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By making use of the Altair OptiStruct software , a topologically optimized design is automatically obtained , substituted by pre-selected unit cells before a size optimisation ensures that the overall target density is achieved .
 concept or principle: software; concept or principle: topologically; engineering feature: design; concept or principle: unit cells; machanical property: density
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: software; concept or principle: topologically; engineering feature: design; concept or principle: unit cells; machanical property: density