Perhaps you should try some spelling variations:
"modified passive estimation algorithms" » "modified passive estimation algorithm", "modified passive optimization algorithms", "modified passive optimisation algorithm", "modified pose estimation algorithms"
"modified adaptive ventilation algorithm" » "modified adaptive estimation algorithm", "modified adaptive evolution algorithm", "modified adaptive quantization algorithm", "modified invasive ventilation algorithm"

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"modified adaptive ventilation algorithm\") OR (\"modified passive estimation algorithms\"))~".
• Removing quotes may allow a broader search: (( modified adaptive ventilation algorithm ) OR ( modified passive estimation algorithms ))~.
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