3301
A novel compulsively constricted wire arc additive manufacturing（CC-WAAM）method was proposed with arc and droplets ejected out of a narrow space .
 concept or principle: arc; material: additive; concept or principle: arc; concept or principle: droplets
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: arc, additive, arc, droplets 
Answer:
 concept or principle: arc; material: additive; concept or principle: arc; concept or principle: droplets