170,655 research outputs found
Order-of-Magnitude Influence Diagrams
In this paper, we develop a qualitative theory of influence diagrams that can
be used to model and solve sequential decision making tasks when only
qualitative (or imprecise) information is available. Our approach is based on
an order-of-magnitude approximation of both probabilities and utilities and
allows for specifying partially ordered preferences via sets of utility values.
We also propose a dedicated variable elimination algorithm that can be applied
for solving order-of-magnitude influence diagrams
Nanoferroics: state of art, gradient driven couplings and advanced applications (Authors' review)
Ferroics and multiferroics are unique objects for fundamental physical
research of complex nonlinear processes and phenomena, which occur in them in
micro and nanoscale. Due to the possibility of their physical properties
control by size effects, nanostructured and nanosized ferroics are among the
most promising for advanced applications in nanoelectronics,
nanoelectromechanics, optoelectronics, nonlinear optics and information
technologies. The review discuss and analyze that the thickness of the strained
films, the size and shape of the ferroic and multiferroic nanoparticles are
unique tools for controlling their phase diagrams, long range order parameters,
magnitude of susceptibility, magnetoelectric coupling and domain structure
characteristics at fixed temperature. Significant influence of the
flexochemical effect on the phase transition temperature, polar and dielectric
properties is revealed for thin films and nanoparticles. Obtained results are
important for understanding of the nonlinear physical processes in nanoferroics
as well as for the advanced applications in nanoelectronics.Comment: 23 pages, 15 figure
Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
The temporal variation of the horizontal velocity in subsurface layers
beneath three different types of active regions is studied using the technique
of ring diagrams. In this study, we select active regions (ARs) 10923, 10930,
10935 from three consecutive Carrington rotations: AR 10930 contains a
fast-rotating sunspot in a strong emerging active region while other two have
non-rotating sunspots with emerging flux in AR 10923 and decaying flux in AR
10935. The depth range covered is from the surface to about 12 Mm. In order to
minimize the influence of systematic effects, the selection of active and quiet
regions is made so that these were observed at the same heliographic locations
on the solar disk. We find a significant variation in both components of the
horizontal velocity in active regions as compared to quiet regions. The
magnitude is higher in emerging-flux regions than in the decaying-flux region,
in agreement with earlier findings. Further, we clearly see a significant
temporal variation in depth profiles of both zonal and meridional flow
components in AR 10930, with the variation in the zonal component being more
pronounced. We also notice a significant influence of the plasma motion in
areas closest to the rotating sunspot in AR 10930 while areas surrounding the
non-rotating sunspots in all three cases are least affected by the presence of
the active region in their neighborhood.Comment: Solar Physics (in press), includes 11 figure
Effect of bars on the galaxy properties
Aims: With the aim of assessing the effects of bars on disc galaxy
properties, we present an analysis of different characteristics of spiral
galaxies with strong, weak and without bars. Method: We identified barred
galaxies from the Sloan Digital Sky Survey. By visual inspection, we classified
the face-on spiral galaxies brighter than g<16.5 mag into strong-bar, weak-bar
and unbarred. In order to provide an appropiate quantification of the influence
of bars on galaxy properties, we also constructed a suitable control sample of
unbarred galaxies with similar redshift, magnitude, morphology, bulge sizes,
and local density environment distributions to that of barred galaxies.
Results: We found 522 strong-barred and 770 weak-barred galaxies, representing
a 25.82% of the full sample of spiral galaxies, in good agreement with previous
studies. We also found that strong-barred galaxies show less efficient star
formation activity and older stellar populations compared to weak-barred and
unbarred spirals from the control sample. In addition, there is a significant
excess of strong barred galaxies with red colors. The color-color and
color-magnitude diagrams show that unbarred and weak-barred galaxies are more
extended towards the blue zone, while strong-barred objects are mostly grouped
in the red region. Strong-barred galaxies present an important excess of high
metallicity values, compared to the other types, showing similar 12+log(O/H)
distributions. Regarding the mass-metallicity relation, we found that
weak-barred and unbarred galaxies are fitted by similar curves, while
strong-barred ones show a curve which falls abruptly, with more significance in
the range of low stellar masses (log[Mstar/Msun] < 10.0). These results would
indicate that prominent bars produced an accelerating effect on the gas
processing, reflected in the significant changes in the physical properties of
their host
Effect of optical purity on phase sequence in antiferroelectric liquid crystals
We use the discrete phenomenological model to study theoretically the phase
diagrams in antiferroelectric liquid crystals (AFLCs) as a function of optical
purity and temperature. Recent experiments have shown that in some systems the
number of phases is reduced if the optical purity is extremely high. In some
materials the SmC phase is the only stable tilted smectic phase
in the pure sample. In the scope of the presented model this high sensitivity
of the phase sequence in the AFLCs to optical purity is attributed to the
piezoelectric coupling which is reduced if optical purity is reduced. We limit
our study to three topologically equal phases - SmC, SmC
and SmC and show that the reduction of optical purity forces the
system from the antiferroelectric to the ferroelectric phase with a possible
SmC between them. The effect of the flexoelectric and
quadrupolar coupling is considered as well. If the phase diagram includes only
two phases, SmC and SmC, the flexoelectric coupling is
very small. The materials which exhibit the SmC in a certain
range of optical purity and temperature, can be expected to have a significant
flexoelectric coupling that is comparable with the piezoelectric coupling. And
finally, when temperature is lowered the phase sequence SmA
SmC SmC SmC is
possible only in materials in which quadrupolar coupling is very strong.Comment: 17 pages including 6 figures, submitted to PR
End-to-end distance vector distribution with fixed end orientations for the wormlike chain model
We find exact expressions for the end-to-end distance vector distribution function with fixed end orientations for the wormlike chain model. This function in Fourier-Laplace space adopts the form of infinite continued fractions, which emerges upon exploiting the hierarchical structure of the moment-based expansion. Our results are used to calculate the root-mean-square end displacement in a given direction for a chain with both end orientations fixed. We find that the crossover from rigid to flexible chains is marked by the root-mean-square end displacement slowly losing its angular dependence as the coupling between chain conformation and end orientation wanes. However, the coupling remains strong even for relatively flexible chains, suggesting that the end orientation strongly influences chain conformation for chains that are several persistence lengths long. We then show the behavior of the distribution function by a density plot of the probability as a function of the end-to-end distance vector for a wormlike chain in two dimensions with one end pointed in a fixed direction and the other end free (in its orientation). As we progress from high to low rigidity, the distribution function shifts from being peaked at a location near the full contour length of the chain in the forward direction, corresponding to a straight configuration, to being peaked near zero end separation, as in the Gaussian limit. The function exhibits double peaks in the crossover between these limiting behaviors
Short-range correlations in quark matter
We investigate the role of short-range correlations in quark matter within
the framework of the SU(2) NJL model. Employing a next-to-leading order
expansion in 1/N_c for the quark self energy we construct a fully
self-consistent model that is based on the relations between spectral functions
and self energies. In contrast to the usual quasiparticle approximations we
take the collisional broadening of the quark spectral function consequently
into account. Mesons are dynamically generated in the fashion of a random phase
approximation, using full in-medium propagators in the quark loops. The results
are self-consistently fed back into the quark self energy. Calculations have
been performed for finite chemical potentials at zero temperature. The
short-range correlations do not only generate finite widths in the spectral
functions but also have influence on the chiral phase transition.Comment: 40 pages, 23 figures; revised and extended paper, accepted for
publication in Phys. Rev.
A Tentative Modeling Study of the Effect of Wall Reactions on Oxidation Phenomena
This paper gives details of a tentative modeling study that investigates the
inhibiting effect of internal reactor walls treated with acid..
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