Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A theory of flying/swimming saucers. Exact solutions for rectilinear
  locomotion   We study self-propulsion (or locomotion) of a robot (or an underwater
vehicle) in an inviscid incompressible fluid. The robot's body is rigid, while
its locomotion ability is due to an internal actuator, which can perform
controlled translational and rotational oscillations. Our attention is focused
on two classes of the plane analytic exact solutions, describing rectilinear
locomotion. Solutions of the first class describe the \emph{tumbling
locomotion}, while the second class corresponds to the \emph{zigzag locomotion}
without tumbling. We show, that tumbling locomotion is more efficient. Both
classes of solutions show, that the use of actuator allows to choose any
desired direction and any speed of locomotion. As a special case, we consider
the self-propulsion caused by small-amplitude and high-frequency actuator
oscillations. The exact and elementary character of our solutions makes the
results potentially useful as the tests to verify physical and engineering
models, as well as numerical and asymptotic results. In contrary to many recent
publications in this area, the material is accessible to UG students in
Engineering, Physics, and Applied Mathematics.

12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci