题目内容
二阶欠阻尼系统的有阻尼固有频率ωd、无阻尼固有频率ωn和谐振频率ωr比较()
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The combination of lift and drag makes the rotor spin like a propeller，and the turning shaft spins a plane to make electricity.
Unlike batteries，fuel cells allow easy independent scaling between power(determined by the fuel cell size) and capacity(determined by the fuel reservoir size).
As the protrons mover from the fuel species to the oxidant species, they can be harnessed as an electrical current.
Like a factory, a fuel cell will continue to churn out product (electricity) as long as raw material (fuel) is supplied. This is the key difference between a fuel cell and a battery.
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