1966
Bobbert proposed to use in these applications continuous sheet-based porous structures because they are expected to be less sensitive to such imperfections than beam-based porous structures , to improve fatigue resistance .
 machanical property: porous; material: be; concept or principle: imperfections; machanical property: porous; machanical property: fatigue
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:
 machanical property: porous; material: be; concept or principle: imperfections; machanical property: porous; machanical property: fatigue