nocturnal emission reflex emission of semen during sleep. thermionic emission the application of heat, such as to a filament, resulting in the emission of electrons and ions. thermionic emission
Which means if the equipment if design to has a high factor of safety, the cost to fabricate the equipment will increase and same to the weight too. But if the equipment is design with low cost and low weight, the factor of safety will be low too.
A protection factor of at least 40 means that the Radiation shielding provided by the shelter reduces the radiation dose experienced by at least 40 times that which would be experienced outside the shelter with no shielding. Protection factor is equivalent to the modern term dose reduction factor.