| 2017B. Bohn, M. Griebel and C. Rieger
A representer theorem for deep kernel learning
2017
http://wissrech.ins.uni-bonn.de/research/pub/bohn/INSPreprint_concatRegr.pdf
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| Alexander Effland, Martin Rumpf and Florian Schäfer
Time discrete extrapolation in a Riemannian space of images
In Proc. of International Conference on Scale Space and Variational Methods in Computer Vision, Volume 10302
page 473--485.
Publisher: Springer, Cham
2017
https://dx.doi.org/10.1007/978-3-319-58771-4_38
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| Matthias Erbar, Martin Rumpf, Bernhard Schmitzer and Stefan Simon
Computation of Optimal Transport on Discrete Metric Measure Spaces
Unknown
https://arxiv.org/abs/1707.06859
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| M. Griebel and C. Rieger
Reproducing kernel Hilbert spaces for parametric partial differential equations
SIAM/ASA J. Uncertainty Quantification, 5: 111-137 2017
10.1137/15M1026870
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| Behrend Heeren, Martin Rumpf and Benedikt Wirth
Variational time discretization of Riemannian splines
IMA J. Numer. Anal. 2017
https://arxiv.org/abs/1711.06069
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| Nora Lüthen, Martin Rumpf, Sascha Tölkes and Orestis Vantzos
Branching Structures in Elastic Shape Optimization
2017
https://arxiv.org/abs/1711.03850
Abstract: Fine scale elastic structures are widespread in nature, for instances in plants or bones, whenever stiffness and low weight are required. These patterns frequently refine towards a Dirichlet boundary to ensure an effective load transfer. The paper discusses the optimization of such supporting structures in a specific class of domain patterns in 2D, which composes of periodic and branching period transitions on subdomain facets. These investigations can be considered as a case study to display examples of optimal branching domain patterns. In explicit, a rectangular domain is decomposed into rectangular subdomains, which share facets with neighbouring subdomains or with facets which split on one side into equally sized facets of two different subdomains. On each subdomain one considers an elastic material phase with stiff elasticity coefficients and an approximate void phase with orders of magnitude softer material. For given load on the outer domain boundary, which is distributed on a prescribed fine scale pattern representing the contact area of the shape, the interior elastic phase is optimized with respect to the compliance cost. The elastic stress is supposed to be continuous on the domain and a stress based finite volume discretization is used for the optimization. If in one direction equally sized subdomains with equal adjacent subdomain topology line up, these subdomains are consider as equal copies including the enforced boundary conditions for the stress and form a locally periodic substructure. An alternating descent algorithm is employed for a discrete characteristic function describing the stiff elastic subset on the subdomains and the solution of the elastic state equation. Numerical experiments are shown for compression and shear load on the boundary of a quadratic domain. |
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| Jan Maas, Martin Rumpf and Stefan Simon
Transport based image morphing with intensity modulation
In Proc. of International Conference on Scale Space and Variational Methods in Computer Vision
Publisher: Springer, Cham
2017
http://dx.doi.org/10.1007/978-3-319-58771-4_45
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| Celia Reina and Sergio Conti
Incompressible inelasticity as an essential ingredient for the validity of the kinematic decomposition $F=F^eF^i$
J. Mech. Phys. Solids, 107: 322--342 2017
10.1016/j.jmps.2017.07.004
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| C. Rieger and H. Wendland
Sampling Inequalities for Sparse Grids
Numerische Mathematik 2017
10.1007/s00211-016-0845-7
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| Angkana Rüland, Christian Zillinger and Barbara Zwicknagl
Higher Sobolev Regularity of Convex Integration Solutions in Elasticity: The Dirichlet Problem with Affine Data in int($K^lc$)
2017
https://arxiv.org/abs/1709.02880
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| 2016Sergio Conti, Martin Lenz and Martin Rumpf
Hysteresis in Magnetic Shape Memory Composites: Modeling and Simulation
2016
10.1016/j.jmps.2015.12.010
Abstract: Magnetic shape memory alloys are characterized by the coupling between a structural phase transition and magnetic one. This permits to control the shape change via an external magnetic field, at least in single crystals. Composite materials with single-crystalline particles embedded in a softer matrix have been proposed as a way to overcome the blocking of the transformation at grain boundaries. We investigate hysteresis phenomena for small NiMnGa single crystals embedded in a polymer matrix for slowly varying magnetic fields. The evolution of the microstructure is studied within the rate-independent variational framework proposed by Mielke and Theil (1999). The underlying variational model incorporates linearized elasticity, micromagnetism, stray field and a dissipation term proportional to the volume swept by the phase boundary. The time discretization is based on an incremental minimization of the sum of energy and dissipation. A backtracking approach is employed to approximately ensure the global minimality condition. We illustrate and discuss the influence of the particle geometry (volume fraction, shape, arrangement) and the polymer elastic parameters on the observed hysteresis and compare with recent experimental results.
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| Patrick W. Dondl, Behrend Heeren and Martin Rumpf
Optimization of the branching pattern in coherent phase transitions
C. R. Math. Acad. Sci. Paris, 354(6): 639--644 2016
https://arxiv.org/abs/1512.06620
Abstract: Branching can be observed at the austenite-martensite interface of martensitic phase transformations. For a model problem, Kohn and Müller studied a branching pattern with optimal scaling of the energy with respect to its parameters. Here, we present finite element simulations that suggest a topologically different class of branching patterns and derive a novel, low dimensional family of patterns. After a geometric optimization within this family, the resulting pattern bears a striking resemblance to our simulation. The novel microstructure admits the same scaling exponents but results in a significantly lowered upper energy bound. |
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| Peter Hornung, Martin Rumpf and Stefan Simon
Material Optimization for Nonlinearly Elastic Planar Beams
2016
http://arxiv.org/abs/1604.02267
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| Herbert Koch, Angkana Rüland and Wenhui Shi
The variable coefficient thin obstacle problem: Carleman inequalities
Adv. Math., 301: 820--866 2016
http://dx.doi.org/10.1016/j.aim.2016.06.023
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| Jan Maas, Martin Rumpf and Stefan Simon
Generalized optimal transport with singular sources
2016
http://arxiv.org/abs/1607.01186
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| Celia Reina, Anja Schlömerkemper and Sergio Conti
Derivation of $\bf F=\bf F^\rm e\bf F^\rm p$ as the continuum limit of crystalline slip
J. Mech. Phys. Solids, 89: 231--254 2016
10.1016/j.jmps.2015.12.022
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| Alan D. Rendall and Juan J. L. Velázquez
Veiled singularities for the spherically symmetric massless Einstein-Vlasov system
2016
http://arxiv.org/abs/1604.06576
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| Angkana Rüland, Christian Zillinger and Barbara Zwicknagl
Higher Sobolev regularity of convex integration solutions in elasticity
2016
https://arxiv.org/abs/1610.02529
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| 2015Benjamin Berkels, Alexander Effland and Martin Rumpf
A Posteriori Error Control for the Binary Mumford-Shah Model
ArXiv Preprint 2015
http://arxiv.org/abs/1505.05284
Abstract: The binary Mumford-Shah model is a widespread tool for image segmentation and can be considered as a basic model in shape optimization with a broad range of applications in computer vision, ranging from basic segmentation and labeling to object reconstruction. This paper presents robust a posteriori error estimates for a natural error quantity, namely the area of the non properly segmented region. To this end, a suitable strictly convex and non-constrained relaxation of the originally non-convex functional is investigated and Repin's functional approach for a posteriori error estimation is used to control the numerical error for the relaxed problem in the $L^2$-norm. In combination with a suitable cut out argument, a fully practical estimate for the area mismatch is derived. This estimate is incorporated in an adaptive meshing strategy. Two different adaptive primal-dual finite element schemes, and the most frequently used finite difference discretization are investigated and compared. Numerical experiments show qualitative and quantitative properties of the estimates and demonstrate their usefulness in practical applications. |
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| Benjamin Berkels, Alexander Effland and Martin Rumpf
Time Discrete Geodesic Paths in the Space of Images
SIAM J. Imaging Sci., 8(3): 1457-1488 2015
http://dx.doi.org/10.1137/140970719
Abstract: In this paper the space of images is considered as a Riemannian manifold using the metamorphosis approach, where the underlying Riemannian metric simultaneously measures the cost of image transport and intensity variation. A robust and effective variational time discretization of geodesics paths is proposed. This requires to minimize a discrete path energy consisting of a sum of consecutive image matching functionals over a set of image intensity maps and pairwise matching deformations. For square-integrable input images the existence of discrete, connecting geodesic paths defined as minimizers of this variational problem is shown. Furthermore, Γ-convergence of the underlying discrete path energy to the continuous path energy is proved. This includes a diffeomorphism property for the induced transport and the existence of a square-integrable weak material derivative in space and time. A spatial discretization via finite elements combined with an alternating descent scheme in the set of image intensity maps and the set of matching deformations is presented to approximate discrete geodesic paths numerically. Computational results underline the efficiency of the proposed approach and demonstrate important qualitative properties.
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