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Easy to Handle: Exploring Users' Interactions with an Augmented Reality Human-Machine Interface for Virtual Stops in Automated On-Demand Mobility Scenarios
Get PDFFor the success of future shared automated mobility on-demand (SAMOD) a high quality of service needs to be assured. One key challenge lies in the passenger journey, particularly in finding the designated virtual stop (vStop) for pick-up and identifying the approaching shuttle. Therefore, the new vStop human-machine interface (vStop HMI) concept supports passengers with means of augmented reality (AR). This explorative user study with young adults (N = 44) used a virtual reality (VR) setup to simulate the AR-based vStop HMI and answers two research questions across two consecutive scenarios: (1) When using an AR-based navigation aid like the vStop HMI, users tend to focus heavily on their device while walking, which may increase the risk of negligent roadside behavior. While restricting AR information access during walking might reduce this risk, how does it affect overall user experience? To examine this, we compared a vStop HMI with restricted AR information access against a baseline condition. Results showed positive effects on user experience and acceptance for both HMI versions, although workload was partly negatively affected. (2) When identifying the approaching shuttle, does using the vStop HMI effectively assist users in doing so and lead to positive user experience? Usability testing indicated positive rates of workload, user experience, and acceptance during the shuttle identification task. Overall, the findings suggest that selectively restricting AR information during navigation tasks can help mitigate undesired user behavior in roadside environments while maintaining high levels of pragmatic quality and acceptance. Moreover, the vStop HMI enables seamless shuttle identification, even under complex conditions. By improving these critical stages of the passenger journey, the vStop HMI concept has the potential to enhance the overall quality of SAMOD services and increase public acceptance of future shared, automated, demand-responsive transportation systems
Untersuchung der Flammendynamik in kryogenen Sauerstoff/Methan-Raketenbrennkammern
Get PDFTrotz jahrzehntelanger intensiver Forschung bleiben Verbrennungsinstabilitäten nach wie vor ein bedeutendes Risiko für Flüssigkeitsraketentriebwerke. Durch die Hinwendung zur Treibstoffkombination Sauerstoff/Methan und der diesbezüglich dünnen Forschungslage erhöht sich das Risiko weiter. Die im Rahmen der vorliegenden Dissertation durchgeführten experimentellen Versuche offenbarten sowohl kurzlebige als auch anhaltende Verbrennungsinstabilitäten der ersten longitudinalen Brennkammermode (1L-Mode) für ein charakteristisches Hauptstufen-Injektorelement in einer optisch zugänglichen Raketenbrennkammer. Auch in einem für ein Oberstufen-Triebwerk repräsentativen Experiment sind für bestimmte Betriebsbedingungen Instabilitäten der 1L-Mode aufgetreten. Zusätzlich zeigte sich ebenso eine Anregung der ersten tangentialen Brennkammermode (1T-Mode). Die Motivation dieser Dissertation schöpft sich folglich aus dem Bestreben, ein Verständnis für die Instabilitäten in beiden Versuchsträgern zu erlangen. Der Fokus der vorliegenden Arbeit richtet sich dabei auf die Untersuchung der Flammen-Akustik-Interaktion mittels 2DFlammenvisualisierungen. Die Flammendynamik wurde mittels einzelner Aufnahmen, Sequenzen, aber auch anhand der Dynamic Mode Decomposition untersucht. Die Berechnung zweidimensionaler Rayleigh Indizes zwischen Flammenstrahlung und Druckfeld in der Brennkammer ergaben Werte in Größe und Phasenlage konsistent zum Stabilitätsverhalten. Basierend auf einer Analyse der Flammendynamik scheint der Betrieb des Injektorelements in einem Bereich mit geringer Stabilitätsreserve eine entscheidende Rolle im Entstehungsprozess der Instabilitäten zu spielen. Stark variierende Amplituden des Verbrennungsrauschens dienen dabei als Anregungsquelle von Dynamiken eines breitbandigen Frequenzspektrums wie hydrodynamischen Phänomenen. Durch Synchronisation der Hydrodynamik mit der Akustik können sich dann thermoakustische Instabilitäten ausbilden. Die 1L-Instabilitäten aus den Versuchen repräsentativ für ein Oberstufen Triebwerk wiesen ähnliche Signaturen auf. Die zusätzliche Instabilität der 1T-Mode in diesem Versuchsträger konnte den injektorgekoppelten Instabilitäten zugeordnet werden, welche Gröning in Versuchen mit der gleichen Schubkammer, allerdings mit der Treibstoffkombination Sauerstoff/Wasserstoff, beobachtete. Der hydrodynamische Effekt des Blendenpfeifens als wichtiger Einflussfaktor nach Armbruster konnte ebenfalls bestätigt werden. Als bedeutendes Ergebnis aus der Analyse der Versuchsdaten mit der Treibstoffkombination Sauerstoff/Methan kristallisierte sich der destabilisierende Effekt von zurückversetzten Scher-Koaxial-Injektoren bei der Verbrennung heraus
Exploring sources of ice crystals in cirrus clouds: comparative analysis of two ice nucleation schemes in CAM6
Get PDFIce crystal formation in cirrus clouds is poorly understood, and its representation remains a challenge
in global climate models. To enhance the understanding, a novel ice nucleation parameterization based on the
Kärcher (2022) (K22) scheme is introduced into the NCAR Community Atmosphere Model version 6 (CAM6). To investigate ice formation in cirrus clouds, sensitivity tests are conducted to analyze three ice sources from orographic gravity wave (OGWs), convective detrainment, and turbulence. These tests employ both the K22
scheme and the default Liu and Penner (2005) (LP05) scheme. Model evaluation includes 6-year climatology and nudged simulations representing the Small Particles in Cirrus (SPARTICUS) and O2 = N2 Ratio and CO2 Airborne Southern Ocean Study (ORCAS) campaigns
Potential of RADARSAT Constellation Mission Polarimetric Data for Soil Moisture Estimation in Agriculture
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Capturing patterns and radical changes in long-distance mobility by Flickr data
Get PDFIn contrast to daily travel behaviour, long-distance mobility constitutes a poorly understood area in transport research. Only few national household travel surveys include sections on long-distance travel and these usually focus on the trip to the destination without gathering information about mobility behaviour at the destination. Other sources of data on mobility are either restricted to the national level such as cell phone data or to specific modes of transport such as international flight statistics or floating car data. In addition, the outbreak of the COVID-19 pandemic in 2020 has illustrated how difficult it is to grasp abrupt changes in mobility behaviour.
Against this background this paper investigates the potential of Flickr data for capturing patterns and radical changes in long-distance mobility. Flickr is a social media online platform allowing its users to upload photos and to comment on their own and other users’ photos. It is mainly used for sharing holiday and travel experiences. The results show that Flickr constitutes a viable source of data for capturing patterns and radical changes in long-distance mobility. The distribution of the travel distances, the travel destinations as well as reduction of the mileage of all holiday trips in 2020 in comparison to 2019 due to the pandemic calculated on the basis of the Flickr data is very similar to the same indicators determined on the basis of a national household travel survey, official passenger flight statistics, and other official transportation statistics
Robust control of an actively controlled drogue for autonomous aerial docking
Get PDFAutomating the aerial docking procedure of two aircraft using the probe-and-drogue method can enable fully autonomous docking maneuvers for various applications in the future. For this purpose, a simplified system model of an actively controlled drogue was derived by combining the aerodynamic forces of control surfaces and the drogue body through superposition. Wind tunnel tests and computational fluid dynamics simulations were conducted to identify the aerodynamic coefficients, which were then used for model-based controller design.
Robust control strategies such as sliding mode control, super twisting control, and PID control, which served as a baseline, were implemented and tested in a comprehensive probe-and-drogue simulation under various external disturbances. A super twisting disturbance observer was added to enhance the controllers' performance. Furthermore, all tested control architectures were modified by adding incremental nonlinear dynamic inversion to reduce perturbation rejecting controller gains while preserving control performance.
The derived system model and the implemented controllers were shown to be effective for this control problem. Specifically, the application of incremental nonlinear dynamic inversion can lead to reduced control input variation without compromising control performance
Evaluating Prompt Engineering Strategies for Sentiment Control in AI-Generated Texts
Get PDFThe groundbreaking capabilities of Large Language Models (LLMs) offer new opportunities for enhancing human-computer interaction through emotion-adaptive Artificial Intelligence (AI). However, deliberately controlling the sentiment in these systems remains challenging. The present study investigates the potential of prompt engineering for controlling sentiment in LLM-generated text, providing a resource-sensitive and accessible alternative to existing methods.
Using Ekman's six basic emotions (e.g., joy, disgust), we examine various prompting techniques, including Zero-Shot and Chain-of-Thought prompting using \textit{gpt-3.5-turbo}, and compare it to fine-tuning. Our results indicate that prompt engineering effectively steers emotions in AI-generated texts, offering a practical and cost-effective alternative to fine-tuning, especially in data-constrained settings. In this regard, Few-Shot prompting with human-written examples was the most effective among other techniques, likely due to the additional task-specific guidance. The findings contribute valuable insights towards developing emotion-adaptive AI systems
A comparison of the toxicity and asphyxiation risk during bunkering of LH2, LNG and NH3 by means of a quantitative risk assessment
Get PDFTo achieve the GHG reduction goals, hydrogen, Natural Gas and ammonia are considered as marine fuel in their liquefied form. Hydrogen and Natural Gas need to be liquified at cryogenic temperatures, whereas ammonia can be liquefied through the application of moderate pressure, approximately 10 bar, or through the reduction of temperature to approximately -33 ℃. LNG is already employed in maritime transportation in accordance with established safety protocols. In contrast, the utilization of liquid hydrogen (LH2) and ammonia is currently limited to pilot projects. Both liquid hydrogen and ammonia have the potential to be climate-neutral fuels, depending on the respective production pathway. However, concerns regarding their safety have been raised. Thus, the overarching aim of this investigation is it to addresses these concerns by conducting a comparative analysis of the safety of bunkering these fuels, with a particular focus on toxicity and asphyxiation hazards.
Risk is defined as the “combination of the probability of occurrence of harm and the severity of that harm”. A quantitative risk assessment is thus conducted in two steps: first, to identify the probability through a frequency analysis and second, to identify the severity through a consequence analysis. For this study, an event tree is introduced to combine reliability data for the occurrence of a leak with a model for the ignition probability. The second step of a quantitative risk assessment is the consequence analysis, which quantifies the severity of the harms identified through the event tree. This study will use the necessary safety distance as the threshold for the severity.
The approach outlined above for such a quantitative risk assessment is conducted to compare the toxicity risk of bunkering ammonia and the asphyxiation risk of bunkering liquid hydrogen and liquified natural gas. In the initial phase, a frequency analysis is undertaken. The results are employed to identify the events with the highest frequency of occurrence. In the second step, the events not resulting in an ignition are further investigated. The hazard arising from these events is usually the toxicity of ammonia or the asphyxiation, due to the displacement of oxygen by hydrogen or natural gas (i.e., both substances are not toxic). A Gaussian dispersion model is employed to calculate the safety distance necessary for the different fuels. Subsequently, both the necessary safety distance and the frequency of harmful events of all three fuels are then compared. Result of the study will be the comparison of the safety distances and the frequencies. A fuel that requires smaller safety distances and the harmful event occurs less frequent can be considered safer
Stress resistance of halophilic Archaea from Lunenburg, Germany: implications for astrobiology
Get PDFHere we present the resistance of two halophilic Archaea, Halorubrum (Hrr.) sp. AS12 and Haloarcula (Har.). sp. NS06, isolated from the brine in Lunenburg, Germany, to stress factors including desiccation, radiation and elevated perchlorate concentration. This is the first study to describe the stress resistance of halophilic Archaea isolated from the Lunenburg brine. While Hrr. sp. AS12 tolerates desiccation up to 45 days with a -log3 reduction in survival, Har. sp. NS06 displays a strong decline in viability and no detectable survival following 21 days. In contrast, Hrr. sp. AS12 was more sensitive towards X-Ray irradiation with a significant decline in viability (D₁₀ 228,2 ± 8,9 Gy) while Har. sp. NS06 showed a slight decline in survival following exposure to 1 kGy. The resistance of both strains against germicidal UV-C254nm radiation follows a similar pattern when compared to X-ray exposure with Hrr. sp. AS12 displaying more sensitivity to UV-C radiation (F₁₀ 111,6 ± 6,4 J/m²) compared to Har. sp. NS06 (F₁₀ 194,9 ± 13,7 J/m²). Exposure to He, Ar, and Fe heavy ions up to 500 Gy showed little effect on the survivability; however, the transport control of Hrr. sp. AS12 showed a strong decline (-log3 reduction) in survival. Both strains revealed increased growth in the presence of perchlorates (NaClO₄ and MgClO₄) with a clear preference to NaClO₄ up to 5%. Our results provide a first insight into the stress resistance of these two isolates and will further develop our understanding of the parameters of life on Earth and potentially on other planets