7,114 research outputs found
On the strong anomalous diffusion
The superdiffusion behavior, i.e. , with , in general is not completely characherized by a unique exponent. We study
some systems exhibiting strong anomalous diffusion, i.e. where and is not a linear function of .
This feature is different from the weak superdiffusion regime, i.e.
, as in random shear flows. The strong anomalous diffusion
can be generated by nontrivial chaotic dynamics, e.g. Lagrangian motion in
time-dependent incompressible velocity fields, symplectic maps and
intermittent maps. Typically the function is piecewise linear. This
corresponds to two mechanisms: a weak anomalous diffusion for the typical
events and a ballistic transport for the rare excursions. In order to have
strong anomalous diffusion one needs a violation of the hypothesis of the
central limit theorem, this happens only in a very narrow region of the control
parameters space.Comment: 27 pages, 14 figure
The Young Stellar Population of the Nearby Late-Type Galaxy NGC 1311
We have extracted PSF-fitted stellar photometry from near-ultraviolet,
optical and near-infrared images, obtained with the Hubble Space Telescope, of
the nearby (D ~ 5.5 Mpc) SBm galaxy NGC 1311. The ultraviolet and optical data
reveal a population of hot main sequence stars with ages of 2-10 Myr. We also
find populations of blue supergiants with ages between 10 and 40 Myr and red
supergiants with ages between 10 and 100 Myr. Our near-infrared data shows
evidence of star formation going back ~1 Gyr, in agreement with previous work.
Fits to isochrones indicate a metallicity of Z ~ 0.004. The ratio of blue to
red supergiants is consistent with this metallicity. This indicates that NGC
1311 follows the well-known luminosity-metallicity relation for late-type dwarf
galaxies. About half of the hot main sequence stars and blue supergiants are
found in two regions in the inner part of NGC 1311. These two regions are each
about 200 pc across, and thus have crossing times roughly equal to the 10 Myr
age we find for the dominant young population. The Luminosity Functions of the
supergiants indicate a slowly rising star formation rate (of 0.001 Solar masses
per year) from ~100 Myr ago until ~15 Myr ago, followed by a strong enhancement
(to 0.01 Solar Masses per year) at ~10 Myr ago. We see no compelling evidence
for gaps in the star-forming history of NGC 1311 over the last 100 Myr, and,
with lower significance, none over the last Gyr. This argues against a bursting
mode, and in favor of a gasping or breathing mode for the recent star-formation
history.Comment: AASTex, 34 pages, 13 postscript figures. Accepted for publication by
The Astronomical Journa
A novel algorithm for dynamic student profile adaptation based on learning styles
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.E-learning recommendation systems are used to enhance student performance and knowledge by providing tailor- made services based on the students’ preferences and learning styles, which are typically stored in student profiles. For such systems to remain effective, the profiles need to be able to adapt and reflect the students’ changing behaviour. In this paper, we introduce new algorithms that are designed to track student learning behaviour patterns, capture their learning styles, and maintain dynamic student profiles within a recommendation system (RS). This paper also proposes a new method to extract features that characterise student behaviour to identify students’ learning styles with respect to the Felder-Silverman learning style model (FSLSM). In order to test the efficiency of the proposed algorithm, we present a series of experiments that use a dataset of real students to demonstrate how our proposed algorithm can effectively model a dynamic student profile and adapt to different student learning behaviour. The results revealed that the students could effectively increase their learning efficiency and quality for the courses when the learning styles are identified, and proper recommendations are made by using our method
Roles of the color antisymmetric ghost propagator in the infrared QCD
The results of Coulomb gauge and Landau gauge lattice QCD simulation do not
agree completely with continuum theory. There are indications that the ghost
propagator in the infrared region is not purely color diagonal as in high
energy region. After presenting lattice simulation of configurations produced
with Kogut-Susskind fermion (MILC collaboration) and those with domain wall
fermion (RBC/UKQCD collaboration), I investigate in triple gluon vertex and the
ghost-gluon-ghost vertex how the square of the color antisymmetric ghost
contributes. Then the effect of the vertex correction to the gluon propagator
and the ghost propagator is investigated.
Recent Dyson-Schwinger equation analysis suggests the ghost dressing function
finite and no infrared enhancement or . But the ghost
propagator renormalized by the loop containing a product of color antisymmetric
ghost is expected to behave as with
with , if the fixed point
scenario is valid. I interpret the solution should contain a
vertex correction. The infrared exponent of our lattice Landau gauge gluon
propagator of the RBC/UKQCD is and that of MILC is about
-0.7.
The implication for the Kugo-Ojima color confinement criterion, QCD effective
coupling and the Slavnov identity are given.Comment: 13 pages 10 figures, references added and revised. version to be
published in Few-Body System
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