What is the minimum switch-off time of D (corresponding to
the minimal operational time of D) in order to transfer to S a total amount of energy
Q (where Q > 0 is given)? The device D can also be viewed as a control mechanism for
bringing the system S from an energy level E1 to a higher energy level E2 in finite time
while operating for the minimum time possible. Clearly, the solution of this problem
can have a lot of applications, both civilian