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.
Water is swept through a semi-permeable membrane down a pressure gradient (ultrafiltration). Any solutes in the water, that are small enough, also pass through (solvent drag or convection) much like in the glomerulus. Solute movement is driven by a pressure gradient rather than a concentration gradient.