Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Demagnetization factor for a powder of randomly packed spherical
  particles   The demagnetization factors for randomly packed spherical particle powders
with different porosities, sample aspect ratios and monodisperse, normal and
log-normal particle size distributions have been calculated using a numerical
model. For a relative permeability of 2, comparable to room temperature Gd, the
calculated demagnetization factor is close to the theoretical value. The
normalized standard deviation of the magnetization in the powder was 6.0%-6.7%.
The demagnetization factor decreased significantly, while the standard
deviation of the magnetization increased, for increasing relative permeability.

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The categories of this paper are: dg-ga
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The categories of this paper are: adap-org
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The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: eess
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol