mantle piece

同根派生

However, it seemed better for nucleated pearl production to clean the mantle piece with sterilized sponge block or absorbent tampon than washing according to the appearance data.
这些差异，从统计学角度看没有明显区别，但从表观数据可见，无论是成珠率还是优珠率，育珠细胞小片用海绵块擦和脱脂棉球擦比不擦明显要高，表明小片不擦不利于有核珍珠的培育。
He bit off a large piece of the apple.
他咬下一大块苹果。
I need a piece of string to tie this parcel up.
我需要一根细绳把这包裹扎起来。
The earth has a core and a mantle around it.
地球的中心是地核，地核的周围是地幔。
The mountain was covered with a mantle of snow.
山上覆盖着一层雪。