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The variation of the contact impedance of adhesive conductive EMI shielding tapes under high temperature storage (HTS) of 110degC is investigated. The adhesive tapes under test are implemented as signal return paths in microstrip lines. Changes in the ground plane impedance by adhesive deterioration are analyzed by S-parameter measurements from 1MHz to 3GHz. A circuit model for contact impedance degradation is proposed and applied in simulation of board level shielding. Contact resistance and contact capacitance are found to increase significantly after 2400h, causing a declined magnetic field shielding effectiveness by 30 dB below 500 MHz.
A reinforcement of concrete structures is needed because of the low tensile strength of concrete. Corrosion of the usually used steel reinforcments cause issues during time. Therfore, alternative reinforcements produced from non-corosive materials - like polymer fibers - become more interesting. A polymer fiber has to reach high mechanical properties and a good bonding ability to concrete. Both properties can be influenced by the selection of polymer and the used production process. Two polymers, polypropylene and aliphatic polyketone are tested within this study. First mono-material fibers of each material are produced and tested, later the materials are combined in a core-shell fiber. All fibers are produced by standard extrusion or coextrusion and a later drawing process. The mechanical properties are determined by tensile tests. The calculation of interfacial shear strength from single fiber pull-out tests allows an evaluation of the bonding ability. Additionally, fiber surface before and after pull-out is examined using reflected light microscopy. Contact angle measurements are done to evaluate possible influences of the surface energy and polarity. Density measurements are used to compare weight potential of the different mono-material and core-shell fibers. The results show good mechanical properties for all fiber materials. The interfacial shear strength is ≈ 2-3 times higher for fibers with polyketone compared to the ones with polypropylene at the fibers surface, which can be explained by higher surface energy and polarity of the polyketone compared to polypropylene and different surface deformation during pull-out. Lower densities are reached by fibers containing polypropylene.
We present inductive power transfer (IPT) with a half-bridge converter based on differential relaxation self-oscillation. The oscillation dynamics of the converter automatically adapts to variation in the inductive coupling link and changes in the load, respectively. Design equations based on theoretical circuit analysis reveals a high power transfer efficiency (>90%) for alteration of coupling distance in the strong coupling regime. A prototype system employing GaN-HEMTs confirms the theoretically predicted characteristics of the proposed circuit.
Non-Rest to non-Rest Reference Slews for Agile Imaging Satellites With LQ-minimized Angular Momentum
(2023)
This paper shows a full parametrization non-rest to non-rest slew maneuvers using polynomials. A new modelling formulation is developed which on one hand satisfies exactly the given boundary conditions as well as the kinematic differential equation of the rotating body exactly. The idea is to determine one part of the unknown coefficients by the kinematical boundary conditions and to use the other part as free design parameters to shape the dynamic in between the boundary conditions. In addition, a least squares problem is formulated in order to minimize the angular momentum of the slew. This approach allows optimal slew maneuvers as well as low computational need such that an onboard usage is possible.
SMEs are increasingly forced to shift to more sustainable manufacturing. Industry 4.0 can support the transformation and foster innovation. But, SMEs need solutions with a low barrier to entry in terms of investment, IT knowledge and capacities. A framework based on value and material flow analysis, low investments and user-oriented IT skills is proposed. As an example, it is implemented in the furniture industry and shows a digital twin in terms of monitoring the energy and material flows. In addition, a product-specific allocation of energy consumption, energy peak shaving and other applications are possible.
Psychological safety, the feeling of being comfortable to express one’s ideas or opinions in teams, is a key determinant of successful global virtual teams. Even though there exists considerable knowledge about its antecedents, it is unknown how team-based (e.g., clarification of deliverables and deadlines) and technology-based (e.g., digital reminder nudges/ DRN) interventions foster psychological safety given cultural variations of team members. Based on a survey involving 148 participants, our data shows that both team-based interventions (TBI) and digital nudges foster psychological safety in global virtual teams. TBI are even more effective for high-context, indirect communicators than for low-context, direct communicators. However, digital nudges were equally effective across cultures for building psychological safety. These findings contribute to the literature on psychological safety as we show that not all antecedents hold equally across cultures and to the literature of digital nudges as we show the effectiveness of technology-based interventions in a team context.
Holz ist eine der wichtigsten erneuerbaren Ressourcen und kann recycelt werden, wobei derzeit nur unbehandeltes Holz in mehreren Lebenszyklen verwendet werden kann. Allerdings werden in Altholzsortieranlagen meist behandeltes und unbehandeltes Altholz gemischt angeliefert und es gibt keine automatische Klassifizierung zur sortenreinen Sortierung. Frühere Studien zeigen, dass behandelte und unbehandelte Holzproben mit Hilfe von bildgebender Fluoreszenzabklingzeit Mikroskopie unterschieden werden können. Um den Prozess der Klassifizierung von Altholz anhand von Fluoreszenzabklingzeitbildern zu automatisieren, werden zwei neuronale Netzwerke (NN) evaluiert. Das erste NN ist ein MLP (Multi Layer Perceptron), das das Altholz anhand von Erwartungswert und Standardabweichung eines Fluoreszenzabklingzeitbildes klassifiziert. Das zweite untersuchte NN ist ein CNN (Convolutional Neural Network), das das Holz direkt anhand der Fluoreszenzabklingzeitbilder klassifiziert. Beide Netzwerke sind in Python implementiert, um die spätere Verwendung in einem automatischen Klassifizierungs- und Sortierprozess zu erleichtern. Die Evaluation der NN zeigt vielversprechende Ergebnisse zur automatisierten Klassifikation von Altholz.