8,585 research outputs found
A Cognitive Science Based Machine Learning Architecture
In an attempt to illustrate the application of cognitive science principles to hard AI problems in machine learning we propose the LIDA technology, a cognitive science based architecture capable of more human-like learning. A LIDA based software agent or cognitive robot will be capable of three fundamental, continuously active, humanlike learning mechanisms:\ud
1) perceptual learning, the learning of new objects, categories, relations, etc.,\ud
2) episodic learning of events, the what, where, and when,\ud
3) procedural learning, the learning of new actions and action sequences with which to accomplish new tasks. The paper argues for the use of modular components, each specializing in implementing individual facets of human and animal cognition, as a viable approach towards achieving general intelligence
Mixing Metals in the Early Universe
We investigate the evolution of the metallicity of the intergalactic medium
(IGM) with particular emphasis on its spatial distribution. We propose that
metal enrichment occurs as a two step process. First, supernova (SN) explosions
eject metals into relatively small regions confined to the surroundings of
star-forming galaxies. From a comprehensive treatment of blowout we show that
SNae by themselves fail by more than one order of magnitude to distribute the
products of stellar nucleosynthesis over volumes large enough to pollute the
whole IGM to the metallicity levels observed. Thus, a additional (but as yet
unknown) physical mechanism must be invoked to mix the metals on scales
comparable to the mean distance between the galaxies which are most efficient
pollutants. From this simple hypothesis we derive a number of testable
predictions for the evolution of the IGM metallicity. Specifically, we find
that: (i) the fraction of metals ejected over the star formation history of the
universe is about 50% at z=0; that is, approximately half of the metals today
are found in the IGM; (ii) if the ejected metals were homogeneously mixed with
the baryons in the universe, the average IGM metallicity would be ~ 1/25
Z(solar) at z=3. However, due to spatial inhomogeneities, the mean of the
distribution of metallicities in the diffusive zones has a wide (more than 2
orders of magnitude) spread around this value; (iii) if metals become more
uniformly distributed at z < 1, as assumed, at z = 0 the metallicity of the IGM
is narrowly confined within the range Z ~ 0.1 +/- 0.03 Z(solar). Finally, we
point out that our results can account for the observed metal content of the
intracluster medium.Comment: 26 pages, LaTeX, 8 figures, accepted by MNRA
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