A fatigue test is performed on rotating beam specimens where, for each rotation cycle, thespecimens experience tensile and compressive stresses of equal magnitude. The cycles-to-failureexperience with 69 specimens of 5160H steel from 1.25-in hexagonal bar stock was as follows:L 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210f 2 1 3 5 8 12 6 10 8 5 2 3 2 1 0 1 where L is the life in thousands of cycles, and f is the class frequency of failures.(a) Estimate the mean and standard deviation of the life for the population from which thesample was drawn.(b) Presuming the distribution is normal, how many specimens are predicted to fail at less than115 kcycles?

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w