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Cooperative Trajectory Planning through Negotiation for a Stand-Up Aid
No full textShared control research offers promising opportunities and improvements for people with limited mobility through robotic assistance, for example in wheelchair applications or rehabilitation systems. Such systems also offer a wide range of possibilities for assisting people with limited mobility out of bed. In contrast to existing works in the field of shared control, in which the reference trajectory is assumed to be known to both partners or is specified by one of them in a leader-follower approach, this work aims to enable both partners to influence the reference trajectory. To this end, two existing approaches from the literature are implemented. The first one is a trajectory deformation approach and the other an existing work on cooperative agreement through trajectory negotiation. Both are investigated in simulations and the results show that the cooperative agreement process requires less control effort on the part of the humans to communicate their trajectory request than in trajectory negotiation. The results thus promise an advantage through cooperation already at the trajectory level of a shared control system
Influence of surface chemisorption and release processes of water vapour and carbon dioxide on radiation-induced effects in lithium-based ceramic materials
No full textAdvanced ceramic breeder (ACB) pebbles, composed of lithium orthosilicate (LiSiO) with additions of lithium metatitanate (LiTiO) as the second phase, are currently being developed and extensively tested as the European Union’s reference material for tritium breeding in future thermonuclear fusion reactors. In the present work, the influence of sample preparation, storage conditions, and thermal treatment on the surface microstructure and chemical composition of pellets prepared from the biphasic ACB pebbles was systematically investigated. Surface characterisation was performed using scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDS), attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy, and secondary ion mass spectrometry (SIMS). The gravimetric measurements and thermogravimetry/differential scanning calorimetry (TG/DSC) were applied to study the chemisorption and release processes of water (HO) vapour and carbon dioxide (CO) during storage up to 1050 h at room temperature in air atmosphere of varying humidity and subsequent step-wise thermal treatment up to 900°C. The formation and accumulation of paramagnetic radiation-induced defect centres under exposure to X-rays with energies up to 45 keV were analysed using electron paramagnetic resonance (EPR) spectroscopy. On the basis of the obtained results, it can be concluded that storage in high humidity significantly affects the surface microstructure and chemical composition of the pellets, which leads to the formation of a dense layer of chemisorption products of HO vapour and CO characterised by highly asymmetric structures, primarily consisting of lithium carbonate (LiCO). Although thermal treatment can largely reverse these high humidity-induced changes, it does not fully restore the original state of intrinsic and extrinsic defects, which can subsequently influence the formation and accumulation of paramagnetic centres during irradiation
Chekhov’s Guns and Damocles’ Swords in Real-World Information Security: Post-Quantum Cryptography, Internal Attacker and the Random Oracle
No full textDiese Arbeit behandelt kritische Bedrohungen in realen kryptografischen Anwendungen,
diem¨oglicherweise nicht sofort offensichtlich sind, aber jederzeit
auftreten k¨onnen. Der Autor identifiziert und geht auf drei solche Bedrohungen
ein, die die Sicherheit moderner cyber-physischer Systemnetzwerke in
Frage stellen.
Zunächst wird die Bedrohung durch Quantencomputer untersucht und die
Notwendigkeit für kryptografische Annahmen hervorgehoben, die quantensicher
sind, d.h. sie bleiben sowohl gegenüber klassischen als auch gegenüber
Quantencomputern sicher. Die Arbeit des Autors geht auf diese Herausforderungen
durch eine Reihe von Fortschritten ein, die womöglich quantensichere
Annahmen einbeziehen.
Zweitens wird in der Arbeit die Bedrohung durch interne Angreifer behandelt,
die oft in der industriellen Sicherheit zweitrangig behandelt wurde. Der Autor
argumentiert jedoch, dass das Vernachl¨assigen von Schutzmaßnahmen gegen
interne Angreifer die Gesamtsicherheit untergräbt, da interne Komponenten
kompromittiert werden k¨onnen. Dies wird durch die Entwicklung sicherer
Protokolle f¨ur Anwendungen wie Kontaktverfolgung verdeutlicht, bei denen
das Risiko einer landesweiten Überwachung durch interne Angreifer durch
ein ”honest-but-curious” Modell gemindert wird.
Dar¨uber hinaus präsentiert die Arbeit ein Protokoll f¨ur ausgelagerte Berechnungen,
das es erm¨oglicht, sensible Daten sicher zu verarbeiten, auch wenn
der Server mit Clients kolludieren kann. Dies geschieht durch eine formale
Neubetrachtung eines Paradigmas f¨ur ausgelagerte Berechnungen, das den
Schutz personenbezogener Daten vor internen Bedrohungen gewährleistet.
Schließlich wird die Bedrohung durch den Zufalls-Orakel-Ansatz (Random
Oracle) untersucht, der die Zuverl¨assigkeit des Einsatzes des Random Oracles
in kryptografischen Konstruktionen diskutiert. Obwohl die Random Oracle
Heuristik in der realen Kryptografie von unsch¨atzbarem Wert ist, ist auch Funktionen ersetzt wird. Als Reaktion darauf präsentiert die Arbeit ein sicheres
Kommunikationsprotokoll, das den Bedarf an Zufalls-Orakeln vermeidet
und einen formal fundierteren Ansatz für sichere Nachrichten¨ubertragungen
bietet. Obwohl dieses Protokoll weniger effizient ist als seine Pendants, die
auf dem Zufalls-Orakel basieren, erreicht es wesentliche Verbesserungen
gegen¨uber früheren nicht-Zufalls-Orakel-Konstruktionen.
Insgesamt trägt diese Arbeit zur Entwicklung kryptografischer Lösungen bei,
die unbehandelte Bedrohungen in realen Anwendungen angehen und darauf
abzielen, sowohl die Sicherheit als auch die praktische Anwendbarkeit kryptografischer
Systeme angesichts der sich entwickelnden Herausforderungen
zu verbessern
Efficient Wildland Fire Simulation via Nonlinear Model Order Reduction
No full textWe propose a new hyper-reduction method for a recently introduced nonlinear model reduction framework based on dynamically transformed basis functions and especially well-suited for transport-dominated systems. Furthermore, we discuss applying this new method to a wildland fire model whose dynamics feature traveling combustion waves and local ignition and is thus challenging for classical model reduction schemes based on linear subspaces. The new hyper-reduction framework allows us to construct parameter-dependent reduced-order models (ROMs) with efficient offline/online decomposition. The numerical experiments demonstrate that the ROMs obtained by the novel method outperform those obtained by a classical approach using the proper orthogonal decomposition and the discrete empirical interpolation method in terms of run time and accuracy
Kulturelle Schulentwicklung - von der Vision zur Praxis
No full textDas Video ist Teil des "Digitalen Kulturschule-KITs", welches ein Angebot für Schulleitungen und Schulentwicklungsinteressierte ist, die sich systematisch mit dem Thema Kulturschule auseinandersetzen möchten
Visualization of Defect-Induced Interband Proximity Effect at the Nanoscale
No full textThe majority of superconductors have more than one Fermi surface, on which the electrons pair below the critical temperature, yet their behavior can be well described by a single-band Bardeen-Cooper-Schrieffer theory. This is mostly due to interband scattering, especially in superconductors in the dirty limit, rigidly linking the pairing amplitude of the bands. This has limited experimental studies of the complex physics of multiband superconductivity. Here, we utilize the fact that elementary Pb—as a clean limit system—has two Fermi surfaces that are only weakly coupled by interband scattering, allowing the formation of two separate condensates. By studying stacking fault tetrahedra with a millikelvin scanning tunneling microscope, we show how to locally tune interband coupling ranging from weak to strong coupling and modify the superconducting order parameters from two well separated gaps to one merged gap around defects. The experiments critically test the theory of multiband superconductors and give a route to access a wide range of predicted quantum effects in these systems
Role of the lipid matrix in the action of local anesthetics
No full textThe binding of local anesthetics (LAs) to cell membranes is required for LAs to reach the target ion channels, but lipid interactions may also play a role in a purely membrane-mediated mode of activity. Here, we used solid-state NMR and further biophysical techniques to characterize the effect of six LAs covering a wide range of structures and properties (benzocaine, bupivacaine, mepivacaine, lidocaine, procaine, QX-314) on membranes. Membrane partitioning log D values (between 2.1 and 3.7) varied little with pH, in contrast to octanol partitioning. Membrane thinning was induced by most LAs, except for benzocaine. A conformational change in the lipid headgroup was observed, with a pronounced dependence on the protonation state, indicating the importance of the positive charge that is maintained by most membrane-bound LAs. We found stabilization of negative membrane curvature in the case of benzocaine, and of positive curvature in the case of bupivacaine, procaine, mepivacaine and, most pronouncedly, for QX-314. Comparing the LAs with respect of their influence on membranes as observed in the different experiments, benzocaine and QX-314 were always found at either extreme of the scale, with bupivacaine and lidocaine closer in their effect to benzocaine. This order of influence correlates with the depth of membrane insertion and with the protonation state, both of which were identified as key factors for LA behavior. Finally, we found indications that LAs are able to alter the activity of bacterial mechanosensitive channels without any expected LA binding sites, thus supporting a membrane-mediated activity of LAs
Aggregator electricity price guarantees for households with flexibility potential utilizing thermal building inertia
No full textThis study introduces an approach to mitigate the reluctance of households to adopt dynamic electricity tariffs by proposing individual price contracts tailored to household characteristics. These contracts guarantee individual electricity rates to households with flexibility potential, such as thermal or electrical storage and the thermal mass of buildings, in exchange for granting aggregators operational control. The household-specific contracts are determined and evaluated through a three-step process, combining deterministic and stochastic modeling. First, an optimization problem for the operation of home energy management systems is formulated. The proposed model incorporates the thermal inertia of buildings as a flexibility potential, an aspect frequently overlooked in existing studies. Then, a Monte Carlo simulation of household parameter combinations is run, followed by a quantile regression prediction of household-level low-price guarantees. The simulations of 9404 household configurations in Germany demonstrate that aggregator-managed flexibility consistently lowered electricity costs by an average of 7.36% (2.5 ct/kWh) compared to static tariffs, with 78.4% of households achieving rates below the competitive retail benchmark. Aggregators also realized higher profitability on a per-household basis across all three analyzed years compared to scenarios without flexibility control. Our results demonstrate that building parameters, particularly thermal inertia, substantially influence the available flexibility potential and should be considered a key factor in the design of household-level guarantee contracts. The study contributes to understanding and quantifying uncertainty in dynamic tariffs for households, aiming to advance the utilization of household demand response potential in modern power markets
Passivity preserving model reduction via spectral factorization
No full textWe present a novel model-order reduction (MOR) method for linear time-invariant systems that preserves passivity and is thus suited for structure-preserving MOR for port-Hamiltonian (pH) systems. Our algorithm exploits the well-known spectral factorization of the Popov function by a solution of the Kalman–Yakubovich–Popov (KYP) inequality. It performs MOR directly on the spectral factor inheriting the original system’s sparsity enabling MOR in a large-scale context. Our analysis reveals that the spectral factorization corresponding to the minimal solution of an associated algebraic Riccati equation is preferable from a model reduction perspective and benefits pH-preserving MOR methods such as a modified version of the iterative rational Krylov algorithm (IRKA). Numerical examples demonstrate that our approach can produce high-fidelity reduced-order models close to (unstructured) H2-optimal reduced-order models
Biometric technology roadmapping for personalized augmentative and alternative communication
No full textThe purpose of this paper is to provide a biometric based technology roadmap to advance personalized Augmentative and Alternative Communication (AAC) systems for individuals with disabilities. The proposed technology roadmap introduces two core components: an AAC biometric register and interoperable technological modules. The biometric register provides a structured framework for capturing and transforming physiological and behavioral traits to enable adaptive and context-aware communication. The interoperable module design supports reconfigurable AAC architectures, ensuring compatibility across diverse interfaces and devices. Together, these mechanisms establish a foundation for automated and scalable personalization in AAC technologies. The study demonstrates that the proposed methodology for technology roadmapping effectively connects established research with emerging computational practices. This is confirmed by the results of the case study such as sign language recognition