Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Statistical Properties of a 2D Granular Material Subjected to Cyclic
  Shear   This work focuses on the evolution of structure and stress for an
experimental system of 2D photoelastic particles that is subjected to multiple
cycles of pure shear. Throughout this process, we determine the contact network
and the contact forces using particle tracking and photoelastic techniques.
These data yield the fabric and stress tensors and the distributions of contact
forces in the normal and tangential directions. We then find that there is, to
a reasonable approximation, a functional relation between the system pressure,
$P$, and the mean contact number, $Z$. This relationship applies to the shear
stress $\tau$, except for the strains in the immediate vicinity of the contact
network reversal. By contrast, quantities such as $P$, $\tau$ and $Z$ are
strongly hysteretic functions of the strain, $\epsilon$. We find that the
distributions of normal and tangential forces, when expressed in terms of the
appropriate means, are essentially independent of strain. We close by analyzing
a subset of shear data in terms of strong and weak force networks.

2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs