Vacuum packing preventing the evaporation of volatile components. It is also commonly used to store dry foods over a long period of time, such as cereals, nuts, cured meats, cheese, smoked fish, coffee, and potato chips (crisps). On a more short term basis, vacuum packing can also be used to store fresh foods, such as vegetables, meats, and liquids, because it inhibits bacterial growth. Vacuum packing greatly reduces the bulk of non-food items. For example, clothing and bedding can be stored in bags evacuated with a domestic vacuum cleaner or a dedicated vacuum sealer. This technique is sometimes used to compact household
Close-packing of equal spheres a common radius, "r". Therefore two centers would simply have a distance 2"r". To form an A-B-A-B-... hexagonal close packing of spheres, the coordinate points of the lattice will be the spheres' centers. Suppose, the goal is to fill a box with spheres according to hcp. The box would be placed on the "x"-"y"-"z" coordinate space. First form a row of spheres. The centers will all lie on a straight line. Their "x"-coordinate will vary by 2"r" since the distance between each center of the spheres are touching is 2"r". The "y"-coordinate and z-coordinate will be the same. For simplicity,