TY - CHAP A1 - Bauer, Monika A1 - Gwiazda, Maciej A1 - Müller, Ralf A1 - Decker, Daniel T1 - RTM-Materials Based on Silazane-Resin-Systems T2 - Proceedings, 7th International Conference on High Temperature Ceramic Matrix Composites (HT-CMC 7), September 20 - 22, 2010 in Bayreuth KW - new generation of RTM-resins KW - RTM KW - hybrid resins Y1 - 2010 PB - AVISO Verl.-Ges. CY - Berlin ER - TY - GEN A1 - Stohwasser, Ralf A1 - Giesebrecht, Jan A1 - Kraft, Regine A1 - Müller, Eva-Christiane A1 - Häusler, Karl Georg A1 - Kettenmann, Helmut A1 - Hanisch, Uwe-Karsten A1 - Kloetzel, Peter-Michael T1 - Biochemical analysis of proteasomes from mouse microglia: induction of immunoproteasomes by interferon-gamma and lipopolysaccaride T2 - Glia Y1 - 2000 U6 - https://doi.org/10.1002/(SICI)1098-1136(20000215)29:4<355::AID-GLIA6>3.0.CO;2-4 SN - 1098-1136 SN - 0894-1491 VL - 29 IS - 4 SP - 355 EP - 365 ER - TY - GEN A1 - Heuberger, Maria A1 - Grill, Eva A1 - Saglam, Murat A1 - Ramaioli, Cecilia A1 - Müller, Martin A1 - Strobl, Ralf A1 - Holle, Rolf A1 - Peters, Annette A1 - Schneider, Erich A1 - Lehnen, Nadine T1 - Usability of the Video Head Impulse Test: Lessons from the Population-Based Prospective KORA Study T2 - Frontiers in Neurology Y1 - 2018 U6 - https://doi.org/10.3389/fneur.2018.00659 SN - 1664-2295 VL - 9 ER - TY - GEN A1 - Dornisch, Wolfgang A1 - Schrade, David A1 - Xu, Bai-Xiang A1 - Keip, Marc-André A1 - Müller, Ralf T1 - Coupled phase field simulations of ferroelectric and ferromagnetic layers in multiferroic heterostructures T2 - Archive of Applied Mechanics N2 - The combination of materials with either pronounced ferroelectric or ferromagnetic effect characterizes multiferroic heterostructures, whereby the different materials can be arranged in layers, columns or inclusions. The magnetization can be controlled by the application of electrical fields through a purely mechanical coupling at the interfaces between the different materials. Thus, a magneto-electric coupling effect is obtained. Within a continuum mechanics formulation, a phase field is used to describe the polarization and the magnetization in the ferroelectric and ferromagnetic layers, respectively. The coupling between polarization/magnetization and strains within the layers, in combination with the mechanical coupling at the sharp layer interfaces, yields the magneto-electric coupling within the heterostructure. The continuum formulations for both layers are discretized in order to make the differential equations amenable to a numerical solution with the finite element method. A state-of-the-art approach is used for the ferroelectric layer. The material behavior of the ferromagnetic layer is described by a continuum formulation from the literature, which is discretized using a newly proposed approach for the consistent interpolation of the magnetization vector. Four numerical examples are presented which show the applicability of the newly proposed approach for the ferromagnetic layer as well as the possibility to simulate magneto-electric coupling in multiferroic heterostructures. KW - Multiferroic heterostructure KW - Phase field method KW - Ferroelectric material KW - Ferromagnetic material KW - Finite element method KW - Rotation interpolation Y1 - 2019 U6 - https://doi.org/10.1007/s00419-018-1480-9 SN - 0939-1533 SN - 1432-0681 VL - 89 IS - 6 SP - 1031 EP - 1056 ER - TY - GEN A1 - Nadgir, Omkar A1 - Dornisch, Wolfgang A1 - Müller, Ralf A1 - Keip, Marc-André T1 - A phase-field model for transversely isotropic ferroelectrics T2 - Archive of Applied Mechanics N2 - We propose an electro-mechanically coupled phase-field model for ferroelectric materials that show cubic–tetragonal phase transition. The cubic phase is idealized by an isotropic formulation, and the tetragonal phase is idealized by a transversely isotropic formulation. We consider a classical phase-field model with Ginzburg–Landau-type evolution of the order parameter. The order parameter drives the transition of all involved moduli tensors such as elastic, dielectric and piezoelectric moduli, which in turn maintain their typical features and stability as a result of a selected phase-transition function. The model is described in coordinate-invariant form and implemented into a finite element framework with implicit time integration of the evolution equation. Representative numerical examples in two and three dimensions demonstrate the main features of the constitutive model and the numerical stability of the formulation. KW - Phase-field modeling KW - Ferroelectrics KW - Ginzburg–Landau equation KW - Transverse isotropy KW - Numerical simulations Y1 - 2019 U6 - https://doi.org/10.1007/s00419-019-01543-y SN - 0939-1533 SN - 1432-0681 VL - 89 IS - 6 SP - 1057 EP - 1068 ER - TY - GEN A1 - Dornisch, Wolfgang A1 - Stöckler, Joachim A1 - Müller, Ralf T1 - Dual and approximate dual basis functions for B-splines and NURBS – Comparison and application for an efficient coupling of patches with the isogeometric mortar method T2 - Computer Methods in Applied Mechanics and Engineering N2 - This contribution defines and compares different methods for the computation of dual basis functions for B-splines and Non-Uniform Rational B-splines (NURBS). They are intended to be used as test functions for the isogeometric mortar method, but other fields of application are possible, too. Three different concepts are presented and compared. The first concept is the explicit formula for the computation of dual basis functions for NURBS proposed in the work of Carl de Boor. These dual basis functions entail minimal support, i.e., the support of the dual basis functions is equal to the support of the corresponding B-spline basis functions. In the second concept dual basis functions are derived from the inversion of the Gram matrix. These dual basis functions have global support along the interface. The third concept is the use of approximate dual basis functions, which were initially proposed for the use in harmonic analysis. The support of these functions is local but larger than the support of the associated B-spline basis functions. We propose an extension of the approximate dual basis functions for NURBS basis functions. After providing the general formulas, we elaborate explicit expressions for several degrees of spline basis functions. All three approaches are applied in the frame of the mortar method for the coupling of non-conforming NURBS patches. A method which allows complex discretizations with multiple intersecting interfaces is presented. Numerical examples show that the explicitly defined dual basis functions with minimal support severely deteriorate the global stress convergence behavior of the mechanical analysis. This fact is in accordance with mathematical findings in literature, which state that the optimal reproduction degree of arbitrary functions is not possible without extending the support of the dual basis functions. The dual basis functions computed from the inverse of the Gram matrix yield accurate numerical results but the global support yields significantly higher computational costs in comparison to computations of conforming meshes. Only the approximate dual basis functions yield accurate and efficient computations, where neither accuracy nor efficiency is significantly deteriorated in comparison to computations of conforming meshes. All basic cases of T-intersections and star-intersections are studied. Furthermore, an example which combines all basic cases in a complex discretization is given. The applicability of the presented method for the nonlinear case and for shell formulations is shown with the help of one numerical example. KW - Isogeometric analysis KW - Dual basis functions for NURBS KW - Optimal convergence KW - Mortar method KW - Coupling of non-conforming meshes KW - Approximate dual basis functions for NURBS Y1 - 2017 U6 - https://doi.org/10.1016/j.cma.2016.07.038 SN - 0045-7825 VL - 316 SP - 449 EP - 496 ER - TY - GEN A1 - Hannaske, Carolin A1 - Rich, Beatrice Monique A1 - Müller, Matthias A1 - Woll, Ralf T1 - Deutsch-chinesiche Zusammenarbeit: Kulturelle Eigenarten machen den Unterschied in der Kommunikation T2 - Qualität und Zuverlässigkeit : QZ KW - Kommunikation, China, Deutschland, Kultur Y1 - 2019 SN - 0720-1214 SN - 0033-5126 VL - 64 IS - 11 SP - 12 EP - 14 ER - TY - GEN A1 - Dornisch, Wolfgang A1 - Stöckler, Joachim A1 - Müller, Ralf T1 - Recent advances in isogeometric dual mortar patch coupling T2 - Proceedings of the 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry, October 11-13, 2017 in Stuttgart, Germany N2 - Isogeometric analysis fosters the integration of design and analysis by using the geometry description of the CAD system also for the numerical analysis. Hereby, the use of NURBS surfaces is common but entails the need for a coupling of non-conforming patches. The use of mortar methods allows a coupling which requires neither additional variables nor empirical parameters. In this contribution dual basis functions are used in order to obtain an accurate and efficient mortar method. Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bsz:93-opus-ds-93516 SP - 467 EP - 470 PB - Institute for Structural Mechanics University of Stuttgart CY - Stuttgart ER - TY - GEN A1 - Dornisch, Wolfgang A1 - Schrade, David A1 - Xu, Bai-Xiang A1 - Müller, Ralf T1 - Coupling of phase field models for ferroelectric and ferromagnetic layers in multiferroic heterostructures T2 - VII International Conference on Coupled Problems in Science and Engineering (Coupled Problems 2017) N2 - Heterostructures of ferroelectric and ferromagnetic layers are commonly used to obtain electromagnetic effects. The elastic coupling between the layers is widely acknowledged as the main mechanism responsible for the electro-magneto interaction. Within this contribution we study the coupling of ferroelectric and ferromagnetic layers with well-defined interfaces. The intention is to simulate the switching of the magnetization with the help of electric fields, which has been studied experimentally in [1]. Each layer is simulated by using mechanically coupled phase field modeling, whereby the approaches presented in [2] and [3] will be used. The strains in each layer depend on the direction of the polarization/magnetization. A mismatch of these strains will be compensated by local deformations at the interface as the coupling results from the coherent deformation at the interface. This leads to the possibility to alter the magnetization direction by changing the electric polarization and vice verse. Numerical simulations will illustrate the evolution of the ferroic microstructures with a focus on the strain coupling and the resulting interactions between layers. Y1 - 2017 UR - http://congress.cimne.com/coupled2017/admin/files/fileabstract/a365.pdf PB - CIMNE CY - Barcelona ER - TY - GEN A1 - Aubele, Maria A1 - Grill, Eva A1 - Eggert, Thomas A1 - Schneider, Erich A1 - Strobl, Ralf A1 - Jahn, Klaus A1 - Müller, Martin A1 - Holle, Rolf A1 - Linkohr, Birgit A1 - Heier, Margit A1 - Ladwig, Karl-Heinz A1 - Lehnen, Nadine T1 - Symptoms in unilatral vestibular hypofunction are associated with number of catch-up saccades and retinal errors: results from the population-based KORA FF4study T2 - Frontiers in Neurology N2 - Objective: The presence and intensity of symptoms vary in patients with unilateral vestibular hypofunction. We aimed to determine which saccadic and vestibulo-ocular reflex parameters best predict the presence of symptoms in unilateral vestibular hypofunction in order to better understand vestibular compensation and its implications for rehabilitation therapy. Methods: Video head impulse test data were analyzed from a subpopulation of 23 symptomatic and 10 currently symptom-free participants with unilateral vestibular hypofunction, embedded in the KORA (Cooperative Health Research in the Region of Augsburg) FF4 study, the second follow-up of the KORA S4 population-based health survey (2,279 participants). Results: A higher number of catch-up saccades, a higher percentage of covert saccades, and a larger retinal error at 200 ms after the onset of the head impulse were associated with relevant symptoms in participants with unilateral vestibular hypofunction (p = 0.028, p = 0.046, and p = 0.038, respectively). After stepwise selection, the number of catch-up saccades and retinal error at 200 ms remained in the final logistic regression model, which was significantly better than a null model (p = 0.014). Age, gender, saccade amplitude, saccade latency, and VOR gain were not predictive of the presence of symptoms. Conclusion: The accuracy of saccadic compensation seems to be crucial for the presence of symptoms in unilateral vestibular hypofunction, highlighting the role of specific gaze stabilization exercises in rehabilitation. Early saccades, mainly triggered by the vestibular system, do not seem to compensate accurately enough, resulting in a relevant retinal error and the need for more as well as more accurate catch-up saccades, probably triggered by the visual system. KW - video head impulse test, vHIT, catch-up saccades, unilateral vestibular hypofunction, retinal error, vestibulo-ocular reflex, VOR, population-based survey Y1 - 2023 UR - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10715252/ SN - 1664-2295 VL - 2023 IS - 14 ER -