5,178 research outputs found
Analysing the behaviour of robot teams through relational sequential pattern mining
This report outlines the use of a relational representation in a Multi-Agent
domain to model the behaviour of the whole system. A desired property in this
systems is the ability of the team members to work together to achieve a common
goal in a cooperative manner. The aim is to define a systematic method to
verify the effective collaboration among the members of a team and comparing
the different multi-agent behaviours. Using external observations of a
Multi-Agent System to analyse, model, recognize agent behaviour could be very
useful to direct team actions. In particular, this report focuses on the
challenge of autonomous unsupervised sequential learning of the team's
behaviour from observations. Our approach allows to learn a symbolic sequence
(a relational representation) to translate raw multi-agent, multi-variate
observations of a dynamic, complex environment, into a set of sequential
behaviours that are characteristic of the team in question, represented by a
set of sequences expressed in first-order logic atoms. We propose to use a
relational learning algorithm to mine meaningful frequent patterns among the
relational sequences to characterise team behaviours. We compared the
performance of two teams in the RoboCup four-legged league environment, that
have a very different approach to the game. One uses a Case Based Reasoning
approach, the other uses a pure reactive behaviour.Comment: 25 page
Anaerobic membrane reactor: Biomethane from chicken manure and high-quality effluent
Chicken manure was treated in a pilot scale reactor anaerobic membrane bioreactor constituted by a completely mixed reactor combined with an ultrafiltration tube-shaped membrane in a side-stream configuration. The process operated under mesophilic condition and the inhibition of high concentration of ammonia was avoided using an ammonia stripping system. The experimental plan included a preliminary evaluation, where organic loading rates between 1.0 and 7.6 kgVS/m3/day were tested. The organic load higher than 4 kgVS/m3/d caused the accumulation of volatile fatty acids and process instability. Application of the ammonia stripping was also evaluated. The best performances were achieved using a retention time of 21 days, an organic load between 1.4 and 2.0 kgVS/m3/d, and the recirculation of stripped permeate. Reduction of the ammonia permeate content by 90% through stripping and utilization of a mixture of chicken manure/water/permeate in a ratio of 0.22/0.72/0.72 w/w led to a specific biogas production of 0.59 m3biogas/kgVS and methane content of 66–69%. The ammonia thus removed can be recovered by sulphuric acid treatment as ammonium sulphate, which can be used as a fertilizer. The proposed configuration allowed satisfactory biogas production with appropriate methane percentages, recovery of ammonium sulphate, and a high-quality effluent
Black Hole Lightning from the Peculiar Gamma-Ray Loud Active Galactic Nucleus IC 310
The nearby active galaxy IC 310, located in the outskirts of the Perseus
cluster of galaxies is a bright and variable multi-wavelength emitter from the
radio regime up to very high gamma-ray energies above 100 GeV. Originally, the
nucleus of IC 310 has been classified as a radio galaxy. However, studies of
the multi-wavelength emission showed several properties similarly to those
found from blazars as well as radio galaxies. In late 2012, we have organized
the first contemporaneous multi-wavelength campaign including radio, optical,
X-ray and gamma-ray instruments. During this campaign an exceptionally bright
flare of IC 310 was detected with the MAGIC telescopes in November 2012
reaching an averaged flux level in the night of up to one Crab above 1 TeV with
a hard spectrum over two decades in energy. The intra-night light curve showed
a series of strong outbursts with flux-doubling time scales as fast as a few
minutes. The fast variability constrains the size of the gamma-ray emission
regime to be smaller than 20% of the gravitational radius of its central black
hole. This challenges the shock acceleration models, commonly used to explain
gamma-ray radiation from active galaxies. Here, we will present more details on
the MAGIC data and discuss several possible alternative emission models.Comment: 8 pages, 5 figures, Proceedings of the 34th International Cosmic Ray
Conference, 30 July - 6 August, 2015, The Hague, The Netherland
A precise characterisation of the top quark electro-weak vertices at the ILC
Top quark production in the process at a future linear
electron positron collider with polarised beams is a powerful tool to determine
indirectly the scale of new physics. The presented study, based on a detailed
simulation of the ILD detector concept, assumes a centre-of-mass energy of
GeV and a luminosity of
equally shared between the incoming beam polarisations of . Events are selected in which the top pair
decays semi-leptonically and the cross sections and the forward-backward
asymmetries are determined. Based on these results, the vector, axial vector
and tensorial conserving couplings are extracted separately for the photon
and the component. With the expected precision, a large number of models
in which the top quark acts as a messenger to new physics can be distinguished
with many standard deviations. This will dramatically improve expectations from
e.g. the LHC for electro-weak couplings of the top quark.Comment: This work is an update of arXiv:1307.8102, minor changes w.r.t. v1
(typos, wrong grammar, incomplete sentences etc.
Insights into the particle acceleration of a peculiar gamma -ray radio galaxy IC 310
IC 310 has recently been identified as a gamma-ray emitter based on
observations at GeV energies with Fermi-LAT and at very high energies (VHE, E >
100 GeV) with the MAGIC telescopes. Despite IC 310 having been classified as a
radio galaxy with the jet observed at an angle > 10 degrees, it exhibits a
mixture of multiwavelength properties of a radio galaxy and a blazar, possibly
making it a transitional object. On the night of 12/13th of November 2012 the
MAGIC telescopes observed a series of violent outbursts from the direction of
IC 310 with flux-doubling time scales faster than 5 min and a peculiar spectrum
spreading over 2 orders of magnitude. Such fast variability constrains the size
of the emission region to be smaller than 20% of the gravitational radius of
its central black hole, challenging the shock acceleration models, commonly
used in explanation of gamma-ray radiation from active galaxies. Here we will
show that this emission can be associated with pulsar-like particle
acceleration by the electric field across a magnetospheric gap at the base of
the jet.Comment: 2014 Fermi Symposium proceedings - eConf C14102.
A Search for Ultra-High Energy Counterparts to Gamma-Ray Bursts
A small air shower array operating over many years has been used to search
for ultra-high energy (UHE) gamma radiation ( TeV) associated with
gamma-ray bursts (GRBs) detected by the BATSE instrument on the Compton
Gamma-Ray Observatory (CGRO). Upper limits for a one minute interval after each
burst are presented for seven GRBs located with zenith angles . A excess over background was observed between 10 and
20 minutes following the onset of a GRB on 11 May 1991. The confidence level
that this is due to a real effect and not a background fluctuation is 99.8\%.
If this effect is real then cosmological models are excluded for this burst
because of absorption of UHE gamma rays by the intergalactic radiation fields.Comment: 4 pages LaTeX with one postscript figure. This version does not use
kluwer.sty and will allow automatic postscript generatio
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