91色情片

A 鈥渟mart sieve鈥� that separates tiny particles into different sizes and weighs
them at the same time has been developed at University College London. Haroun
Mahgerefteh and his colleagues blow the particles into a coiled spring. A
鈥渟tepper motor鈥� then gradually pulls the spring apart, so particles fall through
the expanding gaps in ever-increasing sizes. The change in weight of the
apparatus is monitored, so you know how much material has been sieved at each
setting of the spring. Drugs firms could sort and weigh powders with the
sieve.