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Mitigating Gibbs Phenomena in Uncertainty Quantification With a Stochastic Spectral Method

Journal of Verification, Validation and Uncertainty Quantification 2017年第1期2卷 011003页

作者： Tagade, Piyush M. Choi, Han-Lim Computer Simulation Group Samsung Advanced Institute of Technology Samsung R&D Institute India Bangalore560 037 India Department of Aerospace Engineering KAIST 291 Daehak-ro N7-4303 Daejeon34141 Korea Republic of

The use of spectral projection-based methods for simulation of a stochastic system with discontinuous solution exhibits the Gibbs phenomenon, which is characterized by oscillations near discontinuities. This paper investigates a dynamic bi-orthogonality-based approach with appropriate postprocessing for mitigating the effects of the Gibbs phenomenon. The proposed approach uses spectral decomposition of the spatial and stochastic fields in appropriate orthogonal bases, while the dynamic orthogonality (DO) condition is used to derive the resultant closed-form evolution equations. The orthogonal decomposition of the spatial field is exploited to propose a Gegenbauer reprojection-based postprocessing approach, where the orthogonal bases in spatial dimension are reprojected on the Gegenbauer polynomials in the domain of analyticity. The resultant spectral expansion in Gegenbauer series is shown to mitigate the Gibbs phenomenon. Efficacy of the proposed method is demonstrated for simulation of a one-dimensional stochastic Burgers equation and stochastic quasi-one-dimensional flow through a convergent-divergent nozzle. Copyright © 2017 by ASME

关键词： Stochastic systems

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Interpreting encoding and decoding models

arXiv

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arXiv 2018年

作者： Kriegeskorte, Nikolaus Douglas, Pamela K. Department of Psychology Department of Neuroscience Department of Electrical Engineering Zuckerman Mind Brain Behavior Institute Columbia University New YorkNY United States Center for Cognitive Neuroscience University of California Los Angeles CAModeling Simulation Computer Science UCF United States

Encoding and decoding models are widely used in systems, cognitive, and computational neuroscience to make sense of brain-activity data. However, the interpretation of their results requires care. Decoding models can help reveal whether particular information is present in a brain region in a format the decoder can exploit. Encoding models make comprehensive predictions about representational spaces. In the context of sensory experiments, where stimuli are experimentally controlled, encoding models enable us to test and compare brain-computational theories. Encoding and decoding models typically include fitted linear-model components. Sometimes the weights of the fitted linear combinations are interpreted as reflecting, in an encoding model, the contribution of different sensory features to the representation or, in a decoding model, the contribution of different measured brain responses to a decoded feature. Such interpretations can be problematic when the predictor variables or their noise components are correlated and when priors (or penalties) are used to regularize the fit. Encoding and decoding models are evaluated in terms of their generalization performance. The correct interpretation depends on the level of generalization a model achieves (e.g. to new response measurements for the same stimuli, to new stimuli from the same population, or to stimuli from a different population). Significant decoding or encoding performance of a single model (at whatever level of generality) does not provide strong constraints for theory. Many models must be tested and inferentially compared for analyses to drive theoretical progress. Copyright © 2018, The Authors. All rights reserved.

关键词： Brain

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Efficient algorithms for assortative edge switch in large labeled networks 25

Efficient algorithms for assortative edge switch in large la...

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25th High Performance Computing Symposium, HPC 2017, Part of the 2017 Spring simulation Multi-Conference, SpringSim 2017

作者： Bhuiyan, Hasanuzzaman Khan, Maleq Marathe, Madhav Department of Computer Science Network Dynamics and Simulation Science Laboratory Biocomplexity Institute of Virginia Tech. BlacksburgVA United States Department of Electrical Engineering and Computer Science Texas A and M University - Kingsville KingsvilleTX United States

ISBN: (纸本)9781510838222

An assortative edge switch is an operation on a labeled network, where two edges are randomly selected and the end vertices are swapped with each other if the labels of the end vertices of the edges remain invariant. Assortative edge switch has important applications in studying the mixing pattern and dynamic behavior of social networks, modeling and analyzing dynamic networks, and generating random networks. In this paper, we present an efficient sequential algorithm and a distributed-memory parallel algorithm for assortative edge switch. To our knowledge, they are the first efficient algorithms for this problem. The dependencies among successive assortative edge switch operations, the requirement of maintaining the assortative coefficient invariant, keeping the network simple, and balancing the computation loads among the processors pose significant challenges in designing a parallel algorithm. Our parallel algorithm achieves a speedup of 68-772 with 1024 processors for a wide variety of networks. ©2017 Society for Modeling & simulation International (SCS).

关键词： Parallel algorithms

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Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

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Photonics Research 2018年第3期6卷 157-161页

作者： FAJUN XIAO WUYUN SHANG WEIREN ZHU LEI HAN MALIN PREMARATNE TING MEI JIANLIN ZHAO MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Optical Information TechnologySchool of ScienceNorthwestern Polytechnical UniversityXi'an 710129China Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai 200240China Advanced Computing and Simulation Laboratory(AχL) Department of Electrical and Computer Systems Monash UniversityClaytonVlC 3800Australia

We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant *** is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.

关键词： SHG Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

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Maintaining a resonance condition of an rf spin rotator through a feedback loop in a storage ring

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Physical Review Accelerators and Beams 2025年第6期28卷 062801-062801页

作者： V. Hejny A. Andres J. Pretz F. Abusaif A. Aggarwal A. Aksentev B. Alberdi L. Barion I. Bekman M. Beyß C. Böhme B. Breitkreutz N. Canale G. Ciullo S. Dymov N.-O. Fröhlich R. Gebel M. Gaisser K. Grigoryev D. Grzonka J. Hetzel O. Javakhishvili A. Kacharava V. Kamerdzhiev S. Karanth I. Keshelashvili A. Kononov K. Laihem A. Lehrach P. Lenisa N. Lomidze B. Lorentz G. Macharashvili A. Magiera D. Mchedlishvili A. Melnikov F. Müller A. Nass N. N. Nikolaev D. Okropiridze A. Pesce A. Piccoli V. Poncza D. Prasuhn F. Rathmann A. Saleev D. Shergelashvili V. Shmakova R. Shankar N. Shurkhno S. Siddique A. Silenko J. Slim H. Soltner R. Stassen E. J. Stephenson H. Ströher M. Tabidze G. Tagliente Y. Valdau M. Vitz T. Wagner A. Wirzba A. Wrońska P. Wüstner M. Żurek Institut für Kernphysik Forschungszentrum Jülich 52425 Jülich Germany III. Physikalisches Institut B RWTH Aachen University 52056 Aachen Germany Present address: GSI Helmholtzzentrum für Schwerionenforschung GmbH Planckstr. 1 64291 Darmstadt Germany. Present address: Karlsruhe Institute of Technology Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen Germany. Marian Smoluchowski Institute of Physics Jagiellonian University 30348 Cracow Poland Institute for Nuclear Research Russian Academy of Sciences 117312 Moscow Russia Present address: Humboldt-Universität zu Berlin Institut für Physik Newton-StraSSe 15 12489 Berlin Germany. University of Ferrara and Istituto Nazionale di Fisica Nucleare 44100 Ferrara Italy Present address: Institute of Technology and Engineering Forschungszentrum Jülich 52425 Jülich Germany. Present address: Deutsches Elektronen-Synchrotron 22607 Hamburg Germany. Department of Electrical and Computer Engineering Agricultural University of Georgia 0159 Tbilisi Georgia Present address: Faculty of Nuclear Sciences and Physical Engineering Czech Technical University in Prague 160 00 Praha 6 Czech Republic. High Energy Physics Institute Tbilisi State University 0186 Tbilisi Georgia GSI Helmholtzzentrum für Schwerionenforschung GmbH Planckstraße 1 64291 Darmstadt Germany L.D. Landau Institute for Theoretical Physics 142432 Chernogolovka Russia Present address: Ruhr-Universität Bochum Institut für Experimentalphysik I 44801 Bochum Germany. Present address: Brookhaven National Laboratory Upton NY 11973 USA. Present address: Institut für nachhaltige Wasserstoffwirtschaft Forschungszentrum Jülich 52425 Jülich Germany. Bogoliubov Laboratory of Theoretical Physics International Intergovernmental Organization Joint Institute for Nuclear Research 141980 Dubna Russia Institute of Technology and Engineering Forschungszentrum Jülich 52425 Jülich Germany Indiana University Department of Physics Bloomington Indiana 47405 USA and Department of

This paper presents the successful application of a phase-lock feedback system to maintain the resonance condition of a radio frequency (rf) spin rotator (specifically, an rf Wien filter) with respect to a 120 kHz spin precession in the Cooler Synchrotron (COSY) storage ring. Real-time monitoring of the spin precession and the rf Wien filter signal allows the relative phase between the two to be stabilized at an arbitrary setpoint. The feedback system compensates for deviations in the relative phase by adjusting the frequency and/or phase of the rf device as needed. With this method, a variation in the phase relative to the demanded value with a standard deviation of σΔφ≈0.2 rad could be achieved. The system was implemented in two runs aiming at a first direct measurement of the deuteron electric dipole moment in 2018 and 2021. In addition, the difference between a single-bunch beam affected by the spin rotator and a two-bunch system in which only one bunch is exposed to the spin rotator fields is discussed. Both methods have been used during these beam times. The ability to keep the spin precession and the rf fields synchronized is crucial for future investigations of electric dipole moments of charged particles using storage rings.

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Velocity control in a right-turn across traffic scenario for autonomous vehicles using kernel-based reinforcement learning

Velocity control in a right-turn across traffic scenario for...

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2017 Chinese Automation Congress, CAC 2017

作者： Zhang, Yuxiang Gao, Bingzhao Guo, Lulu Chen, Hong Zhao, Jinghua State Key Laboratory of Automotive Simulation and Control Jilin University Changchun China Department of Control Science and Engineering Jilin University Changchun China Computer College Jilin Normal University Siping China

ISBN: (纸本)9781538635247

Recently, advanced control methods like machine leaning are increasingly applied to autonomous vehicle. This paper focuses on velocity control in a right-turn traffic scenario. A Markov Decision Processes(MDPs) is modeled and the actor-critic reinforcement learning architecture is employed. Then the kernel-based least squares policy iteration algorithm(KLSPI) is applied. simulation results show that the proposed method can perform different policy in different cases, which preliminarily verify the rationality. © 2017 IEEE.

关键词： Velocity control

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Proof-of-principle demonstration of a pilot bunch comagnetometer in a stored beam

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Physical Review Research 2025年第2期7卷 023257-023257页

作者： J. Slim F. Rathmann A. Andres V. Hejny A. Nass A. Kacharava P. Lenisa N. N. Nikolaev J. Pretz A. Saleev V. Shmakova H. Soltner F. Abusaif A. Aggarwal A. Aksentev B. Alberdi L. Barion I. Bekman M. Beyß C. Böhme B. Breitkreutz N. Canale G. Ciullo S. Dymov N.-O. Fröhlich R. Gebel M. Gaisser K. Grigoryev D. Grzonka J. Hetzel O. Javakhishvili V. Kamerdzhiev S. Karanth I. Keshelashvili A. Kononov K. Laihem A. Lehrach N. Lomidze B. Lorentz G. Macharashvili A. Magiera D. Mchedlishvili A. Melnikov F. Müller A. Pesce V. Poncza D. Prasuhn D. Shergelashvili N. Shurkhno S. Siddique A. Silenko R. Stassen E. J. Stephenson H. Ströher M. Tabidze G. Tagliente Y. Valdau M. Vitz T. Wagner A. Wirzba A. Wrońska P. Wüstner M. Żurek III. Physikalisches Institut B RWTH Aachen University 52056 Aachen Germany Present address: Deutsches Elektronen-Synchrotron 22607 Hamburg Germany. Institut für Kernphysik Forschungszentrum Jülich 52425 Jülich Germany Present address: Brookhaven National Laboratory Upton New York 11973 USA. University of Ferrara and Istituto Nazionale di Fisica Nucleare 44100 Ferrara Italy L.D. Landau Institute for Theoretical Physics 142432 Chernogolovka Russia Present address: N.N. Bogoliubov Laboratory of Theoretical Physics 141980 Dubna Russia. Present address: Institute for a Sustainable Hydrogen Economy Forschungszentrum Jülich 52428 Jülich Germany. Institute of Technology and Engineering Forschungszentrum Jülich 52425 Jülich Germany Present address: Karlsruhe Institute of Technology 76344 Eggenstein-Leopoldshafen Germany. Marian Smoluchowski Institute of Physics Jagiellonian University 30348 Cracow Poland Institute for Nuclear Research Russian Academy of Sciences 117312 Moscow Russia Present address: Humboldt-Universität zu Berlin Institut für Physik 12489 Berlin Germany. Present address: Institute of Technology and Engineering Forschungszentrum Jülich Jülich Germany. Present address: GSI Helmholtz Centre for Heavy Ion Research 64291 Darmstadt Germany. Department of Electrical and Computer Engineering Agricultural University of Georgia 0159 Tbilisi Georgia Present address: H. Niewodniczański Institute of Nuclear Physics Polish Academy of Sciences 31-342 Kraków Poland. High Energy Physics Institute Tbilisi State University 0186 Tbilisi Georgia GSI Helmholtzzentrum für Schwerionenforschung 64291 Darmstadt Germany Bogoliubov Laboratory of Theoretical Physics Joint Institute for Nuclear Research 141980 Dubna Russia Indiana University Department of Physics Bloomington Indiana 47405 USA Istituto Nazionale di Fisica Nucleare sez. Bari 70125 Bari Italy Institute for Advanced Simulation Forschungszentrum Jülich 52425 Jülich Germany Zentralinstitut für Engineering Elekt

In polarization experiments at storage rings, one of the challenges is to maintain the spin-resonance condition of a radio-frequency spin rotator with the spin precessions of the orbiting particles. Time-dependent variations of the magnetic fields of ring elements lead to unwanted variations of the spin-precession frequency. We report here on a solution to this problem by shielding (or masking) one of the bunches stored in the ring from the high-frequency fields of the spin rotator, so that the masked pilot bunch acts as a comagnetometer for the other signal bunch, tracking fluctuations in the ring on a time scale of about one second. While the new method was developed primarily for searches of electric dipole moments of charged particles, it may have far-reaching implications for future spin physics facilities, such as the EIC and NICA.

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Study of Erase Band and Write Performance in Shingled Mag-netic Recording with Exchanged Coupled Composite Media.

Study of Erase Band and Write Performance in Shingled Mag-ne...

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International Conference on Magnetics (INTERMAG)

作者： J. Chen G. Xie K. Luo W. Cheng P. Lu Y. Wang Wuhan National Laboratory for Optoelectronics Huazhong University of Science and Technology Wuhan China Key Lab of Jiangxi Province for Numerical Simulation and Emulation Technology Ganzhou Gannan Normal University China Electrical and Computer Engineering Department Carnegie Mellon University PA Pittsburgh United States

This paper improves the calculation method of erase band width (EBW) by considering the overwriting side in SMR, more importantly the impact of ECC media on mitigating ATE is explored with EBW and bit error rate. Furthermore, the shingled write heads with different corner angle (CA), tip tapered angle (TA) and skew angle (SA) are studied to reach a tradeoff between adequate write field and moderate EBW. The investigation indicated that the combination of relatively smaller CA, larger TA and smaller SA was beneficial for reducing the EBN, while it weakened the write field. Hence we suggested that an optimized writer design (CA=78°, TA=50°, -10°0-FePt(6nm)/ [CoNi] 5 (4nm) could provide adequate write field and minimize the EBN simultaneously.

关键词： Magnetics Conferences

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A Comparison of Two Anatomical Body Models Derived from the Female Visible Human Project Data

A Comparison of Two Anatomical Body Models Derived from the ...

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Annual International Conference of the IEEE engineering in Medicine and Biology Society

作者： Jackson W. Massey Alexander Prokop Ali E. Yilmaz Department of Electrical and Computer Engineering University of Texas at Austin Austin TX CST-Computer Simulation Technology AG Darmstadt Germany

Two electromagnetic human body models independently developed from the same image dataset - the voxel-based AustinWoman and surface-based VHP-Female models - are compared. In addition to contrasting volumes and cross-section images of their tissues, the power absorbed by the two models under plane-wave excitation is also compared. Five different numerical methods are used to compute the absorbed power and to evaluate modeling and computational errors.

关键词： Computational modeling Bones Numerical models Muscles Skin Solid modeling Density measurement

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Self-Assembled Plasmonic Pyramids from Anisotropic Nanoparticles for High-Efficient SERS

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Journal of Analysis and Testing 2017年第4期1卷 335-343页

作者： Wenjuan Yang Kae Jye Si Pengzhen Guo Dashen Dong Debabrata Sikdar Malin Premaratne Wenlong Cheng Department of Chemical Engineering Faculty of EngineeringMonash UniversityClaytonVIC 3800Australia The Melbourne Centre for Nanofabrication 151 Wellington RoadClaytonVIC 3168Australia Advanced Computing and Simulation Laboratory(AvL) Department of Electrical and Computer Systems EngineeringFaculty of EngineeringMonash UniversityClaytonVIC 3800Australia Department of Chemistry Faculty of Natural SciencesImperial College LondonExhibition RoadSouth KensingtonLondon SW72AZUK

Surface-enhanced Raman scattering(SERS)substrates play important roles for the enhancement of inelastic scattering *** substrates such as roughened electrodes and colloidal aggregates suffer from well-known signal reproducibility issues,whereas for current dominant two-dimensional planar systems,the hot spot distributions are limited by the zero-,one-or two-dimensional *** introduction of a three-dimensional(3D)system such as a pyramid geometry breaks the limitation of a single Cartesian SERS-active area and extends it into the z-direction,with the tip potentially offering additional benefits of strong field enhancement and high ***,current 3D pyramidal designs are restricted to film deposition on prepared pyramid templates or self-assembly in pyramidal molds with spherical building blocks,hence limiting their SERS ***,we report on the fabrication of a new class of low cost and well-defined plasmonic nanoparticle pyramid arrays from different anisotropic shaped nanoparticles using combined top-down lithography and bottom-up self-assembly *** pyramids exhibit novel optical scattering properties that can be exploited for the design of reproducible and sensitive SERS *** SERS intensity was found to decrease drastically in accordance with a power law function as the focal planes move from the apex of the pyramid structure towards the *** comparison to sphere-based building blocks,pyramids assembled from anisotropic rhombic dodecahedral gold nanocrystals with numerous sharp tips exhibited the strongest SERS *** Abstract Macroscale pyramidal array films with plasmonic tunability as a new class of SERS substrate for sensitive detection of chemicals.

关键词： Self-assembly Pyramid Plasmonics Shape anisotropy Surface-enhanced Raman scattering

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