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Theoretical analysis of spectral lineshapes from molecular dynamics

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npj Computational Materials 2019年第1期5卷 430-441页

作者： andrew Cupo Damien Tristant Kyle Rego Vincent Meunier Department of Physics Applied Physicsand AstronomyRensselaer Polytechnic InstituteTroyNYUSA

Conventional methods for calculating anharmonic phonon properties are computationally *** address this issue,a theoretical approach was developed for the accelerated calculation of vibrational lineshapes for spectra obtained from finite-time molecular *** method gives access to the effect of anharmonicity-induced frequency shift and lifetime,as well as simulation *** a toy model we demonstrate at least an order of magnitude reduction in the number of simulation steps needed to obtain converged vibrational properties in nearly all cases considered as compared to the standard extraction *** theory is also illustrated for graphene,hexagonal boron nitride,and silicon at the density functional theory level,with up to nearly a factor of 9 reduction in the required simulation time to reach convergence in the vibrational frequencies and *** general,we expect the newly developed method to outperform the standard procedure when the anharmonicity is sufficiently weak so that well-defined renormalized phonon quasiparticles *** extension of signal analysis to material vibrations represents a state-of-the-art advance in calculating temperature-dependent phonon properties and could be implemented in computational materials discovery packages that search for thermoelectric materials for instance,since the thermal conductivity contribution to ZT depends strongly on these characteristics.

关键词： calculating harmonic analysis

Gaussian process analysis of electron energy loss spectroscopy data:multivariate reconstruction and kernel control

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npj Computational Materials 2021年第1期7卷 1395-1404页

作者： Sergei V.Kalinin andrew R.Lupini Rama K.Vasudevan Maxim Ziatdinov Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTNUSA

Advances in hyperspectral imaging including electron energy loss spectroscopy bring forth the challenges of exploratory and physics-based analysis of multidimensional data *** multivariate linear unmixing methods generally explore similarities in the energy dimension,but ignore correlations in the spatial *** the same time,Gaussian process(GP)explicitly incorporate spatial correlations in the form of kernel functions but is computationally ***,we implement a GP method operating on the full spatial domain and reduced representations in the energy *** this multivariate GP,the information between the components is shared via a common spatial kernel structure,while allowing for variability in the relative noise magnitude or image *** explore the role of kernel constraints on the quality of the reconstruction,and suggest an approach for estimating them from the experimental *** further show that spatial information contained in higher-order components can be reconstructed and spatially localized.

关键词： domain kernel multivariate

Properties of the multiorbital Hubbard models for the iron-based superconductors

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Frontiers of physics 2011年第4期6卷 379-397页

作者： Elbio Dagotto Adriana Moreo andrew Nicholson Qinglong Luo Shuhua Liang Xiaotian Zhang Department of Physics and Astronomy The University of Tennessee Knoxville TN 37996 USA Materials Science and Technology Division Oak Ridge National Laboratory Oak Ridge TN 37831 USA

A brief review of the main properties of multiorbital Hubbard models for the Fe-based superconductors is presented. The emphasis is on the results obtained by our group at the University of Tennessee and Oak ridge National Laboratory, Tennessee, USA, but results by several other groups are also discussed. The models studied here have two, three, and five orbitals, and they are analyzed using a variety of computational and mean-field approximations. A ＂physical region＂ where the properties of the models are in qualitative agreement with neutron scattering, photoemission, and transport results is revealed. A variety of interesting open questions are briefly discussed such as： what are the dominant pairing tendencies in Hubbard models？ Can pairing occur in an interorbital channel？ Are nesting effects of fundamental relevance in the pnictides or approaches based on local moments are more important？ What kind of magnetic states are found in the presence of iron vacancies？ Can charge stripes exist in iron-based superconductors？ Why is transport in the pnictides anisotropic？ The discussion of results includes the description of these and other open problems in this fascinating area of research.

关键词： superconductivity

Probing atomic-scale symmetry breaking by rotationally invariant machine learning of multidimensional electron scattering

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npj Computational Materials 2021年第1期7卷 595-600页

作者： Mark P.Oxley Maxim Ziatdinov Ondrej Dyck andrew R.Lupini Rama Vasudevan Sergei V.Kalinin Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTNUSA Computational Sciences and Engineering Division Oak Ridge National LaboratoryOak RidgeTNUSA

The 4D scanning transmission electron microscopy(STEM)method maps the structure and functionality of solids on the atomic scale,yielding information-rich data sets describing the interatomic electric and magnetic fields,structural and electronic order parameters,and other symmetry breaking distortions.A critical bottleneck is the dearth of analytical tools that can reduce complex 4D-STEM data to physically relevant *** propose an approach for the systematic exploration of 4D-STEM data using rotationally invariant variational autoencoders(rrVAE),which disentangle the general rotation of the object from other latent *** implementation of purely rotational rrVAE is discussed as are applications to simulated data for graphene and zincblende *** rrVAE analysis of experimental 4D-STEM data of defects in graphene is illustrated and compared to the classical center-of-mass *** approach is universal for probing symmetry-breaking phenomena in complex systems and can be implemented for a broad range of diffraction methods.

关键词： symmetry breaking rotational

Defect detection in atomic-resolution images via unsupervised learning with translational invariance

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npj Computational Materials 2021年第1期7卷 1640-1648页

作者： Yueming Guo Sergei V.Kalinin Hui Cai Kai Xiao Sergiy Krylyuk Albert V.Davydov Qianying Guo andrew R.Lupini Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN 37831USA Material Measurement Laboratory National Institute of Standards and TechnologyGaithersburgMD 20899USA

Crystallographic defects can now be routinely imaged at atomic resolution with aberration-corrected scanning transmission electron microscopy(STEM)at high speed,with the potential for vast volumes of data to be acquired in relatively short times or through autonomous experiments that can continue over very long *** detection and classification of defects in the STEM images are needed in order to handle the data in an efficient ***,like many other tasks related to object detection and identification in artificial intelligence,it is challenging to detect and identify defects from STEM ***,it is difficult to deal with crystal structures that have many atoms and low *** methods used for defect detection and classification were based on supervised learning,which requires human-labeled *** this work,we develop an approach for defect detection with unsupervised machine learning based on a one-class support vector machine(OCSVM).We introduce two schemes of image segmentation and data preprocessing,both of which involve taking the Patterson function of each segment as *** demonstrate that this method can be applied to various defects,such as point and line defects in 2D materials and twin boundaries in 3D nanocrystals.

关键词： handle resolution image

An apatite U-Pb thermal history map for the northern Gawler Craton,South Australia

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Geoscience Frontiers 2018年第5期9卷 1293-1308页

作者： James W.Hall Stijn Glorie Anthony J.Reid Samuel C.Boone Alan S.Collins andrew Gleadow Tectonics Resources and Exploration (TRaX) Department of Earth Sciences University of Adelaide Geological Survey of South Australia Department of State Development School of Earth Sciences The University of Melbourne

Apatite U-Pb thermochronology was applied to granitoid basement samples across the northern Gawler Craton to unravel the Proterozoic, post-orogenic, cooling history and to examine the role of major fault zones during cooling. Our observations indicate that cooling following the ~2500 Ma Sleaford Orogeny and ~1700 Ma Kimban Orogeny is restricted to the Christie and Wilgena Domains of the central northern Gawler Craton. The northern Gawler Craton mainly records post-Hiltaba Event(~1590 Ma) U-Pb cooling ages. Cooling following the ~1560 Ma Kararan Orogeny is preserved within the Coober Pedy ridge,Nawa Domain and along major shear zones within the south-western Fowler Domain. The Nawa Domain samples preserve U-Pb cooling ages that are >150 Ma younger than the samples within the Coober Pedy ridge and Fowler Domain, indicating that later(~1300 Ma) fault movement within the Nawa Domain facilitated cooling of these samples, caused by arc collision in the Madura Province of eastern Western Australia. When compared to^(40)Ar/^(39) Ar from muscovite, biotite and hornblende, our new apatite U-Pb ages correlate well, particularly in regions of higher data density. Our data also preserve a progressive younging of U-Pb ages from the nucleus of the craton to the periphery with a stark contrast in U-Pb ages across major structures such as the Karari Shear Zone and the Southern Overthrust, which indicates the timing of reactivation of these major crustal structures. Although this interpolation was based solely on thermochronological data and did not take into account structural or other geological data, these maps are consistent with the structural architecture of the Gawler Craton and reveal the thermal footprint of known tectonic and magmatic events in the Gawler Craton.

关键词： Apatite U-Pb Gawler Craton Karari Shear Zone Thermochronology Hiltaba event

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An Automatic Digital Camera Based Fingerprint Verification System

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International Journal of Systems and Control

International Journal of Systems and Control 2007年第1期 30-45页

作者： Hiew BeeYan andrew Teoh Beng Jin Multimedia University Jalan Ayer Keroh Lama 75450 Melaka Biometrics Engineering Research Center (BERC) Yonsei University Seoul South Korea

The emergence of touch-less fingerprint recognition system brings both advantages and challenges in the automated fingerprint recognition research. In this paper, we proposed a touch-less fingerprint recognition system by using a digital camera. The system frees from the problems in term of deformation caused by the contact pressure, hygienic, maintenance and latent fingerprints that exist in the touch-based fingerprint recognition system. However, fingerprint images that were acquired with digital camera consist of low ridge-valley contrast, defocus and motion blurriness problems. Hence, preprocessing steps are introduced to reduce those problems. The system comprises of preprocessing, Gabor filter feature extraction, Principle Component Analysis and verification using Support Vector Machine. Satisfactory results are attained in our acquired fingerprint database.

关键词： touch-less fingerprint verification preprocessing Gabor filter support vector machine

Manifold learning of four-dimensional scanning transmission electron microscopy

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npj Computational Materials 2019年第1期5卷 1097-1104页

作者： Xin Li Ondrej E.Dyck Mark P.Oxley andrew R.Lupini Leland McInnes John Healy Stephen Jesse Sergei V.Kalinin Center for Nanophase Materials Sciences Oak Ridge National LaboratoryOak RidgeTN 37831USA Institute for Functional Imaging of Materials Oak Ridge National LaboratoryOak RidgeTN 37831USA Tutte Institute for Mathematics and Computing OttawaCanada

Four-dimensional scanning transmission electron microscopy(4D-STEM)of local atomic diffraction patterns is emerging as a powerful technique for probing intricate details of atomic structure and atomic electric ***,efficient processing and interpretation of large volumes of data remain challenging,especially for two-dimensional or light materials because the diffraction signal recorded on the pixelated arrays is *** we employ data-driven manifold leaning approaches for straightforward visualization and exploration analysis of 4D-STEM datasets,distilling real-space neighboring effects on atomically resolved deflection patterns from single-layer graphene,with single dopant atoms,as recorded on a pixelated *** extracted patterns relate to both individual atom sites and sublattice structures,effectively discriminating single dopant anomalies via multimode *** believe manifold learning analysis will accelerate physics discoveries coupled between data-rich imaging mechanisms and materials such as ferroelectric,topological spin,and van der Waals heterostructures.

关键词： manifold straight details

A custom-designed panel sequencing study in 201 Chinese patients with craniosynostosis revealed novel variants and distinct mutation spectra

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Journal of Genetics and Genomics 2021年第2期48卷 167-171页

作者： Yingzhi Wu Meifang Peng Jieyi Chen Jinlong Suo Sihai Zou Yanqing Xu andrew O.M.Wilkie Weiguo Zou Xiongzheng Mu Sijia Wang Department of Plastic Surgery Huashan HospitalFudan UniversityShanghai 200040China State Key Laboratory of Genetic Engineering at School of Life Sciences Fudan UniversityShanghai 200011China CAS Key Laboratory of Computational Biology CAS-MPG Partner Institute for Computational BiologyShanghai Institute of Nutrition and HealthUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai 200031China The State Key Laboratory of Cell Biology CAS Center for Excellence in Molecular Cell ScienceShanghai Institute of Biochemistry and Cell BiologyChinese Academy of SciencesUniversity of Chinese Academy of SciencesShanghai 200031China Department of Oral and Maxillofacial Surgery Affiliated Hospital of StomatologyChongqing Medical UniversityChongqing 401147China Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences Chongqing 401147China Forest ridge School of the Sacred Heart BellevueWA 98006USA MRC Weatherall Institute of Molecular Medicine University of OxfordJohn Radcliffe HospitalOxford 0X39DSUK Center for Excellence in Animal Evolution and Genetics Chinese Academy of SciencesKunming 650223China

Craniosynostosis is a rare disease in which one or more of the cranial sutures in an infant skull prematurely fuses by turning into bone,with a prevalence of 1 in 2,000—2,500 individuals from reports in Western countries(Wilkie et al.,2017).It may restrict the growth of the brain,leading to some degree of morphological and functional abnormalities,and may affect the neurocognitive function of infants(Lattanzi et al.,2017).Genetic variants underlying craniosynostosis have been identified in cohort studies in Western populations.

关键词： patients turning

维普期刊数据库