Perhaps you should try some spelling variations:
"modified passive optimisation algorithm" » "modified passive optimization algorithms", "modified passive estimation algorithm", "modified adaptive optimisation algorithm"
"modified parameter estimation algorithms" » "modified parameter estimation algorithm", "modified parameter optimization algorithms", "modified parameter approximation algorithms", "modified parameter estimates algorithms"

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: (("modified parameter estimation algorithms") OR ("modified passive optimisation algorithm"))~.
• Removing quotes may allow a broader search: (( modified parameter estimation algorithms ) or ( modified passive optimisation algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified parameter estimation algorithms") or ("modified passive optimisation algorithm"))*.