16,365 research outputs found
Nonlinear spin-polarized transport through a ferromagnetic domain wall
A domain wall separating two oppositely magnetized regions in a ferromagnetic
semiconductor exhibits, under appropriate conditions, strongly nonlinear I-V
characteristics similar to those of a p-n diode. We study these characteristics
as functions of wall width and temperature. As the width increases or the
temperature decreases, direct tunneling between the majority spin bands
decreases the effectiveness of the diode. This has important implications for
the zero-field quenched resistance of magnetic semiconductors and for the
design of a recently proposed spin transistor.Comment: 5 pages, 3 figure
Current induced distortion of a magnetic domain wall
We consider the spin torque induced by a current flowing ballistically
through a magnetic domain wall. In addition to a global pressure in the
direction of the electronic flow, the torque has an internal structure of
comparable magnitude due to the precession of the electrons' spins at the
"Larmor" frequency. As a result, the profile of the domain wall is expected to
get distorted by the current and acquires a periodic sur-structure.Comment: 5 pages, 3 eps figure
Using Self-Adaptive Evolutionary Algorithms to Evolve Dynamism-Oriented Maps for a Real Time Strategy Game
9th International Conference on Large Scale Scientific Computations. The final publication is available at link.springer.comThis work presents a procedural content generation system that uses an evolutionary algorithm in order to generate interesting maps for a real-time strategy game, called Planet Wars. Interestingness is here captured by the dynamism of games (i.e., the extent to which they are action-packed). We consider two different approaches to measure the dynamism of the games resulting from these generated maps, one based on fluctuations in the resources controlled by either player and another one based on their confrontations. Both approaches rely on conducting several games on the map under scrutiny using top artificial intelligence (AI) bots for the game. Statistic gathered during these games are then transferred to a fuzzy system that determines the map's level of dynamism. We use an evolutionary algorithm featuring self-adaptation of mutation parameters and variable-length chromosomes (which means maps of different sizes) to produce increasingly dynamic maps.TIN2011-28627-C04-01, P10-TIC-608
Slow light in molecular aggregates nanofilms
We study slow light performance of molecular aggregates arranged in nanofilms
by means of coherent population oscillations (CPO). The molecular cooperative
behavior inside the aggregate enhances the delay of input signals in the GHz
range in comparison with other CPO-based devices. Moreover, the problem of
residual absorption present in CPO processes, is removed. We also propose an
optical switch between different delays by exploiting the optical bistability
of these aggregates.Comment: 4 pages, 4 figure
A method of open cluster membership determination
A new method for the determination of open cluster membership based on a
cumulative effect is proposed. In the field of a plate the relative x and y
coordinate positions of each star with respect to all the other stars are
added. The procedure is carried out for two epochs t_1 and t_2 separately, then
one sum is subtracted from another. For a field star the differences in its
relative coordinate positions of two epochs will be accumulated. For a cluster
star, on the contrary, the changes in relative positions of cluster members at
t_1 and t_2 will be very small. On the histogram of sums the cluster stars will
gather to the left of the diagram, while the field stars will form a tail to
the right. The procedure allows us to efficiently discriminate one group from
another. The greater the distance between t_1 and t_2 and the more cluster
stars present, the greater is the effect. The accumulation method does not
require reference stars, determination of centroids and modelling the
distribution of field stars, necessary in traditional methods. By the proposed
method 240 open clusters have been processed, including stars up to m<13. The
membership probabilities have been calculated and compared to those obtained by
the most commonly used Vasilevskis-Sanders method. The similarity of the
results acquired the two different approaches is satisfactory for the majority
of clusters.Comment: 10 pages, 5 figure
Snake orbits and related magnetic edge states
We study the electron motion near magnetic field steps at which the strength
and/or sign of the magnetic field changes. The energy spectrum for such systems
is found and the electron states (bound and scattered) are compared with their
corresponding classical paths. Several classical properties as the velocity
parallel to the edge, the oscillation frequency perpendicular to the edge and
the extent of the states are compared with their quantum mechanical
counterpart. A class of magnetic edge states is found which do not have a
classical counterpart.Comment: 8 pages, 10 figure
Rotating Superconductors and the London Moment: Thermodynamics versus Microscopics
Comparing various microscopic theories of rotating superconductors to the
conclusions of thermodynamic considerations, we traced their marked difference
to the question of how some thermodynamic quantities (the electrostatic and
chemical potentials) are related to more microscopic ones: The electron's the
work function, mean-field potential and Fermi energy -- certainly a question of
general import.
After the correct identification is established, the relativistic correction
for the London Moment is shown to vanish, with the obvious contribution from
the Fermi velocity being compensated by other contributions such as
electrostatics and interactions.Comment: 23 pages 4 fi
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The role of consumption in material reduction opportunities: the impact of product lifetime in supplying the UK steel demand
Most of the products purchased in the UK are manufactured in other countries. As a result, worldwide greenhouse gases (GHG) emissions released to manufacture all products purchased in the UK are significantly higher than the UK territorial emissions. More than one half of global industrial emissions result from the use of steel, cement, paper, plastics, and aluminium. In this paper, the UK consumption of products that embody these five materials is estimated. For steel, which is the most widely used among these five materials, consumption and accumulation patterns are examined across four product categories. The impact of steel product lifetime extension is examined for the UK as one option for material demand reduction at the consumption stage of the supply chain. Different levels of steel product lifetimes are simulated for the UK in 2050 and their impacts are examined in terms of UK steel production, implicit steel imports, and global carbon dioxide emissions. Steel product lifetime extension promotes a reduction in the need for steel imports, by reducing the demand for new steel, which leads to lower carbon dioxide emissions required to supply the UK steel demand. The results demonstrate the criticality of a focus on the consumption stage, since any interventions made towards demand reduction of end-use goods leads to material reduction across the supply chain
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