The librational dynamics of deformable bodies

Approximative analysis on librational dynamics of deformable satellit

The librational dynamics of satellites

Librational dynamics of satellite

A domain-specific analysis system for examining nuclear reactor simulation data for light-water and sodium-cooled fast reactors

Building a new generation of fission reactors in the United States presents many technical and regulatory challenges. One important challenge is the need to share and present results from new high-fidelity, high-performance simulations in an easily usable way. Since modern multiscale, multi-physics simulations can generate petabytes of data, they will require the development of new techniques and methods to reduce the data to familiar quantities of interest (e.g., pin powers, temperatures) with a more reasonable resolution and size. Furthermore, some of the results from these simulations may be new quantities for which visualization and analysis techniques are not immediately available in the community and need to be developed. This paper describes a new system for managing high-performance simulation results in a domain-specific way that naturally exposes quantities of interest for light water and sodium-cooled fast reactors. It describes requirements to build such a system and the technical challenges faced in its development at all levels (simulation, user interface, etc.). An example comparing results from two different simulation suites for a single assembly in a light-water reactor is presented, along with a detailed discussion of the system's requirements and design.Comment: Article on NiCE's Reactor Analyzer. 23 pages. Keywords: modeling, simulation, analysis, visualization, input-outpu

Roving vehicle motion control Final report

Roving vehicle motion control for unmanned planetary and lunar exploratio

Roving vehicle motion control Quarterly report, 1 Mar. - 31 May 1967

System and subsystem requirements for remote control of roving space vehicle motio

REACLIBaLIVe! (REACLIB Rate Library Interactive Viewer): A Software Package for Graphical Analysis of Nuclear Reaction Rates for Astrophysics

Nucleosynthesis occurs in such diverse astrophysical phenomena as ordinary stars, like our own Sun, supernovae, novae, X-ray bursts, and the Big Bang. Large sets of nuclear reaction rates for hundreds of seed isotopes are utilized in simulations of these nucleosynthesis processes. A cross-platform, Java software package called REACLIB aLIVe! has been developed with intuitive graphical interfaces and interactive controls to produce custom one-dimensional plots of reaction rates. The points used for these plots are calculated from exponential fits whose parameters, along with other quantities, make up the REACLIB Nuclear Reaction Rate Library. The software offers nuclear astrophysicists the capability to rapidly display any of 8000 nuclear reactions in the library, as well as to add new reaction rates and compare them to ones in the library. The plots produced by the software may be exported in the postscript format, which is easily edited and incorporated into papers, presentations, and websites. The software is available over the World Wide Web or as a downloadable Java archive file

Axisymmetric Ab Initio Core-Collapse Supernova Simulations of 12-25 M_sol Stars

We present an overview of four ab initio axisymmetric core-collapse supernova simulations employing detailed spectral neutrino transport computed with our CHIMERA code and initiated from Woosley & Heger (2007) progenitors of mass 12, 15, 20, and 25 M_sol. All four models exhibit shock revival over \sim 200 ms (leading to the possibility of explosion), driven by neutrino energy deposition. Hydrodynamic instabilities that impart substantial asymmetries to the shock aid these revivals, with convection appearing first in the 12 M_sol model and the standing accretion shock instability (SASI) appearing first in the 25 M_sol model. Three of the models have developed pronounced prolate morphologies (the 20 M_sol model has remained approximately spherical). By 500 ms after bounce the mean shock radii in all four models exceed 3,000 km and the diagnostic explosion energies are 0.33, 0.66, 0.65, and 0.70 Bethe (B = $10^{51}$ ergs) for the 12, 15, 20, and 25 M_sol models, respectively, and are increasing. The three least massive of our models are already sufficiently energetic to completely unbind the envelopes of their progenitors (i.e., to explode), as evidenced by our best estimate of their explosion energies, which first become positive at 320, 380, and 440 ms after bounce. By 850 ms the 12 M_sol diagnostic explosion energy has saturated at 0.38 B, and our estimate for the final kinetic energy of the ejecta is \sim 0.3 B, which is comparable to observations for lower-mass progenitors.Comment: Accepted for publication in The Astrophysical Journal Letter