4651
The lack of quantitative , in situ monitoring results from full 3D PBF builds remains a barrier to closed-loop control .
 quantitative, in situ, 3D, builds, closed-loop control
Please list all entity words in the text that fit the category. Output format is "word1, 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} 
Answer:
 quantitative, in situ, 3D, builds, closed-loop control