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4.1 Topology optimization Topology optimization was originally used for mechanical design problems to answer a layout optimization question : how to put the right material in the right place of a pre-defined design space ? The objective was to obtain the expected mechanical properties at minimum material use .
 engineering feature: Topology optimization; concept or principle: Topology; concept or principle: optimization; application: mechanical; engineering feature: design; concept or principle: layout; material: material; concept or principle: design space; concept or principle: mechanical properties; material: material
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:
 engineering feature: Topology optimization; concept or principle: Topology; concept or principle: optimization; application: mechanical; engineering feature: design; concept or principle: layout; material: material; concept or principle: design space; concept or principle: mechanical properties; material: material