The adverb of degree 不已
Adverbs of degree (程度副词) are used to intensify or modify the degree of an adjective or verb.
The adverb 不已 
is used to emphasize a strong degree of emotions and feelings. It is placed after either a two-syllable adjective or a verb.
is used to emphasize a strong degree of emotions and feelings. It is placed after either a two-syllable adjective or a verb.Examples
听了他的讲解，大家一下子清楚了，对他的方法赞叹不已
After hearing his explanation, everyone understood everything and were amazed by his method
tīng le tā de jiǎngjiě, dàjiā yíxiàzi qīngchu le, duì tā de fāngfǎ zàntàn bùyǐ
找到了解决问题的办法，他兴奋不已
He felt endless enthusiasm after finding a solution to his problem
zhǎodào le jiějué wèntí de bànfǎ, tā xīngfèn bùyǐ
我的猫丢了，我伤心不已
My cat is lost. I am very upset
wǒ de māo diū le, wǒ shāngxīn bùyǐ