TY - JOUR AB - Lithium niobate (LiNbO3), a material frequently used in optical applications, hosts different kinds of polarons that significantly affect many of its physical properties. In this study, a variety of electron polarons, namely free, bound, and bipolarons, are analyzed using first-principles calculations. We perform a full structural optimization based on density-functional theory for selected intrinsic defects with special attention to the role of symmetry-breaking distortions that lower the total energy. The cations hosting the various polarons relax to a different degree, with a larger relaxation corresponding to a larger gap between the defect level and the conduction-band edge. The projected density of states reveals that the polaron states are formerly empty Nb 4d states lowered into the band gap. Optical absorption spectra are derived within the independent-particle approximation, corrected by the GW approximation that yields a wider band gap and by including excitonic effects within the Bethe-Salpeter equation. Comparing the calculated spectra with the density of states, we find that the defect peak observed in the optical absorption stems from transitions between the defect level and a continuum of empty Nb 4d states. Signatures of polarons are further analyzed in the reflectivity and other experimentally measurable optical coefficients. AU - Schmidt, Falko AU - Kozub, Agnieszka L. AU - Gerstmann, Uwe AU - Schmidt, Wolf Gero AU - Schindlmayr, Arno ID - 21946 JF - Crystals TI - Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response VL - 11 ER - TY - CONF AB - Population/mixing-time-dependent two-dimensional coherent spectra are presented for exciton-polaritons in a microcavity. Theory based on dynamically-controlled truncation reveals coherent and incoherent contributions to the decay dynamics. AU - Meier, Torsten AU - Paul, Jagannath AU - Rose, Hendrik AU - Wahlstrand, Jared K AU - Bristow, Alan D ID - 43746 SN - 978-1-55752-308-2 T2 - Frontiers in Optics TI - Coherent and incoherent contribution of population dynamics of semiconductor exciton-polaritons ER - TY - CONF AU - Reichelt, Matthias AU - Rose, Hendrik AU - Kosarev, Alexander N. AU - Poltavtsev, Sergey V. AU - Bayer, Manfred AU - Akimov, Ilya A. AU - Schneider, Christian AU - Kamp, Martin AU - Höfling, Sven AU - Meier, Torsten ED - Betz, Markus ED - Elezzabi, Abdulhakem Y. ID - 23474 T2 - Ultrafast Phenomena and Nanophotonics XXV TI - Controlling the emission time of photon echoes by optical freezing of exciton dephasing and rephasing in quantum-dot ensembles VL - 11684 ER - TY - JOUR AU - Murzakhanov, F. F. AU - Yavkin, B. V. AU - Mamin, G. V. AU - Orlinskii, S. B. AU - von Bardeleben, H. J. AU - Biktagirov, Timur AU - Gerstmann, Uwe AU - Soltamov, V. A. ID - 29749 JF - Physical Review B SN - 2469-9950 TI - Hyperfine and nuclear quadrupole splitting of the NV− ground state in 4H-SiC VL - 103 ER - TY - JOUR AU - Aldahhak, Hazem AU - Hogan, Conor AU - Lindner, Susi AU - Appelfeller, Stephan AU - Eisele, Holger AU - Schmidt, Wolf Gero AU - Dähne, Mario AU - Gerstmann, Uwe AU - Franz, Martin ID - 22010 JF - Physical Review B SN - 2469-9950 TI - Electronic structure of the Si(111)3×3R30∘−B surface from theory and photoemission spectroscopy VL - 103 ER - TY - JOUR AU - Rose, Hendrik AU - Popolitova, D. V. AU - Tikhonova, O. V. AU - Meier, Torsten AU - Sharapova, Polina ID - 23478 JF - Physical Review A SN - 2469-9926 TI - Dark-state and loss-induced phenomena in the quantum-optical regime of Λ-type three-level systems VL - 103 ER - TY - JOUR AU - Belobo, Didier Belobo AU - Meier, Torsten ID - 23473 JF - New Journal of Physics SN - 1367-2630 TI - Approximate nonlinear wave solutions of the coupled two-component Gross–Pitaevskii equations with spin–orbit interaction VL - 23 ER - TY - JOUR AU - Nguyen, T. T. Nhung AU - Sollfrank, T. AU - Tegenkamp, C. AU - Rauls, E. AU - Gerstmann, Uwe ID - 22881 JF - Physical Review B SN - 2469-9950 TI - Impact of screening and relaxation on weakly coupled two-dimensional heterostructures VL - 103 ER - TY - JOUR AB - Modern forming processes often allow today the efficient production of complex parts. In order to increase the sustainability of forming processes it would be favorable if the forming of workpieces becomes possible using production waste. At the Chair of Forming and Machining Technology of the Paderborn University (LUF) research is presently conducted with the overall goal to produce workpieces directly from secondary aluminum (e.g., powder and chips). Therefore, friction-based forming processes like friction spinning (or cognate processes) are used due to their high efficiency. As a pre-step, the production of semi-finished parts was the subject of accorded research work at the LUF. Therefore, a friction-based hot extrusion process was used for the full recycling or rework of aluminum chips into profiles. Investigations of the recycled semi-finished products show that they are comparable to conventionally produced semi-finished products in terms of dimensional stability and shape accuracy. An analysis of the mechanical properties of hardness and tensile strength shows that a final product with good and homogeneously distributed properties can be produced. Furthermore, significant correlations to the friction spinning process could be found that are useful for the above-mentioned direct part production from secondary aluminum. AU - Borgert, Thomas AU - Homberg, Werner ID - 21635 JF - Metals SN - 2075-4701 TI - Friction-Induced Recycling Process for User-Specific Semi-Finished Product Production ER - TY - CONF AU - Moritzer, Elmar AU - Flachmann, Felix ID - 23746 SN - 978-1-7138-3075-7 T2 - SPE ANTEC 2021: The Annual Technical Conference for Plastic Professionals TI - Influence of Chemical Blowing Agents on the Filling Behavior of Wood-Plastic-Composite Melts ER - TY - JOUR AU - Bolenz, Lukas AU - Ehlert, Thomas AU - Dechert, Christopher AU - Bertling, René AU - Kenig, Eugeny ID - 23789 JF - Chemical Engineering Research and Design SN - 0263-8762 TI - Modelling of a continuous distillation process with finite reflux ratio using the hydrodynamic analogy approach ER - TY - CONF AB - Driven by the CO2-emission law by the European government and the increasing costs for raw materials as well as energy, the automotive industry is increasingly using multi-material constructions. This leads to a continuous increase in the use of mechanical joining techniques and especially the self-piercing riveting is of particular importance. The reason for this is the wide range of joining possibilities as well as the high load-bearing capacities of the joints. To be able to react to changing boundary conditions, like material thickness or strength variation of the sheets, research work is crucial with regard to the increase of versatility. In this paper, a numerical study of the influences on the selfpiercing riveting process is presented. For this purpose, the influence of different process parameters such as rivet length and die depth on various quality-relevant characteristics were investigated. With the help of the design of experiment, significant influences were determined and interactions between the individual parameters are shown. AU - Kappe, Fabian AU - Bielak, Christian Roman AU - Sartisson, Vadim AU - Bobbert, Mathias AU - Meschut, Gerson ID - 34222 T2 - ESAFORM 2021 TI - Influence of rivet length on joint formation on self-piercing riveting process considering further process parameters ER - TY - CONF AB - In many areas of product manufacturing constructions consist of individual components and metal sheets that are joined together to form complex structures. A simple and industrial common method for joining dissimilar and coated materials is clinching. During the joining process and due to the service load cracks can occur in the area of the joint, propagate due to cyclic loading and consequently lead to structural failure. For the prevention of these damage cases, first of all knowledge about the fracture mechanical material parameters regarding the original material state of the sheet metals used within the clinching process are essential.Within the scope of this paper experimental and numerical preliminary investigations regarding the fracture mechanical behavior of sheet metals used within the clinching process are presented. Due to the low thickness of 1.5 mm of the material sheets, the development of a new specimen is necessary to determine the crack growth rate curve including the fracture mechanical parameters like the threshold against crack growth ΔKI,th and the fracture toughness KIC of the base material HCT590X. For the experimental determination of the crack growth rate curve the numerical calculation of the geometry factor function as well as the calibration function of this special specimen are essential. After the experimental validation of the numerically determined calibration function, crack growth rate curves are determined for the stress ratios R = 0.1 and R = 0.3 to examine the mean stress sensitivity. In addition, the different rolling directions of 0° and 90° in relation to the initial crack are taken into account in order to investigate the influence of the anisotropy due to rolling. AU - Weiß, Deborah AU - Schramm, Britta AU - Kullmer, Gunter ID - 30675 KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 1662-9795 T2 - Key Engineering Materials TI - Numerical and Experimental Fracture Mechanical Investigations of Clinchable Sheet Metals Made of HCT590X VL - 883 ER - TY - JOUR AB - AbstractIn addition to the classical strength calculation, it is important to design components with regard to fracture mechanics because defects and cracks in a component can drastically influence its strength or fatigue behavior. Cracks can propagate due to operational loads and consequently lead to component failure. The fracture mechanical analysis provides information on stable or unstable crack growth as well as about the direction and the growth rate of a crack. For this purpose, sufficient information has to be available about the crack location, the crack length, the component geometry, the component loading and the fracture mechanical material parameters. The fracture mechanical properties are determined experimentally with standardized specimens as defined by the guidelines of the American Society for Testing and Materials. In practice, however, especially in the context with damage cases or formed material fracture mechanical parameters directly for a component are of interest. However, standard specimens often cannot be extracted at all due to the complexity of the component geometry. Therefore, the development of special specimens is required whereby certain arrangements have to be made in advance. These arrangements are presented in the present paper in order to contribute to a holistic investigation chain for the experimental determination of fracture mechanical material parameters with special specimens. AU - Weiß, Deborah AU - Schramm, Britta AU - Kullmer, Gunter ID - 30674 JF - Production Engineering KW - Industrial and Manufacturing Engineering KW - Mechanical Engineering SN - 0944-6524 TI - Holistic investigation chain for the experimental determination of fracture mechanical material parameters with special specimens ER - TY - JOUR AB - Powder X-ray diffraction (XRD) patterns of ordered mesoporous CMK-8 and CMK-9 carbon materials are simulated by geometric modeling. The materials are amorphous at the atomic length scale but exhibit highly symmetric gyroidal structures at the nanometer scale, corresponding to regular, continuous nanopore systems with cubic symmetry. Their structures lead to characteristic low-angle XRD signatures. We introduce a model based on geometrical considerations to simulate CMK-8 and CMK-9 structures with variable volume fraction of carbon (vs. pore volume, i.e., variable 'pore wall thickness'). In addition, we also simulate carbon materials with variable amounts of guest species (e.g., sulfur) residing in their pores. The corresponding XRD patterns are calculated. The carbon volume fraction turns out to have a significant impact on the relative diffraction peak intensities, especially in case of CMK-9 carbon that features a bimodal porosity. Likewise, the presence of guest species in the pores may also strongly affect the relative peak intensities. Our study suggests that careful evaluation of experimental low-angle XRD patterns of (real) CMK-8 or CMK-9 materials offers an opportunity to obtain detailed information about the nanostructural properties in addition to the mere identification of the pore systems geometry. AU - Schwind, Bertram AU - Smått, Jan-Henrik AU - Tiemann, Michael AU - Weinberger, Christian ID - 25894 JF - Microporous and Mesoporous Materials SN - 1387-1811 TI - Modeling of gyroidal mesoporous CMK-8 and CMK-9 carbon nanostructures and their X-Ray diffraction patterns ER - TY - JOUR AB - A comparison of infrared spectroscopic analytical approaches was made in order to assess their applicability for internal structure characterization of SiO2 thin films. Markers for porosity and/or disorder based on the analysis of the asymmetric stretching absorption band of SiO2 between 900−1350 cm−1 were discussed. The shape of this band, which shows a well-defined LO–TO splitting, depends not only on the inherent characteristics of the film under analysis but also on the particular geometry of the IR experiment and the specific surface selection rules of the substrate. Three types of SiO2 thin films with clearly defined porosity ranging from dense films to mesoporous films were investigated by transmission (at different incidence angles), direct specular reflection (at different angles), and diffuse reflection. Two different types of substrate, metallic and semiconducting, were used. The combined effect of substrate and specific technique in the final shape of the band, was discussed, and the efficacy for their applicability to the determination of porosity in thin SiO2 films was critically evaluated. AU - de los Arcos, Teresa AU - Müller, Hendrik AU - Wang, Fuzeng AU - Damerla, Varun Raj AU - Hoppe, Christian AU - Weinberger, Christian AU - Tiemann, Michael AU - Grundmeier, Guido ID - 25897 JF - Vibrational Spectroscopy SN - 0924-2031 TI - Review of infrared spectroscopy techniques for the determination of internal structure in thin SiO2 films ER - TY - THES AU - Olenberg, Alexander ID - 42812 SN - 9783843947855 TI - Untersuchung und Optimierung von strukturierten Packungen mittels CFD-Simulationen ER - TY - JOUR AB - Tailor-made ordered mesoporous materials bear great potential in numerous fields of application where large interfaces are required. However, the inherent surfacechemical properties of conventional materials, such as silica, carbon or organosilica, poses some limitations with respect to their application. Surface manipulation by functionalization with chemically more reactive groups is one way to improve materials for their desired purpose. Another approach is the design of high surface-area composite materials. The surface manipulation, either by functionalization or by introducing guest species, can be performed selectively. This means that when several distinct, i.e. , hierarchical, types of surfaces or pore systems exist in a material, each of them may be chosen for manipulation. Several strategies can be identified to achieve this goal. Molecules or molecule assemblies can be utilized to temporarily protect pores or surfaces (soft protection), while manipulation occurs at the accessible sites. This approach is a recurring motive in this review and can also be applied to rigid template matrices (hard protection). Furthermore, the size of functionalization agents (size protection) and their reactivity/diffusion (kinetic protection) into the pores can also be utilized to achieve selectivity. In addition, challenges in the synthesis and characterization of selectively manipulated ordered mesoporous materials are discussed. AU - Tiemann, Michael AU - Weinberger, Christian ID - 25893 JF - Advanced Materials Interfaces SN - 2196-7350 TI - Selective Modification of Hierarchical Pores and Surfaces in Nanoporous Materials ER - TY - JOUR AU - Fuchs, Christian ID - 41431 IS - 1 JF - tripleC: Communication, Capitalism & Critique TI - Engels@200: Friedrich Engels in the Age of Digital Capitalism VL - 19 ER - TY - JOUR AU - Fuchs, Christian AU - Dyer-Witheford, Nick ID - 41599 JF - 国际社会科学杂志 (Journal of International Social Sciences) 2021 (9) TI - 卡尔·马克思与互联网研究 ER - TY - JOUR AB - In this report, a flame spray pyrolysis setup has been examined with various in situ extraction methods of particle samples along the flame axis. First, two precursor formulations leading to the formation of iron oxide nanoparticles were used in a standardized SpraySyn burner system, and the final particle outcome was characterized by a broad range of established powder characterization techniques (TEM/HRTEM, SAXS, XRD, BET). The characterization of the powder products evidenced that mostly homogeneous gas-to-particle conversion takes place when applying an acidic precursor solution, whereas the absence of the acid leads to a dominant droplet-to-particle pathway. Our study indicates that a droplet-to-particle-pathway could be present even when processing the acidic formulation. However, even if a secondary pathway might take place in this case as well, it is not dominant and nearly negligible. Subsequently, the in situ particle structure evolution was investigated for the dominant gas-to-particle pathway, and particles were extracted along the flame axis for online SMPS and offline TEM/HRTEM analysis. Due to the highly reactive conditions within the flame (high temperatures, turbulent flow field, high particle number concentrations), the extraction of representative samples from spray flames is challenging. In order to handle the reactive conditions, two extraction techniques were tailored in this report. To extract an aerosol sample within the flame for SMPS measurement, a Hole in a Tube probe was adjusted. Thus, the mobility particle diameter as well as the corresponding distribution widths were obtained at different heights above the burner along the flame axis. For TEM/HRTEM image analysis, particle samples were collected thermophoretically by means of a tailored shutter system. Since all sampling grids were protected until reaching the flame axis and due to the low sampling time, momentary captures of local particle structures could be extracted precisely. The particle morphologies have clearly shown an evolution from spherical and paired particles in the flame center to fractal and compact agglomerates at later synthesis stages. AU - Tischendorf, R. AU - Simmler, M. AU - Weinberger, Christian AU - Bieber, M. AU - Reddemann, M. AU - Fröde, F. AU - Lindner, J. AU - Pitsch, H. AU - Kneer, R. AU - Tiemann, Michael AU - Nirschl, H. AU - Schmid, H.-J. ID - 25896 JF - Journal of Aerosol Science SN - 0021-8502 TI - Examination of the evolution of iron oxide nanoparticles in flame spray pyrolysis by tailored in situ particle sampling techniques ER - TY - JOUR AB - Photodynamic therapy (PDT) using TiO2 nanoparticles has become an important alternative treatment for different types of cancer due to their high photocatalytic activity and high absorption of UV-A light. To potentiate this treatment, we have coated commercial glass plates with TiO2 nanoparticles prepared by the sol–gel method (TiO2-m), which exhibit a remarkable selectivity for the irreversible trapping of cancer cells. The physicochemical properties of the deposited TiO2-m nanoparticle coatings have been characterized by a number of complementary surface-analytical techniques and their interaction with leukemia and healthy blood cells were investigated. Scanning electron and atomic force microscopy verify the formation of a compact layer of TiO2-m nanoparticles. The particles are predominantly in the anatase phase and have hydroxyl-terminated surfaces as revealed by Raman, X-ray photoelectron, and infrared spectroscopy, as well as X-ray diffraction. We find that lymphoblastic leukemia cells adhere to the TiO2-m coating and undergo amoeboid-like migration, whereas lymphocytic cells show distinctly weaker interactions with the coating. This evidences the potential of this nanomaterial coating to selectively trap cancer cells and renders it a promising candidate for the development of future prototypes of PDT devices for the treatment of leukemia and other types of cancers with non-adherent cells. AU - Garcia Diosa, Jaime Andres AU - Gonzalez Orive, Alejandro AU - Weinberger, Christian AU - Schwiderek, Sabrina AU - Knust, Steffen AU - Tiemann, Michael AU - Grundmeier, Guido AU - Keller, Adrian AU - Camargo Amado, Ruben Jesus ID - 22635 JF - Journal of Biomedical Materials Research Part B: Applied Biomaterials SN - 1552-4973 TI - TiO2 nanoparticle coatings on glass surfaces for the selective trapping of leukemia cells from peripheral blood VL - 109 ER - TY - JOUR AB - The tetratopic linker 1,1,2,2-tetrakis(4-phosphonophenyl)ethylene (H8TPPE) was used to synthesize the three new porous metal–organic frameworks of composition [M2(H2O)2(H2TPPE)]·xH2O (M = Al3+, Ga3+, Fe3+), denoted as M-CAU-53 under hydrothermal reaction conditions, using the corresponding metal nitrates as starting materials. The crystal structures of the compounds were determined ab initio from powder X-ray diffraction data, revealing small structural differences. Proton conductivity measurements were carried out, indicating different conductivity mechanisms. The differences in proton conductivity could be linked to the individual structures. In addition, a thorough characterization via thermogravimetry, elemental analysis, IR-spectroscopy as well as N2- and H2O-sorption is given. AU - Steinke, Felix AU - Javed, Ali AU - Wöhlbrandt, Stephan AU - Tiemann, Michael AU - Stock, Norbert ID - 25892 JF - Dalton Transactions SN - 1477-9226 TI - New isoreticular phosphonate MOFs based on a tetratopic linker ER - TY - CHAP AU - Eickelmann, Birgit ID - 29061 T2 - Chancen denken. Impulse für eine offene und mutige Gesellschaft im 21. Jahrhundert TI - Etwas anarchischer, freier, ungewohnter (Ein Gespräch mit Birgit Eickelmann) ER - TY - CHAP AU - Eickelmann, Birgit AU - Maaz, Kai ED - Maaz, Kai ED - Becker-Mrotzek, Michael ID - 29062 T2 - Schule weiter denken TI - Ungleichheiten im Bildungssystem – eine unangenehme Konstante. Sinnvolle Maßnahmen und die Grenzen des Möglichen ER - TY - GEN AU - Bonanati, Sabrina AU - Buhl, Heike M. AU - Eickelmann, Birgit ID - 29066 TI - Wie Lernen in digitalen Lernumgebungen motivieren kann – Stichwort: Gamification ER - TY - JOUR AB - Abstract Objective External focus (EF) of attention leads to improved balance performance. Consideration of the neuromodulatory effects of EF may inform its clinical utility in addressing neuroplastic impairments after musculoskeletal injuries. We aimed to determine whether electrocortical activity and balance performance changed with attentional foci that prioritized differing sensory feedback and whether changes in electrocortical activity and balance were associated. Methods Individuals who were healthy (n = 15) performed a single-limb balance task under 3 conditions: internal focus (IF), somatosensory focus [EF with a baton (EF-baton)], and visual focus [EF with a laser (EF-laser)]. Electrocortical activity and postural sway were recorded concurrently using electroencephalography and a triaxial force plate. Electroencephalographic signals were decomposed, localized, and clustered to generate power spectral density in θ and α-2 frequency bands. Postural sway signals were analyzed with center-of-pressure sway metrics (eg, area, distance, velocity) and knee angle. The relationship between percent change in clustered brain activity and task performance metrics was assessed. Results Both EF conditions resulted in increased cortical activity and improved balance performance compared to IF. EF-laser had the largest effect, demonstrating increased frontal θ power (d = 0.64), decreased central θ power (d = −0.30), and decreased bilateral motor, bilateral parietal, and occipital α-2 power (d = −1.38 to −4.27) as well as a shorter path distance (d = −0.94) and a deeper (d = 0.70) and less variable (d = −1.15) knee angle than IF. Weak to moderate associations exist between increases in cortical activity and improved balance performance (ρ = 0.405–0.584). Conclusions EF resulted in increased cortical activity associated with cognitive, motor, somatosensory, and visual processing. EF-laser, which prioritized visual feedback, had the largest and broadest effects. Changes in cortical activity resulting from EF were independently associated with improved balance performance. Impact This study demonstrates that goal-oriented attention results in functional increases in brain activity compared to internally directed self-focus. These results suggest EF may target neurophysiologic impairments and improve balance in clinical populations. AU - Sherman, David A AU - Lehmann, Tim AU - Baumeister, Jochen AU - Gokeler, Alli AU - Donovan, Luke AU - Norte, Grant E ID - 34024 JF - Physical Therapy KW - Physical Therapy KW - Sports Therapy and Rehabilitation SN - 0031-9023 TI - External Focus of Attention Influences Cortical Activity Associated with Single Limb Balance Performance ER - TY - JOUR AB - Whereas initial findings have already identified cortical patterns accompanying proprioceptive deficiencies in patients after anterior cruciate ligament reconstruction (ACLR), little is known about compensatory sensorimotor mechanisms for re-establishing postural control. Therefore, the aim of the present study was to explore leg dependent patterns of cortical contributions to postural control in patients 6 weeks following ACLR. A total of 12 patients after ACLR (25.1 ± 3.2 years, 178.1 ± 9.7 cm, 77.5 ± 14.4 kg) and another 12 gender, age, and activity matched healthy controls participated in this study. All subjects performed 10 × 30 s. single leg stances on each leg, equipped with 64-channel mobile electroencephalography (EEG). Postural stability was quantified by area of sway and sway velocity. Estimations of the weighted phase lag index were conducted as a cortical measure of functional connectivity. The findings showed significant group × leg interactions for increased functional connectivity in the anterior cruciate ligament (ACL) injured leg, predominantly including fronto−parietal [F(1, 22) = 8.41, p ≤ 0.008, η2 = 0.28], fronto−occipital [F(1, 22) = 4.43, p ≤ 0.047, η2 = 0.17], parieto−motor [F(1, 22) = 10.30, p ≤ 0.004, η2 = 0.32], occipito−motor [F(1, 22) = 5.21, p ≤ 0.032, η2 = 0.19], and occipito−parietal [F(1, 22) = 4.60, p ≤ 0.043, η2 = 0.17] intra−hemispherical connections in the contralateral hemisphere and occipito−motor [F(1, 22) = 7.33, p ≤ 0.013, η2 = 0.25] on the ipsilateral hemisphere to the injured leg. Higher functional connectivity in patients after ACLR, attained by increased emphasis of functional connections incorporating the somatosensory and visual areas, may serve as a compensatory mechanism to control postural stability of the injured leg in the early phase of rehabilitation. These preliminary results may help to develop new neurophysiological assessments for detecting functional deficiencies after ACLR in the future. AU - Lehmann, Tim AU - Büchel, Daniel AU - Mouton, Caroline AU - Gokeler, Alli AU - Seil, Romain AU - Baumeister, Jochen ID - 32434 JF - Frontiers in Human Neuroscience KW - Behavioral Neuroscience KW - Biological Psychiatry KW - Psychiatry and Mental health KW - Neurology KW - Neuropsychology and Physiological Psychology SN - 1662-5161 TI - Functional Cortical Connectivity Related to Postural Control in Patients Six Weeks After Anterior Cruciate Ligament Reconstruction VL - 15 ER - TY - JOUR AB - Abstract Mobile Electroencephalography (EEG) provides insights into cortical contributions to postural control. Although changes in theta (4–8 Hz) and alpha frequency power (8–12 Hz) were shown to reflect attentional and sensorimotor processing during balance tasks, information about the effect of stance leg on cortical processing related to postural control is lacking. Therefore, the aim was to examine patterns of cortical activity during single-leg stance with varying surface stability. EEG and force plate data from 21 healthy males (22.43 ± 2.23 years) was recorded during unipedal stance (left/right) on a stable and unstable surface. Using source-space analysis, power spectral density was analyzed in the theta, alpha-1 (8–10 Hz) and alpha-2 (10–12 Hz) frequency bands. Repeated measures ANOVA with the factors leg and surface stability revealed significant interaction effects in the left (p = 0.045, ηp2 = 0.13) and right motor clusters (F = 16.156; p = 0.001, ηp2 = 0.41). Furthermore, significant main effects for surface stability were observed for the fronto-central cluster (theta), left and right motor (alpha-1), as well as for the right parieto-occipital cluster (alpha-1/alpha-2). Leg dependent changes in alpha-2 power may indicate lateralized patterns of cortical processing in motor areas during single-leg stance. Future studies may therefore consider lateralized patterns of cortical activity for the interpretation of postural deficiencies in unilateral lower limb injuries. AU - Büchel, Daniel AU - Lehmann, Tim AU - Ullrich, Sarah AU - Cockcroft, John AU - Louw, Quinette AU - Baumeister, Jochen ID - 32435 IS - 4 JF - Experimental Brain Research KW - General Neuroscience SN - 0014-4819 TI - Stance leg and surface stability modulate cortical activity during human single leg stance VL - 239 ER - TY - JOUR AU - Büchel, Daniel AU - Lehmann, Tim AU - Sandbakk, Øyvind AU - Baumeister, Jochen ID - 35626 IS - 1 JF - Scientific Reports KW - Multidisciplinary SN - 2045-2322 TI - EEG‑derived brain graphs are reliable measures for exploring exercise‑induced changes in brain networks VL - 11 ER - TY - GEN AU - Neukötter, Moritz AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 24475 TI - Theoretische Beschreibung des Tropfenbildungsprozesses bei der Filament Extension Atomization: Entwicklung eines Vorhersagemodells für die Tropfengröße (Poster) ER - TY - GEN AU - Neukötter, Moritz AU - Jesinghausen, Steffen AU - Schmid, Hans-Joachim ID - 30221 TI - Filament Extension Atomization – A novel Process for Powder Production? (Presentation) ER - TY - JOUR AU - Möhring, Julia AU - Krumhöfner, Anika AU - Gräfin von Plettenberg, Elisabeth Gudila Sophia Ida Maria ID - 43016 JF - - TI - Bewegungsförderung in Ganztagsschulen ER - TY - GEN AU - Leineweber, Jonas ID - 33210 TI - Veranstaltungsbericht: Immaterielles Kulturerbe in Nordrhein-Westfalen – Steigerlied und Trinkhallenkultur im Ruhrgebiet erhalten Auszeichnung anlässlich der Neuaufnahmen in das nordrhein-westfälische Landesinventar ER - TY - GEN AU - Leineweber, Jonas ID - 33209 TI - Tagungsbericht: Immaterielles Kulturerbe und regionale Identität. Gesellschaftliche Repräsentation und Partizipation im Schützenwesen ER - TY - JOUR AB - Zinc oxide nanoparticles (ZnO NP) used for the channel region in inverted coplanar setup in Thin Film Transistors (TFT) were the focus of this study. The regions between the source electrode and the ZnO NP and the drain electrode were under investigation as they produce a Schottky barrier in metal-semiconductor interfaces. A more general Thermionic emission theory must be evaluated: one that considers both metal/semiconductor interfaces (MSM structures). Aluminum, gold, and nickel were used as metallization layers for source and drain electrodes. An organic-inorganic nanocomposite was used as a gate dielectric. The TFTs transfer and output characteristics curves were extracted, and a numerical computational program was used for fitting the data; hence information about Schottky Barrier Height (SBH) and ideality factors for each TFT could be estimated. The nickel metallization appears with the lowest SBH among the metals investigated. For this metal and for higher drain-to-source voltages, the SBH tended to converge to some value around 0.3 eV. The developed fitting method showed good fitting accuracy even when the metallization produced different SBH in each metal-semiconductor interface, as was the case for gold metallization. The Schottky effect is also present and was studied when the drain-to-source voltages and/or the gate voltage were increased. AU - Kaufmann, Ivan Rodrigo AU - Zerey, Onur AU - Meyers, Thorsten AU - Reker, Julia AU - Vidor, Fábio AU - Hilleringmann, Ulrich ID - 39383 IS - 5 JF - Nanomaterials KW - General Materials Science KW - General Chemical Engineering SN - 2079-4991 TI - A Study about Schottky Barrier Height and Ideality Factor in Thin Film Transistors with Metal/Zinc Oxide Nanoparticles Structures Aiming Flexible Electronics Application VL - 11 ER - TY - CONF AU - Reker, Julia AU - Meyers, Thorsten AU - Vidor, Fabio F. AU - Joubert, Trudi-Heleen AU - Hilleringmann, Ulrich ID - 39395 T2 - 2021 Smart Systems Integration (SSI) TI - Complementary Inverter Circuits on Flexible Substrates ER - TY - CONF AU - Hilleringmann, Ulrich AU - Petrov, Dmitry AU - Mwammenywa, Ibrahim AU - Kagarura, Geoffrey M. ID - 39381 T2 - 2021 IEEE AFRICON TI - Local Power Control using Wireless Sensor System for Microgrids in Africa ER - TY - CONF AU - Andrews, George AU - Hilleringmann, Ulrich AU - Joubert, Trudi-Heleen ID - 39385 T2 - 2021 IEEE AFRICON TI - The Viability of a Non-Flow Capacitive Biosensing Microsystem for Whole Cell Counting ER - TY - CONF AU - Andrews, George AU - Hilleringmann, Ulrich AU - Joubert, Trudi-Heleen ID - 39386 T2 - 2021 IEEE AFRICON TI - The Viability of a Non-Flow Capacitive Biosensing Microsystem for Whole Cell Counting ER - TY - CHAP AU - Gerhardts, Lara AU - Dehmel, Lukas AU - Meister, Dorothee M. ED - Wolf, Karsten D ED - Rummler, Klaus ED - Bettinger, Patrick ED - Aßmann, Sandra ID - 43143 T2 - Jahrbuch Medienpädagogik 16. Medienpädagogik in Zeiten einer tiefgreifenden Mediatisierung TI - Die berufliche Tabletaneignung von Lehrkräften als Beispiel der Mediatisierung pädagogischer Handlungskontexte. Theoretische Perspektiven und empirische Befunde ER - TY - CHAP AU - Dehmel, Lukas ED - Bernhard-Skala,, Christian ED - Bolten-Bühler, Ricarda ED - Koller, Julia ED - Rohs, Matthias ED - Wahl, Johannes ID - 43142 T2 - Erwachsenenpädagogische Digitalisierungsforschung. Impulse - Befunde - Perspektiven. Bielefeld TI - Zur Entgrenzung der Arbeit des medienpädagogischen Weiterbildungspersonals im Kontext tiefgreifender Mediatisierung ER - TY - JOUR AU - Hälterlein, Jens ID - 43278 IS - 1 JF - Big Data & Society TI - Epistemologies of predictive policing: Mathematical social science, social physics and machine learning VL - 8 ER - TY - JOUR AB - Let E be an ordinary elliptic curve over a finite field and g be a positive integer. Under some technical assumptions, we give an algorithm to span the isomorphism classes of principally polarized abelian varieties in the isogeny class of E⁹ . The varieties are first described as hermitian lattices over (not necessarily maximal) quadratic orders and then geometrically in terms of their algebraic theta null point. We also show how to algebraically compute Siegel modular forms of even weight given as polynomials in the theta constants by a careful choice of an affine lift of the theta null point. We then use these results to give an algebraic computation of Serre’s obstruction for principally polarized abelian threefolds isogenous to E³ and of the Igusa modular form in dimension 4. We illustrate our algorithms with examples of curves with many rational points over finite fields. AU - Kirschmer, Markus AU - Narbonne, Fabien AU - Ritzenthaler, Christophe AU - Robert, Damien ID - 34912 IS - 333 JF - Mathematics of Computation KW - Applied Mathematics KW - Computational Mathematics KW - Algebra and Number Theory SN - 0025-5718 TI - Spanning the isogeny class of a power of an elliptic curve VL - 91 ER - TY - GEN AU - Schroeter-Wittke, Harald ID - 41088 SN - 0540–6226 T2 - Jahrbuch für Evangelische Kirchengeschichte des Rheinlandes TI - Anette Baumann / Alexander Jendorff / Frank Theisen (Hgg.), Religion – Migration – Integration. Studien zu Wechselwirkungen religiös motivierter Mobilität im vormodernen Europa, Tübingen 2019 VL - 70 ER - TY - GEN AU - Schroeter-Wittke, Harald ID - 41090 SN - 0540–6226 T2 - Jahrbuch für Evangelische Kirchengeschichte des Rheinlandes TI - Hendrik Meyer-Magister, Wehrdienst und Verweigerung als komplementäres Handeln. Individualisierungsprozesse im bundesdeutschen Protestantismus der 1950er Jahre (RBRD 7), Tübingen 2019 VL - 70 ER - TY - GEN AU - Schroeter-Wittke, Harald ID - 41091 SN - 0540–6226 T2 - Jahrbuch für Evangelische Kirchengeschichte des Rheinlandes TI - Jutta Stander-Dulisch, Glaubenskrisen, Neue Religionen und der Papst. Religion in „Stern“ und Spiegel“ von 1960 bis 2014, Bielefeld 2019 VL - 70 ER - TY - JOUR AB - The relativistic wave equations determine the dynamics of quantum fields in the context of quantum field theory. One of the conventional tools for dealing with the relativistic bound state problem is the Klein-Fock-Gordon equation. In this work, using a developed scheme, we present how to surmount the centrifugal part and solve the modified Klein-Fock-Gordon equation for the linear combination of Hulthén and Yukawa potentials. In particular, we show that the relativistic energy eigenvalues and corresponding radial wave functions are obtained from supersymmetric quantum mechanics by applying the shape invariance concept. Here, both scalar potential conditions, which are whether equal and nonequal to vector potential, are considered in the calculation. The energy levels and corresponding normalized eigenfunctions are represented as a recursion relation regarding the Jacobi polynomials for arbitrary l states. Beyond that, a closed form of the normalization constant of the wave functions is found. Furthermore, we state that the energy eigenvalues are quite sensitive with potential parameters for the quantum states. The nonrelativistic and relativistic results obtained within SUSY QM overlap entirely with the results obtained by ordinary quantum mechanics, and it displays that the mathematical implementation of SUSY quantum mechanics is quite perfect. AU - Ahmadov, A. I. AU - Aslanova, S. M. AU - Orujova, M. Sh. AU - Badalov, S. V. ED - Vagnozzi, Sunny ID - 44042 JF - Advances in High Energy Physics KW - Nuclear and High Energy Physics SN - 1687-7365 TI - Analytical Bound State Solutions of the Klein-Fock-Gordon Equation for the Sum of Hulthén and Yukawa Potential within SUSY Quantum Mechanics VL - 2021 ER - TY - CONF AU - Meydani, Elnaz AU - Düsing, Christoph AU - Trier, Matthias ID - 44073 T2 - Innovation Through Information Systems: Volume II: A Collection of Latest Research on Technology Issues TI - Towards a Trust-Aware Item Recommendation System on a Graph Autoencoder with Attention Mechanism ER - TY - JOUR AU - Neufeld, Sergej AU - Bocchini, Adriana AU - Schmidt, Wolf Gero ID - 22310 JF - Physical Review Materials SN - 2475-9953 TI - Potassium titanyl phosphate Z- and Y-cut surfaces from density-functional theory ER - TY - JOUR AU - Plaickner, Julian AU - Speiser, Eugen AU - Braun, Christian AU - Schmidt, Wolf Gero AU - Esser, Norbert AU - Sanna, Simone ID - 22008 JF - Physical Review B SN - 2469-9950 TI - Surface localized phonon modes at the Si(553)-Au nanowire system ER - TY - JOUR AU - Meier, Lukas AU - Schmidt, Wolf Gero ID - 40244 IS - 1 JF - physica status solidi (b) KW - Condensed Matter Physics KW - Electronic KW - Optical and Magnetic Materials SN - 0370-1972 TI - GaInP/AlInP(001) Interfaces from Density Functional Theory VL - 259 ER - TY - JOUR AU - Ruiz Alvarado, Isaac Azahel AU - Karmo, Marsel AU - Runge, Erich AU - Schmidt, Wolf Gero ID - 22009 JF - ACS Omega SN - 2470-1343 TI - InP and AlInP(001)(2 × 4) Surface Oxidation from Density Functional Theory ER - TY - JOUR AB - We perform a theoretical analysis of the structural and electronic properties of sodium potassium niobate K1-xNaxNbO3 in the orthorhombic room-temperature phase, based on density-functional theory in combination with the supercell approach. Our results for x=0 and x=0.5 are in very good agreement with experimental measurements and establish that the lattice parameters decrease linearly with increasing Na contents, disproving earlier theoretical studies based on the virtual-crystal approximation that claimed a highly nonlinear behavior with a significant structural distortion and volume reduction in K0.5Na0.5NbO3 compared to both end members of the solid solution. Furthermore, we find that the electronic band gap varies very little between x=0 and x=0.5, reflecting the small changes in the lattice parameters. AU - Bidaraguppe Ramesh, Nithin AU - Schmidt, Falko AU - Schindlmayr, Arno ID - 22960 IS - 8 JF - The European Physical Journal B SN - 1434-6028 TI - Lattice parameters and electronic band gap of orthorhombic potassium sodium niobate K0.5Na0.5NbO3 from density-functional theory VL - 94 ER - TY - JOUR AU - Friedrich, Christoph AU - Blügel, Stefan AU - Schindlmayr, Arno ID - 22761 IS - 3 JF - Physical Review B SN - 2469-9950 TI - Erratum: Efficient implementation of the GW approximation within the all-electron FLAPW method [Phys. Rev. B 81, 125102 (2010)] VL - 104 ER - TY - JOUR AB - Uniaxial anisotropy in nonlinear birefringent crystals limits the efficiency of nonlinear optical interactions and breaks the spatial symmetry of light generated in the parametric down-conversion (PDC) process. Therefore, this effect is usually undesirable and must be compensated for. However, high gain may be used to overcome the destructive role of anisotropy in order to generate bright two-mode correlated twin-beams. In this work, we provide a rigorous theoretical description of the spatial properties of bright squeezed light in the presence of strong anisotropy. We investigate a single crystal and a system of two crystals with an air gap (corresponding to a nonlinear SU(1,1) interferometer) and demonstrate the generation of bright correlated twin-beams in such configurations at high gain due to anisotropy. We explore the mode structure of the generated light and show how anisotropy, together with crystal spacing, can be used for radiation shaping. AU - Riabinin, M. AU - Sharapova, Polina AU - Meier, Torsten ID - 37334 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Bright correlated twin-beam generation and radiation shaping in high-gain parametric down-conversion with anisotropy VL - 29 ER - TY - JOUR AU - Geraldi, Andrea AU - De, Syamsundar AU - Laneve, Alessandro AU - Barkhofen, Sonja AU - Sperling, Jan AU - Mataloni, Paolo AU - Silberhorn, Christine ID - 26287 JF - Physical Review Research SN - 2643-1564 TI - Transient subdiffusion via disordered quantum walks ER - TY - JOUR AU - Tiedau, J. AU - Engelkemeier, M. AU - Brecht, Benjamin AU - Sperling, Jan AU - Silberhorn, Christine ID - 21021 JF - Physical Review Letters SN - 0031-9007 TI - Statistical Benchmarking of Scalable Photonic Quantum Systems VL - 126 ER - TY - JOUR AU - Prasannan, Nidhin AU - De, Syamsundar AU - Barkhofen, Sonja AU - Brecht, Benjamin AU - Silberhorn, Christine AU - Sperling, Jan ID - 26286 JF - Physical Review A SN - 2469-9926 TI - Experimental entanglement characterization of two-rebit states VL - 103 ER - TY - JOUR AU - Köhnke, S. AU - Agudelo, E. AU - Schünemann, M. AU - Schlettwein, O. AU - Vogel, W. AU - Sperling, Jan AU - Hage, B. ID - 26285 JF - Physical Review Letters SN - 0031-9007 TI - Quantum Correlations beyond Entanglement and Discord ER - TY - JOUR AB - Employing the ultrafast control of electronic states of a semiconductor quantum dot in a cavity, we introduce an approach to achieve on-demand emission of single photons with almost perfect indistinguishability and photon pairs with near ideal entanglement. Our scheme is based on optical excitation off resonant to a cavity mode followed by ultrafast control of the electronic states using the time-dependent quantum-confined Stark effect, which then allows for cavity-resonant emission. Our theoretical analysis considers cavity-loss mechanisms, the Stark effect, and phonon-induced dephasing, allowing realistic predictions for finite temperatures. AU - Bauch, David AU - Heinze, Dirk Florian AU - Förstner, Jens AU - Jöns, Klaus AU - Schumacher, Stefan ID - 23816 JF - Physical Review B KW - tet_topic_qd SN - 2469-9950 TI - Ultrafast electric control of cavity mediated single-photon and photon-pair generation with semiconductor quantum dots VL - 104 ER - TY - JOUR AB - AbstractA detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands. AU - Wiebeler, Christian AU - Vollbrecht, Joachim AU - Neuba, Adam AU - Kitzerow, Heinz-Siegfried AU - Schumacher, Stefan ID - 39653 IS - 1 JF - Scientific Reports KW - Multidisciplinary SN - 2045-2322 TI - Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters VL - 11 ER - TY - JOUR AU - Klement, Philip AU - Dehnhardt, Natalie AU - Dong, Chuan-Ding AU - Dobener, Florian AU - Bayliff, Samuel AU - Winkler, Julius AU - Hofmann, Detlev M. AU - Klar, Peter J. AU - Schumacher, Stefan AU - Chatterjee, Sangam AU - Heine, Johanna ID - 40434 IS - 23 JF - Advanced Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 0935-9648 TI - Atomically Thin Sheets of Lead‐Free 1D Hybrid Perovskites Feature Tunable White‐Light Emission from Self‐Trapped Excitons VL - 33 ER - TY - JOUR AU - Barkhausen, Franziska AU - Pukrop, Matthias AU - Schumacher, Stefan AU - Ma, Xuekai ID - 21359 IS - 7 JF - Physical Review B SN - 2469-9950 TI - Structuring coflowing and counterflowing currents of polariton condensates in concentric ring-shaped and elliptical potentials VL - 103 ER - TY - JOUR AU - Franz, Martin AU - Chandola, Sandhya AU - Koy, Maximilian AU - Zielinski, Robert AU - Aldahhak, Hazem AU - Das, Mowpriya AU - Freitag, Matthias AU - Gerstmann, Uwe AU - Liebig, Denise AU - Hoffmann, Adrian Karl AU - Rosin, Maximilian AU - Schmidt, Wolf Gero AU - Hogan, Conor AU - Glorius, Frank AU - Esser, Norbert AU - Dähne, Mario ID - 24975 JF - Nature Chemistry SN - 1755-4330 TI - Controlled growth of ordered monolayers of N-heterocyclic carbenes on silicon ER - TY - JOUR AB - Density-functional theory within a Berry-phase formulation of the dynamical polarization is used to determine the second-order susceptibility χ(2) of lithium niobate (LiNbO3). Defect trapped polarons and bipolarons are found to strongly enhance the nonlinear susceptibility of the material, in particular if localized at NbV–VLi defect pairs. This is essentially a consequence of the polaronic excitation resulting in relaxation-induced gap states. The occupation of these levels leads to strongly enhanced χ(2) coefficients and allows for the spatial and transient modification of the second-harmonic generation of macroscopic samples. AU - Kozub, Agnieszka L. AU - Schindlmayr, Arno AU - Gerstmann, Uwe AU - Schmidt, Wolf Gero ID - 23418 JF - Physical Review B SN - 2469-9950 TI - Polaronic enhancement of second-harmonic generation in lithium niobate VL - 104 ER - TY - CONF AU - Rose, Hendrik AU - Paul, Jagannath AU - Wahlstrand, Jared K. AU - Bristow, Alan D. AU - Meier, Torsten ED - Betz, Markus ED - Elezzabi, Abdulhakem Y. ID - 23475 T2 - Ultrafast Phenomena and Nanophotonics XXV TI - Theoretical analysis and simulations of two-dimensional Fourier transform spectroscopy performed on exciton-polaritons of a quantum-well microcavity system VL - 11684 ER - TY - JOUR AU - Krauss-Kodytek, L. AU - Hannes, W.-R. AU - Meier, Torsten AU - Ruppert, C. AU - Betz, M. ID - 37333 IS - 8 JF - Physical Review B SN - 2469-9950 TI - Nondegenerate two-photon absorption in ZnSe: Experiment and theory VL - 104 ER - TY - JOUR AU - Riabinin, Matvei AU - Sharapova, Polina AU - Bartley, Tim AU - Meier, Torsten ID - 21547 IS - 4 JF - Journal of Physics Communications SN - 2399-6528 TI - Generating two-mode squeezing with multimode measurement-induced nonlinearity VL - 5 ER - TY - JOUR AU - Krauss-Kodytek, L. AU - Hannes, Wolf-Rüdiger AU - Meier, Torsten AU - Ruppert, C. AU - Betz, M. ID - 23472 IS - 8 JF - Physical Review B SN - 2469-9950 TI - Nondegenerate two-photon absorption in ZnSe: Experiment and theory VL - 104 ER - TY - CONF AU - Moritzer, Elmar AU - Flachmann, Felix ID - 26390 T2 - PPS-36 Proceedings TI - Process-reliable Injection Molding of Highly Filled Wood-Plastic-Composites (WPC) ER - TY - JOUR AU - Teichert, Jeannine ID - 44200 IS - 1 JF - Networking Knowledge TI - Mediating close friendship intimacy in times of (social) distance VL - 14 ER - TY - JOUR AU - Grabo, Matti AU - Acar, Emre AU - Kenig, Eugeny ID - 22265 JF - Renewable Energy SN - 0960-1481 TI - Modeling and improvement of a packed bed latent heat storage filled with non-spherical encapsulated PCM-Elements VL - 173 ER - TY - CONF AU - Rostek, Tim AU - Makeieva, Hanna AU - Homberg, Werner ED - Daehn, G. ED - Cao, J. ED - Kinsey, B. ED - Tekkaya, A. E. ED - Vivek, A. ED - Yoshida, Y ID - 21477 SN - 978-3-030-75380-1 T2 - Proceedings of the 13th International Conference on the Technology of Plasticity TI - Cutting Blades for Food Processing Applications Manufactured Using Innovative Spin Forming ER - TY - JOUR AB - The predictive quality of numerical simulations for mechanical joining processes depends on the implemented material model, especially regarding the plasticity of the joining parts. Therefore, experimental material characterization processes are conducted to determine the material properties of sheet metal and generate flow curves. In this regard, there are a number of procedures which are accompanied by varying experimental efforts. This paper presents various methods of determining flow curves for HCT590X as well as EN AW-6014, including varying specimen geometries and diverse hardening laws for extrapolation procedures. The flow curves thus generated are compared considering the variety of plastic strains occurring in mechanical joining processes. The material data generated are implemented in simulation models for the joining technologies, clinching and self-piercing riveting. The influence of the varied methods on the predictive accuracy of the simulation model is analysed. The evaluation of the differing flow curves is achieved by comparing the geometric formation of the joints and the required joining forces of the processes with experimentally investigated joints. AU - Böhnke, Max AU - Kappe, Fabian AU - Bobbert, Mathias AU - Meschut, Gerson ID - 22798 IS - 6 JF - Materials Testing SN - 2195-8572 TI - Influence of various procedures for the determination of flow curves on the predictive accuracy of numerical simulations for mechanical joining processes VL - 63 ER - TY - JOUR AB - The increasing use of multi-material constructions lead to a continuous increase in the use of mechanical joining techniques due to the wide range of joining possibilities as well as the high load-bearing capacities of the joints. Nevertheless, the currently rigid tool systems are not able to react to changing boundary conditions, like changing the material-geometry-combination. Therefore research work is crucial with regard to versatile joining systems. In this paper, a new approach for a versatile self-piercing riveting process considering the joining system as well as the auxiliary joining part is presented. AU - Kappe, Fabian AU - Bobbert, Mathias AU - Meschut, Gerson ID - 34226 JF - Key Engineering Materials KW - Mechanical Engineering KW - Mechanics of Materials KW - General Materials Science SN - 1662-9795 TI - New Approach for Versatile Self Piercing Riveting: Joining System and Auxiliary Part VL - 883 ER - TY - JOUR AU - Wituschek, Simon AU - Kappe, Fabian AU - Lechner, Michael ID - 30200 JF - Production Engineering TI - Investigation of the influence of varying tumbling strategies on a tumbling self-piercing riveting process ER - TY - CHAP AU - Dahms, Frederik AU - Homberg, Werner ID - 22766 SN - 2367-1181 T2 - Forming the Future TI - Investigations and Improvements in 3D-DIC Optical Residual Stress Analysis—A New Temperature Compensation Method ER - TY - JOUR AB - The increase of the thermal conductivity of PUR foam in the insulation of the cabinet is an important cause for aging processes of household refrigerating appliances. To determine the influence of the PUR foam aging on energy consumption, the development of a new measurement method is necessary be- cause current methods influence the aging behavior of household refrigerators and are therefore not applicable in general. Based on a latent heat sink, constructed as an ice water bucket, a new measure- ment method is developed to determine the k ·A value over time. With this method, the k ·A value of four household refrigerating appliances was determined over an interval of 14 months. The k ·A value increased between 3.6% and 11.5% during this period. AU - Paul, Andreas AU - Baumhögger, Elmar AU - Elsner, Andreas AU - Moczarski, Lukas AU - Reineke, Michael AU - Sonnenrein, Gerrit AU - Hueppe, Christian AU - Stamminger, Rainer AU - Hoelscher, Heike AU - Wagner, Hendrik AU - Gries, Ulrich AU - Freiberger, Alfred AU - Becker, Wolfgang AU - Vrabec, Jadran ID - 20921 JF - International Journal of Refrigeration SN - 0140-7007 TI - Determining the heat flow through the cabinet walls of household refrigerating appliances ER - TY - JOUR AB - Domestic refrigeration appliances are standard household commodities. Although policies, such as the energy labelling, prompted technical improvements and decreased appliance energy consumption throughout recent decades, important parameters were disregarded. These refer to the efficiency loss over time and the consumer behaviour. The objective of this contribution was to develop a dynamic energy model to determine the power consumption of refrigeration appliances considering degradation factors and behaviour. These were included by model parameters for direct consumer interactions, such as the storage behaviour, door openings and temperature setting, as well as indirect actions, e.g. exposing an appliance to specific temperature conditions at an installation site. For this, an online-survey was conducted to evaluate the consumer behaviour. A total of 706 consumers participated in the national questionnaire, serving as input for the dynamic energy model. It was found that the efficiency loss increases the power consumption by at least 1% annually, leading to an excess of 10% after 10 years of usage. Another important finding was that 32.5% of appliance’s power consumption results from consumer behaviour, whereas the promotion of behavioural changes leads to a significant decrease of the consumer-induced consumption. Consequently, this study provides a tool to evaluate the impact of policies targeting refrigeration appliances, stressing that efficiency loss and behaviour should be integrated into future policy approaches. AU - Hueppe, Christian AU - Geppert, Jasmin AU - Moenninghoff-Juessen, Julia AU - Wolff, Lena AU - Stamminger, Rainer AU - Paul, Andreas AU - Elsner, Andreas AU - Vrabec, Jadran AU - Wagner, Hendrik AU - Hoelscher, Heike AU - Becker, Wolfgang AU - Gries, Ulrich AU - Freiberger, Alfred ID - 27290 JF - Energy Policy SN - 0301-4215 TI - Investigating the real life energy consumption of refrigeration appliances in Germany: Are present policies sufficient? ER - TY - CONF AU - Jende, Yvonne Kristin ID - 44222 T2 - The Place of Memory and the Memory of Place, International Conference TI - Crossraods of Collective Memory. Canadian Memoir at the Junction of lieux and nœuds de mémoire. ER - TY - CONF AU - Jende, Yvonne Kristin ID - 44221 T2 - Bridges and Barriers: Perspectives of Progress and Preservation, Interdisciplinary and International Conference TI - Truth Be Told, ... or Not? Reality and Perspective in New Sincerity Memoir. ER - TY - CONF AB - The online fitting of a microscopic traffic simulation model to reconstruct the current state of a real traffic area can be challenging depending on the provided data. This paper presents a novel method based on limited data from sensors positioned at specific locations and guarantees a general accordance of reality and simulation in terms of multimodal road traffic counts and vehicle speeds. In these considerations, the actual purpose of research is of particular importance. Here, the research aims at improving the traffic flow by controlling the Traffic Light Systems (TLS) of the examined area which is why the current traffic state and the route choices of individual road users are the matter of interest. An integer optimization problem is derived to fit the current simulation to the latest field measurements. The concept can be transferred to any road traffic network and results in an observation of the current multimodal traffic state matching at the given sensor position. First case studies show promosing results in terms of deviations between reality and simulation. AU - Malena, Kevin AU - Link, Christopher AU - Mertin, Sven AU - Gausemeier, Sandra AU - Trächtler, Ansgar ID - 24159 KW - Microscopic Traffic Simulation KW - Online State Estimation KW - Mixed Road Users KW - Sensor Fusion KW - Integer Programming KW - Route Choice KW - Vehicle2Infrastructure SN - 978-989-758-513-5 T2 - VEHITS 2021 Proceedings of the 7th International Conference on Vehicle Technology and Intelligent Transport Systems TI - Online State Estimation for Microscopic Traffic Simulations using Multiple Data Sources* VL - 7 ER - TY - GEN AU - Berger, Thilo Frederik ID - 44234 TI - Combining Mobility, Heterogeneity, and Leasing Approaches for Online Resource Allocation ER - TY - GEN AU - Pranger, Sebastian ID - 44233 TI - Online k-Facility Reallocation using k-Server Algorithms ER - TY - JOUR AU - Camberg, Alan Adam AU - Andreiev, Anatolii AU - Pramanik, Sudipta AU - Hoyer, Kay-Peter AU - Tröster, Thomas AU - Schaper, Mirko ID - 41508 JF - Materials Science and Engineering: A KW - Mechanical Engineering KW - Mechanics of Materials KW - Condensed Matter Physics KW - General Materials Science SN - 0921-5093 TI - Strength enhancement of AlMg sheet metal parts by rapid heating and subsequent cold die stamping of severely cold-rolled blanks VL - 831 ER - TY - CONF AU - Behler, Felix AU - Ines, Böker ID - 44256 T2 - Sommerschule 21: Aktuelle Perspektiven der Deutsch-Türkischen und Interkulturellen Germanistik im Rahmen der Germanistischen Institutspartnerschaft 'Pader-EgeBosporus'. Organisation: Dr. Swen Schulte Eickholt, Nina Weigel (University of Paderborn), gefördert durch den DAAD. TI - Nationale Identität, Repräsentationen und Transformationen von Held*innentum in der Literatur ER - TY - CONF AU - Behler, Felix ID - 44251 T2 - 4th Trauma and Nightmare International Interdisciplinary Conference. Organisation: Professor Wojciech Owczarski (University of Gdańsk), Professor Paulo Endo (University of São Paulo), Lidia Owczarski (InMind Support) TI - 'I wasn’t there so I can’t know, can I?’ – An Analysis of Transgenerational and Collective Trauma in Solmaz Sharif’s Look (2016) ER - TY - CONF AU - Behler, Felix ID - 44248 T2 - Bridges and Barriers, Interdisziplinäre studentische Konferenz. Organisation: Felix Behler, Yvonne K. Jende, Lisa-Marie Büsken, Cecilie Rasmussen (University of Paderborn) TI - Approaching Barriers of Representation: Speaking Trauma through Verse ER - TY - CONF AU - Behler, Felix ID - 44254 T2 - Cosmopolitanism and World Citizenship International Conference. Organisation: London Centre for Interdisciplinary Research TI - Toward New Heroism: Post-Modern Military Heroes In Between National and Cosmopolitan Telos ER - TY - CONF AU - Behler, Felix ID - 44255 T2 - Barockwerkstatt 2021. Organisation: Professor Sabine Meine (Hochschule für Musik und Tanz Köln) TI - The Battle for the English Landscape’ - Über die gedankliche Konzeptionierung des Englischen Landschaftsgartens ER - TY - CONF AU - Behler, Felix ID - 44253 T2 - Somewhere In Between: Borders and Borderlands. Organisation: London Centre for Interdisciplinary Research TI - Of Transgenerational Borders and Collective Trauma ER - TY - CONF AU - Behler, Felix ID - 44252 T2 - Faces of War International Conference. Organisation: London Centre for Interdisciplinary Research. TI - Representations of Trauma in Contemporary British War Poetry ER - TY - CONF AU - Behler, Felix ID - 44257 T2 - BRITCULT 2021: Investigating the Super-Rich. Organisation: Professor Oliver v. Knebel Doeberitz, Dr. Jonatan Jalle Steller (University of Leipzig) TI - In Between Cultural Heritage and ‘Playground’ for the Wealthy: The Evolution of the British Countryside ER - TY - GEN ED - Behler, Felix ED - Jende, Yvonne Kristin ED - Büsken, Lisa-Marie ED - Rasmussen, Cecilie ID - 44263 TI - Bridges and Barriers, Interdisziplinäre studentische Konferenz ER - TY - CONF AU - Göddecke, Johannes AU - Meschut, Gerson ID - 22264 T2 - 11. Doktorandenseminar Klebtechnik TI - Experimentelle Untersuchung der Dämpfungseigenschaften geklebter Strukturen unter dynamischer Beanspruchung ER - TY - CHAP AB - Self-piercing riveting is an established technique for joining multi-material structures in car body manufacturing. Rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and their surface condition. To shorten the manufacturing process by omitting the heat treatment and the coating process, the authors have elaborated a concept for the use of stainless steel with high strain hardening as a rivet material. The focus of the present investigation is on the evaluation of the influences of the rivet’s geometry and material on its deformation behaviour. Conventional rivets of types P and HD2, a rivet with an improved geometry made of treatable steel 38B2, and rivets made of the stainless steels 1.3815 and 1.4541 are examined. The analysis is conducted by means of multi-step joining tests for two material combinations comprising high-strength steel HCT70X and aluminium EN AW-5083. The joints are cut to provide a cross-section and the deformation behaviour of the different rivets is analysed on the basis of the measured changes in geometry and hardness. In parallel, an examination of the force-stroke curves provides further insights. It can be demonstrated that, besides the geometry, the material strength, in particular, has a significant influence on the deformation behaviour of the rivet. The strength of steel 1.4541 is seen to be too low for the joining task, while the strength of steel 1.3815 is sufficient, and hence the investigation confirms the capability of rivets made of 1.3815 for joining even challenging material combinations. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ED - Daehn, Glenn ED - Cao, Jian ED - Kinsey, Brad ED - Tekkaya, Erman ED - Vivek, Anupam ED - Yoshida, Yoshinori ID - 22930 KW - Self-piercing riveting KW - Lightweight design KW - Deformation behaviour KW - Stainless steel KW - High nitrogen steel T2 - Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series. TI - Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening ER - TY - CONF AB - The use of high-strength steel and aluminium is rising due to the intensified efforts being made in lightweight design, and self-piercing riveting is becoming increasingly important. Conventional rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and the coating. To shorten the manufacturing process, the use of stainless steel with high strain hardening as the rivet material represents a promising approach. This allows the coating of the rivets to be omitted due to the corrosion resistance of the material and, since the strength of the stainless steel is achieved by cold forming, heat treatment is no longer required. In addition, it is possible to adjust the local strength within the rivet. Because of that, the authors have elaborated a concept for using high nitrogen steel 1.3815 as the rivet material. The present investigation focusses on the joint strength in order to evaluate the capability of rivets in high nitrogen steel by comparison to conventional rivets made of treatable steel. Due to certain challenges in the forming process of the high nitrogen steel rivets, deviations result from the targeted rivet geometry. Mainly these deviations cause a lower joint strength with these rivets, which is, however, adequate. All in all, the capability of the new rivet is proven by the results of this investigation. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ID - 22274 KW - Self-piercing Riveting KW - Joining Technology KW - Rivet Geometry KW - Rivet Material KW - High Nitrogen Steel KW - Joint Strength TI - Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel ER - TY - JOUR AB - The number of multi-material joints is increasing as a result of lightweight design. Self-piercing riveting (SPR) is an important mechanical joining technique for multi-material structures. Rivets for SPR are coated to prevent corrosion, but this coating also influences the friction that prevails during the joining process. The aim of the present investigation is to evaluate this influence. The investigation focuses on the common rivet coatings Almac® and zinc-nickel with topcoat as well as on uncoated rivet surfaces. First of all, the coating thickness and the uniformity of the coating distribution are analysed. Friction tests facilitate the classification of the surface properties. The influence of the friction on the characteristic joint parameters and the force-stroke curves is analysed by means of experimental joining tests. More in-depth knowledge of the effects that occur is achieved through the use of numerical simulation. Overall, it is shown that the surface condition of the rivet has an impact on the friction during the joining process and on the resulting joint. However, the detected deviations between different surface conditions do not restrict the operational capability of SPR and the properties of uncoated rivet surfaces, in particular, are similar to those of Almac®-coated rivets. It can thus be assumed that SPR with respect to the joining process is also possible without rivet coating in principle. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ID - 22272 JF - Key Engineering Materials KW - Coating KW - Friction KW - Joining TI - Influence of the Rivet Coating on the Friction during Self-Piercing Riveting VL - 883 ER - TY - GEN AU - Kuball, Clara-Maria AU - Uhe, Benedikt AU - Meschut, Gerson AU - Merklein, Marion ID - 30845 TI - Selective application of different forming temperatures for individual process stages in a rivet manufacturing process with high nitrogen steel ER -