20005 research outputs found
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Enabling Quality-of-Service for avionic wireless sensor networks in ISM and WAIC band using multi-layer improvements to 6TiSCH
No full textReplacing traditional wired connections with wireless systems on the aircraft can significantly reduce weight and fuel consumption. Furthermore, complementing existing wired systems with wireless sensors adds redundancy and fault tolerance. Although many applications are already envisioned under the umbrella of Wireless Avionics Intra-Communications (WAIC), finding a suitable communication technology remains challenging due to diverse Quality of Service (QoS) requirements. In this work we discuss challenges associated with the deployment of an in-cabin wireless sensor network (WSN) using different radio bands and propose a solution based on the IPv6 over the TSCH mode of IEEE 802.15.4 (6TiSCH) protocol stack. By extending the latter with cross-layer as well as layer-specific improvements, different challenges in terms of bounded end-to-end delay and high packet delivery ratio are addressed. The solution is validated in simulations using OMNeT++, showing the feasibility of meeting stringent QoS requirements for in-cabin WSNs
Entwicklungstrends und Herausforderungen einer beruflichen Bildung für eine nachhaltige Entwicklung in Unternehmen am Beispiel der industriellen Elektroberufe
No full textComparison of approaches for parametric sea state estimation using the wave-buoy analogy and neural networks on full-scale measurement sata
No full textMonitoring the surrounding sea state enhances operational safety and energy efficiency of vessels during voyage. The directional sea state can be estimated from measured vessel responses using physics-based models following the Wave-Buoy Analogy (WBA) or data-driven methods like Convolutional Neural Networks (CNNs). This study explores both approaches for parametric sea state estimation using simulation and full-scale measurement data of a barge. The issue of local minimum convergence in the least-squares algorithm is addressed by a modified implementation of the parametric WBA. The modification involves constraining the relative wave direction during optimization, leading to more robustness against outliers in the estimation of the peak period and relative wave direction. The study emphasizes that the methods provide feasible approaches for parametric sea state estimation on the given data, with the WBA requiring knowledge of the vessel-specific conditions and the CNN depending on the representativeness of the training data
Unified graph-theoretic modeling of multi-energy flows in distribution systems
No full textThe increasing complexity of energy systems due to sector coupling and decarbonization calls for unified modeling frameworks that capture the physical and structural interactions between electricity, gas, and heat networks. This paper presents a graph-based modeling approach for multi-energy systems (MES), where each domain is represented as a layer in a multi-layer graph, and coupling technologies are modeled as inter-layer edges via a dedicated coupling layer. A steady-state solver based on a block-structured Newton-Raphson (NR) method is developed to jointly compute flows and state variables across all carriers. The proposed model is tested and validated on a realistic case study based on data from a German distribution network. The results demonstrate convergence, numerical accuracy, and consistent domain interaction, and demonstrate the method’s applicability for system-wide analysis and its potential as a foundation for future optimizations in integrated energy systems.Bundesministerium für Wirtschaft und Energie (BMWE
Stress-based topology optimization considering uncertainties or partial damage
No full textPerforming structural optimization, without taking possible uncertainties into account, can lead to catastrophic consequences. Hence, various types of uncertainties are considered during optimization, and different problem formulations are investigated regarding their numerical efficiency. A special focus in this regard is on stress induced effects. In the case of unpredictable partial damages, it could be demonstrated, that a classical damage patch formulation with a reduced number of patches yields the best performing designs. Regarding other uncertainties, such as material properties, loading, and geometry, a generalized robust formulation is proposed.Werden mögliche Unsicherheiten in der Strukturoptimierung vernachlässigt, kann dies zu katastrophalen Folgen führen. Daher werden während der Optimierung verschiedene Arten von Unsicherheiten betrachtet und unterschiedliche Problemformulierungen hinsichtlich ihrer numerischen Effizienz untersucht. Ein besonderer Fokus liegt dabei auf spannungsinduzierten Effekten. Im Falle von unvorhersehbaren lokalen Schäden konnte gezeigt werden, dass eine klassische Schadenspatch-Formulierung mit einer reduzierten Anzahl von Patches die besten Entwürfe liefert. Sollen andere Unsicherheiten, wie Materialeigenschaften, Belastung und Geometrie berücksichtigt werden, wird eine verallgemeinerte robuste Formulierung vorgeschlagen
Reversible switching through irradiation of capacitors and organic transistors employing dielectrics blended with non-ionic molecular photoswitches
No full textOne promising approach to introduce additional functionalities for sensing and memory applications into conventional organic electronic devices is the introduction of stimuli responsive additives, such as molecular switches. These small organic molecules undergo reversible isomerization between (at least) two isomers when irradiated with light of different wavelength resulting in drastic changes in physicochemical properties such as frontier orbital energy levels, dipole moment and/or molecular geometry. These reversible changes in molecular properties can be exploited to deliberately modify charge transport in organic field-effect transistors and therefore enable optical control over device characteristics.
Here, stimuli-responsiveness of organic transistors is achieved by incorporating the dihydroazulene/vinylheptafulvene (DHA/VHF) molecular switches into the gate dielectric. To systematically explore this novel approach, we firstly provide a detailed evaluation of the dielectric properties of the DHA/VHF blends with the dielectric polymer poly(methyl methacrylate) in metal–insulator–metal capacitors using impedance spectroscopy. Afterwards, these switchable dielectric blends are employed as gate dielectrics in OFETs, allowing optical control over device characteristics and figures of merit such as field-effect mobility and threshold voltage. Furthermore, optical absorption spectroscopy shows that DHA/VHF
molecular switches (unlike the well-known spiropyran/merocyanine photoswitch) exhibit excellent resistance to cycling fatigue when incorporated into insulating PMMA matrices
Fjord5G: A comprehensive 5G dataset for coastal maritime connectivity
No full textIn recent years, the use of machine learning (ML) in cellular networking has increased significantly, enabled by the availability of new ML algorithms and cellular datasets. However, existing 5G datasets focus mainly on land-based vehicular networks, which do not capture the unique challenges of the coastal maritime domain. This includes large distances from base stations, dynamic sea states, such as waves and tides, and varying interference from water surface reflections and nearby vessels. This paper introduces the Fjord5G11https://github.com/ds-kiel/Fjord5G, a 5G dataset for coastal maritime connectivity research. We conduct an extensive measurement campaign aboard research and public ferries in the Kiel Fjord, Germany, collecting GPS-located cellular data along maritime routes. These measurements cover the network conditions encountered in coastal and near-shore regions and provide insights into metrics such as signal strength, modulation, and bandwidth. The resulting dataset includes cellular measurements at a sampling rate of 1 Hz from two mobile network operators, four 5G routers, and two ferries for up to 12 months per router. Initial data analysis reveals key challenges for ML, such as dealing with varying bandwidth and handover events, while highlighting potential features, such as signal strength metrics, that can be exploited to improve coastal maritime connectivity
Advanced glycerol oxidation to formic acid in a multiphasic jet loop reactor using polyoxometalate catalysts
No full textGlycerol is a common byproduct of commercial biodiesel production and can be used for the production of green platform chemicals such as biogenic formic acid (FA). Biogenic FA is industrially produced via selective catalytic oxidation in the OxFA process using various biomass in conventional stirred-tank reactors (STR). However, the reaction is limited by the low oxygen solubility in the aqueous reaction media that typically requires high oxygen pressures of 10–30 bar. This study aims to implement the multiphasic selective oxidation of glycerol to FA in a jet loop reactor (JLR), highlighting the economic and mass transfer advantages compared to the conventional used STR. The multiphasic approach was catalyzed by the homogeneous H5PV2Mo10O40 (HPA-2) polyoxometalate catalyst, already established in the commercial OxFA process. The reactor characterization indicates an efficient and high gas–liquid mass transfer, achieving volumetric mass transfer coefficient values (kl · a values) ranging from 51 to 173 h–1. Afterward, the multiphasic glycerol oxidation reaction to FA was implemented and compared in both reactor concepts under identical reaction conditions. The JLR achieved very high FA space-time-yields (STY) of up to 30.0 gFA LR–1 h–1, highlighting its improved mass transfer and favorable economics already at 5 bar oxygen pressure in a simple glass setup. Determination of the kinetic parameters in the JLR resulted in reaction orders of 0.83 for glycerol and 0.54 for oxygen underlining the importance of an efficient gas–liquid mass transfer. Moreover, the activation energy was determined to be 78.3 kJ mol–1, which is well in line with previous studies carried out for the OxFA process in a STR. The calculated Hatta number of 0.014 for the multiphasic glycerol oxidation in the JLR indicates that the reaction is in the kinetic regime already at low oxygen pressures of 5 bar demonstrating the high potential of the reactor concept for future studies
Leveraging the benefits of information flow tracking for detecting hardware design flaws
No full textHardware design weaknesses, when overlooked, can lead to security vulnerabilities. Their cost of fixing is higher the later they are found in the development life cycle. The challenges of detecting these issues in the early stages of hardware design, compared to software design, can be attributed to limited research or poorly defined design guidelines. Using the existing hardware design weakness classification by the MITRE Corporation, we evaluated how Information Flow Tracking (IFT) can be utilized to identify security weaknesses in hardware designs. First, we provide a classification of design weaknesses tailored to detection using IFT. Second, we present a case study to identify one of such weaknesses using an open-source IFT tool. Additionally, we discuss the challenges of using IFT to detect information-flow-based hardware design weaknesses