Unstable stratification of fluids occurs when each layer is more dense than the one below it.

The entry of water into a compartment on one side of the ship which will cause heeling, in addition to the effects of flooding.

The concentration of a hydrocarbon gas in air above which there is insufficient amount of oxygen to support and propagate combustion.

The oil and gas industry is usually divided into three major sectors: upstream, midstream and downstream.

A metal casing or large-bore piping which carries exhaust gases up through the funnel to the atmosphere.

On the same side from where the wind is blowing from.

Turbines where the blades are upwind of the tower.

Uranium is a chemical element with the symbol U and atomic number 92.

Uranium dioxide or uranium oxide, also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite.

Uranium hexafluoride colloquially known as "hex" in the nuclear industry, is a compound used in the process of enriching uranium, which produces fuel for nuclear reactors and nuclear weapons.

Uranium mining is the process of extraction of uranium ore from the ground.

Uranium ore deposits are economically recoverable concentrations of uranium within the Earth's crust.

Uranium trioxide is used industrially in the reprocessing of nuclear fuel and uranium enrichment.

Uranium-233 was investigated for use in nuclear weapons and as a reactor fuel. It has been used successfully in experimental nuclear reactors and has been proposed for much wider use as a nuclear fuel.

Uranium-238 is the most common isotope of uranium found in nature, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor.

An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities.

Urea, (NH2)2CO, is a common chemical commodity used in a wide range of products.

Resources that are provided to homes and industry such as electricity, water and natural gas.

The utility frequency, line frequency or mains frequency is the nominal frequency of the oscillations of alternating current in a wide area synchronous grid transmitted from a power station to the end-user.

A post or column that supports overhead power lines and associated equipment such as transformers.