Repository for natural sciences and technology
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- ItemAbschlussbericht für die Deutsche Forschungsgemeinschaft zum DFG-Forschungsvorhaben NY 4/79-1 und LE 876/4-1 : Entwicklung von fabrikplanerischen Leitprinzipien zur Planung von flussorientierten Krankenhäusern mit wandlungsfähigen Raum-, Technik- und Organisationskonzepten (MedFAP)(Hannover : Technische Informationsbibliothek, 2025-06) Nyhuis, Peter; Lennerts, KunibertAufgrund der angespannten Finanzierungslage von Krankenhäusern sowie der turbulenten Umwelt, in der Krankenhäuser agieren, wurden Flussorientierung des Layouts und Wandlungsfähigkeit als Anforderungen an Krankenhäuser formuliert. Die Flussorientierung soll ermöglichen, dass der Krankenhausbetrieb und seine Prozesse effizient ablaufen, sodass Kosten eingespart werden können. Die Wandlungsfähigkeit soll Krankenhäuser befähigen, sich auf ändernde Anforderungen aus der Umwelt angemessen einzustellen und somit langfristig betriebsfähig zu bleiben. Sowohl für die Flussorientierung als auch für die Wandlungsfähigkeit bestehen in der Fabrikplanung etablierte Konzepte, für Krankenhäuser bislang nicht. Unter der Arbeitshypothese, dass Fabrik- und Krankenhaussysteme vergleichbar sind, sollten im Rahmen des Forschungsprojektes Konzepte zur Flussorientierung und Wandlungsfähigkeit aus der Fabrikplanung auf Krankenhaussysteme übertragen werden. Zur flussorientierten Gestaltung des Krankenhauslayouts wurden allgemeine Strukturelemente identifiziert sowie deren Gestaltungsmöglichkeiten als Unterstützung der Strukturplanung diskutiert. Außerdem wurde ein Algorithmus erarbeitet, der Krankenhausplaner aufbauend auf den Strukturelementen und unter Berücksichtigung krankenhausindividueller Transportbeziehungen bei der Erstellung des Funktionsschemas unterstützt. Anschließend wurde das Vorgehen zur Dimensionierung beschrieben sowie Restriktionen identifiziert, die bei der Layoutplanung zu berücksichtigen sind. Zudem wurden Ansätze entwickelt, wie diese Restriktionen in einen Algorithmus überführt werden können, der Krankenhausplaner bei der Überführung des Funktionsschemas in ein realisierbares Layout unterstützt. Um Ansätze zur Wandlungsfähigkeit zu erarbeiten, wurden zunächst Krankenhausobjekte, wie bspw. „Mittel für medizinische Leistungen“ oder „Layout“, identifiziert. Mit ihnen ist es möglich, das Krankenhaussystem als Gesamtes zu beschreiben und gleichzeitig im Detail zu gestalten. Je Krankenhausobjekt wurden anschließend Wandlungspotenzialmerkmale identifiziert, bei denen es sich um präzise, objektive Eigenschaften mit Einfluss auf das Wandlungspotenzial eines Objektes handelt. Auf ihrer Grundlage ist es gelungen, ein Reifegradmodell zu entwickeln, mit dem die Bewertung der IST-Wandlungsfähigkeit eines Krankenhaussystems möglich ist. Um die SOLL-Wandlungsfähigkeit eines Krankenhaussystems zu bewerten, wurde eine Szenario-Analyse durchgeführt. Indem IST- und SOLL-Wandlungsfähigkeit gegenübergestellt werden, ist es den Krankenhausplanern mithilfe des Reifegradmodells möglich, zielkonforme Maßnahmen zu treffen. Die erarbeiteten Teilergebnisse wurden in enger Zusammenarbeit mit Krankenhausexperten erarbeitet und mit ihnen validiert. Anpassungen im Projektvorgehen waren zwar nötig, dennoch konnte das übergeordnete Ziel erreicht werden. Darüber hinaus ergaben sich mögliche weiterführende Forschungsaktivitäten, die auf dem Ergebnis dieser Arbeit aufbauen können.
- ItemNanocrystalline Y2O3-modified metal matrix composite coatings with improved resistance to thermocyclic oxidation and V2O5-induced type II hot corrosion(Amsterdam [u.a.] : Elsevier Science, 2024-05-08) Grimme, Christoph; Ma, Kan; Kupec, Robin; Oskay, Ceyhun; White, Emma M. H.; Knowles, Alexander J.; Galetz, Mathias C.Incorporating reactive elements (RE) into turbine coatings is a well-established surface treatment. However, suboptimal RE concentrations can lead to compromised strength, heightened brittleness, and reduced adhesion. In contrast, RE oxides offer advantages of avoiding these detrimental effects, counteracting corrosion phenomena induced by V2O5 compounds and enhancing oxidation resistance. A notable challenge lies in optimizing RE oxide particle incorporation and understanding the influence of particles in coating microstructures. This study focuses on developing Nisingle bondAl and Ni-Cr-Al type metal matrix composite (MMC) coatings on Inconel 617 (IN617), containing up to 11 vol% of Yttria (Y2O3) nanoparticles. Y2O3 nanoparticles and Ni were co-electrodeposited on IN617 followed by either pack aluminizing or a two-step chromizing and aluminizing process. An even distribution of Y2O3 nanoparticles was observed throughout the entire 100 μm coating thickness, leading to significant grain refinement in the sub-micron to nano range in both coating types. Y2O3-strengthened coatings were subjected to oxidation at 1100 °C and hot corrosion at 700 °C and were compared to their Y2O3-free counterparts. Present at grain boundaries, Y2O3 markedly enhanced the oxidation and corrosion resistance by reducing interdiffusion, improving the oxide scale adherence and binding V2O5, highlighting the potential of this method for advanced turbine blade coatings.
- ItemFinal Report for the Emmy Noether Project : ConcSys: Reliable and Efficient Complex, Concurrent Software Systems(Hannover : Technische Informationsbibliothek, 2025-06) Pradel, MichaelThe ConcSys project aims to develop techniques for testing and analyzing complex software systems, with a focus on increasing the correctness and performance of such systems. The project was running from March 2015 until December 2024. In this period, we made significant progress, both in terms of scientific results and in terms of building up a research group. The scientific results include novel techniques for (i) finding and preventing concurrency bugs, (ii) understanding and analyzing software performance, (iii) automated test generation, (iv) program analysis for WebAssembly, and (v) foundations of dynamic analysis. These results are presented in 83 peer-reviewed publications at top-tier conferences and journals in software engineering and programming languages, e.g., ICSE, OOPSLA, PLDI, and FSE. Beyond these scientific results, the project has enabled the PI, Michael Pradel, to build up his own a research group, to establish himself as an internationally recognized leader in the field, and to secure a permanent professorship at the University of Stuttgart. The project has directly and indirectly contributed to the careers of 12 doctoral students, out of which seven have been partially funded by the project and six have already graduated.
- ItemMitigating the Effect of High Overpotential during Al Deposition on Aluminium-Graphite Battery Performance(Weinheim : Wiley-VCH, 2025) Mukundan, Charan; Drillet, Jean-FrancoisThis study investigates the impact of current density on electrode potential during aluminium (Al) dissolution/deposition step from/on an Al foil as well as the charge-discharge behaviour of aluminium-graphite batteries (AGB) in various AlCl3-based electrolytes. Preliminary experiments in a cell with graphite blocking electrodes evidenced higher chemical stability of 1 : 1.5 Urea : AlCl3 electrolyte, followed by 1 : 1.5 TEA : AlCl3 and 1 : 1.5 EMIMCl : AlCl3. In Al−Al symmetric cells, current densities above 1 mA cm−2 led to a notable rise in overpotential up to 100 mV during Al deposition in both TEA : AlCl3 and Urea : AlCl3 electrolytes mostly due to low surface area of native Al foil. Similar trend was observed in AGB full cells, where higher overpotentials during Al deposition caused ‘incomplete’ AlCl₄− intercalation in natural graphite (NG), resulting in capacity fade at current densities in the range between 0.5 and 5 A g−1. By adjusting the upper cut-off voltage (UCV) during charging step as a function of applied current value according to respective electrolyte stability, a significant improvement in specific capacity and energy density was achieved during charging and discharging steps. For instance at 1 A g−1, the specific energy density of AGB increased by 10 % in EMIMCl : AlCl3, 48 % in TEA : AlCl3, and an impressive 250 % in Urea : AlCl3.During long-term cycling post-UCV adjustment, the capacities of AGB increased by 10 %, 13 %, and 27 % for AGBs with EMIMCl : AlCl3, TEA : AlCl3 and Urea : AlCl3, respectively with a negligible capacity fade of less than 1 % for EMIMCl : AlCl3 and TEA : AlCl3, and a 9 % capacity fade for Urea : AlCl3.
- ItemSynthesis of Highly Active and Stable Carbon by a Soft-Template Hydrothermal Route as Pt Substrate for Oxygen Reduction Reaction(Weinheim : Wiley-VCH, 2023) Antony, Jithin; Sakthivel, Mariappan; Drillet, Jean-FrancoisN-doped mesoporous carbon spheres were synthesized by a microwave-assisted ammonia-catalyzed hydrothermal route (CFAHM) by using Pluronic® F127 as a soft-template and m-Aminophenol as both carbon and nitrogen source. Their physical and electrochemical properties were compared with those of carbon samples obtained by a conventional hydrothermal method (CFAH). The best results in terms of particle size, surface area, pore size distribution, conductivity and N-content of the as-prepared CFAHM samples were obtained in 17 M NH4OH at 120 °C for 5 min. After 1100 °C pyrolysis step, conductivity of CFAHM increased to 5.64 S cm−1 compared to 8.64 S cm−1 for CFAH sample. Remarkably, GDE experiments with xylene-swelled CFAHM-supported platinum exhibited an excellent activity for ORR (181 mA cm−2 @ 0.7 V) and ECSA retention (80 % after 10,000 ADT) under half-cell conditions in 1 M H2SO4 at room temperature compared to only 57 mA cm−2 and 13 % for GDE with Pt/CVulcan reference material.
- ItemImpact of Aluminium Electrode Potential during Charging on Aluminium-Ion Battery Performance with TEA-AlCl3 Electrolyte(Weinheim : Wiley-VCH, 2023) Mukundan, Charan; Eckert, Martin; Drillet, Jean-FrancoisIn aluminium (Al) symmetric cell, potentials during Al deposition on an Al foil at 1 mA cm−2 were 60–70 mV higher in TEA-AlCl3 electrolyte compared to those measured with EMIMCl-AlCl3 reference. Because of higher electrochemical stability of TEA-AlCl3 solution, cut-off voltage of charging step in AIB full-cell was set to 2.45 V compared to 2.40 V for the reference cell. During long-term cycling at 1 A g−1, the specific capacity of the AIB cell employing TEA-AlCl3 increased from 60 to 94 mAh g−1 (57 %) after 1000 cycles while that of cell with EMIMCl-AlCl3 was quite constant at about 60 mAh g−1. This behaviour was explained by continuous decreasing in Al electrode potential at End-of-Charge state (EOC) during deposition reaction (charging step) in TEA-AlCl3 allowing an increase in graphite electrode potential and consequently in AIB cell capacity over the whole experiment. This increase in capacity was accompanied by a raise of defect sites in graphite material.
- ItemDFG Final Report: "LIVE: Empirical Studies on the Effects of Liveness on Programming"(Hannover : Technische Informationsbibliothek, 2025-06-13) Hirschfeld, RobertLiveness in programming tools is the impression of changing a program while it is running. Various tools support liveness, including commercial programming systems, such as MS Excel and Jupyter Notebooks. Tool designers assume that liveness improves the programming experience, but this assumption has insufficient and inconclusive empirical backing. This lack of evidence might lead to the promotion of liveness in unsuitable settings and the neglect of important settings, which would waste design and implementation efforts. In this project, we investigated the effects of live tools on debugging. In two controlled experiments we studied the influence of task complexity and delayed interactions on the effects of live tools. Compared to previous experiments on liveness, the participants in our experiments had considerable experience with live tools. In our first experiment we tested whether the influence of live tools on debugging time differs for simple and complex tasks. We found that live tools significantly shorten the time needed to debug defects. At the same time, we could not confirm our main hypothesis that task complexity moderates this effect. However, our results indicate that task complexity indeed influences the effect, but less than suggested by the pilot. For programming tool researchers and designers, our results show that programmers can benefit from live tools, but that they need to consider task complexity and participants' experience with liveness when preparing studies or building tools. With our second experiment, we aimed to better understand the first experiment's observations. Based on Information Foraging Theory, we assumed that live tools reduce the perceived cost of obtaining dynamic information so that programmers consult it more often when helpful. Therefore, we tested whether programmers use live tools less frequently if access to them is delayed. The experiment did not yield sufficiently enough results for a thorough analysis, but the collected data shows no clear decline in live tool usage. Yet, an ongoing post hoc analysis using edit-run cycles suggests that participants' workflows changed. During the first experiment, we found that it is a great challenge to operationalize the complexity of maintenance tasks in programming tool studies. Thus, we conducted a survey to curate a collection of factors from related studies that can help shape the complexity of such tasks. With this collection, researchers can deliberately decide on the complexity level for their studies' tasks. This project also resulted in a novel concept for teaching debugging through contests and improved setups for related studies on liveness conducted in our group.
- ItemFinal report on the DFG Heisenberg project "Quantum Gravity from String Theory"(Hannover : Technische Informationsbibliothek, 2025) Plauschinn, Erik[No abstract available]
- ItemReport on the DFG Project "Approaching Superconductor/Cold Atom Hybrid Quantum Circuits " (KL 930_16-1)(Hannover : Technische Informationsbibliothek, 2025-06-10) Kleiner, Reinhold; Fortagh, JozsefThe project was intended to realize superconductor-cold atom hybrid systems, whereby the atoms are captured and manipulated in the vicinity of a superconducting chip. The chip should operate in the millikelvin range, which enables both subsystems to operate in the quantum regime. The vision: In this geometry, the methods of solid-state physics and quantum optics can be combined to manipulate the atoms or solid-state circuits directly or via photons from microwave to optical frequencies. If successful, the hybrid system offers unique opportunities to study the coupling between macroscopic objects (superconducting qubits, resonators) and natural atoms. In the context of quantum information, one can imagine a hybrid in which the superconducting circuit acts as a processor and the atoms act as a quantum memory. Cold atoms coupled to superconducting resonators could also enable the realization of new quantum gates. At the start of the project, a cold atom/superconductor setup was already in operation, working at a bath temperature of 4.2 K. Measurement systems were also available that allow superconducting microwave structures to be examined in the absence of cold atoms. In these setups, concepts for atom-superconductor coupling could be developed and tested. On the atom side, the focus was on Rydberg atoms, which offer a variety of resonant transitions and enable strong electrical dipole coupling to the superconducting devices. On the superconducting side, chips have been developed that contain resonators optimized for coupling to Rydberg atoms and can be combined with structures to trap the atoms. Originally, magnetic trap structures were considered but, as the project progressed, the focus went to optical dipole traps. A UHV millikelvin system was also available at the start of the project and was designed to incorporate the superconductor-cold atom hybrid systems. In this cryostat, part of the transport path for capturing the atoms and transporting them magnetically to the millikelvin level was demonstrated as part of a previous project. The transport path was completely rebuilt in the project, including the necessary laser and microwave components. A suitable superconducting chip was also installed at the end of the transport path. Unfortunately, the construction of the coil system required for transport turned out to be considerably more difficult than expected and took until the end of the project. The system is now functional, although the actual experiments on the coupled superconductor-cold atom hybrid systems are reserved for further projects.
- ItemReport on the DFG project "Optimization of different strategies for designing an energy harvester based on spin-torque diodes" (BE 2464/21-1)(Hannover : Technische Informationsbibliothek, 2025-06-04) Berkov, DmitrySteadily growing demand for cheap and green energy has caused a rapid development of so called ‘energy harvesting’ devices for producing dc-power from the ambient microwave radiation from various sources like TV and mobile-phone networks, Wi-Fi routers etc. The energy density of this radiation ranges from 1 to 1000 nW/cm^2, so that corresponding technology could be successfully used by low-power applications (digital thermometer, smoke detectors, some sensors in medicine etc.). The main goal of this project was the optimization of various designs for energy harvesters based on spin-torque-diodes (STDs), i.e. devices where dc-voltage is generated when an ac-current flows through a magnetic tunnel junction (MTJ). Using computer simulations, we have studied and optimized three main types of MTJ-based nanodevices: (i) ‘standard’ MTJ nanopillars of the resonant type employing quasi-homogeneous in-plane magnetization oscillations; (ii) MTJs in the out-of-plane precession regime for broadband rectification and (iii) multilayer stacks with the in-plane shape designed for oscillation of domains walls. As the results of this project we have determined optimal geometric and magnetic parameters for all three kinds of spin-torque-based energy harvesters listed above, and predicted corresponding maximal rectification efficiencies in ambient conditions.