The phrase "substitution model" refers to a way of thinking about how something can be replaced by or represented by something similar. It is a way of understanding or explaining how one thing can be used as a substitute for another. Full definition
Codon - substitution models for heterogeneous selection pressure at amino acid sites Yang, Z., R. Nielsen, N. Goldman, and A. K. Pedersen. (nielsenlab.org)
«It is crystal clear that we can not continue to operate our present system of governance, which negates the development of our natural endowments, agro-allied, minerals, water and promotes an import substitution model that is encouraging import dependence. (nigeriapoliticsonline.com)
Analsysis of these implications is presented, based on a logistic substitution model viewing energy technologies like biological species invading an echoniche and substituting in case of superiority for existing speices. (phe.rockefeller.edu)