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Several important but easily overlooked factors , including the surface structure of metallic powder , porosity of powder bed , vaporization and heat loss , were considered to improve the accuracy of the model .
 engineering feature: surface structure; material: metallic powder; machanical property: porosity; machine or equipment: powder bed; concept or principle: heat; process characterization: accuracy; concept or principle: model
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: surface structure, metallic powder, porosity, powder bed, heat, accuracy, model 
Answer:
 engineering feature: surface structure; material: metallic powder; machanical property: porosity; machine or equipment: powder bed; concept or principle: heat; process characterization: accuracy; concept or principle: model