@techreport{21152, abstract = {{In modern lightweight designs, it is important to find a compromise between the strength and the weight of the construction detail. Hence, hybrid structures made of aluminum and steel materials are increasingly being used in automotive applications. Due to limitations in the quality of resistance spot welding, self-piercing riveting can be used as an alternative process to join sheets from different material groups. The aim of this project is to develop a computational method to assess the self-piercing riveted components subjected to the cyclic loads. To achieve this goal, two approaches are followed: Evaluation unsing internal forces: A substitute model is developed to describe the stiffness of self-piercing riveted joints subjected to different loading conditions. The parameters of the substitute model are identified and the internal force components acting on the joint are evaluated. The model provides the basis for the subsequent fatigue life estimation of self-piercing riveted components. For joints subjected to low bending moments, the fatigue life of components can be estimated accurately. Due to lack of specimen geometries producing pure bending and the combination of tension-bending forces, it is not possible to estimate the fatigue life of complex components subjected to high bending moments. Based on the results of [Mesc 16], the methodology is further developed to determine the stresses acting on the joint and to characterize the joining point with the use of simulations. The local concept proposed in the FKM guideline nonlinear provides the basis for the analytical assessment of self-piercing riveted components. In this regard, the cyclic behavior of the material and the local stresses are required as input data. The cyclic behavior of the aluminum EN AW-6181A-T6 and steel HX340LAD sheets were already determined in the previous project. Subsequently, in this project the properties of the rivet made of 38B2 steel are identified. The finite element analysis using elastic-plastic material behavior is used to determine the stresses in the joint subjected to the cyclic loads. To verify the model, the results of simulations and experiments are compared concerning the crack initiation zone as well as the determined number of cycles. To determine the stresses that can be used for the analytical assessment, the damage relevant load components need to be identified. In this regard, it is recommended to use the normal stress perpendicular to the crack propagation direction, the stress of crack opening mode I. Using the damage parameter PRAM and considering the support factors according to the FKM guideline nonlinear, a reliable estimation of the crack initiation zone within the joint is possible. Regarding the joint made of aluminum sheet EN AW-6181A, the methodology is able to provide promising results. However, regarding the joints made of aluminum EN AW-6181A and steel HX340LAD sheets, there is still potential to improve the results. The reasons for this are described in chapter 7.2.5 and 7.2.6. An analytical fatigue assessment is relatively easy to achieve with procedure 1. However, contrary to the objective formulated above, expensive fatigue tests are necessary to determine the failure conditions (strength values). This disadvantage can be circumvented by determining the strength information of individual joining points under different load types using procedure 2. The latter, in return, is not suitable for the assessment of complex components with several joining points. Due to the increasing calculation times of the simulation, the application in this case is not economically reasonable. By the described combination of method 1 and 2, the disadvantages of the two individual concepts can be compensated. An analytical fatigue assessment of self-piercing riveted components can be carried out based on the cyclic material behavior. The objective of the project was achieved.}}, author = {{Otroshi, Mortaza and Meschut, Gerson and Masendorf, Lukas and Esderts, Alfons}}, isbn = {{978-3-86776-602-9}}, pages = {{282}}, publisher = {{Europäische Forschungsgesellschaft für Blechverarbeitung e.V. (EFB)}}, title = {{{Simulationsbasierte Betriebsfestigkeitsanalyse stanzgenieteter Bauteile}}}, year = {{2020}}, } @inproceedings{21174, abstract = {{Overcoming a range of challenges that traditional therapy faces, VRET yields great potential for the treatment of phobias such as acrophobia, the fear of heights. We investigate this potential and present playful user-generated treatment (PUT), a novel game-based approach for VRET. Based on a requirement analysis consisting of a literature review and semi-structured interviews with professional therapists, we designed and implemented the PUT concept as a two-step VR game design. To validate our approach, we conducted two studies. (1) In a study with 31 non-acrophobic subjects, we investigated the effect of content creation on player experience, motivation and height perception, and (2) in an online survey, we collected feedback from professional therapists. Both studies reveal that the PUT approach is well applicable. In particular, the analysis of the user study shows that the design phase leads to increased interest and enjoyment without notably influencing affective measures during the exposure session. Our work can help guiding researchers and practitioners at the intersection of game design and exposure therapy.}}, author = {{Alexandrovsky, Dmitry and Volkmar, Georg and Spliethöver, Maximilian and Finke, Stefan and Herrlich, Marc and Döring, Tanja and Smeddinck, Jan David and Malaka, Rainer}}, booktitle = {{Proceedings of the Annual Symposium on Computer-Human Interaction in Play}}, isbn = {{9781450380744}}, pages = {{32–45}}, publisher = {{Association for Computing Machinery}}, title = {{{Playful User-Generated Treatment: A Novel Game Design Approach for VR Exposure Therapy}}}, doi = {{10.1145/3410404.3414222}}, year = {{2020}}, } @phdthesis{21205, author = {{Wolf, Verena}}, title = {{{Service System Innovation: An Ambidexterity Perspective}}}, year = {{2020}}, } @phdthesis{21209, abstract = {{Die additive Fertigung mittels Laser Powderbed Fusion Verfahren (L-PBF) von Metallen wird zunehmend genutzt, um Funktionsbauteile endkonturnah zu fertigen. Die in der vor-liegenden Arbeit untersuchte Parameter- und Prozessoptimierung liefert einen Beitrag zur wirtschaftlichen Nutzung des L-PBF und zeigt, dass höhere Aufbauraten bei der ganzheit-lichen Betrachtung des Prozesses realisierbar sind. Die Parameter- und Prozessoptimierung erfordert eine Untersuchung des Einflusses der Fertigungs- und Nachbearbeitungsparameter auf das erzeugte Volumen sowie auf die Mikrostruktur und die resultierenden Materialeigenschaften. Das Ziel der vorliegenden Arbeit ist die Entwicklung einer optimierten Prozessführung mit abschließender Bewer-tung der Wirtschaftlichkeit. Mit dem entwickelten Gesamtprozess wird eine um den Faktor 1,6 höhere Aufbaurate erzielt. Des Weiteren wird die Methodik zur Erarbeitung des opti-mierten Prozessfensters beschrieben, sodass die Herangehensweise auf weitere Werk-stoffe angewendet werden kann. Die mechanischen Eigenschaften werden für den stati-schen und dynamischen Lastfall untersucht und mit der Mikrostruktur korreliert. Abschlie-ßend wird die Prozessoptimierung zur Fertigung eines Demonstrators eingesetzt und wirtschaftlich validiert. Die Ergebnisse zeigen, dass durch das hier angewendete Vorge-hen eine Prozesszeitreduktion von 22,5% und eine Kostenreduktion von 11% realisiert werden kann.}}, author = {{Ahlers, Dominik}}, isbn = {{978-3844074246}}, keywords = {{Additive Manufacturing, SLM}}, pages = {{137}}, publisher = {{Shaker}}, title = {{{Parameter- und Prozessoptimierung für den additiven Fertigungsprozess im Pulverbett am Beispiel der Legierung Ti6Al4V }}}, volume = {{19}}, year = {{2020}}, } @inbook{21216, author = {{Jakob, Eva Alexandra and Hansjürgen, Lea}}, booktitle = {{Wettbewerbsfähigkeit von Start-ups, Erfolgreiche Düsseldorfer Unternehmen}}, editor = {{Lutz, Eva and Süß, Stefan}}, pages = {{91--106}}, publisher = {{düsseldorf university press}}, title = {{{Volunteer World GmbH – Schildkrötenretten als Business Case}}}, doi = {{10.1515/9783110663839-008}}, year = {{2020}}, } @article{21239, abstract = {{The electrochemical nitrogen reduction reaction (NRR) to ammonia (NH3) is a promising alternative route for an NH3 synthesis at ambient conditions to the conventional high temperature and pressure Haber--Bosch process without the need for hydrogen gas. Single metal ions or atoms are attractive candidates for the catalytic activation of non-reactive nitrogen (N2), and for future targeted improvement of NRR catalysts, it is of utmost importance to get detailed insights into structure-performance relationships and mechanisms of N2 activation in such structures. Here, we report density functional theory studies on the NRR catalyzed by single Au and Fe atoms supported in graphitic C2N materials. Our results show that the metal atoms present in the structure of C2N are the reactive sites, which catalyze the aforesaid reaction by strong adsorption and activation of N2. We further demonstrate that a lower onset electrode potential is required for Fe--C2N than for Au--C2N. Thus, Fe--C2N is theoretically predicted to be a potentially better NRR catalyst at ambient conditions than Au--C2N owing to the larger adsorption energy of N2 molecules. Furthermore, we have experimentally shown that single sites of Au and Fe supported on nitrogen-doped porous carbon are indeed active NRR catalysts. However, in contrast to our theoretical results, the Au-based catalyst performed slightly better with a Faradaic efficiency (FE) of 10.1{\%} than the Fe-based catalyst with an FE of 8.4{\%} at −0.2 V vs. RHE. The DFT calculations suggest that this difference is due to the competitive hydrogen evolution reaction and higher desorption energy of ammonia.}}, author = {{Sahoo, Sudhir K. and Heske, Julian Joachim and Antonietti, Markus and Qin, Qing and Oschatz, Martin and Kühne, Thomas}}, journal = {{ACS Applied Energy Materials}}, number = {{10}}, pages = {{10061--10069}}, publisher = {{American Chemical Society}}, title = {{{Electrochemical N2 Reduction to Ammonia Using Single Au/Fe Atoms Supported on Nitrogen-Doped Porous Carbon}}}, doi = {{10.1021/acsaem.0c01740}}, volume = {{3}}, year = {{2020}}, } @article{21241, abstract = {{In this work, a high-throughput screening of binary and ternary pnictide- and halide-based compounds is performed to identify promising p-type transparent conductors. Our investigation profits from the emergence of open-access databases based on ab-initio results. The band gap, stability, hole effective mass, and p-type dopability are employed for the materials screening and the validity of these descriptors is discussed. Among the final candidates, BaSiN2 is the most promising compound.}}, author = {{Wiebeler, Hendrik and Kormath Madam Raghupathy, Ramya and Mirhosseini, S. Hossein and Kühne, Thomas}}, journal = {{Journal of Physics: Materials}}, number = {{1}}, pages = {{015004}}, publisher = {{{IOP} Publishing}}, title = {{{Virtual screening of nitrogen-, phosphorous- and halide-containing materials as p-type transparent conductors}}}, doi = {{10.1088/2515-7639/abc762}}, volume = {{4}}, year = {{2020}}, } @article{21257, abstract = {{Digital data on tangible and intangible cultural assets is an essential part of daily life, communication and experience. It has a lasting influence on the perception of cultural identity as well as on the interactions between research, the cultural economy and society. Throughout the last three decades, many cultural heritage institutions have contributed a wealth of digital representations of cultural assets (2D digital reproductions of paintings, sheet music, 3D digital models of sculptures, monuments, rooms, buildings), audio-visual data (music, film, stage performances), and procedural research data such as encoding and annotation formats. The long-term preservation and FAIR availability of research data from the cultural heritage domain is fundamentally important, not only for future academic success in the humanities but also for the cultural identity of individuals and society as a whole. Up to now, no coordinated effort for professional research data management on a national level exists in Germany. NFDI4Culture aims to fill this gap and create a user-centered, research-driven infrastructure that will cover a broad range of research domains from musicology, art history and architecture to performance, theatre, film, and media studies. The research landscape addressed by the consortium is characterized by strong institutional differentiation. Research units in the consortium's community of interest comprise university institutes, art colleges, academies, galleries, libraries, archives and museums. This diverse landscape is also characterized by an abundance of research objects, methodologies and a great potential for data-driven research. In a unique effort carried out by the applicant and co-applicants of this proposal and ten academic societies, this community is interconnected for the first time through a federated approach that is ideally suited to the needs of the participating researchers. To promote collaboration within the NFDI, to share knowledge and technology and to provide extensive support for its users have been the guiding principles of the consortium from the beginning and will be at the heart of all workflows and decision-making processes. Thanks to these principles, NFDI4Culture has gathered strong support ranging from individual researchers to high-level cultural heritage organizations such as the UNESCO, the International Council of Museums, the Open Knowledge Foundation and Wikimedia. On this basis, NFDI4Culture will take innovative measures that promote a cultural change towards a more reflective and sustainable handling of research data and at the same time boost qualification and professionalization in data-driven research in the domain of cultural heritage. This will create a long-lasting impact on science, cultural economy and society as a whole.}}, author = {{Altenhöner, Reinhard and Blümel, Ina and Boehm, Franziska and Bove, Jens and Bicher, Katrin and Bracht, Christian and Brand, Ortrun and Dieckmann, Lisa and Effinger, Maria and Hagener, Malte and Hammes, Andrea and Heller, Lambert and Kailus, Angela and Kohle, Hubertus and Ludwig, Jens and Münzmay, Andreas and Pittroff, Sarah and Razum, Matthias and Röwenstrunk, Daniel and Sack, Harald and Simon, Holger and Schmidt, Dörte and Schrade, Torsten and Walzel, Annika-Valeska and Wiermann, Barbara}}, issn = {{2367-7163}}, journal = {{Research Ideas and Outcomes}}, title = {{{NFDI4Culture - Consortium for research data on material and immaterial cultural heritage}}}, doi = {{10.3897/rio.6.e57036}}, year = {{2020}}, } @inbook{21268, author = {{Huhmann, Tobias and Eilterts, Katja and Schulte, Carsten and Winkelnkemper, Felix}}, booktitle = {{Digitales Lernen in der Grundschule II: Aktuelle Trends in Forschung und Praxis}}, publisher = {{Waxmann Verlag}}, title = {{{Der Darstellungsflüchtigkeit im Geometrieunterricht durch digitale Unterstützung entgegenwirken}}}, year = {{2020}}, } @article{21269, author = {{Ködding, Patrick and Reinhold, Jannik and Scholtysik, Michel and Dumitrescu, Roman}}, issn = {{1690-4524}}, journal = {{Journal of Systemics, Cybernetics and Informatics}}, number = {{2}}, pages = {{pp. 14--19}}, title = {{{Consulting via Research in IMPRESS}}}, volume = {{18}}, year = {{2020}}, }