Consider electron-hole recombination under conditions of strong carrier-pair injection such that the recombination lifetime can be approximated by tau=1/(zeta delta n), delta n is the injection-generated excess carrier concentration and zeta is the recombination parameter of the material. Assume that the source of injection R is set to zero at t = t_0, find an analytic expression for delta n(t), demonstrating that it exhibits power-law rather than exponential behavior.

Compute the pressure drop of 30°c air flowing with a mean velocity of 8 m/s in a circular sheet-metal duct 300 mm in diameter and 15 m long. use a friction factor, f 0.02, and pair = 1.1644 kg/m a. 37.26 pa b. 25.27 pa n c. 29.34 pa d. 30.52 pa

Inspection for bearing condition will include: (clo4) a)-color b)-smell c)-size d)-none of the above

An external consultant recommends that a plant installs a bank of capacitors for power factor correction. this will reduce the peak electrical demand charges by an average of 93 kw every month. the plant current pays $13 per kw in peak demand charges. the capacitor bank will include 223 kw of fixed capacitors, and 183 of variable capacitors. the fixed capacitors cost $59 per kw, and the variable capacitors will cost $65 per kw. the consultant charges 21% of the equipment costs to install the capacitors. because this project will reduce the demand for the electric utility, they are prepared to provide a one-time rebate of $42 per kw of reduced demand. what is the simple payback period for this project (in years)?