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  • 1
    UID:
    almahu_BV046284069
    Format: 1 Online-Ressource (xv, 396 Seiten) : , Illustrationen, Diagramme (teilweise farbig).
    ISBN: 978-3-030-33116-0
    Series Statement: CIM Series in mathematical sciences
    Additional Edition: Erscheint auch als Druck-Ausgabe ISBN 978-3-030-33115-3
    Language: English
    Subjects: Mathematics
    RVK:
    Keywords: Konferenzschrift ; Konferenzschrift
    URL: Volltext  (URL des Erstveröffentlichers)
    URL: Volltext  (URL des Erstveröffentlichers)
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  • 2
    UID:
    gbv_031455034
    Note: Ab Bd. 10 nur noch hrsg. von Philippe G. Ciarlet. - Ab Bd. 17 hrsg. von Qiang Du, Roland Glowinksi, Michael Hintermüller und Endre Süli , Teilw. im Verlag NH/Elsevier, Amsterdam [u.a.], erschienen. - Später im Verlag Elsevier, North Holland, Amsterdam [u.a.], erschienen
    Additional Edition: Digitalisierte Ausg. Handbook of numerical analysis Amsterdam [u.a.] : Elsevier, 1990
    Language: English
    Keywords: Numerische Mathematik
    Author information: Hintermüller, Michael 1970-
    Author information: Ciarlet, Philippe G. 1938-
    Author information: Glowinski, Roland 1937-2022
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  • 3
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14351
    Content: For a Banach space X of R^M-valued functions on a Lipschitz domain, let K(X) ⊂ X be a closed convex set arising from pointwise constraints on the value of the function, its gradient or its divergence, respectively. The main result of the paper establishes, under certain conditions, the density of K(X_0) in K(X_1) where X_0 is densely and continuously embedded in X_1. The proof is constructive, utilizes the theory of mollifiers and can be applied to Sobolev spaces such as H (div,Ω) and W1,p(Ω), in particular. It is also shown that such a density result cannot be expected in general.
    Content: Peer Reviewed
    Note: This is the preprint version of the final publication with doi j.jmaa.2015.01.060, whichcan be found at Elsevier:https://doi.org/10.1016/j.jmaa.2015.01.060
    In: Journal of Mathematical Analysis and Applications, : Elsevier, 2015, 426,2015,1, Seiten 585-593
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14352
    Content: A Fenchel dualization scheme for the one-step time-discretized contact problem of quasi-static elasto-plasticity with combined kinematic-isotropic hardening is considered. The associated path is induced by a coupled Moreau-Yosida / Tichonov regularization of the dual problem. The sequence of solutions to the regularized problems is shown to converge strongly to the optimal displacement- stress-strain triple of the original elasto-plastic contact problem in the space-continuous setting. This property relies on the density of the intersection of certain convex sets which is shown as well. It is also argued that the mappings associated with the resulting problems are Newton- or slantly differentiable. Consequently, each regularized subsystem can be solved mesh-independently at a local superlinear rate of convergence. For efficiency purposes, an inexact path-following approach is proposed and a numerical validation of the theoretical results is given.
    Content: Peer Reviewed
    Note: This is the preprint version of the final publication with doi10.1016/j.cam.2015.06.010,which can be found at Elsevier:http://www.sciencedirect.com/science/article/pii/S0377042715003325
    In: Journal of Computational and Applied Mathematics, , 2016, 292,2016, Seiten 150-173
    Language: English
    URL: Volltext  (kostenfrei)
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  • 5
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14349
    Content: Robust principal component pursuit (RPCP) refers to a decomposition of a data matrix into a low-rank component and a sparse component. In this work, instead of invoking a convex-relaxation model based on the nuclear norm and the `1 -norm as is typically done in this context, RPCP is solved by considering a least-squares problem subject to rank and cardinality constraints. An inexact alternating minimization scheme, with guaranteed global convergence, is employed to solve the resulting constrained minimization problem. In particular, the low-rank matrix subproblem is resolved inexactly by a tailored Riemannian optimization technique, which favorably avoids singular value decompositions in full dimen- sion. For the overall method, a corresponding q-linear convergence theory is established. The numerical experiments show that the newly proposed method compares competitively with a popular convex-relaxation based approach.
    Content: Peer Reviewed
    Note: The final publication is available at Springer via http://dx.doi.org/10.1007/s10851-014-0527-y
    In: Journal of Mathematical Imaging and Vision, : Springer, 2015, 51,2014,3, Seiten 361-377
    Language: English
    URL: Volltext  (kostenfrei)
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  • 6
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14347
    Content: Building upon the results in [M. Hintermüller and T. Surowiec, Pac. J. Optim., 9 (2013), pp. 251–273], a class of noncooperative Nash equilibrium problems is presented, in which the feasible set of each player is perturbed by the decisions of their competitors via a convex constraint. In addition, for every vector of decisions, a common “state” variable is given by the solution of an affine linear equation. The resulting problem is therefore a generalized Nash equilibrium problem (GNEP). The existence of an equilibrium for this problem is demonstrated, and first-order optimality conditions are derived under a constraint qualification. An approximation scheme is proposed, which involves the solution of a parameter-dependent sequence of standard Nash equilibrium problems. An associated path-following strategy based on the Nikaido–Isoda function is then proposed. Function- space-based numerics for parabolic GNEPs and a spot-market model are developed.
    Content: Peer Reviewed
    Note: Copyright © 2015 Society for Industrial and Applied Mathematics
    In: SIAM Journal on Optimization, : Society for Industrial and Applied Mathematics, 2015, 25,2015,3, Seiten 1826-1856
    Language: English
    URL: Volltext  (kostenfrei)
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  • 7
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14348
    Content: Recently, nonconvex regularization models have been introduced in order to provide a better prior for gradient distributions in real images. They are based on using concave energies φ in the total variation–type functional TVφ (u) := φ(|∇u(x)|) dx. In this paper, it is demonstrated that for typical choices of φ, functionals of this type pose several difficulties when extended to the entire space of functions of bounded variation, BV(Ω). In particular, if φ(t) = tq for q ∈ (0, 1), and TVφ is defined directly for piecewise constant functions and extended via weak* lower semicontinuous envelopes to BV(Ω), then it still holds that TVφ (u) = ∞ for u not piecewise constant. If, on the other hand, TVφ is defined analogously via continuously differentiable functions, then TV φ ≡ 0 (!). We study a way to remedy the models through additional multiscale regularization and area strict convergence, provided that the energy φ(t) = tq is linearized for high values. The fact that such energies actually better match reality and improve reconstructions is demonstrated by statistics and numerical experiments.
    Content: Peer Reviewed
    Note: © 2015, Society for Industrial and Applied Mathematics
    In: SIAM Journal on Imaging Sciences, : Society for Industrial and Applied Mathematics, 2015, 8,2015,4, Seiten 2581-2621
    Language: English
    URL: Volltext  (kostenfrei)
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  • 8
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14350
    Content: Blind deconvolution problems arise in many imaging modalities, where both the underlying point spread function, which parameterizes the convolution operator, and the source image need to be identified. In this work, a novel bilevel optimization approach to blind deconvolution is proposed. The lower-level problem refers to the minimization of a total-variation model, as is typically done in non-blind image deconvolution. The upper-level objective takes into account additional statistical information depending on the partic- ular imaging modality. Bilevel problems of such type are investigated system- atically. Analytical properties of the lower-level solution mapping are established based on Robinson’s strong regularity condition. Furthermore, several stationarity conditions are derived from the variational geometry induced by the lower-level problem. Numerically, a projected-gradient-type method is employed to obtain a Clarke-type stationary point and its convergence properties are analyzed. We also implement an efficient version of the proposed algorithm and test it through the experiments on point spread function calibration and multiframe blind deconvolution.
    Content: Peer Reviewed
    Note: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Inverse Problems and Imaging following peer review. The definitive publisher-authenticated version (Michael Hintermüller, Tao Wu;Bilevel optimization for calibrating point spread functions in blind deconvolution;Inverse Problems and Imaging;Pages: 1139 - 1169, Volume 9, Issue 4, November 2015 doi:10.3934/ipi.2015.9.1139 ) is available online at AIMS:http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=11746
    In: Inverse Problems and Imaging, : AIMS, 2015, 9,2015,4, Seiten 1139-1169
    Language: English
    URL: Volltext  (kostenfrei)
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  • 9
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14344
    Content: An adaptive finite element method is developed for a class of optimal control problems with elliptic variational inequality constraints and objective functionals defined on the space of continuous functions, necessitated by a point-tracking requirement with respect to the state variable. A suitable first order stationarity concept is derived for the problem class via a penalty technique. The dual-weighted residual approach for goal-oriented adaptive finite elements is applied and relies on the stationarity system. It yields primal residuals weighted by approxi- mate dual quantities and vice versa as well as complementarity mismatch errors. A report on numerical tests, including the critical case of biactivity, completes this work.
    Content: Peer Reviewed
    Note: The final publication is available at European Mathematical Society Publishing House:http://www.ems-ph.org/journals/show_abstract.php?issn=1463-9963&vol=17&iss=1&rank=2
    In: Interfaces and Free Boundaries, : European Mathematical Society Publishing House, 2015, 17,2015,1, Seiten 21-53
    Language: English
    URL: Volltext  (kostenfrei)
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  • 10
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät
    UID:
    edochu_18452_14345
    Content: In this paper the shape derivative of an objective depending on the solution of an eddy current approximation of Maxwell’s equations is obtained. Using a Lagrangian approach in the spirit of Delfour and Zolésio, the computation of the shape derivative of the solution of the state equation is bypassed. This theoretical result is applied to magnetic impedance tomography, which is an imaging modality aiming at the contactless mapping (identification) of the unknown electrical conductivities inside an object given measurements recorded by receiver coils.
    Content: Peer Reviewed
    Note: The final publication is available online at IOPScience:http://iopscience.iop.org/article/10.1088/0266-5611/31/6/065006/meta
    In: Inverse Problems, : IOPScience Publishing Ltd, 2015, 31,2015,6
    Language: English
    URL: Volltext  (kostenfrei)
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