619
They studied the influence of geometric features of unit cells on the mechanical properties of the porous structures and found that when the porosity changed from 59 % to 88 % , the elastic modulus decreased from 3.03 to 0.58 GPa , which proved that the elastic modulus of porous metals could be readily adjusted through the porosity .
 concept or principle: unit cells; concept or principle: mechanical properties; machanical property: porous; machanical property: porosity; machanical property: elastic modulus; machanical property: GPa; machanical property: elastic modulus; material: porous metals; material: be; machanical property: porosity
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: unit cells; concept or principle: mechanical properties; machanical property: porous; machanical property: porosity; machanical property: elastic modulus; machanical property: GPa; machanical property: elastic modulus; material: porous metals; material: be; machanical property: porosity