Granular material asteroids. Some examples of granular materials are snow, nuts, coal, sand, rice, coffee, corn flakes, fertilizer, and bearing balls. Research into granular materials is thus directly applicable and goes back at least to Charles-Augustin de Coulomb, whose law of friction was originally stated for granular materials. Granular materials are commercially important in applications as diverse as pharmaceutical industry, agriculture, and energy production. Powders are a special class of granular material due to their small particle size, which makes them more cohesive and more easily suspended in a gas. The soldier/physicist Brigadier Ralph Alger Bagnold was an early pioneer of the
Silt out zero visibility. Always using guidelines during penetration dives is an important safety measure as it helps divers find their way out. Surface supplied divers are generally at less risk from silt out as they are connected to the surface by an umbilical and can not get lost, but they may become disorientated, and unable to work effectively. It is also more likely for them to have an umbilical snag in bad visibility, and if assistance is required from the stand-by diver, this is more difficult in a silt out. A severe silt out will make the video cameras on a