How to write an email to a professor to inquire about a visiting researcher position?
I think your email is fine! I'll speak from my experience doing several research internships (I haven't completed my PhD, therefore no postdoc). It obviously depends a lot on your field (ie, your field might be different than mine), but even though I had previous experience and publications, I sent about 100 emails before I got my first phone interview. 

If you have the time to change your email, I might soften the tone a little. You do come off as very eager. For example, I might change the following to: 


  "It would be my great honor and appreciation if you could find time to read this proposal at your convenience and I hope my background in mathematical modeling and experimentation could help me to have a valuable contribution." 


To something more like: 


  "My background in mathematical modeling and experimentation makes me a strong candidate to successfully [work in your lab/collaborate/publish papers/etc]. 


I suggest this because:


saying it would be a "great honor and appreciation" could be interpreted as brown-nosing/sucking up. In America, people are not usually this humble, nor do we usually speak this honorifically about others (but this could depend on your field/where you are applying). 
In America, it is very acceptable to state why you are a strong candidate. Saying things like "I hope I will be successful at..." or "I believe I can..." can make potential bosses feel like you're not sure if you will be successful. Instead, I'd recommend saying "I can..." or "I will..." or "I am..."