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The experimental results showed that UPT in three directions applied to each weld right after arc extinguishing has a minor influence on the surface appearance , which shows no apparent plastic deformation , but has a great improvement in grain refinement .
 concept or principle: experimental; engineering feature: weld; concept or principle: arc; concept or principle: surface; machanical property: plastic deformation; process characterization: grain refinement
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: experimental; engineering feature: weld; concept or principle: arc; concept or principle: surface; machanical property: plastic deformation; process characterization: grain refinement