TY - CHAP AU - Friedberger, Vanessa AU - Kaiser, Michaela AU - Kottmann, Brigitte AU - Schwermann, Anna ED - Fischer, Christian ED - Fischer-Ontrup , Christiane ED - Käpnick, Friedhelm ED - Neuber, Nils ED - Reintjes, Christian ID - 50734 T2 - Potenziale erkennen - Talente entwickeln - Bildung nachhaltig gestalten. Beiträge aus der Begabungsforschung TI - Fallbezogene Reflexionen von Haltung und Professionalisierung pädagogischer Akteur*innen im Kontext begabungs- und leistungsfördernder Schulentwicklung ER - TY - CONF AB - Abstract. Force-displacement measurements and macrosections are commonly used methods to validate numerical models of clinching processes. However, these ex-situ methods often lead to springback of elastic deformations and crack-closing after unloading. In contrast, the in-situ computed tomography (CT) can provide three-dimensional images of the clinching point under loading conditions. So far, the quantity of elastic springback that causes measuring deviations between in- and ex-situ measurements is not determined. In this paper, a method is described to quantitatively compare the results of in-situ CT, ex-situ CT and CT scans of cut specimens, which are prepared for macrosectioning, among each other. The method is applied to a single-lap shear test of two clinched aluminum sheets. Here, the test is conducted to specific process steps, then the specimen is CT scanned in-situ (during loading) and ex-situ (after unloading). Subsequently, the specimens are cut for macrosectioning and CT scanned. Finally, the outer contours and the interfaces of cross section images are determined by digital image analysis and the deviations over the clinching point between ex- and in-situ methods are calculated. AU - Köhler, Daniel AU - Kupfer, Robert AU - Troschitz, Juliane AU - Gude, Maik ID - 51190 SN - 2474-395X T2 - Materials Research Proceedings TI - Comparison of ex- and in-situ investigations of clinched single-lap shear specimens ER - TY - CHAP AU - Köhler, Daniel AU - Stephan, Richard AU - Kupfer, Robert AU - Troschitz, Juliane AU - Brosius, Alexander AU - Gude, Maik ID - 51194 SN - 2194-0525 T2 - Lecture Notes in Production Engineering TI - In-situ Computed Tomography and Transient Dynamic Analysis of a Single-Lap Shear Test with a Composite-Metal Clinch Point ER - TY - JOUR AB - Given a geometrically finite hyperbolic surface of infinite volume it is a classical result of Patterson that the positive Laplace-Beltrami operator has no $L^2$-eigenvalues $\geq 1/4$. In this article we prove a generalization of this result for the joint $L^2$-eigenvalues of the algebra of commuting differential operators on Riemannian locally symmetric spaces $\Gamma\backslash G/K$ of higher rank. We derive dynamical assumptions on the $\Gamma$-action on the geodesic and the Satake compactifications which imply the absence of the corresponding principal eigenvalues. A large class of examples fulfilling these assumptions are the non-compact quotients by Anosov subgroups. AU - Weich, Tobias AU - Wolf, Lasse Lennart ID - 31189 JF - Communications in Mathematical Physics TI - Absence of principal eigenvalues for higher rank locally symmetric spaces VL - 403 ER - TY - CHAP AU - Meyer-Hamme, Johannes ED - Fenn, Monika ED - Zülsdorf-Kersting, Meik ID - 41130 T2 - Geschichtsdidaktik TI - Geschichtstheorie im Geschichtsunterricht ER - TY - CONF AB - Polymer composites represent the industry standard in injection molding for the production of plastic components with increased requirements in terms of heat resistance and stiffness. In the field of laser sintering (LS), these materials are less common so far. In order to extend the available material variety for the LS process, new ceramic-filled Polyamide 613 powders are investigated within the scope of this work. Here, the resulting properties from two different powder production methods are compared. One filled powder is produced by dry blending and the other powder with the same filler and filling ratio is produced by encapsulating the filler particles inside the polymer particles within the dissolution-precipitation process. It was found that encapsulating the filler particles can provide certain benefits for the processability, for example an improved powder flowability or better filler dispersion. However, encapsulating the filler also alters the thermal properties of the precipitated powder. AU - Kletetzka, Ivo AU - Neitzel, Fabian AU - Schmid, Hans-Joachim ED - Beaman, Joseph ID - 51218 KW - Additive Manufacturing KW - Laser Sintering KW - Filled Materials KW - Composites KW - Polyamide 613 T2 - Proceedings of the 34th Annual International Solid Freeform Fabrication Symposium TI - Assessing the Impact of the Powder Production Method on Ceramic-filled Polyamide Composites made by Laser Sintering ER - TY - JOUR AB - Dynamics-induced interchain charge transfer in a polymer aggregate in stack configuration can be understood by single-oligomer polaron energy. AU - Bauch, Fabian AU - Dong, Chuan-Ding AU - Schumacher, Stefan ID - 51093 IS - 38 JF - Journal of Materials Chemistry C KW - Materials Chemistry KW - General Chemistry SN - 2050-7526 TI - Dynamics-induced charge transfer in semiconducting conjugated polymers VL - 11 ER - TY - JOUR AB - Cooperative Driving requires ultra-reliable communications, and it is now clear that no single technology will ever be able to satisfy such stringent requirements, if only because active jamming can kill (almost) any wireless technology. Cooperative driving with multiple communication technologies which complement each other opens new spaces for research and development, but also poses several challenges. The work we present tackles the fallback and recovery mechanisms that the longitudinal controlling system of a platoon of vehicles can implement as a distributed system with multiple communication interfaces. We present a protocol and procedure to correctly compute the safe transition between different controlling algorithms, down to autonomous (or manual) driving when no communication is possible. To empower the study, we also develop a new version of PLEXE, which is an integral part of this contribution as the only Open Source, free simulation tool that enables the study of such systems with a modular approach, and that we deem offers the community the possibility of boosting research in this field. The results we present demonstrate the feasibility of safe fallback, but also highlight that such complex systems require careful design choices, as naïve approaches can lead to instabilities or even collisions, and that such design can only be done with appropriate in-silico experiments. AU - Segata, Michele AU - Lo Cigno, Renato AU - Hardes, Tobias AU - Heinovski, Julian AU - Schettler, Max AU - Bloessl, Bastian AU - Sommer, Christoph AU - Dressler, Falko ID - 51266 IS - 8 JF - IEEE Transactions on Mobile Computing SN - 1536-1233 TI - Multi-Technology Cooperative Driving: An Analysis Based on PLEXE VL - 22 ER - TY - CONF AB - Platooning is a promising application in the field of vehicular networks. It has the potential to improve traffic flow, but also road safety. However, unreliable communication has strong negative effects on platoon stability and, thus, safety on roads. To improve reliability, in this work, we propose using multi-hop communication for platooning using the Decode and Forward (DF) Full-Duplex Relaying (FDR) scheme together with beamforming. We use computer simulations to demonstrate that FDR latency has no observable negative effect on string stability or safety even while performing an emergency brake. We further show that this combined approach reaches a constant Packet Delivery Ratio (PDR) of 100 % even in situations with high interference and/or congestion, where traditional approaches fail. AU - Hardes, Tobias AU - Klingler, Florian AU - Sommer, Christoph ID - 51264 T2 - IEEE Wireless Communications and Networking Conference 2023 (WCNC 2023) TI - Improving Platooning Safety with Full Duplex Relaying and Beamforming ER - TY - JOUR AB - We study the suitability of Unmanned Aerial Vehicles (UAVs) as purely opportunistic airborne virtual network infrastructure to support urban wireless networks, specifically in two Vehicle-to-Everything (V2X) use cases: First, UAVs being used as relays for cooperative awareness applications; second, UAVs being used to coordinate channel access for platooning in urban areas. We do not require that these UAVs alter trajectory nor speed from those of their random, unrelated primary missions, so that these additional tasks can be executed with close-to-zero impact on the execution of their primary missions. Based on extensive computer simulations we show that, within a wide band of acceptable speeds, flight routes (up to a standard deviation of 300 m from the optimum) as well as altitudes, opportunistic relaying of transmissions via UAVs can yield a benefit to system performance that is on the same order of magnitude as that of optimally deployed UAVs. We further show that an opportunistic channel access control can reduce the total number of packet collisions by approx. 86 % compared to a scenario without any UAVs. Moreover, much of the reduction in impact due to suboptimal missions can be recovered simply by moderately increasing the number of UAVs. AU - Hardes, Tobias AU - Sommer, Christoph ID - 51267 JF - Elsevier Computer Communications SN - 0140-3664 TI - Opportunistic Airborne Virtual Network Infrastructure for Urban Wireless Networks ER -