9,458 research outputs found
Improved Online Wilson Score Interval Method for Community Answer Quality Ranking
In this paper, a fast and easy-to-deploy method with a strong
interpretability for community answer quality ranking is proposed. This method
is improved based on the Wilson score interval method [Wilson, 1927], which
retains its advantages and simultaneously improve the degree of satisfaction
with the ranking of the high-quality answers. The improved answer quality score
considers both Wilson score interval and the spotlight index, the latter of
which will be introduced in the article. This method could significantly
improve the ranking of the best answers with high attention in diverse
scenarios.Comment: 8 pages, 13 figure
Common coupled fixed point theorems in -algebra-valued metric spaces
In this paper, we prove some common coupled fixed point theorems for mappings
satisfying different contractive conditions in the context of complete
-algebra-valued metric spaces. Moreover, the paper provides an application
to prove the existence and uniqueness of a solution for Fredholm nonlinear
integral equations.Comment: 12 pages. arXiv admin note: text overlap with arXiv:1506.05545 by
other author
Curvature Estimates for Four-Dimensional Gradient Steady Ricci Solitons
In this paper, we derive certain curvature estimates for 4-dimensional
gradient steady Ricci solitons either with positive Ricci curvature or with
scalar curvature decay
Large Extra Dimensions and Holography
The holographic principle asserts that the entropy of a system cannot exceed
its boundary area in Planck units. However, conventional quantum field theory
fails to describe such systems. In this Letter, we assume the existence of
large extra dimensions and propose a relationship between UV and IR cutoffs
in this case. We find that if , this effective field theory could be a
good description of holographic systems. If these extra dimensions are detected
in future experiments, it will help to prove the validity of the holographic
principle. We also discuss implications for the cosmological constant problem.Comment: Revtex, 4 page
Jones type basic construction on field algebras of -spin models
Let be a finite group. Starting from the field algebra of
-spin models, one can construct the crossed product -algebra
such that it coincides with the -basic
construction for the field algebra and the -invariant
subalgebra of , where is the quantum double of . Under
the natural -module action on ,the
iterated crossed product -algebra can be obtained, which is
-isomorphic to the -basic construction for and the field algebra . Furthermore, one can show that the
iterated crossed product -algebra is a new field algebra and give the
concrete structure with the order and disorder operators.Comment: 14 page
Intrapixel effects of CCD and CMOS detectors
Intrapixel nonuniformity is known to exist in CCD and CMOS image sensors,
though the effects in backside illuminated (BSI) CCDs are too small to be a
concern for most astronomical observations. However, projects like the Large
Synoptic Survey Telescope require precise knowledge of the detector
characteristics, and intrapixel effects may need more attention. By scanning
CCD and CMOS cameras with a small light spot (unresolved by the optics), we
find in the images that the spot's flux, centroid displacement, and ellipticity
vary periodically on the pixel scale in most cases. The amplitude of variation
depends on not only the detector but also how well the spot is sampled by the
pixels. With a spot radius of 2 pixels (encircling 80% energy) as measured, the
flux and the ellipticity extracted from the BSI CCD camera vary by 0.2-0.3%
(rms) and 0.005 (rms), respectively, while the deviation of the centroid
position (rms ~ 0.01 pixel) is not correlated with the pixels. The effects are
more pronounced for the BSI CMOS camera and even worse for the frontside
illuminated CMOS camera. The results suggest that a closer examination of the
intrapixel effects is needed for precision astronomy.Comment: 9 pages, 6 figures, PACCD201
Approximation of Mean Field Games to N-Player Stochastic Games, with Singular Controls
This paper establishes that -player stochastic games with singular
controls, either of bounded velocity or of finite variation, can both be
approximated by mean field games (MFGs) with singular controls of bounded
velocity. More specifically, it shows i) the optimal control to an MFG with
singular controls of a bounded velocity is shown to be an
-NE to an -player game with singular controls of the bounded
velocity, with , and (ii) the optimal
control to this MFG is an -NE to an
-player game with singular controls of finite variation, where
is an error term that depends on .
This work generalizes the classical result on approximation -player games
by MFGs, by allowing for discontinuous controls
Large solar energetic particle event that occurred on 2012 March 7 and its VDA analysis
On 2012 March 7, the STEREO Ahead and Behind spacecraft, along with the
near-earth spacecraft (e.g. SOHO, Wind) situated between the two STEREO
spacecraft, observed an extremely large global solar energetic particle (SEP)
event in Solar Cycle 24. Two successive coronal mass ejections (CMEs) have been
detected close in time. From the multi-point in-situ observations, it can be
found that this SEP event was caused by the first CME, and the second one was
not involved. Using the velocity dispersion analysis (VDA), we find that for
well magnetically connected point, the energetic protons and electrons are
released nearly at the same time. The path lengths to STEREO-B(STB) of protons
and electrons have distinct difference and deviate remarkably from the nominal
Parker spiral path length, which is likely due to the presence of
interplanetary magnetic structures situated between the source and the STB.
Also the VDA method seems only to obtain reasonable results at well-connected
locations and the inferred energetic particles release times in different
energy channels are similar. We suggest that good-connection is crucial for
obtaining both accurate release time and path length simultaneously, agreeing
with the modeling result of Wang & Qin (2015)
New approach for fabrication germanene with Dirac electrons preserved: A first principle study
How to obtain germanene with Dirac electrons preserved is still an open
challenge. Here we report a sandwich-dehydrogenation approach, i.e., to
fabricate germanene through dehydrogenating germanane in a sandwiched
structure. The dehydrogenation can spontaneously occur for the sandwiched
structure, which overcomes the problem of amorphization in the heating
dehydrogenation approach. The obtained germanene preserve the Dirac electronic
properties very well. Moreover, the Fermi velocity of germanene can be
efficiently manipulated through controlling the interlayer spacing between
germanane and the sandwiching surfaces. Our results indicate a guideline for
fabrication of prefect two-dimensional materials.Comment: 23 pages,6 figure
Seed population in large Solar Energetic Particle events and the twin-CME scenario
It has been recently suggested that large solar energetic particle (SEP)
events are often caused by twin CMEs. In the twin-CME scenario, the preceding
CME is to provide both an enhanced turbulence level and enhanced seed
population at the main CME-driven shock. In this work, we study the effect of
the preceding CMEs on the seed population. We examine event-integrated
abundance of iron to oxygen ratio (Fe/O) at energies above 25 MeV/nuc for large
SEP events in solar cycle 23. We find that the Fe/O ratio (normalized to the
reference coronal value of ) for almost all single-CME events
and these events tend to have smaller peak intensities. In comparison, the Fe/O
ratio of twin-CME events scatters in a larger range, reaching as high as ,
suggesting the presence of flare material from perhaps preceding flares. For
extremely large SEP events with peak intensity above pfu, the Fe/O drop
below , indicating that in these extreme events the seed particles are
dominated by coronal material than flare material. The Fe/O ratios of Ground
level enhancement (GLE) events, all being twin-CME events, scatter in a broad
range. For a given Fe/O ratio, GLE events tend to have larger peak intensities
than non-GLE events. Using velocity dispersion analysis (VDA), we find that GLE
events have lower solar particle release (SPR) heights than non-GLE events,
\red{agreeing with earlier results by Reames 2009b
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