2495
The crack propagation path and fracture mechanisms were studied using optical microscopy ( OM ) and scanning electron microscopy ( SEM ) examinations .
 concept or principle: crack propagation; concept or principle: fracture; process characterization: optical microscopy; process characterization: OM; process characterization: scanning electron microscopy; process characterization: SEM
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: crack propagation, fracture, optical microscopy, OM, scanning electron microscopy, SEM 
Answer:
 concept or principle: crack propagation; concept or principle: fracture; process characterization: optical microscopy; process characterization: OM; process characterization: scanning electron microscopy; process characterization: SEM