Perhaps you should try some spelling variations:
world engine » world english, build engine
world empire » world aspire
visual theme » visual time, visual tree, visual thermal
xvii visual » xviii visual, vii visual, xii visual

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: 2019 ieee ((world energy) OR (((world engine) OR (world empire)))) xvii visual theme.
• The words AND, OR and NOT may confuse the search; try adding quotes: "2019 ieee ((world energy) or (((world engine) OR (world empire)))) xvii visual theme".
• Adding a wildcard symbol may retrieve word variants: 2019 ieee ((world energy) or (((world engine) OR (world empire)))) xvii visual theme*.