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Cracks Interaction in the Elastic Composite under Action of the Harmonic Loading Field

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Cracks Interaction in the Elastic Composite under Action of ...

International Seminar/Workshop on Direct and Inverse Problems of Electromagnetic and Acoustic Wave Theory (DIPED)

作者： V. Z. Stankevych I. O. Butrak V. V. Kovalchuk Department of Computational Mechanics of Deformable Systems Pidstryhach Institute for Applied Problems of Mechanics and Mathematics NASU Lviv Ukraine Department of Rolling Stock and Track Lviv Branch of Academician V. Lazaryan Dnipropetrovsk National University of Railway Transport Lviv Ukraine

ISBN: (纸本)9781538661178

A three-layer composite with penny-shaped cracks in the field of harmonic torsional loading is considered. The solutions are chosen in the form of Helmholtz potentials with densities that characterize unknown crack opening functions. The problem is reduced to the solution of the system of two-dimensional boundary integral equations (BIEs). The influence of the frequency of the applied load, the ratio of the elastic constant parameters of the composite on the dynamic stress intensity factors in the defect vicinity is investigated.

关键词： Electromagnetics Electromagnetic scattering Acoustic waves Inverse problems

Stochastic block models with multiple continuous attributes

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arXiv 2018年

作者： Stanley, Natalie Bonacci, Thomas Kwitt, Roland Niethammer, Marc Mucha, Peter J. Curriculum in Bioinformatics and Computational Biology University of North Carolina Chapel Hill Department of Pharmacology & Lineberger Comprehensive Cancer Center University of North Carolina Chapel Hill Department of Computer Science University of Salzburg Department of Computer Science & Biomedical Research Imaging Center University of North Carolina Chapel Hill Carolina Center for Interdisciplinary Applied Mathematics Department of Mathematics University of North Carolina Chapel Hill

The stochastic block model (SBM) is a probabilistic model for community structure in networks. Typically, only the adjacency matrix is used to perform SBM parameter inference. In this paper, we consider circumstances in which nodes have an associated vector of continuous attributes that are also used to learn the node-to-community assignments and corresponding SBM parameters. While this assumption is not realistic for every application, our model assumes that the attributes associated with the nodes in a network’s community can be described by a common multivariate Gaussian model. In this augmented, attributed SBM, the objective is to simultaneously learn the SBM connectivity probabilities with the multivariate Gaussian parameters describing each community. While there are recent examples in the literature that combine connectivity and attribute information to inform community detection, our model is the first augmented stochastic block model to handle multiple continuous attributes. This provides the flexibility in biological data to, for example, augment connectivity information with continuous measurements from multiple experimental modalities. Because the lack of labeled network data often makes community detection results difficult to validate, we highlight the usefulness of our model for two network prediction tasks: link prediction and collaborative filtering. As a result of fitting this attributed stochastic block model, one can predict the attribute vector or connectivity patterns for a new node in the event of the complementary source of information (connectivity or attributes, respectively). We also highlight two biological examples where the attributed stochastic block model provides satisfactory performance in the link prediction and collaborative filtering tasks. Copyright © 2018, The Authors. All rights reserved.

关键词： Population dynamics

Discrete Boltzmann trans-scale modeling of high-speed compressible flows

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Physical Review E 2018年第5期97卷 053312-053312页

作者： Yanbiao Gan Aiguo Xu Guangcai Zhang Yudong Zhang Sauro Succi North China Institute of Aerospace Engineering Langfang 065000 China College of Mathematics and Informatics & FJKLMAA Fujian Normal University Fuzhou 350007 China National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P.O. Box 8009-26 Beijing 100088 China Center for Applied Physics and Technology MOE Key Center for High Energy Density Physics Simulations College of Engineering Peking University Beijing 100871 China Key Laboratory of Transient Physics Nanjing University of Science and Technology Nanjing 210094 China Center for Life Nano Science at La Sapienza Fondazione Istituto Italiano di Tecnologia Viale Regina Margherita 295 00161 Roma Italy Physics Department and Institute for Applied Computational Science John A. Paulson School of Applied Science and Engineering Harvard University Oxford Street 29 Cambridge Massachusetts 02138 USA

We present a general framework for constructing trans-scale discrete Boltzmann models (DBMs) for high-speed compressible flows ranging from continuum to transition regime. This is achieved by designing a higher-order discrete equilibrium distribution function that satisfies additional nonhydrodynamic kinetic moments. To characterize the thermodynamic nonequilibrium (TNE) effects and estimate the condition under which the DBMs at various levels should be used, two measures are presented: (i) the relative TNE strength, describing the relative strength of the (N+1)th order TNE effects to the Nth order one; (ii) the TNE discrepancy between DBM simulation and relevant theoretical analysis. Whether or not the higher-order TNE effects should be taken into account in the modeling and which level of DBM should be adopted is best described by the relative TNE intensity and/or the discrepancy rather than by the value of the Knudsen number. As a model example, a two-dimensional DBM with 26 discrete velocities at Burnett level is formulated, verified, and validated.

关键词： Classical statistical mechanics Classical transport Compressible flows Rarefied flows Nonequilibrium lattice models Lattice-Boltzmann methods

Marginally parametrized spatio-temporal models and stepwise maximum likelihood estimation

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arXiv 2018年

作者： Edwards, Matthew Castruccio, Stefano Hammerling, Dorit School of Mathematics Statistics and Physics Newcastle University Newcastle upon TyneNE1 7RU United Kingdom Department of Applied and Computational Mathematics and Statistics University of Notre Dame Notre DameIN46556 United States Department of Analytics and Integrative Machine Learning National Center for Atmospheric Research BoulderCO80307 United States

In order to learn the complex features of large spatio-temporal data, models with large parameter sets are often required. However, estimating a large number of parameters is often infeasible due to the computational and memory costs of maximum likelihood estimation (MLE).We introduce the class of marginally parametrized (MP) models, where inference can be performed efficiently with a sequence of marginal (estimated) likelihood functions via stepwise maximum likelihood estimation (SMLE). We provide the conditions under which the stepwise estimators are consistent, and we prove that this class of models includes the diagonal vector autoregressive moving average model. We demonstrate that the parameters of this model can be obtained at least three orders of magnitude faster using SMLE compared to MLE, with only a small loss in statistical efficiency. We apply a MP model to a spatio-temporal global climate data set (in order to learn complex features of interest to climate scientists) consisting of over five million data points, and we demonstrate how estimation can be performed in less than an hour on a laptop. Copyright © 2018, The Authors. All rights reserved.

关键词： Climate models

sasPDF: pair distribution function analysis of nanoparticle assemblies from small-angle-scattering data

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arXiv 2019年

作者： Liu, Chia-Hao Janke, Eric Li, Ruipen Juhás, Pavol Gang, Oleg Talapin, Dimitri V. Billinge, Simon J.L. Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Department of Chemistry University of Chicago ChicagoIL60637 United States National Synchrotron Light Source II Brookhaven National Laboratory UptonNY11973 United States Computational Science Initiative Brookhaven National Laboratory UptonNY11973 United States Center for Functional Nanomaterials Energy and Photon Sciences Directorate Brookhaven National Laboratory UptonNY11973 United States Department of Chemical Engineering Columbia University New YorkNY10027 United States Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory UptonNY11973 United States

Ordered magnetic fields around the 3C 84 central black hole

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Astronomy and Astrophysics 2024年 682卷

作者： Paraschos, G.F. Kim, J.-Y. Wielgus, M. Röder, J. Krichbaum, T.P. Ros, E. Agudo, I. Myserlis, I. Moscibrodzka, M. Traianou, E. Zensus, J.A. Blackburn, L. Chan, C.-K. Issaoun, S. Janssen, M. Johnson, M.D. Fish, V.L. Akiyama, K. Alberdi, A. Alef, W. Algaba, J.C. Anantua, R. Asada, K. Azulay, R. Bach, U. Baczko, A.-K. Ball, D. Baloković, M. Barrett, J. Bauböck, M. Benson, B.A. Bintley, D. Blundell, R. Bouman, K.L. Bower, G.C. Boyce, H. Bremer, M. Brinkerink, C.D. Brissenden, R. Britzen, S. Broderick, A.E. Broguiere, D. Bronzwaer, T. Bustamante, S. Byun, D.-Y. Carlstrom, J.E. Ceccobello, C. Chael, A. Chang, D.O. Chatterjee, K. Chatterjee, S. Chen, M.T. Chen, Y. Cheng, X. Cho, I. Christian, P. Conroy, N.S. Conway, J.E. Cordes, J.M. Crawford, T.M. Crew, G.B. Cruz-Osorio, A. Cui, Y. Dahale, R. Davelaar, J. De Laurentis, M. Deane, R. Dempsey, J. Desvignes, G. Dexter, J. Dhruv, V. Doeleman, S.S. Dougal, S. Dzib, S.A. Eatough, R.P. Emami, R. Falcke, H. Farah, J. Fomalont, E. Ford, H.A. Foschi, M. Fraga-Encinas, R. Freeman, W.T. Friberg, P. Fromm, C.M. Fuentes, A. Galison, P. Gammie, C.F. García, R. Gentaz, O. Georgiev, B. Goddi, C. Gold, R. Gómez-Ruiz, A.I. Gómez, J.L. Gu, M. Gurwell, M. Hada, K. Haggard, D. Haworth, K. Hecht, M.H. Hesper, R. Heumann, D. Ho, L.C. Ho, P. Honma, M. Huang, C.L. Huang, L. Hughes, D.H. Ikeda, S. Impellizzeri, C.M.V. Inoue, M. James, D.J. Jannuzi, B.T. Jeter, B. Jaing, W. Jiménez-Rosales, A. Jorstad, S. Joshi, A.V. Jung, T. Karami, M. Karuppusamy, R. Kawashima, T. Keating, G.K. Kettenis, M. Kim, D.-J. Kim, J. Kim, J. Kino, M. Koay, J.Y. Kocherlakota, P. Kofuji, Y. Koch, P.M. Koyama, S. Kramer, C. Kramer, J.A. Kramer, M. Kuo, C.-Y. Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 Bonn53121 Germany Department of Astronomy and Atmospheric Sciences Kyungpook National University Daegu702-701 Korea Republic of Institute of Physics Silesian University in Opava Bezručovo nám. 13 Opava746 01 Czech Republic Instituto de Astrofísica de Andalucía-CSIC Glorieta de la Astronomía s/n Granada18008 Spain Avenida Divina Pastora 7 Local 20 Granada18012 Spain Radboud University PO Box 9010 Nijmegen6500 GL Netherlands Black Hole Initiative at Harvard University 20 Garden Street CambridgeMA02138 United States Center for Astrophysics Harvard and Smithsonian 60 Garden Street CambridgeMA02138 United States Steward Observatory and Department of Astronomy University of Arizona 933 N. Cherry Ave. TucsonAZ85721 United States Data Science Institute University of Arizona 1230 N. Cherry Ave. TucsonAZ85721 United States Program in Applied Mathematics University of Arizona 617 N. Santa Rita TucsonAZ85721 United States Nasa Hubble Fellowship Program Einstein Fellow United States Massachusetts Institute of Technology Haystack Observatory 99 Millstone Road WestfordMA01886 United States National Astronomical Observatory of Japan 2-21-1 Osawa Mitaka Tokyo181-8588 Japan Department of Physics Faculty of Science Universiti Malaya Kuala Lumpur50603 Malaysia Department of Physics and Astronomy The University of Texas at San Antonio One Utsa Circle San AntonioTX78249 United States Institute of Astronomy and Astrophysics Academia Sinica 11F of Astronomy-Mathematics Building AS/NTU No. 1 Sec. 4 Roosevelt Rd. Taipei10617 Taiwan Departament d'Astronomia i Astrofísica Universitat de València C. Dr. Moliner 50 Burjassot València46100 Spain Observatori Astronòmic Universitat de València C. Catedrático José Beltrán 2 Paterna València46980 Spain Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory Onsala43992 Sweden Yale Center for

Context. 3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz. Aims. Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84. Methods. We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. Results. We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency of νm = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field of BSSA = (2.9 ± 1.6) G, and an equipartition magnetic field of Beq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (mnet = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017-2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84. Conclusions. The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However,

关键词： Magnetic fields

Investigation on shock induced stripping breakup process of a liquid droplet 21

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Investigation on shock induced stripping breakup process of ...

21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017

作者： Liu, Yao Guan, Ben Wen, Chih-Yung Shen, Hua Department of Mechanical Engineering The Hong Kong Polytechnic University Hunghom Kowloon Hong Kong Applied Mathematics and Computational Science King Abdullah University of Scienceand Technology Saudi Arabia

ISBN: (数字)9781624104633

ISBN: (纸本)9781624104633

Stripping breakup process of a single liquid droplet under the impact of a planar shock wave is investigated both experimentally and numerically. The droplet breakup experiment is conducted in a horizontal shock tube and the evolution of the droplet is recorded by direct high-speed photography. The experimental images clearly illustrate the droplet interface evolution features from its early to relatively late stage. Compressible Euler equations are solved using an in-house inviscid upwind characteristic space-time conservation element and solution element (CE/SE) method coupled with the HLLC approximate Riemann solver. A reduced five-equation model is employed to demonstrate the air/liquid interface. Numerical results accurately reproduce the water column and axi-symmetric water droplet breakup processes in experiments. The present study confirms the validity of the present numerical method in solving the shock wave induced droplet breakup problem and elaborates the stripping breakup process numerically in a long period. Droplet inner flow pattern is depicted, based on which the drives of protrusions emerged on the droplet surface are clearly seen. The droplet deformation is proved to be determined by not only the outer air flow, but also the inner liquid flow. © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Shock tubes

Global weak solutions for generalized SQG in bounded domains

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arXiv 2017年

作者： Nguyen, Huy Quang PROGRAM IN APPLIED AND COMPUTATIONAL MATHEMATICS PRINCETON UNIVERSITY PRINCETONNJ08544 United States

We prove the existence of global L2 weak solutions for a family of generalized inviscid surface-quasi geostrophic (SQG) equations in bounded domains of the plane. In these equations, the active scalar is transported by a velocity field which is determined by the scalar through a more singular nonlocal operator compared to the SQG equation. The result is obtained by establishing appropriate commutator representations for the weak formulation together with good bounds for them in bounded *** Classification: 35Q35, 35Q86.35Q35, 35Q86 Copyright © 2017, The Authors. All rights reserved.

关键词： Velocity

Constraining the interaction between dark sectors with future HI intensity mapping observations

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Physical Review D 2018年第8期97卷 083504-083504页

作者： Xiaodong Xu Yin-Zhe Ma Amanda Weltman Department of Mathematics and Applied Mathematics University of Cape Town Rondebosch 7701 Cape Town South Africa School of Chemistry and Physics University of KwaZulu-Natal Durban 4000 South Africa NAOC-UKZN Computational Astrophysics Centre (NUCAC) University of KwaZulu-Natal Durban 4000 South Africa School of Natural Sciences Institute for Advanced Study Olden Lane Princeton New Jersey 08540 USA

We study a model of interacting dark matter and dark energy, in which the two components are coupled. We calculate the predictions for the 21-cm intensity mapping power spectra, and forecast the detectability with future single-dish intensity mapping surveys (BINGO, FAST and SKA-I). Since dark energy is turned on at z∼1, which falls into the sensitivity range of these radio surveys, the HI intensity mapping technique is an efficient tool to constrain the interaction. By comparing with current constraints on dark sector interactions, we find that future radio surveys will produce tight and reliable constraints on the coupling parameters.

关键词： Cosmological parameters Dark energy Dark matter Radio, microwave, & sub-mm astronomy