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Potentials of typical plant species from rewetted fenlands for the supply of strategic elements
No full textRewetting of peatlands requires the development of new biomass utilization pathways. The supply of strategic elements with key importance for the development of priority technologies, such as germanium (Ge), silicon (Si) and rare earth elements, from fenland plants is one option. To provide a first estimation of the potential, concentrations of strategic elements were determined in nine biomass samples covering typical fenland vegetation in northeast Germany. Subsequently, a simplified estimation of potential revenue from strategic element recovery was made. The analysed plant species can be classified as high or intermediate Si plant accumulators with highest contents of more than 16.0 g Si kg−1 dry mass (DM) in sedges and common reeds. Ge concentrations were lower with reed canary grass containing the highest amounts of 465.3 µg Ge kg−1 DM. Simultaneous acquisition of Ge and Si could provide higher total element yields and revenues of up to 500 $ ha−1. In contrast, the potentials for supplying rare earth elements appeared to be very low, with common reed containing the highest sum of rare earth elements of 437.4 µg kg−1 DM. Biomass from rewetted fenlands is capable of accumulating strategic elements. More knowledge is required to understand the factors affecting their accumulation
Measurement of real temperatures in metal powder bed fusion: Hyperspectral thermography
No full textDetailed knowledge about the physics of the PBF-LB/M process is still lacking, and the simulation of the fast and small-scale process is challenging. Especially the experimental validation of complex simulations lacks a suitable measurement technique for temperature distributions at high speeds and spatial resolution. The complicated process physics, specifically the rapidly changing emissivity in and around the meltpool, pose a severe challenge for usual thermographic approaches.
Here, we present first results of a hyperspectral measurement approach to reconstruct temperature and emissivity maps during the PBF-LB/M process in a custom manufacturing machine. The camera setup measures the thermal radiation of the process along a line at a rate of 20 kHz, spectrally resolved between 1 µm and 1.6 µm. When the meltpool travels perpendicularly across this line, a typical meltpool can be reconstructed by pointwise fitting for temperature emissivity separation, based on typical spectral emissivities from reference measurements
Dataset on the Creep Properties of EN AW-2618A Aluminum Alloy in the T61 and an overaged condition
No full textThis publication contains comprehensive metadata and test results of constant force creep tests according to DIN EN ISO 204 on the aluminum alloy EN AW-2618A in the T61 condition (8 h/530 °C/quenching in boiling water followed by 28 h/195 °C/air cooling) and in an overaged condition (T61 + 1.000 h/190 °C). The test temperatures cover 160 °C, 180 °C, 190 °C, and 230 °C, and the initial stresses range between 40 MPa and 290 MPa
Von 25 auf 6: Der Bestand der Rembrandt-Zeichnungen in Weimar
No full textDas Rembrandt-Projekt ist ein Teilresultat, das aus der dreijährigen Katalogisierung der niederländischen und flämischen Zeichnungen in den Graphischen Sammlungen erwachsen ist. Es umfasst alle heute Rembrandt zugeschriebenen Blätter, alle rembrandtesken Zeichnungen, die ehemals als Rembrandts angesehen wurden, aber auch alle Zeichnungen, die einmal mit Rembrandt und seiner Schule in Verbindung gebracht wurden
Bestimmung der Aufnahmeraten von VVOCs aus Raumluft in Passivprobenahmesystemen
No full textFür die Bewertung der Innenraumluftqualitat ist die Bestimmung der Konzentration von sehr flüchtigen organischen Verbindungen (very volatile organic compounds — VVOCs) von großer Wichtigkeit. Im Besonderen bei den Deutschen Umweltstudien zur Gesundheit (GerES) des Umweltbundesamts erfolgt die Probenahme von flüchtigen organischen Verbindungen (VOCs) üblicherweise mit Passivsammlern, über deren material- und substanzspezifische Aufnahmeraten Rückschlisse auf die Konzentration der einzelnen Verbindungen gezogen werden können. Ziel dieses Projekts im Ressortforschungsplan (REFOPLAN) ist es, von 55 ausgewählten VVOCs die realen Aufnahmeraten auf Thermodesorptionsrohren als Passivsammlern experimentell zu bestimmen. Dafür wird eine entwickelte Analysemethode
für VWOCs mittels Thermodesorption-Gaschromatographie/Massenspektrometrie (TD-GC/MS) verwendet. Passivsammler mit verschiedenen Adsorbenzien werden für sieben Tage (23°C, 50 % r.E) mit den VVOCs exponiert. Carbograph 5TD weist für die ersten getesteten VVOCs die höchsten Aufnahmeraten auf
On the Reassessment of Bridge Superstructure Vibrations for High-Speed Traffic
No full textThe acceleration thresholds of bridge superstructures remain criti-cal for designing and reassessing railway bridges on high-speed lines, with ballasted track systems historically limited to 3.5 m/s² vertical accelerations due to destabilization risks. As part of the European InBridge4EU project, this study addresses methodological uncertainties in linking vertical bridge vibrations to lateral track creep—a key focus area for modernizing assess-ment protocols. A comparative analysis of two acceleration postprocessing methods (peak identification vs. fatigue-derived rainflow counting) as part of a recently proposed framework was conducted using an example bridge and train combination. Results demonstrate that rainflow counting yields more conservative creep estimates with the bulk of cumulative vibration-induced creep attributable to accelerations exceeding 3 m/s². However, discretizing acceleration ranges into 1 m/s² bins introduced significant errors compared to continuous cycle data, highlighting sensitivity to analysis parameters. These findings underscore the complexity of reconciling laboratory-derived harmonic vibration models with real-world bridge dynamics, where non-uni-form acceleration patterns dominate. The research directly informs ongoing efforts to refine standardized criteria for ballasted track stability, particularly through the InBridge4EU project's systematic re-evaluation of vibration lim-its and their engineering implications. By quantifying discrepancies between computational approaches, this work advances the development of robust protocols for predicting track degradation under high-speed operational loads
Einfluss der Low Transformation Temperature-Schweißzusätze auf die Ermüdungsfestigkeit von Längssteifen
No full textIn dem vorliegenden Beitrag wird die gezielte Applikation zusätzlicher LTT-Schweißlagen zur Einbringung von Druckeigenspannungen in ermüdungskritischen Bereichen an Schweißverbindungen untersucht. Ziel ist die Entwicklung eines wirtschaftlichen Verfahrens zur Erhöhung der Ermüdungslebensdauer, ohne die strukturelle Integrität einer Schweißnaht zu beeinträchtigen. Zu diesem Zweck wurden zunächst Längssteifen aus hochfestem Stahl in der ersten Lage mittels Metall-Lichtbogenschweißen unter Verwendung eines konventionellen Schweißzusatzwerkstoffs geschweißt. Anschließend erfolgte die Auftragung eines Chrom-Nickel-legierten LTT-Schweißzusatzwerkstoffs an die Stirnseiten der Längssteifen
Multi-refining effects of an AC electromagnetic field on the microstructure in AA5754 laser beam welding
No full textFine-grain structure is beneficial to the mechanical properties of the joint. Different kinds of grain and sub-grain structures refined by magnetic field during laser beam welding of AA5754 aluminum alloy are analyzed in this manuscript, and the influences of different magnetic field parameters (magnetic flux density and frequency) in these refining effects are also studied. Using the scanning electron microscope (SEM), the sub-grain structure near the fusion line was obtained, and it was found that the branching promotion and branches refinement can be achieved by the magnetic field. The branches become finer with the magnetic flux density or frequency increases, and this effect is stronger in the dendritic region than in the equiaxed region. The results of electron backscatter diffraction (EBSD) in the equiaxed region show that a high-frequency magnetic field can greatly reduce the average grain size, while a low-frequency one has little effect. A phenomenological nucleation model based on dendrite fragmentation theory was established, and it was introduced into the phase field model to analyze the equiaxed grains evolution process. In addition, another refinement mechanism was also observed. The periodic solidification pattern caused by the unstable solidification in the molten pool can refine the grains, and the magnetic field promotes this kind of grain refinement by promoting the solidification period
Deep Insights into Functionalised Nanoparticles with Photoelectron Spectroscopy
No full textModern instrumentation X-ray photoelectron instrumentation combines soft and hard X-rays. Additonally, in the last years methods were developed for the analysis of the measurement data to elucidate the composition and thickness of coatings of nanoparticles. In this presentation four examples will be presented: quantum dots, silica-coated iron-oxide nanoparticles, mixed Fe-Ni-O nanoparticles and amine-functionalized silica nanoparticles. These different nanoparticles are used for displays, for biomedicine, for water splitting, and as additives and fillers
Materials design using chemical heuristics, workflows, and machine learning
No full textBonds and local atomic environments are key descriptors of material properties, used to establish design rules and heuristics, and serve as descriptors in machine-learned interatomic potentials and the general machine learning of material properties.
Software implementations such as ChemEnv and LobsterEnv identify local atomic environments based on geometrical characteristics and quantum-chemical bonding analysis (here using Crystal Orbital Hamilton Populations as computed with LOBSTER). Fully automated workflows and analysis tools now enable large-scale quantum-chemical bonding analysis. The first part of the lecture will demonstrate how these tools help develop new machine-learning models and intuitive understandings of material properties.
New universal machine-learned interatomic potentials, such as MACE-MP-0, have been developed. The second part of the lecture will showcase how these potentials, combined with DFT, can accelerate research. It will focus on the interplay between DFT and machine-learned interatomic potentials, presenting automated workflows for training, fine-tuning, and benchmarking these potentials, implemented in our software autoplex. Additionally, it will show how to train new interatomic potentials from scratch by exploring potential energy surfaces, with the potential to enhance current universal machine-learned potentials.
The lecture will also discuss the trend toward automation in computational materials science and our recent contributions