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Institution

Sandia National Laboratories

FacilityLivermore, California, United States
About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Combustion. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.


Papers
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Journal ArticleDOI
TL;DR: Using extensive molecular dynamics simulations of an equilibrium, glass-forming Lennard-Jones mixture, it is shown that spatial correlations exist among particles undergoing extremely large ("mobile") or extremely small ("immobile") displacements over a suitably chosen time interval.
Abstract: Using extensive molecular dynamics simulations of an equilibrium, glass-forming Lennard-Jones mixture, we characterize in detail the local atomic motions. We show that spatial correlations exist among particles undergoing extremely large (``mobile'') or extremely small (``immobile'') displacements over a suitably chosen time interval. The immobile particles form the cores of relatively compact clusters, while the mobile particles move cooperatively and form quasi-one-dimensional, stringlike clusters. The strength and length scale of the correlations between mobile particles are found to grow strongly with decreasing temperature, and the mean cluster size appears to diverge near the mode-coupling critical temperature. We show that these correlations in the particle displacements are related to equilibrium fluctuations in the local potential energy and local composition.

443 citations

Journal ArticleDOI
TL;DR: The CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach as discussed by the authors, which views generation and associated loads as a subsystem or a "microgrid" and provides uninterruptible power-supply services, such as disconnecting from the utility during large events (i.e., faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards.
Abstract: The CERTS Microgrid concept captures the emerging potential of distributed generation using a system approach. CERTS views generation and associated loads as a subsystem or a “microgrid.” The sources can operate in parallel to the grid or can operate in island, providing uninterruptible power-supply services. The system can disconnect from the utility during large events (i.e., faults, voltage collapses), but may also intentionally disconnect when the quality of power from the grid falls below certain standards. CERTS Microgrid concepts were demonstrated at a full-scale test bed built near Columbus, OH, and operated by American Electric Power. The testing fully confirmed earlier research that had been conducted initially through analytical simulations, then through laboratory emulations, and finally through factory acceptance testing of individual microgrid components. The islanding and resynchronization method met all Institute of Electrical and Electronics Engineers Standard 1547 and power-quality requirements. The electrical protection system was able to distinguish between normal and faulted operation. The controls were found to be robust under all conditions, including difficult motor starts and high impedance faults.

442 citations

Journal ArticleDOI
TL;DR: In this article, a weight-based method for collapsing multi-year data into a single matrix was proposed, which can be extended to bipartite graphs and moreover approximated in a scalable way using a truncated singular value decomposition.
Abstract: The data in many disciplines such as social networks, Web analysis, etc. is link-based, and the link structure can be exploited for many different data mining tasks. In this article, we consider the problem of temporal link prediction: Given link data for times 1 through T, can we predict the links at time T + 1? If our data has underlying periodic structure, can we predict out even further in time, i.e., links at time T + 2, T + 3, etc.? In this article, we consider bipartite graphs that evolve over time and consider matrix- and tensor-based methods for predicting future links. We present a weight-based method for collapsing multiyear data into a single matrix. We show how the well-known Katz method for link prediction can be extended to bipartite graphs and, moreover, approximated in a scalable way using a truncated singular value decomposition. Using a CANDECOMP/PARAFAC tensor decomposition of the data, we illustrate the usefulness of exploiting the natural three-dimensional structure of temporal link data. Through several numerical experiments, we demonstrate that both matrix- and tensor-based techniques are effective for temporal link prediction despite the inherent difficulty of the problem. Additionally, we show that tensor-based techniques are particularly effective for temporal data with varying periodic patterns.

441 citations

Journal ArticleDOI
TL;DR: In this paper, an embedded-atom method (EAM) potential was constructed for Ag by fitting to experimental and first-principles data, which accurately reproduces the lattice parameter, cohesive energy, elastic constants, phonon frequencies, thermal expansion, lattice-defect energies, as well as energies of alternate structures of Ag.
Abstract: A new embedded-atom method (EAM) potential has been constructed for Ag by fitting to experimental and first-principles data. The potential accurately reproduces the lattice parameter, cohesive energy, elastic constants, phonon frequencies, thermal expansion, lattice-defect energies, as well as energies of alternate structures of Ag. Combining this potential with an existing EAM potential for Cu, a binary potential set for the Cu–Ag system has been constructed by fitting the cross-interaction function to first-principles energies of imaginary Cu–Ag compounds. Although properties used in the fit refer to the 0 K temperature (except for thermal expansion factors of pure Cu and Ag) and do not include liquid configurations, the potentials demonstrate good transferability to high-temperature properties. In particular, the entire Cu–Ag phase diagram calculated with the new potentials in conjunction with Monte Carlo simulations is in satisfactory agreement with experiment. This agreement suggests that EAM potentials accurately fit to 0 K properties can be capable of correctly predicting simple phase diagrams. Possible applications of the new potential set are outlined.

438 citations

Journal ArticleDOI
TL;DR: In this article, Hardy's stress expression is evaluated at a fixed spatial point and uses a localization function to dictate how nearby atoms contribute to the stress at that point; thereby performing a local spatial averaging.
Abstract: Atomistic simulation is a useful method for studying material science phenomena Examination of the state of a simulated material and the determination of its mechanical properties is accomplished by inspecting the stress field within the material However, stress is inherently a continuum concept and has been proven difficult to define in a physically reasonable manner at the atomic scale In this paper, an expression for continuum mechanical stress in atomistic systems derived by Hardy is compared with the expression for atomic stress taken from the virial theorem Hardy's stress expression is evaluated at a fixed spatial point and uses a localization function to dictate how nearby atoms contribute to the stress at that point; thereby performing a local spatial averaging For systems subjected to deformation, finite temperature, or both, the Hardy description of stress as a function of increasing characteristic volume displays a quicker convergence to values expected from continuum theory than volume averages of the local virial stress Results are presented on extending Hardy's spatial averaging technique to include temporal averaging for finite temperature systems Finally, the behaviour of Hardy's expression near a free surface is examined, and is found to be consistent with the mechanical definition for stress

437 citations


Authors

Showing all 21652 results

NameH-indexPapersCitations
Lily Yeh Jan16246773655
Jongmin Lee1502257134772
Jun Liu13861677099
Gerbrand Ceder13768276398
Kevin M. Smith114171178470
Henry F. Schaefer111161168695
Thomas Bein10967742800
David Chandler10742452396
Stephen J. Pearton104191358669
Harold G. Craighead10156940357
Edward Ott10166944649
S. Das Sarma10095158803
Richard M. Crooks9741931105
David W. Murray9769943372
Alán Aspuru-Guzik9762844939
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202340
2022245
20211,510
20201,580
20191,535
20181,514