Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Construction and calibration of a goniometer to measure contact angles
  and calculate the surface free energy in solids with uncertainty analysis   Here, we present the construction and calibration of a low-cost goniometer to
measure contact angles by the sessile drop method. Besides, we propose a simple
and fast method to calculate the uncertainty in the determination of the
surface free energy (SFE) and its polar and dispersive components through the
Owens-Wendt model and tested it by using two testing liquids. The goniometer
performance and the SFE uncertainty were determined on two polymers:
polytetrafluorethylene (PTFE) and polyoxymethylene (POM), by using water and
methylene iodide. The values of contact angle measured were used to calculate
the SFE and its components with their errors. The SFE values obtained for PTFE
were 17.57-17.91 mJ/m^2, with a relative error lower than 5.5 %, whereas those
for POM were 42.80-43.23 mJ/m^2, with a relative error lower than 4.3%. Both
the SFE values and the errors were in the range of those previously reported.
Based on the mathematical analysis of the uncertainty propagation in the
determination of SFE, we concluded that the uncertainty is minimized when the
testing liquids are an apolar liquid and water.

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The categories of this paper are: solv-int
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys