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Because many of the most important defects in Laser Powder Bed Fusion ( L-PBF ) occur at the size and timescales of the melt pool itself , the development of methodologies for monitoring the melt pool is critical .
 concept or principle: defects; manufacturing process: Laser Powder Bed Fusion; manufacturing process: L-PBF; material: melt pool; material: melt pool
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: defects, Laser Powder Bed Fusion, L-PBF, melt pool, melt pool 
Answer:
 concept or principle: defects; manufacturing process: Laser Powder Bed Fusion; manufacturing process: L-PBF; material: melt pool; material: melt pool