62,888 research outputs found
Using Monte Carlo Search With Data Aggregation to Improve Robot Soccer Policies
RoboCup soccer competitions are considered among the most challenging
multi-robot adversarial environments, due to their high dynamism and the
partial observability of the environment. In this paper we introduce a method
based on a combination of Monte Carlo search and data aggregation (MCSDA) to
adapt discrete-action soccer policies for a defender robot to the strategy of
the opponent team. By exploiting a simple representation of the domain, a
supervised learning algorithm is trained over an initial collection of data
consisting of several simulations of human expert policies. Monte Carlo policy
rollouts are then generated and aggregated to previous data to improve the
learned policy over multiple epochs and games. The proposed approach has been
extensively tested both on a soccer-dedicated simulator and on real robots.
Using this method, our learning robot soccer team achieves an improvement in
ball interceptions, as well as a reduction in the number of opponents' goals.
Together with a better performance, an overall more efficient positioning of
the whole team within the field is achieved
Induced Magnetic Ordering by Proton Irradiation in Graphite
We provide evidence that proton irradiation of energy 2.25 MeV on
highly-oriented pyrolytic graphite samples triggers ferro- or ferrimagnetism.
Measurements performed with a superconducting quantum interferometer device
(SQUID) and magnetic force microscopy (MFM) reveal that the magnetic ordering
is stable at room temperature.Comment: 3 Figure
Spin-triplet s-wave local pairing induced by Hund's rule coupling
We show within the dynamical mean field theory that local multiplet
interactions such as Hund's rule coupling produce local pairing
superconductivity in the strongly correlated regime. Spin-triplet
superconductivity driven by the Hund's rule coupling emerges from the pairing
mediated by local fluctuations in pair exchange. In contrast to the
conventional spin-triplet theories, the local orbital degrees of freedom has
the anti-symmetric part of the exchange symmetry, leaving the spatial part as
fully gapped and symmetric s-wave.Comment: 9 pages, 7 figure
Single-Electron Traps: A Quantitative Comparison of Theory and Experiment
We have carried out a coordinated experimental and theoretical study of
single-electron traps based on submicron aluminum islands and aluminum oxide
tunnel junctions. The results of geometrical modeling using a modified version
of MIT's FastCap were used as input data for the general-purpose
single-electron circuit simulator MOSES. The analysis indicates reasonable
quantitative agreement between theory and experiment for those trap
characteristics which are not affected by random offset charges. The observed
differences between theory and experiment (ranging from a few to fifty percent)
can be readily explained by the uncertainty in the exact geometry of the
experimental nanostructures.Comment: 17 pages, 21 figures, RevTex, eps
Coordination motifs and large-scale structural organization in atomic clusters
The structure of nanoclusters is complex to describe due to their
noncrystallinity, even though bonding and packing constraints limit the local
atomic arrangements to only a few types. A computational scheme is presented to
extract coordination motifs from sample atomic configurations. The method is
based on a clustering analysis of multipole moments for atoms in the first
coodination shell. Its power to capture large-scale structural properties is
demonstrated by scanning through the ground state of the Lennard-Jones and
C clusters collected at the Cambridge Cluster Database.Comment: 6 pages, 7 figure
Deriving global structure of the Galactic Magnetic Field from Faraday Rotation Measures of extragalactic sources
We made use of the two latest sets of Rotational Measures (RMs) of
extra-galactic radio sources, namely the NRAO VLA Sky Survey otation Measures
Catalogue, and a compilation by Kronberg&Newton-McGee(2011), to infer the
global structure of the Galactic Magnetic Field (GMF). We have checked that
these two data sets are consistent with each other. Motivated by clear patterns
in the observed distribution of RMs over the sky, we considered GMF models
consisting of the two components: disk (spiral or ring) and halo. The
parameters of these components were determined by fitting different model field
geometries to the observed RMs. We found that the model consisting of a
symmetric (with respect to the Galactic plane) spiral disk and anti-symmetric
halo fits the data best, and reproduces the observed distribution of RMs over
the sky very well. We confirm that ring disk models are disfavored. Our results
favor small pitch angles around -5 degrees and an increased vertical scale of
electron distribution, in agreement with some previous studies. Based on our
fits, we identify two benchmark models suitable for studies of cosmic ray
propagation, including the ultra-high energies.Comment: 15 pages, 14 figures, 4 tables misprints corrected, presentation
improved generally matches the published versio
The triple degenerate star WD1704+481
WD1704+481 is a visual binary in which both components are white dwarfs. We
present spectra of the H-alpha line of both stars which show that one component
(WD1704+481.2 = Sanduleak B = GR 577) is a close binary with two white dwarf
components. Thus, WD1704+481 is the first known triple degenerate star. From
radial velocity measurements of the close binary we find an orbital period of
0.1448d, a mass ratio, q=Mbright/Mfaint of q=0.70+-0.03 and a difference in the
gravitational redshifts of 11.5+-2.3km/s. The masses of the close pair of white
dwarfs predicted by the mass ratio and gravitational redshift difference
combined with theoretical cooling curves are 0.39+-0.05 solar mass and
0.56+-0.07 solar masses. WD1704+481 is therefore also likely to be the first
example of a double degenerate in which the less massive white dwarf is
composed of helium and the other white dwarf is composed of carbon and oxygen.Comment: 5 pages, 4 figure
Suppression of dephasing by qubit motion in superconducting circuits
We suggest and demonstrate a protocol which suppresses dephasing due to the
low-frequency noise by qubit motion, i.e., transfer of the logical qubit of
information in a system of physical qubits. The protocol requires
only the nearest-neighbor coupling and is applicable to different qubit
structures. We further analyze its effectiveness against noises with arbitrary
correlations. Our analysis, together with experiments using up to three
superconducting qubits, shows that for the realistic uncorrelated noises, qubit
motion increases the dephasing time of the logical qubit as . In
general, the protocol provides a diagnostic tool to measure the noise
correlations.Comment: 5 pages with 3 embedded figures, plus supplementary informatio
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