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Upset welding ( UW ) is a welding technique that produces coalescence simultaneously over the entire area of abutting surfaces or progressively along a joint , by the heat obtained from resistance to electric current through the area where those surfaces are in contact .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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