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The results , using 316 L stainless steel powders , have shown that the mass powder flow rate can be effectively controlled and that it is most prominently influenced by the piezo excitation frequency .
 material: 316 L stainless steel powders; process parameter: powder flow rate; material: be; process characterization: excitation
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: 316 L stainless steel powders, powder flow rate, be, excitation 
Answer:
 material: 316 L stainless steel powders; process parameter: powder flow rate; material: be; process characterization: excitation