Researchers in microelectronics have found that a slight scratch on the surface of 5 pts. gallium arsenide causes a zinc dopant to diffuse into the arsenide. When these devices are baked at 850°C the dopant spreads. Its diffusion coefficient at this temperature is 10−11cm^2/s. If it spreads enough to increase the zinc concentrationto 10% of the maximum concentrationat 4×10^−4 cm away from the scratch the device is ruined. How long can we safely bake the device?

Steel is coated with a thin layer of ceramic to protect against corrosion. what do you expect to happen to the coating when the temperature of the steel is increased significantly? explain.

For a gate width of 2 m into the paper, determine the force required to hold the gate abc at its location.

Ashielded metal arc-welding operation is accomplished in a work cell by a fitter and a welder. the fitter takes 5.5 min to load components into the welding fixture at the beginning of the work cycle, and 1.5 min to unload the completed weldment at the end of the cycle. the total ength of the weld seams 1200 mm, and the travel speed used by the welder averages 300 mm/min. every 600 mm of seam length, the welding stick must be changed, which takes 0.8 min. while the fitter is working, the welder is idle (resting): and while the welder is working the fitter is idle. (a) determine the average arc-on time as a fraction of the work cycle time. (b) how much improvement in arc-on time would result if the welder used flux-cored arc welding (manually operated), given that the spool of weld wire must be changed every 10 weldments, and it takes the welder 5.0 min to accomplish the change? (c) what are the production rates for these two cases (weldments completed per hour)? attach your work and solutions.