23,912 research outputs found
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
Radiative capture reaction for Ne formation within a full three-body model
Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can
trigger the rp-process in type I x-ray bursts. In this environment, a
competition between and the
two-proton capture reaction is
expected.
Purpose: Determine the three-body radiative capture reaction rate for
formation including sequential and direct, resonant and
non-resonant contributions on an equal footing.
Method: Two different discretization methods have been applied to generate
Ne states in a full three-body model: the analytical transformed
harmonic oscillator method and the hyperspherical adiabatic expansion method.
The binary --O interaction has been adjusted to reproduce the known
spectrum of the unbound F nucleus. The dominant contributions to
the reaction rate have been
calculated from the inverse photodissociation process.
Results: Three-body calculations provide a reliable description of Ne
states. The agreement with the available experimental data on Ne is
discussed. It is shown that the
reaction rates computed within the two methods agree in a broad range of
temperatures. The present calculations are compared with a previous theoretical
estimation of the reaction rate.
Conclusions: It is found that the full three-body model provides a reaction
rate several orders of magnitude larger than the only previous estimation. The
implications for the rp-process in type I x-ray bursts should be investigated.Comment: 10 pages, 10 figures. Corrected versio
Anomalous quartic couplings in collisions at the LHeC and the FCC-he
We conducted a study on measuring production and on the sensitivity
limits at Confidence Level on thirteen anomalous couplings obtained by
dimension-8 operators which are related to the anomalous quartic
couplings. We consider the main reaction with the sub-process at
the Large Hadron electron Collider (LHeC) and the Future Circular
Collider-hadron electron (FCC-he). For the LHeC, energies of the beams
are taken to be and 140 GeV and the energy of the beams is taken
to be TeV. For the FCC-he, energies of the beams are taken to
be and 140 GeV and the energy of the beams is taken to be TeV, respectively. It is interesting to notice that the LHeC and the FCC-he
will lead to model-independent limits on the anomalous quartic
couplings which are one order of magnitude stringent than the CMS Collaboration
limits, in addition to being competitive with other limits reported in the
literature.Comment: 28 pages, 10 Figures and 13 Table
Contribuciones al muestreo sucesivo: estimador producto multivariante
Se considera el problema de estimar la media de una población finita para la ocasión actual, basándonos en las muestras seleccionadas en dos ocasiones. Se construye un estimador producto multivariante de doble muestreo para la parte solapada de la muestra, para el caso en que dos variables auxiliares se encuentran correlacionadas deforma negativa con la variable objeto de estudio. Se obtienen las expresiones para el estimador óptimo y su varianza. Se calcula la curva que nos proporciona la ganancia en eficiencia del estimador combinado sobre el estimador directo que no utiliza la información obtenida en la primera ocasión. Se obtienen las condiciones bajo las cuales nuestro estimador mejora en precisión al estimador combinado de producto univariante. Finalmente, se incluye un estudio empÃrico para analizar el buen funcionamiento del método propuesto
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