I'm a graduate student in Korea and preparing my thesis.

When I have read some research papers, I often found that some people omit "the"

in front of "noun of ----". Here I list two such examples.

(1) It is clear that the best practices call for INTEGRATION OF environmental managements
(2) 100 samples are collected during PROCESSING OF a product

I learned that "the" is needed before "INTEGRATION" and "PROCESSING". But, Why do the authors omit "the" in front of those nouns?

Specific explanation will be appreciated. Thank you.

C Kim
Just with the context you have provided I am inclined to say that omitting the articles is an error. However, as you probably know, article use is quite idiomatic and speaker dependent as well as being very context dependent. Without a more complete context that's about all I can say and even with the full context I'm not sure I could give you an answer that would be very satisfying.

There are many threads here on the forums that discuss article use, you can use the search function to find them.
I would really like to help you! Tomorrow I'm teaching a FREE session on writing/grammar, and I would love for you to come. Sign up is FREE. My session tomorrow is FREE! Join me! Even if you're not interested in the course after tomorrow, I do private tutoring. Check out the session and my profile here: http://edufire.com/classes/8714-33-ways-to-write-a-sentence-session-1

Thank You,