Perhaps you should try some spelling variations:
"modified channel estimation algorithmss" » "modified channel estimation algorithms", "modified channel estimation algorithm", "modified channel optimization algorithms", "modified channel excitation algorithmss"
"modified objective approximation algorithms" » "modified objective approximation algorithm"

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 channel estimation algorithmss") OR ("modified objective approximation algorithms"))~.
• Removing quotes may allow a broader search: (( modified channel estimation algorithmss ) or ( modified objective approximation algorithms ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified channel estimation algorithmss") or ("modified objective approximation algorithms"))*.