Asphalt driveways are typically less expensive than concrete, costing a minimum of about $2.50 per square foot. An asphalt driveway might last just 20 years; however, while a concrete driveway can last more than 30.
Semipermeable membrane. The diffusion of water through a selectively permeable membrane is called osmosis.This allows only certain particles to go through including water and leaving behind the solutes including salt and other contaminants. In the process of reverse osmosis, thin film composite membranes (TFC or TFM) are used.
Membrane Diffusion. The simplest kind of transport is the unassisted diffusion of solutes across membranes (see Figure 1a). The kinds of molecules that transit in this fashion are more soluble in oil than water and so readily dissolve in and then spontaneously traverse the nonpolar lipid core of the membrane bilayer .