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A new smoothing method for the improvement on the identification and quantification of spectral functions based on the previous knowledge of the signals that are expected to be quantified, is presented. These signals are used as weighted…

Atomic Physics · Physics 2017-01-31 Leonardo Bennun

Wide-field imaging has become a major challenge for modern radio astronomy, which uses high sensitivity acquisition systems that deal with huge amounts of data. In this paper we investigate a fast wide-field imaging solution based on the…

Instrumentation and Methods for Astrophysics · Physics 2019-04-19 Luis F. R. Lucas , Chris J. Skipper , Anna M. M. Scaife

The K-means algorithm is among the most commonly used data clustering methods. However, the regular K-means can only be applied in the input space and it is applicable when clusters are linearly separable. The kernel K-means, which extends…

Machine Learning · Computer Science 2020-12-08 Amir Aradnia , Maryam Amir Haeri , Mohammad Mehdi Ebadzadeh

Multispectral imaging provides valuable information on tissue composition such as hemoglobin oxygen saturation. However, the real-time application of this technique in interventional medicine can be challenging due to the long acquisition…

This paper introduces a data-adaptive non-parametric approach for the estimation of time-varying spectral densities from nonstationary time series. Time-varying spectral densities are commonly estimated by local kernel smoothing. The…

Computation · Statistics 2020-07-21 Anne van Delft , Michael Eichler

For a large Hermitian matrix $A\in \mathbb{C}^{N\times N}$, it is often the case that the only affordable operation is matrix-vector multiplication. In such case, randomized method is a powerful way to estimate the spectral density (or…

Numerical Analysis · Mathematics 2015-11-24 Lin Lin

Restoring images degraded by spatially varying blur is a problem encountered in many disciplines such as astrophysics, computer vision or biomedical imaging. One of the main challenges to perform this task is to design efficient numerical…

Optimization and Control · Mathematics 2015-10-13 Paul Escande , Pierre Weiss

Kernel estimation techniques, such as mean shift, suffer from one major drawback: the kernel bandwidth selection. The bandwidth can be fixed for all the data set or can vary at each points. Automatic bandwidth selection becomes a real…

Computer Vision and Pattern Recognition · Computer Science 2011-11-10 Aurelie Bugeau , Patrick Pérez

Estimating the spectral density function $f(w)$ for some $w\in [-\pi, \pi]$ has been traditionally performed by kernel smoothing the periodogram and related techniques. Kernel smoothing is tantamount to local averaging, i.e., approximating…

Methodology · Statistics 2022-08-05 Tucker McElroy , Dimitris Politis

The resolution limits of classical spectroscopy can be surpassed by quantum-inspired methods leveraging the information contained in the phase of the complex electromagnetic field. Their counterpart in spatial imaging has been widely…

Optics · Physics 2024-09-02 Michał Lipka , Michał Parniak

An Ewald decomposition of the two-dimensional Yukawa potential and its derivative is presented for both the periodic and the free-space case. These modified Bessel functions of the second kind of zeroth and first degrees are used e.g. when…

Computational Engineering, Finance, and Science · Computer Science 2019-11-15 Sara Pålsson , Anna-Karin Tornberg

We present a new methodology, based on the WKB approximation and Fast Fourier Transforms, for the evaluation of wave propagation through inhomogeneous media. This method can accurately resolve fields containing caustics, while still…

Computational Physics · Physics 2024-03-05 Oscar P. Bruno , Martin D. Maas

We study the influence of a graph parameter called modular-width on the time complexity for optimally solving well-known polynomial problems such as Maximum Matching, Triangle Counting, and Maximum $s$-$t$ Vertex-Capacitated Flow. The…

Data Structures and Algorithms · Computer Science 2018-04-27 Stefan Kratsch , Florian Nelles

In this paper, we first describe a matricial Newton-type algorithm designed to solve the multivariable spectrum approximation problem. We then prove its global convergence. Finally, we apply this approximation procedure to multivariate…

Optimization and Control · Mathematics 2008-09-30 Federico Ramponi , Augusto Ferrante , Michele Pavon

In this paper, we give a faster width-dependent algorithm for mixed packing-covering LPs. Mixed packing-covering LPs are fundamental to combinatorial optimization in computer science and operations research. Our algorithm finds a $1+\eps$…

Optimization and Control · Mathematics 2019-10-15 Digvijay Boob , Saurabh Sawlani , Di Wang

The use of multichannel data in line spectral estimation (or frequency estimation) is common for improving the estimation accuracy in array processing, structural health monitoring, wireless communications, and more. Recently proposed…

Information Theory · Computer Science 2018-10-15 Zai Yang , Jinhui Tang , Yonina C. Eldar , Lihua Xie

In this work we propose an efficient and accurate multi-scale optical simulation algorithm by applying a numerical version of slowly varying envelope approximation in FEM. Specifically, we employ the fast iterative method to quickly compute…

Optics · Physics 2024-12-03 Fan Xiao , Jingwei Wang , Zhongfei Xiong , Yuntian Chen

We introduce a new arbitrarily high-order method for the rapid evaluation of hyperbolic potentials (space-time integrals involving the Green's function for the scalar wave equation). With $M$ points in the spatial discretization and $N_t$…

Numerical Analysis · Mathematics 2025-07-11 Nour G. Al Hassanieh , Alex H. Barnett , Leslie Greengard

The representation of subgrid-scale orography is a challenge in the physical parameterization of orographic gravity-wave sources in weather forecasting. A significant hurdle is encoding as much physical information with as simple a…

Atmospheric and Oceanic Physics · Physics 2025-01-16 Ray Chew , Stamen Dolaptchiev , Maja-Sophie Wedel , Ulrich Achatz

A key question in modern statistics is how to make fast and reliable inferences for complex, high-dimensional data. While there has been much interest in sparse techniques, current methods do not generalize well to data with nonlinear…

Methodology · Statistics 2016-11-01 Ann B. Lee , Rafael Izbicki