Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A variational principle for the system of P.D.E. of porous metal
  bearings   Porous metal bearings are widely used in small and micro devices. To compute
the pressure one has to solve the Reynolds equation coupled with the Laplace
equation. We show that it is possible to give to the relevant boundary value
problem a variational formulation. We show that the pressure inside a porous
bearing is less then that of the corresponding non-porous bearing.

21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an