Methods 375 heat stress exposed workers, 674 high-frequency electric field exposed operators, 350 VDT operators and 102 noise exposed workers were examined.

As the doohickey hummed away at a very high frequency-a whopping 6 billion cycles per second-the "piezoelectric" material in it produced a warbling electric field that was easy to detect.

It researched the experimental method of high-pulsed electric field to milk's sterilization, which measured the sterilization ratio in different electric field intensity, treatment time and frequency.