25 Jahre Forschung am S-DALINAC

Als am 18. Oktober 1991 der »Supraleitende Darmstädter Linear-Accelerator«, kurz S-DALINAC, mit einem Festakt eingeweiht wurde, begann eine neue Epoche der Grundlagenforschung an der TH Darmstadt

Experimental observation of N00N state Bloch oscillations

Bloch oscillations of quantum particles manifest themselves as periodic spreading and relocalization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit this phenomenon is deeply rooted into the very foundations of quantum mechanics, all experimental observations so far have only contemplated dynamics of one and two particles initially prepared in separable local states. Evidently, a more general description of genuinely quantum Bloch oscillations will be achieved on excitation of a Bloch oscillator by nonlocal states. Here we report the observation of Bloch oscillations of two-particle N00N states, and discuss the nonlocality on the ground of Bell-like inequalities. The time evolution of two-photon N00N states in Bloch oscillators, whether symmetric, antisymmetric or partially symmetric, reveals transitions from particle antibunching to bunching. Consequently, the initial states can be tailored to produce spatial correlations akin to those of bosons, fermions and anyons, presenting potential applications in photonic quantum simulation

Production and electromagnetic decay of hyperons: a feasibility study with HADES as a phase-0 experiment at FAIR

A feasibility study has been performed in order to investigate the performance of the HADES detector to measure the electromagnetic decays of the hyperon resonances Σ(1385)⁰, Λ(1405) and Λ(1520) as well as the production of double strange baryon systems Ξ⁻ and Λ Λ in p + p reactions at a beam kinetic energy of 4.5 GeV. The existing HADES detector will be upgraded by a new Forward Detector, which extends the detector acceptance into a range of polar angles that plays a crucial role for these investigations. The analysis of each channel is preceded by a consideration of the production cross-sections. Afterwards the expected signal count rates using a target consisting of either liquid hydrogen or polyethylene are summarized

Retrieval methods for legal question answering in German

This thesis investigates the effectiveness of various Information Retrieval (IR) Systems in addressing legal questions formulated in layman’s terms within the German legal domain. The study utilizes the GerLayQA[3] dataset, comprising legal questions sourced from the popular online platform “Frag-einen-Anwalt.de” aiming to evaluate the capability of IR systems to retrieve relevant paragraphs from German legal texts in response to these queries. The research employs a diverse range of retrieval methods, including baseline approaches such as TF-IDF and BM25 and more advanced techniques based on state-of-the-art language models. A significant focus is placed on comparing the performance of pre-trained and fine-tuned Bi-Encoder models and highlighting the impact of domain-specific training on retrieval accuracy. Furthermore, the study explores the potential of a Retrieve-and-Re-Rank pipeline combining the efficiency of Bi-Encoders with the precision of Cross-Encoders. This approach is evaluated against single-stage retrieval methods to assess its viability in the legal domain. This work makes a novel contribution by developing and evaluating a Majority Vote IR model, which aggregates results from multiple retrieval methods through a majority voting mechanism and thereby tries to minimize the effect of any single IR system weakness. This ensemble approach is compared against individual models to determine its effectiveness in improving retrieval performance. The performance of these systems is rigorously evaluated using standard information retrieval metrics, including the Precision@k, Recall@k, F1@k-Score, and the Normalized Discounted Cumulative Gain (NDCG). The results are critically analyzed to identify the strengths and limitations of each approach within the context of German Legal Information Retrieval. This research aims to contribute to the growing field of legal AI by providing insights into the applicability and challenges of various IR techniques for processing German layman legal queries. The findings have implications for developing more accessible and efficient legal information systems, potentially closing the gap between complex legal language and public understanding

Occurrence and origin of thallium in mineral and thermal waters from the northern Upper Rhine Graben and adjacent regions, Germany

Although thallium is a widespread and highly toxic element, it is rarely investigated in environmental chemistry due to its typically low concentrations in water. Consequently, little is known about the occurrence of thallium in groundwater and its origin. Here we show that high thallium concentrations of 5 up to 99 µg/l occur in Hesse exclusively in Na-Cl-waters and are locally clustered within the Taunus Border Zone. These variable concentrations seem to result from different thallium sources, varying mixing ratios of brine components, and varying degrees of thallium incorporation in hydrothermal minerals. We present evidence for a thallium origin from Zechstein (Permian) and Oligocene evaporites. A third possible source are basement brines from the Rhenish Massif. As the evaporite deposits are located tens of kilometers away from thallium-bearing wells, high thallium concentrations appear to be a good indicator of deep and regionally circulating brines

Monitoring Tropical Forest Disturbance and Recovery: A Multi-Temporal L-Band SAR Methodology from Annual to Decadal Scales

Tropical forests harbor a significant portion of global biodiversity but are increasingly degraded by human activity. Assessing restoration efforts requires the systematic monitoring of tropical ecosystem status and recovery. Satellite-borne synthetic aperture radar (SAR) supports monitoring changes in vegetation structure and is of particular utility in tropical regions where clouds obscure optical satellite observations. To characterize tropical forest recovery in the Lowland Chocó Biodiversity Hotspot of Ecuador, we apply over a decade of dual-polarized (HH + HV) L-band SAR datasets from the Japanese Space Agency’s (JAXA) PALSAR and PALSAR-2 sensors. We assess the complementarity of the dual-polarized imagery with less frequently available fully-polarimetric imagery, particularly in the context of their respective temporal and informational trade-offs. We examine the radar image texture associated with the dual-pol radar vegetation index (DpRVI) to assess the associated determination of forest and nonforest areas in a topographically complex region, and we examine the equivalent performance of texture measures derived from the Freeman–Durden polarimetric radar decomposition classification scheme applied to the fully polarimetric data. The results demonstrate that employing a dual-polarimetric decomposition classification scheme and subsequently deriving the associated gray-level co-occurrence matrix mean from the DpRVI substantially improved the classification accuracy (from 88.2% to 97.2%). Through this workflow, we develop a new metric, the Radar Forest Regeneration Index (RFRI), and apply it to describe a chronosequence of a tropical forest recovering from naturally regenerating pasture and cacao plots. Our findings from the Lowland Chocó region are particularly relevant to the upcoming NASA-ISRO NISAR mission, which will enable the comprehensive characterization of vegetation structural parameters and significantly enhance the monitoring of biodiversity conservation efforts in tropical forest ecosystems

Decoding Cobalt’s Influence: An Analysis of Environmental Impacts in the Production of NMC Cathode Active Materials for Lithium-ion Batteries

The increased use of lithium-ion batteries has raised concerns about the sustainability of their usage, prompting the need for an environmental assessment. This study evaluates and compares the environmental impacts of NMC 111 and NMC 811 cathode active materials (CAMs) using Life Cycle Assessment (LCA). To improve the accuracy of the assessment, process simulation with HSC Chemistry was employed to model the production of cobalt sulfate (CoSO₄), a key precursor for NMC cathodes. Using the simulated process data, a custom Life Cycle Inventory (LCI) was generated and the environmental impacts of CoSO₄ production were assessed using the ReCiPe 2016, midpoint impact assessment method in OpenLCA were. This custom cobalt sulphate dataset is integrated into the Ecoinvent database by replacing the default CoSO₄ input in NMC 111 and NMC 811 inventories, allowing for a comparative LCA of both chemistries The results indicate that the modelled cobalt sulfate production route has a lower environmental impact than reported literature values, with a GWP of 12.1 kg CO₂-eq per kg of CoSO₄. The majority of emissions and resource use were found to stem from extraction and early processing stages, rather than final refining. When applied to NMC 111 and NMC 811, the results highlight key trade-offs: NMC 111 exhibits a higher GWP (22.4 kg CO₂-eq/kg) due to its greater cobalt content, while NMC 811, with lower cobalt dependency, has a slightly reduced footprint (21.8 kg CO₂-eq/kg). However, the increased nickel content in NMC 811 introduces additional environmental burdens, emphasizing the need for a balanced assessment when selecting cathode chemistries

Cyber Attack Prevention and Detection for Electric Vehicle Charging

The increasing adoption of Electric Vehicles (EVs) is transforming the automotive landscape, driven by the need for a more sustainable transportation sector. To support the widespread use of EVs, an efficient and reliable charging infrastructure is essential. For this, several related communication protocols and backend systems have been established to manage power delivery, authorization, and billing. The main goals are the security of charge session payments and a power grid-friendly scheduling of EV charging loads. The charging of EVs, however, also involves various security risks in associated use-cases. On the one hand, regarding the use-case of charge authorization and billing, existing protocols fail to protect against relevant adversaries. As a result, backend operators are exposed to the risk of significant financial damages and EV users are exposed to severe privacy risks. On the other hand, regarding the use-case of charge session power control and load balancing, existing processes can be manipulated by compromised systems. As a result, adversaries may be able to cause severe physical damage to involved systems and potentially harm power grid operations. In this dissertation, we address selected security risks. For charge authorization and billing, we present three solutions to enhance the preventive security of EV charging protocols. More specifically, we present concepts (i) for the integration of crypto-agility and the use of Post-Quantum Cryptography (PQC), (ii) for the use of Self-Sovereign Identities (SSIs) to enhance EV user privacy, and (iii) for the adoption of a standardized authorization framework to reduce existing complexity. Regarding manipulations of charge session control, we present several concepts for the analysis, detection, and mitigation of related attacks. More specifically, we present (i) a feasibility analysis of resulting attacks on grid stability and a related co-simulation framework, (ii) different anomaly detection concepts for either large-scale coordinated attacks on the grid or attacks in individual charging sessions, (iii) approaches for improving detection performance, including a Generative Adversarial Network (GAN)-based Intrusion Detection System (IDS) optimization and a combination of large-scale and session-based detection, and (iv) methods for attack mitigation based on IDS outputs. All presented concepts are implemented and evaluated with regard to relevant criteria. Concepts for EV charging protocol security are evaluated regarding performance/usability criteria based on proof-of-concept implementations and regarding security/privacy criteria based on formal protocol analyses using the Tamarin prover. Concepts for the analysis, detection, and mitigation of session control-related attacks are implemented with simulation-based approaches to evaluate their effect on involved systems and their detection/mitigation performance. Used Tamarin models and simulation data are published for reproducibility and future use in related studies. Overall, our results show the presented concepts can provide a significant benefit to the security of EV charging in the sector’s future

Algorithmic Maximization of Energy Productivity to Increase Energy Savings in Production Processes

The industrial sector accounts for 25 % of Germany's gross domestic product and 28 % of total final energy consumption in 2022. This sector is therefore both environmentally and economically significant. With renewables accounting for only 6.3 % of final energy production in this sector in 2022, the environmental need for transformation in industrial energy infrastructure is high. To remain globally competitive, the energy productivity of affected production processes must be maintained. This results in highly complex design and operation problems that require algorithmic support. Therefore, this article presents a mathematical programming approach to maximize energy productivity for surface hardening. The multi-objective optimization integrates process models with an evolutionary algorithm in a unified modeling and solution approach. The optimization provides viable solutions to derive adaption of process parameters capable of reducing the energy intensity of the related production process. The approach is validated by its application to the gas heated chamber oven of the ETA Research Factory

Rapid curing of polysilazane coatings at room temperature via chloride-catalyzed hydrolysis/condensation reactions

Moisture curing of polysilazane coatings at room temperature is of advantage to industrial applications, though it often takes a longer time than the other curing methods. To tackle this problem, tetrabutylammonium chloride (TBAC) is applied in this work as an efficient catalyst for the hydrolysis and condensation reactions of polymethyl(hydro)/polydimethylsilazane coatings under ambient conditions. In the suggested catalytic mechanism, the Si–H group is nucleophilically attacked by chloride ions to form a transient Si–Cl group, which is then nucleophilically substituted by a hydroxyl group from the moisture environment. It is found that by adding TBAC in the polysilazane coating, 1.6 times more of the reactive groups (Si–H, Si–NH) are consumed during the curing process in a shorter time (the dry-to-touch time for the uncatalyzed and the TBAC-catalyzed polysilazane coatings are ca. 19 h and 1 h, respectively), while 2 times more of the Si–O–Si groups are formed. Owing to the significantly enhanced crosslinking rate and degree, the coating quality and the mechanical properties are greatly improved. The hardness and the elastic modulus of the coating are increased by a factor of two and four, respectively