15,795 research outputs found
Levels of abstraction in human supervisory control teams
This paper aims to report a study into the levels of abstraction hierarchy (LOAH) in two energy distribution teams. The original proposition for the LOAH was that it depicted five levels of system representation, working from functional purpose through to physical form to determine causes of a malfunction, or from physical form to functional purpose to determine the purpose of system function. The LOAH has been widely used throughout human supervisory control research to explain individual behaviour. The research seeks to focus on the application the LOAH to human supervisory control teams in semi-automated “intelligent” systems
Modulated phases in a three-dimensional Maier-Saupe model with competing interactions
This work is dedicated to the study of the discrete version of the Maier-Saupe model in the presence of competing interactions. The competition between interactions favoring different orientational ordering produces a rich phase diagram including modulated phases. Using a mean-field approach and Monte Carlo simulations, we show that the proposed model exhibits isotropic and nematic phases and also a series of modulated phases that meet at a multicritical point, a Lifshitz point. Though the Monte Carlo and mean-field phase diagrams show some quantitative disagreements, the Monte Carlo simulations corroborate the general behavior found within the mean-field approximation.We thank P. Gomes, R. Kaul, G. Landi, M. Oliveira, R. Oliveira, and S. Salinas for useful discussions and suggestions. P.F.B. was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and the Condensed Matter Theory Visitors Program at Boston University. N.X. and A.W.S. were funded in part by the NSF under Grant No. DMR-1410126. Some of the calculations were carried out on Boston University's Shared Computing Cluster. (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); Condensed Matter Theory Visitors Program at Boston University; DMR-1410126 - NSF)Accepted manuscrip
Dual time scales in simulated annealing of a two-dimensional Ising spin glass
We apply a generalized Kibble-Zurek out-of-equilibrium scaling ansatz to
simulated annealing when approaching the spin-glass transition at temperature
of the two-dimensional Ising model with random couplings.
Analyzing the spin-glass order parameter and the excess energy as functions of
the system size and the annealing velocity in Monte Carlo simulations with
Metropolis dynamics, we find scaling where the energy relaxes slower than the
spin-glass order parameter, i.e., there are two different dynamic exponents.
The values of the exponents relating the relaxation time scales to the system
length, , are for the relaxation of the order
parameter and for the energy relaxation. We argue that the
behavior with dual time scales arises as a consequence of the entropy-driven
ordering mechanism within droplet theory. We point out that the dynamic
exponents found here for simulated annealing are different from the
temperature-dependent equilibrium dynamic exponent , for which
previous studies have found a divergent behavior; . Thus, our study shows that, within Metropolis dynamics, it is easier
to relax the system to one of its degenerate ground states than to migrate at
low temperatures between regions of the configuration space surrounding
different ground states. In a more general context of optimization, our study
provides an example of robust dense-region solutions for which the excess
energy (the conventional cost function) may not be the best measure of success.Comment: 13 pages, 16 figure
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