Which of the following statements concerning the standard deviation are correct? (a) The standard deviation measures the volatility of a security’s returns. (b) The standard deviation can be negative, positive, or equal to zero. (c) The 95 percent probability range is equal to the mean plus or minus two standard deviations. (d) The lower the standard deviation, the lower the level of risk.

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.

Journeyman training is usually related (clo2) a)-to specific tasks b)-to cost analysis of maintenance task c)-to control process to ensure quality d)-to installation of machinery

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?