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Dew-Point Density Measurements of Gas Mixtures with Low Uncertainty
No full textThe development of models for predicting thermodynamic properties is essential for designing technical systems that reduce energy consumption and minimize environmental impact. A key requirement for advancing these models is high-quality experimental data with low uncertainties. Among such data, dew-point properties of gas mixtures are particularly important for progress in thermodynamics and process engineering. However, measuring properties along the saturation line presents challenges due to effects arising during phase transitions that can distort results. These challenges require advanced experimental techniques, a robust dataset, and a sound uncertainty analysis model.
The current state-of-the-art approach for density and dew-point measurements relies on gravimetric instruments using the Magnetic Suspension Balance (MSB). Although widely used, these instruments have limitations with pure gases and mixtures due to sorption effects. Two major issues near the dew line include: (1) adsorption on the object immersed in the fluid, affecting weight and calculated densities, and (2) selective adsorption on internal surfaces, altering fluid composition. These effects lead to higher uncertainties in characterizing densities and fluid composition. Addressing them is critical for improving data quality and advancing modeling.
An improved gravimetric apparatus for dew-point density measurements, the Four-Sinker Densimeter (FSD), was designed by Moritz et al. (2017). This instrument simultaneously determines fluid density and adsorption loads, partially correcting the distorting effects. Achieving low uncertainties requires accurate calibrations and precise determination of key parameters. Among these, the low-uncertainty determination of sinker volumes is especially critical for accurate buoyancy force estimation—one of the main calibration challenges.
Given the FSD’s complexity and the limitations of existing uncertainty analysis methods, a more accessible method for uncertainty estimation was developed to assess the quality of measured densities and adsorption data.
Since gravimetric systems alone cannot provide detailed information about the adsorbate, gravimetric data analysis was combined with Molecular Dynamics Simulation (MDS). MDS offers insights into selective adsorption of mixture components and the density of the adsorbed phase.
The challenge of measuring dew-point densities of gas mixtures is interdisciplinary. It involves advancing gravimetric techniques, implementing high-accuracy calibrations, developing an accessible uncertainty analysis method, and using MDS for deeper insight.
This work focuses on the setup and commissioning of the FSD. Instrument calibrations and low-uncertainty parameter determinations were performed. A hydrostatic comparator, used to determine the volume of sinkers, was evaluated by measuring 14 objects with varying densities. A novel measurement sequence reduced the time required for volume determination. The comparator showed high precision, with average expanded uncertainties (k = 2) of 0.000041 cm³. Additionally, a simpler comparator suitable for academic or industrial research was developed, though with higher uncertainties.
Subsequently, first measurements were performed using the FSD. Densities of He, Ar, and N₂ were measured from (5.68 to 180.7) kg·m⁻³ and compared with densities from equations of state and literature datasets. Adsorption on gold sinker surfaces was studied up to saturation pressure for CO₂, C₂H₆, and C₃H₈, with observed adsorption loads ϒ between (0.10 and 2.2) µg·cm⁻². Results were compared with literature data and isotherms from the previous state-of-the-art instrument, the tandem-sinker densimeter. Measurements of a binary gas mixture (0.75 CO₂ + 0.25 C₃H₈) were also conducted.
To evaluate data quality, a new methodology for uncertainty analysis was developed. This numerical approach replaces partial derivatives from the Guide to the Expression of Uncertainty in Measurement (GUM), enabling analysis of complex systems. It uses numerically evaluated sensitivity coefficients, hence 'sensitivity analysis method', to assess system behavior. Tested on three case studies—including volume determination and FSD measurements—the method confirmed the FSD’s performance, establishing it as the new state-of-the-art. Where possible, uncertainties were compared to GUM-based or literature values. The method has proven reliable and practical and could become a standard in thermodynamic property research, accessible to researchers of varying expertise.
Adsorption isotherms of pure fluids were used to validate corresponding MDS models, forming a robust foundation for integrating gravimetric analysis and MDS. This integrated method shows promise. Using simulation-derived data, an empirical model was developed to estimate adsorbate density via symbolic regression. Future work will extend these simulations to mixtures, enabling improved correction of sorption effects in gravimetric measurements.
This dissertation thus provides a solid foundation for advancing research on mixture systems. The proposed methodology enables correction of selective adsorption, supporting dew-point density measurements of gas mixtures with low uncertainty.:Nomenclature
Abstract
Kurzfassung
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Summary and Impact
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Development and Evaluation of a Community Health Program to Promote Physical Activity Among Vulnerable Community-Dwelling Older Adults: Protocol for a Prospective Cohort Study
No full textBackground: Vulnerable older adults have a high risk of morbidity and mortality. Regular physical activity (PA) can have a positive effect on the health and health-related behavior of this specific target group. However, evidence of the impact and feasibility of community-based PA promotion interventions for vulnerable older adults is still limited.
Objective: The BeTaSen (Bewegungs-Tandems in den Lebenswelten Chemnitzer Seniorinnen und Senioren: ein Beitrag zur kommunalen Gesundheitsförderung) study aims to evaluate the (1) impact as well as the (2) feasibility, acceptance, and usefulness of a 12-month low-threshold PA intervention program for community-dwelling vulnerable older adults.
Methods: For our population-based prospective observational cohort study, a total of 120 vulnerable older adults (aged 75 years or older) in the area of Chemnitz (Germany) will be recruited to participate in (1) weekly neighborhood-based low-threshold PA meetings with trained mentors (activity tandems) and (2) monthly exercise meetings led by trained exercise instructors. Within the intervention, participants will be encouraged to perform the PA independently. Participants will complete assessments, which will include questionnaires as well as objective measurements of their physical, cognitive, and psychosocial health at 3 different time points (baseline, 6 months after the start, and 6 months after the end of the intervention). Additionally, a process evaluation will be performed, including questionnaires and qualitative interviews, involving the participants, mentors, and municipal project partner representatives.
Results: The BeTaSen project process began in October 2021, with the start of data collection and intervention in August 2022 in the first neighborhoods of the city of Chemnitz. A total of 86 participants were recruited at the time of submission of the manuscript. Longitudinal results are expected by 2025.
Conclusions: This study’s results will provide insights on (1) the PA behavior of vulnerable older adults as well as the impact of PA interventions on health-related outcomes such as cognitive, physical, and psychosocial health, and (2) the feasible and useful components of community-based PA interventions. Thus, this pilot study contributes to future recommendations and provides a basis for further research, such as the development of feasible and sustainable target group–specific interventions in community settings
Wechselbeziehungen zwischen Englischer Linguistik und universitärem Sprachpraxisunterricht
No full textIf the relationship between English linguistics and practical language teaching is discussed in the linguistic literature, it is usually treated as unidirectional, from linguistics to language teaching, and the focus is on learners in the school context. The present contribution, by contrast, explores the relationship between linguistics and practical language teaching systematically and from both perspectives, and it focuses on advanced learners who study English philology at university level. Its author draws not only on the existing research literature but also on her own experience as a researcher and teacher of English language and linguistics. This paper discusses in what ways linguistics can contribute to improving advanced foreign language teaching at university level and argues that insights which were gained from practical language teaching can also contribute to the advancement of linguistic research and teaching (e.g. through the analysis of learner corpora). In spite of the frequently found administrative separation between the philological subjects and the practical language classes offered by language centres at German universities, one may therefore conclude that there are manifold mutual relations between research on and teaching of English linguistics and English as a foreign language at university level.Wenn in der linguistischen Literatur die Beziehung zwischen Englischer Linguistik und fremdsprachlichem Unterricht thematisiert wird, dann meist für eine schulische Lernerzielgruppe und in der Regel als einseitiger Einfluss von der Linguistik auf die Lehre. Im Gegensatz dazu erkundet der vorliegende Beitrag systematisch die Wechselbeziehungen zwischen Linguistik und Sprachpraxisunterricht in den englischsprachigen Philologien an der Universität und bezieht dabei beide Richtungen mit ein. Auf der Grundlage der wissenschaftlichen Forschungsliteratur und eigener Erfahrungen als Forschende und Lehrende in Linguistik und Sprachpraxis wird erörtert, welchen Beitrag die Englische Linguistik für den fortgeschrittenen Fremdsprachenunterricht leisten kann. Darüber hinaus wird argumentiert, dass auch Erkenntnisse, die aus dem sprachpraktischen Unterricht gewonnen wurden, Eingang in die linguisti-
sche Forschung und Lehre finden können (z.B. durch die Analyse von Lernerkorpora). Trotz der häufig vorzufindenden administrativen Trennung zwischen Fachwissenschaften und universitärer Sprachpraxis gibt es folglich vielfältige Verbindungen zwischen linguistischer und sprachpraktischer Forschung und Lehre
Researching possible surface microstructural changes induced by hybrid laser-ECM
No full textHybrid laser electrochemical machining (LECM) is a relatively new technique for machining
advanced multiphase materials like niobium carbide (NbC) cermet. Although previous research has
shown that it can remove material without inducing thermal defects with careful control of energy
balance for thermal load management, its influence on surface microstructural changes remains to
be investigated. Therefore, in this study the surface oxide layer after machining was analysed by
preparing thin samples (1.5 mm thick) with the complete surface processed with ECM and LECM to
be compatible with X-ray photoelectron spectroscopy (XPS) analysis. The oxide states of the
compositional elements i.e. niobium, tungsten, titanium and nickel were investigated, which
remained same for the different processing conditions thereby confirming that material removal
primarily occurs through anodic dissolution and laser assistance accelerates reaction kinetics
Modeling Concept for a Wire ECM Process with High Speed Wire Flushing
No full textWire Electrochemical Machining is – despite all efforts within the last decade – still a manufacturing
process lacking technology readiness for industrial application. Precision and productivity are not yet
competitive in comparison with other technologies. The crucial challenge is to ensure sufficient
flushing with electrolyte medium. In previous investigations the use of high wire speeds up to 12 m/s
had delivered promising results. How far flushing can be further improved with even higher wire
speeds is therefore an interesting field of investigation. In this work a concept for numerical modelling
of the process is presented that will indicate the potential of the process. Quantities like electrolyte
flow, temperature and conductivity are thoroughly investigated. Thus, the concept presented in this
study will eventually lead to the estimation of the achievable productivity of this variant of Wire ECM
as well as insights into the process itself
Highly Sensitive Enhanced Electrochemical Sensors for Direct Detection of Nitro-compounds (N) and Phosphate (P) for Water Quality Monitoring
No full textThis thesis develops highly sensitive electrochemical sensors for continuous monitoring of nitrogen and phosphorus compounds in water. Overuse of these fertilizers dramatically impacts aquatic ecosystems and poses health risks, necessitating efficient field-deployable sensors.
Carbon screen-printed electrodes (CSPE) serve as transducers for all analytes due to their ease of use, high surface area, and minimal sample requirements. Three sensors were developed: (1) Gold nanoparticles (~12 nm) capped with polyethylenimine for nitrite detection, achieving the lowest reported limit of detection (LoD) at 2.5 nM with linear range 0.01-4.0 µM. (2) Eco-friendly chitosan-tetra sulfonated copper phthalocyanine composite for nitrite (40-100 µM, LoD 0.06 µM at pH 6) and nitrate detection (1-10 µM, LoD 0.05 µM at pH 2). (3) Reagent-less phosphate sensor using copper phthalocyanines and modified carbon nanotubes, achieving 0.31 nM LoD in a rangeof 0.001-100 µM.
All sensors demonstrated low interference, high reproducibility (<10% RSD), and successful validation in real samples (tap water, olive water, aquaponics) with 69.94-120% recovery rates. A 3D-printed flow cell integrated all sensors for simultaneous nutrient detection in complex water samples.:Chapter 1 Introduction
Chapter 2 Electrochemical sensors theoretical background
Chapter 3 State of the art on nitrogen and phosphate compounds determination
Chapter 4 Electrochemical detection of nitrite at trace levels
Chapter 5 Electrochemical detection of nitrate and nitrite
Chapter 6 Phosphate electrochemical detection
Chapter 7 Proof of concept and application in real scenario
Chapter 8 Conclusion and outloo
Human Factors in EU Whole Vehicle Type Approval
No full textWe will present results of an EU automotive regulations analysis related to human factors, summarize potential challenges regarding the assessment of compliance to selected requirements and provide an outlook on expected future regulatory developments in the human factors space creating new opportunities and challenges for the parties involved
Evaluation of External HMIs for Automated Shuttles Based on a Real-World Platform
No full textThis study examines Human-Machine Interface (HMI) systems for automated shuttles, focusing on communication with cyclists. Using a Virtual Reality (VR) simulation based on a real automated shuttle platform within the Ride the Future project, four HMI systems were tested: purple light projections, emotional eyes, auditory alerts, and informative text. These systems aimed to enhance safety and trust by signalling the shuttle’s intentions. The study involved 28 participants, including both individuals familiar with the shuttles’ existing communication methods and those encountering them for the first time. Findings indicate that auditory alerts and text-based HMIs were the most effective, being clear and easily understood. In contrast, the purple light was difficult to see in daylight, and the emotional eyes were often misinterpreted. Principal Component Analysis (PCA) identified three key factors: predictability, endangerment, and practicality, underscoring the need for intuitive and simple designs over purely innovative solutions. Participants stressed that clarity and familiarity are crucial for HMI effectiveness. By using simulation while maintaining a foundation in real-world shuttle technology, this study provides controlled yet applicable insights into HMI usability. The findings highlight the potential of HMIs to support automated shuttle integration into public transport by improving road safety and user experience. Future research should assess the long-term impact of these systems in real-world traffic conditions. The motivation for the present study arises from this limitation, aiming to contribute to the field by empirically examining how eHMI functions in an authentic urban traffic environment
(How) can users be motivated to accept a lower minimum range when using smart charging? Results from an online study in Germany
No full textSmart charging is an effective approach to balance the grid in times of ‘green’ energy shortage or overload (Wong et al., 2023). However, smart charging requires more flexibility from users, such as accepting longer charging times and smaller range buffers (Marxen et al., 2023), which may reduce users’ willingness to participate in smart charging (Kämpfe et al., 2022). Behavioural interventions have been shown to be effective in promoting smart charging decisions among BEV users (Kramer et al., 2023). In an online experiment (N = 74) we tested the effectiveness of two interventions motivating users to accept smaller driving ranges: a coping-orientated intervention with energy-efficient driving tips (n = 20) and a monetary intervention (n = 20) against a control group (n = 29). Participants had to choose a preferred minimum range for a hypothetical 150 km trip (from 150 to 400 km) before and after the intervention. Across groups, the preferred range declined following the intervention. A condition × group interaction revealed that only the coping intervention produced a significant reduction (−27 km; p = .002), whereas the monetary intervention had no significant effect (−16 km; p = .082). Thus, users’ range preferences and their mobility flexibility need to be considered when promoting smart charging
Bidirectional Charging Acceptance: Effects of Information Detail, User Characteristics, and Interaction Experience
No full textUser acceptance plays a key role in the transition to intelligent charging infrastructures. A core concept that is part of sustainable energy mobility is bidirectional charging (BC). This technology enables electric vehicles (EVs) not only to draw energy from the grid, but also to feed energy back into it. However, public acceptance of such technologies remains limited. Hence, this study investigates how varying levels of information detail, user characteristics, and interaction with an EV charging prototype app with BC capabilities influence user acceptance. We employed a 3×2 mixed-design experiment (N = 33) measuring the Technology Acceptance Model (TAM) determinants perceived usefulness (PU), perceived ease of use (PEU), and behavioral intention (BI) before and after an interaction with an app prototype for smart charging. These preliminary findings are part of a wider ongoing study that is also investigating users' understanding and mental models of BC. The results suggest that the interaction with the prototype significantly increased BI, PU, and PEU, with the most substantial changes observed in the group with the highest level of information detail. Affinity for Technology Interaction (ATI) emerged as a significant predictor of BI. However, due to an interaction effect between gender and group assignment, the results of this study must be treated with caution. Therefore, we present these findings as preliminary insights into the variables shaping users’ acceptance of BC apps and highlight the need for further research to validate these effects