Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Towards the Realization of Higher Connectivity in MgB2 Conductors:
  In-situ or Sintered Ex-situ?   The two most common types of MgB2 conductor fabrication technique - in-situ
and ex-situ - show increasing conflicts concerning the connectivity, an
effective current-carrying cross-sectional area. An in-situ reaction yields a
strong intergrain coupling with a low packing factor, while an ex-situ process
using pre-reacted MgB2 yields tightly packed grains, however, their coupling is
much weaker. We studied the normal-state resistivity and microstructure of
ex-situ MgB2 bulks synthesized with varied heating conditions under ambient
pressure. The samples heated at moderately high temperatures of ~900{\deg}C for
a long period showed an increased packing factor, a larger intergrain contact
area and a significantly decreased resistivity, all of which indicate the
solid-state self-sintering of MgB2. Consequently the connectivity of the
sintered ex-situ samples exceeded the typical connectivity range 5-15% of the
in-situ samples. Our results show self-sintering develops the superior
connectivity potential of ex-situ MgB2, though its intergrain coupling is not
yet fulfilled, to provide a strong possibility of twice or even much higher
connectivity in optimally sintered ex-situ MgB2 than in in-situ MgB2.

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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: stat
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The categories of this paper are: adap-org
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys