Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Piecewise continuous distribution function method and ultrasound at half
  space   The system of hydrodynamic-type equations, derived by two-side distribution
function for a stratified gas in gravity field is applied to a problem of
ultrasound propagation and attenuation. The background state and linearized
version of the obtained system is studied and compared with the Navier-Stokes
one at arbitrary Knudsen numbers. The WKB solutions for ultrasound in a
stratified medium are constructed in explicit form. The problem of a generation
by a moving plane in a rarefied gas is explored and used as a test while
compared with experiment.

27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
19
The categories of this paper are: eess
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
12
The categories of this paper are: nucl-th
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
30
The categories of this paper are: q-alg