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This paper reviews the state-of-the-art of topological design and manufacturing processes of various types of porous metals , in particular for titanium alloys , biodegradable metals and shape memory alloys .
 concept or principle: state-of-the-art; engineering feature: topological design; manufacturing process: manufacturing processes; material: porous metals; material: titanium alloys; material: biodegradable metals; material: shape memory alloys
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: state-of-the-art; engineering feature: topological design; manufacturing process: manufacturing processes; material: porous metals; material: titanium alloys; material: biodegradable metals; material: shape memory alloys