Perhaps you should try some spelling variations:
"learning-gas sensor segmentation techniques" » "learning-gas sensor augmentation techniques", "learning-gas series segmentation techniques", "learning-gas semantic segmentation techniques", "learning-gas sensors segmentation techniques"
"learning-based code imputation techniques" » "learning-based code implantation technique", "learning-based code augmentation techniques", "learning-based code floatation technique", "learning-based anode imputation techniques"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("learning-gas sensor segmentation techniques") or ("learning-based code imputation techniques"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("learning-gas sensor segmentation techniques") OR ("learning-based code imputation techniques"))*.
• Removing quotes may allow a broader search: (( learning-gas sensor segmentation techniques ) or ( learning-based code imputation techniques ))*.