咖啡豆表面的油脂也会很容易变坏。
Roasts where oils are exposed on the surface of the bean are much more vulnerable.
表明硬铝合金焊头极易发生表面的粘着磨损破坏，使得声学系统谐振特性变坏，效率降低。
It is shown that the horn made of aluminum alloys (e. g. Ly12CZ) is apt to adhesion-wear, that makes the resonance properties worsening and leads to decreasing of the acoustic transmitting efficiency.
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