If anyone wants to contact a senior researcher, he/she can search for the email address of the senior researcher in the published articles. The articles could be available at ResearchGate or LinkedIn. Then, it is possible to get the email from there. Finally, the one who wants the senior researcher can communicate through email. However, this is only for the senior researcher who is corresponding author, because the email of corresponding author is always available within the published article.
For the current question, Dr. Mohammad Mahdi Vaez is not a corresponding author for the article. Due to this, the email is not available. To get the Dr. Mohammad Mahdi Vaez, search by his name in qutation mark. You get his email address soon.
Elias Ezo Based on the original paper, there are two authors. You could contact the contact information listed to request permission and/or request to reach Dr. Mahdi Vaez at [email protected].