Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantitative measurement of combustion gases in harsh environments using
  NDIR spectroscopy   The global climate change calls for a more environmental friendly use of
energy and has led to stricter limits and regulations for the emissions of
various greenhouse gases. Consequently, there is nowadays an increasing need
for the detection of exhaust and natural gases. This need leads to an
ever-growing market for gas sensors, which, at the moment, is dominated by
chemical sensors. Yet, the increasing demands to also measure under harsh
environmental conditions pave the way for non-invasive measurements and thus to
optical detection techniques. Here, we present the development of a
non-dispersive infrared absorption spectroscopy (NDIR) method for application
to optical detection systems operating under harsh environments.

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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
11
The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th