Perhaps you should try some spelling variations:
"material optimization" » "numerical optimization", "criteria optimization", "combinatorial optimization"
"models optimization" » "model optimization", "modeling optimization"
"mathematical optimization" » "mathematics optimization"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("mathematical optimization") OR ((("models optimization") OR ("material optimization")))).
• Removing quotes may allow a broader search: (( mathematical optimization ) or ((( models optimization ) or ( material optimization )))).
• Adding a wildcard symbol may retrieve word variants: (("mathematical optimization") or ((("models optimization") or ("material optimization"))))*.