671,094 research outputs found
Fuzzy Modeling for Uncertain Nonlinear Systems Using Fuzzy Equations and Z-Numbers
In this paper, the uncertainty property is represented by Z-number as the coefficients and variables of the fuzzy equation. This modification for the fuzzy equation is suitable for nonlinear system modeling with uncertain parameters. Here, we use fuzzy equations as the models for the uncertain nonlinear systems. The modeling of the uncertain nonlinear systems is to find the coefficients of the fuzzy equation. However, it is very difficult to obtain Z-number coefficients of the fuzzy equations.
Taking into consideration the modeling case at par with uncertain nonlinear systems, the implementation of neural network technique is contributed in the complex way of dealing the appropriate coefficients of the fuzzy equations. We use the neural network method to approximate Z-number coefficients of the fuzzy equations
Large-scale calculations of supernova neutrino-induced reactions in Z=8-82 target nuclei
Background: In the environment of high neutrino-fluxes provided in
core-collapse supernovae or neutron star mergers, neutrino-induced reactions
with nuclei contribute to the nucleosynthesis processes. A number of
terrestrial neutrino detectors are based on inelastic neutrino-nucleus
scattering and modeling of the respective cross sections allow predictions of
the expected detector reaction rates.
Purpose: To provide a self-consistent microscopic description of
neutrino-nucleus cross sections involving a large pool of Z = 8 - 82 nuclei for
the implementation in models of nucleosynthesis and neutrino detector
simulations.
Methods: Self-consistent theory framework based on relativistic nuclear
energy density functional is employed to determine the nuclear structure of the
initial state and relevant transitions to excited states induced by neutrinos.
The weak neutrino-nucleus interaction is employed in the current-current form
and a complete set of transition operators is taken into account.
Results: We perform large-scale calculations of charged-current
neutrino-nucleus cross sections, including those averaged over supernova
neutrino fluxes, for the set of even-even target nuclei from oxygen toward lead
(Z = 8 - 82), spanning N = 8 - 182 (OPb pool). The model calculations include
allowed and forbidden transitions up to J = 5 multipoles.
Conclusions: The present analysis shows that the self-consistent calculations
result in considerable differences in comparison to previously reported cross
sections, and for a large number of target nuclei the cross sections are
enhanced. Revision in modeling r-process nucleosynthesis based on a
self-consistent description of neutrino-induced reactions would allow an
updated insight into the origin of elements in the Universe and it would
provide the estimate of uncertainties in the calculated element abundance
patterns.Comment: 25 pages, 12 figures, submitted to Physical Review
Reproducing the assembly of massive galaxies within the hierarchical cosmogony
In order to gain insight into the physical mechanisms leading to the
formation of stars and their assembly in galaxies, we compare the predictions
of the MOdel for the Rise of GAlaxies aNd Active nuclei (MORGANA) to the
properties of K- and 850 micron-selected galaxies (such as number counts,
redshift distributions and luminosity functions) by combining MORGANA with the
spectrophotometric model GRASIL. We find that it is possible to reproduce the
K- and 850 micron-band datasets at the same time and with a standard Salpeter
IMF, and ascribe this success to our improved modeling of cooling in DM halos.
We then predict that massively star-forming discs are common at z~2 and
dominate the star-formation rate, but most of them merge with other galaxies
within ~100 Myr. Our preferred model produces an overabundance of bright
galaxies at z<1; this overabundance might be connected to the build-up of the
diffuse stellar component in galaxy clusters, as suggested by Monaco et al.
(2006), but a naive implementation of the mechanism suggested in that paper
does not produce a sufficient slow-down of the evolution of these objects.
Moreover, our model over-predicts the number of 10^{10}-10^{11} M_sun galaxies
at z~1; this is a common behavior of theoretical models as shown by Fontana et
al. (2006). These findings show that, while the overall build-up of the stellar
mass is correctly reproduced by galaxy formation models, the ``downsizing''
trend of galaxies is not fully reproduced yet. This hints to some missing
feedback mechanism in order to reproduce at the same time the formation of both
the massive and the small galaxies.Comment: 14 pages; 11 figures; accepted for publication by MNRA
An Application of Multi-band Forced Photometry to One Square Degree of SERVS: Accurate Photometric Redshifts and Implications for Future Science
We apply The Tractor image modeling code to improve upon existing multi-band
photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS).
SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5 micron
over five well-studied deep fields spanning 18 square degrees. In concert with
data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to
provide a census of the properties of massive galaxies out to z ~ 5. To
accomplish this, we are using The Tractor to perform "forced photometry." This
technique employs prior measurements of source positions and surface brightness
profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic
Observations (VIDEO) survey to model and fit the fluxes at lower-resolution
bands. We discuss our implementation of The Tractor over a square degree test
region within the XMM-LSS field with deep imaging in 12 NIR/optical bands. Our
new multi-band source catalogs offer a number of advantages over traditional
position-matched catalogs, including 1) consistent source cross-identification
between bands, 2) de-blending of sources that are clearly resolved in the
fiducial band but blended in the lower-resolution SERVS data, 3) a higher
source detection fraction in each band, 4) a larger number of candidate
galaxies in the redshift range 5 < z < 6, and 5) a statistically significant
improvement in the photometric redshift accuracy as evidenced by the
significant decrease in the fraction of outliers compared to spectroscopic
redshifts. Thus, forced photometry using The Tractor offers a means of
improving the accuracy of multi-band extragalactic surveys designed for galaxy
evolution studies. We will extend our application of this technique to the full
SERVS footprint in the future.Comment: accepted to ApJ, 22 pages, 12 figure
High-performance Parallel Solver for Integral Equations of Electromagnetics Based on Galerkin Method
A new parallel solver for the volumetric integral equations (IE) of
electrodynamics is presented. The solver is based on the Galerkin method which
ensures the convergent numerical solution. The main features include: (i) the
memory usage is 8 times lower, compared to analogous IE based algorithms,
without additional restriction on the background media; (ii) accurate and
stable method to compute matrix coefficients corresponding to the IE; (iii)
high degree of parallelism. The solver's computational efficiency is shown on a
problem of magnetotelluric sounding of the high conductivity contrast media. A
good agreement with the results obtained with the second order finite element
method is demonstrated. Due to effective approach to parallelization and
distributed data storage the program exhibits perfect scalability on different
hardware platforms.Comment: The main results of this paper were presented at IAMG 2015 conference
Frieberg, Germany. 28 pages, 11 figure
Design, implementation, and testing of advanced virtual coordinate-measuring machines
Copyright @ 2011 IEEE. This article has been made available through the Brunel Open Access Publishing Fund.Advanced virtual coordinate-measuring machines (CMMs) (AVCMMs) have recently been developed at Brunel University, which provide vivid graphical representation and powerful simulation of CMM operations, together with Monte-Carlo-based uncertainty evaluation. In an integrated virtual environment, the user can plan an inspection strategy for a given task, carry out virtual measurements, and evaluate the uncertainty associated with the measurement results, all without the need of using a physical machine. The obtained estimate of uncertainty can serve as a rapid feedback for the user to optimize the inspection plan in the AVCMM before actual measurements or as an evaluation of the measurement results performed. This paper details the methodology, design, and implementation of the AVCMM system, including CMM modeling, probe contact and collision detection, error modeling and simulation, and uncertainty evaluation. This paper further reports experimental results for the testing of the AVCMM
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