1. Introduction
In the pulp industry is important to determine the
cleanliness of the final product by counting number
and the size of the impurities. After a final drying
process, the pulp comes out continuously as a web
product several meters wide and few mm. thick, which
is cut into sheets, piled up in bales and sold in units
made up of several bales. Depending on the raw
material and on the overall chemical and mechanical
process, the final product can have different degrees of
cleanliness that highly influence the quality of the
product and can therefore be sold for different
applications and clients at different prices.
www.elsevier.com/locate/compind
Computers in Industry 56 (2005) 935–942
* Corresponding author. Tel.: +34 91336 3061;
fax: +34 91336 3010.
E-mail addresses: campoy@etsii.upm.es (P. Campoy),
jcanaval@ence.es (J. Canaval), danipena@tiscali.es (D. Pen˜a).
1 Tel.: +34 98687 2303; fax: +34 98687 3364.
2 Tel.: +34 65488 5112.
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doi:10.1016/j.compind.2005.05.018