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High-resolution is a key trend in the development of synthetic aperture radar (SAR), which enables the capture of fine details and accurate representation of backscattering properties. However, traditional high-resolution SAR imaging…

Signal Processing · Electrical Eng. & Systems 2023-04-11 Guoru Zhou , Zhongqiu Xu , Yizhe Fan , Zhe Zhang , Xiaolan Qiu , Bingchen Zhang , Kun Fu , Yirong Wu

In many applications of tomography, the acquired projections are either limited in number or contain a significant amount of noise. In these cases, standard reconstruction methods tend to produce artifacts that can make further analysis…

Numerical Analysis · Mathematics 2016-04-11 D. M. Pelt , K. J. Batenburg

Traveltime tomography is a very effective tool to reconstruct acoustic, seismic or electromagnetic wave speed distribution. To infer the velocity image of the medium from the measurements of first arrivals is a typical example of ill-posed…

Geophysics · Physics 2007-05-23 G. Vignoli , L. Zanzi

Despite a variety of available techniques the issue of the proper regularization parameter choice for inverse problems still remains one of the biggest challenges. The main difficulty lies in constructing a rule, allowing to compute the…

Numerical Analysis · Mathematics 2017-10-13 Ernesto De Vito , Massimo Fornasier , Valeriya Naumova

In this paper, we propose a stochastic Primal-Dual Hybrid Gradient (PDHG) approach for solving a wide spectrum of regularized stochastic minimization problems, where the regularization term is composite with a linear function. It has been…

Machine Learning · Computer Science 2018-02-02 Linbo Qiao , Tianyi Lin , Qi Qin , Xicheng Lu

In this article, we introduce a novel algorithm for efficient near-field synthetic aperture radar (SAR) imaging for irregular scanning geometries. With the emergence of fifth-generation (5G) millimeter-wave (mmWave) devices, near-field SAR…

Signal Processing · Electrical Eng. & Systems 2023-05-04 Josiah Smith , Murat Torlak

In parallel magnetic resonance imaging (pMRI), to find a joint solution for the image and coil sensitivity functions is a nonlinear and nonconvex problem. A class of algorithms reconstruct sensitivity encoded images of the coils first…

Medical Physics · Physics 2014-08-05 Cishen Zhang , Ifat-Al Baqee

In this paper, based on the Tikhonov regularization technique, we study a monotone general variational inequality (GVI) by considering an associated strongly monotone GVI, depending on a regularization parameter $\alpha,$ such that the…

Optimization and Control · Mathematics 2025-03-11 Pham Ky Anh , Trinh Ngoc Hai , Nguyen Van Manh

We propose a regularization-based deblurring method that works efficiently for galaxy images. The spatial resolution of a ground-based telescope is generally limited by seeing conditions and much worse than space-based telescopes. This…

Instrumentation and Methods for Astrophysics · Physics 2022-09-21 Kazumi Murata , Tsutomu T. Takeuchi

We introduce a novel family of invariant, convex, and non-quadratic functionals that we employ to derive regularized solutions of ill-posed linear inverse imaging problems. The proposed regularizers involve the Schatten norms of the Hessian…

Optimization and Control · Mathematics 2014-02-20 Stamatios Lefkimmiatis , John Paul Ward , Michael Unser

Tikhonov regularization for projected solutions of large-scale ill-posed problems is considered. The Golub-Kahan iterative bidiagonalization is used to project the problem onto a subspace and regularization then applied to find a subspace…

Numerical Analysis · Mathematics 2022-08-16 Rosemary A. Renaut , Saeed Vatankhah , Vahid E. Ardestani

Primal-dual splitting involving proximity operators in order to be able to find some approximation to the minimizer for a general form of Tikhonov type functional is in the focus of this work. This approximation is produced by a pair of…

Numerical Analysis · Mathematics 2019-03-19 Erdem Altuntac

In parallel magnetic resonance imaging (pMRI) reconstruction without using estimation of coil sensitivity functions, one group of algorithms reconstruct sensitivity encoded images of the coils first followed by the magnitude only image…

Medical Physics · Physics 2013-11-12 Cishen Zhang , Ifat Al Baqee

Low-rank modeling has many important applications in computer vision and machine learning. While the matrix rank is often approximated by the convex nuclear norm, the use of nonconvex low-rank regularizers has demonstrated better empirical…

Machine Learning · Computer Science 2018-07-25 Quanming Yao , James T. Kwok , Taifeng Wang , Tie-Yan Liu

A nonlinear optimization method is proposed for the solution of inverse medium problems with spatially varying properties. To avoid the prohibitively large number of unknown control variables resulting from standard grid-based…

Numerical Analysis · Mathematics 2023-07-28 Yannik G. Gleichmann , Marcus J. Grote

Random feature approximation is arguably one of the most popular techniques to speed up kernel methods in large scale algorithms and provides a theoretical approach to the analysis of deep neural networks. We analyze generalization…

Machine Learning · Computer Science 2023-08-30 Mike Nguyen , Nicole Mücke

Synthetic aperture radar (SAR) is a day or night any-weather imaging modality that is an important tool in remote sensing. Most existing SAR image formation methods result in a maximum a posteriori image which approximates the reflectivity…

Applications · Statistics 2020-07-14 Victor Churchill , Anne Gelb

Inverse problems arise in a wide spectrum of applications in fields ranging from engineering to scientific computation. Connected with the rise of interest in inverse problems is the development and analysis of regularization methods, such…

Numerical Analysis · Mathematics 2025-05-12 Abinash Nayak

Tikhonov regularization involves minimizing the combination of a data discrepancy term and a regularizing term, and is the standard approach for solving inverse problems. The use of non-convex regularizers, such as those defined by trained…

Optimization and Control · Mathematics 2023-02-20 Daniel Obmann , Markus Haltmeier

We consider linear inverse problems that are formulated in the continuous domain. The object of recovery is a function that is assumed to minimize a convex objective functional. The solutions are constrained by imposing a continuous-domain…

Information Theory · Computer Science 2018-08-15 Harshit Gupta , Julien Fageot , Michael Unser