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Since after sintering , the pieces density rarely exceeds 50 % of the theoretical value , this technology seems not to be suitable for structural parts .
 manufacturing process: sintering; machanical property: density; concept or principle: theoretical; concept or principle: technology; material: be
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:
 manufacturing process: sintering; machanical property: density; concept or principle: theoretical; concept or principle: technology; material: be