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Since an open porous implant has large surface area , only alloys with slow degradation rate should be considered for making the porous structure , e.g .
 application: porous implant; process parameter: surface area; material: alloys; process characterization: degradation rate; material: be; machanical property: porous
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:
 application: porous implant; process parameter: surface area; material: alloys; process characterization: degradation rate; material: be; machanical property: porous