symbol list and nomenclature I received this comment from a reviewer in journal of "Optimal Control Application and Methods": "The notations need to be added in the revision to add the readability, because many symbols appeared are not very familiar with the readers. For instance, what is the meaning of &lt;…> in (2) and (3)?" 

Is it necessary add a nomenclature with a list of used symbols of variables, operators and abbreviations?
Is there any specific position for this section ?
Is it necessary add a nomenclature with a list of used symbols of
  variables, operators and abbreviations?


You should treat this comment like any other comment from a reviewer: It tells you that one potential reader of your paper (and, if the editor did a good job, a qualified one) had a hard time understanding your paper. Hence, you should improve the presentation of your paper in this respect, so you should make the effort and help potential readers. (There may be the chance that this particular journel even requests a nomenclature, but I did not check this…)


  Is there any specific position for this section ?


For this, there are two good answers here.