655
While a lot of research effort has been focused on different technologies ( such as Powder Bed Fusion ) , there is still quite limited knowledge concerning the structural response of Wire-and-Arc Additive Manufactured ( WAAM ) metallic elements , as very few experimental campaigns aimed at assessing their geometrical and mechanical properties have been carried out .
 concept or principle: research; concept or principle: technologies; material: as; manufacturing process: Bed Fusion; manufacturing process: Additive Manufactured; manufacturing process: WAAM; material: metallic elements; material: as; concept or principle: experimental; concept or principle: mechanical properties
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; concept or principle: technologies; material: as; manufacturing process: Bed Fusion; manufacturing process: Additive Manufactured; manufacturing process: WAAM; material: metallic elements; material: as; concept or principle: experimental; concept or principle: mechanical properties