Recent Submissions
Investigation of chip jamming and drill breakage in deep-hole drilling using Smoothed Particle Hydrodynamics
(2024) Baumann, Andreas; Eberhard, Peter
Single-lip deep hole drilling is characterized by a high-quality hole and a high level of productivity achieved. It is performed using high feed rates in a single pass, and, therefore, chips must be removed by the cooling liquid. However, chip jamming is a significant problem when chips wrap around the tool, leading to marks on the borehole wall and an increased drilling torque, potentially causing sudden tool failure. The Smoothed Particle Hydrodynamics method is applied to simulate the challenging fluid flow and elastic bodies. A first approach is developed to model the effects of chip jamming and the possible consequence of drill breakage for a deeper understanding of the process behavior.
Gestión de la Recarga del Acuífero: una contribución a la solución del problema del agua en Lima, Perú : Informe final del proyecto NEWA-LIMA
(Stuttgart : Universität Stuttgart, 2025) Fesch, Katharina; Hügler, Michael; León, Christian D.; Perez, Hiraida; Stauder, Stefan; Xanke, Julian; Manrique, Elizabeth (Übersetzerin)
El proyecto NEWA-LIMA “Nuevos recursos hídricos y tratamiento innovador de aguas residuales para regiones metropolitanas áridas, tomando como ejemplo Lima, Perú”, financiado por el Ministerio del Ambiente de Alemania (BMUV) durante el período 2022 a 2024 tuvo como objetivo demostrar que la Recarga Gestionada de Acuíferos es un método natural y de bajo costo para el uso a largo plazo de los recursos hídricos subterráneos, contribuyendo de este modo a la solución de los problemas de agua en Lima.
Lima es una de las regiones metropolitanas más áridas del mundo, por lo que el abastecimiento de agua para sus 10 millones de habitantes, así como para la industria y el comercio, representa un gran desafío que requerirá de inversiones significativas en los próximos años. Los ríos locales llevan agua solamente durante la época de avenida en los Andes y los recursos de agua subterránea son limitados. Este informe presenta las soluciones desarrolladas y los resultados obtenidos en este proyecto. Tras exhaustivas investigaciones preliminares, se construyó una planta piloto MAR en el terreno de una planta de tratamiento de aguas residuales (PTAR) en el valle del río Lurín. Constó de tres pozas de tierra para la infiltración de las aguas residuales tratadas, así como varios piezómetros. Fue operada en colaboración con la Empresa de Servicio de Agua Potable y Alcantarillado de Lima (SEDAPAL) durante un periodo de 17 meses. El rendimiento de depuración del paso por el suelo fue registrado mediante exhaustivos análisis microbiológicos y químicos del agua, incluidas sustancias antropogénicas y el innovador “análisis relacionado con el impacto” (WBA). Las investigaciones complementarias a pequeña escala con adsorción de carbón activado y ósmosis inversa evaluaron el uso de estas tecnologías avanzadas de tratamiento de agua. Se revisó el marco legal vigente y las implicaciones sociales de los proyectos MAR en Perú. La elaboración de un modelo local de aguas subterráneas y de un concepto para el uso de filtros percoladores en el tratamiento de aguas residuales sirvieron para definir recomendaciones respecto a una aplicación MAR a gran escala en el valle de Lurín.
Surface water extent monitoring using the Global WaterPack product: automated extraction, refinement, and analysis
(2025) Jalali Jirandehi, Masoud
Monitoring and analyzing surface water dynamics is critical for understanding hydrological variations, climate change impacts, and water resource management. Traditional methods of surface water storage monitoring rely on in-situ measurements, which are often spatially and temporally limited. Remote sensing has revolutionized this field by enabling large-scale, consistent, and continuous observations of area and height water storages.
This study presents a methodology for generating accurate water area time series using the Global WaterPack (GWP), a monthly satellite-derived dataset. Developed by the German Aerospace Center (DLR), the GWP dataset is specifically designed for monitoring surface water dynamics on a global scale. A Python-based processing tool is developed to systematically extract and analyze lake and river water extents, mitigating key challenges such as cloud contamination, defining proper threshold, and classification inaccuracies. By integrating high-frequency surface water observations from GWP with the Prior Lake Database PLD (a static dataset for extracting the initial search area), and the SWOT (The Surface Water and Ocean Topography) prior River Database (SWORD), which provides a standardized framework of high-resolution river nodes and reaches, this tool enhances the reliability of time-series analysis. This framework improves surface water change detection, reduces computational complexity, and refines water occurrence assessments under diverse hydroclimatic conditions.
The workflow automates the entire process, allowing users to select lakes interactively via a geospatial interface or upload coordinate lists for batch processing. Key steps include (1) downloading images, (2) defining the search area, (3) normalization, (4) generating a water occurrence map, (5) defining constant water and land masks, (6) residual analysis, (7) deriving and applying thresholds, (8) generating time series plots, and (9) correlation analysis. Advanced filtering methods, such as threshold-based classification and residual analysis, refine water occurrence measurements, while an adaptive thresholding approach using the Cumulative Distribution Function (CDF) enhances water body delineation accuracy.
To evaluate the reliability of the extracted data, the resulting surface area time series are compared against altimetry-derived water height records using correlation analysis. The analysis revealed clear seasonal and interannual variations in lake water areas, aligning well with natural hydrological patterns. Many lakes showed strong positive correlations between satellite-derived surface area and altimetry-based water levels, validating the method’s effectiveness. However, weaker correlations in some cases were attributed to issues like cloud cover, sensor limitations, and complex hydrodynamics. The study emphasized that a fixed threshold is insufficient for all systems, whereas the corrected method provided more reliable results across diverse conditions. Although river analysis showed varied hydraulic responses, the tool proved useful for monitoring floods, seasonal changes, and long-term water trends, especially with proper calibration.
By providing an automated, scalable, and accurate tool for water body monitoring, this thesis contributes to advancing hydrological analysis using remote sensing and geospatial processing techniques. The developed tool can aid in climate studies, water resource management, and flood risk assessment, offering a valuable framework for long-term surface water monitoring.
TR12 centers in diamond as a room temperature atomic scale vector magnetometer
(2022) Foglszinger, Jonas; Denisenko, Andrej; Kornher, Thomas; Schreck, Matthias; Knolle, Wolfgang; Yavkin, Boris; Kolesov, Roman; Wrachtrup, Jörg
The family of room temperature atomic scale magnetometers is currently limited to nitrogen-vacancy centers in diamond. However, nitrogen-vacancy centers are insensitive to strong off-axis magnetic fields. In this work, we show that the well-known TR12 radiative defect in diamond, exhibits strong optically detected magnetic resonance (ODMR) signal under optical saturation. We also demonstrate that the spin system responsible for the magnetic resonance is an excited triplet state that can be coherently controlled at room temperature on a single defect level. The high optically detected magnetic resonance contrast, which is maintained even for strong off-axis magnetic fields, suggests that TR12 centers can be used for vector magnetometry even at high field.
Nanoscale analysis of frozen honey by atom probe tomography
(2022) Schwarz, Tim M.; Ott, Jonas; Solodenko, Helena; Schmitz, Guido; Stender, Patrick
Three-dimensional reconstruction of the analysed volume is one of the main goals of atom probe tomography (APT) and can deliver nearly atomic resolution (~ 0.2 nm spatial resolution) and chemical information with a mass sensitivity down to the ppm range. Extending this technique to frozen biological systems would have an enormous impact on the structural analysis of biomolecules. In previous works, we have shown that it is possible to measure frozen liquids with APT. In this paper, we demonstrate the ability of APT to trace nanoscale precipitation in frozen natural honey. While the mass signals of the common sugar fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved correct stoichiometric values via different interpretation approaches for the peaks and thus determined the water content reliably. Next, we use honey to investigate the spatial resolution capabilities as a step toward the measurement of biological molecules in solution in 3D with sub-nanometer resolution. This may take analytical techniques to a new level, since methods of chemical characterization for cryogenic samples, especially biological samples, are still limited.
Experimental evaluation of heat transfer effect on turbocompressor performance operating with helium-neon gas mixtures
(2022) Podeur, Maxime; Vogt, Damian M.
Within the framework of the Future Circular Collider (FCC) currently being investigated at CERN, the entire cryogenic cycle had to be revised with respect to the existing Large Hadron Collider (LHC). In particular, a novel pre-cooling cycle had to be developed for this purpose. This led to a closed-loop cryogenic cycle operating with a mixture of helium and neon, also called Nelium. To better understand the challenges and opportunities associated with the design and operation of radial compressors with such light gases, a closed loop test facility has been designed, built and commissioned at the ITSM (University of Stuttgart). The test facility has been developed to operate with air as well as with helium-neon gas mixtures of varying mixing ratios ranging from pure neon to pure helium. In this paper, the test facility architecture and operation procedure are briefly introduced together with a description of the newly installed compressor stage. Experimental performance measurements are then compared to adiabatic and diabatic numerical simulation validating respectively the pressure rise and diabatic stage efficiency for various gases. The heat transfer effect on compressor stage performance is then described and the respective contribution of the influencing factors are quantified.
In situ laboratory for plastic degradation in the Red Sea
(2022) Brümmer, Franz; Schnepf, Uwe; Resch, Julia; Jemmali, Raouf; Abdi, Rahma; Kamel, Hesham Mostafa; Bonten, Christian; Müller, Ralph-Walter
Degradation and fragmentation of plastics in the environment are still poorly understood. This is partly caused by the lack of long-term studies and methods that determine weathering duration. We here present a novel study object that preserves information on plastic age: microplastic (MP) resin pellets from the wreck of the SS Hamada, a ship that foundered twenty-nine years ago at the coast of Wadi el Gemal national park, Egypt. Its sinking date enabled us to precisely determine how long MP rested in the wreck and a nearby beach, on which part of the load was washed off. Pellets from both sampling sites were analyzed by microscopy, X-ray tomography, spectroscopy, calorimetry, gel permeation chromatography, and rheology. Most pellets were made of low-density polyethylene, but a minor proportion also consisted of high-density polyethylene. MP from inside the wreck showed no signs of degradation compared to pristine reference samples. Contrary, beached plastics exhibited changes on all structural levels, which sometimes caused fragmentation. These findings provide further evidence that plastic degradation under saltwater conditions is comparatively slow, whereas UV radiation and high temperatures on beaches are major drivers of that process. Future long-term studies should focus on underlying mechanisms and timescales of plastic degradation.
Integrating a dynamic central metabolism model of cancer cells with a hybrid 3D multiscale model for vascular hepatocellular carcinoma growth
(2022) Lapin, Alexey; Perfahl, Holger; Jain, Harsh Vardhan; Reuss, Matthias
We develop here a novel modelling approach with the aim of closing the conceptual gap between tumour-level metabolic processes and the metabolic processes occurring in individual cancer cells. In particular, the metabolism in hepatocellular carcinoma derived cell lines (HEPG2 cells) has been well characterized but implementations of multiscale models integrating this known metabolism have not been previously reported. We therefore extend a previously published multiscale model of vascular tumour growth, and integrate it with an experimentally verified network of central metabolism in HEPG2 cells. This resultant combined model links spatially heterogeneous vascular tumour growth with known metabolic networks within tumour cells and accounts for blood flow, angiogenesis, vascular remodelling and nutrient/growth factor transport within a growing tumour, as well as the movement of, and interactions between normal and cancer cells. Model simulations report for the first time, predictions of spatially resolved time courses of core metabolites in HEPG2 cells. These simulations can be performed at a sufficient scale to incorporate clinically relevant features of different tumour systems using reasonable computational resources. Our results predict larger than expected temporal and spatial heterogeneity in the intracellular concentrations of glucose, oxygen, lactate pyruvate, f16bp and Acetyl-CoA. The integrated multiscale model developed here provides an ideal quantitative framework in which to study the relationship between dosage, timing, and scheduling of anti-neoplastic agents and the physiological effects of tumour metabolism at the cellular level. Such models, therefore, have the potential to inform treatment decisions when drug response is dependent on the metabolic state of individual cancer cells.
Long-lived circular Rydberg qubits of alkaline-earth atoms in optical tweezers
(2024) Hölzl, Christian; Götzelmann, Aaron; Pultinevicius, Einius; Wirth, Moritz; Meinert, Florian
Characterization of a novel TNF receptor 2 agonist to promote immune modulatory responses
(2024) Huber, Carina; Kontermann, Roland (Prof. Dr.)