The most common shielding gases used for these main arc welding processes include argon (Ar), helium (He), carbon dioxide (CO2) and oxygen (O2). While Ar, He and CO2 may be used by themselves (i.e. 100%) for certain applications, in other cases the four gases are mixed together in different combinations to form shielding gas blends.
Cluster reduction in speech is when a consonant cluster, that is two or three consonants occurring in sequence in a word (like ândâ in friend), is reduced by a child into a single consonant through omission.
A consonant digraph consists of two adjacent consonants that produce one sound. The digraphs sh, ch, and th represent unique sounds that are not usually associated with any individual letters of the alphabet. The digraphs kn and gn are associated with the sound of /n/, and the digraph ph is associated with the sound of /f/. Learning to recognize the consonant digraphs is very helpful to beginning readers and writers because many early reading words contain these special two letter combinations.