Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A degenerating convection-diffusion system modelling froth flotation
  with drainage   Froth flotation is a common unit operation used in mineral processing. It
serves to separate valuable mineral particles from worthless gangue particles
in finely ground ores. The valuable mineral particles are hydrophobic and
attach to bubbles of air injected into the pulp. This creates bubble-particle
aggregates that rise to the top of the flotation column where they accumulate
to a froth or foam layer that is removed through a launder for further
processing. At the same time, the hydrophilic gangue particles settle and are
removed continuously. The drainage of liquid due to capillarity is essential
for the formation of a stable froth layer. This effect is included into a
previously formulated hyperbolic system of partial differential equations that
models the volume fractions of floating aggregates and settling hydrophilic
solids [R. B\"{u}rger, S. Diehl and M.C. Mart\'i, {\it IMA J. Appl. Math.} {\bf
84} (2019) 930--973]. The construction of desired steady-state solutions with a
froth layer is detailed and feasibility conditions on the feed volume fractions
and the volumetric flows of feed, underflow and wash water are visualized in
so-called operating charts. A monotone numerical scheme is derived and employed
to simulate the dynamic behaviour of a flotation column. It is also proven
that, under a suitable Courant-Friedrichs-Lewy (CFL) condition, the approximate
volume fractions are bounded between zero and one when the initial data are.

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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph