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.
Deletion requires children to be able to remove individual or blended sounds from words or to identify words once a phoneme or phonemes have been removed. Words may include consonant blends, where two or more sounds are together as a cluster or blend (each consonant retains its own sound, for example, /sn/ in snail).