Consider the axial laminar flow between two parallel porous plates separated by a distance 2W. There is a transverse velocity yw into the channel through the top plate and out through the bottom plate at the same value. Develop an expression for the axial velocity profile u( y) for fully developed flow

On solidification from a melt, the polymer polyethylene forms a semi-crystalline spherulite structure. (i) sketch an individual spherulite and label the amorphous and crystalline regions. (ii) draw a schematic to show the changes in specific volume with temperature during cooling from the melt, comparing it to the theoretical extremes of fully crystalline and fully amorphous (indicate tm and tg)