Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Wind Tunnel in Your Classroom: The Design and Implementation of a
  Portable Wind Tunnel for Use in the Science Classroom   This article describes a wind tunnel's ease of construction and its uses as a
visualization tool that integrates concepts at the primary and secondary
levels. An Appendix contains detailed building instructions. A web site (under
construction) will provide sample lesson plans, visualization and application
tips, animations and links to background

25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math