Search Results for author: Tuomo Valkonen

Found 14 papers, 5 papers with code

Proximal methods for point source localisation

1 code implementation6 Dec 2022 Tuomo Valkonen

Point source localisation is generally modelled as a Lasso-type problem on measures.

Non-planar sensing skins for structural health monitoring based on electrical resistance tomography

no code implementations8 Dec 2020 Jyrki Jauhiainen, Mohammad Pour-Ghaz, Tuomo Valkonen, Aku Seppänen

Electrical resistance tomography (ERT) -based distributed surface sensing systems, or sensing skins, offer alternative sensing techniques for structural health monitoring, providing capabilities for distributed sensing of, for example, damage, strain and temperature.

Image Reconstruction Computational Physics Numerical Analysis Differential Geometry Numerical Analysis

Inverse problems with second-order Total Generalized Variation constraints

no code implementations19 May 2020 Kristian Bredies, Tuomo Valkonen

Total Generalized Variation (TGV) has recently been introduced as penalty functional for modelling images with edges as well as smooth variations.

Image Denoising

Predictive online optimisation with applications to optical flow

1 code implementation8 Feb 2020 Tuomo Valkonen

To prove convergence we need a predictor for the dual variable based on (proximal) gradient flow.

Optical Flow Estimation

Primal-dual proximal splitting and generalized conjugation in non-smooth non-convex optimization

1 code implementation9 Jan 2019 Christian Clason, Stanislav Mazurenko, Tuomo Valkonen

We demonstrate that difficult non-convex non-smooth optimization problems, such as Nash equilibrium problems and anisotropic as well as isotropic Potts segmentation model, can be written in terms of generalized conjugates of convex functionals.

Optimization and Control

Acceleration and global convergence of a first-order primal--dual method for nonconvex problems

no code implementations9 Feb 2018 Christian Clason, Stanislav Mazurenko, Tuomo Valkonen

The primal--dual hybrid gradient method (PDHGM, also known as the Chambolle--Pock method) has proved very successful for convex optimization problems involving linear operators arising in image processing and inverse problems.

Optimization and Control

Primal-dual extragradient methods for nonlinear nonsmooth PDE-constrained optimization

1 code implementation20 Jun 2016 Christian Clason, Tuomo Valkonen

We study the extension of the Chambolle--Pock primal-dual algorithm to nonsmooth optimization problems involving nonlinear operators between function spaces.

Optimization and Control

Acceleration of the PDHGM on strongly convex subspaces

no code implementations20 Nov 2015 Tuomo Valkonen, Thomas Pock

We propose several variants of the primal-dual method due to Chambolle and Pock.

Deblurring Denoising

Diffusion tensor imaging with deterministic error bounds

no code implementations7 Sep 2015 Artur Gorokh, Yury Korolev, Tuomo Valkonen

Errors in the data and the forward operator of an inverse problem can be handily modelled using partial order in Banach lattices.

The structure of optimal parameters for image restoration problems

no code implementations8 May 2015 Juan Carlos De Los Reyes, Carola-Bibiane Schönlieb, Tuomo Valkonen

The analysis is done on the original -- in image restoration typically non-smooth variational problem -- as well as on a smoothed approximation set in Hilbert space which is the one considered in numerical computations.

Image Restoration

Bilevel approaches for learning of variational imaging models

1 code implementation8 May 2015 Luca Calatroni, Cao Chung, Juan Carlos De Los Reyes, Carola-Bibiane Schönlieb, Tuomo Valkonen

We review some recent learning approaches in variational imaging, based on bilevel optimisation, and emphasize the importance of their treatment in function space.

The jump set under geometric regularisation. Part 2: Higher-order approaches

no code implementations9 Jul 2014 Tuomo Valkonen

In Part 1, we developed a new technique based on Lipschitz pushforwards for proving the jump set containment property $\mathcal{H}^{m-1}(J_u \setminus J_f)=0$ of solutions $u$ to total variation denoising.

Denoising

The jump set under geometric regularisation. Part 1: Basic technique and first-order denoising

no code implementations6 Jul 2014 Tuomo Valkonen

Their proof unfortunately depends heavily on the co-area formula, as do many results in this area, and as such is not directly extensible to higher-order, curvature-based, and other advanced geometric regularisers, such as total generalised variation (TGV) and Euler's elastica.

Denoising

Imaging with Kantorovich-Rubinstein discrepancy

no code implementations1 Jul 2014 Jan Lellmann, Dirk A. Lorenz, Carola Schönlieb, Tuomo Valkonen

We propose the use of the Kantorovich-Rubinstein norm from optimal transport in imaging problems.

Image Denoising

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