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It was discovered that the tribological performance of SLM stainless steel sample will be better if the pores can be drastically reduced with refined grains .
 concept or principle: tribological performance; manufacturing process: SLM; material: steel; concept or principle: sample; material: be; machanical property: pores; material: be; concept or principle: grains
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: tribological performance; manufacturing process: SLM; material: steel; concept or principle: sample; material: be; machanical property: pores; material: be; concept or principle: grains