Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The fractional - order controllers: Methods for their synthesis and
  application   This paper deals with fractional-order controllers. We outline mathematical
description of fractional controllers and methods of their synthesis and
application. Synthesis method is a modified root locus method for
fractional-order systems and fractional-order controllers. In the next section
we describe how to apply the fractional controller on control systems.

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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin