5.32 the outer surface of a steel gear is to be hardened by increasing its carbon content; the carbon is to be supplied from an external carbon-rich atmosphere, which is maintained at an elevated temperature. a diffusion heat treatment at 850 (1 123 k) for 10 min increases the carbon concentration to 0.90 wt% at a position 1.0 mm below the surface. estimate the diffusion time required at 650℃ (923 k) to achieve this same concentration also at a 10- mm position. assume that the surface carbon content is the same for both heat treatments, which is maintained constant. use the diffusion data in table 5.2 for c diffusion in a-fe

it is very hard for the climatologists to precisely predict how will the global temperatures be changing so there's lots of models, some of which differ significantly, this is due to multiple factors, and probably the most important is the human activity.

humans have been a key factor in climate change around the globe since the start of the industrial revolution, and in the past few decades the consequences are becoming more obvious. there's lots of emission of pollutants in the atmosphere as well as changing the environment on the surface itself, so it's really hard to predict how will that go in the future because there's some countries that are reducing the damage and are going towards green energy, while others are stubbornly continuing with pollution and damages to the environment.