Hi
I would like to read Dissertation and Thesis of my area of interest from online sources like ProQuest, OATD, OpenThesis, etc but every document have some sort of mathematics models in it and that I am unable to understand. I don't mind to learn math but I don't really know.. from where should I really start. I would be very thankful for your help.

Mathematics is usually important in most of engineering topics especially in academa. You can start by looking which Math subject is more related to your area. Is it differential equations, probability or integrals? Then there are sufficient online resources for each subject.