Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Novel method for photovoltaic energy conversion using surface acoustic
  waves in piezoelectric semiconductors
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex