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An ultrasonic phased array system , consisting of a 5 MHz 64 Element phased array transducer , was used to inspect the WAAM sample non-destructively .
 Element, transducer, WAAM, sample
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:
 Element, transducer, WAAM, sample