例如噪音、放射源的使用、可能坠落的物体等。
Years ago, to 'hedge' against a potential drop in prices, a number of gold-mining companies agreed to sell much of their future production.多年前，为了“对冲”金价下跌的可能性，众多金矿公司同意预售大量未来将开采的黄金。
The results showed that the activation of sodium sulfide to the smithsonite due to the HS- ion adsorbed on the smithsonite's surface and lead to the zeta potential drop.结果表明，硫化钠对菱锌矿的活化作用主要通过HS-吸附在菱锌矿表面，降低菱锌矿表面电位实现；
