Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Improvement of critical current density in Fe-sheathed MgB2 tapes by
  ZrSi2, ZrB2 and WSi2 doping   Fe-sheathed MgB2 tapes were prepared through the in situ powder-in-tube
technique by 5 at.% ZrSi2, ZrB2 and WSi2 doping, respectively. The doping
effect of these compounds on the microstructure and superconducting properties
of MgB2 tapes has been investigated by using x-ray diffraction, scanning
electron microscope, transport measurements and DC susceptibility measurements.
Compared to the undoped samples, Jc for all the doped samples were much
improved; the best result in terms of Jc was achieved for ZrSi2 doping, by up
to a factor of 3.4 at 4.2 K in magnetic fields up to 12 T. Moreover, these
dopants did not significantly decrease the transition temperature. The Jc-B
curves of WSi2-doped tapes show better performance in higher magnetic fields in
comparison to undoped tapes, suggesting that pinning centers effective in a
high-field region were possibly introduced.

31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
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The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph