Discrete-time signals with different frequencies can be equal; this is one manifestation of aliasing and folded aliases. Determine which of the following discrete-time cosine signals are equal (i. e., plots of xi[n]versus n will be identical):

x_1[n] = cos (0.9pi n + 0.1pi)
x_2[n] = cos (-2.9pi n + 0.1pi)
x_3[n] = cos (5.1pi n - 0.1pi)
x_4[n] = cos (6.9pi n - 0.1pi)
x_5[n] = cos (-7.1pi n - 0.1pi)

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.

Condition monitoring is a major component of. (clo4) a)- predictive maintenance. b)-preventive maintenance c)-proactive maintenance d)-reactive maintenance.