检索结果-内蒙古大学图书馆

Improved time integration for phase-field crystal models of solidification

学校读者我要写书评

暂无评论

PAMM 2023年第1期23卷

作者： Maik Punke Steven M. Wise Axel Voigt Marco Salvalaglio Institute of Scientific Computing TU Dresden 01062 Dresden Germany Department of Mathematics The University of Tennessee Knoxville TN 37996 USA Dresden Center for Computational Materials Science TU Dresden 01062 Dresden Germany

We optimize a numerical time-stabilization routine for a class of phase-field crystal (PFC) models of solidification. By numerical experiments, we demonstrate that our simple approach can improve the accuracy of underlying time integration schemes by a few orders of magnitude. We investigate different time integration schemes. Moreover, as a prototypical example for applications, we extend our numerical approach to a PFC model of solidification with an explicit temperature coupling.

关键词：

Minimum tracking linear response Hubbard and Hund corrected Density Functional Theory in CP2K

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Chai, Ziwei Si, Rutong Chen, Mingyang Teobaldi, Gilberto O'Regan, David D. Liu, Li-Min Beijing Computational Science Research Center Beijing100193 China School of Physics Beihang University Beijing100191 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing100083 China Scientific Computing Department STFC UKRI Rutherford Appleton Laboratory Harwell Campus DidcotOX11 0QX United Kingdom School of Physics SFI AMBER Centre CRANN Institute Trinity College Dublin The University of Dublin Ireland

We present the implementation of the Hubbard (U) and Hund (J) corrected Density Functional Theory (DFT+U+J) functionality in the Quickstep program, which is part of the CP2K suite. The tensorial and Löwdin subspace representations are implemented and compared. Full analytical DFT+U+J forces are implemented and benchmarked for the tensorial and Löwdin representations. We also present the implementation of the recently proposed minimum-tracking linear-response method that enables the U and J parameters to be calculated on first principles basis without reference to the Kohn-Sham eigensystem. These implementations are benchmarked against recent results for different materials properties including DFT+U band gap opening in NiO, the relative stability of various polaron distributions in TiO2, the dependence of the calculated TiO2 band gap on +J corrections, and, finally, the role of the +U and +J corrections for the computed properties of a series of the hexahydrated transition metals. Our implementation provides results consistent with those already reported in the literature from comparable methods. We conclude the contribution with tests on the influence of the Löwdin orthonormalization on the occupancies, calculated parameters, and derived properties. © 2024, CC BY.

关键词： Titanium dioxide

Ab initio vibrational free energies including anharmonicity for multicomponent alloys

学校读者我要写书评

暂无评论

arXiv 2019年

作者： Grabowski, Blazej Ikeda, Yuji Körmann, Fritz Freysoldt, Christoph Duff, Andrew Ian Shapeev, Alexander Neugebauer, Jörg Department for Computational Materials Design Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Str. 1 Düsseldorf40237 Germany Department of Materials Science and Engineering Delft University of Technology Mekelweg 2 Delft2628 CD Netherlands Scientific Computing Department STFC Daresbury Laboratory Hartree Centre Warrington United Kingdom Skolkovo Institute of Science and Technology Skolkovo Innovation Center Nobel St. 3 Moscow143026 Russia

A density-functional-theory based approach to efficiently compute numerically exact vibrational free energies|including anharmonicity|for chemically complex multicomponent alloys is developed. It is based on a combination of thermodynamic integration and a machine-learning potential. We demonstrate the performance of the approach by computing the anharmonic free energy of the prototypical five-component VNbMoTaW refractory high entropy alloy. Copyright © 2019, The Authors. All rights reserved.

关键词： Computation theory

Blood Cancer Detection and Classification using Auto Encoder and Regularized Extreme Learning Machine

学校读者我要写书评

暂无评论

Blood Cancer Detection and Classification using Auto Encoder...

International Conference on Communication and Electronics Systems (ICCES)

作者： N. Kanimozhi Swikruti Nayak Keshav Kumar K Vinda Manjramkar Ranjeet Kumar D. Suganthi Department of Computational Intelligence School of Computing SRM Institute of Science and Technology Kattankulathur Chennai Tamilnadu India Department of Computer Science and Engineering JECRC University Jaipur Rajasthan India Department of Humanities and Mathematics G. Narayanamma Institute of Technology and Science (for Women) Shaikpet Hyderabad Telangana India Zoology B.N. Bandodkar College of Science (Autonomous) Thane Maharashtra India Department of Electronics & Communication University College of Engineering & Technology Vinoba Bhave University Hazaribagh Jharkhand India Department of Computer Science Saveetha College of Liberal Arts and Sciences Saveetha Institute of Medical and Technical Sciences Chennai

Leukaemia is considered as the most common type of blood cancer. The length of time one requires to recover from this disease is determined by how quickly it is recognized and treated. Leukaemia develops when the bone marrow generates an abnormally large amount of white blood cells. Since images of human blood samples are studied under the microscope, haematologists employ techniques such as microscopic colour imaging, image segmentation, grouping, and classification to diagnose patients as fast as possible. Microscopy may identify blood cancer in visible and immature white blood cells in a variety of methods. Early and accurate diagnosis of leukaemia is critical for clinicians to properly treat patients. After the input image is provided, the gaussian filter is used to perform image enhancement, and the Wiener filter is used in image Deblurring, Adaptive K-Means clustering technique, Colour feature, Texture feature, GLCM and Hausdroff are also used, and lastly the Model is trained using AE and RELM. The proposed system outperforms conventional models such as RELM and ELM, which generates an accuracy of 98.45%.

关键词：

Rubric-based holistic review: A promising route to equitable graduate admissions in physics

学校读者我要写书评

暂无评论

Physical Review Physics Education Research 2022年第2期18卷 020140-020140页

作者： Nicholas T. Young K. Tollefson Remco G. T. Zegers Marcos D. Caballero Department of Physics and Astronomy Michigan State University East Lansing Michigan 48824 USA Department of Computational Mathematics Science and Engineering Michigan State University East Lansing Michigan 48824 USA National Superconducting Cyclotron Laboratory Michigan State University East Lansing Michigan 48824 USA Joint Institute for Nuclear Astrophysics Michigan State University East Lansing Michigan 48824 USA Center for Computing in Science Education and Department of Physics University of Oslo N-0316 Oslo Norway CREATE for STEM Institute Michigan State University East Lansing Michigan 48824 USA

As systematic inequities in higher education and society have been brought to the forefront, graduate programs are interested in increasing the diversity of their applicants and enrollees. Yet, structures in place to evaluate applicants may not support such aims. One potential solution to support those aims is rubric-based holistic review. Starting in 2018, our physics department implemented a rubric-based holistic review process for all applicants to our graduate program. The rubric assessed applicants on 18 metrics covering their grades, test scores, research experiences, noncognitive competencies, and fit with the program. We then compared faculty’s ratings of applicants by admission status, sex, and undergraduate program over a three-year period. We find that the rubric scores show statistically significant differences between admitted and nonadmitted students as hoped. We also find that differences in rubric scores based on sex or undergraduate program reflected known systematic inequities such as applicants from smaller and less prestigious undergraduate universities scoring lower on the physics GRE and women performing more volunteer work in academia. Our results then suggest rubric-based holistic review as a possible route to making graduate admissions in physics more equitable.

关键词： Diversity & inclusion Educational policy Graduate students

Quantum-assisted quantum compiling

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Khatri, Sumeet LaRose, Ryan Poremba, Alexander Cincio, Lukasz Sornborger, Andrew T. Coles, Patrick J. Theoretical Division Los Alamos National Laboratory Los AlamosNM United States Hearne Institute for Theoretical Physics Department of Physics and Astronomy Louisiana State University Baton RougeLA United States Department of Computational Mathematics Science and Engineering Department of Physics and Astronomy Michigan State University East LansingMI United States Computing and Mathematical Sciences California Institute of Technology PasadenaCA United States Information Sciences Los Alamos National Laboratory Los AlamosNM United States

Compiling quantum algorithms for near-term quantum computers (accounting for connectivity and native gate alphabets) is a major challenge that has received significant attention both by industry and academia. Avoiding the exponential overhead of classical simulation of quantum dynamics will allow compilation of larger algorithms, and a strategy for this is to evaluate an algorithm’s cost on a quantum computer. To this end, we propose a variational hybrid quantum-classical algorithm called quantum-assisted quantum compiling (QAQC). In QAQC, we use the overlap between a target unitary U and a trainable unitary V as the cost function to be evaluated on the quantum computer. More precisely, to ensure that QAQC scales well with problem size, our cost involves not only the global overlap Tr(V †U) but also the local overlaps with respect to individual qubits. We introduce novel short-depth quantum circuits to quantify the terms in our cost function, and we prove that our cost cannot be efficiently approximated with a classical algorithm under reasonable complexity assumptions. We present both gradient-free and gradient-based approaches to minimizing this cost. As a demonstration of QAQC, we compile various one-qubit gates on IBM’s and Rigetti’s quantum computers into their respective native gate alphabets. Furthermore, we successfully simulate QAQC up to a problem size of 9 qubits, and these simulations highlight both the scalability of our cost function as well as the noise resilience of QAQC. Future applications of QAQC include algorithm depth compression, black-box compiling, noise mitigation, and benchmarking. Copyright © 2018, The Authors. All rights reserved.

关键词： Qubits

What we should learn from pandemic publishing

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Sikdar, Satyaki Venturini, Sara Charpignon, Marie-Laure Kumar, Sagar Rinaldi, Francesco Tudisco, Francesco Fortunato, Santo Majumder, Maimuna S. Luddy School of Informatics Computing and Engineering Indiana University BloomingtonIN United States Department of Computer Science Loyola University Chicago ChicagoIL United States Senseable City Laboratory Massachusetts Institute of Technology CambridgeMA United States Department of Mathematics "Tullio Levi-Civita" University of Padova Padova Italy Institute for Data Systems and Society Massachusetts Institute of Technology CambridgeMA United States Network Science Institute Northeastern University BostonMA United States School of Mathematics The University of Edinburgh Edinburgh United Kingdom School of Mathematics Gran Sasso Science Institute L’Aquila Italy Department of Pediatrics Harvard Medical School BostonMA United States Computational Health Informatics Program Boston Children’s Hospital BostonMA United States

Since the emergence of COVID-19, discussions of ongoing pandemic-related research have accounted for an unprecedented share of media coverage and debate in the public sphere1. The urgency of the pandemic forced researchers to operate on an accelerated timeline, as both policymakers and the public relied on the most current evidence to guide their decisions and behaviors. With high demand for rapid pandemic-related insights and lower barriers to entry via preprint servers, the volume of COVID-19 articles skyrocketed2. The pressing need for research triggered the participation of many researchers with expertise in the science of infectious disease outbreaks (‘outbreak scientists’), who were joined by researchers from other disciplines (‘bellwethers’) and more junior researchers still in training (‘newcomers’) with the common goal of advancing the frontiers of pandemic science and informing policy decisions3. Please see Box 1 for details of this taxonomy. © 2024, CC BY-NC-ND.

关键词： COVID-19

Personalized and uncertainty-aware coronary hemodynamics simulations: From Bayesian estimation to improved multi-fidelity uncertainty quantification

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Menon, Karthik Zanoni, Andrea Khan, Owais Geraci, Gianluca Nieman, Koen Schiavazzi, Daniele E. Marsden, Alison L. Stanford School of Medicine StanfordCA United States Institute for Computational and Mathematical Engineering Stanford University StanfordCA United States Department of Electrical Computer and Biomedical Engineering Toronto Metropolitan University TorontoON Canada Center for Computing Research Sandia National Laboratories AlbuquerqueNM United States Division of Cardiovascular Medicine Stanford School of Medicine StanfordCA United States Department of Radiology Stanford School of Medicine StanfordCA United States Department of Applied and Computational Mathematics and Statistics University of Notre Dame Notre DameIN United States Department of Bioengineering Stanford University StanfordCA United States

Background: Non-invasive simulations of coronary hemodynamics have improved clinical risk stratification and treatment outcomes for coronary artery disease, compared to relying on anatomical imaging alone. However, simulations typically use empirical approaches to distribute total coronary flow amongst the arteries in the coronary tree, which ignores patient variability, the presence of disease, and other clinical factors. Further, uncertainty in the clinical data often remains unaccounted for in the modeling pipeline. Objective: We present an end-to-end uncertainty-aware pipeline to (1) personalize coronary flow simulations by incorporating vessel-specific coronary flows as well as cardiac function;and (2) predict clinical and biomechanical quantities of interest with improved precision, while accounting for uncertainty in the clinical data. Methods: We assimilate patient-specific measurements of myocardial blood flow from clinical CT myocardial perfusion imaging to estimate branch-specific coronary artery flows. Simulated noise in the clinical data is used to estimate the joint posterior distributions of the model parameters using adaptive Markov Chain Monte Carlo sampling. Additionally, the posterior predictive distribution for the relevant quantities of interest is determined using a new approach combining multi-fidelity Monte Carlo estimation with non-linear, data-driven dimensionality reduction. This leads to improved correlations between high- and low-fidelity model outputs. Results: Our framework accurately recapitulates clinically measured cardiac function as well as branch-specific coronary flows under measurement noise uncertainty. We observe substantial reductions in confidence intervals for estimated quantities of interest compared to single-fidelity Monte Carlo estimation and state-of-the-art multi-fidelity Monte Carlo methods. This holds especially true for quantities of interest that showed limited correlation between the low- and high-fidelity model

关键词： Monte Carlo methods

A topographic mechanism for arcing of dryland vegetation bands

学校读者我要写书评

暂无评论

arXiv 2018年

作者： Gandhi, Punit Werner, Lucien Iams, Sarah Gowda, Karna Silber, Mary Mathematical Biosciences Institute Ohio State University ColumbusOH43210 United States Department of Computing and Mathematical Sciences California Institute of Technology PasadenaCA91125 United States John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Department of Physics University of Illinois at Urbana-Champaign UrbanaIL61801 United States Committee on Computational and Applied Mathematics Department of Statistics University of Chicago ChicagoIL60637 United States

Banded patterns consisting of alternating bare soil and dense vegetation have been observed in water-limited ecosystems across the globe, often appearing along gently sloped terrain with the stripes aligned transverse to the elevation gradient. In many cases these vegetation bands are arced, with field observations suggesting a link between the orientation of arcing relative to the grade and the curvature of the underlying terrain. We modify the water transport in the Klausmeier model of water-biomass interactions, originally posed on a uniform hillslope, to qualitatively capture the influence of terrain curvature on the vegetation patterns. Numerical simulations of this modified model indicate that the vegetation bands change arcing-direction from convex-downslope when growing on top of a ridge to convex-upslope when growing in a valley. This behavior is consistent with observations from remote sensing data that we present here. Model simulations show further that whether bands grow on ridges, valleys, or both depends on the precipitation level. A survey of three banded vegetation sites, each with a different aridity level, indicates qualitatively similar behavior. Copyright © 2018, The Authors. All rights reserved.

关键词： Ecology