Perhaps you should try some spelling variations:
"mathematical optimisation" » "mathematical optimization", "mathematics optimization", "mathematical simulation"
"materials optimization" » "material optimization", "criteria optimization", "models 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 optimisation") OR ("materials optimization")).
• Removing quotes may allow a broader search: (( mathematical optimisation ) or ( materials optimization )).
• Adding a wildcard symbol may retrieve word variants: (("mathematical optimisation") or ("materials optimization"))*.