Article
Computer Science, Interdisciplinary Applications
Severiano Gonzalez-Pinto, Domingo Hernandez-Abreu, Maria S. Perez-Rodriguez, Arash Sarshar, Steven Roberts, Adrian Sandu
Summary: This work proposes a unified formulation of splitting time integration schemes in the framework of general-structure additive Runge-Kutta (GARK) methods. New IMIM-GARK splitting methods are developed and tested using parabolic systems. Classical splitting methods can be studied in this unified framework.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Computer Science, Interdisciplinary Applications
Xiaofeng Cai, Sebastiano Boscarino, Jing-Mei Qiu
Summary: The paper introduces a semi-Lagrangian discontinuous Galerkin method coupled with Runge-Kutta exponential integrators for solving nonlinear Vlasov dynamics, achieving high spatial and temporal accuracy. Inherit advantages from the SLDG method, the proposed method performs well in resolving complex solution structures, conserves mass and positivity, and can evolve with adaptive time stepping.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Engineering, Multidisciplinary
Nanyi Zheng, Xiaofeng Cai, Jing-Mei Qiu, Jianxian Qiu
Summary: In this paper, a fourth-order conservative semi-Lagrangian finite volume weighted essentially non-oscillatory scheme is proposed for two-dimensional linear transport equations. The scheme achieves fourth-order accuracy in space by introducing a special upstream cell and a new WENO reconstruction operator. Mass conservation and positivity of the numerical solution are ensured through the nature of the reconstruction operator and a positivity-preserving limiter. The scheme is coupled with a fourth-order Runge-Kutta exponential integrator for high-order temporal accuracy.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Computer Science, Interdisciplinary Applications
Brian C. Vermeire, Siavash Hedayati Nasab
Summary: This paper introduces a family of accelerated implicit-explicit (AIMEX) schemes for solving stiff systems of equations. AIMEX schemes can significantly improve stability and allowable time step sizes.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
Chang Yang, Michel Mehrenberger
Summary: This paper introduces a highly accurate monotonicity-preserving Semi-Lagrangian scheme for Vlasov-Poisson simulations, which uses a limiter to avoid accuracy loss and clipping near extrema while maintaining monotonicity. The scheme preserves the monotonicity of the solution for locally monotonic data, while maintaining good properties and high accuracy similar to the unlimited scheme. Numerical tests show that the limited scheme is more diffusive compared to cubic splines, but has better L-1 conservation, making it advantageous for problems with sharp gradients.
JOURNAL OF COMPUTATIONAL PHYSICS
(2021)
Article
Mathematics, Applied
Ben S. Southworth, Oliver Krzysik, Will Pazner, Hans De Sterck
Summary: This paper introduces a theoretical and algorithmic preconditioning framework for solving the systems of equations that arise from fully implicit Runge-Kutta methods applied to linear numerical PDEs. The preconditioned operator is proven to have a condition number bounded by a small constant, independent of the spatial mesh and time-step size, and with weak dependence on number of stages/polynomial order.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2022)
Article
Mathematics, Applied
Emil M. Constantinescu
Summary: We propose a new method that extends conservative explicit multirate methods to implicit explicit-multirate methods. We develop extensions of order one and two with different stability properties on the implicit side. The method is suitable for time-stepping adaptive mesh refinement PDE discretizations with different degrees of stiffness. A numerical example with an advection-diffusion problem illustrates the new method's properties.
APPLIED MATHEMATICS LETTERS
(2022)
Article
Mathematics, Applied
Md Masud Rana, Victoria E. Howle, Katharine Long, Ashley Meek, William Milestone
Summary: A new preconditioner based on LDU factorization and algebraic multigrid subsolves is introduced for scalability in implicit Runge-Kutta time integration of large, structured systems. Experimental results show that this new preconditioner outperforms others, especially as spatial discretization becomes more refined and temporal order is increased.
SIAM JOURNAL ON SCIENTIFIC COMPUTING
(2021)
Article
Computer Science, Interdisciplinary Applications
Hongtao Liu, Xiaofeng Cai, Yong Cao, Giovanni Lapenta
Summary: This paper introduces a novel kinetic scheme called ECSL for the Vlasov-Ampere system, which retains the efficiency of explicit schemes while maintaining energy conservation and unconditional stability properties. The ECSL method includes a conservative Semi-Lagrangian scheme and a novel field solver, ensuring conservation of total energy and mass on a fully discrete level. The ECSL scheme provides reliable solutions even with insufficient spatial and temporal resolution, making it a promising tool for multiscale and lengthy simulations.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mathematics, Applied
Adam Preuss, Jessica Lipoth, Raymond J. Spiteri
Summary: Many mathematical models of natural phenomena are described by partial differential equations with additive contributions from different physical processes. This study compares the performance of two different additive splitting techniques and finds that dynamic linearization generally outperforms physics-based splitting.
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2022)
Article
Mathematics, Applied
Isabel Cordero-Carrion, Samuel Santos-Perez, Clara Martinez-Vidallach
Summary: We present the Minimally-Implicit Runge-Kutta (MIRK) methods for the numerical evolution of the resistive relativistic magnetohydrodynamic (RRMHD) equations, which can handle constraints by introducing an augmented system of evolution equations. Compared to previous approaches, the MIRK methods provide stable numerical evolutions, reduce the number of variable recoveries, have similar computational cost to standard explicit methods, and can be easily implemented in numerical codes with explicit schemes.
APPLIED MATHEMATICS AND COMPUTATION
(2023)
Article
Computer Science, Interdisciplinary Applications
Hongtao Liu, Mengyu Chen, Xiaofeng Cai, Yong Cao, Giovanni Lapenta
Summary: In this paper, a method combining immersed finite element (IFE) with conservative semi-Lagrangian (CSL) kinetic scheme is developed for plasma-material interactions. The IFE-CSL method offers advantages in treating complex boundary conditions, mass conservation, and avoiding the Courant-Friedrichs-Lewy (CFL) condition. The IFE method based on structured interface-independent meshes is used to discretize the field equation, while the CSL scheme combined with a halfway ghost-cell method is proposed for the Vlasov equation, allowing for mass conservation and convenient handling of curved boundaries. The IFE and CSL methods are coupled through the charge density, using appropriate solvers for the linear or nonlinear Poisson equation.
JOURNAL OF COMPUTATIONAL PHYSICS
(2023)
Article
Mathematics, Applied
Boscarino Sebastiano
Summary: The aim of this work is to apply a semi-implicit (SI) strategy in an implicit-explicit (IMEX) Runge-Kutta (RK) setting to 1D time-dependent partial differential equations (PDEs) with high order spatial derivatives. This strategy allows for the construction of simple linearly implicit schemes without Newton's iteration and does not impose severe time step restrictions. The effectiveness and stability of the scheme is demonstrated through numerical experiments on various types of equations.
JOURNAL OF SCIENTIFIC COMPUTING
(2023)
Article
Mathematics, Applied
Hongtao Liu, Xiaofeng Cai, Giovanni Lapenta, Yong Cao
Summary: This paper presents a conservative semi-Lagrangian (CSL) kinetic scheme coupled with an implicit finite element method (IFEM) for multidimensional electromagnetic plasma simulations. The method removes CFL limitations in phase space, ensures mass conservation, and maintains the positivity of the distribution function. Additionally, the method is efficient in handling general field boundary conditions and is demonstrated through various numerical experiments.
COMMUNICATIONS IN NONLINEAR SCIENCE AND NUMERICAL SIMULATION
(2021)
Article
Computer Science, Interdisciplinary Applications
Joseph Nakao, Jiajie Chen, Jing-Mei Qiu
Summary: We propose a new Eulerian-Lagrangian Runge-Kutta finite volume method for numerically solving convection and convection-diffusion equations. The method allows large time steps and achieves high-order spatial reconstruction and temporal accuracy.
JOURNAL OF COMPUTATIONAL PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
Shaokang Xu, S. Maeyama, T-H Watanabe
Summary: This study reveals the similarities and differences between the anomalous tungsten particle transport based on nonlinear gyrokinetic simulations and the linear gyrokinetic study. The nonlinear excitation of the linearly stable modes is found to play a significant role in the anomalous tungsten particle transport.
Article
Physics, Fluids & Plasmas
E. Narita, M. Honda, S. Maeyama, T-H Watanabe
Summary: A neural-network based model has been developed to accurately forecast the saturation time of turbulent heat fluxes in nonlinear gyrokinetic simulations. The model focuses on wavenumber space images to represent turbulence characteristics and utilizes a convolutional neural network to detect differences between images and classify the phase of turbulence evolution. It can also predict the simulation time with high accuracy and enable the search for an ideal initial condition that leads to rapid simulation saturation.
Article
Physics, Fluids & Plasmas
H. Masui, A. Ishizawa, K. Imadera, Y. Kishimoto, Y. Nakamura
Summary: The nonlinear saturation mechanism of ion-temperature-gradient turbulence at finite normalized pressure is identified by analyzing the nonlinear entropy transfer in global gyrokinetic simulations of the turbulence.
Article
Physics, Fluids & Plasmas
S. Kawagoe, A. Ishizawa, N. Aiba, Y. Nakamura
Summary: In this study, helical distortion in the core region of weakly reversed magnetic shear tokamak plasmas and its formation mechanism are investigated using three-dimensional magnetohydrodynamic (MHD) equilibrium calculations and MHD stability analysis. Two different types of helical equilibrium states are found, and their origins are revealed through linear stability analysis.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Multidisciplinary Sciences
Shinya Maeyama, Tomo-Hiko Watanabe, Motoki Nakata, Masanori Nunami, Yuuichi Asahi, Akihiro Ishizawa
Summary: This study explores the cross-link interaction between electron- and ion-scale turbulences in fusion plasma and its implications. The authors find that electron-scale turbulence disturbs ion-scale micro-instability and reduces large-scale turbulent fluctuations, demonstrating the possibility of reduced heat flux through cross-scale interactions.
NATURE COMMUNICATIONS
(2022)
Article
Engineering, Electrical & Electronic
Hang Xu, Hiroharu Kamada, Shinichi Nomura, Hirotaka Chikaraishi, Hiroaki Tsutsui, Takanori Isobe
Summary: This paper addresses the problem of estimating magnetic reluctance and magnetic flux density in electromagnet equipment with a wide air gap, where magnetic flux spreads. A model utilizing magnetic circuit and Biot-Savart law is proposed and validated through comparison with experimental results.
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY
(2022)
Article
Physics, Fluids & Plasmas
Mitsuru Honda, Emi Narita, Shinya Maeyama, Tomo-Hiko Watanabe
Summary: A multimodal convolutional neural network model was developed to predict electrostatic turbulent heat fluxes based on images and values generated by nonlinear gyrokinetic simulations. The model successfully predicted times and fluxes with high accuracy for both test data and unknown cases.
CONTRIBUTIONS TO PLASMA PHYSICS
(2023)
Article
Physics, Fluids & Plasmas
T. -h. Watanabe, S. Maeyama, M. Nakata
Summary: Multi-scale gyrokinetic theory and simulations have revealed cross-scale interactions between the trapped electron mode (TEM) and the electron temperature gradient (ETG) turbulence in a toroidal magnetized plasma. The TEM instability growth rate is reduced in the presence of ETG turbulence, which is well represented by effective diffusion. A theoretical model based on stochastic forcing by the ETG turbulence accurately describes the observed turbulent diffusion coefficient in multi-scale turbulence simulations.
Article
Physics, Fluids & Plasmas
T. -H. Watanabe, J. Hiwatari, S. Maeyama
Summary: The study extends the analysis of eigenvalue feedback instability in a magnetosphere-ionosphere (M-I) coupling model to understand the stabilization mechanism of high-frequency shear Alfven modes. It is found that the stabilization of high-frequency modes is attributed to the change of effective impedance due to the non-uniform ionospheric conductivity, rather than the collision-induced flow shear. Low-frequency modes relevant to auroral arc excitation remain unstable. An effective impedance model incorporating the inhomogeneous conductivity profile is also developed as an extension of the height-integrated ionosphere model.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
M. Niiro, A. Ishizawa, Y. Nakamura, S. Maeyama, T-H Watanabe
Summary: This study investigates the plasma beta dependence of ion temperature gradient (ITG) driven turbulence. It is found that the Shafranov shift cancels out the electromagnetic stabilizing effect on the ITG mode, leading to an unchanged growth rate as beta increases. The turbulent energy transport does not decrease with beta as suggested by the s - alpha model. Additionally, the Shafranov shift significantly increases the critical onset beta value for the kinetic ballooning mode.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Multidisciplinary
Shaokang Xu, S. Maeyama, T. -H. Watanabe
Summary: Turbulence-driven heavy ion transport in hot magnetized plasma is investigated using gyrokinetic theory and simulations. A finite heavy ion parallel compressibility pinch is discovered, contrary to the conventional understanding. Perturbation theory clarifies the frequency dependence of the pinch, resolving the discrepancy with experimental observations. Additionally, a nonlocal approach predicts strong anisotropy of the pinch on a magnetic surface. The research also reveals the effects of heavy ion mass on the pinch and the possibility of pinch direction reversal in nonlinear trapped electron mode turbulence through inverse cascade.
PHYSICAL REVIEW RESEARCH
(2022)
Article
Computer Science, Interdisciplinary Applications
Usman Riaz, E. Seegyoung Seol, Robert Hager, Mark S. Shephard
Summary: The accurate representation and effective discretization of a problem domain into a mesh are crucial for achieving high-quality simulation results and computational efficiency. This work presents recent developments in extending an automated tokamak modeling and meshing infrastructure to better support the near flux field following meshing requirements of the XGC Gyro-kinetic Code.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Zhenglu Li, Gabriel Antonius, Yang-Hao Chan, Steven G. Louie
Summary: This article presents a workflow for practical calculations of electron-phonon coupling and includes the effect of many-electron correlations using GW perturbation theory. The workflow combines different software packages to enable accurate calculations at the level of quasiparticle band structures.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Akihiro Koide, Sara Rabouli, Pierre Le Meur, Sylvain Tricot, Philippe Schieffer, Didier Sebilleau, Calogero R. Natoli
Summary: We present the MsSpec Atomic Scattering Amplitude Package (MASAP), which includes a computation program and a graphical interface for generating atomic scattering amplitude (ASA). The study investigates the applicability of plane wave (PW) and curved spherical wave (SW) scattering in describing electron propagation. The results show that the imaginary part of the optical potential enhances the elastic scattering in the forward direction but causes damping effects in other directions.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
A. Bagci, Gustavo A. Aucar
Summary: The electron repulsion integrals over Slater-type orbitals with non-integer principal quantum numbers are investigated in this study. These integrals are important in calculations of many-electron systems. New relationships free from hyper-geometric functions are derived to simplify the calculations. With the use of auxiliary functions and straightforward recurrence relationships, these integrals can be efficiently computed, providing initial conditions for the evaluation of expectation values and potentials.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Andrzej Daniluk
Summary: RHEED_DIFF_2D is an open-source software for qualitative numerical simulations of RHEED oscillation intensity changes with layer deposition, used for interpreting heteroepitaxial structures under different scattering crystal potential models.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Niklas Kuehl, Hendrik Fischer, Michael Hinze, Thomas Rung
Summary: The article presents a strategy and algorithm for simulation-accompanying, incremental Singular Value Decomposition (SVD) for time-evolving, spatially parallel discrete data sets. The proposed method improves computational efficiency by introducing a bunch matrix, resulting in higher accuracy and practical applicability.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Jose M. Rodriguez-Borbon, Xian Wang, Adrian P. Dieguez, Khaled Z. Ibrahim, Bryan M. Wong
Summary: This paper presents an open-source software package called TRAVOLTA for massively parallelized quantum optimal control calculations on GPUs. The TRAVOLTA package is an improvement on the previous NIC-CAGE algorithm and incorporates algorithmic improvements for faster convergence. Three different variants of GPU parallelization are examined to evaluate their performance in constructing optimal control fields in various quantum systems. The benchmarks show that the GPU-enhanced TRAVOLTA code produces the same results as previous CPU-based algorithms but with a speedup of more than ten times. The GPU enhancements and algorithmic improvements allow large quantum optimal control calculations to be efficiently executed on modern multi-core computational hardware.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Weijie Hua
Summary: This work introduces a program called MCNOX for computing and analyzing ultrafast nonlinear X-ray spectra. It is designed for cutting-edge applications in photochemistry/photophysics enabled by X-ray free-electron lasers and high harmonic generation light sources. The program can calculate steady-state X-ray absorption spectroscopy and three types of ultrafast nonlinear X-ray spectra, and it is capable of identifying major electronic transitions and providing physical and chemical insights from complex signals.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Leandro Benatto, Omar Mesquita, Lucimara S. Roman, Rodrigo B. Capaz, Graziani Candiotto, Marlus Koehler
Summary: Photoluminescence Quenching Simulator (PLQ-Sim) is a user-friendly software for studying the dynamics of photoexcited states at the interface between organic semiconductors. It provides important information on organic photovoltaic and photothermal devices and calculates transfer rates and quenching efficiency.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Dongming Li, James Kestyn, Eric Polizzi
Summary: This study introduces a practical and efficient approach to calculate the all-electron full potential band structure in real space using a finite element basis. Instead of the k-space method, this method solves the Kohn-Sham equation self-consistently within a larger finite system enclosing the unit-cell. Non-self-consistent calculations are then performed in the Brillouin zone to obtain the band structure results, which are found to be in excellent agreement with the pseudopotential k-space method. Furthermore, the study successfully observes the band bending of core electrons.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
R. Kleiber, M. Borchardt, R. Hatzky, A. Koenies, H. Leyh, A. Mishchenko, J. Riemann, C. Slaby, J. M. Garcia-Regana, E. Sanchez, M. Cole
Summary: This paper describes the current state of the EUTERPE code, focusing on the implemented models and their numerical implementation. The code is capable of solving the multi-species electromagnetic gyrokinetic equations in a three-dimensional domain. It utilizes noise reduction techniques and grid resolution transformation for efficient computation. Additionally, various hybrid models are implemented for comparison and the study of plasma-particle interactions. The code is parallelized for high scalability on multiple CPUs.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Pengliang Yang
Summary: This paper presents an open source software called SMIwiz, which combines seismic modelling, reverse time migration, and full waveform inversion into a unified computer implementation. SMIwiz supports both 2D and 3D simulations and provides various computational recipes for efficient calculation. Its independent processing and batchwise job scheduling ensure scalability, and its viability is demonstrated through applications on benchmark models.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Christian Tantardini, Miroslav Ilias, Matteo Giantomassi, Alexander G. Kvashnin, Valeria Pershina, Xavier Gonze
Summary: Material discovery has been an active research field, and this study focuses on developing pseudopotentials for actinides and super-heavy elements. These pseudopotentials are crucial for accurate first-principles calculations and simulations.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
S. Blanes, F. Casas, C. Gonzalez, M. Thalhammer
Summary: This paper explores the extension of modified potential operator splitting methods to specific classes of nonlinear evolution equations. Numerical experiments confirm the advantages of the proposed fourth-order modified operator splitting method over traditional splitting methods in dealing with Gross-Pitaevskii systems.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
Article
Computer Science, Interdisciplinary Applications
Siegfried Kaidisch, Thomas U. Hilger, Andreas Krassnigg, Wolfgang Lucha
Summary: Motivated by a use case in theoretical hadron physics, this paper revisits an application of a pole-sum fit to dressing functions of a confined quark propagator. Specifically, it investigates approaches to determine the number and positions of singularities closest to the origin for a function known numerically on a specific grid on the positive real axis. Comparing the efficiency of standard techniques to a pure artificial-neural-network approach and a combination of both, it finds that the combined approach is more efficient. This approach can be applied to similar situations where the positions of poles need to be estimated quickly and reliably from real-axis information alone.
COMPUTER PHYSICS COMMUNICATIONS
(2024)
