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Iterative multiscale methods for electronic structure calculations offer several advantages for large-scale problems. Here we examine a nonlinear full approximation scheme (FAS) multigrid method for solving fixed potential and…

Materials Science · Physics 2007-05-23 Nimal Wijesekera , Guogang Feng , Thomas L. Beck

A compact Marx generator was built to mimic a spark-gap Tesla transformer. The generator produced radio-frequency pulses of up to $\pm$200 kV and $\pm$15 A with a frequency between 110 to 280 kHz at a repetition rate of 120 Hz. The…

Instrumentation and Detectors · Physics 2024-05-24 B. H. McGuyer

Characterizing whether a Markov process of discrete random variables has an homogeneous continuous-time realization is a hard problem. In practice, this problem reduces to deciding when a given Markov matrix can be written as the…

Probability · Mathematics 2021-06-23 Marta Casanellas , Jesús Fernández-Sánchez , Jordi Roca-Lacostena

Tensor structured Markov chains are part of stochastic models of many practical applications, e.g., in the description of complex production or telephone networks. The most interesting question in Markov chain models is the determination of…

Numerical Analysis · Mathematics 2015-05-08 Matthias Bolten , Karsten Kahl , Sonja Sokolović

A reinforcement learning approach to design optimised graded metamaterials for mechanical energy confinement and amplification is described. Through the proximal policy optimisation algorithm, the reinforcement agent is trained to optimally…

Applied Physics · Physics 2023-02-27 Luca Rosafalco , Jacopo Maria De Ponti , Luca Iorio , Raffaele Ardito , Alberto Corigliano

We use a power grid model with $M$ generators and $N$ consumption units to optimize the grid and its control. Each consumer demand is drawn from a predefined finite-size-support distribution, thus simulating the instantaneous load…

Statistical Mechanics · Physics 2009-10-21 Lenka Zdeborová , Aurélien Decelle , Michael Chertkov

Pseudorandom circuits generate quantum states and unitary operators which are approximately distributed according to the unitarily invariant Haar measure. We explore how several design parameters affect the efficiency of pseudo-random…

Quantum Physics · Physics 2009-11-13 Yaakov S. Weinstein , Winton G. Brown , Lorenza Viola

In applications of linear algebra including nuclear physics and structural dynamics, there is a need to deal with uncertainty in the matrices. We focus on matrices that depend on a set of parameters $\omega$ and we are interested in the…

Numerical Analysis · Mathematics 2019-04-23 Koen Ruymbeek , Karl Meerbergen , Wim Michiels

A wind farm can provide reactive power at sub-transmission and transmission buses in order to support and improve voltage profiles. It is common for the reactive power capability of a wind farm to be evaluated as the sum of the individual…

Optimization and Control · Mathematics 2022-07-12 Nawaf Nazir , Mads Almassalkhi , Ian Hiskens

The problem of identifying sparse solutions for the link structure and dynamics of an unknown linear, time-invariant network is posed as finding sparse solutions x to Ax=b. If the sensing matrix A satisfies a rank condition, this problem…

Dynamical Systems · Mathematics 2014-11-18 David Hayden , Young Hwan Chang , Jorge Goncalves , Claire Tomlin

Parallel transmission has been a very promising candidate technology to mitigate the inevitable radio-frequency field inhomogeneity in magnetic resonance imaging (MRI) at ultra-high field (UHF). For the first few years, pulse design…

Instrumentation and Detectors · Physics 2013-11-06 Andres Hoyos Idrobo , Pierre Weiss , Aurélien Massire , Alexis Amadon , Nicolas Boulant

Matrix Product State (MPS) wavefunctions have many applications in quantum information and condensed matter physics. One application is to represent states in the thermodynamic limit directly, using a small set of position independent…

Statistical Mechanics · Physics 2010-08-30 L. Michel , I. P. McCulloch

We consider a charged spinless quantum particle confined to a graph consisting of a loop to which a halfline lead is attached; this system is placed into a homogeneous magnetic field perpendicular to the loop plane. We derive the reflection…

Quantum Physics · Physics 2009-10-30 Pavel Exner

Despite strong connections through shared application areas, research efforts on power market optimization (e.g., unit commitment) and power network optimization (e.g., optimal power flow) remain largely independent. A notable illustration…

Optimization and Control · Mathematics 2020-09-02 Carleton Coffrin , Bernard Knueven , Jesse Holzer , Marc Vuffray

A new approach to solving eigenvalue optimization problems for large structured matrices is proposed and studied. The class of optimization problems considered is related to computing structured pseudospectra and their extremal points, and…

Numerical Analysis · Mathematics 2022-06-22 Nicola Guglielmi , Christian Lubich , Stefano Sicilia

A novel strategy is proposed for the coupling of field and circuit equations when modeling power devices in the low-frequency regime. The resulting systems of differential-algebraic equations have a particular geometric structure which…

Numerical Analysis · Mathematics 2024-04-25 Herbert Egger , Idoia Cortes Garcia , Vsevolod Shashkov , Michael Wiesheu

Pendry and MacKinnon meaningful discretization of Maxwell's equations was put forward specifically as part of a finite-element numerical algorithm. By contrast with a numerical approach, in the same spirit evoked by the relationships…

Optics · Physics 2023-03-14 Ovidiu-Zeno Lipan , Aldo De Sabata

In (relativistic) electronic structure methods, the quaternion matrix eigenvalue problem and the linear response (Bethe-Salpeter) eigenvalue problem for excitation energies are two frequently encountered structured eigenvalue problems.…

Chemical Physics · Physics 2021-12-01 Zhendong Li

This paper deals with the old yet unsolved problem of defining and evaluating the stored electromagnetic energy - a quantity essential for calculating the quality factor, which reflects the intrinsic bandwidth of the considered…

Classical Physics · Physics 2016-07-07 Miloslav Capek , Lukas Jelinek , Guy A. E. Vandenbosch

Part I of this paper embeds the AC power flow problem with voltage control and exponential load model in the complex plane. Modeling the action of network controllers that regulate the magnitude of voltage phasors is a challenging task in…

Systems and Control · Computer Science 2016-09-07 Sina Sadeghi Baghsorkhi , Sergey Pavlovich Suetin
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