5,932 research outputs found
Comptomization and radiation spectra of X-ray sources. Calculation of the Monte Carlo method
The results of computations of the Comptomization of low frequency radiation in weakly relativistic plasma are presented. The influence of photoabsorption by iron ions on a hard X-ray spectrum is considered
Derivative based global sensitivity measures
The method of derivative based global sensitivity measures (DGSM) has
recently become popular among practitioners. It has a strong link with the
Morris screening method and Sobol' sensitivity indices and has several
advantages over them. DGSM are very easy to implement and evaluate numerically.
The computational time required for numerical evaluation of DGSM is generally
much lower than that for estimation of Sobol' sensitivity indices. This paper
presents a survey of recent advances in DGSM concerning lower and upper bounds
on the values of Sobol' total sensitivity indices . Using these
bounds it is possible in most cases to get a good practical estimation of the
values of . Several examples are used to illustrate an
application of DGSM
Azimuthal Angular Distributions in EDDE as Spin-Parity Analyser and Glueball Filter for LHC
Exclusive Double Diffractive Events (EDDE) are analysed as the source of
information about the central system. Experimental possibilities for exotic
particles searches are considered. From the reggeized tensor current picture
some azimuthal angle dependences were obtained to fit the data from WA102
experiment and to make predictions for LHC collider.Comment: LaTeX, 20 pages, 7 figures, references are adde
Multidimensional sampling for simulation and integration: measures, discrepancies, and quasi-random numbers
This is basically a review of the field of Quasi-Monte Carlo intended for
computational physicists and other potential users of quasi-random numbers. As
such, much of the material is not new, but is presented here in a style
hopefully more accessible to physicists than the specialized mathematical
literature. There are also some new results: On the practical side we give
important empirical properties of large quasi-random point sets, especially the
exact quadratic discrepancies; on the theoretical side, there is the exact
distribution of quadratic discrepancy for random point sets.Comment: 51 pages. Full paper, including all figures also available at:
ftp://ftp.nikhef.nl/pub/preprints/96-017.ps.gz Accepted for publication in
Comp.Phys.Comm. Fixed some typos, corrected formula 108,figure 11 and table
Magnetogenesis in Higgs-Starobinsky inflation
In the framework of mixed Higgs-Starobinsky inflation, we consider the
generation of Abelian gauge fields due to their nonminimal coupling to gravity
(in two different formulations of gravity -- metric and Palatini). We couple
the gauge-field invariants and
to an integer power of the scalar curvature
in Jordan frame and, treating these interactions perturbatively, switch
to the Einstein frame where they lead to effective kinetic and axial couplings
between gauge fields and inflaton. We determine the power spectra, energy
densities, correlation length, and helicality of the generated gauge fields for
different values of the nonminimal coupling constants and parameter . We
analytically estimate the spectral index of the magnetic power spectrum
and show that for it is possible to get the scale-invariant or even
red-tilted spectrum for a wide range of modes that implies larger correlation
length of the generated fields. On the other hand, the magnitude of these
fields typically decreases in time becoming very small in the end of inflation.
Thus, it is difficult to obtain both large magnitude and correlation length of
the gauge field in the frame of this model.Comment: 20 pages, 7 figures, submitted to Phys. Rev.
Spatial inversion of gyrotropy parameter in conductivity tensor and charge transport peculiarities
Charge transfer is discussed for the case when gyrotropy parameter (Hall coefficient) varies along transport л-direction and inverses its sign. This situation takes place in contacts of the serially joined materials having electron and hole types of conductivity. Spatial inhomogeneity of conductivity and inversion of Hall coefficient sign are analyzed in terms of electric potential and current density distribution. It is shown that under inhomogeneous magnetic field the steady current skinning takes place in plate sample
A recommender system for process discovery
Over the last decade, several algorithms for process discovery and process conformance have been proposed. Still, it is well-accepted that there is no dominant algorithm in any of these two disciplines, and then it is often difficult to apply them successfully. Most of these algorithms need a close-to expert knowledge in order to be applied satisfactorily. In this paper, we present a recommender system that uses portfolio-based algorithm selection strategies to face the following problems: to find the best discovery algorithm for the data at hand, and to allow bridging the gap between general users and process mining algorithms. Experiments performed with the developed tool witness the usefulness of the approach for a variety of instances.Peer ReviewedPostprint (author’s final draft
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