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In this research work , a comparison is made between two different WAAM technologies , GMAW ( gas metal arc welding ) and PAW ( plasma arc welding ) .
 concept or principle: research; manufacturing process: WAAM; concept or principle: technologies; manufacturing process: GMAW; manufacturing process: gas metal arc welding; manufacturing process: PAW; manufacturing process: plasma arc welding
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: research; manufacturing process: WAAM; concept or principle: technologies; manufacturing process: GMAW; manufacturing process: gas metal arc welding; manufacturing process: PAW; manufacturing process: plasma arc welding