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The optimized structure is fabricated via selective laser melting of maraging steel , which is a high-strength , iron-nickel steel that can not easily be made porous with conventional methods .
 concept or principle: structure; concept or principle: fabricated; manufacturing process: selective laser melting; material: maraging steel; material: steel; material: be; machanical property: porous
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: structure, fabricated, selective laser melting, maraging steel, steel, be, porous 
Answer:
 concept or principle: structure; concept or principle: fabricated; manufacturing process: selective laser melting; material: maraging steel; material: steel; material: be; machanical property: porous