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While early works mainly focused on the theoretical consideration of the structural design of the unit cells , recent efforts put more emphasis on integrating topology optimization with AM , e.g .
 concept or principle: theoretical; engineering feature: structural design; concept or principle: unit cells; engineering feature: topology optimization; manufacturing process: AM
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 concept or principle: theoretical; engineering feature: structural design; concept or principle: unit cells; engineering feature: topology optimization; manufacturing process: AM