Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modeling nonlinearity and hysteresis due to critical-state flux
  penetration in hard superconductors   The nonlinear surface impedance of a thin superconducting strip carrying a
microwave current has been calculated numerically from first principles based
upon flux penetration due to a current-induced critical state. The calculations
approach analytic results in the appropriate limit. The technique is useful for
design of passive superconducting microwave circuits.

32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th