Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Optimized Control of Variable Speed Hydropower for Provision of Fast
  Frequency Reserves
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex