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Interaction of crossflow modes with forward-facing steps: insights gained from DNS
No full textIn recent studies, both experiments and simulations have explored how surface roughness affects laminar-turbulent transition in swept-wing scenarios. This work specifically addresses the effects of forward-facing steps (FFS) and is inspired by the experimental observations of Rius-Vidales &
Kotsonis [1], which identified a non-monotonic relationship between step height and the location of transition. Notably, an unprecedented delay in transition —compared to scenarios without FFS— occurs when stationary crossflow vortices interact with a shallow FFS. Conversely, the interaction with a higher FFS leads to an upstream advancement of the transition front location.
The present work aims to replicate the experimental setup and conditions described in [1] via direct numerical simulation (DNS), with the ultimate goal of further elucidating the flow physics behind the observed experimental behaviors
A Serious Game as a Tool for User-centered Design of Mobility Solutions
No full textBefore the implementation of new mobility solutions, it is often difficult to encourage and enable potential users to participate in the design process, to predict acceptance, and to determine the influence of individual design pa-rameters on use intentions. A serious game involving repeated mobility choices and, at the same time, fun to play might be a useful tool to allow for user studies and participation in this situation. We developed a concept of such a game in the context of intermodal transport. A first prototype was im-plemented and subjected to an early test with respect to user experience and usability through an evaluation with seven experts. At the current state of development, flow experience, measured by the flow short scale (FKS), was medium. Usability, measured by the system usability scale (SUS), was low, and the heuristic evaluation yielded many hints for improvement. Based on the insights gained, the development of the game will be continued to pre-pare it for a user test assessing the potential of the method for studying user preferences in the transport system
Extraction of spatially confined small-scale waves from high-resolution all-sky airglow images based on machine learning
No full textLimitations and Potentials of Quantum Computing for InSAR Phase Unwrapping
No full textPhase unwrapping is the reconstruction of an absolute phase given its values modulo . This post-processing step is commonly used in synthetic aperture radar interferometry (InSAR) for applications such as estimating topographic height and surface deformation. Conventional InSAR unwrapping techniques are designed for large-scale phase correction, focusing on overall consistency and often relying on auxiliary data, such as additional acquisitions or ground data, to compensate for significant local height changes. Motivated by recent advances in quantum algorithms for optimisation and phase retrieval, we explore the potential of gate-based quantum computing and hybrid quantum approaches for addressing the phase unwrapping problem. We provide an overview of the fundamental and practical limitations of quantum computing, with particular emphasis on the constraints imposed by the current noisy intermediate-scale quantum era. Furthermore, we highlight three promising directions for improved phase unwrapping: accelerating existing optimisation methods, enabling direct access to formulations, and enhancing the performance of machine learning-based approaches
UWB-Based Vulnerable Road Users Protection System at Intersections: Concept, Measurements and First Results
No full textMultipath-enhanced device-free localization (MDFL) leverages user-induced fading in the received power of both line-of-sight (LoS) and multipath components (MPCs) to localize unequipped vulnerable road users (VRUs). In this paper, we report real-world measurement campaign at a busy intersection to evaluate the feasibility of MDFL for sensing VRUs in complex outdoor environments. We describe the measurement setup, the processing pipeline, and characterize pedestrian-induced power changes on LoS and MPCs across links, showing repeatable, geometry consistent power changes
along the pedestrian trajectory. The results confirm that a sensing repetition rate of 8 Hz is sufficient in order to detect a pedestrian at walking speed. Overall, the measurements demonstrate the feasibility of using MDFL at road intersections for VRU sensing and localization
Modeling and Energetic Assessment of Reactor Technologies for Solar Energy Conversion into Fuels and Chemicals
No full textAcknowledging the continued demand for chemical energy carriers and hydrocarbon feedstocks as material inputs for the chemical industry while moving away from fossil hydrocarbons resources in an effort to reduce the resulting carbon dioxide (CO2) emissions, this work is concerned with the study and energetic assessment of solar driven chemical fuel processing technologies via mathematical modeling and simulation. Specifically, three reactor technologies implementing photo-electrochemical, photo-thermal and electrochemical energy conversion are discussed against the background of the FlowPhotoChem research project that developed and demonstrated experimentally these directly or indirectly light driven technologies followed by the integration of the individual reactors into an integrated system for the production of ethylene (C2H4) from CO2 and water (H2O). To aid understanding of these reactor technologies and as prerequisite for numerical simulation, mathematical models on the level of the individual reactors are developed, and associated model parameters are determined via measurement or theoretical calculation. For the photo-electrochemical and electrochemical reactors, zero-dimensional, phenomenological models based on the description via polarization curves are employed. The Chosen phenomenological approach is efficient in terms of modeling effort and computational time while providing sufficient predictive accuracy for the uses within this work considering the limited availability of experimental data. On the other hand, for the photo-thermal reactor, a spatially resolved (three-dimensional), comprehensive multiphysics model was developed, taking into account heat- and multi-component species mass transfer including chemical reactions in porous media. Macroscopic, effective equations and parameters are derived starting from the microscopic or pore level description via the homogenization method. Space discretization of the model equations is performed with the Voronoi box based finite volume method and time discretization with the implicit Euler scheme. The implementation of the discretized equations is realized in the Julia programming language utilizing the package VoronoiFVM.jl. The development of the comprehensive model is motivated by the better availability of experimental data resulting from the close involvement in the development of the reactor and the fact that a phenomenological model with desirable characteristics as for the other two reactors is not expected to exist. Validation of the individual reactor models is performed by comparison with experimental data and metrics for energy conversion efficiency from solar to chemical energy for the respective reactor technologies are derived and evaluated for relevant operating conditions. The models on the individual reactor level are then integrated into a stationary System model which is implemented in the process simulation software Aspen Custom Modeler where the system model closely resembles the physical system constructed in the FlowPhotoChem project. First, the system model is applied to simulate the operating Point exhibiting the highest solar-to-chemical efficiency during experimental testing showing good agreement between simulation and experiment. Second, the parameter space is explored via simulation and improved operating conditions are identified. The work concludes with a summary and an outlook on future research directions taking Advantage of the computational tools developed in this work
Monitoring urban green space for climate-resilient development in the face of rapid urbanization: A tale of two Vietnamese cities
Full text linkUrban green space (UGS) contributes to sustainable and climate-resilient urban development by providing ecosystem services and enhancing public health. In rapidly urbanizing cities, UGS is compromised by expanding built infrastructure, leading to loss and fragmentation of green areas. This study employs a resource-efficient remote sensing approach for monitoring UGS dynamics in two examples of rapid urbanization, Hanoi and Ho Chi Minh City (HCMC) in Vietnam. The approach identifies UGS by applying a ground-truthed threshold to Normalized Difference Vegetation Index quartile maps (NDVI–P75) from nine years of open-access Sentinel-2 imagery before blending it with national census data. The results indicate a pronounced spatial heterogeneity in UGS distributions, with low densities in urban cores and greater availability in the peripheral districts of both metropolises. The temporal analysis shows diverging trends: while UGS areas in Hanoi are relatively stable overall but declining per capita due to ongoing urbanization, HCMC experiences a general decline in both UGS indicators. The findings emphasize the urgent need for implementing integrated UGS strategies that account for the diverse socio-economic drivers of UGS loss. By offering a robust and reproducible methodology for monitoring UGS, this research highlights the potential of remote sensing tools to inform urban planning and policy development. This approach is highly transferable to other urban contexts globally, demonstrating an effective and transparent pathway to foster climate-justice and “sustainable cities and communities” in line with the United Nations’ Sustainable Development Goal No. 11
