2077
In L-PBF and at macro level , the top surfaces of the round holes have the tendency to sag or collapse , and the cross section of the channel has to be optimized .
 manufacturing process: L-PBF; engineering feature: macro level; concept or principle: surfaces; concept or principle: cross section; application: channel; material: be
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:
 manufacturing process: L-PBF; engineering feature: macro level; concept or principle: surfaces; concept or principle: cross section; application: channel; material: be