109,482 research outputs found
Genetic Exponentially Fitted Method for Solving Multi-dimensional Drift-diffusion Equations
A general approach was proposed in this article to develop high-order
exponentially fitted basis functions for finite element approximations of
multi-dimensional drift-diffusion equations for modeling biomolecular
electrodiffusion processes. Such methods are highly desirable for achieving
numerical stability and efficiency. We found that by utilizing the one-one
correspondence between continuous piecewise polynomial space of degree
and the divergence-free vector space of degree , one can construct
high-order 2-D exponentially fitted basis functions that are strictly
interpolative at a selected node set but are discontinuous on edges in general,
spanning nonconforming finite element spaces. First order convergence was
proved for the methods constructed from divergence-free Raviart-Thomas space
at two different node set
A very important process of nucleosynthesis in stars
When some nuclei are free from strong gravitational field, they are unstable and will become stable nuclei by competitions of following processes: (1) neutron-evaporation; (2) spontaneous fission; and (3) beta prime 3-decay. At the initial stage, (1) and (2) are important and (3) can be ignored. The qualitative results are as follows: (1) it seems that nuclei with A 100 come from the spontaneous fission and beta prime decay of neutron-evaporated nuclei with A similiar to 140-440, which can replace the r-process; (2) the super-heavy elements with Z=114--126 (A similiar to 330--360) can be formed. They can be observed in cosmic rage if they have the halftime T 10 to the 7th poweer years; (3) the peak in the rare-earth elements comes from the symmetric fission of super-heavy elements; (4) there are more neutron-rich nuclei in the fragments; and (5) the abundances of a 83 elements in cosmic rays are one order of magnitude higher than that in the solar system
Nucleosynthesis in the terrestrial and solar atmospheres
Variations of Delta D, delta C-13, Delta C-14 and Delta O-18 with time were measured by a lot of experiments. Many abnormalities of isotope abundances in cosmic rays were found by balloons and satellites. It is suggested that these abnormalities are related to nuclearsynthesis in the terrestrial and solar atmospheres and are closely related to solar activities
Updating the Estimation of the Supply of Storage Model
An updated supply of storage equation is estimated to reflect recent developments in the theoretical and empirical literature. Among the findings is an inverse relationship between storage cost adjusted price spread and a proxy measure of convenience yield, and a curvilinear relationship between stocks-to-use ratio and implied volatility.supply of storage, implied volatility, convenience yield, Research Methods/ Statistical Methods, Q11, Q14, G10,
Intrinsic Cavity QED and Emergent Quasi-Normal Modes for Single Photon
We propose a special cavity design that is constructed by terminating a
one-dimensional waveguide with a perfect mirror at one end and doping a
two-level atom at the other. We show that this atom plays the intrinsic role of
a semi-transparent mirror for single photon transports such that quasi-normal
modes (QNM's) emerge spontaneously in the cavity system. This atomic mirror has
its reflection coefficient tunable through its level spacing and its coupling
to the cavity field, for which the cavity system can be regarded as a two-end
resonator with a continuously tunable leakage. The overall investigation
predicts the existence of quasi-bound states in the waveguide continuum. Solid
state implementations based on a dc-SQUID circuit and a defected line resonator
embedded in a photonic crystal are illustrated to show the experimental
accessibility of the generic model.Comment: 4 pages,5 figures, Comments welcom
Effect of initial configuration on network-based recommendation
In this paper, based on a weighted object network, we propose a
recommendation algorithm, which is sensitive to the configuration of initial
resource distribution. Even under the simplest case with binary resource, the
current algorithm has remarkably higher accuracy than the widely applied global
ranking method and collaborative filtering. Furthermore, we introduce a free
parameter to regulate the initial configuration of resource. The
numerical results indicate that decreasing the initial resource located on
popular objects can further improve the algorithmic accuracy. More
significantly, we argue that a better algorithm should simultaneously have
higher accuracy and be more personal. According to a newly proposed measure
about the degree of personalization, we demonstrate that a degree-dependent
initial configuration can outperform the uniform case for both accuracy and
personalization strength.Comment: 4 pages and 3 figure
Globally Optimal Crowdsourcing Quality Management
We study crowdsourcing quality management, that is, given worker responses to
a set of tasks, our goal is to jointly estimate the true answers for the tasks,
as well as the quality of the workers. Prior work on this problem relies
primarily on applying Expectation-Maximization (EM) on the underlying maximum
likelihood problem to estimate true answers as well as worker quality.
Unfortunately, EM only provides a locally optimal solution rather than a
globally optimal one. Other solutions to the problem (that do not leverage EM)
fail to provide global optimality guarantees as well. In this paper, we focus
on filtering, where tasks require the evaluation of a yes/no predicate, and
rating, where tasks elicit integer scores from a finite domain. We design
algorithms for finding the global optimal estimates of correct task answers and
worker quality for the underlying maximum likelihood problem, and characterize
the complexity of these algorithms. Our algorithms conceptually consider all
mappings from tasks to true answers (typically a very large number), leveraging
two key ideas to reduce, by several orders of magnitude, the number of mappings
under consideration, while preserving optimality. We also demonstrate that
these algorithms often find more accurate estimates than EM-based algorithms.
This paper makes an important contribution towards understanding the inherent
complexity of globally optimal crowdsourcing quality management
A large accretion disk of extreme eccentricity in the TDE ASASSN-14li
In the canonical model for tidal disruption events (TDEs), the stellar debris
circularizes quickly to form an accretion disk of size about twice the orbital
pericenter of the star. Most TDEs and candidates discovered in the optical/UV
have broad optical emission lines with complex and diverse profiles of puzzling
origin. Liu et al. recently developed a relativistic elliptical disk model of
constant eccentricity in radius for the broad optical emission lines of TDEs
and well reproduced the double-peaked line profiles of the TDE candidate
PTF09djl with a large and extremely eccentric accretion disk. In this paper, we
show that the optical emission lines of the TDE ASASSN-14li with radically
different profiles are well modelled with the relativistic elliptical disk
model, too. The accretion disk of ASASSN-14li has an eccentricity 0.97 and
semimajor axis of 847 times the Schwarzschild radius (r_S) of the black hole
(BH). It forms as the consequence of tidal disruption of a star passing by a
massive BH with orbital pericenter 25r_S. The optical emission lines of
ASASSN-14li are powered by an extended X-ray source of flat radial distribution
overlapping the bulk of the accretion disk and the single-peaked asymmetric
line profiles are mainly due to the orbital motion of the emitting matter
within the disk plane of inclination about 26\degr and of pericenter
orientation closely toward the observer. Our results suggest that modelling the
complex line profiles is powerful in probing the structures of accretion disks
and coronal X-ray sources in TDEs.Comment: 10 pages, 8 figures, accepted for publication in the MNRA
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