4,238 research outputs found
Exploring Outliers in Crowdsourced Ranking for QoE
Outlier detection is a crucial part of robust evaluation for crowdsourceable
assessment of Quality of Experience (QoE) and has attracted much attention in
recent years. In this paper, we propose some simple and fast algorithms for
outlier detection and robust QoE evaluation based on the nonconvex optimization
principle. Several iterative procedures are designed with or without knowing
the number of outliers in samples. Theoretical analysis is given to show that
such procedures can reach statistically good estimates under mild conditions.
Finally, experimental results with simulated and real-world crowdsourcing
datasets show that the proposed algorithms could produce similar performance to
Huber-LASSO approach in robust ranking, yet with nearly 8 or 90 times speed-up,
without or with a prior knowledge on the sparsity size of outliers,
respectively. Therefore the proposed methodology provides us a set of helpful
tools for robust QoE evaluation with crowdsourcing data.Comment: accepted by ACM Multimedia 2017 (Oral presentation). arXiv admin
note: text overlap with arXiv:1407.763
Dependence of X-Ray Burst Models on Nuclear Reaction Rates
X-ray bursts are thermonuclear flashes on the surface of accreting neutron
stars and reliable burst models are needed to interpret observations in terms
of properties of the neutron star and the binary system. We investigate the
dependence of X-ray burst models on uncertainties in (p,),
(,), and (,p) nuclear reaction rates using fully
self-consistent burst models that account for the feedbacks between changes in
nuclear energy generation and changes in astrophysical conditions. A two-step
approach first identified sensitive nuclear reaction rates in a single-zone
model with ignition conditions chosen to match calculations with a
state-of-the-art 1D multi-zone model based on the {\Kepler} stellar evolution
code. All relevant reaction rates on neutron deficient isotopes up to mass 106
were individually varied by a factor of 100 up and down. Calculations of the 84
highest impact reaction rate changes were then repeated in the 1D multi-zone
model. We find a number of uncertain reaction rates that affect predictions of
light curves and burst ashes significantly. The results provide insights into
the nuclear processes that shape X-ray burst observables and guidance for
future nuclear physics work to reduce nuclear uncertainties in X-ray burst
models.Comment: 24 pages, 13 figures, 4 tables, submitte
Proton Drip-Line Calculations and the Rp-process
One-proton and two-proton separation energies are calculated for proton-rich
nuclei in the region . The method is based on Skyrme Hartree-Fock
calculations of Coulomb displacement energies of mirror nuclei in combination
with the experimental masses of the neutron-rich nuclei. The implications for
the proton drip line and the astrophysical rp-process are discussed. This is
done within the framework of a detailed analysis of the sensitivity of rp
process calculations in type I X-ray burst models on nuclear masses. We find
that the remaining mass uncertainties, in particular for some nuclei with
, still lead to large uncertainties in calculations of X-ray burst light
curves. Further experimental or theoretical improvements of nuclear mass data
are necessary before observed X-ray burst light curves can be used to obtain
quantitative constraints on ignition conditions and neutron star properties. We
identify a list of nuclei for which improved mass data would be most important.Comment: 20 pages, 9 figures, 2 table
The DNA60IFX contest
We present the full story of Genome Biology's recent DNA60IFX contest, as told by the curators and winner of what turned out to be a memorable and hotly contested bioinformatics challenge. Full solutions, including scripts, are available at http://genomebiology.com/about/update/DNA60_ANSWER
Models for Type I X-Ray Bursts with Improved Nuclear Physics
Multi-zone models of Type I X-ray bursts are presented that use an adaptive
nuclear reaction network of unprecedented size, up to 1300 isotopes. Sequences
of up to 15 bursts are followed for two choices of accretion rate and
metallicity. At 0.1 Eddington (and 0.02 Eddington for low metallicity),
combined hydrogen-helium flashes occur. The rise times, shapes, and tails of
these light curves are sensitive to the efficiency of nuclear burning at
various waiting points along the rp-process path and these sensitivities are
explored. The bursts show "compositional inertia", in that their properties
depend on the fact that accretion occurs onto the ashes of previous bursts
which contain left-over hydrogen, helium and CNO nuclei. This acts to reduce
the sensitivity of burst properties to metallicity. For the accretion rates
studied, only the first anomalous burst in one model produces nuclei as heavy
as A=100, other bursts make chiefly nuclei with A~64. The amount of carbon
remaining after hydrogen-helium bursts is typically <1% by mass, and decreases
further as the ashes are periodically heated by subsequent bursts. At the lower
accretion rate of 0.02 Eddington and solar metallicity, the bursts ignite in a
hydrogen-free helium layer. At the base of this layer, up to 90% of the helium
has already burned to carbon prior to the unstable ignition. These
helium-ignited bursts have briefer, brighter light curves with shorter tails,
very rapid rise times (<0.1 s), and ashes lighter than the iron group.Comment: Submitted to the Astrophysical Journal (42 pages; 27 figures
Extracting the rp-process from X-ray burst light curves
The light curves of type I X-ray bursts (XRBs) result from energy released
from the atmosphere of a neutron star when accreted hydrogen and helium ignite
and burn explosively via the rp-process. Since charged particle reaction rates
are both density and very temperature dependent, a simulation model must
provide accurate values of these variables to predict the reaction flow. This
paper uses a self-consistent one-dimensional model calculation with a constant
accretion rate of dM/dt=5e16g/s (0.045 Eddington) and reports on the detailed
rp-process reaction flow of a given burst.Comment: 4 pages, submitted to Nucl. Phys. A as part of the Nuclei in Cosmos 8
proceeding
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