Surface Functional Groups/Notation
The notation used does not necessarily represent a triple bond - for example, using one of the examples that you have provided:


  $\equiv\text{Si}-\text{OH}$


Which is for the functional group silanol, that is defined by the $\ce{Si-O-H}$ connectivity, it's chemical structure is 



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Using this example, the hydrogens represented by the  ≡ symbol can be replaced by other chemicals forming other members of the silanol functional group, for example, Trimethylsilanol: