4435
In order to study the special constriction effect and physical process features during compulsively constricted WAAM ( CC-WAAM ) , the dynamic behaviours of arc , droplets , and molten pool were visually investigated .
 physical process, WAAM, dynamic, arc, droplets, molten pool
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:
 physical process, WAAM, dynamic, arc, droplets, molten pool