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IEEE Annual International Symposium Virtual Reality

作者： A. Sharma Xinlian Liu P. Miller A. Nakano R.K. Kalia P. Vashishta Wei Zhao T.J. Campbell A. Haas Concurrent Computing Laboratory for Materials Simulations Biological Computation and Visualization Center Department of Computer Science Department of Physics & Astronomy Louisiana State University LA USA Naval Oceanographic Office Major Shared Resource Center Stennis Space Center Logicon Inc. MS USA

ISBN: (纸本)0769514928

Recent advances in parallel computing have made it possible for scientists to perform atomistic simulations of materials involving billions of atoms. An immersive and interactive virtual environment such as ImmersaDesk is an ideal platform for exploring complex material processes in these simulations. However rendering such large datasets at an interactive speed is a major challenge. To solve this problem we have developed a visualization system by incorporating parallel and distributed computing paradigms. The system uses a parallelized fast visibility-culling algorithm based on the octree data structure to reduce the number of atoms sent to the graphics pipeline. An adaptive multiresolution algorithm based on atomic density is employed to further reduce the load on the graphics pipeline. The resulting system renders a billion-atom system at nearly interactive frame rates on a dual processor SGI Onyx2 with an InfiniteReality2 graphics pipeline connected to a 4-node PC cluster.

关键词： Graphics Pipelines Computational modeling Parallel processing Virtual environment Data visualization Distributed computing Data structures Clustering algorithms Rendering (computer graphics)

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SCIRun/BioPSE: integrated problem solving environment for bioelectric field problems and visualization

SCIRun/BioPSE: integrated problem solving environment for bi...

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IEEE International Symposium on Biomedical Imaging

作者： R.S. MacLeod O.M. Weinstein J. Davison de St Germain D.H. Brooks C.R. Johnson S.G. Parker Scientific Computing and Imaging Institute University of Utah Salt Lake UT USA Department of Electrical and Computer Engineering Northeastern University Boston MA USA Center for Bioelectric Field Modeling Simulation and Visualization NIH/NCRR

SCIRun is a general purpose problem solving environment that seeks to integrate the steps of preparing, executing, and visualizing simulations of physical and biological systems. The implementation of SCIRun is by means of an interactive dataflow network consisting of modules and data pipes exposed as a visual programming language. SCIRun also contains specific modules for bioelectric field simulations and visualizations and the combination of SCIRun with this package is known as BioPSE (***/software/biopse). This software has been in the public domain since 2000 and in that time we have developed strategies for software development, engineering, testing, documentation, and training. We have also continued to expand the scope of the SCIRun/BioPSE package not only through our own codes but by constructing bridges to other systems, both open source and proprietary. We have also created a repository for relevant sample networks and datasets with the aim of allowing diverse groups to test and evaluate algorithms using identical data and to share their results with the community for comparison of performance and accuracy. We present here a summary of the software system and describe specific experiences and conclusions with regard to creating and managing a large open source software project carried out within a university setting.

关键词： Biopsy Problem-solving Bioelectric phenomena Data visualization Biological system modeling Packaging Biological systems Computer languages Software packages Programming

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Tele-Immersive Collaboration Using High-Resolution Video in Tiled Displays Environment

Tele-Immersive Collaboration Using High-Resolution Video in ...

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International Conference on Advanced Information Networking and Applications Workshops (AINAW)

作者： Yasuo Ebara Nobuyuki Kukimoto Jason Leigh Koji Koyamada Academic Center for Computing and Media Studies Kyoto University Kyoto Japan Department of Informatics Tohwa University Fukuoka Japan Electronic Visualization Laboratory University of Illinois Chicago IL USA Center for the Promotion of Excellence in Higher Education Kyoto University Kyoto Japan

In tele-communication via WAN, the existence of co- researchers by transmission of a video in real scene is important in order to realize high-presence, and its display by the large-scale screen is effective. However, the video image by wide-area display using a projector and large screen is low-resolution, and sufficient presence is not obtained. In this paper, we constructed the scalable tiled displays environment by two or more LCD panels and tried to display a high-resolution video image on the large-scale display. Moreover, we located an small IEEE1394 camera at the center of tiled displays, and discussed the possibility of remote communication which eye-to-eye contact can realize with each other. From these results, we have showed that the existence of participant and ambiance in remote place realized to display in high-presence on local tiled displays environment, and high-resolution display of hand-written characters on tiled displays have become clearer when compared to DV stream on plasma display. Moreover, we have examined that user's gaze was tendency to face front for tiled displays in the case of center position.

关键词： Collaboration Large screen displays Liquid crystal displays Plasma displays Videoconference Large-scale systems Cameras Computer displays Layout Internet

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Learning orbital dynamics of binary black hole systems from gravitational wave measurements

arXiv

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arXiv 2021年

作者： Keith, Brendan Khadse, Akshay Field, Scott E. Brown University United States Department of Physics and Astronomy The University of Mississippi UniversityMS38677 United States Department of Mathematics Center for Scientific Computing and Visualization Research University of Massachusetts DartmouthMA02747 United States

We introduce a gravitational waveform inversion strategy that discovers mechanical models of binary black hole (BBH) systems. We show that only a single time series of (possibly noisy) waveform data is necessary to construct the equations of motion for a BBH system. Starting with a class of universal differential equations parameterized by feed-forward neural networks, our strategy involves the construction of a space of plausible mechanical models and a physics-informed constrained optimization within that space to minimize the waveform error. We apply our method to various BBH systems including extreme and comparable mass ratio systems in eccentric and non-eccentric orbits. We show that the resulting differential equations apply to time durations longer than the training interval, and relativistic effects, such as perihelion precession, radiation reaction, and orbital plunge, are automatically accounted for. The methods outlined here provide a new, data-driven approach to studying the dynamics of binary black hole systems. Copyright © 2021, The Authors. All rights reserved.

关键词： Constrained optimization

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Maximizing adaptivity in hierarchical topological models

Maximizing adaptivity in hierarchical topological models

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International Conference on Shape Modeling and Applications

作者： P.-T. Bremer V. Pascucci B. Hamann Department of Computer Science University of Illinois Urbana-Champaign USA Lawrence Livermore National Laboratory Center for Applied Scientific Computing USA Institute for Data Analysis and Visualization Department of Computer Science University of California Davis USA

We present an approach to hierarchically encode the topology of functions over triangulated surfaces. Its Morse-Smale complex, a well known structure in computational topology, describes the topology of a function. Following concepts of Morse theory, a Morse-Smale complex (and therefore a function's topology) can be simplified by successively canceling pairs of critical points. We demonstrate how cancellations can be effectively encoded to produce a highly adaptive topology-based multi-resolution representation of a given function. Contrary to the approach, we avoid encoding the complete complex in a traditional mesh hierarchy. Instead, the information is split into a new structure we call a cancellation forest and a traditional dependency graph. The combination of this new structure with a traditional mesh hierarchy proofs to be significantly more flexible than the one previously reported. In particular, we can create hierarchies that are guaranteed to be of logarithmic height.

关键词： Topology Data visualization Data analysis Computer science Encoding Level set Shape Scientific computing Laboratories Transfer functions

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Coupling of Length Scales: Hybrid Molecular Dynamics and Finite Element Approach for Multiscale Nanodevice Simulations

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MRS Online Proceedings Library 2011年第1期653卷 1-6页

作者： Elefterios Lidorikis Martina E. Bachlechner Rajiv K. Kalia George Z. Voyiadjis Aiichiro Nakano Priya Vashishta Concurrent Computing Laboratory for Materials Simulations and Biological Computation & Visualization Center Department of Physics & Astronomy and Department of Computer Science Louisiana State University Baton Rouge USA Advanced Computational Solid Mechanics Laboratory Department of Civil and Environmental Engineering Louisiana State University Baton Rouge USA

A hybrid molecular-dynamics/finite-element simulation scheme is applied to describe multiscale phenomena in nanodevices. The quality of both static and dynamic coupling between atomistic and continuum regions is studied. The hybrid scheme is used for the Si/Si3N4 interface problem (static coupling), and for the projectile impact on Si problem (dynamic coupling). Excellent agreement is found between hybrid and full molecular dynamics simulation results in the static case, and no wave reflections are found at the atomistic/continuum hand-shake in the dynamic case. The hybrid scheme is thus validated a powerful and cost effective method for performing multiscale simulations of nanodevices.

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Mode coupling mechanism for late-time Kerr tails

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Physical Review D 2014年第4期89卷 044037-044037页

作者： Lior M. Burko Gaurav Khanna Department of Physics Chemistry and Mathematics Alabama A&M University Normal Alabama 35762 USA Theiss Research La Jolla California 92037 USA Department of Physics and Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth North Dartmouth Massachusetts 02747 USA

We consider the decay rate for scalar fields in Kerr spacetime. We consider pure initial (azimuthal) multipoles ℓ′ with respect to the class that includes Boyer-Lindquist coordinates, and focus attention on the decay rate of the multipole ℓ. We use an iterative method proposed by Gleiser, Price, and Pullin, and identify the mode-coupling mechanism through the iterations in powers of the square of the Kerr black hole’s specific angular momentum that gives rise to a decay rate formula recently proposed by Zenginoğlu, Khanna, and Burko. Modes ℓ may be excited through different channels, each leading to its own decay rate. The asymptotic decay rate of the mode ℓ is the slowest of the decay rate of the various channels. In some cases, more than one channel leads to the same decay rate, and then the amplitude of the mode is the sum of the amplitudes of the partial fields generated by the individual channels. We also show that one may identify the asymptotically dominant channel of mode excitations and obtain approximate results for the mode of interest by studying the dominant channel. The results of the dominant channel approximation approach the full-mode results at late times, and their difference approaches zero quadratically in inverse time.

关键词： DECAY rates (Radioactivity) SCALAR field theory BLACK holes (Astronomy) ANGULAR momentum (Nuclear physics) KERR black holes

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Impact of subdominant modes on the interpretation of gravitational-wave signals from heavy binary black hole systems

arXiv

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arXiv 2019年

作者： Shaik, Feroz H. Lange, Jacob Field, Scott E. O'Shaughnessy, Richard Varma, Vijay Kidder, Lawrence E. Pfeiffer, Harald P. Wysocki, Daniel Department of Physics Department of Mathematics Center for Scientific Computing & Visualization Research University of Massachusetts Dartmouth DartmouthMA02747 United States Center for Computational Relativity and Gravitation Rochester Institute of Technology RochesterNY14623 United States Department of Mathematics Center for Scientific Computing & Visualization Research University of Massachusetts Dartmouth DartmouthMA02747 United States Theoretical Astrophysics California Institute of Technology PasadenaCA91125 United States Cornell Center for Astrophysics and Planetary Science Cornell University IthacaNY14853 United States Am Mühlenberg 1 Potsdam14476 Germany

Over the past year, a handful of new gravitational wave models have been developed to include multiple harmonic modes thereby enabling for the first time fully Bayesian inference studies including higher modes to be performed. Using one recently-developed numerical relativity surrogate model, NRHybSur3dq8, we investigate the importance of higher modes on parameter inference of coalescing massive binary black holes. We focus on examples relevant to the current three-detector network of observatories, with detector-frame masses and signal amplitudes consistent with plausible candidates for the next few observing runs. We show that for such systems the higher mode content will be important for interpreting coalescing binary black holes, reducing systematic bias, and computing properties of the remnant object. For asymmetric binaries with mass ratios q > 1, higher modes are critical, and their omission usually produces substantial parameter biases. Even for comparable-mass binaries and at low signal amplitude, the omission of higher modes can influence posterior probability distributions. We discuss the impact of our results on source population inference and self-consistency tests of general relativity. Copyright © 2019, The Authors. All rights reserved.

关键词： Stars

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Improved analysis of GW190412 with a precessing numerical relativity surrogate waveform model

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Physical Review D 2021年第10期103卷 104027-104027页

作者： Tousif Islam Scott E. Field Carl-Johan Haster Rory Smith Department of Physics and Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth Massachusetts 02747 USA Department of Mathematics and Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth Massachusetts 02747 USA LIGO Laboratory Massachusetts Institute of Technology 185 Albany St Cambridge Massachusetts 02139 USA Department of Physics and Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Ave Cambridge Massachusetts 02139 USA School of Physics and Astronomy Monash University Vic 3800 Australia OzGrav: The ARC Centre of Excellence for Gravitational Wave Discovery Clayton VIC 3800 Australia

The recent observation of GW190412, the first high-mass ratio binary black hole merger, by the LIGO-Virgo Collaboration (LVC) provides a unique opportunity to probe the impact of subdominant harmonics and precession effects encoded in a gravitational wave signal. We present refined estimates of source parameters for GW190412 using nrsur7dq4, a recently developed numerical relativity waveform surrogate model that includes all ℓ≤4 spin-weighted spherical harmonic modes as well as the full physical effects of precession. We compare our results with two different variants of phenomenological precessing binary black hole waveform models, imrphenompv3hm and imrphenomxphm, as well as to the LVC results. Our results are broadly in agreement with imrphenomxphm results and the reported LVC analysis compiled with the seobnrv4phm waveform model, but in tension with imrphenompv3hm. Using the nrsur7dq4 model, we provide a tighter constraint on the mass ratio (0.26−0.06+0.08) as compared to the LVC estimate of 0.28−0.07+0.13 (both reported as median values with 90% credible intervals). We also constrain the binary to be more face on, and find a broader posterior for the spin precession parameter. We further find that even though ℓ=4 harmonic modes have negligible signal-to-noise ratio, omission of these modes will influence the estimated posterior distribution of several source parameters including chirp mass, effective inspiral spin, luminosity distance, and inclination. We also find that commonly used model approximations, such as neglecting the asymmetric modes (which are generically excited during precession), have negligible impact on parameter recovery for moderate signal-to-noise ratio events similar to GW190412.

关键词： Gravitational waves

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Remnant black hole properties from numerical-relativity-informed perturbation theory and implications for waveform modeling

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Physical Review D 2023年第6期108卷 064048-064048页

作者： Tousif Islam Scott E. Field Gaurav Khanna Department of Physics University of Massachusetts Dartmouth Massachusetts 02747 USA Department of Mathematics University of Massachusetts Dartmouth Massachusetts 02747 USA Center for Scientific Computing and Visualization Research University of Massachusetts Dartmouth Massachusetts 02747 USA Department of Physics and Center for Computational Research University of Rhode Island Kingston Rhode Island 02881 USA

During binary black hole (BBH) mergers, energy and momenta are carried away from the binary system as gravitational radiation. Access to the radiated energy and momenta allows us to predict the properties of the remnant black hole. We develop a Python package gw_remnant to extract the remnant mass, remnant spin, peak luminosity, and the final kick imparted on the remnant black hole from the gravitational waveforms. Using this package, we extract the remnant properties of the final black hole in case of nonspinning BBH mergers with mass ratios ranging from q=2.5 to q=1000 using waveform modes generated from BHPTNRSur1dq1e4, a recently developed numerical-relativity-informed surrogate model based on the black hole perturbation theory framework. We validate our results against the remnant properties estimated from numerical relativity (NR) surrogate models in the comparable mass-ratio regime and against recently available high-mass-ratio NR simulations at q=[15,32,64]. We find that our remnant property estimates computed from fluxes at future null infinity closely match the estimates obtained from the NR surrogate model of apparent horizon data. Using Gaussian process regression fitting methods, we train a surrogate model, BHPTNR_Remnant, for the properties of the remnant black hole arising from BBH mergers with mass ratios from q=2.5 to q=1000. Finally, we discuss potential improvements in the BHPTNRSur1dq1e4 waveform model when including remnant information. We make both the gw_remnant and BHPTNR_Remnant packages publicly available.

关键词： General relativity Gravitational waves

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