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Due to the slightly different microstructure , the contribution of each strengthening mechanism was slightly different in identical samples made with virgin powder .
 concept or principle: microstructure; concept or principle: strengthening mechanism; concept or principle: samples; material: virgin powder
Given options, please tell me the categories of all the listed entity words.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} 
 Entities: microstructure, strengthening mechanism, samples, virgin powder 
Answer:
 concept or principle: microstructure; concept or principle: strengthening mechanism; concept or principle: samples; material: virgin powder