Hello NPV
Your best choice is self publishing. Go to 
http://www.createspace.com it's a company that belongs to Amazon, which means you will be immediately listed in all Amazon's stores around the globe. The thing is you have to do everything yourself, that means the design of every little detail has to be yours, content, cover, back cover and even the spine. This includes colors, fonts, sizes, etc. So if anything goes wrong it will be your fault because nobody reviews it. This means you should have had several testfolders that guarantee that your diagrams are correct.
The good news is that the royalties are higher than with usual publishing and you don't need to invest anything, if someone buys one book, then one book is printed, if nobody buys the book,no books are printed.
If you run into some trouble just write here or send me a pm and I'll gladly answer it.
Good luck, your models look very interesting.