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This paper focuses on regularisation methods using models up to the third order to search for up to second-order critical points of a finite-sum minimisation problem. The variant presented belongs to the framework of [3]: it employs random…

Numerical Analysis · Mathematics 2021-04-05 Stefania Bellavia , Gianmarco Gurioli , Benedetta Morini , Philippe L. Toint

We propose an automatic parameter selection strategy for the problem of image super-resolution for images corrupted by blur and additive white Gaussian noise with unknown standard deviation. The proposed approach exploits the structure of…

Numerical Analysis · Mathematics 2021-08-31 Monica Pragliola , Luca Calatroni , Alessandro Lanza , Fiorella Sgallari

Goal: This work aims at developing a novel calibration-free fast parallel MRI (pMRI) reconstruction method incorporate with discrete-time optimal control framework. The reconstruction model is designed to learn a regularization that…

Image and Video Processing · Electrical Eng. & Systems 2022-01-25 Wanyu Bian , Yunmei Chen , Xiaojing Ye

We reformulate the gain correction problem of the radio interferometry as an optimization problem with regularization, which is solved efficiently with an iterative algorithm. Combining this new method with our previously proposed imaging…

Instrumentation and Methods for Astrophysics · Physics 2024-12-05 Shiro Ikeda , Takeshi Nakazato , Takashi Tsukagoshi , Tsutomu T. Takeuchi , Masayuki Yamaguchi

Proper regularization is crucial in inverse problems to achieve high-quality reconstruction, even with an ill-conditioned measurement system. This is particularly true for three-dimensional photoacoustic tomography, which is computationally…

Optimization and Control · Mathematics 2024-09-26 Chao Wang , Alexandre H. Thiery

$\ell_1$ regularization is used to preserve edges or enforce sparsity in a solution to an inverse problem. We investigate the Split Bregman and the Majorization-Minimization iterative methods that turn this non-smooth minimization problem…

Numerical Analysis · Mathematics 2024-12-16 Brian Sweeney , Rosemary Renaut , Malena Español

The characteristic feature of inverse problems is their instability with respect to data perturbations. In order to stabilize the inversion process, regularization methods have to be developed and applied. In this work we introduce and…

Numerical Analysis · Mathematics 2022-08-22 Andrea Ebner , Jürgen Frikel , Dirk Lorenz , Johannes Schwab , Markus Haltmeier

We demonstrate how one can choose the smoothing parameter in image denoising by a statistical multiresolution criterion, both globally and locally. Using inhomogeneous diffusion and total variation regularization as examples for localized…

Methodology · Statistics 2010-02-01 Thomas Hotz , Philipp Marnitz , Rahel Stichtenoth , Laurie Davies , Zakhar Kabluchko , Axel Munk

In order to determine the 3D structure of a thick sample, researchers have recently combined ptychography (for high resolution) and tomography (for 3D imaging) in a single experiment. 2-step methods are usually adopted for reconstruction,…

Image and Video Processing · Electrical Eng. & Systems 2020-07-21 Huibin Chang , Pablo Enfedaque , Stefano Marchesini

For many algorithms, parameter tuning remains a challenging and critical task, which becomes tedious and infeasible in a multi-parameter setting. Multi-penalty regularization, successfully used for solving undetermined sparse regression of…

Machine Learning · Statistics 2017-10-12 Markus Grasmair , Timo Klock , Valeriya Naumova

This paper studies the problem of reconstructing binary matrices that are only accessible through few evaluations of their discrete X-rays. Such question is prominently motivated by the demand in material science for developing a tool for…

Combinatorics · Mathematics 2007-05-23 Alberto Del Lungo , Andrea Frosini , Maurice Nivat , Laurent Vuillon

The truncated singular value decomposition may be used to find the solution of linear discrete ill-posed problems in conjunction with Tikhonov regularization and requires the estimation of a regularization parameter that balances between…

Numerical Analysis · Mathematics 2022-08-16 Rosemary A. Renaut , Anthony W. Helmstetter , Saeed Vatankhah

Recommendation algorithm plays an important role in recommendation system (RS), which predicts users' interests and preferences for some given items based on their known information. Recently, a recommendation algorithm based on the graph…

Information Retrieval · Computer Science 2023-07-06 Guangrui Yang , Lihua Yang , Qing Zhang , Zhihua Yang

We develop a robust convex algorithm to select the regularization parameter in model selection. In practice this would be automated in order to save practitioners time from having to tune it manually. In particular, we implement and test…

Optimization and Control · Mathematics 2014-12-03 Dustin Tran

Feature selection identifies subsets of informative features and reduces dimensions in the original feature space, helping provide insights into data generation or a variety of domain problems. Existing methods mainly depend on feature…

Machine Learning · Computer Science 2021-06-07 Xinxing Wu , Qiang Cheng

A two-dimensional tomographic problem is studied. The target is assumed to be a homogeneous object bounded by a smooth curve. A Non Uniform Rational Basis Splines (NURBS) curve is used as computational representation of the boundary. This…

Numerical Analysis · Mathematics 2017-08-08 Heikki Haario , Aki Kallonen , Marko Laine , Esa Niemi , Zenith Purisha , Samuli Siltanen

The problem of an accurate tip radius and shape characterization is very important for determination of surface mechanical and chemical properties on the basis of the scanning probe microscopy measurements. We think that the most favorable…

Instrumentation and Detectors · Physics 2011-05-10 G. Jozwiak , A. Henrykowski , A. Masalska , T. Gotszalk , I. Ritz , H. Steigmann

We propose a novel automatic parameter selection strategy for variational imaging problems under Poisson noise corruption. The selection of a suitable regularization parameter, whose value is crucial in order to achieve high quality…

Numerical Analysis · Mathematics 2022-07-22 Francesca Bevilacqua , Alessandro Lanza , Monica Pragliola , Fiorella Sgallari

Parameter identification problems typically consist of a model equation, e.g. a (system of) ordinary or partial differential equation(s), and the observation equation. In the conventional reduced setting, the model equation is eliminated…

Numerical Analysis · Mathematics 2016-03-18 Barbara Kaltenbacher

Simulation is a useful tool in situations where training data for machine learning models is costly to annotate or even hard to acquire. In this work, we propose a reinforcement learning-based method for automatically adjusting the…

Machine Learning · Computer Science 2019-05-15 Nataniel Ruiz , Samuel Schulter , Manmohan Chandraker
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