexes. Further salt metathesis allows to replace the alkoxide ligands by the thermally more robust siloxide ligands. In case an asymmetric NHC, i.e., 1‐butyl‐3‐methylimidazol‐2‐ylidene, is reacted with the trisalkoxide precursor, a mixture of two isomers of the corresponding product is observed; these two isomers interconvert to some extent at elevated temperature. Selected complexes are subjected to single‐crystal X‐ray analysis. The molybdenum nitrido NHC complexes show moderate activity in alkyne cross‐metathesis.
Ferribactin- und Pyoverdin-Chromophore als Bausteine antimikrobieller Polymere
(2025) Greulich, Andreas P.; Laschat, Sabine (Prof. Dr.)
Biotechnological production, isolation and characterisation of (2R,3S)‐2,3‐dihydroxy‐2,3‐dihydrobenzoate
(2025) Kiel, Martina; Barrantes, Israel; Pieper, Dietmar H.; Engesser, Karl‐Heinrich
Bacterial Rieske non‐heme iron oxygenases catalyse the transformation of a wide range of aromatic compounds to vicinal cis ‐dihydrodiols. Such compounds have been successfully applied in chemoenzymatic synthetic routes for, for example, pharmaceuticals, natural products and polymers. In the case of benzoate, only (1 S ,2 R )‐ cis ‐1,2‐dihydroxy‐2‐hydrobenzoate is readily accessible via enzymatic transformation, but not the regioisomeric cis ‐2,3‐dihydroxy‐2,3‐dihydrobenzoate (2,3‐DD) or cis ‐3,4‐dihydroxy‐3,4‐dihydrobenzoate. While trace amounts of putative cis ‐2,3‐DD have been obtained before by using p ‐cumate 2,3‐dioxygenase (PCDO) or a combination of chlorobenzene dioxygenase and nitrilase, none of these approaches enabled its production and isolation at a greater scale for potential use as a chiral building block in organic synthesis. We here provide a protocol for biotransformation of benzoate yielding (2 R ,3 S )‐2,3‐dihydroxy‐2,3‐dihydrobenzoate using the PCDO of Pseudomonas citronellolis strain EB200 with negligible formation of side products. An isolation procedure suitable for production of the 2,3‐DD sodium salt monohydrate at high purity (> 95%) at a gram scale, and a comprehensive characterisation of this novel metabolite is given.
Security analysis of the German EUDI-Wallet
(2025) Sang, Florian
The amended eIDAS regulation requires every member state of the European Union to provide a European Digital Identity Wallet (EUDI-Wallet) by 2026. Citizens of member states will be able to use the EUDI-Wallet to identify themselves, digitally sign contracts, and securely store and share digital documents across Europe. To ensure interoperability, a common set of standards is employed as a foundation for all EUDI-Wallet implementations. Among other protocols, OpenID for Verifiable Credential Issuance (OID4VCI) and OpenID for Verifiable Presentations (OID4VP) must be supported by every EUDI-Wallet implementation for exchanging identities. These protocols define mechanisms for issuance and presentation of Personal Identification Data (PID).
The integrity and authenticity of the exchanged PID are crucial for the trustworthiness of the EUDI-Wallet ecosystem. Ensuring the security of EUDI-Wallet protocols is essential to maintain user trust and enable widespread adoption of the EUDI-Wallet across Europe. The identification of potential vulnerabilities in the security of EUDI-Wallet concepts early in development is highly important to ensure that EUDI-Wallet implementations provide strong security guarantees.
In this work, we conduct an informal security analysis of the protocols for PID issuance and presentation, as defined in the architecture concept of the German EUDI-Wallet. We define three security properties that the German EUDI-Wallet should provide: Freshness of Presentations, Authentication, and Session Integrity. Under an attacker model and security assumptions that we define in this work, we demonstrate that the first two properties hold, while Session Integrity requires the additional assumption of a vigilant user.
A method for the quality‐aware automated selection of deployment technologies
(2025) Stötzner, Miles; Krieger, Niklas; Speth, Sandro; Weller, Marcel; Becker, Steffen; Weder, Benjamin; Soldani, Jacopo; Morlock, Valentin
Domain. The deployment of distributed multi‐component cloud applications typically requires a combination of multiple heterogeneous deployment technologies. A different combination of deployment technologies should be chosen due to varying deployment qualities, such as the functional suitability and reliability of the deployment technologies for the deployment of the components. A suboptimal selection of deployment technologies makes the deployment error‐prone.
Problem. Selecting and maintaining the combination of deployment technologies requires modeling effort and expertise.
Contributions. We present a method that automatically selects deployment technologies based on a knowledge base of deployment scenarios and corresponding deployment qualities of deployment technologies.
Evaluation. We show the practical applicability and the usefulness of our method. For the practical applicability, we conduct two case studies based on an open‐source reference architecture application and a real‐world industry application using a prototypical implementation of our method. For the usefulness, we conduct a user study in which participants assign deployment technologies with and without our method.
Conclusions. Our method is a useful contribution that reduces the modeling effort and the required expertise when maintaining the combination of deployment technologies. Further, our method enhances the deployment quality.