检索结果-内蒙古大学图书馆

SSRN 2022年

作者： Grebenko, Artem K. Drozdov, Grigorii Gladush, Yuriy G. Ostanin, Igor Zhukov, Sergey S. Melentyev, Aleksandr V. Khabushev, Eldar M. Tsapenko, Alexey P. Krasnikov, Dmitry V. Afinogenov, Boris Temiryazev, Alexei G. Dremov, Viacheslav V. Dumitricã, Traian Li, Mengjun Hijazi, Hussein Podzorov, Vitaly Feldman, Leonard C. Nasibulin, Albert G. Skolkovo Institute of Science and Technology Nobel str. 3 Moscow121205 Russia Center for Photonics and 2D Materials Moscow Institute of Physics and Technology Institute Lane 9 Dolgoprudny Russia Scientific Computation Program University of Minnesota Minneapolis55455 United States University of Twente PO Box 217 Enschede7500 AE Netherlands Aalto University Department of Applied Physics Puumiehenkuja 2 EspooFI-00076 Finland Faculty of Physics Lomonosov Moscow State University Leninskie gory 1 Moscow Russia Kotel'nikov Institute of Radioengineering and Electronics of RAS Fryazino Branch Vvedensky Sq. 1 Fryazino Russia Russian Quantum Center Moscow121205 Russia Department of Mechanical Engineering University of Minnesota Minneapolis55455 United States Department of Physics Rutgers University PiscatawayNJ08854 United States Aalto University P.O. Box 16100 AaltoFI-00076 Finland Intel Corporation AlbuquerqueNM United States

Fabrication of nanostructured metasurfaces poses a significant technological and fundamental challenge. Despite developing novel material systems that support reversible elongation and distortion, their nanoscale patterning and control of optical properties remain an open problem. Herein we report the atomic force microscope lithography (AFML) application for nanoscale patterning of single-walled carbon nanotube films and the associated optical reflection coefficient tuning. Large scale mesoscopic distinct element method (MDEM) atomic force nanoindentation simulations of single-walled carbon nanotube samples comprising entangled dendritic nanotube bundles with branches extending down to individual tubes explain the mesoscale mechanism of local irreversible densification and further predict its impact on mechanical properties. All observed and calculated phenomena support each other and present a platform for developing AFML patterned optical devices using nanofibrous matter. © 2022, The Authors. All rights reserved.

关键词： Carbon films

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Local ultra-densification of single-walled carbon nanotube films: modeling and experiment

arXiv

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arXiv 2022年

作者： Grebenko, Artem K. Drozdov, Grigorii Gladush, Yuriy G. Ostanin, Igor Zhukov, Sergey S. Melentyev, Aleksandr V. Khabushev, Eldar M. Tsapenko, Alexey P. Krasnikov, Dmitry V. Afinogenov, Boris Temiryazev, Alexei G. Dremov, Viacheslav V. Dumitricã, Traian Li, Mengjun Hijazi, Hussein Podzorov, Vitaly Feldman, Leonard C. Nasibulin, Albert G. Skolkovo Institute of Science and Technology Nobel str. 3 Moscow121205 Russia Center for Photonics and 2D Materials Moscow Institute of Physics and Technology Institute Lane 9 Dolgoprudny Russia Scientific Computation Program University of Minnesota Minneapolis55455 United States University of Twente PO Box 217 Enschede7500 AE Netherlands Aalto University Department of Applied Physics Puumiehenkuja 2 EspooFI-00076 Finland Faculty of Physics Lomonosov Moscow State University Leninskie gory 1 Moscow Russia Kotel'nikov Institute of Radioengineering and Electronics of RAS Fryazino Branch Vvedensky Sq. 1 Fryazino Russia Russian Quantum Center Bolshoy Boulevard Moscow30 s1 Russia Department of Mechanical Engineering University of Minnesota Minneapolis55455 United States Department of Physics Rutgers University PiscatawayNJ08854 United States Intel Corporation AlbuquerqueNM United States Aalto University P.O. Box 16100 AaltoFI-00076 Finland

Fabrication of nanostructured metasurfaces poses a significant technological and fundamental challenge. Despite developing novel systems that support reversible elongation and distortion, their nanoscale patterning and control of optical properties remain an open problem. Herein we report the atomic force microscope lithography (AFML) application for nanoscale patterning of single-walled carbon nanotube films and the associated reflection coefficient tuning. We present models of bundling reorganization, formed-pattern stability, and energy distribution describing mechanical behavior with mesoscopic distinct element method (MDEM). All observed and calculated phenomena support each other and present a platform for developing AFML patterned optical devices using meshy nanostructured matter. Copyright © 2022, The Authors. All rights reserved.

关键词： Carbon films

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Characterizing the nonlinear structure of shared variability in cortical neuron populations using latent variable models

arXiv

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arXiv 2019年

作者： Whiteway, Matthew R. Socha, Karolina Bonin, Vincent Butts, Daniel A. Program in Applied Mathematics and Statistics and Scientific Computation University of Maryland College ParkMD United States Neuro-Electronics Research Flanders Leuven Belgium Department of Biology Leuven Brain Institute KU Leuven Leuven Belgium VIB Leuven Belgium Department of Biology and Program in Neuroscience and Cognitive Sciences University of Maryland College ParkMD United States

Sensory neurons often have variable responses to repeated presentations of the same stimulus, which can significantly degrade the stimulus information contained in those responses. This information can in principle be preserved if variability is shared across many neurons, but depends on the structure of the shared variability and its relationship to sensory encoding at the population level. The structure of this shared variability in neural activity can be characterized by latent variable models, although they have thus far typically been used under restrictive mathematical assumptions, such as assuming linear transformations between the latent variables and neural activity. Here we introduce two nonlinear latent variable models for analyzing large-scale neural *** first present a general nonlinear latent variable model that is agnostic to the stimulus tuning properties of the individual neurons, and is hence well suited for exploring neural populations whose tuning properties are not well characterized. This motivates a second class of model, the Generalized Affine Model, which simultaneously determines each neuron's stimulus selectivity and a set of latent variables that modulate these stimulus-driven responses both additively and multiplicatively. While these approaches can detect very general nonlinear relationships in shared neural variability, we find that neural activity recorded in anesthetized primary visual cortex (V1) is best described by a single additive and single multiplicative latent variable, i.e., an "affine model". In contrast, application of the same models to recordings in awake macaque prefrontal cortex discover more general nonlinearities to compactly describe the population response variability. These results thus demonstrate how nonlinear latent variable models can be used to describe population variability, and suggest that a range of methods is necessary to study different brain regions under different experimental conditions. C

关键词： Neurons

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Non-local corrections to the typical medium theory of Anderson localization

arXiv

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arXiv 2021年

作者： Terletska, Hanna Moilanen, A. Tam, K.-M. Zhang, Y. Wang, Y. Eisenbach, M. Vidhyadhiraja, N.S. Chioncel, L. Moreno, J. Department of Physics & Astronomy Computational Science Program Middle Tennessee State University MurfreesboroTN37132 United States Department of Physics & Astronomy Louisiana State University Baton RougeLA70803 United States Center for Computation & Technology Louisiana State University Baton RougeLA70803 United States Kavli Institute for Theoretical Sciences University of the Chinese Academy of Sciences Beijing100190 China Pittsburgh Supercomputing Center Carnegie Mellon University PA15213 United States Center for Computational Sciences Oak Ridge National Laboratory Oak RidgeTN37831 United States Theoretical Sciences Unit Jawaharlal Nehru Centre for Advanced Scientific Research Bangalore India Theoretical Physics III Center for Electronic Correlations and Magnetism Institute of Physics University of Augsburg Augsburg Center for Innovative Technologies University of Augsburg AugsburgD-86135 Germany

We use the recently developed finite cluster typical medium approach to study the Anderson localization transition in three dimensions. Applying our method to the box and binary alloy disorder distributions, we find a fast convergence with the cluster size. We demonstrate the importance of the typical medium environment and the non-local spatial correlations for the proper characterization of the localization transition. As the cluster size increases, our typical medium cluster method recovers the correct critical disorder strength for the transition. Our findings highlight the importance of the non-local cluster corrections for capturing the localization behavior of the mobility edge trajectories. Our results demonstrate that the typical medium cluster approach developed here provides a consistent and systematic description of the Anderson localization transition in the framework of the effective medium embedding schemes. © 2021, CC BY.

关键词： Cluster analysis

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The estimation of the effective reproductive number from disease outbreak data

arXiv

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arXiv 2020年

作者： Cintrón-Arias, Ariel Castillo-Chávez, Carlos Bettencourt, Luís M.A. Lloyd, Alun L. Banks, H.T. Statistical and Applied Mathematical Sciences Institute 19 T. W. Alexander Drive P.O. Box 14006 Research Triangle ParkNC27709-4006 United States Department of Mathematics and Statistics Arizona State University P.O. Box 871804 TempeAZ85287 - 1804 Los Alamos National Laboratory Mail Stop B284 Los AlamosNM87545 United States Biomathematics Graduate Program Department of Mathematics North Carolina State University RaleighNC27695 United States Center for Research in Scientific Computation North Carolina State University P.O. Box 8205 RaleighNC27695

We consider a single outbreak susceptible-infected-recovered (SIR) model and corresponding estimation procedures for the effective reproductive number R(t). We discuss the estimation of the underlying SIR parameters with a generalized least squares (GLS) estimation technique. We do this in the context of appropriate statistical models for the measurement process. We use asymptotic statistical theories to derive the mean and variance of the limiting (Gaussian) sampling distribution and to perform post statistical analysis of the inverse problems. We illustrate the ideas and pitfalls (e.g., large condition numbers on the corresponding Fisher information matrix) with both synthetic and influenza incidence data sets. Copyright © 2020, The Authors. All rights reserved.

关键词： Parameter estimation

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A Stochastic MPEC Approach for Grid Tariff Design with Demand Side Flexibility

TechRxiv

引用

TechRxiv 2019年

作者： Askeland, Magnus Burandt, Thorsten Gabriel, Steven A. SINTEF Energy Research Department of Electric Power Engineering Norwegian University of Science and Technology Trondheim Norway Technical University of Berlin The Energy Transportation Environment Department German Institute for Economic Research DIW Berlin Berlin Germany Department of Industrial Economics and Technology Management Norwegian University of Science and Technology Trondheim Norway Department of Mechanical Engineering Applied Math & Statistics Scientific Computation Program University of Maryland College Park Maryland United States

As the end-users increasingly can provide flexibility to the power system, it is important to consider how this flexibility can be activated as a resource for the grid. Electricity network tariffs are one option that can be used to activate this flexibility. Therefore, by designing efficient grid tariffs, it might be possible to reduce the total costs in the power system by incentivizing a change in consumption patterns. This paper provides a methodology for optimal grid tariff design under decentralized decision-making and uncertainty in demand, power prices, and renewable generation. A bilevel model is formulated to adequately describe the interaction between the end-users and a distribution system operator. In addition, a centralized decision-making model is provided for benchmarking purposes. The bilevel model is reformulated as a mixed-integer linear problem solvable by branch-and-cut techniques. Results for a deterministic example and a stochastic case study are presented and discussed. © 2019, CC BY-SA.

关键词： Decision making

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Low-rank solution methods for stochastic eigenvalue problems

arXiv

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arXiv 2018年

作者： Elman, Howard C. Su, Tengfei Department of Computer Science Institute for Advanced Computer Studies University of Maryland College ParkMD20742 United States Applied Mathematics & Statistics Scientific Computation Program University of Maryland College ParkMD20742 United States

We study efficient solution methods for stochastic eigenvalue problems arising from discretization of self-adjoint partial differential equations with random data. With the stochastic Galerkin approach, the solutions are represented as generalized polynomial chaos expansions. A low-rank variant of the inverse subspace iteration algorithm is presented for computing one or several minimal eigenvalues and corresponding eigenvectors of parameter-dependent matrices. In the algorithm, the iterates are approximated by low-rank matrices, which leads to significant cost savings. The algorithm is tested on two benchmark problems, a stochastic diffusion problem with some poorly separated eigenvalues, and an operator derived from a discrete stochastic Stokes problem whose minimal eigenvalue is related to the inf-sup stability constant. Numerical experiments show that the low-rank algorithm produces accurate solutions compared to the Monte Carlo method, and it uses much less computational time than the original algorithm without low-rank approximation. Copyright © 2018, The Authors. All rights reserved.

关键词： Eigenvalues and eigenfunctions

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The locus coeruleus: In-vivo characterization with advanced MRI methods and associations with memory in older adults at risk for Alzheimer’s disease

引用

Alzheimer's & Dementia 2020年第S4期16卷

作者： Seraphina K. Solders Alexandra L. Clark Alexandra J. Weigand Scott F. Sorg Vitaly Galinsky Lawrence R. Frank Mark W. Bondi University of California San Diego School of Medicine San Diego CA USA University of California San Diego Neurosciences Graduate Program San Diego CA USA Research and Psychology Services VA San Diego Healthcare System (VASDHS) San Diego CA USA San Diego State University/University of California San Diego Joint Doctoral Program in Clinical Psychology San Diego CA USA University of California San Diego Center for Scientific Computation in Imaging San Diego CA USA

Background The locus coeruleus (LC) is the brain’s main source of norepinephrine and plays a key role in modulating attention and memory processes. In Alzheimer’s disease (AD), the LC has been identified as an early site of tau accumulation and this tau pathology may spread via its connections to the transentorhinal cortex (TEC). Historically, this region has been nearly impossible to study in vivo . However, recent advances in structural magnetic resonance imaging (MRI) have provided opportunities to capture the integrity of LC neurons and their projections. We utilized a combination of neuromelanin-sensitive and diffusion tensor MRI to examine LC integrity and its role in memory. Method 31 older adults (26 cognitively normal; 5 MCI) underwent T1 fast spin echo and diffusion MRI scans as well as neuropsychological testing. Bilateral LC contrast ratios (CRs) were calculated as neuromelanin-related signal intensities relative to a reference region. In a subset of participants (n=12; 10 cognitively normal, 2 MCI) LC-TEC white matter pathways were reconstructed using probabilistic tractography in FSL and average fractional anisotropy (FA) was extracted. Logical Memory and CVLT-2 were used to assess verbal learning and memory. Result Results revealed lower bilateral LC-CRs was associated with poorer performance on measures of story learning (LMI; r =0.425, p =.045) and word-list recall (CVLT-2 Short Delay Recall: r =.481, p =.006; CVLT-2 Long Delay Recall: r =.375, p =.038). Tractography analyses indicated that higher FA of the left LC-TEC tract was associated with poorer story learning (LM1: r =-.651, p =.02), whereas higher FA of the right LC-TEC tract was associated with poorer word-list recall (CVLT-2 Short Delay Recall: r =-.599, p =.039; CVLT-2 Short Delay Cued Recall, r =-.705, p =.01). Conclusion Preliminary results indicate that neuromelanin and tractography MRI methods can be utilized for in vivo characterization of the human LC. Lower neuromelanin signal, but

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Densification of single-walled carbon nanotube films: Mesoscopic distinct element method simulations and experimental validation

arXiv

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arXiv 2020年

作者： Drozdov, Grigorii Ostanin, Igor Xu, Hao Wang, Yuezhou Dumitrică, Traian Grebenko, Artem Tsapenko, Alexey P. Gladush, Yuriy Ermolaev, Georgy Volkov, Valentyn S. Eibl, Sebastian Rüde, Ulrich Nasibulin, Albert G. Scientific Computation Program University of Minnesota Twin CitiesMN55455 United States Multi-Scale Mechanics Faculty of Engineering Technology MESA+ University of Twente Enschede7500 AE Netherlands Skolkovo Institute of Science and Technology Nobel St. 3 Moscow Russia Department of Aerospace Engineering and Mechanics University of Minnesota Twin CitiesMN55455 United States Integrated Engineering Minnesota State University MankatoMN56001 United States Department of Mechanical Engineering University of Minnesota Twin CitiesMN55455 United States Moscow Institute of Physics and Technology Institute Lane 9 Dolgoprudniy Russia Department of Applied Physics Aalto University School of Science AaltoFI-00076 Finland Center for Photonics and 2D Materials Moscow Institute of Physics and Technology Dolgoprudny141700 Russia Friedrich-Alexander University Erlangen-Nuremberg Cauerstr.11 Erlangen91052 Germany Aalto University Department of Materials Science and Engineering Aalto00076 Finland

Nanometer thin single-walled carbon nanotube (CNT) films collected from the aerosol chemical deposition reactors have gathered attention for their promising applications. Densification of these pristine films provides an important way to manipulate the mechanical, electronic, and optical properties. To elucidate the underlying microstructural level restructuring, which is ultimately responsible for the change in properties, we perform large scale vector-based mesoscopic distinct element method simulations in conjunction with electron microscopy and spectroscopic ellipsometry characterization of pristine and densified films by drop-cast volatile liquid processing. Matching the microscopy observations, pristine CNT films with finite thickness are modeled as self-assembled CNT networks comprising entangled dendritic bundles with branches extending down to individual CNTs. Simulations of the film under uniaxial compression uncover an ultra-soft densification regime extending to a ~75% strain, which is likely accessible with the surface tensional forces arising from liquid surface tension during the evaporation. When removing the loads, the pre-compressed samples evolve into homogeneously densified films with thickness values depending on both the pre-compression level and the sample microstructure. The significant reduction in thickness, confirmed by our spectroscopic ellipsometry, is attributed to the underlying structural changes occurring at the 100 nm scale, including the zipping of the thinnest dendritic branches. Copyright © 2020, The Authors. All rights reserved.

关键词： Carbon films

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BioWorkbench: A high-performance framework for managing and analyzing bioinformatics experiments

arXiv

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arXiv 2018年

作者： Mondelli, Maria Luiza Magalhães, Thiago Loss, Guilherme Wilde, Michael Foster, Ian Mattoso, Marta Katz, Daniel S. Barbosa, Helio J.C. Vasconcelos, Ana Tereza R. Ocaña, Kary Gadelha, Luiz M.R. National Laboratory for Scientific Computing Petrópolis Brazil Computation Institute Argonne National Laboratory University of Chicago Chicago United States Computer and Systems Engineering Program Federal University of Rio de Janeiro Brazil National Center for Supercomputing Applications University of Illinois Urbana United States Federal University of Juiz de Fora Minas Gerais Brazil

Advances in sequencing techniques have led to exponential growth in biological data, demanding the development of large-scale bioinformatics experiments. Because these experiments are computation- and data-intensive, they require high-performance computing (HPC) techniques and can benefit from specialized technologies such as scientific Workflow Management Systems (SWfMS) and databases. In this work, we present BioWorkbench, a framework for managing and analyzing bioinformatics experiments. This framework automatically collects provenance data, including both performance data from workflow execution and data from the scientific domain of the workflow application. Provenance data can be analyzed through a web application that abstracts a set of queries to the provenance database, simplifying access to provenance information. We evaluate BioWorkbench using three case studies: SwiftPhylo, a phylogenetic tree assembly workflow;SwiftGECKO, a comparative genomics workflow;and RASflow, a RASopathy analysis workflow. We analyze each workflow from both computational and scientific domain perspectives, by using queries to a provenance and annotation database. Some of these queries are available as a pre-built feature of the BioWorkbench web application. Through the provenance data, we show that the framework is scalable and achieves high-performance, reducing up to 98% of the case studies execution time. We also show how the application of machine learning techniques can enrich the analysis process. Copyright © 2018, The Authors. All rights reserved.

关键词： Bioinformatics

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