Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Use of a sigmoid function to describe second peak in magnetization loops   Order-disorder transitions of a vortex lattice transfer type-II
superconductors from a low critical current state to a high one. The similar
transition between different current states can be caused by electromagnetic
granularity. A sigmoid curve is proposed to describe the corresponding peak in
a field dependence of the macroscopic critical density. Using the extended
critical state model, analytic expressions are obtained for the field
dependencies of the local critical current density, the depth of equilibrium
surface region, and the macroscopic critical current density. The expressions
are well fit to published data.

7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int