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The Athena++ Adaptive Mesh Refinement Framework: Design and Magnetohydrodynamic Solvers

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Astrophysical Journal, Supplement Series 2020年第1期249卷

作者： Stone, James M. Tomida, Kengo White, Christopher J. Felker, Kyle G. Department of Astrophysical Sciences Princeton University Princeton 08544 NJ United States Program in Applied and Computational Mathematics Princeton University Princeton 08544 NJ United States Department of Earth and Space Science Osaka University Toyonaka Osaka 560-0043 Japan Kavli Institute for Theoretical Physics University of California Santa Barbara Santa Barbara 93107 CA United States School of Natural Sciences Institute for Advanced Study Princeton 08544 NJ United States Astronomical Institute Tohoku University Sendai Miyagi 980-8578 Japan Argonne National Laboratory Lemont 60439 IL United States

The design and implementation of a new framework for adaptive mesh refinement calculations are described. It is intended primarily for applications in astrophysical fluid dynamics, but its flexible and modular design enables its use for a wide variety of physics. The framework works with both uniform and nonuniform grids in Cartesian and curvilinear coordinate systems. It adopts a dynamic execution model based on a simple design called a "task list"that improves parallel performance by overlapping communication and computation, simplifies the inclusion of a diverse range of physics, and even enables multiphysics models involving different physics in different regions of the calculation. We describe physics modules implemented in this framework for both nonrelativistic and relativistic magnetohydrodynamics (MHD). These modules adopt mature and robust algorithms originally developed for the Athena MHD code and incorporate new extensions: support for curvilinear coordinates, higher-order time integrators, more realistic physics such as a general equation of state, and diffusion terms that can be integrated with super-time-stepping algorithms. The modules show excellent performance and scaling, with well over 80% parallel efficiency on over half a million threads. The source code has been made publicly available. © 2020. The American Astronomical Society. All rights reserved..

关键词： Astronomy software Magnetohydrodynamics

Cloud-AC-OPF: Model reduction technique for multi-scenario optimal power flow via chance-constrained optimization

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arXiv 2019年

作者： Frolov, Vladimir Roald, Line Chertkov, Michael Skolkovo Institute of Science and Technology Nobel Street 3 Moscow Region143026 Russia Electrical & Computer Engineering University of Wisconsin 1415 Engineering Drive MadisonWI53706 United States Center for Nonlinear Studies and Theoretical Division T-4 LANL Los AlamosNM87545 United States Program in Applied Mathematics University of Arizona TucsonAZ85721 United States

—Many practical planning and operational applications in power systems require simultaneous consideration of a large number of operating conditions or Multi-Scenario AC-Optimal Power Flow (MS-AC-OPF) solution. However, when the number of exogenously prescribed conditions is large, solving the problem as a collection of single AC-OPFs may be time-consuming or simply intractable computationally. In this paper, we suggest a model reduction approach, coined Cloud-AC-OPF, which replaces a collection of samples by their compact representation in terms of mean and standard deviation. Instead of determining an optimal generation dispatch for each sample individually, we parametrize the generation dispatch as an affine function. The Cloud-AC-OPF is mathematically similar to a generalized Chance-Constrained AC-OPF (CC-AC-OPF) of the type recently discussed in the literature, but conceptually different as it discusses applications to long-term planning. We further propose a tractable formulation and implementation, and illustrate our construction on the example of 30-bus IEEE model. Copyright © 2019, The Authors. All rights reserved.

关键词： Acoustic generators

On the verification of adaptive three-dimensional multiresolution computations of the magnetohydrodynamic equations

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arXiv 2019年

作者： Gomes, Anna Karina Fontes Domingues, Margarete Oliveira Mendes, Odim Schneider, Kai Post-graduation Program in Applied Computing National Institute for Space Research São José dos Campos Brazil Associated Laboratory for Computing and Applied Mathematics National Institute for Space Research São José dos Campos Brazil Space Geophysics Division National Institute for Space Research São José dos Campos Brazil Institut de Mathématiques de Marseille Aix-Marseille Université CNRS Centrale Marseille I2M UMR 7373

Magnetohydrodynamics is an important tool to study the dynamics of plasma Space Physics. In this context, we introduce a three-dimensional magnetohydrodynamic solver with divergence-cleaning in the adaptive multiresolution CARMEN code. The numerical scheme is based on a finite volume discretization that ensures the conservation of physical quantities. The adaptive multiresolution approach allows for automatic identification of local structures in the numerical solution and thus provides an adaptive mesh refined only in regions where the solution needs more improved resolution. We assess the three-dimensional magnetohydrodynamic CARMEN code and compare its results with the ones from the well-known FLASH code. Copyright © 2019, The Authors. All rights reserved.

关键词： Magnetohydrodynamics

Pharmacoinformatics and cellular studies of algal peptides as novel functional molecules to modulate type-2 diabetes markers

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Clinical Nutrition ESPEN 2024年 63卷 1119-1119页

作者： Nurkolis, F. Kurniawan, R. Basrowi, R.W. Sundjaya, T. Taslim, N.A. Hardinsyah, H. Tjandrawinata, R.R. Tallei, T.E. Kim, B. Tsopmo, A. Department of Biological Sciences Faculty of Sciences and Technology State Islamic University of Sunan Kalijaga (UIN Sunan Kalijaga) Yogyakarta Editorial Board of Journal of Indonesian Specialized Nutrition Jakarta Graduate from School of Medicine Faculty of Medicine Hasanuddin University Makassar Diabetes Connection Care Eka Hospital Bumi Serpong Damai Tangerang Magister Occupational Medicine Department of Community Medicine Faculty of Medicine Universitas Indonesia Indonesia Health Collaborative Center (HCC) Jakarta Indonesia Departement of Epidemiology Faculty of Public Health Universitas Indonesia Jakarta Division of Clinical Nutrition Department of Nutrition Faculty of Medicine Hasanuddin University Makassar Division of Applied Nutrition Faculty of Human Ecology Department of Community Nutrition IPB University Bogor Biotechnology Faculty of Biotechnology Atma Jaya Catholic University of Indonesia Jakarta Biology Faculty of Mathematics and Natural Sciences Universitas Sam Ratulangi Manado Indonesia Pathology College of Korean Medicine Kyung Hee University Seoul Republic Of Korea Food Science and Nutrition Program Department of Chemistry Carleton University Ottawa Canada

Setting the physical scale of dimensional reduction in causal dynamical triangulations

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arXiv 2018年

作者： Cooperman, Joshua H. Dorghabekov, Manuchehr Department of Physics and Astronomy Bucknell University LewisburgPA United States Physics Program Bard College Annandale-on-Hudson NY United States Applied Mathematics and Informatics Program American University of Central Asia Bishkek Kyrgyzstan

Within the causal dynamical triangulations approach to the quantization of gravity, striking evidence has emerged for the dynamical reduction of spacetime dimension on sufficiently small scales. Specifically, the spectral dimension decreases from the topological value of 4 towards a value near 2 as the scale being probed decreases. The physical scales over which this dimensional reduction occurs have not previously been ascertained. We present and implement a method to determine these scales in units of either the Planck length or the quantum spacetime geometry’s effective de Sitter length. We find that dynamical reduction of the spectral dimension occurs over physical scales of the order of 10 Planck lengths, which, for the numerical simulation considered below, corresponds to the order of 10−1 de Sitter lengths. Copyright © 2018, The Authors. All rights reserved.

关键词： Triangulation

On collisions times of 'self-sorting' interacting particles in one-dimension with random initial positions and velocities

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arXiv 2017年

作者： Lega, Joceline Sethuraman, Sunder Young, Alexander L. Department of Mathematics University of Arizona Program in Applied Mathematics University of Arizona

We investigate a one-dimensional system of N particles, initially distributed with random positions and velocities, interacting through binary collisions. The collision rule is such that there is a time after which the N particles do not interact and become sorted according to their velocities. When the collisions are elastic, we derive asymptotic distributions for the final collision time of a single particle and the final collision time of the system as the number of particles approaches infinity, under different assumptions for the initial distributions of the particles' positions and velocities. For comparison, a numerical investigation is carried out to determine how a non-elastic collision rule, which conserves neither momentum nor energy, affects the median collision time of a particle and the median final collision time of the *** Codes 82C22, 62G30 (Primary) 82C23, 62-04, 62E20 (Secondary) Copyright © 2017, The Authors. All rights reserved.

关键词： Velocity

Uncovering multiscale order in the prime numbers via scattering

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arXiv 2018年

作者： Torquato, .S. Zhang, .G. De Courcy-Ireland, M. Department of Chemistry Department of Physics Princeton Institute for the Science and Technology of Materials Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Mathematics Princeton University PrincetonNJ08544 United States

The prime numbers have been a source of fascination for millenia and continue to surprise us. Motivated by the hyperuniformity concept, which has attracted recent attention in physics and materials science, we show that the prime numbers in certain large intervals possess unanticipated order across length scales and represent the first example of a new class of many-particle systems with pure point diffraction patterns, which we call effectively limit-periodic. In particular, the primes in this regime are hyperuniform. This is shown analytically using the structure factor S(k), proportional to the scattering intensity from a many-particle system. Remarkably, the structure factor for primes is characterized by dense Bragg peaks, like a quasicrystal, but positioned at certain rational wavenumbers, like a limit-periodic point pattern. We identify a transition between ordered and disordered prime regimes that depends on the intervals studied. Our analysis leads to an algorithm that enables one to predict primes with high accuracy. Effective limit-periodicity deserves future investigation in physics, independent of its link to the primes. Copyright © 2018, The Authors. All rights reserved.

关键词：

HIDDEN MULTISCALE ORDER IN THE PRIMES

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arXiv 2018年

作者： Torquato, Salvatore Zhang, Ge Courcy-Ireland, Matthew De Department of Chemistry Department of Physics Princeton Institute for the Science and Technology of Materials Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 Department of Chemistry Princeton University PrincetonNJ08544 United States Department of Mathematics Princeton University PrincetonNJ08544 United States

We study the pair correlations between prime numbers in an interval M ≤ p ≤ M + L with M → ∞, L/M → β > 0. By analyzing the structure factor, we prove, conditionally on the Hardy-Littlewood conjecture on prime pairs, that the primes are characterized by unanticipated multiscale order. Specifically, their limiting structure factor is that of a union of an infinite number of periodic systems and is characterized by dense set of Dirac delta functions. Primes in dyadic intervals are the first examples of what we call effectively limit-periodic point configurations. This behavior implies anomalously suppressed density fluctuations compared to uncorrelated (Poisson) systems at large length scales, which is now known as hyperuniformity. Using a scalar order metric τ calculated from the structure factor, we identify a transition between the order exhibited when L is comparable to M and the uncorrelated behavior when L is only logarithmic in M. Our analysis for the structure factor leads to an algorithm to reconstruct primes in a dyadic interval with high accuracy. Copyright © 2018, The Authors. All rights reserved.

关键词： Delta functions

Derivative-free superiorization: Principle and algorithm

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arXiv 2019年

作者： Censor, Yair Garduño, Edgar Helou, Elias S. Herman, Gabor T. Department of Mathematics University of Haifa Mt. Carmel Haifa3498838 Israel Departamento de Ciencias de la Computación Instituto de Investigaciones en Matemáticas Aplicadas y en Sistemas Universidad Nacional Autónoma de México Cd. Universitaria Mexico CityC.P. 04510 Mexico Department of Applied Mathematics and Statistics University of São Paulo São Carlos São Paulo13566-590 Brazil Computer Science Ph.D. Program Graduate Center City University of New York New YorkNY10016 United States

The superiorization methodology is intended to work with input data of constrained minimization problems, that is, a target function and a set of constraints. However, it is based on an antipodal way of thinking to what leads to constrained minimization methods. Instead of adapting unconstrained minimization algorithms to handling constraints, it adapts feasibility-seeking algorithms to reduce (not necessarily minimize) target function values. This is done by inserting target-function-reducing perturbations into a feasibility-seeking algorithm while retaining its feasibility-seeking ability and without paying a high computational price. A superiorized algorithm that employs component-wise target function reduction steps is presented. This enables derivative-free superiorization (DFS), meaning that superiorization can be applied to target functions that have no calculable partial derivatives or subgradients. The numerical behavior of our derivative-free superiorization algorithm is illustrated on a data set generated by simulating a problem of image reconstruction from projections. The plots of proximity-target curves of our experiments demonstrate the advantage of the proposed derivative-free superiorization algorithm. Copyright © 2019, The Authors. All rights reserved.

关键词： Constrained optimization