21,815 research outputs found
Multicanonical Spin Glass Simulations
We report a Monte Carlo simulation of the Edwards-Anderson spin glass
model within the recently introduced multicanonical ensemble. Replica on
lattices of size up to are investigated. Once a true groundstate
is found, we are able to give a lower bound on the number of statistically
independent groundstates sampled. Temperature dependence of the energy, entropy
and other quantities of interest are easily calculable. In particular we report
the groundstate results. Computations involving the spin glass order parameter
are more tedious. Our data indicate that the large increase of the
ergodicity time is reduced to an approximately power law. Altogether the
results suggest that the multicanonical ensemble improves the situation of
simulations for spin glasses and other systems which have to cope with similar
problems of conflicting constraints.Comment: 24 page
Measuring Workload Differences Between Short-term Memory and Long-term Memory Scenarios in a Simulated Flight Environment
Four highly experienced Air Force pilots each flew four simulated flight scenarios. Two scenarios required a great deal of aircraft maneuvering. The other two scenarios involved less maneuvering, but required remembering a number of items. All scenarios were designed to be equaly challenging. Pilot's Subjective Ratings for Activity-level, Complexity, Difficulty, Stress, and Workload were higher for the manuevering scenarios than the memory scenarios. At a moderate workload level, keeping the pilots active resulted in better aircraft control. When required to monitor and remember items, aircraft control tended to decrease. Pilots tended to weigh information about the spatial positioning and performance of their aircraft more heavily than other items
Exchange Monte Carlo Method and Application to Spin Glass Simulations
We propose an efficient Monte Carlo algorithm for simulating a
``hardly-relaxing" system, in which many replicas with different temperatures
are simultaneously simulated and a virtual process exchanging configurations of
these replica is introduced. This exchange process is expected to let the
system at low temperatures escape from a local minimum. By using this algorithm
the three-dimensional Ising spin glass model is studied. The ergodicity
time in this method is found much smaller than that of the multi-canonical
method. In particular the time correlation function almost follows an
exponential decay whose relaxation time is comparable to the ergodicity time at
low temperatures. It suggests that the system relaxes very rapidly through the
exchange process even in the low temperature phase.Comment: 10 pages + uuencoded 5 Postscript figures, REVTe
Recent Results of Multimagnetical Simulations of the Ising Model
To investigate order-order interfaces, we perform multimagnetical Monte Carlo
simulations of the and Ising model. Stringent tests of the numerical
methods are performed by reproducing with high precision exact results. In
the physically more interesting case we estimate the amplitude of
the critical interfacial tension.Comment: talk presented at the workshop "Dynamics of First Order Phase
Transitions", Juelich June 1-3; FSU-SCRI-92C-87 preprint; 7 pages; sorry no
figures; needs vanilla.st
The impact of physical and mental tasks on pilot mental workoad
Seven instrument-rated pilots with a wide range of backgrounds and experience levels flew four different scenarios on a fixed-base simulator. The Baseline scenario was the simplest of the four and had few mental and physical tasks. An activity scenario had many physical but few mental tasks. The Planning scenario had few physical and many mental taks. A Combined scenario had high mental and physical task loads. The magnitude of each pilot's altitude and airspeed deviations was measured, subjective workload ratings were recorded, and the degree of pilot compliance with assigned memory/planning tasks was noted. Mental and physical performance was a strong function of the manual activity level, but not influenced by the mental task load. High manual task loads resulted in a large percentage of mental errors even under low mental task loads. Although all the pilots gave similar subjective ratings when the manual task load was high, subjective ratings showed greater individual differences with high mental task loads. Altitude or airspeed deviations and subjective ratings were most correlated when the total task load was very high. Although airspeed deviations, altitude deviations, and subjective workload ratings were similar for both low experience and high experience pilots, at very high total task loads, mental performance was much lower for the low experience pilots
Effect of time span and task load on pilot mental workload
Two sets of experiments were run to examine how the mental workload of a pilot might be measured. The effects of continuous manual control activity versus discrete assigned mental tasks (including the length of time between receiving an assignment and executing it) were examined. The first experiment evaluated the strengths and weaknesses of measuring mental workload with an objective perforamance (altitude deviations) and five subjective ratings (activity level, complexity, difficulty, stress, and workload). The second set of experiments built upon the first set by increasing workload intensities and adding another performance measure: airspeed deviation. The results are discussed for both low and high experience pilots
Effect of time span and task load on pilot mental workload
Two sets of simulations designed to examine how a pilot's mental workload is affected by continuous manual-control activity versus discrete mental tasks that included the length of time between receiving an assignment and executing it are described. The first experiment evaluated two types of measures: objective performance indicators and subjective ratings. Subjective ratings for the two missions were different, but the objective performance measures were similar. In the second experiments, workload levels were increased and a second performance measure was taken. Mental workload had no influence on either performance-based workload measure. Subjective ratings discriminated among the scenarios and correlated with performance measures for high-workload flights. The number of mental tasks performed did not influence error rates, although high manual workloads did increase errors
Isospectrality and heat content
We present examples of isospectral operators that do not have the same heat
content. Several of these examples are planar polygons that are isospectral for
the Laplace operator with Dirichlet boundary conditions. These include examples
with infinitely many components. Other planar examples have mixed Dirichlet and
Neumann boundary conditions. We also consider Schr\"{o}dinger operators acting
in with Dirichlet boundary conditions, and show that an abundance of
isospectral deformations do not preserve the heat content.Comment: 18 page
Multicanonical Study of the 3D Ising Spin Glass
We simulated the Edwards-Anderson Ising spin glass model in three dimensions
via the recently proposed multicanonical ensemble. Physical quantities such as
energy density, specific heat and entropy are evaluated at all temperatures. We
studied their finite size scaling, as well as the zero temperature limit to
explore the ground state properties.Comment: FSU-SCRI-92-121; 7 pages; sorry, no figures include
A Multicanonical Algorithm and the Surface Free Energy in SU(3) Pure Gauge Theory
We present a multicanonical algorithm for the SU(3) pure gauge theory at the
deconfinement phase transition. We measure the tunneling times for lattices of
size L^3x2 for L=8,10, and 12. In contrast to the canonical algorithm the
tunneling time increases only moderately with L. Finally, we determine the
interfacial free energy applying the multicanonical algorithm.Comment: 6 pages, HLRZ-92-3
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