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arXiv 2023年

作者： Yao, C. Li, J. Hao, L. Yan, R. Wang, C. Lei, A. Ding, Y.-K. Zheng, J. Department of Plasma Physics and Fusion Engineering CAS Key Laboratory of Geospace Environment University of Science and Technology of China Anhui Hefei230026 China Research Center of Laser Fusion Sichuan Mianyang621900 China Shanghai Jiao Tong University Shanghai200240 China Institute of Applied Physics and Computational Mathematics Beijing100088 China Department of Modern Mechanics University of Science and Technology of China Anhui Hefei230026 China Shanghai Institute of Laser Plasma China Academy of Engineering Physics Shanghai201800 China Joint Laboratory on High Power Laser and Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai201800 China

We investigate the hot electrons generated from two-plasmon decay (TPD) instability driven by laser pulses with intensity modulated by a frequency ∆ωm. Our primary focus lies on scenarios where ∆ωm is on the same order of the TPD growth rate γ0 (∆ωm ∼ γ0), corresponding to moderate laser frequency bandwidths for TPD mitigation. With ∆ωm conveniently modeled by a basic two-color scheme of the laser wave fields in fully-kinetic particle-in-cell simulations, we demonstrate that the energies of TPD modes and hot electrons exhibit intermittent evolution at the frequency ∆ωm, particularly when ∆ωm ∼ γ0. With the dynamic TPD behavior, the overall ratio of hot electron energy to the incident laser energy, fhot, changes significantly with ∆ωm. While fhot drops notably with increasing ∆ωm at large ∆ωm limit as expected, it goes anomalously beyond the hot electron energy ratio for a single-frequency incident laser pulse with the same average intensity when ∆ωm falls below a specific threshold frequency ∆ωc. We find this threshold frequency primarily depends on γ0 and the collisional damping rate of plasma waves, with relatively lower sensitivity to the density scale length. We develop a scaling model characterizing the relation of ∆ωc and laser plasma conditions, enabling the potential extention of our findings to more complex and realistic scenarios. © 2023, CC BY.

关键词： Laser pulses

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Casimir preserving numerical method for global multi-layer quasi-geostrophic turbulence

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Journal of computational Physics 2025年 538卷

作者： Arnout D. Franken Erwin Luesink Sagy R. Ephrati Bernard J. Geurts Multiscale Modelling and Simulation Department of Applied Mathematics Faculty EEMCS University of Twente Enschede PO Box 217 7500 AE the Netherlands Now at Korteweg-de Vries Institute of Mathematics University of Amsterdam the Netherlands Department of Mathematical Sciences Chalmers University of Technology Gothenburg 412 96 Sweden Multiscale Physics Center for Computational Energy Research Department of Applied Physics Eindhoven University of Technology Eindhoven the Netherlands

Accurate long-term predictions of large-scale flow features on planets are crucial for understanding global atmospheric and oceanic systems, necessitating the development of numerical methods that can preserve essential physical structures over extended simulation periods without excessive computational costs. Recent advancements in the study of global single-layer barotropic models have led to novel numerical methods based on Lie–Poisson discretization that preserve energy, enstrophy and higher-order moments of potential vorticity. This paper extends this approach to more complex stratified quasi-geostrophic (QG) systems on the sphere. These multi-layered models provide a more comprehensive representation of atmospheric and oceanic dynamics by accounting for vertical variations in density, pressure, and velocity fields. In this work, we present a formulation of the multi-layer QG equations on the full globe. This allows for extending the Lie–Poisson discretization to multi-layer QG models, ensuring consistency with the underlying structure and enabling long-term simulations without additional regularization. The numerical method is benchmarked through simulations of forced geostrophic turbulence and the long-term behaviour of unforced multi-layered systems. These results demonstrate the structure-preserving properties and robustness of the proposed numerical method, paving the way for a better understanding of the role of high-order conserved quantities in large-scale geophysical flow dynamics.

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The inverse-deformation approach to fracture

arXiv

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arXiv 2020年

作者： Rosakis, Phoebus Healey, Timothy J. Alyanak, Ugur Department of Mathematics and Applied Mathematics University of Crete Heraklion Crete70013 Greece Institute of Applied and Computational Mathematics Foundation for Research and Technology-Hellas Voutes Crete70013 Greece Department of Mathematics Cornell University IthacaNY14853 United States Field of Theoretical and Applied Mechanics Cornell University IthacaNY14853 United States

We propose a one-dimensional, nonconvex elastic constitutive model with higher gradients that can predict spontaneous fracture at a critical load via a bifurcation analysis. It overcomes the problem of discontinuous deformations without additional field variables, such as damage or phase-field variables, and without a priori specified surface energy. Our main tool is the use of the inverse deformation, which can be extended to be a piecewise smooth mapping even when the original deformation has discontinuities describing cracks opening. We exploit this via the inverse-deformation formulation of finite elasticity due to Shield and Carlson, including higher gradients in the energy. The problem is amenable to a rigorous global bifurcation analysis in the presence of a unilateral constraint. Fracture under hard loading occurs on a bifurcating solution branch at a critical applied stretch level and fractured solutions are found to have surface energy arising from higher gradient effects. Copyright © 2020, The Authors. All rights reserved.

关键词： Bifurcation (mathematics)

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Single and double charge transfer in the Ne2++He collision within time-dependent density-functional theory

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Physical Review A 2021年第3期103卷 032816-032816页

作者： Wandong Yu Cong-Zhang Gao Shunsuke A. Sato Alberto Castro Angel Rubio Baoren Wei Institute of Modern Physics Department of Nuclear Science and Technology Fudan University Shanghai 200433 China Key Laboratory of Nuclear Physics and Ion-beam Application (MOE) Fudan University Shanghai 200433 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Center for Computational Sciences University of Tsukuba 1-1-1 Tennodai Tsukuba Ibaraki Japan Max Planck Institute for the Structure and Dynamics of Matter Luruper Chaussee 149 22761 Hamburg Germany ARAID Foundation 50018 Zaragoza Spain Institute for Biocomputation and Physics of Complex Systems University of Zaragoza Calle Mariano Esquillor 50018 Zaragoza Spain

We calculate the charge-transfer cross sections for the Ne2++He collision. To this end, we employ Ehrenfest molecular dynamics with time-dependent density-functional theory. The active electrons of the projectile are handled by applying an initial velocity to the Kohn-Sham orbitals via a Galilean boost. The dynamical calculations are performed in an inverse collision framework—the reference frame considers Ne2+ to be initially at rest, which ensures numerically converged final-time scattering states. The charge-transfer probabilities are extracted by extending the particle number projection technique to be able to handle the degenerate Ne2+ ion. Compared with experimental data available at 10–3000 keV, a fairly good agreement is found for the calculated single- and double-charge transfer cross sections, superior to other theoretical calculations for this Ne2++He collision. A time-resolved analysis of the charge-transfer probabilities finds that ionization to the continuum also takes place after the charge transfer has occurred. To account for it, the final scattering states should be followed for a long time, approximately 350 fs, until they stabilize.

关键词： Atomic & molecular collisions Charge-transfer collisions

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Real-Time Krylov Theory for Quantum Computing Algorithms

arXiv

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arXiv 2022年

作者： Shen, Yizhi Klymko, Katherine Sud, James Williams-Young, David B. de Jong, Wibe A. Tubman, Norm M. NASA Ames Research Center Moffett FieldCA94035 United States KBR 601 Jefferson St. HoustonTX77002 United States Department of Chemistry Massachusetts Institute of Technology CambridgeMA02139 United States NERSC Lawrence Berkeley National Laboratory BerkeleyCA94720 United States USRA Research Institute for Advanced Computer Science Mountain ViewCA94043 United States Applied Mathematics and Computational Research Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

Quantum computers provide alternative avenues to access ground and excited state properties of systems difficult to simulate on classical hardware. New approaches using subspaces generated by real-time evolution have shown efficiency in extracting eigenstate information, but the full capabilities of such approaches are still not understood. In recent work, we developed the variational quantum phase estimation (VQPE) method, a compact and efficient real-time algorithm to extract eigenvalues using quantum hardware. Here we build on that work by theoretically and numerically exploring a generalized Krylov scheme where the Krylov subspace is constructed through a parametrized real-time evolution, applicable to the VQPE algorithm as well as others. We establish an error bound that justifies the fast convergence of our spectral approximation. We also derive how the overlap with high energy eigenstates becomes suppressed from real-time subspace diagonalization and we visualize the process that shows the signature phase cancellations at specific eigenenergies. We investigate various algorithm implementations and consider performance when stochasticity is added to the target Hamiltonian in the form of spectral statistics. To demonstrate the practicality of such real-time evolution methods, we discuss its application to fundamental problems in quantum computation such as electronic structure predictions for strongly correlated systems. © 2022, CC BY.

关键词： Quantum computers

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Superconductivity in twisted bilayer WSe2

arXiv

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arXiv 2024年

作者： Guo, Yinjie Pack, Jordan Swann, Joshua Holtzman, Luke Cothrine, Matthew Watanabe, Kenji Taniguchi, Takashi Mandrus, David G. Barmak, Katayun Hone, James Millis, Andrew J. Pasupathy, Abhay N. Dean, Cory R. Department of Physics Columbia University New YorkNY10027 United States Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Department of Materials Science and Engineering University of Tennessee KnoxvilleTN37996 United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Materials Science and Technology Division Oak Ridge National Laboratory Oak RidgeTN37831 United States Department of Mechanical Engineering Columbia University New YorkNY10027 United States Center for Computational Quantum Physics Flatiron Institute New York United States Condensed Matter Physics and Materials Science Division Brookhaven National Laboratory Upton United States

The discovery of superconductivity in twisted bilayer and twisted trilayer graphene[1–5] has generated tremendous interest. The key feature of these systems is an interplay between interlayer coupling and a moiré superlattice that gives rise to low-energy flat bands with strong correlations[6]. Flat bands can also be induced by moiré patterns in lattice-mismatched and or twisted heterostructures of other two-dimensional materials such as transition metal dichalcogenides (TMDs)[7–11]. Although a wide range of correlated phenomenon have indeed been observed in the moiré TMDs[12–24], robust demonstration of superconductivity has remained absent[12]. Here we report superconductivity in 5 degree twisted bilayer WSe2 (tWSe2) with a maximum critical temperature of 426 mK. The superconducting state appears in a limited region of displacement field and density that is adjacent to a metallic state with Fermi surface reconstruction believed to arise from antiferromagnetic order[25]. A sharp boundary is observed between the superconducting and magnetic phases at low temperature, reminiscent of spin-fluctuation mediated superconductivity[26]. Our results establish that moiré flat-band superconductivity extends beyond graphene structures. Material properties that are absent in graphene but intrinsic among the TMDs such as a native band gap, large spin-orbit coupling, spin-valley locking, and magnetism offer the possibility to access a broader superconducting parameter space than graphene-only structures. © 2024, CC BY.

关键词： Graphene

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Dual Ligand-Induced Photoelectrochemical Sensing by Integrating Pt/MoS2 Heterostructure and AU Polyhedra for Sensitive Detection of SARS-CoV-2

SSRN

引用

SSRN 2022年

作者： Li, Haolin Zhao, Jialin Wu, Ting Fu, Zhao Zhang, Wei Lian, Zheng Cai, Shuangfei Yang, Rong CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety Center of Materials Science and Optoelectronics Engineering CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology University of Chinese Academy of Sciences Beijing100190 China Sino-Danish College Sino-Danish Center for Education and Research University of Chinese Academy of Sciences Beijing100049 China Institute of Applied Physics and Computational Mathematics Beijing100088 China

The continuous evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with discovery of multiple mutants, has caused widespread panic and concern worldwide. The rapid antigen detection method via a single ligand recognition, although currently implemented in many countries, remains challenging for mutated antigens. Herein, we present a novel strategy using a dual recognition by two types of targeted ligands, based on photoelectrochemical (PEC) sensing for detection of SARS-CoV-2 spike protein. To demonstrate this strategy, the specific antibodies are modified onto the photoactive material with a supported nanostructure, created by loading the Pt nanoparticles onto MoS2 nanosheets (Pt/MoS2) to boost photon-to-electricity conversion efficiency. By subsequent binding of the targeted aptamers to the Au polyhedra, which act as a signal amplifier to suppress PEC photocurrent by competing with the Pt/MoS2 for the absorption of excitation light energy, the dual recognition is successfully achieved. The constructed biosensor not only shows satisfactory stability, and high sensitivity, but is effective for test of the pseudovirus of SARS-CoV-2. The work provides useful advance for the development of PEC biosensors for sensitive detection of SARS-CoV-2. © 2022, The Authors. All rights reserved.

关键词： Coronavirus

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Democratizing Uncertainty Quantification

arXiv

引用

arXiv 2024年

作者： Seelinger, Linus Reinarz, Anne Lykkegaard, Mikkel B. Akers, Robert Alghamdi, Amal M.A. Aristoff, David Bangerth, Wolfgang Bénézech, Jean Diez, Matteo Frey, Kurt Jakeman, John D. Jørgensen, Jakob S. Kim, Ki-Tae Kent, Benjamin M. Martinelli, Massimiliano Parno, Matthew Pellegrini, Riccardo Petra, Noemi Riis, Nicolai A.B. Rosenfeld, Katherine Serani, Andrea Tamellini, Lorenzo Villa, Umberto Dodwell, Tim J. Scheichl, Robert Scientific Computing Center Karlsruhe Institute of Technology Karlsruhe Germany Department of Computer Science Durham University Durham United Kingdom digiLab Exeter United Kingdom UK Atomic Energy Authority Oxford United Kingdom Lyngby Denmark Department of Mathematics Colorado State University Fort CollinsCO United States Department of Mathematics Department of Geosciences Colorado State University Fort CollinsCO United States Centre for Integrated Materials Processes and Structures Department of Mechanical Engineering University of Bath Bath United Kingdom National Research Council Institute of Marine Engineering Rome Italy Institute for Disease Modeling Global Health Division Bill & Melinda Gates Foundation United States Optimization and Uncertainty Quantification Sandia National Laboratories AlbuquerqueNM United States University of California Merced United States National Research Council-Institute for Applied Mathematics and Information Technologies "E. Magenes" Pavia Italy Solea Energy ThetfordVT United States Copenhagen Imaging ApS Herlev Denmark The University of Texas Austin United States Heidelberg University Germany

Uncertainty Quantification (UQ) is vital to safety-critical model-based analyses, but the widespread adoption of sophisticated UQ methods is limited by technical complexity. In this paper, we introduce UM-Bridge (the UQ and Modeling Bridge), a high-level abstraction and software protocol that facilitates universal interoperability of UQ software with simulation codes. It breaks down the technical complexity of advanced UQ applications and enables separation of concerns between experts. UM-Bridge democratizes UQ by allowing effective interdisciplinary collaboration, accelerating the development of advanced UQ methods, and making it easy to perform UQ analyses from prototype to High Performance Computing (HPC) scale. In addition, we present a library of ready-to-run UQ benchmark problems, all easily accessible through UM-Bridge. These benchmarks support UQ methodology research, enabling reproducible performance comparisons. We demonstrate UM-Bridge with several scientific applications, harnessing HPC resources even using UQ codes not designed with HPC support. © 2024, CC BY-NC-ND.

关键词： Application programs

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Neural Network Potential Surfaces: A Comparison of two Approaches

引用

Procedia Computer Science 2020年 178卷 345-354页

作者： Anthony Chazirakis Vassia Kirieri Ilias-Marios Sarris Evangelia Kalligiannaki Vagelis Harmandaris Department of Mathematics and Applied Mathematics University of Crete Heraklion GR-70013 Crete Greece Department of Physics University of Crete Heraklion GR-70013 Crete Greece Institute of Applied and Computational Mathematics IACM-FORTH Heraklion GR-70013 Crete Greece Computation-Based Science and Technology Research Center The Cyprus Institute Nicosia 2121 Cyprus

Molecular dynamics simulations often involve excessive degrees of freedom, and therefore the computational cost is prohibitively high. Coarse-graining high-dimensional molecular systems is a well-established procedure to increase the space- and time- scales accessible. The coarse-level potential energy must be estimated to derive correctly structural and dynamical properties of the reduced system. Here we examine the artificial neural networks as a potential tool to represent high-dimensional potential-energy surfaces. The simulated coarse configurations are fed to the neural network while taking care to represent each pseudo-atom’s chemical environment properly. Then, the neural network is trained to reproduce the molecular energy. In this work, we present two approaches designed to preserve the physical symmetries of the coarse system. The first approach introduces symmetry functions and the second local coordinates. We implement these techniques, and we apply and compare them for two molecular systems, a bulk methane system, and a liquid water system.

关键词： Molecular dynamics Coarse-grained models Neural Networks Potential of Mean Force

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Covariant density and velocity perturbations of the quasi-Newtonian cosmological model in f(T) gravity

arXiv

引用

arXiv 2021年

作者： Sami, Heba Sahlu, Shambel Abebe, Amare Dunsby, Peter K.S. Center for Space Research North-West University South Africa Astronomy and Astrophysics Research Development Department Entoto Observatory and Research Center Ethiopian Space Science and Technology Institute Ethiopia Department of Physics College of Natural and Computational Science Wolkite University Ethiopia Cosmology and Gravity Group Department of Mathematics and Applied Mathematics University of Cape Town Rondebosch Cape Town7701 South Africa

We investigate classes of shear-free cosmological dust models with irrotational fluid flows within the framework of f(T) gravity. In particular, we use the 1+3 covariant formalism and present the covariant linearised evolution and constraint equations describing such models. We then derive the integrability conditions describing a consistent evolution of the linearised field equations of these quasi-Newtonian universes in the f(T) gravitational theory. Finally, we derive the evolution equations for the density and velocity perturbations of the quasi-Newtonian universe. We explore the behaviour of the matter density contrast for two models - f(T) = µT0(T/T0)n and the more generalised case, where f(T) = T + µT0(T/T0)n, with and without the application of the quasi-static approximation. Our numerical solutions show that these f(T) theories can be suitable alternatives to study the background dynamics, whereas the growth of energy density fluctuations change dramatically from the expected ΛCDM behaviour even for small deviations away from the general relativistic limits of the underlying f(T) theory. Moreover, applying the so-called quasi-static approximation yields exact-solution results that are orders of magnitude different from the numerically integrated solutions of the full system, suggesting that these approximations are not applicable here. Copyright © 2021, The Authors. All rights reserved.

关键词： Flow of fluids

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