57,514 research outputs found
Sonic simulation of the SPS power beam
A Satellite Power System Microwave Transmission Simulator is described. The simulator generates and transmits a beam audible sound energy which is mathematically similar to the microwave beam which would transmit energy to Earth from a Solar Power Satellite. This allows areas such as power beam formation to be studied in a laboratory environment
Atomic Quantum Simulation of U(N) and SU(N) Non-Abelian Lattice Gauge Theories
Using ultracold alkaline-earth atoms in optical lattices, we construct a
quantum simulator for U(N) and SU(N) lattice gauge theories with fermionic
matter based on quantum link models. These systems share qualitative features
with QCD, including chiral symmetry breaking and restoration at non-zero
temperature or baryon density. Unlike classical simulations, a quantum
simulator does not suffer from sign problems and can address the corresponding
chiral dynamics in real time.Comment: 12 pages, 5 figures. Main text plus one basic introduction to the
topic and one supplementary material on implementation. Final versio
A pilot in the loop analysis of helicopter acceleration/deceleration maneuvers
Helicopter flight acceleration/deceleration maneuvers are quantified and put to use in the fields of handling qualities, flight training and evaluation of simulator fidelity. The three specific cases include the normal speed change maneuver, the nap-of-the-Earth dash/quickstop, and the decelerating approach to hover. All of these maneuvers share common generic features in terms of pilot adaptation and mathematical description; yet each differs in terms of the essential feedback loop structure, implications for handling qualities requirements, and simulator fidelity criteria
Use of the tilt cue in a simulated heading tracking task
The task was performed with subjects using visual-only cues and combined visual and roll-axis motion cues. Half of the experimental trials were conducted with the simulator rotating about the horizontal axis; to suppress the tilt cue, the remaining trials were conducted with the simulator cab tilted 90 deg so that roll-axis motions were about earth vertical. The presence of the tilt cue allowed a substantial and statistically significant reduction in performance scores. When the tilt cue was suppressed, the availability of motion cues did not result in significant performance improvement. These effects were accounted for by the optimal-control pilot/vehicle model, wherein the presence or absence of various motion cues was represented by appropriate definition of the perceptual quantities assumed to be used by the human operator
OMV mission simulator
The Orbital Maneuvering Vehicle (OMV) will be remotely piloted during rendezvous, docking, or proximity operations with target spacecraft from a ground control console (GCC). The real-time mission simulator and graphics being used to design a console pilot-machine interface are discussed. A real-time orbital dynamics simulator drives the visual displays. The dynamics simulator includes a J2 oblate earth gravity model and a generalized 1962 rotating atmospheric and drag model. The simulator also provides a variable-length communication delay to represent use of the Tracking and Data Relay Satellite System (TDRSS) and NASA Communications (NASCOM). Input parameter files determine the graphics display. This feature allows rapid prototyping since displays can be easily modified from pilot recommendations. A series of pilot reviews are being held to determine an effective pilot-machine interface. Pilots fly missions with nominal to 3-sigma dispersions in translational or rotational axes. Console dimensions, switch type and layout, hand controllers, and graphic interfaces are evaluated by the pilots and the GCC simulator is modified for subsequent runs. Initial results indicate a pilot preference for analog versus digital displays and for two 3-degree-of-freedom hand controllers
Quantum Simulation of Non-Abelian Lattice Gauge Theories
We use quantum link models to construct a quantum simulator for U(N) and
SU(N) lattice gauge theories. These models replace Wilson's classical link
variables by quantum link operators, reducing the link Hilbert space to a
finite number of dimensions. We show how to embody these quantum link models
with fermionic matter with ultracold alkaline-earth atoms using optical
lattices. Unlike classical simulations, a quantum simulator does not suffer
from sign problems and can thus address the corresponding dynamics in real
time. Using exact diagonalization results we show that these systems share
qualitative features with QCD, including chiral symmetry breaking and we study
the expansion of a chirally restored region in space in real time.Comment: 7 pages, 3 figures, 31st International Symposium on Lattice Field
Theory LATTICE 2013, July 29 - August 3, 2013, Mainz, German
Theoretical Reflectance Spectra of Earth-Like Planets through Their Evolutions: Impact of Clouds on the Detectability of Oxygen, Water, and Methane with Future Direct Imaging Missions
In the near-future, atmospheric characterization of Earth-like planets in the
habitable zone will become possible via reflectance spectroscopy with future
telescopes such as the proposed LUVOIR and HabEx missions. While previous
studies have considered the effect of clouds on the reflectance spectra of
Earth-like planets, the molecular detectability considering a wide range of
cloud properties has not been previously explored in detail. In this study, we
explore the effect of cloud altitude and coverage on the reflectance spectra of
Earth-like planets at different geological epochs and examine the detectability
of , , and with test parameters
for the future mission concept, LUVOIR, using a coronagraph noise simulator
previously designed for WFIRST-AFTA. Considering an Earth-like planet located
at 5 pc away, we have found that for the proposed LUVOIR telescope, the
detection of the A-band feature (0.76 m) will take
approximately 100, 30, and 10 hours for the majority of the cloud parameter
space modeled for the atmospheres with 10\%, 50\%, and 100\% of modern Earth
O abundances, respectively. Especially, for {the case of \%} of
modern Earth O abundance, the feature will be detectable with integration
time hours as long as there are lower altitude ( km)
clouds with a global coverage of . For the 1\% of modern Earth
abundance case, however, it will take more than 100 hours for
all the cloud parameters we modeled.Comment: 16 pages, 10 figures, accepted for publication in A
Geodynamo and mantle convection simulations on the Earth Simulator using the Yin-Yang grid
We have developed finite difference codes based on the Yin-Yang grid for the
geodynamo simulation and the mantle convection simulation. The Yin-Yang grid is
a kind of spherical overset grid that is composed of two identical component
grids. The intrinsic simplicity of the mesh configuration of the Yin-Yang grid
enables us to develop highly optimized simulation codes on massively parallel
supercomputers. The Yin-Yang geodynamo code has achieved 15.2 Tflops with 4096
processors on the Earth Simulator. This represents 46% of the theoretical peak
performance. The Yin-Yang mantle code has enabled us to carry out mantle
convection simulations in realistic regimes with a Rayleigh number of
including strongly temperature-dependent viscosity with spatial contrast up to
.Comment: Plenary talk at SciDAC 200
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