Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: The Critical Role of the Boundary Layer Thickness for the Initiation of
  Aeolian Sediment Transport
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol