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arXiv 2021年

作者： Kilpatrick, Charles D. Coulter, David A. Arcavi, Iair Brink, Thomas G. Dimitriadis, Georgios Filippenko, Alexei V. Foley, Ryan J. Howell, D. Andrew Jones, David O. Makler, Martin Piro, Anthony L. Rojas-Bravo, César Sand, David J. Swift, Jonathan J. Tucker, Douglas Zheng, Weikang Allam, Sahar S. Annis, James T. Antilen, Juanita Bachmann, Tristan G. Bloom, Joshua S. Bom, Clecio R. Bostroem, K. Azalee Brout, Dillon Burke, Jamison Butler, Robert E. Butner, Melissa Campillay, Abdo Clever, Karoli E. Conselice, Christopher J. Cooke, Jeff Dage, Kristen C. de Carvalho, Reinaldo R. Jaeger, Thomas D.E. Desai, Shantanu Garcia, Alyssa Garcia-Bellido, Juan Gill, Mandeep S.S. Girish, Nachiket Hallakoun, Na'Ama Herner, Kenneth Hiramatsu, Daichi Holz, Daniel E. Huber, Grace Kawash, Adam M. McCully, Curtis Medallon, Sophia A. Metzger, Brian D. Modak, Shaunak Morgan, Robert Muñoz, Ricardo R. Muñoz-Elgueta, Nahir Murakami, Yukei S. Olivares, Felipe E. Palmese, Antonella Patra, Kishore Pereira, Maria E.S. Pessi, Thallis L. Pineda-Garcia, J. Quirola-Vásquez, Jonathan Ramirez-Ruiz, Enrico Rembold, Sandro Barboza Rest, Armin Rodríguez, Ósmar Santana-Silva, Luidhy Sherman, Nora F. Siebert, Matthew R. Smith, Carli Smith, J. Allyn Soares-Santos, Marcelle Stacey, Holland Stahl, Benjamin E. Strader, Jay Strasburger, Erika Sunseri, James Tinyanont, Samaporn Tucker, Brad E. Ulloa, Natalie Valenti, Stefano Vasylyev, Sergiy Wiesner, Matthew P. Zhang, Keto D. Northwestern University EvanstonIL60208 United States Department of Astronomy and Astrophysics University of California Santa CruzCA95064 United States The School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel CIFAR Azrieli Global Scholars program CIFAR Toronto Canada Department of Astronomy University of California BerkeleyCA94720-3411 United States Miller Institute for Basic Research in Science University of California BerkeleyCA94720 United States Department of Physics University of California Santa BarbaraCA93106-9530 United States Las Cumbres Observatory 6740 Cortona Dr Suite 102 GoletaCA93117-5575 United States International Center for Advanced Studies & Instituto de Ciencias Físicas ECyT-UNSAM & CONICET Buenos Aires1650 Argentina Centro Brasileiro de Pesquisas Físicas Rua Dr. Xavier Sigaud 150 Rio de Janeiro RJCEP 22290-180 Brazil The Observatories of the Carnegie Institution for Science 813 Santa Barbara St. PasadenaCA91101 United States Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Thacher Observatory Thacher School 5025 Thacher Rd. OjaiCA93023 United States Fermi National Accelerator Laboratory P. O. Box 500 BataviaIL60510 United States Departamento de Astronomía Universidad de Chile Camino El Observatorio 1515 Las Condes Santiago Chile Department of Astronomy and Astrophysics University of Chicago ChicagoIL60637 United States Lawrence Berkeley National Laboratory 1 Cyclotron Road MS 50B-4206 BerkeleyCA94720-3411 United States Centro Federal de Educação Tecnológica Celso Suckow da Fonseca Rodovia Mário Covas lote J2 quadra J Itaguaí RJCEP 23810-000 Brazil Department of Physics and Astronomy University of California DavisCA95616 United States Center for Astrophysics Harvard & Smithsonian 60 Garden St CambridgeMA02138 United States Department of Astronomy Indiana University 727 E. Third St. BloomingtonIN47405 United States Dep

We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star–black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg2 for the 90th percentile best localization), covering a total of 51 deg2 and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host-galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an rband decline rate of 0.68 mag day−1, similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most −17.8 mag (50% confidence). Our data are not constraining for "red" kilonovae and rule out "blue" kilonovae with M > 0.5 M* (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles ◦ assuming an initial jet opening angle of ∼ 5.2◦ and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources. © 2021, CC BY.

关键词： Stars

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Advances in understanding high-mass X-ray binaries with INTEGRAL and Future Directions

arXiv

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arXiv 2020年

作者： Kretschmar, Peter Fürst, Felix Sidoli, Lara Bozzo, Enrico Alfonso-Garzón, Julia Bodaghee, Arash Chaty, Sylvain Chernyakova, Masha Ferrigno, Carlo Manousakis, Antonios Negueruela, Ignacio Postnov, Konstantin Paizis, Adamantia Reig, Pablo Rodes-Roca, José Joaquín Tsygankov, Sergey Bird, Antony J. né Kühnel, Matthias Bissinger Blay, Pere Caballero, Isabel Coe, Malcolm J. Domingo, Albert Doroshenko, Victor Ducci, Lorenzo Falanga, Maurizio Grebenev, Sergei A. Grinberg, Victoria Hemphill, Paul Kreykenbohm, Ingo née Fritz, Sonja Kreykenbohm Li, Jian Lutovinov, Alexander A. Martínez-Núñez, Silvia Mas-Hesse, J. Miguel Masetti, Nicola McBride, Vanessa A. Neronov, Andrii Pottschmidt, Katja Rodriguez, Jérôme Romano, Patrizia Rothschild, Richard E. Santangelo, Andrea Sguera, Vito Staubert, Rüdiger Tomsick, John A. Torrejón, José Miguel Torres, Diego F. Walter, Roland Wilms, Jörn Wilson-Hodge, Colleen A. Zhang, Shu E-28692 Spain E-28692 Spain INAF - IASF Istituto di Astrofisica Spaziale e Fisica Cosmica Via A. Corti 12 MilanoI-20133 Italy Department of Astronomy ISDC University of Geneva Chemin d'Ecogia 16 VersoixCH-1290 Switzerland E-28692 Spain Department of Chemistry Physics and Astronomy Georgia College and State University MilledgevilleGA31061 United States AIM CEA CNRS Université Paris-Saclay Université de Paris Gif-sur-YvetteF-91191 France Université de Paris CNRS Astroparticule et Cosmologie ParisF-75006 France School of Physical Sciences and CfAR Dublin City University Dublin 9 Ireland Dublin Institute for Advanced Studies 31 Fitzwilliam Place Dublin 2 Ireland Department of Applied Physics & Astronomy University of Sharjah Sharjah United Arab Emirates Sharjah United Arab Emirates Department of Applied Physics University of Alicante AlicanteE-03080 Spain Sternberg Astronomical Institute Moscow State University Moscow119234 Russia Kazan Federal University Kazan Russia Institute of Astrophysics Foundation for Research and Technology-Hellas Heraklion Crete71110 Greece University of Crete Physics Department Institute of Theoretical & Computational Physics Heraklion Crete70013 Greece Department of Physics Systems Engineering and Signal Theory University of Alicante AlicanteE-03690 Spain University Institute of Physics Applied to Sciences and Technologies University of Alicante AlicanteE-03690 Spain Department of Physics and Astronomy University of Turku FI-20014 Finland Space Research Institute The Russian Academy of Sciences Profsoyuznaya Str. 84/32 Moscow117997 Russia School of Physics and Astronomy Faculty of Physical Sciences and Engineering University of Southampton SouthamptonSO17 1BJ United Kingdom Erwin-Rommel-Strae 1 Erlangen91058 Germany Universidad Internacional de Valencia - VIU C/Pintor Sorolla 21 Valencia46002 Spain E-28692 Spain Institut für Astronomie und Astrophysik Universität Tübingen Sand 1 Tübingen

High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies. In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system. We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields. We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations. Copyright © 2020, The Authors. All rights reserved.

关键词： Galaxies

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Direct evidence for shock-powered optical emission in a nova

arXiv

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arXiv 2020年

作者： Aydi, Elias Sokolovsky, Kirill V. Chomiuk, Laura Steinberg, Elad Li, Kwan Lok Vurm, Indrek Metzger, Brian D. Strader, Jay Mukai, Koji Pejcha, Ondřej Shen, Ken J. Wade, Gregg A. Kuschnig, Rainer Moffat, Anthony F.J. Pablo, Herbert Pigulski, Andrzej Popowicz, Adam Weiss, Werner Zwintz, Konstanze Izzo, Luca Pollard, Karen R. Handler, Gerald Ryder, Stuart D. Filipović, Miroslav D. Alsaberi, Rami Z.E. Manojlović, Perica de Oliveira, Raimundo Lopes Walter, Frederick M. Vallely, Patrick J. Buckley, David A.H. Brown, Michael J.I. Harvey, Eamonn J. Kawash, Adam Kniazev, Alexei Kochanek, Christopher S. Linford, Justin Mikolajewska, Joanna Molaro, Paolo Orio, Marina Page, Kim L. Shappee, Benjamin J. Sokoloski, Jennifer L. Center for Data Intensive and Time Domain Astronomy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Sternberg Astronomical Institute Moscow State University Universitetskii pr. 13 Moscow119992 Russia Astro Space Center of Lebedev Physical Institute Profsoyuznaya St. 84/32 Moscow117997 Russia Columbia Astrophysics Laboratory Department of Physics Columbia University New YorkNY10027 United States Racah Institute of Physics Hebrew University Jerusalem91904 Israel Department of Physics UNIST Ulsan44919 Korea Republic of Institute of Astronomy National Tsing Hua University Hsinchu30013 Taiwan Tartu Observatory University of Tartu Tõravere Tartumaa61602 Estonia CRESST X-ray Astrophysics Laboratory NASA GSFC GreenbeltMD20771 United States Department of Physics University of Maryland Baltimore County 1000 Hilltop Circle BaltimoreMD21250 United States Institute of Theoretical Physics Faculty of Mathematics and Physics Charles University Prague Czech Republic Department of Astronomy Theoretical Astrophysics Center University of California BerkeleyCA94720 United States Department of Physics and Space Science Royal Military College of Canada PO Box 17000 Station Forces KingstonONK7K 7B4 Canada Institute of Communication Networks and Satellite Communications Graz University of Technology Infeldgasse 12 Graz8010 Austria Dépt. de Physique Univ. De Montréal C.P. 6128 Succ. Centre-Ville Centre de Recherche en Astrophysique du Quéebec MontréealQCH3C 3J7 Canada AAVSO 49 Bay State Rd CambridgeMA02138 United States Instytut Astronomiczny Uniwersytet Wroclawski Kopernika 11 Wroclaw51-622 Poland Silesian University of Technology Institute of Electronics Akademicka 16 Gliwice44-100 Poland Institute for Astrophysics University of Vienna Tuerkenschanzstrasse 17 ViennaA-1180 Austria Universität Innsbruck Institut für Astro- und Teilchenphysik Technikerstrasse 25 InnsbruckA-6020 Austria D

Classical novae are thermonuclear explosions that occur on the surfaces of white dwarf stars in interacting binary systems1. It has long been thought that the luminosity of classical novae is powered by continued nuclear burning on the surface of the white dwarf after the initial runaway2. However, recent observations of GeV γrays from classical novae have hinted that shocks internal to the nova ejecta may dominate the nova emission. Shocks have also been suggested to power the luminosity of events as diverse as stellar mergers3, supernovae4, and tidal disruption events5, but observational confirmation has been lacking. Here we report simultaneous space-based optical and γ-ray observations of the 2018 nova V906 Carinae (ASASSN-18fv), revealing a remarkable series of distinct correlated flares in both bands. The optical and γ-ray flares occur simultaneously, implying a common origin in shocks. During the flares, the nova luminosity doubles, implying that the bulk of the luminosity is shock-powered. Furthermore, we detect concurrent but weak X-ray emission from deeply embedded shocks, confirming that the shock power does not appear in the X-ray band and supporting its emergence at longer wavelengths. Our data, spanning the spectrum from radio to γ-ray, provide direct evidence that shocks can power substantial luminosity in classical novae and other optical transients. Copyright © 2020, The Authors. All rights reserved.

关键词： Luminance

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Multiscale strategies for computing optimal transport

The Journal of Machine Learning Research

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The Journal of Machine Learning Research 2017年第1期18卷

作者： Samuel Gerber Mauro Maggioni Kitware NC Department of Mathematics Applied Mathematics Institute for Data Intensive Engineering and Science Johns Hopkins University Baltimore MD

This paper presents a multiscale approach to efficiently compute approximate optimal transport plans between point sets. It is particularly well-suited for point sets that are in high-dimensions, but are close to being intrinsically low-dimensional. The approach is based on an adaptive multiscale decomposition of the point sets. The multiscale decomposition yields a sequence of optimal transport problems, that are solved in a top-to-bottom fashion from the coarsest to the finest scale. We provide numerical evidence that this multiscale approach scales approximately linearly, in time and memory, in the number of nodes, instead of quadratically or worse for a direct solution. Empirically, the multiscale approach results in less than one percent relative error in the objective function. Furthermore, the multiscale plans constructed are of interest by themselves as they may be used to introduce novel features and notions of distances between point sets. An analysis of sets of brain MRI based on optimal transport distances illustrates the effectiveness of the proposed method on a real world data set. The application demonstrates that multiscale optimal transport distances have the potential to improve on state-of-the-art metrics currently used in computational anatomy.

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data management at scale

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Information Services & Use 2016年第1-2期36卷 27-33页

作者： Choudhury, G. Sayeed Sheridan Libraries Institute for Data Intensive Engineering and Science Johns Hopkins University 3400 N. Charles Street Baltimore MD 21218 USA. E-mail:

This paper offers a high-level, non-scientific assessment regarding the impact of research library based data management services, particularly related to predictive data analytics – an area where the corporate sector has arguably made more tangible impact. The fundamental premise rests upon the assertion that research libraries should consider the potential consequences, need for interpretation and degree of control to better allocate and optimize scarce resources for data management. By doing so, it may be possible to support broader goals of data management at scale, identify network effects through linked data and highlight possibilities for partnerships, including with the corporate sector.

关键词： data management Big data data analytics

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Searches After Gravitational-waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo’s Third Observing Run

arXiv

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arXiv 2019年

作者： Lundquist, M.J. Paterson, K. Fong, W. Sand, D.J. Andrews, J.E. Shivaei, I. Daly, P.N. Valenti, S. Yang, S. Christensen, E. Gibbs, A.R. Shelly, F. Wyatt, S. Kuhn, O. Amaro, R.C. Arcavi, I. Behroozi, P. Butler, N. Chomiuk, L. Corsi, A. Drout, M.R. Egami, E. Fan, X. Foley, R.J. Frye, B. Gabor, P. Green, E.M. Grier, C.J. Guzman, F. Hamden, E. Howell, D.A. Jannuzi, B.T. Kelly, P. Milne, P. Moe, M. Nugent, A. Olszewski, E. Palazzi, E. Paschalidis, V. Psaltis, D. Reichart, D. Rest, A. Rossi, A. Schroeder, G. Smith, P.S. Smith, N. Spekkens, K. Strader, J. Stark, D.P. Trilling, D. Veillet, C. Wagner, M. Weiner, B. Wheeler, J.C. Williams, G.G. Zabludoff, A. Steward Observatory University of Arizona 933 North Cherry Avenue TucsonAZ85721-0065 United States Center for Interdisciplinary Exploration and Research in Astrophysics Department of Physics and Astronomy Northwestern University 2145 Sheridan Road EvanstonIL60208-3112 United States Hubble Fellow Department of Physics University of California 1 Shields Avenue DavisCA95616-5270 United States Department of Physics and Astronomy Galileo Galilei University of Padova Vicolo dell’Osservatorio 3 PadovaI-35122 Italy INAF Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 PadovaI-35122 Italy Lunar and Planetary Lab Department of Planetary Sciences University of Arizona TucsonAZ85721 United States Large Binocular Telescope Observatory 933 North Cherry Avenue TucsonAZ United States School of Physics and Astronomy Tel Aviv University Tel Aviv69978 Israel School of Earth and Space Exploration Arizona State University TempeAZ85287 United States Center for Data Intensive and Time Domain Astronomy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Department of Physics and Astronomy Texas Tech University Box 1051 LubbockTX79409-1051 United States Department of Astronomy and Astrophysics University of Toronto 50 St. George Street TorontoONM5S 3H4 Canada Observatories of the Carnegie Institution for Science 813 Santa Barbara St. PasadenaCA91101 United States Department of Astronomy and Astrophysics University of California Santa CruzCA95064 United States Vatican Observatory Vatican City00120 Vat College of Optical Sciences University of Arizona 1630 E University Blvd TucsonAZ85719 United States Las Cumbres Observatory 6740 Cortona Drive Suite 102 GoletaCA93117-5575 United States College of Science & Engineering Minnesota Institute for Astrophysics University of Minnesota 115 Union St. SE MinneapolisMN55455 United States INAF - Osservatorio di Astrofisica e Scienza dello Spazio -

We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter, located primarily in the Northern Hemisphere. We provide an overview of SAGUARO’s telescopic resources, pipeline for transient detection, and database for candidate visualization. We describe SAGUARO’s discovery component, which utilizes the 5 deg2 field-of-view optical imager on the Mt. Lemmon 1.5m telescope, reaching limits of ≈ 21.3 AB mag while rapidly tiling large areas. We also describe the follow-up component of SAGUARO, used for rapid vetting and monitoring of Copyright © 2019, The Authors. All rights reserved.

关键词： Gravity waves

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ESICM LIVES 2016: part one Milan, Italy. 1-5 October 2016 Abstracts

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intensive CARE MEDICINE EXPERIMENTAL 2016年第SUPPL 1期4卷 1-1页

作者： [Anonymous] Academic Medical Center University of Amsterdam Amsterdam Netherlands UMCU Utrecht Netherlands Autonomous University of Barcelona Barcelona Spain Hospital São Francisco Xavier Lisbon Portugal CHU Henri Mondor Medical ICU Créteil France Université de Paris Est-Créteil Groupe de Recherche Clinique CARMAS Créteil France Hôpital Tenon APHP Medical and Surgical ICU Paris France Université Paris Diderot Sorbonne Paris Cité UMR 1153 Paris France Interdepartmental Division of Critical Care University of Toronto Toronto Canada University Health Network University of Toronto Critical Care Medicine Toronto Canada University of Milan - Bicocca Health Sciences School of Medicine and Surgery Monza Italy St Michael’s Hospital University of Toronto Anesthesia Toronto Canada CHU d’Angers Medical ICU Angers France Interdepartmental Division of Critical Care University of Toronto Saint Michael’s Hospital and Keenan Research Centre Toronto Canada University of Birmingham Institute for Inflammation and Ageing Birmingham UK University of Sheffield Mathematics and Statistics Help Centre Sheffield UK Heart of England NHS Foundation Trust Intensive Care Medicine Birmingham UK Department of Surgery University Hospitals Birmingham NHS Trust Birmingham UK University Hospitals Birmingham NHS Trust Anaesthesia and Critical Care Medicine Birmingham UK Queen’s University of Belfast Wellcome-Wolfson Institute for Experimental Medicine Belfast UK Royal Victoria Hospital Intensive Care Medicine Belfast UK University of Warwick Warwick Clinical Trials Unit Coventry UK University of Bari ‘Aldo Moro’ Bari Italy Hospital Israelita Albert Einstein São Paulo Brazil Mayo Clinic Jacksonville USA Mahidol University Faculty of Tropical Medicine Bangkok Thailand University Medical Center Utrecht Intensive Care Utrecht Netherlands University Medical Center Utrecht Julius Center for Health Sciences and Primary Care Utrecht Netherlands Academic Medical Center University of Amste

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The open connectome project data cluster: Scalable analysis and vision for high-throughput neuroscience

The open connectome project data cluster: Scalable analysis ...

引用

25th International Conference on Scientific and Statistical database Management, SSDBM 2013

作者： Burns, Randal Roncal, William Gray Kleissas, Dean Lillaney, Kunal Manavalan, Priya Perlman, Eric Berger, Daniel R. Bock, Davi D. Chung, Kwanghun Grosenick, Logan Kasthuri, Narayanan Weiler, Nicholas C. Deisseroth, Karl Kazhdan, Michael Lichtman, Jeff Reid, R. Clay Smith, Stephen J. Szalay, Alexander S. Vogelstein, Joshua T. Vogelstein, R. Jacob Department of Computer Science Institute for Data Intensive Engineering and Science Johns Hopkins University United States Applied Physics Laboratory Johns Hopkins University United States Department of Statistical Science and Mathematics Institute for Brain Science Duke University United States Janelia Farm Research Campus Howard Hughes Medical Institute United States Department of Molecular and Cellular Biology Harvard University United States Department of Computational Neuroscience Massachusetts Institute of Technology United States Allen Institute for Brain Science United States Department of Physics and Astronomy Institute for Data Intensive Engineering and Science Johns Hopkins University United States Department of Bioengineering Stanford University United States Department of Molecular and Cellular Physiology Stan- Ford University United States

ISBN: (纸本)9781450319218

We describe a scalable database cluster for the spatial analysis and annotation of high-throughput brain imaging data, initially for 3-d electron microscopy image stacks, but for time-series and multi-channel data as well. The system was designed primarily for workloads that build connectomes- neural connectivity maps of the brain-using the parallel execution of computer vision algorithms on high-performance compute clusters. These services and open-science data sets are publicly available at ***. The system design inherits much from NoSQL scale-out and data-intensive computing architectures. We distribute data to cluster nodes by partitioning a spatial index. We direct I/O to different systems-reads to parallel disk arrays and writes to solid-state storage-to avoid I/O interference and maximize throughput. All programming interfaces are RESTful Web services, which are simple and stateless, improving scalability and usability. We include a performance evaluation of the production system, highlighting the effectiveness of spatial data organization. Copyright © 2013 ACM.

关键词： Digital storage

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Migrating a (large) science database to the cloud 10

Migrating a (large) science database to the cloud

引用

Proceedings of the 19th ACM International Symposium on High Performance Distributed Computing

作者： Thakar, Ani Szalay, Alex Johns Hopkins University Institute for Data Intensive Engineering and Science 3701 San Martin Drive Baltimore MD 21218-2695 United States

ISBN: (纸本)9781605589428

We report on attempts to put an existing scientific (astronomical) database - the Sloan Digital Sky Survey (SDSS) science archive [1] - in the cloud. Based on our experience, it is either very frustrating or impossible at this time to migrate an existing, complex SQL Server database into current cloud service offerings such as Amazon (EC2) and Microsoft (SQL Azure). Certainly it is impossible to migrate a large database in excess of a TB, but even with (much) smaller databases, the limitations of cloud services make it very difficult to migrate the data to the cloud without making changes to the schema and settings (for example, inability to migrate a spatial indexing library, and several other user-defined functions and stored procedures) that would invalidate performance comparisons between cloud and on-premise versions. So it is not surprising that our preliminary performance comparisons show a very large (an order of magnitude) performance discrepancy with the Amazon cloud version of the SDSS database. We have also not yet investigated the performance tweaks that could be possible within the cloud. Although we managed to successfully migrate (a subset of) the SDSS catalog database to Amazon EC2, we were not able to access the database in a meaningful way from the outside world. Even though this was advertised as a public dataset on the AWS blog, it was not clear how other users or the public would be able to access this data in a meaningful way, if at all. These difficulties suggest that much work and coordination needs to occur between cloud service providers and their potential database clients before science databases can successfully and effectively be deployed in the cloud. This is true not just for large scientific databases but all databases that make extensive use of advanced database management system (DBMS) features for performance and user convenience. © Copyright 2010 ACM.

关键词： Windows operating system

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Lagrangian Refined Kolmogorov Similarity Hypothesis for Gradient Time Evolution and Correlation in Turbulent Flows

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Physical Review Letters 2010年第8期104卷 084502-084502页

作者： Huidan Yu Charles Meneveau Department of Mechanical Engineering Institute for Data Intensive Engineering and Science Johns Hopkins University Baltimore Maryland 21218 US

We study time evolution of velocity and pressure gradients in isotropic turbulence by quantifying their autocorrelation functions and decorrelation time scales. The Lagrangian analysis uses data in a public database generated by direct numerical simulation at a Reynolds number Reλ≈433. It is confirmed that when averaging over the entire domain, correlation functions decay on time scales on the order of the global Kolmogorov turnover time scale. However, when performing the analysis in different subregions of the flow, turbulence intermittency leads to large spatial variability in the decay time scales. Remarkably, excellent collapse of the autocorrelation functions is recovered when using a locally defined Kolmogorov time scale. This provides new evidence for the validity of Kolmogorov’s refined similarity hypothesis, but from a Lagrangian viewpoint that provides a natural frame to describe the dynamics of turbulence.

关键词： Reynolds number

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