934 research outputs found
Analysis of radial segregation of granular mixtures in a rotating drum
This paper considers the segregation of a granular mixture in a rotating
drum. Extending a recent kinematic model for grain transport on sandpile
surfaces to the case of rotating drums, an analysis is presented for radial
segregation in the rolling regime, where a thin layer is avalanching down while
the rest of the material follows rigid body rotation. We argue that segregation
is driven not just by differences in the angle of repose of the species, as has
been assumed in earlier investigations, but also by differences in the size and
surface properties of the grains. The cases of grains differing only in size
(slightly or widely) and only in surface properties are considered, and the
predictions are in qualitative agreement with observations. The model yields
results inconsistent with the assumptions for more general cases, and we
speculate on how this may be corrected.Comment: 12 pages inclusive of 10 PostScript (*.eps) figures, uses svjour,
psfrag and graphicx. Submitted for publication to Euro. Phys. J.
Variational Bayes with Intractable Likelihood
Variational Bayes (VB) is rapidly becoming a popular tool for Bayesian
inference in statistical modeling. However, the existing VB algorithms are
restricted to cases where the likelihood is tractable, which precludes the use
of VB in many interesting situations such as in state space models and in
approximate Bayesian computation (ABC), where application of VB methods was
previously impossible. This paper extends the scope of application of VB to
cases where the likelihood is intractable, but can be estimated unbiasedly. The
proposed VB method therefore makes it possible to carry out Bayesian inference
in many statistical applications, including state space models and ABC. The
method is generic in the sense that it can be applied to almost all statistical
models without requiring too much model-based derivation, which is a drawback
of many existing VB algorithms. We also show how the proposed method can be
used to obtain highly accurate VB approximations of marginal posterior
distributions.Comment: 40 pages, 6 figure
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