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This study presents the surface characteristics of aB-built specimens manufactured by selective laser melting ( SLM ) , where improvement of the surface can be achieved by post-processing operations .
 concept or principle: surface; concept or principle: manufactured; manufacturing process: selective laser melting; manufacturing process: SLM; concept or principle: surface; material: be; concept or principle: post-processing
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, manufactured, selective laser melting, SLM, surface, be, post-processing 
Answer:
 concept or principle: surface; concept or principle: manufactured; manufacturing process: selective laser melting; manufacturing process: SLM; concept or principle: surface; material: be; concept or principle: post-processing