What is the location of the nomenclature section in a scientific paper?
The correct position for a nomenclature section is the location normally used by the journal in question. While as Paul suggests, the logical location for this should be at the start of the paper, in many journals, the nomenclature section is placed at the end, largely because it does not "look as good" to have the nomenclature section right on the first page (which is optically the "prime real estate" of the paper).