Perhaps you should try some spelling variations:
"mathematics optimization" » "mathematical optimization"
"materials optimization" » "material optimization", "criteria optimization", "mathematical optimization"
"modeling optimization" » "learning optimization"
"models optimization" » "model 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: (("mathematics optimization") OR ((("materials optimization") OR ((("models optimization") OR ("modeling optimization")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"mathematics optimization\") or (((\"materials optimization\") or (((\"models optimization\") OR (\"modeling optimization\"))))))".
• Removing quotes may allow a broader search: (( mathematics optimization ) or ((( materials optimization ) or ((( models optimization ) OR ( modeling optimization )))))).
• Adding a wildcard symbol may retrieve word variants: (("mathematics optimization") or ((("materials optimization") or ((("models optimization") OR ("modeling optimization"))))))*.