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arXiv 2024年

作者： Carson, Erin Lund, Kathryn Ma, Yuxin Oktay, Eda Department of Numerical Mathematics Faculty of Mathematics and Physics Charles University Sokolovská 49/83 Praha 8186 75 Czech Republic Computational Methods in Systems and Control Theory Max Planck Institute for Dynamics of Complex Technical Systems Sandtorstr. 1 Magdeburg39106 Germany Computational Mathematics Theme Building R71 STFC Rutherford Appleton Laboratory Harwell Oxford Didcot OxfordshireOX11 0QX United Kingdom Department of Mathematics Chemnitz University of Technology Reichenhainer Str. 41 Chemnitz09126 Germany

Block classical Gram-Schmidt (BCGS) is commonly used for orthogonalizing a set of vectors X in distributed computing environments due to its favorable communication properties relative to other orthogonalization approaches, such as modified Gram-Schmidt or Householder. However, it is known that BCGS (as well as recently developed low-synchronization variants of BCGS) can suffer from a significant loss of orthogonality in finite-precision arithmetic, which can contribute to instability and inaccurate solutions in downstream applications such as s-step Krylov subspace methods. A common solution to improve the orthogonality among the vectors is reorthogonalization. Focusing on the "Pythagorean" variant of BCGS, introduced in [E. Carson, K. Lund, & M. Rozložník. SIAM J. Matrix Anal. Appl. 42(3), pp. 1365–1380, 2021], which guarantees an O(Ε)κ2(X) bound on the loss of orthogonality as long as O(Ε)κ2(X) MSC Codes 65-04, 65F25, 65G50, 65Y20 Copyright © 2024, The Authors. All rights reserved.

关键词： Matrix algebra

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Soft-Landing dynamics of a Type of Four-Legged Space Lander

SSRN

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SSRN 2024年

作者： Shi, Tengfei Shi, Tengfei Yang, Yinping Zhang, Zhijuan Liu, Cuicui Liu, Caishan Ma, Daolin Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Aerospace Engineering Southwest Jiaotong University Chengdu610031 China State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing100871 China Institute of Dynamics and Control College of Mechanical Engineering and Applied Electronics Technology Beijing University of Technology Beijing100871 China China Academy of Space Technology Beijing100094 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of Marine Intelligent Equipment and System Ministry of Education Shanghai200240 China

Analyzing the landing dynamics response is essential for enhancing the success rate of surface explorations on Mars, the moon, or asteroids. This paper develops a comprehensive dynamics model for a space lander equipped with four sets of buffer legs, each consisting of a primary strut, two secondary struts, and a footpad, during its soft landing process. The degrees of freedom of the main body and the footpads are defined as generalized coordinates to describe the motion of the space lander. The compression force of the buffer struts is obtained by interpolating real experimental data, and the contact force between the footpad and the ground is calculated using Archimedes law for granular media. Then, the dynamical model for the lander in terms of minimal degrees of freedom can be constructed by applying the Lagrange equations of the second kind. The proposed dynamics model is validated by the experiments of a single-legged lander vertical touchdown and a four-legged lander free touchdown. Moreover, histories of buffer force, acceleration of the main body, and other key physical quantities are computed to investigate the landing process. This highly efficient and accurate dynamics model provides a method to perform extensive simulations to design and optimize a soft landing process. © 2024, The Authors. All rights reserved.

关键词： Landing

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Harmonic-Gaussian double-well potential stochastic resonance with its application to enhance weak fault characteristics of machinery

arXiv

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arXiv 2023年

作者： Qiao, Zijian Chen, Shuai Lai, Zhihui Zhou, Shengtong Sanjuán, Miguel A.F. School of Mechanical Engineering and Mechanics Ningbo University Ningbo315211 China State Key Laboratory of Performance Monitoring and Protecting of Rail Transit Infrastructure East China Jiaotong University Nanchang330013 China Yangjiang529500 China Zhejiang Provincial Key Laboratory of Part Rolling Technology Ningbo315211 China Guangdong Provincial Key Laboratory of Micro/Nano Optomechatronics Engineering College of Mechatronics and Control Engineering Shenzhen University Shenzhen518060 China Nonlinear Dynamics Chaos and Complex Systems Group Departamento de Física Universidad Rey Juan Carlos Tulipán s/n Móstoles Madrid28933 Spain

Noise is ubiquitous and unwanted in detecting weak signals, which would give rise to incorrect filtering frequency-band selection in signal filtering-based methods including fast kurtogram, teager energy operators and wavelet packet transform filters and meanwhile would result in incorrect selection of useful components and even mode mixing, end effects and etc. in signal decomposition-based methods including empirical mode decomposition, singular value decomposition and local mean decomposition. On the contrary, noise in stochastic resonance (SR) is beneficial to enhance weak signals of interest embedded in signals with strong background noise. Taking into account that nonlinear systems are crucial ingredients to activate the SR, here we investigate the SR in the cases of overdamped and underdamped harmonic-Gaussian double-well potential systems subjected to noise and a periodic signal. We derive and measure the analytic expression of the output signal-to-noise ratio (SNR) and the steady-state probability density (SPD) function under approximate adiabatic conditions. When the harmonic-Gaussian double-well potential loses its stability, we can observe the antiresonance phenomenon, whereas adding the damped factor into the overdamped system can change the stability of the harmonic-Gaussian double-well potential, resulting that the antiresonance behavior disappears in the underdamped system. Then, we use the overdamped and underdamped harmonic-Gaussian double-well potential SR to enhance weak useful characteristics for diagnosing incipient rotating machinery failures. Theoretical and experimental results show that adjusting both noise intensity and system parameters can activate overdamped and underdamped harmonic-Gaussian double-well potential SR in which there is a bell-shaped peak for the SNR. Additionally, the underdamped harmonic-Gaussian double-well potential SR is independent of frequency-shifted and rescaling transform to process large machine parameter signal

关键词： Empirical mode decomposition

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Kinetostatic Modeling of Compliant Mechanisms Via Reduced-Mode Cosserat Rod Model

SSRN

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SSRN 2023年

作者： Wu, Ke Wang, Wei Li, Xin Hu, Junzhe Chen, Pengyu Cheng, Ran Sun, Qidi Liu, Lifu Zhou, Luna Xu, Xin Zhang, Shucheng Deng, Zicheng Chen, Rui Zheng, Gang INRIA Lille-Nord Europe 40 Avenue Halley Villeneuve d’Ascq59650 France State Key Laboratory of Mechanical Transmission University of Chongqing Chongqing400030 China LS2N - équipe ReV - Robotique Et Vivant Institut Mines Telecom Atlantique Nantes France Chongqing University China Chongqing University University of Cincinnati Joint Co-op Institute Chongqing University Chongqing400044 China Center for Robotics Research University of Cincinnati CincinnatiOH45221 United States MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi’an710072 China Hong Kong

Compliant mechanisms (CMs), which are normally composed of rigid blocks and flexible members, utilize the elastic deflection of all these built-in flexible members, totransfer motion, force and energy. In the current literature, geometrically nonlinear Euler Bernoulli beam theory and its related methods are commonly used for modelingthese flexible members. However, its governing ordinary differential equation (ODE) only considers the main contributor to beam deflections: bending, without taking careof shear and axial stretch along the beam. To take care of more possible strains, Cosserat rod theory, serves as a better alternative for high accuracy. However, it stillsuffers from relatively complex modeling and time-consuming computation. In this paper, we propose a reduced-mode Cosserat rod model to bypass the need ofconducting complex modeling, providing a more compact formulation. The detailed derivations are presented step by step, and we also propose a mode selectionmethod to meet the requirements of different engineering scenarios. Numerical examples are provided to verify the reduced-mode model as well as the feasibility ofmodeling CMs. In particular, modeling flexible springs and related mechanisms has been proved valid via this proposed model. © 2023, The Authors. All rights reserved.

关键词： Boundary value problems

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An active metasurface enhanced with moiré ferroelectricity

arXiv

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arXiv 2024年

作者： Kim, Dong Seob Xiao, Chengxin Dominguez, Roy C. Liu, Zhida Abudayyeh, Hamza Lee, Kyoungpyo Mayorga-Luna, Rigo Kim, Hyunsue Watanabe, Kenji Taniguchi, Takashi Shih, Chih-Kang Miyahara, Yoichi Yao, Wang Li, Xiaoqin Department of Physics Center for Complex Quantum Systems The University of Texas at Austin AustinTX78712 United States Center for Dynamics and Control of Materials Texas Materials Institute The University of Texas at Austin AustinTX78712 United States New Cornerstone Science Laboratory Department of Physics The University of Hong Kong Hong Kong Department of Physics Texas State University San MarcosTX78666 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 Texas State University San MarcosTX78666 United States

Semiconductor moiré systems, characterized by their periodic spatial light emission, unveil a new paradigm of active metasurfaces. Here, we show that ferroelectric moiré domains formed in a twisted hexagonal boron nitride (t-hBN) substrate can modulate light emission from an adjacent semiconductor MoSe2 monolayer, enhancing its functionality as an active metasurface. The electrostatic potential at the surface of the t-hBN substrate provides a simple way to confine excitons in the MoSe2 monolayer. The excitons confined within the domains and at the domain walls are spectrally separated due to a pronounced Stark shift. Moreover, the patterned light emission can be dynamically controlled by electrically gating the ferroelectric domains, introducing a novel functionality beyond conventional semiconductor moiré systems. Our findings chart an exciting pathway for integrating nanometer-scale moiré ferroelectric domains with various optically active functional layers, paving the way for advanced nanophotonic applications. Copyright © 2024, The Authors. All rights reserved.

关键词： Excitons

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Digital Metamaterials: Designing 3D Digital Metamaterial for Elastic Waves: From Elastic Wave Polarizer to Vibration control (Adv. Sci. 16/2019)

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Advanced Science 2019年第16期6卷 1970097-1970097页

作者： Huan Liu Quan Zhang Kai Zhang Gengkai Hu Huiling Duan State Key Laboratory of Turbulence and Complex Systems Department of Mechanics and Engineering Science BIC-ESAT College of Engineering Peking university Beijing 100871 China School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China Key Laboratory of Dynamics and Control of Flight Vehicle School of Aerospace Engineering Beijing Institute of Technology Beijing 100081 China CAPT HEDPS and IFSA Collaborative Innovation Center of MoE Peking University Beijing 100871 China

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Correction: COVID-19 Vaccine Tweets After Vaccine Rollout: Sentiment-Based Topic Modeling

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Journal of medical Internet research 2022年第3期24卷 e37841页

作者： Luwen Huangfu Yiwen Mo Peijie Zhang Daniel Dajun Zeng Saike He Fowler College of Business San Diego State University San Diego CA United States. Center for Human Dynamics in the Mobile Age San Diego State University San Diego CA United States. The State Key Laboratory of Management and Control for Complex Systems Institute of Automation Chinese Academy of Sciences Beijing China. University of Chinese Academy of Sciences Beijing China.

[This corrects the article DOI: 10.2196/31726.].

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Metamorphosis of discontinuity lines and rectification of magnetic flux avalanches in the presence of noncentrosymmetric pinning forces

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Physical Review B 2021年第22期103卷 224514-224514页

作者： M. Motta L. Burger Lu Jiang J. D. González Acosta Ž. L. Jelić F. Colauto W. A. Ortiz T. H. Johansen M. V. Milošević C. Cirillo C. Attanasio Cun Xue A. V. Silhanek B. Vanderheyden Departamento de Física Universidade Federal de São Carlos 13565-905 São Carlos São Paulo Brazil Montefiore Research Unit Department of Electrical Engineering and Computer Science Université de Liège 4000 Sart Tilman Belgium School of Aeronautics Northwestern Polytechnical University Xi'an 710072 China Facultad de Ingeniería Universidad del Magdalena Santa Marta Colombia Departement Fysica Universiteit Antwerpen Groenenborgerlaan 171 B-2020 Antwerpen Belgium Nokia Bell Labs Antwerp Belgium Department of Physics University of Oslo POB 1048 Blindern 0316 Oslo Norway CNR-SPIN c/o Università degli Studi di Salerno I-84084 Fisciano (Sa) Italy Dipartimento di Fisica “E.R. Caianiello” Università degli Studi di Salerno I-84084 Fisciano (Sa) Italy School of Mechanics Civil Engineering and Architecture and MIIT Key Laboratory of Dynamics and Control of Complex Systems Northwestern Polytechnical University Xi'an 710072 China Experimental Physics of Nanostructured Materials Q-MAT CESAM Université de Liège B-4000 Sart Tilman Belgium

Considering a noncentrosymmetric pinning texture composed of a square array of triangular holes, the magnetic flux penetration and expulsion are investigated experimentally and theoretically. A direct visualization of the magnetic landscape obtained using a magneto-optical technique on a Nb film is complemented by a multiscale numerical modeling. This combined approach allows the magnetic flux dynamics to be identified from the single flux quantum limit up to the macroscopic electromagnetic response. Within the theoretical framework provided by time-dependent Ginzburg-Landau simulations, an estimation of the in-plane current anisotropy is obtained and its dependence with the radius of the curvature of hole vertices is addressed. These simulations show that current crowding plays an important role in channeling the flux motion, favoring hole-to-hole flux hopping rather than promoting interstitial flux displacement in between the holes. The resulting anisotropy of the critical current density gives rise to a distinct pattern of discontinuity lines for increasing and decreasing applied magnetic fields, in sharp contrast to the invariable patterns reported for centrosymmetric pinning potentials. This observation is partially accounted for by the rectification effect, as demonstrated by finite-element modeling. At low temperatures, where magnetic field penetration is dominated by thermomagnetic instabilities, highly directional magnetic flux avalanches with a fingerlike shape are observed to propagate along the easy axis of the pinning potential. This morphology is reproduced by numerical simulations. Our findings demonstrate that anisotropic pinning landscapes and, in particular, ratchet potentials produce subtle modifications to the critical state field profile that are reflected in the distribution of discontinuity lines.

关键词： Flux pinning Magneto-optical effect Monolayer films Superconductors Finite-element method Landau-Ginzburg theory

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26th Annual Computational Neuroscience Meeting (CNS*2017) of the Organization for Computational Neuroscience Antwerp, Belgium, July 15-20, 2017

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BMC NEUROSCIENCE 2017年第SUPPL 1期18卷 59-59页

作者： [Anonymous] Indiana University Purdue University Indianapolis Indianapolis IN 46032 USA Stark Neurosciences Research Institute Indiana University School of Medicine Indianapolis IN 46032 USA Department of Mathematics East Carolina University Greenville NC 27858 USA Jülich Supercomputing Centre Forschungszentrum Jülich 52425 Jülich Germany Future Systems Swiss National Supercomputing Centre 8092 Zurich Switzerland User Engagement and Support Swiss National Supercomputing Centre 6900 Lugano Switzerland Institut de Neurosciences des Systèmes Aix Marseille Univ 13005 Marseille France Simulation Lab Neuroscience Forschungszentrum Jülich Jülich Germany Department of Experimental Psychology Ghent University 9000 Ghent Belgium Donders Center for Cognitive Neuroimaging Radboud University 6525HR Nijmegen The Netherlands Department of Electrical Computer and Energy Engineering University of Colorado Boulder CO 80309 USA Department of Neurosurgery Johns Hopkins School of Medicine Baltimore MD 21287 USA Department of Neurology Johns Hopkins School of Medicine Baltimore MD 21287 USA Department of Otolaryngology Johns Hopkins School of Medicine Baltimore MD 21287 USA INSERM U968 Paris France Sorbonne Universités UPMC University Paris 06 UMR_S 968 Institut de la Vision Paris France CNRS UMR_7210 Paris France Department of Computer Architecture and Technology University of Granada (CITIC) Granada Spain Sorbonne Universités UPMC Univ Paris 06 INSERM CNRS Institut de la Vision Paris France Department of Adaptive Machine Systems Osaka University Osaka Japan Department of Computer Science University of Cergy-Pontoise Cergy-Pontoise France Department of Physics and Astronomy College of Charleston Charleston SC 29424 USA School of Physics Faculty of Science University of Sydney Sydney NSW 2006 Australia Center of Excellence for Integrative Brain Function Australian Research Council Sydney Australia Max Planck Institute for Human Cognitive and Brain Sciences Saxony Lei

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26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 Antwerp, Belgium. 15-20 July 2017 Abstracts

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BMC NEUROSCIENCE 2017年第SUPPL 1期18卷 95-176页

作者： [Anonymous] Department of Neuroscience Yale University New Haven CT 06520 USA Department Physiology & Pharmacology SUNY Downstate Brooklyn NY 11203 USA NYU School of Engineering 6 MetroTech Center Brooklyn NY 11201 USA Departament de Matemàtica Aplicada Universitat Politècnica de Catalunya Barcelona 08028 Spain Institut de Neurobiologie de la Méditerrannée (INMED) INSERM UMR901 Aix-Marseille Univ Marseille France Center of Neural Science New York University New York NY USA Aix-Marseille Univ INSERM INS Inst Neurosci Syst Marseille France Laboratoire de Physique Théorique et Modélisation CNRS UMR 8089 Université de Cergy-Pontoise 95300 Cergy-Pontoise Cedex France Department of Mathematics and Computer Science ENSAT Abdelmalek Essaadi’s University Tangier Morocco Laboratory of Natural Computation Department of Information and Electrical Engineering and Applied Mathematics University of Salerno 84084 Fisciano SA Italy Department of Medicine University of Salerno 84083 Lancusi SA Italy Dipartimento di Fisica Università degli Studi Aldo Moro Bari and INFN Sezione Di Bari Italy Data Analysis Department Ghent University Ghent Belgium Coma Science Group University of Liège Liège Belgium Cruces Hospital and Ikerbasque Research Center Bilbao Spain BIOtech Department of Industrial Engineering University of Trento and IRCS-PAT FBK 38010 Trento Italy Department of Data Analysis Ghent University Ghent 9000 Belgium The Wellcome Trust Centre for Neuroimaging University College London London WC1N 3BG UK Department of Electronic Engineering NED University of Engineering and Technology Karachi Pakistan Blue Brain Project École Polytechnique Fédérale de Lausanne Lausanne Switzerland Departement of Mathematics Swansea University Swansea Wales UK Laboratory for Topology and Neuroscience at the Brain Mind Institute École polytechnique fédérale de Lausanne Lausanne Switzerland Institute of Mathematics University of Aberdeen Aberdeen Scotland UK Department of Integrativ

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