Summary of Transient Diffusion Problems

Determine the geometry of the problem (e.g., ID, 2D, 3D, radial, spherical) and identify any symmetries. 

Make a sketch of the physical problem and show the initial concentration profile and your expectation for how the concentration profile will evolve as a function of time 

Obtain the general solution to the problem (by looking it up in a reference text, consulting your friend in the math department, or solving the partial differential equation using your amazing mathematical skills). 

Apply the boundary and initial conditions to the general solution obtained above in order to obtain the exact solution. 

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