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In this study , the effect of shielding gas flow velocity on porosity and melt pool geometry in laser powder bed fusion additive manufacturing is studied .
 concept or principle: gas; machanical property: porosity; material: melt pool; concept or principle: geometry; manufacturing process: laser powder bed fusion additive manufacturing
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: gas, porosity, melt pool, geometry, laser powder bed fusion additive manufacturing 
Answer:
 concept or principle: gas; machanical property: porosity; material: melt pool; concept or principle: geometry; manufacturing process: laser powder bed fusion additive manufacturing