999
This study will lay a solid foundation for subsequent feedback control for layer geometry in WAAM .
 concept or principle: lay; process parameter: feedback; process parameter: layer; concept or principle: geometry; manufacturing process: WAAM
Please list all entity words in the text that fit the category.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} 
Answer:
 concept or principle: lay; process parameter: feedback; process parameter: layer; concept or principle: geometry; manufacturing process: WAAM