Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hidden and self-excited attractors in electromechanical systems with and
  without equilibria   This paper studies hidden oscillations appearing in electromechanical systems
with and without equilibria. Three different systems with such effects are
considered: translational oscillator-rotational actuator, drilling system
actuated by a DC-motor and drilling system actuated by induction motor. We
demonstrate that all three systems experience hidden oscillations in sense of
mathematical definition. But from physical point of view in certain cases it is
quite easy to localize there oscillations.

17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
18
The categories of this paper are: econ
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph