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
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 -