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This is due to factors such as the high friction within the powder particles , their random agglomeration and the absence of an external force to compress the powder and improve packaging .
 material: as; concept or principle: friction; material: powder particles; concept or principle: force; material: powder
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:
 material: as; concept or principle: friction; material: powder particles; concept or principle: force; material: powder