628 research outputs found
Co-Evolutionary Learning for Cognitive Computer Generated Entities
In this paper, an approach is advocated to use a hybrid approach towards learning behaviour for computer generated entities (CGEs) in a serious gaming setting. Hereby, an agent equipped with cognitive model is used but this agent is enhanced with Machine Learning (ML) capabilities. This facilitates the agent to exhibit human like behaviour but avoid an expert having to define all parameters explicitly. More in particular, the ML approach utilizes co-evolution as a learning paradigm. An evaluation in the domain of one-versus-one air combat shows promising results
Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions
Excess contributions to the free energy due to interfaces occur for many
problems encountered in the statistical physics of condensed matter when
coexistence between different phases is possible (e.g. wetting phenomena,
nucleation, crystal growth, etc.). This article reviews two methods to estimate
both interfacial free energies and line tensions by Monte Carlo simulations of
simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid
exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is
based on thermodynamic integration. This method is useful to study flat and
inclined interfaces for Ising lattices, allowing also the estimation of line
tensions of three-phase contact lines, when the interfaces meet walls (where
"surface fields" may act). A generalization to off-lattice systems is described
as well.
The second method is based on the sampling of the order parameter
distribution of the system throughout the two-phase coexistence region of the
model. Both the interface free energies of flat interfaces and of (spherical or
cylindrical) droplets (or bubbles) can be estimated, including also systems
with walls, where sphere-cap shaped wall-attached droplets occur. The
curvature-dependence of the interfacial free energy is discussed, and estimates
for the line tensions are compared to results from the thermodynamic
integration method. Basic limitations of all these methods are critically
discussed, and an outlook on other approaches is given
Architektury kognitywne, czyli jak zbudowaÄ sztuczny umysĹ
Architektury kognitywne (AK) sÄ
prĂłbÄ
stworzenia modeli komputerowych
integrujÄ
cych wiedzÄ o dziaĹaniu umysĹu. Ich zadaniem jest implementacja konkretnych
schematĂłw dziaĹania funkcji poznawczych umoĹźliwiajÄ
ca testowanie tych funkcji na
szerokiej gamie zagadnieĹ. Wiele architektur kognitywnych opracowano w celu
symulacji procesu komunikacji pomiÄdzy czĹowiekiem i zĹoĹźonymi maszynami (HCI,
Human-Computer Interfaces), symulowania czasów reakcji oraz róşnych
psychofizycznych zaleĹźnoĹci. MoĹźna to do pewnego stopnia osiÄ
gnÄ
Ä budujÄ
c modele
ukĹadu poznawczego na poziomie symbolicznym, z wiedzÄ
w postaci reguĹ logicznych.
IstniejÄ
teĹź projekty, ktĂłre prĂłbujÄ
powiÄ
zaÄ procesy poznawcze z aktywacjÄ
moduĹĂłw
reprezentujÄ
cych konkretne obszary mĂłzgu, zgodnie z obserwacjami w eksperymentach
z funkcjonalnym rezonansem magnetycznym (fMRI). DuĹźÄ
grupÄ stanowiÄ
architektury
oparte na podejĹciu logicznym, ktĂłre majÄ
na celu symulacjÄ wyĹźszych czynnoĹci
poznawczych, przede wszystkim procesĂłw myĹlenia i rozumowania. NiektĂłre z
projektĂłw rozwoju architektur poznawczych skupiajÄ
wiÄksze grupy badawcze
dziaĹajÄ
ce od wielu dziesiÄcioleci.
OgĂłlnie architektury kognitywne podzieliÄ moĹźna na 3 duĹźe grupy: architektury
symboliczne (oparte na funkcjonalnym rozumieniu procesĂłw poznawczych);
architektury emergentne, oparte na modelach koneksjonistycznych; oraz architektury
hybrydowe, wykorzystujÄ
ce zarĂłwno modele neuronowe jak i reguĹy symboliczne. W
ostatnich latach znacznie wzrosĹo zainteresowanie architekturami inspirowanymi przez
neurobiologiÄ (BICA, Brain Inspired Cognitive Architectures). Jak sklasyfikowaÄ róşne
architektury, jakie wyzwania naleĹźy przed nimi postawiÄ, jak oceniaÄ postÄpy w ich
rozwoju, czego nam brakuje do stworzenia peĹnego modelu umysĹu? Krytyczny przeglÄ
d
istniejÄ
cych architektur kognitywnych, ich ograniczeĹ i moĹźliwoĹci pozwala na
sformuĹowanie ogĂłlnych wnioskĂłw dotyczÄ
cych kierunkĂłw ich rozwoju czego nam brakuje do stworzenia peĹnego modelu umysĹu? Krytyczny przeglÄ
d
istniejÄ
cych architektur kognitywnych, ich ograniczeĹ i moĹźliwoĹci pozwala na
sformuĹowanie ogĂłlnych wnioskĂłw dotyczÄ
cych kierunkĂłw ich rozwoju oraz
wysuniÄcie wĹasnych propozycji budowy nowej architektury
Towards Machine Wald
The past century has seen a steady increase in the need of estimating and
predicting complex systems and making (possibly critical) decisions with
limited information. Although computers have made possible the numerical
evaluation of sophisticated statistical models, these models are still designed
\emph{by humans} because there is currently no known recipe or algorithm for
dividing the design of a statistical model into a sequence of arithmetic
operations. Indeed enabling computers to \emph{think} as \emph{humans} have the
ability to do when faced with uncertainty is challenging in several major ways:
(1) Finding optimal statistical models remains to be formulated as a well posed
problem when information on the system of interest is incomplete and comes in
the form of a complex combination of sample data, partial knowledge of
constitutive relations and a limited description of the distribution of input
random variables. (2) The space of admissible scenarios along with the space of
relevant information, assumptions, and/or beliefs, tend to be infinite
dimensional, whereas calculus on a computer is necessarily discrete and finite.
With this purpose, this paper explores the foundations of a rigorous framework
for the scientific computation of optimal statistical estimators/models and
reviews their connections with Decision Theory, Machine Learning, Bayesian
Inference, Stochastic Optimization, Robust Optimization, Optimal Uncertainty
Quantification and Information Based Complexity.Comment: 37 page
CANDELS : constraining the AGN-merger connection with host morphologies at z ~ 2
Using Hubble Space Telescope/WFC3 imaging taken as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we examine the role that major galaxy mergers play in triggering active galactic nucleus (AGN) activity at z ~ 2. Our sample consists of 72 moderate-luminosity (L X ~ 1042-44 erg s-1) AGNs at 1.5 < z < 2.5 that are selected using the 4 Ms Chandra observations in the Chandra Deep Field South, the deepest X-ray observations to date. Employing visual classifications, we have analyzed the rest-frame optical morphologies of the AGN host galaxies and compared them to a mass-matched control sample of 216 non-active galaxies at the same redshift. We find that most of the AGNs reside in disk galaxies (51.4+5.8 - 5.9%), while a smaller percentage are found in spheroids (27.8+5.8 - 4.6%). Roughly 16.7+5.3 - 3.5% of the AGN hosts have highly disturbed morphologies and appear to be involved in a major merger or interaction, while most of the hosts (55.6+5.6 - 5.9%) appear relatively relaxed and undisturbed. These fractions are statistically consistent with the fraction of control galaxies that show similar morphological disturbances. These results suggest that the hosts of moderate-luminosity AGNs are no more likely to be involved in an ongoing merger or interaction relative to non-active galaxies of similar mass at z ~ 2. The high disk fraction observed among the AGN hosts also appears to be at odds with predictions that merger-driven accretion should be the dominant AGN fueling mode at z ~ 2, even at moderate X-ray luminosities. Although we cannot rule out that minor mergers are responsible for triggering these systems, the presence of a large population of relatively undisturbed disk-like hosts suggests that the stochastic accretion of gas plays a greater role in fueling AGN activity at z ~ 2 than previously thought
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2
The peculiar object P/2010 A2 was discovered by the LINEAR near-Earth
asteroid survey in January 2010 and given a cometary designation due to the
presence of a trail of material, although there was no central condensation or
coma. The appearance of this object, in an asteroidal orbit (small eccentricity
and inclination) in the inner main asteroid belt attracted attention as a
potential new member of the recently recognized class of 'Main Belt Comets'
(MBCs). If confirmed, this new object would greatly expand the range in
heliocentric distance over which MBCs are found. Here we present observations
taken from the unique viewing geometry provided by ESA's Rosetta spacecraft,
far from the Earth, that demonstrate that the trail is due to a single event
rather than a period of cometary activity, in agreement with independent
results from the Hubble Space Telescope (HST). The trail is made up of
relatively large particles of millimetre to centimetre size that remain close
to the parent asteroid. The shape of the trail can be explained by an initial
impact ejecting large clumps of debris that disintegrated and dispersed almost
immediately. We determine that this was an asteroid collision that occurred
around February 10, 2009.Comment: Published in Nature on 14/10/2010. 25 pages, includes supplementary
materia
Piecewise Boolean Algebras and Their Domains
We characterise piecewise Boolean domains, that is, those domains that arise
as Boolean subalgebras of a piecewise Boolean algebra. This leads to equivalent
descriptions of the category of piecewise Boolean algebras: either as piecewise
Boolean domains equipped with an orientation, or as full structure sheaves on
piecewise Boolean domains.Comment: 11 page
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