42,607 research outputs found
On the Randi\'{c} index and conditional parameters of a graph
The aim of this paper is to study some parameters of simple graphs related
with the degree of the vertices. So, our main tool is the matrix
whose ()-entry is where denotes the degree of the vertex . We study
the Randi\'{c} index and some interesting particular cases of conditional
excess, conditional Wiener index, and conditional diameter. In particular,
using the matrix or its eigenvalues, we obtain tight bounds on the
studied parameters.Comment: arXiv admin note: text overlap with arXiv:math/060243
Reactions induced by Be in a four-body continuum-discretized coupled-channels framework
We investigate the elastic scattering of Be on Pb at beam
energies above (50 MeV) and below (40 MeV) the Coulomb barrier. The reaction is
described within a four-body framework using the Continuum-Discretized
Coupled-Channels (CDCC) method. The Be projectile states are generated
using the analytical Transformed Harmonic Oscillator (THO) basis in
hyperspherical coordinates. Our calculations confirm the importance of
continuum effects at low energies.Comment: 2 pages, 1 figure. Proceedings of the International Scientific
Meeting on Nuclear Physics, RABIDA15, La R\'abida (Spain), June 1-5, 201
Analytical transformed harmonic oscillator basis for three-body nuclei of astrophysical interest: Application to 6He
Recently, a square-integrable discrete basis, obtained performing a simple
analytical local scale transformation to the harmonic oscillator basis, has
been proposed and successfully applied to study the properties of two-body
systems. Here, the method is generalized to study three-body systems. To test
the goodness of the formalism and establish its applicability and limitations,
the capture reaction rate for the nucleosynthesis of the Borromean nucleus 6He
(4He + n + n) is addressed. Results are compared with previous publications and
with calculations based on actual three-body continuum wave functions, which
can be generated for this simple case. The obtained results encourage the
application to other Borromean nuclei of astrophysical interest such as 9Be and
12C, for which actual three-body continuum calculations are very involved.Comment: Accepted in Phys. Rev.
Polydispersity Effects in the Dynamics and Stability of Bubbling Flows
The occurrence of swarms of small bubbles in a variety of industrial systems
enhances their performance. However, the effects that size polydispersity may
produce on the stability of kinematic waves, the gain factor, mean bubble
velocity, kinematic and dynamic wave velocities is, to our knowledge, not yet
well established. We found that size polydispersity enhances the stability of a
bubble column by a factor of about 23% as a function of frequency and for a
particular type of bubble column. In this way our model predicts effects that
might be verified experimentally but this, however, remain to be assessed. Our
results reinforce the point of view advocated in this work in the sense that a
description of a bubble column based on the concept of randomness of a bubble
cloud and average properties of the fluid motion, may be a useful approach that
has not been exploited in engineering systems.Comment: 11 pages, 2 figures, presented at the 3rd NEXT-SigmaPhi International
Conference, 13-18 August, 2005, Kolymbari, Cret
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