<unk>  is a heat-reducing mechanism that is typically implemented in electronic devices and indoor buildings to ensure proper heat transfer and circulation from within. Unlike its counterpart passive<unk> ,<unk>  is entirely dependent on energy consumption in order to operate. It uses various mechanical systems that consume energy to dissipate heat. It is commonly implemented in systems that are unable to maintain their temperature through passive means.<unk>  systems are usually powered through the use of electricity or thermal energy but it's possible for some systems to be powered by solar energy or even hydroelectric energy. They need to be well-maintained and sustainable in order for them to perform its necessary tasks or the possibility of damages within objects could occur. Various applications of commercial<unk>  systems include indoor air conditioners, computer fans, and heat pumps.
Active cooling
Depot injection
Transcranial magnetic stimulation
Electrical brain stimulation
Stimulant maintenance
Transcranial direct-current stimulation
Functional electrical stimulation
Glucagon rescue