A zoom lens, including in order from an object side to an image side: a first lens unit; a second lens unit; a third lens unit; and a fourth lens unit, in which the second lens unit includes four lenses as a whole, in which a first lens and a second lens are disposed successively in order from the object side to the image side, and the following conditional expressions are satisfied: 7. The phase-change material includes at least one metal and is reversibly phase-changeable, switchable, to a detectable metallic glass state or to a detectable crystalline state thereof. Another version of the shared component exists on the system and is useable by any number of other computer programs. The conversion of said first power to said second power is performed in at least two steps, a first one of such steps including the step of converting down said first power to an intermediate DC power at an intermediate DC voltage lower than said first DC voltage but higher than said second DC voltage. The design and size of the device is particularly useful in morbidly obese individuals that require cardiac compressions in order to optimize resuscitation efforts.